From 479b0ebfc061cf35d70c623688751726174a025d Mon Sep 17 00:00:00 2001 From: zrj Date: Tue, 7 Jan 2020 20:08:17 +0200 Subject: [PATCH] Remove few unused texi sources on gdb branch. As it was done in 874e15d007943a40fad40d5e25620e2bf00235a1 --- contrib/gdb-7/gdb/doc/LRS | 197 - contrib/gdb-7/gdb/doc/a4rc.sed | 11 - contrib/gdb-7/gdb/doc/agentexpr.texi | 767 - contrib/gdb-7/gdb/doc/all-cfg.texi | 45 - contrib/gdb-7/gdb/doc/annotate.texinfo | 852 - contrib/gdb-7/gdb/doc/fdl.texi | 505 - contrib/gdb-7/gdb/doc/gdb.texinfo | 41708 ----------------------- contrib/gdb-7/gdb/doc/gdbint.texinfo | 8155 ----- contrib/gdb-7/gdb/doc/gpl.texi | 735 - contrib/gdb-7/gdb/doc/stabs.texinfo | 4125 --- contrib/gdb-7/gdb/doc/stack_frame.txt | 39 - 11 files changed, 57139 deletions(-) delete mode 100644 contrib/gdb-7/gdb/doc/LRS delete mode 100644 contrib/gdb-7/gdb/doc/a4rc.sed delete mode 100644 contrib/gdb-7/gdb/doc/agentexpr.texi delete mode 100644 contrib/gdb-7/gdb/doc/all-cfg.texi delete mode 100644 contrib/gdb-7/gdb/doc/annotate.texinfo delete mode 100644 contrib/gdb-7/gdb/doc/fdl.texi delete mode 100644 contrib/gdb-7/gdb/doc/gdb.texinfo delete mode 100644 contrib/gdb-7/gdb/doc/gdbint.texinfo delete mode 100644 contrib/gdb-7/gdb/doc/gpl.texi delete mode 100644 contrib/gdb-7/gdb/doc/stabs.texinfo delete mode 100644 contrib/gdb-7/gdb/doc/stack_frame.txt diff --git a/contrib/gdb-7/gdb/doc/LRS b/contrib/gdb-7/gdb/doc/LRS deleted file mode 100644 index 7e25d432a3..0000000000 --- a/contrib/gdb-7/gdb/doc/LRS +++ /dev/null @@ -1,197 +0,0 @@ -What's LRS? -=========== - -LRS, or Live Range Splitting is an optimization technique which allows -a user variable to reside in different locations during different parts -of a function. - -For example, a variable might reside in the stack for part of a function -and in a register during a loop and in a different register during -another loop. - -Clearly, if a variable may reside in different locations, then the -compiler must describe to the debugger where the variable resides for -any given part of the function. - -This document describes the debug format for encoding these extensions -in stabs. - -Since these extensions are gcc specific, these additional symbols and -stabs can be disabled by the gcc command option -gstabs. - - -GNU extensions for LRS under stabs: -=================================== - - -range symbols: -------------- - - A range symbol will be used to mark the beginning or end of a - live range (the range which describes where a symbol is active, - or live). These symbols will later be referenced in the stabs for - debug purposes. For simplicity, we'll use the terms "range_start" - and "range_end" to identify the range symbols which mark the beginning - and end of a live range respectively. - - Any text symbol which would normally appear in the symbol table - (eg. a function name) can be used as range symbol. If an address - is needed to delimit a live range and does not match any of the - values of symbols which would normally appear in the symbol table, - a new symbol will be added to the table whose value is that address. - - The three new symbol types described below have been added for this - purpose. - - For efficiency, the compiler should use existing symbols as range - symbols whenever possible; this reduces the number of additional - symbols which need to be added to the symbol table. - - -New debug symbol type for defining ranges: ------------------------------------------- - - range_off - contains PC function offset for start/end of a live range. - Its location is relative to the function start and therefore - eliminates the need for additional relocation. - - This symbol has a values in the text section, and does not have a name. - - NOTE: the following may not be needed but are included here just - in case. - range - contains PC value of beginning or end of a live range - (relocs required). - - NOTE: the following will be required if we desire LRS debugging - to work with old style a.out stabs. - range_abs - contains absolute PC value of start/end of a live - range. The range_abs debug symbol is provided for - completeness, in case there is a need to describe addresses - in ROM, etc. - - -Live range: ------------ - - The compiler and debugger view a variable with multiple homes as - a primary symbol and aliases for that symbol. The primary symbol - describes the default home of the variable while aliases describe - alternate homes for the variable. - - A live range defines the interval of instructions beginning with - range_start and ending at range_end-1, and is used to specify a - range of instructions where an alias is active or "live". So, - the actual end of the range will be one less than the value of the - range_end symbol. - - Ranges do not have to be nested. Eg. Two ranges may intersect while - each range contains subranges which are not in the other range. - - There does not have to be a 1-1 mapping from range_start to - range_end symbols. Eg. Two range_starts can share the same - range_end, while one symbol's range_start can be another symbol's - range_end. - - When a variable's storage class changes (eg. from stack to register, - or from one register to another), a new symbol entry will be - added to the symbol table with stabs describing the new type, - and appropriate live ranges refering to the variable's initial - symbol index. - - For variables which are defined in the source but optimized away, - a symbol should be emitted with the live range l(0,0). - - Live ranges for aliases of a particular variable should always - be disjoint. Overlapping ranges for aliases of the same variable - will be treated as an error by the debugger, and the overlapping - range will be ignored. - - If no live range information is given, the live range will be assumed to - span the symbol's entire lexical scope. - - -New stabs string identifiers: ------------------------------ - - "id" in "#id" in the following section refers to a numeric value. - - New stab syntax for live range: l(,) - - - "#id" where #id identifies the text symbol (range symbol) to - use as the start of live range (range_start). The value for - the referenced text symbol is the starting address of the - live range. - - - "#id" where #id identifies the text symbol (range symbol) to - use as the end of live range (range_end). The value for - the referenced text symbol is ONE BYTE PAST the ending - address of the live range. - - - New stab syntax for identifying symbols. - - - "#id=" - - Uses: - :... - When used in front of a symbol name, "#id=" defines a - unique reference number for this symbol. The reference - number can be used later when defining aliases for this - symbol. - - When used as the entire stab string, "#id=" identifies this - nameless symbol as being the symbol for which "#id" refers to. - - - - "#id" where "#id" refers to the symbol for which the string - "#id=" identifies. - Uses: - :;;... - Defines an alias for the symbol identified by the reference - number ID. - l(,) - When used within a live range, "#id" refers to the text - symbol identified by "#id=" to use as the range symbol. - - - "l(,)" - specifies a live range for a - symbol. Multiple "l" specifiers can be combined to represent - mutiple live ranges, separated by semicolons. - - - - -Example: -======== - -Consider a program of the form: - - void foo(){ - int a = ...; - ... - while (b--) - c += a; - .. - d = a; - .. - } - -Assume that "a" lives in the stack at offset -8, except for inside the -loop where "a" resides in register "r5". - -The way to describe this is to create a stab for the variable "a" which -describes "a" as living in the stack and an alias for the variable "a" -which describes it as living in register "r5" in the loop. - -Let's assume that "#1" and "#2" are symbols which bound the area where -"a" lives in a register. - -The stabs to describe "a" and its alias would look like this: - - .stabs "#3=a:1",128,0,8,-8 - .stabs "#3:r1;l(#1,#2)",64,0,0,5 - - -This design implies that the debugger will keep a chain of aliases for -any given variable with aliases and that chain will be searched first -to find out if an alias is active. If no alias is active, then the -debugger will assume that the main variable is active. diff --git a/contrib/gdb-7/gdb/doc/a4rc.sed b/contrib/gdb-7/gdb/doc/a4rc.sed deleted file mode 100644 index 22922904ef..0000000000 --- a/contrib/gdb-7/gdb/doc/a4rc.sed +++ /dev/null @@ -1,11 +0,0 @@ -/--- Papersize params:/,/--- end papersize params/c\ -%------- Papersize params:\ -%% A4 paper (297x210mm)\ -%%\ -\\totalwidth=297mm % total width of paper\ -\\totalheight=210mm % total height of paper\ -\\hmargin=5mm % horizontal margin width\ -\\vmargin=10mm % vertical margin width\ -\\secskip=.6pc % space between refcard secs\ -\\lskip=1pt % extra skip between \\sec entries\ -%------- end papersize params diff --git a/contrib/gdb-7/gdb/doc/agentexpr.texi b/contrib/gdb-7/gdb/doc/agentexpr.texi deleted file mode 100644 index ab243cc77b..0000000000 --- a/contrib/gdb-7/gdb/doc/agentexpr.texi +++ /dev/null @@ -1,767 +0,0 @@ -@c \input texinfo -@c %**start of header -@c @setfilename agentexpr.info -@c @settitle GDB Agent Expressions -@c @setchapternewpage off -@c %**end of header - -@c This file is part of the GDB manual. -@c -@c Copyright (C) 2003-2013 Free Software Foundation, Inc. -@c -@c See the file gdb.texinfo for copying conditions. - -@node Agent Expressions -@appendix The GDB Agent Expression Mechanism - -In some applications, it is not feasible for the debugger to interrupt -the program's execution long enough for the developer to learn anything -helpful about its behavior. If the program's correctness depends on its -real-time behavior, delays introduced by a debugger might cause the -program to fail, even when the code itself is correct. It is useful to -be able to observe the program's behavior without interrupting it. - -Using GDB's @code{trace} and @code{collect} commands, the user can -specify locations in the program, and arbitrary expressions to evaluate -when those locations are reached. Later, using the @code{tfind} -command, she can examine the values those expressions had when the -program hit the trace points. The expressions may also denote objects -in memory --- structures or arrays, for example --- whose values GDB -should record; while visiting a particular tracepoint, the user may -inspect those objects as if they were in memory at that moment. -However, because GDB records these values without interacting with the -user, it can do so quickly and unobtrusively, hopefully not disturbing -the program's behavior. - -When GDB is debugging a remote target, the GDB @dfn{agent} code running -on the target computes the values of the expressions itself. To avoid -having a full symbolic expression evaluator on the agent, GDB translates -expressions in the source language into a simpler bytecode language, and -then sends the bytecode to the agent; the agent then executes the -bytecode, and records the values for GDB to retrieve later. - -The bytecode language is simple; there are forty-odd opcodes, the bulk -of which are the usual vocabulary of C operands (addition, subtraction, -shifts, and so on) and various sizes of literals and memory reference -operations. The bytecode interpreter operates strictly on machine-level -values --- various sizes of integers and floating point numbers --- and -requires no information about types or symbols; thus, the interpreter's -internal data structures are simple, and each bytecode requires only a -few native machine instructions to implement it. The interpreter is -small, and strict limits on the memory and time required to evaluate an -expression are easy to determine, making it suitable for use by the -debugging agent in real-time applications. - -@menu -* General Bytecode Design:: Overview of the interpreter. -* Bytecode Descriptions:: What each one does. -* Using Agent Expressions:: How agent expressions fit into the big picture. -* Varying Target Capabilities:: How to discover what the target can do. -* Rationale:: Why we did it this way. -@end menu - - -@c @node Rationale -@c @section Rationale - - -@node General Bytecode Design -@section General Bytecode Design - -The agent represents bytecode expressions as an array of bytes. Each -instruction is one byte long (thus the term @dfn{bytecode}). Some -instructions are followed by operand bytes; for example, the @code{goto} -instruction is followed by a destination for the jump. - -The bytecode interpreter is a stack-based machine; most instructions pop -their operands off the stack, perform some operation, and push the -result back on the stack for the next instruction to consume. Each -element of the stack may contain either a integer or a floating point -value; these values are as many bits wide as the largest integer that -can be directly manipulated in the source language. Stack elements -carry no record of their type; bytecode could push a value as an -integer, then pop it as a floating point value. However, GDB will not -generate code which does this. In C, one might define the type of a -stack element as follows: -@example -union agent_val @{ - LONGEST l; - DOUBLEST d; -@}; -@end example -@noindent -where @code{LONGEST} and @code{DOUBLEST} are @code{typedef} names for -the largest integer and floating point types on the machine. - -By the time the bytecode interpreter reaches the end of the expression, -the value of the expression should be the only value left on the stack. -For tracing applications, @code{trace} bytecodes in the expression will -have recorded the necessary data, and the value on the stack may be -discarded. For other applications, like conditional breakpoints, the -value may be useful. - -Separate from the stack, the interpreter has two registers: -@table @code -@item pc -The address of the next bytecode to execute. - -@item start -The address of the start of the bytecode expression, necessary for -interpreting the @code{goto} and @code{if_goto} instructions. - -@end table -@noindent -Neither of these registers is directly visible to the bytecode language -itself, but they are useful for defining the meanings of the bytecode -operations. - -There are no instructions to perform side effects on the running -program, or call the program's functions; we assume that these -expressions are only used for unobtrusive debugging, not for patching -the running code. - -Most bytecode instructions do not distinguish between the various sizes -of values, and operate on full-width values; the upper bits of the -values are simply ignored, since they do not usually make a difference -to the value computed. The exceptions to this rule are: -@table @asis - -@item memory reference instructions (@code{ref}@var{n}) -There are distinct instructions to fetch different word sizes from -memory. Once on the stack, however, the values are treated as full-size -integers. They may need to be sign-extended; the @code{ext} instruction -exists for this purpose. - -@item the sign-extension instruction (@code{ext} @var{n}) -These clearly need to know which portion of their operand is to be -extended to occupy the full length of the word. - -@end table - -If the interpreter is unable to evaluate an expression completely for -some reason (a memory location is inaccessible, or a divisor is zero, -for example), we say that interpretation ``terminates with an error''. -This means that the problem is reported back to the interpreter's caller -in some helpful way. In general, code using agent expressions should -assume that they may attempt to divide by zero, fetch arbitrary memory -locations, and misbehave in other ways. - -Even complicated C expressions compile to a few bytecode instructions; -for example, the expression @code{x + y * z} would typically produce -code like the following, assuming that @code{x} and @code{y} live in -registers, and @code{z} is a global variable holding a 32-bit -@code{int}: -@example -reg 1 -reg 2 -const32 @i{address of z} -ref32 -ext 32 -mul -add -end -@end example - -In detail, these mean: -@table @code - -@item reg 1 -Push the value of register 1 (presumably holding @code{x}) onto the -stack. - -@item reg 2 -Push the value of register 2 (holding @code{y}). - -@item const32 @i{address of z} -Push the address of @code{z} onto the stack. - -@item ref32 -Fetch a 32-bit word from the address at the top of the stack; replace -the address on the stack with the value. Thus, we replace the address -of @code{z} with @code{z}'s value. - -@item ext 32 -Sign-extend the value on the top of the stack from 32 bits to full -length. This is necessary because @code{z} is a signed integer. - -@item mul -Pop the top two numbers on the stack, multiply them, and push their -product. Now the top of the stack contains the value of the expression -@code{y * z}. - -@item add -Pop the top two numbers, add them, and push the sum. Now the top of the -stack contains the value of @code{x + y * z}. - -@item end -Stop executing; the value left on the stack top is the value to be -recorded. - -@end table - - -@node Bytecode Descriptions -@section Bytecode Descriptions - -Each bytecode description has the following form: - -@table @asis - -@item @code{add} (0x02): @var{a} @var{b} @result{} @var{a+b} - -Pop the top two stack items, @var{a} and @var{b}, as integers; push -their sum, as an integer. - -@end table - -In this example, @code{add} is the name of the bytecode, and -@code{(0x02)} is the one-byte value used to encode the bytecode, in -hexadecimal. The phrase ``@var{a} @var{b} @result{} @var{a+b}'' shows -the stack before and after the bytecode executes. Beforehand, the stack -must contain at least two values, @var{a} and @var{b}; since the top of -the stack is to the right, @var{b} is on the top of the stack, and -@var{a} is underneath it. After execution, the bytecode will have -popped @var{a} and @var{b} from the stack, and replaced them with a -single value, @var{a+b}. There may be other values on the stack below -those shown, but the bytecode affects only those shown. - -Here is another example: - -@table @asis - -@item @code{const8} (0x22) @var{n}: @result{} @var{n} -Push the 8-bit integer constant @var{n} on the stack, without sign -extension. - -@end table - -In this example, the bytecode @code{const8} takes an operand @var{n} -directly from the bytecode stream; the operand follows the @code{const8} -bytecode itself. We write any such operands immediately after the name -of the bytecode, before the colon, and describe the exact encoding of -the operand in the bytecode stream in the body of the bytecode -description. - -For the @code{const8} bytecode, there are no stack items given before -the @result{}; this simply means that the bytecode consumes no values -from the stack. If a bytecode consumes no values, or produces no -values, the list on either side of the @result{} may be empty. - -If a value is written as @var{a}, @var{b}, or @var{n}, then the bytecode -treats it as an integer. If a value is written is @var{addr}, then the -bytecode treats it as an address. - -We do not fully describe the floating point operations here; although -this design can be extended in a clean way to handle floating point -values, they are not of immediate interest to the customer, so we avoid -describing them, to save time. - - -@table @asis - -@item @code{float} (0x01): @result{} - -Prefix for floating-point bytecodes. Not implemented yet. - -@item @code{add} (0x02): @var{a} @var{b} @result{} @var{a+b} -Pop two integers from the stack, and push their sum, as an integer. - -@item @code{sub} (0x03): @var{a} @var{b} @result{} @var{a-b} -Pop two integers from the stack, subtract the top value from the -next-to-top value, and push the difference. - -@item @code{mul} (0x04): @var{a} @var{b} @result{} @var{a*b} -Pop two integers from the stack, multiply them, and push the product on -the stack. Note that, when one multiplies two @var{n}-bit numbers -yielding another @var{n}-bit number, it is irrelevant whether the -numbers are signed or not; the results are the same. - -@item @code{div_signed} (0x05): @var{a} @var{b} @result{} @var{a/b} -Pop two signed integers from the stack; divide the next-to-top value by -the top value, and push the quotient. If the divisor is zero, terminate -with an error. - -@item @code{div_unsigned} (0x06): @var{a} @var{b} @result{} @var{a/b} -Pop two unsigned integers from the stack; divide the next-to-top value -by the top value, and push the quotient. If the divisor is zero, -terminate with an error. - -@item @code{rem_signed} (0x07): @var{a} @var{b} @result{} @var{a modulo b} -Pop two signed integers from the stack; divide the next-to-top value by -the top value, and push the remainder. If the divisor is zero, -terminate with an error. - -@item @code{rem_unsigned} (0x08): @var{a} @var{b} @result{} @var{a modulo b} -Pop two unsigned integers from the stack; divide the next-to-top value -by the top value, and push the remainder. If the divisor is zero, -terminate with an error. - -@item @code{lsh} (0x09): @var{a} @var{b} @result{} @var{a<>b} -Pop two integers from the stack; let @var{a} be the next-to-top value, -and @var{b} be the top value. Shift @var{a} right by @var{b} bits, -inserting copies of the top bit at the high end, and push the result. - -@item @code{rsh_unsigned} (0x0b): @var{a} @var{b} @result{} @var{a>>b} -Pop two integers from the stack; let @var{a} be the next-to-top value, -and @var{b} be the top value. Shift @var{a} right by @var{b} bits, -inserting zero bits at the high end, and push the result. - -@item @code{log_not} (0x0e): @var{a} @result{} @var{!a} -Pop an integer from the stack; if it is zero, push the value one; -otherwise, push the value zero. - -@item @code{bit_and} (0x0f): @var{a} @var{b} @result{} @var{a&b} -Pop two integers from the stack, and push their bitwise @code{and}. - -@item @code{bit_or} (0x10): @var{a} @var{b} @result{} @var{a|b} -Pop two integers from the stack, and push their bitwise @code{or}. - -@item @code{bit_xor} (0x11): @var{a} @var{b} @result{} @var{a^b} -Pop two integers from the stack, and push their bitwise -exclusive-@code{or}. - -@item @code{bit_not} (0x12): @var{a} @result{} @var{~a} -Pop an integer from the stack, and push its bitwise complement. - -@item @code{equal} (0x13): @var{a} @var{b} @result{} @var{a=b} -Pop two integers from the stack; if they are equal, push the value one; -otherwise, push the value zero. - -@item @code{less_signed} (0x14): @var{a} @var{b} @result{} @var{a @var{a} @var{a} -Push another copy of the stack's top element. - -@item @code{swap} (0x2b): @var{a} @var{b} => @var{b} @var{a} -Exchange the top two items on the stack. - -@item @code{pop} (0x29): @var{a} => -Discard the top value on the stack. - -@item @code{pick} (0x32) @var{n}: @var{a} @dots{} @var{b} => @var{a} @dots{} @var{b} @var{a} -Duplicate an item from the stack and push it on the top of the stack. -@var{n}, a single byte, indicates the stack item to copy. If @var{n} -is zero, this is the same as @code{dup}; if @var{n} is one, it copies -the item under the top item, etc. If @var{n} exceeds the number of -items on the stack, terminate with an error. - -@item @code{rot} (0x33): @var{a} @var{b} @var{c} => @var{c} @var{b} @var{a} -Rotate the top three items on the stack. - -@item @code{if_goto} (0x20) @var{offset}: @var{a} @result{} -Pop an integer off the stack; if it is non-zero, branch to the given -offset in the bytecode string. Otherwise, continue to the next -instruction in the bytecode stream. In other words, if @var{a} is -non-zero, set the @code{pc} register to @code{start} + @var{offset}. -Thus, an offset of zero denotes the beginning of the expression. - -The @var{offset} is stored as a sixteen-bit unsigned value, stored -immediately following the @code{if_goto} bytecode. It is always stored -most significant byte first, regardless of the target's normal -endianness. The offset is not guaranteed to fall at any particular -alignment within the bytecode stream; thus, on machines where fetching a -16-bit on an unaligned address raises an exception, you should fetch the -offset one byte at a time. - -@item @code{goto} (0x21) @var{offset}: @result{} -Branch unconditionally to @var{offset}; in other words, set the -@code{pc} register to @code{start} + @var{offset}. - -The offset is stored in the same way as for the @code{if_goto} bytecode. - -@item @code{const8} (0x22) @var{n}: @result{} @var{n} -@itemx @code{const16} (0x23) @var{n}: @result{} @var{n} -@itemx @code{const32} (0x24) @var{n}: @result{} @var{n} -@itemx @code{const64} (0x25) @var{n}: @result{} @var{n} -Push the integer constant @var{n} on the stack, without sign extension. -To produce a small negative value, push a small twos-complement value, -and then sign-extend it using the @code{ext} bytecode. - -The constant @var{n} is stored in the appropriate number of bytes -following the @code{const}@var{b} bytecode. The constant @var{n} is -always stored most significant byte first, regardless of the target's -normal endianness. The constant is not guaranteed to fall at any -particular alignment within the bytecode stream; thus, on machines where -fetching a 16-bit on an unaligned address raises an exception, you -should fetch @var{n} one byte at a time. - -@item @code{reg} (0x26) @var{n}: @result{} @var{a} -Push the value of register number @var{n}, without sign extension. The -registers are numbered following GDB's conventions. - -The register number @var{n} is encoded as a 16-bit unsigned integer -immediately following the @code{reg} bytecode. It is always stored most -significant byte first, regardless of the target's normal endianness. -The register number is not guaranteed to fall at any particular -alignment within the bytecode stream; thus, on machines where fetching a -16-bit on an unaligned address raises an exception, you should fetch the -register number one byte at a time. - -@item @code{getv} (0x2c) @var{n}: @result{} @var{v} -Push the value of trace state variable number @var{n}, without sign -extension. - -The variable number @var{n} is encoded as a 16-bit unsigned integer -immediately following the @code{getv} bytecode. It is always stored most -significant byte first, regardless of the target's normal endianness. -The variable number is not guaranteed to fall at any particular -alignment within the bytecode stream; thus, on machines where fetching a -16-bit on an unaligned address raises an exception, you should fetch the -register number one byte at a time. - -@item @code{setv} (0x2d) @var{n}: @result{} @var{v} -Set trace state variable number @var{n} to the value found on the top -of the stack. The stack is unchanged, so that the value is readily -available if the assignment is part of a larger expression. The -handling of @var{n} is as described for @code{getv}. - -@item @code{trace} (0x0c): @var{addr} @var{size} @result{} -Record the contents of the @var{size} bytes at @var{addr} in a trace -buffer, for later retrieval by GDB. - -@item @code{trace_quick} (0x0d) @var{size}: @var{addr} @result{} @var{addr} -Record the contents of the @var{size} bytes at @var{addr} in a trace -buffer, for later retrieval by GDB. @var{size} is a single byte -unsigned integer following the @code{trace} opcode. - -This bytecode is equivalent to the sequence @code{dup const8 @var{size} -trace}, but we provide it anyway to save space in bytecode strings. - -@item @code{trace16} (0x30) @var{size}: @var{addr} @result{} @var{addr} -Identical to trace_quick, except that @var{size} is a 16-bit big-endian -unsigned integer, not a single byte. This should probably have been -named @code{trace_quick16}, for consistency. - -@item @code{tracev} (0x2e) @var{n}: @result{} @var{a} -Record the value of trace state variable number @var{n} in the trace -buffer. The handling of @var{n} is as described for @code{getv}. - -@item @code{tracenz} (0x2f) @var{addr} @var{size} @result{} -Record the bytes at @var{addr} in a trace buffer, for later retrieval -by GDB. Stop at either the first zero byte, or when @var{size} bytes -have been recorded, whichever occurs first. - -@item @code{printf} (0x34) @var{numargs} @var{string} @result{} -Do a formatted print, in the style of the C function @code{printf}). -The value of @var{numargs} is the number of arguments to expect on the -stack, while @var{string} is the format string, prefixed with a -two-byte length. The last byte of the string must be zero, and is -included in the length. The format string includes escaped sequences -just as it appears in C source, so for instance the format string -@code{"\t%d\n"} is six characters long, and the output will consist of -a tab character, a decimal number, and a newline. At the top of the -stack, above the values to be printed, this bytecode will pop a -``function'' and ``channel''. If the function is nonzero, then the -target may treat it as a function and call it, passing the channel as -a first argument, as with the C function @code{fprintf}. If the -function is zero, then the target may simply call a standard formatted -print function of its choice. In all, this bytecode pops 2 + -@var{numargs} stack elements, and pushes nothing. - -@item @code{end} (0x27): @result{} -Stop executing bytecode; the result should be the top element of the -stack. If the purpose of the expression was to compute an lvalue or a -range of memory, then the next-to-top of the stack is the lvalue's -address, and the top of the stack is the lvalue's size, in bytes. - -@end table - - -@node Using Agent Expressions -@section Using Agent Expressions - -Agent expressions can be used in several different ways by @value{GDBN}, -and the debugger can generate different bytecode sequences as appropriate. - -One possibility is to do expression evaluation on the target rather -than the host, such as for the conditional of a conditional -tracepoint. In such a case, @value{GDBN} compiles the source -expression into a bytecode sequence that simply gets values from -registers or memory, does arithmetic, and returns a result. - -Another way to use agent expressions is for tracepoint data -collection. @value{GDBN} generates a different bytecode sequence for -collection; in addition to bytecodes that do the calculation, -@value{GDBN} adds @code{trace} bytecodes to save the pieces of -memory that were used. - -@itemize @bullet - -@item -The user selects trace points in the program's code at which GDB should -collect data. - -@item -The user specifies expressions to evaluate at each trace point. These -expressions may denote objects in memory, in which case those objects' -contents are recorded as the program runs, or computed values, in which -case the values themselves are recorded. - -@item -GDB transmits the tracepoints and their associated expressions to the -GDB agent, running on the debugging target. - -@item -The agent arranges to be notified when a trace point is hit. - -@item -When execution on the target reaches a trace point, the agent evaluates -the expressions associated with that trace point, and records the -resulting values and memory ranges. - -@item -Later, when the user selects a given trace event and inspects the -objects and expression values recorded, GDB talks to the agent to -retrieve recorded data as necessary to meet the user's requests. If the -user asks to see an object whose contents have not been recorded, GDB -reports an error. - -@end itemize - - -@node Varying Target Capabilities -@section Varying Target Capabilities - -Some targets don't support floating-point, and some would rather not -have to deal with @code{long long} operations. Also, different targets -will have different stack sizes, and different bytecode buffer lengths. - -Thus, GDB needs a way to ask the target about itself. We haven't worked -out the details yet, but in general, GDB should be able to send the -target a packet asking it to describe itself. The reply should be a -packet whose length is explicit, so we can add new information to the -packet in future revisions of the agent, without confusing old versions -of GDB, and it should contain a version number. It should contain at -least the following information: - -@itemize @bullet - -@item -whether floating point is supported - -@item -whether @code{long long} is supported - -@item -maximum acceptable size of bytecode stack - -@item -maximum acceptable length of bytecode expressions - -@item -which registers are actually available for collection - -@item -whether the target supports disabled tracepoints - -@end itemize - -@node Rationale -@section Rationale - -Some of the design decisions apparent above are arguable. - -@table @b - -@item What about stack overflow/underflow? -GDB should be able to query the target to discover its stack size. -Given that information, GDB can determine at translation time whether a -given expression will overflow the stack. But this spec isn't about -what kinds of error-checking GDB ought to do. - -@item Why are you doing everything in LONGEST? - -Speed isn't important, but agent code size is; using LONGEST brings in a -bunch of support code to do things like division, etc. So this is a -serious concern. - -First, note that you don't need different bytecodes for different -operand sizes. You can generate code without @emph{knowing} how big the -stack elements actually are on the target. If the target only supports -32-bit ints, and you don't send any 64-bit bytecodes, everything just -works. The observation here is that the MIPS and the Alpha have only -fixed-size registers, and you can still get C's semantics even though -most instructions only operate on full-sized words. You just need to -make sure everything is properly sign-extended at the right times. So -there is no need for 32- and 64-bit variants of the bytecodes. Just -implement everything using the largest size you support. - -GDB should certainly check to see what sizes the target supports, so the -user can get an error earlier, rather than later. But this information -is not necessary for correctness. - - -@item Why don't you have @code{>} or @code{<=} operators? -I want to keep the interpreter small, and we don't need them. We can -combine the @code{less_} opcodes with @code{log_not}, and swap the order -of the operands, yielding all four asymmetrical comparison operators. -For example, @code{(x <= y)} is @code{! (x > y)}, which is @code{! (y < -x)}. - -@item Why do you have @code{log_not}? -@itemx Why do you have @code{ext}? -@itemx Why do you have @code{zero_ext}? -These are all easily synthesized from other instructions, but I expect -them to be used frequently, and they're simple, so I include them to -keep bytecode strings short. - -@code{log_not} is equivalent to @code{const8 0 equal}; it's used in half -the relational operators. - -@code{ext @var{n}} is equivalent to @code{const8 @var{s-n} lsh const8 -@var{s-n} rsh_signed}, where @var{s} is the size of the stack elements; -it follows @code{ref@var{m}} and @var{reg} bytecodes when the value -should be signed. See the next bulleted item. - -@code{zero_ext @var{n}} is equivalent to @code{const@var{m} @var{mask} -log_and}; it's used whenever we push the value of a register, because we -can't assume the upper bits of the register aren't garbage. - -@item Why not have sign-extending variants of the @code{ref} operators? -Because that would double the number of @code{ref} operators, and we -need the @code{ext} bytecode anyway for accessing bitfields. - -@item Why not have constant-address variants of the @code{ref} operators? -Because that would double the number of @code{ref} operators again, and -@code{const32 @var{address} ref32} is only one byte longer. - -@item Why do the @code{ref@var{n}} operators have to support unaligned fetches? -GDB will generate bytecode that fetches multi-byte values at unaligned -addresses whenever the executable's debugging information tells it to. -Furthermore, GDB does not know the value the pointer will have when GDB -generates the bytecode, so it cannot determine whether a particular -fetch will be aligned or not. - -In particular, structure bitfields may be several bytes long, but follow -no alignment rules; members of packed structures are not necessarily -aligned either. - -In general, there are many cases where unaligned references occur in -correct C code, either at the programmer's explicit request, or at the -compiler's discretion. Thus, it is simpler to make the GDB agent -bytecodes work correctly in all circumstances than to make GDB guess in -each case whether the compiler did the usual thing. - -@item Why are there no side-effecting operators? -Because our current client doesn't want them? That's a cheap answer. I -think the real answer is that I'm afraid of implementing function -calls. We should re-visit this issue after the present contract is -delivered. - -@item Why aren't the @code{goto} ops PC-relative? -The interpreter has the base address around anyway for PC bounds -checking, and it seemed simpler. - -@item Why is there only one offset size for the @code{goto} ops? -Offsets are currently sixteen bits. I'm not happy with this situation -either: - -Suppose we have multiple branch ops with different offset sizes. As I -generate code left-to-right, all my jumps are forward jumps (there are -no loops in expressions), so I never know the target when I emit the -jump opcode. Thus, I have to either always assume the largest offset -size, or do jump relaxation on the code after I generate it, which seems -like a big waste of time. - -I can imagine a reasonable expression being longer than 256 bytes. I -can't imagine one being longer than 64k. Thus, we need 16-bit offsets. -This kind of reasoning is so bogus, but relaxation is pathetic. - -The other approach would be to generate code right-to-left. Then I'd -always know my offset size. That might be fun. - -@item Where is the function call bytecode? - -When we add side-effects, we should add this. - -@item Why does the @code{reg} bytecode take a 16-bit register number? - -Intel's IA-64 architecture has 128 general-purpose registers, -and 128 floating-point registers, and I'm sure it has some random -control registers. - -@item Why do we need @code{trace} and @code{trace_quick}? -Because GDB needs to record all the memory contents and registers an -expression touches. If the user wants to evaluate an expression -@code{x->y->z}, the agent must record the values of @code{x} and -@code{x->y} as well as the value of @code{x->y->z}. - -@item Don't the @code{trace} bytecodes make the interpreter less general? -They do mean that the interpreter contains special-purpose code, but -that doesn't mean the interpreter can only be used for that purpose. If -an expression doesn't use the @code{trace} bytecodes, they don't get in -its way. - -@item Why doesn't @code{trace_quick} consume its arguments the way everything else does? -In general, you do want your operators to consume their arguments; it's -consistent, and generally reduces the amount of stack rearrangement -necessary. However, @code{trace_quick} is a kludge to save space; it -only exists so we needn't write @code{dup const8 @var{SIZE} trace} -before every memory reference. Therefore, it's okay for it not to -consume its arguments; it's meant for a specific context in which we -know exactly what it should do with the stack. If we're going to have a -kludge, it should be an effective kludge. - -@item Why does @code{trace16} exist? -That opcode was added by the customer that contracted Cygnus for the -data tracing work. I personally think it is unnecessary; objects that -large will be quite rare, so it is okay to use @code{dup const16 -@var{size} trace} in those cases. - -Whatever we decide to do with @code{trace16}, we should at least leave -opcode 0x30 reserved, to remain compatible with the customer who added -it. - -@end table diff --git a/contrib/gdb-7/gdb/doc/all-cfg.texi b/contrib/gdb-7/gdb/doc/all-cfg.texi deleted file mode 100644 index 75f3033102..0000000000 --- a/contrib/gdb-7/gdb/doc/all-cfg.texi +++ /dev/null @@ -1,45 +0,0 @@ -@c GDB MANUAL configuration file. -@c -@c Copyright (C) 1993-2013 Free Software Foundation, Inc. -@c -@c NOTE: While the GDB manual is configurable (by changing these -@c switches), its configuration is ***NOT*** automatically tied in to -@c source configuration---because the authors expect that, save in -@c unusual cases, the most inclusive form of the manual is appropriate -@c no matter how the program itself is configured. -@c -@c The only automatically-varying variable is the GDB version number, -@c which the Makefile rewrites based on the VERSION variable from -@c `../Makefile.in'. -@c -@c GDB version number is recorded in the variable GDBVN -@include GDBvn.texi -@c -@c ---------------------------------------------------------------------- -@c PLATFORM FLAGS: -@set GENERIC -@c -@c HP PA-RISC target ONLY: -@clear HPPA -@c -@c Refrain from discussing how to configure sw and format doc? -@clear PRECONFIGURED -@c -@c ---------------------------------------------------------------------- -@c STRINGS: -@c -@c Name of GDB program. Used also for (gdb) prompt string. -@set GDBP gdb -@c -@c Name of GDB product. Used in running text. -@set GDBN @sc{gdb} -@c -@c Name of host. Should not be used in generic configs, but generic -@c value may catch some flubs. -@set HOST machine specific -@c -@c Name of GCC product -@set NGCC @sc{gcc} -@c -@c Name of GCC program -@set GCC gcc diff --git a/contrib/gdb-7/gdb/doc/annotate.texinfo b/contrib/gdb-7/gdb/doc/annotate.texinfo deleted file mode 100644 index 05e1409ea6..0000000000 --- a/contrib/gdb-7/gdb/doc/annotate.texinfo +++ /dev/null @@ -1,852 +0,0 @@ -\input texinfo @c -*-texinfo-*- -@c %**start of header -@setfilename annotate.info - -@c This is a dir.info fragment to support semi-automated addition of -@c manuals to an info tree. -@dircategory Software development -@direntry -* Annotate: (annotate). The obsolete annotation interface. -@end direntry - -@c -@include gdb-cfg.texi -@c -@settitle @value{GDBN}'s Obsolete Annotations -@setchapternewpage off -@c %**end of header - -@set EDITION 1.0 -@set DATE July 2003 - -@c NOTE: cagney/2003-07-28: -@c Don't make this migration document an appendix of GDB's user guide. -@c By keeping this separate, the size of the user guide is contained. If -@c the user guide to get much bigger it would need to switch to a larger, -@c more expensive, form factor and would drive up the manuals publication -@c cost. Having a smaller cheaper manual helps the GNU Press with its sales. - -@copying -Copyright @copyright{} 1994-2013 Free Software Foundation, Inc. - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, with no Front-Cover Texts, and with no Back-Cover -Texts. A copy of the license is included in the section entitled ``GNU -Free Documentation License''. -@end copying - -@ifnottex -This file documents @value{GDBN}'s obsolete annotations. - -@insertcopying -@end ifnottex - -@titlepage -@title @value{GDBN}'s Obsolete Annotations -@subtitle Edition @value{EDITION} -@subtitle @value{DATE} -@author Free Software Foundation -@page -@vskip 0pt plus 1filll -@insertcopying -@end titlepage - -@ifnottex -@node Top -@top GDB Annotations - -This document describes the obsolete level two annotation interface -implemented in older @value{GDBN} versions. - -@ignore -This is Edition @value{EDITION}, @value{DATE}. -@end ignore -@end ifnottex - -@menu -* Annotations Overview:: What annotations are; the general syntax. -* Limitations:: Limitations of the annotation interface. -* Migrating to GDB/MI:: Migrating to GDB/MI -* Server Prefix:: Issuing a command without affecting user state. -* Value Annotations:: Values are marked as such. -* Frame Annotations:: Stack frames are annotated. -* Displays:: @value{GDBN} can be told to display something periodically. -* Prompting:: Annotations marking @value{GDBN}'s need for input. -* Errors:: Annotations for error messages. -* Breakpoint Info:: Information on breakpoints. -* Invalidation:: Some annotations describe things now invalid. -* Annotations for Running:: - Whether the program is running, how it stopped, etc. -* Source Annotations:: Annotations describing source code. -* Multi-threaded Apps:: An annotation that reports multi-threadedness. - -* GNU Free Documentation License:: -@end menu - -@contents - -@node Annotations Overview -@chapter What is an Annotation? -@cindex annotations - -To produce obsolete level two annotations, start @value{GDBN} with the -@code{--annotate=2} option. - -Annotations start with a newline character, two @samp{control-z} -characters, and the name of the annotation. If there is no additional -information associated with this annotation, the name of the annotation -is followed immediately by a newline. If there is additional -information, the name of the annotation is followed by a space, the -additional information, and a newline. The additional information -cannot contain newline characters. - -Any output not beginning with a newline and two @samp{control-z} -characters denotes literal output from @value{GDBN}. Currently there is -no need for @value{GDBN} to output a newline followed by two -@samp{control-z} characters, but if there was such a need, the -annotations could be extended with an @samp{escape} annotation which -means those three characters as output. - -A simple example of starting up @value{GDBN} with annotations is: - -@smallexample -$ gdb --annotate=2 -GNU GDB 5.0 -Copyright 2000 Free Software Foundation, Inc. -GDB is free software, covered by the GNU General Public License, -and you are welcome to change it and/or distribute copies of it -under certain conditions. -Type "show copying" to see the conditions. -There is absolutely no warranty for GDB. Type "show warranty" -for details. -This GDB was configured as "sparc-sun-sunos4.1.3" - -^Z^Zpre-prompt -(gdb) -^Z^Zprompt -quit - -^Z^Zpost-prompt -$ -@end smallexample - -Here @samp{quit} is input to @value{GDBN}; the rest is output from -@value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z} -denotes a @samp{control-z} character) are annotations; the rest is -output from @value{GDBN}. - -@node Limitations -@chapter Limitations of the Annotation Interface - -The level two annotations mechanism is known to have a number of -technical and architectural limitations. As a consequence, in 2001, -with the release of @value{GDBN} 5.1 and the addition of @sc{gdb/mi}, -the annotation interface was marked as deprecated. - -This chapter discusses the known problems. - -@section Dependant on @sc{cli} output - -The annotation interface works by interspersing markups with -@value{GDBN} normal command-line interpreter output. Unfortunately, this -makes the annotation client dependant on not just the annotations, but -also the @sc{cli} output. This is because the client is forced to -assume that specific @value{GDBN} commands provide specific information. -Any change to @value{GDBN}'s @sc{cli} output modifies or removes that -information and, consequently, likely breaks the client. - -Since the @sc{gdb/mi} output is independent of the @sc{cli}, it does not -have this problem. - -@section Scalability - -The annotation interface relies on value annotations (@pxref{Value -Annotations}) and the display mechanism as a way of obtaining up-to-date -value information. These mechanisms are not scalable. - -In a graphical environment, where many values can be displayed -simultaneously, a serious performance problem occurs when the client -tries to first extract from @value{GDBN}, and then re-display, all those -values. The client should instead only request and update the values -that changed. - -The @sc{gdb/mi} Variable Objects provide just that mechanism. - -@section Correctness - -The annotation interface assumes that a variable's value can only be -changed when the target is running. This assumption is not correct. A -single assignment to a single variable can result in the entire target, -and all displayed values, needing an update. - -The @sc{gdb/mi} Variable Objects include a mechanism for efficiently -reporting such changes. - -@section Reliability - -The @sc{gdb/mi} interface includes a dedicated test directory -(@file{gdb/gdb.mi}), and any addition or fix to @sc{gdb/mi} must include -testsuite changes. - -@section Maintainability - -The annotation mechanism was implemented by interspersing @sc{cli} print -statements with various annotations. As a consequence, any @sc{cli} -output change can alter the annotation output. - -Since the @sc{gdb/mi} output is independent of the @sc{cli}, and the -@sc{gdb/mi} is increasingly implemented independent of the @sc{cli} -code, its long term maintenance is much easier. - -@node Migrating to GDB/MI -@chapter Migrating to @sc{gdb/mi} - -By using the @samp{interp mi} command, it is possible for annotation -clients to invoke @sc{gdb/mi} commands, and hence access the -@sc{gdb/mi}. By doing this, existing annotation clients have a -migration path from this obsolete interface to @sc{gdb/mi}. - -@node Server Prefix -@chapter The Server Prefix -@cindex server prefix for annotations - -To issue a command to @value{GDBN} without affecting certain aspects of -the state which is seen by users, prefix it with @samp{server }. This -means that this command will not affect the command history, nor will it -affect @value{GDBN}'s notion of which command to repeat if @key{RET} is -pressed on a line by itself. - -The server prefix does not affect the recording of values into the value -history; to print a value without recording it into the value history, -use the @code{output} command instead of the @code{print} command. - -@node Value Annotations -@chapter Values - -@emph{Value Annotations have been removed. @sc{gdb/mi} instead provides -Variable Objects.} - -@cindex annotations for values -When a value is printed in various contexts, @value{GDBN} uses -annotations to delimit the value from the surrounding text. - -@findex value-history-begin -@findex value-history-value -@findex value-history-end -If a value is printed using @code{print} and added to the value history, -the annotation looks like - -@smallexample -^Z^Zvalue-history-begin @var{history-number} @var{value-flags} -@var{history-string} -^Z^Zvalue-history-value -@var{the-value} -^Z^Zvalue-history-end -@end smallexample - -@noindent -where @var{history-number} is the number it is getting in the value -history, @var{history-string} is a string, such as @samp{$5 = }, which -introduces the value to the user, @var{the-value} is the output -corresponding to the value itself, and @var{value-flags} is @samp{*} for -a value which can be dereferenced and @samp{-} for a value which cannot. - -@findex value-begin -@findex value-end -If the value is not added to the value history (it is an invalid float -or it is printed with the @code{output} command), the annotation is similar: - -@smallexample -^Z^Zvalue-begin @var{value-flags} -@var{the-value} -^Z^Zvalue-end -@end smallexample - -@findex arg-begin -@findex arg-name-end -@findex arg-value -@findex arg-end -When @value{GDBN} prints an argument to a function (for example, in the output -from the @code{backtrace} command), it annotates it as follows: - -@smallexample -^Z^Zarg-begin -@var{argument-name} -^Z^Zarg-name-end -@var{separator-string} -^Z^Zarg-value @var{value-flags} -@var{the-value} -^Z^Zarg-end -@end smallexample - -@noindent -where @var{argument-name} is the name of the argument, -@var{separator-string} is text which separates the name from the value -for the user's benefit (such as @samp{=}), and @var{value-flags} and -@var{the-value} have the same meanings as in a -@code{value-history-begin} annotation. - -@findex field-begin -@findex field-name-end -@findex field-value -@findex field-end -When printing a structure, @value{GDBN} annotates it as follows: - -@smallexample -^Z^Zfield-begin @var{value-flags} -@var{field-name} -^Z^Zfield-name-end -@var{separator-string} -^Z^Zfield-value -@var{the-value} -^Z^Zfield-end -@end smallexample - -@noindent -where @var{field-name} is the name of the field, @var{separator-string} -is text which separates the name from the value for the user's benefit -(such as @samp{=}), and @var{value-flags} and @var{the-value} have the -same meanings as in a @code{value-history-begin} annotation. - -When printing an array, @value{GDBN} annotates it as follows: - -@smallexample -^Z^Zarray-section-begin @var{array-index} @var{value-flags} -@end smallexample - -@noindent -where @var{array-index} is the index of the first element being -annotated and @var{value-flags} has the same meaning as in a -@code{value-history-begin} annotation. This is followed by any number -of elements, where is element can be either a single element: - -@findex elt -@smallexample -@samp{,} @var{whitespace} ; @r{omitted for the first element} -@var{the-value} -^Z^Zelt -@end smallexample - -or a repeated element - -@findex elt-rep -@findex elt-rep-end -@smallexample -@samp{,} @var{whitespace} ; @r{omitted for the first element} -@var{the-value} -^Z^Zelt-rep @var{number-of-repetitions} -@var{repetition-string} -^Z^Zelt-rep-end -@end smallexample - -In both cases, @var{the-value} is the output for the value of the -element and @var{whitespace} can contain spaces, tabs, and newlines. In -the repeated case, @var{number-of-repetitions} is the number of -consecutive array elements which contain that value, and -@var{repetition-string} is a string which is designed to convey to the -user that repetition is being depicted. - -@findex array-section-end -Once all the array elements have been output, the array annotation is -ended with - -@smallexample -^Z^Zarray-section-end -@end smallexample - -@node Frame Annotations -@chapter Frames - -@emph{Value Annotations have been removed. @sc{gdb/mi} instead provides -a number of frame commands.} - -@emph{Frame annotations are no longer available. The @sc{gdb/mi} -provides @samp{-stack-list-arguments}, @samp{-stack-list-locals}, and -@samp{-stack-list-frames} commands.} - -@cindex annotations for frames -Whenever @value{GDBN} prints a frame, it annotates it. For example, this applies -to frames printed when @value{GDBN} stops, output from commands such as -@code{backtrace} or @code{up}, etc. - -@findex frame-begin -The frame annotation begins with - -@smallexample -^Z^Zframe-begin @var{level} @var{address} -@var{level-string} -@end smallexample - -@noindent -where @var{level} is the number of the frame (0 is the innermost frame, -and other frames have positive numbers), @var{address} is the address of -the code executing in that frame, and @var{level-string} is a string -designed to convey the level to the user. @var{address} is in the form -@samp{0x} followed by one or more lowercase hex digits (note that this -does not depend on the language). The frame ends with - -@findex frame-end -@smallexample -^Z^Zframe-end -@end smallexample - -Between these annotations is the main body of the frame, which can -consist of - -@itemize @bullet -@item -@findex function-call -@smallexample -^Z^Zfunction-call -@var{function-call-string} -@end smallexample - -where @var{function-call-string} is text designed to convey to the user -that this frame is associated with a function call made by @value{GDBN} to a -function in the program being debugged. - -@item -@findex signal-handler-caller -@smallexample -^Z^Zsignal-handler-caller -@var{signal-handler-caller-string} -@end smallexample - -where @var{signal-handler-caller-string} is text designed to convey to -the user that this frame is associated with whatever mechanism is used -by this operating system to call a signal handler (it is the frame which -calls the signal handler, not the frame for the signal handler itself). - -@item -A normal frame. - -@findex frame-address -@findex frame-address-end -This can optionally (depending on whether this is thought of as -interesting information for the user to see) begin with - -@smallexample -^Z^Zframe-address -@var{address} -^Z^Zframe-address-end -@var{separator-string} -@end smallexample - -where @var{address} is the address executing in the frame (the same -address as in the @code{frame-begin} annotation, but printed in a form -which is intended for user consumption---in particular, the syntax varies -depending on the language), and @var{separator-string} is a string -intended to separate this address from what follows for the user's -benefit. - -@findex frame-function-name -@findex frame-args -Then comes - -@smallexample -^Z^Zframe-function-name -@var{function-name} -^Z^Zframe-args -@var{arguments} -@end smallexample - -where @var{function-name} is the name of the function executing in the -frame, or @samp{??} if not known, and @var{arguments} are the arguments -to the frame, with parentheses around them (each argument is annotated -individually as well, @pxref{Value Annotations}). - -@findex frame-source-begin -@findex frame-source-file -@findex frame-source-file-end -@findex frame-source-line -@findex frame-source-end -If source information is available, a reference to it is then printed: - -@smallexample -^Z^Zframe-source-begin -@var{source-intro-string} -^Z^Zframe-source-file -@var{filename} -^Z^Zframe-source-file-end -: -^Z^Zframe-source-line -@var{line-number} -^Z^Zframe-source-end -@end smallexample - -where @var{source-intro-string} separates for the user's benefit the -reference from the text which precedes it, @var{filename} is the name of -the source file, and @var{line-number} is the line number within that -file (the first line is line 1). - -@findex frame-where -If @value{GDBN} prints some information about where the frame is from (which -library, which load segment, etc.; currently only done on the RS/6000), -it is annotated with - -@smallexample -^Z^Zframe-where -@var{information} -@end smallexample - -Then, if source is to actually be displayed for this frame (for example, -this is not true for output from the @code{backtrace} command), then a -@code{source} annotation (@pxref{Source Annotations}) is displayed. Unlike -most annotations, this is output instead of the normal text which would be -output, not in addition. -@end itemize - -@node Displays -@chapter Displays - -@emph{Display Annotations have been removed. @sc{gdb/mi} instead -provides Variable Objects.} - -@findex display-begin -@findex display-number-end -@findex display-format -@findex display-expression -@findex display-expression-end -@findex display-value -@findex display-end -@cindex annotations for display -When @value{GDBN} is told to display something using the @code{display} command, -the results of the display are annotated: - -@smallexample -^Z^Zdisplay-begin -@var{number} -^Z^Zdisplay-number-end -@var{number-separator} -^Z^Zdisplay-format -@var{format} -^Z^Zdisplay-expression -@var{expression} -^Z^Zdisplay-expression-end -@var{expression-separator} -^Z^Zdisplay-value -@var{value} -^Z^Zdisplay-end -@end smallexample - -@noindent -where @var{number} is the number of the display, @var{number-separator} -is intended to separate the number from what follows for the user, -@var{format} includes information such as the size, format, or other -information about how the value is being displayed, @var{expression} is -the expression being displayed, @var{expression-separator} is intended -to separate the expression from the text that follows for the user, -and @var{value} is the actual value being displayed. - -@node Prompting -@chapter Annotation for @value{GDBN} Input - -@cindex annotations for prompts -When @value{GDBN} prompts for input, it annotates this fact so it is possible -to know when to send output, when the output from a given command is -over, etc. - -Different kinds of input each have a different @dfn{input type}. Each -input type has three annotations: a @code{pre-} annotation, which -denotes the beginning of any prompt which is being output, a plain -annotation, which denotes the end of the prompt, and then a @code{post-} -annotation which denotes the end of any echo which may (or may not) be -associated with the input. For example, the @code{prompt} input type -features the following annotations: - -@smallexample -^Z^Zpre-prompt -^Z^Zprompt -^Z^Zpost-prompt -@end smallexample - -The input types are - -@table @code -@findex pre-prompt -@findex prompt -@findex post-prompt -@item prompt -When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt). - -@findex pre-commands -@findex commands -@findex post-commands -@item commands -When @value{GDBN} prompts for a set of commands, like in the @code{commands} -command. The annotations are repeated for each command which is input. - -@findex pre-overload-choice -@findex overload-choice -@findex post-overload-choice -@item overload-choice -When @value{GDBN} wants the user to select between various overloaded functions. - -@findex pre-query -@findex query -@findex post-query -@item query -When @value{GDBN} wants the user to confirm a potentially dangerous operation. - -@findex pre-prompt-for-continue -@findex prompt-for-continue -@findex post-prompt-for-continue -@item prompt-for-continue -When @value{GDBN} is asking the user to press return to continue. Note: Don't -expect this to work well; instead use @code{set height 0} to disable -prompting. This is because the counting of lines is buggy in the -presence of annotations. -@end table - -@node Errors -@chapter Errors -@cindex annotations for errors, warnings and interrupts - -@findex quit -@smallexample -^Z^Zquit -@end smallexample - -This annotation occurs right before @value{GDBN} responds to an interrupt. - -@findex error -@smallexample -^Z^Zerror -@end smallexample - -This annotation occurs right before @value{GDBN} responds to an error. - -Quit and error annotations indicate that any annotations which @value{GDBN} was -in the middle of may end abruptly. For example, if a -@code{value-history-begin} annotation is followed by a @code{error}, one -cannot expect to receive the matching @code{value-history-end}. One -cannot expect not to receive it either, however; an error annotation -does not necessarily mean that @value{GDBN} is immediately returning all the way -to the top level. - -@findex error-begin -A quit or error annotation may be preceded by - -@smallexample -^Z^Zerror-begin -@end smallexample - -Any output between that and the quit or error annotation is the error -message. - -Warning messages are not yet annotated. -@c If we want to change that, need to fix warning(), type_error(), -@c range_error(), and possibly other places. - -@node Breakpoint Info -@chapter Information on Breakpoints - -@emph{Breakpoint Annotations have been removed. @sc{gdb/mi} instead -provides breakpoint commands.} - -@cindex annotations for breakpoints -The output from the @code{info breakpoints} command is annotated as follows: - -@findex breakpoints-headers -@findex breakpoints-table -@smallexample -^Z^Zbreakpoints-headers -@var{header-entry} -^Z^Zbreakpoints-table -@end smallexample - -@noindent -where @var{header-entry} has the same syntax as an entry (see below) but -instead of containing data, it contains strings which are intended to -convey the meaning of each field to the user. This is followed by any -number of entries. If a field does not apply for this entry, it is -omitted. Fields may contain trailing whitespace. Each entry consists -of: - -@findex record -@findex field -@smallexample -^Z^Zrecord -^Z^Zfield 0 -@var{number} -^Z^Zfield 1 -@var{type} -^Z^Zfield 2 -@var{disposition} -^Z^Zfield 3 -@var{enable} -^Z^Zfield 4 -@var{address} -^Z^Zfield 5 -@var{what} -^Z^Zfield 6 -@var{frame} -^Z^Zfield 7 -@var{condition} -^Z^Zfield 8 -@var{ignore-count} -^Z^Zfield 9 -@var{commands} -@end smallexample - -Note that @var{address} is intended for user consumption---the syntax -varies depending on the language. - -The output ends with - -@findex breakpoints-table-end -@smallexample -^Z^Zbreakpoints-table-end -@end smallexample - -@node Invalidation -@chapter Invalidation Notices - -@cindex annotations for invalidation messages -The following annotations say that certain pieces of state may have -changed. - -@table @code -@findex frames-invalid -@item ^Z^Zframes-invalid - -The frames (for example, output from the @code{backtrace} command) may -have changed. - -@findex breakpoints-invalid -@item ^Z^Zbreakpoints-invalid - -The breakpoints may have changed. For example, the user just added or -deleted a breakpoint. -@end table - -@node Annotations for Running -@chapter Running the Program -@cindex annotations for running programs - -@findex starting -@findex stopping -When the program starts executing due to a @value{GDBN} command such as -@code{step} or @code{continue}, - -@smallexample -^Z^Zstarting -@end smallexample - -is output. When the program stops, - -@smallexample -^Z^Zstopped -@end smallexample - -is output. Before the @code{stopped} annotation, a variety of -annotations describe how the program stopped. - -@table @code -@findex exited -@item ^Z^Zexited @var{exit-status} -The program exited, and @var{exit-status} is the exit status (zero for -successful exit, otherwise nonzero). - -@findex signalled -@findex signal-name -@findex signal-name-end -@findex signal-string -@findex signal-string-end -@item ^Z^Zsignalled -The program exited with a signal. After the @code{^Z^Zsignalled}, the -annotation continues: - -@smallexample -@var{intro-text} -^Z^Zsignal-name -@var{name} -^Z^Zsignal-name-end -@var{middle-text} -^Z^Zsignal-string -@var{string} -^Z^Zsignal-string-end -@var{end-text} -@end smallexample - -@noindent -where @var{name} is the name of the signal, such as @code{SIGILL} or -@code{SIGSEGV}, and @var{string} is the explanation of the signal, such -as @code{Illegal Instruction} or @code{Segmentation fault}. -@var{intro-text}, @var{middle-text}, and @var{end-text} are for the -user's benefit and have no particular format. - -@findex signal -@item ^Z^Zsignal -The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is -just saying that the program received the signal, not that it was -terminated with it. - -@findex breakpoint -@item ^Z^Zbreakpoint @var{number} -The program hit breakpoint number @var{number}. - -@findex watchpoint -@item ^Z^Zwatchpoint @var{number} -The program hit watchpoint number @var{number}. -@end table - -@node Source Annotations -@chapter Displaying Source -@cindex annotations for source display - -@findex source -The following annotation is used instead of displaying source code: - -@smallexample -^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr} -@end smallexample - -where @var{filename} is an absolute file name indicating which source -file, @var{line} is the line number within that file (where 1 is the -first line in the file), @var{character} is the character position -within the file (where 0 is the first character in the file) (for most -debug formats this will necessarily point to the beginning of a line), -@var{middle} is @samp{middle} if @var{addr} is in the middle of the -line, or @samp{beg} if @var{addr} is at the beginning of the line, and -@var{addr} is the address in the target program associated with the -source which is being displayed. @var{addr} is in the form @samp{0x} -followed by one or more lowercase hex digits (note that this does not -depend on the language). - -@node Multi-threaded Apps -@chapter Multi-threaded Applications -@cindex annotations for multi-threaded apps - -The following annotations report thread related changes of state. - -@table @code -@findex new-thread@r{, annotation} -@item ^Z^Znew-thread - -This annotation is issued once for each thread that is created apart from -the main thread, which is not reported. - -@findex thread-changed@r{, annotation} -@item ^Z^Zthread-changed - -The selected thread has changed. This may occur at the request of the -user with the @code{thread} command, or as a result of execution, -e.g., another thread hits a breakpoint. - -@end table - -@node GNU Free Documentation License -@appendix GNU Free Documentation License -@include fdl.texi - -@ignore -@node Index -@unnumbered Index - -@printindex fn -@end ignore - -@bye diff --git a/contrib/gdb-7/gdb/doc/fdl.texi b/contrib/gdb-7/gdb/doc/fdl.texi deleted file mode 100644 index 7c26c34b07..0000000000 --- a/contrib/gdb-7/gdb/doc/fdl.texi +++ /dev/null @@ -1,505 +0,0 @@ -@c The GNU Free Documentation License. -@center Version 1.3, 3 November 2008 - -@c This file is intended to be included within another document, -@c hence no sectioning command or @node. - -@display -Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. -@uref{http://fsf.org/} - -Everyone is permitted to copy and distribute verbatim copies -of this license document, but changing it is not allowed. -@end display - -@enumerate 0 -@item -PREAMBLE - -The purpose of this License is to make a manual, textbook, or other -functional and useful document @dfn{free} in the sense of freedom: to -assure everyone the effective freedom to copy and redistribute it, -with or without modifying it, either commercially or noncommercially. -Secondarily, this License preserves for the author and publisher a way -to get credit for their work, while not being considered responsible -for modifications made by others. - -This License is a kind of ``copyleft'', which means that derivative -works of the document must themselves be free in the same sense. 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However, you can override filename with makeinfo -o. -@setfilename gdb.info -@c -@include gdb-cfg.texi -@c -@settitle Debugging with @value{GDBN} -@setchapternewpage odd -@c %**end of header - -@iftex -@c @smallbook -@c @cropmarks -@end iftex - -@finalout -@c To avoid file-name clashes between index.html and Index.html, when -@c the manual is produced on a Posix host and then moved to a -@c case-insensitive filesystem (e.g., MS-Windows), we separate the -@c indices into two: Concept Index and all the rest. -@syncodeindex ky fn -@syncodeindex tp fn - -@c readline appendices use @vindex, @findex and @ftable, -@c annotate.texi and gdbmi use @findex. -@syncodeindex vr fn - -@c !!set GDB manual's edition---not the same as GDB version! -@c This is updated by GNU Press. -@set EDITION Tenth - -@c !!set GDB edit command default editor -@set EDITOR /bin/ex - -@c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER. - -@c This is a dir.info fragment to support semi-automated addition of -@c manuals to an info tree. -@dircategory Software development -@direntry -* Gdb: (gdb). The GNU debugger. -@end direntry - -@copying -Copyright @copyright{} 1988-2013 Free Software Foundation, Inc. - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with the -Invariant Sections being ``Free Software'' and ``Free Software Needs -Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,'' -and with the Back-Cover Texts as in (a) below. - -(a) The FSF's Back-Cover Text is: ``You are free to copy and modify -this GNU Manual. Buying copies from GNU Press supports the FSF in -developing GNU and promoting software freedom.'' -@end copying - -@ifnottex -This file documents the @sc{gnu} debugger @value{GDBN}. - -This is the @value{EDITION} Edition, of @cite{Debugging with -@value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN} -@ifset VERSION_PACKAGE -@value{VERSION_PACKAGE} -@end ifset -Version @value{GDBVN}. - -@insertcopying -@end ifnottex - -@titlepage -@title Debugging with @value{GDBN} -@subtitle The @sc{gnu} Source-Level Debugger -@sp 1 -@subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN} -@ifset VERSION_PACKAGE -@sp 1 -@subtitle @value{VERSION_PACKAGE} -@end ifset -@author Richard Stallman, Roland Pesch, Stan Shebs, et al. -@page -@tex -{\parskip=0pt -\hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par -\hfill {\it Debugging with @value{GDBN}}\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex - -@vskip 0pt plus 1filll -Published by the Free Software Foundation @* -51 Franklin Street, Fifth Floor, -Boston, MA 02110-1301, USA@* -ISBN 978-0-9831592-3-0 @* - -@insertcopying -@end titlepage -@page - -@ifnottex -@node Top, Summary, (dir), (dir) - -@top Debugging with @value{GDBN} - -This file describes @value{GDBN}, the @sc{gnu} symbolic debugger. - -This is the @value{EDITION} Edition, for @value{GDBN} -@ifset VERSION_PACKAGE -@value{VERSION_PACKAGE} -@end ifset -Version @value{GDBVN}. - -Copyright (C) 1988-2013 Free Software Foundation, Inc. - -This edition of the GDB manual is dedicated to the memory of Fred -Fish. Fred was a long-standing contributor to GDB and to Free -software in general. We will miss him. - -@menu -* Summary:: Summary of @value{GDBN} -* Sample Session:: A sample @value{GDBN} session - -* Invocation:: Getting in and out of @value{GDBN} -* Commands:: @value{GDBN} commands -* Running:: Running programs under @value{GDBN} -* Stopping:: Stopping and continuing -* Reverse Execution:: Running programs backward -* Process Record and Replay:: Recording inferior's execution and replaying it -* Stack:: Examining the stack -* Source:: Examining source files -* Data:: Examining data -* Optimized Code:: Debugging optimized code -* Macros:: Preprocessor Macros -* Tracepoints:: Debugging remote targets non-intrusively -* Overlays:: Debugging programs that use overlays - -* Languages:: Using @value{GDBN} with different languages - -* Symbols:: Examining the symbol table -* Altering:: Altering execution -* GDB Files:: @value{GDBN} files -* Targets:: Specifying a debugging target -* Remote Debugging:: Debugging remote programs -* Configurations:: Configuration-specific information -* Controlling GDB:: Controlling @value{GDBN} -* Extending GDB:: Extending @value{GDBN} -* Interpreters:: Command Interpreters -* TUI:: @value{GDBN} Text User Interface -* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs -* GDB/MI:: @value{GDBN}'s Machine Interface. -* Annotations:: @value{GDBN}'s annotation interface. -* JIT Interface:: Using the JIT debugging interface. -* In-Process Agent:: In-Process Agent - -* GDB Bugs:: Reporting bugs in @value{GDBN} - -@ifset SYSTEM_READLINE -* Command Line Editing: (rluserman). Command Line Editing -* Using History Interactively: (history). Using History Interactively -@end ifset -@ifclear SYSTEM_READLINE -* Command Line Editing:: Command Line Editing -* Using History Interactively:: Using History Interactively -@end ifclear -* In Memoriam:: In Memoriam -* Formatting Documentation:: How to format and print @value{GDBN} documentation -* Installing GDB:: Installing GDB -* Maintenance Commands:: Maintenance Commands -* Remote Protocol:: GDB Remote Serial Protocol -* Agent Expressions:: The GDB Agent Expression Mechanism -* Target Descriptions:: How targets can describe themselves to - @value{GDBN} -* Operating System Information:: Getting additional information from - the operating system -* Trace File Format:: GDB trace file format -* Index Section Format:: .gdb_index section format -* Copying:: GNU General Public License says - how you can copy and share GDB -* GNU Free Documentation License:: The license for this documentation -* Concept Index:: Index of @value{GDBN} concepts -* Command and Variable Index:: Index of @value{GDBN} commands, variables, - functions, and Python data types -@end menu - -@end ifnottex - -@contents - -@node Summary -@unnumbered Summary of @value{GDBN} - -The purpose of a debugger such as @value{GDBN} is to allow you to see what is -going on ``inside'' another program while it executes---or what another -program was doing at the moment it crashed. - -@value{GDBN} can do four main kinds of things (plus other things in support of -these) to help you catch bugs in the act: - -@itemize @bullet -@item -Start your program, specifying anything that might affect its behavior. - -@item -Make your program stop on specified conditions. - -@item -Examine what has happened, when your program has stopped. - -@item -Change things in your program, so you can experiment with correcting the -effects of one bug and go on to learn about another. -@end itemize - -You can use @value{GDBN} to debug programs written in C and C@t{++}. -For more information, see @ref{Supported Languages,,Supported Languages}. -For more information, see @ref{C,,C and C++}. - -Support for D is partial. For information on D, see -@ref{D,,D}. - -@cindex Modula-2 -Support for Modula-2 is partial. For information on Modula-2, see -@ref{Modula-2,,Modula-2}. - -Support for OpenCL C is partial. For information on OpenCL C, see -@ref{OpenCL C,,OpenCL C}. - -@cindex Pascal -Debugging Pascal programs which use sets, subranges, file variables, or -nested functions does not currently work. @value{GDBN} does not support -entering expressions, printing values, or similar features using Pascal -syntax. - -@cindex Fortran -@value{GDBN} can be used to debug programs written in Fortran, although -it may be necessary to refer to some variables with a trailing -underscore. - -@value{GDBN} can be used to debug programs written in Objective-C, -using either the Apple/NeXT or the GNU Objective-C runtime. - -@menu -* Free Software:: Freely redistributable software -* Free Documentation:: Free Software Needs Free Documentation -* Contributors:: Contributors to GDB -@end menu - -@node Free Software -@unnumberedsec Free Software - -@value{GDBN} is @dfn{free software}, protected by the @sc{gnu} -General Public License -(GPL). The GPL gives you the freedom to copy or adapt a licensed -program---but every person getting a copy also gets with it the -freedom to modify that copy (which means that they must get access to -the source code), and the freedom to distribute further copies. -Typical software companies use copyrights to limit your freedoms; the -Free Software Foundation uses the GPL to preserve these freedoms. - -Fundamentally, the General Public License is a license which says that -you have these freedoms and that you cannot take these freedoms away -from anyone else. - -@node Free Documentation -@unnumberedsec Free Software Needs Free Documentation - -The biggest deficiency in the free software community today is not in -the software---it is the lack of good free documentation that we can -include with the free software. Many of our most important -programs do not come with free reference manuals and free introductory -texts. Documentation is an essential part of any software package; -when an important free software package does not come with a free -manual and a free tutorial, that is a major gap. We have many such -gaps today. - -Consider Perl, for instance. The tutorial manuals that people -normally use are non-free. How did this come about? Because the -authors of those manuals published them with restrictive terms---no -copying, no modification, source files not available---which exclude -them from the free software world. - -That wasn't the first time this sort of thing happened, and it was far -from the last. Many times we have heard a GNU user eagerly describe a -manual that he is writing, his intended contribution to the community, -only to learn that he had ruined everything by signing a publication -contract to make it non-free. - -Free documentation, like free software, is a matter of freedom, not -price. The problem with the non-free manual is not that publishers -charge a price for printed copies---that in itself is fine. (The Free -Software Foundation sells printed copies of manuals, too.) The -problem is the restrictions on the use of the manual. Free manuals -are available in source code form, and give you permission to copy and -modify. Non-free manuals do not allow this. - -The criteria of freedom for a free manual are roughly the same as for -free software. Redistribution (including the normal kinds of -commercial redistribution) must be permitted, so that the manual can -accompany every copy of the program, both on-line and on paper. - -Permission for modification of the technical content is crucial too. -When people modify the software, adding or changing features, if they -are conscientious they will change the manual too---so they can -provide accurate and clear documentation for the modified program. A -manual that leaves you no choice but to write a new manual to document -a changed version of the program is not really available to our -community. - -Some kinds of limits on the way modification is handled are -acceptable. For example, requirements to preserve the original -author's copyright notice, the distribution terms, or the list of -authors, are ok. It is also no problem to require modified versions -to include notice that they were modified. Even entire sections that -may not be deleted or changed are acceptable, as long as they deal -with nontechnical topics (like this one). These kinds of restrictions -are acceptable because they don't obstruct the community's normal use -of the manual. - -However, it must be possible to modify all the @emph{technical} -content of the manual, and then distribute the result in all the usual -media, through all the usual channels. Otherwise, the restrictions -obstruct the use of the manual, it is not free, and we need another -manual to replace it. - -Please spread the word about this issue. Our community continues to -lose manuals to proprietary publishing. If we spread the word that -free software needs free reference manuals and free tutorials, perhaps -the next person who wants to contribute by writing documentation will -realize, before it is too late, that only free manuals contribute to -the free software community. - -If you are writing documentation, please insist on publishing it under -the GNU Free Documentation License or another free documentation -license. Remember that this decision requires your approval---you -don't have to let the publisher decide. Some commercial publishers -will use a free license if you insist, but they will not propose the -option; it is up to you to raise the issue and say firmly that this is -what you want. If the publisher you are dealing with refuses, please -try other publishers. If you're not sure whether a proposed license -is free, write to @email{licensing@@gnu.org}. - -You can encourage commercial publishers to sell more free, copylefted -manuals and tutorials by buying them, and particularly by buying -copies from the publishers that paid for their writing or for major -improvements. Meanwhile, try to avoid buying non-free documentation -at all. Check the distribution terms of a manual before you buy it, -and insist that whoever seeks your business must respect your freedom. -Check the history of the book, and try to reward the publishers that -have paid or pay the authors to work on it. - -The Free Software Foundation maintains a list of free documentation -published by other publishers, at -@url{http://www.fsf.org/doc/other-free-books.html}. - -@node Contributors -@unnumberedsec Contributors to @value{GDBN} - -Richard Stallman was the original author of @value{GDBN}, and of many -other @sc{gnu} programs. Many others have contributed to its -development. This section attempts to credit major contributors. One -of the virtues of free software is that everyone is free to contribute -to it; with regret, we cannot actually acknowledge everyone here. The -file @file{ChangeLog} in the @value{GDBN} distribution approximates a -blow-by-blow account. - -Changes much prior to version 2.0 are lost in the mists of time. - -@quotation -@emph{Plea:} Additions to this section are particularly welcome. If you -or your friends (or enemies, to be evenhanded) have been unfairly -omitted from this list, we would like to add your names! -@end quotation - -So that they may not regard their many labors as thankless, we -particularly thank those who shepherded @value{GDBN} through major -releases: -Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0); -Jim Blandy (release 4.18); -Jason Molenda (release 4.17); -Stan Shebs (release 4.14); -Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9); -Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4); -John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); -Jim Kingdon (releases 3.5, 3.4, and 3.3); -and Randy Smith (releases 3.2, 3.1, and 3.0). - -Richard Stallman, assisted at various times by Peter TerMaat, Chris -Hanson, and Richard Mlynarik, handled releases through 2.8. - -Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support -in @value{GDBN}, with significant additional contributions from Per -Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++} -demangler. Early work on C@t{++} was by Peter TerMaat (who also did -much general update work leading to release 3.0). - -@value{GDBN} uses the BFD subroutine library to examine multiple -object-file formats; BFD was a joint project of David V. -Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore. - -David Johnson wrote the original COFF support; Pace Willison did -the original support for encapsulated COFF. - -Brent Benson of Harris Computer Systems contributed DWARF 2 support. - -Adam de Boor and Bradley Davis contributed the ISI Optimum V support. -Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS -support. -Jean-Daniel Fekete contributed Sun 386i support. -Chris Hanson improved the HP9000 support. -Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support. -David Johnson contributed Encore Umax support. -Jyrki Kuoppala contributed Altos 3068 support. -Jeff Law contributed HP PA and SOM support. -Keith Packard contributed NS32K support. -Doug Rabson contributed Acorn Risc Machine support. -Bob Rusk contributed Harris Nighthawk CX-UX support. -Chris Smith contributed Convex support (and Fortran debugging). -Jonathan Stone contributed Pyramid support. -Michael Tiemann contributed SPARC support. -Tim Tucker contributed support for the Gould NP1 and Gould Powernode. -Pace Willison contributed Intel 386 support. -Jay Vosburgh contributed Symmetry support. -Marko Mlinar contributed OpenRISC 1000 support. - -Andreas Schwab contributed M68K @sc{gnu}/Linux support. - -Rich Schaefer and Peter Schauer helped with support of SunOS shared -libraries. - -Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree -about several machine instruction sets. - -Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop -remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM -contributed remote debugging modules for the i960, VxWorks, A29K UDI, -and RDI targets, respectively. - -Brian Fox is the author of the readline libraries providing -command-line editing and command history. - -Andrew Beers of SUNY Buffalo wrote the language-switching code, the -Modula-2 support, and contributed the Languages chapter of this manual. - -Fred Fish wrote most of the support for Unix System Vr4. -He also enhanced the command-completion support to cover C@t{++} overloaded -symbols. - -Hitachi America (now Renesas America), Ltd. sponsored the support for -H8/300, H8/500, and Super-H processors. - -NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors. - -Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D -processors. - -Toshiba sponsored the support for the TX39 Mips processor. - -Matsushita sponsored the support for the MN10200 and MN10300 processors. - -Fujitsu sponsored the support for SPARClite and FR30 processors. - -Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware -watchpoints. - -Michael Snyder added support for tracepoints. - -Stu Grossman wrote gdbserver. - -Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made -nearly innumerable bug fixes and cleanups throughout @value{GDBN}. - -The following people at the Hewlett-Packard Company contributed -support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0 -(narrow mode), HP's implementation of kernel threads, HP's aC@t{++} -compiler, and the Text User Interface (nee Terminal User Interface): -Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann, -Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase -provided HP-specific information in this manual. - -DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project. -Robert Hoehne made significant contributions to the DJGPP port. - -Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its -development since 1991. Cygnus engineers who have worked on @value{GDBN} -fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin -Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim -Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler, -Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek -Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In -addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton, -JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug -Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff -Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner, -Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin -Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela -Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David -Zuhn have made contributions both large and small. - -Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for -Cygnus Solutions, implemented the original @sc{gdb/mi} interface. - -Jim Blandy added support for preprocessor macros, while working for Red -Hat. - -Andrew Cagney designed @value{GDBN}'s architecture vector. Many -people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick -Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei -Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason -Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped -with the migration of old architectures to this new framework. - -Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s -unwinder framework, this consisting of a fresh new design featuring -frame IDs, independent frame sniffers, and the sentinel frame. Mark -Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the -libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and -trad unwinders. The architecture-specific changes, each involving a -complete rewrite of the architecture's frame code, were carried out by -Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane -Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel -Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei -Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich -Weigand. - -Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from -Tensilica, Inc.@: contributed support for Xtensa processors. Others -who have worked on the Xtensa port of @value{GDBN} in the past include -Steve Tjiang, John Newlin, and Scott Foehner. - -Michael Eager and staff of Xilinx, Inc., contributed support for the -Xilinx MicroBlaze architecture. - -@node Sample Session -@chapter A Sample @value{GDBN} Session - -You can use this manual at your leisure to read all about @value{GDBN}. -However, a handful of commands are enough to get started using the -debugger. This chapter illustrates those commands. - -@iftex -In this sample session, we emphasize user input like this: @b{input}, -to make it easier to pick out from the surrounding output. -@end iftex - -@c FIXME: this example may not be appropriate for some configs, where -@c FIXME...primary interest is in remote use. - -One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro -processor) exhibits the following bug: sometimes, when we change its -quote strings from the default, the commands used to capture one macro -definition within another stop working. In the following short @code{m4} -session, we define a macro @code{foo} which expands to @code{0000}; we -then use the @code{m4} built-in @code{defn} to define @code{bar} as the -same thing. However, when we change the open quote string to -@code{} and the close quote string to @code{}, the same -procedure fails to define a new synonym @code{baz}: - -@smallexample -$ @b{cd gnu/m4} -$ @b{./m4} -@b{define(foo,0000)} - -@b{foo} -0000 -@b{define(bar,defn(`foo'))} - -@b{bar} -0000 -@b{changequote(,)} - -@b{define(baz,defn(foo))} -@b{baz} -@b{Ctrl-d} -m4: End of input: 0: fatal error: EOF in string -@end smallexample - -@noindent -Let us use @value{GDBN} to try to see what is going on. - -@smallexample -$ @b{@value{GDBP} m4} -@c FIXME: this falsifies the exact text played out, to permit smallbook -@c FIXME... format to come out better. -@value{GDBN} is free software and you are welcome to distribute copies - of it under certain conditions; type "show copying" to see - the conditions. -There is absolutely no warranty for @value{GDBN}; type "show warranty" - for details. - -@value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc... -(@value{GDBP}) -@end smallexample - -@noindent -@value{GDBN} reads only enough symbol data to know where to find the -rest when needed; as a result, the first prompt comes up very quickly. -We now tell @value{GDBN} to use a narrower display width than usual, so -that examples fit in this manual. - -@smallexample -(@value{GDBP}) @b{set width 70} -@end smallexample - -@noindent -We need to see how the @code{m4} built-in @code{changequote} works. -Having looked at the source, we know the relevant subroutine is -@code{m4_changequote}, so we set a breakpoint there with the @value{GDBN} -@code{break} command. - -@smallexample -(@value{GDBP}) @b{break m4_changequote} -Breakpoint 1 at 0x62f4: file builtin.c, line 879. -@end smallexample - -@noindent -Using the @code{run} command, we start @code{m4} running under @value{GDBN} -control; as long as control does not reach the @code{m4_changequote} -subroutine, the program runs as usual: - -@smallexample -(@value{GDBP}) @b{run} -Starting program: /work/Editorial/gdb/gnu/m4/m4 -@b{define(foo,0000)} - -@b{foo} -0000 -@end smallexample - -@noindent -To trigger the breakpoint, we call @code{changequote}. @value{GDBN} -suspends execution of @code{m4}, displaying information about the -context where it stops. - -@smallexample -@b{changequote(,)} - -Breakpoint 1, m4_changequote (argc=3, argv=0x33c70) - at builtin.c:879 -879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3)) -@end smallexample - -@noindent -Now we use the command @code{n} (@code{next}) to advance execution to -the next line of the current function. - -@smallexample -(@value{GDBP}) @b{n} -882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\ - : nil, -@end smallexample - -@noindent -@code{set_quotes} looks like a promising subroutine. We can go into it -by using the command @code{s} (@code{step}) instead of @code{next}. -@code{step} goes to the next line to be executed in @emph{any} -subroutine, so it steps into @code{set_quotes}. - -@smallexample -(@value{GDBP}) @b{s} -set_quotes (lq=0x34c78 "", rq=0x34c88 "") - at input.c:530 -530 if (lquote != def_lquote) -@end smallexample - -@noindent -The display that shows the subroutine where @code{m4} is now -suspended (and its arguments) is called a stack frame display. It -shows a summary of the stack. We can use the @code{backtrace} -command (which can also be spelled @code{bt}), to see where we are -in the stack as a whole: the @code{backtrace} command displays a -stack frame for each active subroutine. - -@smallexample -(@value{GDBP}) @b{bt} -#0 set_quotes (lq=0x34c78 "", rq=0x34c88 "") - at input.c:530 -#1 0x6344 in m4_changequote (argc=3, argv=0x33c70) - at builtin.c:882 -#2 0x8174 in expand_macro (sym=0x33320) at macro.c:242 -#3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30) - at macro.c:71 -#4 0x79dc in expand_input () at macro.c:40 -#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195 -@end smallexample - -@noindent -We step through a few more lines to see what happens. The first two -times, we can use @samp{s}; the next two times we use @code{n} to avoid -falling into the @code{xstrdup} subroutine. - -@smallexample -(@value{GDBP}) @b{s} -0x3b5c 532 if (rquote != def_rquote) -(@value{GDBP}) @b{s} -0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \ -def_lquote : xstrdup(lq); -(@value{GDBP}) @b{n} -536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ - : xstrdup(rq); -(@value{GDBP}) @b{n} -538 len_lquote = strlen(rquote); -@end smallexample - -@noindent -The last line displayed looks a little odd; we can examine the variables -@code{lquote} and @code{rquote} to see if they are in fact the new left -and right quotes we specified. We use the command @code{p} -(@code{print}) to see their values. - -@smallexample -(@value{GDBP}) @b{p lquote} -$1 = 0x35d40 "" -(@value{GDBP}) @b{p rquote} -$2 = 0x35d50 "" -@end smallexample - -@noindent -@code{lquote} and @code{rquote} are indeed the new left and right quotes. -To look at some context, we can display ten lines of source -surrounding the current line with the @code{l} (@code{list}) command. - -@smallexample -(@value{GDBP}) @b{l} -533 xfree(rquote); -534 -535 lquote = (lq == nil || *lq == '\0') ? def_lquote\ - : xstrdup (lq); -536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ - : xstrdup (rq); -537 -538 len_lquote = strlen(rquote); -539 len_rquote = strlen(lquote); -540 @} -541 -542 void -@end smallexample - -@noindent -Let us step past the two lines that set @code{len_lquote} and -@code{len_rquote}, and then examine the values of those variables. - -@smallexample -(@value{GDBP}) @b{n} -539 len_rquote = strlen(lquote); -(@value{GDBP}) @b{n} -540 @} -(@value{GDBP}) @b{p len_lquote} -$3 = 9 -(@value{GDBP}) @b{p len_rquote} -$4 = 7 -@end smallexample - -@noindent -That certainly looks wrong, assuming @code{len_lquote} and -@code{len_rquote} are meant to be the lengths of @code{lquote} and -@code{rquote} respectively. We can set them to better values using -the @code{p} command, since it can print the value of -any expression---and that expression can include subroutine calls and -assignments. - -@smallexample -(@value{GDBP}) @b{p len_lquote=strlen(lquote)} -$5 = 7 -(@value{GDBP}) @b{p len_rquote=strlen(rquote)} -$6 = 9 -@end smallexample - -@noindent -Is that enough to fix the problem of using the new quotes with the -@code{m4} built-in @code{defn}? We can allow @code{m4} to continue -executing with the @code{c} (@code{continue}) command, and then try the -example that caused trouble initially: - -@smallexample -(@value{GDBP}) @b{c} -Continuing. - -@b{define(baz,defn(foo))} - -baz -0000 -@end smallexample - -@noindent -Success! The new quotes now work just as well as the default ones. The -problem seems to have been just the two typos defining the wrong -lengths. We allow @code{m4} exit by giving it an EOF as input: - -@smallexample -@b{Ctrl-d} -Program exited normally. -@end smallexample - -@noindent -The message @samp{Program exited normally.} is from @value{GDBN}; it -indicates @code{m4} has finished executing. We can end our @value{GDBN} -session with the @value{GDBN} @code{quit} command. - -@smallexample -(@value{GDBP}) @b{quit} -@end smallexample - -@node Invocation -@chapter Getting In and Out of @value{GDBN} - -This chapter discusses how to start @value{GDBN}, and how to get out of it. -The essentials are: -@itemize @bullet -@item -type @samp{@value{GDBP}} to start @value{GDBN}. -@item -type @kbd{quit} or @kbd{Ctrl-d} to exit. -@end itemize - -@menu -* Invoking GDB:: How to start @value{GDBN} -* Quitting GDB:: How to quit @value{GDBN} -* Shell Commands:: How to use shell commands inside @value{GDBN} -* Logging Output:: How to log @value{GDBN}'s output to a file -@end menu - -@node Invoking GDB -@section Invoking @value{GDBN} - -Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started, -@value{GDBN} reads commands from the terminal until you tell it to exit. - -You can also run @code{@value{GDBP}} with a variety of arguments and options, -to specify more of your debugging environment at the outset. - -The command-line options described here are designed -to cover a variety of situations; in some environments, some of these -options may effectively be unavailable. - -The most usual way to start @value{GDBN} is with one argument, -specifying an executable program: - -@smallexample -@value{GDBP} @var{program} -@end smallexample - -@noindent -You can also start with both an executable program and a core file -specified: - -@smallexample -@value{GDBP} @var{program} @var{core} -@end smallexample - -You can, instead, specify a process ID as a second argument, if you want -to debug a running process: - -@smallexample -@value{GDBP} @var{program} 1234 -@end smallexample - -@noindent -would attach @value{GDBN} to process @code{1234} (unless you also have a file -named @file{1234}; @value{GDBN} does check for a core file first). - -Taking advantage of the second command-line argument requires a fairly -complete operating system; when you use @value{GDBN} as a remote -debugger attached to a bare board, there may not be any notion of -``process'', and there is often no way to get a core dump. @value{GDBN} -will warn you if it is unable to attach or to read core dumps. - -You can optionally have @code{@value{GDBP}} pass any arguments after the -executable file to the inferior using @code{--args}. This option stops -option processing. -@smallexample -@value{GDBP} --args gcc -O2 -c foo.c -@end smallexample -This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set -@code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}. - -You can run @code{@value{GDBP}} without printing the front material, which describes -@value{GDBN}'s non-warranty, by specifying @code{-silent}: - -@smallexample -@value{GDBP} -silent -@end smallexample - -@noindent -You can further control how @value{GDBN} starts up by using command-line -options. @value{GDBN} itself can remind you of the options available. - -@noindent -Type - -@smallexample -@value{GDBP} -help -@end smallexample - -@noindent -to display all available options and briefly describe their use -(@samp{@value{GDBP} -h} is a shorter equivalent). - -All options and command line arguments you give are processed -in sequential order. The order makes a difference when the -@samp{-x} option is used. - - -@menu -* File Options:: Choosing files -* Mode Options:: Choosing modes -* Startup:: What @value{GDBN} does during startup -@end menu - -@node File Options -@subsection Choosing Files - -When @value{GDBN} starts, it reads any arguments other than options as -specifying an executable file and core file (or process ID). This is -the same as if the arguments were specified by the @samp{-se} and -@samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the -first argument that does not have an associated option flag as -equivalent to the @samp{-se} option followed by that argument; and the -second argument that does not have an associated option flag, if any, as -equivalent to the @samp{-c}/@samp{-p} option followed by that argument.) -If the second argument begins with a decimal digit, @value{GDBN} will -first attempt to attach to it as a process, and if that fails, attempt -to open it as a corefile. If you have a corefile whose name begins with -a digit, you can prevent @value{GDBN} from treating it as a pid by -prefixing it with @file{./}, e.g.@: @file{./12345}. - -If @value{GDBN} has not been configured to included core file support, -such as for most embedded targets, then it will complain about a second -argument and ignore it. - -Many options have both long and short forms; both are shown in the -following list. @value{GDBN} also recognizes the long forms if you truncate -them, so long as enough of the option is present to be unambiguous. -(If you prefer, you can flag option arguments with @samp{--} rather -than @samp{-}, though we illustrate the more usual convention.) - -@c NOTE: the @cindex entries here use double dashes ON PURPOSE. This -@c way, both those who look for -foo and --foo in the index, will find -@c it. - -@table @code -@item -symbols @var{file} -@itemx -s @var{file} -@cindex @code{--symbols} -@cindex @code{-s} -Read symbol table from file @var{file}. - -@item -exec @var{file} -@itemx -e @var{file} -@cindex @code{--exec} -@cindex @code{-e} -Use file @var{file} as the executable file to execute when appropriate, -and for examining pure data in conjunction with a core dump. - -@item -se @var{file} -@cindex @code{--se} -Read symbol table from file @var{file} and use it as the executable -file. - -@item -core @var{file} -@itemx -c @var{file} -@cindex @code{--core} -@cindex @code{-c} -Use file @var{file} as a core dump to examine. - -@item -pid @var{number} -@itemx -p @var{number} -@cindex @code{--pid} -@cindex @code{-p} -Connect to process ID @var{number}, as with the @code{attach} command. - -@item -command @var{file} -@itemx -x @var{file} -@cindex @code{--command} -@cindex @code{-x} -Execute commands from file @var{file}. The contents of this file is -evaluated exactly as the @code{source} command would. -@xref{Command Files,, Command files}. - -@item -eval-command @var{command} -@itemx -ex @var{command} -@cindex @code{--eval-command} -@cindex @code{-ex} -Execute a single @value{GDBN} command. - -This option may be used multiple times to call multiple commands. It may -also be interleaved with @samp{-command} as required. - -@smallexample -@value{GDBP} -ex 'target sim' -ex 'load' \ - -x setbreakpoints -ex 'run' a.out -@end smallexample - -@item -init-command @var{file} -@itemx -ix @var{file} -@cindex @code{--init-command} -@cindex @code{-ix} -Execute commands from file @var{file} before loading the inferior (but -after loading gdbinit files). -@xref{Startup}. - -@item -init-eval-command @var{command} -@itemx -iex @var{command} -@cindex @code{--init-eval-command} -@cindex @code{-iex} -Execute a single @value{GDBN} command before loading the inferior (but -after loading gdbinit files). -@xref{Startup}. - -@item -directory @var{directory} -@itemx -d @var{directory} -@cindex @code{--directory} -@cindex @code{-d} -Add @var{directory} to the path to search for source and script files. - -@item -r -@itemx -readnow -@cindex @code{--readnow} -@cindex @code{-r} -Read each symbol file's entire symbol table immediately, rather than -the default, which is to read it incrementally as it is needed. -This makes startup slower, but makes future operations faster. - -@end table - -@node Mode Options -@subsection Choosing Modes - -You can run @value{GDBN} in various alternative modes---for example, in -batch mode or quiet mode. - -@table @code -@anchor{-nx} -@item -nx -@itemx -n -@cindex @code{--nx} -@cindex @code{-n} -Do not execute commands found in any initialization file. -There are three init files, loaded in the following order: - -@table @code -@item @file{system.gdbinit} -This is the system-wide init file. -Its location is specified with the @code{--with-system-gdbinit} -configure option (@pxref{System-wide configuration}). -It is loaded first when @value{GDBN} starts, before command line options -have been processed. -@item @file{~/.gdbinit} -This is the init file in your home directory. -It is loaded next, after @file{system.gdbinit}, and before -command options have been processed. -@item @file{./.gdbinit} -This is the init file in the current directory. -It is loaded last, after command line options other than @code{-x} and -@code{-ex} have been processed. Command line options @code{-x} and -@code{-ex} are processed last, after @file{./.gdbinit} has been loaded. -@end table - -For further documentation on startup processing, @xref{Startup}. -For documentation on how to write command files, -@xref{Command Files,,Command Files}. - -@anchor{-nh} -@item -nh -@cindex @code{--nh} -Do not execute commands found in @file{~/.gdbinit}, the init file -in your home directory. -@xref{Startup}. - -@item -quiet -@itemx -silent -@itemx -q -@cindex @code{--quiet} -@cindex @code{--silent} -@cindex @code{-q} -``Quiet''. Do not print the introductory and copyright messages. These -messages are also suppressed in batch mode. - -@item -batch -@cindex @code{--batch} -Run in batch mode. Exit with status @code{0} after processing all the -command files specified with @samp{-x} (and all commands from -initialization files, if not inhibited with @samp{-n}). Exit with -nonzero status if an error occurs in executing the @value{GDBN} commands -in the command files. Batch mode also disables pagination, sets unlimited -terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm -off} were in effect (@pxref{Messages/Warnings}). - -Batch mode may be useful for running @value{GDBN} as a filter, for -example to download and run a program on another computer; in order to -make this more useful, the message - -@smallexample -Program exited normally. -@end smallexample - -@noindent -(which is ordinarily issued whenever a program running under -@value{GDBN} control terminates) is not issued when running in batch -mode. - -@item -batch-silent -@cindex @code{--batch-silent} -Run in batch mode exactly like @samp{-batch}, but totally silently. All -@value{GDBN} output to @code{stdout} is prevented (@code{stderr} is -unaffected). This is much quieter than @samp{-silent} and would be useless -for an interactive session. - -This is particularly useful when using targets that give @samp{Loading section} -messages, for example. - -Note that targets that give their output via @value{GDBN}, as opposed to -writing directly to @code{stdout}, will also be made silent. - -@item -return-child-result -@cindex @code{--return-child-result} -The return code from @value{GDBN} will be the return code from the child -process (the process being debugged), with the following exceptions: - -@itemize @bullet -@item -@value{GDBN} exits abnormally. E.g., due to an incorrect argument or an -internal error. In this case the exit code is the same as it would have been -without @samp{-return-child-result}. -@item -The user quits with an explicit value. E.g., @samp{quit 1}. -@item -The child process never runs, or is not allowed to terminate, in which case -the exit code will be -1. -@end itemize - -This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent}, -when @value{GDBN} is being used as a remote program loader or simulator -interface. - -@item -nowindows -@itemx -nw -@cindex @code{--nowindows} -@cindex @code{-nw} -``No windows''. If @value{GDBN} comes with a graphical user interface -(GUI) built in, then this option tells @value{GDBN} to only use the command-line -interface. If no GUI is available, this option has no effect. - -@item -windows -@itemx -w -@cindex @code{--windows} -@cindex @code{-w} -If @value{GDBN} includes a GUI, then this option requires it to be -used if possible. - -@item -cd @var{directory} -@cindex @code{--cd} -Run @value{GDBN} using @var{directory} as its working directory, -instead of the current directory. - -@item -data-directory @var{directory} -@cindex @code{--data-directory} -Run @value{GDBN} using @var{directory} as its data directory. -The data directory is where @value{GDBN} searches for its -auxiliary files. @xref{Data Files}. - -@item -fullname -@itemx -f -@cindex @code{--fullname} -@cindex @code{-f} -@sc{gnu} Emacs sets this option when it runs @value{GDBN} as a -subprocess. It tells @value{GDBN} to output the full file name and line -number in a standard, recognizable fashion each time a stack frame is -displayed (which includes each time your program stops). This -recognizable format looks like two @samp{\032} characters, followed by -the file name, line number and character position separated by colons, -and a newline. The Emacs-to-@value{GDBN} interface program uses the two -@samp{\032} characters as a signal to display the source code for the -frame. - -@item -annotate @var{level} -@cindex @code{--annotate} -This option sets the @dfn{annotation level} inside @value{GDBN}. Its -effect is identical to using @samp{set annotate @var{level}} -(@pxref{Annotations}). The annotation @var{level} controls how much -information @value{GDBN} prints together with its prompt, values of -expressions, source lines, and other types of output. Level 0 is the -normal, level 1 is for use when @value{GDBN} is run as a subprocess of -@sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs -that control @value{GDBN}, and level 2 has been deprecated. - -The annotation mechanism has largely been superseded by @sc{gdb/mi} -(@pxref{GDB/MI}). - -@item --args -@cindex @code{--args} -Change interpretation of command line so that arguments following the -executable file are passed as command line arguments to the inferior. -This option stops option processing. - -@item -baud @var{bps} -@itemx -b @var{bps} -@cindex @code{--baud} -@cindex @code{-b} -Set the line speed (baud rate or bits per second) of any serial -interface used by @value{GDBN} for remote debugging. - -@item -l @var{timeout} -@cindex @code{-l} -Set the timeout (in seconds) of any communication used by @value{GDBN} -for remote debugging. - -@item -tty @var{device} -@itemx -t @var{device} -@cindex @code{--tty} -@cindex @code{-t} -Run using @var{device} for your program's standard input and output. -@c FIXME: kingdon thinks there is more to -tty. Investigate. - -@c resolve the situation of these eventually -@item -tui -@cindex @code{--tui} -Activate the @dfn{Text User Interface} when starting. The Text User -Interface manages several text windows on the terminal, showing -source, assembly, registers and @value{GDBN} command outputs -(@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this -option if you run @value{GDBN} from Emacs (@pxref{Emacs, , -Using @value{GDBN} under @sc{gnu} Emacs}). - -@c @item -xdb -@c @cindex @code{--xdb} -@c Run in XDB compatibility mode, allowing the use of certain XDB commands. -@c For information, see the file @file{xdb_trans.html}, which is usually -@c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX -@c systems. - -@item -interpreter @var{interp} -@cindex @code{--interpreter} -Use the interpreter @var{interp} for interface with the controlling -program or device. This option is meant to be set by programs which -communicate with @value{GDBN} using it as a back end. -@xref{Interpreters, , Command Interpreters}. - -@samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes -@value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, , -The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The -previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and -selected with @samp{--interpreter=mi1}, is deprecated. Earlier -@sc{gdb/mi} interfaces are no longer supported. - -@item -write -@cindex @code{--write} -Open the executable and core files for both reading and writing. This -is equivalent to the @samp{set write on} command inside @value{GDBN} -(@pxref{Patching}). - -@item -statistics -@cindex @code{--statistics} -This option causes @value{GDBN} to print statistics about time and -memory usage after it completes each command and returns to the prompt. - -@item -version -@cindex @code{--version} -This option causes @value{GDBN} to print its version number and -no-warranty blurb, and exit. - -@end table - -@node Startup -@subsection What @value{GDBN} Does During Startup -@cindex @value{GDBN} startup - -Here's the description of what @value{GDBN} does during session startup: - -@enumerate -@item -Sets up the command interpreter as specified by the command line -(@pxref{Mode Options, interpreter}). - -@item -@cindex init file -Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was -used when building @value{GDBN}; @pxref{System-wide configuration, - ,System-wide configuration and settings}) and executes all the commands in -that file. - -@anchor{Home Directory Init File} -@item -Reads the init file (if any) in your home directory@footnote{On -DOS/Windows systems, the home directory is the one pointed to by the -@code{HOME} environment variable.} and executes all the commands in -that file. - -@anchor{Option -init-eval-command} -@item -Executes commands and command files specified by the @samp{-iex} and -@samp{-ix} options in their specified order. Usually you should use the -@samp{-ex} and @samp{-x} options instead, but this way you can apply -settings before @value{GDBN} init files get executed and before inferior -gets loaded. - -@item -Processes command line options and operands. - -@anchor{Init File in the Current Directory during Startup} -@item -Reads and executes the commands from init file (if any) in the current -working directory as long as @samp{set auto-load local-gdbinit} is set to -@samp{on} (@pxref{Init File in the Current Directory}). -This is only done if the current directory is -different from your home directory. Thus, you can have more than one -init file, one generic in your home directory, and another, specific -to the program you are debugging, in the directory where you invoke -@value{GDBN}. - -@item -If the command line specified a program to debug, or a process to -attach to, or a core file, @value{GDBN} loads any auto-loaded -scripts provided for the program or for its loaded shared libraries. -@xref{Auto-loading}. - -If you wish to disable the auto-loading during startup, -you must do something like the following: - -@smallexample -$ gdb -iex "set auto-load python-scripts off" myprogram -@end smallexample - -Option @samp{-ex} does not work because the auto-loading is then turned -off too late. - -@item -Executes commands and command files specified by the @samp{-ex} and -@samp{-x} options in their specified order. @xref{Command Files}, for -more details about @value{GDBN} command files. - -@item -Reads the command history recorded in the @dfn{history file}. -@xref{Command History}, for more details about the command history and the -files where @value{GDBN} records it. -@end enumerate - -Init files use the same syntax as @dfn{command files} (@pxref{Command -Files}) and are processed by @value{GDBN} in the same way. The init -file in your home directory can set options (such as @samp{set -complaints}) that affect subsequent processing of command line options -and operands. Init files are not executed if you use the @samp{-nx} -option (@pxref{Mode Options, ,Choosing Modes}). - -To display the list of init files loaded by gdb at startup, you -can use @kbd{gdb --help}. - -@cindex init file name -@cindex @file{.gdbinit} -@cindex @file{gdb.ini} -The @value{GDBN} init files are normally called @file{.gdbinit}. -The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to -the limitations of file names imposed by DOS filesystems. The Windows -port of @value{GDBN} uses the standard name, but if it finds a -@file{gdb.ini} file in your home directory, it warns you about that -and suggests to rename the file to the standard name. - - -@node Quitting GDB -@section Quitting @value{GDBN} -@cindex exiting @value{GDBN} -@cindex leaving @value{GDBN} - -@table @code -@kindex quit @r{[}@var{expression}@r{]} -@kindex q @r{(@code{quit})} -@item quit @r{[}@var{expression}@r{]} -@itemx q -To exit @value{GDBN}, use the @code{quit} command (abbreviated -@code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you -do not supply @var{expression}, @value{GDBN} will terminate normally; -otherwise it will terminate using the result of @var{expression} as the -error code. -@end table - -@cindex interrupt -An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather -terminates the action of any @value{GDBN} command that is in progress and -returns to @value{GDBN} command level. It is safe to type the interrupt -character at any time because @value{GDBN} does not allow it to take effect -until a time when it is safe. - -If you have been using @value{GDBN} to control an attached process or -device, you can release it with the @code{detach} command -(@pxref{Attach, ,Debugging an Already-running Process}). - -@node Shell Commands -@section Shell Commands - -If you need to execute occasional shell commands during your -debugging session, there is no need to leave or suspend @value{GDBN}; you can -just use the @code{shell} command. - -@table @code -@kindex shell -@kindex ! -@cindex shell escape -@item shell @var{command-string} -@itemx !@var{command-string} -Invoke a standard shell to execute @var{command-string}. -Note that no space is needed between @code{!} and @var{command-string}. -If it exists, the environment variable @code{SHELL} determines which -shell to run. Otherwise @value{GDBN} uses the default shell -(@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.). -@end table - -The utility @code{make} is often needed in development environments. -You do not have to use the @code{shell} command for this purpose in -@value{GDBN}: - -@table @code -@kindex make -@cindex calling make -@item make @var{make-args} -Execute the @code{make} program with the specified -arguments. This is equivalent to @samp{shell make @var{make-args}}. -@end table - -@node Logging Output -@section Logging Output -@cindex logging @value{GDBN} output -@cindex save @value{GDBN} output to a file - -You may want to save the output of @value{GDBN} commands to a file. -There are several commands to control @value{GDBN}'s logging. - -@table @code -@kindex set logging -@item set logging on -Enable logging. -@item set logging off -Disable logging. -@cindex logging file name -@item set logging file @var{file} -Change the name of the current logfile. The default logfile is @file{gdb.txt}. -@item set logging overwrite [on|off] -By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if -you want @code{set logging on} to overwrite the logfile instead. -@item set logging redirect [on|off] -By default, @value{GDBN} output will go to both the terminal and the logfile. -Set @code{redirect} if you want output to go only to the log file. -@kindex show logging -@item show logging -Show the current values of the logging settings. -@end table - -@node Commands -@chapter @value{GDBN} Commands - -You can abbreviate a @value{GDBN} command to the first few letters of the command -name, if that abbreviation is unambiguous; and you can repeat certain -@value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB} -key to get @value{GDBN} to fill out the rest of a word in a command (or to -show you the alternatives available, if there is more than one possibility). - -@menu -* Command Syntax:: How to give commands to @value{GDBN} -* Completion:: Command completion -* Help:: How to ask @value{GDBN} for help -@end menu - -@node Command Syntax -@section Command Syntax - -A @value{GDBN} command is a single line of input. There is no limit on -how long it can be. It starts with a command name, which is followed by -arguments whose meaning depends on the command name. For example, the -command @code{step} accepts an argument which is the number of times to -step, as in @samp{step 5}. You can also use the @code{step} command -with no arguments. Some commands do not allow any arguments. - -@cindex abbreviation -@value{GDBN} command names may always be truncated if that abbreviation is -unambiguous. Other possible command abbreviations are listed in the -documentation for individual commands. In some cases, even ambiguous -abbreviations are allowed; for example, @code{s} is specially defined as -equivalent to @code{step} even though there are other commands whose -names start with @code{s}. You can test abbreviations by using them as -arguments to the @code{help} command. - -@cindex repeating commands -@kindex RET @r{(repeat last command)} -A blank line as input to @value{GDBN} (typing just @key{RET}) means to -repeat the previous command. Certain commands (for example, @code{run}) -will not repeat this way; these are commands whose unintentional -repetition might cause trouble and which you are unlikely to want to -repeat. User-defined commands can disable this feature; see -@ref{Define, dont-repeat}. - -The @code{list} and @code{x} commands, when you repeat them with -@key{RET}, construct new arguments rather than repeating -exactly as typed. This permits easy scanning of source or memory. - -@value{GDBN} can also use @key{RET} in another way: to partition lengthy -output, in a way similar to the common utility @code{more} -(@pxref{Screen Size,,Screen Size}). Since it is easy to press one -@key{RET} too many in this situation, @value{GDBN} disables command -repetition after any command that generates this sort of display. - -@kindex # @r{(a comment)} -@cindex comment -Any text from a @kbd{#} to the end of the line is a comment; it does -nothing. This is useful mainly in command files (@pxref{Command -Files,,Command Files}). - -@cindex repeating command sequences -@kindex Ctrl-o @r{(operate-and-get-next)} -The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of -commands. This command accepts the current line, like @key{RET}, and -then fetches the next line relative to the current line from the history -for editing. - -@node Completion -@section Command Completion - -@cindex completion -@cindex word completion -@value{GDBN} can fill in the rest of a word in a command for you, if there is -only one possibility; it can also show you what the valid possibilities -are for the next word in a command, at any time. This works for @value{GDBN} -commands, @value{GDBN} subcommands, and the names of symbols in your program. - -Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest -of a word. If there is only one possibility, @value{GDBN} fills in the -word, and waits for you to finish the command (or press @key{RET} to -enter it). For example, if you type - -@c FIXME "@key" does not distinguish its argument sufficiently to permit -@c complete accuracy in these examples; space introduced for clarity. -@c If texinfo enhancements make it unnecessary, it would be nice to -@c replace " @key" by "@key" in the following... -@smallexample -(@value{GDBP}) info bre @key{TAB} -@end smallexample - -@noindent -@value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is -the only @code{info} subcommand beginning with @samp{bre}: - -@smallexample -(@value{GDBP}) info breakpoints -@end smallexample - -@noindent -You can either press @key{RET} at this point, to run the @code{info -breakpoints} command, or backspace and enter something else, if -@samp{breakpoints} does not look like the command you expected. (If you -were sure you wanted @code{info breakpoints} in the first place, you -might as well just type @key{RET} immediately after @samp{info bre}, -to exploit command abbreviations rather than command completion). - -If there is more than one possibility for the next word when you press -@key{TAB}, @value{GDBN} sounds a bell. You can either supply more -characters and try again, or just press @key{TAB} a second time; -@value{GDBN} displays all the possible completions for that word. For -example, you might want to set a breakpoint on a subroutine whose name -begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN} -just sounds the bell. Typing @key{TAB} again displays all the -function names in your program that begin with those characters, for -example: - -@smallexample -(@value{GDBP}) b make_ @key{TAB} -@exdent @value{GDBN} sounds bell; press @key{TAB} again, to see: -make_a_section_from_file make_environ -make_abs_section make_function_type -make_blockvector make_pointer_type -make_cleanup make_reference_type -make_command make_symbol_completion_list -(@value{GDBP}) b make_ -@end smallexample - -@noindent -After displaying the available possibilities, @value{GDBN} copies your -partial input (@samp{b make_} in the example) so you can finish the -command. - -If you just want to see the list of alternatives in the first place, you -can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?} -means @kbd{@key{META} ?}. You can type this either by holding down a -key designated as the @key{META} shift on your keyboard (if there is -one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}. - -@cindex quotes in commands -@cindex completion of quoted strings -Sometimes the string you need, while logically a ``word'', may contain -parentheses or other characters that @value{GDBN} normally excludes from -its notion of a word. To permit word completion to work in this -situation, you may enclose words in @code{'} (single quote marks) in -@value{GDBN} commands. - -The most likely situation where you might need this is in typing the -name of a C@t{++} function. This is because C@t{++} allows function -overloading (multiple definitions of the same function, distinguished -by argument type). For example, when you want to set a breakpoint you -may need to distinguish whether you mean the version of @code{name} -that takes an @code{int} parameter, @code{name(int)}, or the version -that takes a @code{float} parameter, @code{name(float)}. To use the -word-completion facilities in this situation, type a single quote -@code{'} at the beginning of the function name. This alerts -@value{GDBN} that it may need to consider more information than usual -when you press @key{TAB} or @kbd{M-?} to request word completion: - -@smallexample -(@value{GDBP}) b 'bubble( @kbd{M-?} -bubble(double,double) bubble(int,int) -(@value{GDBP}) b 'bubble( -@end smallexample - -In some cases, @value{GDBN} can tell that completing a name requires using -quotes. When this happens, @value{GDBN} inserts the quote for you (while -completing as much as it can) if you do not type the quote in the first -place: - -@smallexample -(@value{GDBP}) b bub @key{TAB} -@exdent @value{GDBN} alters your input line to the following, and rings a bell: -(@value{GDBP}) b 'bubble( -@end smallexample - -@noindent -In general, @value{GDBN} can tell that a quote is needed (and inserts it) if -you have not yet started typing the argument list when you ask for -completion on an overloaded symbol. - -For more information about overloaded functions, see @ref{C Plus Plus -Expressions, ,C@t{++} Expressions}. You can use the command @code{set -overload-resolution off} to disable overload resolution; -see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}. - -@cindex completion of structure field names -@cindex structure field name completion -@cindex completion of union field names -@cindex union field name completion -When completing in an expression which looks up a field in a -structure, @value{GDBN} also tries@footnote{The completer can be -confused by certain kinds of invalid expressions. Also, it only -examines the static type of the expression, not the dynamic type.} to -limit completions to the field names available in the type of the -left-hand-side: - -@smallexample -(@value{GDBP}) p gdb_stdout.@kbd{M-?} -magic to_fputs to_rewind -to_data to_isatty to_write -to_delete to_put to_write_async_safe -to_flush to_read -@end smallexample - -@noindent -This is because the @code{gdb_stdout} is a variable of the type -@code{struct ui_file} that is defined in @value{GDBN} sources as -follows: - -@smallexample -struct ui_file -@{ - int *magic; - ui_file_flush_ftype *to_flush; - ui_file_write_ftype *to_write; - ui_file_write_async_safe_ftype *to_write_async_safe; - ui_file_fputs_ftype *to_fputs; - ui_file_read_ftype *to_read; - ui_file_delete_ftype *to_delete; - ui_file_isatty_ftype *to_isatty; - ui_file_rewind_ftype *to_rewind; - ui_file_put_ftype *to_put; - void *to_data; -@} -@end smallexample - - -@node Help -@section Getting Help -@cindex online documentation -@kindex help - -You can always ask @value{GDBN} itself for information on its commands, -using the command @code{help}. - -@table @code -@kindex h @r{(@code{help})} -@item help -@itemx h -You can use @code{help} (abbreviated @code{h}) with no arguments to -display a short list of named classes of commands: - -@smallexample -(@value{GDBP}) help -List of classes of commands: - -aliases -- Aliases of other commands -breakpoints -- Making program stop at certain points -data -- Examining data -files -- Specifying and examining files -internals -- Maintenance commands -obscure -- Obscure features -running -- Running the program -stack -- Examining the stack -status -- Status inquiries -support -- Support facilities -tracepoints -- Tracing of program execution without - stopping the program -user-defined -- User-defined commands - -Type "help" followed by a class name for a list of -commands in that class. -Type "help" followed by command name for full -documentation. -Command name abbreviations are allowed if unambiguous. -(@value{GDBP}) -@end smallexample -@c the above line break eliminates huge line overfull... - -@item help @var{class} -Using one of the general help classes as an argument, you can get a -list of the individual commands in that class. For example, here is the -help display for the class @code{status}: - -@smallexample -(@value{GDBP}) help status -Status inquiries. - -List of commands: - -@c Line break in "show" line falsifies real output, but needed -@c to fit in smallbook page size. -info -- Generic command for showing things - about the program being debugged -show -- Generic command for showing things - about the debugger - -Type "help" followed by command name for full -documentation. -Command name abbreviations are allowed if unambiguous. -(@value{GDBP}) -@end smallexample - -@item help @var{command} -With a command name as @code{help} argument, @value{GDBN} displays a -short paragraph on how to use that command. - -@kindex apropos -@item apropos @var{args} -The @code{apropos} command searches through all of the @value{GDBN} -commands, and their documentation, for the regular expression specified in -@var{args}. It prints out all matches found. For example: - -@smallexample -apropos alias -@end smallexample - -@noindent -results in: - -@smallexample -@c @group -alias -- Define a new command that is an alias of an existing command -aliases -- Aliases of other commands -d -- Delete some breakpoints or auto-display expressions -del -- Delete some breakpoints or auto-display expressions -delete -- Delete some breakpoints or auto-display expressions -@c @end group -@end smallexample - -@kindex complete -@item complete @var{args} -The @code{complete @var{args}} command lists all the possible completions -for the beginning of a command. Use @var{args} to specify the beginning of the -command you want completed. For example: - -@smallexample -complete i -@end smallexample - -@noindent results in: - -@smallexample -@group -if -ignore -info -inspect -@end group -@end smallexample - -@noindent This is intended for use by @sc{gnu} Emacs. -@end table - -In addition to @code{help}, you can use the @value{GDBN} commands @code{info} -and @code{show} to inquire about the state of your program, or the state -of @value{GDBN} itself. Each command supports many topics of inquiry; this -manual introduces each of them in the appropriate context. The listings -under @code{info} and under @code{show} in the Command, Variable, and -Function Index point to all the sub-commands. @xref{Command and Variable -Index}. - -@c @group -@table @code -@kindex info -@kindex i @r{(@code{info})} -@item info -This command (abbreviated @code{i}) is for describing the state of your -program. For example, you can show the arguments passed to a function -with @code{info args}, list the registers currently in use with @code{info -registers}, or list the breakpoints you have set with @code{info breakpoints}. -You can get a complete list of the @code{info} sub-commands with -@w{@code{help info}}. - -@kindex set -@item set -You can assign the result of an expression to an environment variable with -@code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with -@code{set prompt $}. - -@kindex show -@item show -In contrast to @code{info}, @code{show} is for describing the state of -@value{GDBN} itself. -You can change most of the things you can @code{show}, by using the -related command @code{set}; for example, you can control what number -system is used for displays with @code{set radix}, or simply inquire -which is currently in use with @code{show radix}. - -@kindex info set -To display all the settable parameters and their current -values, you can use @code{show} with no arguments; you may also use -@code{info set}. Both commands produce the same display. -@c FIXME: "info set" violates the rule that "info" is for state of -@c FIXME...program. Ck w/ GNU: "info set" to be called something else, -@c FIXME...or change desc of rule---eg "state of prog and debugging session"? -@end table -@c @end group - -Here are three miscellaneous @code{show} subcommands, all of which are -exceptional in lacking corresponding @code{set} commands: - -@table @code -@kindex show version -@cindex @value{GDBN} version number -@item show version -Show what version of @value{GDBN} is running. You should include this -information in @value{GDBN} bug-reports. If multiple versions of -@value{GDBN} are in use at your site, you may need to determine which -version of @value{GDBN} you are running; as @value{GDBN} evolves, new -commands are introduced, and old ones may wither away. Also, many -system vendors ship variant versions of @value{GDBN}, and there are -variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well. -The version number is the same as the one announced when you start -@value{GDBN}. - -@kindex show copying -@kindex info copying -@cindex display @value{GDBN} copyright -@item show copying -@itemx info copying -Display information about permission for copying @value{GDBN}. - -@kindex show warranty -@kindex info warranty -@item show warranty -@itemx info warranty -Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty, -if your version of @value{GDBN} comes with one. - -@end table - -@node Running -@chapter Running Programs Under @value{GDBN} - -When you run a program under @value{GDBN}, you must first generate -debugging information when you compile it. - -You may start @value{GDBN} with its arguments, if any, in an environment -of your choice. If you are doing native debugging, you may redirect -your program's input and output, debug an already running process, or -kill a child process. - -@menu -* Compilation:: Compiling for debugging -* Starting:: Starting your program -* Arguments:: Your program's arguments -* Environment:: Your program's environment - -* Working Directory:: Your program's working directory -* Input/Output:: Your program's input and output -* Attach:: Debugging an already-running process -* Kill Process:: Killing the child process - -* Inferiors and Programs:: Debugging multiple inferiors and programs -* Threads:: Debugging programs with multiple threads -* Forks:: Debugging forks -* Checkpoint/Restart:: Setting a @emph{bookmark} to return to later -@end menu - -@node Compilation -@section Compiling for Debugging - -In order to debug a program effectively, you need to generate -debugging information when you compile it. This debugging information -is stored in the object file; it describes the data type of each -variable or function and the correspondence between source line numbers -and addresses in the executable code. - -To request debugging information, specify the @samp{-g} option when you run -the compiler. - -Programs that are to be shipped to your customers are compiled with -optimizations, using the @samp{-O} compiler option. However, some -compilers are unable to handle the @samp{-g} and @samp{-O} options -together. Using those compilers, you cannot generate optimized -executables containing debugging information. - -@value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or -without @samp{-O}, making it possible to debug optimized code. We -recommend that you @emph{always} use @samp{-g} whenever you compile a -program. You may think your program is correct, but there is no sense -in pushing your luck. For more information, see @ref{Optimized Code}. - -Older versions of the @sc{gnu} C compiler permitted a variant option -@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this -format; if your @sc{gnu} C compiler has this option, do not use it. - -@value{GDBN} knows about preprocessor macros and can show you their -expansion (@pxref{Macros}). Most compilers do not include information -about preprocessor macros in the debugging information if you specify -the @option{-g} flag alone. Version 3.1 and later of @value{NGCC}, -the @sc{gnu} C compiler, provides macro information if you are using -the DWARF debugging format, and specify the option @option{-g3}. - -@xref{Debugging Options,,Options for Debugging Your Program or GCC, -gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more -information on @value{NGCC} options affecting debug information. - -You will have the best debugging experience if you use the latest -version of the DWARF debugging format that your compiler supports. -DWARF is currently the most expressive and best supported debugging -format in @value{GDBN}. - -@need 2000 -@node Starting -@section Starting your Program -@cindex starting -@cindex running - -@table @code -@kindex run -@kindex r @r{(@code{run})} -@item run -@itemx r -Use the @code{run} command to start your program under @value{GDBN}. -You must first specify the program name (except on VxWorks) with an -argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of -@value{GDBN}}), or by using the @code{file} or @code{exec-file} command -(@pxref{Files, ,Commands to Specify Files}). - -@end table - -If you are running your program in an execution environment that -supports processes, @code{run} creates an inferior process and makes -that process run your program. In some environments without processes, -@code{run} jumps to the start of your program. Other targets, -like @samp{remote}, are always running. If you get an error -message like this one: - -@smallexample -The "remote" target does not support "run". -Try "help target" or "continue". -@end smallexample - -@noindent -then use @code{continue} to run your program. You may need @code{load} -first (@pxref{load}). - -The execution of a program is affected by certain information it -receives from its superior. @value{GDBN} provides ways to specify this -information, which you must do @emph{before} starting your program. (You -can change it after starting your program, but such changes only affect -your program the next time you start it.) This information may be -divided into four categories: - -@table @asis -@item The @emph{arguments.} -Specify the arguments to give your program as the arguments of the -@code{run} command. If a shell is available on your target, the shell -is used to pass the arguments, so that you may use normal conventions -(such as wildcard expansion or variable substitution) in describing -the arguments. -In Unix systems, you can control which shell is used with the -@code{SHELL} environment variable. -@xref{Arguments, ,Your Program's Arguments}. - -@item The @emph{environment.} -Your program normally inherits its environment from @value{GDBN}, but you can -use the @value{GDBN} commands @code{set environment} and @code{unset -environment} to change parts of the environment that affect -your program. @xref{Environment, ,Your Program's Environment}. - -@item The @emph{working directory.} -Your program inherits its working directory from @value{GDBN}. You can set -the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}. -@xref{Working Directory, ,Your Program's Working Directory}. - -@item The @emph{standard input and output.} -Your program normally uses the same device for standard input and -standard output as @value{GDBN} is using. You can redirect input and output -in the @code{run} command line, or you can use the @code{tty} command to -set a different device for your program. -@xref{Input/Output, ,Your Program's Input and Output}. - -@cindex pipes -@emph{Warning:} While input and output redirection work, you cannot use -pipes to pass the output of the program you are debugging to another -program; if you attempt this, @value{GDBN} is likely to wind up debugging the -wrong program. -@end table - -When you issue the @code{run} command, your program begins to execute -immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion -of how to arrange for your program to stop. Once your program has -stopped, you may call functions in your program, using the @code{print} -or @code{call} commands. @xref{Data, ,Examining Data}. - -If the modification time of your symbol file has changed since the last -time @value{GDBN} read its symbols, @value{GDBN} discards its symbol -table, and reads it again. When it does this, @value{GDBN} tries to retain -your current breakpoints. - -@table @code -@kindex start -@item start -@cindex run to main procedure -The name of the main procedure can vary from language to language. -With C or C@t{++}, the main procedure name is always @code{main}, but -other languages such as Ada do not require a specific name for their -main procedure. The debugger provides a convenient way to start the -execution of the program and to stop at the beginning of the main -procedure, depending on the language used. - -The @samp{start} command does the equivalent of setting a temporary -breakpoint at the beginning of the main procedure and then invoking -the @samp{run} command. - -@cindex elaboration phase -Some programs contain an @dfn{elaboration} phase where some startup code is -executed before the main procedure is called. This depends on the -languages used to write your program. In C@t{++}, for instance, -constructors for static and global objects are executed before -@code{main} is called. It is therefore possible that the debugger stops -before reaching the main procedure. However, the temporary breakpoint -will remain to halt execution. - -Specify the arguments to give to your program as arguments to the -@samp{start} command. These arguments will be given verbatim to the -underlying @samp{run} command. Note that the same arguments will be -reused if no argument is provided during subsequent calls to -@samp{start} or @samp{run}. - -It is sometimes necessary to debug the program during elaboration. In -these cases, using the @code{start} command would stop the execution of -your program too late, as the program would have already completed the -elaboration phase. Under these circumstances, insert breakpoints in your -elaboration code before running your program. - -@kindex set exec-wrapper -@item set exec-wrapper @var{wrapper} -@itemx show exec-wrapper -@itemx unset exec-wrapper -When @samp{exec-wrapper} is set, the specified wrapper is used to -launch programs for debugging. @value{GDBN} starts your program -with a shell command of the form @kbd{exec @var{wrapper} -@var{program}}. Quoting is added to @var{program} and its -arguments, but not to @var{wrapper}, so you should add quotes if -appropriate for your shell. The wrapper runs until it executes -your program, and then @value{GDBN} takes control. - -You can use any program that eventually calls @code{execve} with -its arguments as a wrapper. Several standard Unix utilities do -this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending -with @code{exec "$@@"} will also work. - -For example, you can use @code{env} to pass an environment variable to -the debugged program, without setting the variable in your shell's -environment: - -@smallexample -(@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so' -(@value{GDBP}) run -@end smallexample - -This command is available when debugging locally on most targets, excluding -@sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino. - -@kindex set disable-randomization -@item set disable-randomization -@itemx set disable-randomization on -This option (enabled by default in @value{GDBN}) will turn off the native -randomization of the virtual address space of the started program. This option -is useful for multiple debugging sessions to make the execution better -reproducible and memory addresses reusable across debugging sessions. - -This feature is implemented only on certain targets, including @sc{gnu}/Linux. -On @sc{gnu}/Linux you can get the same behavior using - -@smallexample -(@value{GDBP}) set exec-wrapper setarch `uname -m` -R -@end smallexample - -@item set disable-randomization off -Leave the behavior of the started executable unchanged. Some bugs rear their -ugly heads only when the program is loaded at certain addresses. If your bug -disappears when you run the program under @value{GDBN}, that might be because -@value{GDBN} by default disables the address randomization on platforms, such -as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set -disable-randomization off} to try to reproduce such elusive bugs. - -On targets where it is available, virtual address space randomization -protects the programs against certain kinds of security attacks. In these -cases the attacker needs to know the exact location of a concrete executable -code. Randomizing its location makes it impossible to inject jumps misusing -a code at its expected addresses. - -Prelinking shared libraries provides a startup performance advantage but it -makes addresses in these libraries predictable for privileged processes by -having just unprivileged access at the target system. Reading the shared -library binary gives enough information for assembling the malicious code -misusing it. Still even a prelinked shared library can get loaded at a new -random address just requiring the regular relocation process during the -startup. Shared libraries not already prelinked are always loaded at -a randomly chosen address. - -Position independent executables (PIE) contain position independent code -similar to the shared libraries and therefore such executables get loaded at -a randomly chosen address upon startup. PIE executables always load even -already prelinked shared libraries at a random address. You can build such -executable using @command{gcc -fPIE -pie}. - -Heap (malloc storage), stack and custom mmap areas are always placed randomly -(as long as the randomization is enabled). - -@item show disable-randomization -Show the current setting of the explicit disable of the native randomization of -the virtual address space of the started program. - -@end table - -@node Arguments -@section Your Program's Arguments - -@cindex arguments (to your program) -The arguments to your program can be specified by the arguments of the -@code{run} command. -They are passed to a shell, which expands wildcard characters and -performs redirection of I/O, and thence to your program. Your -@code{SHELL} environment variable (if it exists) specifies what shell -@value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses -the default shell (@file{/bin/sh} on Unix). - -On non-Unix systems, the program is usually invoked directly by -@value{GDBN}, which emulates I/O redirection via the appropriate system -calls, and the wildcard characters are expanded by the startup code of -the program, not by the shell. - -@code{run} with no arguments uses the same arguments used by the previous -@code{run}, or those set by the @code{set args} command. - -@table @code -@kindex set args -@item set args -Specify the arguments to be used the next time your program is run. If -@code{set args} has no arguments, @code{run} executes your program -with no arguments. Once you have run your program with arguments, -using @code{set args} before the next @code{run} is the only way to run -it again without arguments. - -@kindex show args -@item show args -Show the arguments to give your program when it is started. -@end table - -@node Environment -@section Your Program's Environment - -@cindex environment (of your program) -The @dfn{environment} consists of a set of environment variables and -their values. Environment variables conventionally record such things as -your user name, your home directory, your terminal type, and your search -path for programs to run. Usually you set up environment variables with -the shell and they are inherited by all the other programs you run. When -debugging, it can be useful to try running your program with a modified -environment without having to start @value{GDBN} over again. - -@table @code -@kindex path -@item path @var{directory} -Add @var{directory} to the front of the @code{PATH} environment variable -(the search path for executables) that will be passed to your program. -The value of @code{PATH} used by @value{GDBN} does not change. -You may specify several directory names, separated by whitespace or by a -system-dependent separator character (@samp{:} on Unix, @samp{;} on -MS-DOS and MS-Windows). If @var{directory} is already in the path, it -is moved to the front, so it is searched sooner. - -You can use the string @samp{$cwd} to refer to whatever is the current -working directory at the time @value{GDBN} searches the path. If you -use @samp{.} instead, it refers to the directory where you executed the -@code{path} command. @value{GDBN} replaces @samp{.} in the -@var{directory} argument (with the current path) before adding -@var{directory} to the search path. -@c 'path' is explicitly nonrepeatable, but RMS points out it is silly to -@c document that, since repeating it would be a no-op. - -@kindex show paths -@item show paths -Display the list of search paths for executables (the @code{PATH} -environment variable). - -@kindex show environment -@item show environment @r{[}@var{varname}@r{]} -Print the value of environment variable @var{varname} to be given to -your program when it starts. If you do not supply @var{varname}, -print the names and values of all environment variables to be given to -your program. You can abbreviate @code{environment} as @code{env}. - -@kindex set environment -@item set environment @var{varname} @r{[}=@var{value}@r{]} -Set environment variable @var{varname} to @var{value}. The value -changes for your program only, not for @value{GDBN} itself. @var{value} may -be any string; the values of environment variables are just strings, and -any interpretation is supplied by your program itself. The @var{value} -parameter is optional; if it is eliminated, the variable is set to a -null value. -@c "any string" here does not include leading, trailing -@c blanks. Gnu asks: does anyone care? - -For example, this command: - -@smallexample -set env USER = foo -@end smallexample - -@noindent -tells the debugged program, when subsequently run, that its user is named -@samp{foo}. (The spaces around @samp{=} are used for clarity here; they -are not actually required.) - -@kindex unset environment -@item unset environment @var{varname} -Remove variable @var{varname} from the environment to be passed to your -program. This is different from @samp{set env @var{varname} =}; -@code{unset environment} removes the variable from the environment, -rather than assigning it an empty value. -@end table - -@emph{Warning:} On Unix systems, @value{GDBN} runs your program using -the shell indicated -by your @code{SHELL} environment variable if it exists (or -@code{/bin/sh} if not). If your @code{SHELL} variable names a shell -that runs an initialization file---such as @file{.cshrc} for C-shell, or -@file{.bashrc} for BASH---any variables you set in that file affect -your program. You may wish to move setting of environment variables to -files that are only run when you sign on, such as @file{.login} or -@file{.profile}. - -@node Working Directory -@section Your Program's Working Directory - -@cindex working directory (of your program) -Each time you start your program with @code{run}, it inherits its -working directory from the current working directory of @value{GDBN}. -The @value{GDBN} working directory is initially whatever it inherited -from its parent process (typically the shell), but you can specify a new -working directory in @value{GDBN} with the @code{cd} command. - -The @value{GDBN} working directory also serves as a default for the commands -that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to -Specify Files}. - -@table @code -@kindex cd -@cindex change working directory -@item cd @r{[}@var{directory}@r{]} -Set the @value{GDBN} working directory to @var{directory}. If not -given, @var{directory} uses @file{'~'}. - -@kindex pwd -@item pwd -Print the @value{GDBN} working directory. -@end table - -It is generally impossible to find the current working directory of -the process being debugged (since a program can change its directory -during its run). If you work on a system where @value{GDBN} is -configured with the @file{/proc} support, you can use the @code{info -proc} command (@pxref{SVR4 Process Information}) to find out the -current working directory of the debuggee. - -@node Input/Output -@section Your Program's Input and Output - -@cindex redirection -@cindex i/o -@cindex terminal -By default, the program you run under @value{GDBN} does input and output to -the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal -to its own terminal modes to interact with you, but it records the terminal -modes your program was using and switches back to them when you continue -running your program. - -@table @code -@kindex info terminal -@item info terminal -Displays information recorded by @value{GDBN} about the terminal modes your -program is using. -@end table - -You can redirect your program's input and/or output using shell -redirection with the @code{run} command. For example, - -@smallexample -run > outfile -@end smallexample - -@noindent -starts your program, diverting its output to the file @file{outfile}. - -@kindex tty -@cindex controlling terminal -Another way to specify where your program should do input and output is -with the @code{tty} command. This command accepts a file name as -argument, and causes this file to be the default for future @code{run} -commands. It also resets the controlling terminal for the child -process, for future @code{run} commands. For example, - -@smallexample -tty /dev/ttyb -@end smallexample - -@noindent -directs that processes started with subsequent @code{run} commands -default to do input and output on the terminal @file{/dev/ttyb} and have -that as their controlling terminal. - -An explicit redirection in @code{run} overrides the @code{tty} command's -effect on the input/output device, but not its effect on the controlling -terminal. - -When you use the @code{tty} command or redirect input in the @code{run} -command, only the input @emph{for your program} is affected. The input -for @value{GDBN} still comes from your terminal. @code{tty} is an alias -for @code{set inferior-tty}. - -@cindex inferior tty -@cindex set inferior controlling terminal -You can use the @code{show inferior-tty} command to tell @value{GDBN} to -display the name of the terminal that will be used for future runs of your -program. - -@table @code -@item set inferior-tty /dev/ttyb -@kindex set inferior-tty -Set the tty for the program being debugged to /dev/ttyb. - -@item show inferior-tty -@kindex show inferior-tty -Show the current tty for the program being debugged. -@end table - -@node Attach -@section Debugging an Already-running Process -@kindex attach -@cindex attach - -@table @code -@item attach @var{process-id} -This command attaches to a running process---one that was started -outside @value{GDBN}. (@code{info files} shows your active -targets.) The command takes as argument a process ID. The usual way to -find out the @var{process-id} of a Unix process is with the @code{ps} utility, -or with the @samp{jobs -l} shell command. - -@code{attach} does not repeat if you press @key{RET} a second time after -executing the command. -@end table - -To use @code{attach}, your program must be running in an environment -which supports processes; for example, @code{attach} does not work for -programs on bare-board targets that lack an operating system. You must -also have permission to send the process a signal. - -When you use @code{attach}, the debugger finds the program running in -the process first by looking in the current working directory, then (if -the program is not found) by using the source file search path -(@pxref{Source Path, ,Specifying Source Directories}). You can also use -the @code{file} command to load the program. @xref{Files, ,Commands to -Specify Files}. - -The first thing @value{GDBN} does after arranging to debug the specified -process is to stop it. You can examine and modify an attached process -with all the @value{GDBN} commands that are ordinarily available when -you start processes with @code{run}. You can insert breakpoints; you -can step and continue; you can modify storage. If you would rather the -process continue running, you may use the @code{continue} command after -attaching @value{GDBN} to the process. - -@table @code -@kindex detach -@item detach -When you have finished debugging the attached process, you can use the -@code{detach} command to release it from @value{GDBN} control. Detaching -the process continues its execution. After the @code{detach} command, -that process and @value{GDBN} become completely independent once more, and you -are ready to @code{attach} another process or start one with @code{run}. -@code{detach} does not repeat if you press @key{RET} again after -executing the command. -@end table - -If you exit @value{GDBN} while you have an attached process, you detach -that process. If you use the @code{run} command, you kill that process. -By default, @value{GDBN} asks for confirmation if you try to do either of these -things; you can control whether or not you need to confirm by using the -@code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and -Messages}). - -@node Kill Process -@section Killing the Child Process - -@table @code -@kindex kill -@item kill -Kill the child process in which your program is running under @value{GDBN}. -@end table - -This command is useful if you wish to debug a core dump instead of a -running process. @value{GDBN} ignores any core dump file while your program -is running. - -On some operating systems, a program cannot be executed outside @value{GDBN} -while you have breakpoints set on it inside @value{GDBN}. You can use the -@code{kill} command in this situation to permit running your program -outside the debugger. - -The @code{kill} command is also useful if you wish to recompile and -relink your program, since on many systems it is impossible to modify an -executable file while it is running in a process. In this case, when you -next type @code{run}, @value{GDBN} notices that the file has changed, and -reads the symbol table again (while trying to preserve your current -breakpoint settings). - -@node Inferiors and Programs -@section Debugging Multiple Inferiors and Programs - -@value{GDBN} lets you run and debug multiple programs in a single -session. In addition, @value{GDBN} on some systems may let you run -several programs simultaneously (otherwise you have to exit from one -before starting another). In the most general case, you can have -multiple threads of execution in each of multiple processes, launched -from multiple executables. - -@cindex inferior -@value{GDBN} represents the state of each program execution with an -object called an @dfn{inferior}. An inferior typically corresponds to -a process, but is more general and applies also to targets that do not -have processes. Inferiors may be created before a process runs, and -may be retained after a process exits. Inferiors have unique -identifiers that are different from process ids. Usually each -inferior will also have its own distinct address space, although some -embedded targets may have several inferiors running in different parts -of a single address space. Each inferior may in turn have multiple -threads running in it. - -To find out what inferiors exist at any moment, use @w{@code{info -inferiors}}: - -@table @code -@kindex info inferiors -@item info inferiors -Print a list of all inferiors currently being managed by @value{GDBN}. - -@value{GDBN} displays for each inferior (in this order): - -@enumerate -@item -the inferior number assigned by @value{GDBN} - -@item -the target system's inferior identifier - -@item -the name of the executable the inferior is running. - -@end enumerate - -@noindent -An asterisk @samp{*} preceding the @value{GDBN} inferior number -indicates the current inferior. - -For example, -@end table -@c end table here to get a little more width for example - -@smallexample -(@value{GDBP}) info inferiors - Num Description Executable - 2 process 2307 hello -* 1 process 3401 goodbye -@end smallexample - -To switch focus between inferiors, use the @code{inferior} command: - -@table @code -@kindex inferior @var{infno} -@item inferior @var{infno} -Make inferior number @var{infno} the current inferior. The argument -@var{infno} is the inferior number assigned by @value{GDBN}, as shown -in the first field of the @samp{info inferiors} display. -@end table - - -You can get multiple executables into a debugging session via the -@code{add-inferior} and @w{@code{clone-inferior}} commands. On some -systems @value{GDBN} can add inferiors to the debug session -automatically by following calls to @code{fork} and @code{exec}. To -remove inferiors from the debugging session use the -@w{@code{remove-inferiors}} command. - -@table @code -@kindex add-inferior -@item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] -Adds @var{n} inferiors to be run using @var{executable} as the -executable. @var{n} defaults to 1. If no executable is specified, -the inferiors begins empty, with no program. You can still assign or -change the program assigned to the inferior at any time by using the -@code{file} command with the executable name as its argument. - -@kindex clone-inferior -@item clone-inferior [ -copies @var{n} ] [ @var{infno} ] -Adds @var{n} inferiors ready to execute the same program as inferior -@var{infno}. @var{n} defaults to 1. @var{infno} defaults to the -number of the current inferior. This is a convenient command when you -want to run another instance of the inferior you are debugging. - -@smallexample -(@value{GDBP}) info inferiors - Num Description Executable -* 1 process 29964 helloworld -(@value{GDBP}) clone-inferior -Added inferior 2. -1 inferiors added. -(@value{GDBP}) info inferiors - Num Description Executable - 2 helloworld -* 1 process 29964 helloworld -@end smallexample - -You can now simply switch focus to inferior 2 and run it. - -@kindex remove-inferiors -@item remove-inferiors @var{infno}@dots{} -Removes the inferior or inferiors @var{infno}@dots{}. It is not -possible to remove an inferior that is running with this command. For -those, use the @code{kill} or @code{detach} command first. - -@end table - -To quit debugging one of the running inferiors that is not the current -inferior, you can either detach from it by using the @w{@code{detach -inferior}} command (allowing it to run independently), or kill it -using the @w{@code{kill inferiors}} command: - -@table @code -@kindex detach inferiors @var{infno}@dots{} -@item detach inferior @var{infno}@dots{} -Detach from the inferior or inferiors identified by @value{GDBN} -inferior number(s) @var{infno}@dots{}. Note that the inferior's entry -still stays on the list of inferiors shown by @code{info inferiors}, -but its Description will show @samp{}. - -@kindex kill inferiors @var{infno}@dots{} -@item kill inferiors @var{infno}@dots{} -Kill the inferior or inferiors identified by @value{GDBN} inferior -number(s) @var{infno}@dots{}. Note that the inferior's entry still -stays on the list of inferiors shown by @code{info inferiors}, but its -Description will show @samp{}. -@end table - -After the successful completion of a command such as @code{detach}, -@code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after -a normal process exit, the inferior is still valid and listed with -@code{info inferiors}, ready to be restarted. - - -To be notified when inferiors are started or exit under @value{GDBN}'s -control use @w{@code{set print inferior-events}}: - -@table @code -@kindex set print inferior-events -@cindex print messages on inferior start and exit -@item set print inferior-events -@itemx set print inferior-events on -@itemx set print inferior-events off -The @code{set print inferior-events} command allows you to enable or -disable printing of messages when @value{GDBN} notices that new -inferiors have started or that inferiors have exited or have been -detached. By default, these messages will not be printed. - -@kindex show print inferior-events -@item show print inferior-events -Show whether messages will be printed when @value{GDBN} detects that -inferiors have started, exited or have been detached. -@end table - -Many commands will work the same with multiple programs as with a -single program: e.g., @code{print myglobal} will simply display the -value of @code{myglobal} in the current inferior. - - -Occasionaly, when debugging @value{GDBN} itself, it may be useful to -get more info about the relationship of inferiors, programs, address -spaces in a debug session. You can do that with the @w{@code{maint -info program-spaces}} command. - -@table @code -@kindex maint info program-spaces -@item maint info program-spaces -Print a list of all program spaces currently being managed by -@value{GDBN}. - -@value{GDBN} displays for each program space (in this order): - -@enumerate -@item -the program space number assigned by @value{GDBN} - -@item -the name of the executable loaded into the program space, with e.g., -the @code{file} command. - -@end enumerate - -@noindent -An asterisk @samp{*} preceding the @value{GDBN} program space number -indicates the current program space. - -In addition, below each program space line, @value{GDBN} prints extra -information that isn't suitable to display in tabular form. For -example, the list of inferiors bound to the program space. - -@smallexample -(@value{GDBP}) maint info program-spaces - Id Executable - 2 goodbye - Bound inferiors: ID 1 (process 21561) -* 1 hello -@end smallexample - -Here we can see that no inferior is running the program @code{hello}, -while @code{process 21561} is running the program @code{goodbye}. On -some targets, it is possible that multiple inferiors are bound to the -same program space. The most common example is that of debugging both -the parent and child processes of a @code{vfork} call. For example, - -@smallexample -(@value{GDBP}) maint info program-spaces - Id Executable -* 1 vfork-test - Bound inferiors: ID 2 (process 18050), ID 1 (process 18045) -@end smallexample - -Here, both inferior 2 and inferior 1 are running in the same program -space as a result of inferior 1 having executed a @code{vfork} call. -@end table - -@node Threads -@section Debugging Programs with Multiple Threads - -@cindex threads of execution -@cindex multiple threads -@cindex switching threads -In some operating systems, such as HP-UX and Solaris, a single program -may have more than one @dfn{thread} of execution. The precise semantics -of threads differ from one operating system to another, but in general -the threads of a single program are akin to multiple processes---except -that they share one address space (that is, they can all examine and -modify the same variables). On the other hand, each thread has its own -registers and execution stack, and perhaps private memory. - -@value{GDBN} provides these facilities for debugging multi-thread -programs: - -@itemize @bullet -@item automatic notification of new threads -@item @samp{thread @var{threadno}}, a command to switch among threads -@item @samp{info threads}, a command to inquire about existing threads -@item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}}, -a command to apply a command to a list of threads -@item thread-specific breakpoints -@item @samp{set print thread-events}, which controls printing of -messages on thread start and exit. -@item @samp{set libthread-db-search-path @var{path}}, which lets -the user specify which @code{libthread_db} to use if the default choice -isn't compatible with the program. -@end itemize - -@quotation -@emph{Warning:} These facilities are not yet available on every -@value{GDBN} configuration where the operating system supports threads. -If your @value{GDBN} does not support threads, these commands have no -effect. For example, a system without thread support shows no output -from @samp{info threads}, and always rejects the @code{thread} command, -like this: - -@smallexample -(@value{GDBP}) info threads -(@value{GDBP}) thread 1 -Thread ID 1 not known. Use the "info threads" command to -see the IDs of currently known threads. -@end smallexample -@c FIXME to implementors: how hard would it be to say "sorry, this GDB -@c doesn't support threads"? -@end quotation - -@cindex focus of debugging -@cindex current thread -The @value{GDBN} thread debugging facility allows you to observe all -threads while your program runs---but whenever @value{GDBN} takes -control, one thread in particular is always the focus of debugging. -This thread is called the @dfn{current thread}. Debugging commands show -program information from the perspective of the current thread. - -@cindex @code{New} @var{systag} message -@cindex thread identifier (system) -@c FIXME-implementors!! It would be more helpful if the [New...] message -@c included GDB's numeric thread handle, so you could just go to that -@c thread without first checking `info threads'. -Whenever @value{GDBN} detects a new thread in your program, it displays -the target system's identification for the thread with a message in the -form @samp{[New @var{systag}]}. @var{systag} is a thread identifier -whose form varies depending on the particular system. For example, on -@sc{gnu}/Linux, you might see - -@smallexample -[New Thread 0x41e02940 (LWP 25582)] -@end smallexample - -@noindent -when @value{GDBN} notices a new thread. In contrast, on an SGI system, -the @var{systag} is simply something like @samp{process 368}, with no -further qualifier. - -@c FIXME!! (1) Does the [New...] message appear even for the very first -@c thread of a program, or does it only appear for the -@c second---i.e.@: when it becomes obvious we have a multithread -@c program? -@c (2) *Is* there necessarily a first thread always? Or do some -@c multithread systems permit starting a program with multiple -@c threads ab initio? - -@cindex thread number -@cindex thread identifier (GDB) -For debugging purposes, @value{GDBN} associates its own thread -number---always a single integer---with each thread in your program. - -@table @code -@kindex info threads -@item info threads @r{[}@var{id}@dots{}@r{]} -Display a summary of all threads currently in your program. Optional -argument @var{id}@dots{} is one or more thread ids separated by spaces, and -means to print information only about the specified thread or threads. -@value{GDBN} displays for each thread (in this order): - -@enumerate -@item -the thread number assigned by @value{GDBN} - -@item -the target system's thread identifier (@var{systag}) - -@item -the thread's name, if one is known. A thread can either be named by -the user (see @code{thread name}, below), or, in some cases, by the -program itself. - -@item -the current stack frame summary for that thread -@end enumerate - -@noindent -An asterisk @samp{*} to the left of the @value{GDBN} thread number -indicates the current thread. - -For example, -@end table -@c end table here to get a little more width for example - -@smallexample -(@value{GDBP}) info threads - Id Target Id Frame - 3 process 35 thread 27 0x34e5 in sigpause () - 2 process 35 thread 23 0x34e5 in sigpause () -* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8) - at threadtest.c:68 -@end smallexample - -On Solaris, you can display more information about user threads with a -Solaris-specific command: - -@table @code -@item maint info sol-threads -@kindex maint info sol-threads -@cindex thread info (Solaris) -Display info on Solaris user threads. -@end table - -@table @code -@kindex thread @var{threadno} -@item thread @var{threadno} -Make thread number @var{threadno} the current thread. The command -argument @var{threadno} is the internal @value{GDBN} thread number, as -shown in the first field of the @samp{info threads} display. -@value{GDBN} responds by displaying the system identifier of the thread -you selected, and its current stack frame summary: - -@smallexample -(@value{GDBP}) thread 2 -[Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))] -#0 some_function (ignore=0x0) at example.c:8 -8 printf ("hello\n"); -@end smallexample - -@noindent -As with the @samp{[New @dots{}]} message, the form of the text after -@samp{Switching to} depends on your system's conventions for identifying -threads. - -@vindex $_thread@r{, convenience variable} -The debugger convenience variable @samp{$_thread} contains the number -of the current thread. You may find this useful in writing breakpoint -conditional expressions, command scripts, and so forth. See -@xref{Convenience Vars,, Convenience Variables}, for general -information on convenience variables. - -@kindex thread apply -@cindex apply command to several threads -@item thread apply [@var{threadno} | all] @var{command} -The @code{thread apply} command allows you to apply the named -@var{command} to one or more threads. Specify the numbers of the -threads that you want affected with the command argument -@var{threadno}. It can be a single thread number, one of the numbers -shown in the first field of the @samp{info threads} display; or it -could be a range of thread numbers, as in @code{2-4}. To apply a -command to all threads, type @kbd{thread apply all @var{command}}. - -@kindex thread name -@cindex name a thread -@item thread name [@var{name}] -This command assigns a name to the current thread. If no argument is -given, any existing user-specified name is removed. The thread name -appears in the @samp{info threads} display. - -On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to -determine the name of the thread as given by the OS. On these -systems, a name specified with @samp{thread name} will override the -system-give name, and removing the user-specified name will cause -@value{GDBN} to once again display the system-specified name. - -@kindex thread find -@cindex search for a thread -@item thread find [@var{regexp}] -Search for and display thread ids whose name or @var{systag} -matches the supplied regular expression. - -As well as being the complement to the @samp{thread name} command, -this command also allows you to identify a thread by its target -@var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag} -is the LWP id. - -@smallexample -(@value{GDBN}) thread find 26688 -Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)' -(@value{GDBN}) info thread 4 - Id Target Id Frame - 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select () -@end smallexample - -@kindex set print thread-events -@cindex print messages on thread start and exit -@item set print thread-events -@itemx set print thread-events on -@itemx set print thread-events off -The @code{set print thread-events} command allows you to enable or -disable printing of messages when @value{GDBN} notices that new threads have -started or that threads have exited. By default, these messages will -be printed if detection of these events is supported by the target. -Note that these messages cannot be disabled on all targets. - -@kindex show print thread-events -@item show print thread-events -Show whether messages will be printed when @value{GDBN} detects that threads -have started and exited. -@end table - -@xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for -more information about how @value{GDBN} behaves when you stop and start -programs with multiple threads. - -@xref{Set Watchpoints,,Setting Watchpoints}, for information about -watchpoints in programs with multiple threads. - -@anchor{set libthread-db-search-path} -@table @code -@kindex set libthread-db-search-path -@cindex search path for @code{libthread_db} -@item set libthread-db-search-path @r{[}@var{path}@r{]} -If this variable is set, @var{path} is a colon-separated list of -directories @value{GDBN} will use to search for @code{libthread_db}. -If you omit @var{path}, @samp{libthread-db-search-path} will be reset to -its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems). -Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH} -macro. - -On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper'' -@code{libthread_db} library to obtain information about threads in the -inferior process. @value{GDBN} will use @samp{libthread-db-search-path} -to find @code{libthread_db}. @value{GDBN} also consults first if inferior -specific thread debugging library loading is enabled -by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}). - -A special entry @samp{$sdir} for @samp{libthread-db-search-path} -refers to the default system directories that are -normally searched for loading shared libraries. The @samp{$sdir} entry -is the only kind not needing to be enabled by @samp{set auto-load libthread-db} -(@pxref{libthread_db.so.1 file}). - -A special entry @samp{$pdir} for @samp{libthread-db-search-path} -refers to the directory from which @code{libpthread} -was loaded in the inferior process. - -For any @code{libthread_db} library @value{GDBN} finds in above directories, -@value{GDBN} attempts to initialize it with the current inferior process. -If this initialization fails (which could happen because of a version -mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN} -will unload @code{libthread_db}, and continue with the next directory. -If none of @code{libthread_db} libraries initialize successfully, -@value{GDBN} will issue a warning and thread debugging will be disabled. - -Setting @code{libthread-db-search-path} is currently implemented -only on some platforms. - -@kindex show libthread-db-search-path -@item show libthread-db-search-path -Display current libthread_db search path. - -@kindex set debug libthread-db -@kindex show debug libthread-db -@cindex debugging @code{libthread_db} -@item set debug libthread-db -@itemx show debug libthread-db -Turns on or off display of @code{libthread_db}-related events. -Use @code{1} to enable, @code{0} to disable. -@end table - -@node Forks -@section Debugging Forks - -@cindex fork, debugging programs which call -@cindex multiple processes -@cindex processes, multiple -On most systems, @value{GDBN} has no special support for debugging -programs which create additional processes using the @code{fork} -function. When a program forks, @value{GDBN} will continue to debug the -parent process and the child process will run unimpeded. If you have -set a breakpoint in any code which the child then executes, the child -will get a @code{SIGTRAP} signal which (unless it catches the signal) -will cause it to terminate. - -However, if you want to debug the child process there is a workaround -which isn't too painful. Put a call to @code{sleep} in the code which -the child process executes after the fork. It may be useful to sleep -only if a certain environment variable is set, or a certain file exists, -so that the delay need not occur when you don't want to run @value{GDBN} -on the child. While the child is sleeping, use the @code{ps} program to -get its process ID. Then tell @value{GDBN} (a new invocation of -@value{GDBN} if you are also debugging the parent process) to attach to -the child process (@pxref{Attach}). From that point on you can debug -the child process just like any other process which you attached to. - -On some systems, @value{GDBN} provides support for debugging programs that -create additional processes using the @code{fork} or @code{vfork} functions. -Currently, the only platforms with this feature are HP-UX (11.x and later -only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later). - -By default, when a program forks, @value{GDBN} will continue to debug -the parent process and the child process will run unimpeded. - -If you want to follow the child process instead of the parent process, -use the command @w{@code{set follow-fork-mode}}. - -@table @code -@kindex set follow-fork-mode -@item set follow-fork-mode @var{mode} -Set the debugger response to a program call of @code{fork} or -@code{vfork}. A call to @code{fork} or @code{vfork} creates a new -process. The @var{mode} argument can be: - -@table @code -@item parent -The original process is debugged after a fork. The child process runs -unimpeded. This is the default. - -@item child -The new process is debugged after a fork. The parent process runs -unimpeded. - -@end table - -@kindex show follow-fork-mode -@item show follow-fork-mode -Display the current debugger response to a @code{fork} or @code{vfork} call. -@end table - -@cindex debugging multiple processes -On Linux, if you want to debug both the parent and child processes, use the -command @w{@code{set detach-on-fork}}. - -@table @code -@kindex set detach-on-fork -@item set detach-on-fork @var{mode} -Tells gdb whether to detach one of the processes after a fork, or -retain debugger control over them both. - -@table @code -@item on -The child process (or parent process, depending on the value of -@code{follow-fork-mode}) will be detached and allowed to run -independently. This is the default. - -@item off -Both processes will be held under the control of @value{GDBN}. -One process (child or parent, depending on the value of -@code{follow-fork-mode}) is debugged as usual, while the other -is held suspended. - -@end table - -@kindex show detach-on-fork -@item show detach-on-fork -Show whether detach-on-fork mode is on/off. -@end table - -If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN} -will retain control of all forked processes (including nested forks). -You can list the forked processes under the control of @value{GDBN} by -using the @w{@code{info inferiors}} command, and switch from one fork -to another by using the @code{inferior} command (@pxref{Inferiors and -Programs, ,Debugging Multiple Inferiors and Programs}). - -To quit debugging one of the forked processes, you can either detach -from it by using the @w{@code{detach inferiors}} command (allowing it -to run independently), or kill it using the @w{@code{kill inferiors}} -command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors -and Programs}. - -If you ask to debug a child process and a @code{vfork} is followed by an -@code{exec}, @value{GDBN} executes the new target up to the first -breakpoint in the new target. If you have a breakpoint set on -@code{main} in your original program, the breakpoint will also be set on -the child process's @code{main}. - -On some systems, when a child process is spawned by @code{vfork}, you -cannot debug the child or parent until an @code{exec} call completes. - -If you issue a @code{run} command to @value{GDBN} after an @code{exec} -call executes, the new target restarts. To restart the parent -process, use the @code{file} command with the parent executable name -as its argument. By default, after an @code{exec} call executes, -@value{GDBN} discards the symbols of the previous executable image. -You can change this behaviour with the @w{@code{set follow-exec-mode}} -command. - -@table @code -@kindex set follow-exec-mode -@item set follow-exec-mode @var{mode} - -Set debugger response to a program call of @code{exec}. An -@code{exec} call replaces the program image of a process. - -@code{follow-exec-mode} can be: - -@table @code -@item new -@value{GDBN} creates a new inferior and rebinds the process to this -new inferior. The program the process was running before the -@code{exec} call can be restarted afterwards by restarting the -original inferior. - -For example: - -@smallexample -(@value{GDBP}) info inferiors -(gdb) info inferior - Id Description Executable -* 1 prog1 -(@value{GDBP}) run -process 12020 is executing new program: prog2 -Program exited normally. -(@value{GDBP}) info inferiors - Id Description Executable -* 2 prog2 - 1 prog1 -@end smallexample - -@item same -@value{GDBN} keeps the process bound to the same inferior. The new -executable image replaces the previous executable loaded in the -inferior. Restarting the inferior after the @code{exec} call, with -e.g., the @code{run} command, restarts the executable the process was -running after the @code{exec} call. This is the default mode. - -For example: - -@smallexample -(@value{GDBP}) info inferiors - Id Description Executable -* 1 prog1 -(@value{GDBP}) run -process 12020 is executing new program: prog2 -Program exited normally. -(@value{GDBP}) info inferiors - Id Description Executable -* 1 prog2 -@end smallexample - -@end table -@end table - -You can use the @code{catch} command to make @value{GDBN} stop whenever -a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set -Catchpoints, ,Setting Catchpoints}. - -@node Checkpoint/Restart -@section Setting a @emph{Bookmark} to Return to Later - -@cindex checkpoint -@cindex restart -@cindex bookmark -@cindex snapshot of a process -@cindex rewind program state - -On certain operating systems@footnote{Currently, only -@sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a -program's state, called a @dfn{checkpoint}, and come back to it -later. - -Returning to a checkpoint effectively undoes everything that has -happened in the program since the @code{checkpoint} was saved. This -includes changes in memory, registers, and even (within some limits) -system state. Effectively, it is like going back in time to the -moment when the checkpoint was saved. - -Thus, if you're stepping thru a program and you think you're -getting close to the point where things go wrong, you can save -a checkpoint. Then, if you accidentally go too far and miss -the critical statement, instead of having to restart your program -from the beginning, you can just go back to the checkpoint and -start again from there. - -This can be especially useful if it takes a lot of time or -steps to reach the point where you think the bug occurs. - -To use the @code{checkpoint}/@code{restart} method of debugging: - -@table @code -@kindex checkpoint -@item checkpoint -Save a snapshot of the debugged program's current execution state. -The @code{checkpoint} command takes no arguments, but each checkpoint -is assigned a small integer id, similar to a breakpoint id. - -@kindex info checkpoints -@item info checkpoints -List the checkpoints that have been saved in the current debugging -session. For each checkpoint, the following information will be -listed: - -@table @code -@item Checkpoint ID -@item Process ID -@item Code Address -@item Source line, or label -@end table - -@kindex restart @var{checkpoint-id} -@item restart @var{checkpoint-id} -Restore the program state that was saved as checkpoint number -@var{checkpoint-id}. All program variables, registers, stack frames -etc.@: will be returned to the values that they had when the checkpoint -was saved. In essence, gdb will ``wind back the clock'' to the point -in time when the checkpoint was saved. - -Note that breakpoints, @value{GDBN} variables, command history etc. -are not affected by restoring a checkpoint. In general, a checkpoint -only restores things that reside in the program being debugged, not in -the debugger. - -@kindex delete checkpoint @var{checkpoint-id} -@item delete checkpoint @var{checkpoint-id} -Delete the previously-saved checkpoint identified by @var{checkpoint-id}. - -@end table - -Returning to a previously saved checkpoint will restore the user state -of the program being debugged, plus a significant subset of the system -(OS) state, including file pointers. It won't ``un-write'' data from -a file, but it will rewind the file pointer to the previous location, -so that the previously written data can be overwritten. For files -opened in read mode, the pointer will also be restored so that the -previously read data can be read again. - -Of course, characters that have been sent to a printer (or other -external device) cannot be ``snatched back'', and characters received -from eg.@: a serial device can be removed from internal program buffers, -but they cannot be ``pushed back'' into the serial pipeline, ready to -be received again. Similarly, the actual contents of files that have -been changed cannot be restored (at this time). - -However, within those constraints, you actually can ``rewind'' your -program to a previously saved point in time, and begin debugging it -again --- and you can change the course of events so as to debug a -different execution path this time. - -@cindex checkpoints and process id -Finally, there is one bit of internal program state that will be -different when you return to a checkpoint --- the program's process -id. Each checkpoint will have a unique process id (or @var{pid}), -and each will be different from the program's original @var{pid}. -If your program has saved a local copy of its process id, this could -potentially pose a problem. - -@subsection A Non-obvious Benefit of Using Checkpoints - -On some systems such as @sc{gnu}/Linux, address space randomization -is performed on new processes for security reasons. This makes it -difficult or impossible to set a breakpoint, or watchpoint, on an -absolute address if you have to restart the program, since the -absolute location of a symbol will change from one execution to the -next. - -A checkpoint, however, is an @emph{identical} copy of a process. -Therefore if you create a checkpoint at (eg.@:) the start of main, -and simply return to that checkpoint instead of restarting the -process, you can avoid the effects of address randomization and -your symbols will all stay in the same place. - -@node Stopping -@chapter Stopping and Continuing - -The principal purposes of using a debugger are so that you can stop your -program before it terminates; or so that, if your program runs into -trouble, you can investigate and find out why. - -Inside @value{GDBN}, your program may stop for any of several reasons, -such as a signal, a breakpoint, or reaching a new line after a -@value{GDBN} command such as @code{step}. You may then examine and -change variables, set new breakpoints or remove old ones, and then -continue execution. Usually, the messages shown by @value{GDBN} provide -ample explanation of the status of your program---but you can also -explicitly request this information at any time. - -@table @code -@kindex info program -@item info program -Display information about the status of your program: whether it is -running or not, what process it is, and why it stopped. -@end table - -@menu -* Breakpoints:: Breakpoints, watchpoints, and catchpoints -* Continuing and Stepping:: Resuming execution -* Skipping Over Functions and Files:: - Skipping over functions and files -* Signals:: Signals -* Thread Stops:: Stopping and starting multi-thread programs -@end menu - -@node Breakpoints -@section Breakpoints, Watchpoints, and Catchpoints - -@cindex breakpoints -A @dfn{breakpoint} makes your program stop whenever a certain point in -the program is reached. For each breakpoint, you can add conditions to -control in finer detail whether your program stops. You can set -breakpoints with the @code{break} command and its variants (@pxref{Set -Breaks, ,Setting Breakpoints}), to specify the place where your program -should stop by line number, function name or exact address in the -program. - -On some systems, you can set breakpoints in shared libraries before -the executable is run. There is a minor limitation on HP-UX systems: -you must wait until the executable is run in order to set breakpoints -in shared library routines that are not called directly by the program -(for example, routines that are arguments in a @code{pthread_create} -call). - -@cindex watchpoints -@cindex data breakpoints -@cindex memory tracing -@cindex breakpoint on memory address -@cindex breakpoint on variable modification -A @dfn{watchpoint} is a special breakpoint that stops your program -when the value of an expression changes. The expression may be a value -of a variable, or it could involve values of one or more variables -combined by operators, such as @samp{a + b}. This is sometimes called -@dfn{data breakpoints}. You must use a different command to set -watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside -from that, you can manage a watchpoint like any other breakpoint: you -enable, disable, and delete both breakpoints and watchpoints using the -same commands. - -You can arrange to have values from your program displayed automatically -whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,, -Automatic Display}. - -@cindex catchpoints -@cindex breakpoint on events -A @dfn{catchpoint} is another special breakpoint that stops your program -when a certain kind of event occurs, such as the throwing of a C@t{++} -exception or the loading of a library. As with watchpoints, you use a -different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting -Catchpoints}), but aside from that, you can manage a catchpoint like any -other breakpoint. (To stop when your program receives a signal, use the -@code{handle} command; see @ref{Signals, ,Signals}.) - -@cindex breakpoint numbers -@cindex numbers for breakpoints -@value{GDBN} assigns a number to each breakpoint, watchpoint, or -catchpoint when you create it; these numbers are successive integers -starting with one. In many of the commands for controlling various -features of breakpoints you use the breakpoint number to say which -breakpoint you want to change. Each breakpoint may be @dfn{enabled} or -@dfn{disabled}; if disabled, it has no effect on your program until you -enable it again. - -@cindex breakpoint ranges -@cindex ranges of breakpoints -Some @value{GDBN} commands accept a range of breakpoints on which to -operate. A breakpoint range is either a single breakpoint number, like -@samp{5}, or two such numbers, in increasing order, separated by a -hyphen, like @samp{5-7}. When a breakpoint range is given to a command, -all breakpoints in that range are operated on. - -@menu -* Set Breaks:: Setting breakpoints -* Set Watchpoints:: Setting watchpoints -* Set Catchpoints:: Setting catchpoints -* Delete Breaks:: Deleting breakpoints -* Disabling:: Disabling breakpoints -* Conditions:: Break conditions -* Break Commands:: Breakpoint command lists -* Dynamic Printf:: Dynamic printf -* Save Breakpoints:: How to save breakpoints in a file -* Static Probe Points:: Listing static probe points -* Error in Breakpoints:: ``Cannot insert breakpoints'' -* Breakpoint-related Warnings:: ``Breakpoint address adjusted...'' -@end menu - -@node Set Breaks -@subsection Setting Breakpoints - -@c FIXME LMB what does GDB do if no code on line of breakpt? -@c consider in particular declaration with/without initialization. -@c -@c FIXME 2 is there stuff on this already? break at fun start, already init? - -@kindex break -@kindex b @r{(@code{break})} -@vindex $bpnum@r{, convenience variable} -@cindex latest breakpoint -Breakpoints are set with the @code{break} command (abbreviated -@code{b}). The debugger convenience variable @samp{$bpnum} records the -number of the breakpoint you've set most recently; see @ref{Convenience -Vars,, Convenience Variables}, for a discussion of what you can do with -convenience variables. - -@table @code -@item break @var{location} -Set a breakpoint at the given @var{location}, which can specify a -function name, a line number, or an address of an instruction. -(@xref{Specify Location}, for a list of all the possible ways to -specify a @var{location}.) The breakpoint will stop your program just -before it executes any of the code in the specified @var{location}. - -When using source languages that permit overloading of symbols, such as -C@t{++}, a function name may refer to more than one possible place to break. -@xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of -that situation. - -It is also possible to insert a breakpoint that will stop the program -only if a specific thread (@pxref{Thread-Specific Breakpoints}) -or a specific task (@pxref{Ada Tasks}) hits that breakpoint. - -@item break -When called without any arguments, @code{break} sets a breakpoint at -the next instruction to be executed in the selected stack frame -(@pxref{Stack, ,Examining the Stack}). In any selected frame but the -innermost, this makes your program stop as soon as control -returns to that frame. This is similar to the effect of a -@code{finish} command in the frame inside the selected frame---except -that @code{finish} does not leave an active breakpoint. If you use -@code{break} without an argument in the innermost frame, @value{GDBN} stops -the next time it reaches the current location; this may be useful -inside loops. - -@value{GDBN} normally ignores breakpoints when it resumes execution, until at -least one instruction has been executed. If it did not do this, you -would be unable to proceed past a breakpoint without first disabling the -breakpoint. This rule applies whether or not the breakpoint already -existed when your program stopped. - -@item break @dots{} if @var{cond} -Set a breakpoint with condition @var{cond}; evaluate the expression -@var{cond} each time the breakpoint is reached, and stop only if the -value is nonzero---that is, if @var{cond} evaluates as true. -@samp{@dots{}} stands for one of the possible arguments described -above (or no argument) specifying where to break. @xref{Conditions, -,Break Conditions}, for more information on breakpoint conditions. - -@kindex tbreak -@item tbreak @var{args} -Set a breakpoint enabled only for one stop. @var{args} are the -same as for the @code{break} command, and the breakpoint is set in the same -way, but the breakpoint is automatically deleted after the first time your -program stops there. @xref{Disabling, ,Disabling Breakpoints}. - -@kindex hbreak -@cindex hardware breakpoints -@item hbreak @var{args} -Set a hardware-assisted breakpoint. @var{args} are the same as for the -@code{break} command and the breakpoint is set in the same way, but the -breakpoint requires hardware support and some target hardware may not -have this support. The main purpose of this is EPROM/ROM code -debugging, so you can set a breakpoint at an instruction without -changing the instruction. This can be used with the new trap-generation -provided by SPARClite DSU and most x86-based targets. These targets -will generate traps when a program accesses some data or instruction -address that is assigned to the debug registers. However the hardware -breakpoint registers can take a limited number of breakpoints. For -example, on the DSU, only two data breakpoints can be set at a time, and -@value{GDBN} will reject this command if more than two are used. Delete -or disable unused hardware breakpoints before setting new ones -(@pxref{Disabling, ,Disabling Breakpoints}). -@xref{Conditions, ,Break Conditions}. -For remote targets, you can restrict the number of hardware -breakpoints @value{GDBN} will use, see @ref{set remote -hardware-breakpoint-limit}. - -@kindex thbreak -@item thbreak @var{args} -Set a hardware-assisted breakpoint enabled only for one stop. @var{args} -are the same as for the @code{hbreak} command and the breakpoint is set in -the same way. However, like the @code{tbreak} command, -the breakpoint is automatically deleted after the -first time your program stops there. Also, like the @code{hbreak} -command, the breakpoint requires hardware support and some target hardware -may not have this support. @xref{Disabling, ,Disabling Breakpoints}. -See also @ref{Conditions, ,Break Conditions}. - -@kindex rbreak -@cindex regular expression -@cindex breakpoints at functions matching a regexp -@cindex set breakpoints in many functions -@item rbreak @var{regex} -Set breakpoints on all functions matching the regular expression -@var{regex}. This command sets an unconditional breakpoint on all -matches, printing a list of all breakpoints it set. Once these -breakpoints are set, they are treated just like the breakpoints set with -the @code{break} command. You can delete them, disable them, or make -them conditional the same way as any other breakpoint. - -The syntax of the regular expression is the standard one used with tools -like @file{grep}. Note that this is different from the syntax used by -shells, so for instance @code{foo*} matches all functions that include -an @code{fo} followed by zero or more @code{o}s. There is an implicit -@code{.*} leading and trailing the regular expression you supply, so to -match only functions that begin with @code{foo}, use @code{^foo}. - -@cindex non-member C@t{++} functions, set breakpoint in -When debugging C@t{++} programs, @code{rbreak} is useful for setting -breakpoints on overloaded functions that are not members of any special -classes. - -@cindex set breakpoints on all functions -The @code{rbreak} command can be used to set breakpoints in -@strong{all} the functions in a program, like this: - -@smallexample -(@value{GDBP}) rbreak . -@end smallexample - -@item rbreak @var{file}:@var{regex} -If @code{rbreak} is called with a filename qualification, it limits -the search for functions matching the given regular expression to the -specified @var{file}. This can be used, for example, to set breakpoints on -every function in a given file: - -@smallexample -(@value{GDBP}) rbreak file.c:. -@end smallexample - -The colon separating the filename qualifier from the regex may -optionally be surrounded by spaces. - -@kindex info breakpoints -@cindex @code{$_} and @code{info breakpoints} -@item info breakpoints @r{[}@var{n}@dots{}@r{]} -@itemx info break @r{[}@var{n}@dots{}@r{]} -Print a table of all breakpoints, watchpoints, and catchpoints set and -not deleted. Optional argument @var{n} means print information only -about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)). -For each breakpoint, following columns are printed: - -@table @emph -@item Breakpoint Numbers -@item Type -Breakpoint, watchpoint, or catchpoint. -@item Disposition -Whether the breakpoint is marked to be disabled or deleted when hit. -@item Enabled or Disabled -Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints -that are not enabled. -@item Address -Where the breakpoint is in your program, as a memory address. For a -pending breakpoint whose address is not yet known, this field will -contain @samp{}. Such breakpoint won't fire until a shared -library that has the symbol or line referred by breakpoint is loaded. -See below for details. A breakpoint with several locations will -have @samp{} in this field---see below for details. -@item What -Where the breakpoint is in the source for your program, as a file and -line number. For a pending breakpoint, the original string passed to -the breakpoint command will be listed as it cannot be resolved until -the appropriate shared library is loaded in the future. -@end table - -@noindent -If a breakpoint is conditional, there are two evaluation modes: ``host'' and -``target''. If mode is ``host'', breakpoint condition evaluation is done by -@value{GDBN} on the host's side. If it is ``target'', then the condition -is evaluated by the target. The @code{info break} command shows -the condition on the line following the affected breakpoint, together with -its condition evaluation mode in between parentheses. - -Breakpoint commands, if any, are listed after that. A pending breakpoint is -allowed to have a condition specified for it. The condition is not parsed for -validity until a shared library is loaded that allows the pending -breakpoint to resolve to a valid location. - -@noindent -@code{info break} with a breakpoint -number @var{n} as argument lists only that breakpoint. The -convenience variable @code{$_} and the default examining-address for -the @code{x} command are set to the address of the last breakpoint -listed (@pxref{Memory, ,Examining Memory}). - -@noindent -@code{info break} displays a count of the number of times the breakpoint -has been hit. This is especially useful in conjunction with the -@code{ignore} command. You can ignore a large number of breakpoint -hits, look at the breakpoint info to see how many times the breakpoint -was hit, and then run again, ignoring one less than that number. This -will get you quickly to the last hit of that breakpoint. - -@noindent -For a breakpoints with an enable count (xref) greater than 1, -@code{info break} also displays that count. - -@end table - -@value{GDBN} allows you to set any number of breakpoints at the same place in -your program. There is nothing silly or meaningless about this. When -the breakpoints are conditional, this is even useful -(@pxref{Conditions, ,Break Conditions}). - -@cindex multiple locations, breakpoints -@cindex breakpoints, multiple locations -It is possible that a breakpoint corresponds to several locations -in your program. Examples of this situation are: - -@itemize @bullet -@item -Multiple functions in the program may have the same name. - -@item -For a C@t{++} constructor, the @value{NGCC} compiler generates several -instances of the function body, used in different cases. - -@item -For a C@t{++} template function, a given line in the function can -correspond to any number of instantiations. - -@item -For an inlined function, a given source line can correspond to -several places where that function is inlined. -@end itemize - -In all those cases, @value{GDBN} will insert a breakpoint at all -the relevant locations. - -A breakpoint with multiple locations is displayed in the breakpoint -table using several rows---one header row, followed by one row for -each breakpoint location. The header row has @samp{} in the -address column. The rows for individual locations contain the actual -addresses for locations, and show the functions to which those -locations belong. The number column for a location is of the form -@var{breakpoint-number}.@var{location-number}. - -For example: - -@smallexample -Num Type Disp Enb Address What -1 breakpoint keep y - stop only if i==1 - breakpoint already hit 1 time -1.1 y 0x080486a2 in void foo() at t.cc:8 -1.2 y 0x080486ca in void foo() at t.cc:8 -@end smallexample - -Each location can be individually enabled or disabled by passing -@var{breakpoint-number}.@var{location-number} as argument to the -@code{enable} and @code{disable} commands. Note that you cannot -delete the individual locations from the list, you can only delete the -entire list of locations that belong to their parent breakpoint (with -the @kbd{delete @var{num}} command, where @var{num} is the number of -the parent breakpoint, 1 in the above example). Disabling or enabling -the parent breakpoint (@pxref{Disabling}) affects all of the locations -that belong to that breakpoint. - -@cindex pending breakpoints -It's quite common to have a breakpoint inside a shared library. -Shared libraries can be loaded and unloaded explicitly, -and possibly repeatedly, as the program is executed. To support -this use case, @value{GDBN} updates breakpoint locations whenever -any shared library is loaded or unloaded. Typically, you would -set a breakpoint in a shared library at the beginning of your -debugging session, when the library is not loaded, and when the -symbols from the library are not available. When you try to set -breakpoint, @value{GDBN} will ask you if you want to set -a so called @dfn{pending breakpoint}---breakpoint whose address -is not yet resolved. - -After the program is run, whenever a new shared library is loaded, -@value{GDBN} reevaluates all the breakpoints. When a newly loaded -shared library contains the symbol or line referred to by some -pending breakpoint, that breakpoint is resolved and becomes an -ordinary breakpoint. When a library is unloaded, all breakpoints -that refer to its symbols or source lines become pending again. - -This logic works for breakpoints with multiple locations, too. For -example, if you have a breakpoint in a C@t{++} template function, and -a newly loaded shared library has an instantiation of that template, -a new location is added to the list of locations for the breakpoint. - -Except for having unresolved address, pending breakpoints do not -differ from regular breakpoints. You can set conditions or commands, -enable and disable them and perform other breakpoint operations. - -@value{GDBN} provides some additional commands for controlling what -happens when the @samp{break} command cannot resolve breakpoint -address specification to an address: - -@kindex set breakpoint pending -@kindex show breakpoint pending -@table @code -@item set breakpoint pending auto -This is the default behavior. When @value{GDBN} cannot find the breakpoint -location, it queries you whether a pending breakpoint should be created. - -@item set breakpoint pending on -This indicates that an unrecognized breakpoint location should automatically -result in a pending breakpoint being created. - -@item set breakpoint pending off -This indicates that pending breakpoints are not to be created. Any -unrecognized breakpoint location results in an error. This setting does -not affect any pending breakpoints previously created. - -@item show breakpoint pending -Show the current behavior setting for creating pending breakpoints. -@end table - -The settings above only affect the @code{break} command and its -variants. Once breakpoint is set, it will be automatically updated -as shared libraries are loaded and unloaded. - -@cindex automatic hardware breakpoints -For some targets, @value{GDBN} can automatically decide if hardware or -software breakpoints should be used, depending on whether the -breakpoint address is read-only or read-write. This applies to -breakpoints set with the @code{break} command as well as to internal -breakpoints set by commands like @code{next} and @code{finish}. For -breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware -breakpoints. - -You can control this automatic behaviour with the following commands:: - -@kindex set breakpoint auto-hw -@kindex show breakpoint auto-hw -@table @code -@item set breakpoint auto-hw on -This is the default behavior. When @value{GDBN} sets a breakpoint, it -will try to use the target memory map to decide if software or hardware -breakpoint must be used. - -@item set breakpoint auto-hw off -This indicates @value{GDBN} should not automatically select breakpoint -type. If the target provides a memory map, @value{GDBN} will warn when -trying to set software breakpoint at a read-only address. -@end table - -@value{GDBN} normally implements breakpoints by replacing the program code -at the breakpoint address with a special instruction, which, when -executed, given control to the debugger. By default, the program -code is so modified only when the program is resumed. As soon as -the program stops, @value{GDBN} restores the original instructions. This -behaviour guards against leaving breakpoints inserted in the -target should gdb abrubptly disconnect. However, with slow remote -targets, inserting and removing breakpoint can reduce the performance. -This behavior can be controlled with the following commands:: - -@kindex set breakpoint always-inserted -@kindex show breakpoint always-inserted -@table @code -@item set breakpoint always-inserted off -All breakpoints, including newly added by the user, are inserted in -the target only when the target is resumed. All breakpoints are -removed from the target when it stops. - -@item set breakpoint always-inserted on -Causes all breakpoints to be inserted in the target at all times. If -the user adds a new breakpoint, or changes an existing breakpoint, the -breakpoints in the target are updated immediately. A breakpoint is -removed from the target only when breakpoint itself is removed. - -@cindex non-stop mode, and @code{breakpoint always-inserted} -@item set breakpoint always-inserted auto -This is the default mode. If @value{GDBN} is controlling the inferior -in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if -@code{breakpoint always-inserted} mode is on. If @value{GDBN} is -controlling the inferior in all-stop mode, @value{GDBN} behaves as if -@code{breakpoint always-inserted} mode is off. -@end table - -@value{GDBN} handles conditional breakpoints by evaluating these conditions -when a breakpoint breaks. If the condition is true, then the process being -debugged stops, otherwise the process is resumed. - -If the target supports evaluating conditions on its end, @value{GDBN} may -download the breakpoint, together with its conditions, to it. - -This feature can be controlled via the following commands: - -@kindex set breakpoint condition-evaluation -@kindex show breakpoint condition-evaluation -@table @code -@item set breakpoint condition-evaluation host -This option commands @value{GDBN} to evaluate the breakpoint -conditions on the host's side. Unconditional breakpoints are sent to -the target which in turn receives the triggers and reports them back to GDB -for condition evaluation. This is the standard evaluation mode. - -@item set breakpoint condition-evaluation target -This option commands @value{GDBN} to download breakpoint conditions -to the target at the moment of their insertion. The target -is responsible for evaluating the conditional expression and reporting -breakpoint stop events back to @value{GDBN} whenever the condition -is true. Due to limitations of target-side evaluation, some conditions -cannot be evaluated there, e.g., conditions that depend on local data -that is only known to the host. Examples include -conditional expressions involving convenience variables, complex types -that cannot be handled by the agent expression parser and expressions -that are too long to be sent over to the target, specially when the -target is a remote system. In these cases, the conditions will be -evaluated by @value{GDBN}. - -@item set breakpoint condition-evaluation auto -This is the default mode. If the target supports evaluating breakpoint -conditions on its end, @value{GDBN} will download breakpoint conditions to -the target (limitations mentioned previously apply). If the target does -not support breakpoint condition evaluation, then @value{GDBN} will fallback -to evaluating all these conditions on the host's side. -@end table - - -@cindex negative breakpoint numbers -@cindex internal @value{GDBN} breakpoints -@value{GDBN} itself sometimes sets breakpoints in your program for -special purposes, such as proper handling of @code{longjmp} (in C -programs). These internal breakpoints are assigned negative numbers, -starting with @code{-1}; @samp{info breakpoints} does not display them. -You can see these breakpoints with the @value{GDBN} maintenance command -@samp{maint info breakpoints} (@pxref{maint info breakpoints}). - - -@node Set Watchpoints -@subsection Setting Watchpoints - -@cindex setting watchpoints -You can use a watchpoint to stop execution whenever the value of an -expression changes, without having to predict a particular place where -this may happen. (This is sometimes called a @dfn{data breakpoint}.) -The expression may be as simple as the value of a single variable, or -as complex as many variables combined by operators. Examples include: - -@itemize @bullet -@item -A reference to the value of a single variable. - -@item -An address cast to an appropriate data type. For example, -@samp{*(int *)0x12345678} will watch a 4-byte region at the specified -address (assuming an @code{int} occupies 4 bytes). - -@item -An arbitrarily complex expression, such as @samp{a*b + c/d}. The -expression can use any operators valid in the program's native -language (@pxref{Languages}). -@end itemize - -You can set a watchpoint on an expression even if the expression can -not be evaluated yet. For instance, you can set a watchpoint on -@samp{*global_ptr} before @samp{global_ptr} is initialized. -@value{GDBN} will stop when your program sets @samp{global_ptr} and -the expression produces a valid value. If the expression becomes -valid in some other way than changing a variable (e.g.@: if the memory -pointed to by @samp{*global_ptr} becomes readable as the result of a -@code{malloc} call), @value{GDBN} may not stop until the next time -the expression changes. - -@cindex software watchpoints -@cindex hardware watchpoints -Depending on your system, watchpoints may be implemented in software or -hardware. @value{GDBN} does software watchpointing by single-stepping your -program and testing the variable's value each time, which is hundreds of -times slower than normal execution. (But this may still be worth it, to -catch errors where you have no clue what part of your program is the -culprit.) - -On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other -x86-based targets, @value{GDBN} includes support for hardware -watchpoints, which do not slow down the running of your program. - -@table @code -@kindex watch -@item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]} -Set a watchpoint for an expression. @value{GDBN} will break when the -expression @var{expr} is written into by the program and its value -changes. The simplest (and the most popular) use of this command is -to watch the value of a single variable: - -@smallexample -(@value{GDBP}) watch foo -@end smallexample - -If the command includes a @code{@r{[}thread @var{threadnum}@r{]}} -argument, @value{GDBN} breaks only when the thread identified by -@var{threadnum} changes the value of @var{expr}. If any other threads -change the value of @var{expr}, @value{GDBN} will not break. Note -that watchpoints restricted to a single thread in this way only work -with Hardware Watchpoints. - -Ordinarily a watchpoint respects the scope of variables in @var{expr} -(see below). The @code{-location} argument tells @value{GDBN} to -instead watch the memory referred to by @var{expr}. In this case, -@value{GDBN} will evaluate @var{expr}, take the address of the result, -and watch the memory at that address. The type of the result is used -to determine the size of the watched memory. If the expression's -result does not have an address, then @value{GDBN} will print an -error. - -The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation -of masked watchpoints, if the current architecture supports this -feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC -Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition -to an address to watch. The mask specifies that some bits of an address -(the bits which are reset in the mask) should be ignored when matching -the address accessed by the inferior against the watchpoint address. -Thus, a masked watchpoint watches many addresses simultaneously---those -addresses whose unmasked bits are identical to the unmasked bits in the -watchpoint address. The @code{mask} argument implies @code{-location}. -Examples: - -@smallexample -(@value{GDBP}) watch foo mask 0xffff00ff -(@value{GDBP}) watch *0xdeadbeef mask 0xffffff00 -@end smallexample - -@kindex rwatch -@item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]} -Set a watchpoint that will break when the value of @var{expr} is read -by the program. - -@kindex awatch -@item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]} -Set a watchpoint that will break when @var{expr} is either read from -or written into by the program. - -@kindex info watchpoints @r{[}@var{n}@dots{}@r{]} -@item info watchpoints @r{[}@var{n}@dots{}@r{]} -This command prints a list of watchpoints, using the same format as -@code{info break} (@pxref{Set Breaks}). -@end table - -If you watch for a change in a numerically entered address you need to -dereference it, as the address itself is just a constant number which will -never change. @value{GDBN} refuses to create a watchpoint that watches -a never-changing value: - -@smallexample -(@value{GDBP}) watch 0x600850 -Cannot watch constant value 0x600850. -(@value{GDBP}) watch *(int *) 0x600850 -Watchpoint 1: *(int *) 6293584 -@end smallexample - -@value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware -watchpoints execute very quickly, and the debugger reports a change in -value at the exact instruction where the change occurs. If @value{GDBN} -cannot set a hardware watchpoint, it sets a software watchpoint, which -executes more slowly and reports the change in value at the next -@emph{statement}, not the instruction, after the change occurs. - -@cindex use only software watchpoints -You can force @value{GDBN} to use only software watchpoints with the -@kbd{set can-use-hw-watchpoints 0} command. With this variable set to -zero, @value{GDBN} will never try to use hardware watchpoints, even if -the underlying system supports them. (Note that hardware-assisted -watchpoints that were set @emph{before} setting -@code{can-use-hw-watchpoints} to zero will still use the hardware -mechanism of watching expression values.) - -@table @code -@item set can-use-hw-watchpoints -@kindex set can-use-hw-watchpoints -Set whether or not to use hardware watchpoints. - -@item show can-use-hw-watchpoints -@kindex show can-use-hw-watchpoints -Show the current mode of using hardware watchpoints. -@end table - -For remote targets, you can restrict the number of hardware -watchpoints @value{GDBN} will use, see @ref{set remote -hardware-breakpoint-limit}. - -When you issue the @code{watch} command, @value{GDBN} reports - -@smallexample -Hardware watchpoint @var{num}: @var{expr} -@end smallexample - -@noindent -if it was able to set a hardware watchpoint. - -Currently, the @code{awatch} and @code{rwatch} commands can only set -hardware watchpoints, because accesses to data that don't change the -value of the watched expression cannot be detected without examining -every instruction as it is being executed, and @value{GDBN} does not do -that currently. If @value{GDBN} finds that it is unable to set a -hardware breakpoint with the @code{awatch} or @code{rwatch} command, it -will print a message like this: - -@smallexample -Expression cannot be implemented with read/access watchpoint. -@end smallexample - -Sometimes, @value{GDBN} cannot set a hardware watchpoint because the -data type of the watched expression is wider than what a hardware -watchpoint on the target machine can handle. For example, some systems -can only watch regions that are up to 4 bytes wide; on such systems you -cannot set hardware watchpoints for an expression that yields a -double-precision floating-point number (which is typically 8 bytes -wide). As a work-around, it might be possible to break the large region -into a series of smaller ones and watch them with separate watchpoints. - -If you set too many hardware watchpoints, @value{GDBN} might be unable -to insert all of them when you resume the execution of your program. -Since the precise number of active watchpoints is unknown until such -time as the program is about to be resumed, @value{GDBN} might not be -able to warn you about this when you set the watchpoints, and the -warning will be printed only when the program is resumed: - -@smallexample -Hardware watchpoint @var{num}: Could not insert watchpoint -@end smallexample - -@noindent -If this happens, delete or disable some of the watchpoints. - -Watching complex expressions that reference many variables can also -exhaust the resources available for hardware-assisted watchpoints. -That's because @value{GDBN} needs to watch every variable in the -expression with separately allocated resources. - -If you call a function interactively using @code{print} or @code{call}, -any watchpoints you have set will be inactive until @value{GDBN} reaches another -kind of breakpoint or the call completes. - -@value{GDBN} automatically deletes watchpoints that watch local -(automatic) variables, or expressions that involve such variables, when -they go out of scope, that is, when the execution leaves the block in -which these variables were defined. In particular, when the program -being debugged terminates, @emph{all} local variables go out of scope, -and so only watchpoints that watch global variables remain set. If you -rerun the program, you will need to set all such watchpoints again. One -way of doing that would be to set a code breakpoint at the entry to the -@code{main} function and when it breaks, set all the watchpoints. - -@cindex watchpoints and threads -@cindex threads and watchpoints -In multi-threaded programs, watchpoints will detect changes to the -watched expression from every thread. - -@quotation -@emph{Warning:} In multi-threaded programs, software watchpoints -have only limited usefulness. If @value{GDBN} creates a software -watchpoint, it can only watch the value of an expression @emph{in a -single thread}. If you are confident that the expression can only -change due to the current thread's activity (and if you are also -confident that no other thread can become current), then you can use -software watchpoints as usual. However, @value{GDBN} may not notice -when a non-current thread's activity changes the expression. (Hardware -watchpoints, in contrast, watch an expression in all threads.) -@end quotation - -@xref{set remote hardware-watchpoint-limit}. - -@node Set Catchpoints -@subsection Setting Catchpoints -@cindex catchpoints, setting -@cindex exception handlers -@cindex event handling - -You can use @dfn{catchpoints} to cause the debugger to stop for certain -kinds of program events, such as C@t{++} exceptions or the loading of a -shared library. Use the @code{catch} command to set a catchpoint. - -@table @code -@kindex catch -@item catch @var{event} -Stop when @var{event} occurs. @var{event} can be any of the following: -@table @code -@item throw -@cindex stop on C@t{++} exceptions -The throwing of a C@t{++} exception. - -@item catch -The catching of a C@t{++} exception. - -@item exception -@cindex Ada exception catching -@cindex catch Ada exceptions -An Ada exception being raised. If an exception name is specified -at the end of the command (eg @code{catch exception Program_Error}), -the debugger will stop only when this specific exception is raised. -Otherwise, the debugger stops execution when any Ada exception is raised. - -When inserting an exception catchpoint on a user-defined exception whose -name is identical to one of the exceptions defined by the language, the -fully qualified name must be used as the exception name. Otherwise, -@value{GDBN} will assume that it should stop on the pre-defined exception -rather than the user-defined one. For instance, assuming an exception -called @code{Constraint_Error} is defined in package @code{Pck}, then -the command to use to catch such exceptions is @kbd{catch exception -Pck.Constraint_Error}. - -@item exception unhandled -An exception that was raised but is not handled by the program. - -@item assert -A failed Ada assertion. - -@item exec -@cindex break on fork/exec -A call to @code{exec}. This is currently only available for HP-UX -and @sc{gnu}/Linux. - -@item syscall -@itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{} -@cindex break on a system call. -A call to or return from a system call, a.k.a.@: @dfn{syscall}. A -syscall is a mechanism for application programs to request a service -from the operating system (OS) or one of the OS system services. -@value{GDBN} can catch some or all of the syscalls issued by the -debuggee, and show the related information for each syscall. If no -argument is specified, calls to and returns from all system calls -will be caught. - -@var{name} can be any system call name that is valid for the -underlying OS. Just what syscalls are valid depends on the OS. On -GNU and Unix systems, you can find the full list of valid syscall -names on @file{/usr/include/asm/unistd.h}. - -@c For MS-Windows, the syscall names and the corresponding numbers -@c can be found, e.g., on this URL: -@c http://www.metasploit.com/users/opcode/syscalls.html -@c but we don't support Windows syscalls yet. - -Normally, @value{GDBN} knows in advance which syscalls are valid for -each OS, so you can use the @value{GDBN} command-line completion -facilities (@pxref{Completion,, command completion}) to list the -available choices. - -You may also specify the system call numerically. A syscall's -number is the value passed to the OS's syscall dispatcher to -identify the requested service. When you specify the syscall by its -name, @value{GDBN} uses its database of syscalls to convert the name -into the corresponding numeric code, but using the number directly -may be useful if @value{GDBN}'s database does not have the complete -list of syscalls on your system (e.g., because @value{GDBN} lags -behind the OS upgrades). - -The example below illustrates how this command works if you don't provide -arguments to it: - -@smallexample -(@value{GDBP}) catch syscall -Catchpoint 1 (syscall) -(@value{GDBP}) r -Starting program: /tmp/catch-syscall - -Catchpoint 1 (call to syscall 'close'), \ - 0xffffe424 in __kernel_vsyscall () -(@value{GDBP}) c -Continuing. - -Catchpoint 1 (returned from syscall 'close'), \ - 0xffffe424 in __kernel_vsyscall () -(@value{GDBP}) -@end smallexample - -Here is an example of catching a system call by name: - -@smallexample -(@value{GDBP}) catch syscall chroot -Catchpoint 1 (syscall 'chroot' [61]) -(@value{GDBP}) r -Starting program: /tmp/catch-syscall - -Catchpoint 1 (call to syscall 'chroot'), \ - 0xffffe424 in __kernel_vsyscall () -(@value{GDBP}) c -Continuing. - -Catchpoint 1 (returned from syscall 'chroot'), \ - 0xffffe424 in __kernel_vsyscall () -(@value{GDBP}) -@end smallexample - -An example of specifying a system call numerically. In the case -below, the syscall number has a corresponding entry in the XML -file, so @value{GDBN} finds its name and prints it: - -@smallexample -(@value{GDBP}) catch syscall 252 -Catchpoint 1 (syscall(s) 'exit_group') -(@value{GDBP}) r -Starting program: /tmp/catch-syscall - -Catchpoint 1 (call to syscall 'exit_group'), \ - 0xffffe424 in __kernel_vsyscall () -(@value{GDBP}) c -Continuing. - -Program exited normally. -(@value{GDBP}) -@end smallexample - -However, there can be situations when there is no corresponding name -in XML file for that syscall number. In this case, @value{GDBN} prints -a warning message saying that it was not able to find the syscall name, -but the catchpoint will be set anyway. See the example below: - -@smallexample -(@value{GDBP}) catch syscall 764 -warning: The number '764' does not represent a known syscall. -Catchpoint 2 (syscall 764) -(@value{GDBP}) -@end smallexample - -If you configure @value{GDBN} using the @samp{--without-expat} option, -it will not be able to display syscall names. Also, if your -architecture does not have an XML file describing its system calls, -you will not be able to see the syscall names. It is important to -notice that these two features are used for accessing the syscall -name database. In either case, you will see a warning like this: - -@smallexample -(@value{GDBP}) catch syscall -warning: Could not open "syscalls/i386-linux.xml" -warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'. -GDB will not be able to display syscall names. -Catchpoint 1 (syscall) -(@value{GDBP}) -@end smallexample - -Of course, the file name will change depending on your architecture and system. - -Still using the example above, you can also try to catch a syscall by its -number. In this case, you would see something like: - -@smallexample -(@value{GDBP}) catch syscall 252 -Catchpoint 1 (syscall(s) 252) -@end smallexample - -Again, in this case @value{GDBN} would not be able to display syscall's names. - -@item fork -A call to @code{fork}. This is currently only available for HP-UX -and @sc{gnu}/Linux. - -@item vfork -A call to @code{vfork}. This is currently only available for HP-UX -and @sc{gnu}/Linux. - -@item load @r{[}regexp@r{]} -@itemx unload @r{[}regexp@r{]} -The loading or unloading of a shared library. If @var{regexp} is -given, then the catchpoint will stop only if the regular expression -matches one of the affected libraries. - -@item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]} -The delivery of a signal. - -With no arguments, this catchpoint will catch any signal that is not -used internally by @value{GDBN}, specifically, all signals except -@samp{SIGTRAP} and @samp{SIGINT}. - -With the argument @samp{all}, all signals, including those used by -@value{GDBN}, will be caught. This argument cannot be used with other -signal names. - -Otherwise, the arguments are a list of signal names as given to -@code{handle} (@pxref{Signals}). Only signals specified in this list -will be caught. - -One reason that @code{catch signal} can be more useful than -@code{handle} is that you can attach commands and conditions to the -catchpoint. - -When a signal is caught by a catchpoint, the signal's @code{stop} and -@code{print} settings, as specified by @code{handle}, are ignored. -However, whether the signal is still delivered to the inferior depends -on the @code{pass} setting; this can be changed in the catchpoint's -commands. - -@end table - -@item tcatch @var{event} -Set a catchpoint that is enabled only for one stop. The catchpoint is -automatically deleted after the first time the event is caught. - -@end table - -Use the @code{info break} command to list the current catchpoints. - -There are currently some limitations to C@t{++} exception handling -(@code{catch throw} and @code{catch catch}) in @value{GDBN}: - -@itemize @bullet -@item -If you call a function interactively, @value{GDBN} normally returns -control to you when the function has finished executing. If the call -raises an exception, however, the call may bypass the mechanism that -returns control to you and cause your program either to abort or to -simply continue running until it hits a breakpoint, catches a signal -that @value{GDBN} is listening for, or exits. This is the case even if -you set a catchpoint for the exception; catchpoints on exceptions are -disabled within interactive calls. - -@item -You cannot raise an exception interactively. - -@item -You cannot install an exception handler interactively. -@end itemize - -@cindex raise exceptions -Sometimes @code{catch} is not the best way to debug exception handling: -if you need to know exactly where an exception is raised, it is better to -stop @emph{before} the exception handler is called, since that way you -can see the stack before any unwinding takes place. If you set a -breakpoint in an exception handler instead, it may not be easy to find -out where the exception was raised. - -To stop just before an exception handler is called, you need some -knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are -raised by calling a library function named @code{__raise_exception} -which has the following ANSI C interface: - -@smallexample - /* @var{addr} is where the exception identifier is stored. - @var{id} is the exception identifier. */ - void __raise_exception (void **addr, void *id); -@end smallexample - -@noindent -To make the debugger catch all exceptions before any stack -unwinding takes place, set a breakpoint on @code{__raise_exception} -(@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}). - -With a conditional breakpoint (@pxref{Conditions, ,Break Conditions}) -that depends on the value of @var{id}, you can stop your program when -a specific exception is raised. You can use multiple conditional -breakpoints to stop your program when any of a number of exceptions are -raised. - - -@node Delete Breaks -@subsection Deleting Breakpoints - -@cindex clearing breakpoints, watchpoints, catchpoints -@cindex deleting breakpoints, watchpoints, catchpoints -It is often necessary to eliminate a breakpoint, watchpoint, or -catchpoint once it has done its job and you no longer want your program -to stop there. This is called @dfn{deleting} the breakpoint. A -breakpoint that has been deleted no longer exists; it is forgotten. - -With the @code{clear} command you can delete breakpoints according to -where they are in your program. With the @code{delete} command you can -delete individual breakpoints, watchpoints, or catchpoints by specifying -their breakpoint numbers. - -It is not necessary to delete a breakpoint to proceed past it. @value{GDBN} -automatically ignores breakpoints on the first instruction to be executed -when you continue execution without changing the execution address. - -@table @code -@kindex clear -@item clear -Delete any breakpoints at the next instruction to be executed in the -selected stack frame (@pxref{Selection, ,Selecting a Frame}). When -the innermost frame is selected, this is a good way to delete a -breakpoint where your program just stopped. - -@item clear @var{location} -Delete any breakpoints set at the specified @var{location}. -@xref{Specify Location}, for the various forms of @var{location}; the -most useful ones are listed below: - -@table @code -@item clear @var{function} -@itemx clear @var{filename}:@var{function} -Delete any breakpoints set at entry to the named @var{function}. - -@item clear @var{linenum} -@itemx clear @var{filename}:@var{linenum} -Delete any breakpoints set at or within the code of the specified -@var{linenum} of the specified @var{filename}. -@end table - -@cindex delete breakpoints -@kindex delete -@kindex d @r{(@code{delete})} -@item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} -Delete the breakpoints, watchpoints, or catchpoints of the breakpoint -ranges specified as arguments. If no argument is specified, delete all -breakpoints (@value{GDBN} asks confirmation, unless you have @code{set -confirm off}). You can abbreviate this command as @code{d}. -@end table - -@node Disabling -@subsection Disabling Breakpoints - -@cindex enable/disable a breakpoint -Rather than deleting a breakpoint, watchpoint, or catchpoint, you might -prefer to @dfn{disable} it. This makes the breakpoint inoperative as if -it had been deleted, but remembers the information on the breakpoint so -that you can @dfn{enable} it again later. - -You disable and enable breakpoints, watchpoints, and catchpoints with -the @code{enable} and @code{disable} commands, optionally specifying -one or more breakpoint numbers as arguments. Use @code{info break} to -print a list of all breakpoints, watchpoints, and catchpoints if you -do not know which numbers to use. - -Disabling and enabling a breakpoint that has multiple locations -affects all of its locations. - -A breakpoint, watchpoint, or catchpoint can have any of several -different states of enablement: - -@itemize @bullet -@item -Enabled. The breakpoint stops your program. A breakpoint set -with the @code{break} command starts out in this state. -@item -Disabled. The breakpoint has no effect on your program. -@item -Enabled once. The breakpoint stops your program, but then becomes -disabled. -@item -Enabled for a count. The breakpoint stops your program for the next -N times, then becomes disabled. -@item -Enabled for deletion. The breakpoint stops your program, but -immediately after it does so it is deleted permanently. A breakpoint -set with the @code{tbreak} command starts out in this state. -@end itemize - -You can use the following commands to enable or disable breakpoints, -watchpoints, and catchpoints: - -@table @code -@kindex disable -@kindex dis @r{(@code{disable})} -@item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} -Disable the specified breakpoints---or all breakpoints, if none are -listed. A disabled breakpoint has no effect but is not forgotten. All -options such as ignore-counts, conditions and commands are remembered in -case the breakpoint is enabled again later. You may abbreviate -@code{disable} as @code{dis}. - -@kindex enable -@item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} -Enable the specified breakpoints (or all defined breakpoints). They -become effective once again in stopping your program. - -@item enable @r{[}breakpoints@r{]} once @var{range}@dots{} -Enable the specified breakpoints temporarily. @value{GDBN} disables any -of these breakpoints immediately after stopping your program. - -@item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{} -Enable the specified breakpoints temporarily. @value{GDBN} records -@var{count} with each of the specified breakpoints, and decrements a -breakpoint's count when it is hit. When any count reaches 0, -@value{GDBN} disables that breakpoint. If a breakpoint has an ignore -count (@pxref{Conditions, ,Break Conditions}), that will be -decremented to 0 before @var{count} is affected. - -@item enable @r{[}breakpoints@r{]} delete @var{range}@dots{} -Enable the specified breakpoints to work once, then die. @value{GDBN} -deletes any of these breakpoints as soon as your program stops there. -Breakpoints set by the @code{tbreak} command start out in this state. -@end table - -@c FIXME: I think the following ``Except for [...] @code{tbreak}'' is -@c confusing: tbreak is also initially enabled. -Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks, -,Setting Breakpoints}), breakpoints that you set are initially enabled; -subsequently, they become disabled or enabled only when you use one of -the commands above. (The command @code{until} can set and delete a -breakpoint of its own, but it does not change the state of your other -breakpoints; see @ref{Continuing and Stepping, ,Continuing and -Stepping}.) - -@node Conditions -@subsection Break Conditions -@cindex conditional breakpoints -@cindex breakpoint conditions - -@c FIXME what is scope of break condition expr? Context where wanted? -@c in particular for a watchpoint? -The simplest sort of breakpoint breaks every time your program reaches a -specified place. You can also specify a @dfn{condition} for a -breakpoint. A condition is just a Boolean expression in your -programming language (@pxref{Expressions, ,Expressions}). A breakpoint with -a condition evaluates the expression each time your program reaches it, -and your program stops only if the condition is @emph{true}. - -This is the converse of using assertions for program validation; in that -situation, you want to stop when the assertion is violated---that is, -when the condition is false. In C, if you want to test an assertion expressed -by the condition @var{assert}, you should set the condition -@samp{! @var{assert}} on the appropriate breakpoint. - -Conditions are also accepted for watchpoints; you may not need them, -since a watchpoint is inspecting the value of an expression anyhow---but -it might be simpler, say, to just set a watchpoint on a variable name, -and specify a condition that tests whether the new value is an interesting -one. - -Break conditions can have side effects, and may even call functions in -your program. This can be useful, for example, to activate functions -that log program progress, or to use your own print functions to -format special data structures. The effects are completely predictable -unless there is another enabled breakpoint at the same address. (In -that case, @value{GDBN} might see the other breakpoint first and stop your -program without checking the condition of this one.) Note that -breakpoint commands are usually more convenient and flexible than break -conditions for the -purpose of performing side effects when a breakpoint is reached -(@pxref{Break Commands, ,Breakpoint Command Lists}). - -Breakpoint conditions can also be evaluated on the target's side if -the target supports it. Instead of evaluating the conditions locally, -@value{GDBN} encodes the expression into an agent expression -(@pxref{Agent Expressions}) suitable for execution on the target, -independently of @value{GDBN}. Global variables become raw memory -locations, locals become stack accesses, and so forth. - -In this case, @value{GDBN} will only be notified of a breakpoint trigger -when its condition evaluates to true. This mechanism may provide faster -response times depending on the performance characteristics of the target -since it does not need to keep @value{GDBN} informed about -every breakpoint trigger, even those with false conditions. - -Break conditions can be specified when a breakpoint is set, by using -@samp{if} in the arguments to the @code{break} command. @xref{Set -Breaks, ,Setting Breakpoints}. They can also be changed at any time -with the @code{condition} command. - -You can also use the @code{if} keyword with the @code{watch} command. -The @code{catch} command does not recognize the @code{if} keyword; -@code{condition} is the only way to impose a further condition on a -catchpoint. - -@table @code -@kindex condition -@item condition @var{bnum} @var{expression} -Specify @var{expression} as the break condition for breakpoint, -watchpoint, or catchpoint number @var{bnum}. After you set a condition, -breakpoint @var{bnum} stops your program only if the value of -@var{expression} is true (nonzero, in C). When you use -@code{condition}, @value{GDBN} checks @var{expression} immediately for -syntactic correctness, and to determine whether symbols in it have -referents in the context of your breakpoint. If @var{expression} uses -symbols not referenced in the context of the breakpoint, @value{GDBN} -prints an error message: - -@smallexample -No symbol "foo" in current context. -@end smallexample - -@noindent -@value{GDBN} does -not actually evaluate @var{expression} at the time the @code{condition} -command (or a command that sets a breakpoint with a condition, like -@code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}. - -@item condition @var{bnum} -Remove the condition from breakpoint number @var{bnum}. It becomes -an ordinary unconditional breakpoint. -@end table - -@cindex ignore count (of breakpoint) -A special case of a breakpoint condition is to stop only when the -breakpoint has been reached a certain number of times. This is so -useful that there is a special way to do it, using the @dfn{ignore -count} of the breakpoint. Every breakpoint has an ignore count, which -is an integer. Most of the time, the ignore count is zero, and -therefore has no effect. But if your program reaches a breakpoint whose -ignore count is positive, then instead of stopping, it just decrements -the ignore count by one and continues. As a result, if the ignore count -value is @var{n}, the breakpoint does not stop the next @var{n} times -your program reaches it. - -@table @code -@kindex ignore -@item ignore @var{bnum} @var{count} -Set the ignore count of breakpoint number @var{bnum} to @var{count}. -The next @var{count} times the breakpoint is reached, your program's -execution does not stop; other than to decrement the ignore count, @value{GDBN} -takes no action. - -To make the breakpoint stop the next time it is reached, specify -a count of zero. - -When you use @code{continue} to resume execution of your program from a -breakpoint, you can specify an ignore count directly as an argument to -@code{continue}, rather than using @code{ignore}. @xref{Continuing and -Stepping,,Continuing and Stepping}. - -If a breakpoint has a positive ignore count and a condition, the -condition is not checked. Once the ignore count reaches zero, -@value{GDBN} resumes checking the condition. - -You could achieve the effect of the ignore count with a condition such -as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that -is decremented each time. @xref{Convenience Vars, ,Convenience -Variables}. -@end table - -Ignore counts apply to breakpoints, watchpoints, and catchpoints. - - -@node Break Commands -@subsection Breakpoint Command Lists - -@cindex breakpoint commands -You can give any breakpoint (or watchpoint or catchpoint) a series of -commands to execute when your program stops due to that breakpoint. For -example, you might want to print the values of certain expressions, or -enable other breakpoints. - -@table @code -@kindex commands -@kindex end@r{ (breakpoint commands)} -@item commands @r{[}@var{range}@dots{}@r{]} -@itemx @dots{} @var{command-list} @dots{} -@itemx end -Specify a list of commands for the given breakpoints. The commands -themselves appear on the following lines. Type a line containing just -@code{end} to terminate the commands. - -To remove all commands from a breakpoint, type @code{commands} and -follow it immediately with @code{end}; that is, give no commands. - -With no argument, @code{commands} refers to the last breakpoint, -watchpoint, or catchpoint set (not to the breakpoint most recently -encountered). If the most recent breakpoints were set with a single -command, then the @code{commands} will apply to all the breakpoints -set by that command. This applies to breakpoints set by -@code{rbreak}, and also applies when a single @code{break} command -creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous -Expressions}). -@end table - -Pressing @key{RET} as a means of repeating the last @value{GDBN} command is -disabled within a @var{command-list}. - -You can use breakpoint commands to start your program up again. Simply -use the @code{continue} command, or @code{step}, or any other command -that resumes execution. - -Any other commands in the command list, after a command that resumes -execution, are ignored. This is because any time you resume execution -(even with a simple @code{next} or @code{step}), you may encounter -another breakpoint---which could have its own command list, leading to -ambiguities about which list to execute. - -@kindex silent -If the first command you specify in a command list is @code{silent}, the -usual message about stopping at a breakpoint is not printed. This may -be desirable for breakpoints that are to print a specific message and -then continue. If none of the remaining commands print anything, you -see no sign that the breakpoint was reached. @code{silent} is -meaningful only at the beginning of a breakpoint command list. - -The commands @code{echo}, @code{output}, and @code{printf} allow you to -print precisely controlled output, and are often useful in silent -breakpoints. @xref{Output, ,Commands for Controlled Output}. - -For example, here is how you could use breakpoint commands to print the -value of @code{x} at entry to @code{foo} whenever @code{x} is positive. - -@smallexample -break foo if x>0 -commands -silent -printf "x is %d\n",x -cont -end -@end smallexample - -One application for breakpoint commands is to compensate for one bug so -you can test for another. Put a breakpoint just after the erroneous line -of code, give it a condition to detect the case in which something -erroneous has been done, and give it commands to assign correct values -to any variables that need them. End with the @code{continue} command -so that your program does not stop, and start with the @code{silent} -command so that no output is produced. Here is an example: - -@smallexample -break 403 -commands -silent -set x = y + 4 -cont -end -@end smallexample - -@node Dynamic Printf -@subsection Dynamic Printf - -@cindex dynamic printf -@cindex dprintf -The dynamic printf command @code{dprintf} combines a breakpoint with -formatted printing of your program's data to give you the effect of -inserting @code{printf} calls into your program on-the-fly, without -having to recompile it. - -In its most basic form, the output goes to the GDB console. However, -you can set the variable @code{dprintf-style} for alternate handling. -For instance, you can ask to format the output by calling your -program's @code{printf} function. This has the advantage that the -characters go to the program's output device, so they can recorded in -redirects to files and so forth. - -If you are doing remote debugging with a stub or agent, you can also -ask to have the printf handled by the remote agent. In addition to -ensuring that the output goes to the remote program's device along -with any other output the program might produce, you can also ask that -the dprintf remain active even after disconnecting from the remote -target. Using the stub/agent is also more efficient, as it can do -everything without needing to communicate with @value{GDBN}. - -@table @code -@kindex dprintf -@item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}] -Whenever execution reaches @var{location}, print the values of one or -more @var{expressions} under the control of the string @var{template}. -To print several values, separate them with commas. - -@item set dprintf-style @var{style} -Set the dprintf output to be handled in one of several different -styles enumerated below. A change of style affects all existing -dynamic printfs immediately. (If you need individual control over the -print commands, simply define normal breakpoints with -explicitly-supplied command lists.) - -@item gdb -@kindex dprintf-style gdb -Handle the output using the @value{GDBN} @code{printf} command. - -@item call -@kindex dprintf-style call -Handle the output by calling a function in your program (normally -@code{printf}). - -@item agent -@kindex dprintf-style agent -Have the remote debugging agent (such as @code{gdbserver}) handle -the output itself. This style is only available for agents that -support running commands on the target. - -@item set dprintf-function @var{function} -Set the function to call if the dprintf style is @code{call}. By -default its value is @code{printf}. You may set it to any expression. -that @value{GDBN} can evaluate to a function, as per the @code{call} -command. - -@item set dprintf-channel @var{channel} -Set a ``channel'' for dprintf. If set to a non-empty value, -@value{GDBN} will evaluate it as an expression and pass the result as -a first argument to the @code{dprintf-function}, in the manner of -@code{fprintf} and similar functions. Otherwise, the dprintf format -string will be the first argument, in the manner of @code{printf}. - -As an example, if you wanted @code{dprintf} output to go to a logfile -that is a standard I/O stream assigned to the variable @code{mylog}, -you could do the following: - -@example -(gdb) set dprintf-style call -(gdb) set dprintf-function fprintf -(gdb) set dprintf-channel mylog -(gdb) dprintf 25,"at line 25, glob=%d\n",glob -Dprintf 1 at 0x123456: file main.c, line 25. -(gdb) info break -1 dprintf keep y 0x00123456 in main at main.c:25 - call (void) fprintf (mylog,"at line 25, glob=%d\n",glob) - continue -(gdb) -@end example - -Note that the @code{info break} displays the dynamic printf commands -as normal breakpoint commands; you can thus easily see the effect of -the variable settings. - -@item set disconnected-dprintf on -@itemx set disconnected-dprintf off -@kindex set disconnected-dprintf -Choose whether @code{dprintf} commands should continue to run if -@value{GDBN} has disconnected from the target. This only applies -if the @code{dprintf-style} is @code{agent}. - -@item show disconnected-dprintf off -@kindex show disconnected-dprintf -Show the current choice for disconnected @code{dprintf}. - -@end table - -@value{GDBN} does not check the validity of function and channel, -relying on you to supply values that are meaningful for the contexts -in which they are being used. For instance, the function and channel -may be the values of local variables, but if that is the case, then -all enabled dynamic prints must be at locations within the scope of -those locals. If evaluation fails, @value{GDBN} will report an error. - -@node Save Breakpoints -@subsection How to save breakpoints to a file - -To save breakpoint definitions to a file use the @w{@code{save -breakpoints}} command. - -@table @code -@kindex save breakpoints -@cindex save breakpoints to a file for future sessions -@item save breakpoints [@var{filename}] -This command saves all current breakpoint definitions together with -their commands and ignore counts, into a file @file{@var{filename}} -suitable for use in a later debugging session. This includes all -types of breakpoints (breakpoints, watchpoints, catchpoints, -tracepoints). To read the saved breakpoint definitions, use the -@code{source} command (@pxref{Command Files}). Note that watchpoints -with expressions involving local variables may fail to be recreated -because it may not be possible to access the context where the -watchpoint is valid anymore. Because the saved breakpoint definitions -are simply a sequence of @value{GDBN} commands that recreate the -breakpoints, you can edit the file in your favorite editing program, -and remove the breakpoint definitions you're not interested in, or -that can no longer be recreated. -@end table - -@node Static Probe Points -@subsection Static Probe Points - -@cindex static probe point, SystemTap -@value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands -for Statically Defined Tracing, and the probes are designed to have a tiny -runtime code and data footprint, and no dynamic relocations. They are -usable from assembly, C and C@t{++} languages. See -@uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation} -for a good reference on how the @acronym{SDT} probes are implemented. - -Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/}) -@acronym{SDT} probes are supported on ELF-compatible systems. See -@uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps} -for more information on how to add @code{SystemTap} @acronym{SDT} probes -in your applications. - -@cindex semaphores on static probe points -Some probes have an associated semaphore variable; for instance, this -happens automatically if you defined your probe using a DTrace-style -@file{.d} file. If your probe has a semaphore, @value{GDBN} will -automatically enable it when you specify a breakpoint using the -@samp{-probe-stap} notation. But, if you put a breakpoint at a probe's -location by some other method (e.g., @code{break file:line}), then -@value{GDBN} will not automatically set the semaphore. - -You can examine the available static static probes using @code{info -probes}, with optional arguments: - -@table @code -@kindex info probes -@item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]} -If given, @var{provider} is a regular expression used to match against provider -names when selecting which probes to list. If omitted, probes by all -probes from all providers are listed. - -If given, @var{name} is a regular expression to match against probe names -when selecting which probes to list. If omitted, probe names are not -considered when deciding whether to display them. - -If given, @var{objfile} is a regular expression used to select which -object files (executable or shared libraries) to examine. If not -given, all object files are considered. - -@item info probes all -List the available static probes, from all types. -@end table - -@vindex $_probe_arg@r{, convenience variable} -A probe may specify up to twelve arguments. These are available at the -point at which the probe is defined---that is, when the current PC is -at the probe's location. The arguments are available using the -convenience variables (@pxref{Convenience Vars}) -@code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is -an integer of the appropriate size; types are not preserved. The -convenience variable @code{$_probe_argc} holds the number of arguments -at the current probe point. - -These variables are always available, but attempts to access them at -any location other than a probe point will cause @value{GDBN} to give -an error message. - - -@c @ifclear BARETARGET -@node Error in Breakpoints -@subsection ``Cannot insert breakpoints'' - -If you request too many active hardware-assisted breakpoints and -watchpoints, you will see this error message: - -@c FIXME: the precise wording of this message may change; the relevant -@c source change is not committed yet (Sep 3, 1999). -@smallexample -Stopped; cannot insert breakpoints. -You may have requested too many hardware breakpoints and watchpoints. -@end smallexample - -@noindent -This message is printed when you attempt to resume the program, since -only then @value{GDBN} knows exactly how many hardware breakpoints and -watchpoints it needs to insert. - -When this message is printed, you need to disable or remove some of the -hardware-assisted breakpoints and watchpoints, and then continue. - -@node Breakpoint-related Warnings -@subsection ``Breakpoint address adjusted...'' -@cindex breakpoint address adjusted - -Some processor architectures place constraints on the addresses at -which breakpoints may be placed. For architectures thus constrained, -@value{GDBN} will attempt to adjust the breakpoint's address to comply -with the constraints dictated by the architecture. - -One example of such an architecture is the Fujitsu FR-V. The FR-V is -a VLIW architecture in which a number of RISC-like instructions may be -bundled together for parallel execution. The FR-V architecture -constrains the location of a breakpoint instruction within such a -bundle to the instruction with the lowest address. @value{GDBN} -honors this constraint by adjusting a breakpoint's address to the -first in the bundle. - -It is not uncommon for optimized code to have bundles which contain -instructions from different source statements, thus it may happen that -a breakpoint's address will be adjusted from one source statement to -another. Since this adjustment may significantly alter @value{GDBN}'s -breakpoint related behavior from what the user expects, a warning is -printed when the breakpoint is first set and also when the breakpoint -is hit. - -A warning like the one below is printed when setting a breakpoint -that's been subject to address adjustment: - -@smallexample -warning: Breakpoint address adjusted from 0x00010414 to 0x00010410. -@end smallexample - -Such warnings are printed both for user settable and @value{GDBN}'s -internal breakpoints. If you see one of these warnings, you should -verify that a breakpoint set at the adjusted address will have the -desired affect. If not, the breakpoint in question may be removed and -other breakpoints may be set which will have the desired behavior. -E.g., it may be sufficient to place the breakpoint at a later -instruction. A conditional breakpoint may also be useful in some -cases to prevent the breakpoint from triggering too often. - -@value{GDBN} will also issue a warning when stopping at one of these -adjusted breakpoints: - -@smallexample -warning: Breakpoint 1 address previously adjusted from 0x00010414 -to 0x00010410. -@end smallexample - -When this warning is encountered, it may be too late to take remedial -action except in cases where the breakpoint is hit earlier or more -frequently than expected. - -@node Continuing and Stepping -@section Continuing and Stepping - -@cindex stepping -@cindex continuing -@cindex resuming execution -@dfn{Continuing} means resuming program execution until your program -completes normally. In contrast, @dfn{stepping} means executing just -one more ``step'' of your program, where ``step'' may mean either one -line of source code, or one machine instruction (depending on what -particular command you use). Either when continuing or when stepping, -your program may stop even sooner, due to a breakpoint or a signal. (If -it stops due to a signal, you may want to use @code{handle}, or use -@samp{signal 0} to resume execution. @xref{Signals, ,Signals}.) - -@table @code -@kindex continue -@kindex c @r{(@code{continue})} -@kindex fg @r{(resume foreground execution)} -@item continue @r{[}@var{ignore-count}@r{]} -@itemx c @r{[}@var{ignore-count}@r{]} -@itemx fg @r{[}@var{ignore-count}@r{]} -Resume program execution, at the address where your program last stopped; -any breakpoints set at that address are bypassed. The optional argument -@var{ignore-count} allows you to specify a further number of times to -ignore a breakpoint at this location; its effect is like that of -@code{ignore} (@pxref{Conditions, ,Break Conditions}). - -The argument @var{ignore-count} is meaningful only when your program -stopped due to a breakpoint. At other times, the argument to -@code{continue} is ignored. - -The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the -debugged program is deemed to be the foreground program) are provided -purely for convenience, and have exactly the same behavior as -@code{continue}. -@end table - -To resume execution at a different place, you can use @code{return} -(@pxref{Returning, ,Returning from a Function}) to go back to the -calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a -Different Address}) to go to an arbitrary location in your program. - -A typical technique for using stepping is to set a breakpoint -(@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the -beginning of the function or the section of your program where a problem -is believed to lie, run your program until it stops at that breakpoint, -and then step through the suspect area, examining the variables that are -interesting, until you see the problem happen. - -@table @code -@kindex step -@kindex s @r{(@code{step})} -@item step -Continue running your program until control reaches a different source -line, then stop it and return control to @value{GDBN}. This command is -abbreviated @code{s}. - -@quotation -@c "without debugging information" is imprecise; actually "without line -@c numbers in the debugging information". (gcc -g1 has debugging info but -@c not line numbers). But it seems complex to try to make that -@c distinction here. -@emph{Warning:} If you use the @code{step} command while control is -within a function that was compiled without debugging information, -execution proceeds until control reaches a function that does have -debugging information. Likewise, it will not step into a function which -is compiled without debugging information. To step through functions -without debugging information, use the @code{stepi} command, described -below. -@end quotation - -The @code{step} command only stops at the first instruction of a source -line. This prevents the multiple stops that could otherwise occur in -@code{switch} statements, @code{for} loops, etc. @code{step} continues -to stop if a function that has debugging information is called within -the line. In other words, @code{step} @emph{steps inside} any functions -called within the line. - -Also, the @code{step} command only enters a function if there is line -number information for the function. Otherwise it acts like the -@code{next} command. This avoids problems when using @code{cc -gl} -on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there -was any debugging information about the routine. - -@item step @var{count} -Continue running as in @code{step}, but do so @var{count} times. If a -breakpoint is reached, or a signal not related to stepping occurs before -@var{count} steps, stepping stops right away. - -@kindex next -@kindex n @r{(@code{next})} -@item next @r{[}@var{count}@r{]} -Continue to the next source line in the current (innermost) stack frame. -This is similar to @code{step}, but function calls that appear within -the line of code are executed without stopping. Execution stops when -control reaches a different line of code at the original stack level -that was executing when you gave the @code{next} command. This command -is abbreviated @code{n}. - -An argument @var{count} is a repeat count, as for @code{step}. - - -@c FIX ME!! Do we delete this, or is there a way it fits in with -@c the following paragraph? --- Vctoria -@c -@c @code{next} within a function that lacks debugging information acts like -@c @code{step}, but any function calls appearing within the code of the -@c function are executed without stopping. - -The @code{next} command only stops at the first instruction of a -source line. This prevents multiple stops that could otherwise occur in -@code{switch} statements, @code{for} loops, etc. - -@kindex set step-mode -@item set step-mode -@cindex functions without line info, and stepping -@cindex stepping into functions with no line info -@itemx set step-mode on -The @code{set step-mode on} command causes the @code{step} command to -stop at the first instruction of a function which contains no debug line -information rather than stepping over it. - -This is useful in cases where you may be interested in inspecting the -machine instructions of a function which has no symbolic info and do not -want @value{GDBN} to automatically skip over this function. - -@item set step-mode off -Causes the @code{step} command to step over any functions which contains no -debug information. This is the default. - -@item show step-mode -Show whether @value{GDBN} will stop in or step over functions without -source line debug information. - -@kindex finish -@kindex fin @r{(@code{finish})} -@item finish -Continue running until just after function in the selected stack frame -returns. Print the returned value (if any). This command can be -abbreviated as @code{fin}. - -Contrast this with the @code{return} command (@pxref{Returning, -,Returning from a Function}). - -@kindex until -@kindex u @r{(@code{until})} -@cindex run until specified location -@item until -@itemx u -Continue running until a source line past the current line, in the -current stack frame, is reached. This command is used to avoid single -stepping through a loop more than once. It is like the @code{next} -command, except that when @code{until} encounters a jump, it -automatically continues execution until the program counter is greater -than the address of the jump. - -This means that when you reach the end of a loop after single stepping -though it, @code{until} makes your program continue execution until it -exits the loop. In contrast, a @code{next} command at the end of a loop -simply steps back to the beginning of the loop, which forces you to step -through the next iteration. - -@code{until} always stops your program if it attempts to exit the current -stack frame. - -@code{until} may produce somewhat counterintuitive results if the order -of machine code does not match the order of the source lines. For -example, in the following excerpt from a debugging session, the @code{f} -(@code{frame}) command shows that execution is stopped at line -@code{206}; yet when we use @code{until}, we get to line @code{195}: - -@smallexample -(@value{GDBP}) f -#0 main (argc=4, argv=0xf7fffae8) at m4.c:206 -206 expand_input(); -(@value{GDBP}) until -195 for ( ; argc > 0; NEXTARG) @{ -@end smallexample - -This happened because, for execution efficiency, the compiler had -generated code for the loop closure test at the end, rather than the -start, of the loop---even though the test in a C @code{for}-loop is -written before the body of the loop. The @code{until} command appeared -to step back to the beginning of the loop when it advanced to this -expression; however, it has not really gone to an earlier -statement---not in terms of the actual machine code. - -@code{until} with no argument works by means of single -instruction stepping, and hence is slower than @code{until} with an -argument. - -@item until @var{location} -@itemx u @var{location} -Continue running your program until either the specified location is -reached, or the current stack frame returns. @var{location} is any of -the forms described in @ref{Specify Location}. -This form of the command uses temporary breakpoints, and -hence is quicker than @code{until} without an argument. The specified -location is actually reached only if it is in the current frame. This -implies that @code{until} can be used to skip over recursive function -invocations. For instance in the code below, if the current location is -line @code{96}, issuing @code{until 99} will execute the program up to -line @code{99} in the same invocation of factorial, i.e., after the inner -invocations have returned. - -@smallexample -94 int factorial (int value) -95 @{ -96 if (value > 1) @{ -97 value *= factorial (value - 1); -98 @} -99 return (value); -100 @} -@end smallexample - - -@kindex advance @var{location} -@item advance @var{location} -Continue running the program up to the given @var{location}. An argument is -required, which should be of one of the forms described in -@ref{Specify Location}. -Execution will also stop upon exit from the current stack -frame. This command is similar to @code{until}, but @code{advance} will -not skip over recursive function calls, and the target location doesn't -have to be in the same frame as the current one. - - -@kindex stepi -@kindex si @r{(@code{stepi})} -@item stepi -@itemx stepi @var{arg} -@itemx si -Execute one machine instruction, then stop and return to the debugger. - -It is often useful to do @samp{display/i $pc} when stepping by machine -instructions. This makes @value{GDBN} automatically display the next -instruction to be executed, each time your program stops. @xref{Auto -Display,, Automatic Display}. - -An argument is a repeat count, as in @code{step}. - -@need 750 -@kindex nexti -@kindex ni @r{(@code{nexti})} -@item nexti -@itemx nexti @var{arg} -@itemx ni -Execute one machine instruction, but if it is a function call, -proceed until the function returns. - -An argument is a repeat count, as in @code{next}. -@end table - -@node Skipping Over Functions and Files -@section Skipping Over Functions and Files -@cindex skipping over functions and files - -The program you are debugging may contain some functions which are -uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to -skip a function or all functions in a file when stepping. - -For example, consider the following C function: - -@smallexample -101 int func() -102 @{ -103 foo(boring()); -104 bar(boring()); -105 @} -@end smallexample - -@noindent -Suppose you wish to step into the functions @code{foo} and @code{bar}, but you -are not interested in stepping through @code{boring}. If you run @code{step} -at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll -step over both @code{foo} and @code{boring}! - -One solution is to @code{step} into @code{boring} and use the @code{finish} -command to immediately exit it. But this can become tedious if @code{boring} -is called from many places. - -A more flexible solution is to execute @kbd{skip boring}. This instructs -@value{GDBN} never to step into @code{boring}. Now when you execute -@code{step} at line 103, you'll step over @code{boring} and directly into -@code{foo}. - -You can also instruct @value{GDBN} to skip all functions in a file, with, for -example, @code{skip file boring.c}. - -@table @code -@kindex skip function -@item skip @r{[}@var{linespec}@r{]} -@itemx skip function @r{[}@var{linespec}@r{]} -After running this command, the function named by @var{linespec} or the -function containing the line named by @var{linespec} will be skipped over when -stepping. @xref{Specify Location}. - -If you do not specify @var{linespec}, the function you're currently debugging -will be skipped. - -(If you have a function called @code{file} that you want to skip, use -@kbd{skip function file}.) - -@kindex skip file -@item skip file @r{[}@var{filename}@r{]} -After running this command, any function whose source lives in @var{filename} -will be skipped over when stepping. - -If you do not specify @var{filename}, functions whose source lives in the file -you're currently debugging will be skipped. -@end table - -Skips can be listed, deleted, disabled, and enabled, much like breakpoints. -These are the commands for managing your list of skips: - -@table @code -@kindex info skip -@item info skip @r{[}@var{range}@r{]} -Print details about the specified skip(s). If @var{range} is not specified, -print a table with details about all functions and files marked for skipping. -@code{info skip} prints the following information about each skip: - -@table @emph -@item Identifier -A number identifying this skip. -@item Type -The type of this skip, either @samp{function} or @samp{file}. -@item Enabled or Disabled -Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}. -@item Address -For function skips, this column indicates the address in memory of the function -being skipped. If you've set a function skip on a function which has not yet -been loaded, this field will contain @samp{}. Once a shared library -which has the function is loaded, @code{info skip} will show the function's -address here. -@item What -For file skips, this field contains the filename being skipped. For functions -skips, this field contains the function name and its line number in the file -where it is defined. -@end table - -@kindex skip delete -@item skip delete @r{[}@var{range}@r{]} -Delete the specified skip(s). If @var{range} is not specified, delete all -skips. - -@kindex skip enable -@item skip enable @r{[}@var{range}@r{]} -Enable the specified skip(s). If @var{range} is not specified, enable all -skips. - -@kindex skip disable -@item skip disable @r{[}@var{range}@r{]} -Disable the specified skip(s). If @var{range} is not specified, disable all -skips. - -@end table - -@node Signals -@section Signals -@cindex signals - -A signal is an asynchronous event that can happen in a program. The -operating system defines the possible kinds of signals, and gives each -kind a name and a number. For example, in Unix @code{SIGINT} is the -signal a program gets when you type an interrupt character (often @kbd{Ctrl-c}); -@code{SIGSEGV} is the signal a program gets from referencing a place in -memory far away from all the areas in use; @code{SIGALRM} occurs when -the alarm clock timer goes off (which happens only if your program has -requested an alarm). - -@cindex fatal signals -Some signals, including @code{SIGALRM}, are a normal part of the -functioning of your program. Others, such as @code{SIGSEGV}, indicate -errors; these signals are @dfn{fatal} (they kill your program immediately) if the -program has not specified in advance some other way to handle the signal. -@code{SIGINT} does not indicate an error in your program, but it is normally -fatal so it can carry out the purpose of the interrupt: to kill the program. - -@value{GDBN} has the ability to detect any occurrence of a signal in your -program. You can tell @value{GDBN} in advance what to do for each kind of -signal. - -@cindex handling signals -Normally, @value{GDBN} is set up to let the non-erroneous signals like -@code{SIGALRM} be silently passed to your program -(so as not to interfere with their role in the program's functioning) -but to stop your program immediately whenever an error signal happens. -You can change these settings with the @code{handle} command. - -@table @code -@kindex info signals -@kindex info handle -@item info signals -@itemx info handle -Print a table of all the kinds of signals and how @value{GDBN} has been told to -handle each one. You can use this to see the signal numbers of all -the defined types of signals. - -@item info signals @var{sig} -Similar, but print information only about the specified signal number. - -@code{info handle} is an alias for @code{info signals}. - -@item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]} -Set a catchpoint for the indicated signals. @xref{Set Catchpoints}, -for details about this command. - -@kindex handle -@item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]} -Change the way @value{GDBN} handles signal @var{signal}. @var{signal} -can be the number of a signal or its name (with or without the -@samp{SIG} at the beginning); a list of signal numbers of the form -@samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the -known signals. Optional arguments @var{keywords}, described below, -say what change to make. -@end table - -@c @group -The keywords allowed by the @code{handle} command can be abbreviated. -Their full names are: - -@table @code -@item nostop -@value{GDBN} should not stop your program when this signal happens. It may -still print a message telling you that the signal has come in. - -@item stop -@value{GDBN} should stop your program when this signal happens. This implies -the @code{print} keyword as well. - -@item print -@value{GDBN} should print a message when this signal happens. - -@item noprint -@value{GDBN} should not mention the occurrence of the signal at all. This -implies the @code{nostop} keyword as well. - -@item pass -@itemx noignore -@value{GDBN} should allow your program to see this signal; your program -can handle the signal, or else it may terminate if the signal is fatal -and not handled. @code{pass} and @code{noignore} are synonyms. - -@item nopass -@itemx ignore -@value{GDBN} should not allow your program to see this signal. -@code{nopass} and @code{ignore} are synonyms. -@end table -@c @end group - -When a signal stops your program, the signal is not visible to the -program until you -continue. Your program sees the signal then, if @code{pass} is in -effect for the signal in question @emph{at that time}. In other words, -after @value{GDBN} reports a signal, you can use the @code{handle} -command with @code{pass} or @code{nopass} to control whether your -program sees that signal when you continue. - -The default is set to @code{nostop}, @code{noprint}, @code{pass} for -non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and -@code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the -erroneous signals. - -You can also use the @code{signal} command to prevent your program from -seeing a signal, or cause it to see a signal it normally would not see, -or to give it any signal at any time. For example, if your program stopped -due to some sort of memory reference error, you might store correct -values into the erroneous variables and continue, hoping to see more -execution; but your program would probably terminate immediately as -a result of the fatal signal once it saw the signal. To prevent this, -you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your -Program a Signal}. - -@cindex extra signal information -@anchor{extra signal information} - -On some targets, @value{GDBN} can inspect extra signal information -associated with the intercepted signal, before it is actually -delivered to the program being debugged. This information is exported -by the convenience variable @code{$_siginfo}, and consists of data -that is passed by the kernel to the signal handler at the time of the -receipt of a signal. The data type of the information itself is -target dependent. You can see the data type using the @code{ptype -$_siginfo} command. On Unix systems, it typically corresponds to the -standard @code{siginfo_t} type, as defined in the @file{signal.h} -system header. - -Here's an example, on a @sc{gnu}/Linux system, printing the stray -referenced address that raised a segmentation fault. - -@smallexample -@group -(@value{GDBP}) continue -Program received signal SIGSEGV, Segmentation fault. -0x0000000000400766 in main () -69 *(int *)p = 0; -(@value{GDBP}) ptype $_siginfo -type = struct @{ - int si_signo; - int si_errno; - int si_code; - union @{ - int _pad[28]; - struct @{...@} _kill; - struct @{...@} _timer; - struct @{...@} _rt; - struct @{...@} _sigchld; - struct @{...@} _sigfault; - struct @{...@} _sigpoll; - @} _sifields; -@} -(@value{GDBP}) ptype $_siginfo._sifields._sigfault -type = struct @{ - void *si_addr; -@} -(@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr -$1 = (void *) 0x7ffff7ff7000 -@end group -@end smallexample - -Depending on target support, @code{$_siginfo} may also be writable. - -@node Thread Stops -@section Stopping and Starting Multi-thread Programs - -@cindex stopped threads -@cindex threads, stopped - -@cindex continuing threads -@cindex threads, continuing - -@value{GDBN} supports debugging programs with multiple threads -(@pxref{Threads,, Debugging Programs with Multiple Threads}). There -are two modes of controlling execution of your program within the -debugger. In the default mode, referred to as @dfn{all-stop mode}, -when any thread in your program stops (for example, at a breakpoint -or while being stepped), all other threads in the program are also stopped by -@value{GDBN}. On some targets, @value{GDBN} also supports -@dfn{non-stop mode}, in which other threads can continue to run freely while -you examine the stopped thread in the debugger. - -@menu -* All-Stop Mode:: All threads stop when GDB takes control -* Non-Stop Mode:: Other threads continue to execute -* Background Execution:: Running your program asynchronously -* Thread-Specific Breakpoints:: Controlling breakpoints -* Interrupted System Calls:: GDB may interfere with system calls -* Observer Mode:: GDB does not alter program behavior -@end menu - -@node All-Stop Mode -@subsection All-Stop Mode - -@cindex all-stop mode - -In all-stop mode, whenever your program stops under @value{GDBN} for any reason, -@emph{all} threads of execution stop, not just the current thread. This -allows you to examine the overall state of the program, including -switching between threads, without worrying that things may change -underfoot. - -Conversely, whenever you restart the program, @emph{all} threads start -executing. @emph{This is true even when single-stepping} with commands -like @code{step} or @code{next}. - -In particular, @value{GDBN} cannot single-step all threads in lockstep. -Since thread scheduling is up to your debugging target's operating -system (not controlled by @value{GDBN}), other threads may -execute more than one statement while the current thread completes a -single step. Moreover, in general other threads stop in the middle of a -statement, rather than at a clean statement boundary, when the program -stops. - -You might even find your program stopped in another thread after -continuing or even single-stepping. This happens whenever some other -thread runs into a breakpoint, a signal, or an exception before the -first thread completes whatever you requested. - -@cindex automatic thread selection -@cindex switching threads automatically -@cindex threads, automatic switching -Whenever @value{GDBN} stops your program, due to a breakpoint or a -signal, it automatically selects the thread where that breakpoint or -signal happened. @value{GDBN} alerts you to the context switch with a -message such as @samp{[Switching to Thread @var{n}]} to identify the -thread. - -On some OSes, you can modify @value{GDBN}'s default behavior by -locking the OS scheduler to allow only a single thread to run. - -@table @code -@item set scheduler-locking @var{mode} -@cindex scheduler locking mode -@cindex lock scheduler -Set the scheduler locking mode. If it is @code{off}, then there is no -locking and any thread may run at any time. If @code{on}, then only the -current thread may run when the inferior is resumed. The @code{step} -mode optimizes for single-stepping; it prevents other threads -from preempting the current thread while you are stepping, so that -the focus of debugging does not change unexpectedly. -Other threads only rarely (or never) get a chance to run -when you step. They are more likely to run when you @samp{next} over a -function call, and they are completely free to run when you use commands -like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another -thread hits a breakpoint during its timeslice, @value{GDBN} does not change -the current thread away from the thread that you are debugging. - -@item show scheduler-locking -Display the current scheduler locking mode. -@end table - -@cindex resume threads of multiple processes simultaneously -By default, when you issue one of the execution commands such as -@code{continue}, @code{next} or @code{step}, @value{GDBN} allows only -threads of the current inferior to run. For example, if @value{GDBN} -is attached to two inferiors, each with two threads, the -@code{continue} command resumes only the two threads of the current -inferior. This is useful, for example, when you debug a program that -forks and you want to hold the parent stopped (so that, for instance, -it doesn't run to exit), while you debug the child. In other -situations, you may not be interested in inspecting the current state -of any of the processes @value{GDBN} is attached to, and you may want -to resume them all until some breakpoint is hit. In the latter case, -you can instruct @value{GDBN} to allow all threads of all the -inferiors to run with the @w{@code{set schedule-multiple}} command. - -@table @code -@kindex set schedule-multiple -@item set schedule-multiple -Set the mode for allowing threads of multiple processes to be resumed -when an execution command is issued. When @code{on}, all threads of -all processes are allowed to run. When @code{off}, only the threads -of the current process are resumed. The default is @code{off}. The -@code{scheduler-locking} mode takes precedence when set to @code{on}, -or while you are stepping and set to @code{step}. - -@item show schedule-multiple -Display the current mode for resuming the execution of threads of -multiple processes. -@end table - -@node Non-Stop Mode -@subsection Non-Stop Mode - -@cindex non-stop mode - -@c This section is really only a place-holder, and needs to be expanded -@c with more details. - -For some multi-threaded targets, @value{GDBN} supports an optional -mode of operation in which you can examine stopped program threads in -the debugger while other threads continue to execute freely. This -minimizes intrusion when debugging live systems, such as programs -where some threads have real-time constraints or must continue to -respond to external events. This is referred to as @dfn{non-stop} mode. - -In non-stop mode, when a thread stops to report a debugging event, -@emph{only} that thread is stopped; @value{GDBN} does not stop other -threads as well, in contrast to the all-stop mode behavior. Additionally, -execution commands such as @code{continue} and @code{step} apply by default -only to the current thread in non-stop mode, rather than all threads as -in all-stop mode. This allows you to control threads explicitly in -ways that are not possible in all-stop mode --- for example, stepping -one thread while allowing others to run freely, stepping -one thread while holding all others stopped, or stepping several threads -independently and simultaneously. - -To enter non-stop mode, use this sequence of commands before you run -or attach to your program: - -@smallexample -# Enable the async interface. -set target-async 1 - -# If using the CLI, pagination breaks non-stop. -set pagination off - -# Finally, turn it on! -set non-stop on -@end smallexample - -You can use these commands to manipulate the non-stop mode setting: - -@table @code -@kindex set non-stop -@item set non-stop on -Enable selection of non-stop mode. -@item set non-stop off -Disable selection of non-stop mode. -@kindex show non-stop -@item show non-stop -Show the current non-stop enablement setting. -@end table - -Note these commands only reflect whether non-stop mode is enabled, -not whether the currently-executing program is being run in non-stop mode. -In particular, the @code{set non-stop} preference is only consulted when -@value{GDBN} starts or connects to the target program, and it is generally -not possible to switch modes once debugging has started. Furthermore, -since not all targets support non-stop mode, even when you have enabled -non-stop mode, @value{GDBN} may still fall back to all-stop operation by -default. - -In non-stop mode, all execution commands apply only to the current thread -by default. That is, @code{continue} only continues one thread. -To continue all threads, issue @code{continue -a} or @code{c -a}. - -You can use @value{GDBN}'s background execution commands -(@pxref{Background Execution}) to run some threads in the background -while you continue to examine or step others from @value{GDBN}. -The MI execution commands (@pxref{GDB/MI Program Execution}) are -always executed asynchronously in non-stop mode. - -Suspending execution is done with the @code{interrupt} command when -running in the background, or @kbd{Ctrl-c} during foreground execution. -In all-stop mode, this stops the whole process; -but in non-stop mode the interrupt applies only to the current thread. -To stop the whole program, use @code{interrupt -a}. - -Other execution commands do not currently support the @code{-a} option. - -In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make -that thread current, as it does in all-stop mode. This is because the -thread stop notifications are asynchronous with respect to @value{GDBN}'s -command interpreter, and it would be confusing if @value{GDBN} unexpectedly -changed to a different thread just as you entered a command to operate on the -previously current thread. - -@node Background Execution -@subsection Background Execution - -@cindex foreground execution -@cindex background execution -@cindex asynchronous execution -@cindex execution, foreground, background and asynchronous - -@value{GDBN}'s execution commands have two variants: the normal -foreground (synchronous) behavior, and a background -(asynchronous) behavior. In foreground execution, @value{GDBN} waits for -the program to report that some thread has stopped before prompting for -another command. In background execution, @value{GDBN} immediately gives -a command prompt so that you can issue other commands while your program runs. - -You need to explicitly enable asynchronous mode before you can use -background execution commands. You can use these commands to -manipulate the asynchronous mode setting: - -@table @code -@kindex set target-async -@item set target-async on -Enable asynchronous mode. -@item set target-async off -Disable asynchronous mode. -@kindex show target-async -@item show target-async -Show the current target-async setting. -@end table - -If the target doesn't support async mode, @value{GDBN} issues an error -message if you attempt to use the background execution commands. - -To specify background execution, add a @code{&} to the command. For example, -the background form of the @code{continue} command is @code{continue&}, or -just @code{c&}. The execution commands that accept background execution -are: - -@table @code -@kindex run& -@item run -@xref{Starting, , Starting your Program}. - -@item attach -@kindex attach& -@xref{Attach, , Debugging an Already-running Process}. - -@item step -@kindex step& -@xref{Continuing and Stepping, step}. - -@item stepi -@kindex stepi& -@xref{Continuing and Stepping, stepi}. - -@item next -@kindex next& -@xref{Continuing and Stepping, next}. - -@item nexti -@kindex nexti& -@xref{Continuing and Stepping, nexti}. - -@item continue -@kindex continue& -@xref{Continuing and Stepping, continue}. - -@item finish -@kindex finish& -@xref{Continuing and Stepping, finish}. - -@item until -@kindex until& -@xref{Continuing and Stepping, until}. - -@end table - -Background execution is especially useful in conjunction with non-stop -mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}. -However, you can also use these commands in the normal all-stop mode with -the restriction that you cannot issue another execution command until the -previous one finishes. Examples of commands that are valid in all-stop -mode while the program is running include @code{help} and @code{info break}. - -You can interrupt your program while it is running in the background by -using the @code{interrupt} command. - -@table @code -@kindex interrupt -@item interrupt -@itemx interrupt -a - -Suspend execution of the running program. In all-stop mode, -@code{interrupt} stops the whole process, but in non-stop mode, it stops -only the current thread. To stop the whole program in non-stop mode, -use @code{interrupt -a}. -@end table - -@node Thread-Specific Breakpoints -@subsection Thread-Specific Breakpoints - -When your program has multiple threads (@pxref{Threads,, Debugging -Programs with Multiple Threads}), you can choose whether to set -breakpoints on all threads, or on a particular thread. - -@table @code -@cindex breakpoints and threads -@cindex thread breakpoints -@kindex break @dots{} thread @var{threadno} -@item break @var{linespec} thread @var{threadno} -@itemx break @var{linespec} thread @var{threadno} if @dots{} -@var{linespec} specifies source lines; there are several ways of -writing them (@pxref{Specify Location}), but the effect is always to -specify some source line. - -Use the qualifier @samp{thread @var{threadno}} with a breakpoint command -to specify that you only want @value{GDBN} to stop the program when a -particular thread reaches this breakpoint. @var{threadno} is one of the -numeric thread identifiers assigned by @value{GDBN}, shown in the first -column of the @samp{info threads} display. - -If you do not specify @samp{thread @var{threadno}} when you set a -breakpoint, the breakpoint applies to @emph{all} threads of your -program. - -You can use the @code{thread} qualifier on conditional breakpoints as -well; in this case, place @samp{thread @var{threadno}} before or -after the breakpoint condition, like this: - -@smallexample -(@value{GDBP}) break frik.c:13 thread 28 if bartab > lim -@end smallexample - -@end table - -@node Interrupted System Calls -@subsection Interrupted System Calls - -@cindex thread breakpoints and system calls -@cindex system calls and thread breakpoints -@cindex premature return from system calls -There is an unfortunate side effect when using @value{GDBN} to debug -multi-threaded programs. If one thread stops for a -breakpoint, or for some other reason, and another thread is blocked in a -system call, then the system call may return prematurely. This is a -consequence of the interaction between multiple threads and the signals -that @value{GDBN} uses to implement breakpoints and other events that -stop execution. - -To handle this problem, your program should check the return value of -each system call and react appropriately. This is good programming -style anyways. - -For example, do not write code like this: - -@smallexample - sleep (10); -@end smallexample - -The call to @code{sleep} will return early if a different thread stops -at a breakpoint or for some other reason. - -Instead, write this: - -@smallexample - int unslept = 10; - while (unslept > 0) - unslept = sleep (unslept); -@end smallexample - -A system call is allowed to return early, so the system is still -conforming to its specification. But @value{GDBN} does cause your -multi-threaded program to behave differently than it would without -@value{GDBN}. - -Also, @value{GDBN} uses internal breakpoints in the thread library to -monitor certain events such as thread creation and thread destruction. -When such an event happens, a system call in another thread may return -prematurely, even though your program does not appear to stop. - -@node Observer Mode -@subsection Observer Mode - -If you want to build on non-stop mode and observe program behavior -without any chance of disruption by @value{GDBN}, you can set -variables to disable all of the debugger's attempts to modify state, -whether by writing memory, inserting breakpoints, etc. These operate -at a low level, intercepting operations from all commands. - -When all of these are set to @code{off}, then @value{GDBN} is said to -be @dfn{observer mode}. As a convenience, the variable -@code{observer} can be set to disable these, plus enable non-stop -mode. - -Note that @value{GDBN} will not prevent you from making nonsensical -combinations of these settings. For instance, if you have enabled -@code{may-insert-breakpoints} but disabled @code{may-write-memory}, -then breakpoints that work by writing trap instructions into the code -stream will still not be able to be placed. - -@table @code - -@kindex observer -@item set observer on -@itemx set observer off -When set to @code{on}, this disables all the permission variables -below (except for @code{insert-fast-tracepoints}), plus enables -non-stop debugging. Setting this to @code{off} switches back to -normal debugging, though remaining in non-stop mode. - -@item show observer -Show whether observer mode is on or off. - -@kindex may-write-registers -@item set may-write-registers on -@itemx set may-write-registers off -This controls whether @value{GDBN} will attempt to alter the values of -registers, such as with assignment expressions in @code{print}, or the -@code{jump} command. It defaults to @code{on}. - -@item show may-write-registers -Show the current permission to write registers. - -@kindex may-write-memory -@item set may-write-memory on -@itemx set may-write-memory off -This controls whether @value{GDBN} will attempt to alter the contents -of memory, such as with assignment expressions in @code{print}. It -defaults to @code{on}. - -@item show may-write-memory -Show the current permission to write memory. - -@kindex may-insert-breakpoints -@item set may-insert-breakpoints on -@itemx set may-insert-breakpoints off -This controls whether @value{GDBN} will attempt to insert breakpoints. -This affects all breakpoints, including internal breakpoints defined -by @value{GDBN}. It defaults to @code{on}. - -@item show may-insert-breakpoints -Show the current permission to insert breakpoints. - -@kindex may-insert-tracepoints -@item set may-insert-tracepoints on -@itemx set may-insert-tracepoints off -This controls whether @value{GDBN} will attempt to insert (regular) -tracepoints at the beginning of a tracing experiment. It affects only -non-fast tracepoints, fast tracepoints being under the control of -@code{may-insert-fast-tracepoints}. It defaults to @code{on}. - -@item show may-insert-tracepoints -Show the current permission to insert tracepoints. - -@kindex may-insert-fast-tracepoints -@item set may-insert-fast-tracepoints on -@itemx set may-insert-fast-tracepoints off -This controls whether @value{GDBN} will attempt to insert fast -tracepoints at the beginning of a tracing experiment. It affects only -fast tracepoints, regular (non-fast) tracepoints being under the -control of @code{may-insert-tracepoints}. It defaults to @code{on}. - -@item show may-insert-fast-tracepoints -Show the current permission to insert fast tracepoints. - -@kindex may-interrupt -@item set may-interrupt on -@itemx set may-interrupt off -This controls whether @value{GDBN} will attempt to interrupt or stop -program execution. When this variable is @code{off}, the -@code{interrupt} command will have no effect, nor will -@kbd{Ctrl-c}. It defaults to @code{on}. - -@item show may-interrupt -Show the current permission to interrupt or stop the program. - -@end table - -@node Reverse Execution -@chapter Running programs backward -@cindex reverse execution -@cindex running programs backward - -When you are debugging a program, it is not unusual to realize that -you have gone too far, and some event of interest has already happened. -If the target environment supports it, @value{GDBN} can allow you to -``rewind'' the program by running it backward. - -A target environment that supports reverse execution should be able -to ``undo'' the changes in machine state that have taken place as the -program was executing normally. Variables, registers etc.@: should -revert to their previous values. Obviously this requires a great -deal of sophistication on the part of the target environment; not -all target environments can support reverse execution. - -When a program is executed in reverse, the instructions that -have most recently been executed are ``un-executed'', in reverse -order. The program counter runs backward, following the previous -thread of execution in reverse. As each instruction is ``un-executed'', -the values of memory and/or registers that were changed by that -instruction are reverted to their previous states. After executing -a piece of source code in reverse, all side effects of that code -should be ``undone'', and all variables should be returned to their -prior values@footnote{ -Note that some side effects are easier to undo than others. For instance, -memory and registers are relatively easy, but device I/O is hard. Some -targets may be able undo things like device I/O, and some may not. - -The contract between @value{GDBN} and the reverse executing target -requires only that the target do something reasonable when -@value{GDBN} tells it to execute backwards, and then report the -results back to @value{GDBN}. Whatever the target reports back to -@value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN} -assumes that the memory and registers that the target reports are in a -consistant state, but @value{GDBN} accepts whatever it is given. -}. - -If you are debugging in a target environment that supports -reverse execution, @value{GDBN} provides the following commands. - -@table @code -@kindex reverse-continue -@kindex rc @r{(@code{reverse-continue})} -@item reverse-continue @r{[}@var{ignore-count}@r{]} -@itemx rc @r{[}@var{ignore-count}@r{]} -Beginning at the point where your program last stopped, start executing -in reverse. Reverse execution will stop for breakpoints and synchronous -exceptions (signals), just like normal execution. Behavior of -asynchronous signals depends on the target environment. - -@kindex reverse-step -@kindex rs @r{(@code{step})} -@item reverse-step @r{[}@var{count}@r{]} -Run the program backward until control reaches the start of a -different source line; then stop it, and return control to @value{GDBN}. - -Like the @code{step} command, @code{reverse-step} will only stop -at the beginning of a source line. It ``un-executes'' the previously -executed source line. If the previous source line included calls to -debuggable functions, @code{reverse-step} will step (backward) into -the called function, stopping at the beginning of the @emph{last} -statement in the called function (typically a return statement). - -Also, as with the @code{step} command, if non-debuggable functions are -called, @code{reverse-step} will run thru them backward without stopping. - -@kindex reverse-stepi -@kindex rsi @r{(@code{reverse-stepi})} -@item reverse-stepi @r{[}@var{count}@r{]} -Reverse-execute one machine instruction. Note that the instruction -to be reverse-executed is @emph{not} the one pointed to by the program -counter, but the instruction executed prior to that one. For instance, -if the last instruction was a jump, @code{reverse-stepi} will take you -back from the destination of the jump to the jump instruction itself. - -@kindex reverse-next -@kindex rn @r{(@code{reverse-next})} -@item reverse-next @r{[}@var{count}@r{]} -Run backward to the beginning of the previous line executed in -the current (innermost) stack frame. If the line contains function -calls, they will be ``un-executed'' without stopping. Starting from -the first line of a function, @code{reverse-next} will take you back -to the caller of that function, @emph{before} the function was called, -just as the normal @code{next} command would take you from the last -line of a function back to its return to its caller -@footnote{Unless the code is too heavily optimized.}. - -@kindex reverse-nexti -@kindex rni @r{(@code{reverse-nexti})} -@item reverse-nexti @r{[}@var{count}@r{]} -Like @code{nexti}, @code{reverse-nexti} executes a single instruction -in reverse, except that called functions are ``un-executed'' atomically. -That is, if the previously executed instruction was a return from -another function, @code{reverse-nexti} will continue to execute -in reverse until the call to that function (from the current stack -frame) is reached. - -@kindex reverse-finish -@item reverse-finish -Just as the @code{finish} command takes you to the point where the -current function returns, @code{reverse-finish} takes you to the point -where it was called. Instead of ending up at the end of the current -function invocation, you end up at the beginning. - -@kindex set exec-direction -@item set exec-direction -Set the direction of target execution. -@item set exec-direction reverse -@cindex execute forward or backward in time -@value{GDBN} will perform all execution commands in reverse, until the -exec-direction mode is changed to ``forward''. Affected commands include -@code{step, stepi, next, nexti, continue, and finish}. The @code{return} -command cannot be used in reverse mode. -@item set exec-direction forward -@value{GDBN} will perform all execution commands in the normal fashion. -This is the default. -@end table - - -@node Process Record and Replay -@chapter Recording Inferior's Execution and Replaying It -@cindex process record and replay -@cindex recording inferior's execution and replaying it - -On some platforms, @value{GDBN} provides a special @dfn{process record -and replay} target that can record a log of the process execution, and -replay it later with both forward and reverse execution commands. - -@cindex replay mode -When this target is in use, if the execution log includes the record -for the next instruction, @value{GDBN} will debug in @dfn{replay -mode}. In the replay mode, the inferior does not really execute code -instructions. Instead, all the events that normally happen during -code execution are taken from the execution log. While code is not -really executed in replay mode, the values of registers (including the -program counter register) and the memory of the inferior are still -changed as they normally would. Their contents are taken from the -execution log. - -@cindex record mode -If the record for the next instruction is not in the execution log, -@value{GDBN} will debug in @dfn{record mode}. In this mode, the -inferior executes normally, and @value{GDBN} records the execution log -for future replay. - -The process record and replay target supports reverse execution -(@pxref{Reverse Execution}), even if the platform on which the -inferior runs does not. However, the reverse execution is limited in -this case by the range of the instructions recorded in the execution -log. In other words, reverse execution on platforms that don't -support it directly can only be done in the replay mode. - -When debugging in the reverse direction, @value{GDBN} will work in -replay mode as long as the execution log includes the record for the -previous instruction; otherwise, it will work in record mode, if the -platform supports reverse execution, or stop if not. - -For architecture environments that support process record and replay, -@value{GDBN} provides the following commands: - -@table @code -@kindex target record -@kindex target record-full -@kindex target record-btrace -@kindex record -@kindex record full -@kindex record btrace -@kindex rec -@kindex rec full -@kindex rec btrace -@item record @var{method} -This command starts the process record and replay target. The -recording method can be specified as parameter. Without a parameter -the command uses the @code{full} recording method. The following -recording methods are available: - -@table @code -@item full -Full record/replay recording using @value{GDBN}'s software record and -replay implementation. This method allows replaying and reverse -execution. - -@item btrace -Hardware-supported instruction recording. This method does not allow -replaying and reverse execution. - -This recording method may not be available on all processors. -@end table - -The process record and replay target can only debug a process that is -already running. Therefore, you need first to start the process with -the @kbd{run} or @kbd{start} commands, and then start the recording -with the @kbd{record @var{method}} command. - -Both @code{record @var{method}} and @code{rec @var{method}} are -aliases of @code{target record-@var{method}}. - -@cindex displaced stepping, and process record and replay -Displaced stepping (@pxref{Maintenance Commands,, displaced stepping}) -will be automatically disabled when process record and replay target -is started. That's because the process record and replay target -doesn't support displaced stepping. - -@cindex non-stop mode, and process record and replay -@cindex asynchronous execution, and process record and replay -If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in -the asynchronous execution mode (@pxref{Background Execution}), not -all recording methods are available. The @code{full} recording method -does not support these two modes. - -@kindex record stop -@kindex rec s -@item record stop -Stop the process record and replay target. When process record and -replay target stops, the entire execution log will be deleted and the -inferior will either be terminated, or will remain in its final state. - -When you stop the process record and replay target in record mode (at -the end of the execution log), the inferior will be stopped at the -next instruction that would have been recorded. In other words, if -you record for a while and then stop recording, the inferior process -will be left in the same state as if the recording never happened. - -On the other hand, if the process record and replay target is stopped -while in replay mode (that is, not at the end of the execution log, -but at some earlier point), the inferior process will become ``live'' -at that earlier state, and it will then be possible to continue the -usual ``live'' debugging of the process from that state. - -When the inferior process exits, or @value{GDBN} detaches from it, -process record and replay target will automatically stop itself. - -@kindex record save -@item record save @var{filename} -Save the execution log to a file @file{@var{filename}}. -Default filename is @file{gdb_record.@var{process_id}}, where -@var{process_id} is the process ID of the inferior. - -This command may not be available for all recording methods. - -@kindex record restore -@item record restore @var{filename} -Restore the execution log from a file @file{@var{filename}}. -File must have been created with @code{record save}. - -@kindex set record full -@item set record full insn-number-max @var{limit} -Set the limit of instructions to be recorded for the @code{full} -recording method. Default value is 200000. - -If @var{limit} is a positive number, then @value{GDBN} will start -deleting instructions from the log once the number of the record -instructions becomes greater than @var{limit}. For every new recorded -instruction, @value{GDBN} will delete the earliest recorded -instruction to keep the number of recorded instructions at the limit. -(Since deleting recorded instructions loses information, @value{GDBN} -lets you control what happens when the limit is reached, by means of -the @code{stop-at-limit} option, described below.) - -If @var{limit} is zero, @value{GDBN} will never delete recorded -instructions from the execution log. The number of recorded -instructions is unlimited in this case. - -@kindex show record full -@item show record full insn-number-max -Show the limit of instructions to be recorded with the @code{full} -recording method. - -@item set record full stop-at-limit -Control the behavior of the @code{full} recording method when the -number of recorded instructions reaches the limit. If ON (the -default), @value{GDBN} will stop when the limit is reached for the -first time and ask you whether you want to stop the inferior or -continue running it and recording the execution log. If you decide -to continue recording, each new recorded instruction will cause the -oldest one to be deleted. - -If this option is OFF, @value{GDBN} will automatically delete the -oldest record to make room for each new one, without asking. - -@item show record full stop-at-limit -Show the current setting of @code{stop-at-limit}. - -@item set record full memory-query -Control the behavior when @value{GDBN} is unable to record memory -changes caused by an instruction for the @code{full} recording method. -If ON, @value{GDBN} will query whether to stop the inferior in that -case. - -If this option is OFF (the default), @value{GDBN} will automatically -ignore the effect of such instructions on memory. Later, when -@value{GDBN} replays this execution log, it will mark the log of this -instruction as not accessible, and it will not affect the replay -results. - -@item show record full memory-query -Show the current setting of @code{memory-query}. - -@kindex info record -@item info record -Show various statistics about the recording depending on the recording -method: - -@table @code -@item full -For the @code{full} recording method, it shows the state of process -record and its in-memory execution log buffer, including: - -@itemize @bullet -@item -Whether in record mode or replay mode. -@item -Lowest recorded instruction number (counting from when the current execution log started recording instructions). -@item -Highest recorded instruction number. -@item -Current instruction about to be replayed (if in replay mode). -@item -Number of instructions contained in the execution log. -@item -Maximum number of instructions that may be contained in the execution log. -@end itemize - -@item btrace -For the @code{btrace} recording method, it shows the number of -instructions that have been recorded and the number of blocks of -sequential control-flow that is formed by the recorded instructions. -@end table - -@kindex record delete -@kindex rec del -@item record delete -When record target runs in replay mode (``in the past''), delete the -subsequent execution log and begin to record a new execution log starting -from the current address. This means you will abandon the previously -recorded ``future'' and begin recording a new ``future''. - -@kindex record instruction-history -@kindex rec instruction-history -@item record instruction-history -Disassembles instructions from the recorded execution log. By -default, ten instructions are disassembled. This can be changed using -the @code{set record instruction-history-size} command. Instructions -are printed in execution order. There are several ways to specify -what part of the execution log to disassemble: - -@table @code -@item record instruction-history @var{insn} -Disassembles ten instructions starting from instruction number -@var{insn}. - -@item record instruction-history @var{insn}, +/-@var{n} -Disassembles @var{n} instructions around instruction number -@var{insn}. If @var{n} is preceded with @code{+}, disassembles -@var{n} instructions after instruction number @var{insn}. If -@var{n} is preceded with @code{-}, disassembles @var{n} -instructions before instruction number @var{insn}. - -@item record instruction-history -Disassembles ten more instructions after the last disassembly. - -@item record instruction-history - -Disassembles ten more instructions before the last disassembly. - -@item record instruction-history @var{begin} @var{end} -Disassembles instructions beginning with instruction number -@var{begin} until instruction number @var{end}. The instruction -number @var{end} is not included. -@end table - -This command may not be available for all recording methods. - -@kindex set record -@item set record instruction-history-size -Define how many instructions to disassemble in the @code{record -instruction-history} command. The default value is 10. - -@kindex show record -@item show record instruction-history-size -Show how many instructions to disassemble in the @code{record -instruction-history} command. - -@kindex record function-call-history -@kindex rec function-call-history -@item record function-call-history -Prints the execution history at function granularity. It prints one -line for each sequence of instructions that belong to the same -function giving the name of that function, the source lines -for this instruction sequence (if the @code{/l} modifier is -specified), and the instructions numbers that form the sequence (if -the @code{/i} modifier is specified). - -@smallexample -(@value{GDBP}) @b{list 1, 10} -1 void foo (void) -2 @{ -3 @} -4 -5 void bar (void) -6 @{ -7 ... -8 foo (); -9 ... -10 @} -(@value{GDBP}) @b{record function-call-history /l} -1 foo.c:6-8 bar -2 foo.c:2-3 foo -3 foo.c:9-10 bar -@end smallexample - -By default, ten lines are printed. This can be changed using the -@code{set record function-call-history-size} command. Functions are -printed in execution order. There are several ways to specify what -to print: - -@table @code -@item record function-call-history @var{func} -Prints ten functions starting from function number @var{func}. - -@item record function-call-history @var{func}, +/-@var{n} -Prints @var{n} functions around function number @var{func}. If -@var{n} is preceded with @code{+}, prints @var{n} functions after -function number @var{func}. If @var{n} is preceded with @code{-}, -prints @var{n} functions before function number @var{func}. - -@item record function-call-history -Prints ten more functions after the last ten-line print. - -@item record function-call-history - -Prints ten more functions before the last ten-line print. - -@item record function-call-history @var{begin} @var{end} -Prints functions beginning with function number @var{begin} until -function number @var{end}. The function number @var{end} is not -included. -@end table - -This command may not be available for all recording methods. - -@item set record function-call-history-size -Define how many lines to print in the -@code{record function-call-history} command. The default value is 10. - -@item show record function-call-history-size -Show how many lines to print in the -@code{record function-call-history} command. -@end table - - -@node Stack -@chapter Examining the Stack - -When your program has stopped, the first thing you need to know is where it -stopped and how it got there. - -@cindex call stack -Each time your program performs a function call, information about the call -is generated. -That information includes the location of the call in your program, -the arguments of the call, -and the local variables of the function being called. -The information is saved in a block of data called a @dfn{stack frame}. -The stack frames are allocated in a region of memory called the @dfn{call -stack}. - -When your program stops, the @value{GDBN} commands for examining the -stack allow you to see all of this information. - -@cindex selected frame -One of the stack frames is @dfn{selected} by @value{GDBN} and many -@value{GDBN} commands refer implicitly to the selected frame. In -particular, whenever you ask @value{GDBN} for the value of a variable in -your program, the value is found in the selected frame. There are -special @value{GDBN} commands to select whichever frame you are -interested in. @xref{Selection, ,Selecting a Frame}. - -When your program stops, @value{GDBN} automatically selects the -currently executing frame and describes it briefly, similar to the -@code{frame} command (@pxref{Frame Info, ,Information about a Frame}). - -@menu -* Frames:: Stack frames -* Backtrace:: Backtraces -* Selection:: Selecting a frame -* Frame Info:: Information on a frame - -@end menu - -@node Frames -@section Stack Frames - -@cindex frame, definition -@cindex stack frame -The call stack is divided up into contiguous pieces called @dfn{stack -frames}, or @dfn{frames} for short; each frame is the data associated -with one call to one function. The frame contains the arguments given -to the function, the function's local variables, and the address at -which the function is executing. - -@cindex initial frame -@cindex outermost frame -@cindex innermost frame -When your program is started, the stack has only one frame, that of the -function @code{main}. This is called the @dfn{initial} frame or the -@dfn{outermost} frame. Each time a function is called, a new frame is -made. Each time a function returns, the frame for that function invocation -is eliminated. If a function is recursive, there can be many frames for -the same function. The frame for the function in which execution is -actually occurring is called the @dfn{innermost} frame. This is the most -recently created of all the stack frames that still exist. - -@cindex frame pointer -Inside your program, stack frames are identified by their addresses. A -stack frame consists of many bytes, each of which has its own address; each -kind of computer has a convention for choosing one byte whose -address serves as the address of the frame. Usually this address is kept -in a register called the @dfn{frame pointer register} -(@pxref{Registers, $fp}) while execution is going on in that frame. - -@cindex frame number -@value{GDBN} assigns numbers to all existing stack frames, starting with -zero for the innermost frame, one for the frame that called it, -and so on upward. These numbers do not really exist in your program; -they are assigned by @value{GDBN} to give you a way of designating stack -frames in @value{GDBN} commands. - -@c The -fomit-frame-pointer below perennially causes hbox overflow -@c underflow problems. -@cindex frameless execution -Some compilers provide a way to compile functions so that they operate -without stack frames. (For example, the @value{NGCC} option -@smallexample -@samp{-fomit-frame-pointer} -@end smallexample -generates functions without a frame.) -This is occasionally done with heavily used library functions to save -the frame setup time. @value{GDBN} has limited facilities for dealing -with these function invocations. If the innermost function invocation -has no stack frame, @value{GDBN} nevertheless regards it as though -it had a separate frame, which is numbered zero as usual, allowing -correct tracing of the function call chain. However, @value{GDBN} has -no provision for frameless functions elsewhere in the stack. - -@table @code -@kindex frame@r{, command} -@cindex current stack frame -@item frame @var{args} -The @code{frame} command allows you to move from one stack frame to another, -and to print the stack frame you select. @var{args} may be either the -address of the frame or the stack frame number. Without an argument, -@code{frame} prints the current stack frame. - -@kindex select-frame -@cindex selecting frame silently -@item select-frame -The @code{select-frame} command allows you to move from one stack frame -to another without printing the frame. This is the silent version of -@code{frame}. -@end table - -@node Backtrace -@section Backtraces - -@cindex traceback -@cindex call stack traces -A backtrace is a summary of how your program got where it is. It shows one -line per frame, for many frames, starting with the currently executing -frame (frame zero), followed by its caller (frame one), and on up the -stack. - -@table @code -@kindex backtrace -@kindex bt @r{(@code{backtrace})} -@item backtrace -@itemx bt -Print a backtrace of the entire stack: one line per frame for all -frames in the stack. - -You can stop the backtrace at any time by typing the system interrupt -character, normally @kbd{Ctrl-c}. - -@item backtrace @var{n} -@itemx bt @var{n} -Similar, but print only the innermost @var{n} frames. - -@item backtrace -@var{n} -@itemx bt -@var{n} -Similar, but print only the outermost @var{n} frames. - -@item backtrace full -@itemx bt full -@itemx bt full @var{n} -@itemx bt full -@var{n} -Print the values of the local variables also. @var{n} specifies the -number of frames to print, as described above. -@end table - -@kindex where -@kindex info stack -The names @code{where} and @code{info stack} (abbreviated @code{info s}) -are additional aliases for @code{backtrace}. - -@cindex multiple threads, backtrace -In a multi-threaded program, @value{GDBN} by default shows the -backtrace only for the current thread. To display the backtrace for -several or all of the threads, use the command @code{thread apply} -(@pxref{Threads, thread apply}). For example, if you type @kbd{thread -apply all backtrace}, @value{GDBN} will display the backtrace for all -the threads; this is handy when you debug a core dump of a -multi-threaded program. - -Each line in the backtrace shows the frame number and the function name. -The program counter value is also shown---unless you use @code{set -print address off}. The backtrace also shows the source file name and -line number, as well as the arguments to the function. The program -counter value is omitted if it is at the beginning of the code for that -line number. - -Here is an example of a backtrace. It was made with the command -@samp{bt 3}, so it shows the innermost three frames. - -@smallexample -@group -#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) - at builtin.c:993 -#1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242 -#2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08) - at macro.c:71 -(More stack frames follow...) -@end group -@end smallexample - -@noindent -The display for frame zero does not begin with a program counter -value, indicating that your program has stopped at the beginning of the -code for line @code{993} of @code{builtin.c}. - -@noindent -The value of parameter @code{data} in frame 1 has been replaced by -@code{@dots{}}. By default, @value{GDBN} prints the value of a parameter -only if it is a scalar (integer, pointer, enumeration, etc). See command -@kbd{set print frame-arguments} in @ref{Print Settings} for more details -on how to configure the way function parameter values are printed. - -@cindex optimized out, in backtrace -@cindex function call arguments, optimized out -If your program was compiled with optimizations, some compilers will -optimize away arguments passed to functions if those arguments are -never used after the call. Such optimizations generate code that -passes arguments through registers, but doesn't store those arguments -in the stack frame. @value{GDBN} has no way of displaying such -arguments in stack frames other than the innermost one. Here's what -such a backtrace might look like: - -@smallexample -@group -#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) - at builtin.c:993 -#1 0x6e38 in expand_macro (sym=) at macro.c:242 -#2 0x6840 in expand_token (obs=0x0, t=, td=0xf7fffb08) - at macro.c:71 -(More stack frames follow...) -@end group -@end smallexample - -@noindent -The values of arguments that were not saved in their stack frames are -shown as @samp{}. - -If you need to display the values of such optimized-out arguments, -either deduce that from other variables whose values depend on the one -you are interested in, or recompile without optimizations. - -@cindex backtrace beyond @code{main} function -@cindex program entry point -@cindex startup code, and backtrace -Most programs have a standard user entry point---a place where system -libraries and startup code transition into user code. For C this is -@code{main}@footnote{ -Note that embedded programs (the so-called ``free-standing'' -environment) are not required to have a @code{main} function as the -entry point. They could even have multiple entry points.}. -When @value{GDBN} finds the entry function in a backtrace -it will terminate the backtrace, to avoid tracing into highly -system-specific (and generally uninteresting) code. - -If you need to examine the startup code, or limit the number of levels -in a backtrace, you can change this behavior: - -@table @code -@item set backtrace past-main -@itemx set backtrace past-main on -@kindex set backtrace -Backtraces will continue past the user entry point. - -@item set backtrace past-main off -Backtraces will stop when they encounter the user entry point. This is the -default. - -@item show backtrace past-main -@kindex show backtrace -Display the current user entry point backtrace policy. - -@item set backtrace past-entry -@itemx set backtrace past-entry on -Backtraces will continue past the internal entry point of an application. -This entry point is encoded by the linker when the application is built, -and is likely before the user entry point @code{main} (or equivalent) is called. - -@item set backtrace past-entry off -Backtraces will stop when they encounter the internal entry point of an -application. This is the default. - -@item show backtrace past-entry -Display the current internal entry point backtrace policy. - -@item set backtrace limit @var{n} -@itemx set backtrace limit 0 -@cindex backtrace limit -Limit the backtrace to @var{n} levels. A value of zero means -unlimited. - -@item show backtrace limit -Display the current limit on backtrace levels. -@end table - -You can control how file names are displayed. - -@table @code -@item set filename-display -@itemx set filename-display relative -@cindex filename-display -Display file names relative to the compilation directory. This is the default. - -@item set filename-display basename -Display only basename of a filename. - -@item set filename-display absolute -Display an absolute filename. - -@item show filename-display -Show the current way to display filenames. -@end table - -@node Selection -@section Selecting a Frame - -Most commands for examining the stack and other data in your program work on -whichever stack frame is selected at the moment. Here are the commands for -selecting a stack frame; all of them finish by printing a brief description -of the stack frame just selected. - -@table @code -@kindex frame@r{, selecting} -@kindex f @r{(@code{frame})} -@item frame @var{n} -@itemx f @var{n} -Select frame number @var{n}. Recall that frame zero is the innermost -(currently executing) frame, frame one is the frame that called the -innermost one, and so on. The highest-numbered frame is the one for -@code{main}. - -@item frame @var{addr} -@itemx f @var{addr} -Select the frame at address @var{addr}. This is useful mainly if the -chaining of stack frames has been damaged by a bug, making it -impossible for @value{GDBN} to assign numbers properly to all frames. In -addition, this can be useful when your program has multiple stacks and -switches between them. - -On the SPARC architecture, @code{frame} needs two addresses to -select an arbitrary frame: a frame pointer and a stack pointer. - -On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack -pointer and a program counter. - -On the 29k architecture, it needs three addresses: a register stack -pointer, a program counter, and a memory stack pointer. - -@kindex up -@item up @var{n} -Move @var{n} frames up the stack. For positive numbers @var{n}, this -advances toward the outermost frame, to higher frame numbers, to frames -that have existed longer. @var{n} defaults to one. - -@kindex down -@kindex do @r{(@code{down})} -@item down @var{n} -Move @var{n} frames down the stack. For positive numbers @var{n}, this -advances toward the innermost frame, to lower frame numbers, to frames -that were created more recently. @var{n} defaults to one. You may -abbreviate @code{down} as @code{do}. -@end table - -All of these commands end by printing two lines of output describing the -frame. The first line shows the frame number, the function name, the -arguments, and the source file and line number of execution in that -frame. The second line shows the text of that source line. - -@need 1000 -For example: - -@smallexample -@group -(@value{GDBP}) up -#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) - at env.c:10 -10 read_input_file (argv[i]); -@end group -@end smallexample - -After such a printout, the @code{list} command with no arguments -prints ten lines centered on the point of execution in the frame. -You can also edit the program at the point of execution with your favorite -editing program by typing @code{edit}. -@xref{List, ,Printing Source Lines}, -for details. - -@table @code -@kindex down-silently -@kindex up-silently -@item up-silently @var{n} -@itemx down-silently @var{n} -These two commands are variants of @code{up} and @code{down}, -respectively; they differ in that they do their work silently, without -causing display of the new frame. They are intended primarily for use -in @value{GDBN} command scripts, where the output might be unnecessary and -distracting. -@end table - -@node Frame Info -@section Information About a Frame - -There are several other commands to print information about the selected -stack frame. - -@table @code -@item frame -@itemx f -When used without any argument, this command does not change which -frame is selected, but prints a brief description of the currently -selected stack frame. It can be abbreviated @code{f}. With an -argument, this command is used to select a stack frame. -@xref{Selection, ,Selecting a Frame}. - -@kindex info frame -@kindex info f @r{(@code{info frame})} -@item info frame -@itemx info f -This command prints a verbose description of the selected stack frame, -including: - -@itemize @bullet -@item -the address of the frame -@item -the address of the next frame down (called by this frame) -@item -the address of the next frame up (caller of this frame) -@item -the language in which the source code corresponding to this frame is written -@item -the address of the frame's arguments -@item -the address of the frame's local variables -@item -the program counter saved in it (the address of execution in the caller frame) -@item -which registers were saved in the frame -@end itemize - -@noindent The verbose description is useful when -something has gone wrong that has made the stack format fail to fit -the usual conventions. - -@item info frame @var{addr} -@itemx info f @var{addr} -Print a verbose description of the frame at address @var{addr}, without -selecting that frame. The selected frame remains unchanged by this -command. This requires the same kind of address (more than one for some -architectures) that you specify in the @code{frame} command. -@xref{Selection, ,Selecting a Frame}. - -@kindex info args -@item info args -Print the arguments of the selected frame, each on a separate line. - -@item info locals -@kindex info locals -Print the local variables of the selected frame, each on a separate -line. These are all variables (declared either static or automatic) -accessible at the point of execution of the selected frame. - -@end table - - -@node Source -@chapter Examining Source Files - -@value{GDBN} can print parts of your program's source, since the debugging -information recorded in the program tells @value{GDBN} what source files were -used to build it. When your program stops, @value{GDBN} spontaneously prints -the line where it stopped. Likewise, when you select a stack frame -(@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where -execution in that frame has stopped. You can print other portions of -source files by explicit command. - -If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may -prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using -@value{GDBN} under @sc{gnu} Emacs}. - -@menu -* List:: Printing source lines -* Specify Location:: How to specify code locations -* Edit:: Editing source files -* Search:: Searching source files -* Source Path:: Specifying source directories -* Machine Code:: Source and machine code -@end menu - -@node List -@section Printing Source Lines - -@kindex list -@kindex l @r{(@code{list})} -To print lines from a source file, use the @code{list} command -(abbreviated @code{l}). By default, ten lines are printed. -There are several ways to specify what part of the file you want to -print; see @ref{Specify Location}, for the full list. - -Here are the forms of the @code{list} command most commonly used: - -@table @code -@item list @var{linenum} -Print lines centered around line number @var{linenum} in the -current source file. - -@item list @var{function} -Print lines centered around the beginning of function -@var{function}. - -@item list -Print more lines. If the last lines printed were printed with a -@code{list} command, this prints lines following the last lines -printed; however, if the last line printed was a solitary line printed -as part of displaying a stack frame (@pxref{Stack, ,Examining the -Stack}), this prints lines centered around that line. - -@item list - -Print lines just before the lines last printed. -@end table - -@cindex @code{list}, how many lines to display -By default, @value{GDBN} prints ten source lines with any of these forms of -the @code{list} command. You can change this using @code{set listsize}: - -@table @code -@kindex set listsize -@item set listsize @var{count} -Make the @code{list} command display @var{count} source lines (unless -the @code{list} argument explicitly specifies some other number). -Setting @var{count} to 0 means there's no limit. - -@kindex show listsize -@item show listsize -Display the number of lines that @code{list} prints. -@end table - -Repeating a @code{list} command with @key{RET} discards the argument, -so it is equivalent to typing just @code{list}. This is more useful -than listing the same lines again. An exception is made for an -argument of @samp{-}; that argument is preserved in repetition so that -each repetition moves up in the source file. - -In general, the @code{list} command expects you to supply zero, one or two -@dfn{linespecs}. Linespecs specify source lines; there are several ways -of writing them (@pxref{Specify Location}), but the effect is always -to specify some source line. - -Here is a complete description of the possible arguments for @code{list}: - -@table @code -@item list @var{linespec} -Print lines centered around the line specified by @var{linespec}. - -@item list @var{first},@var{last} -Print lines from @var{first} to @var{last}. Both arguments are -linespecs. When a @code{list} command has two linespecs, and the -source file of the second linespec is omitted, this refers to -the same source file as the first linespec. - -@item list ,@var{last} -Print lines ending with @var{last}. - -@item list @var{first}, -Print lines starting with @var{first}. - -@item list + -Print lines just after the lines last printed. - -@item list - -Print lines just before the lines last printed. - -@item list -As described in the preceding table. -@end table - -@node Specify Location -@section Specifying a Location -@cindex specifying location -@cindex linespec - -Several @value{GDBN} commands accept arguments that specify a location -of your program's code. Since @value{GDBN} is a source-level -debugger, a location usually specifies some line in the source code; -for that reason, locations are also known as @dfn{linespecs}. - -Here are all the different ways of specifying a code location that -@value{GDBN} understands: - -@table @code -@item @var{linenum} -Specifies the line number @var{linenum} of the current source file. - -@item -@var{offset} -@itemx +@var{offset} -Specifies the line @var{offset} lines before or after the @dfn{current -line}. For the @code{list} command, the current line is the last one -printed; for the breakpoint commands, this is the line at which -execution stopped in the currently selected @dfn{stack frame} -(@pxref{Frames, ,Frames}, for a description of stack frames.) When -used as the second of the two linespecs in a @code{list} command, -this specifies the line @var{offset} lines up or down from the first -linespec. - -@item @var{filename}:@var{linenum} -Specifies the line @var{linenum} in the source file @var{filename}. -If @var{filename} is a relative file name, then it will match any -source file name with the same trailing components. For example, if -@var{filename} is @samp{gcc/expr.c}, then it will match source file -name of @file{/build/trunk/gcc/expr.c}, but not -@file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}. - -@item @var{function} -Specifies the line that begins the body of the function @var{function}. -For example, in C, this is the line with the open brace. - -@item @var{function}:@var{label} -Specifies the line where @var{label} appears in @var{function}. - -@item @var{filename}:@var{function} -Specifies the line that begins the body of the function @var{function} -in the file @var{filename}. You only need the file name with a -function name to avoid ambiguity when there are identically named -functions in different source files. - -@item @var{label} -Specifies the line at which the label named @var{label} appears. -@value{GDBN} searches for the label in the function corresponding to -the currently selected stack frame. If there is no current selected -stack frame (for instance, if the inferior is not running), then -@value{GDBN} will not search for a label. - -@item *@var{address} -Specifies the program address @var{address}. For line-oriented -commands, such as @code{list} and @code{edit}, this specifies a source -line that contains @var{address}. For @code{break} and other -breakpoint oriented commands, this can be used to set breakpoints in -parts of your program which do not have debugging information or -source files. - -Here @var{address} may be any expression valid in the current working -language (@pxref{Languages, working language}) that specifies a code -address. In addition, as a convenience, @value{GDBN} extends the -semantics of expressions used in locations to cover the situations -that frequently happen during debugging. Here are the various forms -of @var{address}: - -@table @code -@item @var{expression} -Any expression valid in the current working language. - -@item @var{funcaddr} -An address of a function or procedure derived from its name. In C, -C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is -simply the function's name @var{function} (and actually a special case -of a valid expression). In Pascal and Modula-2, this is -@code{&@var{function}}. In Ada, this is @code{@var{function}'Address} -(although the Pascal form also works). - -This form specifies the address of the function's first instruction, -before the stack frame and arguments have been set up. - -@item '@var{filename}'::@var{funcaddr} -Like @var{funcaddr} above, but also specifies the name of the source -file explicitly. This is useful if the name of the function does not -specify the function unambiguously, e.g., if there are several -functions with identical names in different source files. -@end table - -@cindex breakpoint at static probe point -@item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name} -The @sc{gnu}/Linux tool @code{SystemTap} provides a way for -applications to embed static probes. @xref{Static Probe Points}, for more -information on finding and using static probes. This form of linespec -specifies the location of such a static probe. - -If @var{objfile} is given, only probes coming from that shared library -or executable matching @var{objfile} as a regular expression are considered. -If @var{provider} is given, then only probes from that provider are considered. -If several probes match the spec, @value{GDBN} will insert a breakpoint at -each one of those probes. - -@end table - - -@node Edit -@section Editing Source Files -@cindex editing source files - -@kindex edit -@kindex e @r{(@code{edit})} -To edit the lines in a source file, use the @code{edit} command. -The editing program of your choice -is invoked with the current line set to -the active line in the program. -Alternatively, there are several ways to specify what part of the file you -want to print if you want to see other parts of the program: - -@table @code -@item edit @var{location} -Edit the source file specified by @code{location}. Editing starts at -that @var{location}, e.g., at the specified source line of the -specified file. @xref{Specify Location}, for all the possible forms -of the @var{location} argument; here are the forms of the @code{edit} -command most commonly used: - -@table @code -@item edit @var{number} -Edit the current source file with @var{number} as the active line number. - -@item edit @var{function} -Edit the file containing @var{function} at the beginning of its definition. -@end table - -@end table - -@subsection Choosing your Editor -You can customize @value{GDBN} to use any editor you want -@footnote{ -The only restriction is that your editor (say @code{ex}), recognizes the -following command-line syntax: -@smallexample -ex +@var{number} file -@end smallexample -The optional numeric value +@var{number} specifies the number of the line in -the file where to start editing.}. -By default, it is @file{@value{EDITOR}}, but you can change this -by setting the environment variable @code{EDITOR} before using -@value{GDBN}. For example, to configure @value{GDBN} to use the -@code{vi} editor, you could use these commands with the @code{sh} shell: -@smallexample -EDITOR=/usr/bin/vi -export EDITOR -gdb @dots{} -@end smallexample -or in the @code{csh} shell, -@smallexample -setenv EDITOR /usr/bin/vi -gdb @dots{} -@end smallexample - -@node Search -@section Searching Source Files -@cindex searching source files - -There are two commands for searching through the current source file for a -regular expression. - -@table @code -@kindex search -@kindex forward-search -@kindex fo @r{(@code{forward-search})} -@item forward-search @var{regexp} -@itemx search @var{regexp} -The command @samp{forward-search @var{regexp}} checks each line, -starting with the one following the last line listed, for a match for -@var{regexp}. It lists the line that is found. You can use the -synonym @samp{search @var{regexp}} or abbreviate the command name as -@code{fo}. - -@kindex reverse-search -@item reverse-search @var{regexp} -The command @samp{reverse-search @var{regexp}} checks each line, starting -with the one before the last line listed and going backward, for a match -for @var{regexp}. It lists the line that is found. You can abbreviate -this command as @code{rev}. -@end table - -@node Source Path -@section Specifying Source Directories - -@cindex source path -@cindex directories for source files -Executable programs sometimes do not record the directories of the source -files from which they were compiled, just the names. Even when they do, -the directories could be moved between the compilation and your debugging -session. @value{GDBN} has a list of directories to search for source files; -this is called the @dfn{source path}. Each time @value{GDBN} wants a source file, -it tries all the directories in the list, in the order they are present -in the list, until it finds a file with the desired name. - -For example, suppose an executable references the file -@file{/usr/src/foo-1.0/lib/foo.c}, and our source path is -@file{/mnt/cross}. The file is first looked up literally; if this -fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this -fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error -message is printed. @value{GDBN} does not look up the parts of the -source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}. -Likewise, the subdirectories of the source path are not searched: if -the source path is @file{/mnt/cross}, and the binary refers to -@file{foo.c}, @value{GDBN} would not find it under -@file{/mnt/cross/usr/src/foo-1.0/lib}. - -Plain file names, relative file names with leading directories, file -names containing dots, etc.@: are all treated as described above; for -instance, if the source path is @file{/mnt/cross}, and the source file -is recorded as @file{../lib/foo.c}, @value{GDBN} would first try -@file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after -that---@file{/mnt/cross/foo.c}. - -Note that the executable search path is @emph{not} used to locate the -source files. - -Whenever you reset or rearrange the source path, @value{GDBN} clears out -any information it has cached about where source files are found and where -each line is in the file. - -@kindex directory -@kindex dir -When you start @value{GDBN}, its source path includes only @samp{cdir} -and @samp{cwd}, in that order. -To add other directories, use the @code{directory} command. - -The search path is used to find both program source files and @value{GDBN} -script files (read using the @samp{-command} option and @samp{source} command). - -In addition to the source path, @value{GDBN} provides a set of commands -that manage a list of source path substitution rules. A @dfn{substitution -rule} specifies how to rewrite source directories stored in the program's -debug information in case the sources were moved to a different -directory between compilation and debugging. A rule is made of -two strings, the first specifying what needs to be rewritten in -the path, and the second specifying how it should be rewritten. -In @ref{set substitute-path}, we name these two parts @var{from} and -@var{to} respectively. @value{GDBN} does a simple string replacement -of @var{from} with @var{to} at the start of the directory part of the -source file name, and uses that result instead of the original file -name to look up the sources. - -Using the previous example, suppose the @file{foo-1.0} tree has been -moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell -@value{GDBN} to replace @file{/usr/src} in all source path names with -@file{/mnt/cross}. The first lookup will then be -@file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location -of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path -substitution rule, use the @code{set substitute-path} command -(@pxref{set substitute-path}). - -To avoid unexpected substitution results, a rule is applied only if the -@var{from} part of the directory name ends at a directory separator. -For instance, a rule substituting @file{/usr/source} into -@file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but -not to @file{/usr/sourceware/foo-2.0}. And because the substitution -is applied only at the beginning of the directory name, this rule will -not be applied to @file{/root/usr/source/baz.c} either. - -In many cases, you can achieve the same result using the @code{directory} -command. However, @code{set substitute-path} can be more efficient in -the case where the sources are organized in a complex tree with multiple -subdirectories. With the @code{directory} command, you need to add each -subdirectory of your project. If you moved the entire tree while -preserving its internal organization, then @code{set substitute-path} -allows you to direct the debugger to all the sources with one single -command. - -@code{set substitute-path} is also more than just a shortcut command. -The source path is only used if the file at the original location no -longer exists. On the other hand, @code{set substitute-path} modifies -the debugger behavior to look at the rewritten location instead. So, if -for any reason a source file that is not relevant to your executable is -located at the original location, a substitution rule is the only -method available to point @value{GDBN} at the new location. - -@cindex @samp{--with-relocated-sources} -@cindex default source path substitution -You can configure a default source path substitution rule by -configuring @value{GDBN} with the -@samp{--with-relocated-sources=@var{dir}} option. The @var{dir} -should be the name of a directory under @value{GDBN}'s configured -prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and -directory names in debug information under @var{dir} will be adjusted -automatically if the installed @value{GDBN} is moved to a new -location. This is useful if @value{GDBN}, libraries or executables -with debug information and corresponding source code are being moved -together. - -@table @code -@item directory @var{dirname} @dots{} -@item dir @var{dirname} @dots{} -Add directory @var{dirname} to the front of the source path. Several -directory names may be given to this command, separated by @samp{:} -(@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as -part of absolute file names) or -whitespace. You may specify a directory that is already in the source -path; this moves it forward, so @value{GDBN} searches it sooner. - -@kindex cdir -@kindex cwd -@vindex $cdir@r{, convenience variable} -@vindex $cwd@r{, convenience variable} -@cindex compilation directory -@cindex current directory -@cindex working directory -@cindex directory, current -@cindex directory, compilation -You can use the string @samp{$cdir} to refer to the compilation -directory (if one is recorded), and @samp{$cwd} to refer to the current -working directory. @samp{$cwd} is not the same as @samp{.}---the former -tracks the current working directory as it changes during your @value{GDBN} -session, while the latter is immediately expanded to the current -directory at the time you add an entry to the source path. - -@item directory -Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation. - -@c RET-repeat for @code{directory} is explicitly disabled, but since -@c repeating it would be a no-op we do not say that. (thanks to RMS) - -@item set directories @var{path-list} -@kindex set directories -Set the source path to @var{path-list}. -@samp{$cdir:$cwd} are added if missing. - -@item show directories -@kindex show directories -Print the source path: show which directories it contains. - -@anchor{set substitute-path} -@item set substitute-path @var{from} @var{to} -@kindex set substitute-path -Define a source path substitution rule, and add it at the end of the -current list of existing substitution rules. If a rule with the same -@var{from} was already defined, then the old rule is also deleted. - -For example, if the file @file{/foo/bar/baz.c} was moved to -@file{/mnt/cross/baz.c}, then the command - -@smallexample -(@value{GDBP}) set substitute-path /usr/src /mnt/cross -@end smallexample - -@noindent -will tell @value{GDBN} to replace @samp{/usr/src} with -@samp{/mnt/cross}, which will allow @value{GDBN} to find the file -@file{baz.c} even though it was moved. - -In the case when more than one substitution rule have been defined, -the rules are evaluated one by one in the order where they have been -defined. The first one matching, if any, is selected to perform -the substitution. - -For instance, if we had entered the following commands: - -@smallexample -(@value{GDBP}) set substitute-path /usr/src/include /mnt/include -(@value{GDBP}) set substitute-path /usr/src /mnt/src -@end smallexample - -@noindent -@value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into -@file{/mnt/include/defs.h} by using the first rule. However, it would -use the second rule to rewrite @file{/usr/src/lib/foo.c} into -@file{/mnt/src/lib/foo.c}. - - -@item unset substitute-path [path] -@kindex unset substitute-path -If a path is specified, search the current list of substitution rules -for a rule that would rewrite that path. Delete that rule if found. -A warning is emitted by the debugger if no rule could be found. - -If no path is specified, then all substitution rules are deleted. - -@item show substitute-path [path] -@kindex show substitute-path -If a path is specified, then print the source path substitution rule -which would rewrite that path, if any. - -If no path is specified, then print all existing source path substitution -rules. - -@end table - -If your source path is cluttered with directories that are no longer of -interest, @value{GDBN} may sometimes cause confusion by finding the wrong -versions of source. You can correct the situation as follows: - -@enumerate -@item -Use @code{directory} with no argument to reset the source path to its default value. - -@item -Use @code{directory} with suitable arguments to reinstall the -directories you want in the source path. You can add all the -directories in one command. -@end enumerate - -@node Machine Code -@section Source and Machine Code -@cindex source line and its code address - -You can use the command @code{info line} to map source lines to program -addresses (and vice versa), and the command @code{disassemble} to display -a range of addresses as machine instructions. You can use the command -@code{set disassemble-next-line} to set whether to disassemble next -source line when execution stops. When run under @sc{gnu} Emacs -mode, the @code{info line} command causes the arrow to point to the -line specified. Also, @code{info line} prints addresses in symbolic form as -well as hex. - -@table @code -@kindex info line -@item info line @var{linespec} -Print the starting and ending addresses of the compiled code for -source line @var{linespec}. You can specify source lines in any of -the ways documented in @ref{Specify Location}. -@end table - -For example, we can use @code{info line} to discover the location of -the object code for the first line of function -@code{m4_changequote}: - -@c FIXME: I think this example should also show the addresses in -@c symbolic form, as they usually would be displayed. -@smallexample -(@value{GDBP}) info line m4_changequote -Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350. -@end smallexample - -@noindent -@cindex code address and its source line -We can also inquire (using @code{*@var{addr}} as the form for -@var{linespec}) what source line covers a particular address: -@smallexample -(@value{GDBP}) info line *0x63ff -Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. -@end smallexample - -@cindex @code{$_} and @code{info line} -@cindex @code{x} command, default address -@kindex x@r{(examine), and} info line -After @code{info line}, the default address for the @code{x} command -is changed to the starting address of the line, so that @samp{x/i} is -sufficient to begin examining the machine code (@pxref{Memory, -,Examining Memory}). Also, this address is saved as the value of the -convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience -Variables}). - -@table @code -@kindex disassemble -@cindex assembly instructions -@cindex instructions, assembly -@cindex machine instructions -@cindex listing machine instructions -@item disassemble -@itemx disassemble /m -@itemx disassemble /r -This specialized command dumps a range of memory as machine -instructions. It can also print mixed source+disassembly by specifying -the @code{/m} modifier and print the raw instructions in hex as well as -in symbolic form by specifying the @code{/r}. -The default memory range is the function surrounding the -program counter of the selected frame. A single argument to this -command is a program counter value; @value{GDBN} dumps the function -surrounding this value. When two arguments are given, they should -be separated by a comma, possibly surrounded by whitespace. The -arguments specify a range of addresses to dump, in one of two forms: - -@table @code -@item @var{start},@var{end} -the addresses from @var{start} (inclusive) to @var{end} (exclusive) -@item @var{start},+@var{length} -the addresses from @var{start} (inclusive) to -@code{@var{start}+@var{length}} (exclusive). -@end table - -@noindent -When 2 arguments are specified, the name of the function is also -printed (since there could be several functions in the given range). - -The argument(s) can be any expression yielding a numeric value, such as -@samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}. - -If the range of memory being disassembled contains current program counter, -the instruction at that location is shown with a @code{=>} marker. -@end table - -The following example shows the disassembly of a range of addresses of -HP PA-RISC 2.0 code: - -@smallexample -(@value{GDBP}) disas 0x32c4, 0x32e4 -Dump of assembler code from 0x32c4 to 0x32e4: - 0x32c4 : addil 0,dp - 0x32c8 : ldw 0x22c(sr0,r1),r26 - 0x32cc : ldil 0x3000,r31 - 0x32d0 : ble 0x3f8(sr4,r31) - 0x32d4 : ldo 0(r31),rp - 0x32d8 : addil -0x800,dp - 0x32dc : ldo 0x588(r1),r26 - 0x32e0 : ldil 0x3000,r31 -End of assembler dump. -@end smallexample - -Here is an example showing mixed source+assembly for Intel x86, when the -program is stopped just after function prologue: - -@smallexample -(@value{GDBP}) disas /m main -Dump of assembler code for function main: -5 @{ - 0x08048330 <+0>: push %ebp - 0x08048331 <+1>: mov %esp,%ebp - 0x08048333 <+3>: sub $0x8,%esp - 0x08048336 <+6>: and $0xfffffff0,%esp - 0x08048339 <+9>: sub $0x10,%esp - -6 printf ("Hello.\n"); -=> 0x0804833c <+12>: movl $0x8048440,(%esp) - 0x08048343 <+19>: call 0x8048284 - -7 return 0; -8 @} - 0x08048348 <+24>: mov $0x0,%eax - 0x0804834d <+29>: leave - 0x0804834e <+30>: ret - -End of assembler dump. -@end smallexample - -Here is another example showing raw instructions in hex for AMD x86-64, - -@smallexample -(gdb) disas /r 0x400281,+10 -Dump of assembler code from 0x400281 to 0x40028b: - 0x0000000000400281: 38 36 cmp %dh,(%rsi) - 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax - 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx) - 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al -End of assembler dump. -@end smallexample - -Addresses cannot be specified as a linespec (@pxref{Specify Location}). -So, for example, if you want to disassemble function @code{bar} -in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar} -and not @samp{disassemble foo.c:bar}. - -Some architectures have more than one commonly-used set of instruction -mnemonics or other syntax. - -For programs that were dynamically linked and use shared libraries, -instructions that call functions or branch to locations in the shared -libraries might show a seemingly bogus location---it's actually a -location of the relocation table. On some architectures, @value{GDBN} -might be able to resolve these to actual function names. - -@table @code -@kindex set disassembly-flavor -@cindex Intel disassembly flavor -@cindex AT&T disassembly flavor -@item set disassembly-flavor @var{instruction-set} -Select the instruction set to use when disassembling the -program via the @code{disassemble} or @code{x/i} commands. - -Currently this command is only defined for the Intel x86 family. You -can set @var{instruction-set} to either @code{intel} or @code{att}. -The default is @code{att}, the AT&T flavor used by default by Unix -assemblers for x86-based targets. - -@kindex show disassembly-flavor -@item show disassembly-flavor -Show the current setting of the disassembly flavor. -@end table - -@table @code -@kindex set disassemble-next-line -@kindex show disassemble-next-line -@item set disassemble-next-line -@itemx show disassemble-next-line -Control whether or not @value{GDBN} will disassemble the next source -line or instruction when execution stops. If ON, @value{GDBN} will -display disassembly of the next source line when execution of the -program being debugged stops. This is @emph{in addition} to -displaying the source line itself, which @value{GDBN} always does if -possible. If the next source line cannot be displayed for some reason -(e.g., if @value{GDBN} cannot find the source file, or there's no line -info in the debug info), @value{GDBN} will display disassembly of the -next @emph{instruction} instead of showing the next source line. If -AUTO, @value{GDBN} will display disassembly of next instruction only -if the source line cannot be displayed. This setting causes -@value{GDBN} to display some feedback when you step through a function -with no line info or whose source file is unavailable. The default is -OFF, which means never display the disassembly of the next line or -instruction. -@end table - - -@node Data -@chapter Examining Data - -@cindex printing data -@cindex examining data -@kindex print -@kindex inspect -The usual way to examine data in your program is with the @code{print} -command (abbreviated @code{p}), or its synonym @code{inspect}. It -evaluates and prints the value of an expression of the language your -program is written in (@pxref{Languages, ,Using @value{GDBN} with -Different Languages}). It may also print the expression using a -Python-based pretty-printer (@pxref{Pretty Printing}). - -@table @code -@item print @var{expr} -@itemx print /@var{f} @var{expr} -@var{expr} is an expression (in the source language). By default the -value of @var{expr} is printed in a format appropriate to its data type; -you can choose a different format by specifying @samp{/@var{f}}, where -@var{f} is a letter specifying the format; see @ref{Output Formats,,Output -Formats}. - -@item print -@itemx print /@var{f} -@cindex reprint the last value -If you omit @var{expr}, @value{GDBN} displays the last value again (from the -@dfn{value history}; @pxref{Value History, ,Value History}). This allows you to -conveniently inspect the same value in an alternative format. -@end table - -A more low-level way of examining data is with the @code{x} command. -It examines data in memory at a specified address and prints it in a -specified format. @xref{Memory, ,Examining Memory}. - -If you are interested in information about types, or about how the -fields of a struct or a class are declared, use the @code{ptype @var{exp}} -command rather than @code{print}. @xref{Symbols, ,Examining the Symbol -Table}. - -@cindex exploring hierarchical data structures -@kindex explore -Another way of examining values of expressions and type information is -through the Python extension command @code{explore} (available only if -the @value{GDBN} build is configured with @code{--with-python}). It -offers an interactive way to start at the highest level (or, the most -abstract level) of the data type of an expression (or, the data type -itself) and explore all the way down to leaf scalar values/fields -embedded in the higher level data types. - -@table @code -@item explore @var{arg} -@var{arg} is either an expression (in the source language), or a type -visible in the current context of the program being debugged. -@end table - -The working of the @code{explore} command can be illustrated with an -example. If a data type @code{struct ComplexStruct} is defined in your -C program as - -@smallexample -struct SimpleStruct -@{ - int i; - double d; -@}; - -struct ComplexStruct -@{ - struct SimpleStruct *ss_p; - int arr[10]; -@}; -@end smallexample - -@noindent -followed by variable declarations as - -@smallexample -struct SimpleStruct ss = @{ 10, 1.11 @}; -struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @}; -@end smallexample - -@noindent -then, the value of the variable @code{cs} can be explored using the -@code{explore} command as follows. - -@smallexample -(gdb) explore cs -The value of `cs' is a struct/class of type `struct ComplexStruct' with -the following fields: - - ss_p = - arr = - -Enter the field number of choice: -@end smallexample - -@noindent -Since the fields of @code{cs} are not scalar values, you are being -prompted to chose the field you want to explore. Let's say you choose -the field @code{ss_p} by entering @code{0}. Then, since this field is a -pointer, you will be asked if it is pointing to a single value. From -the declaration of @code{cs} above, it is indeed pointing to a single -value, hence you enter @code{y}. If you enter @code{n}, then you will -be asked if it were pointing to an array of values, in which case this -field will be explored as if it were an array. - -@smallexample -`cs.ss_p' is a pointer to a value of type `struct SimpleStruct' -Continue exploring it as a pointer to a single value [y/n]: y -The value of `*(cs.ss_p)' is a struct/class of type `struct -SimpleStruct' with the following fields: - - i = 10 .. (Value of type `int') - d = 1.1100000000000001 .. (Value of type `double') - -Press enter to return to parent value: -@end smallexample - -@noindent -If the field @code{arr} of @code{cs} was chosen for exploration by -entering @code{1} earlier, then since it is as array, you will be -prompted to enter the index of the element in the array that you want -to explore. - -@smallexample -`cs.arr' is an array of `int'. -Enter the index of the element you want to explore in `cs.arr': 5 - -`(cs.arr)[5]' is a scalar value of type `int'. - -(cs.arr)[5] = 4 - -Press enter to return to parent value: -@end smallexample - -In general, at any stage of exploration, you can go deeper towards the -leaf values by responding to the prompts appropriately, or hit the -return key to return to the enclosing data structure (the @i{higher} -level data structure). - -Similar to exploring values, you can use the @code{explore} command to -explore types. Instead of specifying a value (which is typically a -variable name or an expression valid in the current context of the -program being debugged), you specify a type name. If you consider the -same example as above, your can explore the type -@code{struct ComplexStruct} by passing the argument -@code{struct ComplexStruct} to the @code{explore} command. - -@smallexample -(gdb) explore struct ComplexStruct -@end smallexample - -@noindent -By responding to the prompts appropriately in the subsequent interactive -session, you can explore the type @code{struct ComplexStruct} in a -manner similar to how the value @code{cs} was explored in the above -example. - -The @code{explore} command also has two sub-commands, -@code{explore value} and @code{explore type}. The former sub-command is -a way to explicitly specify that value exploration of the argument is -being invoked, while the latter is a way to explicitly specify that type -exploration of the argument is being invoked. - -@table @code -@item explore value @var{expr} -@cindex explore value -This sub-command of @code{explore} explores the value of the -expression @var{expr} (if @var{expr} is an expression valid in the -current context of the program being debugged). The behavior of this -command is identical to that of the behavior of the @code{explore} -command being passed the argument @var{expr}. - -@item explore type @var{arg} -@cindex explore type -This sub-command of @code{explore} explores the type of @var{arg} (if -@var{arg} is a type visible in the current context of program being -debugged), or the type of the value/expression @var{arg} (if @var{arg} -is an expression valid in the current context of the program being -debugged). If @var{arg} is a type, then the behavior of this command is -identical to that of the @code{explore} command being passed the -argument @var{arg}. If @var{arg} is an expression, then the behavior of -this command will be identical to that of the @code{explore} command -being passed the type of @var{arg} as the argument. -@end table - -@menu -* Expressions:: Expressions -* Ambiguous Expressions:: Ambiguous Expressions -* Variables:: Program variables -* Arrays:: Artificial arrays -* Output Formats:: Output formats -* Memory:: Examining memory -* Auto Display:: Automatic display -* Print Settings:: Print settings -* Pretty Printing:: Python pretty printing -* Value History:: Value history -* Convenience Vars:: Convenience variables -* Convenience Funs:: Convenience functions -* Registers:: Registers -* Floating Point Hardware:: Floating point hardware -* Vector Unit:: Vector Unit -* OS Information:: Auxiliary data provided by operating system -* Memory Region Attributes:: Memory region attributes -* Dump/Restore Files:: Copy between memory and a file -* Core File Generation:: Cause a program dump its core -* Character Sets:: Debugging programs that use a different - character set than GDB does -* Caching Remote Data:: Data caching for remote targets -* Searching Memory:: Searching memory for a sequence of bytes -@end menu - -@node Expressions -@section Expressions - -@cindex expressions -@code{print} and many other @value{GDBN} commands accept an expression and -compute its value. Any kind of constant, variable or operator defined -by the programming language you are using is valid in an expression in -@value{GDBN}. This includes conditional expressions, function calls, -casts, and string constants. It also includes preprocessor macros, if -you compiled your program to include this information; see -@ref{Compilation}. - -@cindex arrays in expressions -@value{GDBN} supports array constants in expressions input by -the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example, -you can use the command @code{print @{1, 2, 3@}} to create an array -of three integers. If you pass an array to a function or assign it -to a program variable, @value{GDBN} copies the array to memory that -is @code{malloc}ed in the target program. - -Because C is so widespread, most of the expressions shown in examples in -this manual are in C. @xref{Languages, , Using @value{GDBN} with Different -Languages}, for information on how to use expressions in other -languages. - -In this section, we discuss operators that you can use in @value{GDBN} -expressions regardless of your programming language. - -@cindex casts, in expressions -Casts are supported in all languages, not just in C, because it is so -useful to cast a number into a pointer in order to examine a structure -at that address in memory. -@c FIXME: casts supported---Mod2 true? - -@value{GDBN} supports these operators, in addition to those common -to programming languages: - -@table @code -@item @@ -@samp{@@} is a binary operator for treating parts of memory as arrays. -@xref{Arrays, ,Artificial Arrays}, for more information. - -@item :: -@samp{::} allows you to specify a variable in terms of the file or -function where it is defined. @xref{Variables, ,Program Variables}. - -@cindex @{@var{type}@} -@cindex type casting memory -@cindex memory, viewing as typed object -@cindex casts, to view memory -@item @{@var{type}@} @var{addr} -Refers to an object of type @var{type} stored at address @var{addr} in -memory. @var{addr} may be any expression whose value is an integer or -pointer (but parentheses are required around binary operators, just as in -a cast). This construct is allowed regardless of what kind of data is -normally supposed to reside at @var{addr}. -@end table - -@node Ambiguous Expressions -@section Ambiguous Expressions -@cindex ambiguous expressions - -Expressions can sometimes contain some ambiguous elements. For instance, -some programming languages (notably Ada, C@t{++} and Objective-C) permit -a single function name to be defined several times, for application in -different contexts. This is called @dfn{overloading}. Another example -involving Ada is generics. A @dfn{generic package} is similar to C@t{++} -templates and is typically instantiated several times, resulting in -the same function name being defined in different contexts. - -In some cases and depending on the language, it is possible to adjust -the expression to remove the ambiguity. For instance in C@t{++}, you -can specify the signature of the function you want to break on, as in -@kbd{break @var{function}(@var{types})}. In Ada, using the fully -qualified name of your function often makes the expression unambiguous -as well. - -When an ambiguity that needs to be resolved is detected, the debugger -has the capability to display a menu of numbered choices for each -possibility, and then waits for the selection with the prompt @samp{>}. -The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}} -aborts the current command. If the command in which the expression was -used allows more than one choice to be selected, the next option in the -menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible -choices. - -For example, the following session excerpt shows an attempt to set a -breakpoint at the overloaded symbol @code{String::after}. -We choose three particular definitions of that function name: - -@c FIXME! This is likely to change to show arg type lists, at least -@smallexample -@group -(@value{GDBP}) b String::after -[0] cancel -[1] all -[2] file:String.cc; line number:867 -[3] file:String.cc; line number:860 -[4] file:String.cc; line number:875 -[5] file:String.cc; line number:853 -[6] file:String.cc; line number:846 -[7] file:String.cc; line number:735 -> 2 4 6 -Breakpoint 1 at 0xb26c: file String.cc, line 867. -Breakpoint 2 at 0xb344: file String.cc, line 875. -Breakpoint 3 at 0xafcc: file String.cc, line 846. -Multiple breakpoints were set. -Use the "delete" command to delete unwanted - breakpoints. -(@value{GDBP}) -@end group -@end smallexample - -@table @code -@kindex set multiple-symbols -@item set multiple-symbols @var{mode} -@cindex multiple-symbols menu - -This option allows you to adjust the debugger behavior when an expression -is ambiguous. - -By default, @var{mode} is set to @code{all}. If the command with which -the expression is used allows more than one choice, then @value{GDBN} -automatically selects all possible choices. For instance, inserting -a breakpoint on a function using an ambiguous name results in a breakpoint -inserted on each possible match. However, if a unique choice must be made, -then @value{GDBN} uses the menu to help you disambiguate the expression. -For instance, printing the address of an overloaded function will result -in the use of the menu. - -When @var{mode} is set to @code{ask}, the debugger always uses the menu -when an ambiguity is detected. - -Finally, when @var{mode} is set to @code{cancel}, the debugger reports -an error due to the ambiguity and the command is aborted. - -@kindex show multiple-symbols -@item show multiple-symbols -Show the current value of the @code{multiple-symbols} setting. -@end table - -@node Variables -@section Program Variables - -The most common kind of expression to use is the name of a variable -in your program. - -Variables in expressions are understood in the selected stack frame -(@pxref{Selection, ,Selecting a Frame}); they must be either: - -@itemize @bullet -@item -global (or file-static) -@end itemize - -@noindent or - -@itemize @bullet -@item -visible according to the scope rules of the -programming language from the point of execution in that frame -@end itemize - -@noindent This means that in the function - -@smallexample -foo (a) - int a; -@{ - bar (a); - @{ - int b = test (); - bar (b); - @} -@} -@end smallexample - -@noindent -you can examine and use the variable @code{a} whenever your program is -executing within the function @code{foo}, but you can only use or -examine the variable @code{b} while your program is executing inside -the block where @code{b} is declared. - -@cindex variable name conflict -There is an exception: you can refer to a variable or function whose -scope is a single source file even if the current execution point is not -in this file. But it is possible to have more than one such variable or -function with the same name (in different source files). If that -happens, referring to that name has unpredictable effects. If you wish, -you can specify a static variable in a particular function or file by -using the colon-colon (@code{::}) notation: - -@cindex colon-colon, context for variables/functions -@ifnotinfo -@c info cannot cope with a :: index entry, but why deprive hard copy readers? -@cindex @code{::}, context for variables/functions -@end ifnotinfo -@smallexample -@var{file}::@var{variable} -@var{function}::@var{variable} -@end smallexample - -@noindent -Here @var{file} or @var{function} is the name of the context for the -static @var{variable}. In the case of file names, you can use quotes to -make sure @value{GDBN} parses the file name as a single word---for example, -to print a global value of @code{x} defined in @file{f2.c}: - -@smallexample -(@value{GDBP}) p 'f2.c'::x -@end smallexample - -The @code{::} notation is normally used for referring to -static variables, since you typically disambiguate uses of local variables -in functions by selecting the appropriate frame and using the -simple name of the variable. However, you may also use this notation -to refer to local variables in frames enclosing the selected frame: - -@smallexample -void -foo (int a) -@{ - if (a < 10) - bar (a); - else - process (a); /* Stop here */ -@} - -int -bar (int a) -@{ - foo (a + 5); -@} -@end smallexample - -@noindent -For example, if there is a breakpoint at the commented line, -here is what you might see -when the program stops after executing the call @code{bar(0)}: - -@smallexample -(@value{GDBP}) p a -$1 = 10 -(@value{GDBP}) p bar::a -$2 = 5 -(@value{GDBP}) up 2 -#2 0x080483d0 in foo (a=5) at foobar.c:12 -(@value{GDBP}) p a -$3 = 5 -(@value{GDBP}) p bar::a -$4 = 0 -@end smallexample - -@cindex C@t{++} scope resolution -These uses of @samp{::} are very rarely in conflict with the very similar -use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++} -scope resolution operator in @value{GDBN} expressions. -@c FIXME: Um, so what happens in one of those rare cases where it's in -@c conflict?? --mew - -@cindex wrong values -@cindex variable values, wrong -@cindex function entry/exit, wrong values of variables -@cindex optimized code, wrong values of variables -@quotation -@emph{Warning:} Occasionally, a local variable may appear to have the -wrong value at certain points in a function---just after entry to a new -scope, and just before exit. -@end quotation -You may see this problem when you are stepping by machine instructions. -This is because, on most machines, it takes more than one instruction to -set up a stack frame (including local variable definitions); if you are -stepping by machine instructions, variables may appear to have the wrong -values until the stack frame is completely built. On exit, it usually -also takes more than one machine instruction to destroy a stack frame; -after you begin stepping through that group of instructions, local -variable definitions may be gone. - -This may also happen when the compiler does significant optimizations. -To be sure of always seeing accurate values, turn off all optimization -when compiling. - -@cindex ``No symbol "foo" in current context'' -Another possible effect of compiler optimizations is to optimize -unused variables out of existence, or assign variables to registers (as -opposed to memory addresses). Depending on the support for such cases -offered by the debug info format used by the compiler, @value{GDBN} -might not be able to display values for such local variables. If that -happens, @value{GDBN} will print a message like this: - -@smallexample -No symbol "foo" in current context. -@end smallexample - -To solve such problems, either recompile without optimizations, or use a -different debug info format, if the compiler supports several such -formats. @xref{Compilation}, for more information on choosing compiler -options. @xref{C, ,C and C@t{++}}, for more information about debug -info formats that are best suited to C@t{++} programs. - -If you ask to print an object whose contents are unknown to -@value{GDBN}, e.g., because its data type is not completely specified -by the debug information, @value{GDBN} will say @samp{}. @xref{Symbols, incomplete type}, for more about this. - -If you append @kbd{@@entry} string to a function parameter name you get its -value at the time the function got called. If the value is not available an -error message is printed. Entry values are available only with some compilers. -Entry values are normally also printed at the function parameter list according -to @ref{set print entry-values}. - -@smallexample -Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29 -29 i++; -(gdb) next -30 e (i); -(gdb) print i -$1 = 31 -(gdb) print i@@entry -$2 = 30 -@end smallexample - -Strings are identified as arrays of @code{char} values without specified -signedness. Arrays of either @code{signed char} or @code{unsigned char} get -printed as arrays of 1 byte sized integers. @code{-fsigned-char} or -@code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN} -defines literal string type @code{"char"} as @code{char} without a sign. -For program code - -@smallexample -char var0[] = "A"; -signed char var1[] = "A"; -@end smallexample - -You get during debugging -@smallexample -(gdb) print var0 -$1 = "A" -(gdb) print var1 -$2 = @{65 'A', 0 '\0'@} -@end smallexample - -@node Arrays -@section Artificial Arrays - -@cindex artificial array -@cindex arrays -@kindex @@@r{, referencing memory as an array} -It is often useful to print out several successive objects of the -same type in memory; a section of an array, or an array of -dynamically determined size for which only a pointer exists in the -program. - -You can do this by referring to a contiguous span of memory as an -@dfn{artificial array}, using the binary operator @samp{@@}. The left -operand of @samp{@@} should be the first element of the desired array -and be an individual object. The right operand should be the desired length -of the array. The result is an array value whose elements are all of -the type of the left argument. The first element is actually the left -argument; the second element comes from bytes of memory immediately -following those that hold the first element, and so on. Here is an -example. If a program says - -@smallexample -int *array = (int *) malloc (len * sizeof (int)); -@end smallexample - -@noindent -you can print the contents of @code{array} with - -@smallexample -p *array@@len -@end smallexample - -The left operand of @samp{@@} must reside in memory. Array values made -with @samp{@@} in this way behave just like other arrays in terms of -subscripting, and are coerced to pointers when used in expressions. -Artificial arrays most often appear in expressions via the value history -(@pxref{Value History, ,Value History}), after printing one out. - -Another way to create an artificial array is to use a cast. -This re-interprets a value as if it were an array. -The value need not be in memory: -@smallexample -(@value{GDBP}) p/x (short[2])0x12345678 -$1 = @{0x1234, 0x5678@} -@end smallexample - -As a convenience, if you leave the array length out (as in -@samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill -the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}: -@smallexample -(@value{GDBP}) p/x (short[])0x12345678 -$2 = @{0x1234, 0x5678@} -@end smallexample - -Sometimes the artificial array mechanism is not quite enough; in -moderately complex data structures, the elements of interest may not -actually be adjacent---for example, if you are interested in the values -of pointers in an array. One useful work-around in this situation is -to use a convenience variable (@pxref{Convenience Vars, ,Convenience -Variables}) as a counter in an expression that prints the first -interesting value, and then repeat that expression via @key{RET}. For -instance, suppose you have an array @code{dtab} of pointers to -structures, and you are interested in the values of a field @code{fv} -in each structure. Here is an example of what you might type: - -@smallexample -set $i = 0 -p dtab[$i++]->fv -@key{RET} -@key{RET} -@dots{} -@end smallexample - -@node Output Formats -@section Output Formats - -@cindex formatted output -@cindex output formats -By default, @value{GDBN} prints a value according to its data type. Sometimes -this is not what you want. For example, you might want to print a number -in hex, or a pointer in decimal. Or you might want to view data in memory -at a certain address as a character string or as an instruction. To do -these things, specify an @dfn{output format} when you print a value. - -The simplest use of output formats is to say how to print a value -already computed. This is done by starting the arguments of the -@code{print} command with a slash and a format letter. The format -letters supported are: - -@table @code -@item x -Regard the bits of the value as an integer, and print the integer in -hexadecimal. - -@item d -Print as integer in signed decimal. - -@item u -Print as integer in unsigned decimal. - -@item o -Print as integer in octal. - -@item t -Print as integer in binary. The letter @samp{t} stands for ``two''. -@footnote{@samp{b} cannot be used because these format letters are also -used with the @code{x} command, where @samp{b} stands for ``byte''; -see @ref{Memory,,Examining Memory}.} - -@item a -@cindex unknown address, locating -@cindex locate address -Print as an address, both absolute in hexadecimal and as an offset from -the nearest preceding symbol. You can use this format used to discover -where (in what function) an unknown address is located: - -@smallexample -(@value{GDBP}) p/a 0x54320 -$3 = 0x54320 <_initialize_vx+396> -@end smallexample - -@noindent -The command @code{info symbol 0x54320} yields similar results. -@xref{Symbols, info symbol}. - -@item c -Regard as an integer and print it as a character constant. This -prints both the numerical value and its character representation. The -character representation is replaced with the octal escape @samp{\nnn} -for characters outside the 7-bit @sc{ascii} range. - -Without this format, @value{GDBN} displays @code{char}, -@w{@code{unsigned char}}, and @w{@code{signed char}} data as character -constants. Single-byte members of vectors are displayed as integer -data. - -@item f -Regard the bits of the value as a floating point number and print -using typical floating point syntax. - -@item s -@cindex printing strings -@cindex printing byte arrays -Regard as a string, if possible. With this format, pointers to single-byte -data are displayed as null-terminated strings and arrays of single-byte data -are displayed as fixed-length strings. Other values are displayed in their -natural types. - -Without this format, @value{GDBN} displays pointers to and arrays of -@code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as -strings. Single-byte members of a vector are displayed as an integer -array. - -@item r -@cindex raw printing -Print using the @samp{raw} formatting. By default, @value{GDBN} will -use a Python-based pretty-printer, if one is available (@pxref{Pretty -Printing}). This typically results in a higher-level display of the -value's contents. The @samp{r} format bypasses any Python -pretty-printer which might exist. -@end table - -For example, to print the program counter in hex (@pxref{Registers}), type - -@smallexample -p/x $pc -@end smallexample - -@noindent -Note that no space is required before the slash; this is because command -names in @value{GDBN} cannot contain a slash. - -To reprint the last value in the value history with a different format, -you can use the @code{print} command with just a format and no -expression. For example, @samp{p/x} reprints the last value in hex. - -@node Memory -@section Examining Memory - -You can use the command @code{x} (for ``examine'') to examine memory in -any of several formats, independently of your program's data types. - -@cindex examining memory -@table @code -@kindex x @r{(examine memory)} -@item x/@var{nfu} @var{addr} -@itemx x @var{addr} -@itemx x -Use the @code{x} command to examine memory. -@end table - -@var{n}, @var{f}, and @var{u} are all optional parameters that specify how -much memory to display and how to format it; @var{addr} is an -expression giving the address where you want to start displaying memory. -If you use defaults for @var{nfu}, you need not type the slash @samp{/}. -Several commands set convenient defaults for @var{addr}. - -@table @r -@item @var{n}, the repeat count -The repeat count is a decimal integer; the default is 1. It specifies -how much memory (counting by units @var{u}) to display. -@c This really is **decimal**; unaffected by 'set radix' as of GDB -@c 4.1.2. - -@item @var{f}, the display format -The display format is one of the formats used by @code{print} -(@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c}, -@samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions). -The default is @samp{x} (hexadecimal) initially. The default changes -each time you use either @code{x} or @code{print}. - -@item @var{u}, the unit size -The unit size is any of - -@table @code -@item b -Bytes. -@item h -Halfwords (two bytes). -@item w -Words (four bytes). This is the initial default. -@item g -Giant words (eight bytes). -@end table - -Each time you specify a unit size with @code{x}, that size becomes the -default unit the next time you use @code{x}. For the @samp{i} format, -the unit size is ignored and is normally not written. For the @samp{s} format, -the unit size defaults to @samp{b}, unless it is explicitly given. -Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display -32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings. -Note that the results depend on the programming language of the -current compilation unit. If the language is C, the @samp{s} -modifier will use the UTF-16 encoding while @samp{w} will use -UTF-32. The encoding is set by the programming language and cannot -be altered. - -@item @var{addr}, starting display address -@var{addr} is the address where you want @value{GDBN} to begin displaying -memory. The expression need not have a pointer value (though it may); -it is always interpreted as an integer address of a byte of memory. -@xref{Expressions, ,Expressions}, for more information on expressions. The default for -@var{addr} is usually just after the last address examined---but several -other commands also set the default address: @code{info breakpoints} (to -the address of the last breakpoint listed), @code{info line} (to the -starting address of a line), and @code{print} (if you use it to display -a value from memory). -@end table - -For example, @samp{x/3uh 0x54320} is a request to display three halfwords -(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}), -starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four -words (@samp{w}) of memory above the stack pointer (here, @samp{$sp}; -@pxref{Registers, ,Registers}) in hexadecimal (@samp{x}). - -Since the letters indicating unit sizes are all distinct from the -letters specifying output formats, you do not have to remember whether -unit size or format comes first; either order works. The output -specifications @samp{4xw} and @samp{4wx} mean exactly the same thing. -(However, the count @var{n} must come first; @samp{wx4} does not work.) - -Even though the unit size @var{u} is ignored for the formats @samp{s} -and @samp{i}, you might still want to use a count @var{n}; for example, -@samp{3i} specifies that you want to see three machine instructions, -including any operands. For convenience, especially when used with -the @code{display} command, the @samp{i} format also prints branch delay -slot instructions, if any, beyond the count specified, which immediately -follow the last instruction that is within the count. The command -@code{disassemble} gives an alternative way of inspecting machine -instructions; see @ref{Machine Code,,Source and Machine Code}. - -All the defaults for the arguments to @code{x} are designed to make it -easy to continue scanning memory with minimal specifications each time -you use @code{x}. For example, after you have inspected three machine -instructions with @samp{x/3i @var{addr}}, you can inspect the next seven -with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command, -the repeat count @var{n} is used again; the other arguments default as -for successive uses of @code{x}. - -When examining machine instructions, the instruction at current program -counter is shown with a @code{=>} marker. For example: - -@smallexample -(@value{GDBP}) x/5i $pc-6 - 0x804837f : mov %esp,%ebp - 0x8048381 : push %ecx - 0x8048382 : sub $0x4,%esp -=> 0x8048385 : movl $0x8048460,(%esp) - 0x804838c : call 0x80482d4 -@end smallexample - -@cindex @code{$_}, @code{$__}, and value history -The addresses and contents printed by the @code{x} command are not saved -in the value history because there is often too much of them and they -would get in the way. Instead, @value{GDBN} makes these values available for -subsequent use in expressions as values of the convenience variables -@code{$_} and @code{$__}. After an @code{x} command, the last address -examined is available for use in expressions in the convenience variable -@code{$_}. The contents of that address, as examined, are available in -the convenience variable @code{$__}. - -If the @code{x} command has a repeat count, the address and contents saved -are from the last memory unit printed; this is not the same as the last -address printed if several units were printed on the last line of output. - -@cindex remote memory comparison -@cindex verify remote memory image -When you are debugging a program running on a remote target machine -(@pxref{Remote Debugging}), you may wish to verify the program's image in the -remote machine's memory against the executable file you downloaded to -the target. The @code{compare-sections} command is provided for such -situations. - -@table @code -@kindex compare-sections -@item compare-sections @r{[}@var{section-name}@r{]} -Compare the data of a loadable section @var{section-name} in the -executable file of the program being debugged with the same section in -the remote machine's memory, and report any mismatches. With no -arguments, compares all loadable sections. This command's -availability depends on the target's support for the @code{"qCRC"} -remote request. -@end table - -@node Auto Display -@section Automatic Display -@cindex automatic display -@cindex display of expressions - -If you find that you want to print the value of an expression frequently -(to see how it changes), you might want to add it to the @dfn{automatic -display list} so that @value{GDBN} prints its value each time your program stops. -Each expression added to the list is given a number to identify it; -to remove an expression from the list, you specify that number. -The automatic display looks like this: - -@smallexample -2: foo = 38 -3: bar[5] = (struct hack *) 0x3804 -@end smallexample - -@noindent -This display shows item numbers, expressions and their current values. As with -displays you request manually using @code{x} or @code{print}, you can -specify the output format you prefer; in fact, @code{display} decides -whether to use @code{print} or @code{x} depending your format -specification---it uses @code{x} if you specify either the @samp{i} -or @samp{s} format, or a unit size; otherwise it uses @code{print}. - -@table @code -@kindex display -@item display @var{expr} -Add the expression @var{expr} to the list of expressions to display -each time your program stops. @xref{Expressions, ,Expressions}. - -@code{display} does not repeat if you press @key{RET} again after using it. - -@item display/@var{fmt} @var{expr} -For @var{fmt} specifying only a display format and not a size or -count, add the expression @var{expr} to the auto-display list but -arrange to display it each time in the specified format @var{fmt}. -@xref{Output Formats,,Output Formats}. - -@item display/@var{fmt} @var{addr} -For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a -number of units, add the expression @var{addr} as a memory address to -be examined each time your program stops. Examining means in effect -doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}. -@end table - -For example, @samp{display/i $pc} can be helpful, to see the machine -instruction about to be executed each time execution stops (@samp{$pc} -is a common name for the program counter; @pxref{Registers, ,Registers}). - -@table @code -@kindex delete display -@kindex undisplay -@item undisplay @var{dnums}@dots{} -@itemx delete display @var{dnums}@dots{} -Remove items from the list of expressions to display. Specify the -numbers of the displays that you want affected with the command -argument @var{dnums}. It can be a single display number, one of the -numbers shown in the first field of the @samp{info display} display; -or it could be a range of display numbers, as in @code{2-4}. - -@code{undisplay} does not repeat if you press @key{RET} after using it. -(Otherwise you would just get the error @samp{No display number @dots{}}.) - -@kindex disable display -@item disable display @var{dnums}@dots{} -Disable the display of item numbers @var{dnums}. A disabled display -item is not printed automatically, but is not forgotten. It may be -enabled again later. Specify the numbers of the displays that you -want affected with the command argument @var{dnums}. It can be a -single display number, one of the numbers shown in the first field of -the @samp{info display} display; or it could be a range of display -numbers, as in @code{2-4}. - -@kindex enable display -@item enable display @var{dnums}@dots{} -Enable display of item numbers @var{dnums}. It becomes effective once -again in auto display of its expression, until you specify otherwise. -Specify the numbers of the displays that you want affected with the -command argument @var{dnums}. It can be a single display number, one -of the numbers shown in the first field of the @samp{info display} -display; or it could be a range of display numbers, as in @code{2-4}. - -@item display -Display the current values of the expressions on the list, just as is -done when your program stops. - -@kindex info display -@item info display -Print the list of expressions previously set up to display -automatically, each one with its item number, but without showing the -values. This includes disabled expressions, which are marked as such. -It also includes expressions which would not be displayed right now -because they refer to automatic variables not currently available. -@end table - -@cindex display disabled out of scope -If a display expression refers to local variables, then it does not make -sense outside the lexical context for which it was set up. Such an -expression is disabled when execution enters a context where one of its -variables is not defined. For example, if you give the command -@code{display last_char} while inside a function with an argument -@code{last_char}, @value{GDBN} displays this argument while your program -continues to stop inside that function. When it stops elsewhere---where -there is no variable @code{last_char}---the display is disabled -automatically. The next time your program stops where @code{last_char} -is meaningful, you can enable the display expression once again. - -@node Print Settings -@section Print Settings - -@cindex format options -@cindex print settings -@value{GDBN} provides the following ways to control how arrays, structures, -and symbols are printed. - -@noindent -These settings are useful for debugging programs in any language: - -@table @code -@kindex set print -@item set print address -@itemx set print address on -@cindex print/don't print memory addresses -@value{GDBN} prints memory addresses showing the location of stack -traces, structure values, pointer values, breakpoints, and so forth, -even when it also displays the contents of those addresses. The default -is @code{on}. For example, this is what a stack frame display looks like with -@code{set print address on}: - -@smallexample -@group -(@value{GDBP}) f -#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") - at input.c:530 -530 if (lquote != def_lquote) -@end group -@end smallexample - -@item set print address off -Do not print addresses when displaying their contents. For example, -this is the same stack frame displayed with @code{set print address off}: - -@smallexample -@group -(@value{GDBP}) set print addr off -(@value{GDBP}) f -#0 set_quotes (lq="<<", rq=">>") at input.c:530 -530 if (lquote != def_lquote) -@end group -@end smallexample - -You can use @samp{set print address off} to eliminate all machine -dependent displays from the @value{GDBN} interface. For example, with -@code{print address off}, you should get the same text for backtraces on -all machines---whether or not they involve pointer arguments. - -@kindex show print -@item show print address -Show whether or not addresses are to be printed. -@end table - -When @value{GDBN} prints a symbolic address, it normally prints the -closest earlier symbol plus an offset. If that symbol does not uniquely -identify the address (for example, it is a name whose scope is a single -source file), you may need to clarify. One way to do this is with -@code{info line}, for example @samp{info line *0x4537}. Alternately, -you can set @value{GDBN} to print the source file and line number when -it prints a symbolic address: - -@table @code -@item set print symbol-filename on -@cindex source file and line of a symbol -@cindex symbol, source file and line -Tell @value{GDBN} to print the source file name and line number of a -symbol in the symbolic form of an address. - -@item set print symbol-filename off -Do not print source file name and line number of a symbol. This is the -default. - -@item show print symbol-filename -Show whether or not @value{GDBN} will print the source file name and -line number of a symbol in the symbolic form of an address. -@end table - -Another situation where it is helpful to show symbol filenames and line -numbers is when disassembling code; @value{GDBN} shows you the line -number and source file that corresponds to each instruction. - -Also, you may wish to see the symbolic form only if the address being -printed is reasonably close to the closest earlier symbol: - -@table @code -@item set print max-symbolic-offset @var{max-offset} -@cindex maximum value for offset of closest symbol -Tell @value{GDBN} to only display the symbolic form of an address if the -offset between the closest earlier symbol and the address is less than -@var{max-offset}. The default is 0, which tells @value{GDBN} -to always print the symbolic form of an address if any symbol precedes it. - -@item show print max-symbolic-offset -Ask how large the maximum offset is that @value{GDBN} prints in a -symbolic address. -@end table - -@cindex wild pointer, interpreting -@cindex pointer, finding referent -If you have a pointer and you are not sure where it points, try -@samp{set print symbol-filename on}. Then you can determine the name -and source file location of the variable where it points, using -@samp{p/a @var{pointer}}. This interprets the address in symbolic form. -For example, here @value{GDBN} shows that a variable @code{ptt} points -at another variable @code{t}, defined in @file{hi2.c}: - -@smallexample -(@value{GDBP}) set print symbol-filename on -(@value{GDBP}) p/a ptt -$4 = 0xe008 -@end smallexample - -@quotation -@emph{Warning:} For pointers that point to a local variable, @samp{p/a} -does not show the symbol name and filename of the referent, even with -the appropriate @code{set print} options turned on. -@end quotation - -You can also enable @samp{/a}-like formatting all the time using -@samp{set print symbol on}: - -@table @code -@item set print symbol on -Tell @value{GDBN} to print the symbol corresponding to an address, if -one exists. - -@item set print symbol off -Tell @value{GDBN} not to print the symbol corresponding to an -address. In this mode, @value{GDBN} will still print the symbol -corresponding to pointers to functions. This is the default. - -@item show print symbol -Show whether @value{GDBN} will display the symbol corresponding to an -address. -@end table - -Other settings control how different kinds of objects are printed: - -@table @code -@item set print array -@itemx set print array on -@cindex pretty print arrays -Pretty print arrays. This format is more convenient to read, -but uses more space. The default is off. - -@item set print array off -Return to compressed format for arrays. - -@item show print array -Show whether compressed or pretty format is selected for displaying -arrays. - -@cindex print array indexes -@item set print array-indexes -@itemx set print array-indexes on -Print the index of each element when displaying arrays. May be more -convenient to locate a given element in the array or quickly find the -index of a given element in that printed array. The default is off. - -@item set print array-indexes off -Stop printing element indexes when displaying arrays. - -@item show print array-indexes -Show whether the index of each element is printed when displaying -arrays. - -@item set print elements @var{number-of-elements} -@cindex number of array elements to print -@cindex limit on number of printed array elements -Set a limit on how many elements of an array @value{GDBN} will print. -If @value{GDBN} is printing a large array, it stops printing after it has -printed the number of elements set by the @code{set print elements} command. -This limit also applies to the display of strings. -When @value{GDBN} starts, this limit is set to 200. -Setting @var{number-of-elements} to zero means that the printing is unlimited. - -@item show print elements -Display the number of elements of a large array that @value{GDBN} will print. -If the number is 0, then the printing is unlimited. - -@item set print frame-arguments @var{value} -@kindex set print frame-arguments -@cindex printing frame argument values -@cindex print all frame argument values -@cindex print frame argument values for scalars only -@cindex do not print frame argument values -This command allows to control how the values of arguments are printed -when the debugger prints a frame (@pxref{Frames}). The possible -values are: - -@table @code -@item all -The values of all arguments are printed. - -@item scalars -Print the value of an argument only if it is a scalar. The value of more -complex arguments such as arrays, structures, unions, etc, is replaced -by @code{@dots{}}. This is the default. Here is an example where -only scalar arguments are shown: - -@smallexample -#1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green) - at frame-args.c:23 -@end smallexample - -@item none -None of the argument values are printed. Instead, the value of each argument -is replaced by @code{@dots{}}. In this case, the example above now becomes: - -@smallexample -#1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{}) - at frame-args.c:23 -@end smallexample -@end table - -By default, only scalar arguments are printed. This command can be used -to configure the debugger to print the value of all arguments, regardless -of their type. However, it is often advantageous to not print the value -of more complex parameters. For instance, it reduces the amount of -information printed in each frame, making the backtrace more readable. -Also, it improves performance when displaying Ada frames, because -the computation of large arguments can sometimes be CPU-intensive, -especially in large applications. Setting @code{print frame-arguments} -to @code{scalars} (the default) or @code{none} avoids this computation, -thus speeding up the display of each Ada frame. - -@item show print frame-arguments -Show how the value of arguments should be displayed when printing a frame. - -@anchor{set print entry-values} -@item set print entry-values @var{value} -@kindex set print entry-values -Set printing of frame argument values at function entry. In some cases -@value{GDBN} can determine the value of function argument which was passed by -the function caller, even if the value was modified inside the called function -and therefore is different. With optimized code, the current value could be -unavailable, but the entry value may still be known. - -The default value is @code{default} (see below for its description). Older -@value{GDBN} behaved as with the setting @code{no}. Compilers not supporting -this feature will behave in the @code{default} setting the same way as with the -@code{no} setting. - -This functionality is currently supported only by DWARF 2 debugging format and -the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With -@value{NGCC}, you need to specify @option{-O -g} during compilation, to get -this information. - -The @var{value} parameter can be one of the following: - -@table @code -@item no -Print only actual parameter values, never print values from function entry -point. -@smallexample -#0 equal (val=5) -#0 different (val=6) -#0 lost (val=) -#0 born (val=10) -#0 invalid (val=) -@end smallexample - -@item only -Print only parameter values from function entry point. The actual parameter -values are never printed. -@smallexample -#0 equal (val@@entry=5) -#0 different (val@@entry=5) -#0 lost (val@@entry=5) -#0 born (val@@entry=) -#0 invalid (val@@entry=) -@end smallexample - -@item preferred -Print only parameter values from function entry point. If value from function -entry point is not known while the actual value is known, print the actual -value for such parameter. -@smallexample -#0 equal (val@@entry=5) -#0 different (val@@entry=5) -#0 lost (val@@entry=5) -#0 born (val=10) -#0 invalid (val@@entry=) -@end smallexample - -@item if-needed -Print actual parameter values. If actual parameter value is not known while -value from function entry point is known, print the entry point value for such -parameter. -@smallexample -#0 equal (val=5) -#0 different (val=6) -#0 lost (val@@entry=5) -#0 born (val=10) -#0 invalid (val=) -@end smallexample - -@item both -Always print both the actual parameter value and its value from function entry -point, even if values of one or both are not available due to compiler -optimizations. -@smallexample -#0 equal (val=5, val@@entry=5) -#0 different (val=6, val@@entry=5) -#0 lost (val=, val@@entry=5) -#0 born (val=10, val@@entry=) -#0 invalid (val=, val@@entry=) -@end smallexample - -@item compact -Print the actual parameter value if it is known and also its value from -function entry point if it is known. If neither is known, print for the actual -value @code{}. If not in MI mode (@pxref{GDB/MI}) and if both -values are known and identical, print the shortened -@code{param=param@@entry=VALUE} notation. -@smallexample -#0 equal (val=val@@entry=5) -#0 different (val=6, val@@entry=5) -#0 lost (val@@entry=5) -#0 born (val=10) -#0 invalid (val=) -@end smallexample - -@item default -Always print the actual parameter value. Print also its value from function -entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and -if both values are known and identical, print the shortened -@code{param=param@@entry=VALUE} notation. -@smallexample -#0 equal (val=val@@entry=5) -#0 different (val=6, val@@entry=5) -#0 lost (val=, val@@entry=5) -#0 born (val=10) -#0 invalid (val=) -@end smallexample -@end table - -For analysis messages on possible failures of frame argument values at function -entry resolution see @ref{set debug entry-values}. - -@item show print entry-values -Show the method being used for printing of frame argument values at function -entry. - -@item set print repeats -@cindex repeated array elements -Set the threshold for suppressing display of repeated array -elements. When the number of consecutive identical elements of an -array exceeds the threshold, @value{GDBN} prints the string -@code{""}, where @var{n} is the number of -identical repetitions, instead of displaying the identical elements -themselves. Setting the threshold to zero will cause all elements to -be individually printed. The default threshold is 10. - -@item show print repeats -Display the current threshold for printing repeated identical -elements. - -@item set print null-stop -@cindex @sc{null} elements in arrays -Cause @value{GDBN} to stop printing the characters of an array when the first -@sc{null} is encountered. This is useful when large arrays actually -contain only short strings. -The default is off. - -@item show print null-stop -Show whether @value{GDBN} stops printing an array on the first -@sc{null} character. - -@item set print pretty on -@cindex print structures in indented form -@cindex indentation in structure display -Cause @value{GDBN} to print structures in an indented format with one member -per line, like this: - -@smallexample -@group -$1 = @{ - next = 0x0, - flags = @{ - sweet = 1, - sour = 1 - @}, - meat = 0x54 "Pork" -@} -@end group -@end smallexample - -@item set print pretty off -Cause @value{GDBN} to print structures in a compact format, like this: - -@smallexample -@group -$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \ -meat = 0x54 "Pork"@} -@end group -@end smallexample - -@noindent -This is the default format. - -@item show print pretty -Show which format @value{GDBN} is using to print structures. - -@item set print sevenbit-strings on -@cindex eight-bit characters in strings -@cindex octal escapes in strings -Print using only seven-bit characters; if this option is set, -@value{GDBN} displays any eight-bit characters (in strings or -character values) using the notation @code{\}@var{nnn}. This setting is -best if you are working in English (@sc{ascii}) and you use the -high-order bit of characters as a marker or ``meta'' bit. - -@item set print sevenbit-strings off -Print full eight-bit characters. This allows the use of more -international character sets, and is the default. - -@item show print sevenbit-strings -Show whether or not @value{GDBN} is printing only seven-bit characters. - -@item set print union on -@cindex unions in structures, printing -Tell @value{GDBN} to print unions which are contained in structures -and other unions. This is the default setting. - -@item set print union off -Tell @value{GDBN} not to print unions which are contained in -structures and other unions. @value{GDBN} will print @code{"@{...@}"} -instead. - -@item show print union -Ask @value{GDBN} whether or not it will print unions which are contained in -structures and other unions. - -For example, given the declarations - -@smallexample -typedef enum @{Tree, Bug@} Species; -typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms; -typedef enum @{Caterpillar, Cocoon, Butterfly@} - Bug_forms; - -struct thing @{ - Species it; - union @{ - Tree_forms tree; - Bug_forms bug; - @} form; -@}; - -struct thing foo = @{Tree, @{Acorn@}@}; -@end smallexample - -@noindent -with @code{set print union on} in effect @samp{p foo} would print - -@smallexample -$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@} -@end smallexample - -@noindent -and with @code{set print union off} in effect it would print - -@smallexample -$1 = @{it = Tree, form = @{...@}@} -@end smallexample - -@noindent -@code{set print union} affects programs written in C-like languages -and in Pascal. -@end table - -@need 1000 -@noindent -These settings are of interest when debugging C@t{++} programs: - -@table @code -@cindex demangling C@t{++} names -@item set print demangle -@itemx set print demangle on -Print C@t{++} names in their source form rather than in the encoded -(``mangled'') form passed to the assembler and linker for type-safe -linkage. The default is on. - -@item show print demangle -Show whether C@t{++} names are printed in mangled or demangled form. - -@item set print asm-demangle -@itemx set print asm-demangle on -Print C@t{++} names in their source form rather than their mangled form, even -in assembler code printouts such as instruction disassemblies. -The default is off. - -@item show print asm-demangle -Show whether C@t{++} names in assembly listings are printed in mangled -or demangled form. - -@cindex C@t{++} symbol decoding style -@cindex symbol decoding style, C@t{++} -@kindex set demangle-style -@item set demangle-style @var{style} -Choose among several encoding schemes used by different compilers to -represent C@t{++} names. The choices for @var{style} are currently: - -@table @code -@item auto -Allow @value{GDBN} to choose a decoding style by inspecting your program. -This is the default. - -@item gnu -Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm. - -@item hp -Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm. - -@item lucid -Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm. - -@item arm -Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}. -@strong{Warning:} this setting alone is not sufficient to allow -debugging @code{cfront}-generated executables. @value{GDBN} would -require further enhancement to permit that. - -@end table -If you omit @var{style}, you will see a list of possible formats. - -@item show demangle-style -Display the encoding style currently in use for decoding C@t{++} symbols. - -@item set print object -@itemx set print object on -@cindex derived type of an object, printing -@cindex display derived types -When displaying a pointer to an object, identify the @emph{actual} -(derived) type of the object rather than the @emph{declared} type, using -the virtual function table. Note that the virtual function table is -required---this feature can only work for objects that have run-time -type identification; a single virtual method in the object's declared -type is sufficient. Note that this setting is also taken into account when -working with variable objects via MI (@pxref{GDB/MI}). - -@item set print object off -Display only the declared type of objects, without reference to the -virtual function table. This is the default setting. - -@item show print object -Show whether actual, or declared, object types are displayed. - -@item set print static-members -@itemx set print static-members on -@cindex static members of C@t{++} objects -Print static members when displaying a C@t{++} object. The default is on. - -@item set print static-members off -Do not print static members when displaying a C@t{++} object. - -@item show print static-members -Show whether C@t{++} static members are printed or not. - -@item set print pascal_static-members -@itemx set print pascal_static-members on -@cindex static members of Pascal objects -@cindex Pascal objects, static members display -Print static members when displaying a Pascal object. The default is on. - -@item set print pascal_static-members off -Do not print static members when displaying a Pascal object. - -@item show print pascal_static-members -Show whether Pascal static members are printed or not. - -@c These don't work with HP ANSI C++ yet. -@item set print vtbl -@itemx set print vtbl on -@cindex pretty print C@t{++} virtual function tables -@cindex virtual functions (C@t{++}) display -@cindex VTBL display -Pretty print C@t{++} virtual function tables. The default is off. -(The @code{vtbl} commands do not work on programs compiled with the HP -ANSI C@t{++} compiler (@code{aCC}).) - -@item set print vtbl off -Do not pretty print C@t{++} virtual function tables. - -@item show print vtbl -Show whether C@t{++} virtual function tables are pretty printed, or not. -@end table - -@node Pretty Printing -@section Pretty Printing - -@value{GDBN} provides a mechanism to allow pretty-printing of values using -Python code. It greatly simplifies the display of complex objects. This -mechanism works for both MI and the CLI. - -@menu -* Pretty-Printer Introduction:: Introduction to pretty-printers -* Pretty-Printer Example:: An example pretty-printer -* Pretty-Printer Commands:: Pretty-printer commands -@end menu - -@node Pretty-Printer Introduction -@subsection Pretty-Printer Introduction - -When @value{GDBN} prints a value, it first sees if there is a pretty-printer -registered for the value. If there is then @value{GDBN} invokes the -pretty-printer to print the value. Otherwise the value is printed normally. - -Pretty-printers are normally named. This makes them easy to manage. -The @samp{info pretty-printer} command will list all the installed -pretty-printers with their names. -If a pretty-printer can handle multiple data types, then its -@dfn{subprinters} are the printers for the individual data types. -Each such subprinter has its own name. -The format of the name is @var{printer-name};@var{subprinter-name}. - -Pretty-printers are installed by @dfn{registering} them with @value{GDBN}. -Typically they are automatically loaded and registered when the corresponding -debug information is loaded, thus making them available without having to -do anything special. - -There are three places where a pretty-printer can be registered. - -@itemize @bullet -@item -Pretty-printers registered globally are available when debugging -all inferiors. - -@item -Pretty-printers registered with a program space are available only -when debugging that program. -@xref{Progspaces In Python}, for more details on program spaces in Python. - -@item -Pretty-printers registered with an objfile are loaded and unloaded -with the corresponding objfile (e.g., shared library). -@xref{Objfiles In Python}, for more details on objfiles in Python. -@end itemize - -@xref{Selecting Pretty-Printers}, for further information on how -pretty-printers are selected, - -@xref{Writing a Pretty-Printer}, for implementing pretty printers -for new types. - -@node Pretty-Printer Example -@subsection Pretty-Printer Example - -Here is how a C@t{++} @code{std::string} looks without a pretty-printer: - -@smallexample -(@value{GDBP}) print s -$1 = @{ - static npos = 4294967295, - _M_dataplus = @{ - > = @{ - <__gnu_cxx::new_allocator> = @{ - @}, - @}, - members of std::basic_string, - std::allocator >::_Alloc_hider: - _M_p = 0x804a014 "abcd" - @} -@} -@end smallexample - -With a pretty-printer for @code{std::string} only the contents are printed: - -@smallexample -(@value{GDBP}) print s -$2 = "abcd" -@end smallexample - -@node Pretty-Printer Commands -@subsection Pretty-Printer Commands -@cindex pretty-printer commands - -@table @code -@kindex info pretty-printer -@item info pretty-printer [@var{object-regexp} [@var{name-regexp}]] -Print the list of installed pretty-printers. -This includes disabled pretty-printers, which are marked as such. - -@var{object-regexp} is a regular expression matching the objects -whose pretty-printers to list. -Objects can be @code{global}, the program space's file -(@pxref{Progspaces In Python}), -and the object files within that program space (@pxref{Objfiles In Python}). -@xref{Selecting Pretty-Printers}, for details on how @value{GDBN} -looks up a printer from these three objects. - -@var{name-regexp} is a regular expression matching the name of the printers -to list. - -@kindex disable pretty-printer -@item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]] -Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}. -A disabled pretty-printer is not forgotten, it may be enabled again later. - -@kindex enable pretty-printer -@item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]] -Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}. -@end table - -Example: - -Suppose we have three pretty-printers installed: one from library1.so -named @code{foo} that prints objects of type @code{foo}, and -another from library2.so named @code{bar} that prints two types of objects, -@code{bar1} and @code{bar2}. - -@smallexample -(gdb) info pretty-printer -library1.so: - foo -library2.so: - bar - bar1 - bar2 -(gdb) info pretty-printer library2 -library2.so: - bar - bar1 - bar2 -(gdb) disable pretty-printer library1 -1 printer disabled -2 of 3 printers enabled -(gdb) info pretty-printer -library1.so: - foo [disabled] -library2.so: - bar - bar1 - bar2 -(gdb) disable pretty-printer library2 bar:bar1 -1 printer disabled -1 of 3 printers enabled -(gdb) info pretty-printer library2 -library1.so: - foo [disabled] -library2.so: - bar - bar1 [disabled] - bar2 -(gdb) disable pretty-printer library2 bar -1 printer disabled -0 of 3 printers enabled -(gdb) info pretty-printer library2 -library1.so: - foo [disabled] -library2.so: - bar [disabled] - bar1 [disabled] - bar2 -@end smallexample - -Note that for @code{bar} the entire printer can be disabled, -as can each individual subprinter. - -@node Value History -@section Value History - -@cindex value history -@cindex history of values printed by @value{GDBN} -Values printed by the @code{print} command are saved in the @value{GDBN} -@dfn{value history}. This allows you to refer to them in other expressions. -Values are kept until the symbol table is re-read or discarded -(for example with the @code{file} or @code{symbol-file} commands). -When the symbol table changes, the value history is discarded, -since the values may contain pointers back to the types defined in the -symbol table. - -@cindex @code{$} -@cindex @code{$$} -@cindex history number -The values printed are given @dfn{history numbers} by which you can -refer to them. These are successive integers starting with one. -@code{print} shows you the history number assigned to a value by -printing @samp{$@var{num} = } before the value; here @var{num} is the -history number. - -To refer to any previous value, use @samp{$} followed by the value's -history number. The way @code{print} labels its output is designed to -remind you of this. Just @code{$} refers to the most recent value in -the history, and @code{$$} refers to the value before that. -@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2} -is the value just prior to @code{$$}, @code{$$1} is equivalent to -@code{$$}, and @code{$$0} is equivalent to @code{$}. - -For example, suppose you have just printed a pointer to a structure and -want to see the contents of the structure. It suffices to type - -@smallexample -p *$ -@end smallexample - -If you have a chain of structures where the component @code{next} points -to the next one, you can print the contents of the next one with this: - -@smallexample -p *$.next -@end smallexample - -@noindent -You can print successive links in the chain by repeating this -command---which you can do by just typing @key{RET}. - -Note that the history records values, not expressions. If the value of -@code{x} is 4 and you type these commands: - -@smallexample -print x -set x=5 -@end smallexample - -@noindent -then the value recorded in the value history by the @code{print} command -remains 4 even though the value of @code{x} has changed. - -@table @code -@kindex show values -@item show values -Print the last ten values in the value history, with their item numbers. -This is like @samp{p@ $$9} repeated ten times, except that @code{show -values} does not change the history. - -@item show values @var{n} -Print ten history values centered on history item number @var{n}. - -@item show values + -Print ten history values just after the values last printed. If no more -values are available, @code{show values +} produces no display. -@end table - -Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the -same effect as @samp{show values +}. - -@node Convenience Vars -@section Convenience Variables - -@cindex convenience variables -@cindex user-defined variables -@value{GDBN} provides @dfn{convenience variables} that you can use within -@value{GDBN} to hold on to a value and refer to it later. These variables -exist entirely within @value{GDBN}; they are not part of your program, and -setting a convenience variable has no direct effect on further execution -of your program. That is why you can use them freely. - -Convenience variables are prefixed with @samp{$}. Any name preceded by -@samp{$} can be used for a convenience variable, unless it is one of -the predefined machine-specific register names (@pxref{Registers, ,Registers}). -(Value history references, in contrast, are @emph{numbers} preceded -by @samp{$}. @xref{Value History, ,Value History}.) - -You can save a value in a convenience variable with an assignment -expression, just as you would set a variable in your program. -For example: - -@smallexample -set $foo = *object_ptr -@end smallexample - -@noindent -would save in @code{$foo} the value contained in the object pointed to by -@code{object_ptr}. - -Using a convenience variable for the first time creates it, but its -value is @code{void} until you assign a new value. You can alter the -value with another assignment at any time. - -Convenience variables have no fixed types. You can assign a convenience -variable any type of value, including structures and arrays, even if -that variable already has a value of a different type. The convenience -variable, when used as an expression, has the type of its current value. - -@table @code -@kindex show convenience -@cindex show all user variables and functions -@item show convenience -Print a list of convenience variables used so far, and their values, -as well as a list of the convenience functions. -Abbreviated @code{show conv}. - -@kindex init-if-undefined -@cindex convenience variables, initializing -@item init-if-undefined $@var{variable} = @var{expression} -Set a convenience variable if it has not already been set. This is useful -for user-defined commands that keep some state. It is similar, in concept, -to using local static variables with initializers in C (except that -convenience variables are global). It can also be used to allow users to -override default values used in a command script. - -If the variable is already defined then the expression is not evaluated so -any side-effects do not occur. -@end table - -One of the ways to use a convenience variable is as a counter to be -incremented or a pointer to be advanced. For example, to print -a field from successive elements of an array of structures: - -@smallexample -set $i = 0 -print bar[$i++]->contents -@end smallexample - -@noindent -Repeat that command by typing @key{RET}. - -Some convenience variables are created automatically by @value{GDBN} and given -values likely to be useful. - -@table @code -@vindex $_@r{, convenience variable} -@item $_ -The variable @code{$_} is automatically set by the @code{x} command to -the last address examined (@pxref{Memory, ,Examining Memory}). Other -commands which provide a default address for @code{x} to examine also -set @code{$_} to that address; these commands include @code{info line} -and @code{info breakpoint}. The type of @code{$_} is @code{void *} -except when set by the @code{x} command, in which case it is a pointer -to the type of @code{$__}. - -@vindex $__@r{, convenience variable} -@item $__ -The variable @code{$__} is automatically set by the @code{x} command -to the value found in the last address examined. Its type is chosen -to match the format in which the data was printed. - -@item $_exitcode -@vindex $_exitcode@r{, convenience variable} -The variable @code{$_exitcode} is automatically set to the exit code when -the program being debugged terminates. - -@item $_probe_argc -@itemx $_probe_arg0@dots{}$_probe_arg11 -Arguments to a static probe. @xref{Static Probe Points}. - -@item $_sdata -@vindex $_sdata@r{, inspect, convenience variable} -The variable @code{$_sdata} contains extra collected static tracepoint -data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that -@code{$_sdata} could be empty, if not inspecting a trace buffer, or -if extra static tracepoint data has not been collected. - -@item $_siginfo -@vindex $_siginfo@r{, convenience variable} -The variable @code{$_siginfo} contains extra signal information -(@pxref{extra signal information}). Note that @code{$_siginfo} -could be empty, if the application has not yet received any signals. -For example, it will be empty before you execute the @code{run} command. - -@item $_tlb -@vindex $_tlb@r{, convenience variable} -The variable @code{$_tlb} is automatically set when debugging -applications running on MS-Windows in native mode or connected to -gdbserver that supports the @code{qGetTIBAddr} request. -@xref{General Query Packets}. -This variable contains the address of the thread information block. - -@end table - -On HP-UX systems, if you refer to a function or variable name that -begins with a dollar sign, @value{GDBN} searches for a user or system -name first, before it searches for a convenience variable. - -@node Convenience Funs -@section Convenience Functions - -@cindex convenience functions -@value{GDBN} also supplies some @dfn{convenience functions}. These -have a syntax similar to convenience variables. A convenience -function can be used in an expression just like an ordinary function; -however, a convenience function is implemented internally to -@value{GDBN}. - -These functions require @value{GDBN} to be configured with -@code{Python} support. - -@table @code - -@item $_memeq(@var{buf1}, @var{buf2}, @var{length}) -@findex $_memeq@r{, convenience function} -Returns one if the @var{length} bytes at the addresses given by -@var{buf1} and @var{buf2} are equal. -Otherwise it returns zero. - -@item $_regex(@var{str}, @var{regex}) -@findex $_regex@r{, convenience function} -Returns one if the string @var{str} matches the regular expression -@var{regex}. Otherwise it returns zero. -The syntax of the regular expression is that specified by @code{Python}'s -regular expression support. - -@item $_streq(@var{str1}, @var{str2}) -@findex $_streq@r{, convenience function} -Returns one if the strings @var{str1} and @var{str2} are equal. -Otherwise it returns zero. - -@item $_strlen(@var{str}) -@findex $_strlen@r{, convenience function} -Returns the length of string @var{str}. - -@end table - -@value{GDBN} provides the ability to list and get help on -convenience functions. - -@table @code -@item help function -@kindex help function -@cindex show all convenience functions -Print a list of all convenience functions. -@end table - -@node Registers -@section Registers - -@cindex registers -You can refer to machine register contents, in expressions, as variables -with names starting with @samp{$}. The names of registers are different -for each machine; use @code{info registers} to see the names used on -your machine. - -@table @code -@kindex info registers -@item info registers -Print the names and values of all registers except floating-point -and vector registers (in the selected stack frame). - -@kindex info all-registers -@cindex floating point registers -@item info all-registers -Print the names and values of all registers, including floating-point -and vector registers (in the selected stack frame). - -@item info registers @var{regname} @dots{} -Print the @dfn{relativized} value of each specified register @var{regname}. -As discussed in detail below, register values are normally relative to -the selected stack frame. @var{regname} may be any register name valid on -the machine you are using, with or without the initial @samp{$}. -@end table - -@cindex stack pointer register -@cindex program counter register -@cindex process status register -@cindex frame pointer register -@cindex standard registers -@value{GDBN} has four ``standard'' register names that are available (in -expressions) on most machines---whenever they do not conflict with an -architecture's canonical mnemonics for registers. The register names -@code{$pc} and @code{$sp} are used for the program counter register and -the stack pointer. @code{$fp} is used for a register that contains a -pointer to the current stack frame, and @code{$ps} is used for a -register that contains the processor status. For example, -you could print the program counter in hex with - -@smallexample -p/x $pc -@end smallexample - -@noindent -or print the instruction to be executed next with - -@smallexample -x/i $pc -@end smallexample - -@noindent -or add four to the stack pointer@footnote{This is a way of removing -one word from the stack, on machines where stacks grow downward in -memory (most machines, nowadays). This assumes that the innermost -stack frame is selected; setting @code{$sp} is not allowed when other -stack frames are selected. To pop entire frames off the stack, -regardless of machine architecture, use @code{return}; -see @ref{Returning, ,Returning from a Function}.} with - -@smallexample -set $sp += 4 -@end smallexample - -Whenever possible, these four standard register names are available on -your machine even though the machine has different canonical mnemonics, -so long as there is no conflict. The @code{info registers} command -shows the canonical names. For example, on the SPARC, @code{info -registers} displays the processor status register as @code{$psr} but you -can also refer to it as @code{$ps}; and on x86-based machines @code{$ps} -is an alias for the @sc{eflags} register. - -@value{GDBN} always considers the contents of an ordinary register as an -integer when the register is examined in this way. Some machines have -special registers which can hold nothing but floating point; these -registers are considered to have floating point values. There is no way -to refer to the contents of an ordinary register as floating point value -(although you can @emph{print} it as a floating point value with -@samp{print/f $@var{regname}}). - -Some registers have distinct ``raw'' and ``virtual'' data formats. This -means that the data format in which the register contents are saved by -the operating system is not the same one that your program normally -sees. For example, the registers of the 68881 floating point -coprocessor are always saved in ``extended'' (raw) format, but all C -programs expect to work with ``double'' (virtual) format. In such -cases, @value{GDBN} normally works with the virtual format only (the format -that makes sense for your program), but the @code{info registers} command -prints the data in both formats. - -@cindex SSE registers (x86) -@cindex MMX registers (x86) -Some machines have special registers whose contents can be interpreted -in several different ways. For example, modern x86-based machines -have SSE and MMX registers that can hold several values packed -together in several different formats. @value{GDBN} refers to such -registers in @code{struct} notation: - -@smallexample -(@value{GDBP}) print $xmm1 -$1 = @{ - v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@}, - v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@}, - v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000", - v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@}, - v4_int32 = @{0, 20657912, 11, 13@}, - v2_int64 = @{88725056443645952, 55834574859@}, - uint128 = 0x0000000d0000000b013b36f800000000 -@} -@end smallexample - -@noindent -To set values of such registers, you need to tell @value{GDBN} which -view of the register you wish to change, as if you were assigning -value to a @code{struct} member: - -@smallexample - (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF -@end smallexample - -Normally, register values are relative to the selected stack frame -(@pxref{Selection, ,Selecting a Frame}). This means that you get the -value that the register would contain if all stack frames farther in -were exited and their saved registers restored. In order to see the -true contents of hardware registers, you must select the innermost -frame (with @samp{frame 0}). - -However, @value{GDBN} must deduce where registers are saved, from the machine -code generated by your compiler. If some registers are not saved, or if -@value{GDBN} is unable to locate the saved registers, the selected stack -frame makes no difference. - -@node Floating Point Hardware -@section Floating Point Hardware -@cindex floating point - -Depending on the configuration, @value{GDBN} may be able to give -you more information about the status of the floating point hardware. - -@table @code -@kindex info float -@item info float -Display hardware-dependent information about the floating -point unit. The exact contents and layout vary depending on the -floating point chip. Currently, @samp{info float} is supported on -the ARM and x86 machines. -@end table - -@node Vector Unit -@section Vector Unit -@cindex vector unit - -Depending on the configuration, @value{GDBN} may be able to give you -more information about the status of the vector unit. - -@table @code -@kindex info vector -@item info vector -Display information about the vector unit. The exact contents and -layout vary depending on the hardware. -@end table - -@node OS Information -@section Operating System Auxiliary Information -@cindex OS information - -@value{GDBN} provides interfaces to useful OS facilities that can help -you debug your program. - -@cindex auxiliary vector -@cindex vector, auxiliary -Some operating systems supply an @dfn{auxiliary vector} to programs at -startup. This is akin to the arguments and environment that you -specify for a program, but contains a system-dependent variety of -binary values that tell system libraries important details about the -hardware, operating system, and process. Each value's purpose is -identified by an integer tag; the meanings are well-known but system-specific. -Depending on the configuration and operating system facilities, -@value{GDBN} may be able to show you this information. For remote -targets, this functionality may further depend on the remote stub's -support of the @samp{qXfer:auxv:read} packet, see -@ref{qXfer auxiliary vector read}. - -@table @code -@kindex info auxv -@item info auxv -Display the auxiliary vector of the inferior, which can be either a -live process or a core dump file. @value{GDBN} prints each tag value -numerically, and also shows names and text descriptions for recognized -tags. Some values in the vector are numbers, some bit masks, and some -pointers to strings or other data. @value{GDBN} displays each value in the -most appropriate form for a recognized tag, and in hexadecimal for -an unrecognized tag. -@end table - -On some targets, @value{GDBN} can access operating system-specific -information and show it to you. The types of information available -will differ depending on the type of operating system running on the -target. The mechanism used to fetch the data is described in -@ref{Operating System Information}. For remote targets, this -functionality depends on the remote stub's support of the -@samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}. - -@table @code -@kindex info os -@item info os @var{infotype} - -Display OS information of the requested type. - -On @sc{gnu}/Linux, the following values of @var{infotype} are valid: - -@anchor{linux info os infotypes} -@table @code -@kindex info os processes -@item processes -Display the list of processes on the target. For each process, -@value{GDBN} prints the process identifier, the name of the user, the -command corresponding to the process, and the list of processor cores -that the process is currently running on. (To understand what these -properties mean, for this and the following info types, please consult -the general @sc{gnu}/Linux documentation.) - -@kindex info os procgroups -@item procgroups -Display the list of process groups on the target. For each process, -@value{GDBN} prints the identifier of the process group that it belongs -to, the command corresponding to the process group leader, the process -identifier, and the command line of the process. The list is sorted -first by the process group identifier, then by the process identifier, -so that processes belonging to the same process group are grouped together -and the process group leader is listed first. - -@kindex info os threads -@item threads -Display the list of threads running on the target. For each thread, -@value{GDBN} prints the identifier of the process that the thread -belongs to, the command of the process, the thread identifier, and the -processor core that it is currently running on. The main thread of a -process is not listed. - -@kindex info os files -@item files -Display the list of open file descriptors on the target. For each -file descriptor, @value{GDBN} prints the identifier of the process -owning the descriptor, the command of the owning process, the value -of the descriptor, and the target of the descriptor. - -@kindex info os sockets -@item sockets -Display the list of Internet-domain sockets on the target. For each -socket, @value{GDBN} prints the address and port of the local and -remote endpoints, the current state of the connection, the creator of -the socket, the IP address family of the socket, and the type of the -connection. - -@kindex info os shm -@item shm -Display the list of all System V shared-memory regions on the target. -For each shared-memory region, @value{GDBN} prints the region key, -the shared-memory identifier, the access permissions, the size of the -region, the process that created the region, the process that last -attached to or detached from the region, the current number of live -attaches to the region, and the times at which the region was last -attached to, detach from, and changed. - -@kindex info os semaphores -@item semaphores -Display the list of all System V semaphore sets on the target. For each -semaphore set, @value{GDBN} prints the semaphore set key, the semaphore -set identifier, the access permissions, the number of semaphores in the -set, the user and group of the owner and creator of the semaphore set, -and the times at which the semaphore set was operated upon and changed. - -@kindex info os msg -@item msg -Display the list of all System V message queues on the target. For each -message queue, @value{GDBN} prints the message queue key, the message -queue identifier, the access permissions, the current number of bytes -on the queue, the current number of messages on the queue, the processes -that last sent and received a message on the queue, the user and group -of the owner and creator of the message queue, the times at which a -message was last sent and received on the queue, and the time at which -the message queue was last changed. - -@kindex info os modules -@item modules -Display the list of all loaded kernel modules on the target. For each -module, @value{GDBN} prints the module name, the size of the module in -bytes, the number of times the module is used, the dependencies of the -module, the status of the module, and the address of the loaded module -in memory. -@end table - -@item info os -If @var{infotype} is omitted, then list the possible values for -@var{infotype} and the kind of OS information available for each -@var{infotype}. If the target does not return a list of possible -types, this command will report an error. -@end table - -@node Memory Region Attributes -@section Memory Region Attributes -@cindex memory region attributes - -@dfn{Memory region attributes} allow you to describe special handling -required by regions of your target's memory. @value{GDBN} uses -attributes to determine whether to allow certain types of memory -accesses; whether to use specific width accesses; and whether to cache -target memory. By default the description of memory regions is -fetched from the target (if the current target supports this), but the -user can override the fetched regions. - -Defined memory regions can be individually enabled and disabled. When a -memory region is disabled, @value{GDBN} uses the default attributes when -accessing memory in that region. Similarly, if no memory regions have -been defined, @value{GDBN} uses the default attributes when accessing -all memory. - -When a memory region is defined, it is given a number to identify it; -to enable, disable, or remove a memory region, you specify that number. - -@table @code -@kindex mem -@item mem @var{lower} @var{upper} @var{attributes}@dots{} -Define a memory region bounded by @var{lower} and @var{upper} with -attributes @var{attributes}@dots{}, and add it to the list of regions -monitored by @value{GDBN}. Note that @var{upper} == 0 is a special -case: it is treated as the target's maximum memory address. -(0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.) - -@item mem auto -Discard any user changes to the memory regions and use target-supplied -regions, if available, or no regions if the target does not support. - -@kindex delete mem -@item delete mem @var{nums}@dots{} -Remove memory regions @var{nums}@dots{} from the list of regions -monitored by @value{GDBN}. - -@kindex disable mem -@item disable mem @var{nums}@dots{} -Disable monitoring of memory regions @var{nums}@dots{}. -A disabled memory region is not forgotten. -It may be enabled again later. - -@kindex enable mem -@item enable mem @var{nums}@dots{} -Enable monitoring of memory regions @var{nums}@dots{}. - -@kindex info mem -@item info mem -Print a table of all defined memory regions, with the following columns -for each region: - -@table @emph -@item Memory Region Number -@item Enabled or Disabled. -Enabled memory regions are marked with @samp{y}. -Disabled memory regions are marked with @samp{n}. - -@item Lo Address -The address defining the inclusive lower bound of the memory region. - -@item Hi Address -The address defining the exclusive upper bound of the memory region. - -@item Attributes -The list of attributes set for this memory region. -@end table -@end table - - -@subsection Attributes - -@subsubsection Memory Access Mode -The access mode attributes set whether @value{GDBN} may make read or -write accesses to a memory region. - -While these attributes prevent @value{GDBN} from performing invalid -memory accesses, they do nothing to prevent the target system, I/O DMA, -etc.@: from accessing memory. - -@table @code -@item ro -Memory is read only. -@item wo -Memory is write only. -@item rw -Memory is read/write. This is the default. -@end table - -@subsubsection Memory Access Size -The access size attribute tells @value{GDBN} to use specific sized -accesses in the memory region. Often memory mapped device registers -require specific sized accesses. If no access size attribute is -specified, @value{GDBN} may use accesses of any size. - -@table @code -@item 8 -Use 8 bit memory accesses. -@item 16 -Use 16 bit memory accesses. -@item 32 -Use 32 bit memory accesses. -@item 64 -Use 64 bit memory accesses. -@end table - -@c @subsubsection Hardware/Software Breakpoints -@c The hardware/software breakpoint attributes set whether @value{GDBN} -@c will use hardware or software breakpoints for the internal breakpoints -@c used by the step, next, finish, until, etc. commands. -@c -@c @table @code -@c @item hwbreak -@c Always use hardware breakpoints -@c @item swbreak (default) -@c @end table - -@subsubsection Data Cache -The data cache attributes set whether @value{GDBN} will cache target -memory. While this generally improves performance by reducing debug -protocol overhead, it can lead to incorrect results because @value{GDBN} -does not know about volatile variables or memory mapped device -registers. - -@table @code -@item cache -Enable @value{GDBN} to cache target memory. -@item nocache -Disable @value{GDBN} from caching target memory. This is the default. -@end table - -@subsection Memory Access Checking -@value{GDBN} can be instructed to refuse accesses to memory that is -not explicitly described. This can be useful if accessing such -regions has undesired effects for a specific target, or to provide -better error checking. The following commands control this behaviour. - -@table @code -@kindex set mem inaccessible-by-default -@item set mem inaccessible-by-default [on|off] -If @code{on} is specified, make @value{GDBN} treat memory not -explicitly described by the memory ranges as non-existent and refuse accesses -to such memory. The checks are only performed if there's at least one -memory range defined. If @code{off} is specified, make @value{GDBN} -treat the memory not explicitly described by the memory ranges as RAM. -The default value is @code{on}. -@kindex show mem inaccessible-by-default -@item show mem inaccessible-by-default -Show the current handling of accesses to unknown memory. -@end table - - -@c @subsubsection Memory Write Verification -@c The memory write verification attributes set whether @value{GDBN} -@c will re-reads data after each write to verify the write was successful. -@c -@c @table @code -@c @item verify -@c @item noverify (default) -@c @end table - -@node Dump/Restore Files -@section Copy Between Memory and a File -@cindex dump/restore files -@cindex append data to a file -@cindex dump data to a file -@cindex restore data from a file - -You can use the commands @code{dump}, @code{append}, and -@code{restore} to copy data between target memory and a file. The -@code{dump} and @code{append} commands write data to a file, and the -@code{restore} command reads data from a file back into the inferior's -memory. Files may be in binary, Motorola S-record, Intel hex, or -Tektronix Hex format; however, @value{GDBN} can only append to binary -files. - -@table @code - -@kindex dump -@item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr} -@itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr} -Dump the contents of memory from @var{start_addr} to @var{end_addr}, -or the value of @var{expr}, to @var{filename} in the given format. - -The @var{format} parameter may be any one of: -@table @code -@item binary -Raw binary form. -@item ihex -Intel hex format. -@item srec -Motorola S-record format. -@item tekhex -Tektronix Hex format. -@end table - -@value{GDBN} uses the same definitions of these formats as the -@sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If -@var{format} is omitted, @value{GDBN} dumps the data in raw binary -form. - -@kindex append -@item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr} -@itemx append @r{[}binary@r{]} value @var{filename} @var{expr} -Append the contents of memory from @var{start_addr} to @var{end_addr}, -or the value of @var{expr}, to the file @var{filename}, in raw binary form. -(@value{GDBN} can only append data to files in raw binary form.) - -@kindex restore -@item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end} -Restore the contents of file @var{filename} into memory. The -@code{restore} command can automatically recognize any known @sc{bfd} -file format, except for raw binary. To restore a raw binary file you -must specify the optional keyword @code{binary} after the filename. - -If @var{bias} is non-zero, its value will be added to the addresses -contained in the file. Binary files always start at address zero, so -they will be restored at address @var{bias}. Other bfd files have -a built-in location; they will be restored at offset @var{bias} -from that location. - -If @var{start} and/or @var{end} are non-zero, then only data between -file offset @var{start} and file offset @var{end} will be restored. -These offsets are relative to the addresses in the file, before -the @var{bias} argument is applied. - -@end table - -@node Core File Generation -@section How to Produce a Core File from Your Program -@cindex dump core from inferior - -A @dfn{core file} or @dfn{core dump} is a file that records the memory -image of a running process and its process status (register values -etc.). Its primary use is post-mortem debugging of a program that -crashed while it ran outside a debugger. A program that crashes -automatically produces a core file, unless this feature is disabled by -the user. @xref{Files}, for information on invoking @value{GDBN} in -the post-mortem debugging mode. - -Occasionally, you may wish to produce a core file of the program you -are debugging in order to preserve a snapshot of its state. -@value{GDBN} has a special command for that. - -@table @code -@kindex gcore -@kindex generate-core-file -@item generate-core-file [@var{file}] -@itemx gcore [@var{file}] -Produce a core dump of the inferior process. The optional argument -@var{file} specifies the file name where to put the core dump. If not -specified, the file name defaults to @file{core.@var{pid}}, where -@var{pid} is the inferior process ID. - -Note that this command is implemented only for some systems (as of -this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390). -@end table - -@node Character Sets -@section Character Sets -@cindex character sets -@cindex charset -@cindex translating between character sets -@cindex host character set -@cindex target character set - -If the program you are debugging uses a different character set to -represent characters and strings than the one @value{GDBN} uses itself, -@value{GDBN} can automatically translate between the character sets for -you. The character set @value{GDBN} uses we call the @dfn{host -character set}; the one the inferior program uses we call the -@dfn{target character set}. - -For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which -uses the ISO Latin 1 character set, but you are using @value{GDBN}'s -remote protocol (@pxref{Remote Debugging}) to debug a program -running on an IBM mainframe, which uses the @sc{ebcdic} character set, -then the host character set is Latin-1, and the target character set is -@sc{ebcdic}. If you give @value{GDBN} the command @code{set -target-charset EBCDIC-US}, then @value{GDBN} translates between -@sc{ebcdic} and Latin 1 as you print character or string values, or use -character and string literals in expressions. - -@value{GDBN} has no way to automatically recognize which character set -the inferior program uses; you must tell it, using the @code{set -target-charset} command, described below. - -Here are the commands for controlling @value{GDBN}'s character set -support: - -@table @code -@item set target-charset @var{charset} -@kindex set target-charset -Set the current target character set to @var{charset}. To display the -list of supported target character sets, type -@kbd{@w{set target-charset @key{TAB}@key{TAB}}}. - -@item set host-charset @var{charset} -@kindex set host-charset -Set the current host character set to @var{charset}. - -By default, @value{GDBN} uses a host character set appropriate to the -system it is running on; you can override that default using the -@code{set host-charset} command. On some systems, @value{GDBN} cannot -automatically determine the appropriate host character set. In this -case, @value{GDBN} uses @samp{UTF-8}. - -@value{GDBN} can only use certain character sets as its host character -set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}}, -@value{GDBN} will list the host character sets it supports. - -@item set charset @var{charset} -@kindex set charset -Set the current host and target character sets to @var{charset}. As -above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}}, -@value{GDBN} will list the names of the character sets that can be used -for both host and target. - -@item show charset -@kindex show charset -Show the names of the current host and target character sets. - -@item show host-charset -@kindex show host-charset -Show the name of the current host character set. - -@item show target-charset -@kindex show target-charset -Show the name of the current target character set. - -@item set target-wide-charset @var{charset} -@kindex set target-wide-charset -Set the current target's wide character set to @var{charset}. This is -the character set used by the target's @code{wchar_t} type. To -display the list of supported wide character sets, type -@kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}. - -@item show target-wide-charset -@kindex show target-wide-charset -Show the name of the current target's wide character set. -@end table - -Here is an example of @value{GDBN}'s character set support in action. -Assume that the following source code has been placed in the file -@file{charset-test.c}: - -@smallexample -#include - -char ascii_hello[] - = @{72, 101, 108, 108, 111, 44, 32, 119, - 111, 114, 108, 100, 33, 10, 0@}; -char ibm1047_hello[] - = @{200, 133, 147, 147, 150, 107, 64, 166, - 150, 153, 147, 132, 90, 37, 0@}; - -main () -@{ - printf ("Hello, world!\n"); -@} -@end smallexample - -In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays -containing the string @samp{Hello, world!} followed by a newline, -encoded in the @sc{ascii} and @sc{ibm1047} character sets. - -We compile the program, and invoke the debugger on it: - -@smallexample -$ gcc -g charset-test.c -o charset-test -$ gdb -nw charset-test -GNU gdb 2001-12-19-cvs -Copyright 2001 Free Software Foundation, Inc. -@dots{} -(@value{GDBP}) -@end smallexample - -We can use the @code{show charset} command to see what character sets -@value{GDBN} is currently using to interpret and display characters and -strings: - -@smallexample -(@value{GDBP}) show charset -The current host and target character set is `ISO-8859-1'. -(@value{GDBP}) -@end smallexample - -For the sake of printing this manual, let's use @sc{ascii} as our -initial character set: -@smallexample -(@value{GDBP}) set charset ASCII -(@value{GDBP}) show charset -The current host and target character set is `ASCII'. -(@value{GDBP}) -@end smallexample - -Let's assume that @sc{ascii} is indeed the correct character set for our -host system --- in other words, let's assume that if @value{GDBN} prints -characters using the @sc{ascii} character set, our terminal will display -them properly. Since our current target character set is also -@sc{ascii}, the contents of @code{ascii_hello} print legibly: - -@smallexample -(@value{GDBP}) print ascii_hello -$1 = 0x401698 "Hello, world!\n" -(@value{GDBP}) print ascii_hello[0] -$2 = 72 'H' -(@value{GDBP}) -@end smallexample - -@value{GDBN} uses the target character set for character and string -literals you use in expressions: - -@smallexample -(@value{GDBP}) print '+' -$3 = 43 '+' -(@value{GDBP}) -@end smallexample - -The @sc{ascii} character set uses the number 43 to encode the @samp{+} -character. - -@value{GDBN} relies on the user to tell it which character set the -target program uses. If we print @code{ibm1047_hello} while our target -character set is still @sc{ascii}, we get jibberish: - -@smallexample -(@value{GDBP}) print ibm1047_hello -$4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%" -(@value{GDBP}) print ibm1047_hello[0] -$5 = 200 '\310' -(@value{GDBP}) -@end smallexample - -If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB}, -@value{GDBN} tells us the character sets it supports: - -@smallexample -(@value{GDBP}) set target-charset -ASCII EBCDIC-US IBM1047 ISO-8859-1 -(@value{GDBP}) set target-charset -@end smallexample - -We can select @sc{ibm1047} as our target character set, and examine the -program's strings again. Now the @sc{ascii} string is wrong, but -@value{GDBN} translates the contents of @code{ibm1047_hello} from the -target character set, @sc{ibm1047}, to the host character set, -@sc{ascii}, and they display correctly: - -@smallexample -(@value{GDBP}) set target-charset IBM1047 -(@value{GDBP}) show charset -The current host character set is `ASCII'. -The current target character set is `IBM1047'. -(@value{GDBP}) print ascii_hello -$6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012" -(@value{GDBP}) print ascii_hello[0] -$7 = 72 '\110' -(@value{GDBP}) print ibm1047_hello -$8 = 0x4016a8 "Hello, world!\n" -(@value{GDBP}) print ibm1047_hello[0] -$9 = 200 'H' -(@value{GDBP}) -@end smallexample - -As above, @value{GDBN} uses the target character set for character and -string literals you use in expressions: - -@smallexample -(@value{GDBP}) print '+' -$10 = 78 '+' -(@value{GDBP}) -@end smallexample - -The @sc{ibm1047} character set uses the number 78 to encode the @samp{+} -character. - -@node Caching Remote Data -@section Caching Data of Remote Targets -@cindex caching data of remote targets - -@value{GDBN} caches data exchanged between the debugger and a -remote target (@pxref{Remote Debugging}). Such caching generally improves -performance, because it reduces the overhead of the remote protocol by -bundling memory reads and writes into large chunks. Unfortunately, simply -caching everything would lead to incorrect results, since @value{GDBN} -does not necessarily know anything about volatile values, memory-mapped I/O -addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode}) -memory can be changed @emph{while} a gdb command is executing. -Therefore, by default, @value{GDBN} only caches data -known to be on the stack@footnote{In non-stop mode, it is moderately -rare for a running thread to modify the stack of a stopped thread -in a way that would interfere with a backtrace, and caching of -stack reads provides a significant speed up of remote backtraces.}. -Other regions of memory can be explicitly marked as -cacheable; see @pxref{Memory Region Attributes}. - -@table @code -@kindex set remotecache -@item set remotecache on -@itemx set remotecache off -This option no longer does anything; it exists for compatibility -with old scripts. - -@kindex show remotecache -@item show remotecache -Show the current state of the obsolete remotecache flag. - -@kindex set stack-cache -@item set stack-cache on -@itemx set stack-cache off -Enable or disable caching of stack accesses. When @code{ON}, use -caching. By default, this option is @code{ON}. - -@kindex show stack-cache -@item show stack-cache -Show the current state of data caching for memory accesses. - -@kindex info dcache -@item info dcache @r{[}line@r{]} -Print the information about the data cache performance. The -information displayed includes the dcache width and depth, and for -each cache line, its number, address, and how many times it was -referenced. This command is useful for debugging the data cache -operation. - -If a line number is specified, the contents of that line will be -printed in hex. - -@item set dcache size @var{size} -@cindex dcache size -@kindex set dcache size -Set maximum number of entries in dcache (dcache depth above). - -@item set dcache line-size @var{line-size} -@cindex dcache line-size -@kindex set dcache line-size -Set number of bytes each dcache entry caches (dcache width above). -Must be a power of 2. - -@item show dcache size -@kindex show dcache size -Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}. - -@item show dcache line-size -@kindex show dcache line-size -Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}. - -@end table - -@node Searching Memory -@section Search Memory -@cindex searching memory - -Memory can be searched for a particular sequence of bytes with the -@code{find} command. - -@table @code -@kindex find -@item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]} -@itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]} -Search memory for the sequence of bytes specified by @var{val1}, @var{val2}, -etc. The search begins at address @var{start_addr} and continues for either -@var{len} bytes or through to @var{end_addr} inclusive. -@end table - -@var{s} and @var{n} are optional parameters. -They may be specified in either order, apart or together. - -@table @r -@item @var{s}, search query size -The size of each search query value. - -@table @code -@item b -bytes -@item h -halfwords (two bytes) -@item w -words (four bytes) -@item g -giant words (eight bytes) -@end table - -All values are interpreted in the current language. -This means, for example, that if the current source language is C/C@t{++} -then searching for the string ``hello'' includes the trailing '\0'. - -If the value size is not specified, it is taken from the -value's type in the current language. -This is useful when one wants to specify the search -pattern as a mixture of types. -Note that this means, for example, that in the case of C-like languages -a search for an untyped 0x42 will search for @samp{(int) 0x42} -which is typically four bytes. - -@item @var{n}, maximum number of finds -The maximum number of matches to print. The default is to print all finds. -@end table - -You can use strings as search values. Quote them with double-quotes - (@code{"}). -The string value is copied into the search pattern byte by byte, -regardless of the endianness of the target and the size specification. - -The address of each match found is printed as well as a count of the -number of matches found. - -The address of the last value found is stored in convenience variable -@samp{$_}. -A count of the number of matches is stored in @samp{$numfound}. - -For example, if stopped at the @code{printf} in this function: - -@smallexample -void -hello () -@{ - static char hello[] = "hello-hello"; - static struct @{ char c; short s; int i; @} - __attribute__ ((packed)) mixed - = @{ 'c', 0x1234, 0x87654321 @}; - printf ("%s\n", hello); -@} -@end smallexample - -@noindent -you get during debugging: - -@smallexample -(gdb) find &hello[0], +sizeof(hello), "hello" -0x804956d -1 pattern found -(gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o' -0x8049567 -0x804956d -2 patterns found -(gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l' -0x8049567 -1 pattern found -(gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321 -0x8049560 -1 pattern found -(gdb) print $numfound -$1 = 1 -(gdb) print $_ -$2 = (void *) 0x8049560 -@end smallexample - -@node Optimized Code -@chapter Debugging Optimized Code -@cindex optimized code, debugging -@cindex debugging optimized code - -Almost all compilers support optimization. With optimization -disabled, the compiler generates assembly code that corresponds -directly to your source code, in a simplistic way. As the compiler -applies more powerful optimizations, the generated assembly code -diverges from your original source code. With help from debugging -information generated by the compiler, @value{GDBN} can map from -the running program back to constructs from your original source. - -@value{GDBN} is more accurate with optimization disabled. If you -can recompile without optimization, it is easier to follow the -progress of your program during debugging. But, there are many cases -where you may need to debug an optimized version. - -When you debug a program compiled with @samp{-g -O}, remember that the -optimizer has rearranged your code; the debugger shows you what is -really there. Do not be too surprised when the execution path does not -exactly match your source file! An extreme example: if you define a -variable, but never use it, @value{GDBN} never sees that -variable---because the compiler optimizes it out of existence. - -Some things do not work as well with @samp{-g -O} as with just -@samp{-g}, particularly on machines with instruction scheduling. If in -doubt, recompile with @samp{-g} alone, and if this fixes the problem, -please report it to us as a bug (including a test case!). -@xref{Variables}, for more information about debugging optimized code. - -@menu -* Inline Functions:: How @value{GDBN} presents inlining -* Tail Call Frames:: @value{GDBN} analysis of jumps to functions -@end menu - -@node Inline Functions -@section Inline Functions -@cindex inline functions, debugging - -@dfn{Inlining} is an optimization that inserts a copy of the function -body directly at each call site, instead of jumping to a shared -routine. @value{GDBN} displays inlined functions just like -non-inlined functions. They appear in backtraces. You can view their -arguments and local variables, step into them with @code{step}, skip -them with @code{next}, and escape from them with @code{finish}. -You can check whether a function was inlined by using the -@code{info frame} command. - -For @value{GDBN} to support inlined functions, the compiler must -record information about inlining in the debug information --- -@value{NGCC} using the @sc{dwarf 2} format does this, and several -other compilers do also. @value{GDBN} only supports inlined functions -when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1 -do not emit two required attributes (@samp{DW_AT_call_file} and -@samp{DW_AT_call_line}); @value{GDBN} does not display inlined -function calls with earlier versions of @value{NGCC}. It instead -displays the arguments and local variables of inlined functions as -local variables in the caller. - -The body of an inlined function is directly included at its call site; -unlike a non-inlined function, there are no instructions devoted to -the call. @value{GDBN} still pretends that the call site and the -start of the inlined function are different instructions. Stepping to -the call site shows the call site, and then stepping again shows -the first line of the inlined function, even though no additional -instructions are executed. - -This makes source-level debugging much clearer; you can see both the -context of the call and then the effect of the call. Only stepping by -a single instruction using @code{stepi} or @code{nexti} does not do -this; single instruction steps always show the inlined body. - -There are some ways that @value{GDBN} does not pretend that inlined -function calls are the same as normal calls: - -@itemize @bullet -@item -Setting breakpoints at the call site of an inlined function may not -work, because the call site does not contain any code. @value{GDBN} -may incorrectly move the breakpoint to the next line of the enclosing -function, after the call. This limitation will be removed in a future -version of @value{GDBN}; until then, set a breakpoint on an earlier line -or inside the inlined function instead. - -@item -@value{GDBN} cannot locate the return value of inlined calls after -using the @code{finish} command. This is a limitation of compiler-generated -debugging information; after @code{finish}, you can step to the next line -and print a variable where your program stored the return value. - -@end itemize - -@node Tail Call Frames -@section Tail Call Frames -@cindex tail call frames, debugging - -Function @code{B} can call function @code{C} in its very last statement. In -unoptimized compilation the call of @code{C} is immediately followed by return -instruction at the end of @code{B} code. Optimizing compiler may replace the -call and return in function @code{B} into one jump to function @code{C} -instead. Such use of a jump instruction is called @dfn{tail call}. - -During execution of function @code{C}, there will be no indication in the -function call stack frames that it was tail-called from @code{B}. If function -@code{A} regularly calls function @code{B} which tail-calls function @code{C}, -then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in -some cases @value{GDBN} can determine that @code{C} was tail-called from -@code{B}, and it will then create fictitious call frame for that, with the -return address set up as if @code{B} called @code{C} normally. - -This functionality is currently supported only by DWARF 2 debugging format and -the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With -@value{NGCC}, you need to specify @option{-O -g} during compilation, to get -this information. - -@kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame -kind by text @code{tail call frame} such as in this sample @value{GDBN} output: - -@smallexample -(gdb) x/i $pc - 2 - 0x40066b : jmp 0x400640 -(gdb) info frame -Stack level 1, frame at 0x7fffffffda30: - rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5 - tail call frame, caller of frame at 0x7fffffffda30 - source language c++. - Arglist at unknown address. - Locals at unknown address, Previous frame's sp is 0x7fffffffda30 -@end smallexample - -The detection of all the possible code path executions can find them ambiguous. -There is no execution history stored (possible @ref{Reverse Execution} is never -used for this purpose) and the last known caller could have reached the known -callee by multiple different jump sequences. In such case @value{GDBN} still -tries to show at least all the unambiguous top tail callers and all the -unambiguous bottom tail calees, if any. - -@table @code -@anchor{set debug entry-values} -@item set debug entry-values -@kindex set debug entry-values -When set to on, enables printing of analysis messages for both frame argument -values at function entry and tail calls. It will show all the possible valid -tail calls code paths it has considered. It will also print the intersection -of them with the final unambiguous (possibly partial or even empty) code path -result. - -@item show debug entry-values -@kindex show debug entry-values -Show the current state of analysis messages printing for both frame argument -values at function entry and tail calls. -@end table - -The analysis messages for tail calls can for example show why the virtual tail -call frame for function @code{c} has not been recognized (due to the indirect -reference by variable @code{x}): - -@smallexample -static void __attribute__((noinline, noclone)) c (void); -void (*x) (void) = c; -static void __attribute__((noinline, noclone)) a (void) @{ x++; @} -static void __attribute__((noinline, noclone)) c (void) @{ a (); @} -int main (void) @{ x (); return 0; @} - -Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find -DW_TAG_GNU_call_site 0x40039a in main -a () at t.c:3 -3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @} -(gdb) bt -#0 a () at t.c:3 -#1 0x000000000040039a in main () at t.c:5 -@end smallexample - -Another possibility is an ambiguous virtual tail call frames resolution: - -@smallexample -int i; -static void __attribute__((noinline, noclone)) f (void) @{ i++; @} -static void __attribute__((noinline, noclone)) e (void) @{ f (); @} -static void __attribute__((noinline, noclone)) d (void) @{ f (); @} -static void __attribute__((noinline, noclone)) c (void) @{ d (); @} -static void __attribute__((noinline, noclone)) b (void) -@{ if (i) c (); else e (); @} -static void __attribute__((noinline, noclone)) a (void) @{ b (); @} -int main (void) @{ a (); return 0; @} - -tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d) -tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e) -tailcall: reduced: 0x4004d2(a) | -(gdb) bt -#0 f () at t.c:2 -#1 0x00000000004004d2 in a () at t.c:8 -#2 0x0000000000400395 in main () at t.c:9 -@end smallexample - -@set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f} -@set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f} - -@c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK. -@ifset HAVE_MAKEINFO_CLICK -@set ARROW @click{} -@set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}} -@set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}} -@end ifset -@ifclear HAVE_MAKEINFO_CLICK -@set ARROW -> -@set CALLSEQ1B @value{CALLSEQ1A} -@set CALLSEQ2B @value{CALLSEQ2A} -@end ifclear - -Frames #0 and #2 are real, #1 is a virtual tail call frame. -The code can have possible execution paths @value{CALLSEQ1B} or -@value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state. - -@code{initial:} state shows some random possible calling sequence @value{GDBN} -has found. It then finds another possible calling sequcen - that one is -prefixed by @code{compare:}. The non-ambiguous intersection of these two is -printed as the @code{reduced:} calling sequence. That one could have many -futher @code{compare:} and @code{reduced:} statements as long as there remain -any non-ambiguous sequence entries. - -For the frame of function @code{b} in both cases there are different possible -@code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is -also ambigous. The only non-ambiguous frame is the one for function @code{a}, -therefore this one is displayed to the user while the ambiguous frames are -omitted. - -There can be also reasons why printing of frame argument values at function -entry may fail: - -@smallexample -int v; -static void __attribute__((noinline, noclone)) c (int i) @{ v++; @} -static void __attribute__((noinline, noclone)) a (int i); -static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @} -static void __attribute__((noinline, noclone)) a (int i) -@{ if (i) b (i - 1); else c (0); @} -int main (void) @{ a (5); return 0; @} - -(gdb) bt -#0 c (i=i@@entry=0) at t.c:2 -#1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found -function "a" at 0x400420 can call itself via tail calls -i=) at t.c:6 -#2 0x000000000040036e in main () at t.c:7 -@end smallexample - -@value{GDBN} cannot find out from the inferior state if and how many times did -function @code{a} call itself (via function @code{b}) as these calls would be -tail calls. Such tail calls would modify thue @code{i} variable, therefore -@value{GDBN} cannot be sure the value it knows would be right - @value{GDBN} -prints @code{} instead. - -@node Macros -@chapter C Preprocessor Macros - -Some languages, such as C and C@t{++}, provide a way to define and invoke -``preprocessor macros'' which expand into strings of tokens. -@value{GDBN} can evaluate expressions containing macro invocations, show -the result of macro expansion, and show a macro's definition, including -where it was defined. - -You may need to compile your program specially to provide @value{GDBN} -with information about preprocessor macros. Most compilers do not -include macros in their debugging information, even when you compile -with the @option{-g} flag. @xref{Compilation}. - -A program may define a macro at one point, remove that definition later, -and then provide a different definition after that. Thus, at different -points in the program, a macro may have different definitions, or have -no definition at all. If there is a current stack frame, @value{GDBN} -uses the macros in scope at that frame's source code line. Otherwise, -@value{GDBN} uses the macros in scope at the current listing location; -see @ref{List}. - -Whenever @value{GDBN} evaluates an expression, it always expands any -macro invocations present in the expression. @value{GDBN} also provides -the following commands for working with macros explicitly. - -@table @code - -@kindex macro expand -@cindex macro expansion, showing the results of preprocessor -@cindex preprocessor macro expansion, showing the results of -@cindex expanding preprocessor macros -@item macro expand @var{expression} -@itemx macro exp @var{expression} -Show the results of expanding all preprocessor macro invocations in -@var{expression}. Since @value{GDBN} simply expands macros, but does -not parse the result, @var{expression} need not be a valid expression; -it can be any string of tokens. - -@kindex macro exp1 -@item macro expand-once @var{expression} -@itemx macro exp1 @var{expression} -@cindex expand macro once -@i{(This command is not yet implemented.)} Show the results of -expanding those preprocessor macro invocations that appear explicitly in -@var{expression}. Macro invocations appearing in that expansion are -left unchanged. This command allows you to see the effect of a -particular macro more clearly, without being confused by further -expansions. Since @value{GDBN} simply expands macros, but does not -parse the result, @var{expression} need not be a valid expression; it -can be any string of tokens. - -@kindex info macro -@cindex macro definition, showing -@cindex definition of a macro, showing -@cindex macros, from debug info -@item info macro [-a|-all] [--] @var{macro} -Show the current definition or all definitions of the named @var{macro}, -and describe the source location or compiler command-line where that -definition was established. The optional double dash is to signify the end of -argument processing and the beginning of @var{macro} for non C-like macros where -the macro may begin with a hyphen. - -@kindex info macros -@item info macros @var{linespec} -Show all macro definitions that are in effect at the location specified -by @var{linespec}, and describe the source location or compiler -command-line where those definitions were established. - -@kindex macro define -@cindex user-defined macros -@cindex defining macros interactively -@cindex macros, user-defined -@item macro define @var{macro} @var{replacement-list} -@itemx macro define @var{macro}(@var{arglist}) @var{replacement-list} -Introduce a definition for a preprocessor macro named @var{macro}, -invocations of which are replaced by the tokens given in -@var{replacement-list}. The first form of this command defines an -``object-like'' macro, which takes no arguments; the second form -defines a ``function-like'' macro, which takes the arguments given in -@var{arglist}. - -A definition introduced by this command is in scope in every -expression evaluated in @value{GDBN}, until it is removed with the -@code{macro undef} command, described below. The definition overrides -all definitions for @var{macro} present in the program being debugged, -as well as any previous user-supplied definition. - -@kindex macro undef -@item macro undef @var{macro} -Remove any user-supplied definition for the macro named @var{macro}. -This command only affects definitions provided with the @code{macro -define} command, described above; it cannot remove definitions present -in the program being debugged. - -@kindex macro list -@item macro list -List all the macros defined using the @code{macro define} command. -@end table - -@cindex macros, example of debugging with -Here is a transcript showing the above commands in action. First, we -show our source files: - -@smallexample -$ cat sample.c -#include -#include "sample.h" - -#define M 42 -#define ADD(x) (M + x) - -main () -@{ -#define N 28 - printf ("Hello, world!\n"); -#undef N - printf ("We're so creative.\n"); -#define N 1729 - printf ("Goodbye, world!\n"); -@} -$ cat sample.h -#define Q < -$ -@end smallexample - -Now, we compile the program using the @sc{gnu} C compiler, -@value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the -minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3} -and @option{-gdwarf-4}; we recommend always choosing the most recent -version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler -includes information about preprocessor macros in the debugging -information. - -@smallexample -$ gcc -gdwarf-2 -g3 sample.c -o sample -$ -@end smallexample - -Now, we start @value{GDBN} on our sample program: - -@smallexample -$ gdb -nw sample -GNU gdb 2002-05-06-cvs -Copyright 2002 Free Software Foundation, Inc. -GDB is free software, @dots{} -(@value{GDBP}) -@end smallexample - -We can expand macros and examine their definitions, even when the -program is not running. @value{GDBN} uses the current listing position -to decide which macro definitions are in scope: - -@smallexample -(@value{GDBP}) list main -3 -4 #define M 42 -5 #define ADD(x) (M + x) -6 -7 main () -8 @{ -9 #define N 28 -10 printf ("Hello, world!\n"); -11 #undef N -12 printf ("We're so creative.\n"); -(@value{GDBP}) info macro ADD -Defined at /home/jimb/gdb/macros/play/sample.c:5 -#define ADD(x) (M + x) -(@value{GDBP}) info macro Q -Defined at /home/jimb/gdb/macros/play/sample.h:1 - included at /home/jimb/gdb/macros/play/sample.c:2 -#define Q < -(@value{GDBP}) macro expand ADD(1) -expands to: (42 + 1) -(@value{GDBP}) macro expand-once ADD(1) -expands to: once (M + 1) -(@value{GDBP}) -@end smallexample - -In the example above, note that @code{macro expand-once} expands only -the macro invocation explicit in the original text --- the invocation of -@code{ADD} --- but does not expand the invocation of the macro @code{M}, -which was introduced by @code{ADD}. - -Once the program is running, @value{GDBN} uses the macro definitions in -force at the source line of the current stack frame: - -@smallexample -(@value{GDBP}) break main -Breakpoint 1 at 0x8048370: file sample.c, line 10. -(@value{GDBP}) run -Starting program: /home/jimb/gdb/macros/play/sample - -Breakpoint 1, main () at sample.c:10 -10 printf ("Hello, world!\n"); -(@value{GDBP}) -@end smallexample - -At line 10, the definition of the macro @code{N} at line 9 is in force: - -@smallexample -(@value{GDBP}) info macro N -Defined at /home/jimb/gdb/macros/play/sample.c:9 -#define N 28 -(@value{GDBP}) macro expand N Q M -expands to: 28 < 42 -(@value{GDBP}) print N Q M -$1 = 1 -(@value{GDBP}) -@end smallexample - -As we step over directives that remove @code{N}'s definition, and then -give it a new definition, @value{GDBN} finds the definition (or lack -thereof) in force at each point: - -@smallexample -(@value{GDBP}) next -Hello, world! -12 printf ("We're so creative.\n"); -(@value{GDBP}) info macro N -The symbol `N' has no definition as a C/C++ preprocessor macro -at /home/jimb/gdb/macros/play/sample.c:12 -(@value{GDBP}) next -We're so creative. -14 printf ("Goodbye, world!\n"); -(@value{GDBP}) info macro N -Defined at /home/jimb/gdb/macros/play/sample.c:13 -#define N 1729 -(@value{GDBP}) macro expand N Q M -expands to: 1729 < 42 -(@value{GDBP}) print N Q M -$2 = 0 -(@value{GDBP}) -@end smallexample - -In addition to source files, macros can be defined on the compilation command -line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in -such a way, @value{GDBN} displays the location of their definition as line zero -of the source file submitted to the compiler. - -@smallexample -(@value{GDBP}) info macro __STDC__ -Defined at /home/jimb/gdb/macros/play/sample.c:0 --D__STDC__=1 -(@value{GDBP}) -@end smallexample - - -@node Tracepoints -@chapter Tracepoints -@c This chapter is based on the documentation written by Michael -@c Snyder, David Taylor, Jim Blandy, and Elena Zannoni. - -@cindex tracepoints -In some applications, it is not feasible for the debugger to interrupt -the program's execution long enough for the developer to learn -anything helpful about its behavior. If the program's correctness -depends on its real-time behavior, delays introduced by a debugger -might cause the program to change its behavior drastically, or perhaps -fail, even when the code itself is correct. It is useful to be able -to observe the program's behavior without interrupting it. - -Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can -specify locations in the program, called @dfn{tracepoints}, and -arbitrary expressions to evaluate when those tracepoints are reached. -Later, using the @code{tfind} command, you can examine the values -those expressions had when the program hit the tracepoints. The -expressions may also denote objects in memory---structures or arrays, -for example---whose values @value{GDBN} should record; while visiting -a particular tracepoint, you may inspect those objects as if they were -in memory at that moment. However, because @value{GDBN} records these -values without interacting with you, it can do so quickly and -unobtrusively, hopefully not disturbing the program's behavior. - -The tracepoint facility is currently available only for remote -targets. @xref{Targets}. In addition, your remote target must know -how to collect trace data. This functionality is implemented in the -remote stub; however, none of the stubs distributed with @value{GDBN} -support tracepoints as of this writing. The format of the remote -packets used to implement tracepoints are described in @ref{Tracepoint -Packets}. - -It is also possible to get trace data from a file, in a manner reminiscent -of corefiles; you specify the filename, and use @code{tfind} to search -through the file. @xref{Trace Files}, for more details. - -This chapter describes the tracepoint commands and features. - -@menu -* Set Tracepoints:: -* Analyze Collected Data:: -* Tracepoint Variables:: -* Trace Files:: -@end menu - -@node Set Tracepoints -@section Commands to Set Tracepoints - -Before running such a @dfn{trace experiment}, an arbitrary number of -tracepoints can be set. A tracepoint is actually a special type of -breakpoint (@pxref{Set Breaks}), so you can manipulate it using -standard breakpoint commands. For instance, as with breakpoints, -tracepoint numbers are successive integers starting from one, and many -of the commands associated with tracepoints take the tracepoint number -as their argument, to identify which tracepoint to work on. - -For each tracepoint, you can specify, in advance, some arbitrary set -of data that you want the target to collect in the trace buffer when -it hits that tracepoint. The collected data can include registers, -local variables, or global data. Later, you can use @value{GDBN} -commands to examine the values these data had at the time the -tracepoint was hit. - -Tracepoints do not support every breakpoint feature. Ignore counts on -tracepoints have no effect, and tracepoints cannot run @value{GDBN} -commands when they are hit. Tracepoints may not be thread-specific -either. - -@cindex fast tracepoints -Some targets may support @dfn{fast tracepoints}, which are inserted in -a different way (such as with a jump instead of a trap), that is -faster but possibly restricted in where they may be installed. - -@cindex static tracepoints -@cindex markers, static tracepoints -@cindex probing markers, static tracepoints -Regular and fast tracepoints are dynamic tracing facilities, meaning -that they can be used to insert tracepoints at (almost) any location -in the target. Some targets may also support controlling @dfn{static -tracepoints} from @value{GDBN}. With static tracing, a set of -instrumentation points, also known as @dfn{markers}, are embedded in -the target program, and can be activated or deactivated by name or -address. These are usually placed at locations which facilitate -investigating what the target is actually doing. @value{GDBN}'s -support for static tracing includes being able to list instrumentation -points, and attach them with @value{GDBN} defined high level -tracepoints that expose the whole range of convenience of -@value{GDBN}'s tracepoints support. Namely, support for collecting -registers values and values of global or local (to the instrumentation -point) variables; tracepoint conditions and trace state variables. -The act of installing a @value{GDBN} static tracepoint on an -instrumentation point, or marker, is referred to as @dfn{probing} a -static tracepoint marker. - -@code{gdbserver} supports tracepoints on some target systems. -@xref{Server,,Tracepoints support in @code{gdbserver}}. - -This section describes commands to set tracepoints and associated -conditions and actions. - -@menu -* Create and Delete Tracepoints:: -* Enable and Disable Tracepoints:: -* Tracepoint Passcounts:: -* Tracepoint Conditions:: -* Trace State Variables:: -* Tracepoint Actions:: -* Listing Tracepoints:: -* Listing Static Tracepoint Markers:: -* Starting and Stopping Trace Experiments:: -* Tracepoint Restrictions:: -@end menu - -@node Create and Delete Tracepoints -@subsection Create and Delete Tracepoints - -@table @code -@cindex set tracepoint -@kindex trace -@item trace @var{location} -The @code{trace} command is very similar to the @code{break} command. -Its argument @var{location} can be a source line, a function name, or -an address in the target program. @xref{Specify Location}. The -@code{trace} command defines a tracepoint, which is a point in the -target program where the debugger will briefly stop, collect some -data, and then allow the program to continue. Setting a tracepoint or -changing its actions takes effect immediately if the remote stub -supports the @samp{InstallInTrace} feature (@pxref{install tracepoint -in tracing}). -If remote stub doesn't support the @samp{InstallInTrace} feature, all -these changes don't take effect until the next @code{tstart} -command, and once a trace experiment is running, further changes will -not have any effect until the next trace experiment starts. In addition, -@value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose -address is not yet resolved. (This is similar to pending breakpoints.) -Pending tracepoints are not downloaded to the target and not installed -until they are resolved. The resolution of pending tracepoints requires -@value{GDBN} support---when debugging with the remote target, and -@value{GDBN} disconnects from the remote stub (@pxref{disconnected -tracing}), pending tracepoints can not be resolved (and downloaded to -the remote stub) while @value{GDBN} is disconnected. - -Here are some examples of using the @code{trace} command: - -@smallexample -(@value{GDBP}) @b{trace foo.c:121} // a source file and line number - -(@value{GDBP}) @b{trace +2} // 2 lines forward - -(@value{GDBP}) @b{trace my_function} // first source line of function - -(@value{GDBP}) @b{trace *my_function} // EXACT start address of function - -(@value{GDBP}) @b{trace *0x2117c4} // an address -@end smallexample - -@noindent -You can abbreviate @code{trace} as @code{tr}. - -@item trace @var{location} if @var{cond} -Set a tracepoint with condition @var{cond}; evaluate the expression -@var{cond} each time the tracepoint is reached, and collect data only -if the value is nonzero---that is, if @var{cond} evaluates as true. -@xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more -information on tracepoint conditions. - -@item ftrace @var{location} [ if @var{cond} ] -@cindex set fast tracepoint -@cindex fast tracepoints, setting -@kindex ftrace -The @code{ftrace} command sets a fast tracepoint. For targets that -support them, fast tracepoints will use a more efficient but possibly -less general technique to trigger data collection, such as a jump -instruction instead of a trap, or some sort of hardware support. It -may not be possible to create a fast tracepoint at the desired -location, in which case the command will exit with an explanatory -message. - -@value{GDBN} handles arguments to @code{ftrace} exactly as for -@code{trace}. - -On 32-bit x86-architecture systems, fast tracepoints normally need to -be placed at an instruction that is 5 bytes or longer, but can be -placed at 4-byte instructions if the low 64K of memory of the target -program is available to install trampolines. Some Unix-type systems, -such as @sc{gnu}/Linux, exclude low addresses from the program's -address space; but for instance with the Linux kernel it is possible -to let @value{GDBN} use this area by doing a @command{sysctl} command -to set the @code{mmap_min_addr} kernel parameter, as in - -@example -sudo sysctl -w vm.mmap_min_addr=32768 -@end example - -@noindent -which sets the low address to 32K, which leaves plenty of room for -trampolines. The minimum address should be set to a page boundary. - -@item strace @var{location} [ if @var{cond} ] -@cindex set static tracepoint -@cindex static tracepoints, setting -@cindex probe static tracepoint marker -@kindex strace -The @code{strace} command sets a static tracepoint. For targets that -support it, setting a static tracepoint probes a static -instrumentation point, or marker, found at @var{location}. It may not -be possible to set a static tracepoint at the desired location, in -which case the command will exit with an explanatory message. - -@value{GDBN} handles arguments to @code{strace} exactly as for -@code{trace}, with the addition that the user can also specify -@code{-m @var{marker}} as @var{location}. This probes the marker -identified by the @var{marker} string identifier. This identifier -depends on the static tracepoint backend library your program is -using. You can find all the marker identifiers in the @samp{ID} field -of the @code{info static-tracepoint-markers} command output. -@xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint -Markers}. For example, in the following small program using the UST -tracing engine: - -@smallexample -main () -@{ - trace_mark(ust, bar33, "str %s", "FOOBAZ"); -@} -@end smallexample - -@noindent -the marker id is composed of joining the first two arguments to the -@code{trace_mark} call with a slash, which translates to: - -@smallexample -(@value{GDBP}) info static-tracepoint-markers -Cnt Enb ID Address What -1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22 - Data: "str %s" -[etc...] -@end smallexample - -@noindent -so you may probe the marker above with: - -@smallexample -(@value{GDBP}) strace -m ust/bar33 -@end smallexample - -Static tracepoints accept an extra collect action --- @code{collect -$_sdata}. This collects arbitrary user data passed in the probe point -call to the tracing library. In the UST example above, you'll see -that the third argument to @code{trace_mark} is a printf-like format -string. The user data is then the result of running that formating -string against the following arguments. Note that @code{info -static-tracepoint-markers} command output lists that format string in -the @samp{Data:} field. - -You can inspect this data when analyzing the trace buffer, by printing -the $_sdata variable like any other variable available to -@value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}. - -@vindex $tpnum -@cindex last tracepoint number -@cindex recent tracepoint number -@cindex tracepoint number -The convenience variable @code{$tpnum} records the tracepoint number -of the most recently set tracepoint. - -@kindex delete tracepoint -@cindex tracepoint deletion -@item delete tracepoint @r{[}@var{num}@r{]} -Permanently delete one or more tracepoints. With no argument, the -default is to delete all tracepoints. Note that the regular -@code{delete} command can remove tracepoints also. - -Examples: - -@smallexample -(@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints - -(@value{GDBP}) @b{delete trace} // remove all tracepoints -@end smallexample - -@noindent -You can abbreviate this command as @code{del tr}. -@end table - -@node Enable and Disable Tracepoints -@subsection Enable and Disable Tracepoints - -These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}. - -@table @code -@kindex disable tracepoint -@item disable tracepoint @r{[}@var{num}@r{]} -Disable tracepoint @var{num}, or all tracepoints if no argument -@var{num} is given. A disabled tracepoint will have no effect during -a trace experiment, but it is not forgotten. You can re-enable -a disabled tracepoint using the @code{enable tracepoint} command. -If the command is issued during a trace experiment and the debug target -has support for disabling tracepoints during a trace experiment, then the -change will be effective immediately. Otherwise, it will be applied to the -next trace experiment. - -@kindex enable tracepoint -@item enable tracepoint @r{[}@var{num}@r{]} -Enable tracepoint @var{num}, or all tracepoints. If this command is -issued during a trace experiment and the debug target supports enabling -tracepoints during a trace experiment, then the enabled tracepoints will -become effective immediately. Otherwise, they will become effective the -next time a trace experiment is run. -@end table - -@node Tracepoint Passcounts -@subsection Tracepoint Passcounts - -@table @code -@kindex passcount -@cindex tracepoint pass count -@item passcount @r{[}@var{n} @r{[}@var{num}@r{]]} -Set the @dfn{passcount} of a tracepoint. The passcount is a way to -automatically stop a trace experiment. If a tracepoint's passcount is -@var{n}, then the trace experiment will be automatically stopped on -the @var{n}'th time that tracepoint is hit. If the tracepoint number -@var{num} is not specified, the @code{passcount} command sets the -passcount of the most recently defined tracepoint. If no passcount is -given, the trace experiment will run until stopped explicitly by the -user. - -Examples: - -@smallexample -(@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2} - -(@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.} -(@value{GDBP}) @b{trace foo} -(@value{GDBP}) @b{pass 3} -(@value{GDBP}) @b{trace bar} -(@value{GDBP}) @b{pass 2} -(@value{GDBP}) @b{trace baz} -(@value{GDBP}) @b{pass 1} // Stop tracing when foo has been -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has} -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times} -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.} -@end smallexample -@end table - -@node Tracepoint Conditions -@subsection Tracepoint Conditions -@cindex conditional tracepoints -@cindex tracepoint conditions - -The simplest sort of tracepoint collects data every time your program -reaches a specified place. You can also specify a @dfn{condition} for -a tracepoint. A condition is just a Boolean expression in your -programming language (@pxref{Expressions, ,Expressions}). A -tracepoint with a condition evaluates the expression each time your -program reaches it, and data collection happens only if the condition -is true. - -Tracepoint conditions can be specified when a tracepoint is set, by -using @samp{if} in the arguments to the @code{trace} command. -@xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can -also be set or changed at any time with the @code{condition} command, -just as with breakpoints. - -Unlike breakpoint conditions, @value{GDBN} does not actually evaluate -the conditional expression itself. Instead, @value{GDBN} encodes the -expression into an agent expression (@pxref{Agent Expressions}) -suitable for execution on the target, independently of @value{GDBN}. -Global variables become raw memory locations, locals become stack -accesses, and so forth. - -For instance, suppose you have a function that is usually called -frequently, but should not be called after an error has occurred. You -could use the following tracepoint command to collect data about calls -of that function that happen while the error code is propagating -through the program; an unconditional tracepoint could end up -collecting thousands of useless trace frames that you would have to -search through. - -@smallexample -(@value{GDBP}) @kbd{trace normal_operation if errcode > 0} -@end smallexample - -@node Trace State Variables -@subsection Trace State Variables -@cindex trace state variables - -A @dfn{trace state variable} is a special type of variable that is -created and managed by target-side code. The syntax is the same as -that for GDB's convenience variables (a string prefixed with ``$''), -but they are stored on the target. They must be created explicitly, -using a @code{tvariable} command. They are always 64-bit signed -integers. - -Trace state variables are remembered by @value{GDBN}, and downloaded -to the target along with tracepoint information when the trace -experiment starts. There are no intrinsic limits on the number of -trace state variables, beyond memory limitations of the target. - -@cindex convenience variables, and trace state variables -Although trace state variables are managed by the target, you can use -them in print commands and expressions as if they were convenience -variables; @value{GDBN} will get the current value from the target -while the trace experiment is running. Trace state variables share -the same namespace as other ``$'' variables, which means that you -cannot have trace state variables with names like @code{$23} or -@code{$pc}, nor can you have a trace state variable and a convenience -variable with the same name. - -@table @code - -@item tvariable $@var{name} [ = @var{expression} ] -@kindex tvariable -The @code{tvariable} command creates a new trace state variable named -@code{$@var{name}}, and optionally gives it an initial value of -@var{expression}. @var{expression} is evaluated when this command is -entered; the result will be converted to an integer if possible, -otherwise @value{GDBN} will report an error. A subsequent -@code{tvariable} command specifying the same name does not create a -variable, but instead assigns the supplied initial value to the -existing variable of that name, overwriting any previous initial -value. The default initial value is 0. - -@item info tvariables -@kindex info tvariables -List all the trace state variables along with their initial values. -Their current values may also be displayed, if the trace experiment is -currently running. - -@item delete tvariable @r{[} $@var{name} @dots{} @r{]} -@kindex delete tvariable -Delete the given trace state variables, or all of them if no arguments -are specified. - -@end table - -@node Tracepoint Actions -@subsection Tracepoint Action Lists - -@table @code -@kindex actions -@cindex tracepoint actions -@item actions @r{[}@var{num}@r{]} -This command will prompt for a list of actions to be taken when the -tracepoint is hit. If the tracepoint number @var{num} is not -specified, this command sets the actions for the one that was most -recently defined (so that you can define a tracepoint and then say -@code{actions} without bothering about its number). You specify the -actions themselves on the following lines, one action at a time, and -terminate the actions list with a line containing just @code{end}. So -far, the only defined actions are @code{collect}, @code{teval}, and -@code{while-stepping}. - -@code{actions} is actually equivalent to @code{commands} (@pxref{Break -Commands, ,Breakpoint Command Lists}), except that only the defined -actions are allowed; any other @value{GDBN} command is rejected. - -@cindex remove actions from a tracepoint -To remove all actions from a tracepoint, type @samp{actions @var{num}} -and follow it immediately with @samp{end}. - -@smallexample -(@value{GDBP}) @b{collect @var{data}} // collect some data - -(@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data - -(@value{GDBP}) @b{end} // signals the end of actions. -@end smallexample - -In the following example, the action list begins with @code{collect} -commands indicating the things to be collected when the tracepoint is -hit. Then, in order to single-step and collect additional data -following the tracepoint, a @code{while-stepping} command is used, -followed by the list of things to be collected after each step in a -sequence of single steps. The @code{while-stepping} command is -terminated by its own separate @code{end} command. Lastly, the action -list is terminated by an @code{end} command. - -@smallexample -(@value{GDBP}) @b{trace foo} -(@value{GDBP}) @b{actions} -Enter actions for tracepoint 1, one per line: -> collect bar,baz -> collect $regs -> while-stepping 12 - > collect $pc, arr[i] - > end -end -@end smallexample - -@kindex collect @r{(tracepoints)} -@item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{} -Collect values of the given expressions when the tracepoint is hit. -This command accepts a comma-separated list of any valid expressions. -In addition to global, static, or local variables, the following -special arguments are supported: - -@table @code -@item $regs -Collect all registers. - -@item $args -Collect all function arguments. - -@item $locals -Collect all local variables. - -@item $_ret -Collect the return address. This is helpful if you want to see more -of a backtrace. - -@item $_probe_argc -Collects the number of arguments from the static probe at which the -tracepoint is located. -@xref{Static Probe Points}. - -@item $_probe_arg@var{n} -@var{n} is an integer between 0 and 11. Collects the @var{n}th argument -from the static probe at which the tracepoint is located. -@xref{Static Probe Points}. - -@item $_sdata -@vindex $_sdata@r{, collect} -Collect static tracepoint marker specific data. Only available for -static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action -Lists}. On the UST static tracepoints library backend, an -instrumentation point resembles a @code{printf} function call. The -tracing library is able to collect user specified data formatted to a -character string using the format provided by the programmer that -instrumented the program. Other backends have similar mechanisms. -Here's an example of a UST marker call: - -@smallexample - const char master_name[] = "$your_name"; - trace_mark(channel1, marker1, "hello %s", master_name) -@end smallexample - -In this case, collecting @code{$_sdata} collects the string -@samp{hello $yourname}. When analyzing the trace buffer, you can -inspect @samp{$_sdata} like any other variable available to -@value{GDBN}. -@end table - -You can give several consecutive @code{collect} commands, each one -with a single argument, or one @code{collect} command with several -arguments separated by commas; the effect is the same. - -The optional @var{mods} changes the usual handling of the arguments. -@code{s} requests that pointers to chars be handled as strings, in -particular collecting the contents of the memory being pointed at, up -to the first zero. The upper bound is by default the value of the -@code{print elements} variable; if @code{s} is followed by a decimal -number, that is the upper bound instead. So for instance -@samp{collect/s25 mystr} collects as many as 25 characters at -@samp{mystr}. - -The command @code{info scope} (@pxref{Symbols, info scope}) is -particularly useful for figuring out what data to collect. - -@kindex teval @r{(tracepoints)} -@item teval @var{expr1}, @var{expr2}, @dots{} -Evaluate the given expressions when the tracepoint is hit. This -command accepts a comma-separated list of expressions. The results -are discarded, so this is mainly useful for assigning values to trace -state variables (@pxref{Trace State Variables}) without adding those -values to the trace buffer, as would be the case if the @code{collect} -action were used. - -@kindex while-stepping @r{(tracepoints)} -@item while-stepping @var{n} -Perform @var{n} single-step instruction traces after the tracepoint, -collecting new data after each step. The @code{while-stepping} -command is followed by the list of what to collect while stepping -(followed by its own @code{end} command): - -@smallexample -> while-stepping 12 - > collect $regs, myglobal - > end -> -@end smallexample - -@noindent -Note that @code{$pc} is not automatically collected by -@code{while-stepping}; you need to explicitly collect that register if -you need it. You may abbreviate @code{while-stepping} as @code{ws} or -@code{stepping}. - -@item set default-collect @var{expr1}, @var{expr2}, @dots{} -@kindex set default-collect -@cindex default collection action -This variable is a list of expressions to collect at each tracepoint -hit. It is effectively an additional @code{collect} action prepended -to every tracepoint action list. The expressions are parsed -individually for each tracepoint, so for instance a variable named -@code{xyz} may be interpreted as a global for one tracepoint, and a -local for another, as appropriate to the tracepoint's location. - -@item show default-collect -@kindex show default-collect -Show the list of expressions that are collected by default at each -tracepoint hit. - -@end table - -@node Listing Tracepoints -@subsection Listing Tracepoints - -@table @code -@kindex info tracepoints @r{[}@var{n}@dots{}@r{]} -@kindex info tp @r{[}@var{n}@dots{}@r{]} -@cindex information about tracepoints -@item info tracepoints @r{[}@var{num}@dots{}@r{]} -Display information about the tracepoint @var{num}. If you don't -specify a tracepoint number, displays information about all the -tracepoints defined so far. The format is similar to that used for -@code{info breakpoints}; in fact, @code{info tracepoints} is the same -command, simply restricting itself to tracepoints. - -A tracepoint's listing may include additional information specific to -tracing: - -@itemize @bullet -@item -its passcount as given by the @code{passcount @var{n}} command - -@item -the state about installed on target of each location -@end itemize - -@smallexample -(@value{GDBP}) @b{info trace} -Num Type Disp Enb Address What -1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7 - while-stepping 20 - collect globfoo, $regs - end - collect globfoo2 - end - pass count 1200 -2 tracepoint keep y - collect $eip -2.1 y 0x0804859c in func4 at change-loc.h:35 - installed on target -2.2 y 0xb7ffc480 in func4 at change-loc.h:35 - installed on target -2.3 y set_tracepoint -3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29 - not installed on target -(@value{GDBP}) -@end smallexample - -@noindent -This command can be abbreviated @code{info tp}. -@end table - -@node Listing Static Tracepoint Markers -@subsection Listing Static Tracepoint Markers - -@table @code -@kindex info static-tracepoint-markers -@cindex information about static tracepoint markers -@item info static-tracepoint-markers -Display information about all static tracepoint markers defined in the -program. - -For each marker, the following columns are printed: - -@table @emph -@item Count -An incrementing counter, output to help readability. This is not a -stable identifier. -@item ID -The marker ID, as reported by the target. -@item Enabled or Disabled -Probed markers are tagged with @samp{y}. @samp{n} identifies marks -that are not enabled. -@item Address -Where the marker is in your program, as a memory address. -@item What -Where the marker is in the source for your program, as a file and line -number. If the debug information included in the program does not -allow @value{GDBN} to locate the source of the marker, this column -will be left blank. -@end table - -@noindent -In addition, the following information may be printed for each marker: - -@table @emph -@item Data -User data passed to the tracing library by the marker call. In the -UST backend, this is the format string passed as argument to the -marker call. -@item Static tracepoints probing the marker -The list of static tracepoints attached to the marker. -@end table - -@smallexample -(@value{GDBP}) info static-tracepoint-markers -Cnt ID Enb Address What -1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25 - Data: number1 %d number2 %d - Probed by static tracepoints: #2 -2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24 - Data: str %s -(@value{GDBP}) -@end smallexample -@end table - -@node Starting and Stopping Trace Experiments -@subsection Starting and Stopping Trace Experiments - -@table @code -@kindex tstart [ @var{notes} ] -@cindex start a new trace experiment -@cindex collected data discarded -@item tstart -This command starts the trace experiment, and begins collecting data. -It has the side effect of discarding all the data collected in the -trace buffer during the previous trace experiment. If any arguments -are supplied, they are taken as a note and stored with the trace -experiment's state. The notes may be arbitrary text, and are -especially useful with disconnected tracing in a multi-user context; -the notes can explain what the trace is doing, supply user contact -information, and so forth. - -@kindex tstop [ @var{notes} ] -@cindex stop a running trace experiment -@item tstop -This command stops the trace experiment. If any arguments are -supplied, they are recorded with the experiment as a note. This is -useful if you are stopping a trace started by someone else, for -instance if the trace is interfering with the system's behavior and -needs to be stopped quickly. - -@strong{Note}: a trace experiment and data collection may stop -automatically if any tracepoint's passcount is reached -(@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full. - -@kindex tstatus -@cindex status of trace data collection -@cindex trace experiment, status of -@item tstatus -This command displays the status of the current trace data -collection. -@end table - -Here is an example of the commands we described so far: - -@smallexample -(@value{GDBP}) @b{trace gdb_c_test} -(@value{GDBP}) @b{actions} -Enter actions for tracepoint #1, one per line. -> collect $regs,$locals,$args -> while-stepping 11 - > collect $regs - > end -> end -(@value{GDBP}) @b{tstart} - [time passes @dots{}] -(@value{GDBP}) @b{tstop} -@end smallexample - -@anchor{disconnected tracing} -@cindex disconnected tracing -You can choose to continue running the trace experiment even if -@value{GDBN} disconnects from the target, voluntarily or -involuntarily. For commands such as @code{detach}, the debugger will -ask what you want to do with the trace. But for unexpected -terminations (@value{GDBN} crash, network outage), it would be -unfortunate to lose hard-won trace data, so the variable -@code{disconnected-tracing} lets you decide whether the trace should -continue running without @value{GDBN}. - -@table @code -@item set disconnected-tracing on -@itemx set disconnected-tracing off -@kindex set disconnected-tracing -Choose whether a tracing run should continue to run if @value{GDBN} -has disconnected from the target. Note that @code{detach} or -@code{quit} will ask you directly what to do about a running trace no -matter what this variable's setting, so the variable is mainly useful -for handling unexpected situations, such as loss of the network. - -@item show disconnected-tracing -@kindex show disconnected-tracing -Show the current choice for disconnected tracing. - -@end table - -When you reconnect to the target, the trace experiment may or may not -still be running; it might have filled the trace buffer in the -meantime, or stopped for one of the other reasons. If it is running, -it will continue after reconnection. - -Upon reconnection, the target will upload information about the -tracepoints in effect. @value{GDBN} will then compare that -information to the set of tracepoints currently defined, and attempt -to match them up, allowing for the possibility that the numbers may -have changed due to creation and deletion in the meantime. If one of -the target's tracepoints does not match any in @value{GDBN}, the -debugger will create a new tracepoint, so that you have a number with -which to specify that tracepoint. This matching-up process is -necessarily heuristic, and it may result in useless tracepoints being -created; you may simply delete them if they are of no use. - -@cindex circular trace buffer -If your target agent supports a @dfn{circular trace buffer}, then you -can run a trace experiment indefinitely without filling the trace -buffer; when space runs out, the agent deletes already-collected trace -frames, oldest first, until there is enough room to continue -collecting. This is especially useful if your tracepoints are being -hit too often, and your trace gets terminated prematurely because the -buffer is full. To ask for a circular trace buffer, simply set -@samp{circular-trace-buffer} to on. You can set this at any time, -including during tracing; if the agent can do it, it will change -buffer handling on the fly, otherwise it will not take effect until -the next run. - -@table @code -@item set circular-trace-buffer on -@itemx set circular-trace-buffer off -@kindex set circular-trace-buffer -Choose whether a tracing run should use a linear or circular buffer -for trace data. A linear buffer will not lose any trace data, but may -fill up prematurely, while a circular buffer will discard old trace -data, but it will have always room for the latest tracepoint hits. - -@item show circular-trace-buffer -@kindex show circular-trace-buffer -Show the current choice for the trace buffer. Note that this may not -match the agent's current buffer handling, nor is it guaranteed to -match the setting that might have been in effect during a past run, -for instance if you are looking at frames from a trace file. - -@end table - -@table @code -@item set trace-buffer-size @var{n} -@kindex set trace-buffer-size -Request that the target use a trace buffer of @var{n} bytes. Not all -targets will honor the request; they may have a compiled-in size for -the trace buffer, or some other limitation. Set to a value of -@code{-1} to let the target use whatever size it likes. This is also -the default. - -@item show trace-buffer-size -@kindex show trace-buffer-size -Show the current requested size for the trace buffer. Note that this -will only match the actual size if the target supports size-setting, -and was able to handle the requested size. For instance, if the -target can only change buffer size between runs, this variable will -not reflect the change until the next run starts. Use @code{tstatus} -to get a report of the actual buffer size. -@end table - -@table @code -@item set trace-user @var{text} -@kindex set trace-user - -@item show trace-user -@kindex show trace-user - -@item set trace-notes @var{text} -@kindex set trace-notes -Set the trace run's notes. - -@item show trace-notes -@kindex show trace-notes -Show the trace run's notes. - -@item set trace-stop-notes @var{text} -@kindex set trace-stop-notes -Set the trace run's stop notes. The handling of the note is as for -@code{tstop} arguments; the set command is convenient way to fix a -stop note that is mistaken or incomplete. - -@item show trace-stop-notes -@kindex show trace-stop-notes -Show the trace run's stop notes. - -@end table - -@node Tracepoint Restrictions -@subsection Tracepoint Restrictions - -@cindex tracepoint restrictions -There are a number of restrictions on the use of tracepoints. As -described above, tracepoint data gathering occurs on the target -without interaction from @value{GDBN}. Thus the full capabilities of -the debugger are not available during data gathering, and then at data -examination time, you will be limited by only having what was -collected. The following items describe some common problems, but it -is not exhaustive, and you may run into additional difficulties not -mentioned here. - -@itemize @bullet - -@item -Tracepoint expressions are intended to gather objects (lvalues). Thus -the full flexibility of GDB's expression evaluator is not available. -You cannot call functions, cast objects to aggregate types, access -convenience variables or modify values (except by assignment to trace -state variables). Some language features may implicitly call -functions (for instance Objective-C fields with accessors), and therefore -cannot be collected either. - -@item -Collection of local variables, either individually or in bulk with -@code{$locals} or @code{$args}, during @code{while-stepping} may -behave erratically. The stepping action may enter a new scope (for -instance by stepping into a function), or the location of the variable -may change (for instance it is loaded into a register). The -tracepoint data recorded uses the location information for the -variables that is correct for the tracepoint location. When the -tracepoint is created, it is not possible, in general, to determine -where the steps of a @code{while-stepping} sequence will advance the -program---particularly if a conditional branch is stepped. - -@item -Collection of an incompletely-initialized or partially-destroyed object -may result in something that @value{GDBN} cannot display, or displays -in a misleading way. - -@item -When @value{GDBN} displays a pointer to character it automatically -dereferences the pointer to also display characters of the string -being pointed to. However, collecting the pointer during tracing does -not automatically collect the string. You need to explicitly -dereference the pointer and provide size information if you want to -collect not only the pointer, but the memory pointed to. For example, -@code{*ptr@@50} can be used to collect the 50 element array pointed to -by @code{ptr}. - -@item -It is not possible to collect a complete stack backtrace at a -tracepoint. Instead, you may collect the registers and a few hundred -bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300} -(adjust to use the name of the actual stack pointer register on your -target architecture, and the amount of stack you wish to capture). -Then the @code{backtrace} command will show a partial backtrace when -using a trace frame. The number of stack frames that can be examined -depends on the sizes of the frames in the collected stack. Note that -if you ask for a block so large that it goes past the bottom of the -stack, the target agent may report an error trying to read from an -invalid address. - -@item -If you do not collect registers at a tracepoint, @value{GDBN} can -infer that the value of @code{$pc} must be the same as the address of -the tracepoint and use that when you are looking at a trace frame -for that tracepoint. However, this cannot work if the tracepoint has -multiple locations (for instance if it was set in a function that was -inlined), or if it has a @code{while-stepping} loop. In those cases -@value{GDBN} will warn you that it can't infer @code{$pc}, and default -it to zero. - -@end itemize - -@node Analyze Collected Data -@section Using the Collected Data - -After the tracepoint experiment ends, you use @value{GDBN} commands -for examining the trace data. The basic idea is that each tracepoint -collects a trace @dfn{snapshot} every time it is hit and another -snapshot every time it single-steps. All these snapshots are -consecutively numbered from zero and go into a buffer, and you can -examine them later. The way you examine them is to @dfn{focus} on a -specific trace snapshot. When the remote stub is focused on a trace -snapshot, it will respond to all @value{GDBN} requests for memory and -registers by reading from the buffer which belongs to that snapshot, -rather than from @emph{real} memory or registers of the program being -debugged. This means that @strong{all} @value{GDBN} commands -(@code{print}, @code{info registers}, @code{backtrace}, etc.) will -behave as if we were currently debugging the program state as it was -when the tracepoint occurred. Any requests for data that are not in -the buffer will fail. - -@menu -* tfind:: How to select a trace snapshot -* tdump:: How to display all data for a snapshot -* save tracepoints:: How to save tracepoints for a future run -@end menu - -@node tfind -@subsection @code{tfind @var{n}} - -@kindex tfind -@cindex select trace snapshot -@cindex find trace snapshot -The basic command for selecting a trace snapshot from the buffer is -@code{tfind @var{n}}, which finds trace snapshot number @var{n}, -counting from zero. If no argument @var{n} is given, the next -snapshot is selected. - -Here are the various forms of using the @code{tfind} command. - -@table @code -@item tfind start -Find the first snapshot in the buffer. This is a synonym for -@code{tfind 0} (since 0 is the number of the first snapshot). - -@item tfind none -Stop debugging trace snapshots, resume @emph{live} debugging. - -@item tfind end -Same as @samp{tfind none}. - -@item tfind -No argument means find the next trace snapshot. - -@item tfind - -Find the previous trace snapshot before the current one. This permits -retracing earlier steps. - -@item tfind tracepoint @var{num} -Find the next snapshot associated with tracepoint @var{num}. Search -proceeds forward from the last examined trace snapshot. If no -argument @var{num} is given, it means find the next snapshot collected -for the same tracepoint as the current snapshot. - -@item tfind pc @var{addr} -Find the next snapshot associated with the value @var{addr} of the -program counter. Search proceeds forward from the last examined trace -snapshot. If no argument @var{addr} is given, it means find the next -snapshot with the same value of PC as the current snapshot. - -@item tfind outside @var{addr1}, @var{addr2} -Find the next snapshot whose PC is outside the given range of -addresses (exclusive). - -@item tfind range @var{addr1}, @var{addr2} -Find the next snapshot whose PC is between @var{addr1} and -@var{addr2} (inclusive). - -@item tfind line @r{[}@var{file}:@r{]}@var{n} -Find the next snapshot associated with the source line @var{n}. If -the optional argument @var{file} is given, refer to line @var{n} in -that source file. Search proceeds forward from the last examined -trace snapshot. If no argument @var{n} is given, it means find the -next line other than the one currently being examined; thus saying -@code{tfind line} repeatedly can appear to have the same effect as -stepping from line to line in a @emph{live} debugging session. -@end table - -The default arguments for the @code{tfind} commands are specifically -designed to make it easy to scan through the trace buffer. For -instance, @code{tfind} with no argument selects the next trace -snapshot, and @code{tfind -} with no argument selects the previous -trace snapshot. So, by giving one @code{tfind} command, and then -simply hitting @key{RET} repeatedly you can examine all the trace -snapshots in order. Or, by saying @code{tfind -} and then hitting -@key{RET} repeatedly you can examine the snapshots in reverse order. -The @code{tfind line} command with no argument selects the snapshot -for the next source line executed. The @code{tfind pc} command with -no argument selects the next snapshot with the same program counter -(PC) as the current frame. The @code{tfind tracepoint} command with -no argument selects the next trace snapshot collected by the same -tracepoint as the current one. - -In addition to letting you scan through the trace buffer manually, -these commands make it easy to construct @value{GDBN} scripts that -scan through the trace buffer and print out whatever collected data -you are interested in. Thus, if we want to examine the PC, FP, and SP -registers from each trace frame in the buffer, we can say this: - -@smallexample -(@value{GDBP}) @b{tfind start} -(@value{GDBP}) @b{while ($trace_frame != -1)} -> printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \ - $trace_frame, $pc, $sp, $fp -> tfind -> end - -Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44 -Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44 -Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44 -Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44 -Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44 -Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44 -Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44 -Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44 -Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44 -Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44 -Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14 -@end smallexample - -Or, if we want to examine the variable @code{X} at each source line in -the buffer: - -@smallexample -(@value{GDBP}) @b{tfind start} -(@value{GDBP}) @b{while ($trace_frame != -1)} -> printf "Frame %d, X == %d\n", $trace_frame, X -> tfind line -> end - -Frame 0, X = 1 -Frame 7, X = 2 -Frame 13, X = 255 -@end smallexample - -@node tdump -@subsection @code{tdump} -@kindex tdump -@cindex dump all data collected at tracepoint -@cindex tracepoint data, display - -This command takes no arguments. It prints all the data collected at -the current trace snapshot. - -@smallexample -(@value{GDBP}) @b{trace 444} -(@value{GDBP}) @b{actions} -Enter actions for tracepoint #2, one per line: -> collect $regs, $locals, $args, gdb_long_test -> end - -(@value{GDBP}) @b{tstart} - -(@value{GDBP}) @b{tfind line 444} -#0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66) -at gdb_test.c:444 -444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", ) - -(@value{GDBP}) @b{tdump} -Data collected at tracepoint 2, trace frame 1: -d0 0xc4aa0085 -995491707 -d1 0x18 24 -d2 0x80 128 -d3 0x33 51 -d4 0x71aea3d 119204413 -d5 0x22 34 -d6 0xe0 224 -d7 0x380035 3670069 -a0 0x19e24a 1696330 -a1 0x3000668 50333288 -a2 0x100 256 -a3 0x322000 3284992 -a4 0x3000698 50333336 -a5 0x1ad3cc 1758156 -fp 0x30bf3c 0x30bf3c -sp 0x30bf34 0x30bf34 -ps 0x0 0 -pc 0x20b2c8 0x20b2c8 -fpcontrol 0x0 0 -fpstatus 0x0 0 -fpiaddr 0x0 0 -p = 0x20e5b4 "gdb-test" -p1 = (void *) 0x11 -p2 = (void *) 0x22 -p3 = (void *) 0x33 -p4 = (void *) 0x44 -p5 = (void *) 0x55 -p6 = (void *) 0x66 -gdb_long_test = 17 '\021' - -(@value{GDBP}) -@end smallexample - -@code{tdump} works by scanning the tracepoint's current collection -actions and printing the value of each expression listed. So -@code{tdump} can fail, if after a run, you change the tracepoint's -actions to mention variables that were not collected during the run. - -Also, for tracepoints with @code{while-stepping} loops, @code{tdump} -uses the collected value of @code{$pc} to distinguish between trace -frames that were collected at the tracepoint hit, and frames that were -collected while stepping. This allows it to correctly choose whether -to display the basic list of collections, or the collections from the -body of the while-stepping loop. However, if @code{$pc} was not collected, -then @code{tdump} will always attempt to dump using the basic collection -list, and may fail if a while-stepping frame does not include all the -same data that is collected at the tracepoint hit. -@c This is getting pretty arcane, example would be good. - -@node save tracepoints -@subsection @code{save tracepoints @var{filename}} -@kindex save tracepoints -@kindex save-tracepoints -@cindex save tracepoints for future sessions - -This command saves all current tracepoint definitions together with -their actions and passcounts, into a file @file{@var{filename}} -suitable for use in a later debugging session. To read the saved -tracepoint definitions, use the @code{source} command (@pxref{Command -Files}). The @w{@code{save-tracepoints}} command is a deprecated -alias for @w{@code{save tracepoints}} - -@node Tracepoint Variables -@section Convenience Variables for Tracepoints -@cindex tracepoint variables -@cindex convenience variables for tracepoints - -@table @code -@vindex $trace_frame -@item (int) $trace_frame -The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no -snapshot is selected. - -@vindex $tracepoint -@item (int) $tracepoint -The tracepoint for the current trace snapshot. - -@vindex $trace_line -@item (int) $trace_line -The line number for the current trace snapshot. - -@vindex $trace_file -@item (char []) $trace_file -The source file for the current trace snapshot. - -@vindex $trace_func -@item (char []) $trace_func -The name of the function containing @code{$tracepoint}. -@end table - -Note: @code{$trace_file} is not suitable for use in @code{printf}, -use @code{output} instead. - -Here's a simple example of using these convenience variables for -stepping through all the trace snapshots and printing some of their -data. Note that these are not the same as trace state variables, -which are managed by the target. - -@smallexample -(@value{GDBP}) @b{tfind start} - -(@value{GDBP}) @b{while $trace_frame != -1} -> output $trace_file -> printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint -> tfind -> end -@end smallexample - -@node Trace Files -@section Using Trace Files -@cindex trace files - -In some situations, the target running a trace experiment may no -longer be available; perhaps it crashed, or the hardware was needed -for a different activity. To handle these cases, you can arrange to -dump the trace data into a file, and later use that file as a source -of trace data, via the @code{target tfile} command. - -@table @code - -@kindex tsave -@item tsave [ -r ] @var{filename} -Save the trace data to @var{filename}. By default, this command -assumes that @var{filename} refers to the host filesystem, so if -necessary @value{GDBN} will copy raw trace data up from the target and -then save it. If the target supports it, you can also supply the -optional argument @code{-r} (``remote'') to direct the target to save -the data directly into @var{filename} in its own filesystem, which may be -more efficient if the trace buffer is very large. (Note, however, that -@code{target tfile} can only read from files accessible to the host.) - -@kindex target tfile -@kindex tfile -@item target tfile @var{filename} -Use the file named @var{filename} as a source of trace data. Commands -that examine data work as they do with a live target, but it is not -possible to run any new trace experiments. @code{tstatus} will report -the state of the trace run at the moment the data was saved, as well -as the current trace frame you are examining. @var{filename} must be -on a filesystem accessible to the host. - -@end table - -@node Overlays -@chapter Debugging Programs That Use Overlays -@cindex overlays - -If your program is too large to fit completely in your target system's -memory, you can sometimes use @dfn{overlays} to work around this -problem. @value{GDBN} provides some support for debugging programs that -use overlays. - -@menu -* How Overlays Work:: A general explanation of overlays. -* Overlay Commands:: Managing overlays in @value{GDBN}. -* Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are - mapped by asking the inferior. -* Overlay Sample Program:: A sample program using overlays. -@end menu - -@node How Overlays Work -@section How Overlays Work -@cindex mapped overlays -@cindex unmapped overlays -@cindex load address, overlay's -@cindex mapped address -@cindex overlay area - -Suppose you have a computer whose instruction address space is only 64 -kilobytes long, but which has much more memory which can be accessed by -other means: special instructions, segment registers, or memory -management hardware, for example. Suppose further that you want to -adapt a program which is larger than 64 kilobytes to run on this system. - -One solution is to identify modules of your program which are relatively -independent, and need not call each other directly; call these modules -@dfn{overlays}. Separate the overlays from the main program, and place -their machine code in the larger memory. Place your main program in -instruction memory, but leave at least enough space there to hold the -largest overlay as well. - -Now, to call a function located in an overlay, you must first copy that -overlay's machine code from the large memory into the space set aside -for it in the instruction memory, and then jump to its entry point -there. - -@c NB: In the below the mapped area's size is greater or equal to the -@c size of all overlays. This is intentional to remind the developer -@c that overlays don't necessarily need to be the same size. - -@smallexample -@group - Data Instruction Larger -Address Space Address Space Address Space -+-----------+ +-----------+ +-----------+ -| | | | | | -+-----------+ +-----------+ +-----------+<-- overlay 1 -| program | | main | .----| overlay 1 | load address -| variables | | program | | +-----------+ -| and heap | | | | | | -+-----------+ | | | +-----------+<-- overlay 2 -| | +-----------+ | | | load address -+-----------+ | | | .-| overlay 2 | - | | | | | | - mapped --->+-----------+ | | +-----------+ - address | | | | | | - | overlay | <-' | | | - | area | <---' +-----------+<-- overlay 3 - | | <---. | | load address - +-----------+ `--| overlay 3 | - | | | | - +-----------+ | | - +-----------+ - | | - +-----------+ - - @anchor{A code overlay}A code overlay -@end group -@end smallexample - -The diagram (@pxref{A code overlay}) shows a system with separate data -and instruction address spaces. To map an overlay, the program copies -its code from the larger address space to the instruction address space. -Since the overlays shown here all use the same mapped address, only one -may be mapped at a time. For a system with a single address space for -data and instructions, the diagram would be similar, except that the -program variables and heap would share an address space with the main -program and the overlay area. - -An overlay loaded into instruction memory and ready for use is called a -@dfn{mapped} overlay; its @dfn{mapped address} is its address in the -instruction memory. An overlay not present (or only partially present) -in instruction memory is called @dfn{unmapped}; its @dfn{load address} -is its address in the larger memory. The mapped address is also called -the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also -called the @dfn{load memory address}, or @dfn{LMA}. - -Unfortunately, overlays are not a completely transparent way to adapt a -program to limited instruction memory. They introduce a new set of -global constraints you must keep in mind as you design your program: - -@itemize @bullet - -@item -Before calling or returning to a function in an overlay, your program -must make sure that overlay is actually mapped. Otherwise, the call or -return will transfer control to the right address, but in the wrong -overlay, and your program will probably crash. - -@item -If the process of mapping an overlay is expensive on your system, you -will need to choose your overlays carefully to minimize their effect on -your program's performance. - -@item -The executable file you load onto your system must contain each -overlay's instructions, appearing at the overlay's load address, not its -mapped address. However, each overlay's instructions must be relocated -and its symbols defined as if the overlay were at its mapped address. -You can use GNU linker scripts to specify different load and relocation -addresses for pieces of your program; see @ref{Overlay Description,,, -ld.info, Using ld: the GNU linker}. - -@item -The procedure for loading executable files onto your system must be able -to load their contents into the larger address space as well as the -instruction and data spaces. - -@end itemize - -The overlay system described above is rather simple, and could be -improved in many ways: - -@itemize @bullet - -@item -If your system has suitable bank switch registers or memory management -hardware, you could use those facilities to make an overlay's load area -contents simply appear at their mapped address in instruction space. -This would probably be faster than copying the overlay to its mapped -area in the usual way. - -@item -If your overlays are small enough, you could set aside more than one -overlay area, and have more than one overlay mapped at a time. - -@item -You can use overlays to manage data, as well as instructions. In -general, data overlays are even less transparent to your design than -code overlays: whereas code overlays only require care when you call or -return to functions, data overlays require care every time you access -the data. Also, if you change the contents of a data overlay, you -must copy its contents back out to its load address before you can copy a -different data overlay into the same mapped area. - -@end itemize - - -@node Overlay Commands -@section Overlay Commands - -To use @value{GDBN}'s overlay support, each overlay in your program must -correspond to a separate section of the executable file. The section's -virtual memory address and load memory address must be the overlay's -mapped and load addresses. Identifying overlays with sections allows -@value{GDBN} to determine the appropriate address of a function or -variable, depending on whether the overlay is mapped or not. - -@value{GDBN}'s overlay commands all start with the word @code{overlay}; -you can abbreviate this as @code{ov} or @code{ovly}. The commands are: - -@table @code -@item overlay off -@kindex overlay -Disable @value{GDBN}'s overlay support. When overlay support is -disabled, @value{GDBN} assumes that all functions and variables are -always present at their mapped addresses. By default, @value{GDBN}'s -overlay support is disabled. - -@item overlay manual -@cindex manual overlay debugging -Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN} -relies on you to tell it which overlays are mapped, and which are not, -using the @code{overlay map-overlay} and @code{overlay unmap-overlay} -commands described below. - -@item overlay map-overlay @var{overlay} -@itemx overlay map @var{overlay} -@cindex map an overlay -Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must -be the name of the object file section containing the overlay. When an -overlay is mapped, @value{GDBN} assumes it can find the overlay's -functions and variables at their mapped addresses. @value{GDBN} assumes -that any other overlays whose mapped ranges overlap that of -@var{overlay} are now unmapped. - -@item overlay unmap-overlay @var{overlay} -@itemx overlay unmap @var{overlay} -@cindex unmap an overlay -Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay} -must be the name of the object file section containing the overlay. -When an overlay is unmapped, @value{GDBN} assumes it can find the -overlay's functions and variables at their load addresses. - -@item overlay auto -Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN} -consults a data structure the overlay manager maintains in the inferior -to see which overlays are mapped. For details, see @ref{Automatic -Overlay Debugging}. - -@item overlay load-target -@itemx overlay load -@cindex reloading the overlay table -Re-read the overlay table from the inferior. Normally, @value{GDBN} -re-reads the table @value{GDBN} automatically each time the inferior -stops, so this command should only be necessary if you have changed the -overlay mapping yourself using @value{GDBN}. This command is only -useful when using automatic overlay debugging. - -@item overlay list-overlays -@itemx overlay list -@cindex listing mapped overlays -Display a list of the overlays currently mapped, along with their mapped -addresses, load addresses, and sizes. - -@end table - -Normally, when @value{GDBN} prints a code address, it includes the name -of the function the address falls in: - -@smallexample -(@value{GDBP}) print main -$3 = @{int ()@} 0x11a0
-@end smallexample -@noindent -When overlay debugging is enabled, @value{GDBN} recognizes code in -unmapped overlays, and prints the names of unmapped functions with -asterisks around them. For example, if @code{foo} is a function in an -unmapped overlay, @value{GDBN} prints it this way: - -@smallexample -(@value{GDBP}) overlay list -No sections are mapped. -(@value{GDBP}) print foo -$5 = @{int (int)@} 0x100000 <*foo*> -@end smallexample -@noindent -When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's -name normally: - -@smallexample -(@value{GDBP}) overlay list -Section .ov.foo.text, loaded at 0x100000 - 0x100034, - mapped at 0x1016 - 0x104a -(@value{GDBP}) print foo -$6 = @{int (int)@} 0x1016 -@end smallexample - -When overlay debugging is enabled, @value{GDBN} can find the correct -address for functions and variables in an overlay, whether or not the -overlay is mapped. This allows most @value{GDBN} commands, like -@code{break} and @code{disassemble}, to work normally, even on unmapped -code. However, @value{GDBN}'s breakpoint support has some limitations: - -@itemize @bullet -@item -@cindex breakpoints in overlays -@cindex overlays, setting breakpoints in -You can set breakpoints in functions in unmapped overlays, as long as -@value{GDBN} can write to the overlay at its load address. -@item -@value{GDBN} can not set hardware or simulator-based breakpoints in -unmapped overlays. However, if you set a breakpoint at the end of your -overlay manager (and tell @value{GDBN} which overlays are now mapped, if -you are using manual overlay management), @value{GDBN} will re-set its -breakpoints properly. -@end itemize - - -@node Automatic Overlay Debugging -@section Automatic Overlay Debugging -@cindex automatic overlay debugging - -@value{GDBN} can automatically track which overlays are mapped and which -are not, given some simple co-operation from the overlay manager in the -inferior. If you enable automatic overlay debugging with the -@code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN} -looks in the inferior's memory for certain variables describing the -current state of the overlays. - -Here are the variables your overlay manager must define to support -@value{GDBN}'s automatic overlay debugging: - -@table @asis - -@item @code{_ovly_table}: -This variable must be an array of the following structures: - -@smallexample -struct -@{ - /* The overlay's mapped address. */ - unsigned long vma; - - /* The size of the overlay, in bytes. */ - unsigned long size; - - /* The overlay's load address. */ - unsigned long lma; - - /* Non-zero if the overlay is currently mapped; - zero otherwise. */ - unsigned long mapped; -@} -@end smallexample - -@item @code{_novlys}: -This variable must be a four-byte signed integer, holding the total -number of elements in @code{_ovly_table}. - -@end table - -To decide whether a particular overlay is mapped or not, @value{GDBN} -looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and -@code{lma} members equal the VMA and LMA of the overlay's section in the -executable file. When @value{GDBN} finds a matching entry, it consults -the entry's @code{mapped} member to determine whether the overlay is -currently mapped. - -In addition, your overlay manager may define a function called -@code{_ovly_debug_event}. If this function is defined, @value{GDBN} -will silently set a breakpoint there. If the overlay manager then -calls this function whenever it has changed the overlay table, this -will enable @value{GDBN} to accurately keep track of which overlays -are in program memory, and update any breakpoints that may be set -in overlays. This will allow breakpoints to work even if the -overlays are kept in ROM or other non-writable memory while they -are not being executed. - -@node Overlay Sample Program -@section Overlay Sample Program -@cindex overlay example program - -When linking a program which uses overlays, you must place the overlays -at their load addresses, while relocating them to run at their mapped -addresses. To do this, you must write a linker script (@pxref{Overlay -Description,,, ld.info, Using ld: the GNU linker}). Unfortunately, -since linker scripts are specific to a particular host system, target -architecture, and target memory layout, this manual cannot provide -portable sample code demonstrating @value{GDBN}'s overlay support. - -However, the @value{GDBN} source distribution does contain an overlaid -program, with linker scripts for a few systems, as part of its test -suite. The program consists of the following files from -@file{gdb/testsuite/gdb.base}: - -@table @file -@item overlays.c -The main program file. -@item ovlymgr.c -A simple overlay manager, used by @file{overlays.c}. -@item foo.c -@itemx bar.c -@itemx baz.c -@itemx grbx.c -Overlay modules, loaded and used by @file{overlays.c}. -@item d10v.ld -@itemx m32r.ld -Linker scripts for linking the test program on the @code{d10v-elf} -and @code{m32r-elf} targets. -@end table - -You can build the test program using the @code{d10v-elf} GCC -cross-compiler like this: - -@smallexample -$ d10v-elf-gcc -g -c overlays.c -$ d10v-elf-gcc -g -c ovlymgr.c -$ d10v-elf-gcc -g -c foo.c -$ d10v-elf-gcc -g -c bar.c -$ d10v-elf-gcc -g -c baz.c -$ d10v-elf-gcc -g -c grbx.c -$ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \ - baz.o grbx.o -Wl,-Td10v.ld -o overlays -@end smallexample - -The build process is identical for any other architecture, except that -you must substitute the appropriate compiler and linker script for the -target system for @code{d10v-elf-gcc} and @code{d10v.ld}. - - -@node Languages -@chapter Using @value{GDBN} with Different Languages -@cindex languages - -Although programming languages generally have common aspects, they are -rarely expressed in the same manner. For instance, in ANSI C, -dereferencing a pointer @code{p} is accomplished by @code{*p}, but in -Modula-2, it is accomplished by @code{p^}. Values can also be -represented (and displayed) differently. Hex numbers in C appear as -@samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}. - -@cindex working language -Language-specific information is built into @value{GDBN} for some languages, -allowing you to express operations like the above in your program's -native language, and allowing @value{GDBN} to output values in a manner -consistent with the syntax of your program's native language. The -language you use to build expressions is called the @dfn{working -language}. - -@menu -* Setting:: Switching between source languages -* Show:: Displaying the language -* Checks:: Type and range checks -* Supported Languages:: Supported languages -* Unsupported Languages:: Unsupported languages -@end menu - -@node Setting -@section Switching Between Source Languages - -There are two ways to control the working language---either have @value{GDBN} -set it automatically, or select it manually yourself. You can use the -@code{set language} command for either purpose. On startup, @value{GDBN} -defaults to setting the language automatically. The working language is -used to determine how expressions you type are interpreted, how values -are printed, etc. - -In addition to the working language, every source file that -@value{GDBN} knows about has its own working language. For some object -file formats, the compiler might indicate which language a particular -source file is in. However, most of the time @value{GDBN} infers the -language from the name of the file. The language of a source file -controls whether C@t{++} names are demangled---this way @code{backtrace} can -show each frame appropriately for its own language. There is no way to -set the language of a source file from within @value{GDBN}, but you can -set the language associated with a filename extension. @xref{Show, , -Displaying the Language}. - -This is most commonly a problem when you use a program, such -as @code{cfront} or @code{f2c}, that generates C but is written in -another language. In that case, make the -program use @code{#line} directives in its C output; that way -@value{GDBN} will know the correct language of the source code of the original -program, and will display that source code, not the generated C code. - -@menu -* Filenames:: Filename extensions and languages. -* Manually:: Setting the working language manually -* Automatically:: Having @value{GDBN} infer the source language -@end menu - -@node Filenames -@subsection List of Filename Extensions and Languages - -If a source file name ends in one of the following extensions, then -@value{GDBN} infers that its language is the one indicated. - -@table @file -@item .ada -@itemx .ads -@itemx .adb -@itemx .a -Ada source file. - -@item .c -C source file - -@item .C -@itemx .cc -@itemx .cp -@itemx .cpp -@itemx .cxx -@itemx .c++ -C@t{++} source file - -@item .d -D source file - -@item .m -Objective-C source file - -@item .f -@itemx .F -Fortran source file - -@item .mod -Modula-2 source file - -@item .s -@itemx .S -Assembler source file. This actually behaves almost like C, but -@value{GDBN} does not skip over function prologues when stepping. -@end table - -In addition, you may set the language associated with a filename -extension. @xref{Show, , Displaying the Language}. - -@node Manually -@subsection Setting the Working Language - -If you allow @value{GDBN} to set the language automatically, -expressions are interpreted the same way in your debugging session and -your program. - -@kindex set language -If you wish, you may set the language manually. To do this, issue the -command @samp{set language @var{lang}}, where @var{lang} is the name of -a language, such as -@code{c} or @code{modula-2}. -For a list of the supported languages, type @samp{set language}. - -Setting the language manually prevents @value{GDBN} from updating the working -language automatically. This can lead to confusion if you try -to debug a program when the working language is not the same as the -source language, when an expression is acceptable to both -languages---but means different things. For instance, if the current -source file were written in C, and @value{GDBN} was parsing Modula-2, a -command such as: - -@smallexample -print a = b + c -@end smallexample - -@noindent -might not have the effect you intended. In C, this means to add -@code{b} and @code{c} and place the result in @code{a}. The result -printed would be the value of @code{a}. In Modula-2, this means to compare -@code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value. - -@node Automatically -@subsection Having @value{GDBN} Infer the Source Language - -To have @value{GDBN} set the working language automatically, use -@samp{set language local} or @samp{set language auto}. @value{GDBN} -then infers the working language. That is, when your program stops in a -frame (usually by encountering a breakpoint), @value{GDBN} sets the -working language to the language recorded for the function in that -frame. If the language for a frame is unknown (that is, if the function -or block corresponding to the frame was defined in a source file that -does not have a recognized extension), the current working language is -not changed, and @value{GDBN} issues a warning. - -This may not seem necessary for most programs, which are written -entirely in one source language. However, program modules and libraries -written in one source language can be used by a main program written in -a different source language. Using @samp{set language auto} in this -case frees you from having to set the working language manually. - -@node Show -@section Displaying the Language - -The following commands help you find out which language is the -working language, and also what language source files were written in. - -@table @code -@item show language -@kindex show language -Display the current working language. This is the -language you can use with commands such as @code{print} to -build and compute expressions that may involve variables in your program. - -@item info frame -@kindex info frame@r{, show the source language} -Display the source language for this frame. This language becomes the -working language if you use an identifier from this frame. -@xref{Frame Info, ,Information about a Frame}, to identify the other -information listed here. - -@item info source -@kindex info source@r{, show the source language} -Display the source language of this source file. -@xref{Symbols, ,Examining the Symbol Table}, to identify the other -information listed here. -@end table - -In unusual circumstances, you may have source files with extensions -not in the standard list. You can then set the extension associated -with a language explicitly: - -@table @code -@item set extension-language @var{ext} @var{language} -@kindex set extension-language -Tell @value{GDBN} that source files with extension @var{ext} are to be -assumed as written in the source language @var{language}. - -@item info extensions -@kindex info extensions -List all the filename extensions and the associated languages. -@end table - -@node Checks -@section Type and Range Checking - -Some languages are designed to guard you against making seemingly common -errors through a series of compile- and run-time checks. These include -checking the type of arguments to functions and operators and making -sure mathematical overflows are caught at run time. Checks such as -these help to ensure a program's correctness once it has been compiled -by eliminating type mismatches and providing active checks for range -errors when your program is running. - -By default @value{GDBN} checks for these errors according to the -rules of the current source language. Although @value{GDBN} does not check -the statements in your program, it can check expressions entered directly -into @value{GDBN} for evaluation via the @code{print} command, for example. - -@menu -* Type Checking:: An overview of type checking -* Range Checking:: An overview of range checking -@end menu - -@cindex type checking -@cindex checks, type -@node Type Checking -@subsection An Overview of Type Checking - -Some languages, such as C and C@t{++}, are strongly typed, meaning that the -arguments to operators and functions have to be of the correct type, -otherwise an error occurs. These checks prevent type mismatch -errors from ever causing any run-time problems. For example, - -@smallexample -int klass::my_method(char *b) @{ return b ? 1 : 2; @} - -(@value{GDBP}) print obj.my_method (0) -$1 = 2 -@exdent but -(@value{GDBP}) print obj.my_method (0x1234) -Cannot resolve method klass::my_method to any overloaded instance -@end smallexample - -The second example fails because in C@t{++} the integer constant -@samp{0x1234} is not type-compatible with the pointer parameter type. - -For the expressions you use in @value{GDBN} commands, you can tell -@value{GDBN} to not enforce strict type checking or -to treat any mismatches as errors and abandon the expression; -When type checking is disabled, @value{GDBN} successfully evaluates -expressions like the second example above. - -Even if type checking is off, there may be other reasons -related to type that prevent @value{GDBN} from evaluating an expression. -For instance, @value{GDBN} does not know how to add an @code{int} and -a @code{struct foo}. These particular type errors have nothing to do -with the language in use and usually arise from expressions which make -little sense to evaluate anyway. - -@value{GDBN} provides some additional commands for controlling type checking: - -@kindex set check type -@kindex show check type -@table @code -@item set check type on -@itemx set check type off -Set strict type checking on or off. If any type mismatches occur in -evaluating an expression while type checking is on, @value{GDBN} prints a -message and aborts evaluation of the expression. - -@item show check type -Show the current setting of type checking and whether @value{GDBN} -is enforcing strict type checking rules. -@end table - -@cindex range checking -@cindex checks, range -@node Range Checking -@subsection An Overview of Range Checking - -In some languages (such as Modula-2), it is an error to exceed the -bounds of a type; this is enforced with run-time checks. Such range -checking is meant to ensure program correctness by making sure -computations do not overflow, or indices on an array element access do -not exceed the bounds of the array. - -For expressions you use in @value{GDBN} commands, you can tell -@value{GDBN} to treat range errors in one of three ways: ignore them, -always treat them as errors and abandon the expression, or issue -warnings but evaluate the expression anyway. - -A range error can result from numerical overflow, from exceeding an -array index bound, or when you type a constant that is not a member -of any type. Some languages, however, do not treat overflows as an -error. In many implementations of C, mathematical overflow causes the -result to ``wrap around'' to lower values---for example, if @var{m} is -the largest integer value, and @var{s} is the smallest, then - -@smallexample -@var{m} + 1 @result{} @var{s} -@end smallexample - -This, too, is specific to individual languages, and in some cases -specific to individual compilers or machines. @xref{Supported Languages, , -Supported Languages}, for further details on specific languages. - -@value{GDBN} provides some additional commands for controlling the range checker: - -@kindex set check range -@kindex show check range -@table @code -@item set check range auto -Set range checking on or off based on the current working language. -@xref{Supported Languages, ,Supported Languages}, for the default settings for -each language. - -@item set check range on -@itemx set check range off -Set range checking on or off, overriding the default setting for the -current working language. A warning is issued if the setting does not -match the language default. If a range error occurs and range checking is on, -then a message is printed and evaluation of the expression is aborted. - -@item set check range warn -Output messages when the @value{GDBN} range checker detects a range error, -but attempt to evaluate the expression anyway. Evaluating the -expression may still be impossible for other reasons, such as accessing -memory that the process does not own (a typical example from many Unix -systems). - -@item show range -Show the current setting of the range checker, and whether or not it is -being set automatically by @value{GDBN}. -@end table - -@node Supported Languages -@section Supported Languages - -@value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java, -OpenCL C, Pascal, assembly, Modula-2, and Ada. -@c This is false ... -Some @value{GDBN} features may be used in expressions regardless of the -language you use: the @value{GDBN} @code{@@} and @code{::} operators, -and the @samp{@{type@}addr} construct (@pxref{Expressions, -,Expressions}) can be used with the constructs of any supported -language. - -The following sections detail to what degree each source language is -supported by @value{GDBN}. These sections are not meant to be language -tutorials or references, but serve only as a reference guide to what the -@value{GDBN} expression parser accepts, and what input and output -formats should look like for different languages. There are many good -books written on each of these languages; please look to these for a -language reference or tutorial. - -@menu -* C:: C and C@t{++} -* D:: D -* Go:: Go -* Objective-C:: Objective-C -* OpenCL C:: OpenCL C -* Fortran:: Fortran -* Pascal:: Pascal -* Modula-2:: Modula-2 -* Ada:: Ada -@end menu - -@node C -@subsection C and C@t{++} - -@cindex C and C@t{++} -@cindex expressions in C or C@t{++} - -Since C and C@t{++} are so closely related, many features of @value{GDBN} apply -to both languages. Whenever this is the case, we discuss those languages -together. - -@cindex C@t{++} -@cindex @code{g++}, @sc{gnu} C@t{++} compiler -@cindex @sc{gnu} C@t{++} -The C@t{++} debugging facilities are jointly implemented by the C@t{++} -compiler and @value{GDBN}. Therefore, to debug your C@t{++} code -effectively, you must compile your C@t{++} programs with a supported -C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++} -compiler (@code{aCC}). - -@menu -* C Operators:: C and C@t{++} operators -* C Constants:: C and C@t{++} constants -* C Plus Plus Expressions:: C@t{++} expressions -* C Defaults:: Default settings for C and C@t{++} -* C Checks:: C and C@t{++} type and range checks -* Debugging C:: @value{GDBN} and C -* Debugging C Plus Plus:: @value{GDBN} features for C@t{++} -* Decimal Floating Point:: Numbers in Decimal Floating Point format -@end menu - -@node C Operators -@subsubsection C and C@t{++} Operators - -@cindex C and C@t{++} operators - -Operators must be defined on values of specific types. For instance, -@code{+} is defined on numbers, but not on structures. Operators are -often defined on groups of types. - -For the purposes of C and C@t{++}, the following definitions hold: - -@itemize @bullet - -@item -@emph{Integral types} include @code{int} with any of its storage-class -specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}. - -@item -@emph{Floating-point types} include @code{float}, @code{double}, and -@code{long double} (if supported by the target platform). - -@item -@emph{Pointer types} include all types defined as @code{(@var{type} *)}. - -@item -@emph{Scalar types} include all of the above. - -@end itemize - -@noindent -The following operators are supported. They are listed here -in order of increasing precedence: - -@table @code -@item , -The comma or sequencing operator. Expressions in a comma-separated list -are evaluated from left to right, with the result of the entire -expression being the last expression evaluated. - -@item = -Assignment. The value of an assignment expression is the value -assigned. Defined on scalar types. - -@item @var{op}= -Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}}, -and translated to @w{@code{@var{a} = @var{a op b}}}. -@w{@code{@var{op}=}} and @code{=} have the same precedence. -@var{op} is any one of the operators @code{|}, @code{^}, @code{&}, -@code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}. - -@item ?: -The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought -of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an -integral type. - -@item || -Logical @sc{or}. Defined on integral types. - -@item && -Logical @sc{and}. Defined on integral types. - -@item | -Bitwise @sc{or}. Defined on integral types. - -@item ^ -Bitwise exclusive-@sc{or}. Defined on integral types. - -@item & -Bitwise @sc{and}. Defined on integral types. - -@item ==@r{, }!= -Equality and inequality. Defined on scalar types. The value of these -expressions is 0 for false and non-zero for true. - -@item <@r{, }>@r{, }<=@r{, }>= -Less than, greater than, less than or equal, greater than or equal. -Defined on scalar types. The value of these expressions is 0 for false -and non-zero for true. - -@item <<@r{, }>> -left shift, and right shift. Defined on integral types. - -@item @@ -The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). - -@item +@r{, }- -Addition and subtraction. Defined on integral types, floating-point types and -pointer types. - -@item *@r{, }/@r{, }% -Multiplication, division, and modulus. Multiplication and division are -defined on integral and floating-point types. Modulus is defined on -integral types. - -@item ++@r{, }-- -Increment and decrement. When appearing before a variable, the -operation is performed before the variable is used in an expression; -when appearing after it, the variable's value is used before the -operation takes place. - -@item * -Pointer dereferencing. Defined on pointer types. Same precedence as -@code{++}. - -@item & -Address operator. Defined on variables. Same precedence as @code{++}. - -For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is -allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})} -to examine the address -where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is -stored. - -@item - -Negative. Defined on integral and floating-point types. Same -precedence as @code{++}. - -@item ! -Logical negation. Defined on integral types. Same precedence as -@code{++}. - -@item ~ -Bitwise complement operator. Defined on integral types. Same precedence as -@code{++}. - - -@item .@r{, }-> -Structure member, and pointer-to-structure member. For convenience, -@value{GDBN} regards the two as equivalent, choosing whether to dereference a -pointer based on the stored type information. -Defined on @code{struct} and @code{union} data. - -@item .*@r{, }->* -Dereferences of pointers to members. - -@item [] -Array indexing. @code{@var{a}[@var{i}]} is defined as -@code{*(@var{a}+@var{i})}. Same precedence as @code{->}. - -@item () -Function parameter list. Same precedence as @code{->}. - -@item :: -C@t{++} scope resolution operator. Defined on @code{struct}, @code{union}, -and @code{class} types. - -@item :: -Doubled colons also represent the @value{GDBN} scope operator -(@pxref{Expressions, ,Expressions}). Same precedence as @code{::}, -above. -@end table - -If an operator is redefined in the user code, @value{GDBN} usually -attempts to invoke the redefined version instead of using the operator's -predefined meaning. - -@node C Constants -@subsubsection C and C@t{++} Constants - -@cindex C and C@t{++} constants - -@value{GDBN} allows you to express the constants of C and C@t{++} in the -following ways: - -@itemize @bullet -@item -Integer constants are a sequence of digits. Octal constants are -specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants -by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter -@samp{l}, specifying that the constant should be treated as a -@code{long} value. - -@item -Floating point constants are a sequence of digits, followed by a decimal -point, followed by a sequence of digits, and optionally followed by an -exponent. An exponent is of the form: -@samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another -sequence of digits. The @samp{+} is optional for positive exponents. -A floating-point constant may also end with a letter @samp{f} or -@samp{F}, specifying that the constant should be treated as being of -the @code{float} (as opposed to the default @code{double}) type; or with -a letter @samp{l} or @samp{L}, which specifies a @code{long double} -constant. - -@item -Enumerated constants consist of enumerated identifiers, or their -integral equivalents. - -@item -Character constants are a single character surrounded by single quotes -(@code{'}), or a number---the ordinal value of the corresponding character -(usually its @sc{ascii} value). Within quotes, the single character may -be represented by a letter or by @dfn{escape sequences}, which are of -the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation -of the character's ordinal value; or of the form @samp{\@var{x}}, where -@samp{@var{x}} is a predefined special character---for example, -@samp{\n} for newline. - -Wide character constants can be written by prefixing a character -constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide -form of @samp{x}. The target wide character set is used when -computing the value of this constant (@pxref{Character Sets}). - -@item -String constants are a sequence of character constants surrounded by -double quotes (@code{"}). Any valid character constant (as described -above) may appear. Double quotes within the string must be preceded by -a backslash, so for instance @samp{"a\"b'c"} is a string of five -characters. - -Wide string constants can be written by prefixing a string constant -with @samp{L}, as in C. The target wide character set is used when -computing the value of this constant (@pxref{Character Sets}). - -@item -Pointer constants are an integral value. You can also write pointers -to constants using the C operator @samp{&}. - -@item -Array constants are comma-separated lists surrounded by braces @samp{@{} -and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of -integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array, -and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers. -@end itemize - -@node C Plus Plus Expressions -@subsubsection C@t{++} Expressions - -@cindex expressions in C@t{++} -@value{GDBN} expression handling can interpret most C@t{++} expressions. - -@cindex debugging C@t{++} programs -@cindex C@t{++} compilers -@cindex debug formats and C@t{++} -@cindex @value{NGCC} and C@t{++} -@quotation -@emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use -the proper compiler and the proper debug format. Currently, -@value{GDBN} works best when debugging C@t{++} code that is compiled -with the most recent version of @value{NGCC} possible. The DWARF -debugging format is preferred; @value{NGCC} defaults to this on most -popular platforms. Other compilers and/or debug formats are likely to -work badly or not at all when using @value{GDBN} to debug C@t{++} -code. @xref{Compilation}. -@end quotation - -@enumerate - -@cindex member functions -@item -Member function calls are allowed; you can use expressions like - -@smallexample -count = aml->GetOriginal(x, y) -@end smallexample - -@vindex this@r{, inside C@t{++} member functions} -@cindex namespace in C@t{++} -@item -While a member function is active (in the selected stack frame), your -expressions have the same namespace available as the member function; -that is, @value{GDBN} allows implicit references to the class instance -pointer @code{this} following the same rules as C@t{++}. @code{using} -declarations in the current scope are also respected by @value{GDBN}. - -@cindex call overloaded functions -@cindex overloaded functions, calling -@cindex type conversions in C@t{++} -@item -You can call overloaded functions; @value{GDBN} resolves the function -call to the right definition, with some restrictions. @value{GDBN} does not -perform overload resolution involving user-defined type conversions, -calls to constructors, or instantiations of templates that do not exist -in the program. It also cannot handle ellipsis argument lists or -default arguments. - -It does perform integral conversions and promotions, floating-point -promotions, arithmetic conversions, pointer conversions, conversions of -class objects to base classes, and standard conversions such as those of -functions or arrays to pointers; it requires an exact match on the -number of function arguments. - -Overload resolution is always performed, unless you have specified -@code{set overload-resolution off}. @xref{Debugging C Plus Plus, -,@value{GDBN} Features for C@t{++}}. - -You must specify @code{set overload-resolution off} in order to use an -explicit function signature to call an overloaded function, as in -@smallexample -p 'foo(char,int)'('x', 13) -@end smallexample - -The @value{GDBN} command-completion facility can simplify this; -see @ref{Completion, ,Command Completion}. - -@cindex reference declarations -@item -@value{GDBN} understands variables declared as C@t{++} references; you can use -them in expressions just as you do in C@t{++} source---they are automatically -dereferenced. - -In the parameter list shown when @value{GDBN} displays a frame, the values of -reference variables are not displayed (unlike other variables); this -avoids clutter, since references are often used for large structures. -The @emph{address} of a reference variable is always shown, unless -you have specified @samp{set print address off}. - -@item -@value{GDBN} supports the C@t{++} name resolution operator @code{::}---your -expressions can use it just as expressions in your program do. Since -one scope may be defined in another, you can use @code{::} repeatedly if -necessary, for example in an expression like -@samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows -resolving name scope by reference to source files, in both C and C@t{++} -debugging (@pxref{Variables, ,Program Variables}). - -@item -@value{GDBN} performs argument-dependent lookup, following the C@t{++} -specification. -@end enumerate - -@node C Defaults -@subsubsection C and C@t{++} Defaults - -@cindex C and C@t{++} defaults - -If you allow @value{GDBN} to set range checking automatically, it -defaults to @code{off} whenever the working language changes to -C or C@t{++}. This happens regardless of whether you or @value{GDBN} -selects the working language. - -If you allow @value{GDBN} to set the language automatically, it -recognizes source files whose names end with @file{.c}, @file{.C}, or -@file{.cc}, etc, and when @value{GDBN} enters code compiled from one of -these files, it sets the working language to C or C@t{++}. -@xref{Automatically, ,Having @value{GDBN} Infer the Source Language}, -for further details. - -@node C Checks -@subsubsection C and C@t{++} Type and Range Checks - -@cindex C and C@t{++} checks - -By default, when @value{GDBN} parses C or C@t{++} expressions, strict type -checking is used. However, if you turn type checking off, @value{GDBN} -will allow certain non-standard conversions, such as promoting integer -constants to pointers. - -Range checking, if turned on, is done on mathematical operations. Array -indices are not checked, since they are often used to index a pointer -that is not itself an array. - -@node Debugging C -@subsubsection @value{GDBN} and C - -The @code{set print union} and @code{show print union} commands apply to -the @code{union} type. When set to @samp{on}, any @code{union} that is -inside a @code{struct} or @code{class} is also printed. Otherwise, it -appears as @samp{@{...@}}. - -The @code{@@} operator aids in the debugging of dynamic arrays, formed -with pointers and a memory allocation function. @xref{Expressions, -,Expressions}. - -@node Debugging C Plus Plus -@subsubsection @value{GDBN} Features for C@t{++} - -@cindex commands for C@t{++} - -Some @value{GDBN} commands are particularly useful with C@t{++}, and some are -designed specifically for use with C@t{++}. Here is a summary: - -@table @code -@cindex break in overloaded functions -@item @r{breakpoint menus} -When you want a breakpoint in a function whose name is overloaded, -@value{GDBN} has the capability to display a menu of possible breakpoint -locations to help you specify which function definition you want. -@xref{Ambiguous Expressions,,Ambiguous Expressions}. - -@cindex overloading in C@t{++} -@item rbreak @var{regex} -Setting breakpoints using regular expressions is helpful for setting -breakpoints on overloaded functions that are not members of any special -classes. -@xref{Set Breaks, ,Setting Breakpoints}. - -@cindex C@t{++} exception handling -@item catch throw -@itemx catch catch -Debug C@t{++} exception handling using these commands. @xref{Set -Catchpoints, , Setting Catchpoints}. - -@cindex inheritance -@item ptype @var{typename} -Print inheritance relationships as well as other information for type -@var{typename}. -@xref{Symbols, ,Examining the Symbol Table}. - -@item info vtbl @var{expression}. -The @code{info vtbl} command can be used to display the virtual -method tables of the object computed by @var{expression}. This shows -one entry per virtual table; there may be multiple virtual tables when -multiple inheritance is in use. - -@cindex C@t{++} symbol display -@item set print demangle -@itemx show print demangle -@itemx set print asm-demangle -@itemx show print asm-demangle -Control whether C@t{++} symbols display in their source form, both when -displaying code as C@t{++} source and when displaying disassemblies. -@xref{Print Settings, ,Print Settings}. - -@item set print object -@itemx show print object -Choose whether to print derived (actual) or declared types of objects. -@xref{Print Settings, ,Print Settings}. - -@item set print vtbl -@itemx show print vtbl -Control the format for printing virtual function tables. -@xref{Print Settings, ,Print Settings}. -(The @code{vtbl} commands do not work on programs compiled with the HP -ANSI C@t{++} compiler (@code{aCC}).) - -@kindex set overload-resolution -@cindex overloaded functions, overload resolution -@item set overload-resolution on -Enable overload resolution for C@t{++} expression evaluation. The default -is on. For overloaded functions, @value{GDBN} evaluates the arguments -and searches for a function whose signature matches the argument types, -using the standard C@t{++} conversion rules (see @ref{C Plus Plus -Expressions, ,C@t{++} Expressions}, for details). -If it cannot find a match, it emits a message. - -@item set overload-resolution off -Disable overload resolution for C@t{++} expression evaluation. For -overloaded functions that are not class member functions, @value{GDBN} -chooses the first function of the specified name that it finds in the -symbol table, whether or not its arguments are of the correct type. For -overloaded functions that are class member functions, @value{GDBN} -searches for a function whose signature @emph{exactly} matches the -argument types. - -@kindex show overload-resolution -@item show overload-resolution -Show the current setting of overload resolution. - -@item @r{Overloaded symbol names} -You can specify a particular definition of an overloaded symbol, using -the same notation that is used to declare such symbols in C@t{++}: type -@code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can -also use the @value{GDBN} command-line word completion facilities to list the -available choices, or to finish the type list for you. -@xref{Completion,, Command Completion}, for details on how to do this. -@end table - -@node Decimal Floating Point -@subsubsection Decimal Floating Point format -@cindex decimal floating point format - -@value{GDBN} can examine, set and perform computations with numbers in -decimal floating point format, which in the C language correspond to the -@code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as -specified by the extension to support decimal floating-point arithmetic. - -There are two encodings in use, depending on the architecture: BID (Binary -Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for -PowerPC. @value{GDBN} will use the appropriate encoding for the configured -target. - -Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN} -to manipulate decimal floating point numbers, it is not possible to convert -(using a cast, for example) integers wider than 32-bit to decimal float. - -In addition, in order to imitate @value{GDBN}'s behaviour with binary floating -point computations, error checking in decimal float operations ignores -underflow, overflow and divide by zero exceptions. - -In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers -to inspect @code{_Decimal128} values stored in floating point registers. -See @ref{PowerPC,,PowerPC} for more details. - -@node D -@subsection D - -@cindex D -@value{GDBN} can be used to debug programs written in D and compiled with -GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D -specific feature --- dynamic arrays. - -@node Go -@subsection Go - -@cindex Go (programming language) -@value{GDBN} can be used to debug programs written in Go and compiled with -@file{gccgo} or @file{6g} compilers. - -Here is a summary of the Go-specific features and restrictions: - -@table @code -@cindex current Go package -@item The current Go package -The name of the current package does not need to be specified when -specifying global variables and functions. - -For example, given the program: - -@example -package main -var myglob = "Shall we?" -func main () @{ - // ... -@} -@end example - -When stopped inside @code{main} either of these work: - -@example -(gdb) p myglob -(gdb) p main.myglob -@end example - -@cindex builtin Go types -@item Builtin Go types -The @code{string} type is recognized by @value{GDBN} and is printed -as a string. - -@cindex builtin Go functions -@item Builtin Go functions -The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof} -function and handles it internally. - -@cindex restrictions on Go expressions -@item Restrictions on Go expressions -All Go operators are supported except @code{&^}. -The Go @code{_} ``blank identifier'' is not supported. -Automatic dereferencing of pointers is not supported. -@end table - -@node Objective-C -@subsection Objective-C - -@cindex Objective-C -This section provides information about some commands and command -options that are useful for debugging Objective-C code. See also -@ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a -few more commands specific to Objective-C support. - -@menu -* Method Names in Commands:: -* The Print Command with Objective-C:: -@end menu - -@node Method Names in Commands -@subsubsection Method Names in Commands - -The following commands have been extended to accept Objective-C method -names as line specifications: - -@kindex clear@r{, and Objective-C} -@kindex break@r{, and Objective-C} -@kindex info line@r{, and Objective-C} -@kindex jump@r{, and Objective-C} -@kindex list@r{, and Objective-C} -@itemize -@item @code{clear} -@item @code{break} -@item @code{info line} -@item @code{jump} -@item @code{list} -@end itemize - -A fully qualified Objective-C method name is specified as - -@smallexample --[@var{Class} @var{methodName}] -@end smallexample - -where the minus sign is used to indicate an instance method and a -plus sign (not shown) is used to indicate a class method. The class -name @var{Class} and method name @var{methodName} are enclosed in -brackets, similar to the way messages are specified in Objective-C -source code. For example, to set a breakpoint at the @code{create} -instance method of class @code{Fruit} in the program currently being -debugged, enter: - -@smallexample -break -[Fruit create] -@end smallexample - -To list ten program lines around the @code{initialize} class method, -enter: - -@smallexample -list +[NSText initialize] -@end smallexample - -In the current version of @value{GDBN}, the plus or minus sign is -required. In future versions of @value{GDBN}, the plus or minus -sign will be optional, but you can use it to narrow the search. It -is also possible to specify just a method name: - -@smallexample -break create -@end smallexample - -You must specify the complete method name, including any colons. If -your program's source files contain more than one @code{create} method, -you'll be presented with a numbered list of classes that implement that -method. Indicate your choice by number, or type @samp{0} to exit if -none apply. - -As another example, to clear a breakpoint established at the -@code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter: - -@smallexample -clear -[NSWindow makeKeyAndOrderFront:] -@end smallexample - -@node The Print Command with Objective-C -@subsubsection The Print Command With Objective-C -@cindex Objective-C, print objects -@kindex print-object -@kindex po @r{(@code{print-object})} - -The print command has also been extended to accept methods. For example: - -@smallexample -print -[@var{object} hash] -@end smallexample - -@cindex print an Objective-C object description -@cindex @code{_NSPrintForDebugger}, and printing Objective-C objects -@noindent -will tell @value{GDBN} to send the @code{hash} message to @var{object} -and print the result. Also, an additional command has been added, -@code{print-object} or @code{po} for short, which is meant to print -the description of an object. However, this command may only work -with certain Objective-C libraries that have a particular hook -function, @code{_NSPrintForDebugger}, defined. - -@node OpenCL C -@subsection OpenCL C - -@cindex OpenCL C -This section provides information about @value{GDBN}s OpenCL C support. - -@menu -* OpenCL C Datatypes:: -* OpenCL C Expressions:: -* OpenCL C Operators:: -@end menu - -@node OpenCL C Datatypes -@subsubsection OpenCL C Datatypes - -@cindex OpenCL C Datatypes -@value{GDBN} supports the builtin scalar and vector datatypes specified -by OpenCL 1.1. In addition the half- and double-precision floating point -data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL -extensions are also known to @value{GDBN}. - -@node OpenCL C Expressions -@subsubsection OpenCL C Expressions - -@cindex OpenCL C Expressions -@value{GDBN} supports accesses to vector components including the access as -lvalue where possible. Since OpenCL C is based on C99 most C expressions -supported by @value{GDBN} can be used as well. - -@node OpenCL C Operators -@subsubsection OpenCL C Operators - -@cindex OpenCL C Operators -@value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and -vector data types. - -@node Fortran -@subsection Fortran -@cindex Fortran-specific support in @value{GDBN} - -@value{GDBN} can be used to debug programs written in Fortran, but it -currently supports only the features of Fortran 77 language. - -@cindex trailing underscore, in Fortran symbols -Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers -among them) append an underscore to the names of variables and -functions. When you debug programs compiled by those compilers, you -will need to refer to variables and functions with a trailing -underscore. - -@menu -* Fortran Operators:: Fortran operators and expressions -* Fortran Defaults:: Default settings for Fortran -* Special Fortran Commands:: Special @value{GDBN} commands for Fortran -@end menu - -@node Fortran Operators -@subsubsection Fortran Operators and Expressions - -@cindex Fortran operators and expressions - -Operators must be defined on values of specific types. For instance, -@code{+} is defined on numbers, but not on characters or other non- -arithmetic types. Operators are often defined on groups of types. - -@table @code -@item ** -The exponentiation operator. It raises the first operand to the power -of the second one. - -@item : -The range operator. Normally used in the form of array(low:high) to -represent a section of array. - -@item % -The access component operator. Normally used to access elements in derived -types. Also suitable for unions. As unions aren't part of regular Fortran, -this can only happen when accessing a register that uses a gdbarch-defined -union type. -@end table - -@node Fortran Defaults -@subsubsection Fortran Defaults - -@cindex Fortran Defaults - -Fortran symbols are usually case-insensitive, so @value{GDBN} by -default uses case-insensitive matches for Fortran symbols. You can -change that with the @samp{set case-insensitive} command, see -@ref{Symbols}, for the details. - -@node Special Fortran Commands -@subsubsection Special Fortran Commands - -@cindex Special Fortran commands - -@value{GDBN} has some commands to support Fortran-specific features, -such as displaying common blocks. - -@table @code -@cindex @code{COMMON} blocks, Fortran -@kindex info common -@item info common @r{[}@var{common-name}@r{]} -This command prints the values contained in the Fortran @code{COMMON} -block whose name is @var{common-name}. With no argument, the names of -all @code{COMMON} blocks visible at the current program location are -printed. -@end table - -@node Pascal -@subsection Pascal - -@cindex Pascal support in @value{GDBN}, limitations -Debugging Pascal programs which use sets, subranges, file variables, or -nested functions does not currently work. @value{GDBN} does not support -entering expressions, printing values, or similar features using Pascal -syntax. - -The Pascal-specific command @code{set print pascal_static-members} -controls whether static members of Pascal objects are displayed. -@xref{Print Settings, pascal_static-members}. - -@node Modula-2 -@subsection Modula-2 - -@cindex Modula-2, @value{GDBN} support - -The extensions made to @value{GDBN} to support Modula-2 only support -output from the @sc{gnu} Modula-2 compiler (which is currently being -developed). Other Modula-2 compilers are not currently supported, and -attempting to debug executables produced by them is most likely -to give an error as @value{GDBN} reads in the executable's symbol -table. - -@cindex expressions in Modula-2 -@menu -* M2 Operators:: Built-in operators -* Built-In Func/Proc:: Built-in functions and procedures -* M2 Constants:: Modula-2 constants -* M2 Types:: Modula-2 types -* M2 Defaults:: Default settings for Modula-2 -* Deviations:: Deviations from standard Modula-2 -* M2 Checks:: Modula-2 type and range checks -* M2 Scope:: The scope operators @code{::} and @code{.} -* GDB/M2:: @value{GDBN} and Modula-2 -@end menu - -@node M2 Operators -@subsubsection Operators -@cindex Modula-2 operators - -Operators must be defined on values of specific types. For instance, -@code{+} is defined on numbers, but not on structures. Operators are -often defined on groups of types. For the purposes of Modula-2, the -following definitions hold: - -@itemize @bullet - -@item -@emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and -their subranges. - -@item -@emph{Character types} consist of @code{CHAR} and its subranges. - -@item -@emph{Floating-point types} consist of @code{REAL}. - -@item -@emph{Pointer types} consist of anything declared as @code{POINTER TO -@var{type}}. - -@item -@emph{Scalar types} consist of all of the above. - -@item -@emph{Set types} consist of @code{SET} and @code{BITSET} types. - -@item -@emph{Boolean types} consist of @code{BOOLEAN}. -@end itemize - -@noindent -The following operators are supported, and appear in order of -increasing precedence: - -@table @code -@item , -Function argument or array index separator. - -@item := -Assignment. The value of @var{var} @code{:=} @var{value} is -@var{value}. - -@item <@r{, }> -Less than, greater than on integral, floating-point, or enumerated -types. - -@item <=@r{, }>= -Less than or equal to, greater than or equal to -on integral, floating-point and enumerated types, or set inclusion on -set types. Same precedence as @code{<}. - -@item =@r{, }<>@r{, }# -Equality and two ways of expressing inequality, valid on scalar types. -Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is -available for inequality, since @code{#} conflicts with the script -comment character. - -@item IN -Set membership. Defined on set types and the types of their members. -Same precedence as @code{<}. - -@item OR -Boolean disjunction. Defined on boolean types. - -@item AND@r{, }& -Boolean conjunction. Defined on boolean types. - -@item @@ -The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). - -@item +@r{, }- -Addition and subtraction on integral and floating-point types, or union -and difference on set types. - -@item * -Multiplication on integral and floating-point types, or set intersection -on set types. - -@item / -Division on floating-point types, or symmetric set difference on set -types. Same precedence as @code{*}. - -@item DIV@r{, }MOD -Integer division and remainder. Defined on integral types. Same -precedence as @code{*}. - -@item - -Negative. Defined on @code{INTEGER} and @code{REAL} data. - -@item ^ -Pointer dereferencing. Defined on pointer types. - -@item NOT -Boolean negation. Defined on boolean types. Same precedence as -@code{^}. - -@item . -@code{RECORD} field selector. Defined on @code{RECORD} data. Same -precedence as @code{^}. - -@item [] -Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}. - -@item () -Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence -as @code{^}. - -@item ::@r{, }. -@value{GDBN} and Modula-2 scope operators. -@end table - -@quotation -@emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN} -treats the use of the operator @code{IN}, or the use of operators -@code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#}, -@code{<=}, and @code{>=} on sets as an error. -@end quotation - - -@node Built-In Func/Proc -@subsubsection Built-in Functions and Procedures -@cindex Modula-2 built-ins - -Modula-2 also makes available several built-in procedures and functions. -In describing these, the following metavariables are used: - -@table @var - -@item a -represents an @code{ARRAY} variable. - -@item c -represents a @code{CHAR} constant or variable. - -@item i -represents a variable or constant of integral type. - -@item m -represents an identifier that belongs to a set. Generally used in the -same function with the metavariable @var{s}. The type of @var{s} should -be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}). - -@item n -represents a variable or constant of integral or floating-point type. - -@item r -represents a variable or constant of floating-point type. - -@item t -represents a type. - -@item v -represents a variable. - -@item x -represents a variable or constant of one of many types. See the -explanation of the function for details. -@end table - -All Modula-2 built-in procedures also return a result, described below. - -@table @code -@item ABS(@var{n}) -Returns the absolute value of @var{n}. - -@item CAP(@var{c}) -If @var{c} is a lower case letter, it returns its upper case -equivalent, otherwise it returns its argument. - -@item CHR(@var{i}) -Returns the character whose ordinal value is @var{i}. - -@item DEC(@var{v}) -Decrements the value in the variable @var{v} by one. Returns the new value. - -@item DEC(@var{v},@var{i}) -Decrements the value in the variable @var{v} by @var{i}. Returns the -new value. - -@item EXCL(@var{m},@var{s}) -Removes the element @var{m} from the set @var{s}. Returns the new -set. - -@item FLOAT(@var{i}) -Returns the floating point equivalent of the integer @var{i}. - -@item HIGH(@var{a}) -Returns the index of the last member of @var{a}. - -@item INC(@var{v}) -Increments the value in the variable @var{v} by one. Returns the new value. - -@item INC(@var{v},@var{i}) -Increments the value in the variable @var{v} by @var{i}. Returns the -new value. - -@item INCL(@var{m},@var{s}) -Adds the element @var{m} to the set @var{s} if it is not already -there. Returns the new set. - -@item MAX(@var{t}) -Returns the maximum value of the type @var{t}. - -@item MIN(@var{t}) -Returns the minimum value of the type @var{t}. - -@item ODD(@var{i}) -Returns boolean TRUE if @var{i} is an odd number. - -@item ORD(@var{x}) -Returns the ordinal value of its argument. For example, the ordinal -value of a character is its @sc{ascii} value (on machines supporting the -@sc{ascii} character set). @var{x} must be of an ordered type, which include -integral, character and enumerated types. - -@item SIZE(@var{x}) -Returns the size of its argument. @var{x} can be a variable or a type. - -@item TRUNC(@var{r}) -Returns the integral part of @var{r}. - -@item TSIZE(@var{x}) -Returns the size of its argument. @var{x} can be a variable or a type. - -@item VAL(@var{t},@var{i}) -Returns the member of the type @var{t} whose ordinal value is @var{i}. -@end table - -@quotation -@emph{Warning:} Sets and their operations are not yet supported, so -@value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as -an error. -@end quotation - -@cindex Modula-2 constants -@node M2 Constants -@subsubsection Constants - -@value{GDBN} allows you to express the constants of Modula-2 in the following -ways: - -@itemize @bullet - -@item -Integer constants are simply a sequence of digits. When used in an -expression, a constant is interpreted to be type-compatible with the -rest of the expression. Hexadecimal integers are specified by a -trailing @samp{H}, and octal integers by a trailing @samp{B}. - -@item -Floating point constants appear as a sequence of digits, followed by a -decimal point and another sequence of digits. An optional exponent can -then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where -@samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the -digits of the floating point constant must be valid decimal (base 10) -digits. - -@item -Character constants consist of a single character enclosed by a pair of -like quotes, either single (@code{'}) or double (@code{"}). They may -also be expressed by their ordinal value (their @sc{ascii} value, usually) -followed by a @samp{C}. - -@item -String constants consist of a sequence of characters enclosed by a -pair of like quotes, either single (@code{'}) or double (@code{"}). -Escape sequences in the style of C are also allowed. @xref{C -Constants, ,C and C@t{++} Constants}, for a brief explanation of escape -sequences. - -@item -Enumerated constants consist of an enumerated identifier. - -@item -Boolean constants consist of the identifiers @code{TRUE} and -@code{FALSE}. - -@item -Pointer constants consist of integral values only. - -@item -Set constants are not yet supported. -@end itemize - -@node M2 Types -@subsubsection Modula-2 Types -@cindex Modula-2 types - -Currently @value{GDBN} can print the following data types in Modula-2 -syntax: array types, record types, set types, pointer types, procedure -types, enumerated types, subrange types and base types. You can also -print the contents of variables declared using these type. -This section gives a number of simple source code examples together with -sample @value{GDBN} sessions. - -The first example contains the following section of code: - -@smallexample -VAR - s: SET OF CHAR ; - r: [20..40] ; -@end smallexample - -@noindent -and you can request @value{GDBN} to interrogate the type and value of -@code{r} and @code{s}. - -@smallexample -(@value{GDBP}) print s -@{'A'..'C', 'Z'@} -(@value{GDBP}) ptype s -SET OF CHAR -(@value{GDBP}) print r -21 -(@value{GDBP}) ptype r -[20..40] -@end smallexample - -@noindent -Likewise if your source code declares @code{s} as: - -@smallexample -VAR - s: SET ['A'..'Z'] ; -@end smallexample - -@noindent -then you may query the type of @code{s} by: - -@smallexample -(@value{GDBP}) ptype s -type = SET ['A'..'Z'] -@end smallexample - -@noindent -Note that at present you cannot interactively manipulate set -expressions using the debugger. - -The following example shows how you might declare an array in Modula-2 -and how you can interact with @value{GDBN} to print its type and contents: - -@smallexample -VAR - s: ARRAY [-10..10] OF CHAR ; -@end smallexample - -@smallexample -(@value{GDBP}) ptype s -ARRAY [-10..10] OF CHAR -@end smallexample - -Note that the array handling is not yet complete and although the type -is printed correctly, expression handling still assumes that all -arrays have a lower bound of zero and not @code{-10} as in the example -above. - -Here are some more type related Modula-2 examples: - -@smallexample -TYPE - colour = (blue, red, yellow, green) ; - t = [blue..yellow] ; -VAR - s: t ; -BEGIN - s := blue ; -@end smallexample - -@noindent -The @value{GDBN} interaction shows how you can query the data type -and value of a variable. - -@smallexample -(@value{GDBP}) print s -$1 = blue -(@value{GDBP}) ptype t -type = [blue..yellow] -@end smallexample - -@noindent -In this example a Modula-2 array is declared and its contents -displayed. Observe that the contents are written in the same way as -their @code{C} counterparts. - -@smallexample -VAR - s: ARRAY [1..5] OF CARDINAL ; -BEGIN - s[1] := 1 ; -@end smallexample - -@smallexample -(@value{GDBP}) print s -$1 = @{1, 0, 0, 0, 0@} -(@value{GDBP}) ptype s -type = ARRAY [1..5] OF CARDINAL -@end smallexample - -The Modula-2 language interface to @value{GDBN} also understands -pointer types as shown in this example: - -@smallexample -VAR - s: POINTER TO ARRAY [1..5] OF CARDINAL ; -BEGIN - NEW(s) ; - s^[1] := 1 ; -@end smallexample - -@noindent -and you can request that @value{GDBN} describes the type of @code{s}. - -@smallexample -(@value{GDBP}) ptype s -type = POINTER TO ARRAY [1..5] OF CARDINAL -@end smallexample - -@value{GDBN} handles compound types as we can see in this example. -Here we combine array types, record types, pointer types and subrange -types: - -@smallexample -TYPE - foo = RECORD - f1: CARDINAL ; - f2: CHAR ; - f3: myarray ; - END ; - - myarray = ARRAY myrange OF CARDINAL ; - myrange = [-2..2] ; -VAR - s: POINTER TO ARRAY myrange OF foo ; -@end smallexample - -@noindent -and you can ask @value{GDBN} to describe the type of @code{s} as shown -below. - -@smallexample -(@value{GDBP}) ptype s -type = POINTER TO ARRAY [-2..2] OF foo = RECORD - f1 : CARDINAL; - f2 : CHAR; - f3 : ARRAY [-2..2] OF CARDINAL; -END -@end smallexample - -@node M2 Defaults -@subsubsection Modula-2 Defaults -@cindex Modula-2 defaults - -If type and range checking are set automatically by @value{GDBN}, they -both default to @code{on} whenever the working language changes to -Modula-2. This happens regardless of whether you or @value{GDBN} -selected the working language. - -If you allow @value{GDBN} to set the language automatically, then entering -code compiled from a file whose name ends with @file{.mod} sets the -working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} -Infer the Source Language}, for further details. - -@node Deviations -@subsubsection Deviations from Standard Modula-2 -@cindex Modula-2, deviations from - -A few changes have been made to make Modula-2 programs easier to debug. -This is done primarily via loosening its type strictness: - -@itemize @bullet -@item -Unlike in standard Modula-2, pointer constants can be formed by -integers. This allows you to modify pointer variables during -debugging. (In standard Modula-2, the actual address contained in a -pointer variable is hidden from you; it can only be modified -through direct assignment to another pointer variable or expression that -returned a pointer.) - -@item -C escape sequences can be used in strings and characters to represent -non-printable characters. @value{GDBN} prints out strings with these -escape sequences embedded. Single non-printable characters are -printed using the @samp{CHR(@var{nnn})} format. - -@item -The assignment operator (@code{:=}) returns the value of its right-hand -argument. - -@item -All built-in procedures both modify @emph{and} return their argument. -@end itemize - -@node M2 Checks -@subsubsection Modula-2 Type and Range Checks -@cindex Modula-2 checks - -@quotation -@emph{Warning:} in this release, @value{GDBN} does not yet perform type or -range checking. -@end quotation -@c FIXME remove warning when type/range checks added - -@value{GDBN} considers two Modula-2 variables type equivalent if: - -@itemize @bullet -@item -They are of types that have been declared equivalent via a @code{TYPE -@var{t1} = @var{t2}} statement - -@item -They have been declared on the same line. (Note: This is true of the -@sc{gnu} Modula-2 compiler, but it may not be true of other compilers.) -@end itemize - -As long as type checking is enabled, any attempt to combine variables -whose types are not equivalent is an error. - -Range checking is done on all mathematical operations, assignment, array -index bounds, and all built-in functions and procedures. - -@node M2 Scope -@subsubsection The Scope Operators @code{::} and @code{.} -@cindex scope -@cindex @code{.}, Modula-2 scope operator -@cindex colon, doubled as scope operator -@ifinfo -@vindex colon-colon@r{, in Modula-2} -@c Info cannot handle :: but TeX can. -@end ifinfo -@ifnotinfo -@vindex ::@r{, in Modula-2} -@end ifnotinfo - -There are a few subtle differences between the Modula-2 scope operator -(@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have -similar syntax: - -@smallexample - -@var{module} . @var{id} -@var{scope} :: @var{id} -@end smallexample - -@noindent -where @var{scope} is the name of a module or a procedure, -@var{module} the name of a module, and @var{id} is any declared -identifier within your program, except another module. - -Using the @code{::} operator makes @value{GDBN} search the scope -specified by @var{scope} for the identifier @var{id}. If it is not -found in the specified scope, then @value{GDBN} searches all scopes -enclosing the one specified by @var{scope}. - -Using the @code{.} operator makes @value{GDBN} search the current scope for -the identifier specified by @var{id} that was imported from the -definition module specified by @var{module}. With this operator, it is -an error if the identifier @var{id} was not imported from definition -module @var{module}, or if @var{id} is not an identifier in -@var{module}. - -@node GDB/M2 -@subsubsection @value{GDBN} and Modula-2 - -Some @value{GDBN} commands have little use when debugging Modula-2 programs. -Five subcommands of @code{set print} and @code{show print} apply -specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle}, -@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four -apply to C@t{++}, and the last to the C @code{union} type, which has no direct -analogue in Modula-2. - -The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available -with any language, is not useful with Modula-2. Its -intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be -created in Modula-2 as they can in C or C@t{++}. However, because an -address can be specified by an integral constant, the construct -@samp{@{@var{type}@}@var{adrexp}} is still useful. - -@cindex @code{#} in Modula-2 -In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is -interpreted as the beginning of a comment. Use @code{<>} instead. - -@node Ada -@subsection Ada -@cindex Ada - -The extensions made to @value{GDBN} for Ada only support -output from the @sc{gnu} Ada (GNAT) compiler. -Other Ada compilers are not currently supported, and -attempting to debug executables produced by them is most likely -to be difficult. - - -@cindex expressions in Ada -@menu -* Ada Mode Intro:: General remarks on the Ada syntax - and semantics supported by Ada mode - in @value{GDBN}. -* Omissions from Ada:: Restrictions on the Ada expression syntax. -* Additions to Ada:: Extensions of the Ada expression syntax. -* Stopping Before Main Program:: Debugging the program during elaboration. -* Ada Tasks:: Listing and setting breakpoints in tasks. -* Ada Tasks and Core Files:: Tasking Support when Debugging Core Files -* Ravenscar Profile:: Tasking Support when using the Ravenscar - Profile -* Ada Glitches:: Known peculiarities of Ada mode. -@end menu - -@node Ada Mode Intro -@subsubsection Introduction -@cindex Ada mode, general - -The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression -syntax, with some extensions. -The philosophy behind the design of this subset is - -@itemize @bullet -@item -That @value{GDBN} should provide basic literals and access to operations for -arithmetic, dereferencing, field selection, indexing, and subprogram calls, -leaving more sophisticated computations to subprograms written into the -program (which therefore may be called from @value{GDBN}). - -@item -That type safety and strict adherence to Ada language restrictions -are not particularly important to the @value{GDBN} user. - -@item -That brevity is important to the @value{GDBN} user. -@end itemize - -Thus, for brevity, the debugger acts as if all names declared in -user-written packages are directly visible, even if they are not visible -according to Ada rules, thus making it unnecessary to fully qualify most -names with their packages, regardless of context. Where this causes -ambiguity, @value{GDBN} asks the user's intent. - -The debugger will start in Ada mode if it detects an Ada main program. -As for other languages, it will enter Ada mode when stopped in a program that -was translated from an Ada source file. - -While in Ada mode, you may use `@t{--}' for comments. This is useful -mostly for documenting command files. The standard @value{GDBN} comment -(@samp{#}) still works at the beginning of a line in Ada mode, but not in the -middle (to allow based literals). - -The debugger supports limited overloading. Given a subprogram call in which -the function symbol has multiple definitions, it will use the number of -actual parameters and some information about their types to attempt to narrow -the set of definitions. It also makes very limited use of context, preferring -procedures to functions in the context of the @code{call} command, and -functions to procedures elsewhere. - -@node Omissions from Ada -@subsubsection Omissions from Ada -@cindex Ada, omissions from - -Here are the notable omissions from the subset: - -@itemize @bullet -@item -Only a subset of the attributes are supported: - -@itemize @minus -@item -@t{'First}, @t{'Last}, and @t{'Length} - on array objects (not on types and subtypes). - -@item -@t{'Min} and @t{'Max}. - -@item -@t{'Pos} and @t{'Val}. - -@item -@t{'Tag}. - -@item -@t{'Range} on array objects (not subtypes), but only as the right -operand of the membership (@code{in}) operator. - -@item -@t{'Access}, @t{'Unchecked_Access}, and -@t{'Unrestricted_Access} (a GNAT extension). - -@item -@t{'Address}. -@end itemize - -@item -The names in -@code{Characters.Latin_1} are not available and -concatenation is not implemented. Thus, escape characters in strings are -not currently available. - -@item -Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise -equality of representations. They will generally work correctly -for strings and arrays whose elements have integer or enumeration types. -They may not work correctly for arrays whose element -types have user-defined equality, for arrays of real values -(in particular, IEEE-conformant floating point, because of negative -zeroes and NaNs), and for arrays whose elements contain unused bits with -indeterminate values. - -@item -The other component-by-component array operations (@code{and}, @code{or}, -@code{xor}, @code{not}, and relational tests other than equality) -are not implemented. - -@item -@cindex array aggregates (Ada) -@cindex record aggregates (Ada) -@cindex aggregates (Ada) -There is limited support for array and record aggregates. They are -permitted only on the right sides of assignments, as in these examples: - -@smallexample -(@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6) -(@value{GDBP}) set An_Array := (1, others => 0) -(@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6) -(@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9)) -(@value{GDBP}) set A_Record := (1, "Peter", True); -(@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True) -@end smallexample - -Changing a -discriminant's value by assigning an aggregate has an -undefined effect if that discriminant is used within the record. -However, you can first modify discriminants by directly assigning to -them (which normally would not be allowed in Ada), and then performing an -aggregate assignment. For example, given a variable @code{A_Rec} -declared to have a type such as: - -@smallexample -type Rec (Len : Small_Integer := 0) is record - Id : Integer; - Vals : IntArray (1 .. Len); -end record; -@end smallexample - -you can assign a value with a different size of @code{Vals} with two -assignments: - -@smallexample -(@value{GDBP}) set A_Rec.Len := 4 -(@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4)) -@end smallexample - -As this example also illustrates, @value{GDBN} is very loose about the usual -rules concerning aggregates. You may leave out some of the -components of an array or record aggregate (such as the @code{Len} -component in the assignment to @code{A_Rec} above); they will retain their -original values upon assignment. You may freely use dynamic values as -indices in component associations. You may even use overlapping or -redundant component associations, although which component values are -assigned in such cases is not defined. - -@item -Calls to dispatching subprograms are not implemented. - -@item -The overloading algorithm is much more limited (i.e., less selective) -than that of real Ada. It makes only limited use of the context in -which a subexpression appears to resolve its meaning, and it is much -looser in its rules for allowing type matches. As a result, some -function calls will be ambiguous, and the user will be asked to choose -the proper resolution. - -@item -The @code{new} operator is not implemented. - -@item -Entry calls are not implemented. - -@item -Aside from printing, arithmetic operations on the native VAX floating-point -formats are not supported. - -@item -It is not possible to slice a packed array. - -@item -The names @code{True} and @code{False}, when not part of a qualified name, -are interpreted as if implicitly prefixed by @code{Standard}, regardless of -context. -Should your program -redefine these names in a package or procedure (at best a dubious practice), -you will have to use fully qualified names to access their new definitions. -@end itemize - -@node Additions to Ada -@subsubsection Additions to Ada -@cindex Ada, deviations from - -As it does for other languages, @value{GDBN} makes certain generic -extensions to Ada (@pxref{Expressions}): - -@itemize @bullet -@item -If the expression @var{E} is a variable residing in memory (typically -a local variable or array element) and @var{N} is a positive integer, -then @code{@var{E}@@@var{N}} displays the values of @var{E} and the -@var{N}-1 adjacent variables following it in memory as an array. In -Ada, this operator is generally not necessary, since its prime use is -in displaying parts of an array, and slicing will usually do this in -Ada. However, there are occasional uses when debugging programs in -which certain debugging information has been optimized away. - -@item -@code{@var{B}::@var{var}} means ``the variable named @var{var} that -appears in function or file @var{B}.'' When @var{B} is a file name, -you must typically surround it in single quotes. - -@item -The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type -@var{type} that appears at address @var{addr}.'' - -@item -A name starting with @samp{$} is a convenience variable -(@pxref{Convenience Vars}) or a machine register (@pxref{Registers}). -@end itemize - -In addition, @value{GDBN} provides a few other shortcuts and outright -additions specific to Ada: - -@itemize @bullet -@item -The assignment statement is allowed as an expression, returning -its right-hand operand as its value. Thus, you may enter - -@smallexample -(@value{GDBP}) set x := y + 3 -(@value{GDBP}) print A(tmp := y + 1) -@end smallexample - -@item -The semicolon is allowed as an ``operator,'' returning as its value -the value of its right-hand operand. -This allows, for example, -complex conditional breaks: - -@smallexample -(@value{GDBP}) break f -(@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100) -@end smallexample - -@item -Rather than use catenation and symbolic character names to introduce special -characters into strings, one may instead use a special bracket notation, -which is also used to print strings. A sequence of characters of the form -@samp{["@var{XX}"]} within a string or character literal denotes the -(single) character whose numeric encoding is @var{XX} in hexadecimal. The -sequence of characters @samp{["""]} also denotes a single quotation mark -in strings. For example, -@smallexample - "One line.["0a"]Next line.["0a"]" -@end smallexample -@noindent -contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) -after each period. - -@item -The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and -@t{'Max} is optional (and is ignored in any case). For example, it is valid -to write - -@smallexample -(@value{GDBP}) print 'max(x, y) -@end smallexample - -@item -When printing arrays, @value{GDBN} uses positional notation when the -array has a lower bound of 1, and uses a modified named notation otherwise. -For example, a one-dimensional array of three integers with a lower bound -of 3 might print as - -@smallexample -(3 => 10, 17, 1) -@end smallexample - -@noindent -That is, in contrast to valid Ada, only the first component has a @code{=>} -clause. - -@item -You may abbreviate attributes in expressions with any unique, -multi-character subsequence of -their names (an exact match gets preference). -For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh} -in place of @t{a'length}. - -@item -@cindex quoting Ada internal identifiers -Since Ada is case-insensitive, the debugger normally maps identifiers you type -to lower case. The GNAT compiler uses upper-case characters for -some of its internal identifiers, which are normally of no interest to users. -For the rare occasions when you actually have to look at them, -enclose them in angle brackets to avoid the lower-case mapping. -For example, -@smallexample -(@value{GDBP}) print [0] -@end smallexample - -@item -Printing an object of class-wide type or dereferencing an -access-to-class-wide value will display all the components of the object's -specific type (as indicated by its run-time tag). Likewise, component -selection on such a value will operate on the specific type of the -object. - -@end itemize - -@node Stopping Before Main Program -@subsubsection Stopping at the Very Beginning - -@cindex breakpointing Ada elaboration code -It is sometimes necessary to debug the program during elaboration, and -before reaching the main procedure. -As defined in the Ada Reference -Manual, the elaboration code is invoked from a procedure called -@code{adainit}. To run your program up to the beginning of -elaboration, simply use the following two commands: -@code{tbreak adainit} and @code{run}. - -@node Ada Tasks -@subsubsection Extensions for Ada Tasks -@cindex Ada, tasking - -Support for Ada tasks is analogous to that for threads (@pxref{Threads}). -@value{GDBN} provides the following task-related commands: - -@table @code -@kindex info tasks -@item info tasks -This command shows a list of current Ada tasks, as in the following example: - - -@smallexample -@iftex -@leftskip=0.5cm -@end iftex -(@value{GDBP}) info tasks - ID TID P-ID Pri State Name - 1 8088000 0 15 Child Activation Wait main_task - 2 80a4000 1 15 Accept Statement b - 3 809a800 1 15 Child Activation Wait a -* 4 80ae800 3 15 Runnable c - -@end smallexample - -@noindent -In this listing, the asterisk before the last task indicates it to be the -task currently being inspected. - -@table @asis -@item ID -Represents @value{GDBN}'s internal task number. - -@item TID -The Ada task ID. - -@item P-ID -The parent's task ID (@value{GDBN}'s internal task number). - -@item Pri -The base priority of the task. - -@item State -Current state of the task. - -@table @code -@item Unactivated -The task has been created but has not been activated. It cannot be -executing. - -@item Runnable -The task is not blocked for any reason known to Ada. (It may be waiting -for a mutex, though.) It is conceptually "executing" in normal mode. - -@item Terminated -The task is terminated, in the sense of ARM 9.3 (5). Any dependents -that were waiting on terminate alternatives have been awakened and have -terminated themselves. - -@item Child Activation Wait -The task is waiting for created tasks to complete activation. - -@item Accept Statement -The task is waiting on an accept or selective wait statement. - -@item Waiting on entry call -The task is waiting on an entry call. - -@item Async Select Wait -The task is waiting to start the abortable part of an asynchronous -select statement. - -@item Delay Sleep -The task is waiting on a select statement with only a delay -alternative open. - -@item Child Termination Wait -The task is sleeping having completed a master within itself, and is -waiting for the tasks dependent on that master to become terminated or -waiting on a terminate Phase. - -@item Wait Child in Term Alt -The task is sleeping waiting for tasks on terminate alternatives to -finish terminating. - -@item Accepting RV with @var{taskno} -The task is accepting a rendez-vous with the task @var{taskno}. -@end table - -@item Name -Name of the task in the program. - -@end table - -@kindex info task @var{taskno} -@item info task @var{taskno} -This command shows detailled informations on the specified task, as in -the following example: -@smallexample -@iftex -@leftskip=0.5cm -@end iftex -(@value{GDBP}) info tasks - ID TID P-ID Pri State Name - 1 8077880 0 15 Child Activation Wait main_task -* 2 807c468 1 15 Runnable task_1 -(@value{GDBP}) info task 2 -Ada Task: 0x807c468 -Name: task_1 -Thread: 0x807f378 -Parent: 1 (main_task) -Base Priority: 15 -State: Runnable -@end smallexample - -@item task -@kindex task@r{ (Ada)} -@cindex current Ada task ID -This command prints the ID of the current task. - -@smallexample -@iftex -@leftskip=0.5cm -@end iftex -(@value{GDBP}) info tasks - ID TID P-ID Pri State Name - 1 8077870 0 15 Child Activation Wait main_task -* 2 807c458 1 15 Runnable t -(@value{GDBP}) task -[Current task is 2] -@end smallexample - -@item task @var{taskno} -@cindex Ada task switching -This command is like the @code{thread @var{threadno}} -command (@pxref{Threads}). It switches the context of debugging -from the current task to the given task. - -@smallexample -@iftex -@leftskip=0.5cm -@end iftex -(@value{GDBP}) info tasks - ID TID P-ID Pri State Name - 1 8077870 0 15 Child Activation Wait main_task -* 2 807c458 1 15 Runnable t -(@value{GDBP}) task 1 -[Switching to task 1] -#0 0x8067726 in pthread_cond_wait () -(@value{GDBP}) bt -#0 0x8067726 in pthread_cond_wait () -#1 0x8056714 in system.os_interface.pthread_cond_wait () -#2 0x805cb63 in system.task_primitives.operations.sleep () -#3 0x806153e in system.tasking.stages.activate_tasks () -#4 0x804aacc in un () at un.adb:5 -@end smallexample - -@item break @var{linespec} task @var{taskno} -@itemx break @var{linespec} task @var{taskno} if @dots{} -@cindex breakpoints and tasks, in Ada -@cindex task breakpoints, in Ada -@kindex break @dots{} task @var{taskno}@r{ (Ada)} -These commands are like the @code{break @dots{} thread @dots{}} -command (@pxref{Thread Stops}). -@var{linespec} specifies source lines, as described -in @ref{Specify Location}. - -Use the qualifier @samp{task @var{taskno}} with a breakpoint command -to specify that you only want @value{GDBN} to stop the program when a -particular Ada task reaches this breakpoint. @var{taskno} is one of the -numeric task identifiers assigned by @value{GDBN}, shown in the first -column of the @samp{info tasks} display. - -If you do not specify @samp{task @var{taskno}} when you set a -breakpoint, the breakpoint applies to @emph{all} tasks of your -program. - -You can use the @code{task} qualifier on conditional breakpoints as -well; in this case, place @samp{task @var{taskno}} before the -breakpoint condition (before the @code{if}). - -For example, - -@smallexample -@iftex -@leftskip=0.5cm -@end iftex -(@value{GDBP}) info tasks - ID TID P-ID Pri State Name - 1 140022020 0 15 Child Activation Wait main_task - 2 140045060 1 15 Accept/Select Wait t2 - 3 140044840 1 15 Runnable t1 -* 4 140056040 1 15 Runnable t3 -(@value{GDBP}) b 15 task 2 -Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15. -(@value{GDBP}) cont -Continuing. -task # 1 running -task # 2 running - -Breakpoint 5, test_task_debug () at test_task_debug.adb:15 -15 flush; -(@value{GDBP}) info tasks - ID TID P-ID Pri State Name - 1 140022020 0 15 Child Activation Wait main_task -* 2 140045060 1 15 Runnable t2 - 3 140044840 1 15 Runnable t1 - 4 140056040 1 15 Delay Sleep t3 -@end smallexample -@end table - -@node Ada Tasks and Core Files -@subsubsection Tasking Support when Debugging Core Files -@cindex Ada tasking and core file debugging - -When inspecting a core file, as opposed to debugging a live program, -tasking support may be limited or even unavailable, depending on -the platform being used. -For instance, on x86-linux, the list of tasks is available, but task -switching is not supported. On Tru64, however, task switching will work -as usual. - -On certain platforms, including Tru64, the debugger needs to perform some -memory writes in order to provide Ada tasking support. When inspecting -a core file, this means that the core file must be opened with read-write -privileges, using the command @samp{"set write on"} (@pxref{Patching}). -Under these circumstances, you should make a backup copy of the core -file before inspecting it with @value{GDBN}. - -@node Ravenscar Profile -@subsubsection Tasking Support when using the Ravenscar Profile -@cindex Ravenscar Profile - -The @dfn{Ravenscar Profile} is a subset of the Ada tasking features, -specifically designed for systems with safety-critical real-time -requirements. - -@table @code -@kindex set ravenscar task-switching on -@cindex task switching with program using Ravenscar Profile -@item set ravenscar task-switching on -Allows task switching when debugging a program that uses the Ravenscar -Profile. This is the default. - -@kindex set ravenscar task-switching off -@item set ravenscar task-switching off -Turn off task switching when debugging a program that uses the Ravenscar -Profile. This is mostly intended to disable the code that adds support -for the Ravenscar Profile, in case a bug in either @value{GDBN} or in -the Ravenscar runtime is preventing @value{GDBN} from working properly. -To be effective, this command should be run before the program is started. - -@kindex show ravenscar task-switching -@item show ravenscar task-switching -Show whether it is possible to switch from task to task in a program -using the Ravenscar Profile. - -@end table - -@node Ada Glitches -@subsubsection Known Peculiarities of Ada Mode -@cindex Ada, problems - -Besides the omissions listed previously (@pxref{Omissions from Ada}), -we know of several problems with and limitations of Ada mode in -@value{GDBN}, -some of which will be fixed with planned future releases of the debugger -and the GNU Ada compiler. - -@itemize @bullet -@item -Static constants that the compiler chooses not to materialize as objects in -storage are invisible to the debugger. - -@item -Named parameter associations in function argument lists are ignored (the -argument lists are treated as positional). - -@item -Many useful library packages are currently invisible to the debugger. - -@item -Fixed-point arithmetic, conversions, input, and output is carried out using -floating-point arithmetic, and may give results that only approximate those on -the host machine. - -@item -The GNAT compiler never generates the prefix @code{Standard} for any of -the standard symbols defined by the Ada language. @value{GDBN} knows about -this: it will strip the prefix from names when you use it, and will never -look for a name you have so qualified among local symbols, nor match against -symbols in other packages or subprograms. If you have -defined entities anywhere in your program other than parameters and -local variables whose simple names match names in @code{Standard}, -GNAT's lack of qualification here can cause confusion. When this happens, -you can usually resolve the confusion -by qualifying the problematic names with package -@code{Standard} explicitly. -@end itemize - -Older versions of the compiler sometimes generate erroneous debugging -information, resulting in the debugger incorrectly printing the value -of affected entities. In some cases, the debugger is able to work -around an issue automatically. In other cases, the debugger is able -to work around the issue, but the work-around has to be specifically -enabled. - -@kindex set ada trust-PAD-over-XVS -@kindex show ada trust-PAD-over-XVS -@table @code - -@item set ada trust-PAD-over-XVS on -Configure GDB to strictly follow the GNAT encoding when computing the -value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS} -types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for -a complete description of the encoding used by the GNAT compiler). -This is the default. - -@item set ada trust-PAD-over-XVS off -This is related to the encoding using by the GNAT compiler. If @value{GDBN} -sometimes prints the wrong value for certain entities, changing @code{ada -trust-PAD-over-XVS} to @code{off} activates a work-around which may fix -the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to -@code{off}, but this incurs a slight performance penalty, so it is -recommended to leave this setting to @code{on} unless necessary. - -@end table - -@node Unsupported Languages -@section Unsupported Languages - -@cindex unsupported languages -@cindex minimal language -In addition to the other fully-supported programming languages, -@value{GDBN} also provides a pseudo-language, called @code{minimal}. -It does not represent a real programming language, but provides a set -of capabilities close to what the C or assembly languages provide. -This should allow most simple operations to be performed while debugging -an application that uses a language currently not supported by @value{GDBN}. - -If the language is set to @code{auto}, @value{GDBN} will automatically -select this language if the current frame corresponds to an unsupported -language. - -@node Symbols -@chapter Examining the Symbol Table - -The commands described in this chapter allow you to inquire about the -symbols (names of variables, functions and types) defined in your -program. This information is inherent in the text of your program and -does not change as your program executes. @value{GDBN} finds it in your -program's symbol table, in the file indicated when you started @value{GDBN} -(@pxref{File Options, ,Choosing Files}), or by one of the -file-management commands (@pxref{Files, ,Commands to Specify Files}). - -@cindex symbol names -@cindex names of symbols -@cindex quoting names -Occasionally, you may need to refer to symbols that contain unusual -characters, which @value{GDBN} ordinarily treats as word delimiters. The -most frequent case is in referring to static variables in other -source files (@pxref{Variables,,Program Variables}). File names -are recorded in object files as debugging symbols, but @value{GDBN} would -ordinarily parse a typical file name, like @file{foo.c}, as the three words -@samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize -@samp{foo.c} as a single symbol, enclose it in single quotes; for example, - -@smallexample -p 'foo.c'::x -@end smallexample - -@noindent -looks up the value of @code{x} in the scope of the file @file{foo.c}. - -@table @code -@cindex case-insensitive symbol names -@cindex case sensitivity in symbol names -@kindex set case-sensitive -@item set case-sensitive on -@itemx set case-sensitive off -@itemx set case-sensitive auto -Normally, when @value{GDBN} looks up symbols, it matches their names -with case sensitivity determined by the current source language. -Occasionally, you may wish to control that. The command @code{set -case-sensitive} lets you do that by specifying @code{on} for -case-sensitive matches or @code{off} for case-insensitive ones. If -you specify @code{auto}, case sensitivity is reset to the default -suitable for the source language. The default is case-sensitive -matches for all languages except for Fortran, for which the default is -case-insensitive matches. - -@kindex show case-sensitive -@item show case-sensitive -This command shows the current setting of case sensitivity for symbols -lookups. - -@kindex set print type methods -@item set print type methods -@itemx set print type methods on -@itemx set print type methods off -Normally, when @value{GDBN} prints a class, it displays any methods -declared in that class. You can control this behavior either by -passing the appropriate flag to @code{ptype}, or using @command{set -print type methods}. Specifying @code{on} will cause @value{GDBN} to -display the methods; this is the default. Specifying @code{off} will -cause @value{GDBN} to omit the methods. - -@kindex show print type methods -@item show print type methods -This command shows the current setting of method display when printing -classes. - -@kindex set print type typedefs -@item set print type typedefs -@itemx set print type typedefs on -@itemx set print type typedefs off - -Normally, when @value{GDBN} prints a class, it displays any typedefs -defined in that class. You can control this behavior either by -passing the appropriate flag to @code{ptype}, or using @command{set -print type typedefs}. Specifying @code{on} will cause @value{GDBN} to -display the typedef definitions; this is the default. Specifying -@code{off} will cause @value{GDBN} to omit the typedef definitions. -Note that this controls whether the typedef definition itself is -printed, not whether typedef names are substituted when printing other -types. - -@kindex show print type typedefs -@item show print type typedefs -This command shows the current setting of typedef display when -printing classes. - -@kindex info address -@cindex address of a symbol -@item info address @var{symbol} -Describe where the data for @var{symbol} is stored. For a register -variable, this says which register it is kept in. For a non-register -local variable, this prints the stack-frame offset at which the variable -is always stored. - -Note the contrast with @samp{print &@var{symbol}}, which does not work -at all for a register variable, and for a stack local variable prints -the exact address of the current instantiation of the variable. - -@kindex info symbol -@cindex symbol from address -@cindex closest symbol and offset for an address -@item info symbol @var{addr} -Print the name of a symbol which is stored at the address @var{addr}. -If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the -nearest symbol and an offset from it: - -@smallexample -(@value{GDBP}) info symbol 0x54320 -_initialize_vx + 396 in section .text -@end smallexample - -@noindent -This is the opposite of the @code{info address} command. You can use -it to find out the name of a variable or a function given its address. - -For dynamically linked executables, the name of executable or shared -library containing the symbol is also printed: - -@smallexample -(@value{GDBP}) info symbol 0x400225 -_start + 5 in section .text of /tmp/a.out -(@value{GDBP}) info symbol 0x2aaaac2811cf -__read_nocancel + 6 in section .text of /usr/lib64/libc.so.6 -@end smallexample - -@kindex whatis -@item whatis[/@var{flags}] [@var{arg}] -Print the data type of @var{arg}, which can be either an expression -or a name of a data type. With no argument, print the data type of -@code{$}, the last value in the value history. - -If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it -is not actually evaluated, and any side-effecting operations (such as -assignments or function calls) inside it do not take place. - -If @var{arg} is a variable or an expression, @code{whatis} prints its -literal type as it is used in the source code. If the type was -defined using a @code{typedef}, @code{whatis} will @emph{not} print -the data type underlying the @code{typedef}. If the type of the -variable or the expression is a compound data type, such as -@code{struct} or @code{class}, @code{whatis} never prints their -fields or methods. It just prints the @code{struct}/@code{class} -name (a.k.a.@: its @dfn{tag}). If you want to see the members of -such a compound data type, use @code{ptype}. - -If @var{arg} is a type name that was defined using @code{typedef}, -@code{whatis} @dfn{unrolls} only one level of that @code{typedef}. -Unrolling means that @code{whatis} will show the underlying type used -in the @code{typedef} declaration of @var{arg}. However, if that -underlying type is also a @code{typedef}, @code{whatis} will not -unroll it. - -For C code, the type names may also have the form @samp{class -@var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union -@var{union-tag}} or @samp{enum @var{enum-tag}}. - -@var{flags} can be used to modify how the type is displayed. -Available flags are: - -@table @code -@item r -Display in ``raw'' form. Normally, @value{GDBN} substitutes template -parameters and typedefs defined in a class when printing the class' -members. The @code{/r} flag disables this. - -@item m -Do not print methods defined in the class. - -@item M -Print methods defined in the class. This is the default, but the flag -exists in case you change the default with @command{set print type methods}. - -@item t -Do not print typedefs defined in the class. Note that this controls -whether the typedef definition itself is printed, not whether typedef -names are substituted when printing other types. - -@item T -Print typedefs defined in the class. This is the default, but the flag -exists in case you change the default with @command{set print type typedefs}. -@end table - -@kindex ptype -@item ptype[/@var{flags}] [@var{arg}] -@code{ptype} accepts the same arguments as @code{whatis}, but prints a -detailed description of the type, instead of just the name of the type. -@xref{Expressions, ,Expressions}. - -Contrary to @code{whatis}, @code{ptype} always unrolls any -@code{typedef}s in its argument declaration, whether the argument is -a variable, expression, or a data type. This means that @code{ptype} -of a variable or an expression will not print literally its type as -present in the source code---use @code{whatis} for that. @code{typedef}s at -the pointer or reference targets are also unrolled. Only @code{typedef}s of -fields, methods and inner @code{class typedef}s of @code{struct}s, -@code{class}es and @code{union}s are not unrolled even with @code{ptype}. - -For example, for this variable declaration: - -@smallexample -typedef double real_t; -struct complex @{ real_t real; double imag; @}; -typedef struct complex complex_t; -complex_t var; -real_t *real_pointer_var; -@end smallexample - -@noindent -the two commands give this output: - -@smallexample -@group -(@value{GDBP}) whatis var -type = complex_t -(@value{GDBP}) ptype var -type = struct complex @{ - real_t real; - double imag; -@} -(@value{GDBP}) whatis complex_t -type = struct complex -(@value{GDBP}) whatis struct complex -type = struct complex -(@value{GDBP}) ptype struct complex -type = struct complex @{ - real_t real; - double imag; -@} -(@value{GDBP}) whatis real_pointer_var -type = real_t * -(@value{GDBP}) ptype real_pointer_var -type = double * -@end group -@end smallexample - -@noindent -As with @code{whatis}, using @code{ptype} without an argument refers to -the type of @code{$}, the last value in the value history. - -@cindex incomplete type -Sometimes, programs use opaque data types or incomplete specifications -of complex data structure. If the debug information included in the -program does not allow @value{GDBN} to display a full declaration of -the data type, it will say @samp{}. For example, -given these declarations: - -@smallexample - struct foo; - struct foo *fooptr; -@end smallexample - -@noindent -but no definition for @code{struct foo} itself, @value{GDBN} will say: - -@smallexample - (@value{GDBP}) ptype foo - $1 = -@end smallexample - -@noindent -``Incomplete type'' is C terminology for data types that are not -completely specified. - -@kindex info types -@item info types @var{regexp} -@itemx info types -Print a brief description of all types whose names match the regular -expression @var{regexp} (or all types in your program, if you supply -no argument). Each complete typename is matched as though it were a -complete line; thus, @samp{i type value} gives information on all -types in your program whose names include the string @code{value}, but -@samp{i type ^value$} gives information only on types whose complete -name is @code{value}. - -This command differs from @code{ptype} in two ways: first, like -@code{whatis}, it does not print a detailed description; second, it -lists all source files where a type is defined. - -@kindex info type-printers -@item info type-printers -Versions of @value{GDBN} that ship with Python scripting enabled may -have ``type printers'' available. When using @command{ptype} or -@command{whatis}, these printers are consulted when the name of a type -is needed. @xref{Type Printing API}, for more information on writing -type printers. - -@code{info type-printers} displays all the available type printers. - -@kindex enable type-printer -@kindex disable type-printer -@item enable type-printer @var{name}@dots{} -@item disable type-printer @var{name}@dots{} -These commands can be used to enable or disable type printers. - -@kindex info scope -@cindex local variables -@item info scope @var{location} -List all the variables local to a particular scope. This command -accepts a @var{location} argument---a function name, a source line, or -an address preceded by a @samp{*}, and prints all the variables local -to the scope defined by that location. (@xref{Specify Location}, for -details about supported forms of @var{location}.) For example: - -@smallexample -(@value{GDBP}) @b{info scope command_line_handler} -Scope for command_line_handler: -Symbol rl is an argument at stack/frame offset 8, length 4. -Symbol linebuffer is in static storage at address 0x150a18, length 4. -Symbol linelength is in static storage at address 0x150a1c, length 4. -Symbol p is a local variable in register $esi, length 4. -Symbol p1 is a local variable in register $ebx, length 4. -Symbol nline is a local variable in register $edx, length 4. -Symbol repeat is a local variable at frame offset -8, length 4. -@end smallexample - -@noindent -This command is especially useful for determining what data to collect -during a @dfn{trace experiment}, see @ref{Tracepoint Actions, -collect}. - -@kindex info source -@item info source -Show information about the current source file---that is, the source file for -the function containing the current point of execution: -@itemize @bullet -@item -the name of the source file, and the directory containing it, -@item -the directory it was compiled in, -@item -its length, in lines, -@item -which programming language it is written in, -@item -whether the executable includes debugging information for that file, and -if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and -@item -whether the debugging information includes information about -preprocessor macros. -@end itemize - - -@kindex info sources -@item info sources -Print the names of all source files in your program for which there is -debugging information, organized into two lists: files whose symbols -have already been read, and files whose symbols will be read when needed. - -@kindex info functions -@item info functions -Print the names and data types of all defined functions. - -@item info functions @var{regexp} -Print the names and data types of all defined functions -whose names contain a match for regular expression @var{regexp}. -Thus, @samp{info fun step} finds all functions whose names -include @code{step}; @samp{info fun ^step} finds those whose names -start with @code{step}. If a function name contains characters -that conflict with the regular expression language (e.g.@: -@samp{operator*()}), they may be quoted with a backslash. - -@kindex info variables -@item info variables -Print the names and data types of all variables that are defined -outside of functions (i.e.@: excluding local variables). - -@item info variables @var{regexp} -Print the names and data types of all variables (except for local -variables) whose names contain a match for regular expression -@var{regexp}. - -@kindex info classes -@cindex Objective-C, classes and selectors -@item info classes -@itemx info classes @var{regexp} -Display all Objective-C classes in your program, or -(with the @var{regexp} argument) all those matching a particular regular -expression. - -@kindex info selectors -@item info selectors -@itemx info selectors @var{regexp} -Display all Objective-C selectors in your program, or -(with the @var{regexp} argument) all those matching a particular regular -expression. - -@ignore -This was never implemented. -@kindex info methods -@item info methods -@itemx info methods @var{regexp} -The @code{info methods} command permits the user to examine all defined -methods within C@t{++} program, or (with the @var{regexp} argument) a -specific set of methods found in the various C@t{++} classes. Many -C@t{++} classes provide a large number of methods. Thus, the output -from the @code{ptype} command can be overwhelming and hard to use. The -@code{info-methods} command filters the methods, printing only those -which match the regular-expression @var{regexp}. -@end ignore - -@cindex opaque data types -@kindex set opaque-type-resolution -@item set opaque-type-resolution on -Tell @value{GDBN} to resolve opaque types. An opaque type is a type -declared as a pointer to a @code{struct}, @code{class}, or -@code{union}---for example, @code{struct MyType *}---that is used in one -source file although the full declaration of @code{struct MyType} is in -another source file. The default is on. - -A change in the setting of this subcommand will not take effect until -the next time symbols for a file are loaded. - -@item set opaque-type-resolution off -Tell @value{GDBN} not to resolve opaque types. In this case, the type -is printed as follows: -@smallexample -@{@} -@end smallexample - -@kindex show opaque-type-resolution -@item show opaque-type-resolution -Show whether opaque types are resolved or not. - -@kindex maint print symbols -@cindex symbol dump -@kindex maint print psymbols -@cindex partial symbol dump -@item maint print symbols @var{filename} -@itemx maint print psymbols @var{filename} -@itemx maint print msymbols @var{filename} -Write a dump of debugging symbol data into the file @var{filename}. -These commands are used to debug the @value{GDBN} symbol-reading code. Only -symbols with debugging data are included. If you use @samp{maint print -symbols}, @value{GDBN} includes all the symbols for which it has already -collected full details: that is, @var{filename} reflects symbols for -only those files whose symbols @value{GDBN} has read. You can use the -command @code{info sources} to find out which files these are. If you -use @samp{maint print psymbols} instead, the dump shows information about -symbols that @value{GDBN} only knows partially---that is, symbols defined in -files that @value{GDBN} has skimmed, but not yet read completely. Finally, -@samp{maint print msymbols} dumps just the minimal symbol information -required for each object file from which @value{GDBN} has read some symbols. -@xref{Files, ,Commands to Specify Files}, for a discussion of how -@value{GDBN} reads symbols (in the description of @code{symbol-file}). - -@kindex maint info symtabs -@kindex maint info psymtabs -@cindex listing @value{GDBN}'s internal symbol tables -@cindex symbol tables, listing @value{GDBN}'s internal -@cindex full symbol tables, listing @value{GDBN}'s internal -@cindex partial symbol tables, listing @value{GDBN}'s internal -@item maint info symtabs @r{[} @var{regexp} @r{]} -@itemx maint info psymtabs @r{[} @var{regexp} @r{]} - -List the @code{struct symtab} or @code{struct partial_symtab} -structures whose names match @var{regexp}. If @var{regexp} is not -given, list them all. The output includes expressions which you can -copy into a @value{GDBN} debugging this one to examine a particular -structure in more detail. For example: - -@smallexample -(@value{GDBP}) maint info psymtabs dwarf2read -@{ objfile /home/gnu/build/gdb/gdb - ((struct objfile *) 0x82e69d0) - @{ psymtab /home/gnu/src/gdb/dwarf2read.c - ((struct partial_symtab *) 0x8474b10) - readin no - fullname (null) - text addresses 0x814d3c8 -- 0x8158074 - globals (* (struct partial_symbol **) 0x8507a08 @@ 9) - statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882) - dependencies (none) - @} -@} -(@value{GDBP}) maint info symtabs -(@value{GDBP}) -@end smallexample -@noindent -We see that there is one partial symbol table whose filename contains -the string @samp{dwarf2read}, belonging to the @samp{gdb} executable; -and we see that @value{GDBN} has not read in any symtabs yet at all. -If we set a breakpoint on a function, that will cause @value{GDBN} to -read the symtab for the compilation unit containing that function: - -@smallexample -(@value{GDBP}) break dwarf2_psymtab_to_symtab -Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c, -line 1574. -(@value{GDBP}) maint info symtabs -@{ objfile /home/gnu/build/gdb/gdb - ((struct objfile *) 0x82e69d0) - @{ symtab /home/gnu/src/gdb/dwarf2read.c - ((struct symtab *) 0x86c1f38) - dirname (null) - fullname (null) - blockvector ((struct blockvector *) 0x86c1bd0) (primary) - linetable ((struct linetable *) 0x8370fa0) - debugformat DWARF 2 - @} -@} -(@value{GDBP}) -@end smallexample -@end table - - -@node Altering -@chapter Altering Execution - -Once you think you have found an error in your program, you might want to -find out for certain whether correcting the apparent error would lead to -correct results in the rest of the run. You can find the answer by -experiment, using the @value{GDBN} features for altering execution of the -program. - -For example, you can store new values into variables or memory -locations, give your program a signal, restart it at a different -address, or even return prematurely from a function. - -@menu -* Assignment:: Assignment to variables -* Jumping:: Continuing at a different address -* Signaling:: Giving your program a signal -* Returning:: Returning from a function -* Calling:: Calling your program's functions -* Patching:: Patching your program -@end menu - -@node Assignment -@section Assignment to Variables - -@cindex assignment -@cindex setting variables -To alter the value of a variable, evaluate an assignment expression. -@xref{Expressions, ,Expressions}. For example, - -@smallexample -print x=4 -@end smallexample - -@noindent -stores the value 4 into the variable @code{x}, and then prints the -value of the assignment expression (which is 4). -@xref{Languages, ,Using @value{GDBN} with Different Languages}, for more -information on operators in supported languages. - -@kindex set variable -@cindex variables, setting -If you are not interested in seeing the value of the assignment, use the -@code{set} command instead of the @code{print} command. @code{set} is -really the same as @code{print} except that the expression's value is -not printed and is not put in the value history (@pxref{Value History, -,Value History}). The expression is evaluated only for its effects. - -If the beginning of the argument string of the @code{set} command -appears identical to a @code{set} subcommand, use the @code{set -variable} command instead of just @code{set}. This command is identical -to @code{set} except for its lack of subcommands. For example, if your -program has a variable @code{width}, you get an error if you try to set -a new value with just @samp{set width=13}, because @value{GDBN} has the -command @code{set width}: - -@smallexample -(@value{GDBP}) whatis width -type = double -(@value{GDBP}) p width -$4 = 13 -(@value{GDBP}) set width=47 -Invalid syntax in expression. -@end smallexample - -@noindent -The invalid expression, of course, is @samp{=47}. In -order to actually set the program's variable @code{width}, use - -@smallexample -(@value{GDBP}) set var width=47 -@end smallexample - -Because the @code{set} command has many subcommands that can conflict -with the names of program variables, it is a good idea to use the -@code{set variable} command instead of just @code{set}. For example, if -your program has a variable @code{g}, you run into problems if you try -to set a new value with just @samp{set g=4}, because @value{GDBN} has -the command @code{set gnutarget}, abbreviated @code{set g}: - -@smallexample -@group -(@value{GDBP}) whatis g -type = double -(@value{GDBP}) p g -$1 = 1 -(@value{GDBP}) set g=4 -(@value{GDBP}) p g -$2 = 1 -(@value{GDBP}) r -The program being debugged has been started already. -Start it from the beginning? (y or n) y -Starting program: /home/smith/cc_progs/a.out -"/home/smith/cc_progs/a.out": can't open to read symbols: - Invalid bfd target. -(@value{GDBP}) show g -The current BFD target is "=4". -@end group -@end smallexample - -@noindent -The program variable @code{g} did not change, and you silently set the -@code{gnutarget} to an invalid value. In order to set the variable -@code{g}, use - -@smallexample -(@value{GDBP}) set var g=4 -@end smallexample - -@value{GDBN} allows more implicit conversions in assignments than C; you can -freely store an integer value into a pointer variable or vice versa, -and you can convert any structure to any other structure that is the -same length or shorter. -@comment FIXME: how do structs align/pad in these conversions? -@comment /doc@cygnus.com 18dec1990 - -To store values into arbitrary places in memory, use the @samp{@{@dots{}@}} -construct to generate a value of specified type at a specified address -(@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers -to memory location @code{0x83040} as an integer (which implies a certain size -and representation in memory), and - -@smallexample -set @{int@}0x83040 = 4 -@end smallexample - -@noindent -stores the value 4 into that memory location. - -@node Jumping -@section Continuing at a Different Address - -Ordinarily, when you continue your program, you do so at the place where -it stopped, with the @code{continue} command. You can instead continue at -an address of your own choosing, with the following commands: - -@table @code -@kindex jump -@kindex j @r{(@code{jump})} -@item jump @var{linespec} -@itemx j @var{linespec} -@itemx jump @var{location} -@itemx j @var{location} -Resume execution at line @var{linespec} or at address given by -@var{location}. Execution stops again immediately if there is a -breakpoint there. @xref{Specify Location}, for a description of the -different forms of @var{linespec} and @var{location}. It is common -practice to use the @code{tbreak} command in conjunction with -@code{jump}. @xref{Set Breaks, ,Setting Breakpoints}. - -The @code{jump} command does not change the current stack frame, or -the stack pointer, or the contents of any memory location or any -register other than the program counter. If line @var{linespec} is in -a different function from the one currently executing, the results may -be bizarre if the two functions expect different patterns of arguments or -of local variables. For this reason, the @code{jump} command requests -confirmation if the specified line is not in the function currently -executing. However, even bizarre results are predictable if you are -well acquainted with the machine-language code of your program. -@end table - -@c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt. -On many systems, you can get much the same effect as the @code{jump} -command by storing a new value into the register @code{$pc}. The -difference is that this does not start your program running; it only -changes the address of where it @emph{will} run when you continue. For -example, - -@smallexample -set $pc = 0x485 -@end smallexample - -@noindent -makes the next @code{continue} command or stepping command execute at -address @code{0x485}, rather than at the address where your program stopped. -@xref{Continuing and Stepping, ,Continuing and Stepping}. - -The most common occasion to use the @code{jump} command is to back -up---perhaps with more breakpoints set---over a portion of a program -that has already executed, in order to examine its execution in more -detail. - -@c @group -@node Signaling -@section Giving your Program a Signal -@cindex deliver a signal to a program - -@table @code -@kindex signal -@item signal @var{signal} -Resume execution where your program stopped, but immediately give it the -signal @var{signal}. @var{signal} can be the name or the number of a -signal. For example, on many systems @code{signal 2} and @code{signal -SIGINT} are both ways of sending an interrupt signal. - -Alternatively, if @var{signal} is zero, continue execution without -giving a signal. This is useful when your program stopped on account of -a signal and would ordinarily see the signal when resumed with the -@code{continue} command; @samp{signal 0} causes it to resume without a -signal. - -@code{signal} does not repeat when you press @key{RET} a second time -after executing the command. -@end table -@c @end group - -Invoking the @code{signal} command is not the same as invoking the -@code{kill} utility from the shell. Sending a signal with @code{kill} -causes @value{GDBN} to decide what to do with the signal depending on -the signal handling tables (@pxref{Signals}). The @code{signal} command -passes the signal directly to your program. - - -@node Returning -@section Returning from a Function - -@table @code -@cindex returning from a function -@kindex return -@item return -@itemx return @var{expression} -You can cancel execution of a function call with the @code{return} -command. If you give an -@var{expression} argument, its value is used as the function's return -value. -@end table - -When you use @code{return}, @value{GDBN} discards the selected stack frame -(and all frames within it). You can think of this as making the -discarded frame return prematurely. If you wish to specify a value to -be returned, give that value as the argument to @code{return}. - -This pops the selected stack frame (@pxref{Selection, ,Selecting a -Frame}), and any other frames inside of it, leaving its caller as the -innermost remaining frame. That frame becomes selected. The -specified value is stored in the registers used for returning values -of functions. - -The @code{return} command does not resume execution; it leaves the -program stopped in the state that would exist if the function had just -returned. In contrast, the @code{finish} command (@pxref{Continuing -and Stepping, ,Continuing and Stepping}) resumes execution until the -selected stack frame returns naturally. - -@value{GDBN} needs to know how the @var{expression} argument should be set for -the inferior. The concrete registers assignment depends on the OS ABI and the -type being returned by the selected stack frame. For example it is common for -OS ABI to return floating point values in FPU registers while integer values in -CPU registers. Still some ABIs return even floating point values in CPU -registers. Larger integer widths (such as @code{long long int}) also have -specific placement rules. @value{GDBN} already knows the OS ABI from its -current target so it needs to find out also the type being returned to make the -assignment into the right register(s). - -Normally, the selected stack frame has debug info. @value{GDBN} will always -use the debug info instead of the implicit type of @var{expression} when the -debug info is available. For example, if you type @kbd{return -1}, and the -function in the current stack frame is declared to return a @code{long long -int}, @value{GDBN} transparently converts the implicit @code{int} value of -1 -into a @code{long long int}: - -@smallexample -Breakpoint 1, func () at gdb.base/return-nodebug.c:29 -29 return 31; -(@value{GDBP}) return -1 -Make func return now? (y or n) y -#0 0x004004f6 in main () at gdb.base/return-nodebug.c:43 -43 printf ("result=%lld\n", func ()); -(@value{GDBP}) -@end smallexample - -However, if the selected stack frame does not have a debug info, e.g., if the -function was compiled without debug info, @value{GDBN} has to find out the type -to return from user. Specifying a different type by mistake may set the value -in different inferior registers than the caller code expects. For example, -typing @kbd{return -1} with its implicit type @code{int} would set only a part -of a @code{long long int} result for a debug info less function (on 32-bit -architectures). Therefore the user is required to specify the return type by -an appropriate cast explicitly: - -@smallexample -Breakpoint 2, 0x0040050b in func () -(@value{GDBP}) return -1 -Return value type not available for selected stack frame. -Please use an explicit cast of the value to return. -(@value{GDBP}) return (long long int) -1 -Make selected stack frame return now? (y or n) y -#0 0x00400526 in main () -(@value{GDBP}) -@end smallexample - -@node Calling -@section Calling Program Functions - -@table @code -@cindex calling functions -@cindex inferior functions, calling -@item print @var{expr} -Evaluate the expression @var{expr} and display the resulting value. -@var{expr} may include calls to functions in the program being -debugged. - -@kindex call -@item call @var{expr} -Evaluate the expression @var{expr} without displaying @code{void} -returned values. - -You can use this variant of the @code{print} command if you want to -execute a function from your program that does not return anything -(a.k.a.@: @dfn{a void function}), but without cluttering the output -with @code{void} returned values that @value{GDBN} will otherwise -print. If the result is not void, it is printed and saved in the -value history. -@end table - -It is possible for the function you call via the @code{print} or -@code{call} command to generate a signal (e.g., if there's a bug in -the function, or if you passed it incorrect arguments). What happens -in that case is controlled by the @code{set unwindonsignal} command. - -Similarly, with a C@t{++} program it is possible for the function you -call via the @code{print} or @code{call} command to generate an -exception that is not handled due to the constraints of the dummy -frame. In this case, any exception that is raised in the frame, but has -an out-of-frame exception handler will not be found. GDB builds a -dummy-frame for the inferior function call, and the unwinder cannot -seek for exception handlers outside of this dummy-frame. What happens -in that case is controlled by the -@code{set unwind-on-terminating-exception} command. - -@table @code -@item set unwindonsignal -@kindex set unwindonsignal -@cindex unwind stack in called functions -@cindex call dummy stack unwinding -Set unwinding of the stack if a signal is received while in a function -that @value{GDBN} called in the program being debugged. If set to on, -@value{GDBN} unwinds the stack it created for the call and restores -the context to what it was before the call. If set to off (the -default), @value{GDBN} stops in the frame where the signal was -received. - -@item show unwindonsignal -@kindex show unwindonsignal -Show the current setting of stack unwinding in the functions called by -@value{GDBN}. - -@item set unwind-on-terminating-exception -@kindex set unwind-on-terminating-exception -@cindex unwind stack in called functions with unhandled exceptions -@cindex call dummy stack unwinding on unhandled exception. -Set unwinding of the stack if a C@t{++} exception is raised, but left -unhandled while in a function that @value{GDBN} called in the program being -debugged. If set to on (the default), @value{GDBN} unwinds the stack -it created for the call and restores the context to what it was before -the call. If set to off, @value{GDBN} the exception is delivered to -the default C@t{++} exception handler and the inferior terminated. - -@item show unwind-on-terminating-exception -@kindex show unwind-on-terminating-exception -Show the current setting of stack unwinding in the functions called by -@value{GDBN}. - -@end table - -@cindex weak alias functions -Sometimes, a function you wish to call is actually a @dfn{weak alias} -for another function. In such case, @value{GDBN} might not pick up -the type information, including the types of the function arguments, -which causes @value{GDBN} to call the inferior function incorrectly. -As a result, the called function will function erroneously and may -even crash. A solution to that is to use the name of the aliased -function instead. - -@node Patching -@section Patching Programs - -@cindex patching binaries -@cindex writing into executables -@cindex writing into corefiles - -By default, @value{GDBN} opens the file containing your program's -executable code (or the corefile) read-only. This prevents accidental -alterations to machine code; but it also prevents you from intentionally -patching your program's binary. - -If you'd like to be able to patch the binary, you can specify that -explicitly with the @code{set write} command. For example, you might -want to turn on internal debugging flags, or even to make emergency -repairs. - -@table @code -@kindex set write -@item set write on -@itemx set write off -If you specify @samp{set write on}, @value{GDBN} opens executable and -core files for both reading and writing; if you specify @kbd{set write -off} (the default), @value{GDBN} opens them read-only. - -If you have already loaded a file, you must load it again (using the -@code{exec-file} or @code{core-file} command) after changing @code{set -write}, for your new setting to take effect. - -@item show write -@kindex show write -Display whether executable files and core files are opened for writing -as well as reading. -@end table - -@node GDB Files -@chapter @value{GDBN} Files - -@value{GDBN} needs to know the file name of the program to be debugged, -both in order to read its symbol table and in order to start your -program. To debug a core dump of a previous run, you must also tell -@value{GDBN} the name of the core dump file. - -@menu -* Files:: Commands to specify files -* Separate Debug Files:: Debugging information in separate files -* MiniDebugInfo:: Debugging information in a special section -* Index Files:: Index files speed up GDB -* Symbol Errors:: Errors reading symbol files -* Data Files:: GDB data files -@end menu - -@node Files -@section Commands to Specify Files - -@cindex symbol table -@cindex core dump file - -You may want to specify executable and core dump file names. The usual -way to do this is at start-up time, using the arguments to -@value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and -Out of @value{GDBN}}). - -Occasionally it is necessary to change to a different file during a -@value{GDBN} session. Or you may run @value{GDBN} and forget to -specify a file you want to use. Or you are debugging a remote target -via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver} -Program}). In these situations the @value{GDBN} commands to specify -new files are useful. - -@table @code -@cindex executable file -@kindex file -@item file @var{filename} -Use @var{filename} as the program to be debugged. It is read for its -symbols and for the contents of pure memory. It is also the program -executed when you use the @code{run} command. If you do not specify a -directory and the file is not found in the @value{GDBN} working directory, -@value{GDBN} uses the environment variable @code{PATH} as a list of -directories to search, just as the shell does when looking for a program -to run. You can change the value of this variable, for both @value{GDBN} -and your program, using the @code{path} command. - -@cindex unlinked object files -@cindex patching object files -You can load unlinked object @file{.o} files into @value{GDBN} using -the @code{file} command. You will not be able to ``run'' an object -file, but you can disassemble functions and inspect variables. Also, -if the underlying BFD functionality supports it, you could use -@kbd{gdb -write} to patch object files using this technique. Note -that @value{GDBN} can neither interpret nor modify relocations in this -case, so branches and some initialized variables will appear to go to -the wrong place. But this feature is still handy from time to time. - -@item file -@code{file} with no argument makes @value{GDBN} discard any information it -has on both executable file and the symbol table. - -@kindex exec-file -@item exec-file @r{[} @var{filename} @r{]} -Specify that the program to be run (but not the symbol table) is found -in @var{filename}. @value{GDBN} searches the environment variable @code{PATH} -if necessary to locate your program. Omitting @var{filename} means to -discard information on the executable file. - -@kindex symbol-file -@item symbol-file @r{[} @var{filename} @r{]} -Read symbol table information from file @var{filename}. @code{PATH} is -searched when necessary. Use the @code{file} command to get both symbol -table and program to run from the same file. - -@code{symbol-file} with no argument clears out @value{GDBN} information on your -program's symbol table. - -The @code{symbol-file} command causes @value{GDBN} to forget the contents of -some breakpoints and auto-display expressions. This is because they may -contain pointers to the internal data recording symbols and data types, -which are part of the old symbol table data being discarded inside -@value{GDBN}. - -@code{symbol-file} does not repeat if you press @key{RET} again after -executing it once. - -When @value{GDBN} is configured for a particular environment, it -understands debugging information in whatever format is the standard -generated for that environment; you may use either a @sc{gnu} compiler, or -other compilers that adhere to the local conventions. -Best results are usually obtained from @sc{gnu} compilers; for example, -using @code{@value{NGCC}} you can generate debugging information for -optimized code. - -For most kinds of object files, with the exception of old SVR3 systems -using COFF, the @code{symbol-file} command does not normally read the -symbol table in full right away. Instead, it scans the symbol table -quickly to find which source files and which symbols are present. The -details are read later, one source file at a time, as they are needed. - -The purpose of this two-stage reading strategy is to make @value{GDBN} -start up faster. For the most part, it is invisible except for -occasional pauses while the symbol table details for a particular source -file are being read. (The @code{set verbose} command can turn these -pauses into messages if desired. @xref{Messages/Warnings, ,Optional -Warnings and Messages}.) - -We have not implemented the two-stage strategy for COFF yet. When the -symbol table is stored in COFF format, @code{symbol-file} reads the -symbol table data in full right away. Note that ``stabs-in-COFF'' -still does the two-stage strategy, since the debug info is actually -in stabs format. - -@kindex readnow -@cindex reading symbols immediately -@cindex symbols, reading immediately -@item symbol-file @r{[} -readnow @r{]} @var{filename} -@itemx file @r{[} -readnow @r{]} @var{filename} -You can override the @value{GDBN} two-stage strategy for reading symbol -tables by using the @samp{-readnow} option with any of the commands that -load symbol table information, if you want to be sure @value{GDBN} has the -entire symbol table available. - -@c FIXME: for now no mention of directories, since this seems to be in -@c flux. 13mar1992 status is that in theory GDB would look either in -@c current dir or in same dir as myprog; but issues like competing -@c GDB's, or clutter in system dirs, mean that in practice right now -@c only current dir is used. FFish says maybe a special GDB hierarchy -@c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol -@c files. - -@kindex core-file -@item core-file @r{[}@var{filename}@r{]} -@itemx core -Specify the whereabouts of a core dump file to be used as the ``contents -of memory''. Traditionally, core files contain only some parts of the -address space of the process that generated them; @value{GDBN} can access the -executable file itself for other parts. - -@code{core-file} with no argument specifies that no core file is -to be used. - -Note that the core file is ignored when your program is actually running -under @value{GDBN}. So, if you have been running your program and you -wish to debug a core file instead, you must kill the subprocess in which -the program is running. To do this, use the @code{kill} command -(@pxref{Kill Process, ,Killing the Child Process}). - -@kindex add-symbol-file -@cindex dynamic linking -@item add-symbol-file @var{filename} @var{address} -@itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} -@itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{} -The @code{add-symbol-file} command reads additional symbol table -information from the file @var{filename}. You would use this command -when @var{filename} has been dynamically loaded (by some other means) -into the program that is running. @var{address} should be the memory -address at which the file has been loaded; @value{GDBN} cannot figure -this out for itself. You can additionally specify an arbitrary number -of @samp{-s @var{section} @var{address}} pairs, to give an explicit -section name and base address for that section. You can specify any -@var{address} as an expression. - -The symbol table of the file @var{filename} is added to the symbol table -originally read with the @code{symbol-file} command. You can use the -@code{add-symbol-file} command any number of times; the new symbol data -thus read keeps adding to the old. To discard all old symbol data -instead, use the @code{symbol-file} command without any arguments. - -@cindex relocatable object files, reading symbols from -@cindex object files, relocatable, reading symbols from -@cindex reading symbols from relocatable object files -@cindex symbols, reading from relocatable object files -@cindex @file{.o} files, reading symbols from -Although @var{filename} is typically a shared library file, an -executable file, or some other object file which has been fully -relocated for loading into a process, you can also load symbolic -information from relocatable @file{.o} files, as long as: - -@itemize @bullet -@item -the file's symbolic information refers only to linker symbols defined in -that file, not to symbols defined by other object files, -@item -every section the file's symbolic information refers to has actually -been loaded into the inferior, as it appears in the file, and -@item -you can determine the address at which every section was loaded, and -provide these to the @code{add-symbol-file} command. -@end itemize - -@noindent -Some embedded operating systems, like Sun Chorus and VxWorks, can load -relocatable files into an already running program; such systems -typically make the requirements above easy to meet. However, it's -important to recognize that many native systems use complex link -procedures (@code{.linkonce} section factoring and C@t{++} constructor table -assembly, for example) that make the requirements difficult to meet. In -general, one cannot assume that using @code{add-symbol-file} to read a -relocatable object file's symbolic information will have the same effect -as linking the relocatable object file into the program in the normal -way. - -@code{add-symbol-file} does not repeat if you press @key{RET} after using it. - -@kindex add-symbol-file-from-memory -@cindex @code{syscall DSO} -@cindex load symbols from memory -@item add-symbol-file-from-memory @var{address} -Load symbols from the given @var{address} in a dynamically loaded -object file whose image is mapped directly into the inferior's memory. -For example, the Linux kernel maps a @code{syscall DSO} into each -process's address space; this DSO provides kernel-specific code for -some system calls. The argument can be any expression whose -evaluation yields the address of the file's shared object file header. -For this command to work, you must have used @code{symbol-file} or -@code{exec-file} commands in advance. - -@kindex add-shared-symbol-files -@kindex assf -@item add-shared-symbol-files @var{library-file} -@itemx assf @var{library-file} -The @code{add-shared-symbol-files} command can currently be used only -in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an -alias for the @code{dll-symbols} command (@pxref{Cygwin Native}). -@value{GDBN} automatically looks for shared libraries, however if -@value{GDBN} does not find yours, you can invoke -@code{add-shared-symbol-files}. It takes one argument: the shared -library's file name. @code{assf} is a shorthand alias for -@code{add-shared-symbol-files}. - -@kindex section -@item section @var{section} @var{addr} -The @code{section} command changes the base address of the named -@var{section} of the exec file to @var{addr}. This can be used if the -exec file does not contain section addresses, (such as in the -@code{a.out} format), or when the addresses specified in the file -itself are wrong. Each section must be changed separately. The -@code{info files} command, described below, lists all the sections and -their addresses. - -@kindex info files -@kindex info target -@item info files -@itemx info target -@code{info files} and @code{info target} are synonymous; both print the -current target (@pxref{Targets, ,Specifying a Debugging Target}), -including the names of the executable and core dump files currently in -use by @value{GDBN}, and the files from which symbols were loaded. The -command @code{help target} lists all possible targets rather than -current ones. - -@kindex maint info sections -@item maint info sections -Another command that can give you extra information about program sections -is @code{maint info sections}. In addition to the section information -displayed by @code{info files}, this command displays the flags and file -offset of each section in the executable and core dump files. In addition, -@code{maint info sections} provides the following command options (which -may be arbitrarily combined): - -@table @code -@item ALLOBJ -Display sections for all loaded object files, including shared libraries. -@item @var{sections} -Display info only for named @var{sections}. -@item @var{section-flags} -Display info only for sections for which @var{section-flags} are true. -The section flags that @value{GDBN} currently knows about are: -@table @code -@item ALLOC -Section will have space allocated in the process when loaded. -Set for all sections except those containing debug information. -@item LOAD -Section will be loaded from the file into the child process memory. -Set for pre-initialized code and data, clear for @code{.bss} sections. -@item RELOC -Section needs to be relocated before loading. -@item READONLY -Section cannot be modified by the child process. -@item CODE -Section contains executable code only. -@item DATA -Section contains data only (no executable code). -@item ROM -Section will reside in ROM. -@item CONSTRUCTOR -Section contains data for constructor/destructor lists. -@item HAS_CONTENTS -Section is not empty. -@item NEVER_LOAD -An instruction to the linker to not output the section. -@item COFF_SHARED_LIBRARY -A notification to the linker that the section contains -COFF shared library information. -@item IS_COMMON -Section contains common symbols. -@end table -@end table -@kindex set trust-readonly-sections -@cindex read-only sections -@item set trust-readonly-sections on -Tell @value{GDBN} that readonly sections in your object file -really are read-only (i.e.@: that their contents will not change). -In that case, @value{GDBN} can fetch values from these sections -out of the object file, rather than from the target program. -For some targets (notably embedded ones), this can be a significant -enhancement to debugging performance. - -The default is off. - -@item set trust-readonly-sections off -Tell @value{GDBN} not to trust readonly sections. This means that -the contents of the section might change while the program is running, -and must therefore be fetched from the target when needed. - -@item show trust-readonly-sections -Show the current setting of trusting readonly sections. -@end table - -All file-specifying commands allow both absolute and relative file names -as arguments. @value{GDBN} always converts the file name to an absolute file -name and remembers it that way. - -@cindex shared libraries -@anchor{Shared Libraries} -@value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix, -and IBM RS/6000 AIX shared libraries. - -On MS-Windows @value{GDBN} must be linked with the Expat library to support -shared libraries. @xref{Expat}. - -@value{GDBN} automatically loads symbol definitions from shared libraries -when you use the @code{run} command, or when you examine a core file. -(Before you issue the @code{run} command, @value{GDBN} does not understand -references to a function in a shared library, however---unless you are -debugging a core file). - -On HP-UX, if the program loads a library explicitly, @value{GDBN} -automatically loads the symbols at the time of the @code{shl_load} call. - -@c FIXME: some @value{GDBN} release may permit some refs to undef -@c FIXME...symbols---eg in a break cmd---assuming they are from a shared -@c FIXME...lib; check this from time to time when updating manual - -There are times, however, when you may wish to not automatically load -symbol definitions from shared libraries, such as when they are -particularly large or there are many of them. - -To control the automatic loading of shared library symbols, use the -commands: - -@table @code -@kindex set auto-solib-add -@item set auto-solib-add @var{mode} -If @var{mode} is @code{on}, symbols from all shared object libraries -will be loaded automatically when the inferior begins execution, you -attach to an independently started inferior, or when the dynamic linker -informs @value{GDBN} that a new library has been loaded. If @var{mode} -is @code{off}, symbols must be loaded manually, using the -@code{sharedlibrary} command. The default value is @code{on}. - -@cindex memory used for symbol tables -If your program uses lots of shared libraries with debug info that -takes large amounts of memory, you can decrease the @value{GDBN} -memory footprint by preventing it from automatically loading the -symbols from shared libraries. To that end, type @kbd{set -auto-solib-add off} before running the inferior, then load each -library whose debug symbols you do need with @kbd{sharedlibrary -@var{regexp}}, where @var{regexp} is a regular expression that matches -the libraries whose symbols you want to be loaded. - -@kindex show auto-solib-add -@item show auto-solib-add -Display the current autoloading mode. -@end table - -@cindex load shared library -To explicitly load shared library symbols, use the @code{sharedlibrary} -command: - -@table @code -@kindex info sharedlibrary -@kindex info share -@item info share @var{regex} -@itemx info sharedlibrary @var{regex} -Print the names of the shared libraries which are currently loaded -that match @var{regex}. If @var{regex} is omitted then print -all shared libraries that are loaded. - -@kindex sharedlibrary -@kindex share -@item sharedlibrary @var{regex} -@itemx share @var{regex} -Load shared object library symbols for files matching a -Unix regular expression. -As with files loaded automatically, it only loads shared libraries -required by your program for a core file or after typing @code{run}. If -@var{regex} is omitted all shared libraries required by your program are -loaded. - -@item nosharedlibrary -@kindex nosharedlibrary -@cindex unload symbols from shared libraries -Unload all shared object library symbols. This discards all symbols -that have been loaded from all shared libraries. Symbols from shared -libraries that were loaded by explicit user requests are not -discarded. -@end table - -Sometimes you may wish that @value{GDBN} stops and gives you control -when any of shared library events happen. The best way to do this is -to use @code{catch load} and @code{catch unload} (@pxref{Set -Catchpoints}). - -@value{GDBN} also supports the the @code{set stop-on-solib-events} -command for this. This command exists for historical reasons. It is -less useful than setting a catchpoint, because it does not allow for -conditions or commands as a catchpoint does. - -@table @code -@item set stop-on-solib-events -@kindex set stop-on-solib-events -This command controls whether @value{GDBN} should give you control -when the dynamic linker notifies it about some shared library event. -The most common event of interest is loading or unloading of a new -shared library. - -@item show stop-on-solib-events -@kindex show stop-on-solib-events -Show whether @value{GDBN} stops and gives you control when shared -library events happen. -@end table - -Shared libraries are also supported in many cross or remote debugging -configurations. @value{GDBN} needs to have access to the target's libraries; -this can be accomplished either by providing copies of the libraries -on the host system, or by asking @value{GDBN} to automatically retrieve the -libraries from the target. If copies of the target libraries are -provided, they need to be the same as the target libraries, although the -copies on the target can be stripped as long as the copies on the host are -not. - -@cindex where to look for shared libraries -For remote debugging, you need to tell @value{GDBN} where the target -libraries are, so that it can load the correct copies---otherwise, it -may try to load the host's libraries. @value{GDBN} has two variables -to specify the search directories for target libraries. - -@table @code -@cindex prefix for shared library file names -@cindex system root, alternate -@kindex set solib-absolute-prefix -@kindex set sysroot -@item set sysroot @var{path} -Use @var{path} as the system root for the program being debugged. Any -absolute shared library paths will be prefixed with @var{path}; many -runtime loaders store the absolute paths to the shared library in the -target program's memory. If you use @code{set sysroot} to find shared -libraries, they need to be laid out in the same way that they are on -the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy -under @var{path}. - -If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will -retrieve the target libraries from the remote system. This is only -supported when using a remote target that supports the @code{remote get} -command (@pxref{File Transfer,,Sending files to a remote system}). -The part of @var{path} following the initial @file{remote:} -(if present) is used as system root prefix on the remote file system. -@footnote{If you want to specify a local system root using a directory -that happens to be named @file{remote:}, you need to use some equivalent -variant of the name like @file{./remote:}.} - -For targets with an MS-DOS based filesystem, such as MS-Windows and -SymbianOS, @value{GDBN} tries prefixing a few variants of the target -absolute file name with @var{path}. But first, on Unix hosts, -@value{GDBN} converts all backslash directory separators into forward -slashes, because the backslash is not a directory separator on Unix: - -@smallexample - c:\foo\bar.dll @result{} c:/foo/bar.dll -@end smallexample - -Then, @value{GDBN} attempts prefixing the target file name with -@var{path}, and looks for the resulting file name in the host file -system: - -@smallexample - c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll -@end smallexample - -If that does not find the shared library, @value{GDBN} tries removing -the @samp{:} character from the drive spec, both for convenience, and, -for the case of the host file system not supporting file names with -colons: - -@smallexample - c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll -@end smallexample - -This makes it possible to have a system root that mirrors a target -with more than one drive. E.g., you may want to setup your local -copies of the target system shared libraries like so (note @samp{c} vs -@samp{z}): - -@smallexample - @file{/path/to/sysroot/c/sys/bin/foo.dll} - @file{/path/to/sysroot/c/sys/bin/bar.dll} - @file{/path/to/sysroot/z/sys/bin/bar.dll} -@end smallexample - -@noindent -and point the system root at @file{/path/to/sysroot}, so that -@value{GDBN} can find the correct copies of both -@file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}. - -If that still does not find the shared library, @value{GDBN} tries -removing the whole drive spec from the target file name: - -@smallexample - c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll -@end smallexample - -This last lookup makes it possible to not care about the drive name, -if you don't want or need to. - -The @code{set solib-absolute-prefix} command is an alias for @code{set -sysroot}. - -@cindex default system root -@cindex @samp{--with-sysroot} -You can set the default system root by using the configure-time -@samp{--with-sysroot} option. If the system root is inside -@value{GDBN}'s configured binary prefix (set with @samp{--prefix} or -@samp{--exec-prefix}), then the default system root will be updated -automatically if the installed @value{GDBN} is moved to a new -location. - -@kindex show sysroot -@item show sysroot -Display the current shared library prefix. - -@kindex set solib-search-path -@item set solib-search-path @var{path} -If this variable is set, @var{path} is a colon-separated list of -directories to search for shared libraries. @samp{solib-search-path} -is used after @samp{sysroot} fails to locate the library, or if the -path to the library is relative instead of absolute. If you want to -use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set -@samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from -finding your host's libraries. @samp{sysroot} is preferred; setting -it to a nonexistent directory may interfere with automatic loading -of shared library symbols. - -@kindex show solib-search-path -@item show solib-search-path -Display the current shared library search path. - -@cindex DOS file-name semantics of file names. -@kindex set target-file-system-kind (unix|dos-based|auto) -@kindex show target-file-system-kind -@item set target-file-system-kind @var{kind} -Set assumed file system kind for target reported file names. - -Shared library file names as reported by the target system may not -make sense as is on the system @value{GDBN} is running on. For -example, when remote debugging a target that has MS-DOS based file -system semantics, from a Unix host, the target may be reporting to -@value{GDBN} a list of loaded shared libraries with file names such as -@file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of -drive letters, so the @samp{c:\} prefix is not normally understood as -indicating an absolute file name, and neither is the backslash -normally considered a directory separator character. In that case, -the native file system would interpret this whole absolute file name -as a relative file name with no directory components. This would make -it impossible to point @value{GDBN} at a copy of the remote target's -shared libraries on the host using @code{set sysroot}, and impractical -with @code{set solib-search-path}. Setting -@code{target-file-system-kind} to @code{dos-based} tells @value{GDBN} -to interpret such file names similarly to how the target would, and to -map them to file names valid on @value{GDBN}'s native file system -semantics. The value of @var{kind} can be @code{"auto"}, in addition -to one of the supported file system kinds. In that case, @value{GDBN} -tries to determine the appropriate file system variant based on the -current target's operating system (@pxref{ABI, ,Configuring the -Current ABI}). The supported file system settings are: - -@table @code -@item unix -Instruct @value{GDBN} to assume the target file system is of Unix -kind. Only file names starting the forward slash (@samp{/}) character -are considered absolute, and the directory separator character is also -the forward slash. - -@item dos-based -Instruct @value{GDBN} to assume the target file system is DOS based. -File names starting with either a forward slash, or a drive letter -followed by a colon (e.g., @samp{c:}), are considered absolute, and -both the slash (@samp{/}) and the backslash (@samp{\\}) characters are -considered directory separators. - -@item auto -Instruct @value{GDBN} to use the file system kind associated with the -target operating system (@pxref{ABI, ,Configuring the Current ABI}). -This is the default. -@end table -@end table - -@cindex file name canonicalization -@cindex base name differences -When processing file names provided by the user, @value{GDBN} -frequently needs to compare them to the file names recorded in the -program's debug info. Normally, @value{GDBN} compares just the -@dfn{base names} of the files as strings, which is reasonably fast -even for very large programs. (The base name of a file is the last -portion of its name, after stripping all the leading directories.) -This shortcut in comparison is based upon the assumption that files -cannot have more than one base name. This is usually true, but -references to files that use symlinks or similar filesystem -facilities violate that assumption. If your program records files -using such facilities, or if you provide file names to @value{GDBN} -using symlinks etc., you can set @code{basenames-may-differ} to -@code{true} to instruct @value{GDBN} to completely canonicalize each -pair of file names it needs to compare. This will make file-name -comparisons accurate, but at a price of a significant slowdown. - -@table @code -@item set basenames-may-differ -@kindex set basenames-may-differ -Set whether a source file may have multiple base names. - -@item show basenames-may-differ -@kindex show basenames-may-differ -Show whether a source file may have multiple base names. -@end table - -@node Separate Debug Files -@section Debugging Information in Separate Files -@cindex separate debugging information files -@cindex debugging information in separate files -@cindex @file{.debug} subdirectories -@cindex debugging information directory, global -@cindex global debugging information directories -@cindex build ID, and separate debugging files -@cindex @file{.build-id} directory - -@value{GDBN} allows you to put a program's debugging information in a -file separate from the executable itself, in a way that allows -@value{GDBN} to find and load the debugging information automatically. -Since debugging information can be very large---sometimes larger -than the executable code itself---some systems distribute debugging -information for their executables in separate files, which users can -install only when they need to debug a problem. - -@value{GDBN} supports two ways of specifying the separate debug info -file: - -@itemize @bullet -@item -The executable contains a @dfn{debug link} that specifies the name of -the separate debug info file. The separate debug file's name is -usually @file{@var{executable}.debug}, where @var{executable} is the -name of the corresponding executable file without leading directories -(e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the -debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC) -checksum for the debug file, which @value{GDBN} uses to validate that -the executable and the debug file came from the same build. - -@item -The executable contains a @dfn{build ID}, a unique bit string that is -also present in the corresponding debug info file. (This is supported -only on some operating systems, notably those which use the ELF format -for binary files and the @sc{gnu} Binutils.) For more details about -this feature, see the description of the @option{--build-id} -command-line option in @ref{Options, , Command Line Options, ld.info, -The GNU Linker}. The debug info file's name is not specified -explicitly by the build ID, but can be computed from the build ID, see -below. -@end itemize - -Depending on the way the debug info file is specified, @value{GDBN} -uses two different methods of looking for the debug file: - -@itemize @bullet -@item -For the ``debug link'' method, @value{GDBN} looks up the named file in -the directory of the executable file, then in a subdirectory of that -directory named @file{.debug}, and finally under each one of the global debug -directories, in a subdirectory whose name is identical to the leading -directories of the executable's absolute file name. - -@item -For the ``build ID'' method, @value{GDBN} looks in the -@file{.build-id} subdirectory of each one of the global debug directories for -a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the -first 2 hex characters of the build ID bit string, and @var{nnnnnnnn} -are the rest of the bit string. (Real build ID strings are 32 or more -hex characters, not 10.) -@end itemize - -So, for example, suppose you ask @value{GDBN} to debug -@file{/usr/bin/ls}, which has a debug link that specifies the -file @file{ls.debug}, and a build ID whose value in hex is -@code{abcdef1234}. If the list of the global debug directories includes -@file{/usr/lib/debug}, then @value{GDBN} will look for the following -debug information files, in the indicated order: - -@itemize @minus -@item -@file{/usr/lib/debug/.build-id/ab/cdef1234.debug} -@item -@file{/usr/bin/ls.debug} -@item -@file{/usr/bin/.debug/ls.debug} -@item -@file{/usr/lib/debug/usr/bin/ls.debug}. -@end itemize - -@anchor{debug-file-directory} -Global debugging info directories default to what is set by @value{GDBN} -configure option @option{--with-separate-debug-dir}. During @value{GDBN} run -you can also set the global debugging info directories, and view the list -@value{GDBN} is currently using. - -@table @code - -@kindex set debug-file-directory -@item set debug-file-directory @var{directories} -Set the directories which @value{GDBN} searches for separate debugging -information files to @var{directory}. Multiple path components can be set -concatenating them by a path separator. - -@kindex show debug-file-directory -@item show debug-file-directory -Show the directories @value{GDBN} searches for separate debugging -information files. - -@end table - -@cindex @code{.gnu_debuglink} sections -@cindex debug link sections -A debug link is a special section of the executable file named -@code{.gnu_debuglink}. The section must contain: - -@itemize -@item -A filename, with any leading directory components removed, followed by -a zero byte, -@item -zero to three bytes of padding, as needed to reach the next four-byte -boundary within the section, and -@item -a four-byte CRC checksum, stored in the same endianness used for the -executable file itself. The checksum is computed on the debugging -information file's full contents by the function given below, passing -zero as the @var{crc} argument. -@end itemize - -Any executable file format can carry a debug link, as long as it can -contain a section named @code{.gnu_debuglink} with the contents -described above. - -@cindex @code{.note.gnu.build-id} sections -@cindex build ID sections -The build ID is a special section in the executable file (and in other -ELF binary files that @value{GDBN} may consider). This section is -often named @code{.note.gnu.build-id}, but that name is not mandatory. -It contains unique identification for the built files---the ID remains -the same across multiple builds of the same build tree. The default -algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the -content for the build ID string. The same section with an identical -value is present in the original built binary with symbols, in its -stripped variant, and in the separate debugging information file. - -The debugging information file itself should be an ordinary -executable, containing a full set of linker symbols, sections, and -debugging information. The sections of the debugging information file -should have the same names, addresses, and sizes as the original file, -but they need not contain any data---much like a @code{.bss} section -in an ordinary executable. - -The @sc{gnu} binary utilities (Binutils) package includes the -@samp{objcopy} utility that can produce -the separated executable / debugging information file pairs using the -following commands: - -@smallexample -@kbd{objcopy --only-keep-debug foo foo.debug} -@kbd{strip -g foo} -@end smallexample - -@noindent -These commands remove the debugging -information from the executable file @file{foo} and place it in the file -@file{foo.debug}. You can use the first, second or both methods to link the -two files: - -@itemize @bullet -@item -The debug link method needs the following additional command to also leave -behind a debug link in @file{foo}: - -@smallexample -@kbd{objcopy --add-gnu-debuglink=foo.debug foo} -@end smallexample - -Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains -a version of the @code{strip} command such that the command @kbd{strip foo -f -foo.debug} has the same functionality as the two @code{objcopy} commands and -the @code{ln -s} command above, together. - -@item -Build ID gets embedded into the main executable using @code{ld --build-id} or -the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus -compatibility fixes for debug files separation are present in @sc{gnu} binary -utilities (Binutils) package since version 2.18. -@end itemize - -@noindent - -@cindex CRC algorithm definition -The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in -IEEE 802.3 using the polynomial: - -@c TexInfo requires naked braces for multi-digit exponents for Tex -@c output, but this causes HTML output to barf. HTML has to be set using -@c raw commands. So we end up having to specify this equation in 2 -@c different ways! -@ifhtml -@display -@html - x32 + x26 + x23 + x22 + x16 + x12 + x11 - + x10 + x8 + x7 + x5 + x4 + x2 + x + 1 -@end html -@end display -@end ifhtml -@ifnothtml -@display - @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}} - @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1} -@end display -@end ifnothtml - -The function is computed byte at a time, taking the least -significant bit of each byte first. The initial pattern -@code{0xffffffff} is used, to ensure leading zeros affect the CRC and -the final result is inverted to ensure trailing zeros also affect the -CRC. - -@emph{Note:} This is the same CRC polynomial as used in handling the -@dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol, -, @value{GDBN} Remote Serial Protocol}). However in the -case of the Remote Serial Protocol, the CRC is computed @emph{most} -significant bit first, and the result is not inverted, so trailing -zeros have no effect on the CRC value. - -To complete the description, we show below the code of the function -which produces the CRC used in @code{.gnu_debuglink}. Inverting the -initially supplied @code{crc} argument means that an initial call to -this function passing in zero will start computing the CRC using -@code{0xffffffff}. - -@kindex gnu_debuglink_crc32 -@smallexample -unsigned long -gnu_debuglink_crc32 (unsigned long crc, - unsigned char *buf, size_t len) -@{ - static const unsigned long crc32_table[256] = - @{ - 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, - 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, - 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, - 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, - 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, - 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, - 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, - 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, - 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, - 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a, - 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, - 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, - 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, - 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, - 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e, - 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, - 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, - 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, - 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, - 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, - 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, - 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, - 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010, - 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, - 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, - 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, - 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, - 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, - 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344, - 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, - 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, - 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, - 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, - 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c, - 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, - 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, - 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, - 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, - 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, - 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, - 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, - 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242, - 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, - 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, - 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278, - 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, - 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, - 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, - 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, - 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, - 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, - 0x2d02ef8d - @}; - unsigned char *end; - - crc = ~crc & 0xffffffff; - for (end = buf + len; buf < end; ++buf) - crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8); - return ~crc & 0xffffffff; -@} -@end smallexample - -@noindent -This computation does not apply to the ``build ID'' method. - -@node MiniDebugInfo -@section Debugging information in a special section -@cindex separate debug sections -@cindex @samp{.gnu_debugdata} section - -Some systems ship pre-built executables and libraries that have a -special @samp{.gnu_debugdata} section. This feature is called -@dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and -is used to supply extra symbols for backtraces. - -The intent of this section is to provide extra minimal debugging -information for use in simple backtraces. It is not intended to be a -replacement for full separate debugging information (@pxref{Separate -Debug Files}). The example below shows the intended use; however, -@value{GDBN} does not currently put restrictions on what sort of -debugging information might be included in the section. - -@value{GDBN} has support for this extension. If the section exists, -then it is used provided that no other source of debugging information -can be found, and that @value{GDBN} was configured with LZMA support. - -This section can be easily created using @command{objcopy} and other -standard utilities: - -@smallexample -# Extract the dynamic symbols from the main binary, there is no need -# to also have these in the normal symbol table -nm -D @var{binary} --format=posix --defined-only \ - | awk '@{ print $1 @}' | sort > dynsyms - -# Extract all the text (i.e. function) symbols from the debuginfo . -nm @var{binary} --format=posix --defined-only \ - | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \ - | sort > funcsyms - -# Keep all the function symbols not already in the dynamic symbol -# table. -comm -13 dynsyms funcsyms > keep_symbols - -# Copy the full debuginfo, keeping only a minimal set of symbols and -# removing some unnecessary sections. -objcopy -S --remove-section .gdb_index --remove-section .comment \ - --keep-symbols=keep_symbols @var{binary} mini_debuginfo - -# Inject the compressed data into the .gnu_debugdata section of the -# original binary. -xz mini_debuginfo -objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary} -@end smallexample - -@node Index Files -@section Index Files Speed Up @value{GDBN} -@cindex index files -@cindex @samp{.gdb_index} section - -When @value{GDBN} finds a symbol file, it scans the symbols in the -file in order to construct an internal symbol table. This lets most -@value{GDBN} operations work quickly---at the cost of a delay early -on. For large programs, this delay can be quite lengthy, so -@value{GDBN} provides a way to build an index, which speeds up -startup. - -The index is stored as a section in the symbol file. @value{GDBN} can -write the index to a file, then you can put it into the symbol file -using @command{objcopy}. - -To create an index file, use the @code{save gdb-index} command: - -@table @code -@item save gdb-index @var{directory} -@kindex save gdb-index -Create an index file for each symbol file currently known by -@value{GDBN}. Each file is named after its corresponding symbol file, -with @samp{.gdb-index} appended, and is written into the given -@var{directory}. -@end table - -Once you have created an index file you can merge it into your symbol -file, here named @file{symfile}, using @command{objcopy}: - -@smallexample -$ objcopy --add-section .gdb_index=symfile.gdb-index \ - --set-section-flags .gdb_index=readonly symfile symfile -@end smallexample - -@value{GDBN} will normally ignore older versions of @file{.gdb_index} -sections that have been deprecated. Usually they are deprecated because -they are missing a new feature or have performance issues. -To tell @value{GDBN} to use a deprecated index section anyway -specify @code{set use-deprecated-index-sections on}. -The default is @code{off}. -This can speed up startup, but may result in some functionality being lost. -@xref{Index Section Format}. - -@emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on} -must be done before gdb reads the file. The following will not work: - -@smallexample -$ gdb -ex "set use-deprecated-index-sections on" -@end smallexample - -Instead you must do, for example, - -@smallexample -$ gdb -iex "set use-deprecated-index-sections on" -@end smallexample - -There are currently some limitation on indices. They only work when -for DWARF debugging information, not stabs. And, they do not -currently work for programs using Ada. - -@node Symbol Errors -@section Errors Reading Symbol Files - -While reading a symbol file, @value{GDBN} occasionally encounters problems, -such as symbol types it does not recognize, or known bugs in compiler -output. By default, @value{GDBN} does not notify you of such problems, since -they are relatively common and primarily of interest to people -debugging compilers. If you are interested in seeing information -about ill-constructed symbol tables, you can either ask @value{GDBN} to print -only one message about each such type of problem, no matter how many -times the problem occurs; or you can ask @value{GDBN} to print more messages, -to see how many times the problems occur, with the @code{set -complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and -Messages}). - -The messages currently printed, and their meanings, include: - -@table @code -@item inner block not inside outer block in @var{symbol} - -The symbol information shows where symbol scopes begin and end -(such as at the start of a function or a block of statements). This -error indicates that an inner scope block is not fully contained -in its outer scope blocks. - -@value{GDBN} circumvents the problem by treating the inner block as if it had -the same scope as the outer block. In the error message, @var{symbol} -may be shown as ``@code{(don't know)}'' if the outer block is not a -function. - -@item block at @var{address} out of order - -The symbol information for symbol scope blocks should occur in -order of increasing addresses. This error indicates that it does not -do so. - -@value{GDBN} does not circumvent this problem, and has trouble -locating symbols in the source file whose symbols it is reading. (You -can often determine what source file is affected by specifying -@code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and -Messages}.) - -@item bad block start address patched - -The symbol information for a symbol scope block has a start address -smaller than the address of the preceding source line. This is known -to occur in the SunOS 4.1.1 (and earlier) C compiler. - -@value{GDBN} circumvents the problem by treating the symbol scope block as -starting on the previous source line. - -@item bad string table offset in symbol @var{n} - -@cindex foo -Symbol number @var{n} contains a pointer into the string table which is -larger than the size of the string table. - -@value{GDBN} circumvents the problem by considering the symbol to have the -name @code{foo}, which may cause other problems if many symbols end up -with this name. - -@item unknown symbol type @code{0x@var{nn}} - -The symbol information contains new data types that @value{GDBN} does -not yet know how to read. @code{0x@var{nn}} is the symbol type of the -uncomprehended information, in hexadecimal. - -@value{GDBN} circumvents the error by ignoring this symbol information. -This usually allows you to debug your program, though certain symbols -are not accessible. If you encounter such a problem and feel like -debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint -on @code{complain}, then go up to the function @code{read_dbx_symtab} -and examine @code{*bufp} to see the symbol. - -@item stub type has NULL name - -@value{GDBN} could not find the full definition for a struct or class. - -@item const/volatile indicator missing (ok if using g++ v1.x), got@dots{} -The symbol information for a C@t{++} member function is missing some -information that recent versions of the compiler should have output for -it. - -@item info mismatch between compiler and debugger - -@value{GDBN} could not parse a type specification output by the compiler. - -@end table - -@node Data Files -@section GDB Data Files - -@cindex prefix for data files -@value{GDBN} will sometimes read an auxiliary data file. These files -are kept in a directory known as the @dfn{data directory}. - -You can set the data directory's name, and view the name @value{GDBN} -is currently using. - -@table @code -@kindex set data-directory -@item set data-directory @var{directory} -Set the directory which @value{GDBN} searches for auxiliary data files -to @var{directory}. - -@kindex show data-directory -@item show data-directory -Show the directory @value{GDBN} searches for auxiliary data files. -@end table - -@cindex default data directory -@cindex @samp{--with-gdb-datadir} -You can set the default data directory by using the configure-time -@samp{--with-gdb-datadir} option. If the data directory is inside -@value{GDBN}'s configured binary prefix (set with @samp{--prefix} or -@samp{--exec-prefix}), then the default data directory will be updated -automatically if the installed @value{GDBN} is moved to a new -location. - -The data directory may also be specified with the -@code{--data-directory} command line option. -@xref{Mode Options}. - -@node Targets -@chapter Specifying a Debugging Target - -@cindex debugging target -A @dfn{target} is the execution environment occupied by your program. - -Often, @value{GDBN} runs in the same host environment as your program; -in that case, the debugging target is specified as a side effect when -you use the @code{file} or @code{core} commands. When you need more -flexibility---for example, running @value{GDBN} on a physically separate -host, or controlling a standalone system over a serial port or a -realtime system over a TCP/IP connection---you can use the @code{target} -command to specify one of the target types configured for @value{GDBN} -(@pxref{Target Commands, ,Commands for Managing Targets}). - -@cindex target architecture -It is possible to build @value{GDBN} for several different @dfn{target -architectures}. When @value{GDBN} is built like that, you can choose -one of the available architectures with the @kbd{set architecture} -command. - -@table @code -@kindex set architecture -@kindex show architecture -@item set architecture @var{arch} -This command sets the current target architecture to @var{arch}. The -value of @var{arch} can be @code{"auto"}, in addition to one of the -supported architectures. - -@item show architecture -Show the current target architecture. - -@item set processor -@itemx processor -@kindex set processor -@kindex show processor -These are alias commands for, respectively, @code{set architecture} -and @code{show architecture}. -@end table - -@menu -* Active Targets:: Active targets -* Target Commands:: Commands for managing targets -* Byte Order:: Choosing target byte order -@end menu - -@node Active Targets -@section Active Targets - -@cindex stacking targets -@cindex active targets -@cindex multiple targets - -There are multiple classes of targets such as: processes, executable files or -recording sessions. Core files belong to the process class, making core file -and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently -on multiple active targets, one in each class. This allows you to (for -example) start a process and inspect its activity, while still having access to -the executable file after the process finishes. Or if you start process -recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are -presented a virtual layer of the recording target, while the process target -remains stopped at the chronologically last point of the process execution. - -Use the @code{core-file} and @code{exec-file} commands to select a new core -file or executable target (@pxref{Files, ,Commands to Specify Files}). To -specify as a target a process that is already running, use the @code{attach} -command (@pxref{Attach, ,Debugging an Already-running Process}). - -@node Target Commands -@section Commands for Managing Targets - -@table @code -@item target @var{type} @var{parameters} -Connects the @value{GDBN} host environment to a target machine or -process. A target is typically a protocol for talking to debugging -facilities. You use the argument @var{type} to specify the type or -protocol of the target machine. - -Further @var{parameters} are interpreted by the target protocol, but -typically include things like device names or host names to connect -with, process numbers, and baud rates. - -The @code{target} command does not repeat if you press @key{RET} again -after executing the command. - -@kindex help target -@item help target -Displays the names of all targets available. To display targets -currently selected, use either @code{info target} or @code{info files} -(@pxref{Files, ,Commands to Specify Files}). - -@item help target @var{name} -Describe a particular target, including any parameters necessary to -select it. - -@kindex set gnutarget -@item set gnutarget @var{args} -@value{GDBN} uses its own library BFD to read your files. @value{GDBN} -knows whether it is reading an @dfn{executable}, -a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format -with the @code{set gnutarget} command. Unlike most @code{target} commands, -with @code{gnutarget} the @code{target} refers to a program, not a machine. - -@quotation -@emph{Warning:} To specify a file format with @code{set gnutarget}, -you must know the actual BFD name. -@end quotation - -@noindent -@xref{Files, , Commands to Specify Files}. - -@kindex show gnutarget -@item show gnutarget -Use the @code{show gnutarget} command to display what file format -@code{gnutarget} is set to read. If you have not set @code{gnutarget}, -@value{GDBN} will determine the file format for each file automatically, -and @code{show gnutarget} displays @samp{The current BFD target is "auto"}. -@end table - -@cindex common targets -Here are some common targets (available, or not, depending on the GDB -configuration): - -@table @code -@kindex target -@item target exec @var{program} -@cindex executable file target -An executable file. @samp{target exec @var{program}} is the same as -@samp{exec-file @var{program}}. - -@item target core @var{filename} -@cindex core dump file target -A core dump file. @samp{target core @var{filename}} is the same as -@samp{core-file @var{filename}}. - -@item target remote @var{medium} -@cindex remote target -A remote system connected to @value{GDBN} via a serial line or network -connection. This command tells @value{GDBN} to use its own remote -protocol over @var{medium} for debugging. @xref{Remote Debugging}. - -For example, if you have a board connected to @file{/dev/ttya} on the -machine running @value{GDBN}, you could say: - -@smallexample -target remote /dev/ttya -@end smallexample - -@code{target remote} supports the @code{load} command. This is only -useful if you have some other way of getting the stub to the target -system, and you can put it somewhere in memory where it won't get -clobbered by the download. - -@item target sim @r{[}@var{simargs}@r{]} @dots{} -@cindex built-in simulator target -Builtin CPU simulator. @value{GDBN} includes simulators for most architectures. -In general, -@smallexample - target sim - load - run -@end smallexample -@noindent -works; however, you cannot assume that a specific memory map, device -drivers, or even basic I/O is available, although some simulators do -provide these. For info about any processor-specific simulator details, -see the appropriate section in @ref{Embedded Processors, ,Embedded -Processors}. - -@end table - -Some configurations may include these targets as well: - -@table @code - -@item target nrom @var{dev} -@cindex NetROM ROM emulator target -NetROM ROM emulator. This target only supports downloading. - -@end table - -Different targets are available on different configurations of @value{GDBN}; -your configuration may have more or fewer targets. - -Many remote targets require you to download the executable's code once -you've successfully established a connection. You may wish to control -various aspects of this process. - -@table @code - -@item set hash -@kindex set hash@r{, for remote monitors} -@cindex hash mark while downloading -This command controls whether a hash mark @samp{#} is displayed while -downloading a file to the remote monitor. If on, a hash mark is -displayed after each S-record is successfully downloaded to the -monitor. - -@item show hash -@kindex show hash@r{, for remote monitors} -Show the current status of displaying the hash mark. - -@item set debug monitor -@kindex set debug monitor -@cindex display remote monitor communications -Enable or disable display of communications messages between -@value{GDBN} and the remote monitor. - -@item show debug monitor -@kindex show debug monitor -Show the current status of displaying communications between -@value{GDBN} and the remote monitor. -@end table - -@table @code - -@kindex load @var{filename} -@item load @var{filename} -@anchor{load} -Depending on what remote debugging facilities are configured into -@value{GDBN}, the @code{load} command may be available. Where it exists, it -is meant to make @var{filename} (an executable) available for debugging -on the remote system---by downloading, or dynamic linking, for example. -@code{load} also records the @var{filename} symbol table in @value{GDBN}, like -the @code{add-symbol-file} command. - -If your @value{GDBN} does not have a @code{load} command, attempting to -execute it gets the error message ``@code{You can't do that when your -target is @dots{}}'' - -The file is loaded at whatever address is specified in the executable. -For some object file formats, you can specify the load address when you -link the program; for other formats, like a.out, the object file format -specifies a fixed address. -@c FIXME! This would be a good place for an xref to the GNU linker doc. - -Depending on the remote side capabilities, @value{GDBN} may be able to -load programs into flash memory. - -@code{load} does not repeat if you press @key{RET} again after using it. -@end table - -@node Byte Order -@section Choosing Target Byte Order - -@cindex choosing target byte order -@cindex target byte order - -Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH, -offer the ability to run either big-endian or little-endian byte -orders. Usually the executable or symbol will include a bit to -designate the endian-ness, and you will not need to worry about -which to use. However, you may still find it useful to adjust -@value{GDBN}'s idea of processor endian-ness manually. - -@table @code -@kindex set endian -@item set endian big -Instruct @value{GDBN} to assume the target is big-endian. - -@item set endian little -Instruct @value{GDBN} to assume the target is little-endian. - -@item set endian auto -Instruct @value{GDBN} to use the byte order associated with the -executable. - -@item show endian -Display @value{GDBN}'s current idea of the target byte order. - -@end table - -Note that these commands merely adjust interpretation of symbolic -data on the host, and that they have absolutely no effect on the -target system. - - -@node Remote Debugging -@chapter Debugging Remote Programs -@cindex remote debugging - -If you are trying to debug a program running on a machine that cannot run -@value{GDBN} in the usual way, it is often useful to use remote debugging. -For example, you might use remote debugging on an operating system kernel, -or on a small system which does not have a general purpose operating system -powerful enough to run a full-featured debugger. - -Some configurations of @value{GDBN} have special serial or TCP/IP interfaces -to make this work with particular debugging targets. In addition, -@value{GDBN} comes with a generic serial protocol (specific to @value{GDBN}, -but not specific to any particular target system) which you can use if you -write the remote stubs---the code that runs on the remote system to -communicate with @value{GDBN}. - -Other remote targets may be available in your -configuration of @value{GDBN}; use @code{help target} to list them. - -@menu -* Connecting:: Connecting to a remote target -* File Transfer:: Sending files to a remote system -* Server:: Using the gdbserver program -* Remote Configuration:: Remote configuration -* Remote Stub:: Implementing a remote stub -@end menu - -@node Connecting -@section Connecting to a Remote Target - -On the @value{GDBN} host machine, you will need an unstripped copy of -your program, since @value{GDBN} needs symbol and debugging information. -Start up @value{GDBN} as usual, using the name of the local copy of your -program as the first argument. - -@cindex @code{target remote} -@value{GDBN} can communicate with the target over a serial line, or -over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In -each case, @value{GDBN} uses the same protocol for debugging your -program; only the medium carrying the debugging packets varies. The -@code{target remote} command establishes a connection to the target. -Its arguments indicate which medium to use: - -@table @code - -@item target remote @var{serial-device} -@cindex serial line, @code{target remote} -Use @var{serial-device} to communicate with the target. For example, -to use a serial line connected to the device named @file{/dev/ttyb}: - -@smallexample -target remote /dev/ttyb -@end smallexample - -If you're using a serial line, you may want to give @value{GDBN} the -@w{@samp{--baud}} option, or use the @code{set remotebaud} command -(@pxref{Remote Configuration, set remotebaud}) before the -@code{target} command. - -@item target remote @code{@var{host}:@var{port}} -@itemx target remote @code{tcp:@var{host}:@var{port}} -@cindex @acronym{TCP} port, @code{target remote} -Debug using a @acronym{TCP} connection to @var{port} on @var{host}. -The @var{host} may be either a host name or a numeric @acronym{IP} -address; @var{port} must be a decimal number. The @var{host} could be -the target machine itself, if it is directly connected to the net, or -it might be a terminal server which in turn has a serial line to the -target. - -For example, to connect to port 2828 on a terminal server named -@code{manyfarms}: - -@smallexample -target remote manyfarms:2828 -@end smallexample - -If your remote target is actually running on the same machine as your -debugger session (e.g.@: a simulator for your target running on the -same host), you can omit the hostname. For example, to connect to -port 1234 on your local machine: - -@smallexample -target remote :1234 -@end smallexample -@noindent - -Note that the colon is still required here. - -@item target remote @code{udp:@var{host}:@var{port}} -@cindex @acronym{UDP} port, @code{target remote} -Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to -connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}: - -@smallexample -target remote udp:manyfarms:2828 -@end smallexample - -When using a @acronym{UDP} connection for remote debugging, you should -keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP} -can silently drop packets on busy or unreliable networks, which will -cause havoc with your debugging session. - -@item target remote | @var{command} -@cindex pipe, @code{target remote} to -Run @var{command} in the background and communicate with it using a -pipe. The @var{command} is a shell command, to be parsed and expanded -by the system's command shell, @code{/bin/sh}; it should expect remote -protocol packets on its standard input, and send replies on its -standard output. You could use this to run a stand-alone simulator -that speaks the remote debugging protocol, to make net connections -using programs like @code{ssh}, or for other similar tricks. - -If @var{command} closes its standard output (perhaps by exiting), -@value{GDBN} will try to send it a @code{SIGTERM} signal. (If the -program has already exited, this will have no effect.) - -@end table - -Once the connection has been established, you can use all the usual -commands to examine and change data. The remote program is already -running; you can use @kbd{step} and @kbd{continue}, and you do not -need to use @kbd{run}. - -@cindex interrupting remote programs -@cindex remote programs, interrupting -Whenever @value{GDBN} is waiting for the remote program, if you type the -interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the -program. This may or may not succeed, depending in part on the hardware -and the serial drivers the remote system uses. If you type the -interrupt character once again, @value{GDBN} displays this prompt: - -@smallexample -Interrupted while waiting for the program. -Give up (and stop debugging it)? (y or n) -@end smallexample - -If you type @kbd{y}, @value{GDBN} abandons the remote debugging session. -(If you decide you want to try again later, you can use @samp{target -remote} again to connect once more.) If you type @kbd{n}, @value{GDBN} -goes back to waiting. - -@table @code -@kindex detach (remote) -@item detach -When you have finished debugging the remote program, you can use the -@code{detach} command to release it from @value{GDBN} control. -Detaching from the target normally resumes its execution, but the results -will depend on your particular remote stub. After the @code{detach} -command, @value{GDBN} is free to connect to another target. - -@kindex disconnect -@item disconnect -The @code{disconnect} command behaves like @code{detach}, except that -the target is generally not resumed. It will wait for @value{GDBN} -(this instance or another one) to connect and continue debugging. After -the @code{disconnect} command, @value{GDBN} is again free to connect to -another target. - -@cindex send command to remote monitor -@cindex extend @value{GDBN} for remote targets -@cindex add new commands for external monitor -@kindex monitor -@item monitor @var{cmd} -This command allows you to send arbitrary commands directly to the -remote monitor. Since @value{GDBN} doesn't care about the commands it -sends like this, this command is the way to extend @value{GDBN}---you -can add new commands that only the external monitor will understand -and implement. -@end table - -@node File Transfer -@section Sending files to a remote system -@cindex remote target, file transfer -@cindex file transfer -@cindex sending files to remote systems - -Some remote targets offer the ability to transfer files over the same -connection used to communicate with @value{GDBN}. This is convenient -for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems -running @code{gdbserver} over a network interface. For other targets, -e.g.@: embedded devices with only a single serial port, this may be -the only way to upload or download files. - -Not all remote targets support these commands. - -@table @code -@kindex remote put -@item remote put @var{hostfile} @var{targetfile} -Copy file @var{hostfile} from the host system (the machine running -@value{GDBN}) to @var{targetfile} on the target system. - -@kindex remote get -@item remote get @var{targetfile} @var{hostfile} -Copy file @var{targetfile} from the target system to @var{hostfile} -on the host system. - -@kindex remote delete -@item remote delete @var{targetfile} -Delete @var{targetfile} from the target system. - -@end table - -@node Server -@section Using the @code{gdbserver} Program - -@kindex gdbserver -@cindex remote connection without stubs -@code{gdbserver} is a control program for Unix-like systems, which -allows you to connect your program with a remote @value{GDBN} via -@code{target remote}---but without linking in the usual debugging stub. - -@code{gdbserver} is not a complete replacement for the debugging stubs, -because it requires essentially the same operating-system facilities -that @value{GDBN} itself does. In fact, a system that can run -@code{gdbserver} to connect to a remote @value{GDBN} could also run -@value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless, -because it is a much smaller program than @value{GDBN} itself. It is -also easier to port than all of @value{GDBN}, so you may be able to get -started more quickly on a new system by using @code{gdbserver}. -Finally, if you develop code for real-time systems, you may find that -the tradeoffs involved in real-time operation make it more convenient to -do as much development work as possible on another system, for example -by cross-compiling. You can use @code{gdbserver} to make a similar -choice for debugging. - -@value{GDBN} and @code{gdbserver} communicate via either a serial line -or a TCP connection, using the standard @value{GDBN} remote serial -protocol. - -@quotation -@emph{Warning:} @code{gdbserver} does not have any built-in security. -Do not run @code{gdbserver} connected to any public network; a -@value{GDBN} connection to @code{gdbserver} provides access to the -target system with the same privileges as the user running -@code{gdbserver}. -@end quotation - -@subsection Running @code{gdbserver} -@cindex arguments, to @code{gdbserver} -@cindex @code{gdbserver}, command-line arguments - -Run @code{gdbserver} on the target system. You need a copy of the -program you want to debug, including any libraries it requires. -@code{gdbserver} does not need your program's symbol table, so you can -strip the program if necessary to save space. @value{GDBN} on the host -system does all the symbol handling. - -To use the server, you must tell it how to communicate with @value{GDBN}; -the name of your program; and the arguments for your program. The usual -syntax is: - -@smallexample -target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ] -@end smallexample - -@var{comm} is either a device name (to use a serial line), or a TCP -hostname and portnumber, or @code{-} or @code{stdio} to use -stdin/stdout of @code{gdbserver}. -For example, to debug Emacs with the argument -@samp{foo.txt} and communicate with @value{GDBN} over the serial port -@file{/dev/com1}: - -@smallexample -target> gdbserver /dev/com1 emacs foo.txt -@end smallexample - -@code{gdbserver} waits passively for the host @value{GDBN} to communicate -with it. - -To use a TCP connection instead of a serial line: - -@smallexample -target> gdbserver host:2345 emacs foo.txt -@end smallexample - -The only difference from the previous example is the first argument, -specifying that you are communicating with the host @value{GDBN} via -TCP. The @samp{host:2345} argument means that @code{gdbserver} is to -expect a TCP connection from machine @samp{host} to local TCP port 2345. -(Currently, the @samp{host} part is ignored.) You can choose any number -you want for the port number as long as it does not conflict with any -TCP ports already in use on the target system (for example, @code{23} is -reserved for @code{telnet}).@footnote{If you choose a port number that -conflicts with another service, @code{gdbserver} prints an error message -and exits.} You must use the same port number with the host @value{GDBN} -@code{target remote} command. - -The @code{stdio} connection is useful when starting @code{gdbserver} -with ssh: - -@smallexample -(gdb) target remote | ssh -T hostname gdbserver - hello -@end smallexample - -The @samp{-T} option to ssh is provided because we don't need a remote pty, -and we don't want escape-character handling. Ssh does this by default when -a command is provided, the flag is provided to make it explicit. -You could elide it if you want to. - -Programs started with stdio-connected gdbserver have @file{/dev/null} for -@code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for -display through a pipe connected to gdbserver. -Both @code{stdout} and @code{stderr} use the same pipe. - -@subsubsection Attaching to a Running Program -@cindex attach to a program, @code{gdbserver} -@cindex @option{--attach}, @code{gdbserver} option - -On some targets, @code{gdbserver} can also attach to running programs. -This is accomplished via the @code{--attach} argument. The syntax is: - -@smallexample -target> gdbserver --attach @var{comm} @var{pid} -@end smallexample - -@var{pid} is the process ID of a currently running process. It isn't necessary -to point @code{gdbserver} at a binary for the running process. - -@pindex pidof -You can debug processes by name instead of process ID if your target has the -@code{pidof} utility: - -@smallexample -target> gdbserver --attach @var{comm} `pidof @var{program}` -@end smallexample - -In case more than one copy of @var{program} is running, or @var{program} -has multiple threads, most versions of @code{pidof} support the -@code{-s} option to only return the first process ID. - -@subsubsection Multi-Process Mode for @code{gdbserver} -@cindex @code{gdbserver}, multiple processes -@cindex multiple processes with @code{gdbserver} - -When you connect to @code{gdbserver} using @code{target remote}, -@code{gdbserver} debugs the specified program only once. When the -program exits, or you detach from it, @value{GDBN} closes the connection -and @code{gdbserver} exits. - -If you connect using @kbd{target extended-remote}, @code{gdbserver} -enters multi-process mode. When the debugged program exits, or you -detach from it, @value{GDBN} stays connected to @code{gdbserver} even -though no program is running. The @code{run} and @code{attach} -commands instruct @code{gdbserver} to run or attach to a new program. -The @code{run} command uses @code{set remote exec-file} (@pxref{set -remote exec-file}) to select the program to run. Command line -arguments are supported, except for wildcard expansion and I/O -redirection (@pxref{Arguments}). - -@cindex @option{--multi}, @code{gdbserver} option -To start @code{gdbserver} without supplying an initial command to run -or process ID to attach, use the @option{--multi} command line option. -Then you can connect using @kbd{target extended-remote} and start -the program you want to debug. - -In multi-process mode @code{gdbserver} does not automatically exit unless you -use the option @option{--once}. You can terminate it by using -@code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the -conditions under which @code{gdbserver} terminates depend on how @value{GDBN} -connects to it (@kbd{target remote} or @kbd{target extended-remote}). The -@option{--multi} option to @code{gdbserver} has no influence on that. - -@subsubsection TCP port allocation lifecycle of @code{gdbserver} - -This section applies only when @code{gdbserver} is run to listen on a TCP port. - -@code{gdbserver} normally terminates after all of its debugged processes have -terminated in @kbd{target remote} mode. On the other hand, for @kbd{target -extended-remote}, @code{gdbserver} stays running even with no processes left. -@value{GDBN} normally terminates the spawned debugged process on its exit, -which normally also terminates @code{gdbserver} in the @kbd{target remote} -mode. Therefore, when the connection drops unexpectedly, and @value{GDBN} -cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver} -stays running even in the @kbd{target remote} mode. - -When @code{gdbserver} stays running, @value{GDBN} can connect to it again later. -Such reconnecting is useful for features like @ref{disconnected tracing}. For -completeness, at most one @value{GDBN} can be connected at a time. - -@cindex @option{--once}, @code{gdbserver} option -By default, @code{gdbserver} keeps the listening TCP port open, so that -additional connections are possible. However, if you start @code{gdbserver} -with the @option{--once} option, it will stop listening for any further -connection attempts after connecting to the first @value{GDBN} session. This -means no further connections to @code{gdbserver} will be possible after the -first one. It also means @code{gdbserver} will terminate after the first -connection with remote @value{GDBN} has closed, even for unexpectedly closed -connections and even in the @kbd{target extended-remote} mode. The -@option{--once} option allows reusing the same port number for connecting to -multiple instances of @code{gdbserver} running on the same host, since each -instance closes its port after the first connection. - -@subsubsection Other Command-Line Arguments for @code{gdbserver} - -@cindex @option{--debug}, @code{gdbserver} option -The @option{--debug} option tells @code{gdbserver} to display extra -status information about the debugging process. -@cindex @option{--remote-debug}, @code{gdbserver} option -The @option{--remote-debug} option tells @code{gdbserver} to display -remote protocol debug output. These options are intended for -@code{gdbserver} development and for bug reports to the developers. - -@cindex @option{--wrapper}, @code{gdbserver} option -The @option{--wrapper} option specifies a wrapper to launch programs -for debugging. The option should be followed by the name of the -wrapper, then any command-line arguments to pass to the wrapper, then -@kbd{--} indicating the end of the wrapper arguments. - -@code{gdbserver} runs the specified wrapper program with a combined -command line including the wrapper arguments, then the name of the -program to debug, then any arguments to the program. The wrapper -runs until it executes your program, and then @value{GDBN} gains control. - -You can use any program that eventually calls @code{execve} with -its arguments as a wrapper. Several standard Unix utilities do -this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending -with @code{exec "$@@"} will also work. - -For example, you can use @code{env} to pass an environment variable to -the debugged program, without setting the variable in @code{gdbserver}'s -environment: - -@smallexample -$ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog -@end smallexample - -@subsection Connecting to @code{gdbserver} - -Run @value{GDBN} on the host system. - -First make sure you have the necessary symbol files. Load symbols for -your application using the @code{file} command before you connect. Use -@code{set sysroot} to locate target libraries (unless your @value{GDBN} -was compiled with the correct sysroot using @code{--with-sysroot}). - -The symbol file and target libraries must exactly match the executable -and libraries on the target, with one exception: the files on the host -system should not be stripped, even if the files on the target system -are. Mismatched or missing files will lead to confusing results -during debugging. On @sc{gnu}/Linux targets, mismatched or missing -files may also prevent @code{gdbserver} from debugging multi-threaded -programs. - -Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}). -For TCP connections, you must start up @code{gdbserver} prior to using -the @code{target remote} command. Otherwise you may get an error whose -text depends on the host system, but which usually looks something like -@samp{Connection refused}. Don't use the @code{load} -command in @value{GDBN} when using @code{gdbserver}, since the program is -already on the target. - -@subsection Monitor Commands for @code{gdbserver} -@cindex monitor commands, for @code{gdbserver} -@anchor{Monitor Commands for gdbserver} - -During a @value{GDBN} session using @code{gdbserver}, you can use the -@code{monitor} command to send special requests to @code{gdbserver}. -Here are the available commands. - -@table @code -@item monitor help -List the available monitor commands. - -@item monitor set debug 0 -@itemx monitor set debug 1 -Disable or enable general debugging messages. - -@item monitor set remote-debug 0 -@itemx monitor set remote-debug 1 -Disable or enable specific debugging messages associated with the remote -protocol (@pxref{Remote Protocol}). - -@item monitor set libthread-db-search-path [PATH] -@cindex gdbserver, search path for @code{libthread_db} -When this command is issued, @var{path} is a colon-separated list of -directories to search for @code{libthread_db} (@pxref{Threads,,set -libthread-db-search-path}). If you omit @var{path}, -@samp{libthread-db-search-path} will be reset to its default value. - -The special entry @samp{$pdir} for @samp{libthread-db-search-path} is -not supported in @code{gdbserver}. - -@item monitor exit -Tell gdbserver to exit immediately. This command should be followed by -@code{disconnect} to close the debugging session. @code{gdbserver} will -detach from any attached processes and kill any processes it created. -Use @code{monitor exit} to terminate @code{gdbserver} at the end -of a multi-process mode debug session. - -@end table - -@subsection Tracepoints support in @code{gdbserver} -@cindex tracepoints support in @code{gdbserver} - -On some targets, @code{gdbserver} supports tracepoints, fast -tracepoints and static tracepoints. - -For fast or static tracepoints to work, a special library called the -@dfn{in-process agent} (IPA), must be loaded in the inferior process. -This library is built and distributed as an integral part of -@code{gdbserver}. In addition, support for static tracepoints -requires building the in-process agent library with static tracepoints -support. At present, the UST (LTTng Userspace Tracer, -@url{http://lttng.org/ust}) tracing engine is supported. This support -is automatically available if UST development headers are found in the -standard include path when @code{gdbserver} is built, or if -@code{gdbserver} was explicitly configured using @option{--with-ust} -to point at such headers. You can explicitly disable the support -using @option{--with-ust=no}. - -There are several ways to load the in-process agent in your program: - -@table @code -@item Specifying it as dependency at link time - -You can link your program dynamically with the in-process agent -library. On most systems, this is accomplished by adding -@code{-linproctrace} to the link command. - -@item Using the system's preloading mechanisms - -You can force loading the in-process agent at startup time by using -your system's support for preloading shared libraries. Many Unixes -support the concept of preloading user defined libraries. In most -cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so} -in the environment. See also the description of @code{gdbserver}'s -@option{--wrapper} command line option. - -@item Using @value{GDBN} to force loading the agent at run time - -On some systems, you can force the inferior to load a shared library, -by calling a dynamic loader function in the inferior that takes care -of dynamically looking up and loading a shared library. On most Unix -systems, the function is @code{dlopen}. You'll use the @code{call} -command for that. For example: - -@smallexample -(@value{GDBP}) call dlopen ("libinproctrace.so", ...) -@end smallexample - -Note that on most Unix systems, for the @code{dlopen} function to be -available, the program needs to be linked with @code{-ldl}. -@end table - -On systems that have a userspace dynamic loader, like most Unix -systems, when you connect to @code{gdbserver} using @code{target -remote}, you'll find that the program is stopped at the dynamic -loader's entry point, and no shared library has been loaded in the -program's address space yet, including the in-process agent. In that -case, before being able to use any of the fast or static tracepoints -features, you need to let the loader run and load the shared -libraries. The simplest way to do that is to run the program to the -main procedure. E.g., if debugging a C or C@t{++} program, start -@code{gdbserver} like so: - -@smallexample -$ gdbserver :9999 myprogram -@end smallexample - -Start GDB and connect to @code{gdbserver} like so, and run to main: - -@smallexample -$ gdb myprogram -(@value{GDBP}) target remote myhost:9999 -0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2 -(@value{GDBP}) b main -(@value{GDBP}) continue -@end smallexample - -The in-process tracing agent library should now be loaded into the -process; you can confirm it with the @code{info sharedlibrary} -command, which will list @file{libinproctrace.so} as loaded in the -process. You are now ready to install fast tracepoints, list static -tracepoint markers, probe static tracepoints markers, and start -tracing. - -@node Remote Configuration -@section Remote Configuration - -@kindex set remote -@kindex show remote -This section documents the configuration options available when -debugging remote programs. For the options related to the File I/O -extensions of the remote protocol, see @ref{system, -system-call-allowed}. - -@table @code -@item set remoteaddresssize @var{bits} -@cindex address size for remote targets -@cindex bits in remote address -Set the maximum size of address in a memory packet to the specified -number of bits. @value{GDBN} will mask off the address bits above -that number, when it passes addresses to the remote target. The -default value is the number of bits in the target's address. - -@item show remoteaddresssize -Show the current value of remote address size in bits. - -@item set remotebaud @var{n} -@cindex baud rate for remote targets -Set the baud rate for the remote serial I/O to @var{n} baud. The -value is used to set the speed of the serial port used for debugging -remote targets. - -@item show remotebaud -Show the current speed of the remote connection. - -@item set remotebreak -@cindex interrupt remote programs -@cindex BREAK signal instead of Ctrl-C -@anchor{set remotebreak} -If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote -when you type @kbd{Ctrl-c} to interrupt the program running -on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C} -character instead. The default is off, since most remote systems -expect to see @samp{Ctrl-C} as the interrupt signal. - -@item show remotebreak -Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to -interrupt the remote program. - -@item set remoteflow on -@itemx set remoteflow off -@kindex set remoteflow -Enable or disable hardware flow control (@code{RTS}/@code{CTS}) -on the serial port used to communicate to the remote target. - -@item show remoteflow -@kindex show remoteflow -Show the current setting of hardware flow control. - -@item set remotelogbase @var{base} -Set the base (a.k.a.@: radix) of logging serial protocol -communications to @var{base}. Supported values of @var{base} are: -@code{ascii}, @code{octal}, and @code{hex}. The default is -@code{ascii}. - -@item show remotelogbase -Show the current setting of the radix for logging remote serial -protocol. - -@item set remotelogfile @var{file} -@cindex record serial communications on file -Record remote serial communications on the named @var{file}. The -default is not to record at all. - -@item show remotelogfile. -Show the current setting of the file name on which to record the -serial communications. - -@item set remotetimeout @var{num} -@cindex timeout for serial communications -@cindex remote timeout -Set the timeout limit to wait for the remote target to respond to -@var{num} seconds. The default is 2 seconds. - -@item show remotetimeout -Show the current number of seconds to wait for the remote target -responses. - -@cindex limit hardware breakpoints and watchpoints -@cindex remote target, limit break- and watchpoints -@anchor{set remote hardware-watchpoint-limit} -@anchor{set remote hardware-breakpoint-limit} -@item set remote hardware-watchpoint-limit @var{limit} -@itemx set remote hardware-breakpoint-limit @var{limit} -Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or -watchpoints. A limit of -1, the default, is treated as unlimited. - -@cindex limit hardware watchpoints length -@cindex remote target, limit watchpoints length -@anchor{set remote hardware-watchpoint-length-limit} -@item set remote hardware-watchpoint-length-limit @var{limit} -Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of -a remote hardware watchpoint. A limit of -1, the default, is treated -as unlimited. - -@item show remote hardware-watchpoint-length-limit -Show the current limit (in bytes) of the maximum length of -a remote hardware watchpoint. - -@item set remote exec-file @var{filename} -@itemx show remote exec-file -@anchor{set remote exec-file} -@cindex executable file, for remote target -Select the file used for @code{run} with @code{target -extended-remote}. This should be set to a filename valid on the -target system. If it is not set, the target will use a default -filename (e.g.@: the last program run). - -@item set remote interrupt-sequence -@cindex interrupt remote programs -@cindex select Ctrl-C, BREAK or BREAK-g -Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or -@samp{BREAK-g} as the -sequence to the remote target in order to interrupt the execution. -@samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which -is high level of serial line for some certain time. -Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g. -It is @code{BREAK} signal followed by character @code{g}. - -@item show interrupt-sequence -Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g} -is sent by @value{GDBN} to interrupt the remote program. -@code{BREAK-g} is BREAK signal followed by @code{g} and -also known as Magic SysRq g. - -@item set remote interrupt-on-connect -@cindex send interrupt-sequence on start -Specify whether interrupt-sequence is sent to remote target when -@value{GDBN} connects to it. This is mostly needed when you debug -Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g} -which is known as Magic SysRq g in order to connect @value{GDBN}. - -@item show interrupt-on-connect -Show whether interrupt-sequence is sent -to remote target when @value{GDBN} connects to it. - -@kindex set tcp -@kindex show tcp -@item set tcp auto-retry on -@cindex auto-retry, for remote TCP target -Enable auto-retry for remote TCP connections. This is useful if the remote -debugging agent is launched in parallel with @value{GDBN}; there is a race -condition because the agent may not become ready to accept the connection -before @value{GDBN} attempts to connect. When auto-retry is -enabled, if the initial attempt to connect fails, @value{GDBN} reattempts -to establish the connection using the timeout specified by -@code{set tcp connect-timeout}. - -@item set tcp auto-retry off -Do not auto-retry failed TCP connections. - -@item show tcp auto-retry -Show the current auto-retry setting. - -@item set tcp connect-timeout @var{seconds} -@cindex connection timeout, for remote TCP target -@cindex timeout, for remote target connection -Set the timeout for establishing a TCP connection to the remote target to -@var{seconds}. The timeout affects both polling to retry failed connections -(enabled by @code{set tcp auto-retry on}) and waiting for connections -that are merely slow to complete, and represents an approximate cumulative -value. - -@item show tcp connect-timeout -Show the current connection timeout setting. -@end table - -@cindex remote packets, enabling and disabling -The @value{GDBN} remote protocol autodetects the packets supported by -your debugging stub. If you need to override the autodetection, you -can use these commands to enable or disable individual packets. Each -packet can be set to @samp{on} (the remote target supports this -packet), @samp{off} (the remote target does not support this packet), -or @samp{auto} (detect remote target support for this packet). They -all default to @samp{auto}. For more information about each packet, -see @ref{Remote Protocol}. - -During normal use, you should not have to use any of these commands. -If you do, that may be a bug in your remote debugging stub, or a bug -in @value{GDBN}. You may want to report the problem to the -@value{GDBN} developers. - -For each packet @var{name}, the command to enable or disable the -packet is @code{set remote @var{name}-packet}. The available settings -are: - -@multitable @columnfractions 0.28 0.32 0.25 -@item Command Name -@tab Remote Packet -@tab Related Features - -@item @code{fetch-register} -@tab @code{p} -@tab @code{info registers} - -@item @code{set-register} -@tab @code{P} -@tab @code{set} - -@item @code{binary-download} -@tab @code{X} -@tab @code{load}, @code{set} - -@item @code{read-aux-vector} -@tab @code{qXfer:auxv:read} -@tab @code{info auxv} - -@item @code{symbol-lookup} -@tab @code{qSymbol} -@tab Detecting multiple threads - -@item @code{attach} -@tab @code{vAttach} -@tab @code{attach} - -@item @code{verbose-resume} -@tab @code{vCont} -@tab Stepping or resuming multiple threads - -@item @code{run} -@tab @code{vRun} -@tab @code{run} - -@item @code{software-breakpoint} -@tab @code{Z0} -@tab @code{break} - -@item @code{hardware-breakpoint} -@tab @code{Z1} -@tab @code{hbreak} - -@item @code{write-watchpoint} -@tab @code{Z2} -@tab @code{watch} - -@item @code{read-watchpoint} -@tab @code{Z3} -@tab @code{rwatch} - -@item @code{access-watchpoint} -@tab @code{Z4} -@tab @code{awatch} - -@item @code{target-features} -@tab @code{qXfer:features:read} -@tab @code{set architecture} - -@item @code{library-info} -@tab @code{qXfer:libraries:read} -@tab @code{info sharedlibrary} - -@item @code{memory-map} -@tab @code{qXfer:memory-map:read} -@tab @code{info mem} - -@item @code{read-sdata-object} -@tab @code{qXfer:sdata:read} -@tab @code{print $_sdata} - -@item @code{read-spu-object} -@tab @code{qXfer:spu:read} -@tab @code{info spu} - -@item @code{write-spu-object} -@tab @code{qXfer:spu:write} -@tab @code{info spu} - -@item @code{read-siginfo-object} -@tab @code{qXfer:siginfo:read} -@tab @code{print $_siginfo} - -@item @code{write-siginfo-object} -@tab @code{qXfer:siginfo:write} -@tab @code{set $_siginfo} - -@item @code{threads} -@tab @code{qXfer:threads:read} -@tab @code{info threads} - -@item @code{get-thread-local-@*storage-address} -@tab @code{qGetTLSAddr} -@tab Displaying @code{__thread} variables - -@item @code{get-thread-information-block-address} -@tab @code{qGetTIBAddr} -@tab Display MS-Windows Thread Information Block. - -@item @code{search-memory} -@tab @code{qSearch:memory} -@tab @code{find} - -@item @code{supported-packets} -@tab @code{qSupported} -@tab Remote communications parameters - -@item @code{pass-signals} -@tab @code{QPassSignals} -@tab @code{handle @var{signal}} - -@item @code{program-signals} -@tab @code{QProgramSignals} -@tab @code{handle @var{signal}} - -@item @code{hostio-close-packet} -@tab @code{vFile:close} -@tab @code{remote get}, @code{remote put} - -@item @code{hostio-open-packet} -@tab @code{vFile:open} -@tab @code{remote get}, @code{remote put} - -@item @code{hostio-pread-packet} -@tab @code{vFile:pread} -@tab @code{remote get}, @code{remote put} - -@item @code{hostio-pwrite-packet} -@tab @code{vFile:pwrite} -@tab @code{remote get}, @code{remote put} - -@item @code{hostio-unlink-packet} -@tab @code{vFile:unlink} -@tab @code{remote delete} - -@item @code{hostio-readlink-packet} -@tab @code{vFile:readlink} -@tab Host I/O - -@item @code{noack-packet} -@tab @code{QStartNoAckMode} -@tab Packet acknowledgment - -@item @code{osdata} -@tab @code{qXfer:osdata:read} -@tab @code{info os} - -@item @code{query-attached} -@tab @code{qAttached} -@tab Querying remote process attach state. - -@item @code{trace-buffer-size} -@tab @code{QTBuffer:size} -@tab @code{set trace-buffer-size} - -@item @code{traceframe-info} -@tab @code{qXfer:traceframe-info:read} -@tab Traceframe info - -@item @code{install-in-trace} -@tab @code{InstallInTrace} -@tab Install tracepoint in tracing - -@item @code{disable-randomization} -@tab @code{QDisableRandomization} -@tab @code{set disable-randomization} - -@item @code{conditional-breakpoints-packet} -@tab @code{Z0 and Z1} -@tab @code{Support for target-side breakpoint condition evaluation} -@end multitable - -@node Remote Stub -@section Implementing a Remote Stub - -@cindex debugging stub, example -@cindex remote stub, example -@cindex stub example, remote debugging -The stub files provided with @value{GDBN} implement the target side of the -communication protocol, and the @value{GDBN} side is implemented in the -@value{GDBN} source file @file{remote.c}. Normally, you can simply allow -these subroutines to communicate, and ignore the details. (If you're -implementing your own stub file, you can still ignore the details: start -with one of the existing stub files. @file{sparc-stub.c} is the best -organized, and therefore the easiest to read.) - -@cindex remote serial debugging, overview -To debug a program running on another machine (the debugging -@dfn{target} machine), you must first arrange for all the usual -prerequisites for the program to run by itself. For example, for a C -program, you need: - -@enumerate -@item -A startup routine to set up the C runtime environment; these usually -have a name like @file{crt0}. The startup routine may be supplied by -your hardware supplier, or you may have to write your own. - -@item -A C subroutine library to support your program's -subroutine calls, notably managing input and output. - -@item -A way of getting your program to the other machine---for example, a -download program. These are often supplied by the hardware -manufacturer, but you may have to write your own from hardware -documentation. -@end enumerate - -The next step is to arrange for your program to use a serial port to -communicate with the machine where @value{GDBN} is running (the @dfn{host} -machine). In general terms, the scheme looks like this: - -@table @emph -@item On the host, -@value{GDBN} already understands how to use this protocol; when everything -else is set up, you can simply use the @samp{target remote} command -(@pxref{Targets,,Specifying a Debugging Target}). - -@item On the target, -you must link with your program a few special-purpose subroutines that -implement the @value{GDBN} remote serial protocol. The file containing these -subroutines is called a @dfn{debugging stub}. - -On certain remote targets, you can use an auxiliary program -@code{gdbserver} instead of linking a stub into your program. -@xref{Server,,Using the @code{gdbserver} Program}, for details. -@end table - -The debugging stub is specific to the architecture of the remote -machine; for example, use @file{sparc-stub.c} to debug programs on -@sc{sparc} boards. - -@cindex remote serial stub list -These working remote stubs are distributed with @value{GDBN}: - -@table @code - -@item i386-stub.c -@cindex @file{i386-stub.c} -@cindex Intel -@cindex i386 -For Intel 386 and compatible architectures. - -@item m68k-stub.c -@cindex @file{m68k-stub.c} -@cindex Motorola 680x0 -@cindex m680x0 -For Motorola 680x0 architectures. - -@item sh-stub.c -@cindex @file{sh-stub.c} -@cindex Renesas -@cindex SH -For Renesas SH architectures. - -@item sparc-stub.c -@cindex @file{sparc-stub.c} -@cindex Sparc -For @sc{sparc} architectures. - -@item sparcl-stub.c -@cindex @file{sparcl-stub.c} -@cindex Fujitsu -@cindex SparcLite -For Fujitsu @sc{sparclite} architectures. - -@end table - -The @file{README} file in the @value{GDBN} distribution may list other -recently added stubs. - -@menu -* Stub Contents:: What the stub can do for you -* Bootstrapping:: What you must do for the stub -* Debug Session:: Putting it all together -@end menu - -@node Stub Contents -@subsection What the Stub Can Do for You - -@cindex remote serial stub -The debugging stub for your architecture supplies these three -subroutines: - -@table @code -@item set_debug_traps -@findex set_debug_traps -@cindex remote serial stub, initialization -This routine arranges for @code{handle_exception} to run when your -program stops. You must call this subroutine explicitly in your -program's startup code. - -@item handle_exception -@findex handle_exception -@cindex remote serial stub, main routine -This is the central workhorse, but your program never calls it -explicitly---the setup code arranges for @code{handle_exception} to -run when a trap is triggered. - -@code{handle_exception} takes control when your program stops during -execution (for example, on a breakpoint), and mediates communications -with @value{GDBN} on the host machine. This is where the communications -protocol is implemented; @code{handle_exception} acts as the @value{GDBN} -representative on the target machine. It begins by sending summary -information on the state of your program, then continues to execute, -retrieving and transmitting any information @value{GDBN} needs, until you -execute a @value{GDBN} command that makes your program resume; at that point, -@code{handle_exception} returns control to your own code on the target -machine. - -@item breakpoint -@cindex @code{breakpoint} subroutine, remote -Use this auxiliary subroutine to make your program contain a -breakpoint. Depending on the particular situation, this may be the only -way for @value{GDBN} to get control. For instance, if your target -machine has some sort of interrupt button, you won't need to call this; -pressing the interrupt button transfers control to -@code{handle_exception}---in effect, to @value{GDBN}. On some machines, -simply receiving characters on the serial port may also trigger a trap; -again, in that situation, you don't need to call @code{breakpoint} from -your own program---simply running @samp{target remote} from the host -@value{GDBN} session gets control. - -Call @code{breakpoint} if none of these is true, or if you simply want -to make certain your program stops at a predetermined point for the -start of your debugging session. -@end table - -@node Bootstrapping -@subsection What You Must Do for the Stub - -@cindex remote stub, support routines -The debugging stubs that come with @value{GDBN} are set up for a particular -chip architecture, but they have no information about the rest of your -debugging target machine. - -First of all you need to tell the stub how to communicate with the -serial port. - -@table @code -@item int getDebugChar() -@findex getDebugChar -Write this subroutine to read a single character from the serial port. -It may be identical to @code{getchar} for your target system; a -different name is used to allow you to distinguish the two if you wish. - -@item void putDebugChar(int) -@findex putDebugChar -Write this subroutine to write a single character to the serial port. -It may be identical to @code{putchar} for your target system; a -different name is used to allow you to distinguish the two if you wish. -@end table - -@cindex control C, and remote debugging -@cindex interrupting remote targets -If you want @value{GDBN} to be able to stop your program while it is -running, you need to use an interrupt-driven serial driver, and arrange -for it to stop when it receives a @code{^C} (@samp{\003}, the control-C -character). That is the character which @value{GDBN} uses to tell the -remote system to stop. - -Getting the debugging target to return the proper status to @value{GDBN} -probably requires changes to the standard stub; one quick and dirty way -is to just execute a breakpoint instruction (the ``dirty'' part is that -@value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}). - -Other routines you need to supply are: - -@table @code -@item void exceptionHandler (int @var{exception_number}, void *@var{exception_address}) -@findex exceptionHandler -Write this function to install @var{exception_address} in the exception -handling tables. You need to do this because the stub does not have any -way of knowing what the exception handling tables on your target system -are like (for example, the processor's table might be in @sc{rom}, -containing entries which point to a table in @sc{ram}). -@var{exception_number} is the exception number which should be changed; -its meaning is architecture-dependent (for example, different numbers -might represent divide by zero, misaligned access, etc). When this -exception occurs, control should be transferred directly to -@var{exception_address}, and the processor state (stack, registers, -and so on) should be just as it is when a processor exception occurs. So if -you want to use a jump instruction to reach @var{exception_address}, it -should be a simple jump, not a jump to subroutine. - -For the 386, @var{exception_address} should be installed as an interrupt -gate so that interrupts are masked while the handler runs. The gate -should be at privilege level 0 (the most privileged level). The -@sc{sparc} and 68k stubs are able to mask interrupts themselves without -help from @code{exceptionHandler}. - -@item void flush_i_cache() -@findex flush_i_cache -On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the -instruction cache, if any, on your target machine. If there is no -instruction cache, this subroutine may be a no-op. - -On target machines that have instruction caches, @value{GDBN} requires this -function to make certain that the state of your program is stable. -@end table - -@noindent -You must also make sure this library routine is available: - -@table @code -@item void *memset(void *, int, int) -@findex memset -This is the standard library function @code{memset} that sets an area of -memory to a known value. If you have one of the free versions of -@code{libc.a}, @code{memset} can be found there; otherwise, you must -either obtain it from your hardware manufacturer, or write your own. -@end table - -If you do not use the GNU C compiler, you may need other standard -library subroutines as well; this varies from one stub to another, -but in general the stubs are likely to use any of the common library -subroutines which @code{@value{NGCC}} generates as inline code. - - -@node Debug Session -@subsection Putting it All Together - -@cindex remote serial debugging summary -In summary, when your program is ready to debug, you must follow these -steps. - -@enumerate -@item -Make sure you have defined the supporting low-level routines -(@pxref{Bootstrapping,,What You Must Do for the Stub}): -@display -@code{getDebugChar}, @code{putDebugChar}, -@code{flush_i_cache}, @code{memset}, @code{exceptionHandler}. -@end display - -@item -Insert these lines in your program's startup code, before the main -procedure is called: - -@smallexample -set_debug_traps(); -breakpoint(); -@end smallexample - -On some machines, when a breakpoint trap is raised, the hardware -automatically makes the PC point to the instruction after the -breakpoint. If your machine doesn't do that, you may need to adjust -@code{handle_exception} to arrange for it to return to the instruction -after the breakpoint on this first invocation, so that your program -doesn't keep hitting the initial breakpoint instead of making -progress. - -@item -For the 680x0 stub only, you need to provide a variable called -@code{exceptionHook}. Normally you just use: - -@smallexample -void (*exceptionHook)() = 0; -@end smallexample - -@noindent -but if before calling @code{set_debug_traps}, you set it to point to a -function in your program, that function is called when -@code{@value{GDBN}} continues after stopping on a trap (for example, bus -error). The function indicated by @code{exceptionHook} is called with -one parameter: an @code{int} which is the exception number. - -@item -Compile and link together: your program, the @value{GDBN} debugging stub for -your target architecture, and the supporting subroutines. - -@item -Make sure you have a serial connection between your target machine and -the @value{GDBN} host, and identify the serial port on the host. - -@item -@c The "remote" target now provides a `load' command, so we should -@c document that. FIXME. -Download your program to your target machine (or get it there by -whatever means the manufacturer provides), and start it. - -@item -Start @value{GDBN} on the host, and connect to the target -(@pxref{Connecting,,Connecting to a Remote Target}). - -@end enumerate - -@node Configurations -@chapter Configuration-Specific Information - -While nearly all @value{GDBN} commands are available for all native and -cross versions of the debugger, there are some exceptions. This chapter -describes things that are only available in certain configurations. - -There are three major categories of configurations: native -configurations, where the host and target are the same, embedded -operating system configurations, which are usually the same for several -different processor architectures, and bare embedded processors, which -are quite different from each other. - -@menu -* Native:: -* Embedded OS:: -* Embedded Processors:: -* Architectures:: -@end menu - -@node Native -@section Native - -This section describes details specific to particular native -configurations. - -@menu -* HP-UX:: HP-UX -* BSD libkvm Interface:: Debugging BSD kernel memory images -* SVR4 Process Information:: SVR4 process information -* DJGPP Native:: Features specific to the DJGPP port -* Cygwin Native:: Features specific to the Cygwin port -* Hurd Native:: Features specific to @sc{gnu} Hurd -* Darwin:: Features specific to Darwin -@end menu - -@node HP-UX -@subsection HP-UX - -On HP-UX systems, if you refer to a function or variable name that -begins with a dollar sign, @value{GDBN} searches for a user or system -name first, before it searches for a convenience variable. - - -@node BSD libkvm Interface -@subsection BSD libkvm Interface - -@cindex libkvm -@cindex kernel memory image -@cindex kernel crash dump - -BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory -interface that provides a uniform interface for accessing kernel virtual -memory images, including live systems and crash dumps. @value{GDBN} -uses this interface to allow you to debug live kernels and kernel crash -dumps on many native BSD configurations. This is implemented as a -special @code{kvm} debugging target. For debugging a live system, load -the currently running kernel into @value{GDBN} and connect to the -@code{kvm} target: - -@smallexample -(@value{GDBP}) @b{target kvm} -@end smallexample - -For debugging crash dumps, provide the file name of the crash dump as an -argument: - -@smallexample -(@value{GDBP}) @b{target kvm /var/crash/bsd.0} -@end smallexample - -Once connected to the @code{kvm} target, the following commands are -available: - -@table @code -@kindex kvm -@item kvm pcb -Set current context from the @dfn{Process Control Block} (PCB) address. - -@item kvm proc -Set current context from proc address. This command isn't available on -modern FreeBSD systems. -@end table - -@node SVR4 Process Information -@subsection SVR4 Process Information -@cindex /proc -@cindex examine process image -@cindex process info via @file{/proc} - -Many versions of SVR4 and compatible systems provide a facility called -@samp{/proc} that can be used to examine the image of a running -process using file-system subroutines. - -If @value{GDBN} is configured for an operating system with this -facility, the command @code{info proc} is available to report -information about the process running your program, or about any -process running on your system. This includes, as of this writing, -@sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but -not HP-UX, for example. - -This command may also work on core files that were created on a system -that has the @samp{/proc} facility. - -@table @code -@kindex info proc -@cindex process ID -@item info proc -@itemx info proc @var{process-id} -Summarize available information about any running process. If a -process ID is specified by @var{process-id}, display information about -that process; otherwise display information about the program being -debugged. The summary includes the debugged process ID, the command -line used to invoke it, its current working directory, and its -executable file's absolute file name. - -On some systems, @var{process-id} can be of the form -@samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID -within a process. If the optional @var{pid} part is missing, it means -a thread from the process being debugged (the leading @samp{/} still -needs to be present, or else @value{GDBN} will interpret the number as -a process ID rather than a thread ID). - -@item info proc cmdline -@cindex info proc cmdline -Show the original command line of the process. This command is -specific to @sc{gnu}/Linux. - -@item info proc cwd -@cindex info proc cwd -Show the current working directory of the process. This command is -specific to @sc{gnu}/Linux. - -@item info proc exe -@cindex info proc exe -Show the name of executable of the process. This command is specific -to @sc{gnu}/Linux. - -@item info proc mappings -@cindex memory address space mappings -Report the memory address space ranges accessible in the program, with -information on whether the process has read, write, or execute access -rights to each range. On @sc{gnu}/Linux systems, each memory range -includes the object file which is mapped to that range, instead of the -memory access rights to that range. - -@item info proc stat -@itemx info proc status -@cindex process detailed status information -These subcommands are specific to @sc{gnu}/Linux systems. They show -the process-related information, including the user ID and group ID; -how many threads are there in the process; its virtual memory usage; -the signals that are pending, blocked, and ignored; its TTY; its -consumption of system and user time; its stack size; its @samp{nice} -value; etc. For more information, see the @samp{proc} man page -(type @kbd{man 5 proc} from your shell prompt). - -@item info proc all -Show all the information about the process described under all of the -above @code{info proc} subcommands. - -@ignore -@comment These sub-options of 'info proc' were not included when -@comment procfs.c was re-written. Keep their descriptions around -@comment against the day when someone finds the time to put them back in. -@kindex info proc times -@item info proc times -Starting time, user CPU time, and system CPU time for your program and -its children. - -@kindex info proc id -@item info proc id -Report on the process IDs related to your program: its own process ID, -the ID of its parent, the process group ID, and the session ID. -@end ignore - -@item set procfs-trace -@kindex set procfs-trace -@cindex @code{procfs} API calls -This command enables and disables tracing of @code{procfs} API calls. - -@item show procfs-trace -@kindex show procfs-trace -Show the current state of @code{procfs} API call tracing. - -@item set procfs-file @var{file} -@kindex set procfs-file -Tell @value{GDBN} to write @code{procfs} API trace to the named -@var{file}. @value{GDBN} appends the trace info to the previous -contents of the file. The default is to display the trace on the -standard output. - -@item show procfs-file -@kindex show procfs-file -Show the file to which @code{procfs} API trace is written. - -@item proc-trace-entry -@itemx proc-trace-exit -@itemx proc-untrace-entry -@itemx proc-untrace-exit -@kindex proc-trace-entry -@kindex proc-trace-exit -@kindex proc-untrace-entry -@kindex proc-untrace-exit -These commands enable and disable tracing of entries into and exits -from the @code{syscall} interface. - -@item info pidlist -@kindex info pidlist -@cindex process list, QNX Neutrino -For QNX Neutrino only, this command displays the list of all the -processes and all the threads within each process. - -@item info meminfo -@kindex info meminfo -@cindex mapinfo list, QNX Neutrino -For QNX Neutrino only, this command displays the list of all mapinfos. -@end table - -@node DJGPP Native -@subsection Features for Debugging @sc{djgpp} Programs -@cindex @sc{djgpp} debugging -@cindex native @sc{djgpp} debugging -@cindex MS-DOS-specific commands - -@cindex DPMI -@sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and -MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs -that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on -top of real-mode DOS systems and their emulations. - -@value{GDBN} supports native debugging of @sc{djgpp} programs, and -defines a few commands specific to the @sc{djgpp} port. This -subsection describes those commands. - -@table @code -@kindex info dos -@item info dos -This is a prefix of @sc{djgpp}-specific commands which print -information about the target system and important OS structures. - -@kindex sysinfo -@cindex MS-DOS system info -@cindex free memory information (MS-DOS) -@item info dos sysinfo -This command displays assorted information about the underlying -platform: the CPU type and features, the OS version and flavor, the -DPMI version, and the available conventional and DPMI memory. - -@cindex GDT -@cindex LDT -@cindex IDT -@cindex segment descriptor tables -@cindex descriptor tables display -@item info dos gdt -@itemx info dos ldt -@itemx info dos idt -These 3 commands display entries from, respectively, Global, Local, -and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor -tables are data structures which store a descriptor for each segment -that is currently in use. The segment's selector is an index into a -descriptor table; the table entry for that index holds the -descriptor's base address and limit, and its attributes and access -rights. - -A typical @sc{djgpp} program uses 3 segments: a code segment, a data -segment (used for both data and the stack), and a DOS segment (which -allows access to DOS/BIOS data structures and absolute addresses in -conventional memory). However, the DPMI host will usually define -additional segments in order to support the DPMI environment. - -@cindex garbled pointers -These commands allow to display entries from the descriptor tables. -Without an argument, all entries from the specified table are -displayed. An argument, which should be an integer expression, means -display a single entry whose index is given by the argument. For -example, here's a convenient way to display information about the -debugged program's data segment: - -@smallexample -@exdent @code{(@value{GDBP}) info dos ldt $ds} -@exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)} -@end smallexample - -@noindent -This comes in handy when you want to see whether a pointer is outside -the data segment's limit (i.e.@: @dfn{garbled}). - -@cindex page tables display (MS-DOS) -@item info dos pde -@itemx info dos pte -These two commands display entries from, respectively, the Page -Directory and the Page Tables. Page Directories and Page Tables are -data structures which control how virtual memory addresses are mapped -into physical addresses. A Page Table includes an entry for every -page of memory that is mapped into the program's address space; there -may be several Page Tables, each one holding up to 4096 entries. A -Page Directory has up to 4096 entries, one each for every Page Table -that is currently in use. - -Without an argument, @kbd{info dos pde} displays the entire Page -Directory, and @kbd{info dos pte} displays all the entries in all of -the Page Tables. An argument, an integer expression, given to the -@kbd{info dos pde} command means display only that entry from the Page -Directory table. An argument given to the @kbd{info dos pte} command -means display entries from a single Page Table, the one pointed to by -the specified entry in the Page Directory. - -@cindex direct memory access (DMA) on MS-DOS -These commands are useful when your program uses @dfn{DMA} (Direct -Memory Access), which needs physical addresses to program the DMA -controller. - -These commands are supported only with some DPMI servers. - -@cindex physical address from linear address -@item info dos address-pte @var{addr} -This command displays the Page Table entry for a specified linear -address. The argument @var{addr} is a linear address which should -already have the appropriate segment's base address added to it, -because this command accepts addresses which may belong to @emph{any} -segment. For example, here's how to display the Page Table entry for -the page where a variable @code{i} is stored: - -@smallexample -@exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i} -@exdent @code{Page Table entry for address 0x11a00d30:} -@exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30} -@end smallexample - -@noindent -This says that @code{i} is stored at offset @code{0xd30} from the page -whose physical base address is @code{0x02698000}, and shows all the -attributes of that page. - -Note that you must cast the addresses of variables to a @code{char *}, -since otherwise the value of @code{__djgpp_base_address}, the base -address of all variables and functions in a @sc{djgpp} program, will -be added using the rules of C pointer arithmetics: if @code{i} is -declared an @code{int}, @value{GDBN} will add 4 times the value of -@code{__djgpp_base_address} to the address of @code{i}. - -Here's another example, it displays the Page Table entry for the -transfer buffer: - -@smallexample -@exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)} -@exdent @code{Page Table entry for address 0x29110:} -@exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110} -@end smallexample - -@noindent -(The @code{+ 3} offset is because the transfer buffer's address is the -3rd member of the @code{_go32_info_block} structure.) The output -clearly shows that this DPMI server maps the addresses in conventional -memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and -linear (@code{0x29110}) addresses are identical. - -This command is supported only with some DPMI servers. -@end table - -@cindex DOS serial data link, remote debugging -In addition to native debugging, the DJGPP port supports remote -debugging via a serial data link. The following commands are specific -to remote serial debugging in the DJGPP port of @value{GDBN}. - -@table @code -@kindex set com1base -@kindex set com1irq -@kindex set com2base -@kindex set com2irq -@kindex set com3base -@kindex set com3irq -@kindex set com4base -@kindex set com4irq -@item set com1base @var{addr} -This command sets the base I/O port address of the @file{COM1} serial -port. - -@item set com1irq @var{irq} -This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use -for the @file{COM1} serial port. - -There are similar commands @samp{set com2base}, @samp{set com3irq}, -etc.@: for setting the port address and the @code{IRQ} lines for the -other 3 COM ports. - -@kindex show com1base -@kindex show com1irq -@kindex show com2base -@kindex show com2irq -@kindex show com3base -@kindex show com3irq -@kindex show com4base -@kindex show com4irq -The related commands @samp{show com1base}, @samp{show com1irq} etc.@: -display the current settings of the base address and the @code{IRQ} -lines used by the COM ports. - -@item info serial -@kindex info serial -@cindex DOS serial port status -This command prints the status of the 4 DOS serial ports. For each -port, it prints whether it's active or not, its I/O base address and -IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the -counts of various errors encountered so far. -@end table - - -@node Cygwin Native -@subsection Features for Debugging MS Windows PE Executables -@cindex MS Windows debugging -@cindex native Cygwin debugging -@cindex Cygwin-specific commands - -@value{GDBN} supports native debugging of MS Windows programs, including -DLLs with and without symbolic debugging information. - -@cindex Ctrl-BREAK, MS-Windows -@cindex interrupt debuggee on MS-Windows -MS-Windows programs that call @code{SetConsoleMode} to switch off the -special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted -by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows -supports @kbd{C-@key{BREAK}} as an alternative interrupt key -sequence, which can be used to interrupt the debuggee even if it -ignores @kbd{C-c}. - -There are various additional Cygwin-specific commands, described in -this section. Working with DLLs that have no debugging symbols is -described in @ref{Non-debug DLL Symbols}. - -@table @code -@kindex info w32 -@item info w32 -This is a prefix of MS Windows-specific commands which print -information about the target system and important OS structures. - -@item info w32 selector -This command displays information returned by -the Win32 API @code{GetThreadSelectorEntry} function. -It takes an optional argument that is evaluated to -a long value to give the information about this given selector. -Without argument, this command displays information -about the six segment registers. - -@item info w32 thread-information-block -This command displays thread specific information stored in the -Thread Information Block (readable on the X86 CPU family using @code{$fs} -selector for 32-bit programs and @code{$gs} for 64-bit programs). - -@kindex info dll -@item info dll -This is a Cygwin-specific alias of @code{info shared}. - -@kindex dll-symbols -@item dll-symbols -This command loads symbols from a dll similarly to -add-sym command but without the need to specify a base address. - -@kindex set cygwin-exceptions -@cindex debugging the Cygwin DLL -@cindex Cygwin DLL, debugging -@item set cygwin-exceptions @var{mode} -If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that -happen inside the Cygwin DLL. If @var{mode} is @code{off}, -@value{GDBN} will delay recognition of exceptions, and may ignore some -exceptions which seem to be caused by internal Cygwin DLL -``bookkeeping''. This option is meant primarily for debugging the -Cygwin DLL itself; the default value is @code{off} to avoid annoying -@value{GDBN} users with false @code{SIGSEGV} signals. - -@kindex show cygwin-exceptions -@item show cygwin-exceptions -Displays whether @value{GDBN} will break on exceptions that happen -inside the Cygwin DLL itself. - -@kindex set new-console -@item set new-console @var{mode} -If @var{mode} is @code{on} the debuggee will -be started in a new console on next start. -If @var{mode} is @code{off}, the debuggee will -be started in the same console as the debugger. - -@kindex show new-console -@item show new-console -Displays whether a new console is used -when the debuggee is started. - -@kindex set new-group -@item set new-group @var{mode} -This boolean value controls whether the debuggee should -start a new group or stay in the same group as the debugger. -This affects the way the Windows OS handles -@samp{Ctrl-C}. - -@kindex show new-group -@item show new-group -Displays current value of new-group boolean. - -@kindex set debugevents -@item set debugevents -This boolean value adds debug output concerning kernel events related -to the debuggee seen by the debugger. This includes events that -signal thread and process creation and exit, DLL loading and -unloading, console interrupts, and debugging messages produced by the -Windows @code{OutputDebugString} API call. - -@kindex set debugexec -@item set debugexec -This boolean value adds debug output concerning execute events -(such as resume thread) seen by the debugger. - -@kindex set debugexceptions -@item set debugexceptions -This boolean value adds debug output concerning exceptions in the -debuggee seen by the debugger. - -@kindex set debugmemory -@item set debugmemory -This boolean value adds debug output concerning debuggee memory reads -and writes by the debugger. - -@kindex set shell -@item set shell -This boolean values specifies whether the debuggee is called -via a shell or directly (default value is on). - -@kindex show shell -@item show shell -Displays if the debuggee will be started with a shell. - -@end table - -@menu -* Non-debug DLL Symbols:: Support for DLLs without debugging symbols -@end menu - -@node Non-debug DLL Symbols -@subsubsection Support for DLLs without Debugging Symbols -@cindex DLLs with no debugging symbols -@cindex Minimal symbols and DLLs - -Very often on windows, some of the DLLs that your program relies on do -not include symbolic debugging information (for example, -@file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging -symbols in a DLL, it relies on the minimal amount of symbolic -information contained in the DLL's export table. This section -describes working with such symbols, known internally to @value{GDBN} as -``minimal symbols''. - -Note that before the debugged program has started execution, no DLLs -will have been loaded. The easiest way around this problem is simply to -start the program --- either by setting a breakpoint or letting the -program run once to completion. It is also possible to force -@value{GDBN} to load a particular DLL before starting the executable --- -see the shared library information in @ref{Files}, or the -@code{dll-symbols} command in @ref{Cygwin Native}. Currently, -explicitly loading symbols from a DLL with no debugging information will -cause the symbol names to be duplicated in @value{GDBN}'s lookup table, -which may adversely affect symbol lookup performance. - -@subsubsection DLL Name Prefixes - -In keeping with the naming conventions used by the Microsoft debugging -tools, DLL export symbols are made available with a prefix based on the -DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is -also entered into the symbol table, so @code{CreateFileA} is often -sufficient. In some cases there will be name clashes within a program -(particularly if the executable itself includes full debugging symbols) -necessitating the use of the fully qualified name when referring to the -contents of the DLL. Use single-quotes around the name to avoid the -exclamation mark (``!'') being interpreted as a language operator. - -Note that the internal name of the DLL may be all upper-case, even -though the file name of the DLL is lower-case, or vice-versa. Since -symbols within @value{GDBN} are @emph{case-sensitive} this may cause -some confusion. If in doubt, try the @code{info functions} and -@code{info variables} commands or even @code{maint print msymbols} -(@pxref{Symbols}). Here's an example: - -@smallexample -(@value{GDBP}) info function CreateFileA -All functions matching regular expression "CreateFileA": - -Non-debugging symbols: -0x77e885f4 CreateFileA -0x77e885f4 KERNEL32!CreateFileA -@end smallexample - -@smallexample -(@value{GDBP}) info function ! -All functions matching regular expression "!": - -Non-debugging symbols: -0x6100114c cygwin1!__assert -0x61004034 cygwin1!_dll_crt0@@0 -0x61004240 cygwin1!dll_crt0(per_process *) -[etc...] -@end smallexample - -@subsubsection Working with Minimal Symbols - -Symbols extracted from a DLL's export table do not contain very much -type information. All that @value{GDBN} can do is guess whether a symbol -refers to a function or variable depending on the linker section that -contains the symbol. Also note that the actual contents of the memory -contained in a DLL are not available unless the program is running. This -means that you cannot examine the contents of a variable or disassemble -a function within a DLL without a running program. - -Variables are generally treated as pointers and dereferenced -automatically. For this reason, it is often necessary to prefix a -variable name with the address-of operator (``&'') and provide explicit -type information in the command. Here's an example of the type of -problem: - -@smallexample -(@value{GDBP}) print 'cygwin1!__argv' -$1 = 268572168 -@end smallexample - -@smallexample -(@value{GDBP}) x 'cygwin1!__argv' -0x10021610: "\230y\"" -@end smallexample - -And two possible solutions: - -@smallexample -(@value{GDBP}) print ((char **)'cygwin1!__argv')[0] -$2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram" -@end smallexample - -@smallexample -(@value{GDBP}) x/2x &'cygwin1!__argv' -0x610c0aa8 : 0x10021608 0x00000000 -(@value{GDBP}) x/x 0x10021608 -0x10021608: 0x0022fd98 -(@value{GDBP}) x/s 0x0022fd98 -0x22fd98: "/cygdrive/c/mydirectory/myprogram" -@end smallexample - -Setting a break point within a DLL is possible even before the program -starts execution. However, under these circumstances, @value{GDBN} can't -examine the initial instructions of the function in order to skip the -function's frame set-up code. You can work around this by using ``*&'' -to set the breakpoint at a raw memory address: - -@smallexample -(@value{GDBP}) break *&'python22!PyOS_Readline' -Breakpoint 1 at 0x1e04eff0 -@end smallexample - -The author of these extensions is not entirely convinced that setting a -break point within a shared DLL like @file{kernel32.dll} is completely -safe. - -@node Hurd Native -@subsection Commands Specific to @sc{gnu} Hurd Systems -@cindex @sc{gnu} Hurd debugging - -This subsection describes @value{GDBN} commands specific to the -@sc{gnu} Hurd native debugging. - -@table @code -@item set signals -@itemx set sigs -@kindex set signals@r{, Hurd command} -@kindex set sigs@r{, Hurd command} -This command toggles the state of inferior signal interception by -@value{GDBN}. Mach exceptions, such as breakpoint traps, are not -affected by this command. @code{sigs} is a shorthand alias for -@code{signals}. - -@item show signals -@itemx show sigs -@kindex show signals@r{, Hurd command} -@kindex show sigs@r{, Hurd command} -Show the current state of intercepting inferior's signals. - -@item set signal-thread -@itemx set sigthread -@kindex set signal-thread -@kindex set sigthread -This command tells @value{GDBN} which thread is the @code{libc} signal -thread. That thread is run when a signal is delivered to a running -process. @code{set sigthread} is the shorthand alias of @code{set -signal-thread}. - -@item show signal-thread -@itemx show sigthread -@kindex show signal-thread -@kindex show sigthread -These two commands show which thread will run when the inferior is -delivered a signal. - -@item set stopped -@kindex set stopped@r{, Hurd command} -This commands tells @value{GDBN} that the inferior process is stopped, -as with the @code{SIGSTOP} signal. The stopped process can be -continued by delivering a signal to it. - -@item show stopped -@kindex show stopped@r{, Hurd command} -This command shows whether @value{GDBN} thinks the debuggee is -stopped. - -@item set exceptions -@kindex set exceptions@r{, Hurd command} -Use this command to turn off trapping of exceptions in the inferior. -When exception trapping is off, neither breakpoints nor -single-stepping will work. To restore the default, set exception -trapping on. - -@item show exceptions -@kindex show exceptions@r{, Hurd command} -Show the current state of trapping exceptions in the inferior. - -@item set task pause -@kindex set task@r{, Hurd commands} -@cindex task attributes (@sc{gnu} Hurd) -@cindex pause current task (@sc{gnu} Hurd) -This command toggles task suspension when @value{GDBN} has control. -Setting it to on takes effect immediately, and the task is suspended -whenever @value{GDBN} gets control. Setting it to off will take -effect the next time the inferior is continued. If this option is set -to off, you can use @code{set thread default pause on} or @code{set -thread pause on} (see below) to pause individual threads. - -@item show task pause -@kindex show task@r{, Hurd commands} -Show the current state of task suspension. - -@item set task detach-suspend-count -@cindex task suspend count -@cindex detach from task, @sc{gnu} Hurd -This command sets the suspend count the task will be left with when -@value{GDBN} detaches from it. - -@item show task detach-suspend-count -Show the suspend count the task will be left with when detaching. - -@item set task exception-port -@itemx set task excp -@cindex task exception port, @sc{gnu} Hurd -This command sets the task exception port to which @value{GDBN} will -forward exceptions. The argument should be the value of the @dfn{send -rights} of the task. @code{set task excp} is a shorthand alias. - -@item set noninvasive -@cindex noninvasive task options -This command switches @value{GDBN} to a mode that is the least -invasive as far as interfering with the inferior is concerned. This -is the same as using @code{set task pause}, @code{set exceptions}, and -@code{set signals} to values opposite to the defaults. - -@item info send-rights -@itemx info receive-rights -@itemx info port-rights -@itemx info port-sets -@itemx info dead-names -@itemx info ports -@itemx info psets -@cindex send rights, @sc{gnu} Hurd -@cindex receive rights, @sc{gnu} Hurd -@cindex port rights, @sc{gnu} Hurd -@cindex port sets, @sc{gnu} Hurd -@cindex dead names, @sc{gnu} Hurd -These commands display information about, respectively, send rights, -receive rights, port rights, port sets, and dead names of a task. -There are also shorthand aliases: @code{info ports} for @code{info -port-rights} and @code{info psets} for @code{info port-sets}. - -@item set thread pause -@kindex set thread@r{, Hurd command} -@cindex thread properties, @sc{gnu} Hurd -@cindex pause current thread (@sc{gnu} Hurd) -This command toggles current thread suspension when @value{GDBN} has -control. Setting it to on takes effect immediately, and the current -thread is suspended whenever @value{GDBN} gets control. Setting it to -off will take effect the next time the inferior is continued. -Normally, this command has no effect, since when @value{GDBN} has -control, the whole task is suspended. However, if you used @code{set -task pause off} (see above), this command comes in handy to suspend -only the current thread. - -@item show thread pause -@kindex show thread@r{, Hurd command} -This command shows the state of current thread suspension. - -@item set thread run -This command sets whether the current thread is allowed to run. - -@item show thread run -Show whether the current thread is allowed to run. - -@item set thread detach-suspend-count -@cindex thread suspend count, @sc{gnu} Hurd -@cindex detach from thread, @sc{gnu} Hurd -This command sets the suspend count @value{GDBN} will leave on a -thread when detaching. This number is relative to the suspend count -found by @value{GDBN} when it notices the thread; use @code{set thread -takeover-suspend-count} to force it to an absolute value. - -@item show thread detach-suspend-count -Show the suspend count @value{GDBN} will leave on the thread when -detaching. - -@item set thread exception-port -@itemx set thread excp -Set the thread exception port to which to forward exceptions. This -overrides the port set by @code{set task exception-port} (see above). -@code{set thread excp} is the shorthand alias. - -@item set thread takeover-suspend-count -Normally, @value{GDBN}'s thread suspend counts are relative to the -value @value{GDBN} finds when it notices each thread. This command -changes the suspend counts to be absolute instead. - -@item set thread default -@itemx show thread default -@cindex thread default settings, @sc{gnu} Hurd -Each of the above @code{set thread} commands has a @code{set thread -default} counterpart (e.g., @code{set thread default pause}, @code{set -thread default exception-port}, etc.). The @code{thread default} -variety of commands sets the default thread properties for all -threads; you can then change the properties of individual threads with -the non-default commands. -@end table - -@node Darwin -@subsection Darwin -@cindex Darwin - -@value{GDBN} provides the following commands specific to the Darwin target: - -@table @code -@item set debug darwin @var{num} -@kindex set debug darwin -When set to a non zero value, enables debugging messages specific to -the Darwin support. Higher values produce more verbose output. - -@item show debug darwin -@kindex show debug darwin -Show the current state of Darwin messages. - -@item set debug mach-o @var{num} -@kindex set debug mach-o -When set to a non zero value, enables debugging messages while -@value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the -file format used on Darwin for object and executable files.) Higher -values produce more verbose output. This is a command to diagnose -problems internal to @value{GDBN} and should not be needed in normal -usage. - -@item show debug mach-o -@kindex show debug mach-o -Show the current state of Mach-O file messages. - -@item set mach-exceptions on -@itemx set mach-exceptions off -@kindex set mach-exceptions -On Darwin, faults are first reported as a Mach exception and are then -mapped to a Posix signal. Use this command to turn on trapping of -Mach exceptions in the inferior. This might be sometimes useful to -better understand the cause of a fault. The default is off. - -@item show mach-exceptions -@kindex show mach-exceptions -Show the current state of exceptions trapping. -@end table - - -@node Embedded OS -@section Embedded Operating Systems - -This section describes configurations involving the debugging of -embedded operating systems that are available for several different -architectures. - -@menu -* VxWorks:: Using @value{GDBN} with VxWorks -@end menu - -@value{GDBN} includes the ability to debug programs running on -various real-time operating systems. - -@node VxWorks -@subsection Using @value{GDBN} with VxWorks - -@cindex VxWorks - -@table @code - -@kindex target vxworks -@item target vxworks @var{machinename} -A VxWorks system, attached via TCP/IP. The argument @var{machinename} -is the target system's machine name or IP address. - -@end table - -On VxWorks, @code{load} links @var{filename} dynamically on the -current target system as well as adding its symbols in @value{GDBN}. - -@value{GDBN} enables developers to spawn and debug tasks running on networked -VxWorks targets from a Unix host. Already-running tasks spawned from -the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on -both the Unix host and on the VxWorks target. The program -@code{@value{GDBP}} is installed and executed on the Unix host. (It may be -installed with the name @code{vxgdb}, to distinguish it from a -@value{GDBN} for debugging programs on the host itself.) - -@table @code -@item VxWorks-timeout @var{args} -@kindex vxworks-timeout -All VxWorks-based targets now support the option @code{vxworks-timeout}. -This option is set by the user, and @var{args} represents the number of -seconds @value{GDBN} waits for responses to rpc's. You might use this if -your VxWorks target is a slow software simulator or is on the far side -of a thin network line. -@end table - -The following information on connecting to VxWorks was current when -this manual was produced; newer releases of VxWorks may use revised -procedures. - -@findex INCLUDE_RDB -To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel -to include the remote debugging interface routines in the VxWorks -library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the -VxWorks configuration file @file{configAll.h} and rebuild your VxWorks -kernel. The resulting kernel contains @file{rdb.a}, and spawns the -source debugging task @code{tRdbTask} when VxWorks is booted. For more -information on configuring and remaking VxWorks, see the manufacturer's -manual. -@c VxWorks, see the @cite{VxWorks Programmer's Guide}. - -Once you have included @file{rdb.a} in your VxWorks system image and set -your Unix execution search path to find @value{GDBN}, you are ready to -run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or -@code{vxgdb}, depending on your installation). - -@value{GDBN} comes up showing the prompt: - -@smallexample -(vxgdb) -@end smallexample - -@menu -* VxWorks Connection:: Connecting to VxWorks -* VxWorks Download:: VxWorks download -* VxWorks Attach:: Running tasks -@end menu - -@node VxWorks Connection -@subsubsection Connecting to VxWorks - -The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the -network. To connect to a target whose host name is ``@code{tt}'', type: - -@smallexample -(vxgdb) target vxworks tt -@end smallexample - -@need 750 -@value{GDBN} displays messages like these: - -@smallexample -Attaching remote machine across net... -Connected to tt. -@end smallexample - -@need 1000 -@value{GDBN} then attempts to read the symbol tables of any object modules -loaded into the VxWorks target since it was last booted. @value{GDBN} locates -these files by searching the directories listed in the command search -path (@pxref{Environment, ,Your Program's Environment}); if it fails -to find an object file, it displays a message such as: - -@smallexample -prog.o: No such file or directory. -@end smallexample - -When this happens, add the appropriate directory to the search path with -the @value{GDBN} command @code{path}, and execute the @code{target} -command again. - -@node VxWorks Download -@subsubsection VxWorks Download - -@cindex download to VxWorks -If you have connected to the VxWorks target and you want to debug an -object that has not yet been loaded, you can use the @value{GDBN} -@code{load} command to download a file from Unix to VxWorks -incrementally. The object file given as an argument to the @code{load} -command is actually opened twice: first by the VxWorks target in order -to download the code, then by @value{GDBN} in order to read the symbol -table. This can lead to problems if the current working directories on -the two systems differ. If both systems have NFS mounted the same -filesystems, you can avoid these problems by using absolute paths. -Otherwise, it is simplest to set the working directory on both systems -to the directory in which the object file resides, and then to reference -the file by its name, without any path. For instance, a program -@file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks -and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this -program, type this on VxWorks: - -@smallexample --> cd "@var{vxpath}/vw/demo/rdb" -@end smallexample - -@noindent -Then, in @value{GDBN}, type: - -@smallexample -(vxgdb) cd @var{hostpath}/vw/demo/rdb -(vxgdb) load prog.o -@end smallexample - -@value{GDBN} displays a response similar to this: - -@smallexample -Reading symbol data from wherever/vw/demo/rdb/prog.o... done. -@end smallexample - -You can also use the @code{load} command to reload an object module -after editing and recompiling the corresponding source file. Note that -this makes @value{GDBN} delete all currently-defined breakpoints, -auto-displays, and convenience variables, and to clear the value -history. (This is necessary in order to preserve the integrity of -debugger's data structures that reference the target system's symbol -table.) - -@node VxWorks Attach -@subsubsection Running Tasks - -@cindex running VxWorks tasks -You can also attach to an existing task using the @code{attach} command as -follows: - -@smallexample -(vxgdb) attach @var{task} -@end smallexample - -@noindent -where @var{task} is the VxWorks hexadecimal task ID. The task can be running -or suspended when you attach to it. Running tasks are suspended at -the time of attachment. - -@node Embedded Processors -@section Embedded Processors - -This section goes into details specific to particular embedded -configurations. - -@cindex send command to simulator -Whenever a specific embedded processor has a simulator, @value{GDBN} -allows to send an arbitrary command to the simulator. - -@table @code -@item sim @var{command} -@kindex sim@r{, a command} -Send an arbitrary @var{command} string to the simulator. Consult the -documentation for the specific simulator in use for information about -acceptable commands. -@end table - - -@menu -* ARM:: ARM RDI -* M32R/D:: Renesas M32R/D -* M68K:: Motorola M68K -* MicroBlaze:: Xilinx MicroBlaze -* MIPS Embedded:: MIPS Embedded -* OpenRISC 1000:: OpenRisc 1000 -* PowerPC Embedded:: PowerPC Embedded -* PA:: HP PA Embedded -* Sparclet:: Tsqware Sparclet -* Sparclite:: Fujitsu Sparclite -* Z8000:: Zilog Z8000 -* AVR:: Atmel AVR -* CRIS:: CRIS -* Super-H:: Renesas Super-H -@end menu - -@node ARM -@subsection ARM -@cindex ARM RDI - -@table @code -@kindex target rdi -@item target rdi @var{dev} -ARM Angel monitor, via RDI library interface to ADP protocol. You may -use this target to communicate with both boards running the Angel -monitor, or with the EmbeddedICE JTAG debug device. - -@kindex target rdp -@item target rdp @var{dev} -ARM Demon monitor. - -@end table - -@value{GDBN} provides the following ARM-specific commands: - -@table @code -@item set arm disassembler -@kindex set arm -This commands selects from a list of disassembly styles. The -@code{"std"} style is the standard style. - -@item show arm disassembler -@kindex show arm -Show the current disassembly style. - -@item set arm apcs32 -@cindex ARM 32-bit mode -This command toggles ARM operation mode between 32-bit and 26-bit. - -@item show arm apcs32 -Display the current usage of the ARM 32-bit mode. - -@item set arm fpu @var{fputype} -This command sets the ARM floating-point unit (FPU) type. The -argument @var{fputype} can be one of these: - -@table @code -@item auto -Determine the FPU type by querying the OS ABI. -@item softfpa -Software FPU, with mixed-endian doubles on little-endian ARM -processors. -@item fpa -GCC-compiled FPA co-processor. -@item softvfp -Software FPU with pure-endian doubles. -@item vfp -VFP co-processor. -@end table - -@item show arm fpu -Show the current type of the FPU. - -@item set arm abi -This command forces @value{GDBN} to use the specified ABI. - -@item show arm abi -Show the currently used ABI. - -@item set arm fallback-mode (arm|thumb|auto) -@value{GDBN} uses the symbol table, when available, to determine -whether instructions are ARM or Thumb. This command controls -@value{GDBN}'s default behavior when the symbol table is not -available. The default is @samp{auto}, which causes @value{GDBN} to -use the current execution mode (from the @code{T} bit in the @code{CPSR} -register). - -@item show arm fallback-mode -Show the current fallback instruction mode. - -@item set arm force-mode (arm|thumb|auto) -This command overrides use of the symbol table to determine whether -instructions are ARM or Thumb. The default is @samp{auto}, which -causes @value{GDBN} to use the symbol table and then the setting -of @samp{set arm fallback-mode}. - -@item show arm force-mode -Show the current forced instruction mode. - -@item set debug arm -Toggle whether to display ARM-specific debugging messages from the ARM -target support subsystem. - -@item show debug arm -Show whether ARM-specific debugging messages are enabled. -@end table - -The following commands are available when an ARM target is debugged -using the RDI interface: - -@table @code -@item rdilogfile @r{[}@var{file}@r{]} -@kindex rdilogfile -@cindex ADP (Angel Debugger Protocol) logging -Set the filename for the ADP (Angel Debugger Protocol) packet log. -With an argument, sets the log file to the specified @var{file}. With -no argument, show the current log file name. The default log file is -@file{rdi.log}. - -@item rdilogenable @r{[}@var{arg}@r{]} -@kindex rdilogenable -Control logging of ADP packets. With an argument of 1 or @code{"yes"} -enables logging, with an argument 0 or @code{"no"} disables it. With -no arguments displays the current setting. When logging is enabled, -ADP packets exchanged between @value{GDBN} and the RDI target device -are logged to a file. - -@item set rdiromatzero -@kindex set rdiromatzero -@cindex ROM at zero address, RDI -Tell @value{GDBN} whether the target has ROM at address 0. If on, -vector catching is disabled, so that zero address can be used. If off -(the default), vector catching is enabled. For this command to take -effect, it needs to be invoked prior to the @code{target rdi} command. - -@item show rdiromatzero -@kindex show rdiromatzero -Show the current setting of ROM at zero address. - -@item set rdiheartbeat -@kindex set rdiheartbeat -@cindex RDI heartbeat -Enable or disable RDI heartbeat packets. It is not recommended to -turn on this option, since it confuses ARM and EPI JTAG interface, as -well as the Angel monitor. - -@item show rdiheartbeat -@kindex show rdiheartbeat -Show the setting of RDI heartbeat packets. -@end table - -@table @code -@item target sim @r{[}@var{simargs}@r{]} @dots{} -The @value{GDBN} ARM simulator accepts the following optional arguments. - -@table @code -@item --swi-support=@var{type} -Tell the simulator which SWI interfaces to support. -@var{type} may be a comma separated list of the following values. -The default value is @code{all}. - -@table @code -@item none -@item demon -@item angel -@item redboot -@item all -@end table -@end table -@end table - -@node M32R/D -@subsection Renesas M32R/D and M32R/SDI - -@table @code -@kindex target m32r -@item target m32r @var{dev} -Renesas M32R/D ROM monitor. - -@kindex target m32rsdi -@item target m32rsdi @var{dev} -Renesas M32R SDI server, connected via parallel port to the board. -@end table - -The following @value{GDBN} commands are specific to the M32R monitor: - -@table @code -@item set download-path @var{path} -@kindex set download-path -@cindex find downloadable @sc{srec} files (M32R) -Set the default path for finding downloadable @sc{srec} files. - -@item show download-path -@kindex show download-path -Show the default path for downloadable @sc{srec} files. - -@item set board-address @var{addr} -@kindex set board-address -@cindex M32-EVA target board address -Set the IP address for the M32R-EVA target board. - -@item show board-address -@kindex show board-address -Show the current IP address of the target board. - -@item set server-address @var{addr} -@kindex set server-address -@cindex download server address (M32R) -Set the IP address for the download server, which is the @value{GDBN}'s -host machine. - -@item show server-address -@kindex show server-address -Display the IP address of the download server. - -@item upload @r{[}@var{file}@r{]} -@kindex upload@r{, M32R} -Upload the specified @sc{srec} @var{file} via the monitor's Ethernet -upload capability. If no @var{file} argument is given, the current -executable file is uploaded. - -@item tload @r{[}@var{file}@r{]} -@kindex tload@r{, M32R} -Test the @code{upload} command. -@end table - -The following commands are available for M32R/SDI: - -@table @code -@item sdireset -@kindex sdireset -@cindex reset SDI connection, M32R -This command resets the SDI connection. - -@item sdistatus -@kindex sdistatus -This command shows the SDI connection status. - -@item debug_chaos -@kindex debug_chaos -@cindex M32R/Chaos debugging -Instructs the remote that M32R/Chaos debugging is to be used. - -@item use_debug_dma -@kindex use_debug_dma -Instructs the remote to use the DEBUG_DMA method of accessing memory. - -@item use_mon_code -@kindex use_mon_code -Instructs the remote to use the MON_CODE method of accessing memory. - -@item use_ib_break -@kindex use_ib_break -Instructs the remote to set breakpoints by IB break. - -@item use_dbt_break -@kindex use_dbt_break -Instructs the remote to set breakpoints by DBT. -@end table - -@node M68K -@subsection M68k - -The Motorola m68k configuration includes ColdFire support, and a -target command for the following ROM monitor. - -@table @code - -@kindex target dbug -@item target dbug @var{dev} -dBUG ROM monitor for Motorola ColdFire. - -@end table - -@node MicroBlaze -@subsection MicroBlaze -@cindex Xilinx MicroBlaze -@cindex XMD, Xilinx Microprocessor Debugger - -The MicroBlaze is a soft-core processor supported on various Xilinx -FPGAs, such as Spartan or Virtex series. Boards with these processors -usually have JTAG ports which connect to a host system running the Xilinx -Embedded Development Kit (EDK) or Software Development Kit (SDK). -This host system is used to download the configuration bitstream to -the target FPGA. The Xilinx Microprocessor Debugger (XMD) program -communicates with the target board using the JTAG interface and -presents a @code{gdbserver} interface to the board. By default -@code{xmd} uses port @code{1234}. (While it is possible to change -this default port, it requires the use of undocumented @code{xmd} -commands. Contact Xilinx support if you need to do this.) - -Use these GDB commands to connect to the MicroBlaze target processor. - -@table @code -@item target remote :1234 -Use this command to connect to the target if you are running @value{GDBN} -on the same system as @code{xmd}. - -@item target remote @var{xmd-host}:1234 -Use this command to connect to the target if it is connected to @code{xmd} -running on a different system named @var{xmd-host}. - -@item load -Use this command to download a program to the MicroBlaze target. - -@item set debug microblaze @var{n} -Enable MicroBlaze-specific debugging messages if non-zero. - -@item show debug microblaze @var{n} -Show MicroBlaze-specific debugging level. -@end table - -@node MIPS Embedded -@subsection @acronym{MIPS} Embedded - -@cindex @acronym{MIPS} boards -@value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a -@acronym{MIPS} board attached to a serial line. This is available when -you configure @value{GDBN} with @samp{--target=mips-elf}. - -@need 1000 -Use these @value{GDBN} commands to specify the connection to your target board: - -@table @code -@item target mips @var{port} -@kindex target mips @var{port} -To run a program on the board, start up @code{@value{GDBP}} with the -name of your program as the argument. To connect to the board, use the -command @samp{target mips @var{port}}, where @var{port} is the name of -the serial port connected to the board. If the program has not already -been downloaded to the board, you may use the @code{load} command to -download it. You can then use all the usual @value{GDBN} commands. - -For example, this sequence connects to the target board through a serial -port, and loads and runs a program called @var{prog} through the -debugger: - -@smallexample -host$ @value{GDBP} @var{prog} -@value{GDBN} is free software and @dots{} -(@value{GDBP}) target mips /dev/ttyb -(@value{GDBP}) load @var{prog} -(@value{GDBP}) run -@end smallexample - -@item target mips @var{hostname}:@var{portnumber} -On some @value{GDBN} host configurations, you can specify a TCP -connection (for instance, to a serial line managed by a terminal -concentrator) instead of a serial port, using the syntax -@samp{@var{hostname}:@var{portnumber}}. - -@item target pmon @var{port} -@kindex target pmon @var{port} -PMON ROM monitor. - -@item target ddb @var{port} -@kindex target ddb @var{port} -NEC's DDB variant of PMON for Vr4300. - -@item target lsi @var{port} -@kindex target lsi @var{port} -LSI variant of PMON. - -@kindex target r3900 -@item target r3900 @var{dev} -Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips. - -@kindex target array -@item target array @var{dev} -Array Tech LSI33K RAID controller board. - -@end table - - -@noindent -@value{GDBN} also supports these special commands for @acronym{MIPS} targets: - -@table @code -@item set mipsfpu double -@itemx set mipsfpu single -@itemx set mipsfpu none -@itemx set mipsfpu auto -@itemx show mipsfpu -@kindex set mipsfpu -@kindex show mipsfpu -@cindex @acronym{MIPS} remote floating point -@cindex floating point, @acronym{MIPS} remote -If your target board does not support the @acronym{MIPS} floating point -coprocessor, you should use the command @samp{set mipsfpu none} (if you -need this, you may wish to put the command in your @value{GDBN} init -file). This tells @value{GDBN} how to find the return value of -functions which return floating point values. It also allows -@value{GDBN} to avoid saving the floating point registers when calling -functions on the board. If you are using a floating point coprocessor -with only single precision floating point support, as on the @sc{r4650} -processor, use the command @samp{set mipsfpu single}. The default -double precision floating point coprocessor may be selected using -@samp{set mipsfpu double}. - -In previous versions the only choices were double precision or no -floating point, so @samp{set mipsfpu on} will select double precision -and @samp{set mipsfpu off} will select no floating point. - -As usual, you can inquire about the @code{mipsfpu} variable with -@samp{show mipsfpu}. - -@item set timeout @var{seconds} -@itemx set retransmit-timeout @var{seconds} -@itemx show timeout -@itemx show retransmit-timeout -@cindex @code{timeout}, @acronym{MIPS} protocol -@cindex @code{retransmit-timeout}, @acronym{MIPS} protocol -@kindex set timeout -@kindex show timeout -@kindex set retransmit-timeout -@kindex show retransmit-timeout -You can control the timeout used while waiting for a packet, in the @acronym{MIPS} -remote protocol, with the @code{set timeout @var{seconds}} command. The -default is 5 seconds. Similarly, you can control the timeout used while -waiting for an acknowledgment of a packet with the @code{set -retransmit-timeout @var{seconds}} command. The default is 3 seconds. -You can inspect both values with @code{show timeout} and @code{show -retransmit-timeout}. (These commands are @emph{only} available when -@value{GDBN} is configured for @samp{--target=mips-elf}.) - -The timeout set by @code{set timeout} does not apply when @value{GDBN} -is waiting for your program to stop. In that case, @value{GDBN} waits -forever because it has no way of knowing how long the program is going -to run before stopping. - -@item set syn-garbage-limit @var{num} -@kindex set syn-garbage-limit@r{, @acronym{MIPS} remote} -@cindex synchronize with remote @acronym{MIPS} target -Limit the maximum number of characters @value{GDBN} should ignore when -it tries to synchronize with the remote target. The default is 10 -characters. Setting the limit to -1 means there's no limit. - -@item show syn-garbage-limit -@kindex show syn-garbage-limit@r{, @acronym{MIPS} remote} -Show the current limit on the number of characters to ignore when -trying to synchronize with the remote system. - -@item set monitor-prompt @var{prompt} -@kindex set monitor-prompt@r{, @acronym{MIPS} remote} -@cindex remote monitor prompt -Tell @value{GDBN} to expect the specified @var{prompt} string from the -remote monitor. The default depends on the target: -@table @asis -@item pmon target -@samp{PMON} -@item ddb target -@samp{NEC010} -@item lsi target -@samp{PMON>} -@end table - -@item show monitor-prompt -@kindex show monitor-prompt@r{, @acronym{MIPS} remote} -Show the current strings @value{GDBN} expects as the prompt from the -remote monitor. - -@item set monitor-warnings -@kindex set monitor-warnings@r{, @acronym{MIPS} remote} -Enable or disable monitor warnings about hardware breakpoints. This -has effect only for the @code{lsi} target. When on, @value{GDBN} will -display warning messages whose codes are returned by the @code{lsi} -PMON monitor for breakpoint commands. - -@item show monitor-warnings -@kindex show monitor-warnings@r{, @acronym{MIPS} remote} -Show the current setting of printing monitor warnings. - -@item pmon @var{command} -@kindex pmon@r{, @acronym{MIPS} remote} -@cindex send PMON command -This command allows sending an arbitrary @var{command} string to the -monitor. The monitor must be in debug mode for this to work. -@end table - -@node OpenRISC 1000 -@subsection OpenRISC 1000 -@cindex OpenRISC 1000 - -@cindex or1k boards -See OR1k Architecture document (@uref{www.opencores.org}) for more information -about platform and commands. - -@table @code - -@kindex target jtag -@item target jtag jtag://@var{host}:@var{port} - -Connects to remote JTAG server. -JTAG remote server can be either an or1ksim or JTAG server, -connected via parallel port to the board. - -Example: @code{target jtag jtag://localhost:9999} - -@kindex or1ksim -@item or1ksim @var{command} -If connected to @code{or1ksim} OpenRISC 1000 Architectural -Simulator, proprietary commands can be executed. - -@kindex info or1k spr -@item info or1k spr -Displays spr groups. - -@item info or1k spr @var{group} -@itemx info or1k spr @var{groupno} -Displays register names in selected group. - -@item info or1k spr @var{group} @var{register} -@itemx info or1k spr @var{register} -@itemx info or1k spr @var{groupno} @var{registerno} -@itemx info or1k spr @var{registerno} -Shows information about specified spr register. - -@kindex spr -@item spr @var{group} @var{register} @var{value} -@itemx spr @var{register @var{value}} -@itemx spr @var{groupno} @var{registerno @var{value}} -@itemx spr @var{registerno @var{value}} -Writes @var{value} to specified spr register. -@end table - -Some implementations of OpenRISC 1000 Architecture also have hardware trace. -It is very similar to @value{GDBN} trace, except it does not interfere with normal -program execution and is thus much faster. Hardware breakpoints/watchpoint -triggers can be set using: -@table @code -@item $LEA/$LDATA -Load effective address/data -@item $SEA/$SDATA -Store effective address/data -@item $AEA/$ADATA -Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA) -@item $FETCH -Fetch data -@end table - -When triggered, it can capture low level data, like: @code{PC}, @code{LSEA}, -@code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}. - -@code{htrace} commands: -@cindex OpenRISC 1000 htrace -@table @code -@kindex hwatch -@item hwatch @var{conditional} -Set hardware watchpoint on combination of Load/Store Effective Address(es) -or Data. For example: - -@code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)} - -@code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)} - -@kindex htrace -@item htrace info -Display information about current HW trace configuration. - -@item htrace trigger @var{conditional} -Set starting criteria for HW trace. - -@item htrace qualifier @var{conditional} -Set acquisition qualifier for HW trace. - -@item htrace stop @var{conditional} -Set HW trace stopping criteria. - -@item htrace record [@var{data}]* -Selects the data to be recorded, when qualifier is met and HW trace was -triggered. - -@item htrace enable -@itemx htrace disable -Enables/disables the HW trace. - -@item htrace rewind [@var{filename}] -Clears currently recorded trace data. - -If filename is specified, new trace file is made and any newly collected data -will be written there. - -@item htrace print [@var{start} [@var{len}]] -Prints trace buffer, using current record configuration. - -@item htrace mode continuous -Set continuous trace mode. - -@item htrace mode suspend -Set suspend trace mode. - -@end table - -@node PowerPC Embedded -@subsection PowerPC Embedded - -@cindex DVC register -@value{GDBN} supports using the DVC (Data Value Compare) register to -implement in hardware simple hardware watchpoint conditions of the form: - -@smallexample -(@value{GDBP}) watch @var{ADDRESS|VARIABLE} \ - if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION} -@end smallexample - -The DVC register will be automatically used when @value{GDBN} detects -such pattern in a condition expression, and the created watchpoint uses one -debug register (either the @code{exact-watchpoints} option is on and the -variable is scalar, or the variable has a length of one byte). This feature -is available in native @value{GDBN} running on a Linux kernel version 2.6.34 -or newer. - -When running on PowerPC embedded processors, @value{GDBN} automatically uses -ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on, -in which case watchpoints using only one debug register are created when -watching variables of scalar types. - -You can create an artificial array to watch an arbitrary memory -region using one of the following commands (@pxref{Expressions}): - -@smallexample -(@value{GDBP}) watch *((char *) @var{address})@@@var{length} -(@value{GDBP}) watch @{char[@var{length}]@} @var{address} -@end smallexample - -PowerPC embedded processors support masked watchpoints. See the discussion -about the @code{mask} argument in @ref{Set Watchpoints}. - -@cindex ranged breakpoint -PowerPC embedded processors support hardware accelerated -@dfn{ranged breakpoints}. A ranged breakpoint stops execution of -the inferior whenever it executes an instruction at any address within -the range it specifies. To set a ranged breakpoint in @value{GDBN}, -use the @code{break-range} command. - -@value{GDBN} provides the following PowerPC-specific commands: - -@table @code -@kindex break-range -@item break-range @var{start-location}, @var{end-location} -Set a breakpoint for an address range. -@var{start-location} and @var{end-location} can specify a function name, -a line number, an offset of lines from the current line or from the start -location, or an address of an instruction (see @ref{Specify Location}, -for a list of all the possible ways to specify a @var{location}.) -The breakpoint will stop execution of the inferior whenever it -executes an instruction at any address within the specified range, -(including @var{start-location} and @var{end-location}.) - -@kindex set powerpc -@item set powerpc soft-float -@itemx show powerpc soft-float -Force @value{GDBN} to use (or not use) a software floating point calling -convention. By default, @value{GDBN} selects the calling convention based -on the selected architecture and the provided executable file. - -@item set powerpc vector-abi -@itemx show powerpc vector-abi -Force @value{GDBN} to use the specified calling convention for vector -arguments and return values. The valid options are @samp{auto}; -@samp{generic}, to avoid vector registers even if they are present; -@samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE -registers. By default, @value{GDBN} selects the calling convention -based on the selected architecture and the provided executable file. - -@item set powerpc exact-watchpoints -@itemx show powerpc exact-watchpoints -Allow @value{GDBN} to use only one debug register when watching a variable -of scalar type, thus assuming that the variable is accessed through the -address of its first byte. - -@kindex target dink32 -@item target dink32 @var{dev} -DINK32 ROM monitor. - -@kindex target ppcbug -@item target ppcbug @var{dev} -@kindex target ppcbug1 -@item target ppcbug1 @var{dev} -PPCBUG ROM monitor for PowerPC. - -@kindex target sds -@item target sds @var{dev} -SDS monitor, running on a PowerPC board (such as Motorola's ADS). -@end table - -@cindex SDS protocol -The following commands specific to the SDS protocol are supported -by @value{GDBN}: - -@table @code -@item set sdstimeout @var{nsec} -@kindex set sdstimeout -Set the timeout for SDS protocol reads to be @var{nsec} seconds. The -default is 2 seconds. - -@item show sdstimeout -@kindex show sdstimeout -Show the current value of the SDS timeout. - -@item sds @var{command} -@kindex sds@r{, a command} -Send the specified @var{command} string to the SDS monitor. -@end table - - -@node PA -@subsection HP PA Embedded - -@table @code - -@kindex target op50n -@item target op50n @var{dev} -OP50N monitor, running on an OKI HPPA board. - -@kindex target w89k -@item target w89k @var{dev} -W89K monitor, running on a Winbond HPPA board. - -@end table - -@node Sparclet -@subsection Tsqware Sparclet - -@cindex Sparclet - -@value{GDBN} enables developers to debug tasks running on -Sparclet targets from a Unix host. -@value{GDBN} uses code that runs on -both the Unix host and on the Sparclet target. The program -@code{@value{GDBP}} is installed and executed on the Unix host. - -@table @code -@item remotetimeout @var{args} -@kindex remotetimeout -@value{GDBN} supports the option @code{remotetimeout}. -This option is set by the user, and @var{args} represents the number of -seconds @value{GDBN} waits for responses. -@end table - -@cindex compiling, on Sparclet -When compiling for debugging, include the options @samp{-g} to get debug -information and @samp{-Ttext} to relocate the program to where you wish to -load it on the target. You may also want to add the options @samp{-n} or -@samp{-N} in order to reduce the size of the sections. Example: - -@smallexample -sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N -@end smallexample - -You can use @code{objdump} to verify that the addresses are what you intended: - -@smallexample -sparclet-aout-objdump --headers --syms prog -@end smallexample - -@cindex running, on Sparclet -Once you have set -your Unix execution search path to find @value{GDBN}, you are ready to -run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} -(or @code{sparclet-aout-gdb}, depending on your installation). - -@value{GDBN} comes up showing the prompt: - -@smallexample -(gdbslet) -@end smallexample - -@menu -* Sparclet File:: Setting the file to debug -* Sparclet Connection:: Connecting to Sparclet -* Sparclet Download:: Sparclet download -* Sparclet Execution:: Running and debugging -@end menu - -@node Sparclet File -@subsubsection Setting File to Debug - -The @value{GDBN} command @code{file} lets you choose with program to debug. - -@smallexample -(gdbslet) file prog -@end smallexample - -@need 1000 -@value{GDBN} then attempts to read the symbol table of @file{prog}. -@value{GDBN} locates -the file by searching the directories listed in the command search -path. -If the file was compiled with debug information (option @samp{-g}), source -files will be searched as well. -@value{GDBN} locates -the source files by searching the directories listed in the directory search -path (@pxref{Environment, ,Your Program's Environment}). -If it fails -to find a file, it displays a message such as: - -@smallexample -prog: No such file or directory. -@end smallexample - -When this happens, add the appropriate directories to the search paths with -the @value{GDBN} commands @code{path} and @code{dir}, and execute the -@code{target} command again. - -@node Sparclet Connection -@subsubsection Connecting to Sparclet - -The @value{GDBN} command @code{target} lets you connect to a Sparclet target. -To connect to a target on serial port ``@code{ttya}'', type: - -@smallexample -(gdbslet) target sparclet /dev/ttya -Remote target sparclet connected to /dev/ttya -main () at ../prog.c:3 -@end smallexample - -@need 750 -@value{GDBN} displays messages like these: - -@smallexample -Connected to ttya. -@end smallexample - -@node Sparclet Download -@subsubsection Sparclet Download - -@cindex download to Sparclet -Once connected to the Sparclet target, -you can use the @value{GDBN} -@code{load} command to download the file from the host to the target. -The file name and load offset should be given as arguments to the @code{load} -command. -Since the file format is aout, the program must be loaded to the starting -address. You can use @code{objdump} to find out what this value is. The load -offset is an offset which is added to the VMA (virtual memory address) -of each of the file's sections. -For instance, if the program -@file{prog} was linked to text address 0x1201000, with data at 0x12010160 -and bss at 0x12010170, in @value{GDBN}, type: - -@smallexample -(gdbslet) load prog 0x12010000 -Loading section .text, size 0xdb0 vma 0x12010000 -@end smallexample - -If the code is loaded at a different address then what the program was linked -to, you may need to use the @code{section} and @code{add-symbol-file} commands -to tell @value{GDBN} where to map the symbol table. - -@node Sparclet Execution -@subsubsection Running and Debugging - -@cindex running and debugging Sparclet programs -You can now begin debugging the task using @value{GDBN}'s execution control -commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN} -manual for the list of commands. - -@smallexample -(gdbslet) b main -Breakpoint 1 at 0x12010000: file prog.c, line 3. -(gdbslet) run -Starting program: prog -Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3 -3 char *symarg = 0; -(gdbslet) step -4 char *execarg = "hello!"; -(gdbslet) -@end smallexample - -@node Sparclite -@subsection Fujitsu Sparclite - -@table @code - -@kindex target sparclite -@item target sparclite @var{dev} -Fujitsu sparclite boards, used only for the purpose of loading. -You must use an additional command to debug the program. -For example: target remote @var{dev} using @value{GDBN} standard -remote protocol. - -@end table - -@node Z8000 -@subsection Zilog Z8000 - -@cindex Z8000 -@cindex simulator, Z8000 -@cindex Zilog Z8000 simulator - -When configured for debugging Zilog Z8000 targets, @value{GDBN} includes -a Z8000 simulator. - -For the Z8000 family, @samp{target sim} simulates either the Z8002 (the -unsegmented variant of the Z8000 architecture) or the Z8001 (the -segmented variant). The simulator recognizes which architecture is -appropriate by inspecting the object code. - -@table @code -@item target sim @var{args} -@kindex sim -@kindex target sim@r{, with Z8000} -Debug programs on a simulated CPU. If the simulator supports setup -options, specify them via @var{args}. -@end table - -@noindent -After specifying this target, you can debug programs for the simulated -CPU in the same style as programs for your host computer; use the -@code{file} command to load a new program image, the @code{run} command -to run your program, and so on. - -As well as making available all the usual machine registers -(@pxref{Registers, ,Registers}), the Z8000 simulator provides three -additional items of information as specially named registers: - -@table @code - -@item cycles -Counts clock-ticks in the simulator. - -@item insts -Counts instructions run in the simulator. - -@item time -Execution time in 60ths of a second. - -@end table - -You can refer to these values in @value{GDBN} expressions with the usual -conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a -conditional breakpoint that suspends only after at least 5000 -simulated clock ticks. - -@node AVR -@subsection Atmel AVR -@cindex AVR - -When configured for debugging the Atmel AVR, @value{GDBN} supports the -following AVR-specific commands: - -@table @code -@item info io_registers -@kindex info io_registers@r{, AVR} -@cindex I/O registers (Atmel AVR) -This command displays information about the AVR I/O registers. For -each register, @value{GDBN} prints its number and value. -@end table - -@node CRIS -@subsection CRIS -@cindex CRIS - -When configured for debugging CRIS, @value{GDBN} provides the -following CRIS-specific commands: - -@table @code -@item set cris-version @var{ver} -@cindex CRIS version -Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}. -The CRIS version affects register names and sizes. This command is useful in -case autodetection of the CRIS version fails. - -@item show cris-version -Show the current CRIS version. - -@item set cris-dwarf2-cfi -@cindex DWARF-2 CFI and CRIS -Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}. -Change to @samp{off} when using @code{gcc-cris} whose version is below -@code{R59}. - -@item show cris-dwarf2-cfi -Show the current state of using DWARF-2 CFI. - -@item set cris-mode @var{mode} -@cindex CRIS mode -Set the current CRIS mode to @var{mode}. It should only be changed when -debugging in guru mode, in which case it should be set to -@samp{guru} (the default is @samp{normal}). - -@item show cris-mode -Show the current CRIS mode. -@end table - -@node Super-H -@subsection Renesas Super-H -@cindex Super-H - -For the Renesas Super-H processor, @value{GDBN} provides these -commands: - -@table @code -@item set sh calling-convention @var{convention} -@kindex set sh calling-convention -Set the calling-convention used when calling functions from @value{GDBN}. -Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}. -With the @samp{gcc} setting, functions are called using the @value{NGCC} calling -convention. If the DWARF-2 information of the called function specifies -that the function follows the Renesas calling convention, the function -is called using the Renesas calling convention. If the calling convention -is set to @samp{renesas}, the Renesas calling convention is always used, -regardless of the DWARF-2 information. This can be used to override the -default of @samp{gcc} if debug information is missing, or the compiler -does not emit the DWARF-2 calling convention entry for a function. - -@item show sh calling-convention -@kindex show sh calling-convention -Show the current calling convention setting. - -@end table - - -@node Architectures -@section Architectures - -This section describes characteristics of architectures that affect -all uses of @value{GDBN} with the architecture, both native and cross. - -@menu -* AArch64:: -* i386:: -* Alpha:: -* MIPS:: -* HPPA:: HP PA architecture -* SPU:: Cell Broadband Engine SPU architecture -* PowerPC:: -@end menu - -@node AArch64 -@subsection AArch64 -@cindex AArch64 support - -When @value{GDBN} is debugging the AArch64 architecture, it provides the -following special commands: - -@table @code -@item set debug aarch64 -@kindex set debug aarch64 -This command determines whether AArch64 architecture-specific debugging -messages are to be displayed. - -@item show debug aarch64 -Show whether AArch64 debugging messages are displayed. - -@end table - -@node i386 -@subsection x86 Architecture-specific Issues - -@table @code -@item set struct-convention @var{mode} -@kindex set struct-convention -@cindex struct return convention -@cindex struct/union returned in registers -Set the convention used by the inferior to return @code{struct}s and -@code{union}s from functions to @var{mode}. Possible values of -@var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the -default). @code{"default"} or @code{"pcc"} means that @code{struct}s -are returned on the stack, while @code{"reg"} means that a -@code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will -be returned in a register. - -@item show struct-convention -@kindex show struct-convention -Show the current setting of the convention to return @code{struct}s -from functions. -@end table - -@node Alpha -@subsection Alpha - -See the following section. - -@node MIPS -@subsection @acronym{MIPS} - -@cindex stack on Alpha -@cindex stack on @acronym{MIPS} -@cindex Alpha stack -@cindex @acronym{MIPS} stack -Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which -sometimes requires @value{GDBN} to search backward in the object code to -find the beginning of a function. - -@cindex response time, @acronym{MIPS} debugging -To improve response time (especially for embedded applications, where -@value{GDBN} may be restricted to a slow serial line for this search) -you may want to limit the size of this search, using one of these -commands: - -@table @code -@cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS}) -@item set heuristic-fence-post @var{limit} -Restrict @value{GDBN} to examining at most @var{limit} bytes in its -search for the beginning of a function. A value of @var{0} (the -default) means there is no limit. However, except for @var{0}, the -larger the limit the more bytes @code{heuristic-fence-post} must search -and therefore the longer it takes to run. You should only need to use -this command when debugging a stripped executable. - -@item show heuristic-fence-post -Display the current limit. -@end table - -@noindent -These commands are available @emph{only} when @value{GDBN} is configured -for debugging programs on Alpha or @acronym{MIPS} processors. - -Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS} -programs: - -@table @code -@item set mips abi @var{arg} -@kindex set mips abi -@cindex set ABI for @acronym{MIPS} -Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible -values of @var{arg} are: - -@table @samp -@item auto -The default ABI associated with the current binary (this is the -default). -@item o32 -@item o64 -@item n32 -@item n64 -@item eabi32 -@item eabi64 -@end table - -@item show mips abi -@kindex show mips abi -Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior. - -@item set mips compression @var{arg} -@kindex set mips compression -@cindex code compression, @acronym{MIPS} -Tell @value{GDBN} which @acronym{MIPS} compressed -@acronym{ISA, Instruction Set Architecture} encoding is used by the -inferior. @value{GDBN} uses this for code disassembly and other -internal interpretation purposes. This setting is only referred to -when no executable has been associated with the debugging session or -the executable does not provide information about the encoding it uses. -Otherwise this setting is automatically updated from information -provided by the executable. - -Possible values of @var{arg} are @samp{mips16} and @samp{micromips}. -The default compressed @acronym{ISA} encoding is @samp{mips16}, as -executables containing @acronym{MIPS16} code frequently are not -identified as such. - -This setting is ``sticky''; that is, it retains its value across -debugging sessions until reset either explicitly with this command or -implicitly from an executable. - -The compiler and/or assembler typically add symbol table annotations to -identify functions compiled for the @acronym{MIPS16} or -@acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations -are present, @value{GDBN} uses them in preference to the global -compressed @acronym{ISA} encoding setting. - -@item show mips compression -@kindex show mips compression -Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by -@value{GDBN} to debug the inferior. - -@item set mipsfpu -@itemx show mipsfpu -@xref{MIPS Embedded, set mipsfpu}. - -@item set mips mask-address @var{arg} -@kindex set mips mask-address -@cindex @acronym{MIPS} addresses, masking -This command determines whether the most-significant 32 bits of 64-bit -@acronym{MIPS} addresses are masked off. The argument @var{arg} can be -@samp{on}, @samp{off}, or @samp{auto}. The latter is the default -setting, which lets @value{GDBN} determine the correct value. - -@item show mips mask-address -@kindex show mips mask-address -Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or -not. - -@item set remote-mips64-transfers-32bit-regs -@kindex set remote-mips64-transfers-32bit-regs -This command controls compatibility with 64-bit @acronym{MIPS} targets that -transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target -that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr}, -and 64 bits for other registers, set this option to @samp{on}. - -@item show remote-mips64-transfers-32bit-regs -@kindex show remote-mips64-transfers-32bit-regs -Show the current setting of compatibility with older @acronym{MIPS} 64 targets. - -@item set debug mips -@kindex set debug mips -This command turns on and off debugging messages for the @acronym{MIPS}-specific -target code in @value{GDBN}. - -@item show debug mips -@kindex show debug mips -Show the current setting of @acronym{MIPS} debugging messages. -@end table - - -@node HPPA -@subsection HPPA -@cindex HPPA support - -When @value{GDBN} is debugging the HP PA architecture, it provides the -following special commands: - -@table @code -@item set debug hppa -@kindex set debug hppa -This command determines whether HPPA architecture-specific debugging -messages are to be displayed. - -@item show debug hppa -Show whether HPPA debugging messages are displayed. - -@item maint print unwind @var{address} -@kindex maint print unwind@r{, HPPA} -This command displays the contents of the unwind table entry at the -given @var{address}. - -@end table - - -@node SPU -@subsection Cell Broadband Engine SPU architecture -@cindex Cell Broadband Engine -@cindex SPU - -When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture, -it provides the following special commands: - -@table @code -@item info spu event -@kindex info spu -Display SPU event facility status. Shows current event mask -and pending event status. - -@item info spu signal -Display SPU signal notification facility status. Shows pending -signal-control word and signal notification mode of both signal -notification channels. - -@item info spu mailbox -Display SPU mailbox facility status. Shows all pending entries, -in order of processing, in each of the SPU Write Outbound, -SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes. - -@item info spu dma -Display MFC DMA status. Shows all pending commands in the MFC -DMA queue. For each entry, opcode, tag, class IDs, effective -and local store addresses and transfer size are shown. - -@item info spu proxydma -Display MFC Proxy-DMA status. Shows all pending commands in the MFC -Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective -and local store addresses and transfer size are shown. - -@end table - -When @value{GDBN} is debugging a combined PowerPC/SPU application -on the Cell Broadband Engine, it provides in addition the following -special commands: - -@table @code -@item set spu stop-on-load @var{arg} -@kindex set spu -Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN} -will give control to the user when a new SPE thread enters its @code{main} -function. The default is @code{off}. - -@item show spu stop-on-load -@kindex show spu -Show whether to stop for new SPE threads. - -@item set spu auto-flush-cache @var{arg} -Set whether to automatically flush the software-managed cache. When set to -@code{on}, @value{GDBN} will automatically cause the SPE software-managed -cache to be flushed whenever SPE execution stops. This provides a consistent -view of PowerPC memory that is accessed via the cache. If an application -does not use the software-managed cache, this option has no effect. - -@item show spu auto-flush-cache -Show whether to automatically flush the software-managed cache. - -@end table - -@node PowerPC -@subsection PowerPC -@cindex PowerPC architecture - -When @value{GDBN} is debugging the PowerPC architecture, it provides a set of -pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point -numbers stored in the floating point registers. These values must be stored -in two consecutive registers, always starting at an even register like -@code{f0} or @code{f2}. - -The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed -by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0}, -@code{f2} and @code{f3} for @code{$dl1} and so on. - -For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit -wide Extended Floating Point Registers (@samp{f32} through @samp{f63}). - - -@node Controlling GDB -@chapter Controlling @value{GDBN} - -You can alter the way @value{GDBN} interacts with you by using the -@code{set} command. For commands controlling how @value{GDBN} displays -data, see @ref{Print Settings, ,Print Settings}. Other settings are -described here. - -@menu -* Prompt:: Prompt -* Editing:: Command editing -* Command History:: Command history -* Screen Size:: Screen size -* Numbers:: Numbers -* ABI:: Configuring the current ABI -* Auto-loading:: Automatically loading associated files -* Messages/Warnings:: Optional warnings and messages -* Debugging Output:: Optional messages about internal happenings -* Other Misc Settings:: Other Miscellaneous Settings -@end menu - -@node Prompt -@section Prompt - -@cindex prompt - -@value{GDBN} indicates its readiness to read a command by printing a string -called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You -can change the prompt string with the @code{set prompt} command. For -instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change -the prompt in one of the @value{GDBN} sessions so that you can always tell -which one you are talking to. - -@emph{Note:} @code{set prompt} does not add a space for you after the -prompt you set. This allows you to set a prompt which ends in a space -or a prompt that does not. - -@table @code -@kindex set prompt -@item set prompt @var{newprompt} -Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth. - -@kindex show prompt -@item show prompt -Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}} -@end table - -Versions of @value{GDBN} that ship with Python scripting enabled have -prompt extensions. The commands for interacting with these extensions -are: - -@table @code -@kindex set extended-prompt -@item set extended-prompt @var{prompt} -Set an extended prompt that allows for substitutions. -@xref{gdb.prompt}, for a list of escape sequences that can be used for -substitution. Any escape sequences specified as part of the prompt -string are replaced with the corresponding strings each time the prompt -is displayed. - -For example: - -@smallexample -set extended-prompt Current working directory: \w (gdb) -@end smallexample - -Note that when an extended-prompt is set, it takes control of the -@var{prompt_hook} hook. @xref{prompt_hook}, for further information. - -@kindex show extended-prompt -@item show extended-prompt -Prints the extended prompt. Any escape sequences specified as part of -the prompt string with @code{set extended-prompt}, are replaced with the -corresponding strings each time the prompt is displayed. -@end table - -@node Editing -@section Command Editing -@cindex readline -@cindex command line editing - -@value{GDBN} reads its input commands via the @dfn{Readline} interface. This -@sc{gnu} library provides consistent behavior for programs which provide a -command line interface to the user. Advantages are @sc{gnu} Emacs-style -or @dfn{vi}-style inline editing of commands, @code{csh}-like history -substitution, and a storage and recall of command history across -debugging sessions. - -You may control the behavior of command line editing in @value{GDBN} with the -command @code{set}. - -@table @code -@kindex set editing -@cindex editing -@item set editing -@itemx set editing on -Enable command line editing (enabled by default). - -@item set editing off -Disable command line editing. - -@kindex show editing -@item show editing -Show whether command line editing is enabled. -@end table - -@ifset SYSTEM_READLINE -@xref{Command Line Editing, , , rluserman, GNU Readline Library}, -@end ifset -@ifclear SYSTEM_READLINE -@xref{Command Line Editing}, -@end ifclear -for more details about the Readline -interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are -encouraged to read that chapter. - -@node Command History -@section Command History -@cindex command history - -@value{GDBN} can keep track of the commands you type during your -debugging sessions, so that you can be certain of precisely what -happened. Use these commands to manage the @value{GDBN} command -history facility. - -@value{GDBN} uses the @sc{gnu} History library, a part of the Readline -package, to provide the history facility. -@ifset SYSTEM_READLINE -@xref{Using History Interactively, , , history, GNU History Library}, -@end ifset -@ifclear SYSTEM_READLINE -@xref{Using History Interactively}, -@end ifclear -for the detailed description of the History library. - -To issue a command to @value{GDBN} without affecting certain aspects of -the state which is seen by users, prefix it with @samp{server } -(@pxref{Server Prefix}). This -means that this command will not affect the command history, nor will it -affect @value{GDBN}'s notion of which command to repeat if @key{RET} is -pressed on a line by itself. - -@cindex @code{server}, command prefix -The server prefix does not affect the recording of values into the value -history; to print a value without recording it into the value history, -use the @code{output} command instead of the @code{print} command. - -Here is the description of @value{GDBN} commands related to command -history. - -@table @code -@cindex history substitution -@cindex history file -@kindex set history filename -@cindex @env{GDBHISTFILE}, environment variable -@item set history filename @var{fname} -Set the name of the @value{GDBN} command history file to @var{fname}. -This is the file where @value{GDBN} reads an initial command history -list, and where it writes the command history from this session when it -exits. You can access this list through history expansion or through -the history command editing characters listed below. This file defaults -to the value of the environment variable @code{GDBHISTFILE}, or to -@file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable -is not set. - -@cindex save command history -@kindex set history save -@item set history save -@itemx set history save on -Record command history in a file, whose name may be specified with the -@code{set history filename} command. By default, this option is disabled. - -@item set history save off -Stop recording command history in a file. - -@cindex history size -@kindex set history size -@cindex @env{HISTSIZE}, environment variable -@item set history size @var{size} -Set the number of commands which @value{GDBN} keeps in its history list. -This defaults to the value of the environment variable -@code{HISTSIZE}, or to 256 if this variable is not set. -@end table - -History expansion assigns special meaning to the character @kbd{!}. -@ifset SYSTEM_READLINE -@xref{Event Designators, , , history, GNU History Library}, -@end ifset -@ifclear SYSTEM_READLINE -@xref{Event Designators}, -@end ifclear -for more details. - -@cindex history expansion, turn on/off -Since @kbd{!} is also the logical not operator in C, history expansion -is off by default. If you decide to enable history expansion with the -@code{set history expansion on} command, you may sometimes need to -follow @kbd{!} (when it is used as logical not, in an expression) with -a space or a tab to prevent it from being expanded. The readline -history facilities do not attempt substitution on the strings -@kbd{!=} and @kbd{!(}, even when history expansion is enabled. - -The commands to control history expansion are: - -@table @code -@item set history expansion on -@itemx set history expansion -@kindex set history expansion -Enable history expansion. History expansion is off by default. - -@item set history expansion off -Disable history expansion. - -@c @group -@kindex show history -@item show history -@itemx show history filename -@itemx show history save -@itemx show history size -@itemx show history expansion -These commands display the state of the @value{GDBN} history parameters. -@code{show history} by itself displays all four states. -@c @end group -@end table - -@table @code -@kindex show commands -@cindex show last commands -@cindex display command history -@item show commands -Display the last ten commands in the command history. - -@item show commands @var{n} -Print ten commands centered on command number @var{n}. - -@item show commands + -Print ten commands just after the commands last printed. -@end table - -@node Screen Size -@section Screen Size -@cindex size of screen -@cindex pauses in output - -Certain commands to @value{GDBN} may produce large amounts of -information output to the screen. To help you read all of it, -@value{GDBN} pauses and asks you for input at the end of each page of -output. Type @key{RET} when you want to continue the output, or @kbd{q} -to discard the remaining output. Also, the screen width setting -determines when to wrap lines of output. Depending on what is being -printed, @value{GDBN} tries to break the line at a readable place, -rather than simply letting it overflow onto the following line. - -Normally @value{GDBN} knows the size of the screen from the terminal -driver software. For example, on Unix @value{GDBN} uses the termcap data base -together with the value of the @code{TERM} environment variable and the -@code{stty rows} and @code{stty cols} settings. If this is not correct, -you can override it with the @code{set height} and @code{set -width} commands: - -@table @code -@kindex set height -@kindex set width -@kindex show width -@kindex show height -@item set height @var{lpp} -@itemx show height -@itemx set width @var{cpl} -@itemx show width -These @code{set} commands specify a screen height of @var{lpp} lines and -a screen width of @var{cpl} characters. The associated @code{show} -commands display the current settings. - -If you specify a height of zero lines, @value{GDBN} does not pause during -output no matter how long the output is. This is useful if output is to a -file or to an editor buffer. - -Likewise, you can specify @samp{set width 0} to prevent @value{GDBN} -from wrapping its output. - -@item set pagination on -@itemx set pagination off -@kindex set pagination -Turn the output pagination on or off; the default is on. Turning -pagination off is the alternative to @code{set height 0}. Note that -running @value{GDBN} with the @option{--batch} option (@pxref{Mode -Options, -batch}) also automatically disables pagination. - -@item show pagination -@kindex show pagination -Show the current pagination mode. -@end table - -@node Numbers -@section Numbers -@cindex number representation -@cindex entering numbers - -You can always enter numbers in octal, decimal, or hexadecimal in -@value{GDBN} by the usual conventions: octal numbers begin with -@samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers -begin with @samp{0x}. Numbers that neither begin with @samp{0} or -@samp{0x}, nor end with a @samp{.} are, by default, entered in base -10; likewise, the default display for numbers---when no particular -format is specified---is base 10. You can change the default base for -both input and output with the commands described below. - -@table @code -@kindex set input-radix -@item set input-radix @var{base} -Set the default base for numeric input. Supported choices -for @var{base} are decimal 8, 10, or 16. @var{base} must itself be -specified either unambiguously or using the current input radix; for -example, any of - -@smallexample -set input-radix 012 -set input-radix 10. -set input-radix 0xa -@end smallexample - -@noindent -sets the input base to decimal. On the other hand, @samp{set input-radix 10} -leaves the input radix unchanged, no matter what it was, since -@samp{10}, being without any leading or trailing signs of its base, is -interpreted in the current radix. Thus, if the current radix is 16, -@samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't -change the radix. - -@kindex set output-radix -@item set output-radix @var{base} -Set the default base for numeric display. Supported choices -for @var{base} are decimal 8, 10, or 16. @var{base} must itself be -specified either unambiguously or using the current input radix. - -@kindex show input-radix -@item show input-radix -Display the current default base for numeric input. - -@kindex show output-radix -@item show output-radix -Display the current default base for numeric display. - -@item set radix @r{[}@var{base}@r{]} -@itemx show radix -@kindex set radix -@kindex show radix -These commands set and show the default base for both input and output -of numbers. @code{set radix} sets the radix of input and output to -the same base; without an argument, it resets the radix back to its -default value of 10. - -@end table - -@node ABI -@section Configuring the Current ABI - -@value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your -application automatically. However, sometimes you need to override its -conclusions. Use these commands to manage @value{GDBN}'s view of the -current ABI. - -@cindex OS ABI -@kindex set osabi -@kindex show osabi -@cindex Newlib OS ABI and its influence on the longjmp handling - -One @value{GDBN} configuration can debug binaries for multiple operating -system targets, either via remote debugging or native emulation. -@value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use, -but you can override its conclusion using the @code{set osabi} command. -One example where this is useful is in debugging of binaries which use -an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does -not have the same identifying marks that the standard C library for your -platform provides. - -When @value{GDBN} is debugging the AArch64 architecture, it provides a -``Newlib'' OS ABI. This is useful for handling @code{setjmp} and -@code{longjmp} when debugging binaries that use the @sc{newlib} C library. -The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}. - -@table @code -@item show osabi -Show the OS ABI currently in use. - -@item set osabi -With no argument, show the list of registered available OS ABI's. - -@item set osabi @var{abi} -Set the current OS ABI to @var{abi}. -@end table - -@cindex float promotion - -Generally, the way that an argument of type @code{float} is passed to a -function depends on whether the function is prototyped. For a prototyped -(i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged, -according to the architecture's convention for @code{float}. For unprototyped -(i.e.@: K&R style) functions, @code{float} arguments are first promoted to type -@code{double} and then passed. - -Unfortunately, some forms of debug information do not reliably indicate whether -a function is prototyped. If @value{GDBN} calls a function that is not marked -as prototyped, it consults @kbd{set coerce-float-to-double}. - -@table @code -@kindex set coerce-float-to-double -@item set coerce-float-to-double -@itemx set coerce-float-to-double on -Arguments of type @code{float} will be promoted to @code{double} when passed -to an unprototyped function. This is the default setting. - -@item set coerce-float-to-double off -Arguments of type @code{float} will be passed directly to unprototyped -functions. - -@kindex show coerce-float-to-double -@item show coerce-float-to-double -Show the current setting of promoting @code{float} to @code{double}. -@end table - -@kindex set cp-abi -@kindex show cp-abi -@value{GDBN} needs to know the ABI used for your program's C@t{++} -objects. The correct C@t{++} ABI depends on which C@t{++} compiler was -used to build your application. @value{GDBN} only fully supports -programs with a single C@t{++} ABI; if your program contains code using -multiple C@t{++} ABI's or if @value{GDBN} can not identify your -program's ABI correctly, you can tell @value{GDBN} which ABI to use. -Currently supported ABI's include ``gnu-v2'', for @code{g++} versions -before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and -``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may -use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is -``auto''. - -@table @code -@item show cp-abi -Show the C@t{++} ABI currently in use. - -@item set cp-abi -With no argument, show the list of supported C@t{++} ABI's. - -@item set cp-abi @var{abi} -@itemx set cp-abi auto -Set the current C@t{++} ABI to @var{abi}, or return to automatic detection. -@end table - -@node Auto-loading -@section Automatically loading associated files -@cindex auto-loading - -@value{GDBN} sometimes reads files with commands and settings automatically, -without being explicitly told so by the user. We call this feature -@dfn{auto-loading}. While auto-loading is useful for automatically adapting -@value{GDBN} to the needs of your project, it can sometimes produce unexpected -results or introduce security risks (e.g., if the file comes from untrusted -sources). - -Note that loading of these associated files (including the local @file{.gdbinit} -file) requires accordingly configured @code{auto-load safe-path} -(@pxref{Auto-loading safe path}). - -For these reasons, @value{GDBN} includes commands and options to let you -control when to auto-load files and which files should be auto-loaded. - -@table @code -@anchor{set auto-load off} -@kindex set auto-load off -@item set auto-load off -Globally disable loading of all auto-loaded files. -You may want to use this command with the @samp{-iex} option -(@pxref{Option -init-eval-command}) such as: -@smallexample -$ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile} -@end smallexample - -Be aware that system init file (@pxref{System-wide configuration}) -and init files from your home directory (@pxref{Home Directory Init File}) -still get read (as they come from generally trusted directories). -To prevent @value{GDBN} from auto-loading even those init files, use the -@option{-nx} option (@pxref{Mode Options}), in addition to -@code{set auto-load no}. - -@anchor{show auto-load} -@kindex show auto-load -@item show auto-load -Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled -or disabled. - -@smallexample -(gdb) show auto-load -gdb-scripts: Auto-loading of canned sequences of commands scripts is on. -libthread-db: Auto-loading of inferior specific libthread_db is on. -local-gdbinit: Auto-loading of .gdbinit script from current directory - is on. -python-scripts: Auto-loading of Python scripts is on. -safe-path: List of directories from which it is safe to auto-load files - is $debugdir:$datadir/auto-load. -scripts-directory: List of directories from which to load auto-loaded scripts - is $debugdir:$datadir/auto-load. -@end smallexample - -@anchor{info auto-load} -@kindex info auto-load -@item info auto-load -Print whether each specific @samp{auto-load} file(s) have been auto-loaded or -not. - -@smallexample -(gdb) info auto-load -gdb-scripts: -Loaded Script -Yes /home/user/gdb/gdb-gdb.gdb -libthread-db: No auto-loaded libthread-db. -local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been - loaded. -python-scripts: -Loaded Script -Yes /home/user/gdb/gdb-gdb.py -@end smallexample -@end table - -These are various kinds of files @value{GDBN} can automatically load: - -@itemize @bullet -@item -@xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}. -@item -@xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}. -@item -@xref{dotdebug_gdb_scripts section}, -controlled by @ref{set auto-load python-scripts}. -@item -@xref{Init File in the Current Directory}, -controlled by @ref{set auto-load local-gdbinit}. -@item -@xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}. -@end itemize - -These are @value{GDBN} control commands for the auto-loading: - -@multitable @columnfractions .5 .5 -@item @xref{set auto-load off}. -@tab Disable auto-loading globally. -@item @xref{show auto-load}. -@tab Show setting of all kinds of files. -@item @xref{info auto-load}. -@tab Show state of all kinds of files. -@item @xref{set auto-load gdb-scripts}. -@tab Control for @value{GDBN} command scripts. -@item @xref{show auto-load gdb-scripts}. -@tab Show setting of @value{GDBN} command scripts. -@item @xref{info auto-load gdb-scripts}. -@tab Show state of @value{GDBN} command scripts. -@item @xref{set auto-load python-scripts}. -@tab Control for @value{GDBN} Python scripts. -@item @xref{show auto-load python-scripts}. -@tab Show setting of @value{GDBN} Python scripts. -@item @xref{info auto-load python-scripts}. -@tab Show state of @value{GDBN} Python scripts. -@item @xref{set auto-load scripts-directory}. -@tab Control for @value{GDBN} auto-loaded scripts location. -@item @xref{show auto-load scripts-directory}. -@tab Show @value{GDBN} auto-loaded scripts location. -@item @xref{set auto-load local-gdbinit}. -@tab Control for init file in the current directory. -@item @xref{show auto-load local-gdbinit}. -@tab Show setting of init file in the current directory. -@item @xref{info auto-load local-gdbinit}. -@tab Show state of init file in the current directory. -@item @xref{set auto-load libthread-db}. -@tab Control for thread debugging library. -@item @xref{show auto-load libthread-db}. -@tab Show setting of thread debugging library. -@item @xref{info auto-load libthread-db}. -@tab Show state of thread debugging library. -@item @xref{set auto-load safe-path}. -@tab Control directories trusted for automatic loading. -@item @xref{show auto-load safe-path}. -@tab Show directories trusted for automatic loading. -@item @xref{add-auto-load-safe-path}. -@tab Add directory trusted for automatic loading. -@end multitable - -@menu -* Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit} -* libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db} -* objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script} -* Auto-loading safe path:: @samp{set/show/info auto-load safe-path} -* Auto-loading verbose mode:: @samp{set/show debug auto-load} -@xref{Python Auto-loading}. -@end menu - -@node Init File in the Current Directory -@subsection Automatically loading init file in the current directory -@cindex auto-loading init file in the current directory - -By default, @value{GDBN} reads and executes the canned sequences of commands -from init file (if any) in the current working directory, -see @ref{Init File in the Current Directory during Startup}. - -Note that loading of this local @file{.gdbinit} file also requires accordingly -configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}). - -@table @code -@anchor{set auto-load local-gdbinit} -@kindex set auto-load local-gdbinit -@item set auto-load local-gdbinit [on|off] -Enable or disable the auto-loading of canned sequences of commands -(@pxref{Sequences}) found in init file in the current directory. - -@anchor{show auto-load local-gdbinit} -@kindex show auto-load local-gdbinit -@item show auto-load local-gdbinit -Show whether auto-loading of canned sequences of commands from init file in the -current directory is enabled or disabled. - -@anchor{info auto-load local-gdbinit} -@kindex info auto-load local-gdbinit -@item info auto-load local-gdbinit -Print whether canned sequences of commands from init file in the -current directory have been auto-loaded. -@end table - -@node libthread_db.so.1 file -@subsection Automatically loading thread debugging library -@cindex auto-loading libthread_db.so.1 - -This feature is currently present only on @sc{gnu}/Linux native hosts. - -@value{GDBN} reads in some cases thread debugging library from places specific -to the inferior (@pxref{set libthread-db-search-path}). - -The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed -without checking this @samp{set auto-load libthread-db} switch as system -libraries have to be trusted in general. In all other cases of -@samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set -auto-load libthread-db} is enabled before trying to open such thread debugging -library. - -Note that loading of this debugging library also requires accordingly configured -@code{auto-load safe-path} (@pxref{Auto-loading safe path}). - -@table @code -@anchor{set auto-load libthread-db} -@kindex set auto-load libthread-db -@item set auto-load libthread-db [on|off] -Enable or disable the auto-loading of inferior specific thread debugging library. - -@anchor{show auto-load libthread-db} -@kindex show auto-load libthread-db -@item show auto-load libthread-db -Show whether auto-loading of inferior specific thread debugging library is -enabled or disabled. - -@anchor{info auto-load libthread-db} -@kindex info auto-load libthread-db -@item info auto-load libthread-db -Print the list of all loaded inferior specific thread debugging libraries and -for each such library print list of inferior @var{pid}s using it. -@end table - -@node objfile-gdb.gdb file -@subsection The @file{@var{objfile}-gdb.gdb} file -@cindex auto-loading @file{@var{objfile}-gdb.gdb} - -@value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing -canned sequences of commands (@pxref{Sequences}), as long as @samp{set -auto-load gdb-scripts} is set to @samp{on}. - -Note that loading of this script file also requires accordingly configured -@code{auto-load safe-path} (@pxref{Auto-loading safe path}). - -For more background refer to the similar Python scripts auto-loading -description (@pxref{objfile-gdb.py file}). - -@table @code -@anchor{set auto-load gdb-scripts} -@kindex set auto-load gdb-scripts -@item set auto-load gdb-scripts [on|off] -Enable or disable the auto-loading of canned sequences of commands scripts. - -@anchor{show auto-load gdb-scripts} -@kindex show auto-load gdb-scripts -@item show auto-load gdb-scripts -Show whether auto-loading of canned sequences of commands scripts is enabled or -disabled. - -@anchor{info auto-load gdb-scripts} -@kindex info auto-load gdb-scripts -@cindex print list of auto-loaded canned sequences of commands scripts -@item info auto-load gdb-scripts [@var{regexp}] -Print the list of all canned sequences of commands scripts that @value{GDBN} -auto-loaded. -@end table - -If @var{regexp} is supplied only canned sequences of commands scripts with -matching names are printed. - -@node Auto-loading safe path -@subsection Security restriction for auto-loading -@cindex auto-loading safe-path - -As the files of inferior can come from untrusted source (such as submitted by -an application user) @value{GDBN} does not always load any files automatically. -@value{GDBN} provides the @samp{set auto-load safe-path} setting to list -directories trusted for loading files not explicitly requested by user. -Each directory can also be a shell wildcard pattern. - -If the path is not set properly you will see a warning and the file will not -get loaded: - -@smallexample -$ ./gdb -q ./gdb -Reading symbols from /home/user/gdb/gdb...done. -warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been - declined by your `auto-load safe-path' set - to "$debugdir:$datadir/auto-load". -warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been - declined by your `auto-load safe-path' set - to "$debugdir:$datadir/auto-load". -@end smallexample - -@noindent -To instruct @value{GDBN} to go ahead and use the init files anyway, -invoke @value{GDBN} like this: - -@smallexample -$ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb -@end smallexample - -The list of trusted directories is controlled by the following commands: - -@table @code -@anchor{set auto-load safe-path} -@kindex set auto-load safe-path -@item set auto-load safe-path @r{[}@var{directories}@r{]} -Set the list of directories (and their subdirectories) trusted for automatic -loading and execution of scripts. You can also enter a specific trusted file. -Each directory can also be a shell wildcard pattern; wildcards do not match -directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch} -(@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}). -If you omit @var{directories}, @samp{auto-load safe-path} will be reset to -its default value as specified during @value{GDBN} compilation. - -The list of directories uses path separator (@samp{:} on GNU and Unix -systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly -to the @env{PATH} environment variable. - -@anchor{show auto-load safe-path} -@kindex show auto-load safe-path -@item show auto-load safe-path -Show the list of directories trusted for automatic loading and execution of -scripts. - -@anchor{add-auto-load-safe-path} -@kindex add-auto-load-safe-path -@item add-auto-load-safe-path -Add an entry (or list of entries) the list of directories trusted for automatic -loading and execution of scripts. Multiple entries may be delimited by the -host platform path separator in use. -@end table - -This variable defaults to what @code{--with-auto-load-dir} has been configured -to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir} -substitution applies the same as for @ref{set auto-load scripts-directory}. -The default @code{set auto-load safe-path} value can be also overriden by -@value{GDBN} configuration option @option{--with-auto-load-safe-path}. - -Setting this variable to @file{/} disables this security protection, -corresponding @value{GDBN} configuration option is -@option{--without-auto-load-safe-path}. -This variable is supposed to be set to the system directories writable by the -system superuser only. Users can add their source directories in init files in -their home directories (@pxref{Home Directory Init File}). See also deprecated -init file in the current directory -(@pxref{Init File in the Current Directory during Startup}). - -To force @value{GDBN} to load the files it declined to load in the previous -example, you could use one of the following ways: - -@table @asis -@item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb} -Specify this trusted directory (or a file) as additional component of the list. -You have to specify also any existing directories displayed by -by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example). - -@item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}} -Specify this directory as in the previous case but just for a single -@value{GDBN} session. - -@item @kbd{gdb -iex "set auto-load safe-path /" @dots{}} -Disable auto-loading safety for a single @value{GDBN} session. -This assumes all the files you debug during this @value{GDBN} session will come -from trusted sources. - -@item @kbd{./configure --without-auto-load-safe-path} -During compilation of @value{GDBN} you may disable any auto-loading safety. -This assumes all the files you will ever debug with this @value{GDBN} come from -trusted sources. -@end table - -On the other hand you can also explicitly forbid automatic files loading which -also suppresses any such warning messages: - -@table @asis -@item @kbd{gdb -iex "set auto-load no" @dots{}} -You can use @value{GDBN} command-line option for a single @value{GDBN} session. - -@item @file{~/.gdbinit}: @samp{set auto-load no} -Disable auto-loading globally for the user -(@pxref{Home Directory Init File}). While it is improbable, you could also -use system init file instead (@pxref{System-wide configuration}). -@end table - -This setting applies to the file names as entered by user. If no entry matches -@value{GDBN} tries as a last resort to also resolve all the file names into -their canonical form (typically resolving symbolic links) and compare the -entries again. @value{GDBN} already canonicalizes most of the filenames on its -own before starting the comparison so a canonical form of directories is -recommended to be entered. - -@node Auto-loading verbose mode -@subsection Displaying files tried for auto-load -@cindex auto-loading verbose mode - -For better visibility of all the file locations where you can place scripts to -be auto-loaded with inferior --- or to protect yourself against accidental -execution of untrusted scripts --- @value{GDBN} provides a feature for printing -all the files attempted to be loaded. Both existing and non-existing files may -be printed. - -For example the list of directories from which it is safe to auto-load files -(@pxref{Auto-loading safe path}) applies also to canonicalized filenames which -may not be too obvious while setting it up. - -@smallexample -(gdb) set debug auto-load on -(gdb) file ~/src/t/true -auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb" - for objfile "/tmp/true". -auto-load: Updating directories of "/usr:/opt". -auto-load: Using directory "/usr". -auto-load: Using directory "/opt". -warning: File "/tmp/true-gdb.gdb" auto-loading has been declined - by your `auto-load safe-path' set to "/usr:/opt". -@end smallexample - -@table @code -@anchor{set debug auto-load} -@kindex set debug auto-load -@item set debug auto-load [on|off] -Set whether to print the filenames attempted to be auto-loaded. - -@anchor{show debug auto-load} -@kindex show debug auto-load -@item show debug auto-load -Show whether printing of the filenames attempted to be auto-loaded is turned -on or off. -@end table - -@node Messages/Warnings -@section Optional Warnings and Messages - -@cindex verbose operation -@cindex optional warnings -By default, @value{GDBN} is silent about its inner workings. If you are -running on a slow machine, you may want to use the @code{set verbose} -command. This makes @value{GDBN} tell you when it does a lengthy -internal operation, so you will not think it has crashed. - -Currently, the messages controlled by @code{set verbose} are those -which announce that the symbol table for a source file is being read; -see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}. - -@table @code -@kindex set verbose -@item set verbose on -Enables @value{GDBN} output of certain informational messages. - -@item set verbose off -Disables @value{GDBN} output of certain informational messages. - -@kindex show verbose -@item show verbose -Displays whether @code{set verbose} is on or off. -@end table - -By default, if @value{GDBN} encounters bugs in the symbol table of an -object file, it is silent; but if you are debugging a compiler, you may -find this information useful (@pxref{Symbol Errors, ,Errors Reading -Symbol Files}). - -@table @code - -@kindex set complaints -@item set complaints @var{limit} -Permits @value{GDBN} to output @var{limit} complaints about each type of -unusual symbols before becoming silent about the problem. Set -@var{limit} to zero to suppress all complaints; set it to a large number -to prevent complaints from being suppressed. - -@kindex show complaints -@item show complaints -Displays how many symbol complaints @value{GDBN} is permitted to produce. - -@end table - -@anchor{confirmation requests} -By default, @value{GDBN} is cautious, and asks what sometimes seems to be a -lot of stupid questions to confirm certain commands. For example, if -you try to run a program which is already running: - -@smallexample -(@value{GDBP}) run -The program being debugged has been started already. -Start it from the beginning? (y or n) -@end smallexample - -If you are willing to unflinchingly face the consequences of your own -commands, you can disable this ``feature'': - -@table @code - -@kindex set confirm -@cindex flinching -@cindex confirmation -@cindex stupid questions -@item set confirm off -Disables confirmation requests. Note that running @value{GDBN} with -the @option{--batch} option (@pxref{Mode Options, -batch}) also -automatically disables confirmation requests. - -@item set confirm on -Enables confirmation requests (the default). - -@kindex show confirm -@item show confirm -Displays state of confirmation requests. - -@end table - -@cindex command tracing -If you need to debug user-defined commands or sourced files you may find it -useful to enable @dfn{command tracing}. In this mode each command will be -printed as it is executed, prefixed with one or more @samp{+} symbols, the -quantity denoting the call depth of each command. - -@table @code -@kindex set trace-commands -@cindex command scripts, debugging -@item set trace-commands on -Enable command tracing. -@item set trace-commands off -Disable command tracing. -@item show trace-commands -Display the current state of command tracing. -@end table - -@node Debugging Output -@section Optional Messages about Internal Happenings -@cindex optional debugging messages - -@value{GDBN} has commands that enable optional debugging messages from -various @value{GDBN} subsystems; normally these commands are of -interest to @value{GDBN} maintainers, or when reporting a bug. This -section documents those commands. - -@table @code -@kindex set exec-done-display -@item set exec-done-display -Turns on or off the notification of asynchronous commands' -completion. When on, @value{GDBN} will print a message when an -asynchronous command finishes its execution. The default is off. -@kindex show exec-done-display -@item show exec-done-display -Displays the current setting of asynchronous command completion -notification. -@kindex set debug -@cindex ARM AArch64 -@item set debug aarch64 -Turns on or off display of debugging messages related to ARM AArch64. -The default is off. -@kindex show debug -@item show debug aarch64 -Displays the current state of displaying debugging messages related to -ARM AArch64. -@cindex gdbarch debugging info -@cindex architecture debugging info -@item set debug arch -Turns on or off display of gdbarch debugging info. The default is off -@item show debug arch -Displays the current state of displaying gdbarch debugging info. -@item set debug aix-thread -@cindex AIX threads -Display debugging messages about inner workings of the AIX thread -module. -@item show debug aix-thread -Show the current state of AIX thread debugging info display. -@item set debug check-physname -@cindex physname -Check the results of the ``physname'' computation. When reading DWARF -debugging information for C@t{++}, @value{GDBN} attempts to compute -each entity's name. @value{GDBN} can do this computation in two -different ways, depending on exactly what information is present. -When enabled, this setting causes @value{GDBN} to compute the names -both ways and display any discrepancies. -@item show debug check-physname -Show the current state of ``physname'' checking. -@item set debug coff-pe-read -@cindex COFF/PE exported symbols -Control display of debugging messages related to reading of COFF/PE -exported symbols. The default is off. -@item show debug coff-pe-read -Displays the current state of displaying debugging messages related to -reading of COFF/PE exported symbols. -@item set debug dwarf2-die -@cindex DWARF2 DIEs -Dump DWARF2 DIEs after they are read in. -The value is the number of nesting levels to print. -A value of zero turns off the display. -@item show debug dwarf2-die -Show the current state of DWARF2 DIE debugging. -@item set debug dwarf2-read -@cindex DWARF2 Reading -Turns on or off display of debugging messages related to reading -DWARF debug info. The default is off. -@item show debug dwarf2-read -Show the current state of DWARF2 reader debugging. -@item set debug displaced -@cindex displaced stepping debugging info -Turns on or off display of @value{GDBN} debugging info for the -displaced stepping support. The default is off. -@item show debug displaced -Displays the current state of displaying @value{GDBN} debugging info -related to displaced stepping. -@item set debug event -@cindex event debugging info -Turns on or off display of @value{GDBN} event debugging info. The -default is off. -@item show debug event -Displays the current state of displaying @value{GDBN} event debugging -info. -@item set debug expression -@cindex expression debugging info -Turns on or off display of debugging info about @value{GDBN} -expression parsing. The default is off. -@item show debug expression -Displays the current state of displaying debugging info about -@value{GDBN} expression parsing. -@item set debug frame -@cindex frame debugging info -Turns on or off display of @value{GDBN} frame debugging info. The -default is off. -@item show debug frame -Displays the current state of displaying @value{GDBN} frame debugging -info. -@item set debug gnu-nat -@cindex @sc{gnu}/Hurd debug messages -Turns on or off debugging messages from the @sc{gnu}/Hurd debug support. -@item show debug gnu-nat -Show the current state of @sc{gnu}/Hurd debugging messages. -@item set debug infrun -@cindex inferior debugging info -Turns on or off display of @value{GDBN} debugging info for running the inferior. -The default is off. @file{infrun.c} contains GDB's runtime state machine used -for implementing operations such as single-stepping the inferior. -@item show debug infrun -Displays the current state of @value{GDBN} inferior debugging. -@item set debug jit -@cindex just-in-time compilation, debugging messages -Turns on or off debugging messages from JIT debug support. -@item show debug jit -Displays the current state of @value{GDBN} JIT debugging. -@item set debug lin-lwp -@cindex @sc{gnu}/Linux LWP debug messages -@cindex Linux lightweight processes -Turns on or off debugging messages from the Linux LWP debug support. -@item show debug lin-lwp -Show the current state of Linux LWP debugging messages. -@item set debug mach-o -@cindex Mach-O symbols processing -Control display of debugging messages related to Mach-O symbols -processing. The default is off. -@item show debug mach-o -Displays the current state of displaying debugging messages related to -reading of COFF/PE exported symbols. -@item set debug notification -@cindex remote async notification debugging info -Turns on or off debugging messages about remote async notification. -The default is off. -@item show debug notification -Displays the current state of remote async notification debugging messages. -@item set debug observer -@cindex observer debugging info -Turns on or off display of @value{GDBN} observer debugging. This -includes info such as the notification of observable events. -@item show debug observer -Displays the current state of observer debugging. -@item set debug overload -@cindex C@t{++} overload debugging info -Turns on or off display of @value{GDBN} C@t{++} overload debugging -info. This includes info such as ranking of functions, etc. The default -is off. -@item show debug overload -Displays the current state of displaying @value{GDBN} C@t{++} overload -debugging info. -@cindex expression parser, debugging info -@cindex debug expression parser -@item set debug parser -Turns on or off the display of expression parser debugging output. -Internally, this sets the @code{yydebug} variable in the expression -parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for -details. The default is off. -@item show debug parser -Show the current state of expression parser debugging. -@cindex packets, reporting on stdout -@cindex serial connections, debugging -@cindex debug remote protocol -@cindex remote protocol debugging -@cindex display remote packets -@item set debug remote -Turns on or off display of reports on all packets sent back and forth across -the serial line to the remote machine. The info is printed on the -@value{GDBN} standard output stream. The default is off. -@item show debug remote -Displays the state of display of remote packets. -@item set debug serial -Turns on or off display of @value{GDBN} serial debugging info. The -default is off. -@item show debug serial -Displays the current state of displaying @value{GDBN} serial debugging -info. -@item set debug solib-frv -@cindex FR-V shared-library debugging -Turns on or off debugging messages for FR-V shared-library code. -@item show debug solib-frv -Display the current state of FR-V shared-library code debugging -messages. -@item set debug symtab-create -@cindex symbol table creation -Turns on or off display of debugging messages related to symbol table creation. -The default is off. -@item show debug symtab-create -Show the current state of symbol table creation debugging. -@item set debug target -@cindex target debugging info -Turns on or off display of @value{GDBN} target debugging info. This info -includes what is going on at the target level of GDB, as it happens. The -default is 0. Set it to 1 to track events, and to 2 to also track the -value of large memory transfers. Changes to this flag do not take effect -until the next time you connect to a target or use the @code{run} command. -@item show debug target -Displays the current state of displaying @value{GDBN} target debugging -info. -@item set debug timestamp -@cindex timestampping debugging info -Turns on or off display of timestamps with @value{GDBN} debugging info. -When enabled, seconds and microseconds are displayed before each debugging -message. -@item show debug timestamp -Displays the current state of displaying timestamps with @value{GDBN} -debugging info. -@item set debugvarobj -@cindex variable object debugging info -Turns on or off display of @value{GDBN} variable object debugging -info. The default is off. -@item show debugvarobj -Displays the current state of displaying @value{GDBN} variable object -debugging info. -@item set debug xml -@cindex XML parser debugging -Turns on or off debugging messages for built-in XML parsers. -@item show debug xml -Displays the current state of XML debugging messages. -@end table - -@node Other Misc Settings -@section Other Miscellaneous Settings -@cindex miscellaneous settings - -@table @code -@kindex set interactive-mode -@item set interactive-mode -If @code{on}, forces @value{GDBN} to assume that GDB was started -in a terminal. In practice, this means that @value{GDBN} should wait -for the user to answer queries generated by commands entered at -the command prompt. If @code{off}, forces @value{GDBN} to operate -in the opposite mode, and it uses the default answers to all queries. -If @code{auto} (the default), @value{GDBN} tries to determine whether -its standard input is a terminal, and works in interactive-mode if it -is, non-interactively otherwise. - -In the vast majority of cases, the debugger should be able to guess -correctly which mode should be used. But this setting can be useful -in certain specific cases, such as running a MinGW @value{GDBN} -inside a cygwin window. - -@kindex show interactive-mode -@item show interactive-mode -Displays whether the debugger is operating in interactive mode or not. -@end table - -@node Extending GDB -@chapter Extending @value{GDBN} -@cindex extending GDB - -@value{GDBN} provides three mechanisms for extension. The first is based -on composition of @value{GDBN} commands, the second is based on the -Python scripting language, and the third is for defining new aliases of -existing commands. - -To facilitate the use of the first two extensions, @value{GDBN} is capable -of evaluating the contents of a file. When doing so, @value{GDBN} -can recognize which scripting language is being used by looking at -the filename extension. Files with an unrecognized filename extension -are always treated as a @value{GDBN} Command Files. -@xref{Command Files,, Command files}. - -You can control how @value{GDBN} evaluates these files with the following -setting: - -@table @code -@kindex set script-extension -@kindex show script-extension -@item set script-extension off -All scripts are always evaluated as @value{GDBN} Command Files. - -@item set script-extension soft -The debugger determines the scripting language based on filename -extension. If this scripting language is supported, @value{GDBN} -evaluates the script using that language. Otherwise, it evaluates -the file as a @value{GDBN} Command File. - -@item set script-extension strict -The debugger determines the scripting language based on filename -extension, and evaluates the script using that language. If the -language is not supported, then the evaluation fails. - -@item show script-extension -Display the current value of the @code{script-extension} option. - -@end table - -@menu -* Sequences:: Canned Sequences of Commands -* Python:: Scripting @value{GDBN} using Python -* Aliases:: Creating new spellings of existing commands -@end menu - -@node Sequences -@section Canned Sequences of Commands - -Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint -Command Lists}), @value{GDBN} provides two ways to store sequences of -commands for execution as a unit: user-defined commands and command -files. - -@menu -* Define:: How to define your own commands -* Hooks:: Hooks for user-defined commands -* Command Files:: How to write scripts of commands to be stored in a file -* Output:: Commands for controlled output -@end menu - -@node Define -@subsection User-defined Commands - -@cindex user-defined command -@cindex arguments, to user-defined commands -A @dfn{user-defined command} is a sequence of @value{GDBN} commands to -which you assign a new name as a command. This is done with the -@code{define} command. User commands may accept up to 10 arguments -separated by whitespace. Arguments are accessed within the user command -via @code{$arg0@dots{}$arg9}. A trivial example: - -@smallexample -define adder - print $arg0 + $arg1 + $arg2 -end -@end smallexample - -@noindent -To execute the command use: - -@smallexample -adder 1 2 3 -@end smallexample - -@noindent -This defines the command @code{adder}, which prints the sum of -its three arguments. Note the arguments are text substitutions, so they may -reference variables, use complex expressions, or even perform inferior -functions calls. - -@cindex argument count in user-defined commands -@cindex how many arguments (user-defined commands) -In addition, @code{$argc} may be used to find out how many arguments have -been passed. This expands to a number in the range 0@dots{}10. - -@smallexample -define adder - if $argc == 2 - print $arg0 + $arg1 - end - if $argc == 3 - print $arg0 + $arg1 + $arg2 - end -end -@end smallexample - -@table @code - -@kindex define -@item define @var{commandname} -Define a command named @var{commandname}. If there is already a command -by that name, you are asked to confirm that you want to redefine it. -@var{commandname} may be a bare command name consisting of letters, -numbers, dashes, and underscores. It may also start with any predefined -prefix command. For example, @samp{define target my-target} creates -a user-defined @samp{target my-target} command. - -The definition of the command is made up of other @value{GDBN} command lines, -which are given following the @code{define} command. The end of these -commands is marked by a line containing @code{end}. - -@kindex document -@kindex end@r{ (user-defined commands)} -@item document @var{commandname} -Document the user-defined command @var{commandname}, so that it can be -accessed by @code{help}. The command @var{commandname} must already be -defined. This command reads lines of documentation just as @code{define} -reads the lines of the command definition, ending with @code{end}. -After the @code{document} command is finished, @code{help} on command -@var{commandname} displays the documentation you have written. - -You may use the @code{document} command again to change the -documentation of a command. Redefining the command with @code{define} -does not change the documentation. - -@kindex dont-repeat -@cindex don't repeat command -@item dont-repeat -Used inside a user-defined command, this tells @value{GDBN} that this -command should not be repeated when the user hits @key{RET} -(@pxref{Command Syntax, repeat last command}). - -@kindex help user-defined -@item help user-defined -List all user-defined commands and all python commands defined in class -COMAND_USER. The first line of the documentation or docstring is -included (if any). - -@kindex show user -@item show user -@itemx show user @var{commandname} -Display the @value{GDBN} commands used to define @var{commandname} (but -not its documentation). If no @var{commandname} is given, display the -definitions for all user-defined commands. -This does not work for user-defined python commands. - -@cindex infinite recursion in user-defined commands -@kindex show max-user-call-depth -@kindex set max-user-call-depth -@item show max-user-call-depth -@itemx set max-user-call-depth -The value of @code{max-user-call-depth} controls how many recursion -levels are allowed in user-defined commands before @value{GDBN} suspects an -infinite recursion and aborts the command. -This does not apply to user-defined python commands. -@end table - -In addition to the above commands, user-defined commands frequently -use control flow commands, described in @ref{Command Files}. - -When user-defined commands are executed, the -commands of the definition are not printed. An error in any command -stops execution of the user-defined command. - -If used interactively, commands that would ask for confirmation proceed -without asking when used inside a user-defined command. Many @value{GDBN} -commands that normally print messages to say what they are doing omit the -messages when used in a user-defined command. - -@node Hooks -@subsection User-defined Command Hooks -@cindex command hooks -@cindex hooks, for commands -@cindex hooks, pre-command - -@kindex hook -You may define @dfn{hooks}, which are a special kind of user-defined -command. Whenever you run the command @samp{foo}, if the user-defined -command @samp{hook-foo} exists, it is executed (with no arguments) -before that command. - -@cindex hooks, post-command -@kindex hookpost -A hook may also be defined which is run after the command you executed. -Whenever you run the command @samp{foo}, if the user-defined command -@samp{hookpost-foo} exists, it is executed (with no arguments) after -that command. Post-execution hooks may exist simultaneously with -pre-execution hooks, for the same command. - -It is valid for a hook to call the command which it hooks. If this -occurs, the hook is not re-executed, thereby avoiding infinite recursion. - -@c It would be nice if hookpost could be passed a parameter indicating -@c if the command it hooks executed properly or not. FIXME! - -@kindex stop@r{, a pseudo-command} -In addition, a pseudo-command, @samp{stop} exists. Defining -(@samp{hook-stop}) makes the associated commands execute every time -execution stops in your program: before breakpoint commands are run, -displays are printed, or the stack frame is printed. - -For example, to ignore @code{SIGALRM} signals while -single-stepping, but treat them normally during normal execution, -you could define: - -@smallexample -define hook-stop -handle SIGALRM nopass -end - -define hook-run -handle SIGALRM pass -end - -define hook-continue -handle SIGALRM pass -end -@end smallexample - -As a further example, to hook at the beginning and end of the @code{echo} -command, and to add extra text to the beginning and end of the message, -you could define: - -@smallexample -define hook-echo -echo <<<--- -end - -define hookpost-echo -echo --->>>\n -end - -(@value{GDBP}) echo Hello World -<<<---Hello World--->>> -(@value{GDBP}) - -@end smallexample - -You can define a hook for any single-word command in @value{GDBN}, but -not for command aliases; you should define a hook for the basic command -name, e.g.@: @code{backtrace} rather than @code{bt}. -@c FIXME! So how does Joe User discover whether a command is an alias -@c or not? -You can hook a multi-word command by adding @code{hook-} or -@code{hookpost-} to the last word of the command, e.g.@: -@samp{define target hook-remote} to add a hook to @samp{target remote}. - -If an error occurs during the execution of your hook, execution of -@value{GDBN} commands stops and @value{GDBN} issues a prompt -(before the command that you actually typed had a chance to run). - -If you try to define a hook which does not match any known command, you -get a warning from the @code{define} command. - -@node Command Files -@subsection Command Files - -@cindex command files -@cindex scripting commands -A command file for @value{GDBN} is a text file made of lines that are -@value{GDBN} commands. Comments (lines starting with @kbd{#}) may -also be included. An empty line in a command file does nothing; it -does not mean to repeat the last command, as it would from the -terminal. - -You can request the execution of a command file with the @code{source} -command. Note that the @code{source} command is also used to evaluate -scripts that are not Command Files. The exact behavior can be configured -using the @code{script-extension} setting. -@xref{Extending GDB,, Extending GDB}. - -@table @code -@kindex source -@cindex execute commands from a file -@item source [-s] [-v] @var{filename} -Execute the command file @var{filename}. -@end table - -The lines in a command file are generally executed sequentially, -unless the order of execution is changed by one of the -@emph{flow-control commands} described below. The commands are not -printed as they are executed. An error in any command terminates -execution of the command file and control is returned to the console. - -@value{GDBN} first searches for @var{filename} in the current directory. -If the file is not found there, and @var{filename} does not specify a -directory, then @value{GDBN} also looks for the file on the source search path -(specified with the @samp{directory} command); -except that @file{$cdir} is not searched because the compilation directory -is not relevant to scripts. - -If @code{-s} is specified, then @value{GDBN} searches for @var{filename} -on the search path even if @var{filename} specifies a directory. -The search is done by appending @var{filename} to each element of the -search path. So, for example, if @var{filename} is @file{mylib/myscript} -and the search path contains @file{/home/user} then @value{GDBN} will -look for the script @file{/home/user/mylib/myscript}. -The search is also done if @var{filename} is an absolute path. -For example, if @var{filename} is @file{/tmp/myscript} and -the search path contains @file{/home/user} then @value{GDBN} will -look for the script @file{/home/user/tmp/myscript}. -For DOS-like systems, if @var{filename} contains a drive specification, -it is stripped before concatenation. For example, if @var{filename} is -@file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN} -will look for the script @file{c:/tmp/myscript}. - -If @code{-v}, for verbose mode, is given then @value{GDBN} displays -each command as it is executed. The option must be given before -@var{filename}, and is interpreted as part of the filename anywhere else. - -Commands that would ask for confirmation if used interactively proceed -without asking when used in a command file. Many @value{GDBN} commands that -normally print messages to say what they are doing omit the messages -when called from command files. - -@value{GDBN} also accepts command input from standard input. In this -mode, normal output goes to standard output and error output goes to -standard error. Errors in a command file supplied on standard input do -not terminate execution of the command file---execution continues with -the next command. - -@smallexample -gdb < cmds > log 2>&1 -@end smallexample - -(The syntax above will vary depending on the shell used.) This example -will execute commands from the file @file{cmds}. All output and errors -would be directed to @file{log}. - -Since commands stored on command files tend to be more general than -commands typed interactively, they frequently need to deal with -complicated situations, such as different or unexpected values of -variables and symbols, changes in how the program being debugged is -built, etc. @value{GDBN} provides a set of flow-control commands to -deal with these complexities. Using these commands, you can write -complex scripts that loop over data structures, execute commands -conditionally, etc. - -@table @code -@kindex if -@kindex else -@item if -@itemx else -This command allows to include in your script conditionally executed -commands. The @code{if} command takes a single argument, which is an -expression to evaluate. It is followed by a series of commands that -are executed only if the expression is true (its value is nonzero). -There can then optionally be an @code{else} line, followed by a series -of commands that are only executed if the expression was false. The -end of the list is marked by a line containing @code{end}. - -@kindex while -@item while -This command allows to write loops. Its syntax is similar to -@code{if}: the command takes a single argument, which is an expression -to evaluate, and must be followed by the commands to execute, one per -line, terminated by an @code{end}. These commands are called the -@dfn{body} of the loop. The commands in the body of @code{while} are -executed repeatedly as long as the expression evaluates to true. - -@kindex loop_break -@item loop_break -This command exits the @code{while} loop in whose body it is included. -Execution of the script continues after that @code{while}s @code{end} -line. - -@kindex loop_continue -@item loop_continue -This command skips the execution of the rest of the body of commands -in the @code{while} loop in whose body it is included. Execution -branches to the beginning of the @code{while} loop, where it evaluates -the controlling expression. - -@kindex end@r{ (if/else/while commands)} -@item end -Terminate the block of commands that are the body of @code{if}, -@code{else}, or @code{while} flow-control commands. -@end table - - -@node Output -@subsection Commands for Controlled Output - -During the execution of a command file or a user-defined command, normal -@value{GDBN} output is suppressed; the only output that appears is what is -explicitly printed by the commands in the definition. This section -describes three commands useful for generating exactly the output you -want. - -@table @code -@kindex echo -@item echo @var{text} -@c I do not consider backslash-space a standard C escape sequence -@c because it is not in ANSI. -Print @var{text}. Nonprinting characters can be included in -@var{text} using C escape sequences, such as @samp{\n} to print a -newline. @strong{No newline is printed unless you specify one.} -In addition to the standard C escape sequences, a backslash followed -by a space stands for a space. This is useful for displaying a -string with spaces at the beginning or the end, since leading and -trailing spaces are otherwise trimmed from all arguments. -To print @samp{@w{ }and foo =@w{ }}, use the command -@samp{echo \@w{ }and foo = \@w{ }}. - -A backslash at the end of @var{text} can be used, as in C, to continue -the command onto subsequent lines. For example, - -@smallexample -echo This is some text\n\ -which is continued\n\ -onto several lines.\n -@end smallexample - -produces the same output as - -@smallexample -echo This is some text\n -echo which is continued\n -echo onto several lines.\n -@end smallexample - -@kindex output -@item output @var{expression} -Print the value of @var{expression} and nothing but that value: no -newlines, no @samp{$@var{nn} = }. The value is not entered in the -value history either. @xref{Expressions, ,Expressions}, for more information -on expressions. - -@item output/@var{fmt} @var{expression} -Print the value of @var{expression} in format @var{fmt}. You can use -the same formats as for @code{print}. @xref{Output Formats,,Output -Formats}, for more information. - -@kindex printf -@item printf @var{template}, @var{expressions}@dots{} -Print the values of one or more @var{expressions} under the control of -the string @var{template}. To print several values, make -@var{expressions} be a comma-separated list of individual expressions, -which may be either numbers or pointers. Their values are printed as -specified by @var{template}, exactly as a C program would do by -executing the code below: - -@smallexample -printf (@var{template}, @var{expressions}@dots{}); -@end smallexample - -As in @code{C} @code{printf}, ordinary characters in @var{template} -are printed verbatim, while @dfn{conversion specification} introduced -by the @samp{%} character cause subsequent @var{expressions} to be -evaluated, their values converted and formatted according to type and -style information encoded in the conversion specifications, and then -printed. - -For example, you can print two values in hex like this: - -@smallexample -printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo -@end smallexample - -@code{printf} supports all the standard @code{C} conversion -specifications, including the flags and modifiers between the @samp{%} -character and the conversion letter, with the following exceptions: - -@itemize @bullet -@item -The argument-ordering modifiers, such as @samp{2$}, are not supported. - -@item -The modifier @samp{*} is not supported for specifying precision or -width. - -@item -The @samp{'} flag (for separation of digits into groups according to -@code{LC_NUMERIC'}) is not supported. - -@item -The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not -supported. - -@item -The conversion letter @samp{n} (as in @samp{%n}) is not supported. - -@item -The conversion letters @samp{a} and @samp{A} are not supported. -@end itemize - -@noindent -Note that the @samp{ll} type modifier is supported only if the -underlying @code{C} implementation used to build @value{GDBN} supports -the @code{long long int} type, and the @samp{L} type modifier is -supported only if @code{long double} type is available. - -As in @code{C}, @code{printf} supports simple backslash-escape -sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"}, -@samp{\a}, and @samp{\f}, that consist of backslash followed by a -single character. Octal and hexadecimal escape sequences are not -supported. - -Additionally, @code{printf} supports conversion specifications for DFP -(@dfn{Decimal Floating Point}) types using the following length modifiers -together with a floating point specifier. -letters: - -@itemize @bullet -@item -@samp{H} for printing @code{Decimal32} types. - -@item -@samp{D} for printing @code{Decimal64} types. - -@item -@samp{DD} for printing @code{Decimal128} types. -@end itemize - -If the underlying @code{C} implementation used to build @value{GDBN} has -support for the three length modifiers for DFP types, other modifiers -such as width and precision will also be available for @value{GDBN} to use. - -In case there is no such @code{C} support, no additional modifiers will be -available and the value will be printed in the standard way. - -Here's an example of printing DFP types using the above conversion letters: -@smallexample -printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl -@end smallexample - -@kindex eval -@item eval @var{template}, @var{expressions}@dots{} -Convert the values of one or more @var{expressions} under the control of -the string @var{template} to a command line, and call it. - -@end table - -@node Python -@section Scripting @value{GDBN} using Python -@cindex python scripting -@cindex scripting with python - -You can script @value{GDBN} using the @uref{http://www.python.org/, -Python programming language}. This feature is available only if -@value{GDBN} was configured using @option{--with-python}. - -@cindex python directory -Python scripts used by @value{GDBN} should be installed in -@file{@var{data-directory}/python}, where @var{data-directory} is -the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). -This directory, known as the @dfn{python directory}, -is automatically added to the Python Search Path in order to allow -the Python interpreter to locate all scripts installed at this location. - -Additionally, @value{GDBN} commands and convenience functions which -are written in Python and are located in the -@file{@var{data-directory}/python/gdb/command} or -@file{@var{data-directory}/python/gdb/function} directories are -automatically imported when @value{GDBN} starts. - -@menu -* Python Commands:: Accessing Python from @value{GDBN}. -* Python API:: Accessing @value{GDBN} from Python. -* Python Auto-loading:: Automatically loading Python code. -* Python modules:: Python modules provided by @value{GDBN}. -@end menu - -@node Python Commands -@subsection Python Commands -@cindex python commands -@cindex commands to access python - -@value{GDBN} provides two commands for accessing the Python interpreter, -and one related setting: - -@table @code -@kindex python-interactive -@kindex pi -@item python-interactive @r{[}@var{command}@r{]} -@itemx pi @r{[}@var{command}@r{]} -Without an argument, the @code{python-interactive} command can be used -to start an interactive Python prompt. To return to @value{GDBN}, -type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt). - -Alternatively, a single-line Python command can be given as an -argument and evaluated. If the command is an expression, the result -will be printed; otherwise, nothing will be printed. For example: - -@smallexample -(@value{GDBP}) python-interactive 2 + 3 -5 -@end smallexample - -@kindex python -@kindex py -@item python @r{[}@var{command}@r{]} -@itemx py @r{[}@var{command}@r{]} -The @code{python} command can be used to evaluate Python code. - -If given an argument, the @code{python} command will evaluate the -argument as a Python command. For example: - -@smallexample -(@value{GDBP}) python print 23 -23 -@end smallexample - -If you do not provide an argument to @code{python}, it will act as a -multi-line command, like @code{define}. In this case, the Python -script is made up of subsequent command lines, given after the -@code{python} command. This command list is terminated using a line -containing @code{end}. For example: - -@smallexample -(@value{GDBP}) python -Type python script -End with a line saying just "end". ->print 23 ->end -23 -@end smallexample - -@kindex set python print-stack -@item set python print-stack -By default, @value{GDBN} will print only the message component of a -Python exception when an error occurs in a Python script. This can be -controlled using @code{set python print-stack}: if @code{full}, then -full Python stack printing is enabled; if @code{none}, then Python stack -and message printing is disabled; if @code{message}, the default, only -the message component of the error is printed. -@end table - -It is also possible to execute a Python script from the @value{GDBN} -interpreter: - -@table @code -@item source @file{script-name} -The script name must end with @samp{.py} and @value{GDBN} must be configured -to recognize the script language based on filename extension using -the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}. - -@item python execfile ("script-name") -This method is based on the @code{execfile} Python built-in function, -and thus is always available. -@end table - -@node Python API -@subsection Python API -@cindex python api -@cindex programming in python - -@cindex python stdout -@cindex python pagination -At startup, @value{GDBN} overrides Python's @code{sys.stdout} and -@code{sys.stderr} to print using @value{GDBN}'s output-paging streams. -A Python program which outputs to one of these streams may have its -output interrupted by the user (@pxref{Screen Size}). In this -situation, a Python @code{KeyboardInterrupt} exception is thrown. - -@menu -* Basic Python:: Basic Python Functions. -* Exception Handling:: How Python exceptions are translated. -* Values From Inferior:: Python representation of values. -* Types In Python:: Python representation of types. -* Pretty Printing API:: Pretty-printing values. -* Selecting Pretty-Printers:: How GDB chooses a pretty-printer. -* Writing a Pretty-Printer:: Writing a Pretty-Printer. -* Type Printing API:: Pretty-printing types. -* Inferiors In Python:: Python representation of inferiors (processes) -* Events In Python:: Listening for events from @value{GDBN}. -* Threads In Python:: Accessing inferior threads from Python. -* Commands In Python:: Implementing new commands in Python. -* Parameters In Python:: Adding new @value{GDBN} parameters. -* Functions In Python:: Writing new convenience functions. -* Progspaces In Python:: Program spaces. -* Objfiles In Python:: Object files. -* Frames In Python:: Accessing inferior stack frames from Python. -* Blocks In Python:: Accessing frame blocks from Python. -* Symbols In Python:: Python representation of symbols. -* Symbol Tables In Python:: Python representation of symbol tables. -* Breakpoints In Python:: Manipulating breakpoints using Python. -* Finish Breakpoints in Python:: Setting Breakpoints on function return - using Python. -* Lazy Strings In Python:: Python representation of lazy strings. -* Architectures In Python:: Python representation of architectures. -@end menu - -@node Basic Python -@subsubsection Basic Python - -@cindex python functions -@cindex python module -@cindex gdb module -@value{GDBN} introduces a new Python module, named @code{gdb}. All -methods and classes added by @value{GDBN} are placed in this module. -@value{GDBN} automatically @code{import}s the @code{gdb} module for -use in all scripts evaluated by the @code{python} command. - -@findex gdb.PYTHONDIR -@defvar gdb.PYTHONDIR -A string containing the python directory (@pxref{Python}). -@end defvar - -@findex gdb.execute -@defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]}) -Evaluate @var{command}, a string, as a @value{GDBN} CLI command. -If a GDB exception happens while @var{command} runs, it is -translated as described in @ref{Exception Handling,,Exception Handling}. - -@var{from_tty} specifies whether @value{GDBN} ought to consider this -command as having originated from the user invoking it interactively. -It must be a boolean value. If omitted, it defaults to @code{False}. - -By default, any output produced by @var{command} is sent to -@value{GDBN}'s standard output. If the @var{to_string} parameter is -@code{True}, then output will be collected by @code{gdb.execute} and -returned as a string. The default is @code{False}, in which case the -return value is @code{None}. If @var{to_string} is @code{True}, the -@value{GDBN} virtual terminal will be temporarily set to unlimited width -and height, and its pagination will be disabled; @pxref{Screen Size}. -@end defun - -@findex gdb.breakpoints -@defun gdb.breakpoints () -Return a sequence holding all of @value{GDBN}'s breakpoints. -@xref{Breakpoints In Python}, for more information. -@end defun - -@findex gdb.parameter -@defun gdb.parameter (parameter) -Return the value of a @value{GDBN} parameter. @var{parameter} is a -string naming the parameter to look up; @var{parameter} may contain -spaces if the parameter has a multi-part name. For example, -@samp{print object} is a valid parameter name. - -If the named parameter does not exist, this function throws a -@code{gdb.error} (@pxref{Exception Handling}). Otherwise, the -parameter's value is converted to a Python value of the appropriate -type, and returned. -@end defun - -@findex gdb.history -@defun gdb.history (number) -Return a value from @value{GDBN}'s value history (@pxref{Value -History}). @var{number} indicates which history element to return. -If @var{number} is negative, then @value{GDBN} will take its absolute value -and count backward from the last element (i.e., the most recent element) to -find the value to return. If @var{number} is zero, then @value{GDBN} will -return the most recent element. If the element specified by @var{number} -doesn't exist in the value history, a @code{gdb.error} exception will be -raised. - -If no exception is raised, the return value is always an instance of -@code{gdb.Value} (@pxref{Values From Inferior}). -@end defun - -@findex gdb.parse_and_eval -@defun gdb.parse_and_eval (expression) -Parse @var{expression} as an expression in the current language, -evaluate it, and return the result as a @code{gdb.Value}. -@var{expression} must be a string. - -This function can be useful when implementing a new command -(@pxref{Commands In Python}), as it provides a way to parse the -command's argument as an expression. It is also useful simply to -compute values, for example, it is the only way to get the value of a -convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}. -@end defun - -@findex gdb.find_pc_line -@defun gdb.find_pc_line (pc) -Return the @code{gdb.Symtab_and_line} object corresponding to the -@var{pc} value. @xref{Symbol Tables In Python}. If an invalid -value of @var{pc} is passed as an argument, then the @code{symtab} and -@code{line} attributes of the returned @code{gdb.Symtab_and_line} object -will be @code{None} and 0 respectively. -@end defun - -@findex gdb.post_event -@defun gdb.post_event (event) -Put @var{event}, a callable object taking no arguments, into -@value{GDBN}'s internal event queue. This callable will be invoked at -some later point, during @value{GDBN}'s event processing. Events -posted using @code{post_event} will be run in the order in which they -were posted; however, there is no way to know when they will be -processed relative to other events inside @value{GDBN}. - -@value{GDBN} is not thread-safe. If your Python program uses multiple -threads, you must be careful to only call @value{GDBN}-specific -functions in the main @value{GDBN} thread. @code{post_event} ensures -this. For example: - -@smallexample -(@value{GDBP}) python ->import threading -> ->class Writer(): -> def __init__(self, message): -> self.message = message; -> def __call__(self): -> gdb.write(self.message) -> ->class MyThread1 (threading.Thread): -> def run (self): -> gdb.post_event(Writer("Hello ")) -> ->class MyThread2 (threading.Thread): -> def run (self): -> gdb.post_event(Writer("World\n")) -> ->MyThread1().start() ->MyThread2().start() ->end -(@value{GDBP}) Hello World -@end smallexample -@end defun - -@findex gdb.write -@defun gdb.write (string @r{[}, stream{]}) -Print a string to @value{GDBN}'s paginated output stream. The -optional @var{stream} determines the stream to print to. The default -stream is @value{GDBN}'s standard output stream. Possible stream -values are: - -@table @code -@findex STDOUT -@findex gdb.STDOUT -@item gdb.STDOUT -@value{GDBN}'s standard output stream. - -@findex STDERR -@findex gdb.STDERR -@item gdb.STDERR -@value{GDBN}'s standard error stream. - -@findex STDLOG -@findex gdb.STDLOG -@item gdb.STDLOG -@value{GDBN}'s log stream (@pxref{Logging Output}). -@end table - -Writing to @code{sys.stdout} or @code{sys.stderr} will automatically -call this function and will automatically direct the output to the -relevant stream. -@end defun - -@findex gdb.flush -@defun gdb.flush () -Flush the buffer of a @value{GDBN} paginated stream so that the -contents are displayed immediately. @value{GDBN} will flush the -contents of a stream automatically when it encounters a newline in the -buffer. The optional @var{stream} determines the stream to flush. The -default stream is @value{GDBN}'s standard output stream. Possible -stream values are: - -@table @code -@findex STDOUT -@findex gdb.STDOUT -@item gdb.STDOUT -@value{GDBN}'s standard output stream. - -@findex STDERR -@findex gdb.STDERR -@item gdb.STDERR -@value{GDBN}'s standard error stream. - -@findex STDLOG -@findex gdb.STDLOG -@item gdb.STDLOG -@value{GDBN}'s log stream (@pxref{Logging Output}). - -@end table - -Flushing @code{sys.stdout} or @code{sys.stderr} will automatically -call this function for the relevant stream. -@end defun - -@findex gdb.target_charset -@defun gdb.target_charset () -Return the name of the current target character set (@pxref{Character -Sets}). This differs from @code{gdb.parameter('target-charset')} in -that @samp{auto} is never returned. -@end defun - -@findex gdb.target_wide_charset -@defun gdb.target_wide_charset () -Return the name of the current target wide character set -(@pxref{Character Sets}). This differs from -@code{gdb.parameter('target-wide-charset')} in that @samp{auto} is -never returned. -@end defun - -@findex gdb.solib_name -@defun gdb.solib_name (address) -Return the name of the shared library holding the given @var{address} -as a string, or @code{None}. -@end defun - -@findex gdb.decode_line -@defun gdb.decode_line @r{[}expression@r{]} -Return locations of the line specified by @var{expression}, or of the -current line if no argument was given. This function returns a Python -tuple containing two elements. The first element contains a string -holding any unparsed section of @var{expression} (or @code{None} if -the expression has been fully parsed). The second element contains -either @code{None} or another tuple that contains all the locations -that match the expression represented as @code{gdb.Symtab_and_line} -objects (@pxref{Symbol Tables In Python}). If @var{expression} is -provided, it is decoded the way that @value{GDBN}'s inbuilt -@code{break} or @code{edit} commands do (@pxref{Specify Location}). -@end defun - -@defun gdb.prompt_hook (current_prompt) -@anchor{prompt_hook} - -If @var{prompt_hook} is callable, @value{GDBN} will call the method -assigned to this operation before a prompt is displayed by -@value{GDBN}. - -The parameter @code{current_prompt} contains the current @value{GDBN} -prompt. This method must return a Python string, or @code{None}. If -a string is returned, the @value{GDBN} prompt will be set to that -string. If @code{None} is returned, @value{GDBN} will continue to use -the current prompt. - -Some prompts cannot be substituted in @value{GDBN}. Secondary prompts -such as those used by readline for command input, and annotation -related prompts are prohibited from being changed. -@end defun - -@node Exception Handling -@subsubsection Exception Handling -@cindex python exceptions -@cindex exceptions, python - -When executing the @code{python} command, Python exceptions -uncaught within the Python code are translated to calls to -@value{GDBN} error-reporting mechanism. If the command that called -@code{python} does not handle the error, @value{GDBN} will -terminate it and print an error message containing the Python -exception name, the associated value, and the Python call stack -backtrace at the point where the exception was raised. Example: - -@smallexample -(@value{GDBP}) python print foo -Traceback (most recent call last): - File "", line 1, in -NameError: name 'foo' is not defined -@end smallexample - -@value{GDBN} errors that happen in @value{GDBN} commands invoked by -Python code are converted to Python exceptions. The type of the -Python exception depends on the error. - -@ftable @code -@item gdb.error -This is the base class for most exceptions generated by @value{GDBN}. -It is derived from @code{RuntimeError}, for compatibility with earlier -versions of @value{GDBN}. - -If an error occurring in @value{GDBN} does not fit into some more -specific category, then the generated exception will have this type. - -@item gdb.MemoryError -This is a subclass of @code{gdb.error} which is thrown when an -operation tried to access invalid memory in the inferior. - -@item KeyboardInterrupt -User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination -prompt) is translated to a Python @code{KeyboardInterrupt} exception. -@end ftable - -In all cases, your exception handler will see the @value{GDBN} error -message as its value and the Python call stack backtrace at the Python -statement closest to where the @value{GDBN} error occured as the -traceback. - -@findex gdb.GdbError -When implementing @value{GDBN} commands in Python via @code{gdb.Command}, -it is useful to be able to throw an exception that doesn't cause a -traceback to be printed. For example, the user may have invoked the -command incorrectly. Use the @code{gdb.GdbError} exception -to handle this case. Example: - -@smallexample -(gdb) python ->class HelloWorld (gdb.Command): -> """Greet the whole world.""" -> def __init__ (self): -> super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) -> def invoke (self, args, from_tty): -> argv = gdb.string_to_argv (args) -> if len (argv) != 0: -> raise gdb.GdbError ("hello-world takes no arguments") -> print "Hello, World!" ->HelloWorld () ->end -(gdb) hello-world 42 -hello-world takes no arguments -@end smallexample - -@node Values From Inferior -@subsubsection Values From Inferior -@cindex values from inferior, with Python -@cindex python, working with values from inferior - -@cindex @code{gdb.Value} -@value{GDBN} provides values it obtains from the inferior program in -an object of type @code{gdb.Value}. @value{GDBN} uses this object -for its internal bookkeeping of the inferior's values, and for -fetching values when necessary. - -Inferior values that are simple scalars can be used directly in -Python expressions that are valid for the value's data type. Here's -an example for an integer or floating-point value @code{some_val}: - -@smallexample -bar = some_val + 2 -@end smallexample - -@noindent -As result of this, @code{bar} will also be a @code{gdb.Value} object -whose values are of the same type as those of @code{some_val}. - -Inferior values that are structures or instances of some class can -be accessed using the Python @dfn{dictionary syntax}. For example, if -@code{some_val} is a @code{gdb.Value} instance holding a structure, you -can access its @code{foo} element with: - -@smallexample -bar = some_val['foo'] -@end smallexample - -Again, @code{bar} will also be a @code{gdb.Value} object. - -A @code{gdb.Value} that represents a function can be executed via -inferior function call. Any arguments provided to the call must match -the function's prototype, and must be provided in the order specified -by that prototype. - -For example, @code{some_val} is a @code{gdb.Value} instance -representing a function that takes two integers as arguments. To -execute this function, call it like so: - -@smallexample -result = some_val (10,20) -@end smallexample - -Any values returned from a function call will be stored as a -@code{gdb.Value}. - -The following attributes are provided: - -@defvar Value.address -If this object is addressable, this read-only attribute holds a -@code{gdb.Value} object representing the address. Otherwise, -this attribute holds @code{None}. -@end defvar - -@cindex optimized out value in Python -@defvar Value.is_optimized_out -This read-only boolean attribute is true if the compiler optimized out -this value, thus it is not available for fetching from the inferior. -@end defvar - -@defvar Value.type -The type of this @code{gdb.Value}. The value of this attribute is a -@code{gdb.Type} object (@pxref{Types In Python}). -@end defvar - -@defvar Value.dynamic_type -The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time -type information (@acronym{RTTI}) to determine the dynamic type of the -value. If this value is of class type, it will return the class in -which the value is embedded, if any. If this value is of pointer or -reference to a class type, it will compute the dynamic type of the -referenced object, and return a pointer or reference to that type, -respectively. In all other cases, it will return the value's static -type. - -Note that this feature will only work when debugging a C@t{++} program -that includes @acronym{RTTI} for the object in question. Otherwise, -it will just return the static type of the value as in @kbd{ptype foo} -(@pxref{Symbols, ptype}). -@end defvar - -@defvar Value.is_lazy -The value of this read-only boolean attribute is @code{True} if this -@code{gdb.Value} has not yet been fetched from the inferior. -@value{GDBN} does not fetch values until necessary, for efficiency. -For example: - -@smallexample -myval = gdb.parse_and_eval ('somevar') -@end smallexample - -The value of @code{somevar} is not fetched at this time. It will be -fetched when the value is needed, or when the @code{fetch_lazy} -method is invoked. -@end defvar - -The following methods are provided: - -@defun Value.__init__ (@var{val}) -Many Python values can be converted directly to a @code{gdb.Value} via -this object initializer. Specifically: - -@table @asis -@item Python boolean -A Python boolean is converted to the boolean type from the current -language. - -@item Python integer -A Python integer is converted to the C @code{long} type for the -current architecture. - -@item Python long -A Python long is converted to the C @code{long long} type for the -current architecture. - -@item Python float -A Python float is converted to the C @code{double} type for the -current architecture. - -@item Python string -A Python string is converted to a target string, using the current -target encoding. - -@item @code{gdb.Value} -If @code{val} is a @code{gdb.Value}, then a copy of the value is made. - -@item @code{gdb.LazyString} -If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In -Python}), then the lazy string's @code{value} method is called, and -its result is used. -@end table -@end defun - -@defun Value.cast (type) -Return a new instance of @code{gdb.Value} that is the result of -casting this instance to the type described by @var{type}, which must -be a @code{gdb.Type} object. If the cast cannot be performed for some -reason, this method throws an exception. -@end defun - -@defun Value.dereference () -For pointer data types, this method returns a new @code{gdb.Value} object -whose contents is the object pointed to by the pointer. For example, if -@code{foo} is a C pointer to an @code{int}, declared in your C program as - -@smallexample -int *foo; -@end smallexample - -@noindent -then you can use the corresponding @code{gdb.Value} to access what -@code{foo} points to like this: - -@smallexample -bar = foo.dereference () -@end smallexample - -The result @code{bar} will be a @code{gdb.Value} object holding the -value pointed to by @code{foo}. - -A similar function @code{Value.referenced_value} exists which also -returns @code{gdb.Value} objects corresonding to the values pointed to -by pointer values (and additionally, values referenced by reference -values). However, the behavior of @code{Value.dereference} -differs from @code{Value.referenced_value} by the fact that the -behavior of @code{Value.dereference} is identical to applying the C -unary operator @code{*} on a given value. For example, consider a -reference to a pointer @code{ptrref}, declared in your C@t{++} program -as - -@smallexample -typedef int *intptr; -... -int val = 10; -intptr ptr = &val; -intptr &ptrref = ptr; -@end smallexample - -Though @code{ptrref} is a reference value, one can apply the method -@code{Value.dereference} to the @code{gdb.Value} object corresponding -to it and obtain a @code{gdb.Value} which is identical to that -corresponding to @code{val}. However, if you apply the method -@code{Value.referenced_value}, the result would be a @code{gdb.Value} -object identical to that corresponding to @code{ptr}. - -@smallexample -py_ptrref = gdb.parse_and_eval ("ptrref") -py_val = py_ptrref.dereference () -py_ptr = py_ptrref.referenced_value () -@end smallexample - -The @code{gdb.Value} object @code{py_val} is identical to that -corresponding to @code{val}, and @code{py_ptr} is identical to that -corresponding to @code{ptr}. In general, @code{Value.dereference} can -be applied whenever the C unary operator @code{*} can be applied -to the corresponding C value. For those cases where applying both -@code{Value.dereference} and @code{Value.referenced_value} is allowed, -the results obtained need not be identical (as we have seen in the above -example). The results are however identical when applied on -@code{gdb.Value} objects corresponding to pointers (@code{gdb.Value} -objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program. -@end defun - -@defun Value.referenced_value () -For pointer or reference data types, this method returns a new -@code{gdb.Value} object corresponding to the value referenced by the -pointer/reference value. For pointer data types, -@code{Value.dereference} and @code{Value.referenced_value} produce -identical results. The difference between these methods is that -@code{Value.dereference} cannot get the values referenced by reference -values. For example, consider a reference to an @code{int}, declared -in your C@t{++} program as - -@smallexample -int val = 10; -int &ref = val; -@end smallexample - -@noindent -then applying @code{Value.dereference} to the @code{gdb.Value} object -corresponding to @code{ref} will result in an error, while applying -@code{Value.referenced_value} will result in a @code{gdb.Value} object -identical to that corresponding to @code{val}. - -@smallexample -py_ref = gdb.parse_and_eval ("ref") -er_ref = py_ref.dereference () # Results in error -py_val = py_ref.referenced_value () # Returns the referenced value -@end smallexample - -The @code{gdb.Value} object @code{py_val} is identical to that -corresponding to @code{val}. -@end defun - -@defun Value.dynamic_cast (type) -Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast} -operator were used. Consult a C@t{++} reference for details. -@end defun - -@defun Value.reinterpret_cast (type) -Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast} -operator were used. Consult a C@t{++} reference for details. -@end defun - -@defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]}) -If this @code{gdb.Value} represents a string, then this method -converts the contents to a Python string. Otherwise, this method will -throw an exception. - -Strings are recognized in a language-specific way; whether a given -@code{gdb.Value} represents a string is determined by the current -language. - -For C-like languages, a value is a string if it is a pointer to or an -array of characters or ints. The string is assumed to be terminated -by a zero of the appropriate width. However if the optional length -argument is given, the string will be converted to that given length, -ignoring any embedded zeros that the string may contain. - -If the optional @var{encoding} argument is given, it must be a string -naming the encoding of the string in the @code{gdb.Value}, such as -@code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts -the same encodings as the corresponding argument to Python's -@code{string.decode} method, and the Python codec machinery will be used -to convert the string. If @var{encoding} is not given, or if -@var{encoding} is the empty string, then either the @code{target-charset} -(@pxref{Character Sets}) will be used, or a language-specific encoding -will be used, if the current language is able to supply one. - -The optional @var{errors} argument is the same as the corresponding -argument to Python's @code{string.decode} method. - -If the optional @var{length} argument is given, the string will be -fetched and converted to the given length. -@end defun - -@defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]}) -If this @code{gdb.Value} represents a string, then this method -converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings -In Python}). Otherwise, this method will throw an exception. - -If the optional @var{encoding} argument is given, it must be a string -naming the encoding of the @code{gdb.LazyString}. Some examples are: -@samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the -@var{encoding} argument is an encoding that @value{GDBN} does -recognize, @value{GDBN} will raise an error. - -When a lazy string is printed, the @value{GDBN} encoding machinery is -used to convert the string during printing. If the optional -@var{encoding} argument is not provided, or is an empty string, -@value{GDBN} will automatically select the encoding most suitable for -the string type. For further information on encoding in @value{GDBN} -please see @ref{Character Sets}. - -If the optional @var{length} argument is given, the string will be -fetched and encoded to the length of characters specified. If -the @var{length} argument is not provided, the string will be fetched -and encoded until a null of appropriate width is found. -@end defun - -@defun Value.fetch_lazy () -If the @code{gdb.Value} object is currently a lazy value -(@code{gdb.Value.is_lazy} is @code{True}), then the value is -fetched from the inferior. Any errors that occur in the process -will produce a Python exception. - -If the @code{gdb.Value} object is not a lazy value, this method -has no effect. - -This method does not return a value. -@end defun - - -@node Types In Python -@subsubsection Types In Python -@cindex types in Python -@cindex Python, working with types - -@tindex gdb.Type -@value{GDBN} represents types from the inferior using the class -@code{gdb.Type}. - -The following type-related functions are available in the @code{gdb} -module: - -@findex gdb.lookup_type -@defun gdb.lookup_type (name @r{[}, block@r{]}) -This function looks up a type by name. @var{name} is the name of the -type to look up. It must be a string. - -If @var{block} is given, then @var{name} is looked up in that scope. -Otherwise, it is searched for globally. - -Ordinarily, this function will return an instance of @code{gdb.Type}. -If the named type cannot be found, it will throw an exception. -@end defun - -If the type is a structure or class type, or an enum type, the fields -of that type can be accessed using the Python @dfn{dictionary syntax}. -For example, if @code{some_type} is a @code{gdb.Type} instance holding -a structure type, you can access its @code{foo} field with: - -@smallexample -bar = some_type['foo'] -@end smallexample - -@code{bar} will be a @code{gdb.Field} object; see below under the -description of the @code{Type.fields} method for a description of the -@code{gdb.Field} class. - -An instance of @code{Type} has the following attributes: - -@defvar Type.code -The type code for this type. The type code will be one of the -@code{TYPE_CODE_} constants defined below. -@end defvar - -@defvar Type.sizeof -The size of this type, in target @code{char} units. Usually, a -target's @code{char} type will be an 8-bit byte. However, on some -unusual platforms, this type may have a different size. -@end defvar - -@defvar Type.tag -The tag name for this type. The tag name is the name after -@code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all -languages have this concept. If this type has no tag name, then -@code{None} is returned. -@end defvar - -The following methods are provided: - -@defun Type.fields () -For structure and union types, this method returns the fields. Range -types have two fields, the minimum and maximum values. Enum types -have one field per enum constant. Function and method types have one -field per parameter. The base types of C@t{++} classes are also -represented as fields. If the type has no fields, or does not fit -into one of these categories, an empty sequence will be returned. - -Each field is a @code{gdb.Field} object, with some pre-defined attributes: -@table @code -@item bitpos -This attribute is not available for @code{static} fields (as in -C@t{++} or Java). For non-@code{static} fields, the value is the bit -position of the field. For @code{enum} fields, the value is the -enumeration member's integer representation. - -@item name -The name of the field, or @code{None} for anonymous fields. - -@item artificial -This is @code{True} if the field is artificial, usually meaning that -it was provided by the compiler and not the user. This attribute is -always provided, and is @code{False} if the field is not artificial. - -@item is_base_class -This is @code{True} if the field represents a base class of a C@t{++} -structure. This attribute is always provided, and is @code{False} -if the field is not a base class of the type that is the argument of -@code{fields}, or if that type was not a C@t{++} class. - -@item bitsize -If the field is packed, or is a bitfield, then this will have a -non-zero value, which is the size of the field in bits. Otherwise, -this will be zero; in this case the field's size is given by its type. - -@item type -The type of the field. This is usually an instance of @code{Type}, -but it can be @code{None} in some situations. -@end table -@end defun - -@defun Type.array (@var{n1} @r{[}, @var{n2}@r{]}) -Return a new @code{gdb.Type} object which represents an array of this -type. If one argument is given, it is the inclusive upper bound of -the array; in this case the lower bound is zero. If two arguments are -given, the first argument is the lower bound of the array, and the -second argument is the upper bound of the array. An array's length -must not be negative, but the bounds can be. -@end defun - -@defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]}) -Return a new @code{gdb.Type} object which represents a vector of this -type. If one argument is given, it is the inclusive upper bound of -the vector; in this case the lower bound is zero. If two arguments are -given, the first argument is the lower bound of the vector, and the -second argument is the upper bound of the vector. A vector's length -must not be negative, but the bounds can be. - -The difference between an @code{array} and a @code{vector} is that -arrays behave like in C: when used in expressions they decay to a pointer -to the first element whereas vectors are treated as first class values. -@end defun - -@defun Type.const () -Return a new @code{gdb.Type} object which represents a -@code{const}-qualified variant of this type. -@end defun - -@defun Type.volatile () -Return a new @code{gdb.Type} object which represents a -@code{volatile}-qualified variant of this type. -@end defun - -@defun Type.unqualified () -Return a new @code{gdb.Type} object which represents an unqualified -variant of this type. That is, the result is neither @code{const} nor -@code{volatile}. -@end defun - -@defun Type.range () -Return a Python @code{Tuple} object that contains two elements: the -low bound of the argument type and the high bound of that type. If -the type does not have a range, @value{GDBN} will raise a -@code{gdb.error} exception (@pxref{Exception Handling}). -@end defun - -@defun Type.reference () -Return a new @code{gdb.Type} object which represents a reference to this -type. -@end defun - -@defun Type.pointer () -Return a new @code{gdb.Type} object which represents a pointer to this -type. -@end defun - -@defun Type.strip_typedefs () -Return a new @code{gdb.Type} that represents the real type, -after removing all layers of typedefs. -@end defun - -@defun Type.target () -Return a new @code{gdb.Type} object which represents the target type -of this type. - -For a pointer type, the target type is the type of the pointed-to -object. For an array type (meaning C-like arrays), the target type is -the type of the elements of the array. For a function or method type, -the target type is the type of the return value. For a complex type, -the target type is the type of the elements. For a typedef, the -target type is the aliased type. - -If the type does not have a target, this method will throw an -exception. -@end defun - -@defun Type.template_argument (n @r{[}, block@r{]}) -If this @code{gdb.Type} is an instantiation of a template, this will -return a new @code{gdb.Type} which represents the type of the -@var{n}th template argument. - -If this @code{gdb.Type} is not a template type, this will throw an -exception. Ordinarily, only C@t{++} code will have template types. - -If @var{block} is given, then @var{name} is looked up in that scope. -Otherwise, it is searched for globally. -@end defun - - -Each type has a code, which indicates what category this type falls -into. The available type categories are represented by constants -defined in the @code{gdb} module: - -@table @code -@findex TYPE_CODE_PTR -@findex gdb.TYPE_CODE_PTR -@item gdb.TYPE_CODE_PTR -The type is a pointer. - -@findex TYPE_CODE_ARRAY -@findex gdb.TYPE_CODE_ARRAY -@item gdb.TYPE_CODE_ARRAY -The type is an array. - -@findex TYPE_CODE_STRUCT -@findex gdb.TYPE_CODE_STRUCT -@item gdb.TYPE_CODE_STRUCT -The type is a structure. - -@findex TYPE_CODE_UNION -@findex gdb.TYPE_CODE_UNION -@item gdb.TYPE_CODE_UNION -The type is a union. - -@findex TYPE_CODE_ENUM -@findex gdb.TYPE_CODE_ENUM -@item gdb.TYPE_CODE_ENUM -The type is an enum. - -@findex TYPE_CODE_FLAGS -@findex gdb.TYPE_CODE_FLAGS -@item gdb.TYPE_CODE_FLAGS -A bit flags type, used for things such as status registers. - -@findex TYPE_CODE_FUNC -@findex gdb.TYPE_CODE_FUNC -@item gdb.TYPE_CODE_FUNC -The type is a function. - -@findex TYPE_CODE_INT -@findex gdb.TYPE_CODE_INT -@item gdb.TYPE_CODE_INT -The type is an integer type. - -@findex TYPE_CODE_FLT -@findex gdb.TYPE_CODE_FLT -@item gdb.TYPE_CODE_FLT -A floating point type. - -@findex TYPE_CODE_VOID -@findex gdb.TYPE_CODE_VOID -@item gdb.TYPE_CODE_VOID -The special type @code{void}. - -@findex TYPE_CODE_SET -@findex gdb.TYPE_CODE_SET -@item gdb.TYPE_CODE_SET -A Pascal set type. - -@findex TYPE_CODE_RANGE -@findex gdb.TYPE_CODE_RANGE -@item gdb.TYPE_CODE_RANGE -A range type, that is, an integer type with bounds. - -@findex TYPE_CODE_STRING -@findex gdb.TYPE_CODE_STRING -@item gdb.TYPE_CODE_STRING -A string type. Note that this is only used for certain languages with -language-defined string types; C strings are not represented this way. - -@findex TYPE_CODE_BITSTRING -@findex gdb.TYPE_CODE_BITSTRING -@item gdb.TYPE_CODE_BITSTRING -A string of bits. It is deprecated. - -@findex TYPE_CODE_ERROR -@findex gdb.TYPE_CODE_ERROR -@item gdb.TYPE_CODE_ERROR -An unknown or erroneous type. - -@findex TYPE_CODE_METHOD -@findex gdb.TYPE_CODE_METHOD -@item gdb.TYPE_CODE_METHOD -A method type, as found in C@t{++} or Java. - -@findex TYPE_CODE_METHODPTR -@findex gdb.TYPE_CODE_METHODPTR -@item gdb.TYPE_CODE_METHODPTR -A pointer-to-member-function. - -@findex TYPE_CODE_MEMBERPTR -@findex gdb.TYPE_CODE_MEMBERPTR -@item gdb.TYPE_CODE_MEMBERPTR -A pointer-to-member. - -@findex TYPE_CODE_REF -@findex gdb.TYPE_CODE_REF -@item gdb.TYPE_CODE_REF -A reference type. - -@findex TYPE_CODE_CHAR -@findex gdb.TYPE_CODE_CHAR -@item gdb.TYPE_CODE_CHAR -A character type. - -@findex TYPE_CODE_BOOL -@findex gdb.TYPE_CODE_BOOL -@item gdb.TYPE_CODE_BOOL -A boolean type. - -@findex TYPE_CODE_COMPLEX -@findex gdb.TYPE_CODE_COMPLEX -@item gdb.TYPE_CODE_COMPLEX -A complex float type. - -@findex TYPE_CODE_TYPEDEF -@findex gdb.TYPE_CODE_TYPEDEF -@item gdb.TYPE_CODE_TYPEDEF -A typedef to some other type. - -@findex TYPE_CODE_NAMESPACE -@findex gdb.TYPE_CODE_NAMESPACE -@item gdb.TYPE_CODE_NAMESPACE -A C@t{++} namespace. - -@findex TYPE_CODE_DECFLOAT -@findex gdb.TYPE_CODE_DECFLOAT -@item gdb.TYPE_CODE_DECFLOAT -A decimal floating point type. - -@findex TYPE_CODE_INTERNAL_FUNCTION -@findex gdb.TYPE_CODE_INTERNAL_FUNCTION -@item gdb.TYPE_CODE_INTERNAL_FUNCTION -A function internal to @value{GDBN}. This is the type used to represent -convenience functions. -@end table - -Further support for types is provided in the @code{gdb.types} -Python module (@pxref{gdb.types}). - -@node Pretty Printing API -@subsubsection Pretty Printing API - -An example output is provided (@pxref{Pretty Printing}). - -A pretty-printer is just an object that holds a value and implements a -specific interface, defined here. - -@defun pretty_printer.children (self) -@value{GDBN} will call this method on a pretty-printer to compute the -children of the pretty-printer's value. - -This method must return an object conforming to the Python iterator -protocol. Each item returned by the iterator must be a tuple holding -two elements. The first element is the ``name'' of the child; the -second element is the child's value. The value can be any Python -object which is convertible to a @value{GDBN} value. - -This method is optional. If it does not exist, @value{GDBN} will act -as though the value has no children. -@end defun - -@defun pretty_printer.display_hint (self) -The CLI may call this method and use its result to change the -formatting of a value. The result will also be supplied to an MI -consumer as a @samp{displayhint} attribute of the variable being -printed. - -This method is optional. If it does exist, this method must return a -string. - -Some display hints are predefined by @value{GDBN}: - -@table @samp -@item array -Indicate that the object being printed is ``array-like''. The CLI -uses this to respect parameters such as @code{set print elements} and -@code{set print array}. - -@item map -Indicate that the object being printed is ``map-like'', and that the -children of this value can be assumed to alternate between keys and -values. - -@item string -Indicate that the object being printed is ``string-like''. If the -printer's @code{to_string} method returns a Python string of some -kind, then @value{GDBN} will call its internal language-specific -string-printing function to format the string. For the CLI this means -adding quotation marks, possibly escaping some characters, respecting -@code{set print elements}, and the like. -@end table -@end defun - -@defun pretty_printer.to_string (self) -@value{GDBN} will call this method to display the string -representation of the value passed to the object's constructor. - -When printing from the CLI, if the @code{to_string} method exists, -then @value{GDBN} will prepend its result to the values returned by -@code{children}. Exactly how this formatting is done is dependent on -the display hint, and may change as more hints are added. Also, -depending on the print settings (@pxref{Print Settings}), the CLI may -print just the result of @code{to_string} in a stack trace, omitting -the result of @code{children}. - -If this method returns a string, it is printed verbatim. - -Otherwise, if this method returns an instance of @code{gdb.Value}, -then @value{GDBN} prints this value. This may result in a call to -another pretty-printer. - -If instead the method returns a Python value which is convertible to a -@code{gdb.Value}, then @value{GDBN} performs the conversion and prints -the resulting value. Again, this may result in a call to another -pretty-printer. Python scalars (integers, floats, and booleans) and -strings are convertible to @code{gdb.Value}; other types are not. - -Finally, if this method returns @code{None} then no further operations -are peformed in this method and nothing is printed. - -If the result is not one of these types, an exception is raised. -@end defun - -@value{GDBN} provides a function which can be used to look up the -default pretty-printer for a @code{gdb.Value}: - -@findex gdb.default_visualizer -@defun gdb.default_visualizer (value) -This function takes a @code{gdb.Value} object as an argument. If a -pretty-printer for this value exists, then it is returned. If no such -printer exists, then this returns @code{None}. -@end defun - -@node Selecting Pretty-Printers -@subsubsection Selecting Pretty-Printers - -The Python list @code{gdb.pretty_printers} contains an array of -functions or callable objects that have been registered via addition -as a pretty-printer. Printers in this list are called @code{global} -printers, they're available when debugging all inferiors. -Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute. -Each @code{gdb.Objfile} also contains a @code{pretty_printers} -attribute. - -Each function on these lists is passed a single @code{gdb.Value} -argument and should return a pretty-printer object conforming to the -interface definition above (@pxref{Pretty Printing API}). If a function -cannot create a pretty-printer for the value, it should return -@code{None}. - -@value{GDBN} first checks the @code{pretty_printers} attribute of each -@code{gdb.Objfile} in the current program space and iteratively calls -each enabled lookup routine in the list for that @code{gdb.Objfile} -until it receives a pretty-printer object. -If no pretty-printer is found in the objfile lists, @value{GDBN} then -searches the pretty-printer list of the current program space, -calling each enabled function until an object is returned. -After these lists have been exhausted, it tries the global -@code{gdb.pretty_printers} list, again calling each enabled function until an -object is returned. - -The order in which the objfiles are searched is not specified. For a -given list, functions are always invoked from the head of the list, -and iterated over sequentially until the end of the list, or a printer -object is returned. - -For various reasons a pretty-printer may not work. -For example, the underlying data structure may have changed and -the pretty-printer is out of date. - -The consequences of a broken pretty-printer are severe enough that -@value{GDBN} provides support for enabling and disabling individual -printers. For example, if @code{print frame-arguments} is on, -a backtrace can become highly illegible if any argument is printed -with a broken printer. - -Pretty-printers are enabled and disabled by attaching an @code{enabled} -attribute to the registered function or callable object. If this attribute -is present and its value is @code{False}, the printer is disabled, otherwise -the printer is enabled. - -@node Writing a Pretty-Printer -@subsubsection Writing a Pretty-Printer -@cindex writing a pretty-printer - -A pretty-printer consists of two parts: a lookup function to detect -if the type is supported, and the printer itself. - -Here is an example showing how a @code{std::string} printer might be -written. @xref{Pretty Printing API}, for details on the API this class -must provide. - -@smallexample -class StdStringPrinter(object): - "Print a std::string" - - def __init__(self, val): - self.val = val - - def to_string(self): - return self.val['_M_dataplus']['_M_p'] - - def display_hint(self): - return 'string' -@end smallexample - -And here is an example showing how a lookup function for the printer -example above might be written. - -@smallexample -def str_lookup_function(val): - lookup_tag = val.type.tag - if lookup_tag == None: - return None - regex = re.compile("^std::basic_string$") - if regex.match(lookup_tag): - return StdStringPrinter(val) - return None -@end smallexample - -The example lookup function extracts the value's type, and attempts to -match it to a type that it can pretty-print. If it is a type the -printer can pretty-print, it will return a printer object. If not, it -returns @code{None}. - -We recommend that you put your core pretty-printers into a Python -package. If your pretty-printers are for use with a library, we -further recommend embedding a version number into the package name. -This practice will enable @value{GDBN} to load multiple versions of -your pretty-printers at the same time, because they will have -different names. - -You should write auto-loaded code (@pxref{Python Auto-loading}) such that it -can be evaluated multiple times without changing its meaning. An -ideal auto-load file will consist solely of @code{import}s of your -printer modules, followed by a call to a register pretty-printers with -the current objfile. - -Taken as a whole, this approach will scale nicely to multiple -inferiors, each potentially using a different library version. -Embedding a version number in the Python package name will ensure that -@value{GDBN} is able to load both sets of printers simultaneously. -Then, because the search for pretty-printers is done by objfile, and -because your auto-loaded code took care to register your library's -printers with a specific objfile, @value{GDBN} will find the correct -printers for the specific version of the library used by each -inferior. - -To continue the @code{std::string} example (@pxref{Pretty Printing API}), -this code might appear in @code{gdb.libstdcxx.v6}: - -@smallexample -def register_printers(objfile): - objfile.pretty_printers.append(str_lookup_function) -@end smallexample - -@noindent -And then the corresponding contents of the auto-load file would be: - -@smallexample -import gdb.libstdcxx.v6 -gdb.libstdcxx.v6.register_printers(gdb.current_objfile()) -@end smallexample - -The previous example illustrates a basic pretty-printer. -There are a few things that can be improved on. -The printer doesn't have a name, making it hard to identify in a -list of installed printers. The lookup function has a name, but -lookup functions can have arbitrary, even identical, names. - -Second, the printer only handles one type, whereas a library typically has -several types. One could install a lookup function for each desired type -in the library, but one could also have a single lookup function recognize -several types. The latter is the conventional way this is handled. -If a pretty-printer can handle multiple data types, then its -@dfn{subprinters} are the printers for the individual data types. - -The @code{gdb.printing} module provides a formal way of solving these -problems (@pxref{gdb.printing}). -Here is another example that handles multiple types. - -These are the types we are going to pretty-print: - -@smallexample -struct foo @{ int a, b; @}; -struct bar @{ struct foo x, y; @}; -@end smallexample - -Here are the printers: - -@smallexample -class fooPrinter: - """Print a foo object.""" - - def __init__(self, val): - self.val = val - - def to_string(self): - return ("a=<" + str(self.val["a"]) + - "> b=<" + str(self.val["b"]) + ">") - -class barPrinter: - """Print a bar object.""" - - def __init__(self, val): - self.val = val - - def to_string(self): - return ("x=<" + str(self.val["x"]) + - "> y=<" + str(self.val["y"]) + ">") -@end smallexample - -This example doesn't need a lookup function, that is handled by the -@code{gdb.printing} module. Instead a function is provided to build up -the object that handles the lookup. - -@smallexample -import gdb.printing - -def build_pretty_printer(): - pp = gdb.printing.RegexpCollectionPrettyPrinter( - "my_library") - pp.add_printer('foo', '^foo$', fooPrinter) - pp.add_printer('bar', '^bar$', barPrinter) - return pp -@end smallexample - -And here is the autoload support: - -@smallexample -import gdb.printing -import my_library -gdb.printing.register_pretty_printer( - gdb.current_objfile(), - my_library.build_pretty_printer()) -@end smallexample - -Finally, when this printer is loaded into @value{GDBN}, here is the -corresponding output of @samp{info pretty-printer}: - -@smallexample -(gdb) info pretty-printer -my_library.so: - my_library - foo - bar -@end smallexample - -@node Type Printing API -@subsubsection Type Printing API -@cindex type printing API for Python - -@value{GDBN} provides a way for Python code to customize type display. -This is mainly useful for substituting canonical typedef names for -types. - -@cindex type printer -A @dfn{type printer} is just a Python object conforming to a certain -protocol. A simple base class implementing the protocol is provided; -see @ref{gdb.types}. A type printer must supply at least: - -@defivar type_printer enabled -A boolean which is True if the printer is enabled, and False -otherwise. This is manipulated by the @code{enable type-printer} -and @code{disable type-printer} commands. -@end defivar - -@defivar type_printer name -The name of the type printer. This must be a string. This is used by -the @code{enable type-printer} and @code{disable type-printer} -commands. -@end defivar - -@defmethod type_printer instantiate (self) -This is called by @value{GDBN} at the start of type-printing. It is -only called if the type printer is enabled. This method must return a -new object that supplies a @code{recognize} method, as described below. -@end defmethod - - -When displaying a type, say via the @code{ptype} command, @value{GDBN} -will compute a list of type recognizers. This is done by iterating -first over the per-objfile type printers (@pxref{Objfiles In Python}), -followed by the per-progspace type printers (@pxref{Progspaces In -Python}), and finally the global type printers. - -@value{GDBN} will call the @code{instantiate} method of each enabled -type printer. If this method returns @code{None}, then the result is -ignored; otherwise, it is appended to the list of recognizers. - -Then, when @value{GDBN} is going to display a type name, it iterates -over the list of recognizers. For each one, it calls the recognition -function, stopping if the function returns a non-@code{None} value. -The recognition function is defined as: - -@defmethod type_recognizer recognize (self, type) -If @var{type} is not recognized, return @code{None}. Otherwise, -return a string which is to be printed as the name of @var{type}. -@var{type} will be an instance of @code{gdb.Type} (@pxref{Types In -Python}). -@end defmethod - -@value{GDBN} uses this two-pass approach so that type printers can -efficiently cache information without holding on to it too long. For -example, it can be convenient to look up type information in a type -printer and hold it for a recognizer's lifetime; if a single pass were -done then type printers would have to make use of the event system in -order to avoid holding information that could become stale as the -inferior changed. - -@node Inferiors In Python -@subsubsection Inferiors In Python -@cindex inferiors in Python - -@findex gdb.Inferior -Programs which are being run under @value{GDBN} are called inferiors -(@pxref{Inferiors and Programs}). Python scripts can access -information about and manipulate inferiors controlled by @value{GDBN} -via objects of the @code{gdb.Inferior} class. - -The following inferior-related functions are available in the @code{gdb} -module: - -@defun gdb.inferiors () -Return a tuple containing all inferior objects. -@end defun - -@defun gdb.selected_inferior () -Return an object representing the current inferior. -@end defun - -A @code{gdb.Inferior} object has the following attributes: - -@defvar Inferior.num -ID of inferior, as assigned by GDB. -@end defvar - -@defvar Inferior.pid -Process ID of the inferior, as assigned by the underlying operating -system. -@end defvar - -@defvar Inferior.was_attached -Boolean signaling whether the inferior was created using `attach', or -started by @value{GDBN} itself. -@end defvar - -A @code{gdb.Inferior} object has the following methods: - -@defun Inferior.is_valid () -Returns @code{True} if the @code{gdb.Inferior} object is valid, -@code{False} if not. A @code{gdb.Inferior} object will become invalid -if the inferior no longer exists within @value{GDBN}. All other -@code{gdb.Inferior} methods will throw an exception if it is invalid -at the time the method is called. -@end defun - -@defun Inferior.threads () -This method returns a tuple holding all the threads which are valid -when it is called. If there are no valid threads, the method will -return an empty tuple. -@end defun - -@findex Inferior.read_memory -@defun Inferior.read_memory (address, length) -Read @var{length} bytes of memory from the inferior, starting at -@var{address}. Returns a buffer object, which behaves much like an array -or a string. It can be modified and given to the -@code{Inferior.write_memory} function. In @code{Python} 3, the return -value is a @code{memoryview} object. -@end defun - -@findex Inferior.write_memory -@defun Inferior.write_memory (address, buffer @r{[}, length@r{]}) -Write the contents of @var{buffer} to the inferior, starting at -@var{address}. The @var{buffer} parameter must be a Python object -which supports the buffer protocol, i.e., a string, an array or the -object returned from @code{Inferior.read_memory}. If given, @var{length} -determines the number of bytes from @var{buffer} to be written. -@end defun - -@findex gdb.search_memory -@defun Inferior.search_memory (address, length, pattern) -Search a region of the inferior memory starting at @var{address} with -the given @var{length} using the search pattern supplied in -@var{pattern}. The @var{pattern} parameter must be a Python object -which supports the buffer protocol, i.e., a string, an array or the -object returned from @code{gdb.read_memory}. Returns a Python @code{Long} -containing the address where the pattern was found, or @code{None} if -the pattern could not be found. -@end defun - -@node Events In Python -@subsubsection Events In Python -@cindex inferior events in Python - -@value{GDBN} provides a general event facility so that Python code can be -notified of various state changes, particularly changes that occur in -the inferior. - -An @dfn{event} is just an object that describes some state change. The -type of the object and its attributes will vary depending on the details -of the change. All the existing events are described below. - -In order to be notified of an event, you must register an event handler -with an @dfn{event registry}. An event registry is an object in the -@code{gdb.events} module which dispatches particular events. A registry -provides methods to register and unregister event handlers: - -@defun EventRegistry.connect (object) -Add the given callable @var{object} to the registry. This object will be -called when an event corresponding to this registry occurs. -@end defun - -@defun EventRegistry.disconnect (object) -Remove the given @var{object} from the registry. Once removed, the object -will no longer receive notifications of events. -@end defun - -Here is an example: - -@smallexample -def exit_handler (event): - print "event type: exit" - print "exit code: %d" % (event.exit_code) - -gdb.events.exited.connect (exit_handler) -@end smallexample - -In the above example we connect our handler @code{exit_handler} to the -registry @code{events.exited}. Once connected, @code{exit_handler} gets -called when the inferior exits. The argument @dfn{event} in this example is -of type @code{gdb.ExitedEvent}. As you can see in the example the -@code{ExitedEvent} object has an attribute which indicates the exit code of -the inferior. - -The following is a listing of the event registries that are available and -details of the events they emit: - -@table @code - -@item events.cont -Emits @code{gdb.ThreadEvent}. - -Some events can be thread specific when @value{GDBN} is running in non-stop -mode. When represented in Python, these events all extend -@code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead, -events which are emitted by this or other modules might extend this event. -Examples of these events are @code{gdb.BreakpointEvent} and -@code{gdb.ContinueEvent}. - -@defvar ThreadEvent.inferior_thread -In non-stop mode this attribute will be set to the specific thread which was -involved in the emitted event. Otherwise, it will be set to @code{None}. -@end defvar - -Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}. - -This event indicates that the inferior has been continued after a stop. For -inherited attribute refer to @code{gdb.ThreadEvent} above. - -@item events.exited -Emits @code{events.ExitedEvent} which indicates that the inferior has exited. -@code{events.ExitedEvent} has two attributes: -@defvar ExitedEvent.exit_code -An integer representing the exit code, if available, which the inferior -has returned. (The exit code could be unavailable if, for example, -@value{GDBN} detaches from the inferior.) If the exit code is unavailable, -the attribute does not exist. -@end defvar -@defvar ExitedEvent inferior -A reference to the inferior which triggered the @code{exited} event. -@end defvar - -@item events.stop -Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}. - -Indicates that the inferior has stopped. All events emitted by this registry -extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent} -will indicate the stopped thread when @value{GDBN} is running in non-stop -mode. Refer to @code{gdb.ThreadEvent} above for more details. - -Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}. - -This event indicates that the inferior or one of its threads has received as -signal. @code{gdb.SignalEvent} has the following attributes: - -@defvar SignalEvent.stop_signal -A string representing the signal received by the inferior. A list of possible -signal values can be obtained by running the command @code{info signals} in -the @value{GDBN} command prompt. -@end defvar - -Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}. - -@code{gdb.BreakpointEvent} event indicates that one or more breakpoints have -been hit, and has the following attributes: - -@defvar BreakpointEvent.breakpoints -A sequence containing references to all the breakpoints (type -@code{gdb.Breakpoint}) that were hit. -@xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object. -@end defvar -@defvar BreakpointEvent.breakpoint -A reference to the first breakpoint that was hit. -This function is maintained for backward compatibility and is now deprecated -in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute. -@end defvar - -@item events.new_objfile -Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has -been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute: - -@defvar NewObjFileEvent.new_objfile -A reference to the object file (@code{gdb.Objfile}) which has been loaded. -@xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object. -@end defvar - -@end table - -@node Threads In Python -@subsubsection Threads In Python -@cindex threads in python - -@findex gdb.InferiorThread -Python scripts can access information about, and manipulate inferior threads -controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class. - -The following thread-related functions are available in the @code{gdb} -module: - -@findex gdb.selected_thread -@defun gdb.selected_thread () -This function returns the thread object for the selected thread. If there -is no selected thread, this will return @code{None}. -@end defun - -A @code{gdb.InferiorThread} object has the following attributes: - -@defvar InferiorThread.name -The name of the thread. If the user specified a name using -@code{thread name}, then this returns that name. Otherwise, if an -OS-supplied name is available, then it is returned. Otherwise, this -returns @code{None}. - -This attribute can be assigned to. The new value must be a string -object, which sets the new name, or @code{None}, which removes any -user-specified thread name. -@end defvar - -@defvar InferiorThread.num -ID of the thread, as assigned by GDB. -@end defvar - -@defvar InferiorThread.ptid -ID of the thread, as assigned by the operating system. This attribute is a -tuple containing three integers. The first is the Process ID (PID); the second -is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID). -Either the LWPID or TID may be 0, which indicates that the operating system -does not use that identifier. -@end defvar - -A @code{gdb.InferiorThread} object has the following methods: - -@defun InferiorThread.is_valid () -Returns @code{True} if the @code{gdb.InferiorThread} object is valid, -@code{False} if not. A @code{gdb.InferiorThread} object will become -invalid if the thread exits, or the inferior that the thread belongs -is deleted. All other @code{gdb.InferiorThread} methods will throw an -exception if it is invalid at the time the method is called. -@end defun - -@defun InferiorThread.switch () -This changes @value{GDBN}'s currently selected thread to the one represented -by this object. -@end defun - -@defun InferiorThread.is_stopped () -Return a Boolean indicating whether the thread is stopped. -@end defun - -@defun InferiorThread.is_running () -Return a Boolean indicating whether the thread is running. -@end defun - -@defun InferiorThread.is_exited () -Return a Boolean indicating whether the thread is exited. -@end defun - -@node Commands In Python -@subsubsection Commands In Python - -@cindex commands in python -@cindex python commands -You can implement new @value{GDBN} CLI commands in Python. A CLI -command is implemented using an instance of the @code{gdb.Command} -class, most commonly using a subclass. - -@defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]}) -The object initializer for @code{Command} registers the new command -with @value{GDBN}. This initializer is normally invoked from the -subclass' own @code{__init__} method. - -@var{name} is the name of the command. If @var{name} consists of -multiple words, then the initial words are looked for as prefix -commands. In this case, if one of the prefix commands does not exist, -an exception is raised. - -There is no support for multi-line commands. - -@var{command_class} should be one of the @samp{COMMAND_} constants -defined below. This argument tells @value{GDBN} how to categorize the -new command in the help system. - -@var{completer_class} is an optional argument. If given, it should be -one of the @samp{COMPLETE_} constants defined below. This argument -tells @value{GDBN} how to perform completion for this command. If not -given, @value{GDBN} will attempt to complete using the object's -@code{complete} method (see below); if no such method is found, an -error will occur when completion is attempted. - -@var{prefix} is an optional argument. If @code{True}, then the new -command is a prefix command; sub-commands of this command may be -registered. - -The help text for the new command is taken from the Python -documentation string for the command's class, if there is one. If no -documentation string is provided, the default value ``This command is -not documented.'' is used. -@end defun - -@cindex don't repeat Python command -@defun Command.dont_repeat () -By default, a @value{GDBN} command is repeated when the user enters a -blank line at the command prompt. A command can suppress this -behavior by invoking the @code{dont_repeat} method. This is similar -to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}. -@end defun - -@defun Command.invoke (argument, from_tty) -This method is called by @value{GDBN} when this command is invoked. - -@var{argument} is a string. It is the argument to the command, after -leading and trailing whitespace has been stripped. - -@var{from_tty} is a boolean argument. When true, this means that the -command was entered by the user at the terminal; when false it means -that the command came from elsewhere. - -If this method throws an exception, it is turned into a @value{GDBN} -@code{error} call. Otherwise, the return value is ignored. - -@findex gdb.string_to_argv -To break @var{argument} up into an argv-like string use -@code{gdb.string_to_argv}. This function behaves identically to -@value{GDBN}'s internal argument lexer @code{buildargv}. -It is recommended to use this for consistency. -Arguments are separated by spaces and may be quoted. -Example: - -@smallexample -print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"") -['1', '2 "3', '4 "5', "6 '7"] -@end smallexample - -@end defun - -@cindex completion of Python commands -@defun Command.complete (text, word) -This method is called by @value{GDBN} when the user attempts -completion on this command. All forms of completion are handled by -this method, that is, the @key{TAB} and @key{M-?} key bindings -(@pxref{Completion}), and the @code{complete} command (@pxref{Help, -complete}). - -The arguments @var{text} and @var{word} are both strings. @var{text} -holds the complete command line up to the cursor's location. -@var{word} holds the last word of the command line; this is computed -using a word-breaking heuristic. - -The @code{complete} method can return several values: -@itemize @bullet -@item -If the return value is a sequence, the contents of the sequence are -used as the completions. It is up to @code{complete} to ensure that the -contents actually do complete the word. A zero-length sequence is -allowed, it means that there were no completions available. Only -string elements of the sequence are used; other elements in the -sequence are ignored. - -@item -If the return value is one of the @samp{COMPLETE_} constants defined -below, then the corresponding @value{GDBN}-internal completion -function is invoked, and its result is used. - -@item -All other results are treated as though there were no available -completions. -@end itemize -@end defun - -When a new command is registered, it must be declared as a member of -some general class of commands. This is used to classify top-level -commands in the on-line help system; note that prefix commands are not -listed under their own category but rather that of their top-level -command. The available classifications are represented by constants -defined in the @code{gdb} module: - -@table @code -@findex COMMAND_NONE -@findex gdb.COMMAND_NONE -@item gdb.COMMAND_NONE -The command does not belong to any particular class. A command in -this category will not be displayed in any of the help categories. - -@findex COMMAND_RUNNING -@findex gdb.COMMAND_RUNNING -@item gdb.COMMAND_RUNNING -The command is related to running the inferior. For example, -@code{start}, @code{step}, and @code{continue} are in this category. -Type @kbd{help running} at the @value{GDBN} prompt to see a list of -commands in this category. - -@findex COMMAND_DATA -@findex gdb.COMMAND_DATA -@item gdb.COMMAND_DATA -The command is related to data or variables. For example, -@code{call}, @code{find}, and @code{print} are in this category. Type -@kbd{help data} at the @value{GDBN} prompt to see a list of commands -in this category. - -@findex COMMAND_STACK -@findex gdb.COMMAND_STACK -@item gdb.COMMAND_STACK -The command has to do with manipulation of the stack. For example, -@code{backtrace}, @code{frame}, and @code{return} are in this -category. Type @kbd{help stack} at the @value{GDBN} prompt to see a -list of commands in this category. - -@findex COMMAND_FILES -@findex gdb.COMMAND_FILES -@item gdb.COMMAND_FILES -This class is used for file-related commands. For example, -@code{file}, @code{list} and @code{section} are in this category. -Type @kbd{help files} at the @value{GDBN} prompt to see a list of -commands in this category. - -@findex COMMAND_SUPPORT -@findex gdb.COMMAND_SUPPORT -@item gdb.COMMAND_SUPPORT -This should be used for ``support facilities'', generally meaning -things that are useful to the user when interacting with @value{GDBN}, -but not related to the state of the inferior. For example, -@code{help}, @code{make}, and @code{shell} are in this category. Type -@kbd{help support} at the @value{GDBN} prompt to see a list of -commands in this category. - -@findex COMMAND_STATUS -@findex gdb.COMMAND_STATUS -@item gdb.COMMAND_STATUS -The command is an @samp{info}-related command, that is, related to the -state of @value{GDBN} itself. For example, @code{info}, @code{macro}, -and @code{show} are in this category. Type @kbd{help status} at the -@value{GDBN} prompt to see a list of commands in this category. - -@findex COMMAND_BREAKPOINTS -@findex gdb.COMMAND_BREAKPOINTS -@item gdb.COMMAND_BREAKPOINTS -The command has to do with breakpoints. For example, @code{break}, -@code{clear}, and @code{delete} are in this category. Type @kbd{help -breakpoints} at the @value{GDBN} prompt to see a list of commands in -this category. - -@findex COMMAND_TRACEPOINTS -@findex gdb.COMMAND_TRACEPOINTS -@item gdb.COMMAND_TRACEPOINTS -The command has to do with tracepoints. For example, @code{trace}, -@code{actions}, and @code{tfind} are in this category. Type -@kbd{help tracepoints} at the @value{GDBN} prompt to see a list of -commands in this category. - -@findex COMMAND_USER -@findex gdb.COMMAND_USER -@item gdb.COMMAND_USER -The command is a general purpose command for the user, and typically -does not fit in one of the other categories. -Type @kbd{help user-defined} at the @value{GDBN} prompt to see -a list of commands in this category, as well as the list of gdb macros -(@pxref{Sequences}). - -@findex COMMAND_OBSCURE -@findex gdb.COMMAND_OBSCURE -@item gdb.COMMAND_OBSCURE -The command is only used in unusual circumstances, or is not of -general interest to users. For example, @code{checkpoint}, -@code{fork}, and @code{stop} are in this category. Type @kbd{help -obscure} at the @value{GDBN} prompt to see a list of commands in this -category. - -@findex COMMAND_MAINTENANCE -@findex gdb.COMMAND_MAINTENANCE -@item gdb.COMMAND_MAINTENANCE -The command is only useful to @value{GDBN} maintainers. The -@code{maintenance} and @code{flushregs} commands are in this category. -Type @kbd{help internals} at the @value{GDBN} prompt to see a list of -commands in this category. -@end table - -A new command can use a predefined completion function, either by -specifying it via an argument at initialization, or by returning it -from the @code{complete} method. These predefined completion -constants are all defined in the @code{gdb} module: - -@table @code -@findex COMPLETE_NONE -@findex gdb.COMPLETE_NONE -@item gdb.COMPLETE_NONE -This constant means that no completion should be done. - -@findex COMPLETE_FILENAME -@findex gdb.COMPLETE_FILENAME -@item gdb.COMPLETE_FILENAME -This constant means that filename completion should be performed. - -@findex COMPLETE_LOCATION -@findex gdb.COMPLETE_LOCATION -@item gdb.COMPLETE_LOCATION -This constant means that location completion should be done. -@xref{Specify Location}. - -@findex COMPLETE_COMMAND -@findex gdb.COMPLETE_COMMAND -@item gdb.COMPLETE_COMMAND -This constant means that completion should examine @value{GDBN} -command names. - -@findex COMPLETE_SYMBOL -@findex gdb.COMPLETE_SYMBOL -@item gdb.COMPLETE_SYMBOL -This constant means that completion should be done using symbol names -as the source. -@end table - -The following code snippet shows how a trivial CLI command can be -implemented in Python: - -@smallexample -class HelloWorld (gdb.Command): - """Greet the whole world.""" - - def __init__ (self): - super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) - - def invoke (self, arg, from_tty): - print "Hello, World!" - -HelloWorld () -@end smallexample - -The last line instantiates the class, and is necessary to trigger the -registration of the command with @value{GDBN}. Depending on how the -Python code is read into @value{GDBN}, you may need to import the -@code{gdb} module explicitly. - -@node Parameters In Python -@subsubsection Parameters In Python - -@cindex parameters in python -@cindex python parameters -@tindex gdb.Parameter -@tindex Parameter -You can implement new @value{GDBN} parameters using Python. A new -parameter is implemented as an instance of the @code{gdb.Parameter} -class. - -Parameters are exposed to the user via the @code{set} and -@code{show} commands. @xref{Help}. - -There are many parameters that already exist and can be set in -@value{GDBN}. Two examples are: @code{set follow fork} and -@code{set charset}. Setting these parameters influences certain -behavior in @value{GDBN}. Similarly, you can define parameters that -can be used to influence behavior in custom Python scripts and commands. - -@defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]}) -The object initializer for @code{Parameter} registers the new -parameter with @value{GDBN}. This initializer is normally invoked -from the subclass' own @code{__init__} method. - -@var{name} is the name of the new parameter. If @var{name} consists -of multiple words, then the initial words are looked for as prefix -parameters. An example of this can be illustrated with the -@code{set print} set of parameters. If @var{name} is -@code{print foo}, then @code{print} will be searched as the prefix -parameter. In this case the parameter can subsequently be accessed in -@value{GDBN} as @code{set print foo}. - -If @var{name} consists of multiple words, and no prefix parameter group -can be found, an exception is raised. - -@var{command-class} should be one of the @samp{COMMAND_} constants -(@pxref{Commands In Python}). This argument tells @value{GDBN} how to -categorize the new parameter in the help system. - -@var{parameter-class} should be one of the @samp{PARAM_} constants -defined below. This argument tells @value{GDBN} the type of the new -parameter; this information is used for input validation and -completion. - -If @var{parameter-class} is @code{PARAM_ENUM}, then -@var{enum-sequence} must be a sequence of strings. These strings -represent the possible values for the parameter. - -If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence -of a fourth argument will cause an exception to be thrown. - -The help text for the new parameter is taken from the Python -documentation string for the parameter's class, if there is one. If -there is no documentation string, a default value is used. -@end defun - -@defvar Parameter.set_doc -If this attribute exists, and is a string, then its value is used as -the help text for this parameter's @code{set} command. The value is -examined when @code{Parameter.__init__} is invoked; subsequent changes -have no effect. -@end defvar - -@defvar Parameter.show_doc -If this attribute exists, and is a string, then its value is used as -the help text for this parameter's @code{show} command. The value is -examined when @code{Parameter.__init__} is invoked; subsequent changes -have no effect. -@end defvar - -@defvar Parameter.value -The @code{value} attribute holds the underlying value of the -parameter. It can be read and assigned to just as any other -attribute. @value{GDBN} does validation when assignments are made. -@end defvar - -There are two methods that should be implemented in any -@code{Parameter} class. These are: - -@defun Parameter.get_set_string (self) -@value{GDBN} will call this method when a @var{parameter}'s value has -been changed via the @code{set} API (for example, @kbd{set foo off}). -The @code{value} attribute has already been populated with the new -value and may be used in output. This method must return a string. -@end defun - -@defun Parameter.get_show_string (self, svalue) -@value{GDBN} will call this method when a @var{parameter}'s -@code{show} API has been invoked (for example, @kbd{show foo}). The -argument @code{svalue} receives the string representation of the -current value. This method must return a string. -@end defun - -When a new parameter is defined, its type must be specified. The -available types are represented by constants defined in the @code{gdb} -module: - -@table @code -@findex PARAM_BOOLEAN -@findex gdb.PARAM_BOOLEAN -@item gdb.PARAM_BOOLEAN -The value is a plain boolean. The Python boolean values, @code{True} -and @code{False} are the only valid values. - -@findex PARAM_AUTO_BOOLEAN -@findex gdb.PARAM_AUTO_BOOLEAN -@item gdb.PARAM_AUTO_BOOLEAN -The value has three possible states: true, false, and @samp{auto}. In -Python, true and false are represented using boolean constants, and -@samp{auto} is represented using @code{None}. - -@findex PARAM_UINTEGER -@findex gdb.PARAM_UINTEGER -@item gdb.PARAM_UINTEGER -The value is an unsigned integer. The value of 0 should be -interpreted to mean ``unlimited''. - -@findex PARAM_INTEGER -@findex gdb.PARAM_INTEGER -@item gdb.PARAM_INTEGER -The value is a signed integer. The value of 0 should be interpreted -to mean ``unlimited''. - -@findex PARAM_STRING -@findex gdb.PARAM_STRING -@item gdb.PARAM_STRING -The value is a string. When the user modifies the string, any escape -sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are -translated into corresponding characters and encoded into the current -host charset. - -@findex PARAM_STRING_NOESCAPE -@findex gdb.PARAM_STRING_NOESCAPE -@item gdb.PARAM_STRING_NOESCAPE -The value is a string. When the user modifies the string, escapes are -passed through untranslated. - -@findex PARAM_OPTIONAL_FILENAME -@findex gdb.PARAM_OPTIONAL_FILENAME -@item gdb.PARAM_OPTIONAL_FILENAME -The value is a either a filename (a string), or @code{None}. - -@findex PARAM_FILENAME -@findex gdb.PARAM_FILENAME -@item gdb.PARAM_FILENAME -The value is a filename. This is just like -@code{PARAM_STRING_NOESCAPE}, but uses file names for completion. - -@findex PARAM_ZINTEGER -@findex gdb.PARAM_ZINTEGER -@item gdb.PARAM_ZINTEGER -The value is an integer. This is like @code{PARAM_INTEGER}, except 0 -is interpreted as itself. - -@findex PARAM_ENUM -@findex gdb.PARAM_ENUM -@item gdb.PARAM_ENUM -The value is a string, which must be one of a collection string -constants provided when the parameter is created. -@end table - -@node Functions In Python -@subsubsection Writing new convenience functions - -@cindex writing convenience functions -@cindex convenience functions in python -@cindex python convenience functions -@tindex gdb.Function -@tindex Function -You can implement new convenience functions (@pxref{Convenience Vars}) -in Python. A convenience function is an instance of a subclass of the -class @code{gdb.Function}. - -@defun Function.__init__ (name) -The initializer for @code{Function} registers the new function with -@value{GDBN}. The argument @var{name} is the name of the function, -a string. The function will be visible to the user as a convenience -variable of type @code{internal function}, whose name is the same as -the given @var{name}. - -The documentation for the new function is taken from the documentation -string for the new class. -@end defun - -@defun Function.invoke (@var{*args}) -When a convenience function is evaluated, its arguments are converted -to instances of @code{gdb.Value}, and then the function's -@code{invoke} method is called. Note that @value{GDBN} does not -predetermine the arity of convenience functions. Instead, all -available arguments are passed to @code{invoke}, following the -standard Python calling convention. In particular, a convenience -function can have default values for parameters without ill effect. - -The return value of this method is used as its value in the enclosing -expression. If an ordinary Python value is returned, it is converted -to a @code{gdb.Value} following the usual rules. -@end defun - -The following code snippet shows how a trivial convenience function can -be implemented in Python: - -@smallexample -class Greet (gdb.Function): - """Return string to greet someone. -Takes a name as argument.""" - - def __init__ (self): - super (Greet, self).__init__ ("greet") - - def invoke (self, name): - return "Hello, %s!" % name.string () - -Greet () -@end smallexample - -The last line instantiates the class, and is necessary to trigger the -registration of the function with @value{GDBN}. Depending on how the -Python code is read into @value{GDBN}, you may need to import the -@code{gdb} module explicitly. - -Now you can use the function in an expression: - -@smallexample -(gdb) print $greet("Bob") -$1 = "Hello, Bob!" -@end smallexample - -@node Progspaces In Python -@subsubsection Program Spaces In Python - -@cindex progspaces in python -@tindex gdb.Progspace -@tindex Progspace -A program space, or @dfn{progspace}, represents a symbolic view -of an address space. -It consists of all of the objfiles of the program. -@xref{Objfiles In Python}. -@xref{Inferiors and Programs, program spaces}, for more details -about program spaces. - -The following progspace-related functions are available in the -@code{gdb} module: - -@findex gdb.current_progspace -@defun gdb.current_progspace () -This function returns the program space of the currently selected inferior. -@xref{Inferiors and Programs}. -@end defun - -@findex gdb.progspaces -@defun gdb.progspaces () -Return a sequence of all the progspaces currently known to @value{GDBN}. -@end defun - -Each progspace is represented by an instance of the @code{gdb.Progspace} -class. - -@defvar Progspace.filename -The file name of the progspace as a string. -@end defvar - -@defvar Progspace.pretty_printers -The @code{pretty_printers} attribute is a list of functions. It is -used to look up pretty-printers. A @code{Value} is passed to each -function in order; if the function returns @code{None}, then the -search continues. Otherwise, the return value should be an object -which is used to format the value. @xref{Pretty Printing API}, for more -information. -@end defvar - -@defvar Progspace.type_printers -The @code{type_printers} attribute is a list of type printer objects. -@xref{Type Printing API}, for more information. -@end defvar - -@node Objfiles In Python -@subsubsection Objfiles In Python - -@cindex objfiles in python -@tindex gdb.Objfile -@tindex Objfile -@value{GDBN} loads symbols for an inferior from various -symbol-containing files (@pxref{Files}). These include the primary -executable file, any shared libraries used by the inferior, and any -separate debug info files (@pxref{Separate Debug Files}). -@value{GDBN} calls these symbol-containing files @dfn{objfiles}. - -The following objfile-related functions are available in the -@code{gdb} module: - -@findex gdb.current_objfile -@defun gdb.current_objfile () -When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN} -sets the ``current objfile'' to the corresponding objfile. This -function returns the current objfile. If there is no current objfile, -this function returns @code{None}. -@end defun - -@findex gdb.objfiles -@defun gdb.objfiles () -Return a sequence of all the objfiles current known to @value{GDBN}. -@xref{Objfiles In Python}. -@end defun - -Each objfile is represented by an instance of the @code{gdb.Objfile} -class. - -@defvar Objfile.filename -The file name of the objfile as a string. -@end defvar - -@defvar Objfile.pretty_printers -The @code{pretty_printers} attribute is a list of functions. It is -used to look up pretty-printers. A @code{Value} is passed to each -function in order; if the function returns @code{None}, then the -search continues. Otherwise, the return value should be an object -which is used to format the value. @xref{Pretty Printing API}, for more -information. -@end defvar - -@defvar Objfile.type_printers -The @code{type_printers} attribute is a list of type printer objects. -@xref{Type Printing API}, for more information. -@end defvar - -A @code{gdb.Objfile} object has the following methods: - -@defun Objfile.is_valid () -Returns @code{True} if the @code{gdb.Objfile} object is valid, -@code{False} if not. A @code{gdb.Objfile} object can become invalid -if the object file it refers to is not loaded in @value{GDBN} any -longer. All other @code{gdb.Objfile} methods will throw an exception -if it is invalid at the time the method is called. -@end defun - -@node Frames In Python -@subsubsection Accessing inferior stack frames from Python. - -@cindex frames in python -When the debugged program stops, @value{GDBN} is able to analyze its call -stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class -represents a frame in the stack. A @code{gdb.Frame} object is only valid -while its corresponding frame exists in the inferior's stack. If you try -to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error} -exception (@pxref{Exception Handling}). - -Two @code{gdb.Frame} objects can be compared for equality with the @code{==} -operator, like: - -@smallexample -(@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame () -True -@end smallexample - -The following frame-related functions are available in the @code{gdb} module: - -@findex gdb.selected_frame -@defun gdb.selected_frame () -Return the selected frame object. (@pxref{Selection,,Selecting a Frame}). -@end defun - -@findex gdb.newest_frame -@defun gdb.newest_frame () -Return the newest frame object for the selected thread. -@end defun - -@defun gdb.frame_stop_reason_string (reason) -Return a string explaining the reason why @value{GDBN} stopped unwinding -frames, as expressed by the given @var{reason} code (an integer, see the -@code{unwind_stop_reason} method further down in this section). -@end defun - -A @code{gdb.Frame} object has the following methods: - -@defun Frame.is_valid () -Returns true if the @code{gdb.Frame} object is valid, false if not. -A frame object can become invalid if the frame it refers to doesn't -exist anymore in the inferior. All @code{gdb.Frame} methods will throw -an exception if it is invalid at the time the method is called. -@end defun - -@defun Frame.name () -Returns the function name of the frame, or @code{None} if it can't be -obtained. -@end defun - -@defun Frame.architecture () -Returns the @code{gdb.Architecture} object corresponding to the frame's -architecture. @xref{Architectures In Python}. -@end defun - -@defun Frame.type () -Returns the type of the frame. The value can be one of: -@table @code -@item gdb.NORMAL_FRAME -An ordinary stack frame. - -@item gdb.DUMMY_FRAME -A fake stack frame that was created by @value{GDBN} when performing an -inferior function call. - -@item gdb.INLINE_FRAME -A frame representing an inlined function. The function was inlined -into a @code{gdb.NORMAL_FRAME} that is older than this one. - -@item gdb.TAILCALL_FRAME -A frame representing a tail call. @xref{Tail Call Frames}. - -@item gdb.SIGTRAMP_FRAME -A signal trampoline frame. This is the frame created by the OS when -it calls into a signal handler. - -@item gdb.ARCH_FRAME -A fake stack frame representing a cross-architecture call. - -@item gdb.SENTINEL_FRAME -This is like @code{gdb.NORMAL_FRAME}, but it is only used for the -newest frame. -@end table -@end defun - -@defun Frame.unwind_stop_reason () -Return an integer representing the reason why it's not possible to find -more frames toward the outermost frame. Use -@code{gdb.frame_stop_reason_string} to convert the value returned by this -function to a string. The value can be one of: - -@table @code -@item gdb.FRAME_UNWIND_NO_REASON -No particular reason (older frames should be available). - -@item gdb.FRAME_UNWIND_NULL_ID -The previous frame's analyzer returns an invalid result. - -@item gdb.FRAME_UNWIND_OUTERMOST -This frame is the outermost. - -@item gdb.FRAME_UNWIND_UNAVAILABLE -Cannot unwind further, because that would require knowing the -values of registers or memory that have not been collected. - -@item gdb.FRAME_UNWIND_INNER_ID -This frame ID looks like it ought to belong to a NEXT frame, -but we got it for a PREV frame. Normally, this is a sign of -unwinder failure. It could also indicate stack corruption. - -@item gdb.FRAME_UNWIND_SAME_ID -This frame has the same ID as the previous one. That means -that unwinding further would almost certainly give us another -frame with exactly the same ID, so break the chain. Normally, -this is a sign of unwinder failure. It could also indicate -stack corruption. - -@item gdb.FRAME_UNWIND_NO_SAVED_PC -The frame unwinder did not find any saved PC, but we needed -one to unwind further. - -@item gdb.FRAME_UNWIND_FIRST_ERROR -Any stop reason greater or equal to this value indicates some kind -of error. This special value facilitates writing code that tests -for errors in unwinding in a way that will work correctly even if -the list of the other values is modified in future @value{GDBN} -versions. Using it, you could write: -@smallexample -reason = gdb.selected_frame().unwind_stop_reason () -reason_str = gdb.frame_stop_reason_string (reason) -if reason >= gdb.FRAME_UNWIND_FIRST_ERROR: - print "An error occured: %s" % reason_str -@end smallexample -@end table - -@end defun - -@defun Frame.pc () -Returns the frame's resume address. -@end defun - -@defun Frame.block () -Return the frame's code block. @xref{Blocks In Python}. -@end defun - -@defun Frame.function () -Return the symbol for the function corresponding to this frame. -@xref{Symbols In Python}. -@end defun - -@defun Frame.older () -Return the frame that called this frame. -@end defun - -@defun Frame.newer () -Return the frame called by this frame. -@end defun - -@defun Frame.find_sal () -Return the frame's symtab and line object. -@xref{Symbol Tables In Python}. -@end defun - -@defun Frame.read_var (variable @r{[}, block@r{]}) -Return the value of @var{variable} in this frame. If the optional -argument @var{block} is provided, search for the variable from that -block; otherwise start at the frame's current block (which is -determined by the frame's current program counter). @var{variable} -must be a string or a @code{gdb.Symbol} object. @var{block} must be a -@code{gdb.Block} object. -@end defun - -@defun Frame.select () -Set this frame to be the selected frame. @xref{Stack, ,Examining the -Stack}. -@end defun - -@node Blocks In Python -@subsubsection Accessing frame blocks from Python. - -@cindex blocks in python -@tindex gdb.Block - -Within each frame, @value{GDBN} maintains information on each block -stored in that frame. These blocks are organized hierarchically, and -are represented individually in Python as a @code{gdb.Block}. -Please see @ref{Frames In Python}, for a more in-depth discussion on -frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more -detailed technical information on @value{GDBN}'s book-keeping of the -stack. - -A @code{gdb.Block} is iterable. The iterator returns the symbols -(@pxref{Symbols In Python}) local to the block. Python programs -should not assume that a specific block object will always contain a -given symbol, since changes in @value{GDBN} features and -infrastructure may cause symbols move across blocks in a symbol -table. - -The following block-related functions are available in the @code{gdb} -module: - -@findex gdb.block_for_pc -@defun gdb.block_for_pc (pc) -Return the @code{gdb.Block} containing the given @var{pc} value. If the -block cannot be found for the @var{pc} value specified, the function -will return @code{None}. -@end defun - -A @code{gdb.Block} object has the following methods: - -@defun Block.is_valid () -Returns @code{True} if the @code{gdb.Block} object is valid, -@code{False} if not. A block object can become invalid if the block it -refers to doesn't exist anymore in the inferior. All other -@code{gdb.Block} methods will throw an exception if it is invalid at -the time the method is called. The block's validity is also checked -during iteration over symbols of the block. -@end defun - -A @code{gdb.Block} object has the following attributes: - -@defvar Block.start -The start address of the block. This attribute is not writable. -@end defvar - -@defvar Block.end -The end address of the block. This attribute is not writable. -@end defvar - -@defvar Block.function -The name of the block represented as a @code{gdb.Symbol}. If the -block is not named, then this attribute holds @code{None}. This -attribute is not writable. -@end defvar - -@defvar Block.superblock -The block containing this block. If this parent block does not exist, -this attribute holds @code{None}. This attribute is not writable. -@end defvar - -@defvar Block.global_block -The global block associated with this block. This attribute is not -writable. -@end defvar - -@defvar Block.static_block -The static block associated with this block. This attribute is not -writable. -@end defvar - -@defvar Block.is_global -@code{True} if the @code{gdb.Block} object is a global block, -@code{False} if not. This attribute is not -writable. -@end defvar - -@defvar Block.is_static -@code{True} if the @code{gdb.Block} object is a static block, -@code{False} if not. This attribute is not writable. -@end defvar - -@node Symbols In Python -@subsubsection Python representation of Symbols. - -@cindex symbols in python -@tindex gdb.Symbol - -@value{GDBN} represents every variable, function and type as an -entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}. -Similarly, Python represents these symbols in @value{GDBN} with the -@code{gdb.Symbol} object. - -The following symbol-related functions are available in the @code{gdb} -module: - -@findex gdb.lookup_symbol -@defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]}) -This function searches for a symbol by name. The search scope can be -restricted to the parameters defined in the optional domain and block -arguments. - -@var{name} is the name of the symbol. It must be a string. The -optional @var{block} argument restricts the search to symbols visible -in that @var{block}. The @var{block} argument must be a -@code{gdb.Block} object. If omitted, the block for the current frame -is used. The optional @var{domain} argument restricts -the search to the domain type. The @var{domain} argument must be a -domain constant defined in the @code{gdb} module and described later -in this chapter. - -The result is a tuple of two elements. -The first element is a @code{gdb.Symbol} object or @code{None} if the symbol -is not found. -If the symbol is found, the second element is @code{True} if the symbol -is a field of a method's object (e.g., @code{this} in C@t{++}), -otherwise it is @code{False}. -If the symbol is not found, the second element is @code{False}. -@end defun - -@findex gdb.lookup_global_symbol -@defun gdb.lookup_global_symbol (name @r{[}, domain@r{]}) -This function searches for a global symbol by name. -The search scope can be restricted to by the domain argument. - -@var{name} is the name of the symbol. It must be a string. -The optional @var{domain} argument restricts the search to the domain type. -The @var{domain} argument must be a domain constant defined in the @code{gdb} -module and described later in this chapter. - -The result is a @code{gdb.Symbol} object or @code{None} if the symbol -is not found. -@end defun - -A @code{gdb.Symbol} object has the following attributes: - -@defvar Symbol.type -The type of the symbol or @code{None} if no type is recorded. -This attribute is represented as a @code{gdb.Type} object. -@xref{Types In Python}. This attribute is not writable. -@end defvar - -@defvar Symbol.symtab -The symbol table in which the symbol appears. This attribute is -represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In -Python}. This attribute is not writable. -@end defvar - -@defvar Symbol.line -The line number in the source code at which the symbol was defined. -This is an integer. -@end defvar - -@defvar Symbol.name -The name of the symbol as a string. This attribute is not writable. -@end defvar - -@defvar Symbol.linkage_name -The name of the symbol, as used by the linker (i.e., may be mangled). -This attribute is not writable. -@end defvar - -@defvar Symbol.print_name -The name of the symbol in a form suitable for output. This is either -@code{name} or @code{linkage_name}, depending on whether the user -asked @value{GDBN} to display demangled or mangled names. -@end defvar - -@defvar Symbol.addr_class -The address class of the symbol. This classifies how to find the value -of a symbol. Each address class is a constant defined in the -@code{gdb} module and described later in this chapter. -@end defvar - -@defvar Symbol.needs_frame -This is @code{True} if evaluating this symbol's value requires a frame -(@pxref{Frames In Python}) and @code{False} otherwise. Typically, -local variables will require a frame, but other symbols will not. -@end defvar - -@defvar Symbol.is_argument -@code{True} if the symbol is an argument of a function. -@end defvar - -@defvar Symbol.is_constant -@code{True} if the symbol is a constant. -@end defvar - -@defvar Symbol.is_function -@code{True} if the symbol is a function or a method. -@end defvar - -@defvar Symbol.is_variable -@code{True} if the symbol is a variable. -@end defvar - -A @code{gdb.Symbol} object has the following methods: - -@defun Symbol.is_valid () -Returns @code{True} if the @code{gdb.Symbol} object is valid, -@code{False} if not. A @code{gdb.Symbol} object can become invalid if -the symbol it refers to does not exist in @value{GDBN} any longer. -All other @code{gdb.Symbol} methods will throw an exception if it is -invalid at the time the method is called. -@end defun - -@defun Symbol.value (@r{[}frame@r{]}) -Compute the value of the symbol, as a @code{gdb.Value}. For -functions, this computes the address of the function, cast to the -appropriate type. If the symbol requires a frame in order to compute -its value, then @var{frame} must be given. If @var{frame} is not -given, or if @var{frame} is invalid, then this method will throw an -exception. -@end defun - -The available domain categories in @code{gdb.Symbol} are represented -as constants in the @code{gdb} module: - -@table @code -@findex SYMBOL_UNDEF_DOMAIN -@findex gdb.SYMBOL_UNDEF_DOMAIN -@item gdb.SYMBOL_UNDEF_DOMAIN -This is used when a domain has not been discovered or none of the -following domains apply. This usually indicates an error either -in the symbol information or in @value{GDBN}'s handling of symbols. -@findex SYMBOL_VAR_DOMAIN -@findex gdb.SYMBOL_VAR_DOMAIN -@item gdb.SYMBOL_VAR_DOMAIN -This domain contains variables, function names, typedef names and enum -type values. -@findex SYMBOL_STRUCT_DOMAIN -@findex gdb.SYMBOL_STRUCT_DOMAIN -@item gdb.SYMBOL_STRUCT_DOMAIN -This domain holds struct, union and enum type names. -@findex SYMBOL_LABEL_DOMAIN -@findex gdb.SYMBOL_LABEL_DOMAIN -@item gdb.SYMBOL_LABEL_DOMAIN -This domain contains names of labels (for gotos). -@findex SYMBOL_VARIABLES_DOMAIN -@findex gdb.SYMBOL_VARIABLES_DOMAIN -@item gdb.SYMBOL_VARIABLES_DOMAIN -This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it -contains everything minus functions and types. -@findex SYMBOL_FUNCTIONS_DOMAIN -@findex gdb.SYMBOL_FUNCTIONS_DOMAIN -@item gdb.SYMBOL_FUNCTION_DOMAIN -This domain contains all functions. -@findex SYMBOL_TYPES_DOMAIN -@findex gdb.SYMBOL_TYPES_DOMAIN -@item gdb.SYMBOL_TYPES_DOMAIN -This domain contains all types. -@end table - -The available address class categories in @code{gdb.Symbol} are represented -as constants in the @code{gdb} module: - -@table @code -@findex SYMBOL_LOC_UNDEF -@findex gdb.SYMBOL_LOC_UNDEF -@item gdb.SYMBOL_LOC_UNDEF -If this is returned by address class, it indicates an error either in -the symbol information or in @value{GDBN}'s handling of symbols. -@findex SYMBOL_LOC_CONST -@findex gdb.SYMBOL_LOC_CONST -@item gdb.SYMBOL_LOC_CONST -Value is constant int. -@findex SYMBOL_LOC_STATIC -@findex gdb.SYMBOL_LOC_STATIC -@item gdb.SYMBOL_LOC_STATIC -Value is at a fixed address. -@findex SYMBOL_LOC_REGISTER -@findex gdb.SYMBOL_LOC_REGISTER -@item gdb.SYMBOL_LOC_REGISTER -Value is in a register. -@findex SYMBOL_LOC_ARG -@findex gdb.SYMBOL_LOC_ARG -@item gdb.SYMBOL_LOC_ARG -Value is an argument. This value is at the offset stored within the -symbol inside the frame's argument list. -@findex SYMBOL_LOC_REF_ARG -@findex gdb.SYMBOL_LOC_REF_ARG -@item gdb.SYMBOL_LOC_REF_ARG -Value address is stored in the frame's argument list. Just like -@code{LOC_ARG} except that the value's address is stored at the -offset, not the value itself. -@findex SYMBOL_LOC_REGPARM_ADDR -@findex gdb.SYMBOL_LOC_REGPARM_ADDR -@item gdb.SYMBOL_LOC_REGPARM_ADDR -Value is a specified register. Just like @code{LOC_REGISTER} except -the register holds the address of the argument instead of the argument -itself. -@findex SYMBOL_LOC_LOCAL -@findex gdb.SYMBOL_LOC_LOCAL -@item gdb.SYMBOL_LOC_LOCAL -Value is a local variable. -@findex SYMBOL_LOC_TYPEDEF -@findex gdb.SYMBOL_LOC_TYPEDEF -@item gdb.SYMBOL_LOC_TYPEDEF -Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all -have this class. -@findex SYMBOL_LOC_BLOCK -@findex gdb.SYMBOL_LOC_BLOCK -@item gdb.SYMBOL_LOC_BLOCK -Value is a block. -@findex SYMBOL_LOC_CONST_BYTES -@findex gdb.SYMBOL_LOC_CONST_BYTES -@item gdb.SYMBOL_LOC_CONST_BYTES -Value is a byte-sequence. -@findex SYMBOL_LOC_UNRESOLVED -@findex gdb.SYMBOL_LOC_UNRESOLVED -@item gdb.SYMBOL_LOC_UNRESOLVED -Value is at a fixed address, but the address of the variable has to be -determined from the minimal symbol table whenever the variable is -referenced. -@findex SYMBOL_LOC_OPTIMIZED_OUT -@findex gdb.SYMBOL_LOC_OPTIMIZED_OUT -@item gdb.SYMBOL_LOC_OPTIMIZED_OUT -The value does not actually exist in the program. -@findex SYMBOL_LOC_COMPUTED -@findex gdb.SYMBOL_LOC_COMPUTED -@item gdb.SYMBOL_LOC_COMPUTED -The value's address is a computed location. -@end table - -@node Symbol Tables In Python -@subsubsection Symbol table representation in Python. - -@cindex symbol tables in python -@tindex gdb.Symtab -@tindex gdb.Symtab_and_line - -Access to symbol table data maintained by @value{GDBN} on the inferior -is exposed to Python via two objects: @code{gdb.Symtab_and_line} and -@code{gdb.Symtab}. Symbol table and line data for a frame is returned -from the @code{find_sal} method in @code{gdb.Frame} object. -@xref{Frames In Python}. - -For more information on @value{GDBN}'s symbol table management, see -@ref{Symbols, ,Examining the Symbol Table}, for more information. - -A @code{gdb.Symtab_and_line} object has the following attributes: - -@defvar Symtab_and_line.symtab -The symbol table object (@code{gdb.Symtab}) for this frame. -This attribute is not writable. -@end defvar - -@defvar Symtab_and_line.pc -Indicates the start of the address range occupied by code for the -current source line. This attribute is not writable. -@end defvar - -@defvar Symtab_and_line.last -Indicates the end of the address range occupied by code for the current -source line. This attribute is not writable. -@end defvar - -@defvar Symtab_and_line.line -Indicates the current line number for this object. This -attribute is not writable. -@end defvar - -A @code{gdb.Symtab_and_line} object has the following methods: - -@defun Symtab_and_line.is_valid () -Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid, -@code{False} if not. A @code{gdb.Symtab_and_line} object can become -invalid if the Symbol table and line object it refers to does not -exist in @value{GDBN} any longer. All other -@code{gdb.Symtab_and_line} methods will throw an exception if it is -invalid at the time the method is called. -@end defun - -A @code{gdb.Symtab} object has the following attributes: - -@defvar Symtab.filename -The symbol table's source filename. This attribute is not writable. -@end defvar - -@defvar Symtab.objfile -The symbol table's backing object file. @xref{Objfiles In Python}. -This attribute is not writable. -@end defvar - -A @code{gdb.Symtab} object has the following methods: - -@defun Symtab.is_valid () -Returns @code{True} if the @code{gdb.Symtab} object is valid, -@code{False} if not. A @code{gdb.Symtab} object can become invalid if -the symbol table it refers to does not exist in @value{GDBN} any -longer. All other @code{gdb.Symtab} methods will throw an exception -if it is invalid at the time the method is called. -@end defun - -@defun Symtab.fullname () -Return the symbol table's source absolute file name. -@end defun - -@defun Symtab.global_block () -Return the global block of the underlying symbol table. -@xref{Blocks In Python}. -@end defun - -@defun Symtab.static_block () -Return the static block of the underlying symbol table. -@xref{Blocks In Python}. -@end defun - -@node Breakpoints In Python -@subsubsection Manipulating breakpoints using Python - -@cindex breakpoints in python -@tindex gdb.Breakpoint - -Python code can manipulate breakpoints via the @code{gdb.Breakpoint} -class. - -@defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]}) -Create a new breakpoint. @var{spec} is a string naming the -location of the breakpoint, or an expression that defines a -watchpoint. The contents can be any location recognized by the -@code{break} command, or in the case of a watchpoint, by the @code{watch} -command. The optional @var{type} denotes the breakpoint to create -from the types defined later in this chapter. This argument can be -either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type} -defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument -allows the breakpoint to become invisible to the user. The breakpoint -will neither be reported when created, nor will it be listed in the -output from @code{info breakpoints} (but will be listed with the -@code{maint info breakpoints} command). The optional @var{wp_class} -argument defines the class of watchpoint to create, if @var{type} is -@code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is -assumed to be a @code{gdb.WP_WRITE} class. -@end defun - -@defun Breakpoint.stop (self) -The @code{gdb.Breakpoint} class can be sub-classed and, in -particular, you may choose to implement the @code{stop} method. -If this method is defined as a sub-class of @code{gdb.Breakpoint}, -it will be called when the inferior reaches any location of a -breakpoint which instantiates that sub-class. If the method returns -@code{True}, the inferior will be stopped at the location of the -breakpoint, otherwise the inferior will continue. - -If there are multiple breakpoints at the same location with a -@code{stop} method, each one will be called regardless of the -return status of the previous. This ensures that all @code{stop} -methods have a chance to execute at that location. In this scenario -if one of the methods returns @code{True} but the others return -@code{False}, the inferior will still be stopped. - -You should not alter the execution state of the inferior (i.e.@:, step, -next, etc.), alter the current frame context (i.e.@:, change the current -active frame), or alter, add or delete any breakpoint. As a general -rule, you should not alter any data within @value{GDBN} or the inferior -at this time. - -Example @code{stop} implementation: - -@smallexample -class MyBreakpoint (gdb.Breakpoint): - def stop (self): - inf_val = gdb.parse_and_eval("foo") - if inf_val == 3: - return True - return False -@end smallexample -@end defun - -The available watchpoint types represented by constants are defined in the -@code{gdb} module: - -@table @code -@findex WP_READ -@findex gdb.WP_READ -@item gdb.WP_READ -Read only watchpoint. - -@findex WP_WRITE -@findex gdb.WP_WRITE -@item gdb.WP_WRITE -Write only watchpoint. - -@findex WP_ACCESS -@findex gdb.WP_ACCESS -@item gdb.WP_ACCESS -Read/Write watchpoint. -@end table - -@defun Breakpoint.is_valid () -Return @code{True} if this @code{Breakpoint} object is valid, -@code{False} otherwise. A @code{Breakpoint} object can become invalid -if the user deletes the breakpoint. In this case, the object still -exists, but the underlying breakpoint does not. In the cases of -watchpoint scope, the watchpoint remains valid even if execution of the -inferior leaves the scope of that watchpoint. -@end defun - -@defun Breakpoint.delete -Permanently deletes the @value{GDBN} breakpoint. This also -invalidates the Python @code{Breakpoint} object. Any further access -to this object's attributes or methods will raise an error. -@end defun - -@defvar Breakpoint.enabled -This attribute is @code{True} if the breakpoint is enabled, and -@code{False} otherwise. This attribute is writable. -@end defvar - -@defvar Breakpoint.silent -This attribute is @code{True} if the breakpoint is silent, and -@code{False} otherwise. This attribute is writable. - -Note that a breakpoint can also be silent if it has commands and the -first command is @code{silent}. This is not reported by the -@code{silent} attribute. -@end defvar - -@defvar Breakpoint.thread -If the breakpoint is thread-specific, this attribute holds the thread -id. If the breakpoint is not thread-specific, this attribute is -@code{None}. This attribute is writable. -@end defvar - -@defvar Breakpoint.task -If the breakpoint is Ada task-specific, this attribute holds the Ada task -id. If the breakpoint is not task-specific (or the underlying -language is not Ada), this attribute is @code{None}. This attribute -is writable. -@end defvar - -@defvar Breakpoint.ignore_count -This attribute holds the ignore count for the breakpoint, an integer. -This attribute is writable. -@end defvar - -@defvar Breakpoint.number -This attribute holds the breakpoint's number --- the identifier used by -the user to manipulate the breakpoint. This attribute is not writable. -@end defvar - -@defvar Breakpoint.type -This attribute holds the breakpoint's type --- the identifier used to -determine the actual breakpoint type or use-case. This attribute is not -writable. -@end defvar - -@defvar Breakpoint.visible -This attribute tells whether the breakpoint is visible to the user -when set, or when the @samp{info breakpoints} command is run. This -attribute is not writable. -@end defvar - -The available types are represented by constants defined in the @code{gdb} -module: - -@table @code -@findex BP_BREAKPOINT -@findex gdb.BP_BREAKPOINT -@item gdb.BP_BREAKPOINT -Normal code breakpoint. - -@findex BP_WATCHPOINT -@findex gdb.BP_WATCHPOINT -@item gdb.BP_WATCHPOINT -Watchpoint breakpoint. - -@findex BP_HARDWARE_WATCHPOINT -@findex gdb.BP_HARDWARE_WATCHPOINT -@item gdb.BP_HARDWARE_WATCHPOINT -Hardware assisted watchpoint. - -@findex BP_READ_WATCHPOINT -@findex gdb.BP_READ_WATCHPOINT -@item gdb.BP_READ_WATCHPOINT -Hardware assisted read watchpoint. - -@findex BP_ACCESS_WATCHPOINT -@findex gdb.BP_ACCESS_WATCHPOINT -@item gdb.BP_ACCESS_WATCHPOINT -Hardware assisted access watchpoint. -@end table - -@defvar Breakpoint.hit_count -This attribute holds the hit count for the breakpoint, an integer. -This attribute is writable, but currently it can only be set to zero. -@end defvar - -@defvar Breakpoint.location -This attribute holds the location of the breakpoint, as specified by -the user. It is a string. If the breakpoint does not have a location -(that is, it is a watchpoint) the attribute's value is @code{None}. This -attribute is not writable. -@end defvar - -@defvar Breakpoint.expression -This attribute holds a breakpoint expression, as specified by -the user. It is a string. If the breakpoint does not have an -expression (the breakpoint is not a watchpoint) the attribute's value -is @code{None}. This attribute is not writable. -@end defvar - -@defvar Breakpoint.condition -This attribute holds the condition of the breakpoint, as specified by -the user. It is a string. If there is no condition, this attribute's -value is @code{None}. This attribute is writable. -@end defvar - -@defvar Breakpoint.commands -This attribute holds the commands attached to the breakpoint. If -there are commands, this attribute's value is a string holding all the -commands, separated by newlines. If there are no commands, this -attribute is @code{None}. This attribute is not writable. -@end defvar - -@node Finish Breakpoints in Python -@subsubsection Finish Breakpoints - -@cindex python finish breakpoints -@tindex gdb.FinishBreakpoint - -A finish breakpoint is a temporary breakpoint set at the return address of -a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint} -extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled -and deleted when the execution will run out of the breakpoint scope (i.e.@: -@code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered). -Finish breakpoints are thread specific and must be create with the right -thread selected. - -@defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]}) -Create a finish breakpoint at the return address of the @code{gdb.Frame} -object @var{frame}. If @var{frame} is not provided, this defaults to the -newest frame. The optional @var{internal} argument allows the breakpoint to -become invisible to the user. @xref{Breakpoints In Python}, for further -details about this argument. -@end defun - -@defun FinishBreakpoint.out_of_scope (self) -In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN} -@code{return} command, @dots{}), a function may not properly terminate, and -thus never hit the finish breakpoint. When @value{GDBN} notices such a -situation, the @code{out_of_scope} callback will be triggered. - -You may want to sub-class @code{gdb.FinishBreakpoint} and override this -method: - -@smallexample -class MyFinishBreakpoint (gdb.FinishBreakpoint) - def stop (self): - print "normal finish" - return True - - def out_of_scope (): - print "abnormal finish" -@end smallexample -@end defun - -@defvar FinishBreakpoint.return_value -When @value{GDBN} is stopped at a finish breakpoint and the frame -used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this -attribute will contain a @code{gdb.Value} object corresponding to the return -value of the function. The value will be @code{None} if the function return -type is @code{void} or if the return value was not computable. This attribute -is not writable. -@end defvar - -@node Lazy Strings In Python -@subsubsection Python representation of lazy strings. - -@cindex lazy strings in python -@tindex gdb.LazyString - -A @dfn{lazy string} is a string whose contents is not retrieved or -encoded until it is needed. - -A @code{gdb.LazyString} is represented in @value{GDBN} as an -@code{address} that points to a region of memory, an @code{encoding} -that will be used to encode that region of memory, and a @code{length} -to delimit the region of memory that represents the string. The -difference between a @code{gdb.LazyString} and a string wrapped within -a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated -differently by @value{GDBN} when printing. A @code{gdb.LazyString} is -retrieved and encoded during printing, while a @code{gdb.Value} -wrapping a string is immediately retrieved and encoded on creation. - -A @code{gdb.LazyString} object has the following functions: - -@defun LazyString.value () -Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value -will point to the string in memory, but will lose all the delayed -retrieval, encoding and handling that @value{GDBN} applies to a -@code{gdb.LazyString}. -@end defun - -@defvar LazyString.address -This attribute holds the address of the string. This attribute is not -writable. -@end defvar - -@defvar LazyString.length -This attribute holds the length of the string in characters. If the -length is -1, then the string will be fetched and encoded up to the -first null of appropriate width. This attribute is not writable. -@end defvar - -@defvar LazyString.encoding -This attribute holds the encoding that will be applied to the string -when the string is printed by @value{GDBN}. If the encoding is not -set, or contains an empty string, then @value{GDBN} will select the -most appropriate encoding when the string is printed. This attribute -is not writable. -@end defvar - -@defvar LazyString.type -This attribute holds the type that is represented by the lazy string's -type. For a lazy string this will always be a pointer type. To -resolve this to the lazy string's character type, use the type's -@code{target} method. @xref{Types In Python}. This attribute is not -writable. -@end defvar - -@node Architectures In Python -@subsubsection Python representation of architectures -@cindex Python architectures - -@value{GDBN} uses architecture specific parameters and artifacts in a -number of its various computations. An architecture is represented -by an instance of the @code{gdb.Architecture} class. - -A @code{gdb.Architecture} class has the following methods: - -@defun Architecture.name () -Return the name (string value) of the architecture. -@end defun - -@defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]}) -Return a list of disassembled instructions starting from the memory -address @var{start_pc}. The optional arguments @var{end_pc} and -@var{count} determine the number of instructions in the returned list. -If both the optional arguments @var{end_pc} and @var{count} are -specified, then a list of at most @var{count} disassembled instructions -whose start address falls in the closed memory address interval from -@var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not -specified, but @var{count} is specified, then @var{count} number of -instructions starting from the address @var{start_pc} are returned. If -@var{count} is not specified but @var{end_pc} is specified, then all -instructions whose start address falls in the closed memory address -interval from @var{start_pc} to @var{end_pc} are returned. If neither -@var{end_pc} nor @var{count} are specified, then a single instruction at -@var{start_pc} is returned. For all of these cases, each element of the -returned list is a Python @code{dict} with the following string keys: - -@table @code - -@item addr -The value corresponding to this key is a Python long integer capturing -the memory address of the instruction. - -@item asm -The value corresponding to this key is a string value which represents -the instruction with assembly language mnemonics. The assembly -language flavor used is the same as that specified by the current CLI -variable @code{disassembly-flavor}. @xref{Machine Code}. - -@item length -The value corresponding to this key is the length (integer value) of the -instruction in bytes. - -@end table -@end defun - -@node Python Auto-loading -@subsection Python Auto-loading -@cindex Python auto-loading - -When a new object file is read (for example, due to the @code{file} -command, or because the inferior has loaded a shared library), -@value{GDBN} will look for Python support scripts in several ways: -@file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file}) -and @code{.debug_gdb_scripts} section -(@pxref{dotdebug_gdb_scripts section}). - -The auto-loading feature is useful for supplying application-specific -debugging commands and scripts. - -Auto-loading can be enabled or disabled, -and the list of auto-loaded scripts can be printed. - -@table @code -@anchor{set auto-load python-scripts} -@kindex set auto-load python-scripts -@item set auto-load python-scripts [on|off] -Enable or disable the auto-loading of Python scripts. - -@anchor{show auto-load python-scripts} -@kindex show auto-load python-scripts -@item show auto-load python-scripts -Show whether auto-loading of Python scripts is enabled or disabled. - -@anchor{info auto-load python-scripts} -@kindex info auto-load python-scripts -@cindex print list of auto-loaded Python scripts -@item info auto-load python-scripts [@var{regexp}] -Print the list of all Python scripts that @value{GDBN} auto-loaded. - -Also printed is the list of Python scripts that were mentioned in -the @code{.debug_gdb_scripts} section and were not found -(@pxref{dotdebug_gdb_scripts section}). -This is useful because their names are not printed when @value{GDBN} -tries to load them and fails. There may be many of them, and printing -an error message for each one is problematic. - -If @var{regexp} is supplied only Python scripts with matching names are printed. - -Example: - -@smallexample -(gdb) info auto-load python-scripts -Loaded Script -Yes py-section-script.py - full name: /tmp/py-section-script.py -No my-foo-pretty-printers.py -@end smallexample -@end table - -When reading an auto-loaded file, @value{GDBN} sets the -@dfn{current objfile}. This is available via the @code{gdb.current_objfile} -function (@pxref{Objfiles In Python}). This can be useful for -registering objfile-specific pretty-printers. - -@menu -* objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file -* dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section -* Which flavor to choose?:: -@end menu - -@node objfile-gdb.py file -@subsubsection The @file{@var{objfile}-gdb.py} file -@cindex @file{@var{objfile}-gdb.py} - -When a new object file is read, @value{GDBN} looks for -a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below), -where @var{objfile} is the object file's real name, formed by ensuring -that the file name is absolute, following all symlinks, and resolving -@code{.} and @code{..} components. If this file exists and is -readable, @value{GDBN} will evaluate it as a Python script. - -If this file does not exist, then @value{GDBN} will look for -@var{script-name} file in all of the directories as specified below. - -Note that loading of this script file also requires accordingly configured -@code{auto-load safe-path} (@pxref{Auto-loading safe path}). - -For object files using @file{.exe} suffix @value{GDBN} tries to load first the -scripts normally according to its @file{.exe} filename. But if no scripts are -found @value{GDBN} also tries script filenames matching the object file without -its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it -is attempted on any platform. This makes the script filenames compatible -between Unix and MS-Windows hosts. - -@table @code -@anchor{set auto-load scripts-directory} -@kindex set auto-load scripts-directory -@item set auto-load scripts-directory @r{[}@var{directories}@r{]} -Control @value{GDBN} auto-loaded scripts location. Multiple directory entries -may be delimited by the host platform path separator in use -(@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS). - -Each entry here needs to be covered also by the security setting -@code{set auto-load safe-path} (@pxref{set auto-load safe-path}). - -@anchor{with-auto-load-dir} -This variable defaults to @file{$debugdir:$datadir/auto-load}. The default -@code{set auto-load safe-path} value can be also overriden by @value{GDBN} -configuration option @option{--with-auto-load-dir}. - -Any reference to @file{$debugdir} will get replaced by -@var{debug-file-directory} value (@pxref{Separate Debug Files}) and any -reference to @file{$datadir} will get replaced by @var{data-directory} which is -determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and -@file{$datadir} must be placed as a directory component --- either alone or -delimited by @file{/} or @file{\} directory separators, depending on the host -platform. - -The list of directories uses path separator (@samp{:} on GNU and Unix -systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly -to the @env{PATH} environment variable. - -@anchor{show auto-load scripts-directory} -@kindex show auto-load scripts-directory -@item show auto-load scripts-directory -Show @value{GDBN} auto-loaded scripts location. -@end table - -@value{GDBN} does not track which files it has already auto-loaded this way. -@value{GDBN} will load the associated script every time the corresponding -@var{objfile} is opened. -So your @file{-gdb.py} file should be careful to avoid errors if it -is evaluated more than once. - -@node dotdebug_gdb_scripts section -@subsubsection The @code{.debug_gdb_scripts} section -@cindex @code{.debug_gdb_scripts} section - -For systems using file formats like ELF and COFF, -when @value{GDBN} loads a new object file -it will look for a special section named @samp{.debug_gdb_scripts}. -If this section exists, its contents is a list of names of scripts to load. - -@value{GDBN} will look for each specified script file first in the -current directory and then along the source search path -(@pxref{Source Path, ,Specifying Source Directories}), -except that @file{$cdir} is not searched, since the compilation -directory is not relevant to scripts. - -Entries can be placed in section @code{.debug_gdb_scripts} with, -for example, this GCC macro: - -@example -/* Note: The "MS" section flags are to remove duplicates. */ -#define DEFINE_GDB_SCRIPT(script_name) \ - asm("\ -.pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\ -.byte 1\n\ -.asciz \"" script_name "\"\n\ -.popsection \n\ -"); -@end example - -@noindent -Then one can reference the macro in a header or source file like this: - -@example -DEFINE_GDB_SCRIPT ("my-app-scripts.py") -@end example - -The script name may include directories if desired. - -Note that loading of this script file also requires accordingly configured -@code{auto-load safe-path} (@pxref{Auto-loading safe path}). - -If the macro is put in a header, any application or library -using this header will get a reference to the specified script. - -@node Which flavor to choose? -@subsubsection Which flavor to choose? - -Given the multiple ways of auto-loading Python scripts, it might not always -be clear which one to choose. This section provides some guidance. - -Benefits of the @file{-gdb.py} way: - -@itemize @bullet -@item -Can be used with file formats that don't support multiple sections. - -@item -Ease of finding scripts for public libraries. - -Scripts specified in the @code{.debug_gdb_scripts} section are searched for -in the source search path. -For publicly installed libraries, e.g., @file{libstdc++}, there typically -isn't a source directory in which to find the script. - -@item -Doesn't require source code additions. -@end itemize - -Benefits of the @code{.debug_gdb_scripts} way: - -@itemize @bullet -@item -Works with static linking. - -Scripts for libraries done the @file{-gdb.py} way require an objfile to -trigger their loading. When an application is statically linked the only -objfile available is the executable, and it is cumbersome to attach all the -scripts from all the input libraries to the executable's @file{-gdb.py} script. - -@item -Works with classes that are entirely inlined. - -Some classes can be entirely inlined, and thus there may not be an associated -shared library to attach a @file{-gdb.py} script to. - -@item -Scripts needn't be copied out of the source tree. - -In some circumstances, apps can be built out of large collections of internal -libraries, and the build infrastructure necessary to install the -@file{-gdb.py} scripts in a place where @value{GDBN} can find them is -cumbersome. It may be easier to specify the scripts in the -@code{.debug_gdb_scripts} section as relative paths, and add a path to the -top of the source tree to the source search path. -@end itemize - -@node Python modules -@subsection Python modules -@cindex python modules - -@value{GDBN} comes with several modules to assist writing Python code. - -@menu -* gdb.printing:: Building and registering pretty-printers. -* gdb.types:: Utilities for working with types. -* gdb.prompt:: Utilities for prompt value substitution. -@end menu - -@node gdb.printing -@subsubsection gdb.printing -@cindex gdb.printing - -This module provides a collection of utilities for working with -pretty-printers. - -@table @code -@item PrettyPrinter (@var{name}, @var{subprinters}=None) -This class specifies the API that makes @samp{info pretty-printer}, -@samp{enable pretty-printer} and @samp{disable pretty-printer} work. -Pretty-printers should generally inherit from this class. - -@item SubPrettyPrinter (@var{name}) -For printers that handle multiple types, this class specifies the -corresponding API for the subprinters. - -@item RegexpCollectionPrettyPrinter (@var{name}) -Utility class for handling multiple printers, all recognized via -regular expressions. -@xref{Writing a Pretty-Printer}, for an example. - -@item FlagEnumerationPrinter (@var{name}) -A pretty-printer which handles printing of @code{enum} values. Unlike -@value{GDBN}'s built-in @code{enum} printing, this printer attempts to -work properly when there is some overlap between the enumeration -constants. @var{name} is the name of the printer and also the name of -the @code{enum} type to look up. - -@item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False) -Register @var{printer} with the pretty-printer list of @var{obj}. -If @var{replace} is @code{True} then any existing copy of the printer -is replaced. Otherwise a @code{RuntimeError} exception is raised -if a printer with the same name already exists. -@end table - -@node gdb.types -@subsubsection gdb.types -@cindex gdb.types - -This module provides a collection of utilities for working with -@code{gdb.Type} objects. - -@table @code -@item get_basic_type (@var{type}) -Return @var{type} with const and volatile qualifiers stripped, -and with typedefs and C@t{++} references converted to the underlying type. - -C@t{++} example: - -@smallexample -typedef const int const_int; -const_int foo (3); -const_int& foo_ref (foo); -int main () @{ return 0; @} -@end smallexample - -Then in gdb: - -@smallexample -(gdb) start -(gdb) python import gdb.types -(gdb) python foo_ref = gdb.parse_and_eval("foo_ref") -(gdb) python print gdb.types.get_basic_type(foo_ref.type) -int -@end smallexample - -@item has_field (@var{type}, @var{field}) -Return @code{True} if @var{type}, assumed to be a type with fields -(e.g., a structure or union), has field @var{field}. - -@item make_enum_dict (@var{enum_type}) -Return a Python @code{dictionary} type produced from @var{enum_type}. - -@item deep_items (@var{type}) -Returns a Python iterator similar to the standard -@code{gdb.Type.iteritems} method, except that the iterator returned -by @code{deep_items} will recursively traverse anonymous struct or -union fields. For example: - -@smallexample -struct A -@{ - int a; - union @{ - int b0; - int b1; - @}; -@}; -@end smallexample - -@noindent -Then in @value{GDBN}: -@smallexample -(@value{GDBP}) python import gdb.types -(@value{GDBP}) python struct_a = gdb.lookup_type("struct A") -(@value{GDBP}) python print struct_a.keys () -@{['a', '']@} -(@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)] -@{['a', 'b0', 'b1']@} -@end smallexample - -@item get_type_recognizers () -Return a list of the enabled type recognizers for the current context. -This is called by @value{GDBN} during the type-printing process -(@pxref{Type Printing API}). - -@item apply_type_recognizers (recognizers, type_obj) -Apply the type recognizers, @var{recognizers}, to the type object -@var{type_obj}. If any recognizer returns a string, return that -string. Otherwise, return @code{None}. This is called by -@value{GDBN} during the type-printing process (@pxref{Type Printing -API}). - -@item register_type_printer (locus, printer) -This is a convenience function to register a type printer. -@var{printer} is the type printer to register. It must implement the -type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in -which case the printer is registered with that objfile; a -@code{gdb.Progspace}, in which case the printer is registered with -that progspace; or @code{None}, in which case the printer is -registered globally. - -@item TypePrinter -This is a base class that implements the type printer protocol. Type -printers are encouraged, but not required, to derive from this class. -It defines a constructor: - -@defmethod TypePrinter __init__ (self, name) -Initialize the type printer with the given name. The new printer -starts in the enabled state. -@end defmethod - -@end table - -@node gdb.prompt -@subsubsection gdb.prompt -@cindex gdb.prompt - -This module provides a method for prompt value-substitution. - -@table @code -@item substitute_prompt (@var{string}) -Return @var{string} with escape sequences substituted by values. Some -escape sequences take arguments. You can specify arguments inside -``@{@}'' immediately following the escape sequence. - -The escape sequences you can pass to this function are: - -@table @code -@item \\ -Substitute a backslash. -@item \e -Substitute an ESC character. -@item \f -Substitute the selected frame; an argument names a frame parameter. -@item \n -Substitute a newline. -@item \p -Substitute a parameter's value; the argument names the parameter. -@item \r -Substitute a carriage return. -@item \t -Substitute the selected thread; an argument names a thread parameter. -@item \v -Substitute the version of GDB. -@item \w -Substitute the current working directory. -@item \[ -Begin a sequence of non-printing characters. These sequences are -typically used with the ESC character, and are not counted in the string -length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a -blue-colored ``(gdb)'' prompt where the length is five. -@item \] -End a sequence of non-printing characters. -@end table - -For example: - -@smallexample -substitute_prompt (``frame: \f, - print arguments: \p@{print frame-arguments@}'') -@end smallexample - -@exdent will return the string: - -@smallexample -"frame: main, print arguments: scalars" -@end smallexample -@end table - -@node Aliases -@section Creating new spellings of existing commands -@cindex aliases for commands - -It is often useful to define alternate spellings of existing commands. -For example, if a new @value{GDBN} command defined in Python has -a long name to type, it is handy to have an abbreviated version of it -that involves less typing. - -@value{GDBN} itself uses aliases. For example @samp{s} is an alias -of the @samp{step} command even though it is otherwise an ambiguous -abbreviation of other commands like @samp{set} and @samp{show}. - -Aliases are also used to provide shortened or more common versions -of multi-word commands. For example, @value{GDBN} provides the -@samp{tty} alias of the @samp{set inferior-tty} command. - -You can define a new alias with the @samp{alias} command. - -@table @code - -@kindex alias -@item alias [-a] [--] @var{ALIAS} = @var{COMMAND} - -@end table - -@var{ALIAS} specifies the name of the new alias. -Each word of @var{ALIAS} must consist of letters, numbers, dashes and -underscores. - -@var{COMMAND} specifies the name of an existing command -that is being aliased. - -The @samp{-a} option specifies that the new alias is an abbreviation -of the command. Abbreviations are not shown in command -lists displayed by the @samp{help} command. - -The @samp{--} option specifies the end of options, -and is useful when @var{ALIAS} begins with a dash. - -Here is a simple example showing how to make an abbreviation -of a command so that there is less to type. -Suppose you were tired of typing @samp{disas}, the current -shortest unambiguous abbreviation of the @samp{disassemble} command -and you wanted an even shorter version named @samp{di}. -The following will accomplish this. - -@smallexample -(gdb) alias -a di = disas -@end smallexample - -Note that aliases are different from user-defined commands. -With a user-defined command, you also need to write documentation -for it with the @samp{document} command. -An alias automatically picks up the documentation of the existing command. - -Here is an example where we make @samp{elms} an abbreviation of -@samp{elements} in the @samp{set print elements} command. -This is to show that you can make an abbreviation of any part -of a command. - -@smallexample -(gdb) alias -a set print elms = set print elements -(gdb) alias -a show print elms = show print elements -(gdb) set p elms 20 -(gdb) show p elms -Limit on string chars or array elements to print is 200. -@end smallexample - -Note that if you are defining an alias of a @samp{set} command, -and you want to have an alias for the corresponding @samp{show} -command, then you need to define the latter separately. - -Unambiguously abbreviated commands are allowed in @var{COMMAND} and -@var{ALIAS}, just as they are normally. - -@smallexample -(gdb) alias -a set pr elms = set p ele -@end smallexample - -Finally, here is an example showing the creation of a one word -alias for a more complex command. -This creates alias @samp{spe} of the command @samp{set print elements}. - -@smallexample -(gdb) alias spe = set print elements -(gdb) spe 20 -@end smallexample - -@node Interpreters -@chapter Command Interpreters -@cindex command interpreters - -@value{GDBN} supports multiple command interpreters, and some command -infrastructure to allow users or user interface writers to switch -between interpreters or run commands in other interpreters. - -@value{GDBN} currently supports two command interpreters, the console -interpreter (sometimes called the command-line interpreter or @sc{cli}) -and the machine interface interpreter (or @sc{gdb/mi}). This manual -describes both of these interfaces in great detail. - -By default, @value{GDBN} will start with the console interpreter. -However, the user may choose to start @value{GDBN} with another -interpreter by specifying the @option{-i} or @option{--interpreter} -startup options. Defined interpreters include: - -@table @code -@item console -@cindex console interpreter -The traditional console or command-line interpreter. This is the most often -used interpreter with @value{GDBN}. With no interpreter specified at runtime, -@value{GDBN} will use this interpreter. - -@item mi -@cindex mi interpreter -The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily -by programs wishing to use @value{GDBN} as a backend for a debugger GUI -or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi} -Interface}. - -@item mi2 -@cindex mi2 interpreter -The current @sc{gdb/mi} interface. - -@item mi1 -@cindex mi1 interpreter -The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3. - -@end table - -@cindex invoke another interpreter -The interpreter being used by @value{GDBN} may not be dynamically -switched at runtime. Although possible, this could lead to a very -precarious situation. Consider an IDE using @sc{gdb/mi}. If a user -enters the command "interpreter-set console" in a console view, -@value{GDBN} would switch to using the console interpreter, rendering -the IDE inoperable! - -@kindex interpreter-exec -Although you may only choose a single interpreter at startup, you may execute -commands in any interpreter from the current interpreter using the appropriate -command. If you are running the console interpreter, simply use the -@code{interpreter-exec} command: - -@smallexample -interpreter-exec mi "-data-list-register-names" -@end smallexample - -@sc{gdb/mi} has a similar command, although it is only available in versions of -@value{GDBN} which support @sc{gdb/mi} version 2 (or greater). - -@node TUI -@chapter @value{GDBN} Text User Interface -@cindex TUI -@cindex Text User Interface - -@menu -* TUI Overview:: TUI overview -* TUI Keys:: TUI key bindings -* TUI Single Key Mode:: TUI single key mode -* TUI Commands:: TUI-specific commands -* TUI Configuration:: TUI configuration variables -@end menu - -The @value{GDBN} Text User Interface (TUI) is a terminal -interface which uses the @code{curses} library to show the source -file, the assembly output, the program registers and @value{GDBN} -commands in separate text windows. The TUI mode is supported only -on platforms where a suitable version of the @code{curses} library -is available. - -The TUI mode is enabled by default when you invoke @value{GDBN} as -@samp{@value{GDBP} -tui}. -You can also switch in and out of TUI mode while @value{GDBN} runs by -using various TUI commands and key bindings, such as @kbd{C-x C-a}. -@xref{TUI Keys, ,TUI Key Bindings}. - -@node TUI Overview -@section TUI Overview - -In TUI mode, @value{GDBN} can display several text windows: - -@table @emph -@item command -This window is the @value{GDBN} command window with the @value{GDBN} -prompt and the @value{GDBN} output. The @value{GDBN} input is still -managed using readline. - -@item source -The source window shows the source file of the program. The current -line and active breakpoints are displayed in this window. - -@item assembly -The assembly window shows the disassembly output of the program. - -@item register -This window shows the processor registers. Registers are highlighted -when their values change. -@end table - -The source and assembly windows show the current program position -by highlighting the current line and marking it with a @samp{>} marker. -Breakpoints are indicated with two markers. The first marker -indicates the breakpoint type: - -@table @code -@item B -Breakpoint which was hit at least once. - -@item b -Breakpoint which was never hit. - -@item H -Hardware breakpoint which was hit at least once. - -@item h -Hardware breakpoint which was never hit. -@end table - -The second marker indicates whether the breakpoint is enabled or not: - -@table @code -@item + -Breakpoint is enabled. - -@item - -Breakpoint is disabled. -@end table - -The source, assembly and register windows are updated when the current -thread changes, when the frame changes, or when the program counter -changes. - -These windows are not all visible at the same time. The command -window is always visible. The others can be arranged in several -layouts: - -@itemize @bullet -@item -source only, - -@item -assembly only, - -@item -source and assembly, - -@item -source and registers, or - -@item -assembly and registers. -@end itemize - -A status line above the command window shows the following information: - -@table @emph -@item target -Indicates the current @value{GDBN} target. -(@pxref{Targets, ,Specifying a Debugging Target}). - -@item process -Gives the current process or thread number. -When no process is being debugged, this field is set to @code{No process}. - -@item function -Gives the current function name for the selected frame. -The name is demangled if demangling is turned on (@pxref{Print Settings}). -When there is no symbol corresponding to the current program counter, -the string @code{??} is displayed. - -@item line -Indicates the current line number for the selected frame. -When the current line number is not known, the string @code{??} is displayed. - -@item pc -Indicates the current program counter address. -@end table - -@node TUI Keys -@section TUI Key Bindings -@cindex TUI key bindings - -The TUI installs several key bindings in the readline keymaps -@ifset SYSTEM_READLINE -(@pxref{Command Line Editing, , , rluserman, GNU Readline Library}). -@end ifset -@ifclear SYSTEM_READLINE -(@pxref{Command Line Editing}). -@end ifclear -The following key bindings are installed for both TUI mode and the -@value{GDBN} standard mode. - -@table @kbd -@kindex C-x C-a -@item C-x C-a -@kindex C-x a -@itemx C-x a -@kindex C-x A -@itemx C-x A -Enter or leave the TUI mode. When leaving the TUI mode, -the curses window management stops and @value{GDBN} operates using -its standard mode, writing on the terminal directly. When reentering -the TUI mode, control is given back to the curses windows. -The screen is then refreshed. - -@kindex C-x 1 -@item C-x 1 -Use a TUI layout with only one window. The layout will -either be @samp{source} or @samp{assembly}. When the TUI mode -is not active, it will switch to the TUI mode. - -Think of this key binding as the Emacs @kbd{C-x 1} binding. - -@kindex C-x 2 -@item C-x 2 -Use a TUI layout with at least two windows. When the current -layout already has two windows, the next layout with two windows is used. -When a new layout is chosen, one window will always be common to the -previous layout and the new one. - -Think of it as the Emacs @kbd{C-x 2} binding. - -@kindex C-x o -@item C-x o -Change the active window. The TUI associates several key bindings -(like scrolling and arrow keys) with the active window. This command -gives the focus to the next TUI window. - -Think of it as the Emacs @kbd{C-x o} binding. - -@kindex C-x s -@item C-x s -Switch in and out of the TUI SingleKey mode that binds single -keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}). -@end table - -The following key bindings only work in the TUI mode: - -@table @asis -@kindex PgUp -@item @key{PgUp} -Scroll the active window one page up. - -@kindex PgDn -@item @key{PgDn} -Scroll the active window one page down. - -@kindex Up -@item @key{Up} -Scroll the active window one line up. - -@kindex Down -@item @key{Down} -Scroll the active window one line down. - -@kindex Left -@item @key{Left} -Scroll the active window one column left. - -@kindex Right -@item @key{Right} -Scroll the active window one column right. - -@kindex C-L -@item @kbd{C-L} -Refresh the screen. -@end table - -Because the arrow keys scroll the active window in the TUI mode, they -are not available for their normal use by readline unless the command -window has the focus. When another window is active, you must use -other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b} -and @kbd{C-f} to control the command window. - -@node TUI Single Key Mode -@section TUI Single Key Mode -@cindex TUI single key mode - -The TUI also provides a @dfn{SingleKey} mode, which binds several -frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to -switch into this mode, where the following key bindings are used: - -@table @kbd -@kindex c @r{(SingleKey TUI key)} -@item c -continue - -@kindex d @r{(SingleKey TUI key)} -@item d -down - -@kindex f @r{(SingleKey TUI key)} -@item f -finish - -@kindex n @r{(SingleKey TUI key)} -@item n -next - -@kindex q @r{(SingleKey TUI key)} -@item q -exit the SingleKey mode. - -@kindex r @r{(SingleKey TUI key)} -@item r -run - -@kindex s @r{(SingleKey TUI key)} -@item s -step - -@kindex u @r{(SingleKey TUI key)} -@item u -up - -@kindex v @r{(SingleKey TUI key)} -@item v -info locals - -@kindex w @r{(SingleKey TUI key)} -@item w -where -@end table - -Other keys temporarily switch to the @value{GDBN} command prompt. -The key that was pressed is inserted in the editing buffer so that -it is possible to type most @value{GDBN} commands without interaction -with the TUI SingleKey mode. Once the command is entered the TUI -SingleKey mode is restored. The only way to permanently leave -this mode is by typing @kbd{q} or @kbd{C-x s}. - - -@node TUI Commands -@section TUI-specific Commands -@cindex TUI commands - -The TUI has specific commands to control the text windows. -These commands are always available, even when @value{GDBN} is not in -the TUI mode. When @value{GDBN} is in the standard mode, most -of these commands will automatically switch to the TUI mode. - -Note that if @value{GDBN}'s @code{stdout} is not connected to a -terminal, or @value{GDBN} has been started with the machine interface -interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of -these commands will fail with an error, because it would not be -possible or desirable to enable curses window management. - -@table @code -@item info win -@kindex info win -List and give the size of all displayed windows. - -@item layout next -@kindex layout -Display the next layout. - -@item layout prev -Display the previous layout. - -@item layout src -Display the source window only. - -@item layout asm -Display the assembly window only. - -@item layout split -Display the source and assembly window. - -@item layout regs -Display the register window together with the source or assembly window. - -@item focus next -@kindex focus -Make the next window active for scrolling. - -@item focus prev -Make the previous window active for scrolling. - -@item focus src -Make the source window active for scrolling. - -@item focus asm -Make the assembly window active for scrolling. - -@item focus regs -Make the register window active for scrolling. - -@item focus cmd -Make the command window active for scrolling. - -@item refresh -@kindex refresh -Refresh the screen. This is similar to typing @kbd{C-L}. - -@item tui reg float -@kindex tui reg -Show the floating point registers in the register window. - -@item tui reg general -Show the general registers in the register window. - -@item tui reg next -Show the next register group. The list of register groups as well as -their order is target specific. The predefined register groups are the -following: @code{general}, @code{float}, @code{system}, @code{vector}, -@code{all}, @code{save}, @code{restore}. - -@item tui reg system -Show the system registers in the register window. - -@item update -@kindex update -Update the source window and the current execution point. - -@item winheight @var{name} +@var{count} -@itemx winheight @var{name} -@var{count} -@kindex winheight -Change the height of the window @var{name} by @var{count} -lines. Positive counts increase the height, while negative counts -decrease it. - -@item tabset @var{nchars} -@kindex tabset -Set the width of tab stops to be @var{nchars} characters. -@end table - -@node TUI Configuration -@section TUI Configuration Variables -@cindex TUI configuration variables - -Several configuration variables control the appearance of TUI windows. - -@table @code -@item set tui border-kind @var{kind} -@kindex set tui border-kind -Select the border appearance for the source, assembly and register windows. -The possible values are the following: -@table @code -@item space -Use a space character to draw the border. - -@item ascii -Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border. - -@item acs -Use the Alternate Character Set to draw the border. The border is -drawn using character line graphics if the terminal supports them. -@end table - -@item set tui border-mode @var{mode} -@kindex set tui border-mode -@itemx set tui active-border-mode @var{mode} -@kindex set tui active-border-mode -Select the display attributes for the borders of the inactive windows -or the active window. The @var{mode} can be one of the following: -@table @code -@item normal -Use normal attributes to display the border. - -@item standout -Use standout mode. - -@item reverse -Use reverse video mode. - -@item half -Use half bright mode. - -@item half-standout -Use half bright and standout mode. - -@item bold -Use extra bright or bold mode. - -@item bold-standout -Use extra bright or bold and standout mode. -@end table -@end table - -@node Emacs -@chapter Using @value{GDBN} under @sc{gnu} Emacs - -@cindex Emacs -@cindex @sc{gnu} Emacs -A special interface allows you to use @sc{gnu} Emacs to view (and -edit) the source files for the program you are debugging with -@value{GDBN}. - -To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the -executable file you want to debug as an argument. This command starts -@value{GDBN} as a subprocess of Emacs, with input and output through a newly -created Emacs buffer. -@c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.) - -Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two -things: - -@itemize @bullet -@item -All ``terminal'' input and output goes through an Emacs buffer, called -the GUD buffer. - -This applies both to @value{GDBN} commands and their output, and to the input -and output done by the program you are debugging. - -This is useful because it means that you can copy the text of previous -commands and input them again; you can even use parts of the output -in this way. - -All the facilities of Emacs' Shell mode are available for interacting -with your program. In particular, you can send signals the usual -way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a -stop. - -@item -@value{GDBN} displays source code through Emacs. - -Each time @value{GDBN} displays a stack frame, Emacs automatically finds the -source file for that frame and puts an arrow (@samp{=>}) at the -left margin of the current line. Emacs uses a separate buffer for -source display, and splits the screen to show both your @value{GDBN} session -and the source. - -Explicit @value{GDBN} @code{list} or search commands still produce output as -usual, but you probably have no reason to use them from Emacs. -@end itemize - -We call this @dfn{text command mode}. Emacs 22.1, and later, also uses -a graphical mode, enabled by default, which provides further buffers -that can control the execution and describe the state of your program. -@xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}. - -If you specify an absolute file name when prompted for the @kbd{M-x -gdb} argument, then Emacs sets your current working directory to where -your program resides. If you only specify the file name, then Emacs -sets your current working directory to the directory associated -with the previous buffer. In this case, @value{GDBN} may find your -program by searching your environment's @code{PATH} variable, but on -some operating systems it might not find the source. So, although the -@value{GDBN} input and output session proceeds normally, the auxiliary -buffer does not display the current source and line of execution. - -The initial working directory of @value{GDBN} is printed on the top -line of the GUD buffer and this serves as a default for the commands -that specify files for @value{GDBN} to operate on. @xref{Files, -,Commands to Specify Files}. - -By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you -need to call @value{GDBN} by a different name (for example, if you -keep several configurations around, with different names) you can -customize the Emacs variable @code{gud-gdb-command-name} to run the -one you want. - -In the GUD buffer, you can use these special Emacs commands in -addition to the standard Shell mode commands: - -@table @kbd -@item C-h m -Describe the features of Emacs' GUD Mode. - -@item C-c C-s -Execute to another source line, like the @value{GDBN} @code{step} command; also -update the display window to show the current file and location. - -@item C-c C-n -Execute to next source line in this function, skipping all function -calls, like the @value{GDBN} @code{next} command. Then update the display window -to show the current file and location. - -@item C-c C-i -Execute one instruction, like the @value{GDBN} @code{stepi} command; update -display window accordingly. - -@item C-c C-f -Execute until exit from the selected stack frame, like the @value{GDBN} -@code{finish} command. - -@item C-c C-r -Continue execution of your program, like the @value{GDBN} @code{continue} -command. - -@item C-c < -Go up the number of frames indicated by the numeric argument -(@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}), -like the @value{GDBN} @code{up} command. - -@item C-c > -Go down the number of frames indicated by the numeric argument, like the -@value{GDBN} @code{down} command. -@end table - -In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break}) -tells @value{GDBN} to set a breakpoint on the source line point is on. - -In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a -separate frame which shows a backtrace when the GUD buffer is current. -Move point to any frame in the stack and type @key{RET} to make it -become the current frame and display the associated source in the -source buffer. Alternatively, click @kbd{Mouse-2} to make the -selected frame become the current one. In graphical mode, the -speedbar displays watch expressions. - -If you accidentally delete the source-display buffer, an easy way to get -it back is to type the command @code{f} in the @value{GDBN} buffer, to -request a frame display; when you run under Emacs, this recreates -the source buffer if necessary to show you the context of the current -frame. - -The source files displayed in Emacs are in ordinary Emacs buffers -which are visiting the source files in the usual way. You can edit -the files with these buffers if you wish; but keep in mind that @value{GDBN} -communicates with Emacs in terms of line numbers. If you add or -delete lines from the text, the line numbers that @value{GDBN} knows cease -to correspond properly with the code. - -A more detailed description of Emacs' interaction with @value{GDBN} is -given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} -Emacs Manual}). - -@node GDB/MI -@chapter The @sc{gdb/mi} Interface - -@unnumberedsec Function and Purpose - -@cindex @sc{gdb/mi}, its purpose -@sc{gdb/mi} is a line based machine oriented text interface to -@value{GDBN} and is activated by specifying using the -@option{--interpreter} command line option (@pxref{Mode Options}). It -is specifically intended to support the development of systems which -use the debugger as just one small component of a larger system. - -This chapter is a specification of the @sc{gdb/mi} interface. It is written -in the form of a reference manual. - -Note that @sc{gdb/mi} is still under construction, so some of the -features described below are incomplete and subject to change -(@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}). - -@unnumberedsec Notation and Terminology - -@cindex notational conventions, for @sc{gdb/mi} -This chapter uses the following notation: - -@itemize @bullet -@item -@code{|} separates two alternatives. - -@item -@code{[ @var{something} ]} indicates that @var{something} is optional: -it may or may not be given. - -@item -@code{( @var{group} )*} means that @var{group} inside the parentheses -may repeat zero or more times. - -@item -@code{( @var{group} )+} means that @var{group} inside the parentheses -may repeat one or more times. - -@item -@code{"@var{string}"} means a literal @var{string}. -@end itemize - -@ignore -@heading Dependencies -@end ignore - -@menu -* GDB/MI General Design:: -* GDB/MI Command Syntax:: -* GDB/MI Compatibility with CLI:: -* GDB/MI Development and Front Ends:: -* GDB/MI Output Records:: -* GDB/MI Simple Examples:: -* GDB/MI Command Description Format:: -* GDB/MI Breakpoint Commands:: -* GDB/MI Catchpoint Commands:: -* GDB/MI Program Context:: -* GDB/MI Thread Commands:: -* GDB/MI Ada Tasking Commands:: -* GDB/MI Program Execution:: -* GDB/MI Stack Manipulation:: -* GDB/MI Variable Objects:: -* GDB/MI Data Manipulation:: -* GDB/MI Tracepoint Commands:: -* GDB/MI Symbol Query:: -* GDB/MI File Commands:: -@ignore -* GDB/MI Kod Commands:: -* GDB/MI Memory Overlay Commands:: -* GDB/MI Signal Handling Commands:: -@end ignore -* GDB/MI Target Manipulation:: -* GDB/MI File Transfer Commands:: -* GDB/MI Miscellaneous Commands:: -@end menu - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI General Design -@section @sc{gdb/mi} General Design -@cindex GDB/MI General Design - -Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three -parts---commands sent to @value{GDBN}, responses to those commands -and notifications. Each command results in exactly one response, -indicating either successful completion of the command, or an error. -For the commands that do not resume the target, the response contains the -requested information. For the commands that resume the target, the -response only indicates whether the target was successfully resumed. -Notifications is the mechanism for reporting changes in the state of the -target, or in @value{GDBN} state, that cannot conveniently be associated with -a command and reported as part of that command response. - -The important examples of notifications are: -@itemize @bullet - -@item -Exec notifications. These are used to report changes in -target state---when a target is resumed, or stopped. It would not -be feasible to include this information in response of resuming -commands, because one resume commands can result in multiple events in -different threads. Also, quite some time may pass before any event -happens in the target, while a frontend needs to know whether the resuming -command itself was successfully executed. - -@item -Console output, and status notifications. Console output -notifications are used to report output of CLI commands, as well as -diagnostics for other commands. Status notifications are used to -report the progress of a long-running operation. Naturally, including -this information in command response would mean no output is produced -until the command is finished, which is undesirable. - -@item -General notifications. Commands may have various side effects on -the @value{GDBN} or target state beyond their official purpose. For example, -a command may change the selected thread. Although such changes can -be included in command response, using notification allows for more -orthogonal frontend design. - -@end itemize - -There's no guarantee that whenever an MI command reports an error, -@value{GDBN} or the target are in any specific state, and especially, -the state is not reverted to the state before the MI command was -processed. Therefore, whenever an MI command results in an error, -we recommend that the frontend refreshes all the information shown in -the user interface. - - -@menu -* Context management:: -* Asynchronous and non-stop modes:: -* Thread groups:: -@end menu - -@node Context management -@subsection Context management - -In most cases when @value{GDBN} accesses the target, this access is -done in context of a specific thread and frame (@pxref{Frames}). -Often, even when accessing global data, the target requires that a thread -be specified. The CLI interface maintains the selected thread and frame, -and supplies them to target on each command. This is convenient, -because a command line user would not want to specify that information -explicitly on each command, and because user interacts with -@value{GDBN} via a single terminal, so no confusion is possible as -to what thread and frame are the current ones. - -In the case of MI, the concept of selected thread and frame is less -useful. First, a frontend can easily remember this information -itself. Second, a graphical frontend can have more than one window, -each one used for debugging a different thread, and the frontend might -want to access additional threads for internal purposes. This -increases the risk that by relying on implicitly selected thread, the -frontend may be operating on a wrong one. Therefore, each MI command -should explicitly specify which thread and frame to operate on. To -make it possible, each MI command accepts the @samp{--thread} and -@samp{--frame} options, the value to each is @value{GDBN} identifier -for thread and frame to operate on. - -Usually, each top-level window in a frontend allows the user to select -a thread and a frame, and remembers the user selection for further -operations. However, in some cases @value{GDBN} may suggest that the -current thread be changed. For example, when stopping on a breakpoint -it is reasonable to switch to the thread where breakpoint is hit. For -another example, if the user issues the CLI @samp{thread} command via -the frontend, it is desirable to change the frontend's selected thread to the -one specified by user. @value{GDBN} communicates the suggestion to -change current thread using the @samp{=thread-selected} notification. -No such notification is available for the selected frame at the moment. - -Note that historically, MI shares the selected thread with CLI, so -frontends used the @code{-thread-select} to execute commands in the -right context. However, getting this to work right is cumbersome. The -simplest way is for frontend to emit @code{-thread-select} command -before every command. This doubles the number of commands that need -to be sent. The alternative approach is to suppress @code{-thread-select} -if the selected thread in @value{GDBN} is supposed to be identical to the -thread the frontend wants to operate on. However, getting this -optimization right can be tricky. In particular, if the frontend -sends several commands to @value{GDBN}, and one of the commands changes the -selected thread, then the behaviour of subsequent commands will -change. So, a frontend should either wait for response from such -problematic commands, or explicitly add @code{-thread-select} for -all subsequent commands. No frontend is known to do this exactly -right, so it is suggested to just always pass the @samp{--thread} and -@samp{--frame} options. - -@node Asynchronous and non-stop modes -@subsection Asynchronous command execution and non-stop mode - -On some targets, @value{GDBN} is capable of processing MI commands -even while the target is running. This is called @dfn{asynchronous -command execution} (@pxref{Background Execution}). The frontend may -specify a preferrence for asynchronous execution using the -@code{-gdb-set target-async 1} command, which should be emitted before -either running the executable or attaching to the target. After the -frontend has started the executable or attached to the target, it can -find if asynchronous execution is enabled using the -@code{-list-target-features} command. - -Even if @value{GDBN} can accept a command while target is running, -many commands that access the target do not work when the target is -running. Therefore, asynchronous command execution is most useful -when combined with non-stop mode (@pxref{Non-Stop Mode}). Then, -it is possible to examine the state of one thread, while other threads -are running. - -When a given thread is running, MI commands that try to access the -target in the context of that thread may not work, or may work only on -some targets. In particular, commands that try to operate on thread's -stack will not work, on any target. Commands that read memory, or -modify breakpoints, may work or not work, depending on the target. Note -that even commands that operate on global state, such as @code{print}, -@code{set}, and breakpoint commands, still access the target in the -context of a specific thread, so frontend should try to find a -stopped thread and perform the operation on that thread (using the -@samp{--thread} option). - -Which commands will work in the context of a running thread is -highly target dependent. However, the two commands -@code{-exec-interrupt}, to stop a thread, and @code{-thread-info}, -to find the state of a thread, will always work. - -@node Thread groups -@subsection Thread groups -@value{GDBN} may be used to debug several processes at the same time. -On some platfroms, @value{GDBN} may support debugging of several -hardware systems, each one having several cores with several different -processes running on each core. This section describes the MI -mechanism to support such debugging scenarios. - -The key observation is that regardless of the structure of the -target, MI can have a global list of threads, because most commands that -accept the @samp{--thread} option do not need to know what process that -thread belongs to. Therefore, it is not necessary to introduce -neither additional @samp{--process} option, nor an notion of the -current process in the MI interface. The only strictly new feature -that is required is the ability to find how the threads are grouped -into processes. - -To allow the user to discover such grouping, and to support arbitrary -hierarchy of machines/cores/processes, MI introduces the concept of a -@dfn{thread group}. Thread group is a collection of threads and other -thread groups. A thread group always has a string identifier, a type, -and may have additional attributes specific to the type. A new -command, @code{-list-thread-groups}, returns the list of top-level -thread groups, which correspond to processes that @value{GDBN} is -debugging at the moment. By passing an identifier of a thread group -to the @code{-list-thread-groups} command, it is possible to obtain -the members of specific thread group. - -To allow the user to easily discover processes, and other objects, he -wishes to debug, a concept of @dfn{available thread group} is -introduced. Available thread group is an thread group that -@value{GDBN} is not debugging, but that can be attached to, using the -@code{-target-attach} command. The list of available top-level thread -groups can be obtained using @samp{-list-thread-groups --available}. -In general, the content of a thread group may be only retrieved only -after attaching to that thread group. - -Thread groups are related to inferiors (@pxref{Inferiors and -Programs}). Each inferior corresponds to a thread group of a special -type @samp{process}, and some additional operations are permitted on -such thread groups. - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Command Syntax -@section @sc{gdb/mi} Command Syntax - -@menu -* GDB/MI Input Syntax:: -* GDB/MI Output Syntax:: -@end menu - -@node GDB/MI Input Syntax -@subsection @sc{gdb/mi} Input Syntax - -@cindex input syntax for @sc{gdb/mi} -@cindex @sc{gdb/mi}, input syntax -@table @code -@item @var{command} @expansion{} -@code{@var{cli-command} | @var{mi-command}} - -@item @var{cli-command} @expansion{} -@code{[ @var{token} ] @var{cli-command} @var{nl}}, where -@var{cli-command} is any existing @value{GDBN} CLI command. - -@item @var{mi-command} @expansion{} -@code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )* -@code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}} - -@item @var{token} @expansion{} -"any sequence of digits" - -@item @var{option} @expansion{} -@code{"-" @var{parameter} [ " " @var{parameter} ]} - -@item @var{parameter} @expansion{} -@code{@var{non-blank-sequence} | @var{c-string}} - -@item @var{operation} @expansion{} -@emph{any of the operations described in this chapter} - -@item @var{non-blank-sequence} @expansion{} -@emph{anything, provided it doesn't contain special characters such as -"-", @var{nl}, """ and of course " "} - -@item @var{c-string} @expansion{} -@code{""" @var{seven-bit-iso-c-string-content} """} - -@item @var{nl} @expansion{} -@code{CR | CR-LF} -@end table - -@noindent -Notes: - -@itemize @bullet -@item -The CLI commands are still handled by the @sc{mi} interpreter; their -output is described below. - -@item -The @code{@var{token}}, when present, is passed back when the command -finishes. - -@item -Some @sc{mi} commands accept optional arguments as part of the parameter -list. Each option is identified by a leading @samp{-} (dash) and may be -followed by an optional argument parameter. Options occur first in the -parameter list and can be delimited from normal parameters using -@samp{--} (this is useful when some parameters begin with a dash). -@end itemize - -Pragmatics: - -@itemize @bullet -@item -We want easy access to the existing CLI syntax (for debugging). - -@item -We want it to be easy to spot a @sc{mi} operation. -@end itemize - -@node GDB/MI Output Syntax -@subsection @sc{gdb/mi} Output Syntax - -@cindex output syntax of @sc{gdb/mi} -@cindex @sc{gdb/mi}, output syntax -The output from @sc{gdb/mi} consists of zero or more out-of-band records -followed, optionally, by a single result record. This result record -is for the most recent command. The sequence of output records is -terminated by @samp{(gdb)}. - -If an input command was prefixed with a @code{@var{token}} then the -corresponding output for that command will also be prefixed by that same -@var{token}. - -@table @code -@item @var{output} @expansion{} -@code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}} - -@item @var{result-record} @expansion{} -@code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}} - -@item @var{out-of-band-record} @expansion{} -@code{@var{async-record} | @var{stream-record}} - -@item @var{async-record} @expansion{} -@code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}} - -@item @var{exec-async-output} @expansion{} -@code{[ @var{token} ] "*" @var{async-output}} - -@item @var{status-async-output} @expansion{} -@code{[ @var{token} ] "+" @var{async-output}} - -@item @var{notify-async-output} @expansion{} -@code{[ @var{token} ] "=" @var{async-output}} - -@item @var{async-output} @expansion{} -@code{@var{async-class} ( "," @var{result} )* @var{nl}} - -@item @var{result-class} @expansion{} -@code{"done" | "running" | "connected" | "error" | "exit"} - -@item @var{async-class} @expansion{} -@code{"stopped" | @var{others}} (where @var{others} will be added -depending on the needs---this is still in development). - -@item @var{result} @expansion{} -@code{ @var{variable} "=" @var{value}} - -@item @var{variable} @expansion{} -@code{ @var{string} } - -@item @var{value} @expansion{} -@code{ @var{const} | @var{tuple} | @var{list} } - -@item @var{const} @expansion{} -@code{@var{c-string}} - -@item @var{tuple} @expansion{} -@code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" } - -@item @var{list} @expansion{} -@code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "[" -@var{result} ( "," @var{result} )* "]" } - -@item @var{stream-record} @expansion{} -@code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}} - -@item @var{console-stream-output} @expansion{} -@code{"~" @var{c-string}} - -@item @var{target-stream-output} @expansion{} -@code{"@@" @var{c-string}} - -@item @var{log-stream-output} @expansion{} -@code{"&" @var{c-string}} - -@item @var{nl} @expansion{} -@code{CR | CR-LF} - -@item @var{token} @expansion{} -@emph{any sequence of digits}. -@end table - -@noindent -Notes: - -@itemize @bullet -@item -All output sequences end in a single line containing a period. - -@item -The @code{@var{token}} is from the corresponding request. Note that -for all async output, while the token is allowed by the grammar and -may be output by future versions of @value{GDBN} for select async -output messages, it is generally omitted. Frontends should treat -all async output as reporting general changes in the state of the -target and there should be no need to associate async output to any -prior command. - -@item -@cindex status output in @sc{gdb/mi} -@var{status-async-output} contains on-going status information about the -progress of a slow operation. It can be discarded. All status output is -prefixed by @samp{+}. - -@item -@cindex async output in @sc{gdb/mi} -@var{exec-async-output} contains asynchronous state change on the target -(stopped, started, disappeared). All async output is prefixed by -@samp{*}. - -@item -@cindex notify output in @sc{gdb/mi} -@var{notify-async-output} contains supplementary information that the -client should handle (e.g., a new breakpoint information). All notify -output is prefixed by @samp{=}. - -@item -@cindex console output in @sc{gdb/mi} -@var{console-stream-output} is output that should be displayed as is in the -console. It is the textual response to a CLI command. All the console -output is prefixed by @samp{~}. - -@item -@cindex target output in @sc{gdb/mi} -@var{target-stream-output} is the output produced by the target program. -All the target output is prefixed by @samp{@@}. - -@item -@cindex log output in @sc{gdb/mi} -@var{log-stream-output} is output text coming from @value{GDBN}'s internals, for -instance messages that should be displayed as part of an error log. All -the log output is prefixed by @samp{&}. - -@item -@cindex list output in @sc{gdb/mi} -New @sc{gdb/mi} commands should only output @var{lists} containing -@var{values}. - - -@end itemize - -@xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more -details about the various output records. - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Compatibility with CLI -@section @sc{gdb/mi} Compatibility with CLI - -@cindex compatibility, @sc{gdb/mi} and CLI -@cindex @sc{gdb/mi}, compatibility with CLI - -For the developers convenience CLI commands can be entered directly, -but there may be some unexpected behaviour. For example, commands -that query the user will behave as if the user replied yes, breakpoint -command lists are not executed and some CLI commands, such as -@code{if}, @code{when} and @code{define}, prompt for further input with -@samp{>}, which is not valid MI output. - -This feature may be removed at some stage in the future and it is -recommended that front ends use the @code{-interpreter-exec} command -(@pxref{-interpreter-exec}). - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Development and Front Ends -@section @sc{gdb/mi} Development and Front Ends -@cindex @sc{gdb/mi} development - -The application which takes the MI output and presents the state of the -program being debugged to the user is called a @dfn{front end}. - -Although @sc{gdb/mi} is still incomplete, it is currently being used -by a variety of front ends to @value{GDBN}. This makes it difficult -to introduce new functionality without breaking existing usage. This -section tries to minimize the problems by describing how the protocol -might change. - -Some changes in MI need not break a carefully designed front end, and -for these the MI version will remain unchanged. The following is a -list of changes that may occur within one level, so front ends should -parse MI output in a way that can handle them: - -@itemize @bullet -@item -New MI commands may be added. - -@item -New fields may be added to the output of any MI command. - -@item -The range of values for fields with specified values, e.g., -@code{in_scope} (@pxref{-var-update}) may be extended. - -@c The format of field's content e.g type prefix, may change so parse it -@c at your own risk. Yes, in general? - -@c The order of fields may change? Shouldn't really matter but it might -@c resolve inconsistencies. -@end itemize - -If the changes are likely to break front ends, the MI version level -will be increased by one. This will allow the front end to parse the -output according to the MI version. Apart from mi0, new versions of -@value{GDBN} will not support old versions of MI and it will be the -responsibility of the front end to work with the new one. - -@c Starting with mi3, add a new command -mi-version that prints the MI -@c version? - -The best way to avoid unexpected changes in MI that might break your front -end is to make your project known to @value{GDBN} developers and -follow development on @email{gdb@@sourceware.org} and -@email{gdb-patches@@sourceware.org}. -@cindex mailing lists - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Output Records -@section @sc{gdb/mi} Output Records - -@menu -* GDB/MI Result Records:: -* GDB/MI Stream Records:: -* GDB/MI Async Records:: -* GDB/MI Breakpoint Information:: -* GDB/MI Frame Information:: -* GDB/MI Thread Information:: -* GDB/MI Ada Exception Information:: -@end menu - -@node GDB/MI Result Records -@subsection @sc{gdb/mi} Result Records - -@cindex result records in @sc{gdb/mi} -@cindex @sc{gdb/mi}, result records -In addition to a number of out-of-band notifications, the response to a -@sc{gdb/mi} command includes one of the following result indications: - -@table @code -@findex ^done -@item "^done" [ "," @var{results} ] -The synchronous operation was successful, @code{@var{results}} are the return -values. - -@item "^running" -@findex ^running -This result record is equivalent to @samp{^done}. Historically, it -was output instead of @samp{^done} if the command has resumed the -target. This behaviour is maintained for backward compatibility, but -all frontends should treat @samp{^done} and @samp{^running} -identically and rely on the @samp{*running} output record to determine -which threads are resumed. - -@item "^connected" -@findex ^connected -@value{GDBN} has connected to a remote target. - -@item "^error" "," @var{c-string} -@findex ^error -The operation failed. The @code{@var{c-string}} contains the corresponding -error message. - -@item "^exit" -@findex ^exit -@value{GDBN} has terminated. - -@end table - -@node GDB/MI Stream Records -@subsection @sc{gdb/mi} Stream Records - -@cindex @sc{gdb/mi}, stream records -@cindex stream records in @sc{gdb/mi} -@value{GDBN} internally maintains a number of output streams: the console, the -target, and the log. The output intended for each of these streams is -funneled through the @sc{gdb/mi} interface using @dfn{stream records}. - -Each stream record begins with a unique @dfn{prefix character} which -identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output -Syntax}). In addition to the prefix, each stream record contains a -@code{@var{string-output}}. This is either raw text (with an implicit new -line) or a quoted C string (which does not contain an implicit newline). - -@table @code -@item "~" @var{string-output} -The console output stream contains text that should be displayed in the -CLI console window. It contains the textual responses to CLI commands. - -@item "@@" @var{string-output} -The target output stream contains any textual output from the running -target. This is only present when GDB's event loop is truly -asynchronous, which is currently only the case for remote targets. - -@item "&" @var{string-output} -The log stream contains debugging messages being produced by @value{GDBN}'s -internals. -@end table - -@node GDB/MI Async Records -@subsection @sc{gdb/mi} Async Records - -@cindex async records in @sc{gdb/mi} -@cindex @sc{gdb/mi}, async records -@dfn{Async} records are used to notify the @sc{gdb/mi} client of -additional changes that have occurred. Those changes can either be a -consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of -target activity (e.g., target stopped). - -The following is the list of possible async records: - -@table @code - -@item *running,thread-id="@var{thread}" -The target is now running. The @var{thread} field tells which -specific thread is now running, and can be @samp{all} if all threads -are running. The frontend should assume that no interaction with a -running thread is possible after this notification is produced. -The frontend should not assume that this notification is output -only once for any command. @value{GDBN} may emit this notification -several times, either for different threads, because it cannot resume -all threads together, or even for a single thread, if the thread must -be stepped though some code before letting it run freely. - -@item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}" -The target has stopped. The @var{reason} field can have one of the -following values: - -@table @code -@item breakpoint-hit -A breakpoint was reached. -@item watchpoint-trigger -A watchpoint was triggered. -@item read-watchpoint-trigger -A read watchpoint was triggered. -@item access-watchpoint-trigger -An access watchpoint was triggered. -@item function-finished -An -exec-finish or similar CLI command was accomplished. -@item location-reached -An -exec-until or similar CLI command was accomplished. -@item watchpoint-scope -A watchpoint has gone out of scope. -@item end-stepping-range -An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or -similar CLI command was accomplished. -@item exited-signalled -The inferior exited because of a signal. -@item exited -The inferior exited. -@item exited-normally -The inferior exited normally. -@item signal-received -A signal was received by the inferior. -@item solib-event -The inferior has stopped due to a library being loaded or unloaded. -This can happen when @code{stop-on-solib-events} (@pxref{Files}) is -set or when a @code{catch load} or @code{catch unload} catchpoint is -in use (@pxref{Set Catchpoints}). -@item fork -The inferior has forked. This is reported when @code{catch fork} -(@pxref{Set Catchpoints}) has been used. -@item vfork -The inferior has vforked. This is reported in when @code{catch vfork} -(@pxref{Set Catchpoints}) has been used. -@item syscall-entry -The inferior entered a system call. This is reported when @code{catch -syscall} (@pxref{Set Catchpoints}) has been used. -@item syscall-entry -The inferior returned from a system call. This is reported when -@code{catch syscall} (@pxref{Set Catchpoints}) has been used. -@item exec -The inferior called @code{exec}. This is reported when @code{catch exec} -(@pxref{Set Catchpoints}) has been used. -@end table - -The @var{id} field identifies the thread that directly caused the stop --- for example by hitting a breakpoint. Depending on whether all-stop -mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either -stop all threads, or only the thread that directly triggered the stop. -If all threads are stopped, the @var{stopped} field will have the -value of @code{"all"}. Otherwise, the value of the @var{stopped} -field will be a list of thread identifiers. Presently, this list will -always include a single thread, but frontend should be prepared to see -several threads in the list. The @var{core} field reports the -processor core on which the stop event has happened. This field may be absent -if such information is not available. - -@item =thread-group-added,id="@var{id}" -@itemx =thread-group-removed,id="@var{id}" -A thread group was either added or removed. The @var{id} field -contains the @value{GDBN} identifier of the thread group. When a thread -group is added, it generally might not be associated with a running -process. When a thread group is removed, its id becomes invalid and -cannot be used in any way. - -@item =thread-group-started,id="@var{id}",pid="@var{pid}" -A thread group became associated with a running program, -either because the program was just started or the thread group -was attached to a program. The @var{id} field contains the -@value{GDBN} identifier of the thread group. The @var{pid} field -contains process identifier, specific to the operating system. - -@item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"] -A thread group is no longer associated with a running program, -either because the program has exited, or because it was detached -from. The @var{id} field contains the @value{GDBN} identifier of the -thread group. @var{code} is the exit code of the inferior; it exists -only when the inferior exited with some code. - -@item =thread-created,id="@var{id}",group-id="@var{gid}" -@itemx =thread-exited,id="@var{id}",group-id="@var{gid}" -A thread either was created, or has exited. The @var{id} field -contains the @value{GDBN} identifier of the thread. The @var{gid} -field identifies the thread group this thread belongs to. - -@item =thread-selected,id="@var{id}" -Informs that the selected thread was changed as result of the last -command. This notification is not emitted as result of @code{-thread-select} -command but is emitted whenever an MI command that is not documented -to change the selected thread actually changes it. In particular, -invoking, directly or indirectly (via user-defined command), the CLI -@code{thread} command, will generate this notification. - -We suggest that in response to this notification, front ends -highlight the selected thread and cause subsequent commands to apply to -that thread. - -@item =library-loaded,... -Reports that a new library file was loaded by the program. This -notification has 4 fields---@var{id}, @var{target-name}, -@var{host-name}, and @var{symbols-loaded}. The @var{id} field is an -opaque identifier of the library. For remote debugging case, -@var{target-name} and @var{host-name} fields give the name of the -library file on the target, and on the host respectively. For native -debugging, both those fields have the same value. The -@var{symbols-loaded} field is emitted only for backward compatibility -and should not be relied on to convey any useful information. The -@var{thread-group} field, if present, specifies the id of the thread -group in whose context the library was loaded. If the field is -absent, it means the library was loaded in the context of all present -thread groups. - -@item =library-unloaded,... -Reports that a library was unloaded by the program. This notification -has 3 fields---@var{id}, @var{target-name} and @var{host-name} with -the same meaning as for the @code{=library-loaded} notification. -The @var{thread-group} field, if present, specifies the id of the -thread group in whose context the library was unloaded. If the field is -absent, it means the library was unloaded in the context of all present -thread groups. - -@item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum} -@itemx =traceframe-changed,end -Reports that the trace frame was changed and its new number is -@var{tfnum}. The number of the tracepoint associated with this trace -frame is @var{tpnum}. - -@item =tsv-created,name=@var{name},initial=@var{initial} -Reports that the new trace state variable @var{name} is created with -initial value @var{initial}. - -@item =tsv-deleted,name=@var{name} -@itemx =tsv-deleted -Reports that the trace state variable @var{name} is deleted or all -trace state variables are deleted. - -@item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}] -Reports that the trace state variable @var{name} is modified with -the initial value @var{initial}. The current value @var{current} of -trace state variable is optional and is reported if the current -value of trace state variable is known. - -@item =breakpoint-created,bkpt=@{...@} -@itemx =breakpoint-modified,bkpt=@{...@} -@itemx =breakpoint-deleted,id=@var{number} -Reports that a breakpoint was created, modified, or deleted, -respectively. Only user-visible breakpoints are reported to the MI -user. - -The @var{bkpt} argument is of the same form as returned by the various -breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The -@var{number} is the ordinal number of the breakpoint. - -Note that if a breakpoint is emitted in the result record of a -command, then it will not also be emitted in an async record. - -@item =record-started,thread-group="@var{id}" -@itemx =record-stopped,thread-group="@var{id}" -Execution log recording was either started or stopped on an -inferior. The @var{id} is the @value{GDBN} identifier of the thread -group corresponding to the affected inferior. - -@item =cmd-param-changed,param=@var{param},value=@var{value} -Reports that a parameter of the command @code{set @var{param}} is -changed to @var{value}. In the multi-word @code{set} command, -the @var{param} is the whole parameter list to @code{set} command. -For example, In command @code{set check type on}, @var{param} -is @code{check type} and @var{value} is @code{on}. - -@item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"] -Reports that bytes from @var{addr} to @var{data} + @var{len} were -written in an inferior. The @var{id} is the identifier of the -thread group corresponding to the affected inferior. The optional -@code{type="code"} part is reported if the memory written to holds -executable code. -@end table - -@node GDB/MI Breakpoint Information -@subsection @sc{gdb/mi} Breakpoint Information - -When @value{GDBN} reports information about a breakpoint, a -tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the -following fields: - -@table @code -@item number -The breakpoint number. For a breakpoint that represents one location -of a multi-location breakpoint, this will be a dotted pair, like -@samp{1.2}. - -@item type -The type of the breakpoint. For ordinary breakpoints this will be -@samp{breakpoint}, but many values are possible. - -@item catch-type -If the type of the breakpoint is @samp{catchpoint}, then this -indicates the exact type of catchpoint. - -@item disp -This is the breakpoint disposition---either @samp{del}, meaning that -the breakpoint will be deleted at the next stop, or @samp{keep}, -meaning that the breakpoint will not be deleted. - -@item enabled -This indicates whether the breakpoint is enabled, in which case the -value is @samp{y}, or disabled, in which case the value is @samp{n}. -Note that this is not the same as the field @code{enable}. - -@item addr -The address of the breakpoint. This may be a hexidecimal number, -giving the address; or the string @samp{}, for a pending -breakpoint; or the string @samp{}, for a breakpoint with -multiple locations. This field will not be present if no address can -be determined. For example, a watchpoint does not have an address. - -@item func -If known, the function in which the breakpoint appears. -If not known, this field is not present. - -@item filename -The name of the source file which contains this function, if known. -If not known, this field is not present. - -@item fullname -The full file name of the source file which contains this function, if -known. If not known, this field is not present. - -@item line -The line number at which this breakpoint appears, if known. -If not known, this field is not present. - -@item at -If the source file is not known, this field may be provided. If -provided, this holds the address of the breakpoint, possibly followed -by a symbol name. - -@item pending -If this breakpoint is pending, this field is present and holds the -text used to set the breakpoint, as entered by the user. - -@item evaluated-by -Where this breakpoint's condition is evaluated, either @samp{host} or -@samp{target}. - -@item thread -If this is a thread-specific breakpoint, then this identifies the -thread in which the breakpoint can trigger. - -@item task -If this breakpoint is restricted to a particular Ada task, then this -field will hold the task identifier. - -@item cond -If the breakpoint is conditional, this is the condition expression. - -@item ignore -The ignore count of the breakpoint. - -@item enable -The enable count of the breakpoint. - -@item traceframe-usage -FIXME. - -@item static-tracepoint-marker-string-id -For a static tracepoint, the name of the static tracepoint marker. - -@item mask -For a masked watchpoint, this is the mask. - -@item pass -A tracepoint's pass count. - -@item original-location -The location of the breakpoint as originally specified by the user. -This field is optional. - -@item times -The number of times the breakpoint has been hit. - -@item installed -This field is only given for tracepoints. This is either @samp{y}, -meaning that the tracepoint is installed, or @samp{n}, meaning that it -is not. - -@item what -Some extra data, the exact contents of which are type-dependent. - -@end table - -For example, here is what the output of @code{-break-insert} -(@pxref{GDB/MI Breakpoint Commands}) might be: - -@smallexample --> -break-insert main -<- ^done,bkpt=@{number="1",type="breakpoint",disp="keep", - enabled="y",addr="0x08048564",func="main",file="myprog.c", - fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"], - times="0"@} -<- (gdb) -@end smallexample - -@node GDB/MI Frame Information -@subsection @sc{gdb/mi} Frame Information - -Response from many MI commands includes an information about stack -frame. This information is a tuple that may have the following -fields: - -@table @code -@item level -The level of the stack frame. The innermost frame has the level of -zero. This field is always present. - -@item func -The name of the function corresponding to the frame. This field may -be absent if @value{GDBN} is unable to determine the function name. - -@item addr -The code address for the frame. This field is always present. - -@item file -The name of the source files that correspond to the frame's code -address. This field may be absent. - -@item line -The source line corresponding to the frames' code address. This field -may be absent. - -@item from -The name of the binary file (either executable or shared library) the -corresponds to the frame's code address. This field may be absent. - -@end table - -@node GDB/MI Thread Information -@subsection @sc{gdb/mi} Thread Information - -Whenever @value{GDBN} has to report an information about a thread, it -uses a tuple with the following fields: - -@table @code -@item id -The numeric id assigned to the thread by @value{GDBN}. This field is -always present. - -@item target-id -Target-specific string identifying the thread. This field is always present. - -@item details -Additional information about the thread provided by the target. -It is supposed to be human-readable and not interpreted by the -frontend. This field is optional. - -@item state -Either @samp{stopped} or @samp{running}, depending on whether the -thread is presently running. This field is always present. - -@item core -The value of this field is an integer number of the processor core the -thread was last seen on. This field is optional. -@end table - -@node GDB/MI Ada Exception Information -@subsection @sc{gdb/mi} Ada Exception Information - -Whenever a @code{*stopped} record is emitted because the program -stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}), -@value{GDBN} provides the name of the exception that was raised via -the @code{exception-name} field. - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Simple Examples -@section Simple Examples of @sc{gdb/mi} Interaction -@cindex @sc{gdb/mi}, simple examples - -This subsection presents several simple examples of interaction using -the @sc{gdb/mi} interface. In these examples, @samp{->} means that the -following line is passed to @sc{gdb/mi} as input, while @samp{<-} means -the output received from @sc{gdb/mi}. - -Note the line breaks shown in the examples are here only for -readability, they don't appear in the real output. - -@subheading Setting a Breakpoint - -Setting a breakpoint generates synchronous output which contains detailed -information of the breakpoint. - -@smallexample --> -break-insert main -<- ^done,bkpt=@{number="1",type="breakpoint",disp="keep", - enabled="y",addr="0x08048564",func="main",file="myprog.c", - fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"], - times="0"@} -<- (gdb) -@end smallexample - -@subheading Program Execution - -Program execution generates asynchronous records and MI gives the -reason that execution stopped. - -@smallexample --> -exec-run -<- ^running -<- (gdb) -<- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0", - frame=@{addr="0x08048564",func="main", - args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}], - file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@} -<- (gdb) --> -exec-continue -<- ^running -<- (gdb) -<- *stopped,reason="exited-normally" -<- (gdb) -@end smallexample - -@subheading Quitting @value{GDBN} - -Quitting @value{GDBN} just prints the result class @samp{^exit}. - -@smallexample --> (gdb) -<- -gdb-exit -<- ^exit -@end smallexample - -Please note that @samp{^exit} is printed immediately, but it might -take some time for @value{GDBN} to actually exit. During that time, @value{GDBN} -performs necessary cleanups, including killing programs being debugged -or disconnecting from debug hardware, so the frontend should wait till -@value{GDBN} exits and should only forcibly kill @value{GDBN} if it -fails to exit in reasonable time. - -@subheading A Bad Command - -Here's what happens if you pass a non-existent command: - -@smallexample --> -rubbish -<- ^error,msg="Undefined MI command: rubbish" -<- (gdb) -@end smallexample - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Command Description Format -@section @sc{gdb/mi} Command Description Format - -The remaining sections describe blocks of commands. Each block of -commands is laid out in a fashion similar to this section. - -@subheading Motivation - -The motivation for this collection of commands. - -@subheading Introduction - -A brief introduction to this collection of commands as a whole. - -@subheading Commands - -For each command in the block, the following is described: - -@subsubheading Synopsis - -@smallexample - -command @var{args}@dots{} -@end smallexample - -@subsubheading Result - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} CLI command(s), if any. - -@subsubheading Example - -Example(s) formatted for readability. Some of the described commands have -not been implemented yet and these are labeled N.A.@: (not available). - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Breakpoint Commands -@section @sc{gdb/mi} Breakpoint Commands - -@cindex breakpoint commands for @sc{gdb/mi} -@cindex @sc{gdb/mi}, breakpoint commands -This section documents @sc{gdb/mi} commands for manipulating -breakpoints. - -@subheading The @code{-break-after} Command -@findex -break-after - -@subsubheading Synopsis - -@smallexample - -break-after @var{number} @var{count} -@end smallexample - -The breakpoint number @var{number} is not in effect until it has been -hit @var{count} times. To see how this is reflected in the output of -the @samp{-break-list} command, see the description of the -@samp{-break-list} command below. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{ignore}. - -@subsubheading Example - -@smallexample -(gdb) --break-insert main -^done,bkpt=@{number="1",type="breakpoint",disp="keep", -enabled="y",addr="0x000100d0",func="main",file="hello.c", -fullname="/home/foo/hello.c",line="5",thread-groups=["i1"], -times="0"@} -(gdb) --break-after 1 3 -~ -^done -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="1",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", -line="5",thread-groups=["i1"],times="0",ignore="3"@}]@} -(gdb) -@end smallexample - -@ignore -@subheading The @code{-break-catch} Command -@findex -break-catch -@end ignore - -@subheading The @code{-break-commands} Command -@findex -break-commands - -@subsubheading Synopsis - -@smallexample - -break-commands @var{number} [ @var{command1} ... @var{commandN} ] -@end smallexample - -Specifies the CLI commands that should be executed when breakpoint -@var{number} is hit. The parameters @var{command1} to @var{commandN} -are the commands. If no command is specified, any previously-set -commands are cleared. @xref{Break Commands}. Typical use of this -functionality is tracing a program, that is, printing of values of -some variables whenever breakpoint is hit and then continuing. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{commands}. - -@subsubheading Example - -@smallexample -(gdb) --break-insert main -^done,bkpt=@{number="1",type="breakpoint",disp="keep", -enabled="y",addr="0x000100d0",func="main",file="hello.c", -fullname="/home/foo/hello.c",line="5",thread-groups=["i1"], -times="0"@} -(gdb) --break-commands 1 "print v" "continue" -^done -(gdb) -@end smallexample - -@subheading The @code{-break-condition} Command -@findex -break-condition - -@subsubheading Synopsis - -@smallexample - -break-condition @var{number} @var{expr} -@end smallexample - -Breakpoint @var{number} will stop the program only if the condition in -@var{expr} is true. The condition becomes part of the -@samp{-break-list} output (see the description of the @samp{-break-list} -command below). - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{condition}. - -@subsubheading Example - -@smallexample -(gdb) --break-condition 1 1 -^done -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="1",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", -line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@} -(gdb) -@end smallexample - -@subheading The @code{-break-delete} Command -@findex -break-delete - -@subsubheading Synopsis - -@smallexample - -break-delete ( @var{breakpoint} )+ -@end smallexample - -Delete the breakpoint(s) whose number(s) are specified in the argument -list. This is obviously reflected in the breakpoint list. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{delete}. - -@subsubheading Example - -@smallexample -(gdb) --break-delete 1 -^done -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="0",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[]@} -(gdb) -@end smallexample - -@subheading The @code{-break-disable} Command -@findex -break-disable - -@subsubheading Synopsis - -@smallexample - -break-disable ( @var{breakpoint} )+ -@end smallexample - -Disable the named @var{breakpoint}(s). The field @samp{enabled} in the -break list is now set to @samp{n} for the named @var{breakpoint}(s). - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{disable}. - -@subsubheading Example - -@smallexample -(gdb) --break-disable 2 -^done -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="1",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n", -addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", -line="5",thread-groups=["i1"],times="0"@}]@} -(gdb) -@end smallexample - -@subheading The @code{-break-enable} Command -@findex -break-enable - -@subsubheading Synopsis - -@smallexample - -break-enable ( @var{breakpoint} )+ -@end smallexample - -Enable (previously disabled) @var{breakpoint}(s). - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{enable}. - -@subsubheading Example - -@smallexample -(gdb) --break-enable 2 -^done -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="1",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y", -addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", -line="5",thread-groups=["i1"],times="0"@}]@} -(gdb) -@end smallexample - -@subheading The @code{-break-info} Command -@findex -break-info - -@subsubheading Synopsis - -@smallexample - -break-info @var{breakpoint} -@end smallexample - -@c REDUNDANT??? -Get information about a single breakpoint. - -The result is a table of breakpoints. @xref{GDB/MI Breakpoint -Information}, for details on the format of each breakpoint in the -table. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}. - -@subsubheading Example -N.A. - -@subheading The @code{-break-insert} Command -@findex -break-insert - -@subsubheading Synopsis - -@smallexample - -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] - [ -c @var{condition} ] [ -i @var{ignore-count} ] - [ -p @var{thread-id} ] [ @var{location} ] -@end smallexample - -@noindent -If specified, @var{location}, can be one of: - -@itemize @bullet -@item function -@c @item +offset -@c @item -offset -@c @item linenum -@item filename:linenum -@item filename:function -@item *address -@end itemize - -The possible optional parameters of this command are: - -@table @samp -@item -t -Insert a temporary breakpoint. -@item -h -Insert a hardware breakpoint. -@item -f -If @var{location} cannot be parsed (for example if it -refers to unknown files or functions), create a pending -breakpoint. Without this flag, @value{GDBN} will report -an error, and won't create a breakpoint, if @var{location} -cannot be parsed. -@item -d -Create a disabled breakpoint. -@item -a -Create a tracepoint. @xref{Tracepoints}. When this parameter -is used together with @samp{-h}, a fast tracepoint is created. -@item -c @var{condition} -Make the breakpoint conditional on @var{condition}. -@item -i @var{ignore-count} -Initialize the @var{ignore-count}. -@item -p @var{thread-id} -Restrict the breakpoint to the specified @var{thread-id}. -@end table - -@subsubheading Result - -@xref{GDB/MI Breakpoint Information}, for details on the format of the -resulting breakpoint. - -Note: this format is open to change. -@c An out-of-band breakpoint instead of part of the result? - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak}, -@samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}. - -@subsubheading Example - -@smallexample -(gdb) --break-insert main -^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c", -fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"], -times="0"@} -(gdb) --break-insert -t foo -^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c", -fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"], -times="0"@} -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="2",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x0001072c", func="main",file="recursive2.c", -fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"], -times="0"@}, -bkpt=@{number="2",type="breakpoint",disp="del",enabled="y", -addr="0x00010774",func="foo",file="recursive2.c", -fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"], -times="0"@}]@} -(gdb) -@c -break-insert -r foo.* -@c ~int foo(int, int); -@c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c, -@c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"], -@c times="0"@} -@c (gdb) -@end smallexample - -@subheading The @code{-break-list} Command -@findex -break-list - -@subsubheading Synopsis - -@smallexample - -break-list -@end smallexample - -Displays the list of inserted breakpoints, showing the following fields: - -@table @samp -@item Number -number of the breakpoint -@item Type -type of the breakpoint: @samp{breakpoint} or @samp{watchpoint} -@item Disposition -should the breakpoint be deleted or disabled when it is hit: @samp{keep} -or @samp{nokeep} -@item Enabled -is the breakpoint enabled or no: @samp{y} or @samp{n} -@item Address -memory location at which the breakpoint is set -@item What -logical location of the breakpoint, expressed by function name, file -name, line number -@item Thread-groups -list of thread groups to which this breakpoint applies -@item Times -number of times the breakpoint has been hit -@end table - -If there are no breakpoints or watchpoints, the @code{BreakpointTable} -@code{body} field is an empty list. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info break}. - -@subsubheading Example - -@smallexample -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="2",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"], -times="0"@}, -bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y", -addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c", -line="13",thread-groups=["i1"],times="0"@}]@} -(gdb) -@end smallexample - -Here's an example of the result when there are no breakpoints: - -@smallexample -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="0",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[]@} -(gdb) -@end smallexample - -@subheading The @code{-break-passcount} Command -@findex -break-passcount - -@subsubheading Synopsis - -@smallexample - -break-passcount @var{tracepoint-number} @var{passcount} -@end smallexample - -Set the passcount for tracepoint @var{tracepoint-number} to -@var{passcount}. If the breakpoint referred to by @var{tracepoint-number} -is not a tracepoint, error is emitted. This corresponds to CLI -command @samp{passcount}. - -@subheading The @code{-break-watch} Command -@findex -break-watch - -@subsubheading Synopsis - -@smallexample - -break-watch [ -a | -r ] -@end smallexample - -Create a watchpoint. With the @samp{-a} option it will create an -@dfn{access} watchpoint, i.e., a watchpoint that triggers either on a -read from or on a write to the memory location. With the @samp{-r} -option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will -trigger only when the memory location is accessed for reading. Without -either of the options, the watchpoint created is a regular watchpoint, -i.e., it will trigger when the memory location is accessed for writing. -@xref{Set Watchpoints, , Setting Watchpoints}. - -Note that @samp{-break-list} will report a single list of watchpoints and -breakpoints inserted. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and -@samp{rwatch}. - -@subsubheading Example - -Setting a watchpoint on a variable in the @code{main} function: - -@smallexample -(gdb) --break-watch x -^done,wpt=@{number="2",exp="x"@} -(gdb) --exec-continue -^running -(gdb) -*stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@}, -value=@{old="-268439212",new="55"@}, -frame=@{func="main",args=[],file="recursive2.c", -fullname="/home/foo/bar/recursive2.c",line="5"@} -(gdb) -@end smallexample - -Setting a watchpoint on a variable local to a function. @value{GDBN} will stop -the program execution twice: first for the variable changing value, then -for the watchpoint going out of scope. - -@smallexample -(gdb) --break-watch C -^done,wpt=@{number="5",exp="C"@} -(gdb) --exec-continue -^running -(gdb) -*stopped,reason="watchpoint-trigger", -wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@}, -frame=@{func="callee4",args=[], -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@} -(gdb) --exec-continue -^running -(gdb) -*stopped,reason="watchpoint-scope",wpnum="5", -frame=@{func="callee3",args=[@{name="strarg", -value="0x11940 \"A string argument.\""@}], -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@} -(gdb) -@end smallexample - -Listing breakpoints and watchpoints, at different points in the program -execution. Note that once the watchpoint goes out of scope, it is -deleted. - -@smallexample -(gdb) --break-watch C -^done,wpt=@{number="2",exp="C"@} -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="2",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x00010734",func="callee4", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"], -times="1"@}, -bkpt=@{number="2",type="watchpoint",disp="keep", -enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@} -(gdb) --exec-continue -^running -(gdb) -*stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@}, -value=@{old="-276895068",new="3"@}, -frame=@{func="callee4",args=[], -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@} -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="2",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x00010734",func="callee4", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"], -times="1"@}, -bkpt=@{number="2",type="watchpoint",disp="keep", -enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@} -(gdb) --exec-continue -^running -^done,reason="watchpoint-scope",wpnum="2", -frame=@{func="callee3",args=[@{name="strarg", -value="0x11940 \"A string argument.\""@}], -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@} -(gdb) --break-list -^done,BreakpointTable=@{nr_rows="1",nr_cols="6", -hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, -@{width="14",alignment="-1",col_name="type",colhdr="Type"@}, -@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, -@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, -@{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, -@{width="40",alignment="2",col_name="what",colhdr="What"@}], -body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x00010734",func="callee4", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8", -thread-groups=["i1"],times="1"@}]@} -(gdb) -@end smallexample - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Catchpoint Commands -@section @sc{gdb/mi} Catchpoint Commands - -This section documents @sc{gdb/mi} commands for manipulating -catchpoints. - -@subheading The @code{-catch-load} Command -@findex -catch-load - -@subsubheading Synopsis - -@smallexample - -catch-load [ -t ] [ -d ] @var{regexp} -@end smallexample - -Add a catchpoint for library load events. If the @samp{-t} option is used, -the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting -Breakpoints}). If the @samp{-d} option is used, the catchpoint is created -in a disabled state. The @samp{regexp} argument is a regular -expression used to match the name of the loaded library. - - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{catch load}. - -@subsubheading Example - -@smallexample --catch-load -t foo.so -^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y", -what="load of library matching foo.so",catch-type="load",times="0"@} -(gdb) -@end smallexample - - -@subheading The @code{-catch-unload} Command -@findex -catch-unload - -@subsubheading Synopsis - -@smallexample - -catch-unload [ -t ] [ -d ] @var{regexp} -@end smallexample - -Add a catchpoint for library unload events. If the @samp{-t} option is -used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting -Breakpoints}). If the @samp{-d} option is used, the catchpoint is -created in a disabled state. The @samp{regexp} argument is a regular -expression used to match the name of the unloaded library. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{catch unload}. - -@subsubheading Example - -@smallexample --catch-unload -d bar.so -^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n", -what="load of library matching bar.so",catch-type="unload",times="0"@} -(gdb) -@end smallexample - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Program Context -@section @sc{gdb/mi} Program Context - -@subheading The @code{-exec-arguments} Command -@findex -exec-arguments - - -@subsubheading Synopsis - -@smallexample - -exec-arguments @var{args} -@end smallexample - -Set the inferior program arguments, to be used in the next -@samp{-exec-run}. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{set args}. - -@subsubheading Example - -@smallexample -(gdb) --exec-arguments -v word -^done -(gdb) -@end smallexample - - -@ignore -@subheading The @code{-exec-show-arguments} Command -@findex -exec-show-arguments - -@subsubheading Synopsis - -@smallexample - -exec-show-arguments -@end smallexample - -Print the arguments of the program. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{show args}. - -@subsubheading Example -N.A. -@end ignore - - -@subheading The @code{-environment-cd} Command -@findex -environment-cd - -@subsubheading Synopsis - -@smallexample - -environment-cd @var{pathdir} -@end smallexample - -Set @value{GDBN}'s working directory. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{cd}. - -@subsubheading Example - -@smallexample -(gdb) --environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb -^done -(gdb) -@end smallexample - - -@subheading The @code{-environment-directory} Command -@findex -environment-directory - -@subsubheading Synopsis - -@smallexample - -environment-directory [ -r ] [ @var{pathdir} ]+ -@end smallexample - -Add directories @var{pathdir} to beginning of search path for source files. -If the @samp{-r} option is used, the search path is reset to the default -search path. If directories @var{pathdir} are supplied in addition to the -@samp{-r} option, the search path is first reset and then addition -occurs as normal. -Multiple directories may be specified, separated by blanks. Specifying -multiple directories in a single command -results in the directories added to the beginning of the -search path in the same order they were presented in the command. -If blanks are needed as -part of a directory name, double-quotes should be used around -the name. In the command output, the path will show up separated -by the system directory-separator character. The directory-separator -character must not be used -in any directory name. -If no directories are specified, the current search path is displayed. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{dir}. - -@subsubheading Example - -@smallexample -(gdb) --environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb -^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd" -(gdb) --environment-directory "" -^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd" -(gdb) --environment-directory -r /home/jjohnstn/src/gdb /usr/src -^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd" -(gdb) --environment-directory -r -^done,source-path="$cdir:$cwd" -(gdb) -@end smallexample - - -@subheading The @code{-environment-path} Command -@findex -environment-path - -@subsubheading Synopsis - -@smallexample - -environment-path [ -r ] [ @var{pathdir} ]+ -@end smallexample - -Add directories @var{pathdir} to beginning of search path for object files. -If the @samp{-r} option is used, the search path is reset to the original -search path that existed at gdb start-up. If directories @var{pathdir} are -supplied in addition to the -@samp{-r} option, the search path is first reset and then addition -occurs as normal. -Multiple directories may be specified, separated by blanks. Specifying -multiple directories in a single command -results in the directories added to the beginning of the -search path in the same order they were presented in the command. -If blanks are needed as -part of a directory name, double-quotes should be used around -the name. In the command output, the path will show up separated -by the system directory-separator character. The directory-separator -character must not be used -in any directory name. -If no directories are specified, the current path is displayed. - - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{path}. - -@subsubheading Example - -@smallexample -(gdb) --environment-path -^done,path="/usr/bin" -(gdb) --environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin -^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin" -(gdb) --environment-path -r /usr/local/bin -^done,path="/usr/local/bin:/usr/bin" -(gdb) -@end smallexample - - -@subheading The @code{-environment-pwd} Command -@findex -environment-pwd - -@subsubheading Synopsis - -@smallexample - -environment-pwd -@end smallexample - -Show the current working directory. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{pwd}. - -@subsubheading Example - -@smallexample -(gdb) --environment-pwd -^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb" -(gdb) -@end smallexample - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Thread Commands -@section @sc{gdb/mi} Thread Commands - - -@subheading The @code{-thread-info} Command -@findex -thread-info - -@subsubheading Synopsis - -@smallexample - -thread-info [ @var{thread-id} ] -@end smallexample - -Reports information about either a specific thread, if -the @var{thread-id} parameter is present, or about all -threads. When printing information about all threads, -also reports the current thread. - -@subsubheading @value{GDBN} Command - -The @samp{info thread} command prints the same information -about all threads. - -@subsubheading Result - -The result is a list of threads. The following attributes are -defined for a given thread: - -@table @samp -@item current -This field exists only for the current thread. It has the value @samp{*}. - -@item id -The identifier that @value{GDBN} uses to refer to the thread. - -@item target-id -The identifier that the target uses to refer to the thread. - -@item details -Extra information about the thread, in a target-specific format. This -field is optional. - -@item name -The name of the thread. If the user specified a name using the -@code{thread name} command, then this name is given. Otherwise, if -@value{GDBN} can extract the thread name from the target, then that -name is given. If @value{GDBN} cannot find the thread name, then this -field is omitted. - -@item frame -The stack frame currently executing in the thread. - -@item state -The thread's state. The @samp{state} field may have the following -values: - -@table @code -@item stopped -The thread is stopped. Frame information is available for stopped -threads. - -@item running -The thread is running. There's no frame information for running -threads. - -@end table - -@item core -If @value{GDBN} can find the CPU core on which this thread is running, -then this field is the core identifier. This field is optional. - -@end table - -@subsubheading Example - -@smallexample --thread-info -^done,threads=[ -@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)", - frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall", - args=[]@},state="running"@}, -@{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)", - frame=@{level="0",addr="0x0804891f",func="foo", - args=[@{name="i",value="10"@}], - file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}, - state="running"@}], -current-thread-id="1" -(gdb) -@end smallexample - -@subheading The @code{-thread-list-ids} Command -@findex -thread-list-ids - -@subsubheading Synopsis - -@smallexample - -thread-list-ids -@end smallexample - -Produces a list of the currently known @value{GDBN} thread ids. At the -end of the list it also prints the total number of such threads. - -This command is retained for historical reasons, the -@code{-thread-info} command should be used instead. - -@subsubheading @value{GDBN} Command - -Part of @samp{info threads} supplies the same information. - -@subsubheading Example - -@smallexample -(gdb) --thread-list-ids -^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@}, -current-thread-id="1",number-of-threads="3" -(gdb) -@end smallexample - - -@subheading The @code{-thread-select} Command -@findex -thread-select - -@subsubheading Synopsis - -@smallexample - -thread-select @var{threadnum} -@end smallexample - -Make @var{threadnum} the current thread. It prints the number of the new -current thread, and the topmost frame for that thread. - -This command is deprecated in favor of explicitly using the -@samp{--thread} option to each command. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{thread}. - -@subsubheading Example - -@smallexample -(gdb) --exec-next -^running -(gdb) -*stopped,reason="end-stepping-range",thread-id="2",line="187", -file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c" -(gdb) --thread-list-ids -^done, -thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@}, -number-of-threads="3" -(gdb) --thread-select 3 -^done,new-thread-id="3", -frame=@{level="0",func="vprintf", -args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@}, -@{name="arg",value="0x2"@}],file="vprintf.c",line="31"@} -(gdb) -@end smallexample - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Ada Tasking Commands -@section @sc{gdb/mi} Ada Tasking Commands - -@subheading The @code{-ada-task-info} Command -@findex -ada-task-info - -@subsubheading Synopsis - -@smallexample - -ada-task-info [ @var{task-id} ] -@end smallexample - -Reports information about either a specific Ada task, if the -@var{task-id} parameter is present, or about all Ada tasks. - -@subsubheading @value{GDBN} Command - -The @samp{info tasks} command prints the same information -about all Ada tasks (@pxref{Ada Tasks}). - -@subsubheading Result - -The result is a table of Ada tasks. The following columns are -defined for each Ada task: - -@table @samp -@item current -This field exists only for the current thread. It has the value @samp{*}. - -@item id -The identifier that @value{GDBN} uses to refer to the Ada task. - -@item task-id -The identifier that the target uses to refer to the Ada task. - -@item thread-id -The identifier of the thread corresponding to the Ada task. - -This field should always exist, as Ada tasks are always implemented -on top of a thread. But if @value{GDBN} cannot find this corresponding -thread for any reason, the field is omitted. - -@item parent-id -This field exists only when the task was created by another task. -In this case, it provides the ID of the parent task. - -@item priority -The base priority of the task. - -@item state -The current state of the task. For a detailed description of the -possible states, see @ref{Ada Tasks}. - -@item name -The name of the task. - -@end table - -@subsubheading Example - -@smallexample --ada-task-info -^done,tasks=@{nr_rows="3",nr_cols="8", -hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@}, -@{width="3",alignment="1",col_name="id",colhdr="ID"@}, -@{width="9",alignment="1",col_name="task-id",colhdr="TID"@}, -@{width="4",alignment="1",col_name="thread-id",colhdr=""@}, -@{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@}, -@{width="3",alignment="1",col_name="priority",colhdr="Pri"@}, -@{width="22",alignment="-1",col_name="state",colhdr="State"@}, -@{width="1",alignment="2",col_name="name",colhdr="Name"@}], -body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48", -state="Child Termination Wait",name="main_task"@}]@} -(gdb) -@end smallexample - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Program Execution -@section @sc{gdb/mi} Program Execution - -These are the asynchronous commands which generate the out-of-band -record @samp{*stopped}. Currently @value{GDBN} only really executes -asynchronously with remote targets and this interaction is mimicked in -other cases. - -@subheading The @code{-exec-continue} Command -@findex -exec-continue - -@subsubheading Synopsis - -@smallexample - -exec-continue [--reverse] [--all|--thread-group N] -@end smallexample - -Resumes the execution of the inferior program, which will continue -to execute until it reaches a debugger stop event. If the -@samp{--reverse} option is specified, execution resumes in reverse until -it reaches a stop event. Stop events may include -@itemize @bullet -@item -breakpoints or watchpoints -@item -signals or exceptions -@item -the end of the process (or its beginning under @samp{--reverse}) -@item -the end or beginning of a replay log if one is being used. -@end itemize -In all-stop mode (@pxref{All-Stop -Mode}), may resume only one thread, or all threads, depending on the -value of the @samp{scheduler-locking} variable. If @samp{--all} is -specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is -ignored in all-stop mode. If the @samp{--thread-group} options is -specified, then all threads in that thread group are resumed. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} corresponding is @samp{continue}. - -@subsubheading Example - -@smallexample --exec-continue -^running -(gdb) -@@Hello world -*stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{ -func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c", -line="13"@} -(gdb) -@end smallexample - - -@subheading The @code{-exec-finish} Command -@findex -exec-finish - -@subsubheading Synopsis - -@smallexample - -exec-finish [--reverse] -@end smallexample - -Resumes the execution of the inferior program until the current -function is exited. Displays the results returned by the function. -If the @samp{--reverse} option is specified, resumes the reverse -execution of the inferior program until the point where current -function was called. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{finish}. - -@subsubheading Example - -Function returning @code{void}. - -@smallexample --exec-finish -^running -(gdb) -@@hello from foo -*stopped,reason="function-finished",frame=@{func="main",args=[], -file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@} -(gdb) -@end smallexample - -Function returning other than @code{void}. The name of the internal -@value{GDBN} variable storing the result is printed, together with the -value itself. - -@smallexample --exec-finish -^running -(gdb) -*stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo", -args=[@{name="a",value="1"],@{name="b",value="9"@}@}, -file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -gdb-result-var="$1",return-value="0" -(gdb) -@end smallexample - - -@subheading The @code{-exec-interrupt} Command -@findex -exec-interrupt - -@subsubheading Synopsis - -@smallexample - -exec-interrupt [--all|--thread-group N] -@end smallexample - -Interrupts the background execution of the target. Note how the token -associated with the stop message is the one for the execution command -that has been interrupted. The token for the interrupt itself only -appears in the @samp{^done} output. If the user is trying to -interrupt a non-running program, an error message will be printed. - -Note that when asynchronous execution is enabled, this command is -asynchronous just like other execution commands. That is, first the -@samp{^done} response will be printed, and the target stop will be -reported after that using the @samp{*stopped} notification. - -In non-stop mode, only the context thread is interrupted by default. -All threads (in all inferiors) will be interrupted if the -@samp{--all} option is specified. If the @samp{--thread-group} -option is specified, all threads in that group will be interrupted. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{interrupt}. - -@subsubheading Example - -@smallexample -(gdb) -111-exec-continue -111^running - -(gdb) -222-exec-interrupt -222^done -(gdb) -111*stopped,signal-name="SIGINT",signal-meaning="Interrupt", -frame=@{addr="0x00010140",func="foo",args=[],file="try.c", -fullname="/home/foo/bar/try.c",line="13"@} -(gdb) - -(gdb) --exec-interrupt -^error,msg="mi_cmd_exec_interrupt: Inferior not executing." -(gdb) -@end smallexample - -@subheading The @code{-exec-jump} Command -@findex -exec-jump - -@subsubheading Synopsis - -@smallexample - -exec-jump @var{location} -@end smallexample - -Resumes execution of the inferior program at the location specified by -parameter. @xref{Specify Location}, for a description of the -different forms of @var{location}. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{jump}. - -@subsubheading Example - -@smallexample --exec-jump foo.c:10 -*running,thread-id="all" -^running -@end smallexample - - -@subheading The @code{-exec-next} Command -@findex -exec-next - -@subsubheading Synopsis - -@smallexample - -exec-next [--reverse] -@end smallexample - -Resumes execution of the inferior program, stopping when the beginning -of the next source line is reached. - -If the @samp{--reverse} option is specified, resumes reverse execution -of the inferior program, stopping at the beginning of the previous -source line. If you issue this command on the first line of a -function, it will take you back to the caller of that function, to the -source line where the function was called. - - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{next}. - -@subsubheading Example - -@smallexample --exec-next -^running -(gdb) -*stopped,reason="end-stepping-range",line="8",file="hello.c" -(gdb) -@end smallexample - - -@subheading The @code{-exec-next-instruction} Command -@findex -exec-next-instruction - -@subsubheading Synopsis - -@smallexample - -exec-next-instruction [--reverse] -@end smallexample - -Executes one machine instruction. If the instruction is a function -call, continues until the function returns. If the program stops at an -instruction in the middle of a source line, the address will be -printed as well. - -If the @samp{--reverse} option is specified, resumes reverse execution -of the inferior program, stopping at the previous instruction. If the -previously executed instruction was a return from another function, -it will continue to execute in reverse until the call to that function -(from the current stack frame) is reached. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{nexti}. - -@subsubheading Example - -@smallexample -(gdb) --exec-next-instruction -^running - -(gdb) -*stopped,reason="end-stepping-range", -addr="0x000100d4",line="5",file="hello.c" -(gdb) -@end smallexample - - -@subheading The @code{-exec-return} Command -@findex -exec-return - -@subsubheading Synopsis - -@smallexample - -exec-return -@end smallexample - -Makes current function return immediately. Doesn't execute the inferior. -Displays the new current frame. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{return}. - -@subsubheading Example - -@smallexample -(gdb) -200-break-insert callee4 -200^done,bkpt=@{number="1",addr="0x00010734", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@} -(gdb) -000-exec-run -000^running -(gdb) -000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1", -frame=@{func="callee4",args=[], -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@} -(gdb) -205-break-delete -205^done -(gdb) -111-exec-return -111^done,frame=@{level="0",func="callee3", -args=[@{name="strarg", -value="0x11940 \"A string argument.\""@}], -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@} -(gdb) -@end smallexample - - -@subheading The @code{-exec-run} Command -@findex -exec-run - -@subsubheading Synopsis - -@smallexample - -exec-run [--all | --thread-group N] -@end smallexample - -Starts execution of the inferior from the beginning. The inferior -executes until either a breakpoint is encountered or the program -exits. In the latter case the output will include an exit code, if -the program has exited exceptionally. - -When no option is specified, the current inferior is started. If the -@samp{--thread-group} option is specified, it should refer to a thread -group of type @samp{process}, and that thread group will be started. -If the @samp{--all} option is specified, then all inferiors will be started. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{run}. - -@subsubheading Examples - -@smallexample -(gdb) --break-insert main -^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@} -(gdb) --exec-run -^running -(gdb) -*stopped,reason="breakpoint-hit",disp="keep",bkptno="1", -frame=@{func="main",args=[],file="recursive2.c", -fullname="/home/foo/bar/recursive2.c",line="4"@} -(gdb) -@end smallexample - -@noindent -Program exited normally: - -@smallexample -(gdb) --exec-run -^running -(gdb) -x = 55 -*stopped,reason="exited-normally" -(gdb) -@end smallexample - -@noindent -Program exited exceptionally: - -@smallexample -(gdb) --exec-run -^running -(gdb) -x = 55 -*stopped,reason="exited",exit-code="01" -(gdb) -@end smallexample - -Another way the program can terminate is if it receives a signal such as -@code{SIGINT}. In this case, @sc{gdb/mi} displays this: - -@smallexample -(gdb) -*stopped,reason="exited-signalled",signal-name="SIGINT", -signal-meaning="Interrupt" -@end smallexample - - -@c @subheading -exec-signal - - -@subheading The @code{-exec-step} Command -@findex -exec-step - -@subsubheading Synopsis - -@smallexample - -exec-step [--reverse] -@end smallexample - -Resumes execution of the inferior program, stopping when the beginning -of the next source line is reached, if the next source line is not a -function call. If it is, stop at the first instruction of the called -function. If the @samp{--reverse} option is specified, resumes reverse -execution of the inferior program, stopping at the beginning of the -previously executed source line. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{step}. - -@subsubheading Example - -Stepping into a function: - -@smallexample --exec-step -^running -(gdb) -*stopped,reason="end-stepping-range", -frame=@{func="foo",args=[@{name="a",value="10"@}, -@{name="b",value="0"@}],file="recursive2.c", -fullname="/home/foo/bar/recursive2.c",line="11"@} -(gdb) -@end smallexample - -Regular stepping: - -@smallexample --exec-step -^running -(gdb) -*stopped,reason="end-stepping-range",line="14",file="recursive2.c" -(gdb) -@end smallexample - - -@subheading The @code{-exec-step-instruction} Command -@findex -exec-step-instruction - -@subsubheading Synopsis - -@smallexample - -exec-step-instruction [--reverse] -@end smallexample - -Resumes the inferior which executes one machine instruction. If the -@samp{--reverse} option is specified, resumes reverse execution of the -inferior program, stopping at the previously executed instruction. -The output, once @value{GDBN} has stopped, will vary depending on -whether we have stopped in the middle of a source line or not. In the -former case, the address at which the program stopped will be printed -as well. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{stepi}. - -@subsubheading Example - -@smallexample -(gdb) --exec-step-instruction -^running - -(gdb) -*stopped,reason="end-stepping-range", -frame=@{func="foo",args=[],file="try.c", -fullname="/home/foo/bar/try.c",line="10"@} -(gdb) --exec-step-instruction -^running - -(gdb) -*stopped,reason="end-stepping-range", -frame=@{addr="0x000100f4",func="foo",args=[],file="try.c", -fullname="/home/foo/bar/try.c",line="10"@} -(gdb) -@end smallexample - - -@subheading The @code{-exec-until} Command -@findex -exec-until - -@subsubheading Synopsis - -@smallexample - -exec-until [ @var{location} ] -@end smallexample - -Executes the inferior until the @var{location} specified in the -argument is reached. If there is no argument, the inferior executes -until a source line greater than the current one is reached. The -reason for stopping in this case will be @samp{location-reached}. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{until}. - -@subsubheading Example - -@smallexample -(gdb) --exec-until recursive2.c:6 -^running -(gdb) -x = 55 -*stopped,reason="location-reached",frame=@{func="main",args=[], -file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@} -(gdb) -@end smallexample - -@ignore -@subheading -file-clear -Is this going away???? -@end ignore - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Stack Manipulation -@section @sc{gdb/mi} Stack Manipulation Commands - - -@subheading The @code{-stack-info-frame} Command -@findex -stack-info-frame - -@subsubheading Synopsis - -@smallexample - -stack-info-frame -@end smallexample - -Get info on the selected frame. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame} -(without arguments). - -@subsubheading Example - -@smallexample -(gdb) --stack-info-frame -^done,frame=@{level="1",addr="0x0001076c",func="callee3", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@} -(gdb) -@end smallexample - -@subheading The @code{-stack-info-depth} Command -@findex -stack-info-depth - -@subsubheading Synopsis - -@smallexample - -stack-info-depth [ @var{max-depth} ] -@end smallexample - -Return the depth of the stack. If the integer argument @var{max-depth} -is specified, do not count beyond @var{max-depth} frames. - -@subsubheading @value{GDBN} Command - -There's no equivalent @value{GDBN} command. - -@subsubheading Example - -For a stack with frame levels 0 through 11: - -@smallexample -(gdb) --stack-info-depth -^done,depth="12" -(gdb) --stack-info-depth 4 -^done,depth="4" -(gdb) --stack-info-depth 12 -^done,depth="12" -(gdb) --stack-info-depth 11 -^done,depth="11" -(gdb) --stack-info-depth 13 -^done,depth="12" -(gdb) -@end smallexample - -@subheading The @code{-stack-list-arguments} Command -@findex -stack-list-arguments - -@subsubheading Synopsis - -@smallexample - -stack-list-arguments @var{print-values} - [ @var{low-frame} @var{high-frame} ] -@end smallexample - -Display a list of the arguments for the frames between @var{low-frame} -and @var{high-frame} (inclusive). If @var{low-frame} and -@var{high-frame} are not provided, list the arguments for the whole -call stack. If the two arguments are equal, show the single frame -at the corresponding level. It is an error if @var{low-frame} is -larger than the actual number of frames. On the other hand, -@var{high-frame} may be larger than the actual number of frames, in -which case only existing frames will be returned. - -If @var{print-values} is 0 or @code{--no-values}, print only the names of -the variables; if it is 1 or @code{--all-values}, print also their -values; and if it is 2 or @code{--simple-values}, print the name, -type and value for simple data types, and the name and type for arrays, -structures and unions. - -Use of this command to obtain arguments in a single frame is -deprecated in favor of the @samp{-stack-list-variables} command. - -@subsubheading @value{GDBN} Command - -@value{GDBN} does not have an equivalent command. @code{gdbtk} has a -@samp{gdb_get_args} command which partially overlaps with the -functionality of @samp{-stack-list-arguments}. - -@subsubheading Example - -@smallexample -(gdb) --stack-list-frames -^done, -stack=[ -frame=@{level="0",addr="0x00010734",func="callee4", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}, -frame=@{level="1",addr="0x0001076c",func="callee3", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}, -frame=@{level="2",addr="0x0001078c",func="callee2", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@}, -frame=@{level="3",addr="0x000107b4",func="callee1", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@}, -frame=@{level="4",addr="0x000107e0",func="main", -file="../../../devo/gdb/testsuite/gdb.mi/basics.c", -fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}] -(gdb) --stack-list-arguments 0 -^done, -stack-args=[ -frame=@{level="0",args=[]@}, -frame=@{level="1",args=[name="strarg"]@}, -frame=@{level="2",args=[name="intarg",name="strarg"]@}, -frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@}, -frame=@{level="4",args=[]@}] -(gdb) --stack-list-arguments 1 -^done, -stack-args=[ -frame=@{level="0",args=[]@}, -frame=@{level="1", - args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@}, -frame=@{level="2",args=[ -@{name="intarg",value="2"@}, -@{name="strarg",value="0x11940 \"A string argument.\""@}]@}, -@{frame=@{level="3",args=[ -@{name="intarg",value="2"@}, -@{name="strarg",value="0x11940 \"A string argument.\""@}, -@{name="fltarg",value="3.5"@}]@}, -frame=@{level="4",args=[]@}] -(gdb) --stack-list-arguments 0 2 2 -^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}] -(gdb) --stack-list-arguments 1 2 2 -^done,stack-args=[frame=@{level="2", -args=[@{name="intarg",value="2"@}, -@{name="strarg",value="0x11940 \"A string argument.\""@}]@}] -(gdb) -@end smallexample - -@c @subheading -stack-list-exception-handlers - - -@subheading The @code{-stack-list-frames} Command -@findex -stack-list-frames - -@subsubheading Synopsis - -@smallexample - -stack-list-frames [ @var{low-frame} @var{high-frame} ] -@end smallexample - -List the frames currently on the stack. For each frame it displays the -following info: - -@table @samp -@item @var{level} -The frame number, 0 being the topmost frame, i.e., the innermost function. -@item @var{addr} -The @code{$pc} value for that frame. -@item @var{func} -Function name. -@item @var{file} -File name of the source file where the function lives. -@item @var{fullname} -The full file name of the source file where the function lives. -@item @var{line} -Line number corresponding to the @code{$pc}. -@item @var{from} -The shared library where this function is defined. This is only given -if the frame's function is not known. -@end table - -If invoked without arguments, this command prints a backtrace for the -whole stack. If given two integer arguments, it shows the frames whose -levels are between the two arguments (inclusive). If the two arguments -are equal, it shows the single frame at the corresponding level. It is -an error if @var{low-frame} is larger than the actual number of -frames. On the other hand, @var{high-frame} may be larger than the -actual number of frames, in which case only existing frames will be returned. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}. - -@subsubheading Example - -Full stack backtrace: - -@smallexample -(gdb) --stack-list-frames -^done,stack= -[frame=@{level="0",addr="0x0001076c",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@}, -frame=@{level="1",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="2",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="3",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="4",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="5",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="6",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="7",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="8",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="9",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="10",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="11",addr="0x00010738",func="main", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}] -(gdb) -@end smallexample - -Show frames between @var{low_frame} and @var{high_frame}: - -@smallexample -(gdb) --stack-list-frames 3 5 -^done,stack= -[frame=@{level="3",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="4",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, -frame=@{level="5",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}] -(gdb) -@end smallexample - -Show a single frame: - -@smallexample -(gdb) --stack-list-frames 3 3 -^done,stack= -[frame=@{level="3",addr="0x000107a4",func="foo", - file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}] -(gdb) -@end smallexample - - -@subheading The @code{-stack-list-locals} Command -@findex -stack-list-locals - -@subsubheading Synopsis - -@smallexample - -stack-list-locals @var{print-values} -@end smallexample - -Display the local variable names for the selected frame. If -@var{print-values} is 0 or @code{--no-values}, print only the names of -the variables; if it is 1 or @code{--all-values}, print also their -values; and if it is 2 or @code{--simple-values}, print the name, -type and value for simple data types, and the name and type for arrays, -structures and unions. In this last case, a frontend can immediately -display the value of simple data types and create variable objects for -other data types when the user wishes to explore their values in -more detail. - -This command is deprecated in favor of the -@samp{-stack-list-variables} command. - -@subsubheading @value{GDBN} Command - -@samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}. - -@subsubheading Example - -@smallexample -(gdb) --stack-list-locals 0 -^done,locals=[name="A",name="B",name="C"] -(gdb) --stack-list-locals --all-values -^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@}, - @{name="C",value="@{1, 2, 3@}"@}] --stack-list-locals --simple-values -^done,locals=[@{name="A",type="int",value="1"@}, - @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}] -(gdb) -@end smallexample - -@subheading The @code{-stack-list-variables} Command -@findex -stack-list-variables - -@subsubheading Synopsis - -@smallexample - -stack-list-variables @var{print-values} -@end smallexample - -Display the names of local variables and function arguments for the selected frame. If -@var{print-values} is 0 or @code{--no-values}, print only the names of -the variables; if it is 1 or @code{--all-values}, print also their -values; and if it is 2 or @code{--simple-values}, print the name, -type and value for simple data types, and the name and type for arrays, -structures and unions. - -@subsubheading Example - -@smallexample -(gdb) --stack-list-variables --thread 1 --frame 0 --all-values -^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}] -(gdb) -@end smallexample - - -@subheading The @code{-stack-select-frame} Command -@findex -stack-select-frame - -@subsubheading Synopsis - -@smallexample - -stack-select-frame @var{framenum} -@end smallexample - -Change the selected frame. Select a different frame @var{framenum} on -the stack. - -This command in deprecated in favor of passing the @samp{--frame} -option to every command. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} commands are @samp{frame}, @samp{up}, -@samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}. - -@subsubheading Example - -@smallexample -(gdb) --stack-select-frame 2 -^done -(gdb) -@end smallexample - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Variable Objects -@section @sc{gdb/mi} Variable Objects - -@ignore - -@subheading Motivation for Variable Objects in @sc{gdb/mi} - -For the implementation of a variable debugger window (locals, watched -expressions, etc.), we are proposing the adaptation of the existing code -used by @code{Insight}. - -The two main reasons for that are: - -@enumerate 1 -@item -It has been proven in practice (it is already on its second generation). - -@item -It will shorten development time (needless to say how important it is -now). -@end enumerate - -The original interface was designed to be used by Tcl code, so it was -slightly changed so it could be used through @sc{gdb/mi}. This section -describes the @sc{gdb/mi} operations that will be available and gives some -hints about their use. - -@emph{Note}: In addition to the set of operations described here, we -expect the @sc{gui} implementation of a variable window to require, at -least, the following operations: - -@itemize @bullet -@item @code{-gdb-show} @code{output-radix} -@item @code{-stack-list-arguments} -@item @code{-stack-list-locals} -@item @code{-stack-select-frame} -@end itemize - -@end ignore - -@subheading Introduction to Variable Objects - -@cindex variable objects in @sc{gdb/mi} - -Variable objects are "object-oriented" MI interface for examining and -changing values of expressions. Unlike some other MI interfaces that -work with expressions, variable objects are specifically designed for -simple and efficient presentation in the frontend. A variable object -is identified by string name. When a variable object is created, the -frontend specifies the expression for that variable object. The -expression can be a simple variable, or it can be an arbitrary complex -expression, and can even involve CPU registers. After creating a -variable object, the frontend can invoke other variable object -operations---for example to obtain or change the value of a variable -object, or to change display format. - -Variable objects have hierarchical tree structure. Any variable object -that corresponds to a composite type, such as structure in C, has -a number of child variable objects, for example corresponding to each -element of a structure. A child variable object can itself have -children, recursively. Recursion ends when we reach -leaf variable objects, which always have built-in types. Child variable -objects are created only by explicit request, so if a frontend -is not interested in the children of a particular variable object, no -child will be created. - -For a leaf variable object it is possible to obtain its value as a -string, or set the value from a string. String value can be also -obtained for a non-leaf variable object, but it's generally a string -that only indicates the type of the object, and does not list its -contents. Assignment to a non-leaf variable object is not allowed. - -A frontend does not need to read the values of all variable objects each time -the program stops. Instead, MI provides an update command that lists all -variable objects whose values has changed since the last update -operation. This considerably reduces the amount of data that must -be transferred to the frontend. As noted above, children variable -objects are created on demand, and only leaf variable objects have a -real value. As result, gdb will read target memory only for leaf -variables that frontend has created. - -The automatic update is not always desirable. For example, a frontend -might want to keep a value of some expression for future reference, -and never update it. For another example, fetching memory is -relatively slow for embedded targets, so a frontend might want -to disable automatic update for the variables that are either not -visible on the screen, or ``closed''. This is possible using so -called ``frozen variable objects''. Such variable objects are never -implicitly updated. - -Variable objects can be either @dfn{fixed} or @dfn{floating}. For the -fixed variable object, the expression is parsed when the variable -object is created, including associating identifiers to specific -variables. The meaning of expression never changes. For a floating -variable object the values of variables whose names appear in the -expressions are re-evaluated every time in the context of the current -frame. Consider this example: - -@smallexample -void do_work(...) -@{ - struct work_state state; - - if (...) - do_work(...); -@} -@end smallexample - -If a fixed variable object for the @code{state} variable is created in -this function, and we enter the recursive call, the variable -object will report the value of @code{state} in the top-level -@code{do_work} invocation. On the other hand, a floating variable -object will report the value of @code{state} in the current frame. - -If an expression specified when creating a fixed variable object -refers to a local variable, the variable object becomes bound to the -thread and frame in which the variable object is created. When such -variable object is updated, @value{GDBN} makes sure that the -thread/frame combination the variable object is bound to still exists, -and re-evaluates the variable object in context of that thread/frame. - -The following is the complete set of @sc{gdb/mi} operations defined to -access this functionality: - -@multitable @columnfractions .4 .6 -@item @strong{Operation} -@tab @strong{Description} - -@item @code{-enable-pretty-printing} -@tab enable Python-based pretty-printing -@item @code{-var-create} -@tab create a variable object -@item @code{-var-delete} -@tab delete the variable object and/or its children -@item @code{-var-set-format} -@tab set the display format of this variable -@item @code{-var-show-format} -@tab show the display format of this variable -@item @code{-var-info-num-children} -@tab tells how many children this object has -@item @code{-var-list-children} -@tab return a list of the object's children -@item @code{-var-info-type} -@tab show the type of this variable object -@item @code{-var-info-expression} -@tab print parent-relative expression that this variable object represents -@item @code{-var-info-path-expression} -@tab print full expression that this variable object represents -@item @code{-var-show-attributes} -@tab is this variable editable? does it exist here? -@item @code{-var-evaluate-expression} -@tab get the value of this variable -@item @code{-var-assign} -@tab set the value of this variable -@item @code{-var-update} -@tab update the variable and its children -@item @code{-var-set-frozen} -@tab set frozeness attribute -@item @code{-var-set-update-range} -@tab set range of children to display on update -@end multitable - -In the next subsection we describe each operation in detail and suggest -how it can be used. - -@subheading Description And Use of Operations on Variable Objects - -@subheading The @code{-enable-pretty-printing} Command -@findex -enable-pretty-printing - -@smallexample --enable-pretty-printing -@end smallexample - -@value{GDBN} allows Python-based visualizers to affect the output of the -MI variable object commands. However, because there was no way to -implement this in a fully backward-compatible way, a front end must -request that this functionality be enabled. - -Once enabled, this feature cannot be disabled. - -Note that if Python support has not been compiled into @value{GDBN}, -this command will still succeed (and do nothing). - -This feature is currently (as of @value{GDBN} 7.0) experimental, and -may work differently in future versions of @value{GDBN}. - -@subheading The @code{-var-create} Command -@findex -var-create - -@subsubheading Synopsis - -@smallexample - -var-create @{@var{name} | "-"@} - @{@var{frame-addr} | "*" | "@@"@} @var{expression} -@end smallexample - -This operation creates a variable object, which allows the monitoring of -a variable, the result of an expression, a memory cell or a CPU -register. - -The @var{name} parameter is the string by which the object can be -referenced. It must be unique. If @samp{-} is specified, the varobj -system will generate a string ``varNNNNNN'' automatically. It will be -unique provided that one does not specify @var{name} of that format. -The command fails if a duplicate name is found. - -The frame under which the expression should be evaluated can be -specified by @var{frame-addr}. A @samp{*} indicates that the current -frame should be used. A @samp{@@} indicates that a floating variable -object must be created. - -@var{expression} is any expression valid on the current language set (must not -begin with a @samp{*}), or one of the following: - -@itemize @bullet -@item -@samp{*@var{addr}}, where @var{addr} is the address of a memory cell - -@item -@samp{*@var{addr}-@var{addr}} --- a memory address range (TBD) - -@item -@samp{$@var{regname}} --- a CPU register name -@end itemize - -@cindex dynamic varobj -A varobj's contents may be provided by a Python-based pretty-printer. In this -case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs -have slightly different semantics in some cases. If the -@code{-enable-pretty-printing} command is not sent, then @value{GDBN} -will never create a dynamic varobj. This ensures backward -compatibility for existing clients. - -@subsubheading Result - -This operation returns attributes of the newly-created varobj. These -are: - -@table @samp -@item name -The name of the varobj. - -@item numchild -The number of children of the varobj. This number is not necessarily -reliable for a dynamic varobj. Instead, you must examine the -@samp{has_more} attribute. - -@item value -The varobj's scalar value. For a varobj whose type is some sort of -aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value -will not be interesting. - -@item type -The varobj's type. This is a string representation of the type, as -would be printed by the @value{GDBN} CLI. If @samp{print object} -(@pxref{Print Settings, set print object}) is set to @code{on}, the -@emph{actual} (derived) type of the object is shown rather than the -@emph{declared} one. - -@item thread-id -If a variable object is bound to a specific thread, then this is the -thread's identifier. - -@item has_more -For a dynamic varobj, this indicates whether there appear to be any -children available. For a non-dynamic varobj, this will be 0. - -@item dynamic -This attribute will be present and have the value @samp{1} if the -varobj is a dynamic varobj. If the varobj is not a dynamic varobj, -then this attribute will not be present. - -@item displayhint -A dynamic varobj can supply a display hint to the front end. The -value comes directly from the Python pretty-printer object's -@code{display_hint} method. @xref{Pretty Printing API}. -@end table - -Typical output will look like this: - -@smallexample - name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}", - has_more="@var{has_more}" -@end smallexample - - -@subheading The @code{-var-delete} Command -@findex -var-delete - -@subsubheading Synopsis - -@smallexample - -var-delete [ -c ] @var{name} -@end smallexample - -Deletes a previously created variable object and all of its children. -With the @samp{-c} option, just deletes the children. - -Returns an error if the object @var{name} is not found. - - -@subheading The @code{-var-set-format} Command -@findex -var-set-format - -@subsubheading Synopsis - -@smallexample - -var-set-format @var{name} @var{format-spec} -@end smallexample - -Sets the output format for the value of the object @var{name} to be -@var{format-spec}. - -@anchor{-var-set-format} -The syntax for the @var{format-spec} is as follows: - -@smallexample - @var{format-spec} @expansion{} - @{binary | decimal | hexadecimal | octal | natural@} -@end smallexample - -The natural format is the default format choosen automatically -based on the variable type (like decimal for an @code{int}, hex -for pointers, etc.). - -For a variable with children, the format is set only on the -variable itself, and the children are not affected. - -@subheading The @code{-var-show-format} Command -@findex -var-show-format - -@subsubheading Synopsis - -@smallexample - -var-show-format @var{name} -@end smallexample - -Returns the format used to display the value of the object @var{name}. - -@smallexample - @var{format} @expansion{} - @var{format-spec} -@end smallexample - - -@subheading The @code{-var-info-num-children} Command -@findex -var-info-num-children - -@subsubheading Synopsis - -@smallexample - -var-info-num-children @var{name} -@end smallexample - -Returns the number of children of a variable object @var{name}: - -@smallexample - numchild=@var{n} -@end smallexample - -Note that this number is not completely reliable for a dynamic varobj. -It will return the current number of children, but more children may -be available. - - -@subheading The @code{-var-list-children} Command -@findex -var-list-children - -@subsubheading Synopsis - -@smallexample - -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}] -@end smallexample -@anchor{-var-list-children} - -Return a list of the children of the specified variable object and -create variable objects for them, if they do not already exist. With -a single argument or if @var{print-values} has a value of 0 or -@code{--no-values}, print only the names of the variables; if -@var{print-values} is 1 or @code{--all-values}, also print their -values; and if it is 2 or @code{--simple-values} print the name and -value for simple data types and just the name for arrays, structures -and unions. - -@var{from} and @var{to}, if specified, indicate the range of children -to report. If @var{from} or @var{to} is less than zero, the range is -reset and all children will be reported. Otherwise, children starting -at @var{from} (zero-based) and up to and excluding @var{to} will be -reported. - -If a child range is requested, it will only affect the current call to -@code{-var-list-children}, but not future calls to @code{-var-update}. -For this, you must instead use @code{-var-set-update-range}. The -intent of this approach is to enable a front end to implement any -update approach it likes; for example, scrolling a view may cause the -front end to request more children with @code{-var-list-children}, and -then the front end could call @code{-var-set-update-range} with a -different range to ensure that future updates are restricted to just -the visible items. - -For each child the following results are returned: - -@table @var - -@item name -Name of the variable object created for this child. - -@item exp -The expression to be shown to the user by the front end to designate this child. -For example this may be the name of a structure member. - -For a dynamic varobj, this value cannot be used to form an -expression. There is no way to do this at all with a dynamic varobj. - -For C/C@t{++} structures there are several pseudo children returned to -designate access qualifiers. For these pseudo children @var{exp} is -@samp{public}, @samp{private}, or @samp{protected}. In this case the -type and value are not present. - -A dynamic varobj will not report the access qualifying -pseudo-children, regardless of the language. This information is not -available at all with a dynamic varobj. - -@item numchild -Number of children this child has. For a dynamic varobj, this will be -0. - -@item type -The type of the child. If @samp{print object} -(@pxref{Print Settings, set print object}) is set to @code{on}, the -@emph{actual} (derived) type of the object is shown rather than the -@emph{declared} one. - -@item value -If values were requested, this is the value. - -@item thread-id -If this variable object is associated with a thread, this is the thread id. -Otherwise this result is not present. - -@item frozen -If the variable object is frozen, this variable will be present with a value of 1. -@end table - -The result may have its own attributes: - -@table @samp -@item displayhint -A dynamic varobj can supply a display hint to the front end. The -value comes directly from the Python pretty-printer object's -@code{display_hint} method. @xref{Pretty Printing API}. - -@item has_more -This is an integer attribute which is nonzero if there are children -remaining after the end of the selected range. -@end table - -@subsubheading Example - -@smallexample -(gdb) - -var-list-children n - ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp}, - numchild=@var{n},type=@var{type}@},@r{(repeats N times)}] -(gdb) - -var-list-children --all-values n - ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp}, - numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}] -@end smallexample - - -@subheading The @code{-var-info-type} Command -@findex -var-info-type - -@subsubheading Synopsis - -@smallexample - -var-info-type @var{name} -@end smallexample - -Returns the type of the specified variable @var{name}. The type is -returned as a string in the same format as it is output by the -@value{GDBN} CLI: - -@smallexample - type=@var{typename} -@end smallexample - - -@subheading The @code{-var-info-expression} Command -@findex -var-info-expression - -@subsubheading Synopsis - -@smallexample - -var-info-expression @var{name} -@end smallexample - -Returns a string that is suitable for presenting this -variable object in user interface. The string is generally -not valid expression in the current language, and cannot be evaluated. - -For example, if @code{a} is an array, and variable object -@code{A} was created for @code{a}, then we'll get this output: - -@smallexample -(gdb) -var-info-expression A.1 -^done,lang="C",exp="1" -@end smallexample - -@noindent -Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}. - -Note that the output of the @code{-var-list-children} command also -includes those expressions, so the @code{-var-info-expression} command -is of limited use. - -@subheading The @code{-var-info-path-expression} Command -@findex -var-info-path-expression - -@subsubheading Synopsis - -@smallexample - -var-info-path-expression @var{name} -@end smallexample - -Returns an expression that can be evaluated in the current -context and will yield the same value that a variable object has. -Compare this with the @code{-var-info-expression} command, which -result can be used only for UI presentation. Typical use of -the @code{-var-info-path-expression} command is creating a -watchpoint from a variable object. - -This command is currently not valid for children of a dynamic varobj, -and will give an error when invoked on one. - -For example, suppose @code{C} is a C@t{++} class, derived from class -@code{Base}, and that the @code{Base} class has a member called -@code{m_size}. Assume a variable @code{c} is has the type of -@code{C} and a variable object @code{C} was created for variable -@code{c}. Then, we'll get this output: -@smallexample -(gdb) -var-info-path-expression C.Base.public.m_size -^done,path_expr=((Base)c).m_size) -@end smallexample - -@subheading The @code{-var-show-attributes} Command -@findex -var-show-attributes - -@subsubheading Synopsis - -@smallexample - -var-show-attributes @var{name} -@end smallexample - -List attributes of the specified variable object @var{name}: - -@smallexample - status=@var{attr} [ ( ,@var{attr} )* ] -@end smallexample - -@noindent -where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}. - -@subheading The @code{-var-evaluate-expression} Command -@findex -var-evaluate-expression - -@subsubheading Synopsis - -@smallexample - -var-evaluate-expression [-f @var{format-spec}] @var{name} -@end smallexample - -Evaluates the expression that is represented by the specified variable -object and returns its value as a string. The format of the string -can be specified with the @samp{-f} option. The possible values of -this option are the same as for @code{-var-set-format} -(@pxref{-var-set-format}). If the @samp{-f} option is not specified, -the current display format will be used. The current display format -can be changed using the @code{-var-set-format} command. - -@smallexample - value=@var{value} -@end smallexample - -Note that one must invoke @code{-var-list-children} for a variable -before the value of a child variable can be evaluated. - -@subheading The @code{-var-assign} Command -@findex -var-assign - -@subsubheading Synopsis - -@smallexample - -var-assign @var{name} @var{expression} -@end smallexample - -Assigns the value of @var{expression} to the variable object specified -by @var{name}. The object must be @samp{editable}. If the variable's -value is altered by the assign, the variable will show up in any -subsequent @code{-var-update} list. - -@subsubheading Example - -@smallexample -(gdb) --var-assign var1 3 -^done,value="3" -(gdb) --var-update * -^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}] -(gdb) -@end smallexample - -@subheading The @code{-var-update} Command -@findex -var-update - -@subsubheading Synopsis - -@smallexample - -var-update [@var{print-values}] @{@var{name} | "*"@} -@end smallexample - -Reevaluate the expressions corresponding to the variable object -@var{name} and all its direct and indirect children, and return the -list of variable objects whose values have changed; @var{name} must -be a root variable object. Here, ``changed'' means that the result of -@code{-var-evaluate-expression} before and after the -@code{-var-update} is different. If @samp{*} is used as the variable -object names, all existing variable objects are updated, except -for frozen ones (@pxref{-var-set-frozen}). The option -@var{print-values} determines whether both names and values, or just -names are printed. The possible values of this option are the same -as for @code{-var-list-children} (@pxref{-var-list-children}). It is -recommended to use the @samp{--all-values} option, to reduce the -number of MI commands needed on each program stop. - -With the @samp{*} parameter, if a variable object is bound to a -currently running thread, it will not be updated, without any -diagnostic. - -If @code{-var-set-update-range} was previously used on a varobj, then -only the selected range of children will be reported. - -@code{-var-update} reports all the changed varobjs in a tuple named -@samp{changelist}. - -Each item in the change list is itself a tuple holding: - -@table @samp -@item name -The name of the varobj. - -@item value -If values were requested for this update, then this field will be -present and will hold the value of the varobj. - -@item in_scope -@anchor{-var-update} -This field is a string which may take one of three values: - -@table @code -@item "true" -The variable object's current value is valid. - -@item "false" -The variable object does not currently hold a valid value but it may -hold one in the future if its associated expression comes back into -scope. - -@item "invalid" -The variable object no longer holds a valid value. -This can occur when the executable file being debugged has changed, -either through recompilation or by using the @value{GDBN} @code{file} -command. The front end should normally choose to delete these variable -objects. -@end table - -In the future new values may be added to this list so the front should -be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}. - -@item type_changed -This is only present if the varobj is still valid. If the type -changed, then this will be the string @samp{true}; otherwise it will -be @samp{false}. - -When a varobj's type changes, its children are also likely to have -become incorrect. Therefore, the varobj's children are automatically -deleted when this attribute is @samp{true}. Also, the varobj's update -range, when set using the @code{-var-set-update-range} command, is -unset. - -@item new_type -If the varobj's type changed, then this field will be present and will -hold the new type. - -@item new_num_children -For a dynamic varobj, if the number of children changed, or if the -type changed, this will be the new number of children. - -The @samp{numchild} field in other varobj responses is generally not -valid for a dynamic varobj -- it will show the number of children that -@value{GDBN} knows about, but because dynamic varobjs lazily -instantiate their children, this will not reflect the number of -children which may be available. - -The @samp{new_num_children} attribute only reports changes to the -number of children known by @value{GDBN}. This is the only way to -detect whether an update has removed children (which necessarily can -only happen at the end of the update range). - -@item displayhint -The display hint, if any. - -@item has_more -This is an integer value, which will be 1 if there are more children -available outside the varobj's update range. - -@item dynamic -This attribute will be present and have the value @samp{1} if the -varobj is a dynamic varobj. If the varobj is not a dynamic varobj, -then this attribute will not be present. - -@item new_children -If new children were added to a dynamic varobj within the selected -update range (as set by @code{-var-set-update-range}), then they will -be listed in this attribute. -@end table - -@subsubheading Example - -@smallexample -(gdb) --var-assign var1 3 -^done,value="3" -(gdb) --var-update --all-values var1 -^done,changelist=[@{name="var1",value="3",in_scope="true", -type_changed="false"@}] -(gdb) -@end smallexample - -@subheading The @code{-var-set-frozen} Command -@findex -var-set-frozen -@anchor{-var-set-frozen} - -@subsubheading Synopsis - -@smallexample - -var-set-frozen @var{name} @var{flag} -@end smallexample - -Set the frozenness flag on the variable object @var{name}. The -@var{flag} parameter should be either @samp{1} to make the variable -frozen or @samp{0} to make it unfrozen. If a variable object is -frozen, then neither itself, nor any of its children, are -implicitly updated by @code{-var-update} of -a parent variable or by @code{-var-update *}. Only -@code{-var-update} of the variable itself will update its value and -values of its children. After a variable object is unfrozen, it is -implicitly updated by all subsequent @code{-var-update} operations. -Unfreezing a variable does not update it, only subsequent -@code{-var-update} does. - -@subsubheading Example - -@smallexample -(gdb) --var-set-frozen V 1 -^done -(gdb) -@end smallexample - -@subheading The @code{-var-set-update-range} command -@findex -var-set-update-range -@anchor{-var-set-update-range} - -@subsubheading Synopsis - -@smallexample - -var-set-update-range @var{name} @var{from} @var{to} -@end smallexample - -Set the range of children to be returned by future invocations of -@code{-var-update}. - -@var{from} and @var{to} indicate the range of children to report. If -@var{from} or @var{to} is less than zero, the range is reset and all -children will be reported. Otherwise, children starting at @var{from} -(zero-based) and up to and excluding @var{to} will be reported. - -@subsubheading Example - -@smallexample -(gdb) --var-set-update-range V 1 2 -^done -@end smallexample - -@subheading The @code{-var-set-visualizer} command -@findex -var-set-visualizer -@anchor{-var-set-visualizer} - -@subsubheading Synopsis - -@smallexample - -var-set-visualizer @var{name} @var{visualizer} -@end smallexample - -Set a visualizer for the variable object @var{name}. - -@var{visualizer} is the visualizer to use. The special value -@samp{None} means to disable any visualizer in use. - -If not @samp{None}, @var{visualizer} must be a Python expression. -This expression must evaluate to a callable object which accepts a -single argument. @value{GDBN} will call this object with the value of -the varobj @var{name} as an argument (this is done so that the same -Python pretty-printing code can be used for both the CLI and MI). -When called, this object must return an object which conforms to the -pretty-printing interface (@pxref{Pretty Printing API}). - -The pre-defined function @code{gdb.default_visualizer} may be used to -select a visualizer by following the built-in process -(@pxref{Selecting Pretty-Printers}). This is done automatically when -a varobj is created, and so ordinarily is not needed. - -This feature is only available if Python support is enabled. The MI -command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands}) -can be used to check this. - -@subsubheading Example - -Resetting the visualizer: - -@smallexample -(gdb) --var-set-visualizer V None -^done -@end smallexample - -Reselecting the default (type-based) visualizer: - -@smallexample -(gdb) --var-set-visualizer V gdb.default_visualizer -^done -@end smallexample - -Suppose @code{SomeClass} is a visualizer class. A lambda expression -can be used to instantiate this class for a varobj: - -@smallexample -(gdb) --var-set-visualizer V "lambda val: SomeClass()" -^done -@end smallexample - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Data Manipulation -@section @sc{gdb/mi} Data Manipulation - -@cindex data manipulation, in @sc{gdb/mi} -@cindex @sc{gdb/mi}, data manipulation -This section describes the @sc{gdb/mi} commands that manipulate data: -examine memory and registers, evaluate expressions, etc. - -@c REMOVED FROM THE INTERFACE. -@c @subheading -data-assign -@c Change the value of a program variable. Plenty of side effects. -@c @subsubheading GDB Command -@c set variable -@c @subsubheading Example -@c N.A. - -@subheading The @code{-data-disassemble} Command -@findex -data-disassemble - -@subsubheading Synopsis - -@smallexample - -data-disassemble - [ -s @var{start-addr} -e @var{end-addr} ] - | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ] - -- @var{mode} -@end smallexample - -@noindent -Where: - -@table @samp -@item @var{start-addr} -is the beginning address (or @code{$pc}) -@item @var{end-addr} -is the end address -@item @var{filename} -is the name of the file to disassemble -@item @var{linenum} -is the line number to disassemble around -@item @var{lines} -is the number of disassembly lines to be produced. If it is -1, -the whole function will be disassembled, in case no @var{end-addr} is -specified. If @var{end-addr} is specified as a non-zero value, and -@var{lines} is lower than the number of disassembly lines between -@var{start-addr} and @var{end-addr}, only @var{lines} lines are -displayed; if @var{lines} is higher than the number of lines between -@var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr} -are displayed. -@item @var{mode} -is either 0 (meaning only disassembly), 1 (meaning mixed source and -disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning -mixed source and disassembly with raw opcodes). -@end table - -@subsubheading Result - -The result of the @code{-data-disassemble} command will be a list named -@samp{asm_insns}, the contents of this list depend on the @var{mode} -used with the @code{-data-disassemble} command. - -For modes 0 and 2 the @samp{asm_insns} list contains tuples with the -following fields: - -@table @code -@item address -The address at which this instruction was disassembled. - -@item func-name -The name of the function this instruction is within. - -@item offset -The decimal offset in bytes from the start of @samp{func-name}. - -@item inst -The text disassembly for this @samp{address}. - -@item opcodes -This field is only present for mode 2. This contains the raw opcode -bytes for the @samp{inst} field. - -@end table - -For modes 1 and 3 the @samp{asm_insns} list contains tuples named -@samp{src_and_asm_line}, each of which has the following fields: - -@table @code -@item line -The line number within @samp{file}. - -@item file -The file name from the compilation unit. This might be an absolute -file name or a relative file name depending on the compile command -used. - -@item fullname -Absolute file name of @samp{file}. It is converted to a canonical form -using the source file search path -(@pxref{Source Path, ,Specifying Source Directories}) -and after resolving all the symbolic links. - -If the source file is not found this field will contain the path as -present in the debug information. - -@item line_asm_insn -This is a list of tuples containing the disassembly for @samp{line} in -@samp{file}. The fields of each tuple are the same as for -@code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address}, -@samp{func-name}, @samp{offset}, @samp{inst}, and optionally -@samp{opcodes}. - -@end table - -Note that whatever included in the @samp{inst} field, is not -manipulated directly by @sc{gdb/mi}, i.e., it is not possible to -adjust its format. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{disassemble}. - -@subsubheading Example - -Disassemble from the current value of @code{$pc} to @code{$pc + 20}: - -@smallexample -(gdb) --data-disassemble -s $pc -e "$pc + 20" -- 0 -^done, -asm_insns=[ -@{address="0x000107c0",func-name="main",offset="4", -inst="mov 2, %o0"@}, -@{address="0x000107c4",func-name="main",offset="8", -inst="sethi %hi(0x11800), %o2"@}, -@{address="0x000107c8",func-name="main",offset="12", -inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@}, -@{address="0x000107cc",func-name="main",offset="16", -inst="sethi %hi(0x11800), %o2"@}, -@{address="0x000107d0",func-name="main",offset="20", -inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}] -(gdb) -@end smallexample - -Disassemble the whole @code{main} function. Line 32 is part of -@code{main}. - -@smallexample --data-disassemble -f basics.c -l 32 -- 0 -^done,asm_insns=[ -@{address="0x000107bc",func-name="main",offset="0", -inst="save %sp, -112, %sp"@}, -@{address="0x000107c0",func-name="main",offset="4", -inst="mov 2, %o0"@}, -@{address="0x000107c4",func-name="main",offset="8", -inst="sethi %hi(0x11800), %o2"@}, -[@dots{}] -@{address="0x0001081c",func-name="main",offset="96",inst="ret "@}, -@{address="0x00010820",func-name="main",offset="100",inst="restore "@}] -(gdb) -@end smallexample - -Disassemble 3 instructions from the start of @code{main}: - -@smallexample -(gdb) --data-disassemble -f basics.c -l 32 -n 3 -- 0 -^done,asm_insns=[ -@{address="0x000107bc",func-name="main",offset="0", -inst="save %sp, -112, %sp"@}, -@{address="0x000107c0",func-name="main",offset="4", -inst="mov 2, %o0"@}, -@{address="0x000107c4",func-name="main",offset="8", -inst="sethi %hi(0x11800), %o2"@}] -(gdb) -@end smallexample - -Disassemble 3 instructions from the start of @code{main} in mixed mode: - -@smallexample -(gdb) --data-disassemble -f basics.c -l 32 -n 3 -- 1 -^done,asm_insns=[ -src_and_asm_line=@{line="31", -file="../../../src/gdb/testsuite/gdb.mi/basics.c", -fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c", -line_asm_insn=[@{address="0x000107bc", -func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@}, -src_and_asm_line=@{line="32", -file="../../../src/gdb/testsuite/gdb.mi/basics.c", -fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c", -line_asm_insn=[@{address="0x000107c0", -func-name="main",offset="4",inst="mov 2, %o0"@}, -@{address="0x000107c4",func-name="main",offset="8", -inst="sethi %hi(0x11800), %o2"@}]@}] -(gdb) -@end smallexample - - -@subheading The @code{-data-evaluate-expression} Command -@findex -data-evaluate-expression - -@subsubheading Synopsis - -@smallexample - -data-evaluate-expression @var{expr} -@end smallexample - -Evaluate @var{expr} as an expression. The expression could contain an -inferior function call. The function call will execute synchronously. -If the expression contains spaces, it must be enclosed in double quotes. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and -@samp{call}. In @code{gdbtk} only, there's a corresponding -@samp{gdb_eval} command. - -@subsubheading Example - -In the following example, the numbers that precede the commands are the -@dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi} -Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its -output. - -@smallexample -211-data-evaluate-expression A -211^done,value="1" -(gdb) -311-data-evaluate-expression &A -311^done,value="0xefffeb7c" -(gdb) -411-data-evaluate-expression A+3 -411^done,value="4" -(gdb) -511-data-evaluate-expression "A + 3" -511^done,value="4" -(gdb) -@end smallexample - - -@subheading The @code{-data-list-changed-registers} Command -@findex -data-list-changed-registers - -@subsubheading Synopsis - -@smallexample - -data-list-changed-registers -@end smallexample - -Display a list of the registers that have changed. - -@subsubheading @value{GDBN} Command - -@value{GDBN} doesn't have a direct analog for this command; @code{gdbtk} -has the corresponding command @samp{gdb_changed_register_list}. - -@subsubheading Example - -On a PPC MBX board: - -@smallexample -(gdb) --exec-continue -^running - -(gdb) -*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{ -func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c", -line="5"@} -(gdb) --data-list-changed-registers -^done,changed-registers=["0","1","2","4","5","6","7","8","9", -"10","11","13","14","15","16","17","18","19","20","21","22","23", -"24","25","26","27","28","30","31","64","65","66","67","69"] -(gdb) -@end smallexample - - -@subheading The @code{-data-list-register-names} Command -@findex -data-list-register-names - -@subsubheading Synopsis - -@smallexample - -data-list-register-names [ ( @var{regno} )+ ] -@end smallexample - -Show a list of register names for the current target. If no arguments -are given, it shows a list of the names of all the registers. If -integer numbers are given as arguments, it will print a list of the -names of the registers corresponding to the arguments. To ensure -consistency between a register name and its number, the output list may -include empty register names. - -@subsubheading @value{GDBN} Command - -@value{GDBN} does not have a command which corresponds to -@samp{-data-list-register-names}. In @code{gdbtk} there is a -corresponding command @samp{gdb_regnames}. - -@subsubheading Example - -For the PPC MBX board: -@smallexample -(gdb) --data-list-register-names -^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7", -"r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18", -"r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29", -"r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9", -"f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20", -"f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31", -"", "pc","ps","cr","lr","ctr","xer"] -(gdb) --data-list-register-names 1 2 3 -^done,register-names=["r1","r2","r3"] -(gdb) -@end smallexample - -@subheading The @code{-data-list-register-values} Command -@findex -data-list-register-values - -@subsubheading Synopsis - -@smallexample - -data-list-register-values @var{fmt} [ ( @var{regno} )*] -@end smallexample - -Display the registers' contents. @var{fmt} is the format according to -which the registers' contents are to be returned, followed by an optional -list of numbers specifying the registers to display. A missing list of -numbers indicates that the contents of all the registers must be returned. - -Allowed formats for @var{fmt} are: - -@table @code -@item x -Hexadecimal -@item o -Octal -@item t -Binary -@item d -Decimal -@item r -Raw -@item N -Natural -@end table - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info -all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}. - -@subsubheading Example - -For a PPC MBX board (note: line breaks are for readability only, they -don't appear in the actual output): - -@smallexample -(gdb) --data-list-register-values r 64 65 -^done,register-values=[@{number="64",value="0xfe00a300"@}, -@{number="65",value="0x00029002"@}] -(gdb) --data-list-register-values x -^done,register-values=[@{number="0",value="0xfe0043c8"@}, -@{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@}, -@{number="3",value="0x0"@},@{number="4",value="0xa"@}, -@{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@}, -@{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@}, -@{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@}, -@{number="11",value="0x1"@},@{number="12",value="0x0"@}, -@{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@}, -@{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@}, -@{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@}, -@{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@}, -@{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@}, -@{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@}, -@{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@}, -@{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@}, -@{number="29",value="0x0"@},@{number="30",value="0xfe010000"@}, -@{number="31",value="0x0"@},@{number="32",value="0x0"@}, -@{number="33",value="0x0"@},@{number="34",value="0x0"@}, -@{number="35",value="0x0"@},@{number="36",value="0x0"@}, -@{number="37",value="0x0"@},@{number="38",value="0x0"@}, -@{number="39",value="0x0"@},@{number="40",value="0x0"@}, -@{number="41",value="0x0"@},@{number="42",value="0x0"@}, -@{number="43",value="0x0"@},@{number="44",value="0x0"@}, -@{number="45",value="0x0"@},@{number="46",value="0x0"@}, -@{number="47",value="0x0"@},@{number="48",value="0x0"@}, -@{number="49",value="0x0"@},@{number="50",value="0x0"@}, -@{number="51",value="0x0"@},@{number="52",value="0x0"@}, -@{number="53",value="0x0"@},@{number="54",value="0x0"@}, -@{number="55",value="0x0"@},@{number="56",value="0x0"@}, -@{number="57",value="0x0"@},@{number="58",value="0x0"@}, -@{number="59",value="0x0"@},@{number="60",value="0x0"@}, -@{number="61",value="0x0"@},@{number="62",value="0x0"@}, -@{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@}, -@{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@}, -@{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@}, -@{number="69",value="0x20002b03"@}] -(gdb) -@end smallexample - - -@subheading The @code{-data-read-memory} Command -@findex -data-read-memory - -This command is deprecated, use @code{-data-read-memory-bytes} instead. - -@subsubheading Synopsis - -@smallexample - -data-read-memory [ -o @var{byte-offset} ] - @var{address} @var{word-format} @var{word-size} - @var{nr-rows} @var{nr-cols} [ @var{aschar} ] -@end smallexample - -@noindent -where: - -@table @samp -@item @var{address} -An expression specifying the address of the first memory word to be -read. Complex expressions containing embedded white space should be -quoted using the C convention. - -@item @var{word-format} -The format to be used to print the memory words. The notation is the -same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats, -,Output Formats}). - -@item @var{word-size} -The size of each memory word in bytes. - -@item @var{nr-rows} -The number of rows in the output table. - -@item @var{nr-cols} -The number of columns in the output table. - -@item @var{aschar} -If present, indicates that each row should include an @sc{ascii} dump. The -value of @var{aschar} is used as a padding character when a byte is not a -member of the printable @sc{ascii} character set (printable @sc{ascii} -characters are those whose code is between 32 and 126, inclusively). - -@item @var{byte-offset} -An offset to add to the @var{address} before fetching memory. -@end table - -This command displays memory contents as a table of @var{nr-rows} by -@var{nr-cols} words, each word being @var{word-size} bytes. In total, -@code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read -(returned as @samp{total-bytes}). Should less than the requested number -of bytes be returned by the target, the missing words are identified -using @samp{N/A}. The number of bytes read from the target is returned -in @samp{nr-bytes} and the starting address used to read memory in -@samp{addr}. - -The address of the next/previous row or page is available in -@samp{next-row} and @samp{prev-row}, @samp{next-page} and -@samp{prev-page}. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has -@samp{gdb_get_mem} memory read command. - -@subsubheading Example - -Read six bytes of memory starting at @code{bytes+6} but then offset by -@code{-6} bytes. Format as three rows of two columns. One byte per -word. Display each word in hex. - -@smallexample -(gdb) -9-data-read-memory -o -6 -- bytes+6 x 1 3 2 -9^done,addr="0x00001390",nr-bytes="6",total-bytes="6", -next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396", -prev-page="0x0000138a",memory=[ -@{addr="0x00001390",data=["0x00","0x01"]@}, -@{addr="0x00001392",data=["0x02","0x03"]@}, -@{addr="0x00001394",data=["0x04","0x05"]@}] -(gdb) -@end smallexample - -Read two bytes of memory starting at address @code{shorts + 64} and -display as a single word formatted in decimal. - -@smallexample -(gdb) -5-data-read-memory shorts+64 d 2 1 1 -5^done,addr="0x00001510",nr-bytes="2",total-bytes="2", -next-row="0x00001512",prev-row="0x0000150e", -next-page="0x00001512",prev-page="0x0000150e",memory=[ -@{addr="0x00001510",data=["128"]@}] -(gdb) -@end smallexample - -Read thirty two bytes of memory starting at @code{bytes+16} and format -as eight rows of four columns. Include a string encoding with @samp{x} -used as the non-printable character. - -@smallexample -(gdb) -4-data-read-memory bytes+16 x 1 8 4 x -4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32", -next-row="0x000013c0",prev-row="0x0000139c", -next-page="0x000013c0",prev-page="0x00001380",memory=[ -@{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@}, -@{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@}, -@{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@}, -@{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@}, -@{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@}, -@{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@}, -@{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@}, -@{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}] -(gdb) -@end smallexample - -@subheading The @code{-data-read-memory-bytes} Command -@findex -data-read-memory-bytes - -@subsubheading Synopsis - -@smallexample - -data-read-memory-bytes [ -o @var{byte-offset} ] - @var{address} @var{count} -@end smallexample - -@noindent -where: - -@table @samp -@item @var{address} -An expression specifying the address of the first memory word to be -read. Complex expressions containing embedded white space should be -quoted using the C convention. - -@item @var{count} -The number of bytes to read. This should be an integer literal. - -@item @var{byte-offset} -The offsets in bytes relative to @var{address} at which to start -reading. This should be an integer literal. This option is provided -so that a frontend is not required to first evaluate address and then -perform address arithmetics itself. - -@end table - -This command attempts to read all accessible memory regions in the -specified range. First, all regions marked as unreadable in the memory -map (if one is defined) will be skipped. @xref{Memory Region -Attributes}. Second, @value{GDBN} will attempt to read the remaining -regions. For each one, if reading full region results in an errors, -@value{GDBN} will try to read a subset of the region. - -In general, every single byte in the region may be readable or not, -and the only way to read every readable byte is to try a read at -every address, which is not practical. Therefore, @value{GDBN} will -attempt to read all accessible bytes at either beginning or the end -of the region, using a binary division scheme. This heuristic works -well for reading accross a memory map boundary. Note that if a region -has a readable range that is neither at the beginning or the end, -@value{GDBN} will not read it. - -The result record (@pxref{GDB/MI Result Records}) that is output of -the command includes a field named @samp{memory} whose content is a -list of tuples. Each tuple represent a successfully read memory block -and has the following fields: - -@table @code -@item begin -The start address of the memory block, as hexadecimal literal. - -@item end -The end address of the memory block, as hexadecimal literal. - -@item offset -The offset of the memory block, as hexadecimal literal, relative to -the start address passed to @code{-data-read-memory-bytes}. - -@item contents -The contents of the memory block, in hex. - -@end table - - - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{x}. - -@subsubheading Example - -@smallexample -(gdb) --data-read-memory-bytes &a 10 -^done,memory=[@{begin="0xbffff154",offset="0x00000000", - end="0xbffff15e", - contents="01000000020000000300"@}] -(gdb) -@end smallexample - - -@subheading The @code{-data-write-memory-bytes} Command -@findex -data-write-memory-bytes - -@subsubheading Synopsis - -@smallexample - -data-write-memory-bytes @var{address} @var{contents} - -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]} -@end smallexample - -@noindent -where: - -@table @samp -@item @var{address} -An expression specifying the address of the first memory word to be -read. Complex expressions containing embedded white space should be -quoted using the C convention. - -@item @var{contents} -The hex-encoded bytes to write. - -@item @var{count} -Optional argument indicating the number of bytes to be written. If @var{count} -is greater than @var{contents}' length, @value{GDBN} will repeatedly -write @var{contents} until it fills @var{count} bytes. - -@end table - -@subsubheading @value{GDBN} Command - -There's no corresponding @value{GDBN} command. - -@subsubheading Example - -@smallexample -(gdb) --data-write-memory-bytes &a "aabbccdd" -^done -(gdb) -@end smallexample - -@smallexample -(gdb) --data-write-memory-bytes &a "aabbccdd" 16e -^done -(gdb) -@end smallexample - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Tracepoint Commands -@section @sc{gdb/mi} Tracepoint Commands - -The commands defined in this section implement MI support for -tracepoints. For detailed introduction, see @ref{Tracepoints}. - -@subheading The @code{-trace-find} Command -@findex -trace-find - -@subsubheading Synopsis - -@smallexample - -trace-find @var{mode} [@var{parameters}@dots{}] -@end smallexample - -Find a trace frame using criteria defined by @var{mode} and -@var{parameters}. The following table lists permissible -modes and their parameters. For details of operation, see @ref{tfind}. - -@table @samp - -@item none -No parameters are required. Stops examining trace frames. - -@item frame-number -An integer is required as parameter. Selects tracepoint frame with -that index. - -@item tracepoint-number -An integer is required as parameter. Finds next -trace frame that corresponds to tracepoint with the specified number. - -@item pc -An address is required as parameter. Finds -next trace frame that corresponds to any tracepoint at the specified -address. - -@item pc-inside-range -Two addresses are required as parameters. Finds next trace -frame that corresponds to a tracepoint at an address inside the -specified range. Both bounds are considered to be inside the range. - -@item pc-outside-range -Two addresses are required as parameters. Finds -next trace frame that corresponds to a tracepoint at an address outside -the specified range. Both bounds are considered to be inside the range. - -@item line -Line specification is required as parameter. @xref{Specify Location}. -Finds next trace frame that corresponds to a tracepoint at -the specified location. - -@end table - -If @samp{none} was passed as @var{mode}, the response does not -have fields. Otherwise, the response may have the following fields: - -@table @samp -@item found -This field has either @samp{0} or @samp{1} as the value, depending -on whether a matching tracepoint was found. - -@item traceframe -The index of the found traceframe. This field is present iff -the @samp{found} field has value of @samp{1}. - -@item tracepoint -The index of the found tracepoint. This field is present iff -the @samp{found} field has value of @samp{1}. - -@item frame -The information about the frame corresponding to the found trace -frame. This field is present only if a trace frame was found. -@xref{GDB/MI Frame Information}, for description of this field. - -@end table - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{tfind}. - -@subheading -trace-define-variable -@findex -trace-define-variable - -@subsubheading Synopsis - -@smallexample - -trace-define-variable @var{name} [ @var{value} ] -@end smallexample - -Create trace variable @var{name} if it does not exist. If -@var{value} is specified, sets the initial value of the specified -trace variable to that value. Note that the @var{name} should start -with the @samp{$} character. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{tvariable}. - -@subheading -trace-list-variables -@findex -trace-list-variables - -@subsubheading Synopsis - -@smallexample - -trace-list-variables -@end smallexample - -Return a table of all defined trace variables. Each element of the -table has the following fields: - -@table @samp -@item name -The name of the trace variable. This field is always present. - -@item initial -The initial value. This is a 64-bit signed integer. This -field is always present. - -@item current -The value the trace variable has at the moment. This is a 64-bit -signed integer. This field is absent iff current value is -not defined, for example if the trace was never run, or is -presently running. - -@end table - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{tvariables}. - -@subsubheading Example - -@smallexample -(gdb) --trace-list-variables -^done,trace-variables=@{nr_rows="1",nr_cols="3", -hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@}, - @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@}, - @{width="11",alignment="-1",col_name="current",colhdr="Current"@}], -body=[variable=@{name="$trace_timestamp",initial="0"@} - variable=@{name="$foo",initial="10",current="15"@}]@} -(gdb) -@end smallexample - -@subheading -trace-save -@findex -trace-save - -@subsubheading Synopsis - -@smallexample - -trace-save [-r ] @var{filename} -@end smallexample - -Saves the collected trace data to @var{filename}. Without the -@samp{-r} option, the data is downloaded from the target and saved -in a local file. With the @samp{-r} option the target is asked -to perform the save. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{tsave}. - - -@subheading -trace-start -@findex -trace-start - -@subsubheading Synopsis - -@smallexample - -trace-start -@end smallexample - -Starts a tracing experiments. The result of this command does not -have any fields. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{tstart}. - -@subheading -trace-status -@findex -trace-status - -@subsubheading Synopsis - -@smallexample - -trace-status -@end smallexample - -Obtains the status of a tracing experiment. The result may include -the following fields: - -@table @samp - -@item supported -May have a value of either @samp{0}, when no tracing operations are -supported, @samp{1}, when all tracing operations are supported, or -@samp{file} when examining trace file. In the latter case, examining -of trace frame is possible but new tracing experiement cannot be -started. This field is always present. - -@item running -May have a value of either @samp{0} or @samp{1} depending on whether -tracing experiement is in progress on target. This field is present -if @samp{supported} field is not @samp{0}. - -@item stop-reason -Report the reason why the tracing was stopped last time. This field -may be absent iff tracing was never stopped on target yet. The -value of @samp{request} means the tracing was stopped as result of -the @code{-trace-stop} command. The value of @samp{overflow} means -the tracing buffer is full. The value of @samp{disconnection} means -tracing was automatically stopped when @value{GDBN} has disconnected. -The value of @samp{passcount} means tracing was stopped when a -tracepoint was passed a maximal number of times for that tracepoint. -This field is present if @samp{supported} field is not @samp{0}. - -@item stopping-tracepoint -The number of tracepoint whose passcount as exceeded. This field is -present iff the @samp{stop-reason} field has the value of -@samp{passcount}. - -@item frames -@itemx frames-created -The @samp{frames} field is a count of the total number of trace frames -in the trace buffer, while @samp{frames-created} is the total created -during the run, including ones that were discarded, such as when a -circular trace buffer filled up. Both fields are optional. - -@item buffer-size -@itemx buffer-free -These fields tell the current size of the tracing buffer and the -remaining space. These fields are optional. - -@item circular -The value of the circular trace buffer flag. @code{1} means that the -trace buffer is circular and old trace frames will be discarded if -necessary to make room, @code{0} means that the trace buffer is linear -and may fill up. - -@item disconnected -The value of the disconnected tracing flag. @code{1} means that -tracing will continue after @value{GDBN} disconnects, @code{0} means -that the trace run will stop. - -@item trace-file -The filename of the trace file being examined. This field is -optional, and only present when examining a trace file. - -@end table - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{tstatus}. - -@subheading -trace-stop -@findex -trace-stop - -@subsubheading Synopsis - -@smallexample - -trace-stop -@end smallexample - -Stops a tracing experiment. The result of this command has the same -fields as @code{-trace-status}, except that the @samp{supported} and -@samp{running} fields are not output. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{tstop}. - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Symbol Query -@section @sc{gdb/mi} Symbol Query Commands - - -@ignore -@subheading The @code{-symbol-info-address} Command -@findex -symbol-info-address - -@subsubheading Synopsis - -@smallexample - -symbol-info-address @var{symbol} -@end smallexample - -Describe where @var{symbol} is stored. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info address}. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-info-file} Command -@findex -symbol-info-file - -@subsubheading Synopsis - -@smallexample - -symbol-info-file -@end smallexample - -Show the file for the symbol. - -@subsubheading @value{GDBN} Command - -There's no equivalent @value{GDBN} command. @code{gdbtk} has -@samp{gdb_find_file}. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-info-function} Command -@findex -symbol-info-function - -@subsubheading Synopsis - -@smallexample - -symbol-info-function -@end smallexample - -Show which function the symbol lives in. - -@subsubheading @value{GDBN} Command - -@samp{gdb_get_function} in @code{gdbtk}. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-info-line} Command -@findex -symbol-info-line - -@subsubheading Synopsis - -@smallexample - -symbol-info-line -@end smallexample - -Show the core addresses of the code for a source line. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info line}. -@code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-info-symbol} Command -@findex -symbol-info-symbol - -@subsubheading Synopsis - -@smallexample - -symbol-info-symbol @var{addr} -@end smallexample - -Describe what symbol is at location @var{addr}. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info symbol}. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-list-functions} Command -@findex -symbol-list-functions - -@subsubheading Synopsis - -@smallexample - -symbol-list-functions -@end smallexample - -List the functions in the executable. - -@subsubheading @value{GDBN} Command - -@samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and -@samp{gdb_search} in @code{gdbtk}. - -@subsubheading Example -N.A. -@end ignore - - -@subheading The @code{-symbol-list-lines} Command -@findex -symbol-list-lines - -@subsubheading Synopsis - -@smallexample - -symbol-list-lines @var{filename} -@end smallexample - -Print the list of lines that contain code and their associated program -addresses for the given source filename. The entries are sorted in -ascending PC order. - -@subsubheading @value{GDBN} Command - -There is no corresponding @value{GDBN} command. - -@subsubheading Example -@smallexample -(gdb) --symbol-list-lines basics.c -^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}] -(gdb) -@end smallexample - - -@ignore -@subheading The @code{-symbol-list-types} Command -@findex -symbol-list-types - -@subsubheading Synopsis - -@smallexample - -symbol-list-types -@end smallexample - -List all the type names. - -@subsubheading @value{GDBN} Command - -The corresponding commands are @samp{info types} in @value{GDBN}, -@samp{gdb_search} in @code{gdbtk}. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-list-variables} Command -@findex -symbol-list-variables - -@subsubheading Synopsis - -@smallexample - -symbol-list-variables -@end smallexample - -List all the global and static variable names. - -@subsubheading @value{GDBN} Command - -@samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-locate} Command -@findex -symbol-locate - -@subsubheading Synopsis - -@smallexample - -symbol-locate -@end smallexample - -@subsubheading @value{GDBN} Command - -@samp{gdb_loc} in @code{gdbtk}. - -@subsubheading Example -N.A. - - -@subheading The @code{-symbol-type} Command -@findex -symbol-type - -@subsubheading Synopsis - -@smallexample - -symbol-type @var{variable} -@end smallexample - -Show type of @var{variable}. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has -@samp{gdb_obj_variable}. - -@subsubheading Example -N.A. -@end ignore - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI File Commands -@section @sc{gdb/mi} File Commands - -This section describes the GDB/MI commands to specify executable file names -and to read in and obtain symbol table information. - -@subheading The @code{-file-exec-and-symbols} Command -@findex -file-exec-and-symbols - -@subsubheading Synopsis - -@smallexample - -file-exec-and-symbols @var{file} -@end smallexample - -Specify the executable file to be debugged. This file is the one from -which the symbol table is also read. If no file is specified, the -command clears the executable and symbol information. If breakpoints -are set when using this command with no arguments, @value{GDBN} will produce -error messages. Otherwise, no output is produced, except a completion -notification. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{file}. - -@subsubheading Example - -@smallexample -(gdb) --file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx -^done -(gdb) -@end smallexample - - -@subheading The @code{-file-exec-file} Command -@findex -file-exec-file - -@subsubheading Synopsis - -@smallexample - -file-exec-file @var{file} -@end smallexample - -Specify the executable file to be debugged. Unlike -@samp{-file-exec-and-symbols}, the symbol table is @emph{not} read -from this file. If used without argument, @value{GDBN} clears the information -about the executable file. No output is produced, except a completion -notification. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{exec-file}. - -@subsubheading Example - -@smallexample -(gdb) --file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx -^done -(gdb) -@end smallexample - - -@ignore -@subheading The @code{-file-list-exec-sections} Command -@findex -file-list-exec-sections - -@subsubheading Synopsis - -@smallexample - -file-list-exec-sections -@end smallexample - -List the sections of the current executable file. - -@subsubheading @value{GDBN} Command - -The @value{GDBN} command @samp{info file} shows, among the rest, the same -information as this command. @code{gdbtk} has a corresponding command -@samp{gdb_load_info}. - -@subsubheading Example -N.A. -@end ignore - - -@subheading The @code{-file-list-exec-source-file} Command -@findex -file-list-exec-source-file - -@subsubheading Synopsis - -@smallexample - -file-list-exec-source-file -@end smallexample - -List the line number, the current source file, and the absolute path -to the current source file for the current executable. The macro -information field has a value of @samp{1} or @samp{0} depending on -whether or not the file includes preprocessor macro information. - -@subsubheading @value{GDBN} Command - -The @value{GDBN} equivalent is @samp{info source} - -@subsubheading Example - -@smallexample -(gdb) -123-file-list-exec-source-file -123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1" -(gdb) -@end smallexample - - -@subheading The @code{-file-list-exec-source-files} Command -@findex -file-list-exec-source-files - -@subsubheading Synopsis - -@smallexample - -file-list-exec-source-files -@end smallexample - -List the source files for the current executable. - -It will always output both the filename and fullname (absolute file -name) of a source file. - -@subsubheading @value{GDBN} Command - -The @value{GDBN} equivalent is @samp{info sources}. -@code{gdbtk} has an analogous command @samp{gdb_listfiles}. - -@subsubheading Example -@smallexample -(gdb) --file-list-exec-source-files -^done,files=[ -@{file=foo.c,fullname=/home/foo.c@}, -@{file=/home/bar.c,fullname=/home/bar.c@}, -@{file=gdb_could_not_find_fullpath.c@}] -(gdb) -@end smallexample - -@ignore -@subheading The @code{-file-list-shared-libraries} Command -@findex -file-list-shared-libraries - -@subsubheading Synopsis - -@smallexample - -file-list-shared-libraries -@end smallexample - -List the shared libraries in the program. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info shared}. - -@subsubheading Example -N.A. - - -@subheading The @code{-file-list-symbol-files} Command -@findex -file-list-symbol-files - -@subsubheading Synopsis - -@smallexample - -file-list-symbol-files -@end smallexample - -List symbol files. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info file} (part of it). - -@subsubheading Example -N.A. -@end ignore - - -@subheading The @code{-file-symbol-file} Command -@findex -file-symbol-file - -@subsubheading Synopsis - -@smallexample - -file-symbol-file @var{file} -@end smallexample - -Read symbol table info from the specified @var{file} argument. When -used without arguments, clears @value{GDBN}'s symbol table info. No output is -produced, except for a completion notification. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{symbol-file}. - -@subsubheading Example - -@smallexample -(gdb) --file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx -^done -(gdb) -@end smallexample - -@ignore -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Memory Overlay Commands -@section @sc{gdb/mi} Memory Overlay Commands - -The memory overlay commands are not implemented. - -@c @subheading -overlay-auto - -@c @subheading -overlay-list-mapping-state - -@c @subheading -overlay-list-overlays - -@c @subheading -overlay-map - -@c @subheading -overlay-off - -@c @subheading -overlay-on - -@c @subheading -overlay-unmap - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Signal Handling Commands -@section @sc{gdb/mi} Signal Handling Commands - -Signal handling commands are not implemented. - -@c @subheading -signal-handle - -@c @subheading -signal-list-handle-actions - -@c @subheading -signal-list-signal-types -@end ignore - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Target Manipulation -@section @sc{gdb/mi} Target Manipulation Commands - - -@subheading The @code{-target-attach} Command -@findex -target-attach - -@subsubheading Synopsis - -@smallexample - -target-attach @var{pid} | @var{gid} | @var{file} -@end smallexample - -Attach to a process @var{pid} or a file @var{file} outside of -@value{GDBN}, or a thread group @var{gid}. If attaching to a thread -group, the id previously returned by -@samp{-list-thread-groups --available} must be used. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{attach}. - -@subsubheading Example -@smallexample -(gdb) --target-attach 34 -=thread-created,id="1" -*stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@} -^done -(gdb) -@end smallexample - -@ignore -@subheading The @code{-target-compare-sections} Command -@findex -target-compare-sections - -@subsubheading Synopsis - -@smallexample - -target-compare-sections [ @var{section} ] -@end smallexample - -Compare data of section @var{section} on target to the exec file. -Without the argument, all sections are compared. - -@subsubheading @value{GDBN} Command - -The @value{GDBN} equivalent is @samp{compare-sections}. - -@subsubheading Example -N.A. -@end ignore - - -@subheading The @code{-target-detach} Command -@findex -target-detach - -@subsubheading Synopsis - -@smallexample - -target-detach [ @var{pid} | @var{gid} ] -@end smallexample - -Detach from the remote target which normally resumes its execution. -If either @var{pid} or @var{gid} is specified, detaches from either -the specified process, or specified thread group. There's no output. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{detach}. - -@subsubheading Example - -@smallexample -(gdb) --target-detach -^done -(gdb) -@end smallexample - - -@subheading The @code{-target-disconnect} Command -@findex -target-disconnect - -@subsubheading Synopsis - -@smallexample - -target-disconnect -@end smallexample - -Disconnect from the remote target. There's no output and the target is -generally not resumed. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{disconnect}. - -@subsubheading Example - -@smallexample -(gdb) --target-disconnect -^done -(gdb) -@end smallexample - - -@subheading The @code{-target-download} Command -@findex -target-download - -@subsubheading Synopsis - -@smallexample - -target-download -@end smallexample - -Loads the executable onto the remote target. -It prints out an update message every half second, which includes the fields: - -@table @samp -@item section -The name of the section. -@item section-sent -The size of what has been sent so far for that section. -@item section-size -The size of the section. -@item total-sent -The total size of what was sent so far (the current and the previous sections). -@item total-size -The size of the overall executable to download. -@end table - -@noindent -Each message is sent as status record (@pxref{GDB/MI Output Syntax, , -@sc{gdb/mi} Output Syntax}). - -In addition, it prints the name and size of the sections, as they are -downloaded. These messages include the following fields: - -@table @samp -@item section -The name of the section. -@item section-size -The size of the section. -@item total-size -The size of the overall executable to download. -@end table - -@noindent -At the end, a summary is printed. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{load}. - -@subsubheading Example - -Note: each status message appears on a single line. Here the messages -have been broken down so that they can fit onto a page. - -@smallexample -(gdb) --target-download -+download,@{section=".text",section-size="6668",total-size="9880"@} -+download,@{section=".text",section-sent="512",section-size="6668", -total-sent="512",total-size="9880"@} -+download,@{section=".text",section-sent="1024",section-size="6668", -total-sent="1024",total-size="9880"@} -+download,@{section=".text",section-sent="1536",section-size="6668", -total-sent="1536",total-size="9880"@} -+download,@{section=".text",section-sent="2048",section-size="6668", -total-sent="2048",total-size="9880"@} -+download,@{section=".text",section-sent="2560",section-size="6668", -total-sent="2560",total-size="9880"@} -+download,@{section=".text",section-sent="3072",section-size="6668", -total-sent="3072",total-size="9880"@} -+download,@{section=".text",section-sent="3584",section-size="6668", -total-sent="3584",total-size="9880"@} -+download,@{section=".text",section-sent="4096",section-size="6668", -total-sent="4096",total-size="9880"@} -+download,@{section=".text",section-sent="4608",section-size="6668", -total-sent="4608",total-size="9880"@} -+download,@{section=".text",section-sent="5120",section-size="6668", -total-sent="5120",total-size="9880"@} -+download,@{section=".text",section-sent="5632",section-size="6668", -total-sent="5632",total-size="9880"@} -+download,@{section=".text",section-sent="6144",section-size="6668", -total-sent="6144",total-size="9880"@} -+download,@{section=".text",section-sent="6656",section-size="6668", -total-sent="6656",total-size="9880"@} -+download,@{section=".init",section-size="28",total-size="9880"@} -+download,@{section=".fini",section-size="28",total-size="9880"@} -+download,@{section=".data",section-size="3156",total-size="9880"@} -+download,@{section=".data",section-sent="512",section-size="3156", -total-sent="7236",total-size="9880"@} -+download,@{section=".data",section-sent="1024",section-size="3156", -total-sent="7748",total-size="9880"@} -+download,@{section=".data",section-sent="1536",section-size="3156", -total-sent="8260",total-size="9880"@} -+download,@{section=".data",section-sent="2048",section-size="3156", -total-sent="8772",total-size="9880"@} -+download,@{section=".data",section-sent="2560",section-size="3156", -total-sent="9284",total-size="9880"@} -+download,@{section=".data",section-sent="3072",section-size="3156", -total-sent="9796",total-size="9880"@} -^done,address="0x10004",load-size="9880",transfer-rate="6586", -write-rate="429" -(gdb) -@end smallexample - - -@ignore -@subheading The @code{-target-exec-status} Command -@findex -target-exec-status - -@subsubheading Synopsis - -@smallexample - -target-exec-status -@end smallexample - -Provide information on the state of the target (whether it is running or -not, for instance). - -@subsubheading @value{GDBN} Command - -There's no equivalent @value{GDBN} command. - -@subsubheading Example -N.A. - - -@subheading The @code{-target-list-available-targets} Command -@findex -target-list-available-targets - -@subsubheading Synopsis - -@smallexample - -target-list-available-targets -@end smallexample - -List the possible targets to connect to. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{help target}. - -@subsubheading Example -N.A. - - -@subheading The @code{-target-list-current-targets} Command -@findex -target-list-current-targets - -@subsubheading Synopsis - -@smallexample - -target-list-current-targets -@end smallexample - -Describe the current target. - -@subsubheading @value{GDBN} Command - -The corresponding information is printed by @samp{info file} (among -other things). - -@subsubheading Example -N.A. - - -@subheading The @code{-target-list-parameters} Command -@findex -target-list-parameters - -@subsubheading Synopsis - -@smallexample - -target-list-parameters -@end smallexample - -@c ???? -@end ignore - -@subsubheading @value{GDBN} Command - -No equivalent. - -@subsubheading Example -N.A. - - -@subheading The @code{-target-select} Command -@findex -target-select - -@subsubheading Synopsis - -@smallexample - -target-select @var{type} @var{parameters @dots{}} -@end smallexample - -Connect @value{GDBN} to the remote target. This command takes two args: - -@table @samp -@item @var{type} -The type of target, for instance @samp{remote}, etc. -@item @var{parameters} -Device names, host names and the like. @xref{Target Commands, , -Commands for Managing Targets}, for more details. -@end table - -The output is a connection notification, followed by the address at -which the target program is, in the following form: - -@smallexample -^connected,addr="@var{address}",func="@var{function name}", - args=[@var{arg list}] -@end smallexample - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{target}. - -@subsubheading Example - -@smallexample -(gdb) --target-select remote /dev/ttya -^connected,addr="0xfe00a300",func="??",args=[] -(gdb) -@end smallexample - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI File Transfer Commands -@section @sc{gdb/mi} File Transfer Commands - - -@subheading The @code{-target-file-put} Command -@findex -target-file-put - -@subsubheading Synopsis - -@smallexample - -target-file-put @var{hostfile} @var{targetfile} -@end smallexample - -Copy file @var{hostfile} from the host system (the machine running -@value{GDBN}) to @var{targetfile} on the target system. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{remote put}. - -@subsubheading Example - -@smallexample -(gdb) --target-file-put localfile remotefile -^done -(gdb) -@end smallexample - - -@subheading The @code{-target-file-get} Command -@findex -target-file-get - -@subsubheading Synopsis - -@smallexample - -target-file-get @var{targetfile} @var{hostfile} -@end smallexample - -Copy file @var{targetfile} from the target system to @var{hostfile} -on the host system. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{remote get}. - -@subsubheading Example - -@smallexample -(gdb) --target-file-get remotefile localfile -^done -(gdb) -@end smallexample - - -@subheading The @code{-target-file-delete} Command -@findex -target-file-delete - -@subsubheading Synopsis - -@smallexample - -target-file-delete @var{targetfile} -@end smallexample - -Delete @var{targetfile} from the target system. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{remote delete}. - -@subsubheading Example - -@smallexample -(gdb) --target-file-delete remotefile -^done -(gdb) -@end smallexample - - -@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -@node GDB/MI Miscellaneous Commands -@section Miscellaneous @sc{gdb/mi} Commands - -@c @subheading -gdb-complete - -@subheading The @code{-gdb-exit} Command -@findex -gdb-exit - -@subsubheading Synopsis - -@smallexample - -gdb-exit -@end smallexample - -Exit @value{GDBN} immediately. - -@subsubheading @value{GDBN} Command - -Approximately corresponds to @samp{quit}. - -@subsubheading Example - -@smallexample -(gdb) --gdb-exit -^exit -@end smallexample - - -@ignore -@subheading The @code{-exec-abort} Command -@findex -exec-abort - -@subsubheading Synopsis - -@smallexample - -exec-abort -@end smallexample - -Kill the inferior running program. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{kill}. - -@subsubheading Example -N.A. -@end ignore - - -@subheading The @code{-gdb-set} Command -@findex -gdb-set - -@subsubheading Synopsis - -@smallexample - -gdb-set -@end smallexample - -Set an internal @value{GDBN} variable. -@c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ????? - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{set}. - -@subsubheading Example - -@smallexample -(gdb) --gdb-set $foo=3 -^done -(gdb) -@end smallexample - - -@subheading The @code{-gdb-show} Command -@findex -gdb-show - -@subsubheading Synopsis - -@smallexample - -gdb-show -@end smallexample - -Show the current value of a @value{GDBN} variable. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{show}. - -@subsubheading Example - -@smallexample -(gdb) --gdb-show annotate -^done,value="0" -(gdb) -@end smallexample - -@c @subheading -gdb-source - - -@subheading The @code{-gdb-version} Command -@findex -gdb-version - -@subsubheading Synopsis - -@smallexample - -gdb-version -@end smallexample - -Show version information for @value{GDBN}. Used mostly in testing. - -@subsubheading @value{GDBN} Command - -The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by -default shows this information when you start an interactive session. - -@subsubheading Example - -@c This example modifies the actual output from GDB to avoid overfull -@c box in TeX. -@smallexample -(gdb) --gdb-version -~GNU gdb 5.2.1 -~Copyright 2000 Free Software Foundation, Inc. -~GDB is free software, covered by the GNU General Public License, and -~you are welcome to change it and/or distribute copies of it under -~ certain conditions. -~Type "show copying" to see the conditions. -~There is absolutely no warranty for GDB. Type "show warranty" for -~ details. -~This GDB was configured as - "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi". -^done -(gdb) -@end smallexample - -@subheading The @code{-list-features} Command -@findex -list-features - -Returns a list of particular features of the MI protocol that -this version of gdb implements. A feature can be a command, -or a new field in an output of some command, or even an -important bugfix. While a frontend can sometimes detect presence -of a feature at runtime, it is easier to perform detection at debugger -startup. - -The command returns a list of strings, with each string naming an -available feature. Each returned string is just a name, it does not -have any internal structure. The list of possible feature names -is given below. - -Example output: - -@smallexample -(gdb) -list-features -^done,result=["feature1","feature2"] -@end smallexample - -The current list of features is: - -@table @samp -@item frozen-varobjs -Indicates support for the @code{-var-set-frozen} command, as well -as possible presense of the @code{frozen} field in the output -of @code{-varobj-create}. -@item pending-breakpoints -Indicates support for the @option{-f} option to the @code{-break-insert} -command. -@item python -Indicates Python scripting support, Python-based -pretty-printing commands, and possible presence of the -@samp{display_hint} field in the output of @code{-var-list-children} -@item thread-info -Indicates support for the @code{-thread-info} command. -@item data-read-memory-bytes -Indicates support for the @code{-data-read-memory-bytes} and the -@code{-data-write-memory-bytes} commands. -@item breakpoint-notifications -Indicates that changes to breakpoints and breakpoints created via the -CLI will be announced via async records. -@item ada-task-info -Indicates support for the @code{-ada-task-info} command. -@end table - -@subheading The @code{-list-target-features} Command -@findex -list-target-features - -Returns a list of particular features that are supported by the -target. Those features affect the permitted MI commands, but -unlike the features reported by the @code{-list-features} command, the -features depend on which target GDB is using at the moment. Whenever -a target can change, due to commands such as @code{-target-select}, -@code{-target-attach} or @code{-exec-run}, the list of target features -may change, and the frontend should obtain it again. -Example output: - -@smallexample -(gdb) -list-features -^done,result=["async"] -@end smallexample - -The current list of features is: - -@table @samp -@item async -Indicates that the target is capable of asynchronous command -execution, which means that @value{GDBN} will accept further commands -while the target is running. - -@item reverse -Indicates that the target is capable of reverse execution. -@xref{Reverse Execution}, for more information. - -@end table - -@subheading The @code{-list-thread-groups} Command -@findex -list-thread-groups - -@subheading Synopsis - -@smallexample --list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ] -@end smallexample - -Lists thread groups (@pxref{Thread groups}). When a single thread -group is passed as the argument, lists the children of that group. -When several thread group are passed, lists information about those -thread groups. Without any parameters, lists information about all -top-level thread groups. - -Normally, thread groups that are being debugged are reported. -With the @samp{--available} option, @value{GDBN} reports thread groups -available on the target. - -The output of this command may have either a @samp{threads} result or -a @samp{groups} result. The @samp{thread} result has a list of tuples -as value, with each tuple describing a thread (@pxref{GDB/MI Thread -Information}). The @samp{groups} result has a list of tuples as value, -each tuple describing a thread group. If top-level groups are -requested (that is, no parameter is passed), or when several groups -are passed, the output always has a @samp{groups} result. The format -of the @samp{group} result is described below. - -To reduce the number of roundtrips it's possible to list thread groups -together with their children, by passing the @samp{--recurse} option -and the recursion depth. Presently, only recursion depth of 1 is -permitted. If this option is present, then every reported thread group -will also include its children, either as @samp{group} or -@samp{threads} field. - -In general, any combination of option and parameters is permitted, with -the following caveats: - -@itemize @bullet -@item -When a single thread group is passed, the output will typically -be the @samp{threads} result. Because threads may not contain -anything, the @samp{recurse} option will be ignored. - -@item -When the @samp{--available} option is passed, limited information may -be available. In particular, the list of threads of a process might -be inaccessible. Further, specifying specific thread groups might -not give any performance advantage over listing all thread groups. -The frontend should assume that @samp{-list-thread-groups --available} -is always an expensive operation and cache the results. - -@end itemize - -The @samp{groups} result is a list of tuples, where each tuple may -have the following fields: - -@table @code -@item id -Identifier of the thread group. This field is always present. -The identifier is an opaque string; frontends should not try to -convert it to an integer, even though it might look like one. - -@item type -The type of the thread group. At present, only @samp{process} is a -valid type. - -@item pid -The target-specific process identifier. This field is only present -for thread groups of type @samp{process} and only if the process exists. - -@item num_children -The number of children this thread group has. This field may be -absent for an available thread group. - -@item threads -This field has a list of tuples as value, each tuple describing a -thread. It may be present if the @samp{--recurse} option is -specified, and it's actually possible to obtain the threads. - -@item cores -This field is a list of integers, each identifying a core that one -thread of the group is running on. This field may be absent if -such information is not available. - -@item executable -The name of the executable file that corresponds to this thread group. -The field is only present for thread groups of type @samp{process}, -and only if there is a corresponding executable file. - -@end table - -@subheading Example - -@smallexample -@value{GDBP} --list-thread-groups -^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}] --list-thread-groups 17 -^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)", - frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@}, -@{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)", - frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}], - file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]] --list-thread-groups --available -^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}] --list-thread-groups --available --recurse 1 - ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2], - threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@}, - @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..] --list-thread-groups --available --recurse 1 17 18 -^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2], - threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@}, - @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...] -@end smallexample - -@subheading The @code{-info-os} Command -@findex -info-os - -@subsubheading Synopsis - -@smallexample --info-os [ @var{type} ] -@end smallexample - -If no argument is supplied, the command returns a table of available -operating-system-specific information types. If one of these types is -supplied as an argument @var{type}, then the command returns a table -of data of that type. - -The types of information available depend on the target operating -system. - -@subsubheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{info os}. - -@subsubheading Example - -When run on a @sc{gnu}/Linux system, the output will look something -like this: - -@smallexample -@value{GDBP} --info-os -^done,OSDataTable=@{nr_rows="9",nr_cols="3", -hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@}, - @{width="10",alignment="-1",col_name="col1",colhdr="Description"@}, - @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}], -body=[item=@{col0="processes",col1="Listing of all processes", - col2="Processes"@}, - item=@{col0="procgroups",col1="Listing of all process groups", - col2="Process groups"@}, - item=@{col0="threads",col1="Listing of all threads", - col2="Threads"@}, - item=@{col0="files",col1="Listing of all file descriptors", - col2="File descriptors"@}, - item=@{col0="sockets",col1="Listing of all internet-domain sockets", - col2="Sockets"@}, - item=@{col0="shm",col1="Listing of all shared-memory regions", - col2="Shared-memory regions"@}, - item=@{col0="semaphores",col1="Listing of all semaphores", - col2="Semaphores"@}, - item=@{col0="msg",col1="Listing of all message queues", - col2="Message queues"@}, - item=@{col0="modules",col1="Listing of all loaded kernel modules", - col2="Kernel modules"@}]@} -@value{GDBP} --info-os processes -^done,OSDataTable=@{nr_rows="190",nr_cols="4", -hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@}, - @{width="10",alignment="-1",col_name="col1",colhdr="user"@}, - @{width="10",alignment="-1",col_name="col2",colhdr="command"@}, - @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}], -body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@}, - item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@}, - item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@}, - ... - item=@{col0="26446",col1="stan",col2="bash",col3="0"@}, - item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@} -(gdb) -@end smallexample - -(Note that the MI output here includes a @code{"Title"} column that -does not appear in command-line @code{info os}; this column is useful -for MI clients that want to enumerate the types of data, such as in a -popup menu, but is needless clutter on the command line, and -@code{info os} omits it.) - -@subheading The @code{-add-inferior} Command -@findex -add-inferior - -@subheading Synopsis - -@smallexample --add-inferior -@end smallexample - -Creates a new inferior (@pxref{Inferiors and Programs}). The created -inferior is not associated with any executable. Such association may -be established with the @samp{-file-exec-and-symbols} command -(@pxref{GDB/MI File Commands}). The command response has a single -field, @samp{thread-group}, whose value is the identifier of the -thread group corresponding to the new inferior. - -@subheading Example - -@smallexample -@value{GDBP} --add-inferior -^done,thread-group="i3" -@end smallexample - -@subheading The @code{-interpreter-exec} Command -@findex -interpreter-exec - -@subheading Synopsis - -@smallexample --interpreter-exec @var{interpreter} @var{command} -@end smallexample -@anchor{-interpreter-exec} - -Execute the specified @var{command} in the given @var{interpreter}. - -@subheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{interpreter-exec}. - -@subheading Example - -@smallexample -(gdb) --interpreter-exec console "break main" -&"During symbol reading, couldn't parse type; debugger out of date?.\n" -&"During symbol reading, bad structure-type format.\n" -~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n" -^done -(gdb) -@end smallexample - -@subheading The @code{-inferior-tty-set} Command -@findex -inferior-tty-set - -@subheading Synopsis - -@smallexample --inferior-tty-set /dev/pts/1 -@end smallexample - -Set terminal for future runs of the program being debugged. - -@subheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1. - -@subheading Example - -@smallexample -(gdb) --inferior-tty-set /dev/pts/1 -^done -(gdb) -@end smallexample - -@subheading The @code{-inferior-tty-show} Command -@findex -inferior-tty-show - -@subheading Synopsis - -@smallexample --inferior-tty-show -@end smallexample - -Show terminal for future runs of program being debugged. - -@subheading @value{GDBN} Command - -The corresponding @value{GDBN} command is @samp{show inferior-tty}. - -@subheading Example - -@smallexample -(gdb) --inferior-tty-set /dev/pts/1 -^done -(gdb) --inferior-tty-show -^done,inferior_tty_terminal="/dev/pts/1" -(gdb) -@end smallexample - -@subheading The @code{-enable-timings} Command -@findex -enable-timings - -@subheading Synopsis - -@smallexample --enable-timings [yes | no] -@end smallexample - -Toggle the printing of the wallclock, user and system times for an MI -command as a field in its output. This command is to help frontend -developers optimize the performance of their code. No argument is -equivalent to @samp{yes}. - -@subheading @value{GDBN} Command - -No equivalent. - -@subheading Example - -@smallexample -(gdb) --enable-timings -^done -(gdb) --break-insert main -^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", -addr="0x080484ed",func="main",file="myprog.c", -fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"], -times="0"@}, -time=@{wallclock="0.05185",user="0.00800",system="0.00000"@} -(gdb) --enable-timings no -^done -(gdb) --exec-run -^running -(gdb) -*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0", -frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@}, -@{name="argv",value="0xbfb60364"@}],file="myprog.c", -fullname="/home/nickrob/myprog.c",line="73"@} -(gdb) -@end smallexample - -@node Annotations -@chapter @value{GDBN} Annotations - -This chapter describes annotations in @value{GDBN}. Annotations were -designed to interface @value{GDBN} to graphical user interfaces or other -similar programs which want to interact with @value{GDBN} at a -relatively high level. - -The annotation mechanism has largely been superseded by @sc{gdb/mi} -(@pxref{GDB/MI}). - -@ignore -This is Edition @value{EDITION}, @value{DATE}. -@end ignore - -@menu -* Annotations Overview:: What annotations are; the general syntax. -* Server Prefix:: Issuing a command without affecting user state. -* Prompting:: Annotations marking @value{GDBN}'s need for input. -* Errors:: Annotations for error messages. -* Invalidation:: Some annotations describe things now invalid. -* Annotations for Running:: - Whether the program is running, how it stopped, etc. -* Source Annotations:: Annotations describing source code. -@end menu - -@node Annotations Overview -@section What is an Annotation? -@cindex annotations - -Annotations start with a newline character, two @samp{control-z} -characters, and the name of the annotation. If there is no additional -information associated with this annotation, the name of the annotation -is followed immediately by a newline. If there is additional -information, the name of the annotation is followed by a space, the -additional information, and a newline. The additional information -cannot contain newline characters. - -Any output not beginning with a newline and two @samp{control-z} -characters denotes literal output from @value{GDBN}. Currently there is -no need for @value{GDBN} to output a newline followed by two -@samp{control-z} characters, but if there was such a need, the -annotations could be extended with an @samp{escape} annotation which -means those three characters as output. - -The annotation @var{level}, which is specified using the -@option{--annotate} command line option (@pxref{Mode Options}), controls -how much information @value{GDBN} prints together with its prompt, -values of expressions, source lines, and other types of output. Level 0 -is for no annotations, level 1 is for use when @value{GDBN} is run as a -subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable -for programs that control @value{GDBN}, and level 2 annotations have -been made obsolete (@pxref{Limitations, , Limitations of the Annotation -Interface, annotate, GDB's Obsolete Annotations}). - -@table @code -@kindex set annotate -@item set annotate @var{level} -The @value{GDBN} command @code{set annotate} sets the level of -annotations to the specified @var{level}. - -@item show annotate -@kindex show annotate -Show the current annotation level. -@end table - -This chapter describes level 3 annotations. - -A simple example of starting up @value{GDBN} with annotations is: - -@smallexample -$ @kbd{gdb --annotate=3} -GNU gdb 6.0 -Copyright 2003 Free Software Foundation, Inc. -GDB is free software, covered by the GNU General Public License, -and you are welcome to change it and/or distribute copies of it -under certain conditions. -Type "show copying" to see the conditions. -There is absolutely no warranty for GDB. Type "show warranty" -for details. -This GDB was configured as "i386-pc-linux-gnu" - -^Z^Zpre-prompt -(@value{GDBP}) -^Z^Zprompt -@kbd{quit} - -^Z^Zpost-prompt -$ -@end smallexample - -Here @samp{quit} is input to @value{GDBN}; the rest is output from -@value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z} -denotes a @samp{control-z} character) are annotations; the rest is -output from @value{GDBN}. - -@node Server Prefix -@section The Server Prefix -@cindex server prefix - -If you prefix a command with @samp{server } then it will not affect -the command history, nor will it affect @value{GDBN}'s notion of which -command to repeat if @key{RET} is pressed on a line by itself. This -means that commands can be run behind a user's back by a front-end in -a transparent manner. - -The @code{server } prefix does not affect the recording of values into -the value history; to print a value without recording it into the -value history, use the @code{output} command instead of the -@code{print} command. - -Using this prefix also disables confirmation requests -(@pxref{confirmation requests}). - -@node Prompting -@section Annotation for @value{GDBN} Input - -@cindex annotations for prompts -When @value{GDBN} prompts for input, it annotates this fact so it is possible -to know when to send output, when the output from a given command is -over, etc. - -Different kinds of input each have a different @dfn{input type}. Each -input type has three annotations: a @code{pre-} annotation, which -denotes the beginning of any prompt which is being output, a plain -annotation, which denotes the end of the prompt, and then a @code{post-} -annotation which denotes the end of any echo which may (or may not) be -associated with the input. For example, the @code{prompt} input type -features the following annotations: - -@smallexample -^Z^Zpre-prompt -^Z^Zprompt -^Z^Zpost-prompt -@end smallexample - -The input types are - -@table @code -@findex pre-prompt annotation -@findex prompt annotation -@findex post-prompt annotation -@item prompt -When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt). - -@findex pre-commands annotation -@findex commands annotation -@findex post-commands annotation -@item commands -When @value{GDBN} prompts for a set of commands, like in the @code{commands} -command. The annotations are repeated for each command which is input. - -@findex pre-overload-choice annotation -@findex overload-choice annotation -@findex post-overload-choice annotation -@item overload-choice -When @value{GDBN} wants the user to select between various overloaded functions. - -@findex pre-query annotation -@findex query annotation -@findex post-query annotation -@item query -When @value{GDBN} wants the user to confirm a potentially dangerous operation. - -@findex pre-prompt-for-continue annotation -@findex prompt-for-continue annotation -@findex post-prompt-for-continue annotation -@item prompt-for-continue -When @value{GDBN} is asking the user to press return to continue. Note: Don't -expect this to work well; instead use @code{set height 0} to disable -prompting. This is because the counting of lines is buggy in the -presence of annotations. -@end table - -@node Errors -@section Errors -@cindex annotations for errors, warnings and interrupts - -@findex quit annotation -@smallexample -^Z^Zquit -@end smallexample - -This annotation occurs right before @value{GDBN} responds to an interrupt. - -@findex error annotation -@smallexample -^Z^Zerror -@end smallexample - -This annotation occurs right before @value{GDBN} responds to an error. - -Quit and error annotations indicate that any annotations which @value{GDBN} was -in the middle of may end abruptly. For example, if a -@code{value-history-begin} annotation is followed by a @code{error}, one -cannot expect to receive the matching @code{value-history-end}. One -cannot expect not to receive it either, however; an error annotation -does not necessarily mean that @value{GDBN} is immediately returning all the way -to the top level. - -@findex error-begin annotation -A quit or error annotation may be preceded by - -@smallexample -^Z^Zerror-begin -@end smallexample - -Any output between that and the quit or error annotation is the error -message. - -Warning messages are not yet annotated. -@c If we want to change that, need to fix warning(), type_error(), -@c range_error(), and possibly other places. - -@node Invalidation -@section Invalidation Notices - -@cindex annotations for invalidation messages -The following annotations say that certain pieces of state may have -changed. - -@table @code -@findex frames-invalid annotation -@item ^Z^Zframes-invalid - -The frames (for example, output from the @code{backtrace} command) may -have changed. - -@findex breakpoints-invalid annotation -@item ^Z^Zbreakpoints-invalid - -The breakpoints may have changed. For example, the user just added or -deleted a breakpoint. -@end table - -@node Annotations for Running -@section Running the Program -@cindex annotations for running programs - -@findex starting annotation -@findex stopping annotation -When the program starts executing due to a @value{GDBN} command such as -@code{step} or @code{continue}, - -@smallexample -^Z^Zstarting -@end smallexample - -is output. When the program stops, - -@smallexample -^Z^Zstopped -@end smallexample - -is output. Before the @code{stopped} annotation, a variety of -annotations describe how the program stopped. - -@table @code -@findex exited annotation -@item ^Z^Zexited @var{exit-status} -The program exited, and @var{exit-status} is the exit status (zero for -successful exit, otherwise nonzero). - -@findex signalled annotation -@findex signal-name annotation -@findex signal-name-end annotation -@findex signal-string annotation -@findex signal-string-end annotation -@item ^Z^Zsignalled -The program exited with a signal. After the @code{^Z^Zsignalled}, the -annotation continues: - -@smallexample -@var{intro-text} -^Z^Zsignal-name -@var{name} -^Z^Zsignal-name-end -@var{middle-text} -^Z^Zsignal-string -@var{string} -^Z^Zsignal-string-end -@var{end-text} -@end smallexample - -@noindent -where @var{name} is the name of the signal, such as @code{SIGILL} or -@code{SIGSEGV}, and @var{string} is the explanation of the signal, such -as @code{Illegal Instruction} or @code{Segmentation fault}. -@var{intro-text}, @var{middle-text}, and @var{end-text} are for the -user's benefit and have no particular format. - -@findex signal annotation -@item ^Z^Zsignal -The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is -just saying that the program received the signal, not that it was -terminated with it. - -@findex breakpoint annotation -@item ^Z^Zbreakpoint @var{number} -The program hit breakpoint number @var{number}. - -@findex watchpoint annotation -@item ^Z^Zwatchpoint @var{number} -The program hit watchpoint number @var{number}. -@end table - -@node Source Annotations -@section Displaying Source -@cindex annotations for source display - -@findex source annotation -The following annotation is used instead of displaying source code: - -@smallexample -^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr} -@end smallexample - -where @var{filename} is an absolute file name indicating which source -file, @var{line} is the line number within that file (where 1 is the -first line in the file), @var{character} is the character position -within the file (where 0 is the first character in the file) (for most -debug formats this will necessarily point to the beginning of a line), -@var{middle} is @samp{middle} if @var{addr} is in the middle of the -line, or @samp{beg} if @var{addr} is at the beginning of the line, and -@var{addr} is the address in the target program associated with the -source which is being displayed. @var{addr} is in the form @samp{0x} -followed by one or more lowercase hex digits (note that this does not -depend on the language). - -@node JIT Interface -@chapter JIT Compilation Interface -@cindex just-in-time compilation -@cindex JIT compilation interface - -This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation -interface. A JIT compiler is a program or library that generates native -executable code at runtime and executes it, usually in order to achieve good -performance while maintaining platform independence. - -Programs that use JIT compilation are normally difficult to debug because -portions of their code are generated at runtime, instead of being loaded from -object files, which is where @value{GDBN} normally finds the program's symbols -and debug information. In order to debug programs that use JIT compilation, -@value{GDBN} has an interface that allows the program to register in-memory -symbol files with @value{GDBN} at runtime. - -If you are using @value{GDBN} to debug a program that uses this interface, then -it should work transparently so long as you have not stripped the binary. If -you are developing a JIT compiler, then the interface is documented in the rest -of this chapter. At this time, the only known client of this interface is the -LLVM JIT. - -Broadly speaking, the JIT interface mirrors the dynamic loader interface. The -JIT compiler communicates with @value{GDBN} by writing data into a global -variable and calling a fuction at a well-known symbol. When @value{GDBN} -attaches, it reads a linked list of symbol files from the global variable to -find existing code, and puts a breakpoint in the function so that it can find -out about additional code. - -@menu -* Declarations:: Relevant C struct declarations -* Registering Code:: Steps to register code -* Unregistering Code:: Steps to unregister code -* Custom Debug Info:: Emit debug information in a custom format -@end menu - -@node Declarations -@section JIT Declarations - -These are the relevant struct declarations that a C program should include to -implement the interface: - -@smallexample -typedef enum -@{ - JIT_NOACTION = 0, - JIT_REGISTER_FN, - JIT_UNREGISTER_FN -@} jit_actions_t; - -struct jit_code_entry -@{ - struct jit_code_entry *next_entry; - struct jit_code_entry *prev_entry; - const char *symfile_addr; - uint64_t symfile_size; -@}; - -struct jit_descriptor -@{ - uint32_t version; - /* This type should be jit_actions_t, but we use uint32_t - to be explicit about the bitwidth. */ - uint32_t action_flag; - struct jit_code_entry *relevant_entry; - struct jit_code_entry *first_entry; -@}; - -/* GDB puts a breakpoint in this function. */ -void __attribute__((noinline)) __jit_debug_register_code() @{ @}; - -/* Make sure to specify the version statically, because the - debugger may check the version before we can set it. */ -struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @}; -@end smallexample - -If the JIT is multi-threaded, then it is important that the JIT synchronize any -modifications to this global data properly, which can easily be done by putting -a global mutex around modifications to these structures. - -@node Registering Code -@section Registering Code - -To register code with @value{GDBN}, the JIT should follow this protocol: - -@itemize @bullet -@item -Generate an object file in memory with symbols and other desired debug -information. The file must include the virtual addresses of the sections. - -@item -Create a code entry for the file, which gives the start and size of the symbol -file. - -@item -Add it to the linked list in the JIT descriptor. - -@item -Point the relevant_entry field of the descriptor at the entry. - -@item -Set @code{action_flag} to @code{JIT_REGISTER} and call -@code{__jit_debug_register_code}. -@end itemize - -When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the -@code{relevant_entry} pointer so it doesn't have to walk the list looking for -new code. However, the linked list must still be maintained in order to allow -@value{GDBN} to attach to a running process and still find the symbol files. - -@node Unregistering Code -@section Unregistering Code - -If code is freed, then the JIT should use the following protocol: - -@itemize @bullet -@item -Remove the code entry corresponding to the code from the linked list. - -@item -Point the @code{relevant_entry} field of the descriptor at the code entry. - -@item -Set @code{action_flag} to @code{JIT_UNREGISTER} and call -@code{__jit_debug_register_code}. -@end itemize - -If the JIT frees or recompiles code without unregistering it, then @value{GDBN} -and the JIT will leak the memory used for the associated symbol files. - -@node Custom Debug Info -@section Custom Debug Info -@cindex custom JIT debug info -@cindex JIT debug info reader - -Generating debug information in platform-native file formats (like ELF -or COFF) may be an overkill for JIT compilers; especially if all the -debug info is used for is displaying a meaningful backtrace. The -issue can be resolved by having the JIT writers decide on a debug info -format and also provide a reader that parses the debug info generated -by the JIT compiler. This section gives a brief overview on writing -such a parser. More specific details can be found in the source file -@file{gdb/jit-reader.in}, which is also installed as a header at -@file{@var{includedir}/gdb/jit-reader.h} for easy inclusion. - -The reader is implemented as a shared object (so this functionality is -not available on platforms which don't allow loading shared objects at -runtime). Two @value{GDBN} commands, @code{jit-reader-load} and -@code{jit-reader-unload} are provided, to be used to load and unload -the readers from a preconfigured directory. Once loaded, the shared -object is used the parse the debug information emitted by the JIT -compiler. - -@menu -* Using JIT Debug Info Readers:: How to use supplied readers correctly -* Writing JIT Debug Info Readers:: Creating a debug-info reader -@end menu - -@node Using JIT Debug Info Readers -@subsection Using JIT Debug Info Readers -@kindex jit-reader-load -@kindex jit-reader-unload - -Readers can be loaded and unloaded using the @code{jit-reader-load} -and @code{jit-reader-unload} commands. - -@table @code -@item jit-reader-load @var{reader} -Load the JIT reader named @var{reader}. @var{reader} is a shared -object specified as either an absolute or a relative file name. In -the latter case, @value{GDBN} will try to load the reader from a -pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX -system (here @var{libdir} is the system library directory, often -@file{/usr/local/lib}). - -Only one reader can be active at a time; trying to load a second -reader when one is already loaded will result in @value{GDBN} -reporting an error. A new JIT reader can be loaded by first unloading -the current one using @code{jit-reader-unload} and then invoking -@code{jit-reader-load}. - -@item jit-reader-unload -Unload the currently loaded JIT reader. - -@end table - -@node Writing JIT Debug Info Readers -@subsection Writing JIT Debug Info Readers -@cindex writing JIT debug info readers - -As mentioned, a reader is essentially a shared object conforming to a -certain ABI. This ABI is described in @file{jit-reader.h}. - -@file{jit-reader.h} defines the structures, macros and functions -required to write a reader. It is installed (along with -@value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is -the system include directory. - -Readers need to be released under a GPL compatible license. A reader -can be declared as released under such a license by placing the macro -@code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file. - -The entry point for readers is the symbol @code{gdb_init_reader}, -which is expected to be a function with the prototype - -@findex gdb_init_reader -@smallexample -extern struct gdb_reader_funcs *gdb_init_reader (void); -@end smallexample - -@cindex @code{struct gdb_reader_funcs} - -@code{struct gdb_reader_funcs} contains a set of pointers to callback -functions. These functions are executed to read the debug info -generated by the JIT compiler (@code{read}), to unwind stack frames -(@code{unwind}) and to create canonical frame IDs -(@code{get_Frame_id}). It also has a callback that is called when the -reader is being unloaded (@code{destroy}). The struct looks like this - -@smallexample -struct gdb_reader_funcs -@{ - /* Must be set to GDB_READER_INTERFACE_VERSION. */ - int reader_version; - - /* For use by the reader. */ - void *priv_data; - - gdb_read_debug_info *read; - gdb_unwind_frame *unwind; - gdb_get_frame_id *get_frame_id; - gdb_destroy_reader *destroy; -@}; -@end smallexample - -@cindex @code{struct gdb_symbol_callbacks} -@cindex @code{struct gdb_unwind_callbacks} - -The callbacks are provided with another set of callbacks by -@value{GDBN} to do their job. For @code{read}, these callbacks are -passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind} -and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}. -@code{struct gdb_symbol_callbacks} has callbacks to create new object -files and new symbol tables inside those object files. @code{struct -gdb_unwind_callbacks} has callbacks to read registers off the current -frame and to write out the values of the registers in the previous -frame. Both have a callback (@code{target_read}) to read bytes off the -target's address space. - -@node In-Process Agent -@chapter In-Process Agent -@cindex debugging agent -The traditional debugging model is conceptually low-speed, but works fine, -because most bugs can be reproduced in debugging-mode execution. However, -as multi-core or many-core processors are becoming mainstream, and -multi-threaded programs become more and more popular, there should be more -and more bugs that only manifest themselves at normal-mode execution, for -example, thread races, because debugger's interference with the program's -timing may conceal the bugs. On the other hand, in some applications, -it is not feasible for the debugger to interrupt the program's execution -long enough for the developer to learn anything helpful about its behavior. -If the program's correctness depends on its real-time behavior, delays -introduced by a debugger might cause the program to fail, even when the -code itself is correct. It is useful to be able to observe the program's -behavior without interrupting it. - -Therefore, traditional debugging model is too intrusive to reproduce -some bugs. In order to reduce the interference with the program, we can -reduce the number of operations performed by debugger. The -@dfn{In-Process Agent}, a shared library, is running within the same -process with inferior, and is able to perform some debugging operations -itself. As a result, debugger is only involved when necessary, and -performance of debugging can be improved accordingly. Note that -interference with program can be reduced but can't be removed completely, -because the in-process agent will still stop or slow down the program. - -The in-process agent can interpret and execute Agent Expressions -(@pxref{Agent Expressions}) during performing debugging operations. The -agent expressions can be used for different purposes, such as collecting -data in tracepoints, and condition evaluation in breakpoints. - -@anchor{Control Agent} -You can control whether the in-process agent is used as an aid for -debugging with the following commands: - -@table @code -@kindex set agent on -@item set agent on -Causes the in-process agent to perform some operations on behalf of the -debugger. Just which operations requested by the user will be done -by the in-process agent depends on the its capabilities. For example, -if you request to evaluate breakpoint conditions in the in-process agent, -and the in-process agent has such capability as well, then breakpoint -conditions will be evaluated in the in-process agent. - -@kindex set agent off -@item set agent off -Disables execution of debugging operations by the in-process agent. All -of the operations will be performed by @value{GDBN}. - -@kindex show agent -@item show agent -Display the current setting of execution of debugging operations by -the in-process agent. -@end table - -@menu -* In-Process Agent Protocol:: -@end menu - -@node In-Process Agent Protocol -@section In-Process Agent Protocol -@cindex in-process agent protocol - -The in-process agent is able to communicate with both @value{GDBN} and -GDBserver (@pxref{In-Process Agent}). This section documents the protocol -used for communications between @value{GDBN} or GDBserver and the IPA. -In general, @value{GDBN} or GDBserver sends commands -(@pxref{IPA Protocol Commands}) and data to in-process agent, and then -in-process agent replies back with the return result of the command, or -some other information. The data sent to in-process agent is composed -of primitive data types, such as 4-byte or 8-byte type, and composite -types, which are called objects (@pxref{IPA Protocol Objects}). - -@menu -* IPA Protocol Objects:: -* IPA Protocol Commands:: -@end menu - -@node IPA Protocol Objects -@subsection IPA Protocol Objects -@cindex ipa protocol objects - -The commands sent to and results received from agent may contain some -complex data types called @dfn{objects}. - -The in-process agent is running on the same machine with @value{GDBN} -or GDBserver, so it doesn't have to handle as much differences between -two ends as remote protocol (@pxref{Remote Protocol}) tries to handle. -However, there are still some differences of two ends in two processes: - -@enumerate -@item -word size. On some 64-bit machines, @value{GDBN} or GDBserver can be -compiled as a 64-bit executable, while in-process agent is a 32-bit one. -@item -ABI. Some machines may have multiple types of ABI, @value{GDBN} or -GDBserver is compiled with one, and in-process agent is compiled with -the other one. -@end enumerate - -Here are the IPA Protocol Objects: - -@enumerate -@item -agent expression object. It represents an agent expression -(@pxref{Agent Expressions}). -@anchor{agent expression object} -@item -tracepoint action object. It represents a tracepoint action -(@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers, -memory, static trace data and to evaluate expression. -@anchor{tracepoint action object} -@item -tracepoint object. It represents a tracepoint (@pxref{Tracepoints}). -@anchor{tracepoint object} - -@end enumerate - -The following table describes important attributes of each IPA protocol -object: - -@multitable @columnfractions .30 .20 .50 -@headitem Name @tab Size @tab Description -@item @emph{agent expression object} @tab @tab -@item length @tab 4 @tab length of bytes code -@item byte code @tab @var{length} @tab contents of byte code -@item @emph{tracepoint action for collecting memory} @tab @tab -@item 'M' @tab 1 @tab type of tracepoint action -@item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the -address of the lowest byte to collect, otherwise @var{addr} is the offset -of @var{basereg} for memory collecting. -@item len @tab 8 @tab length of memory for collecting -@item basereg @tab 4 @tab the register number containing the starting -memory address for collecting. -@item @emph{tracepoint action for collecting registers} @tab @tab -@item 'R' @tab 1 @tab type of tracepoint action -@item @emph{tracepoint action for collecting static trace data} @tab @tab -@item 'L' @tab 1 @tab type of tracepoint action -@item @emph{tracepoint action for expression evaluation} @tab @tab -@item 'X' @tab 1 @tab type of tracepoint action -@item agent expression @tab length of @tab @ref{agent expression object} -@item @emph{tracepoint object} @tab @tab -@item number @tab 4 @tab number of tracepoint -@item address @tab 8 @tab address of tracepoint inserted on -@item type @tab 4 @tab type of tracepoint -@item enabled @tab 1 @tab enable or disable of tracepoint -@item step_count @tab 8 @tab step -@item pass_count @tab 8 @tab pass -@item numactions @tab 4 @tab number of tracepoint actions -@item hit count @tab 8 @tab hit count -@item trace frame usage @tab 8 @tab trace frame usage -@item compiled_cond @tab 8 @tab compiled condition -@item orig_size @tab 8 @tab orig size -@item condition @tab 4 if condition is NULL otherwise length of -@ref{agent expression object} -@tab zero if condition is NULL, otherwise is -@ref{agent expression object} -@item actions @tab variable -@tab numactions number of @ref{tracepoint action object} -@end multitable - -@node IPA Protocol Commands -@subsection IPA Protocol Commands -@cindex ipa protocol commands - -The spaces in each command are delimiters to ease reading this commands -specification. They don't exist in real commands. - -@table @samp - -@item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head} -Installs a new fast tracepoint described by @var{tracepoint_object} -(@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the -head of @dfn{jumppad}, which is used to jump to data collection routine -in IPA finally. - -Replies: -@table @samp -@item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump} -@var{target_address} is address of tracepoint in the inferior. -@var{gdb_jump_pad_head} is updated head of jumppad. Both of -@var{target_address} and @var{gdb_jump_pad_head} are 8-byte long. -@var{fjump} contains a sequence of instructions jump to jumppad entry. -@var{fjump_size}, 4-byte long, is the size of @var{fjump}. -@item E @var{NN} -for an error - -@end table - -@item close -Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver -is about to kill inferiors. - -@item qTfSTM -@xref{qTfSTM}. -@item qTsSTM -@xref{qTsSTM}. -@item qTSTMat -@xref{qTSTMat}. -@item probe_marker_at:@var{address} -Asks in-process agent to probe the marker at @var{address}. - -Replies: -@table @samp -@item E @var{NN} -for an error -@end table -@item unprobe_marker_at:@var{address} -Asks in-process agent to unprobe the marker at @var{address}. -@end table - -@node GDB Bugs -@chapter Reporting Bugs in @value{GDBN} -@cindex bugs in @value{GDBN} -@cindex reporting bugs in @value{GDBN} - -Your bug reports play an essential role in making @value{GDBN} reliable. - -Reporting a bug may help you by bringing a solution to your problem, or it -may not. But in any case the principal function of a bug report is to help -the entire community by making the next version of @value{GDBN} work better. Bug -reports are your contribution to the maintenance of @value{GDBN}. - -In order for a bug report to serve its purpose, you must include the -information that enables us to fix the bug. - -@menu -* Bug Criteria:: Have you found a bug? -* Bug Reporting:: How to report bugs -@end menu - -@node Bug Criteria -@section Have You Found a Bug? -@cindex bug criteria - -If you are not sure whether you have found a bug, here are some guidelines: - -@itemize @bullet -@cindex fatal signal -@cindex debugger crash -@cindex crash of debugger -@item -If the debugger gets a fatal signal, for any input whatever, that is a -@value{GDBN} bug. Reliable debuggers never crash. - -@cindex error on valid input -@item -If @value{GDBN} produces an error message for valid input, that is a -bug. (Note that if you're cross debugging, the problem may also be -somewhere in the connection to the target.) - -@cindex invalid input -@item -If @value{GDBN} does not produce an error message for invalid input, -that is a bug. However, you should note that your idea of -``invalid input'' might be our idea of ``an extension'' or ``support -for traditional practice''. - -@item -If you are an experienced user of debugging tools, your suggestions -for improvement of @value{GDBN} are welcome in any case. -@end itemize - -@node Bug Reporting -@section How to Report Bugs -@cindex bug reports -@cindex @value{GDBN} bugs, reporting - -A number of companies and individuals offer support for @sc{gnu} products. -If you obtained @value{GDBN} from a support organization, we recommend you -contact that organization first. - -You can find contact information for many support companies and -individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs -distribution. -@c should add a web page ref... - -@ifset BUGURL -@ifset BUGURL_DEFAULT -In any event, we also recommend that you submit bug reports for -@value{GDBN}. The preferred method is to submit them directly using -@uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web -page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can -be used. - -@strong{Do not send bug reports to @samp{info-gdb}, or to -@samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do -not want to receive bug reports. Those that do have arranged to receive -@samp{bug-gdb}. - -The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which -serves as a repeater. The mailing list and the newsgroup carry exactly -the same messages. Often people think of posting bug reports to the -newsgroup instead of mailing them. This appears to work, but it has one -problem which can be crucial: a newsgroup posting often lacks a mail -path back to the sender. Thus, if we need to ask for more information, -we may be unable to reach you. For this reason, it is better to send -bug reports to the mailing list. -@end ifset -@ifclear BUGURL_DEFAULT -In any event, we also recommend that you submit bug reports for -@value{GDBN} to @value{BUGURL}. -@end ifclear -@end ifset - -The fundamental principle of reporting bugs usefully is this: -@strong{report all the facts}. If you are not sure whether to state a -fact or leave it out, state it! - -Often people omit facts because they think they know what causes the -problem and assume that some details do not matter. Thus, you might -assume that the name of the variable you use in an example does not matter. -Well, probably it does not, but one cannot be sure. Perhaps the bug is a -stray memory reference which happens to fetch from the location where that -name is stored in memory; perhaps, if the name were different, the contents -of that location would fool the debugger into doing the right thing despite -the bug. Play it safe and give a specific, complete example. That is the -easiest thing for you to do, and the most helpful. - -Keep in mind that the purpose of a bug report is to enable us to fix the -bug. It may be that the bug has been reported previously, but neither -you nor we can know that unless your bug report is complete and -self-contained. - -Sometimes people give a few sketchy facts and ask, ``Does this ring a -bell?'' Those bug reports are useless, and we urge everyone to -@emph{refuse to respond to them} except to chide the sender to report -bugs properly. - -To enable us to fix the bug, you should include all these things: - -@itemize @bullet -@item -The version of @value{GDBN}. @value{GDBN} announces it if you start -with no arguments; you can also print it at any time using @code{show -version}. - -Without this, we will not know whether there is any point in looking for -the bug in the current version of @value{GDBN}. - -@item -The type of machine you are using, and the operating system name and -version number. - -@item -What compiler (and its version) was used to compile @value{GDBN}---e.g.@: -``@value{GCC}--2.8.1''. - -@item -What compiler (and its version) was used to compile the program you are -debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP -C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version} -to get this information; for other compilers, see the documentation for -those compilers. - -@item -The command arguments you gave the compiler to compile your example and -observe the bug. For example, did you use @samp{-O}? To guarantee -you will not omit something important, list them all. A copy of the -Makefile (or the output from make) is sufficient. - -If we were to try to guess the arguments, we would probably guess wrong -and then we might not encounter the bug. - -@item -A complete input script, and all necessary source files, that will -reproduce the bug. - -@item -A description of what behavior you observe that you believe is -incorrect. For example, ``It gets a fatal signal.'' - -Of course, if the bug is that @value{GDBN} gets a fatal signal, then we -will certainly notice it. But if the bug is incorrect output, we might -not notice unless it is glaringly wrong. You might as well not give us -a chance to make a mistake. - -Even if the problem you experience is a fatal signal, you should still -say so explicitly. Suppose something strange is going on, such as, your -copy of @value{GDBN} is out of synch, or you have encountered a bug in -the C library on your system. (This has happened!) Your copy might -crash and ours would not. If you told us to expect a crash, then when -ours fails to crash, we would know that the bug was not happening for -us. If you had not told us to expect a crash, then we would not be able -to draw any conclusion from our observations. - -@pindex script -@cindex recording a session script -To collect all this information, you can use a session recording program -such as @command{script}, which is available on many Unix systems. -Just run your @value{GDBN} session inside @command{script} and then -include the @file{typescript} file with your bug report. - -Another way to record a @value{GDBN} session is to run @value{GDBN} -inside Emacs and then save the entire buffer to a file. - -@item -If you wish to suggest changes to the @value{GDBN} source, send us context -diffs. If you even discuss something in the @value{GDBN} source, refer to -it by context, not by line number. - -The line numbers in our development sources will not match those in your -sources. Your line numbers would convey no useful information to us. - -@end itemize - -Here are some things that are not necessary: - -@itemize @bullet -@item -A description of the envelope of the bug. - -Often people who encounter a bug spend a lot of time investigating -which changes to the input file will make the bug go away and which -changes will not affect it. - -This is often time consuming and not very useful, because the way we -will find the bug is by running a single example under the debugger -with breakpoints, not by pure deduction from a series of examples. -We recommend that you save your time for something else. - -Of course, if you can find a simpler example to report @emph{instead} -of the original one, that is a convenience for us. Errors in the -output will be easier to spot, running under the debugger will take -less time, and so on. - -However, simplification is not vital; if you do not want to do this, -report the bug anyway and send us the entire test case you used. - -@item -A patch for the bug. - -A patch for the bug does help us if it is a good one. But do not omit -the necessary information, such as the test case, on the assumption that -a patch is all we need. We might see problems with your patch and decide -to fix the problem another way, or we might not understand it at all. - -Sometimes with a program as complicated as @value{GDBN} it is very hard to -construct an example that will make the program follow a certain path -through the code. If you do not send us the example, we will not be able -to construct one, so we will not be able to verify that the bug is fixed. - -And if we cannot understand what bug you are trying to fix, or why your -patch should be an improvement, we will not install it. A test case will -help us to understand. - -@item -A guess about what the bug is or what it depends on. - -Such guesses are usually wrong. Even we cannot guess right about such -things without first using the debugger to find the facts. -@end itemize - -@c The readline documentation is distributed with the readline code -@c and consists of the two following files: -@c rluser.texi -@c hsuser.texi -@c Use -I with makeinfo to point to the appropriate directory, -@c environment var TEXINPUTS with TeX. -@ifclear SYSTEM_READLINE -@include rluser.texi -@include hsuser.texi -@end ifclear - -@node In Memoriam -@appendix In Memoriam - -The @value{GDBN} project mourns the loss of the following long-time -contributors: - -@table @code -@item Fred Fish -Fred was a long-standing contributor to @value{GDBN} (1991-2006), and -to Free Software in general. Outside of @value{GDBN}, he was known in -the Amiga world for his series of Fish Disks, and the GeekGadget project. - -@item Michael Snyder -Michael was one of the Global Maintainers of the @value{GDBN} project, -with contributions recorded as early as 1996, until 2011. In addition -to his day to day participation, he was a large driving force behind -adding Reverse Debugging to @value{GDBN}. -@end table - -Beyond their technical contributions to the project, they were also -enjoyable members of the Free Software Community. We will miss them. - -@node Formatting Documentation -@appendix Formatting Documentation - -@cindex @value{GDBN} reference card -@cindex reference card -The @value{GDBN} 4 release includes an already-formatted reference card, ready -for printing with PostScript or Ghostscript, in the @file{gdb} -subdirectory of the main source directory@footnote{In -@file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN} -release.}. If you can use PostScript or Ghostscript with your printer, -you can print the reference card immediately with @file{refcard.ps}. - -The release also includes the source for the reference card. You -can format it, using @TeX{}, by typing: - -@smallexample -make refcard.dvi -@end smallexample - -The @value{GDBN} reference card is designed to print in @dfn{landscape} -mode on US ``letter'' size paper; -that is, on a sheet 11 inches wide by 8.5 inches -high. You will need to specify this form of printing as an option to -your @sc{dvi} output program. - -@cindex documentation - -All the documentation for @value{GDBN} comes as part of the machine-readable -distribution. The documentation is written in Texinfo format, which is -a documentation system that uses a single source file to produce both -on-line information and a printed manual. You can use one of the Info -formatting commands to create the on-line version of the documentation -and @TeX{} (or @code{texi2roff}) to typeset the printed version. - -@value{GDBN} includes an already formatted copy of the on-line Info -version of this manual in the @file{gdb} subdirectory. The main Info -file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to -subordinate files matching @samp{gdb.info*} in the same directory. If -necessary, you can print out these files, or read them with any editor; -but they are easier to read using the @code{info} subsystem in @sc{gnu} -Emacs or the standalone @code{info} program, available as part of the -@sc{gnu} Texinfo distribution. - -If you want to format these Info files yourself, you need one of the -Info formatting programs, such as @code{texinfo-format-buffer} or -@code{makeinfo}. - -If you have @code{makeinfo} installed, and are in the top level -@value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of -version @value{GDBVN}), you can make the Info file by typing: - -@smallexample -cd gdb -make gdb.info -@end smallexample - -If you want to typeset and print copies of this manual, you need @TeX{}, -a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the -Texinfo definitions file. - -@TeX{} is a typesetting program; it does not print files directly, but -produces output files called @sc{dvi} files. To print a typeset -document, you need a program to print @sc{dvi} files. If your system -has @TeX{} installed, chances are it has such a program. The precise -command to use depends on your system; @kbd{lpr -d} is common; another -(for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may -require a file name without any extension or a @samp{.dvi} extension. - -@TeX{} also requires a macro definitions file called -@file{texinfo.tex}. This file tells @TeX{} how to typeset a document -written in Texinfo format. On its own, @TeX{} cannot either read or -typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB -and is located in the @file{gdb-@var{version-number}/texinfo} -directory. - -If you have @TeX{} and a @sc{dvi} printer program installed, you can -typeset and print this manual. First switch to the @file{gdb} -subdirectory of the main source directory (for example, to -@file{gdb-@value{GDBVN}/gdb}) and type: - -@smallexample -make gdb.dvi -@end smallexample - -Then give @file{gdb.dvi} to your @sc{dvi} printing program. - -@node Installing GDB -@appendix Installing @value{GDBN} -@cindex installation - -@menu -* Requirements:: Requirements for building @value{GDBN} -* Running Configure:: Invoking the @value{GDBN} @file{configure} script -* Separate Objdir:: Compiling @value{GDBN} in another directory -* Config Names:: Specifying names for hosts and targets -* Configure Options:: Summary of options for configure -* System-wide configuration:: Having a system-wide init file -@end menu - -@node Requirements -@section Requirements for Building @value{GDBN} -@cindex building @value{GDBN}, requirements for - -Building @value{GDBN} requires various tools and packages to be available. -Other packages will be used only if they are found. - -@heading Tools/Packages Necessary for Building @value{GDBN} -@table @asis -@item ISO C90 compiler -@value{GDBN} is written in ISO C90. It should be buildable with any -working C90 compiler, e.g.@: GCC. - -@end table - -@heading Tools/Packages Optional for Building @value{GDBN} -@table @asis -@item Expat -@anchor{Expat} -@value{GDBN} can use the Expat XML parsing library. This library may be -included with your operating system distribution; if it is not, you -can get the latest version from @url{http://expat.sourceforge.net}. -The @file{configure} script will search for this library in several -standard locations; if it is installed in an unusual path, you can -use the @option{--with-libexpat-prefix} option to specify its location. - -Expat is used for: - -@itemize @bullet -@item -Remote protocol memory maps (@pxref{Memory Map Format}) -@item -Target descriptions (@pxref{Target Descriptions}) -@item -Remote shared library lists (@xref{Library List Format}, -or alternatively @pxref{Library List Format for SVR4 Targets}) -@item -MS-Windows shared libraries (@pxref{Shared Libraries}) -@item -Traceframe info (@pxref{Traceframe Info Format}) -@item -Branch trace (@pxref{Branch Trace Format}) -@end itemize - -@item zlib -@cindex compressed debug sections -@value{GDBN} will use the @samp{zlib} library, if available, to read -compressed debug sections. Some linkers, such as GNU gold, are capable -of producing binaries with compressed debug sections. If @value{GDBN} -is compiled with @samp{zlib}, it will be able to read the debug -information in such binaries. - -The @samp{zlib} library is likely included with your operating system -distribution; if it is not, you can get the latest version from -@url{http://zlib.net}. - -@item iconv -@value{GDBN}'s features related to character sets (@pxref{Character -Sets}) require a functioning @code{iconv} implementation. If you are -on a GNU system, then this is provided by the GNU C Library. Some -other systems also provide a working @code{iconv}. - -If @value{GDBN} is using the @code{iconv} program which is installed -in a non-standard place, you will need to tell @value{GDBN} where to find it. -This is done with @option{--with-iconv-bin} which specifies the -directory that contains the @code{iconv} program. - -On systems without @code{iconv}, you can install GNU Libiconv. If you -have previously installed Libiconv, you can use the -@option{--with-libiconv-prefix} option to configure. - -@value{GDBN}'s top-level @file{configure} and @file{Makefile} will -arrange to build Libiconv if a directory named @file{libiconv} appears -in the top-most source directory. If Libiconv is built this way, and -if the operating system does not provide a suitable @code{iconv} -implementation, then the just-built library will automatically be used -by @value{GDBN}. One easy way to set this up is to download GNU -Libiconv, unpack it, and then rename the directory holding the -Libiconv source code to @samp{libiconv}. -@end table - -@node Running Configure -@section Invoking the @value{GDBN} @file{configure} Script -@cindex configuring @value{GDBN} -@value{GDBN} comes with a @file{configure} script that automates the process -of preparing @value{GDBN} for installation; you can then use @code{make} to -build the @code{gdb} program. -@iftex -@c irrelevant in info file; it's as current as the code it lives with. -@footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN}, -look at the @file{README} file in the sources; we may have improved the -installation procedures since publishing this manual.} -@end iftex - -The @value{GDBN} distribution includes all the source code you need for -@value{GDBN} in a single directory, whose name is usually composed by -appending the version number to @samp{gdb}. - -For example, the @value{GDBN} version @value{GDBVN} distribution is in the -@file{gdb-@value{GDBVN}} directory. That directory contains: - -@table @code -@item gdb-@value{GDBVN}/configure @r{(and supporting files)} -script for configuring @value{GDBN} and all its supporting libraries - -@item gdb-@value{GDBVN}/gdb -the source specific to @value{GDBN} itself - -@item gdb-@value{GDBVN}/bfd -source for the Binary File Descriptor library - -@item gdb-@value{GDBVN}/include -@sc{gnu} include files - -@item gdb-@value{GDBVN}/libiberty -source for the @samp{-liberty} free software library - -@item gdb-@value{GDBVN}/opcodes -source for the library of opcode tables and disassemblers - -@item gdb-@value{GDBVN}/readline -source for the @sc{gnu} command-line interface - -@item gdb-@value{GDBVN}/glob -source for the @sc{gnu} filename pattern-matching subroutine - -@item gdb-@value{GDBVN}/mmalloc -source for the @sc{gnu} memory-mapped malloc package -@end table - -The simplest way to configure and build @value{GDBN} is to run @file{configure} -from the @file{gdb-@var{version-number}} source directory, which in -this example is the @file{gdb-@value{GDBVN}} directory. - -First switch to the @file{gdb-@var{version-number}} source directory -if you are not already in it; then run @file{configure}. Pass the -identifier for the platform on which @value{GDBN} will run as an -argument. - -For example: - -@smallexample -cd gdb-@value{GDBVN} -./configure @var{host} -make -@end smallexample - -@noindent -where @var{host} is an identifier such as @samp{sun4} or -@samp{decstation}, that identifies the platform where @value{GDBN} will run. -(You can often leave off @var{host}; @file{configure} tries to guess the -correct value by examining your system.) - -Running @samp{configure @var{host}} and then running @code{make} builds the -@file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty} -libraries, then @code{gdb} itself. The configured source files, and the -binaries, are left in the corresponding source directories. - -@need 750 -@file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your -system does not recognize this automatically when you run a different -shell, you may need to run @code{sh} on it explicitly: - -@smallexample -sh configure @var{host} -@end smallexample - -If you run @file{configure} from a directory that contains source -directories for multiple libraries or programs, such as the -@file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, -@file{configure} -creates configuration files for every directory level underneath (unless -you tell it not to, with the @samp{--norecursion} option). - -You should run the @file{configure} script from the top directory in the -source tree, the @file{gdb-@var{version-number}} directory. If you run -@file{configure} from one of the subdirectories, you will configure only -that subdirectory. That is usually not what you want. In particular, -if you run the first @file{configure} from the @file{gdb} subdirectory -of the @file{gdb-@var{version-number}} directory, you will omit the -configuration of @file{bfd}, @file{readline}, and other sibling -directories of the @file{gdb} subdirectory. This leads to build errors -about missing include files such as @file{bfd/bfd.h}. - -You can install @code{@value{GDBP}} anywhere; it has no hardwired paths. -However, you should make sure that the shell on your path (named by -the @samp{SHELL} environment variable) is publicly readable. Remember -that @value{GDBN} uses the shell to start your program---some systems refuse to -let @value{GDBN} debug child processes whose programs are not readable. - -@node Separate Objdir -@section Compiling @value{GDBN} in Another Directory - -If you want to run @value{GDBN} versions for several host or target machines, -you need a different @code{gdb} compiled for each combination of -host and target. @file{configure} is designed to make this easy by -allowing you to generate each configuration in a separate subdirectory, -rather than in the source directory. If your @code{make} program -handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running -@code{make} in each of these directories builds the @code{gdb} -program specified there. - -To build @code{gdb} in a separate directory, run @file{configure} -with the @samp{--srcdir} option to specify where to find the source. -(You also need to specify a path to find @file{configure} -itself from your working directory. If the path to @file{configure} -would be the same as the argument to @samp{--srcdir}, you can leave out -the @samp{--srcdir} option; it is assumed.) - -For example, with version @value{GDBVN}, you can build @value{GDBN} in a -separate directory for a Sun 4 like this: - -@smallexample -@group -cd gdb-@value{GDBVN} -mkdir ../gdb-sun4 -cd ../gdb-sun4 -../gdb-@value{GDBVN}/configure sun4 -make -@end group -@end smallexample - -When @file{configure} builds a configuration using a remote source -directory, it creates a tree for the binaries with the same structure -(and using the same names) as the tree under the source directory. In -the example, you'd find the Sun 4 library @file{libiberty.a} in the -directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in -@file{gdb-sun4/gdb}. - -Make sure that your path to the @file{configure} script has just one -instance of @file{gdb} in it. If your path to @file{configure} looks -like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only -one subdirectory of @value{GDBN}, not the whole package. This leads to -build errors about missing include files such as @file{bfd/bfd.h}. - -One popular reason to build several @value{GDBN} configurations in separate -directories is to configure @value{GDBN} for cross-compiling (where -@value{GDBN} runs on one machine---the @dfn{host}---while debugging -programs that run on another machine---the @dfn{target}). -You specify a cross-debugging target by -giving the @samp{--target=@var{target}} option to @file{configure}. - -When you run @code{make} to build a program or library, you must run -it in a configured directory---whatever directory you were in when you -called @file{configure} (or one of its subdirectories). - -The @code{Makefile} that @file{configure} generates in each source -directory also runs recursively. If you type @code{make} in a source -directory such as @file{gdb-@value{GDBVN}} (or in a separate configured -directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you -will build all the required libraries, and then build GDB. - -When you have multiple hosts or targets configured in separate -directories, you can run @code{make} on them in parallel (for example, -if they are NFS-mounted on each of the hosts); they will not interfere -with each other. - -@node Config Names -@section Specifying Names for Hosts and Targets - -The specifications used for hosts and targets in the @file{configure} -script are based on a three-part naming scheme, but some short predefined -aliases are also supported. The full naming scheme encodes three pieces -of information in the following pattern: - -@smallexample -@var{architecture}-@var{vendor}-@var{os} -@end smallexample - -For example, you can use the alias @code{sun4} as a @var{host} argument, -or as the value for @var{target} in a @code{--target=@var{target}} -option. The equivalent full name is @samp{sparc-sun-sunos4}. - -The @file{configure} script accompanying @value{GDBN} does not provide -any query facility to list all supported host and target names or -aliases. @file{configure} calls the Bourne shell script -@code{config.sub} to map abbreviations to full names; you can read the -script, if you wish, or you can use it to test your guesses on -abbreviations---for example: - -@smallexample -% sh config.sub i386-linux -i386-pc-linux-gnu -% sh config.sub alpha-linux -alpha-unknown-linux-gnu -% sh config.sub hp9k700 -hppa1.1-hp-hpux -% sh config.sub sun4 -sparc-sun-sunos4.1.1 -% sh config.sub sun3 -m68k-sun-sunos4.1.1 -% sh config.sub i986v -Invalid configuration `i986v': machine `i986v' not recognized -@end smallexample - -@noindent -@code{config.sub} is also distributed in the @value{GDBN} source -directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}). - -@node Configure Options -@section @file{configure} Options - -Here is a summary of the @file{configure} options and arguments that -are most often useful for building @value{GDBN}. @file{configure} also has -several other options not listed here. @inforef{What Configure -Does,,configure.info}, for a full explanation of @file{configure}. - -@smallexample -configure @r{[}--help@r{]} - @r{[}--prefix=@var{dir}@r{]} - @r{[}--exec-prefix=@var{dir}@r{]} - @r{[}--srcdir=@var{dirname}@r{]} - @r{[}--norecursion@r{]} @r{[}--rm@r{]} - @r{[}--target=@var{target}@r{]} - @var{host} -@end smallexample - -@noindent -You may introduce options with a single @samp{-} rather than -@samp{--} if you prefer; but you may abbreviate option names if you use -@samp{--}. - -@table @code -@item --help -Display a quick summary of how to invoke @file{configure}. - -@item --prefix=@var{dir} -Configure the source to install programs and files under directory -@file{@var{dir}}. - -@item --exec-prefix=@var{dir} -Configure the source to install programs under directory -@file{@var{dir}}. - -@c avoid splitting the warning from the explanation: -@need 2000 -@item --srcdir=@var{dirname} -@strong{Warning: using this option requires @sc{gnu} @code{make}, or another -@code{make} that implements the @code{VPATH} feature.}@* -Use this option to make configurations in directories separate from the -@value{GDBN} source directories. Among other things, you can use this to -build (or maintain) several configurations simultaneously, in separate -directories. @file{configure} writes configuration-specific files in -the current directory, but arranges for them to use the source in the -directory @var{dirname}. @file{configure} creates directories under -the working directory in parallel to the source directories below -@var{dirname}. - -@item --norecursion -Configure only the directory level where @file{configure} is executed; do not -propagate configuration to subdirectories. - -@item --target=@var{target} -Configure @value{GDBN} for cross-debugging programs running on the specified -@var{target}. Without this option, @value{GDBN} is configured to debug -programs that run on the same machine (@var{host}) as @value{GDBN} itself. - -There is no convenient way to generate a list of all available targets. - -@item @var{host} @dots{} -Configure @value{GDBN} to run on the specified @var{host}. - -There is no convenient way to generate a list of all available hosts. -@end table - -There are many other options available as well, but they are generally -needed for special purposes only. - -@node System-wide configuration -@section System-wide configuration and settings -@cindex system-wide init file - -@value{GDBN} can be configured to have a system-wide init file; -this file will be read and executed at startup (@pxref{Startup, , What -@value{GDBN} does during startup}). - -Here is the corresponding configure option: - -@table @code -@item --with-system-gdbinit=@var{file} -Specify that the default location of the system-wide init file is -@var{file}. -@end table - -If @value{GDBN} has been configured with the option @option{--prefix=$prefix}, -it may be subject to relocation. Two possible cases: - -@itemize @bullet -@item -If the default location of this init file contains @file{$prefix}, -it will be subject to relocation. Suppose that the configure options -are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit}; -if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system -init file is looked for as @file{$install/etc/gdbinit} instead of -@file{$prefix/etc/gdbinit}. - -@item -By contrast, if the default location does not contain the prefix, -it will not be relocated. E.g.@: if @value{GDBN} has been configured with -@option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit}, -then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit}, -wherever @value{GDBN} is installed. -@end itemize - -If the configured location of the system-wide init file (as given by the -@option{--with-system-gdbinit} option at configure time) is in the -data-directory (as specified by @option{--with-gdb-datadir} at configure -time) or in one of its subdirectories, then @value{GDBN} will look for the -system-wide init file in the directory specified by the -@option{--data-directory} command-line option. -Note that the system-wide init file is only read once, during @value{GDBN} -initialization. If the data-directory is changed after @value{GDBN} has -started with the @code{set data-directory} command, the file will not be -reread. - -@node Maintenance Commands -@appendix Maintenance Commands -@cindex maintenance commands -@cindex internal commands - -In addition to commands intended for @value{GDBN} users, @value{GDBN} -includes a number of commands intended for @value{GDBN} developers, -that are not documented elsewhere in this manual. These commands are -provided here for reference. (For commands that turn on debugging -messages, see @ref{Debugging Output}.) - -@table @code -@kindex maint agent -@kindex maint agent-eval -@item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression} -@itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression} -Translate the given @var{expression} into remote agent bytecodes. -This command is useful for debugging the Agent Expression mechanism -(@pxref{Agent Expressions}). The @samp{agent} version produces an -expression useful for data collection, such as by tracepoints, while -@samp{maint agent-eval} produces an expression that evaluates directly -to a result. For instance, a collection expression for @code{globa + -globb} will include bytecodes to record four bytes of memory at each -of the addresses of @code{globa} and @code{globb}, while discarding -the result of the addition, while an evaluation expression will do the -addition and return the sum. -If @code{-at} is given, generate remote agent bytecode for @var{location}. -If not, generate remote agent bytecode for current frame PC address. - -@kindex maint agent-printf -@item maint agent-printf @var{format},@var{expr},... -Translate the given format string and list of argument expressions -into remote agent bytecodes and display them as a disassembled list. -This command is useful for debugging the agent version of dynamic -printf (@pxref{Dynamic Printf}. - -@kindex maint info breakpoints -@item @anchor{maint info breakpoints}maint info breakpoints -Using the same format as @samp{info breakpoints}, display both the -breakpoints you've set explicitly, and those @value{GDBN} is using for -internal purposes. Internal breakpoints are shown with negative -breakpoint numbers. The type column identifies what kind of breakpoint -is shown: - -@table @code -@item breakpoint -Normal, explicitly set breakpoint. - -@item watchpoint -Normal, explicitly set watchpoint. - -@item longjmp -Internal breakpoint, used to handle correctly stepping through -@code{longjmp} calls. - -@item longjmp resume -Internal breakpoint at the target of a @code{longjmp}. - -@item until -Temporary internal breakpoint used by the @value{GDBN} @code{until} command. - -@item finish -Temporary internal breakpoint used by the @value{GDBN} @code{finish} command. - -@item shlib events -Shared library events. - -@end table - -@kindex maint info bfds -@item maint info bfds -This prints information about each @code{bfd} object that is known to -@value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}. - -@kindex set displaced-stepping -@kindex show displaced-stepping -@cindex displaced stepping support -@cindex out-of-line single-stepping -@item set displaced-stepping -@itemx show displaced-stepping -Control whether or not @value{GDBN} will do @dfn{displaced stepping} -if the target supports it. Displaced stepping is a way to single-step -over breakpoints without removing them from the inferior, by executing -an out-of-line copy of the instruction that was originally at the -breakpoint location. It is also known as out-of-line single-stepping. - -@table @code -@item set displaced-stepping on -If the target architecture supports it, @value{GDBN} will use -displaced stepping to step over breakpoints. - -@item set displaced-stepping off -@value{GDBN} will not use displaced stepping to step over breakpoints, -even if such is supported by the target architecture. - -@cindex non-stop mode, and @samp{set displaced-stepping} -@item set displaced-stepping auto -This is the default mode. @value{GDBN} will use displaced stepping -only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target -architecture supports displaced stepping. -@end table - -@kindex maint check-symtabs -@item maint check-symtabs -Check the consistency of psymtabs and symtabs. - -@kindex maint cplus first_component -@item maint cplus first_component @var{name} -Print the first C@t{++} class/namespace component of @var{name}. - -@kindex maint cplus namespace -@item maint cplus namespace -Print the list of possible C@t{++} namespaces. - -@kindex maint demangle -@item maint demangle @var{name} -Demangle a C@t{++} or Objective-C mangled @var{name}. - -@kindex maint deprecate -@kindex maint undeprecate -@cindex deprecated commands -@item maint deprecate @var{command} @r{[}@var{replacement}@r{]} -@itemx maint undeprecate @var{command} -Deprecate or undeprecate the named @var{command}. Deprecated commands -cause @value{GDBN} to issue a warning when you use them. The optional -argument @var{replacement} says which newer command should be used in -favor of the deprecated one; if it is given, @value{GDBN} will mention -the replacement as part of the warning. - -@kindex maint dump-me -@item maint dump-me -@cindex @code{SIGQUIT} signal, dump core of @value{GDBN} -Cause a fatal signal in the debugger and force it to dump its core. -This is supported only on systems which support aborting a program -with the @code{SIGQUIT} signal. - -@kindex maint internal-error -@kindex maint internal-warning -@item maint internal-error @r{[}@var{message-text}@r{]} -@itemx maint internal-warning @r{[}@var{message-text}@r{]} -Cause @value{GDBN} to call the internal function @code{internal_error} -or @code{internal_warning} and hence behave as though an internal error -or internal warning has been detected. In addition to reporting the -internal problem, these functions give the user the opportunity to -either quit @value{GDBN} or create a core file of the current -@value{GDBN} session. - -These commands take an optional parameter @var{message-text} that is -used as the text of the error or warning message. - -Here's an example of using @code{internal-error}: - -@smallexample -(@value{GDBP}) @kbd{maint internal-error testing, 1, 2} -@dots{}/maint.c:121: internal-error: testing, 1, 2 -A problem internal to GDB has been detected. Further -debugging may prove unreliable. -Quit this debugging session? (y or n) @kbd{n} -Create a core file? (y or n) @kbd{n} -(@value{GDBP}) -@end smallexample - -@cindex @value{GDBN} internal error -@cindex internal errors, control of @value{GDBN} behavior - -@kindex maint set internal-error -@kindex maint show internal-error -@kindex maint set internal-warning -@kindex maint show internal-warning -@item maint set internal-error @var{action} [ask|yes|no] -@itemx maint show internal-error @var{action} -@itemx maint set internal-warning @var{action} [ask|yes|no] -@itemx maint show internal-warning @var{action} -When @value{GDBN} reports an internal problem (error or warning) it -gives the user the opportunity to both quit @value{GDBN} and create a -core file of the current @value{GDBN} session. These commands let you -override the default behaviour for each particular @var{action}, -described in the table below. - -@table @samp -@item quit -You can specify that @value{GDBN} should always (yes) or never (no) -quit. The default is to ask the user what to do. - -@item corefile -You can specify that @value{GDBN} should always (yes) or never (no) -create a core file. The default is to ask the user what to do. -@end table - -@kindex maint packet -@item maint packet @var{text} -If @value{GDBN} is talking to an inferior via the serial protocol, -then this command sends the string @var{text} to the inferior, and -displays the response packet. @value{GDBN} supplies the initial -@samp{$} character, the terminating @samp{#} character, and the -checksum. - -@kindex maint print architecture -@item maint print architecture @r{[}@var{file}@r{]} -Print the entire architecture configuration. The optional argument -@var{file} names the file where the output goes. - -@kindex maint print c-tdesc -@item maint print c-tdesc -Print the current target description (@pxref{Target Descriptions}) as -a C source file. The created source file can be used in @value{GDBN} -when an XML parser is not available to parse the description. - -@kindex maint print dummy-frames -@item maint print dummy-frames -Prints the contents of @value{GDBN}'s internal dummy-frame stack. - -@smallexample -(@value{GDBP}) @kbd{b add} -@dots{} -(@value{GDBP}) @kbd{print add(2,3)} -Breakpoint 2, add (a=2, b=3) at @dots{} -58 return (a + b); -The program being debugged stopped while in a function called from GDB. -@dots{} -(@value{GDBP}) @kbd{maint print dummy-frames} -0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6 - top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@} - call_lo=0x01014000 call_hi=0x01014001 -(@value{GDBP}) -@end smallexample - -Takes an optional file parameter. - -@kindex maint print registers -@kindex maint print raw-registers -@kindex maint print cooked-registers -@kindex maint print register-groups -@kindex maint print remote-registers -@item maint print registers @r{[}@var{file}@r{]} -@itemx maint print raw-registers @r{[}@var{file}@r{]} -@itemx maint print cooked-registers @r{[}@var{file}@r{]} -@itemx maint print register-groups @r{[}@var{file}@r{]} -@itemx maint print remote-registers @r{[}@var{file}@r{]} -Print @value{GDBN}'s internal register data structures. - -The command @code{maint print raw-registers} includes the contents of -the raw register cache; the command @code{maint print -cooked-registers} includes the (cooked) value of all registers, -including registers which aren't available on the target nor visible -to user; the command @code{maint print register-groups} includes the -groups that each register is a member of; and the command @code{maint -print remote-registers} includes the remote target's register numbers -and offsets in the `G' packets. @xref{Registers,, Registers, gdbint, -@value{GDBN} Internals}. - -These commands take an optional parameter, a file name to which to -write the information. - -@kindex maint print reggroups -@item maint print reggroups @r{[}@var{file}@r{]} -Print @value{GDBN}'s internal register group data structures. The -optional argument @var{file} tells to what file to write the -information. - -The register groups info looks like this: - -@smallexample -(@value{GDBP}) @kbd{maint print reggroups} - Group Type - general user - float user - all user - vector user - system user - save internal - restore internal -@end smallexample - -@kindex flushregs -@item flushregs -This command forces @value{GDBN} to flush its internal register cache. - -@kindex maint print objfiles -@cindex info for known object files -@item maint print objfiles -Print a dump of all known object files. For each object file, this -command prints its name, address in memory, and all of its psymtabs -and symtabs. - -@kindex maint print section-scripts -@cindex info for known .debug_gdb_scripts-loaded scripts -@item maint print section-scripts [@var{regexp}] -Print a dump of scripts specified in the @code{.debug_gdb_section} section. -If @var{regexp} is specified, only print scripts loaded by object files -matching @var{regexp}. -For each script, this command prints its name as specified in the objfile, -and the full path if known. -@xref{dotdebug_gdb_scripts section}. - -@kindex maint print statistics -@cindex bcache statistics -@item maint print statistics -This command prints, for each object file in the program, various data -about that object file followed by the byte cache (@dfn{bcache}) -statistics for the object file. The objfile data includes the number -of minimal, partial, full, and stabs symbols, the number of types -defined by the objfile, the number of as yet unexpanded psym tables, -the number of line tables and string tables, and the amount of memory -used by the various tables. The bcache statistics include the counts, -sizes, and counts of duplicates of all and unique objects, max, -average, and median entry size, total memory used and its overhead and -savings, and various measures of the hash table size and chain -lengths. - -@kindex maint print target-stack -@cindex target stack description -@item maint print target-stack -A @dfn{target} is an interface between the debugger and a particular -kind of file or process. Targets can be stacked in @dfn{strata}, -so that more than one target can potentially respond to a request. -In particular, memory accesses will walk down the stack of targets -until they find a target that is interested in handling that particular -address. - -This command prints a short description of each layer that was pushed on -the @dfn{target stack}, starting from the top layer down to the bottom one. - -@kindex maint print type -@cindex type chain of a data type -@item maint print type @var{expr} -Print the type chain for a type specified by @var{expr}. The argument -can be either a type name or a symbol. If it is a symbol, the type of -that symbol is described. The type chain produced by this command is -a recursive definition of the data type as stored in @value{GDBN}'s -data structures, including its flags and contained types. - -@kindex maint set dwarf2 always-disassemble -@kindex maint show dwarf2 always-disassemble -@item maint set dwarf2 always-disassemble -@item maint show dwarf2 always-disassemble -Control the behavior of @code{info address} when using DWARF debugging -information. - -The default is @code{off}, which means that @value{GDBN} should try to -describe a variable's location in an easily readable format. When -@code{on}, @value{GDBN} will instead display the DWARF location -expression in an assembly-like format. Note that some locations are -too complex for @value{GDBN} to describe simply; in this case you will -always see the disassembly form. - -Here is an example of the resulting disassembly: - -@smallexample -(gdb) info addr argc -Symbol "argc" is a complex DWARF expression: - 1: DW_OP_fbreg 0 -@end smallexample - -For more information on these expressions, see -@uref{http://www.dwarfstd.org/, the DWARF standard}. - -@kindex maint set dwarf2 max-cache-age -@kindex maint show dwarf2 max-cache-age -@item maint set dwarf2 max-cache-age -@itemx maint show dwarf2 max-cache-age -Control the DWARF 2 compilation unit cache. - -@cindex DWARF 2 compilation units cache -In object files with inter-compilation-unit references, such as those -produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2 -reader needs to frequently refer to previously read compilation units. -This setting controls how long a compilation unit will remain in the -cache if it is not referenced. A higher limit means that cached -compilation units will be stored in memory longer, and more total -memory will be used. Setting it to zero disables caching, which will -slow down @value{GDBN} startup, but reduce memory consumption. - -@kindex maint set profile -@kindex maint show profile -@cindex profiling GDB -@item maint set profile -@itemx maint show profile -Control profiling of @value{GDBN}. - -Profiling will be disabled until you use the @samp{maint set profile} -command to enable it. When you enable profiling, the system will begin -collecting timing and execution count data; when you disable profiling or -exit @value{GDBN}, the results will be written to a log file. Remember that -if you use profiling, @value{GDBN} will overwrite the profiling log file -(often called @file{gmon.out}). If you have a record of important profiling -data in a @file{gmon.out} file, be sure to move it to a safe location. - -Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be -compiled with the @samp{-pg} compiler option. - -@kindex maint set show-debug-regs -@kindex maint show show-debug-regs -@cindex hardware debug registers -@item maint set show-debug-regs -@itemx maint show show-debug-regs -Control whether to show variables that mirror the hardware debug -registers. Use @code{ON} to enable, @code{OFF} to disable. If -enabled, the debug registers values are shown when @value{GDBN} inserts or -removes a hardware breakpoint or watchpoint, and when the inferior -triggers a hardware-assisted breakpoint or watchpoint. - -@kindex maint set show-all-tib -@kindex maint show show-all-tib -@item maint set show-all-tib -@itemx maint show show-all-tib -Control whether to show all non zero areas within a 1k block starting -at thread local base, when using the @samp{info w32 thread-information-block} -command. - -@kindex maint space -@cindex memory used by commands -@item maint space -Control whether to display memory usage for each command. If set to a -nonzero value, @value{GDBN} will display how much memory each command -took, following the command's own output. This can also be requested -by invoking @value{GDBN} with the @option{--statistics} command-line -switch (@pxref{Mode Options}). - -@kindex maint time -@cindex time of command execution -@item maint time -Control whether to display the execution time of @value{GDBN} for each command. -If set to a nonzero value, @value{GDBN} will display how much time it -took to execute each command, following the command's own output. -Both CPU time and wallclock time are printed. -Printing both is useful when trying to determine whether the cost is -CPU or, e.g., disk/network, latency. -Note that the CPU time printed is for @value{GDBN} only, it does not include -the execution time of the inferior because there's no mechanism currently -to compute how much time was spent by @value{GDBN} and how much time was -spent by the program been debugged. -This can also be requested by invoking @value{GDBN} with the -@option{--statistics} command-line switch (@pxref{Mode Options}). - -@kindex maint translate-address -@item maint translate-address @r{[}@var{section}@r{]} @var{addr} -Find the symbol stored at the location specified by the address -@var{addr} and an optional section name @var{section}. If found, -@value{GDBN} prints the name of the closest symbol and an offset from -the symbol's location to the specified address. This is similar to -the @code{info address} command (@pxref{Symbols}), except that this -command also allows to find symbols in other sections. - -If section was not specified, the section in which the symbol was found -is also printed. For dynamically linked executables, the name of -executable or shared library containing the symbol is printed as well. - -@end table - -The following command is useful for non-interactive invocations of -@value{GDBN}, such as in the test suite. - -@table @code -@item set watchdog @var{nsec} -@kindex set watchdog -@cindex watchdog timer -@cindex timeout for commands -Set the maximum number of seconds @value{GDBN} will wait for the -target operation to finish. If this time expires, @value{GDBN} -reports and error and the command is aborted. - -@item show watchdog -Show the current setting of the target wait timeout. -@end table - -@node Remote Protocol -@appendix @value{GDBN} Remote Serial Protocol - -@menu -* Overview:: -* Packets:: -* Stop Reply Packets:: -* General Query Packets:: -* Architecture-Specific Protocol Details:: -* Tracepoint Packets:: -* Host I/O Packets:: -* Interrupts:: -* Notification Packets:: -* Remote Non-Stop:: -* Packet Acknowledgment:: -* Examples:: -* File-I/O Remote Protocol Extension:: -* Library List Format:: -* Library List Format for SVR4 Targets:: -* Memory Map Format:: -* Thread List Format:: -* Traceframe Info Format:: -* Branch Trace Format:: -@end menu - -@node Overview -@section Overview - -There may be occasions when you need to know something about the -protocol---for example, if there is only one serial port to your target -machine, you might want your program to do something special if it -recognizes a packet meant for @value{GDBN}. - -In the examples below, @samp{->} and @samp{<-} are used to indicate -transmitted and received data, respectively. - -@cindex protocol, @value{GDBN} remote serial -@cindex serial protocol, @value{GDBN} remote -@cindex remote serial protocol -All @value{GDBN} commands and responses (other than acknowledgments -and notifications, see @ref{Notification Packets}) are sent as a -@var{packet}. A @var{packet} is introduced with the character -@samp{$}, the actual @var{packet-data}, and the terminating character -@samp{#} followed by a two-digit @var{checksum}: - -@smallexample -@code{$}@var{packet-data}@code{#}@var{checksum} -@end smallexample -@noindent - -@cindex checksum, for @value{GDBN} remote -@noindent -The two-digit @var{checksum} is computed as the modulo 256 sum of all -characters between the leading @samp{$} and the trailing @samp{#} (an -eight bit unsigned checksum). - -Implementors should note that prior to @value{GDBN} 5.0 the protocol -specification also included an optional two-digit @var{sequence-id}: - -@smallexample -@code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum} -@end smallexample - -@cindex sequence-id, for @value{GDBN} remote -@noindent -That @var{sequence-id} was appended to the acknowledgment. @value{GDBN} -has never output @var{sequence-id}s. Stubs that handle packets added -since @value{GDBN} 5.0 must not accept @var{sequence-id}. - -When either the host or the target machine receives a packet, the first -response expected is an acknowledgment: either @samp{+} (to indicate -the package was received correctly) or @samp{-} (to request -retransmission): - -@smallexample --> @code{$}@var{packet-data}@code{#}@var{checksum} -<- @code{+} -@end smallexample -@noindent - -The @samp{+}/@samp{-} acknowledgments can be disabled -once a connection is established. -@xref{Packet Acknowledgment}, for details. - -The host (@value{GDBN}) sends @var{command}s, and the target (the -debugging stub incorporated in your program) sends a @var{response}. In -the case of step and continue @var{command}s, the response is only sent -when the operation has completed, and the target has again stopped all -threads in all attached processes. This is the default all-stop mode -behavior, but the remote protocol also supports @value{GDBN}'s non-stop -execution mode; see @ref{Remote Non-Stop}, for details. - -@var{packet-data} consists of a sequence of characters with the -exception of @samp{#} and @samp{$} (see @samp{X} packet for additional -exceptions). - -@cindex remote protocol, field separator -Fields within the packet should be separated using @samp{,} @samp{;} or -@samp{:}. Except where otherwise noted all numbers are represented in -@sc{hex} with leading zeros suppressed. - -Implementors should note that prior to @value{GDBN} 5.0, the character -@samp{:} could not appear as the third character in a packet (as it -would potentially conflict with the @var{sequence-id}). - -@cindex remote protocol, binary data -@anchor{Binary Data} -Binary data in most packets is encoded either as two hexadecimal -digits per byte of binary data. This allowed the traditional remote -protocol to work over connections which were only seven-bit clean. -Some packets designed more recently assume an eight-bit clean -connection, and use a more efficient encoding to send and receive -binary data. - -The binary data representation uses @code{7d} (@sc{ascii} @samp{@}}) -as an escape character. Any escaped byte is transmitted as the escape -character followed by the original character XORed with @code{0x20}. -For example, the byte @code{0x7d} would be transmitted as the two -bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}), -@code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii} -@samp{@}}) must always be escaped. Responses sent by the stub -must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it -is not interpreted as the start of a run-length encoded sequence -(described next). - -Response @var{data} can be run-length encoded to save space. -Run-length encoding replaces runs of identical characters with one -instance of the repeated character, followed by a @samp{*} and a -repeat count. The repeat count is itself sent encoded, to avoid -binary characters in @var{data}: a value of @var{n} is sent as -@code{@var{n}+29}. For a repeat count greater or equal to 3, this -produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii} -code 32) for a repeat count of 3. (This is because run-length -encoding starts to win for counts 3 or more.) Thus, for example, -@samp{0* } is a run-length encoding of ``0000'': the space character -after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 = -3}} more times. - -The printable characters @samp{#} and @samp{$} or with a numeric value -greater than 126 must not be used. Runs of six repeats (@samp{#}) or -seven repeats (@samp{$}) can be expanded using a repeat count of only -five (@samp{"}). For example, @samp{00000000} can be encoded as -@samp{0*"00}. - -The error response returned for some packets includes a two character -error number. That number is not well defined. - -@cindex empty response, for unsupported packets -For any @var{command} not supported by the stub, an empty response -(@samp{$#00}) should be returned. That way it is possible to extend the -protocol. A newer @value{GDBN} can tell if a packet is supported based -on that response. - -At a minimum, a stub is required to support the @samp{g} and @samp{G} -commands for register access, and the @samp{m} and @samp{M} commands -for memory access. Stubs that only control single-threaded targets -can implement run control with the @samp{c} (continue), and @samp{s} -(step) commands. Stubs that support multi-threading targets should -support the @samp{vCont} command. All other commands are optional. - -@node Packets -@section Packets - -The following table provides a complete list of all currently defined -@var{command}s and their corresponding response @var{data}. -@xref{File-I/O Remote Protocol Extension}, for details about the File -I/O extension of the remote protocol. - -Each packet's description has a template showing the packet's overall -syntax, followed by an explanation of the packet's meaning. We -include spaces in some of the templates for clarity; these are not -part of the packet's syntax. No @value{GDBN} packet uses spaces to -separate its components. For example, a template like @samp{foo -@var{bar} @var{baz}} describes a packet beginning with the three ASCII -bytes @samp{foo}, followed by a @var{bar}, followed directly by a -@var{baz}. @value{GDBN} does not transmit a space character between the -@samp{foo} and the @var{bar}, or between the @var{bar} and the -@var{baz}. - -@cindex @var{thread-id}, in remote protocol -@anchor{thread-id syntax} -Several packets and replies include a @var{thread-id} field to identify -a thread. Normally these are positive numbers with a target-specific -interpretation, formatted as big-endian hex strings. A @var{thread-id} -can also be a literal @samp{-1} to indicate all threads, or @samp{0} to -pick any thread. - -In addition, the remote protocol supports a multiprocess feature in -which the @var{thread-id} syntax is extended to optionally include both -process and thread ID fields, as @samp{p@var{pid}.@var{tid}}. -The @var{pid} (process) and @var{tid} (thread) components each have the -format described above: a positive number with target-specific -interpretation formatted as a big-endian hex string, literal @samp{-1} -to indicate all processes or threads (respectively), or @samp{0} to -indicate an arbitrary process or thread. Specifying just a process, as -@samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an -error to specify all processes but a specific thread, such as -@samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used -for those packets and replies explicitly documented to include a process -ID, rather than a @var{thread-id}. - -The multiprocess @var{thread-id} syntax extensions are only used if both -@value{GDBN} and the stub report support for the @samp{multiprocess} -feature using @samp{qSupported}. @xref{multiprocess extensions}, for -more information. - -Note that all packet forms beginning with an upper- or lower-case -letter, other than those described here, are reserved for future use. - -Here are the packet descriptions. - -@table @samp - -@item ! -@cindex @samp{!} packet -@anchor{extended mode} -Enable extended mode. In extended mode, the remote server is made -persistent. The @samp{R} packet is used to restart the program being -debugged. - -Reply: -@table @samp -@item OK -The remote target both supports and has enabled extended mode. -@end table - -@item ? -@cindex @samp{?} packet -Indicate the reason the target halted. The reply is the same as for -step and continue. This packet has a special interpretation when the -target is in non-stop mode; see @ref{Remote Non-Stop}. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@item A @var{arglen},@var{argnum},@var{arg},@dots{} -@cindex @samp{A} packet -Initialized @code{argv[]} array passed into program. @var{arglen} -specifies the number of bytes in the hex encoded byte stream -@var{arg}. See @code{gdbserver} for more details. - -Reply: -@table @samp -@item OK -The arguments were set. -@item E @var{NN} -An error occurred. -@end table - -@item b @var{baud} -@cindex @samp{b} packet -(Don't use this packet; its behavior is not well-defined.) -Change the serial line speed to @var{baud}. - -JTC: @emph{When does the transport layer state change? When it's -received, or after the ACK is transmitted. In either case, there are -problems if the command or the acknowledgment packet is dropped.} - -Stan: @emph{If people really wanted to add something like this, and get -it working for the first time, they ought to modify ser-unix.c to send -some kind of out-of-band message to a specially-setup stub and have the -switch happen "in between" packets, so that from remote protocol's point -of view, nothing actually happened.} - -@item B @var{addr},@var{mode} -@cindex @samp{B} packet -Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a -breakpoint at @var{addr}. - -Don't use this packet. Use the @samp{Z} and @samp{z} packets instead -(@pxref{insert breakpoint or watchpoint packet}). - -@cindex @samp{bc} packet -@anchor{bc} -@item bc -Backward continue. Execute the target system in reverse. No parameter. -@xref{Reverse Execution}, for more information. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@cindex @samp{bs} packet -@anchor{bs} -@item bs -Backward single step. Execute one instruction in reverse. No parameter. -@xref{Reverse Execution}, for more information. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@item c @r{[}@var{addr}@r{]} -@cindex @samp{c} packet -Continue. @var{addr} is address to resume. If @var{addr} is omitted, -resume at current address. - -This packet is deprecated for multi-threading support. @xref{vCont -packet}. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@item C @var{sig}@r{[};@var{addr}@r{]} -@cindex @samp{C} packet -Continue with signal @var{sig} (hex signal number). If -@samp{;@var{addr}} is omitted, resume at same address. - -This packet is deprecated for multi-threading support. @xref{vCont -packet}. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@item d -@cindex @samp{d} packet -Toggle debug flag. - -Don't use this packet; instead, define a general set packet -(@pxref{General Query Packets}). - -@item D -@itemx D;@var{pid} -@cindex @samp{D} packet -The first form of the packet is used to detach @value{GDBN} from the -remote system. It is sent to the remote target -before @value{GDBN} disconnects via the @code{detach} command. - -The second form, including a process ID, is used when multiprocess -protocol extensions are enabled (@pxref{multiprocess extensions}), to -detach only a specific process. The @var{pid} is specified as a -big-endian hex string. - -Reply: -@table @samp -@item OK -for success -@item E @var{NN} -for an error -@end table - -@item F @var{RC},@var{EE},@var{CF};@var{XX} -@cindex @samp{F} packet -A reply from @value{GDBN} to an @samp{F} packet sent by the target. -This is part of the File-I/O protocol extension. @xref{File-I/O -Remote Protocol Extension}, for the specification. - -@item g -@anchor{read registers packet} -@cindex @samp{g} packet -Read general registers. - -Reply: -@table @samp -@item @var{XX@dots{}} -Each byte of register data is described by two hex digits. The bytes -with the register are transmitted in target byte order. The size of -each register and their position within the @samp{g} packet are -determined by the @value{GDBN} internal gdbarch functions -@code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The -specification of several standard @samp{g} packets is specified below. - -When reading registers from a trace frame (@pxref{Analyze Collected -Data,,Using the Collected Data}), the stub may also return a string of -literal @samp{x}'s in place of the register data digits, to indicate -that the corresponding register has not been collected, thus its value -is unavailable. For example, for an architecture with 4 registers of -4 bytes each, the following reply indicates to @value{GDBN} that -registers 0 and 2 have not been collected, while registers 1 and 3 -have been collected, and both have zero value: - -@smallexample --> @code{g} -<- @code{xxxxxxxx00000000xxxxxxxx00000000} -@end smallexample - -@item E @var{NN} -for an error. -@end table - -@item G @var{XX@dots{}} -@cindex @samp{G} packet -Write general registers. @xref{read registers packet}, for a -description of the @var{XX@dots{}} data. - -Reply: -@table @samp -@item OK -for success -@item E @var{NN} -for an error -@end table - -@item H @var{op} @var{thread-id} -@cindex @samp{H} packet -Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g}, -@samp{G}, et.al.). @var{op} depends on the operation to be performed: -it should be @samp{c} for step and continue operations (note that this -is deprecated, supporting the @samp{vCont} command is a better -option), @samp{g} for other operations. The thread designator -@var{thread-id} has the format and interpretation described in -@ref{thread-id syntax}. - -Reply: -@table @samp -@item OK -for success -@item E @var{NN} -for an error -@end table - -@c FIXME: JTC: -@c 'H': How restrictive (or permissive) is the thread model. If a -@c thread is selected and stopped, are other threads allowed -@c to continue to execute? As I mentioned above, I think the -@c semantics of each command when a thread is selected must be -@c described. For example: -@c -@c 'g': If the stub supports threads and a specific thread is -@c selected, returns the register block from that thread; -@c otherwise returns current registers. -@c -@c 'G' If the stub supports threads and a specific thread is -@c selected, sets the registers of the register block of -@c that thread; otherwise sets current registers. - -@item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]} -@anchor{cycle step packet} -@cindex @samp{i} packet -Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is -present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle -step starting at that address. - -@item I -@cindex @samp{I} packet -Signal, then cycle step. @xref{step with signal packet}. @xref{cycle -step packet}. - -@item k -@cindex @samp{k} packet -Kill request. - -FIXME: @emph{There is no description of how to operate when a specific -thread context has been selected (i.e.@: does 'k' kill only that -thread?)}. - -@item m @var{addr},@var{length} -@cindex @samp{m} packet -Read @var{length} bytes of memory starting at address @var{addr}. -Note that @var{addr} may not be aligned to any particular boundary. - -The stub need not use any particular size or alignment when gathering -data from memory for the response; even if @var{addr} is word-aligned -and @var{length} is a multiple of the word size, the stub is free to -use byte accesses, or not. For this reason, this packet may not be -suitable for accessing memory-mapped I/O devices. -@cindex alignment of remote memory accesses -@cindex size of remote memory accesses -@cindex memory, alignment and size of remote accesses - -Reply: -@table @samp -@item @var{XX@dots{}} -Memory contents; each byte is transmitted as a two-digit hexadecimal -number. The reply may contain fewer bytes than requested if the -server was able to read only part of the region of memory. -@item E @var{NN} -@var{NN} is errno -@end table - -@item M @var{addr},@var{length}:@var{XX@dots{}} -@cindex @samp{M} packet -Write @var{length} bytes of memory starting at address @var{addr}. -@var{XX@dots{}} is the data; each byte is transmitted as a two-digit -hexadecimal number. - -Reply: -@table @samp -@item OK -for success -@item E @var{NN} -for an error (this includes the case where only part of the data was -written). -@end table - -@item p @var{n} -@cindex @samp{p} packet -Read the value of register @var{n}; @var{n} is in hex. -@xref{read registers packet}, for a description of how the returned -register value is encoded. - -Reply: -@table @samp -@item @var{XX@dots{}} -the register's value -@item E @var{NN} -for an error -@item @w{} -Indicating an unrecognized @var{query}. -@end table - -@item P @var{n@dots{}}=@var{r@dots{}} -@anchor{write register packet} -@cindex @samp{P} packet -Write register @var{n@dots{}} with value @var{r@dots{}}. The register -number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex -digits for each byte in the register (target byte order). - -Reply: -@table @samp -@item OK -for success -@item E @var{NN} -for an error -@end table - -@item q @var{name} @var{params}@dots{} -@itemx Q @var{name} @var{params}@dots{} -@cindex @samp{q} packet -@cindex @samp{Q} packet -General query (@samp{q}) and set (@samp{Q}). These packets are -described fully in @ref{General Query Packets}. - -@item r -@cindex @samp{r} packet -Reset the entire system. - -Don't use this packet; use the @samp{R} packet instead. - -@item R @var{XX} -@cindex @samp{R} packet -Restart the program being debugged. @var{XX}, while needed, is ignored. -This packet is only available in extended mode (@pxref{extended mode}). - -The @samp{R} packet has no reply. - -@item s @r{[}@var{addr}@r{]} -@cindex @samp{s} packet -Single step. @var{addr} is the address at which to resume. If -@var{addr} is omitted, resume at same address. - -This packet is deprecated for multi-threading support. @xref{vCont -packet}. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@item S @var{sig}@r{[};@var{addr}@r{]} -@anchor{step with signal packet} -@cindex @samp{S} packet -Step with signal. This is analogous to the @samp{C} packet, but -requests a single-step, rather than a normal resumption of execution. - -This packet is deprecated for multi-threading support. @xref{vCont -packet}. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@item t @var{addr}:@var{PP},@var{MM} -@cindex @samp{t} packet -Search backwards starting at address @var{addr} for a match with pattern -@var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes. -@var{addr} must be at least 3 digits. - -@item T @var{thread-id} -@cindex @samp{T} packet -Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}. - -Reply: -@table @samp -@item OK -thread is still alive -@item E @var{NN} -thread is dead -@end table - -@item v -Packets starting with @samp{v} are identified by a multi-letter name, -up to the first @samp{;} or @samp{?} (or the end of the packet). - -@item vAttach;@var{pid} -@cindex @samp{vAttach} packet -Attach to a new process with the specified process ID @var{pid}. -The process ID is a -hexadecimal integer identifying the process. In all-stop mode, all -threads in the attached process are stopped; in non-stop mode, it may be -attached without being stopped if that is supported by the target. - -@c In non-stop mode, on a successful vAttach, the stub should set the -@c current thread to a thread of the newly-attached process. After -@c attaching, GDB queries for the attached process's thread ID with qC. -@c Also note that, from a user perspective, whether or not the -@c target is stopped on attach in non-stop mode depends on whether you -@c use the foreground or background version of the attach command, not -@c on what vAttach does; GDB does the right thing with respect to either -@c stopping or restarting threads. - -This packet is only available in extended mode (@pxref{extended mode}). - -Reply: -@table @samp -@item E @var{nn} -for an error -@item @r{Any stop packet} -for success in all-stop mode (@pxref{Stop Reply Packets}) -@item OK -for success in non-stop mode (@pxref{Remote Non-Stop}) -@end table - -@item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{} -@cindex @samp{vCont} packet -@anchor{vCont packet} -Resume the inferior, specifying different actions for each thread. -If an action is specified with no @var{thread-id}, then it is applied to any -threads that don't have a specific action specified; if no default action is -specified then other threads should remain stopped in all-stop mode and -in their current state in non-stop mode. -Specifying multiple -default actions is an error; specifying no actions is also an error. -Thread IDs are specified using the syntax described in @ref{thread-id syntax}. - -Currently supported actions are: - -@table @samp -@item c -Continue. -@item C @var{sig} -Continue with signal @var{sig}. The signal @var{sig} should be two hex digits. -@item s -Step. -@item S @var{sig} -Step with signal @var{sig}. The signal @var{sig} should be two hex digits. -@item t -Stop. -@end table - -The optional argument @var{addr} normally associated with the -@samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is -not supported in @samp{vCont}. - -The @samp{t} action is only relevant in non-stop mode -(@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise. -A stop reply should be generated for any affected thread not already stopped. -When a thread is stopped by means of a @samp{t} action, -the corresponding stop reply should indicate that the thread has stopped with -signal @samp{0}, regardless of whether the target uses some other signal -as an implementation detail. - -The stub must support @samp{vCont} if it reports support for -multiprocess extensions (@pxref{multiprocess extensions}). Note that in -this case @samp{vCont} actions can be specified to apply to all threads -in a process by using the @samp{p@var{pid}.-1} form of the -@var{thread-id}. - -Reply: -@xref{Stop Reply Packets}, for the reply specifications. - -@item vCont? -@cindex @samp{vCont?} packet -Request a list of actions supported by the @samp{vCont} packet. - -Reply: -@table @samp -@item vCont@r{[};@var{action}@dots{}@r{]} -The @samp{vCont} packet is supported. Each @var{action} is a supported -command in the @samp{vCont} packet. -@item @w{} -The @samp{vCont} packet is not supported. -@end table - -@item vFile:@var{operation}:@var{parameter}@dots{} -@cindex @samp{vFile} packet -Perform a file operation on the target system. For details, -see @ref{Host I/O Packets}. - -@item vFlashErase:@var{addr},@var{length} -@cindex @samp{vFlashErase} packet -Direct the stub to erase @var{length} bytes of flash starting at -@var{addr}. The region may enclose any number of flash blocks, but -its start and end must fall on block boundaries, as indicated by the -flash block size appearing in the memory map (@pxref{Memory Map -Format}). @value{GDBN} groups flash memory programming operations -together, and sends a @samp{vFlashDone} request after each group; the -stub is allowed to delay erase operation until the @samp{vFlashDone} -packet is received. - -Reply: -@table @samp -@item OK -for success -@item E @var{NN} -for an error -@end table - -@item vFlashWrite:@var{addr}:@var{XX@dots{}} -@cindex @samp{vFlashWrite} packet -Direct the stub to write data to flash address @var{addr}. The data -is passed in binary form using the same encoding as for the @samp{X} -packet (@pxref{Binary Data}). The memory ranges specified by -@samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must -not overlap, and must appear in order of increasing addresses -(although @samp{vFlashErase} packets for higher addresses may already -have been received; the ordering is guaranteed only between -@samp{vFlashWrite} packets). If a packet writes to an address that was -neither erased by a preceding @samp{vFlashErase} packet nor by some other -target-specific method, the results are unpredictable. - - -Reply: -@table @samp -@item OK -for success -@item E.memtype -for vFlashWrite addressing non-flash memory -@item E @var{NN} -for an error -@end table - -@item vFlashDone -@cindex @samp{vFlashDone} packet -Indicate to the stub that flash programming operation is finished. -The stub is permitted to delay or batch the effects of a group of -@samp{vFlashErase} and @samp{vFlashWrite} packets until a -@samp{vFlashDone} packet is received. The contents of the affected -regions of flash memory are unpredictable until the @samp{vFlashDone} -request is completed. - -@item vKill;@var{pid} -@cindex @samp{vKill} packet -Kill the process with the specified process ID. @var{pid} is a -hexadecimal integer identifying the process. This packet is used in -preference to @samp{k} when multiprocess protocol extensions are -supported; see @ref{multiprocess extensions}. - -Reply: -@table @samp -@item E @var{nn} -for an error -@item OK -for success -@end table - -@item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{} -@cindex @samp{vRun} packet -Run the program @var{filename}, passing it each @var{argument} on its -command line. The file and arguments are hex-encoded strings. If -@var{filename} is an empty string, the stub may use a default program -(e.g.@: the last program run). The program is created in the stopped -state. - -@c FIXME: What about non-stop mode? - -This packet is only available in extended mode (@pxref{extended mode}). - -Reply: -@table @samp -@item E @var{nn} -for an error -@item @r{Any stop packet} -for success (@pxref{Stop Reply Packets}) -@end table - -@item vStopped -@cindex @samp{vStopped} packet -@xref{Notification Packets}. - -@item X @var{addr},@var{length}:@var{XX@dots{}} -@anchor{X packet} -@cindex @samp{X} packet -Write data to memory, where the data is transmitted in binary. -@var{addr} is address, @var{length} is number of bytes, -@samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}). - -Reply: -@table @samp -@item OK -for success -@item E @var{NN} -for an error -@end table - -@item z @var{type},@var{addr},@var{kind} -@itemx Z @var{type},@var{addr},@var{kind} -@anchor{insert breakpoint or watchpoint packet} -@cindex @samp{z} packet -@cindex @samp{Z} packets -Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or -watchpoint starting at address @var{address} of kind @var{kind}. - -Each breakpoint and watchpoint packet @var{type} is documented -separately. - -@emph{Implementation notes: A remote target shall return an empty string -for an unrecognized breakpoint or watchpoint packet @var{type}. A -remote target shall support either both or neither of a given -@samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To -avoid potential problems with duplicate packets, the operations should -be implemented in an idempotent way.} - -@item z0,@var{addr},@var{kind} -@itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]} -@cindex @samp{z0} packet -@cindex @samp{Z0} packet -Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address -@var{addr} of type @var{kind}. - -A memory breakpoint is implemented by replacing the instruction at -@var{addr} with a software breakpoint or trap instruction. The -@var{kind} is target-specific and typically indicates the size of -the breakpoint in bytes that should be inserted. E.g., the @sc{arm} -and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some -architectures have additional meanings for @var{kind}; -@var{cond_list} is an optional list of conditional expressions in bytecode -form that should be evaluated on the target's side. These are the -conditions that should be taken into consideration when deciding if -the breakpoint trigger should be reported back to @var{GDBN}. - -The @var{cond_list} parameter is comprised of a series of expressions, -concatenated without separators. Each expression has the following form: - -@table @samp - -@item X @var{len},@var{expr} -@var{len} is the length of the bytecode expression and @var{expr} is the -actual conditional expression in bytecode form. - -@end table - -The optional @var{cmd_list} parameter introduces commands that may be -run on the target, rather than being reported back to @value{GDBN}. -The parameter starts with a numeric flag @var{persist}; if the flag is -nonzero, then the breakpoint may remain active and the commands -continue to be run even when @value{GDBN} disconnects from the target. -Following this flag is a series of expressions concatenated with no -separators. Each expression has the following form: - -@table @samp - -@item X @var{len},@var{expr} -@var{len} is the length of the bytecode expression and @var{expr} is the -actual conditional expression in bytecode form. - -@end table - -see @ref{Architecture-Specific Protocol Details}. - -@emph{Implementation note: It is possible for a target to copy or move -code that contains memory breakpoints (e.g., when implementing -overlays). The behavior of this packet, in the presence of such a -target, is not defined.} - -Reply: -@table @samp -@item OK -success -@item @w{} -not supported -@item E @var{NN} -for an error -@end table - -@item z1,@var{addr},@var{kind} -@itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]} -@cindex @samp{z1} packet -@cindex @samp{Z1} packet -Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at -address @var{addr}. - -A hardware breakpoint is implemented using a mechanism that is not -dependant on being able to modify the target's memory. @var{kind} -and @var{cond_list} have the same meaning as in @samp{Z0} packets. - -@emph{Implementation note: A hardware breakpoint is not affected by code -movement.} - -Reply: -@table @samp -@item OK -success -@item @w{} -not supported -@item E @var{NN} -for an error -@end table - -@item z2,@var{addr},@var{kind} -@itemx Z2,@var{addr},@var{kind} -@cindex @samp{z2} packet -@cindex @samp{Z2} packet -Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}. -@var{kind} is interpreted as the number of bytes to watch. - -Reply: -@table @samp -@item OK -success -@item @w{} -not supported -@item E @var{NN} -for an error -@end table - -@item z3,@var{addr},@var{kind} -@itemx Z3,@var{addr},@var{kind} -@cindex @samp{z3} packet -@cindex @samp{Z3} packet -Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}. -@var{kind} is interpreted as the number of bytes to watch. - -Reply: -@table @samp -@item OK -success -@item @w{} -not supported -@item E @var{NN} -for an error -@end table - -@item z4,@var{addr},@var{kind} -@itemx Z4,@var{addr},@var{kind} -@cindex @samp{z4} packet -@cindex @samp{Z4} packet -Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}. -@var{kind} is interpreted as the number of bytes to watch. - -Reply: -@table @samp -@item OK -success -@item @w{} -not supported -@item E @var{NN} -for an error -@end table - -@end table - -@node Stop Reply Packets -@section Stop Reply Packets -@cindex stop reply packets - -The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont}, -@samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can -receive any of the below as a reply. Except for @samp{?} -and @samp{vStopped}, that reply is only returned -when the target halts. In the below the exact meaning of @dfn{signal -number} is defined by the header @file{include/gdb/signals.h} in the -@value{GDBN} source code. - -As in the description of request packets, we include spaces in the -reply templates for clarity; these are not part of the reply packet's -syntax. No @value{GDBN} stop reply packet uses spaces to separate its -components. - -@table @samp - -@item S @var{AA} -The program received signal number @var{AA} (a two-digit hexadecimal -number). This is equivalent to a @samp{T} response with no -@var{n}:@var{r} pairs. - -@item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{} -@cindex @samp{T} packet reply -The program received signal number @var{AA} (a two-digit hexadecimal -number). This is equivalent to an @samp{S} response, except that the -@samp{@var{n}:@var{r}} pairs can carry values of important registers -and other information directly in the stop reply packet, reducing -round-trip latency. Single-step and breakpoint traps are reported -this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows: - -@itemize @bullet -@item -If @var{n} is a hexadecimal number, it is a register number, and the -corresponding @var{r} gives that register's value. @var{r} is a -series of bytes in target byte order, with each byte given by a -two-digit hex number. - -@item -If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of -the stopped thread, as specified in @ref{thread-id syntax}. - -@item -If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of -the core on which the stop event was detected. - -@item -If @var{n} is a recognized @dfn{stop reason}, it describes a more -specific event that stopped the target. The currently defined stop -reasons are listed below. @var{aa} should be @samp{05}, the trap -signal. At most one stop reason should be present. - -@item -Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair -and go on to the next; this allows us to extend the protocol in the -future. -@end itemize - -The currently defined stop reasons are: - -@table @samp -@item watch -@itemx rwatch -@itemx awatch -The packet indicates a watchpoint hit, and @var{r} is the data address, in -hex. - -@cindex shared library events, remote reply -@item library -The packet indicates that the loaded libraries have changed. -@value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new -list of loaded libraries. @var{r} is ignored. - -@cindex replay log events, remote reply -@item replaylog -The packet indicates that the target cannot continue replaying -logged execution events, because it has reached the end (or the -beginning when executing backward) of the log. The value of @var{r} -will be either @samp{begin} or @samp{end}. @xref{Reverse Execution}, -for more information. -@end table - -@item W @var{AA} -@itemx W @var{AA} ; process:@var{pid} -The process exited, and @var{AA} is the exit status. This is only -applicable to certain targets. - -The second form of the response, including the process ID of the exited -process, can be used only when @value{GDBN} has reported support for -multiprocess protocol extensions; see @ref{multiprocess extensions}. -The @var{pid} is formatted as a big-endian hex string. - -@item X @var{AA} -@itemx X @var{AA} ; process:@var{pid} -The process terminated with signal @var{AA}. - -The second form of the response, including the process ID of the -terminated process, can be used only when @value{GDBN} has reported -support for multiprocess protocol extensions; see @ref{multiprocess -extensions}. The @var{pid} is formatted as a big-endian hex string. - -@item O @var{XX}@dots{} -@samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be -written as the program's console output. This can happen at any time -while the program is running and the debugger should continue to wait -for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode. - -@item F @var{call-id},@var{parameter}@dots{} -@var{call-id} is the identifier which says which host system call should -be called. This is just the name of the function. Translation into the -correct system call is only applicable as it's defined in @value{GDBN}. -@xref{File-I/O Remote Protocol Extension}, for a list of implemented -system calls. - -@samp{@var{parameter}@dots{}} is a list of parameters as defined for -this very system call. - -The target replies with this packet when it expects @value{GDBN} to -call a host system call on behalf of the target. @value{GDBN} replies -with an appropriate @samp{F} packet and keeps up waiting for the next -reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S} -or @samp{s} action is expected to be continued. @xref{File-I/O Remote -Protocol Extension}, for more details. - -@end table - -@node General Query Packets -@section General Query Packets -@cindex remote query requests - -Packets starting with @samp{q} are @dfn{general query packets}; -packets starting with @samp{Q} are @dfn{general set packets}. General -query and set packets are a semi-unified form for retrieving and -sending information to and from the stub. - -The initial letter of a query or set packet is followed by a name -indicating what sort of thing the packet applies to. For example, -@value{GDBN} may use a @samp{qSymbol} packet to exchange symbol -definitions with the stub. These packet names follow some -conventions: - -@itemize @bullet -@item -The name must not contain commas, colons or semicolons. -@item -Most @value{GDBN} query and set packets have a leading upper case -letter. -@item -The names of custom vendor packets should use a company prefix, in -lower case, followed by a period. For example, packets designed at -the Acme Corporation might begin with @samp{qacme.foo} (for querying -foos) or @samp{Qacme.bar} (for setting bars). -@end itemize - -The name of a query or set packet should be separated from any -parameters by a @samp{:}; the parameters themselves should be -separated by @samp{,} or @samp{;}. Stubs must be careful to match the -full packet name, and check for a separator or the end of the packet, -in case two packet names share a common prefix. New packets should not begin -with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL} -packets predate these conventions, and have arguments without any terminator -for the packet name; we suspect they are in widespread use in places that -are difficult to upgrade. The @samp{qC} packet has no arguments, but some -existing stubs (e.g.@: RedBoot) are known to not check for the end of the -packet.}. - -Like the descriptions of the other packets, each description here -has a template showing the packet's overall syntax, followed by an -explanation of the packet's meaning. We include spaces in some of the -templates for clarity; these are not part of the packet's syntax. No -@value{GDBN} packet uses spaces to separate its components. - -Here are the currently defined query and set packets: - -@table @samp - -@item QAgent:1 -@itemx QAgent:0 -Turn on or off the agent as a helper to perform some debugging operations -delegated from @value{GDBN} (@pxref{Control Agent}). - -@item QAllow:@var{op}:@var{val}@dots{} -@cindex @samp{QAllow} packet -Specify which operations @value{GDBN} expects to request of the -target, as a semicolon-separated list of operation name and value -pairs. Possible values for @var{op} include @samp{WriteReg}, -@samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace}, -@samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0, -indicating that @value{GDBN} will not request the operation, or 1, -indicating that it may. (The target can then use this to set up its -own internals optimally, for instance if the debugger never expects to -insert breakpoints, it may not need to install its own trap handler.) - -@item qC -@cindex current thread, remote request -@cindex @samp{qC} packet -Return the current thread ID. - -Reply: -@table @samp -@item QC @var{thread-id} -Where @var{thread-id} is a thread ID as documented in -@ref{thread-id syntax}. -@item @r{(anything else)} -Any other reply implies the old thread ID. -@end table - -@item qCRC:@var{addr},@var{length} -@cindex CRC of memory block, remote request -@cindex @samp{qCRC} packet -Compute the CRC checksum of a block of memory using CRC-32 defined in -IEEE 802.3. The CRC is computed byte at a time, taking the most -significant bit of each byte first. The initial pattern code -@code{0xffffffff} is used to ensure leading zeros affect the CRC. - -@emph{Note:} This is the same CRC used in validating separate debug -files (@pxref{Separate Debug Files, , Debugging Information in Separate -Files}). However the algorithm is slightly different. When validating -separate debug files, the CRC is computed taking the @emph{least} -significant bit of each byte first, and the final result is inverted to -detect trailing zeros. - -Reply: -@table @samp -@item E @var{NN} -An error (such as memory fault) -@item C @var{crc32} -The specified memory region's checksum is @var{crc32}. -@end table - -@item QDisableRandomization:@var{value} -@cindex disable address space randomization, remote request -@cindex @samp{QDisableRandomization} packet -Some target operating systems will randomize the virtual address space -of the inferior process as a security feature, but provide a feature -to disable such randomization, e.g.@: to allow for a more deterministic -debugging experience. On such systems, this packet with a @var{value} -of 1 directs the target to disable address space randomization for -processes subsequently started via @samp{vRun} packets, while a packet -with a @var{value} of 0 tells the target to enable address space -randomization. - -This packet is only available in extended mode (@pxref{extended mode}). - -Reply: -@table @samp -@item OK -The request succeeded. - -@item E @var{nn} -An error occurred. @var{nn} are hex digits. - -@item @w{} -An empty reply indicates that @samp{QDisableRandomization} is not supported -by the stub. -@end table - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). -This should only be done on targets that actually support disabling -address space randomization. - -@item qfThreadInfo -@itemx qsThreadInfo -@cindex list active threads, remote request -@cindex @samp{qfThreadInfo} packet -@cindex @samp{qsThreadInfo} packet -Obtain a list of all active thread IDs from the target (OS). Since there -may be too many active threads to fit into one reply packet, this query -works iteratively: it may require more than one query/reply sequence to -obtain the entire list of threads. The first query of the sequence will -be the @samp{qfThreadInfo} query; subsequent queries in the -sequence will be the @samp{qsThreadInfo} query. - -NOTE: This packet replaces the @samp{qL} query (see below). - -Reply: -@table @samp -@item m @var{thread-id} -A single thread ID -@item m @var{thread-id},@var{thread-id}@dots{} -a comma-separated list of thread IDs -@item l -(lower case letter @samp{L}) denotes end of list. -@end table - -In response to each query, the target will reply with a list of one or -more thread IDs, separated by commas. -@value{GDBN} will respond to each reply with a request for more thread -ids (using the @samp{qs} form of the query), until the target responds -with @samp{l} (lower-case ell, for @dfn{last}). -Refer to @ref{thread-id syntax}, for the format of the @var{thread-id} -fields. - -@item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm} -@cindex get thread-local storage address, remote request -@cindex @samp{qGetTLSAddr} packet -Fetch the address associated with thread local storage specified -by @var{thread-id}, @var{offset}, and @var{lm}. - -@var{thread-id} is the thread ID associated with the -thread for which to fetch the TLS address. @xref{thread-id syntax}. - -@var{offset} is the (big endian, hex encoded) offset associated with the -thread local variable. (This offset is obtained from the debug -information associated with the variable.) - -@var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the -load module associated with the thread local storage. For example, -a @sc{gnu}/Linux system will pass the link map address of the shared -object associated with the thread local storage under consideration. -Other operating environments may choose to represent the load module -differently, so the precise meaning of this parameter will vary. - -Reply: -@table @samp -@item @var{XX}@dots{} -Hex encoded (big endian) bytes representing the address of the thread -local storage requested. - -@item E @var{nn} -An error occurred. @var{nn} are hex digits. - -@item @w{} -An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub. -@end table - -@item qGetTIBAddr:@var{thread-id} -@cindex get thread information block address -@cindex @samp{qGetTIBAddr} packet -Fetch address of the Windows OS specific Thread Information Block. - -@var{thread-id} is the thread ID associated with the thread. - -Reply: -@table @samp -@item @var{XX}@dots{} -Hex encoded (big endian) bytes representing the linear address of the -thread information block. - -@item E @var{nn} -An error occured. This means that either the thread was not found, or the -address could not be retrieved. - -@item @w{} -An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub. -@end table - -@item qL @var{startflag} @var{threadcount} @var{nextthread} -Obtain thread information from RTOS. Where: @var{startflag} (one hex -digit) is one to indicate the first query and zero to indicate a -subsequent query; @var{threadcount} (two hex digits) is the maximum -number of threads the response packet can contain; and @var{nextthread} -(eight hex digits), for subsequent queries (@var{startflag} is zero), is -returned in the response as @var{argthread}. - -Don't use this packet; use the @samp{qfThreadInfo} query instead (see above). - -Reply: -@table @samp -@item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{} -Where: @var{count} (two hex digits) is the number of threads being -returned; @var{done} (one hex digit) is zero to indicate more threads -and one indicates no further threads; @var{argthreadid} (eight hex -digits) is @var{nextthread} from the request packet; @var{thread}@dots{} -is a sequence of thread IDs from the target. @var{threadid} (eight hex -digits). See @code{remote.c:parse_threadlist_response()}. -@end table - -@item qOffsets -@cindex section offsets, remote request -@cindex @samp{qOffsets} packet -Get section offsets that the target used when relocating the downloaded -image. - -Reply: -@table @samp -@item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]} -Relocate the @code{Text} section by @var{xxx} from its original address. -Relocate the @code{Data} section by @var{yyy} from its original address. -If the object file format provides segment information (e.g.@: @sc{elf} -@samp{PT_LOAD} program headers), @value{GDBN} will relocate entire -segments by the supplied offsets. - -@emph{Note: while a @code{Bss} offset may be included in the response, -@value{GDBN} ignores this and instead applies the @code{Data} offset -to the @code{Bss} section.} - -@item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]} -Relocate the first segment of the object file, which conventionally -contains program code, to a starting address of @var{xxx}. If -@samp{DataSeg} is specified, relocate the second segment, which -conventionally contains modifiable data, to a starting address of -@var{yyy}. @value{GDBN} will report an error if the object file -does not contain segment information, or does not contain at least -as many segments as mentioned in the reply. Extra segments are -kept at fixed offsets relative to the last relocated segment. -@end table - -@item qP @var{mode} @var{thread-id} -@cindex thread information, remote request -@cindex @samp{qP} packet -Returns information on @var{thread-id}. Where: @var{mode} is a hex -encoded 32 bit mode; @var{thread-id} is a thread ID -(@pxref{thread-id syntax}). - -Don't use this packet; use the @samp{qThreadExtraInfo} query instead -(see below). - -Reply: see @code{remote.c:remote_unpack_thread_info_response()}. - -@item QNonStop:1 -@itemx QNonStop:0 -@cindex non-stop mode, remote request -@cindex @samp{QNonStop} packet -@anchor{QNonStop} -Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode. -@xref{Remote Non-Stop}, for more information. - -Reply: -@table @samp -@item OK -The request succeeded. - -@item E @var{nn} -An error occurred. @var{nn} are hex digits. - -@item @w{} -An empty reply indicates that @samp{QNonStop} is not supported by -the stub. -@end table - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). -Use of this packet is controlled by the @code{set non-stop} command; -@pxref{Non-Stop Mode}. - -@item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{} -@cindex pass signals to inferior, remote request -@cindex @samp{QPassSignals} packet -@anchor{QPassSignals} -Each listed @var{signal} should be passed directly to the inferior process. -Signals are numbered identically to continue packets and stop replies -(@pxref{Stop Reply Packets}). Each @var{signal} list item should be -strictly greater than the previous item. These signals do not need to stop -the inferior, or be reported to @value{GDBN}. All other signals should be -reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not -combine; any earlier @samp{QPassSignals} list is completely replaced by the -new list. This packet improves performance when using @samp{handle -@var{signal} nostop noprint pass}. - -Reply: -@table @samp -@item OK -The request succeeded. - -@item E @var{nn} -An error occurred. @var{nn} are hex digits. - -@item @w{} -An empty reply indicates that @samp{QPassSignals} is not supported by -the stub. -@end table - -Use of this packet is controlled by the @code{set remote pass-signals} -command (@pxref{Remote Configuration, set remote pass-signals}). -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{} -@cindex signals the inferior may see, remote request -@cindex @samp{QProgramSignals} packet -@anchor{QProgramSignals} -Each listed @var{signal} may be delivered to the inferior process. -Others should be silently discarded. - -In some cases, the remote stub may need to decide whether to deliver a -signal to the program or not without @value{GDBN} involvement. One -example of that is while detaching --- the program's threads may have -stopped for signals that haven't yet had a chance of being reported to -@value{GDBN}, and so the remote stub can use the signal list specified -by this packet to know whether to deliver or ignore those pending -signals. - -This does not influence whether to deliver a signal as requested by a -resumption packet (@pxref{vCont packet}). - -Signals are numbered identically to continue packets and stop replies -(@pxref{Stop Reply Packets}). Each @var{signal} list item should be -strictly greater than the previous item. Multiple -@samp{QProgramSignals} packets do not combine; any earlier -@samp{QProgramSignals} list is completely replaced by the new list. - -Reply: -@table @samp -@item OK -The request succeeded. - -@item E @var{nn} -An error occurred. @var{nn} are hex digits. - -@item @w{} -An empty reply indicates that @samp{QProgramSignals} is not supported -by the stub. -@end table - -Use of this packet is controlled by the @code{set remote program-signals} -command (@pxref{Remote Configuration, set remote program-signals}). -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qRcmd,@var{command} -@cindex execute remote command, remote request -@cindex @samp{qRcmd} packet -@var{command} (hex encoded) is passed to the local interpreter for -execution. Invalid commands should be reported using the output -string. Before the final result packet, the target may also respond -with a number of intermediate @samp{O@var{output}} console output -packets. @emph{Implementors should note that providing access to a -stubs's interpreter may have security implications}. - -Reply: -@table @samp -@item OK -A command response with no output. -@item @var{OUTPUT} -A command response with the hex encoded output string @var{OUTPUT}. -@item E @var{NN} -Indicate a badly formed request. -@item @w{} -An empty reply indicates that @samp{qRcmd} is not recognized. -@end table - -(Note that the @code{qRcmd} packet's name is separated from the -command by a @samp{,}, not a @samp{:}, contrary to the naming -conventions above. Please don't use this packet as a model for new -packets.) - -@item qSearch:memory:@var{address};@var{length};@var{search-pattern} -@cindex searching memory, in remote debugging -@ifnotinfo -@cindex @samp{qSearch:memory} packet -@end ifnotinfo -@cindex @samp{qSearch memory} packet -@anchor{qSearch memory} -Search @var{length} bytes at @var{address} for @var{search-pattern}. -@var{address} and @var{length} are encoded in hex. -@var{search-pattern} is a sequence of bytes, hex encoded. - -Reply: -@table @samp -@item 0 -The pattern was not found. -@item 1,address -The pattern was found at @var{address}. -@item E @var{NN} -A badly formed request or an error was encountered while searching memory. -@item @w{} -An empty reply indicates that @samp{qSearch:memory} is not recognized. -@end table - -@item QStartNoAckMode -@cindex @samp{QStartNoAckMode} packet -@anchor{QStartNoAckMode} -Request that the remote stub disable the normal @samp{+}/@samp{-} -protocol acknowledgments (@pxref{Packet Acknowledgment}). - -Reply: -@table @samp -@item OK -The stub has switched to no-acknowledgment mode. -@value{GDBN} acknowledges this reponse, -but neither the stub nor @value{GDBN} shall send or expect further -@samp{+}/@samp{-} acknowledgments in the current connection. -@item @w{} -An empty reply indicates that the stub does not support no-acknowledgment mode. -@end table - -@item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]} -@cindex supported packets, remote query -@cindex features of the remote protocol -@cindex @samp{qSupported} packet -@anchor{qSupported} -Tell the remote stub about features supported by @value{GDBN}, and -query the stub for features it supports. This packet allows -@value{GDBN} and the remote stub to take advantage of each others' -features. @samp{qSupported} also consolidates multiple feature probes -at startup, to improve @value{GDBN} performance---a single larger -packet performs better than multiple smaller probe packets on -high-latency links. Some features may enable behavior which must not -be on by default, e.g.@: because it would confuse older clients or -stubs. Other features may describe packets which could be -automatically probed for, but are not. These features must be -reported before @value{GDBN} will use them. This ``default -unsupported'' behavior is not appropriate for all packets, but it -helps to keep the initial connection time under control with new -versions of @value{GDBN} which support increasing numbers of packets. - -Reply: -@table @samp -@item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{} -The stub supports or does not support each returned @var{stubfeature}, -depending on the form of each @var{stubfeature} (see below for the -possible forms). -@item @w{} -An empty reply indicates that @samp{qSupported} is not recognized, -or that no features needed to be reported to @value{GDBN}. -@end table - -The allowed forms for each feature (either a @var{gdbfeature} in the -@samp{qSupported} packet, or a @var{stubfeature} in the response) -are: - -@table @samp -@item @var{name}=@var{value} -The remote protocol feature @var{name} is supported, and associated -with the specified @var{value}. The format of @var{value} depends -on the feature, but it must not include a semicolon. -@item @var{name}+ -The remote protocol feature @var{name} is supported, and does not -need an associated value. -@item @var{name}- -The remote protocol feature @var{name} is not supported. -@item @var{name}? -The remote protocol feature @var{name} may be supported, and -@value{GDBN} should auto-detect support in some other way when it is -needed. This form will not be used for @var{gdbfeature} notifications, -but may be used for @var{stubfeature} responses. -@end table - -Whenever the stub receives a @samp{qSupported} request, the -supplied set of @value{GDBN} features should override any previous -request. This allows @value{GDBN} to put the stub in a known -state, even if the stub had previously been communicating with -a different version of @value{GDBN}. - -The following values of @var{gdbfeature} (for the packet sent by @value{GDBN}) -are defined: - -@table @samp -@item multiprocess -This feature indicates whether @value{GDBN} supports multiprocess -extensions to the remote protocol. @value{GDBN} does not use such -extensions unless the stub also reports that it supports them by -including @samp{multiprocess+} in its @samp{qSupported} reply. -@xref{multiprocess extensions}, for details. - -@item xmlRegisters -This feature indicates that @value{GDBN} supports the XML target -description. If the stub sees @samp{xmlRegisters=} with target -specific strings separated by a comma, it will report register -description. - -@item qRelocInsn -This feature indicates whether @value{GDBN} supports the -@samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate -instruction reply packet}). -@end table - -Stubs should ignore any unknown values for -@var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported} -packet supports receiving packets of unlimited length (earlier -versions of @value{GDBN} may reject overly long responses). Additional values -for @var{gdbfeature} may be defined in the future to let the stub take -advantage of new features in @value{GDBN}, e.g.@: incompatible -improvements in the remote protocol---the @samp{multiprocess} feature is -an example of such a feature. The stub's reply should be independent -of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN} -describes all the features it supports, and then the stub replies with -all the features it supports. - -Similarly, @value{GDBN} will silently ignore unrecognized stub feature -responses, as long as each response uses one of the standard forms. - -Some features are flags. A stub which supports a flag feature -should respond with a @samp{+} form response. Other features -require values, and the stub should respond with an @samp{=} -form response. - -Each feature has a default value, which @value{GDBN} will use if -@samp{qSupported} is not available or if the feature is not mentioned -in the @samp{qSupported} response. The default values are fixed; a -stub is free to omit any feature responses that match the defaults. - -Not all features can be probed, but for those which can, the probing -mechanism is useful: in some cases, a stub's internal -architecture may not allow the protocol layer to know some information -about the underlying target in advance. This is especially common in -stubs which may be configured for multiple targets. - -These are the currently defined stub features and their properties: - -@multitable @columnfractions 0.35 0.2 0.12 0.2 -@c NOTE: The first row should be @headitem, but we do not yet require -@c a new enough version of Texinfo (4.7) to use @headitem. -@item Feature Name -@tab Value Required -@tab Default -@tab Probe Allowed - -@item @samp{PacketSize} -@tab Yes -@tab @samp{-} -@tab No - -@item @samp{qXfer:auxv:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:btrace:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:features:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:libraries:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:memory-map:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:sdata:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:spu:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:spu:write} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:siginfo:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:siginfo:write} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:threads:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:traceframe-info:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:uib:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{qXfer:fdpic:read} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{Qbtrace:off} -@tab Yes -@tab @samp{-} -@tab Yes - -@item @samp{Qbtrace:bts} -@tab Yes -@tab @samp{-} -@tab Yes - -@item @samp{QNonStop} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{QPassSignals} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{QStartNoAckMode} -@tab No -@tab @samp{-} -@tab Yes - -@item @samp{multiprocess} -@tab No -@tab @samp{-} -@tab No - -@item @samp{ConditionalBreakpoints} -@tab No -@tab @samp{-} -@tab No - -@item @samp{ConditionalTracepoints} -@tab No -@tab @samp{-} -@tab No - -@item @samp{ReverseContinue} -@tab No -@tab @samp{-} -@tab No - -@item @samp{ReverseStep} -@tab No -@tab @samp{-} -@tab No - -@item @samp{TracepointSource} -@tab No -@tab @samp{-} -@tab No - -@item @samp{QAgent} -@tab No -@tab @samp{-} -@tab No - -@item @samp{QAllow} -@tab No -@tab @samp{-} -@tab No - -@item @samp{QDisableRandomization} -@tab No -@tab @samp{-} -@tab No - -@item @samp{EnableDisableTracepoints} -@tab No -@tab @samp{-} -@tab No - -@item @samp{QTBuffer:size} -@tab No -@tab @samp{-} -@tab No - -@item @samp{tracenz} -@tab No -@tab @samp{-} -@tab No - -@item @samp{BreakpointCommands} -@tab No -@tab @samp{-} -@tab No - -@end multitable - -These are the currently defined stub features, in more detail: - -@table @samp -@cindex packet size, remote protocol -@item PacketSize=@var{bytes} -The remote stub can accept packets up to at least @var{bytes} in -length. @value{GDBN} will send packets up to this size for bulk -transfers, and will never send larger packets. This is a limit on the -data characters in the packet, including the frame and checksum. -There is no trailing NUL byte in a remote protocol packet; if the stub -stores packets in a NUL-terminated format, it should allow an extra -byte in its buffer for the NUL. If this stub feature is not supported, -@value{GDBN} guesses based on the size of the @samp{g} packet response. - -@item qXfer:auxv:read -The remote stub understands the @samp{qXfer:auxv:read} packet -(@pxref{qXfer auxiliary vector read}). - -@item qXfer:btrace:read -The remote stub understands the @samp{qXfer:btrace:read} -packet (@pxref{qXfer btrace read}). - -@item qXfer:features:read -The remote stub understands the @samp{qXfer:features:read} packet -(@pxref{qXfer target description read}). - -@item qXfer:libraries:read -The remote stub understands the @samp{qXfer:libraries:read} packet -(@pxref{qXfer library list read}). - -@item qXfer:libraries-svr4:read -The remote stub understands the @samp{qXfer:libraries-svr4:read} packet -(@pxref{qXfer svr4 library list read}). - -@item qXfer:memory-map:read -The remote stub understands the @samp{qXfer:memory-map:read} packet -(@pxref{qXfer memory map read}). - -@item qXfer:sdata:read -The remote stub understands the @samp{qXfer:sdata:read} packet -(@pxref{qXfer sdata read}). - -@item qXfer:spu:read -The remote stub understands the @samp{qXfer:spu:read} packet -(@pxref{qXfer spu read}). - -@item qXfer:spu:write -The remote stub understands the @samp{qXfer:spu:write} packet -(@pxref{qXfer spu write}). - -@item qXfer:siginfo:read -The remote stub understands the @samp{qXfer:siginfo:read} packet -(@pxref{qXfer siginfo read}). - -@item qXfer:siginfo:write -The remote stub understands the @samp{qXfer:siginfo:write} packet -(@pxref{qXfer siginfo write}). - -@item qXfer:threads:read -The remote stub understands the @samp{qXfer:threads:read} packet -(@pxref{qXfer threads read}). - -@item qXfer:traceframe-info:read -The remote stub understands the @samp{qXfer:traceframe-info:read} -packet (@pxref{qXfer traceframe info read}). - -@item qXfer:uib:read -The remote stub understands the @samp{qXfer:uib:read} -packet (@pxref{qXfer unwind info block}). - -@item qXfer:fdpic:read -The remote stub understands the @samp{qXfer:fdpic:read} -packet (@pxref{qXfer fdpic loadmap read}). - -@item QNonStop -The remote stub understands the @samp{QNonStop} packet -(@pxref{QNonStop}). - -@item QPassSignals -The remote stub understands the @samp{QPassSignals} packet -(@pxref{QPassSignals}). - -@item QStartNoAckMode -The remote stub understands the @samp{QStartNoAckMode} packet and -prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}. - -@item multiprocess -@anchor{multiprocess extensions} -@cindex multiprocess extensions, in remote protocol -The remote stub understands the multiprocess extensions to the remote -protocol syntax. The multiprocess extensions affect the syntax of -thread IDs in both packets and replies (@pxref{thread-id syntax}), and -add process IDs to the @samp{D} packet and @samp{W} and @samp{X} -replies. Note that reporting this feature indicates support for the -syntactic extensions only, not that the stub necessarily supports -debugging of more than one process at a time. The stub must not use -multiprocess extensions in packet replies unless @value{GDBN} has also -indicated it supports them in its @samp{qSupported} request. - -@item qXfer:osdata:read -The remote stub understands the @samp{qXfer:osdata:read} packet -((@pxref{qXfer osdata read}). - -@item ConditionalBreakpoints -The target accepts and implements evaluation of conditional expressions -defined for breakpoints. The target will only report breakpoint triggers -when such conditions are true (@pxref{Conditions, ,Break Conditions}). - -@item ConditionalTracepoints -The remote stub accepts and implements conditional expressions defined -for tracepoints (@pxref{Tracepoint Conditions}). - -@item ReverseContinue -The remote stub accepts and implements the reverse continue packet -(@pxref{bc}). - -@item ReverseStep -The remote stub accepts and implements the reverse step packet -(@pxref{bs}). - -@item TracepointSource -The remote stub understands the @samp{QTDPsrc} packet that supplies -the source form of tracepoint definitions. - -@item QAgent -The remote stub understands the @samp{QAgent} packet. - -@item QAllow -The remote stub understands the @samp{QAllow} packet. - -@item QDisableRandomization -The remote stub understands the @samp{QDisableRandomization} packet. - -@item StaticTracepoint -@cindex static tracepoints, in remote protocol -The remote stub supports static tracepoints. - -@item InstallInTrace -@anchor{install tracepoint in tracing} -The remote stub supports installing tracepoint in tracing. - -@item EnableDisableTracepoints -The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and -@samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints -to be enabled and disabled while a trace experiment is running. - -@item QTBuffer:size -The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size}) -packet that allows to change the size of the trace buffer. - -@item tracenz -@cindex string tracing, in remote protocol -The remote stub supports the @samp{tracenz} bytecode for collecting strings. -See @ref{Bytecode Descriptions} for details about the bytecode. - -@item BreakpointCommands -@cindex breakpoint commands, in remote protocol -The remote stub supports running a breakpoint's command list itself, -rather than reporting the hit to @value{GDBN}. - -@item Qbtrace:off -The remote stub understands the @samp{Qbtrace:off} packet. - -@item Qbtrace:bts -The remote stub understands the @samp{Qbtrace:bts} packet. - -@end table - -@item qSymbol:: -@cindex symbol lookup, remote request -@cindex @samp{qSymbol} packet -Notify the target that @value{GDBN} is prepared to serve symbol lookup -requests. Accept requests from the target for the values of symbols. - -Reply: -@table @samp -@item OK -The target does not need to look up any (more) symbols. -@item qSymbol:@var{sym_name} -The target requests the value of symbol @var{sym_name} (hex encoded). -@value{GDBN} may provide the value by using the -@samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described -below. -@end table - -@item qSymbol:@var{sym_value}:@var{sym_name} -Set the value of @var{sym_name} to @var{sym_value}. - -@var{sym_name} (hex encoded) is the name of a symbol whose value the -target has previously requested. - -@var{sym_value} (hex) is the value for symbol @var{sym_name}. If -@value{GDBN} cannot supply a value for @var{sym_name}, then this field -will be empty. - -Reply: -@table @samp -@item OK -The target does not need to look up any (more) symbols. -@item qSymbol:@var{sym_name} -The target requests the value of a new symbol @var{sym_name} (hex -encoded). @value{GDBN} will continue to supply the values of symbols -(if available), until the target ceases to request them. -@end table - -@item qTBuffer -@itemx QTBuffer -@itemx QTDisconnected -@itemx QTDP -@itemx QTDPsrc -@itemx QTDV -@itemx qTfP -@itemx qTfV -@itemx QTFrame -@itemx qTMinFTPILen - -@xref{Tracepoint Packets}. - -@item qThreadExtraInfo,@var{thread-id} -@cindex thread attributes info, remote request -@cindex @samp{qThreadExtraInfo} packet -Obtain a printable string description of a thread's attributes from -the target OS. @var{thread-id} is a thread ID; -see @ref{thread-id syntax}. This -string may contain anything that the target OS thinks is interesting -for @value{GDBN} to tell the user about the thread. The string is -displayed in @value{GDBN}'s @code{info threads} display. Some -examples of possible thread extra info strings are @samp{Runnable}, or -@samp{Blocked on Mutex}. - -Reply: -@table @samp -@item @var{XX}@dots{} -Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data, -comprising the printable string containing the extra information about -the thread's attributes. -@end table - -(Note that the @code{qThreadExtraInfo} packet's name is separated from -the command by a @samp{,}, not a @samp{:}, contrary to the naming -conventions above. Please don't use this packet as a model for new -packets.) - -@item QTNotes -@itemx qTP -@itemx QTSave -@itemx qTsP -@itemx qTsV -@itemx QTStart -@itemx QTStop -@itemx QTEnable -@itemx QTDisable -@itemx QTinit -@itemx QTro -@itemx qTStatus -@itemx qTV -@itemx qTfSTM -@itemx qTsSTM -@itemx qTSTMat -@xref{Tracepoint Packets}. - -@item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length} -@cindex read special object, remote request -@cindex @samp{qXfer} packet -@anchor{qXfer read} -Read uninterpreted bytes from the target's special data area -identified by the keyword @var{object}. Request @var{length} bytes -starting at @var{offset} bytes into the data. The content and -encoding of @var{annex} is specific to @var{object}; it can supply -additional details about what data to access. - -Here are the specific requests of this form defined so far. All -@samp{qXfer:@var{object}:read:@dots{}} requests use the same reply -formats, listed below. - -@table @samp -@item qXfer:auxv:read::@var{offset},@var{length} -@anchor{qXfer auxiliary vector read} -Access the target's @dfn{auxiliary vector}. @xref{OS Information, -auxiliary vector}. Note @var{annex} must be empty. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:btrace:read:@var{annex}:@var{offset},@var{length} -@anchor{qXfer btrace read} - -Return a description of the current branch trace. -@xref{Branch Trace Format}. The annex part of the generic @samp{qXfer} -packet may have one of the following values: - -@table @code -@item all -Returns all available branch trace. - -@item new -Returns all available branch trace if the branch trace changed since -the last read request. -@end table - -This packet is not probed by default; the remote stub must request it -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:features:read:@var{annex}:@var{offset},@var{length} -@anchor{qXfer target description read} -Access the @dfn{target description}. @xref{Target Descriptions}. The -annex specifies which XML document to access. The main description is -always loaded from the @samp{target.xml} annex. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:libraries:read:@var{annex}:@var{offset},@var{length} -@anchor{qXfer library list read} -Access the target's list of loaded libraries. @xref{Library List Format}. -The annex part of the generic @samp{qXfer} packet must be empty -(@pxref{qXfer read}). - -Targets which maintain a list of libraries in the program's memory do -not need to implement this packet; it is designed for platforms where -the operating system manages the list of loaded libraries. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length} -@anchor{qXfer svr4 library list read} -Access the target's list of loaded libraries when the target is an SVR4 -platform. @xref{Library List Format for SVR4 Targets}. The annex part -of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}). - -This packet is optional for better performance on SVR4 targets. -@value{GDBN} uses memory read packets to read the SVR4 library list otherwise. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:memory-map:read::@var{offset},@var{length} -@anchor{qXfer memory map read} -Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The -annex part of the generic @samp{qXfer} packet must be empty -(@pxref{qXfer read}). - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:sdata:read::@var{offset},@var{length} -@anchor{qXfer sdata read} - -Read contents of the extra collected static tracepoint marker -information. The annex part of the generic @samp{qXfer} packet must -be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint -Action Lists}. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response -(@pxref{qSupported}). - -@item qXfer:siginfo:read::@var{offset},@var{length} -@anchor{qXfer siginfo read} -Read contents of the extra signal information on the target -system. The annex part of the generic @samp{qXfer} packet must be -empty (@pxref{qXfer read}). - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response -(@pxref{qSupported}). - -@item qXfer:spu:read:@var{annex}:@var{offset},@var{length} -@anchor{qXfer spu read} -Read contents of an @code{spufs} file on the target system. The -annex specifies which file to read; it must be of the form -@file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID -in the target process, and @var{name} identifes the @code{spufs} file -in that context to be accessed. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response -(@pxref{qSupported}). - -@item qXfer:threads:read::@var{offset},@var{length} -@anchor{qXfer threads read} -Access the list of threads on target. @xref{Thread List Format}. The -annex part of the generic @samp{qXfer} packet must be empty -(@pxref{qXfer read}). - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:traceframe-info:read::@var{offset},@var{length} -@anchor{qXfer traceframe info read} - -Return a description of the current traceframe's contents. -@xref{Traceframe Info Format}. The annex part of the generic -@samp{qXfer} packet must be empty (@pxref{qXfer read}). - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:uib:read:@var{pc}:@var{offset},@var{length} -@anchor{qXfer unwind info block} - -Return the unwind information block for @var{pc}. This packet is used -on OpenVMS/ia64 to ask the kernel unwind information. - -This packet is not probed by default. - -@item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length} -@anchor{qXfer fdpic loadmap read} -Read contents of @code{loadmap}s on the target system. The -annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap}, -executable @code{loadmap} or interpreter @code{loadmap} to read. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). - -@item qXfer:osdata:read::@var{offset},@var{length} -@anchor{qXfer osdata read} -Access the target's @dfn{operating system information}. -@xref{Operating System Information}. - -@end table - -Reply: -@table @samp -@item m @var{data} -Data @var{data} (@pxref{Binary Data}) has been read from the -target. There may be more data at a higher address (although -it is permitted to return @samp{m} even for the last valid -block of data, as long as at least one byte of data was read). -@var{data} may have fewer bytes than the @var{length} in the -request. - -@item l @var{data} -Data @var{data} (@pxref{Binary Data}) has been read from the target. -There is no more data to be read. @var{data} may have fewer bytes -than the @var{length} in the request. - -@item l -The @var{offset} in the request is at the end of the data. -There is no more data to be read. - -@item E00 -The request was malformed, or @var{annex} was invalid. - -@item E @var{nn} -The offset was invalid, or there was an error encountered reading the data. -@var{nn} is a hex-encoded @code{errno} value. - -@item @w{} -An empty reply indicates the @var{object} string was not recognized by -the stub, or that the object does not support reading. -@end table - -@item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{} -@cindex write data into object, remote request -@anchor{qXfer write} -Write uninterpreted bytes into the target's special data area -identified by the keyword @var{object}, starting at @var{offset} bytes -into the data. @var{data}@dots{} is the binary-encoded data -(@pxref{Binary Data}) to be written. The content and encoding of @var{annex} -is specific to @var{object}; it can supply additional details about what data -to access. - -Here are the specific requests of this form defined so far. All -@samp{qXfer:@var{object}:write:@dots{}} requests use the same reply -formats, listed below. - -@table @samp -@item qXfer:siginfo:write::@var{offset}:@var{data}@dots{} -@anchor{qXfer siginfo write} -Write @var{data} to the extra signal information on the target system. -The annex part of the generic @samp{qXfer} packet must be -empty (@pxref{qXfer write}). - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response -(@pxref{qSupported}). - -@item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{} -@anchor{qXfer spu write} -Write @var{data} to an @code{spufs} file on the target system. The -annex specifies which file to write; it must be of the form -@file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID -in the target process, and @var{name} identifes the @code{spufs} file -in that context to be accessed. - -This packet is not probed by default; the remote stub must request it, -by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). -@end table - -Reply: -@table @samp -@item @var{nn} -@var{nn} (hex encoded) is the number of bytes written. -This may be fewer bytes than supplied in the request. - -@item E00 -The request was malformed, or @var{annex} was invalid. - -@item E @var{nn} -The offset was invalid, or there was an error encountered writing the data. -@var{nn} is a hex-encoded @code{errno} value. - -@item @w{} -An empty reply indicates the @var{object} string was not -recognized by the stub, or that the object does not support writing. -@end table - -@item qXfer:@var{object}:@var{operation}:@dots{} -Requests of this form may be added in the future. When a stub does -not recognize the @var{object} keyword, or its support for -@var{object} does not recognize the @var{operation} keyword, the stub -must respond with an empty packet. - -@item qAttached:@var{pid} -@cindex query attached, remote request -@cindex @samp{qAttached} packet -Return an indication of whether the remote server attached to an -existing process or created a new process. When the multiprocess -protocol extensions are supported (@pxref{multiprocess extensions}), -@var{pid} is an integer in hexadecimal format identifying the target -process. Otherwise, @value{GDBN} will omit the @var{pid} field and -the query packet will be simplified as @samp{qAttached}. - -This query is used, for example, to know whether the remote process -should be detached or killed when a @value{GDBN} session is ended with -the @code{quit} command. - -Reply: -@table @samp -@item 1 -The remote server attached to an existing process. -@item 0 -The remote server created a new process. -@item E @var{NN} -A badly formed request or an error was encountered. -@end table - -@item Qbtrace:bts -Enable branch tracing for the current thread using bts tracing. - -Reply: -@table @samp -@item OK -Branch tracing has been enabled. -@item E.errtext -A badly formed request or an error was encountered. -@end table - -@item Qbtrace:off -Disable branch tracing for the current thread. - -Reply: -@table @samp -@item OK -Branch tracing has been disabled. -@item E.errtext -A badly formed request or an error was encountered. -@end table - -@end table - -@node Architecture-Specific Protocol Details -@section Architecture-Specific Protocol Details - -This section describes how the remote protocol is applied to specific -target architectures. Also see @ref{Standard Target Features}, for -details of XML target descriptions for each architecture. - -@menu -* ARM-Specific Protocol Details:: -* MIPS-Specific Protocol Details:: -@end menu - -@node ARM-Specific Protocol Details -@subsection @acronym{ARM}-specific Protocol Details - -@menu -* ARM Breakpoint Kinds:: -@end menu - -@node ARM Breakpoint Kinds -@subsubsection @acronym{ARM} Breakpoint Kinds -@cindex breakpoint kinds, @acronym{ARM} - -These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets. - -@table @r - -@item 2 -16-bit Thumb mode breakpoint. - -@item 3 -32-bit Thumb mode (Thumb-2) breakpoint. - -@item 4 -32-bit @acronym{ARM} mode breakpoint. - -@end table - -@node MIPS-Specific Protocol Details -@subsection @acronym{MIPS}-specific Protocol Details - -@menu -* MIPS Register packet Format:: -* MIPS Breakpoint Kinds:: -@end menu - -@node MIPS Register packet Format -@subsubsection @acronym{MIPS} Register Packet Format -@cindex register packet format, @acronym{MIPS} - -The following @code{g}/@code{G} packets have previously been defined. -In the below, some thirty-two bit registers are transferred as -sixty-four bits. Those registers should be zero/sign extended (which?) -to fill the space allocated. Register bytes are transferred in target -byte order. The two nibbles within a register byte are transferred -most-significant -- least-significant. - -@table @r - -@item MIPS32 -All registers are transferred as thirty-two bit quantities in the order: -32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point -registers; fsr; fir; fp. - -@item MIPS64 -All registers are transferred as sixty-four bit quantities (including -thirty-two bit registers such as @code{sr}). The ordering is the same -as @code{MIPS32}. - -@end table - -@node MIPS Breakpoint Kinds -@subsubsection @acronym{MIPS} Breakpoint Kinds -@cindex breakpoint kinds, @acronym{MIPS} - -These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets. - -@table @r - -@item 2 -16-bit @acronym{MIPS16} mode breakpoint. - -@item 3 -16-bit @acronym{microMIPS} mode breakpoint. - -@item 4 -32-bit standard @acronym{MIPS} mode breakpoint. - -@item 5 -32-bit @acronym{microMIPS} mode breakpoint. - -@end table - -@node Tracepoint Packets -@section Tracepoint Packets -@cindex tracepoint packets -@cindex packets, tracepoint - -Here we describe the packets @value{GDBN} uses to implement -tracepoints (@pxref{Tracepoints}). - -@table @samp - -@item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]} -@cindex @samp{QTDP} packet -Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena} -is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then -the tracepoint is disabled. @var{step} is the tracepoint's step -count, and @var{pass} is its pass count. If an @samp{F} is present, -then the tracepoint is to be a fast tracepoint, and the @var{flen} is -the number of bytes that the target should copy elsewhere to make room -for the tracepoint. If an @samp{X} is present, it introduces a -tracepoint condition, which consists of a hexadecimal length, followed -by a comma and hex-encoded bytes, in a manner similar to action -encodings as described below. If the trailing @samp{-} is present, -further @samp{QTDP} packets will follow to specify this tracepoint's -actions. - -Replies: -@table @samp -@item OK -The packet was understood and carried out. -@item qRelocInsn -@xref{Tracepoint Packets,,Relocate instruction reply packet}. -@item @w{} -The packet was not recognized. -@end table - -@item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]} -Define actions to be taken when a tracepoint is hit. @var{n} and -@var{addr} must be the same as in the initial @samp{QTDP} packet for -this tracepoint. This packet may only be sent immediately after -another @samp{QTDP} packet that ended with a @samp{-}. If the -trailing @samp{-} is present, further @samp{QTDP} packets will follow, -specifying more actions for this tracepoint. - -In the series of action packets for a given tracepoint, at most one -can have an @samp{S} before its first @var{action}. If such a packet -is sent, it and the following packets define ``while-stepping'' -actions. Any prior packets define ordinary actions --- that is, those -taken when the tracepoint is first hit. If no action packet has an -@samp{S}, then all the packets in the series specify ordinary -tracepoint actions. - -The @samp{@var{action}@dots{}} portion of the packet is a series of -actions, concatenated without separators. Each action has one of the -following forms: - -@table @samp - -@item R @var{mask} -Collect the registers whose bits are set in @var{mask}. @var{mask} is -a hexadecimal number whose @var{i}'th bit is set if register number -@var{i} should be collected. (The least significant bit is numbered -zero.) Note that @var{mask} may be any number of digits long; it may -not fit in a 32-bit word. - -@item M @var{basereg},@var{offset},@var{len} -Collect @var{len} bytes of memory starting at the address in register -number @var{basereg}, plus @var{offset}. If @var{basereg} is -@samp{-1}, then the range has a fixed address: @var{offset} is the -address of the lowest byte to collect. The @var{basereg}, -@var{offset}, and @var{len} parameters are all unsigned hexadecimal -values (the @samp{-1} value for @var{basereg} is a special case). - -@item X @var{len},@var{expr} -Evaluate @var{expr}, whose length is @var{len}, and collect memory as -it directs. @var{expr} is an agent expression, as described in -@ref{Agent Expressions}. Each byte of the expression is encoded as a -two-digit hex number in the packet; @var{len} is the number of bytes -in the expression (and thus one-half the number of hex digits in the -packet). - -@end table - -Any number of actions may be packed together in a single @samp{QTDP} -packet, as long as the packet does not exceed the maximum packet -length (400 bytes, for many stubs). There may be only one @samp{R} -action per tracepoint, and it must precede any @samp{M} or @samp{X} -actions. Any registers referred to by @samp{M} and @samp{X} actions -must be collected by a preceding @samp{R} action. (The -``while-stepping'' actions are treated as if they were attached to a -separate tracepoint, as far as these restrictions are concerned.) - -Replies: -@table @samp -@item OK -The packet was understood and carried out. -@item qRelocInsn -@xref{Tracepoint Packets,,Relocate instruction reply packet}. -@item @w{} -The packet was not recognized. -@end table - -@item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes} -@cindex @samp{QTDPsrc} packet -Specify a source string of tracepoint @var{n} at address @var{addr}. -This is useful to get accurate reproduction of the tracepoints -originally downloaded at the beginning of the trace run. @var{type} -is the name of the tracepoint part, such as @samp{cond} for the -tracepoint's conditional expression (see below for a list of types), while -@var{bytes} is the string, encoded in hexadecimal. - -@var{start} is the offset of the @var{bytes} within the overall source -string, while @var{slen} is the total length of the source string. -This is intended for handling source strings that are longer than will -fit in a single packet. -@c Add detailed example when this info is moved into a dedicated -@c tracepoint descriptions section. - -The available string types are @samp{at} for the location, -@samp{cond} for the conditional, and @samp{cmd} for an action command. -@value{GDBN} sends a separate packet for each command in the action -list, in the same order in which the commands are stored in the list. - -The target does not need to do anything with source strings except -report them back as part of the replies to the @samp{qTfP}/@samp{qTsP} -query packets. - -Although this packet is optional, and @value{GDBN} will only send it -if the target replies with @samp{TracepointSource} @xref{General -Query Packets}, it makes both disconnected tracing and trace files -much easier to use. Otherwise the user must be careful that the -tracepoints in effect while looking at trace frames are identical to -the ones in effect during the trace run; even a small discrepancy -could cause @samp{tdump} not to work, or a particular trace frame not -be found. - -@item QTDV:@var{n}:@var{value} -@cindex define trace state variable, remote request -@cindex @samp{QTDV} packet -Create a new trace state variable, number @var{n}, with an initial -value of @var{value}, which is a 64-bit signed integer. Both @var{n} -and @var{value} are encoded as hexadecimal values. @value{GDBN} has -the option of not using this packet for initial values of zero; the -target should simply create the trace state variables as they are -mentioned in expressions. - -@item QTFrame:@var{n} -@cindex @samp{QTFrame} packet -Select the @var{n}'th tracepoint frame from the buffer, and use the -register and memory contents recorded there to answer subsequent -request packets from @value{GDBN}. - -A successful reply from the stub indicates that the stub has found the -requested frame. The response is a series of parts, concatenated -without separators, describing the frame we selected. Each part has -one of the following forms: - -@table @samp -@item F @var{f} -The selected frame is number @var{n} in the trace frame buffer; -@var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there -was no frame matching the criteria in the request packet. - -@item T @var{t} -The selected trace frame records a hit of tracepoint number @var{t}; -@var{t} is a hexadecimal number. - -@end table - -@item QTFrame:pc:@var{addr} -Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the -currently selected frame whose PC is @var{addr}; -@var{addr} is a hexadecimal number. - -@item QTFrame:tdp:@var{t} -Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the -currently selected frame that is a hit of tracepoint @var{t}; @var{t} -is a hexadecimal number. - -@item QTFrame:range:@var{start}:@var{end} -Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the -currently selected frame whose PC is between @var{start} (inclusive) -and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal -numbers. - -@item QTFrame:outside:@var{start}:@var{end} -Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first -frame @emph{outside} the given range of addresses (exclusive). - -@item qTMinFTPILen -@cindex @samp{qTMinFTPILen} packet -This packet requests the minimum length of instruction at which a fast -tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on -the 32-bit x86 architecture, it is possible to use a 4-byte jump, but -it depends on the target system being able to create trampolines in -the first 64K of memory, which might or might not be possible for that -system. So the reply to this packet will be 4 if it is able to -arrange for that. - -Replies: - -@table @samp -@item 0 -The minimum instruction length is currently unknown. -@item @var{length} -The minimum instruction length is @var{length}, where @var{length} is greater -or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means -that a fast tracepoint may be placed on any instruction regardless of size. -@item E -An error has occurred. -@item @w{} -An empty reply indicates that the request is not supported by the stub. -@end table - -@item QTStart -@cindex @samp{QTStart} packet -Begin the tracepoint experiment. Begin collecting data from -tracepoint hits in the trace frame buffer. This packet supports the -@samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate -instruction reply packet}). - -@item QTStop -@cindex @samp{QTStop} packet -End the tracepoint experiment. Stop collecting trace frames. - -@item QTEnable:@var{n}:@var{addr} -@anchor{QTEnable} -@cindex @samp{QTEnable} packet -Enable tracepoint @var{n} at address @var{addr} in a started tracepoint -experiment. If the tracepoint was previously disabled, then collection -of data from it will resume. - -@item QTDisable:@var{n}:@var{addr} -@anchor{QTDisable} -@cindex @samp{QTDisable} packet -Disable tracepoint @var{n} at address @var{addr} in a started tracepoint -experiment. No more data will be collected from the tracepoint unless -@samp{QTEnable:@var{n}:@var{addr}} is subsequently issued. - -@item QTinit -@cindex @samp{QTinit} packet -Clear the table of tracepoints, and empty the trace frame buffer. - -@item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{} -@cindex @samp{QTro} packet -Establish the given ranges of memory as ``transparent''. The stub -will answer requests for these ranges from memory's current contents, -if they were not collected as part of the tracepoint hit. - -@value{GDBN} uses this to mark read-only regions of memory, like those -containing program code. Since these areas never change, they should -still have the same contents they did when the tracepoint was hit, so -there's no reason for the stub to refuse to provide their contents. - -@item QTDisconnected:@var{value} -@cindex @samp{QTDisconnected} packet -Set the choice to what to do with the tracing run when @value{GDBN} -disconnects from the target. A @var{value} of 1 directs the target to -continue the tracing run, while 0 tells the target to stop tracing if -@value{GDBN} is no longer in the picture. - -@item qTStatus -@cindex @samp{qTStatus} packet -Ask the stub if there is a trace experiment running right now. - -The reply has the form: - -@table @samp - -@item T@var{running}@r{[};@var{field}@r{]}@dots{} -@var{running} is a single digit @code{1} if the trace is presently -running, or @code{0} if not. It is followed by semicolon-separated -optional fields that an agent may use to report additional status. - -@end table - -If the trace is not running, the agent may report any of several -explanations as one of the optional fields: - -@table @samp - -@item tnotrun:0 -No trace has been run yet. - -@item tstop[:@var{text}]:0 -The trace was stopped by a user-originated stop command. The optional -@var{text} field is a user-supplied string supplied as part of the -stop command (for instance, an explanation of why the trace was -stopped manually). It is hex-encoded. - -@item tfull:0 -The trace stopped because the trace buffer filled up. - -@item tdisconnected:0 -The trace stopped because @value{GDBN} disconnected from the target. - -@item tpasscount:@var{tpnum} -The trace stopped because tracepoint @var{tpnum} exceeded its pass count. - -@item terror:@var{text}:@var{tpnum} -The trace stopped because tracepoint @var{tpnum} had an error. The -string @var{text} is available to describe the nature of the error -(for instance, a divide by zero in the condition expression). -@var{text} is hex encoded. - -@item tunknown:0 -The trace stopped for some other reason. - -@end table - -Additional optional fields supply statistical and other information. -Although not required, they are extremely useful for users monitoring -the progress of a trace run. If a trace has stopped, and these -numbers are reported, they must reflect the state of the just-stopped -trace. - -@table @samp - -@item tframes:@var{n} -The number of trace frames in the buffer. - -@item tcreated:@var{n} -The total number of trace frames created during the run. This may -be larger than the trace frame count, if the buffer is circular. - -@item tsize:@var{n} -The total size of the trace buffer, in bytes. - -@item tfree:@var{n} -The number of bytes still unused in the buffer. - -@item circular:@var{n} -The value of the circular trace buffer flag. @code{1} means that the -trace buffer is circular and old trace frames will be discarded if -necessary to make room, @code{0} means that the trace buffer is linear -and may fill up. - -@item disconn:@var{n} -The value of the disconnected tracing flag. @code{1} means that -tracing will continue after @value{GDBN} disconnects, @code{0} means -that the trace run will stop. - -@end table - -@item qTP:@var{tp}:@var{addr} -@cindex tracepoint status, remote request -@cindex @samp{qTP} packet -Ask the stub for the current state of tracepoint number @var{tp} at -address @var{addr}. - -Replies: -@table @samp -@item V@var{hits}:@var{usage} -The tracepoint has been hit @var{hits} times so far during the trace -run, and accounts for @var{usage} in the trace buffer. Note that -@code{while-stepping} steps are not counted as separate hits, but the -steps' space consumption is added into the usage number. - -@end table - -@item qTV:@var{var} -@cindex trace state variable value, remote request -@cindex @samp{qTV} packet -Ask the stub for the value of the trace state variable number @var{var}. - -Replies: -@table @samp -@item V@var{value} -The value of the variable is @var{value}. This will be the current -value of the variable if the user is examining a running target, or a -saved value if the variable was collected in the trace frame that the -user is looking at. Note that multiple requests may result in -different reply values, such as when requesting values while the -program is running. - -@item U -The value of the variable is unknown. This would occur, for example, -if the user is examining a trace frame in which the requested variable -was not collected. -@end table - -@item qTfP -@cindex @samp{qTfP} packet -@itemx qTsP -@cindex @samp{qTsP} packet -These packets request data about tracepoints that are being used by -the target. @value{GDBN} sends @code{qTfP} to get the first piece -of data, and multiple @code{qTsP} to get additional pieces. Replies -to these packets generally take the form of the @code{QTDP} packets -that define tracepoints. (FIXME add detailed syntax) - -@item qTfV -@cindex @samp{qTfV} packet -@itemx qTsV -@cindex @samp{qTsV} packet -These packets request data about trace state variables that are on the -target. @value{GDBN} sends @code{qTfV} to get the first vari of data, -and multiple @code{qTsV} to get additional variables. Replies to -these packets follow the syntax of the @code{QTDV} packets that define -trace state variables. - -@item qTfSTM -@itemx qTsSTM -@anchor{qTfSTM} -@anchor{qTsSTM} -@cindex @samp{qTfSTM} packet -@cindex @samp{qTsSTM} packet -These packets request data about static tracepoint markers that exist -in the target program. @value{GDBN} sends @code{qTfSTM} to get the -first piece of data, and multiple @code{qTsSTM} to get additional -pieces. Replies to these packets take the following form: - -Reply: -@table @samp -@item m @var{address}:@var{id}:@var{extra} -A single marker -@item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{} -a comma-separated list of markers -@item l -(lower case letter @samp{L}) denotes end of list. -@item E @var{nn} -An error occurred. @var{nn} are hex digits. -@item @w{} -An empty reply indicates that the request is not supported by the -stub. -@end table - -@var{address} is encoded in hex. -@var{id} and @var{extra} are strings encoded in hex. - -In response to each query, the target will reply with a list of one or -more markers, separated by commas. @value{GDBN} will respond to each -reply with a request for more markers (using the @samp{qs} form of the -query), until the target responds with @samp{l} (lower-case ell, for -@dfn{last}). - -@item qTSTMat:@var{address} -@anchor{qTSTMat} -@cindex @samp{qTSTMat} packet -This packets requests data about static tracepoint markers in the -target program at @var{address}. Replies to this packet follow the -syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static -tracepoint markers. - -@item QTSave:@var{filename} -@cindex @samp{QTSave} packet -This packet directs the target to save trace data to the file name -@var{filename} in the target's filesystem. @var{filename} is encoded -as a hex string; the interpretation of the file name (relative vs -absolute, wild cards, etc) is up to the target. - -@item qTBuffer:@var{offset},@var{len} -@cindex @samp{qTBuffer} packet -Return up to @var{len} bytes of the current contents of trace buffer, -starting at @var{offset}. The trace buffer is treated as if it were -a contiguous collection of traceframes, as per the trace file format. -The reply consists as many hex-encoded bytes as the target can deliver -in a packet; it is not an error to return fewer than were asked for. -A reply consisting of just @code{l} indicates that no bytes are -available. - -@item QTBuffer:circular:@var{value} -This packet directs the target to use a circular trace buffer if -@var{value} is 1, or a linear buffer if the value is 0. - -@item QTBuffer:size:@var{size} -@anchor{QTBuffer-size} -@cindex @samp{QTBuffer size} packet -This packet directs the target to make the trace buffer be of size -@var{size} if possible. A value of @code{-1} tells the target to -use whatever size it prefers. - -@item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{} -@cindex @samp{QTNotes} packet -This packet adds optional textual notes to the trace run. Allowable -types include @code{user}, @code{notes}, and @code{tstop}, the -@var{text} fields are arbitrary strings, hex-encoded. - -@end table - -@subsection Relocate instruction reply packet -When installing fast tracepoints in memory, the target may need to -relocate the instruction currently at the tracepoint address to a -different address in memory. For most instructions, a simple copy is -enough, but, for example, call instructions that implicitly push the -return address on the stack, and relative branches or other -PC-relative instructions require offset adjustment, so that the effect -of executing the instruction at a different address is the same as if -it had executed in the original location. - -In response to several of the tracepoint packets, the target may also -respond with a number of intermediate @samp{qRelocInsn} request -packets before the final result packet, to have @value{GDBN} handle -this relocation operation. If a packet supports this mechanism, its -documentation will explicitly say so. See for example the above -descriptions for the @samp{QTStart} and @samp{QTDP} packets. The -format of the request is: - -@table @samp -@item qRelocInsn:@var{from};@var{to} - -This requests @value{GDBN} to copy instruction at address @var{from} -to address @var{to}, possibly adjusted so that executing the -instruction at @var{to} has the same effect as executing it at -@var{from}. @value{GDBN} writes the adjusted instruction to target -memory starting at @var{to}. -@end table - -Replies: -@table @samp -@item qRelocInsn:@var{adjusted_size} -Informs the stub the relocation is complete. @var{adjusted_size} is -the length in bytes of resulting relocated instruction sequence. -@item E @var{NN} -A badly formed request was detected, or an error was encountered while -relocating the instruction. -@end table - -@node Host I/O Packets -@section Host I/O Packets -@cindex Host I/O, remote protocol -@cindex file transfer, remote protocol - -The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O -operations on the far side of a remote link. For example, Host I/O is -used to upload and download files to a remote target with its own -filesystem. Host I/O uses the same constant values and data structure -layout as the target-initiated File-I/O protocol. However, the -Host I/O packets are structured differently. The target-initiated -protocol relies on target memory to store parameters and buffers. -Host I/O requests are initiated by @value{GDBN}, and the -target's memory is not involved. @xref{File-I/O Remote Protocol -Extension}, for more details on the target-initiated protocol. - -The Host I/O request packets all encode a single operation along with -its arguments. They have this format: - -@table @samp - -@item vFile:@var{operation}: @var{parameter}@dots{} -@var{operation} is the name of the particular request; the target -should compare the entire packet name up to the second colon when checking -for a supported operation. The format of @var{parameter} depends on -the operation. Numbers are always passed in hexadecimal. Negative -numbers have an explicit minus sign (i.e.@: two's complement is not -used). Strings (e.g.@: filenames) are encoded as a series of -hexadecimal bytes. The last argument to a system call may be a -buffer of escaped binary data (@pxref{Binary Data}). - -@end table - -The valid responses to Host I/O packets are: - -@table @samp - -@item F @var{result} [, @var{errno}] [; @var{attachment}] -@var{result} is the integer value returned by this operation, usually -non-negative for success and -1 for errors. If an error has occured, -@var{errno} will be included in the result. @var{errno} will have a -value defined by the File-I/O protocol (@pxref{Errno Values}). For -operations which return data, @var{attachment} supplies the data as a -binary buffer. Binary buffers in response packets are escaped in the -normal way (@pxref{Binary Data}). See the individual packet -documentation for the interpretation of @var{result} and -@var{attachment}. - -@item @w{} -An empty response indicates that this operation is not recognized. - -@end table - -These are the supported Host I/O operations: - -@table @samp -@item vFile:open: @var{pathname}, @var{flags}, @var{mode} -Open a file at @var{pathname} and return a file descriptor for it, or -return -1 if an error occurs. @var{pathname} is a string, -@var{flags} is an integer indicating a mask of open flags -(@pxref{Open Flags}), and @var{mode} is an integer indicating a mask -of mode bits to use if the file is created (@pxref{mode_t Values}). -@xref{open}, for details of the open flags and mode values. - -@item vFile:close: @var{fd} -Close the open file corresponding to @var{fd} and return 0, or --1 if an error occurs. - -@item vFile:pread: @var{fd}, @var{count}, @var{offset} -Read data from the open file corresponding to @var{fd}. Up to -@var{count} bytes will be read from the file, starting at @var{offset} -relative to the start of the file. The target may read fewer bytes; -common reasons include packet size limits and an end-of-file -condition. The number of bytes read is returned. Zero should only be -returned for a successful read at the end of the file, or if -@var{count} was zero. - -The data read should be returned as a binary attachment on success. -If zero bytes were read, the response should include an empty binary -attachment (i.e.@: a trailing semicolon). The return value is the -number of target bytes read; the binary attachment may be longer if -some characters were escaped. - -@item vFile:pwrite: @var{fd}, @var{offset}, @var{data} -Write @var{data} (a binary buffer) to the open file corresponding -to @var{fd}. Start the write at @var{offset} from the start of the -file. Unlike many @code{write} system calls, there is no -separate @var{count} argument; the length of @var{data} in the -packet is used. @samp{vFile:write} returns the number of bytes written, -which may be shorter than the length of @var{data}, or -1 if an -error occurred. - -@item vFile:unlink: @var{pathname} -Delete the file at @var{pathname} on the target. Return 0, -or -1 if an error occurs. @var{pathname} is a string. - -@item vFile:readlink: @var{filename} -Read value of symbolic link @var{filename} on the target. Return -the number of bytes read, or -1 if an error occurs. - -The data read should be returned as a binary attachment on success. -If zero bytes were read, the response should include an empty binary -attachment (i.e.@: a trailing semicolon). The return value is the -number of target bytes read; the binary attachment may be longer if -some characters were escaped. - -@end table - -@node Interrupts -@section Interrupts -@cindex interrupts (remote protocol) - -When a program on the remote target is running, @value{GDBN} may -attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or -a @code{BREAK} followed by @code{g}, -control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}. - -The precise meaning of @code{BREAK} is defined by the transport -mechanism and may, in fact, be undefined. @value{GDBN} does not -currently define a @code{BREAK} mechanism for any of the network -interfaces except for TCP, in which case @value{GDBN} sends the -@code{telnet} BREAK sequence. - -@samp{Ctrl-C}, on the other hand, is defined and implemented for all -transport mechanisms. It is represented by sending the single byte -@code{0x03} without any of the usual packet overhead described in -the Overview section (@pxref{Overview}). When a @code{0x03} byte is -transmitted as part of a packet, it is considered to be packet data -and does @emph{not} represent an interrupt. E.g., an @samp{X} packet -(@pxref{X packet}), used for binary downloads, may include an unescaped -@code{0x03} as part of its packet. - -@code{BREAK} followed by @code{g} is also known as Magic SysRq g. -When Linux kernel receives this sequence from serial port, -it stops execution and connects to gdb. - -Stubs are not required to recognize these interrupt mechanisms and the -precise meaning associated with receipt of the interrupt is -implementation defined. If the target supports debugging of multiple -threads and/or processes, it should attempt to interrupt all -currently-executing threads and processes. -If the stub is successful at interrupting the -running program, it should send one of the stop -reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result -of successfully stopping the program in all-stop mode, and a stop reply -for each stopped thread in non-stop mode. -Interrupts received while the -program is stopped are discarded. - -@node Notification Packets -@section Notification Packets -@cindex notification packets -@cindex packets, notification - -The @value{GDBN} remote serial protocol includes @dfn{notifications}, -packets that require no acknowledgment. Both the GDB and the stub -may send notifications (although the only notifications defined at -present are sent by the stub). Notifications carry information -without incurring the round-trip latency of an acknowledgment, and so -are useful for low-impact communications where occasional packet loss -is not a problem. - -A notification packet has the form @samp{% @var{data} # -@var{checksum}}, where @var{data} is the content of the notification, -and @var{checksum} is a checksum of @var{data}, computed and formatted -as for ordinary @value{GDBN} packets. A notification's @var{data} -never contains @samp{$}, @samp{%} or @samp{#} characters. Upon -receiving a notification, the recipient sends no @samp{+} or @samp{-} -to acknowledge the notification's receipt or to report its corruption. - -Every notification's @var{data} begins with a name, which contains no -colon characters, followed by a colon character. - -Recipients should silently ignore corrupted notifications and -notifications they do not understand. Recipients should restart -timeout periods on receipt of a well-formed notification, whether or -not they understand it. - -Senders should only send the notifications described here when this -protocol description specifies that they are permitted. In the -future, we may extend the protocol to permit existing notifications in -new contexts; this rule helps older senders avoid confusing newer -recipients. - -(Older versions of @value{GDBN} ignore bytes received until they see -the @samp{$} byte that begins an ordinary packet, so new stubs may -transmit notifications without fear of confusing older clients. There -are no notifications defined for @value{GDBN} to send at the moment, but we -assume that most older stubs would ignore them, as well.) - -Each notification is comprised of three parts: -@table @samp -@item @var{name}:@var{event} -The notification packet is sent by the side that initiates the -exchange (currently, only the stub does that), with @var{event} -carrying the specific information about the notification. -@var{name} is the name of the notification. -@item @var{ack} -The acknowledge sent by the other side, usually @value{GDBN}, to -acknowledge the exchange and request the event. -@end table - -The purpose of an asynchronous notification mechanism is to report to -@value{GDBN} that something interesting happened in the remote stub. - -The remote stub may send notification @var{name}:@var{event} -at any time, but @value{GDBN} acknowledges the notification when -appropriate. The notification event is pending before @value{GDBN} -acknowledges. Only one notification at a time may be pending; if -additional events occur before @value{GDBN} has acknowledged the -previous notification, they must be queued by the stub for later -synchronous transmission in response to @var{ack} packets from -@value{GDBN}. Because the notification mechanism is unreliable, -the stub is permitted to resend a notification if it believes -@value{GDBN} may not have received it. - -Specifically, notifications may appear when @value{GDBN} is not -otherwise reading input from the stub, or when @value{GDBN} is -expecting to read a normal synchronous response or a -@samp{+}/@samp{-} acknowledgment to a packet it has sent. -Notification packets are distinct from any other communication from -the stub so there is no ambiguity. - -After receiving a notification, @value{GDBN} shall acknowledge it by -sending a @var{ack} packet as a regular, synchronous request to the -stub. Such acknowledgment is not required to happen immediately, as -@value{GDBN} is permitted to send other, unrelated packets to the -stub first, which the stub should process normally. - -Upon receiving a @var{ack} packet, if the stub has other queued -events to report to @value{GDBN}, it shall respond by sending a -normal @var{event}. @value{GDBN} shall then send another @var{ack} -packet to solicit further responses; again, it is permitted to send -other, unrelated packets as well which the stub should process -normally. - -If the stub receives a @var{ack} packet and there are no additional -@var{event} to report, the stub shall return an @samp{OK} response. -At this point, @value{GDBN} has finished processing a notification -and the stub has completed sending any queued events. @value{GDBN} -won't accept any new notifications until the final @samp{OK} is -received . If further notification events occur, the stub shall send -a new notification, @value{GDBN} shall accept the notification, and -the process shall be repeated. - -The process of asynchronous notification can be illustrated by the -following example: -@smallexample -<- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;} -@code{...} --> @code{vStopped} -<- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;} --> @code{vStopped} -<- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;} --> @code{vStopped} -<- @code{OK} -@end smallexample - -The following notifications are defined: -@multitable @columnfractions 0.12 0.12 0.38 0.38 - -@item Notification -@tab Ack -@tab Event -@tab Description - -@item Stop -@tab vStopped -@tab @var{reply}. The @var{reply} has the form of a stop reply, as -described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop}, -for information on how these notifications are acknowledged by -@value{GDBN}. -@tab Report an asynchronous stop event in non-stop mode. - -@end multitable - -@node Remote Non-Stop -@section Remote Protocol Support for Non-Stop Mode - -@value{GDBN}'s remote protocol supports non-stop debugging of -multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub -supports non-stop mode, it should report that to @value{GDBN} by including -@samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}). - -@value{GDBN} typically sends a @samp{QNonStop} packet only when -establishing a new connection with the stub. Entering non-stop mode -does not alter the state of any currently-running threads, but targets -must stop all threads in any already-attached processes when entering -all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to -probe the target state after a mode change. - -In non-stop mode, when an attached process encounters an event that -would otherwise be reported with a stop reply, it uses the -asynchronous notification mechanism (@pxref{Notification Packets}) to -inform @value{GDBN}. In contrast to all-stop mode, where all threads -in all processes are stopped when a stop reply is sent, in non-stop -mode only the thread reporting the stop event is stopped. That is, -when reporting a @samp{S} or @samp{T} response to indicate completion -of a step operation, hitting a breakpoint, or a fault, only the -affected thread is stopped; any other still-running threads continue -to run. When reporting a @samp{W} or @samp{X} response, all running -threads belonging to other attached processes continue to run. - -In non-stop mode, the target shall respond to the @samp{?} packet as -follows. First, any incomplete stop reply notification/@samp{vStopped} -sequence in progress is abandoned. The target must begin a new -sequence reporting stop events for all stopped threads, whether or not -it has previously reported those events to @value{GDBN}. The first -stop reply is sent as a synchronous reply to the @samp{?} packet, and -subsequent stop replies are sent as responses to @samp{vStopped} packets -using the mechanism described above. The target must not send -asynchronous stop reply notifications until the sequence is complete. -If all threads are running when the target receives the @samp{?} packet, -or if the target is not attached to any process, it shall respond -@samp{OK}. - -@node Packet Acknowledgment -@section Packet Acknowledgment - -@cindex acknowledgment, for @value{GDBN} remote -@cindex packet acknowledgment, for @value{GDBN} remote -By default, when either the host or the target machine receives a packet, -the first response expected is an acknowledgment: either @samp{+} (to indicate -the package was received correctly) or @samp{-} (to request retransmission). -This mechanism allows the @value{GDBN} remote protocol to operate over -unreliable transport mechanisms, such as a serial line. - -In cases where the transport mechanism is itself reliable (such as a pipe or -TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant. -It may be desirable to disable them in that case to reduce communication -overhead, or for other reasons. This can be accomplished by means of the -@samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}. - -When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or -expect @samp{+}/@samp{-} protocol acknowledgments. The packet -and response format still includes the normal checksum, as described in -@ref{Overview}, but the checksum may be ignored by the receiver. - -If the stub supports @samp{QStartNoAckMode} and prefers to operate in -no-acknowledgment mode, it should report that to @value{GDBN} -by including @samp{QStartNoAckMode+} in its response to @samp{qSupported}; -@pxref{qSupported}. -If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been -disabled via the @code{set remote noack-packet off} command -(@pxref{Remote Configuration}), -@value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub. -Only then may the stub actually turn off packet acknowledgments. -@value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK} -response, which can be safely ignored by the stub. - -Note that @code{set remote noack-packet} command only affects negotiation -between @value{GDBN} and the stub when subsequent connections are made; -it does not affect the protocol acknowledgment state for any current -connection. -Since @samp{+}/@samp{-} acknowledgments are enabled by default when a -new connection is established, -there is also no protocol request to re-enable the acknowledgments -for the current connection, once disabled. - -@node Examples -@section Examples - -Example sequence of a target being re-started. Notice how the restart -does not get any direct output: - -@smallexample --> @code{R00} -<- @code{+} -@emph{target restarts} --> @code{?} -<- @code{+} -<- @code{T001:1234123412341234} --> @code{+} -@end smallexample - -Example sequence of a target being stepped by a single instruction: - -@smallexample --> @code{G1445@dots{}} -<- @code{+} --> @code{s} -<- @code{+} -@emph{time passes} -<- @code{T001:1234123412341234} --> @code{+} --> @code{g} -<- @code{+} -<- @code{1455@dots{}} --> @code{+} -@end smallexample - -@node File-I/O Remote Protocol Extension -@section File-I/O Remote Protocol Extension -@cindex File-I/O remote protocol extension - -@menu -* File-I/O Overview:: -* Protocol Basics:: -* The F Request Packet:: -* The F Reply Packet:: -* The Ctrl-C Message:: -* Console I/O:: -* List of Supported Calls:: -* Protocol-specific Representation of Datatypes:: -* Constants:: -* File-I/O Examples:: -@end menu - -@node File-I/O Overview -@subsection File-I/O Overview -@cindex file-i/o overview - -The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the -target to use the host's file system and console I/O to perform various -system calls. System calls on the target system are translated into a -remote protocol packet to the host system, which then performs the needed -actions and returns a response packet to the target system. -This simulates file system operations even on targets that lack file systems. - -The protocol is defined to be independent of both the host and target systems. -It uses its own internal representation of datatypes and values. Both -@value{GDBN} and the target's @value{GDBN} stub are responsible for -translating the system-dependent value representations into the internal -protocol representations when data is transmitted. - -The communication is synchronous. A system call is possible only when -@value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S} -or @samp{s} packets. While @value{GDBN} handles the request for a system call, -the target is stopped to allow deterministic access to the target's -memory. Therefore File-I/O is not interruptible by target signals. On -the other hand, it is possible to interrupt File-I/O by a user interrupt -(@samp{Ctrl-C}) within @value{GDBN}. - -The target's request to perform a host system call does not finish -the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means, -after finishing the system call, the target returns to continuing the -previous activity (continue, step). No additional continue or step -request from @value{GDBN} is required. - -@smallexample -(@value{GDBP}) continue - <- target requests 'system call X' - target is stopped, @value{GDBN} executes system call - -> @value{GDBN} returns result - ... target continues, @value{GDBN} returns to wait for the target - <- target hits breakpoint and sends a Txx packet -@end smallexample - -The protocol only supports I/O on the console and to regular files on -the host file system. Character or block special devices, pipes, -named pipes, sockets or any other communication method on the host -system are not supported by this protocol. - -File I/O is not supported in non-stop mode. - -@node Protocol Basics -@subsection Protocol Basics -@cindex protocol basics, file-i/o - -The File-I/O protocol uses the @code{F} packet as the request as well -as reply packet. Since a File-I/O system call can only occur when -@value{GDBN} is waiting for a response from the continuing or stepping target, -the File-I/O request is a reply that @value{GDBN} has to expect as a result -of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet. -This @code{F} packet contains all information needed to allow @value{GDBN} -to call the appropriate host system call: - -@itemize @bullet -@item -A unique identifier for the requested system call. - -@item -All parameters to the system call. Pointers are given as addresses -in the target memory address space. Pointers to strings are given as -pointer/length pair. Numerical values are given as they are. -Numerical control flags are given in a protocol-specific representation. - -@end itemize - -At this point, @value{GDBN} has to perform the following actions. - -@itemize @bullet -@item -If the parameters include pointer values to data needed as input to a -system call, @value{GDBN} requests this data from the target with a -standard @code{m} packet request. This additional communication has to be -expected by the target implementation and is handled as any other @code{m} -packet. - -@item -@value{GDBN} translates all value from protocol representation to host -representation as needed. Datatypes are coerced into the host types. - -@item -@value{GDBN} calls the system call. - -@item -It then coerces datatypes back to protocol representation. - -@item -If the system call is expected to return data in buffer space specified -by pointer parameters to the call, the data is transmitted to the -target using a @code{M} or @code{X} packet. This packet has to be expected -by the target implementation and is handled as any other @code{M} or @code{X} -packet. - -@end itemize - -Eventually @value{GDBN} replies with another @code{F} packet which contains all -necessary information for the target to continue. This at least contains - -@itemize @bullet -@item -Return value. - -@item -@code{errno}, if has been changed by the system call. - -@item -``Ctrl-C'' flag. - -@end itemize - -After having done the needed type and value coercion, the target continues -the latest continue or step action. - -@node The F Request Packet -@subsection The @code{F} Request Packet -@cindex file-i/o request packet -@cindex @code{F} request packet - -The @code{F} request packet has the following format: - -@table @samp -@item F@var{call-id},@var{parameter@dots{}} - -@var{call-id} is the identifier to indicate the host system call to be called. -This is just the name of the function. - -@var{parameter@dots{}} are the parameters to the system call. -Parameters are hexadecimal integer values, either the actual values in case -of scalar datatypes, pointers to target buffer space in case of compound -datatypes and unspecified memory areas, or pointer/length pairs in case -of string parameters. These are appended to the @var{call-id} as a -comma-delimited list. All values are transmitted in ASCII -string representation, pointer/length pairs separated by a slash. - -@end table - - - -@node The F Reply Packet -@subsection The @code{F} Reply Packet -@cindex file-i/o reply packet -@cindex @code{F} reply packet - -The @code{F} reply packet has the following format: - -@table @samp - -@item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment} - -@var{retcode} is the return code of the system call as hexadecimal value. - -@var{errno} is the @code{errno} set by the call, in protocol-specific -representation. -This parameter can be omitted if the call was successful. - -@var{Ctrl-C flag} is only sent if the user requested a break. In this -case, @var{errno} must be sent as well, even if the call was successful. -The @var{Ctrl-C flag} itself consists of the character @samp{C}: - -@smallexample -F0,0,C -@end smallexample - -@noindent -or, if the call was interrupted before the host call has been performed: - -@smallexample -F-1,4,C -@end smallexample - -@noindent -assuming 4 is the protocol-specific representation of @code{EINTR}. - -@end table - - -@node The Ctrl-C Message -@subsection The @samp{Ctrl-C} Message -@cindex ctrl-c message, in file-i/o protocol - -If the @samp{Ctrl-C} flag is set in the @value{GDBN} -reply packet (@pxref{The F Reply Packet}), -the target should behave as if it had -gotten a break message. The meaning for the target is ``system call -interrupted by @code{SIGINT}''. Consequentially, the target should actually stop -(as with a break message) and return to @value{GDBN} with a @code{T02} -packet. - -It's important for the target to know in which -state the system call was interrupted. There are two possible cases: - -@itemize @bullet -@item -The system call hasn't been performed on the host yet. - -@item -The system call on the host has been finished. - -@end itemize - -These two states can be distinguished by the target by the value of the -returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system -call hasn't been performed. This is equivalent to the @code{EINTR} handling -on POSIX systems. In any other case, the target may presume that the -system call has been finished --- successfully or not --- and should behave -as if the break message arrived right after the system call. - -@value{GDBN} must behave reliably. If the system call has not been called -yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as -@code{errno} in the packet. If the system call on the host has been finished -before the user requests a break, the full action must be finished by -@value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary. -The @code{F} packet may only be sent when either nothing has happened -or the full action has been completed. - -@node Console I/O -@subsection Console I/O -@cindex console i/o as part of file-i/o - -By default and if not explicitly closed by the target system, the file -descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output -on the @value{GDBN} console is handled as any other file output operation -(@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled -by @value{GDBN} so that after the target read request from file descriptor -0 all following typing is buffered until either one of the following -conditions is met: - -@itemize @bullet -@item -The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the -@code{read} -system call is treated as finished. - -@item -The user presses @key{RET}. This is treated as end of input with a trailing -newline. - -@item -The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing -character (neither newline nor @samp{Ctrl-D}) is appended to the input. - -@end itemize - -If the user has typed more characters than fit in the buffer given to -the @code{read} call, the trailing characters are buffered in @value{GDBN} until -either another @code{read(0, @dots{})} is requested by the target, or debugging -is stopped at the user's request. - - -@node List of Supported Calls -@subsection List of Supported Calls -@cindex list of supported file-i/o calls - -@menu -* open:: -* close:: -* read:: -* write:: -* lseek:: -* rename:: -* unlink:: -* stat/fstat:: -* gettimeofday:: -* isatty:: -* system:: -@end menu - -@node open -@unnumberedsubsubsec open -@cindex open, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int open(const char *pathname, int flags); -int open(const char *pathname, int flags, mode_t mode); -@end smallexample - -@item Request: -@samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}} - -@noindent -@var{flags} is the bitwise @code{OR} of the following values: - -@table @code -@item O_CREAT -If the file does not exist it will be created. The host -rules apply as far as file ownership and time stamps -are concerned. - -@item O_EXCL -When used with @code{O_CREAT}, if the file already exists it is -an error and open() fails. - -@item O_TRUNC -If the file already exists and the open mode allows -writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be -truncated to zero length. - -@item O_APPEND -The file is opened in append mode. - -@item O_RDONLY -The file is opened for reading only. - -@item O_WRONLY -The file is opened for writing only. - -@item O_RDWR -The file is opened for reading and writing. -@end table - -@noindent -Other bits are silently ignored. - - -@noindent -@var{mode} is the bitwise @code{OR} of the following values: - -@table @code -@item S_IRUSR -User has read permission. - -@item S_IWUSR -User has write permission. - -@item S_IRGRP -Group has read permission. - -@item S_IWGRP -Group has write permission. - -@item S_IROTH -Others have read permission. - -@item S_IWOTH -Others have write permission. -@end table - -@noindent -Other bits are silently ignored. - - -@item Return value: -@code{open} returns the new file descriptor or -1 if an error -occurred. - -@item Errors: - -@table @code -@item EEXIST -@var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used. - -@item EISDIR -@var{pathname} refers to a directory. - -@item EACCES -The requested access is not allowed. - -@item ENAMETOOLONG -@var{pathname} was too long. - -@item ENOENT -A directory component in @var{pathname} does not exist. - -@item ENODEV -@var{pathname} refers to a device, pipe, named pipe or socket. - -@item EROFS -@var{pathname} refers to a file on a read-only filesystem and -write access was requested. - -@item EFAULT -@var{pathname} is an invalid pointer value. - -@item ENOSPC -No space on device to create the file. - -@item EMFILE -The process already has the maximum number of files open. - -@item ENFILE -The limit on the total number of files open on the system -has been reached. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node close -@unnumberedsubsubsec close -@cindex close, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int close(int fd); -@end smallexample - -@item Request: -@samp{Fclose,@var{fd}} - -@item Return value: -@code{close} returns zero on success, or -1 if an error occurred. - -@item Errors: - -@table @code -@item EBADF -@var{fd} isn't a valid open file descriptor. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node read -@unnumberedsubsubsec read -@cindex read, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int read(int fd, void *buf, unsigned int count); -@end smallexample - -@item Request: -@samp{Fread,@var{fd},@var{bufptr},@var{count}} - -@item Return value: -On success, the number of bytes read is returned. -Zero indicates end of file. If count is zero, read -returns zero as well. On error, -1 is returned. - -@item Errors: - -@table @code -@item EBADF -@var{fd} is not a valid file descriptor or is not open for -reading. - -@item EFAULT -@var{bufptr} is an invalid pointer value. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node write -@unnumberedsubsubsec write -@cindex write, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int write(int fd, const void *buf, unsigned int count); -@end smallexample - -@item Request: -@samp{Fwrite,@var{fd},@var{bufptr},@var{count}} - -@item Return value: -On success, the number of bytes written are returned. -Zero indicates nothing was written. On error, -1 -is returned. - -@item Errors: - -@table @code -@item EBADF -@var{fd} is not a valid file descriptor or is not open for -writing. - -@item EFAULT -@var{bufptr} is an invalid pointer value. - -@item EFBIG -An attempt was made to write a file that exceeds the -host-specific maximum file size allowed. - -@item ENOSPC -No space on device to write the data. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node lseek -@unnumberedsubsubsec lseek -@cindex lseek, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -long lseek (int fd, long offset, int flag); -@end smallexample - -@item Request: -@samp{Flseek,@var{fd},@var{offset},@var{flag}} - -@var{flag} is one of: - -@table @code -@item SEEK_SET -The offset is set to @var{offset} bytes. - -@item SEEK_CUR -The offset is set to its current location plus @var{offset} -bytes. - -@item SEEK_END -The offset is set to the size of the file plus @var{offset} -bytes. -@end table - -@item Return value: -On success, the resulting unsigned offset in bytes from -the beginning of the file is returned. Otherwise, a -value of -1 is returned. - -@item Errors: - -@table @code -@item EBADF -@var{fd} is not a valid open file descriptor. - -@item ESPIPE -@var{fd} is associated with the @value{GDBN} console. - -@item EINVAL -@var{flag} is not a proper value. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node rename -@unnumberedsubsubsec rename -@cindex rename, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int rename(const char *oldpath, const char *newpath); -@end smallexample - -@item Request: -@samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}} - -@item Return value: -On success, zero is returned. On error, -1 is returned. - -@item Errors: - -@table @code -@item EISDIR -@var{newpath} is an existing directory, but @var{oldpath} is not a -directory. - -@item EEXIST -@var{newpath} is a non-empty directory. - -@item EBUSY -@var{oldpath} or @var{newpath} is a directory that is in use by some -process. - -@item EINVAL -An attempt was made to make a directory a subdirectory -of itself. - -@item ENOTDIR -A component used as a directory in @var{oldpath} or new -path is not a directory. Or @var{oldpath} is a directory -and @var{newpath} exists but is not a directory. - -@item EFAULT -@var{oldpathptr} or @var{newpathptr} are invalid pointer values. - -@item EACCES -No access to the file or the path of the file. - -@item ENAMETOOLONG - -@var{oldpath} or @var{newpath} was too long. - -@item ENOENT -A directory component in @var{oldpath} or @var{newpath} does not exist. - -@item EROFS -The file is on a read-only filesystem. - -@item ENOSPC -The device containing the file has no room for the new -directory entry. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node unlink -@unnumberedsubsubsec unlink -@cindex unlink, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int unlink(const char *pathname); -@end smallexample - -@item Request: -@samp{Funlink,@var{pathnameptr}/@var{len}} - -@item Return value: -On success, zero is returned. On error, -1 is returned. - -@item Errors: - -@table @code -@item EACCES -No access to the file or the path of the file. - -@item EPERM -The system does not allow unlinking of directories. - -@item EBUSY -The file @var{pathname} cannot be unlinked because it's -being used by another process. - -@item EFAULT -@var{pathnameptr} is an invalid pointer value. - -@item ENAMETOOLONG -@var{pathname} was too long. - -@item ENOENT -A directory component in @var{pathname} does not exist. - -@item ENOTDIR -A component of the path is not a directory. - -@item EROFS -The file is on a read-only filesystem. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node stat/fstat -@unnumberedsubsubsec stat/fstat -@cindex fstat, file-i/o system call -@cindex stat, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int stat(const char *pathname, struct stat *buf); -int fstat(int fd, struct stat *buf); -@end smallexample - -@item Request: -@samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@* -@samp{Ffstat,@var{fd},@var{bufptr}} - -@item Return value: -On success, zero is returned. On error, -1 is returned. - -@item Errors: - -@table @code -@item EBADF -@var{fd} is not a valid open file. - -@item ENOENT -A directory component in @var{pathname} does not exist or the -path is an empty string. - -@item ENOTDIR -A component of the path is not a directory. - -@item EFAULT -@var{pathnameptr} is an invalid pointer value. - -@item EACCES -No access to the file or the path of the file. - -@item ENAMETOOLONG -@var{pathname} was too long. - -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@node gettimeofday -@unnumberedsubsubsec gettimeofday -@cindex gettimeofday, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int gettimeofday(struct timeval *tv, void *tz); -@end smallexample - -@item Request: -@samp{Fgettimeofday,@var{tvptr},@var{tzptr}} - -@item Return value: -On success, 0 is returned, -1 otherwise. - -@item Errors: - -@table @code -@item EINVAL -@var{tz} is a non-NULL pointer. - -@item EFAULT -@var{tvptr} and/or @var{tzptr} is an invalid pointer value. -@end table - -@end table - -@node isatty -@unnumberedsubsubsec isatty -@cindex isatty, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int isatty(int fd); -@end smallexample - -@item Request: -@samp{Fisatty,@var{fd}} - -@item Return value: -Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise. - -@item Errors: - -@table @code -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -Note that the @code{isatty} call is treated as a special case: it returns -1 to the target if the file descriptor is attached -to the @value{GDBN} console, 0 otherwise. Implementing through system calls -would require implementing @code{ioctl} and would be more complex than -needed. - - -@node system -@unnumberedsubsubsec system -@cindex system, file-i/o system call - -@table @asis -@item Synopsis: -@smallexample -int system(const char *command); -@end smallexample - -@item Request: -@samp{Fsystem,@var{commandptr}/@var{len}} - -@item Return value: -If @var{len} is zero, the return value indicates whether a shell is -available. A zero return value indicates a shell is not available. -For non-zero @var{len}, the value returned is -1 on error and the -return status of the command otherwise. Only the exit status of the -command is returned, which is extracted from the host's @code{system} -return value by calling @code{WEXITSTATUS(retval)}. In case -@file{/bin/sh} could not be executed, 127 is returned. - -@item Errors: - -@table @code -@item EINTR -The call was interrupted by the user. -@end table - -@end table - -@value{GDBN} takes over the full task of calling the necessary host calls -to perform the @code{system} call. The return value of @code{system} on -the host is simplified before it's returned -to the target. Any termination signal information from the child process -is discarded, and the return value consists -entirely of the exit status of the called command. - -Due to security concerns, the @code{system} call is by default refused -by @value{GDBN}. The user has to allow this call explicitly with the -@code{set remote system-call-allowed 1} command. - -@table @code -@item set remote system-call-allowed -@kindex set remote system-call-allowed -Control whether to allow the @code{system} calls in the File I/O -protocol for the remote target. The default is zero (disabled). - -@item show remote system-call-allowed -@kindex show remote system-call-allowed -Show whether the @code{system} calls are allowed in the File I/O -protocol. -@end table - -@node Protocol-specific Representation of Datatypes -@subsection Protocol-specific Representation of Datatypes -@cindex protocol-specific representation of datatypes, in file-i/o protocol - -@menu -* Integral Datatypes:: -* Pointer Values:: -* Memory Transfer:: -* struct stat:: -* struct timeval:: -@end menu - -@node Integral Datatypes -@unnumberedsubsubsec Integral Datatypes -@cindex integral datatypes, in file-i/o protocol - -The integral datatypes used in the system calls are @code{int}, -@code{unsigned int}, @code{long}, @code{unsigned long}, -@code{mode_t}, and @code{time_t}. - -@code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are -implemented as 32 bit values in this protocol. - -@code{long} and @code{unsigned long} are implemented as 64 bit types. - -@xref{Limits}, for corresponding MIN and MAX values (similar to those -in @file{limits.h}) to allow range checking on host and target. - -@code{time_t} datatypes are defined as seconds since the Epoch. - -All integral datatypes transferred as part of a memory read or write of a -structured datatype e.g.@: a @code{struct stat} have to be given in big endian -byte order. - -@node Pointer Values -@unnumberedsubsubsec Pointer Values -@cindex pointer values, in file-i/o protocol - -Pointers to target data are transmitted as they are. An exception -is made for pointers to buffers for which the length isn't -transmitted as part of the function call, namely strings. Strings -are transmitted as a pointer/length pair, both as hex values, e.g.@: - -@smallexample -@code{1aaf/12} -@end smallexample - -@noindent -which is a pointer to data of length 18 bytes at position 0x1aaf. -The length is defined as the full string length in bytes, including -the trailing null byte. For example, the string @code{"hello world"} -at address 0x123456 is transmitted as - -@smallexample -@code{123456/d} -@end smallexample - -@node Memory Transfer -@unnumberedsubsubsec Memory Transfer -@cindex memory transfer, in file-i/o protocol - -Structured data which is transferred using a memory read or write (for -example, a @code{struct stat}) is expected to be in a protocol-specific format -with all scalar multibyte datatypes being big endian. Translation to -this representation needs to be done both by the target before the @code{F} -packet is sent, and by @value{GDBN} before -it transfers memory to the target. Transferred pointers to structured -data should point to the already-coerced data at any time. - - -@node struct stat -@unnumberedsubsubsec struct stat -@cindex struct stat, in file-i/o protocol - -The buffer of type @code{struct stat} used by the target and @value{GDBN} -is defined as follows: - -@smallexample -struct stat @{ - unsigned int st_dev; /* device */ - unsigned int st_ino; /* inode */ - mode_t st_mode; /* protection */ - unsigned int st_nlink; /* number of hard links */ - unsigned int st_uid; /* user ID of owner */ - unsigned int st_gid; /* group ID of owner */ - unsigned int st_rdev; /* device type (if inode device) */ - unsigned long st_size; /* total size, in bytes */ - unsigned long st_blksize; /* blocksize for filesystem I/O */ - unsigned long st_blocks; /* number of blocks allocated */ - time_t st_atime; /* time of last access */ - time_t st_mtime; /* time of last modification */ - time_t st_ctime; /* time of last change */ -@}; -@end smallexample - -The integral datatypes conform to the definitions given in the -appropriate section (see @ref{Integral Datatypes}, for details) so this -structure is of size 64 bytes. - -The values of several fields have a restricted meaning and/or -range of values. - -@table @code - -@item st_dev -A value of 0 represents a file, 1 the console. - -@item st_ino -No valid meaning for the target. Transmitted unchanged. - -@item st_mode -Valid mode bits are described in @ref{Constants}. Any other -bits have currently no meaning for the target. - -@item st_uid -@itemx st_gid -@itemx st_rdev -No valid meaning for the target. Transmitted unchanged. - -@item st_atime -@itemx st_mtime -@itemx st_ctime -These values have a host and file system dependent -accuracy. Especially on Windows hosts, the file system may not -support exact timing values. -@end table - -The target gets a @code{struct stat} of the above representation and is -responsible for coercing it to the target representation before -continuing. - -Note that due to size differences between the host, target, and protocol -representations of @code{struct stat} members, these members could eventually -get truncated on the target. - -@node struct timeval -@unnumberedsubsubsec struct timeval -@cindex struct timeval, in file-i/o protocol - -The buffer of type @code{struct timeval} used by the File-I/O protocol -is defined as follows: - -@smallexample -struct timeval @{ - time_t tv_sec; /* second */ - long tv_usec; /* microsecond */ -@}; -@end smallexample - -The integral datatypes conform to the definitions given in the -appropriate section (see @ref{Integral Datatypes}, for details) so this -structure is of size 8 bytes. - -@node Constants -@subsection Constants -@cindex constants, in file-i/o protocol - -The following values are used for the constants inside of the -protocol. @value{GDBN} and target are responsible for translating these -values before and after the call as needed. - -@menu -* Open Flags:: -* mode_t Values:: -* Errno Values:: -* Lseek Flags:: -* Limits:: -@end menu - -@node Open Flags -@unnumberedsubsubsec Open Flags -@cindex open flags, in file-i/o protocol - -All values are given in hexadecimal representation. - -@smallexample - O_RDONLY 0x0 - O_WRONLY 0x1 - O_RDWR 0x2 - O_APPEND 0x8 - O_CREAT 0x200 - O_TRUNC 0x400 - O_EXCL 0x800 -@end smallexample - -@node mode_t Values -@unnumberedsubsubsec mode_t Values -@cindex mode_t values, in file-i/o protocol - -All values are given in octal representation. - -@smallexample - S_IFREG 0100000 - S_IFDIR 040000 - S_IRUSR 0400 - S_IWUSR 0200 - S_IXUSR 0100 - S_IRGRP 040 - S_IWGRP 020 - S_IXGRP 010 - S_IROTH 04 - S_IWOTH 02 - S_IXOTH 01 -@end smallexample - -@node Errno Values -@unnumberedsubsubsec Errno Values -@cindex errno values, in file-i/o protocol - -All values are given in decimal representation. - -@smallexample - EPERM 1 - ENOENT 2 - EINTR 4 - EBADF 9 - EACCES 13 - EFAULT 14 - EBUSY 16 - EEXIST 17 - ENODEV 19 - ENOTDIR 20 - EISDIR 21 - EINVAL 22 - ENFILE 23 - EMFILE 24 - EFBIG 27 - ENOSPC 28 - ESPIPE 29 - EROFS 30 - ENAMETOOLONG 91 - EUNKNOWN 9999 -@end smallexample - - @code{EUNKNOWN} is used as a fallback error value if a host system returns - any error value not in the list of supported error numbers. - -@node Lseek Flags -@unnumberedsubsubsec Lseek Flags -@cindex lseek flags, in file-i/o protocol - -@smallexample - SEEK_SET 0 - SEEK_CUR 1 - SEEK_END 2 -@end smallexample - -@node Limits -@unnumberedsubsubsec Limits -@cindex limits, in file-i/o protocol - -All values are given in decimal representation. - -@smallexample - INT_MIN -2147483648 - INT_MAX 2147483647 - UINT_MAX 4294967295 - LONG_MIN -9223372036854775808 - LONG_MAX 9223372036854775807 - ULONG_MAX 18446744073709551615 -@end smallexample - -@node File-I/O Examples -@subsection File-I/O Examples -@cindex file-i/o examples - -Example sequence of a write call, file descriptor 3, buffer is at target -address 0x1234, 6 bytes should be written: - -@smallexample -<- @code{Fwrite,3,1234,6} -@emph{request memory read from target} --> @code{m1234,6} -<- XXXXXX -@emph{return "6 bytes written"} --> @code{F6} -@end smallexample - -Example sequence of a read call, file descriptor 3, buffer is at target -address 0x1234, 6 bytes should be read: - -@smallexample -<- @code{Fread,3,1234,6} -@emph{request memory write to target} --> @code{X1234,6:XXXXXX} -@emph{return "6 bytes read"} --> @code{F6} -@end smallexample - -Example sequence of a read call, call fails on the host due to invalid -file descriptor (@code{EBADF}): - -@smallexample -<- @code{Fread,3,1234,6} --> @code{F-1,9} -@end smallexample - -Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on -host is called: - -@smallexample -<- @code{Fread,3,1234,6} --> @code{F-1,4,C} -<- @code{T02} -@end smallexample - -Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on -host is called: - -@smallexample -<- @code{Fread,3,1234,6} --> @code{X1234,6:XXXXXX} -<- @code{T02} -@end smallexample - -@node Library List Format -@section Library List Format -@cindex library list format, remote protocol - -On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the -same process as your application to manage libraries. In this case, -@value{GDBN} can use the loader's symbol table and normal memory -operations to maintain a list of shared libraries. On other -platforms, the operating system manages loaded libraries. -@value{GDBN} can not retrieve the list of currently loaded libraries -through memory operations, so it uses the @samp{qXfer:libraries:read} -packet (@pxref{qXfer library list read}) instead. The remote stub -queries the target's operating system and reports which libraries -are loaded. - -The @samp{qXfer:libraries:read} packet returns an XML document which -lists loaded libraries and their offsets. Each library has an -associated name and one or more segment or section base addresses, -which report where the library was loaded in memory. - -For the common case of libraries that are fully linked binaries, the -library should have a list of segments. If the target supports -dynamic linking of a relocatable object file, its library XML element -should instead include a list of allocated sections. The segment or -section bases are start addresses, not relocation offsets; they do not -depend on the library's link-time base addresses. - -@value{GDBN} must be linked with the Expat library to support XML -library lists. @xref{Expat}. - -A simple memory map, with one loaded library relocated by a single -offset, looks like this: - -@smallexample - - - - - -@end smallexample - -Another simple memory map, with one loaded library with three -allocated sections (.text, .data, .bss), looks like this: - -@smallexample - - -
-
-
- - -@end smallexample - -The format of a library list is described by this DTD: - -@smallexample - - - - - - - - - -@end smallexample - -In addition, segments and section descriptors cannot be mixed within a -single library element, and you must supply at least one segment or -section for each library. - -@node Library List Format for SVR4 Targets -@section Library List Format for SVR4 Targets -@cindex library list format, remote protocol - -On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader -(e.g.@: @file{ld.so}) and normal memory operations to maintain a list of -shared libraries. Still a special library list provided by this packet is -more efficient for the @value{GDBN} remote protocol. - -The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists -loaded libraries and their SVR4 linker parameters. For each library on SVR4 -target, the following parameters are reported: - -@itemize @minus -@item -@code{name}, the absolute file name from the @code{l_name} field of -@code{struct link_map}. -@item -@code{lm} with address of @code{struct link_map} used for TLS -(Thread Local Storage) access. -@item -@code{l_addr}, the displacement as read from the field @code{l_addr} of -@code{struct link_map}. For prelinked libraries this is not an absolute -memory address. It is a displacement of absolute memory address against -address the file was prelinked to during the library load. -@item -@code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment -@end itemize - -Additionally the single @code{main-lm} attribute specifies address of -@code{struct link_map} used for the main executable. This parameter is used -for TLS access and its presence is optional. - -@value{GDBN} must be linked with the Expat library to support XML -SVR4 library lists. @xref{Expat}. - -A simple memory map, with two loaded libraries (which do not use prelink), -looks like this: - -@smallexample - - - - -@end smallexample - -The format of an SVR4 library list is described by this DTD: - -@smallexample - - - - - - - - - -@end smallexample - -@node Memory Map Format -@section Memory Map Format -@cindex memory map format - -To be able to write into flash memory, @value{GDBN} needs to obtain a -memory map from the target. This section describes the format of the -memory map. - -The memory map is obtained using the @samp{qXfer:memory-map:read} -(@pxref{qXfer memory map read}) packet and is an XML document that -lists memory regions. - -@value{GDBN} must be linked with the Expat library to support XML -memory maps. @xref{Expat}. - -The top-level structure of the document is shown below: - -@smallexample - - - - region... - -@end smallexample - -Each region can be either: - -@itemize - -@item -A region of RAM starting at @var{addr} and extending for @var{length} -bytes from there: - -@smallexample - -@end smallexample - - -@item -A region of read-only memory: - -@smallexample - -@end smallexample - - -@item -A region of flash memory, with erasure blocks @var{blocksize} -bytes in length: - -@smallexample - - @var{blocksize} - -@end smallexample - -@end itemize - -Regions must not overlap. @value{GDBN} assumes that areas of memory not covered -by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X} -packets to write to addresses in such ranges. - -The formal DTD for memory map format is given below: - -@smallexample - - - - - - - - - - - - - - -@end smallexample - -@node Thread List Format -@section Thread List Format -@cindex thread list format - -To efficiently update the list of threads and their attributes, -@value{GDBN} issues the @samp{qXfer:threads:read} packet -(@pxref{qXfer threads read}) and obtains the XML document with -the following structure: - -@smallexample - - - - ... description ... - - -@end smallexample - -Each @samp{thread} element must have the @samp{id} attribute that -identifies the thread (@pxref{thread-id syntax}). The -@samp{core} attribute, if present, specifies which processor core -the thread was last executing on. The content of the of @samp{thread} -element is interpreted as human-readable auxilliary information. - -@node Traceframe Info Format -@section Traceframe Info Format -@cindex traceframe info format - -To be able to know which objects in the inferior can be examined when -inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of -memory ranges, registers and trace state variables that have been -collected in a traceframe. - -This list is obtained using the @samp{qXfer:traceframe-info:read} -(@pxref{qXfer traceframe info read}) packet and is an XML document. - -@value{GDBN} must be linked with the Expat library to support XML -traceframe info discovery. @xref{Expat}. - -The top-level structure of the document is shown below: - -@smallexample - - - - block... - -@end smallexample - -Each traceframe block can be either: - -@itemize - -@item -A region of collected memory starting at @var{addr} and extending for -@var{length} bytes from there: - -@smallexample - -@end smallexample - -@end itemize - -The formal DTD for the traceframe info format is given below: - -@smallexample - - - - - -@end smallexample - -@node Branch Trace Format -@section Branch Trace Format -@cindex branch trace format - -In order to display the branch trace of an inferior thread, -@value{GDBN} needs to obtain the list of branches. This list is -represented as list of sequential code blocks that are connected via -branches. The code in each block has been executed sequentially. - -This list is obtained using the @samp{qXfer:btrace:read} -(@pxref{qXfer btrace read}) packet and is an XML document. - -@value{GDBN} must be linked with the Expat library to support XML -traceframe info discovery. @xref{Expat}. - -The top-level structure of the document is shown below: - -@smallexample - - - - block... - -@end smallexample - -@itemize - -@item -A block of sequentially executed instructions starting at @var{begin} -and ending at @var{end}: - -@smallexample - -@end smallexample - -@end itemize - -The formal DTD for the branch trace format is given below: - -@smallexample - - - - - -@end smallexample - -@include agentexpr.texi - -@node Target Descriptions -@appendix Target Descriptions -@cindex target descriptions - -One of the challenges of using @value{GDBN} to debug embedded systems -is that there are so many minor variants of each processor -architecture in use. It is common practice for vendors to start with -a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example --- -and then make changes to adapt it to a particular market niche. Some -architectures have hundreds of variants, available from dozens of -vendors. This leads to a number of problems: - -@itemize @bullet -@item -With so many different customized processors, it is difficult for -the @value{GDBN} maintainers to keep up with the changes. -@item -Since individual variants may have short lifetimes or limited -audiences, it may not be worthwhile to carry information about every -variant in the @value{GDBN} source tree. -@item -When @value{GDBN} does support the architecture of the embedded system -at hand, the task of finding the correct architecture name to give the -@command{set architecture} command can be error-prone. -@end itemize - -To address these problems, the @value{GDBN} remote protocol allows a -target system to not only identify itself to @value{GDBN}, but to -actually describe its own features. This lets @value{GDBN} support -processor variants it has never seen before --- to the extent that the -descriptions are accurate, and that @value{GDBN} understands them. - -@value{GDBN} must be linked with the Expat library to support XML -target descriptions. @xref{Expat}. - -@menu -* Retrieving Descriptions:: How descriptions are fetched from a target. -* Target Description Format:: The contents of a target description. -* Predefined Target Types:: Standard types available for target - descriptions. -* Standard Target Features:: Features @value{GDBN} knows about. -@end menu - -@node Retrieving Descriptions -@section Retrieving Descriptions - -Target descriptions can be read from the target automatically, or -specified by the user manually. The default behavior is to read the -description from the target. @value{GDBN} retrieves it via the remote -protocol using @samp{qXfer} requests (@pxref{General Query Packets, -qXfer}). The @var{annex} in the @samp{qXfer} packet will be -@samp{target.xml}. The contents of the @samp{target.xml} annex are an -XML document, of the form described in @ref{Target Description -Format}. - -Alternatively, you can specify a file to read for the target description. -If a file is set, the target will not be queried. The commands to -specify a file are: - -@table @code -@cindex set tdesc filename -@item set tdesc filename @var{path} -Read the target description from @var{path}. - -@cindex unset tdesc filename -@item unset tdesc filename -Do not read the XML target description from a file. @value{GDBN} -will use the description supplied by the current target. - -@cindex show tdesc filename -@item show tdesc filename -Show the filename to read for a target description, if any. -@end table - - -@node Target Description Format -@section Target Description Format -@cindex target descriptions, XML format - -A target description annex is an @uref{http://www.w3.org/XML/, XML} -document which complies with the Document Type Definition provided in -the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This -means you can use generally available tools like @command{xmllint} to -check that your feature descriptions are well-formed and valid. -However, to help people unfamiliar with XML write descriptions for -their targets, we also describe the grammar here. - -Target descriptions can identify the architecture of the remote target -and (for some architectures) provide information about custom register -sets. They can also identify the OS ABI of the remote target. -@value{GDBN} can use this information to autoconfigure for your -target, or to warn you if you connect to an unsupported target. - -Here is a simple target description: - -@smallexample - - i386:x86-64 - -@end smallexample - -@noindent -This minimal description only says that the target uses -the x86-64 architecture. - -A target description has the following overall form, with [ ] marking -optional elements and @dots{} marking repeatable elements. The elements -are explained further below. - -@smallexample - - - - @r{[}@var{architecture}@r{]} - @r{[}@var{osabi}@r{]} - @r{[}@var{compatible}@r{]} - @r{[}@var{feature}@dots{}@r{]} - -@end smallexample - -@noindent -The description is generally insensitive to whitespace and line -breaks, under the usual common-sense rules. The XML version -declaration and document type declaration can generally be omitted -(@value{GDBN} does not require them), but specifying them may be -useful for XML validation tools. The @samp{version} attribute for -@samp{} may also be omitted, but we recommend -including it; if future versions of @value{GDBN} use an incompatible -revision of @file{gdb-target.dtd}, they will detect and report -the version mismatch. - -@subsection Inclusion -@cindex target descriptions, inclusion -@cindex XInclude -@ifnotinfo -@cindex -@end ifnotinfo - -It can sometimes be valuable to split a target description up into -several different annexes, either for organizational purposes, or to -share files between different possible target descriptions. You can -divide a description into multiple files by replacing any element of -the target description with an inclusion directive of the form: - -@smallexample - -@end smallexample - -@noindent -When @value{GDBN} encounters an element of this form, it will retrieve -the named XML @var{document}, and replace the inclusion directive with -the contents of that document. If the current description was read -using @samp{qXfer}, then so will be the included document; -@var{document} will be interpreted as the name of an annex. If the -current description was read from a file, @value{GDBN} will look for -@var{document} as a file in the same directory where it found the -original description. - -@subsection Architecture -@cindex - -An @samp{} element has this form: - -@smallexample - @var{arch} -@end smallexample - -@var{arch} is one of the architectures from the set accepted by -@code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}). - -@subsection OS ABI -@cindex @code{} - -This optional field was introduced in @value{GDBN} version 7.0. -Previous versions of @value{GDBN} ignore it. - -An @samp{} element has this form: - -@smallexample - @var{abi-name} -@end smallexample - -@var{abi-name} is an OS ABI name from the same selection accepted by -@w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}). - -@subsection Compatible Architecture -@cindex @code{} - -This optional field was introduced in @value{GDBN} version 7.0. -Previous versions of @value{GDBN} ignore it. - -A @samp{} element has this form: - -@smallexample - @var{arch} -@end smallexample - -@var{arch} is one of the architectures from the set accepted by -@code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}). - -A @samp{} element is used to specify that the target -is able to run binaries in some other than the main target architecture -given by the @samp{} element. For example, on the -Cell Broadband Engine, the main architecture is @code{powerpc:common} -or @code{powerpc:common64}, but the system is able to run binaries -in the @code{spu} architecture as well. The way to describe this -capability with @samp{} is as follows: - -@smallexample - powerpc:common - spu -@end smallexample - -@subsection Features -@cindex - -Each @samp{} describes some logical portion of the target -system. Features are currently used to describe available CPU -registers and the types of their contents. A @samp{} element -has this form: - -@smallexample - - @r{[}@var{type}@dots{}@r{]} - @var{reg}@dots{} - -@end smallexample - -@noindent -Each feature's name should be unique within the description. The name -of a feature does not matter unless @value{GDBN} has some special -knowledge of the contents of that feature; if it does, the feature -should have its standard name. @xref{Standard Target Features}. - -@subsection Types - -Any register's value is a collection of bits which @value{GDBN} must -interpret. The default interpretation is a two's complement integer, -but other types can be requested by name in the register description. -Some predefined types are provided by @value{GDBN} (@pxref{Predefined -Target Types}), and the description can define additional composite types. - -Each type element must have an @samp{id} attribute, which gives -a unique (within the containing @samp{}) name to the type. -Types must be defined before they are used. - -@cindex -Some targets offer vector registers, which can be treated as arrays -of scalar elements. These types are written as @samp{} elements, -specifying the array element type, @var{type}, and the number of elements, -@var{count}: - -@smallexample - -@end smallexample - -@cindex -If a register's value is usefully viewed in multiple ways, define it -with a union type containing the useful representations. The -@samp{} element contains one or more @samp{} elements, -each of which has a @var{name} and a @var{type}: - -@smallexample - - - @dots{} - -@end smallexample - -@cindex -If a register's value is composed from several separate values, define -it with a structure type. There are two forms of the @samp{} -element; a @samp{} element must either contain only bitfields -or contain no bitfields. If the structure contains only bitfields, -its total size in bytes must be specified, each bitfield must have an -explicit start and end, and bitfields are automatically assigned an -integer type. The field's @var{start} should be less than or -equal to its @var{end}, and zero represents the least significant bit. - -@smallexample - - - @dots{} - -@end smallexample - -If the structure contains no bitfields, then each field has an -explicit type, and no implicit padding is added. - -@smallexample - - - @dots{} - -@end smallexample - -@cindex -If a register's value is a series of single-bit flags, define it with -a flags type. The @samp{} element has an explicit @var{size} -and contains one or more @samp{} elements. Each field has a -@var{name}, a @var{start}, and an @var{end}. Only single-bit flags -are supported. - -@smallexample - - - @dots{} - -@end smallexample - -@subsection Registers -@cindex - -Each register is represented as an element with this form: - -@smallexample - -@end smallexample - -@noindent -The components are as follows: - -@table @var - -@item name -The register's name; it must be unique within the target description. - -@item bitsize -The register's size, in bits. - -@item regnum -The register's number. If omitted, a register's number is one greater -than that of the previous register (either in the current feature or in -a preceding feature); the first register in the target description -defaults to zero. This register number is used to read or write -the register; e.g.@: it is used in the remote @code{p} and @code{P} -packets, and registers appear in the @code{g} and @code{G} packets -in order of increasing register number. - -@item save-restore -Whether the register should be preserved across inferior function -calls; this must be either @code{yes} or @code{no}. The default is -@code{yes}, which is appropriate for most registers except for -some system control registers; this is not related to the target's -ABI. - -@item type -The type of the register. @var{type} may be a predefined type, a type -defined in the current feature, or one of the special types @code{int} -and @code{float}. @code{int} is an integer type of the correct size -for @var{bitsize}, and @code{float} is a floating point type (in the -architecture's normal floating point format) of the correct size for -@var{bitsize}. The default is @code{int}. - -@item group -The register group to which this register belongs. @var{group} must -be either @code{general}, @code{float}, or @code{vector}. If no -@var{group} is specified, @value{GDBN} will not display the register -in @code{info registers}. - -@end table - -@node Predefined Target Types -@section Predefined Target Types -@cindex target descriptions, predefined types - -Type definitions in the self-description can build up composite types -from basic building blocks, but can not define fundamental types. Instead, -standard identifiers are provided by @value{GDBN} for the fundamental -types. The currently supported types are: - -@table @code - -@item int8 -@itemx int16 -@itemx int32 -@itemx int64 -@itemx int128 -Signed integer types holding the specified number of bits. - -@item uint8 -@itemx uint16 -@itemx uint32 -@itemx uint64 -@itemx uint128 -Unsigned integer types holding the specified number of bits. - -@item code_ptr -@itemx data_ptr -Pointers to unspecified code and data. The program counter and -any dedicated return address register may be marked as code -pointers; printing a code pointer converts it into a symbolic -address. The stack pointer and any dedicated address registers -may be marked as data pointers. - -@item ieee_single -Single precision IEEE floating point. - -@item ieee_double -Double precision IEEE floating point. - -@item arm_fpa_ext -The 12-byte extended precision format used by ARM FPA registers. - -@item i387_ext -The 10-byte extended precision format used by x87 registers. - -@item i386_eflags -32bit @sc{eflags} register used by x86. - -@item i386_mxcsr -32bit @sc{mxcsr} register used by x86. - -@end table - -@node Standard Target Features -@section Standard Target Features -@cindex target descriptions, standard features - -A target description must contain either no registers or all the -target's registers. If the description contains no registers, then -@value{GDBN} will assume a default register layout, selected based on -the architecture. If the description contains any registers, the -default layout will not be used; the standard registers must be -described in the target description, in such a way that @value{GDBN} -can recognize them. - -This is accomplished by giving specific names to feature elements -which contain standard registers. @value{GDBN} will look for features -with those names and verify that they contain the expected registers; -if any known feature is missing required registers, or if any required -feature is missing, @value{GDBN} will reject the target -description. You can add additional registers to any of the -standard features --- @value{GDBN} will display them just as if -they were added to an unrecognized feature. - -This section lists the known features and their expected contents. -Sample XML documents for these features are included in the -@value{GDBN} source tree, in the directory @file{gdb/features}. - -Names recognized by @value{GDBN} should include the name of the -company or organization which selected the name, and the overall -architecture to which the feature applies; so e.g.@: the feature -containing ARM core registers is named @samp{org.gnu.gdb.arm.core}. - -The names of registers are not case sensitive for the purpose -of recognizing standard features, but @value{GDBN} will only display -registers using the capitalization used in the description. - -@menu -* AArch64 Features:: -* ARM Features:: -* i386 Features:: -* MIPS Features:: -* M68K Features:: -* PowerPC Features:: -* TIC6x Features:: -@end menu - - -@node AArch64 Features -@subsection AArch64 Features -@cindex target descriptions, AArch64 features - -The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64 -targets. It should contain registers @samp{x0} through @samp{x30}, -@samp{sp}, @samp{pc}, and @samp{cpsr}. - -The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present, -it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr}, -and @samp{fpcr}. - -@node ARM Features -@subsection ARM Features -@cindex target descriptions, ARM features - -The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile -ARM targets. -It should contain registers @samp{r0} through @samp{r13}, @samp{sp}, -@samp{lr}, @samp{pc}, and @samp{cpsr}. - -For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core} -feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain -registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc}, -and @samp{xpsr}. - -The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it -should contain registers @samp{f0} through @samp{f7} and @samp{fps}. - -The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present, -it should contain at least registers @samp{wR0} through @samp{wR15} and -@samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon}, -@samp{wCSSF}, and @samp{wCASF} registers are optional. - -The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it -should contain at least registers @samp{d0} through @samp{d15}. If -they are present, @samp{d16} through @samp{d31} should also be included. -@value{GDBN} will synthesize the single-precision registers from -halves of the double-precision registers. - -The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not -need to contain registers; it instructs @value{GDBN} to display the -VFP double-precision registers as vectors and to synthesize the -quad-precision registers from pairs of double-precision registers. -If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also -be present and include 32 double-precision registers. - -@node i386 Features -@subsection i386 Features -@cindex target descriptions, i386 features - -The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64 -targets. It should describe the following registers: - -@itemize @minus -@item -@samp{eax} through @samp{edi} plus @samp{eip} for i386 -@item -@samp{rax} through @samp{r15} plus @samp{rip} for amd64 -@item -@samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es}, -@samp{fs}, @samp{gs} -@item -@samp{st0} through @samp{st7} -@item -@samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff}, -@samp{foseg}, @samp{fooff} and @samp{fop} -@end itemize - -The register sets may be different, depending on the target. - -The @samp{org.gnu.gdb.i386.sse} feature is optional. It should -describe registers: - -@itemize @minus -@item -@samp{xmm0} through @samp{xmm7} for i386 -@item -@samp{xmm0} through @samp{xmm15} for amd64 -@item -@samp{mxcsr} -@end itemize - -The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the -@samp{org.gnu.gdb.i386.sse} feature. It should -describe the upper 128 bits of @sc{ymm} registers: - -@itemize @minus -@item -@samp{ymm0h} through @samp{ymm7h} for i386 -@item -@samp{ymm0h} through @samp{ymm15h} for amd64 -@end itemize - -The @samp{org.gnu.gdb.i386.linux} feature is optional. It should -describe a single register, @samp{orig_eax}. - -@node MIPS Features -@subsection @acronym{MIPS} Features -@cindex target descriptions, @acronym{MIPS} features - -The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets. -It should contain registers @samp{r0} through @samp{r31}, @samp{lo}, -@samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending -on the target. - -The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should -contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause} -registers. They may be 32-bit or 64-bit depending on the target. - -The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though -it may be optional in a future version of @value{GDBN}. It should -contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and -@samp{fir}. They may be 32-bit or 64-bit depending on the target. - -The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should -contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through -@samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should -be 32-bit and the rest may be 32-bit or 64-bit depending on the target. - -The @samp{org.gnu.gdb.mips.linux} feature is optional. It should -contain a single register, @samp{restart}, which is used by the -Linux kernel to control restartable syscalls. - -@node M68K Features -@subsection M68K Features -@cindex target descriptions, M68K features - -@table @code -@item @samp{org.gnu.gdb.m68k.core} -@itemx @samp{org.gnu.gdb.coldfire.core} -@itemx @samp{org.gnu.gdb.fido.core} -One of those features must be always present. -The feature that is present determines which flavor of m68k is -used. The feature that is present should contain registers -@samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp}, -@samp{sp}, @samp{ps} and @samp{pc}. - -@item @samp{org.gnu.gdb.coldfire.fp} -This feature is optional. If present, it should contain registers -@samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and -@samp{fpiaddr}. -@end table - -@node PowerPC Features -@subsection PowerPC Features -@cindex target descriptions, PowerPC features - -The @samp{org.gnu.gdb.power.core} feature is required for PowerPC -targets. It should contain registers @samp{r0} through @samp{r31}, -@samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and -@samp{xer}. They may be 32-bit or 64-bit depending on the target. - -The @samp{org.gnu.gdb.power.fpu} feature is optional. It should -contain registers @samp{f0} through @samp{f31} and @samp{fpscr}. - -The @samp{org.gnu.gdb.power.altivec} feature is optional. It should -contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, -and @samp{vrsave}. - -The @samp{org.gnu.gdb.power.vsx} feature is optional. It should -contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} -will combine these registers with the floating point registers -(@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0} -through @samp{vr31}) to present the 128-bit wide registers @samp{vs0} -through @samp{vs63}, the set of vector registers for POWER7. - -The @samp{org.gnu.gdb.power.spe} feature is optional. It should -contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and -@samp{spefscr}. SPE targets should provide 32-bit registers in -@samp{org.gnu.gdb.power.core} and provide the upper halves in -@samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine -these to present registers @samp{ev0} through @samp{ev31} to the -user. - -@node TIC6x Features -@subsection TMS320C6x Features -@cindex target descriptions, TIC6x features -@cindex target descriptions, TMS320C6x features -The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x -targets. It should contain registers @samp{A0} through @samp{A15}, -registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}. - -The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should -contain registers @samp{A16} through @samp{A31} and @samp{B16} -through @samp{B31}. - -The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should -contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}. - -@node Operating System Information -@appendix Operating System Information -@cindex operating system information - -@menu -* Process list:: -@end menu - -Users of @value{GDBN} often wish to obtain information about the state of -the operating system running on the target---for example the list of -processes, or the list of open files. This section describes the -mechanism that makes it possible. This mechanism is similar to the -target features mechanism (@pxref{Target Descriptions}), but focuses -on a different aspect of target. - -Operating system information is retrived from the target via the -remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata -read}). The object name in the request should be @samp{osdata}, and -the @var{annex} identifies the data to be fetched. - -@node Process list -@appendixsection Process list -@cindex operating system information, process list - -When requesting the process list, the @var{annex} field in the -@samp{qXfer} request should be @samp{processes}. The returned data is -an XML document. The formal syntax of this document is defined in -@file{gdb/features/osdata.dtd}. - -An example document is: - -@smallexample - - - - - 1 - root - /sbin/init - 1,2,3 - - -@end smallexample - -Each item should include a column whose name is @samp{pid}. The value -of that column should identify the process on the target. The -@samp{user} and @samp{command} columns are optional, and will be -displayed by @value{GDBN}. The @samp{cores} column, if present, -should contain a comma-separated list of cores that this process -is running on. Target may provide additional columns, -which @value{GDBN} currently ignores. - -@node Trace File Format -@appendix Trace File Format -@cindex trace file format - -The trace file comes in three parts: a header, a textual description -section, and a trace frame section with binary data. - -The header has the form @code{\x7fTRACE0\n}. The first byte is -@code{0x7f} so as to indicate that the file contains binary data, -while the @code{0} is a version number that may have different values -in the future. - -The description section consists of multiple lines of @sc{ascii} text -separated by newline characters (@code{0xa}). The lines may include a -variety of optional descriptive or context-setting information, such -as tracepoint definitions or register set size. @value{GDBN} will -ignore any line that it does not recognize. An empty line marks the end -of this section. - -@c FIXME add some specific types of data - -The trace frame section consists of a number of consecutive frames. -Each frame begins with a two-byte tracepoint number, followed by a -four-byte size giving the amount of data in the frame. The data in -the frame consists of a number of blocks, each introduced by a -character indicating its type (at least register, memory, and trace -state variable). The data in this section is raw binary, not a -hexadecimal or other encoding; its endianness matches the target's -endianness. - -@c FIXME bi-arch may require endianness/arch info in description section - -@table @code -@item R @var{bytes} -Register block. The number and ordering of bytes matches that of a -@code{g} packet in the remote protocol. Note that these are the -actual bytes, in target order and @value{GDBN} register order, not a -hexadecimal encoding. - -@item M @var{address} @var{length} @var{bytes}... -Memory block. This is a contiguous block of memory, at the 8-byte -address @var{address}, with a 2-byte length @var{length}, followed by -@var{length} bytes. - -@item V @var{number} @var{value} -Trace state variable block. This records the 8-byte signed value -@var{value} of trace state variable numbered @var{number}. - -@end table - -Future enhancements of the trace file format may include additional types -of blocks. - -@node Index Section Format -@appendix @code{.gdb_index} section format -@cindex .gdb_index section format -@cindex index section format - -This section documents the index section that is created by @code{save -gdb-index} (@pxref{Index Files}). The index section is -DWARF-specific; some knowledge of DWARF is assumed in this -description. - -The mapped index file format is designed to be directly -@code{mmap}able on any architecture. In most cases, a datum is -represented using a little-endian 32-bit integer value, called an -@code{offset_type}. Big endian machines must byte-swap the values -before using them. Exceptions to this rule are noted. The data is -laid out such that alignment is always respected. - -A mapped index consists of several areas, laid out in order. - -@enumerate -@item -The file header. This is a sequence of values, of @code{offset_type} -unless otherwise noted: - -@enumerate -@item -The version number, currently 8. Versions 1, 2 and 3 are obsolete. -Version 4 uses a different hashing function from versions 5 and 6. -Version 6 includes symbols for inlined functions, whereas versions 4 -and 5 do not. Version 7 adds attributes to the CU indices in the -symbol table. Version 8 specifies that symbols from DWARF type units -(@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the -compilation unit (@samp{DW_TAG_comp_unit}) using the type. - -@value{GDBN} will only read version 4, 5, or 6 indices -by specifying @code{set use-deprecated-index-sections on}. -GDB has a workaround for potentially broken version 7 indices so it is -currently not flagged as deprecated. - -@item -The offset, from the start of the file, of the CU list. - -@item -The offset, from the start of the file, of the types CU list. Note -that this area can be empty, in which case this offset will be equal -to the next offset. - -@item -The offset, from the start of the file, of the address area. - -@item -The offset, from the start of the file, of the symbol table. - -@item -The offset, from the start of the file, of the constant pool. -@end enumerate - -@item -The CU list. This is a sequence of pairs of 64-bit little-endian -values, sorted by the CU offset. The first element in each pair is -the offset of a CU in the @code{.debug_info} section. The second -element in each pair is the length of that CU. References to a CU -elsewhere in the map are done using a CU index, which is just the -0-based index into this table. Note that if there are type CUs, then -conceptually CUs and type CUs form a single list for the purposes of -CU indices. - -@item -The types CU list. This is a sequence of triplets of 64-bit -little-endian values. In a triplet, the first value is the CU offset, -the second value is the type offset in the CU, and the third value is -the type signature. The types CU list is not sorted. - -@item -The address area. The address area consists of a sequence of address -entries. Each address entry has three elements: - -@enumerate -@item -The low address. This is a 64-bit little-endian value. - -@item -The high address. This is a 64-bit little-endian value. Like -@code{DW_AT_high_pc}, the value is one byte beyond the end. - -@item -The CU index. This is an @code{offset_type} value. -@end enumerate - -@item -The symbol table. This is an open-addressed hash table. The size of -the hash table is always a power of 2. - -Each slot in the hash table consists of a pair of @code{offset_type} -values. The first value is the offset of the symbol's name in the -constant pool. The second value is the offset of the CU vector in the -constant pool. - -If both values are 0, then this slot in the hash table is empty. This -is ok because while 0 is a valid constant pool index, it cannot be a -valid index for both a string and a CU vector. - -The hash value for a table entry is computed by applying an -iterative hash function to the symbol's name. Starting with an -initial value of @code{r = 0}, each (unsigned) character @samp{c} in -the string is incorporated into the hash using the formula depending on the -index version: - -@table @asis -@item Version 4 -The formula is @code{r = r * 67 + c - 113}. - -@item Versions 5 to 7 -The formula is @code{r = r * 67 + tolower (c) - 113}. -@end table - -The terminating @samp{\0} is not incorporated into the hash. - -The step size used in the hash table is computed via -@code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash -value, and @samp{size} is the size of the hash table. The step size -is used to find the next candidate slot when handling a hash -collision. - -The names of C@t{++} symbols in the hash table are canonicalized. We -don't currently have a simple description of the canonicalization -algorithm; if you intend to create new index sections, you must read -the code. - -@item -The constant pool. This is simply a bunch of bytes. It is organized -so that alignment is correct: CU vectors are stored first, followed by -strings. - -A CU vector in the constant pool is a sequence of @code{offset_type} -values. The first value is the number of CU indices in the vector. -Each subsequent value is the index and symbol attributes of a CU in -the CU list. This element in the hash table is used to indicate which -CUs define the symbol and how the symbol is used. -See below for the format of each CU index+attributes entry. - -A string in the constant pool is zero-terminated. -@end enumerate - -Attributes were added to CU index values in @code{.gdb_index} version 7. -If a symbol has multiple uses within a CU then there is one -CU index+attributes value for each use. - -The format of each CU index+attributes entry is as follows -(bit 0 = LSB): - -@table @asis - -@item Bits 0-23 -This is the index of the CU in the CU list. -@item Bits 24-27 -These bits are reserved for future purposes and must be zero. -@item Bits 28-30 -The kind of the symbol in the CU. - -@table @asis -@item 0 -This value is reserved and should not be used. -By reserving zero the full @code{offset_type} value is backwards compatible -with previous versions of the index. -@item 1 -The symbol is a type. -@item 2 -The symbol is a variable or an enum value. -@item 3 -The symbol is a function. -@item 4 -Any other kind of symbol. -@item 5,6,7 -These values are reserved. -@end table - -@item Bit 31 -This bit is zero if the value is global and one if it is static. - -The determination of whether a symbol is global or static is complicated. -The authorative reference is the file @file{dwarf2read.c} in -@value{GDBN} sources. - -@end table - -This pseudo-code describes the computation of a symbol's kind and -global/static attributes in the index. - -@smallexample -is_external = get_attribute (die, DW_AT_external); -language = get_attribute (cu_die, DW_AT_language); -switch (die->tag) - @{ - case DW_TAG_typedef: - case DW_TAG_base_type: - case DW_TAG_subrange_type: - kind = TYPE; - is_static = 1; - break; - case DW_TAG_enumerator: - kind = VARIABLE; - is_static = (language != CPLUS && language != JAVA); - break; - case DW_TAG_subprogram: - kind = FUNCTION; - is_static = ! (is_external || language == ADA); - break; - case DW_TAG_constant: - kind = VARIABLE; - is_static = ! is_external; - break; - case DW_TAG_variable: - kind = VARIABLE; - is_static = ! is_external; - break; - case DW_TAG_namespace: - kind = TYPE; - is_static = 0; - break; - case DW_TAG_class_type: - case DW_TAG_interface_type: - case DW_TAG_structure_type: - case DW_TAG_union_type: - case DW_TAG_enumeration_type: - kind = TYPE; - is_static = (language != CPLUS && language != JAVA); - break; - default: - assert (0); - @} -@end smallexample - -@include gpl.texi - -@node GNU Free Documentation License -@appendix GNU Free Documentation License -@include fdl.texi - -@node Concept Index -@unnumbered Concept Index - -@printindex cp - -@node Command and Variable Index -@unnumbered Command, Variable, and Function Index - -@printindex fn - -@tex -% I think something like @@colophon should be in texinfo. In the -% meantime: -\long\def\colophon{\hbox to0pt{}\vfill -\centerline{The body of this manual is set in} -\centerline{\fontname\tenrm,} -\centerline{with headings in {\bf\fontname\tenbf}} -\centerline{and examples in {\tt\fontname\tentt}.} -\centerline{{\it\fontname\tenit\/},} -\centerline{{\bf\fontname\tenbf}, and} -\centerline{{\sl\fontname\tensl\/}} -\centerline{are used for emphasis.}\vfill} -\page\colophon -% Blame: doc@@cygnus.com, 1991. -@end tex - -@bye diff --git a/contrib/gdb-7/gdb/doc/gdbint.texinfo b/contrib/gdb-7/gdb/doc/gdbint.texinfo deleted file mode 100644 index 4a75c26c59..0000000000 --- a/contrib/gdb-7/gdb/doc/gdbint.texinfo +++ /dev/null @@ -1,8155 +0,0 @@ -\input texinfo @c -*- texinfo -*- -@setfilename gdbint.info -@include gdb-cfg.texi -@settitle @value{GDBN} Internals -@setchapternewpage off -@dircategory Software development -@direntry -* Gdb-Internals: (gdbint). The GNU debugger's internals. -@end direntry - -@copying -Copyright @copyright{} 1990-2013 Free Software Foundation, Inc. -Contributed by Cygnus Solutions. Written by John Gilmore. -Second Edition by Stan Shebs. - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, with no Front-Cover Texts, and with no Back-Cover -Texts. A copy of the license is included in the section entitled ``GNU -Free Documentation License''. -@end copying - -@ifnottex -This file documents the internals of the GNU debugger @value{GDBN}. - -@insertcopying -@end ifnottex - -@syncodeindex vr fn - -@titlepage -@title @value{GDBN} Internals -@subtitle A guide to the internals of the GNU debugger -@author John Gilmore -@author Cygnus Solutions -@author Second Edition: -@author Stan Shebs -@author Cygnus Solutions -@page -@tex -\def\$#1${{#1}} % Kluge: collect RCS revision info without $...$ -\xdef\manvers{\$Revision$} % For use in headers, footers too -{\parskip=0pt -\hfill Cygnus Solutions\par -\hfill \manvers\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex - -@vskip 0pt plus 1filll -@insertcopying -@end titlepage - -@contents - -@node Top -@c Perhaps this should be the title of the document (but only for info, -@c not for TeX). Existing GNU manuals seem inconsistent on this point. -@top Scope of this Document - -This document documents the internals of the GNU debugger, @value{GDBN}. It -includes description of @value{GDBN}'s key algorithms and operations, as well -as the mechanisms that adapt @value{GDBN} to specific hosts and targets. - -@menu -* Summary:: -* Overall Structure:: -* Algorithms:: -* User Interface:: -* libgdb:: -* Values:: -* Stack Frames:: -* Symbol Handling:: -* Language Support:: -* Host Definition:: -* Target Architecture Definition:: -* Target Descriptions:: -* Target Vector Definition:: -* Native Debugging:: -* Support Libraries:: -* Coding Standards:: -* Misc Guidelines:: -* Porting GDB:: -* Versions and Branches:: -* Start of New Year Procedure:: -* Releasing GDB:: -* Testsuite:: -* Hints:: - -* GDB Observers:: @value{GDBN} Currently available observers -* GNU Free Documentation License:: The license for this documentation -* Concept Index:: -* Function and Variable Index:: -@end menu - -@node Summary -@chapter Summary - -@menu -* Requirements:: -* Contributors:: -@end menu - -@node Requirements -@section Requirements -@cindex requirements for @value{GDBN} - -Before diving into the internals, you should understand the formal -requirements and other expectations for @value{GDBN}. Although some -of these may seem obvious, there have been proposals for @value{GDBN} -that have run counter to these requirements. - -First of all, @value{GDBN} is a debugger. It's not designed to be a -front panel for embedded systems. It's not a text editor. It's not a -shell. It's not a programming environment. - -@value{GDBN} is an interactive tool. Although a batch mode is -available, @value{GDBN}'s primary role is to interact with a human -programmer. - -@value{GDBN} should be responsive to the user. A programmer hot on -the trail of a nasty bug, and operating under a looming deadline, is -going to be very impatient of everything, including the response time -to debugger commands. - -@value{GDBN} should be relatively permissive, such as for expressions. -While the compiler should be picky (or have the option to be made -picky), since source code lives for a long time usually, the -programmer doing debugging shouldn't be spending time figuring out to -mollify the debugger. - -@value{GDBN} will be called upon to deal with really large programs. -Executable sizes of 50 to 100 megabytes occur regularly, and we've -heard reports of programs approaching 1 gigabyte in size. - -@value{GDBN} should be able to run everywhere. No other debugger is -available for even half as many configurations as @value{GDBN} -supports. - -@node Contributors -@section Contributors - -The first edition of this document was written by John Gilmore of -Cygnus Solutions. The current second edition was written by Stan Shebs -of Cygnus Solutions, who continues to update the manual. - -Over the years, many others have made additions and changes to this -document. This section attempts to record the significant contributors -to that effort. One of the virtues of free software is that everyone -is free to contribute to it; with regret, we cannot actually -acknowledge everyone here. - -@quotation -@emph{Plea:} This section has only been added relatively recently (four -years after publication of the second edition). Additions to this -section are particularly welcome. If you or your friends (or enemies, -to be evenhanded) have been unfairly omitted from this list, we would -like to add your names! -@end quotation - -A document such as this relies on being kept up to date by numerous -small updates by contributing engineers as they make changes to the -code base. The file @file{ChangeLog} in the @value{GDBN} distribution -approximates a blow-by-blow account. The most prolific contributors to -this important, but low profile task are Andrew Cagney (responsible -for over half the entries), Daniel Jacobowitz, Mark Kettenis, Jim -Blandy and Eli Zaretskii. - -Eli Zaretskii and Daniel Jacobowitz wrote the sections documenting -watchpoints. - -Jeremy Bennett updated the sections on initializing a new architecture -and register representation, and added the section on Frame Interpretation. - - -@node Overall Structure - -@chapter Overall Structure - -@value{GDBN} consists of three major subsystems: user interface, -symbol handling (the @dfn{symbol side}), and target system handling (the -@dfn{target side}). - -The user interface consists of several actual interfaces, plus -supporting code. - -The symbol side consists of object file readers, debugging info -interpreters, symbol table management, source language expression -parsing, type and value printing. - -The target side consists of execution control, stack frame analysis, and -physical target manipulation. - -The target side/symbol side division is not formal, and there are a -number of exceptions. For instance, core file support involves symbolic -elements (the basic core file reader is in BFD) and target elements (it -supplies the contents of memory and the values of registers). Instead, -this division is useful for understanding how the minor subsystems -should fit together. - -@section The Symbol Side - -The symbolic side of @value{GDBN} can be thought of as ``everything -you can do in @value{GDBN} without having a live program running''. -For instance, you can look at the types of variables, and evaluate -many kinds of expressions. - -@section The Target Side - -The target side of @value{GDBN} is the ``bits and bytes manipulator''. -Although it may make reference to symbolic info here and there, most -of the target side will run with only a stripped executable -available---or even no executable at all, in remote debugging cases. - -Operations such as disassembly, stack frame crawls, and register -display, are able to work with no symbolic info at all. In some cases, -such as disassembly, @value{GDBN} will use symbolic info to present addresses -relative to symbols rather than as raw numbers, but it will work either -way. - -@section Configurations - -@cindex host -@cindex target -@dfn{Host} refers to attributes of the system where @value{GDBN} runs. -@dfn{Target} refers to the system where the program being debugged -executes. In most cases they are the same machine, in which case a -third type of @dfn{Native} attributes come into play. - -Defines and include files needed to build on the host are host -support. Examples are tty support, system defined types, host byte -order, host float format. These are all calculated by @code{autoconf} -when the debugger is built. - -Defines and information needed to handle the target format are target -dependent. Examples are the stack frame format, instruction set, -breakpoint instruction, registers, and how to set up and tear down the stack -to call a function. - -Information that is only needed when the host and target are the same, -is native dependent. One example is Unix child process support; if the -host and target are not the same, calling @code{fork} to start the target -process is a bad idea. The various macros needed for finding the -registers in the @code{upage}, running @code{ptrace}, and such are all -in the native-dependent files. - -Another example of native-dependent code is support for features that -are really part of the target environment, but which require -@code{#include} files that are only available on the host system. Core -file handling and @code{setjmp} handling are two common cases. - -When you want to make @value{GDBN} work as the traditional native debugger -on a system, you will need to supply both target and native information. - -@section Source Tree Structure -@cindex @value{GDBN} source tree structure - -The @value{GDBN} source directory has a mostly flat structure---there -are only a few subdirectories. A file's name usually gives a hint as -to what it does; for example, @file{stabsread.c} reads stabs, -@file{dwarf2read.c} reads @sc{DWARF 2}, etc. - -Files that are related to some common task have names that share -common substrings. For example, @file{*-thread.c} files deal with -debugging threads on various platforms; @file{*read.c} files deal with -reading various kinds of symbol and object files; @file{inf*.c} files -deal with direct control of the @dfn{inferior program} (@value{GDBN} -parlance for the program being debugged). - -There are several dozens of files in the @file{*-tdep.c} family. -@samp{tdep} stands for @dfn{target-dependent code}---each of these -files implements debug support for a specific target architecture -(sparc, mips, etc). Usually, only one of these will be used in a -specific @value{GDBN} configuration (sometimes two, closely related). - -Similarly, there are many @file{*-nat.c} files, each one for native -debugging on a specific system (e.g., @file{sparc-linux-nat.c} is for -native debugging of Sparc machines running the Linux kernel). - -The few subdirectories of the source tree are: - -@table @file -@item cli -Code that implements @dfn{CLI}, the @value{GDBN} Command-Line -Interpreter. @xref{User Interface, Command Interpreter}. - -@item gdbserver -Code for the @value{GDBN} remote server. - -@item gdbtk -Code for Insight, the @value{GDBN} TK-based GUI front-end. - -@item mi -The @dfn{GDB/MI}, the @value{GDBN} Machine Interface interpreter. - -@item signals -Target signal translation code. - -@item tui -Code for @dfn{TUI}, the @value{GDBN} Text-mode full-screen User -Interface. @xref{User Interface, TUI}. -@end table - -@node Algorithms - -@chapter Algorithms -@cindex algorithms - -@value{GDBN} uses a number of debugging-specific algorithms. They are -often not very complicated, but get lost in the thicket of special -cases and real-world issues. This chapter describes the basic -algorithms and mentions some of the specific target definitions that -they use. - -@section Prologue Analysis - -@cindex prologue analysis -@cindex call frame information -@cindex CFI (call frame information) -To produce a backtrace and allow the user to manipulate older frames' -variables and arguments, @value{GDBN} needs to find the base addresses -of older frames, and discover where those frames' registers have been -saved. Since a frame's ``callee-saves'' registers get saved by -younger frames if and when they're reused, a frame's registers may be -scattered unpredictably across younger frames. This means that -changing the value of a register-allocated variable in an older frame -may actually entail writing to a save slot in some younger frame. - -Modern versions of GCC emit Dwarf call frame information (``CFI''), -which describes how to find frame base addresses and saved registers. -But CFI is not always available, so as a fallback @value{GDBN} uses a -technique called @dfn{prologue analysis} to find frame sizes and saved -registers. A prologue analyzer disassembles the function's machine -code starting from its entry point, and looks for instructions that -allocate frame space, save the stack pointer in a frame pointer -register, save registers, and so on. Obviously, this can't be done -accurately in general, but it's tractable to do well enough to be very -helpful. Prologue analysis predates the GNU toolchain's support for -CFI; at one time, prologue analysis was the only mechanism -@value{GDBN} used for stack unwinding at all, when the function -calling conventions didn't specify a fixed frame layout. - -In the olden days, function prologues were generated by hand-written, -target-specific code in GCC, and treated as opaque and untouchable by -optimizers. Looking at this code, it was usually straightforward to -write a prologue analyzer for @value{GDBN} that would accurately -understand all the prologues GCC would generate. However, over time -GCC became more aggressive about instruction scheduling, and began to -understand more about the semantics of the prologue instructions -themselves; in response, @value{GDBN}'s analyzers became more complex -and fragile. Keeping the prologue analyzers working as GCC (and the -instruction sets themselves) evolved became a substantial task. - -@cindex @file{prologue-value.c} -@cindex abstract interpretation of function prologues -@cindex pseudo-evaluation of function prologues -To try to address this problem, the code in @file{prologue-value.h} -and @file{prologue-value.c} provides a general framework for writing -prologue analyzers that are simpler and more robust than ad-hoc -analyzers. When we analyze a prologue using the prologue-value -framework, we're really doing ``abstract interpretation'' or -``pseudo-evaluation'': running the function's code in simulation, but -using conservative approximations of the values registers and memory -would hold when the code actually runs. For example, if our function -starts with the instruction: - -@example -addi r1, 42 # add 42 to r1 -@end example -@noindent -we don't know exactly what value will be in @code{r1} after executing -this instruction, but we do know it'll be 42 greater than its original -value. - -If we then see an instruction like: - -@example -addi r1, 22 # add 22 to r1 -@end example -@noindent -we still don't know what @code{r1's} value is, but again, we can say -it is now 64 greater than its original value. - -If the next instruction were: - -@example -mov r2, r1 # set r2 to r1's value -@end example -@noindent -then we can say that @code{r2's} value is now the original value of -@code{r1} plus 64. - -It's common for prologues to save registers on the stack, so we'll -need to track the values of stack frame slots, as well as the -registers. So after an instruction like this: - -@example -mov (fp+4), r2 -@end example -@noindent -then we'd know that the stack slot four bytes above the frame pointer -holds the original value of @code{r1} plus 64. - -And so on. - -Of course, this can only go so far before it gets unreasonable. If we -wanted to be able to say anything about the value of @code{r1} after -the instruction: - -@example -xor r1, r3 # exclusive-or r1 and r3, place result in r1 -@end example -@noindent -then things would get pretty complex. But remember, we're just doing -a conservative approximation; if exclusive-or instructions aren't -relevant to prologues, we can just say @code{r1}'s value is now -``unknown''. We can ignore things that are too complex, if that loss of -information is acceptable for our application. - -So when we say ``conservative approximation'' here, what we mean is an -approximation that is either accurate, or marked ``unknown'', but -never inaccurate. - -Using this framework, a prologue analyzer is simply an interpreter for -machine code, but one that uses conservative approximations for the -contents of registers and memory instead of actual values. Starting -from the function's entry point, you simulate instructions up to the -current PC, or an instruction that you don't know how to simulate. -Now you can examine the state of the registers and stack slots you've -kept track of. - -@itemize @bullet - -@item -To see how large your stack frame is, just check the value of the -stack pointer register; if it's the original value of the SP -minus a constant, then that constant is the stack frame's size. -If the SP's value has been marked as ``unknown'', then that means -the prologue has done something too complex for us to track, and -we don't know the frame size. - -@item -To see where we've saved the previous frame's registers, we just -search the values we've tracked --- stack slots, usually, but -registers, too, if you want --- for something equal to the register's -original value. If the calling conventions suggest a standard place -to save a given register, then we can check there first, but really, -anything that will get us back the original value will probably work. -@end itemize - -This does take some work. But prologue analyzers aren't -quick-and-simple pattern patching to recognize a few fixed prologue -forms any more; they're big, hairy functions. Along with inferior -function calls, prologue analysis accounts for a substantial portion -of the time needed to stabilize a @value{GDBN} port. So it's -worthwhile to look for an approach that will be easier to understand -and maintain. In the approach described above: - -@itemize @bullet - -@item -It's easier to see that the analyzer is correct: you just see -whether the analyzer properly (albeit conservatively) simulates -the effect of each instruction. - -@item -It's easier to extend the analyzer: you can add support for new -instructions, and know that you haven't broken anything that -wasn't already broken before. - -@item -It's orthogonal: to gather new information, you don't need to -complicate the code for each instruction. As long as your domain -of conservative values is already detailed enough to tell you -what you need, then all the existing instruction simulations are -already gathering the right data for you. - -@end itemize - -The file @file{prologue-value.h} contains detailed comments explaining -the framework and how to use it. - - -@section Breakpoint Handling - -@cindex breakpoints -In general, a breakpoint is a user-designated location in the program -where the user wants to regain control if program execution ever reaches -that location. - -There are two main ways to implement breakpoints; either as ``hardware'' -breakpoints or as ``software'' breakpoints. - -@cindex hardware breakpoints -@cindex program counter -Hardware breakpoints are sometimes available as a builtin debugging -features with some chips. Typically these work by having dedicated -register into which the breakpoint address may be stored. If the PC -(shorthand for @dfn{program counter}) -ever matches a value in a breakpoint registers, the CPU raises an -exception and reports it to @value{GDBN}. - -Another possibility is when an emulator is in use; many emulators -include circuitry that watches the address lines coming out from the -processor, and force it to stop if the address matches a breakpoint's -address. - -A third possibility is that the target already has the ability to do -breakpoints somehow; for instance, a ROM monitor may do its own -software breakpoints. So although these are not literally ``hardware -breakpoints'', from @value{GDBN}'s point of view they work the same; -@value{GDBN} need not do anything more than set the breakpoint and wait -for something to happen. - -Since they depend on hardware resources, hardware breakpoints may be -limited in number; when the user asks for more, @value{GDBN} will -start trying to set software breakpoints. (On some architectures, -notably the 32-bit x86 platforms, @value{GDBN} cannot always know -whether there's enough hardware resources to insert all the hardware -breakpoints and watchpoints. On those platforms, @value{GDBN} prints -an error message only when the program being debugged is continued.) - -@cindex software breakpoints -Software breakpoints require @value{GDBN} to do somewhat more work. -The basic theory is that @value{GDBN} will replace a program -instruction with a trap, illegal divide, or some other instruction -that will cause an exception, and then when it's encountered, -@value{GDBN} will take the exception and stop the program. When the -user says to continue, @value{GDBN} will restore the original -instruction, single-step, re-insert the trap, and continue on. - -Since it literally overwrites the program being tested, the program area -must be writable, so this technique won't work on programs in ROM. It -can also distort the behavior of programs that examine themselves, -although such a situation would be highly unusual. - -Also, the software breakpoint instruction should be the smallest size of -instruction, so it doesn't overwrite an instruction that might be a jump -target, and cause disaster when the program jumps into the middle of the -breakpoint instruction. (Strictly speaking, the breakpoint must be no -larger than the smallest interval between instructions that may be jump -targets; perhaps there is an architecture where only even-numbered -instructions may jumped to.) Note that it's possible for an instruction -set not to have any instructions usable for a software breakpoint, -although in practice only the ARC has failed to define such an -instruction. - -Basic breakpoint object handling is in @file{breakpoint.c}. However, -much of the interesting breakpoint action is in @file{infrun.c}. - -@table @code -@cindex insert or remove software breakpoint -@findex target_remove_breakpoint -@findex target_insert_breakpoint -@item target_remove_breakpoint (@var{bp_tgt}) -@itemx target_insert_breakpoint (@var{bp_tgt}) -Insert or remove a software breakpoint at address -@code{@var{bp_tgt}->placed_address}. Returns zero for success, -non-zero for failure. On input, @var{bp_tgt} contains the address of the -breakpoint, and is otherwise initialized to zero. The fields of the -@code{struct bp_target_info} pointed to by @var{bp_tgt} are updated -to contain other information about the breakpoint on output. The field -@code{placed_address} may be updated if the breakpoint was placed at a -related address; the field @code{shadow_contents} contains the real -contents of the bytes where the breakpoint has been inserted, -if reading memory would return the breakpoint instead of the -underlying memory; the field @code{shadow_len} is the length of -memory cached in @code{shadow_contents}, if any; and the field -@code{placed_size} is optionally set and used by the target, if -it could differ from @code{shadow_len}. - -For example, the remote target @samp{Z0} packet does not require -shadowing memory, so @code{shadow_len} is left at zero. However, -the length reported by @code{gdbarch_breakpoint_from_pc} is cached in -@code{placed_size}, so that a matching @samp{z0} packet can be -used to remove the breakpoint. - -@cindex insert or remove hardware breakpoint -@findex target_remove_hw_breakpoint -@findex target_insert_hw_breakpoint -@item target_remove_hw_breakpoint (@var{bp_tgt}) -@itemx target_insert_hw_breakpoint (@var{bp_tgt}) -Insert or remove a hardware-assisted breakpoint at address -@code{@var{bp_tgt}->placed_address}. Returns zero for success, -non-zero for failure. See @code{target_insert_breakpoint} for -a description of the @code{struct bp_target_info} pointed to by -@var{bp_tgt}; the @code{shadow_contents} and -@code{shadow_len} members are not used for hardware breakpoints, -but @code{placed_size} may be. -@end table - -@section Single Stepping - -@section Signal Handling - -@section Thread Handling - -@section Inferior Function Calls - -@section Longjmp Support - -@cindex @code{longjmp} debugging -@value{GDBN} has support for figuring out that the target is doing a -@code{longjmp} and for stopping at the target of the jump, if we are -stepping. This is done with a few specialized internal breakpoints, -which are visible in the output of the @samp{maint info breakpoint} -command. - -@findex gdbarch_get_longjmp_target -To make this work, you need to define a function called -@code{gdbarch_get_longjmp_target}, which will examine the -@code{jmp_buf} structure and extract the @code{longjmp} target address. -Since @code{jmp_buf} is target specific and typically defined in a -target header not available to @value{GDBN}, you will need to -determine the offset of the PC manually and return that; many targets -define a @code{jb_pc_offset} field in the tdep structure to save the -value once calculated. - -@section Watchpoints -@cindex watchpoints - -Watchpoints are a special kind of breakpoints (@pxref{Algorithms, -breakpoints}) which break when data is accessed rather than when some -instruction is executed. When you have data which changes without -your knowing what code does that, watchpoints are the silver bullet to -hunt down and kill such bugs. - -@cindex hardware watchpoints -@cindex software watchpoints -Watchpoints can be either hardware-assisted or not; the latter type is -known as ``software watchpoints.'' @value{GDBN} always uses -hardware-assisted watchpoints if they are available, and falls back on -software watchpoints otherwise. Typical situations where @value{GDBN} -will use software watchpoints are: - -@itemize @bullet -@item -The watched memory region is too large for the underlying hardware -watchpoint support. For example, each x86 debug register can watch up -to 4 bytes of memory, so trying to watch data structures whose size is -more than 16 bytes will cause @value{GDBN} to use software -watchpoints. - -@item -The value of the expression to be watched depends on data held in -registers (as opposed to memory). - -@item -Too many different watchpoints requested. (On some architectures, -this situation is impossible to detect until the debugged program is -resumed.) Note that x86 debug registers are used both for hardware -breakpoints and for watchpoints, so setting too many hardware -breakpoints might cause watchpoint insertion to fail. - -@item -No hardware-assisted watchpoints provided by the target -implementation. -@end itemize - -Software watchpoints are very slow, since @value{GDBN} needs to -single-step the program being debugged and test the value of the -watched expression(s) after each instruction. The rest of this -section is mostly irrelevant for software watchpoints. - -When the inferior stops, @value{GDBN} tries to establish, among other -possible reasons, whether it stopped due to a watchpoint being hit. -It first uses @code{STOPPED_BY_WATCHPOINT} to see if any watchpoint -was hit. If not, all watchpoint checking is skipped. - -Then @value{GDBN} calls @code{target_stopped_data_address} exactly -once. This method returns the address of the watchpoint which -triggered, if the target can determine it. If the triggered address -is available, @value{GDBN} compares the address returned by this -method with each watched memory address in each active watchpoint. -For data-read and data-access watchpoints, @value{GDBN} announces -every watchpoint that watches the triggered address as being hit. -For this reason, data-read and data-access watchpoints -@emph{require} that the triggered address be available; if not, read -and access watchpoints will never be considered hit. For data-write -watchpoints, if the triggered address is available, @value{GDBN} -considers only those watchpoints which match that address; -otherwise, @value{GDBN} considers all data-write watchpoints. For -each data-write watchpoint that @value{GDBN} considers, it evaluates -the expression whose value is being watched, and tests whether the -watched value has changed. Watchpoints whose watched values have -changed are announced as hit. - -@c FIXME move these to the main lists of target/native defns - -@value{GDBN} uses several macros and primitives to support hardware -watchpoints: - -@table @code -@findex TARGET_CAN_USE_HARDWARE_WATCHPOINT -@item TARGET_CAN_USE_HARDWARE_WATCHPOINT (@var{type}, @var{count}, @var{other}) -Return the number of hardware watchpoints of type @var{type} that are -possible to be set. The value is positive if @var{count} watchpoints -of this type can be set, zero if setting watchpoints of this type is -not supported, and negative if @var{count} is more than the maximum -number of watchpoints of type @var{type} that can be set. @var{other} -is non-zero if other types of watchpoints are currently enabled (there -are architectures which cannot set watchpoints of different types at -the same time). - -@findex TARGET_REGION_OK_FOR_HW_WATCHPOINT -@item TARGET_REGION_OK_FOR_HW_WATCHPOINT (@var{addr}, @var{len}) -Return non-zero if hardware watchpoints can be used to watch a region -whose address is @var{addr} and whose length in bytes is @var{len}. - -@cindex insert or remove hardware watchpoint -@findex target_insert_watchpoint -@findex target_remove_watchpoint -@item target_insert_watchpoint (@var{addr}, @var{len}, @var{type}) -@itemx target_remove_watchpoint (@var{addr}, @var{len}, @var{type}) -Insert or remove a hardware watchpoint starting at @var{addr}, for -@var{len} bytes. @var{type} is the watchpoint type, one of the -possible values of the enumerated data type @code{target_hw_bp_type}, -defined by @file{breakpoint.h} as follows: - -@smallexample - enum target_hw_bp_type - @{ - hw_write = 0, /* Common (write) HW watchpoint */ - hw_read = 1, /* Read HW watchpoint */ - hw_access = 2, /* Access (read or write) HW watchpoint */ - hw_execute = 3 /* Execute HW breakpoint */ - @}; -@end smallexample - -@noindent -These two macros should return 0 for success, non-zero for failure. - -@findex target_stopped_data_address -@item target_stopped_data_address (@var{addr_p}) -If the inferior has some watchpoint that triggered, place the address -associated with the watchpoint at the location pointed to by -@var{addr_p} and return non-zero. Otherwise, return zero. This -is required for data-read and data-access watchpoints. It is -not required for data-write watchpoints, but @value{GDBN} uses -it to improve handling of those also. - -@value{GDBN} will only call this method once per watchpoint stop, -immediately after calling @code{STOPPED_BY_WATCHPOINT}. If the -target's watchpoint indication is sticky, i.e., stays set after -resuming, this method should clear it. For instance, the x86 debug -control register has sticky triggered flags. - -@findex target_watchpoint_addr_within_range -@item target_watchpoint_addr_within_range (@var{target}, @var{addr}, @var{start}, @var{length}) -Check whether @var{addr} (as returned by @code{target_stopped_data_address}) -lies within the hardware-defined watchpoint region described by -@var{start} and @var{length}. This only needs to be provided if the -granularity of a watchpoint is greater than one byte, i.e., if the -watchpoint can also trigger on nearby addresses outside of the watched -region. - -@findex HAVE_STEPPABLE_WATCHPOINT -@item HAVE_STEPPABLE_WATCHPOINT -If defined to a non-zero value, it is not necessary to disable a -watchpoint to step over it. Like @code{gdbarch_have_nonsteppable_watchpoint}, -this is usually set when watchpoints trigger at the instruction -which will perform an interesting read or write. It should be -set if there is a temporary disable bit which allows the processor -to step over the interesting instruction without raising the -watchpoint exception again. - -@findex gdbarch_have_nonsteppable_watchpoint -@item int gdbarch_have_nonsteppable_watchpoint (@var{gdbarch}) -If it returns a non-zero value, @value{GDBN} should disable a -watchpoint to step the inferior over it. This is usually set when -watchpoints trigger at the instruction which will perform an -interesting read or write. - -@findex HAVE_CONTINUABLE_WATCHPOINT -@item HAVE_CONTINUABLE_WATCHPOINT -If defined to a non-zero value, it is possible to continue the -inferior after a watchpoint has been hit. This is usually set -when watchpoints trigger at the instruction following an interesting -read or write. - -@findex STOPPED_BY_WATCHPOINT -@item STOPPED_BY_WATCHPOINT (@var{wait_status}) -Return non-zero if stopped by a watchpoint. @var{wait_status} is of -the type @code{struct target_waitstatus}, defined by @file{target.h}. -Normally, this macro is defined to invoke the function pointed to by -the @code{to_stopped_by_watchpoint} member of the structure (of the -type @code{target_ops}, defined on @file{target.h}) that describes the -target-specific operations; @code{to_stopped_by_watchpoint} ignores -the @var{wait_status} argument. - -@value{GDBN} does not require the non-zero value returned by -@code{STOPPED_BY_WATCHPOINT} to be 100% correct, so if a target cannot -determine for sure whether the inferior stopped due to a watchpoint, -it could return non-zero ``just in case''. -@end table - -@subsection Watchpoints and Threads -@cindex watchpoints, with threads - -@value{GDBN} only supports process-wide watchpoints, which trigger -in all threads. @value{GDBN} uses the thread ID to make watchpoints -act as if they were thread-specific, but it cannot set hardware -watchpoints that only trigger in a specific thread. Therefore, even -if the target supports threads, per-thread debug registers, and -watchpoints which only affect a single thread, it should set the -per-thread debug registers for all threads to the same value. On -@sc{gnu}/Linux native targets, this is accomplished by using -@code{ALL_LWPS} in @code{target_insert_watchpoint} and -@code{target_remove_watchpoint} and by using -@code{linux_set_new_thread} to register a handler for newly created -threads. - -@value{GDBN}'s @sc{gnu}/Linux support only reports a single event -at a time, although multiple events can trigger simultaneously for -multi-threaded programs. When multiple events occur, @file{linux-nat.c} -queues subsequent events and returns them the next time the program -is resumed. This means that @code{STOPPED_BY_WATCHPOINT} and -@code{target_stopped_data_address} only need to consult the current -thread's state---the thread indicated by @code{inferior_ptid}. If -two threads have hit watchpoints simultaneously, those routines -will be called a second time for the second thread. - -@subsection x86 Watchpoints -@cindex x86 debug registers -@cindex watchpoints, on x86 - -The 32-bit Intel x86 (a.k.a.@: ia32) processors feature special debug -registers designed to facilitate debugging. @value{GDBN} provides a -generic library of functions that x86-based ports can use to implement -support for watchpoints and hardware-assisted breakpoints. This -subsection documents the x86 watchpoint facilities in @value{GDBN}. - -(At present, the library functions read and write debug registers directly, and are -thus only available for native configurations.) - -To use the generic x86 watchpoint support, a port should do the -following: - -@itemize @bullet -@findex I386_USE_GENERIC_WATCHPOINTS -@item -Define the macro @code{I386_USE_GENERIC_WATCHPOINTS} somewhere in the -target-dependent headers. - -@item -Include the @file{config/i386/nm-i386.h} header file @emph{after} -defining @code{I386_USE_GENERIC_WATCHPOINTS}. - -@item -Add @file{i386-nat.o} to the value of the Make variable -@code{NATDEPFILES} (@pxref{Native Debugging, NATDEPFILES}). - -@item -Provide implementations for the @code{I386_DR_LOW_*} macros described -below. Typically, each macro should call a target-specific function -which does the real work. -@end itemize - -The x86 watchpoint support works by maintaining mirror images of the -debug registers. Values are copied between the mirror images and the -real debug registers via a set of macros which each target needs to -provide: - -@table @code -@findex I386_DR_LOW_SET_CONTROL -@item I386_DR_LOW_SET_CONTROL (@var{val}) -Set the Debug Control (DR7) register to the value @var{val}. - -@findex I386_DR_LOW_SET_ADDR -@item I386_DR_LOW_SET_ADDR (@var{idx}, @var{addr}) -Put the address @var{addr} into the debug register number @var{idx}. - -@findex I386_DR_LOW_RESET_ADDR -@item I386_DR_LOW_RESET_ADDR (@var{idx}) -Reset (i.e.@: zero out) the address stored in the debug register -number @var{idx}. - -@findex I386_DR_LOW_GET_STATUS -@item I386_DR_LOW_GET_STATUS -Return the value of the Debug Status (DR6) register. This value is -used immediately after it is returned by -@code{I386_DR_LOW_GET_STATUS}, so as to support per-thread status -register values. -@end table - -For each one of the 4 debug registers (whose indices are from 0 to 3) -that store addresses, a reference count is maintained by @value{GDBN}, -to allow sharing of debug registers by several watchpoints. This -allows users to define several watchpoints that watch the same -expression, but with different conditions and/or commands, without -wasting debug registers which are in short supply. @value{GDBN} -maintains the reference counts internally, targets don't have to do -anything to use this feature. - -The x86 debug registers can each watch a region that is 1, 2, or 4 -bytes long. The ia32 architecture requires that each watched region -be appropriately aligned: 2-byte region on 2-byte boundary, 4-byte -region on 4-byte boundary. However, the x86 watchpoint support in -@value{GDBN} can watch unaligned regions and regions larger than 4 -bytes (up to 16 bytes) by allocating several debug registers to watch -a single region. This allocation of several registers per a watched -region is also done automatically without target code intervention. - -The generic x86 watchpoint support provides the following API for the -@value{GDBN}'s application code: - -@table @code -@findex i386_region_ok_for_watchpoint -@item i386_region_ok_for_watchpoint (@var{addr}, @var{len}) -The macro @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is set to call -this function. It counts the number of debug registers required to -watch a given region, and returns a non-zero value if that number is -less than 4, the number of debug registers available to x86 -processors. - -@findex i386_stopped_data_address -@item i386_stopped_data_address (@var{addr_p}) -The target function -@code{target_stopped_data_address} is set to call this function. -This -function examines the breakpoint condition bits in the DR6 Debug -Status register, as returned by the @code{I386_DR_LOW_GET_STATUS} -macro, and returns the address associated with the first bit that is -set in DR6. - -@findex i386_stopped_by_watchpoint -@item i386_stopped_by_watchpoint (void) -The macro @code{STOPPED_BY_WATCHPOINT} -is set to call this function. The -argument passed to @code{STOPPED_BY_WATCHPOINT} is ignored. This -function examines the breakpoint condition bits in the DR6 Debug -Status register, as returned by the @code{I386_DR_LOW_GET_STATUS} -macro, and returns true if any bit is set. Otherwise, false is -returned. - -@findex i386_insert_watchpoint -@findex i386_remove_watchpoint -@item i386_insert_watchpoint (@var{addr}, @var{len}, @var{type}) -@itemx i386_remove_watchpoint (@var{addr}, @var{len}, @var{type}) -Insert or remove a watchpoint. The macros -@code{target_insert_watchpoint} and @code{target_remove_watchpoint} -are set to call these functions. @code{i386_insert_watchpoint} first -looks for a debug register which is already set to watch the same -region for the same access types; if found, it just increments the -reference count of that debug register, thus implementing debug -register sharing between watchpoints. If no such register is found, -the function looks for a vacant debug register, sets its mirrored -value to @var{addr}, sets the mirrored value of DR7 Debug Control -register as appropriate for the @var{len} and @var{type} parameters, -and then passes the new values of the debug register and DR7 to the -inferior by calling @code{I386_DR_LOW_SET_ADDR} and -@code{I386_DR_LOW_SET_CONTROL}. If more than one debug register is -required to cover the given region, the above process is repeated for -each debug register. - -@code{i386_remove_watchpoint} does the opposite: it resets the address -in the mirrored value of the debug register and its read/write and -length bits in the mirrored value of DR7, then passes these new -values to the inferior via @code{I386_DR_LOW_RESET_ADDR} and -@code{I386_DR_LOW_SET_CONTROL}. If a register is shared by several -watchpoints, each time a @code{i386_remove_watchpoint} is called, it -decrements the reference count, and only calls -@code{I386_DR_LOW_RESET_ADDR} and @code{I386_DR_LOW_SET_CONTROL} when -the count goes to zero. - -@findex i386_insert_hw_breakpoint -@findex i386_remove_hw_breakpoint -@item i386_insert_hw_breakpoint (@var{bp_tgt}) -@itemx i386_remove_hw_breakpoint (@var{bp_tgt}) -These functions insert and remove hardware-assisted breakpoints. The -macros @code{target_insert_hw_breakpoint} and -@code{target_remove_hw_breakpoint} are set to call these functions. -The argument is a @code{struct bp_target_info *}, as described in -the documentation for @code{target_insert_breakpoint}. -These functions work like @code{i386_insert_watchpoint} and -@code{i386_remove_watchpoint}, respectively, except that they set up -the debug registers to watch instruction execution, and each -hardware-assisted breakpoint always requires exactly one debug -register. - -@findex i386_cleanup_dregs -@item i386_cleanup_dregs (void) -This function clears all the reference counts, addresses, and control -bits in the mirror images of the debug registers. It doesn't affect -the actual debug registers in the inferior process. -@end table - -@noindent -@strong{Notes:} -@enumerate 1 -@item -x86 processors support setting watchpoints on I/O reads or writes. -However, since no target supports this (as of March 2001), and since -@code{enum target_hw_bp_type} doesn't even have an enumeration for I/O -watchpoints, this feature is not yet available to @value{GDBN} running -on x86. - -@item -x86 processors can enable watchpoints locally, for the current task -only, or globally, for all the tasks. For each debug register, -there's a bit in the DR7 Debug Control register that determines -whether the associated address is watched locally or globally. The -current implementation of x86 watchpoint support in @value{GDBN} -always sets watchpoints to be locally enabled, since global -watchpoints might interfere with the underlying OS and are probably -unavailable in many platforms. -@end enumerate - -@section Checkpoints -@cindex checkpoints -@cindex restart -In the abstract, a checkpoint is a point in the execution history of -the program, which the user may wish to return to at some later time. - -Internally, a checkpoint is a saved copy of the program state, including -whatever information is required in order to restore the program to that -state at a later time. This can be expected to include the state of -registers and memory, and may include external state such as the state -of open files and devices. - -There are a number of ways in which checkpoints may be implemented -in gdb, e.g.@: as corefiles, as forked processes, and as some opaque -method implemented on the target side. - -A corefile can be used to save an image of target memory and register -state, which can in principle be restored later --- but corefiles do -not typically include information about external entities such as -open files. Currently this method is not implemented in gdb. - -A forked process can save the state of user memory and registers, -as well as some subset of external (kernel) state. This method -is used to implement checkpoints on Linux, and in principle might -be used on other systems. - -Some targets, e.g.@: simulators, might have their own built-in -method for saving checkpoints, and gdb might be able to take -advantage of that capability without necessarily knowing any -details of how it is done. - - -@section Observing changes in @value{GDBN} internals -@cindex observer pattern interface -@cindex notifications about changes in internals - -In order to function properly, several modules need to be notified when -some changes occur in the @value{GDBN} internals. Traditionally, these -modules have relied on several paradigms, the most common ones being -hooks and gdb-events. Unfortunately, none of these paradigms was -versatile enough to become the standard notification mechanism in -@value{GDBN}. The fact that they only supported one ``client'' was also -a strong limitation. - -A new paradigm, based on the Observer pattern of the @cite{Design -Patterns} book, has therefore been implemented. The goal was to provide -a new interface overcoming the issues with the notification mechanisms -previously available. This new interface needed to be strongly typed, -easy to extend, and versatile enough to be used as the standard -interface when adding new notifications. - -See @ref{GDB Observers} for a brief description of the observers -currently implemented in GDB. The rationale for the current -implementation is also briefly discussed. - -@node User Interface - -@chapter User Interface - -@value{GDBN} has several user interfaces, of which the traditional -command-line interface is perhaps the most familiar. - -@section Command Interpreter - -@cindex command interpreter -@cindex CLI -The command interpreter in @value{GDBN} is fairly simple. It is designed to -allow for the set of commands to be augmented dynamically, and also -has a recursive subcommand capability, where the first argument to -a command may itself direct a lookup on a different command list. - -For instance, the @samp{set} command just starts a lookup on the -@code{setlist} command list, while @samp{set thread} recurses -to the @code{set_thread_cmd_list}. - -@findex add_cmd -@findex add_com -To add commands in general, use @code{add_cmd}. @code{add_com} adds to -the main command list, and should be used for those commands. The usual -place to add commands is in the @code{_initialize_@var{xyz}} routines at -the ends of most source files. - -@findex add_setshow_cmd -@findex add_setshow_cmd_full -To add paired @samp{set} and @samp{show} commands, use -@code{add_setshow_cmd} or @code{add_setshow_cmd_full}. The former is -a slightly simpler interface which is useful when you don't need to -further modify the new command structures, while the latter returns -the new command structures for manipulation. - -@cindex deprecating commands -@findex deprecate_cmd -Before removing commands from the command set it is a good idea to -deprecate them for some time. Use @code{deprecate_cmd} on commands or -aliases to set the deprecated flag. @code{deprecate_cmd} takes a -@code{struct cmd_list_element} as it's first argument. You can use the -return value from @code{add_com} or @code{add_cmd} to deprecate the -command immediately after it is created. - -The first time a command is used the user will be warned and offered a -replacement (if one exists). Note that the replacement string passed to -@code{deprecate_cmd} should be the full name of the command, i.e., the -entire string the user should type at the command line. - -@anchor{UI-Independent Output} -@section UI-Independent Output---the @code{ui_out} Functions -@c This section is based on the documentation written by Fernando -@c Nasser . - -@cindex @code{ui_out} functions -The @code{ui_out} functions present an abstraction level for the -@value{GDBN} output code. They hide the specifics of different user -interfaces supported by @value{GDBN}, and thus free the programmer -from the need to write several versions of the same code, one each for -every UI, to produce output. - -@subsection Overview and Terminology - -In general, execution of each @value{GDBN} command produces some sort -of output, and can even generate an input request. - -Output can be generated for the following purposes: - -@itemize @bullet -@item -to display a @emph{result} of an operation; - -@item -to convey @emph{info} or produce side-effects of a requested -operation; - -@item -to provide a @emph{notification} of an asynchronous event (including -progress indication of a prolonged asynchronous operation); - -@item -to display @emph{error messages} (including warnings); - -@item -to show @emph{debug data}; - -@item -to @emph{query} or prompt a user for input (a special case). -@end itemize - -@noindent -This section mainly concentrates on how to build result output, -although some of it also applies to other kinds of output. - -Generation of output that displays the results of an operation -involves one or more of the following: - -@itemize @bullet -@item -output of the actual data - -@item -formatting the output as appropriate for console output, to make it -easily readable by humans - -@item -machine oriented formatting--a more terse formatting to allow for easy -parsing by programs which read @value{GDBN}'s output - -@item -annotation, whose purpose is to help legacy GUIs to identify interesting -parts in the output -@end itemize - -The @code{ui_out} routines take care of the first three aspects. -Annotations are provided by separate annotation routines. Note that use -of annotations for an interface between a GUI and @value{GDBN} is -deprecated. - -Output can be in the form of a single item, which we call a @dfn{field}; -a @dfn{list} consisting of identical fields; a @dfn{tuple} consisting of -non-identical fields; or a @dfn{table}, which is a tuple consisting of a -header and a body. In a BNF-like form: - -@table @code -@item @expansion{} -@code{
} -@item
@expansion{} -@code{@{ @}} -@item @expansion{} -@code{ } -@item <body> @expansion{} -@code{@{<row>@}} -@end table - - -@subsection General Conventions - -Most @code{ui_out} routines are of type @code{void}, the exceptions are -@code{ui_out_stream_new} (which returns a pointer to the newly created -object) and the @code{make_cleanup} routines. - -The first parameter is always the @code{ui_out} vector object, a pointer -to a @code{struct ui_out}. - -The @var{format} parameter is like in @code{printf} family of functions. -When it is present, there must also be a variable list of arguments -sufficient used to satisfy the @code{%} specifiers in the supplied -format. - -When a character string argument is not used in a @code{ui_out} function -call, a @code{NULL} pointer has to be supplied instead. - - -@subsection Table, Tuple and List Functions - -@cindex list output functions -@cindex table output functions -@cindex tuple output functions -This section introduces @code{ui_out} routines for building lists, -tuples and tables. The routines to output the actual data items -(fields) are presented in the next section. - -To recap: A @dfn{tuple} is a sequence of @dfn{fields}, each field -containing information about an object; a @dfn{list} is a sequence of -fields where each field describes an identical object. - -Use the @dfn{table} functions when your output consists of a list of -rows (tuples) and the console output should include a heading. Use this -even when you are listing just one object but you still want the header. - -@cindex nesting level in @code{ui_out} functions -Tables can not be nested. Tuples and lists can be nested up to a -maximum of five levels. - -The overall structure of the table output code is something like this: - -@smallexample - ui_out_table_begin - ui_out_table_header - @dots{} - ui_out_table_body - ui_out_tuple_begin - ui_out_field_* - @dots{} - ui_out_tuple_end - @dots{} - ui_out_table_end -@end smallexample - -Here is the description of table-, tuple- and list-related @code{ui_out} -functions: - -@deftypefun void ui_out_table_begin (struct ui_out *@var{uiout}, int @var{nbrofcols}, int @var{nr_rows}, const char *@var{tblid}) -The function @code{ui_out_table_begin} marks the beginning of the output -of a table. It should always be called before any other @code{ui_out} -function for a given table. @var{nbrofcols} is the number of columns in -the table. @var{nr_rows} is the number of rows in the table. -@var{tblid} is an optional string identifying the table. The string -pointed to by @var{tblid} is copied by the implementation of -@code{ui_out_table_begin}, so the application can free the string if it -was @code{malloc}ed. - -The companion function @code{ui_out_table_end}, described below, marks -the end of the table's output. -@end deftypefun - -@deftypefun void ui_out_table_header (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{colhdr}) -@code{ui_out_table_header} provides the header information for a single -table column. You call this function several times, one each for every -column of the table, after @code{ui_out_table_begin}, but before -@code{ui_out_table_body}. - -The value of @var{width} gives the column width in characters. The -value of @var{alignment} is one of @code{left}, @code{center}, and -@code{right}, and it specifies how to align the header: left-justify, -center, or right-justify it. @var{colhdr} points to a string that -specifies the column header; the implementation copies that string, so -column header strings in @code{malloc}ed storage can be freed after the -call. -@end deftypefun - -@deftypefun void ui_out_table_body (struct ui_out *@var{uiout}) -This function delimits the table header from the table body. -@end deftypefun - -@deftypefun void ui_out_table_end (struct ui_out *@var{uiout}) -This function signals the end of a table's output. It should be called -after the table body has been produced by the list and field output -functions. - -There should be exactly one call to @code{ui_out_table_end} for each -call to @code{ui_out_table_begin}, otherwise the @code{ui_out} functions -will signal an internal error. -@end deftypefun - -The output of the tuples that represent the table rows must follow the -call to @code{ui_out_table_body} and precede the call to -@code{ui_out_table_end}. You build a tuple by calling -@code{ui_out_tuple_begin} and @code{ui_out_tuple_end}, with suitable -calls to functions which actually output fields between them. - -@deftypefun void ui_out_tuple_begin (struct ui_out *@var{uiout}, const char *@var{id}) -This function marks the beginning of a tuple output. @var{id} points -to an optional string that identifies the tuple; it is copied by the -implementation, and so strings in @code{malloc}ed storage can be freed -after the call. -@end deftypefun - -@deftypefun void ui_out_tuple_end (struct ui_out *@var{uiout}) -This function signals an end of a tuple output. There should be exactly -one call to @code{ui_out_tuple_end} for each call to -@code{ui_out_tuple_begin}, otherwise an internal @value{GDBN} error will -be signaled. -@end deftypefun - -@deftypefun {struct cleanup *} make_cleanup_ui_out_tuple_begin_end (struct ui_out *@var{uiout}, const char *@var{id}) -This function first opens the tuple and then establishes a cleanup -(@pxref{Misc Guidelines, Cleanups}) to close the tuple. -It provides a convenient and correct implementation of the -non-portable@footnote{The function cast is not portable ISO C.} code sequence: -@smallexample -struct cleanup *old_cleanup; -ui_out_tuple_begin (uiout, "..."); -old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end, - uiout); -@end smallexample -@end deftypefun - -@deftypefun void ui_out_list_begin (struct ui_out *@var{uiout}, const char *@var{id}) -This function marks the beginning of a list output. @var{id} points to -an optional string that identifies the list; it is copied by the -implementation, and so strings in @code{malloc}ed storage can be freed -after the call. -@end deftypefun - -@deftypefun void ui_out_list_end (struct ui_out *@var{uiout}) -This function signals an end of a list output. There should be exactly -one call to @code{ui_out_list_end} for each call to -@code{ui_out_list_begin}, otherwise an internal @value{GDBN} error will -be signaled. -@end deftypefun - -@deftypefun {struct cleanup *} make_cleanup_ui_out_list_begin_end (struct ui_out *@var{uiout}, const char *@var{id}) -Similar to @code{make_cleanup_ui_out_tuple_begin_end}, this function -opens a list and then establishes cleanup -(@pxref{Misc Guidelines, Cleanups}) -that will close the list. -@end deftypefun - -@subsection Item Output Functions - -@cindex item output functions -@cindex field output functions -@cindex data output -The functions described below produce output for the actual data -items, or fields, which contain information about the object. - -Choose the appropriate function accordingly to your particular needs. - -@deftypefun void ui_out_field_fmt (struct ui_out *@var{uiout}, char *@var{fldname}, char *@var{format}, ...) -This is the most general output function. It produces the -representation of the data in the variable-length argument list -according to formatting specifications in @var{format}, a -@code{printf}-like format string. The optional argument @var{fldname} -supplies the name of the field. The data items themselves are -supplied as additional arguments after @var{format}. - -This generic function should be used only when it is not possible to -use one of the specialized versions (see below). -@end deftypefun - -@deftypefun void ui_out_field_int (struct ui_out *@var{uiout}, const char *@var{fldname}, int @var{value}) -This function outputs a value of an @code{int} variable. It uses the -@code{"%d"} output conversion specification. @var{fldname} specifies -the name of the field. -@end deftypefun - -@deftypefun void ui_out_field_fmt_int (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{fldname}, int @var{value}) -This function outputs a value of an @code{int} variable. It differs from -@code{ui_out_field_int} in that the caller specifies the desired @var{width} and @var{alignment} of the output. -@var{fldname} specifies -the name of the field. -@end deftypefun - -@deftypefun void ui_out_field_core_addr (struct ui_out *@var{uiout}, const char *@var{fldname}, struct gdbarch *@var{gdbarch}, CORE_ADDR @var{address}) -This function outputs an address as appropriate for @var{gdbarch}. -@end deftypefun - -@deftypefun void ui_out_field_string (struct ui_out *@var{uiout}, const char *@var{fldname}, const char *@var{string}) -This function outputs a string using the @code{"%s"} conversion -specification. -@end deftypefun - -Sometimes, there's a need to compose your output piece by piece using -functions that operate on a stream, such as @code{value_print} or -@code{fprintf_symbol_filtered}. These functions accept an argument of -the type @code{struct ui_file *}, a pointer to a @code{ui_file} object -used to store the data stream used for the output. When you use one -of these functions, you need a way to pass their results stored in a -@code{ui_file} object to the @code{ui_out} functions. To this end, -you first create a @code{ui_stream} object by calling -@code{ui_out_stream_new}, pass the @code{stream} member of that -@code{ui_stream} object to @code{value_print} and similar functions, -and finally call @code{ui_out_field_stream} to output the field you -constructed. When the @code{ui_stream} object is no longer needed, -you should destroy it and free its memory by calling -@code{ui_out_stream_delete}. - -@deftypefun {struct ui_stream *} ui_out_stream_new (struct ui_out *@var{uiout}) -This function creates a new @code{ui_stream} object which uses the -same output methods as the @code{ui_out} object whose pointer is -passed in @var{uiout}. It returns a pointer to the newly created -@code{ui_stream} object. -@end deftypefun - -@deftypefun void ui_out_stream_delete (struct ui_stream *@var{streambuf}) -This functions destroys a @code{ui_stream} object specified by -@var{streambuf}. -@end deftypefun - -@deftypefun void ui_out_field_stream (struct ui_out *@var{uiout}, const char *@var{fieldname}, struct ui_stream *@var{streambuf}) -This function consumes all the data accumulated in -@code{streambuf->stream} and outputs it like -@code{ui_out_field_string} does. After a call to -@code{ui_out_field_stream}, the accumulated data no longer exists, but -the stream is still valid and may be used for producing more fields. -@end deftypefun - -@strong{Important:} If there is any chance that your code could bail -out before completing output generation and reaching the point where -@code{ui_out_stream_delete} is called, it is necessary to set up a -cleanup, to avoid leaking memory and other resources. Here's a -skeleton code to do that: - -@smallexample - struct ui_stream *mybuf = ui_out_stream_new (uiout); - struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf); - ... - do_cleanups (old); -@end smallexample - -If the function already has the old cleanup chain set (for other kinds -of cleanups), you just have to add your cleanup to it: - -@smallexample - mybuf = ui_out_stream_new (uiout); - make_cleanup (ui_out_stream_delete, mybuf); -@end smallexample - -Note that with cleanups in place, you should not call -@code{ui_out_stream_delete} directly, or you would attempt to free the -same buffer twice. - -@subsection Utility Output Functions - -@deftypefun void ui_out_field_skip (struct ui_out *@var{uiout}, const char *@var{fldname}) -This function skips a field in a table. Use it if you have to leave -an empty field without disrupting the table alignment. The argument -@var{fldname} specifies a name for the (missing) filed. -@end deftypefun - -@deftypefun void ui_out_text (struct ui_out *@var{uiout}, const char *@var{string}) -This function outputs the text in @var{string} in a way that makes it -easy to be read by humans. For example, the console implementation of -this method filters the text through a built-in pager, to prevent it -from scrolling off the visible portion of the screen. - -Use this function for printing relatively long chunks of text around -the actual field data: the text it produces is not aligned according -to the table's format. Use @code{ui_out_field_string} to output a -string field, and use @code{ui_out_message}, described below, to -output short messages. -@end deftypefun - -@deftypefun void ui_out_spaces (struct ui_out *@var{uiout}, int @var{nspaces}) -This function outputs @var{nspaces} spaces. It is handy to align the -text produced by @code{ui_out_text} with the rest of the table or -list. -@end deftypefun - -@deftypefun void ui_out_message (struct ui_out *@var{uiout}, int @var{verbosity}, const char *@var{format}, ...) -This function produces a formatted message, provided that the current -verbosity level is at least as large as given by @var{verbosity}. The -current verbosity level is specified by the user with the @samp{set -verbositylevel} command.@footnote{As of this writing (April 2001), -setting verbosity level is not yet implemented, and is always returned -as zero. So calling @code{ui_out_message} with a @var{verbosity} -argument more than zero will cause the message to never be printed.} -@end deftypefun - -@deftypefun void ui_out_wrap_hint (struct ui_out *@var{uiout}, char *@var{indent}) -This function gives the console output filter (a paging filter) a hint -of where to break lines which are too long. Ignored for all other -output consumers. @var{indent}, if non-@code{NULL}, is the string to -be printed to indent the wrapped text on the next line; it must remain -accessible until the next call to @code{ui_out_wrap_hint}, or until an -explicit newline is produced by one of the other functions. If -@var{indent} is @code{NULL}, the wrapped text will not be indented. -@end deftypefun - -@deftypefun void ui_out_flush (struct ui_out *@var{uiout}) -This function flushes whatever output has been accumulated so far, if -the UI buffers output. -@end deftypefun - - -@subsection Examples of Use of @code{ui_out} functions - -@cindex using @code{ui_out} functions -@cindex @code{ui_out} functions, usage examples -This section gives some practical examples of using the @code{ui_out} -functions to generalize the old console-oriented code in -@value{GDBN}. The examples all come from functions defined on the -@file{breakpoints.c} file. - -This example, from the @code{breakpoint_1} function, shows how to -produce a table. - -The original code was: - -@smallexample - if (!found_a_breakpoint++) - @{ - annotate_breakpoints_headers (); - - annotate_field (0); - printf_filtered ("Num "); - annotate_field (1); - printf_filtered ("Type "); - annotate_field (2); - printf_filtered ("Disp "); - annotate_field (3); - printf_filtered ("Enb "); - if (addressprint) - @{ - annotate_field (4); - printf_filtered ("Address "); - @} - annotate_field (5); - printf_filtered ("What\n"); - - annotate_breakpoints_table (); - @} -@end smallexample - -Here's the new version: - -@smallexample - nr_printable_breakpoints = @dots{}; - - if (addressprint) - ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable"); - else - ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable"); - - if (nr_printable_breakpoints > 0) - annotate_breakpoints_headers (); - if (nr_printable_breakpoints > 0) - annotate_field (0); - ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */ - if (nr_printable_breakpoints > 0) - annotate_field (1); - ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */ - if (nr_printable_breakpoints > 0) - annotate_field (2); - ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */ - if (nr_printable_breakpoints > 0) - annotate_field (3); - ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */ - if (addressprint) - @{ - if (nr_printable_breakpoints > 0) - annotate_field (4); - if (print_address_bits <= 32) - ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */ - else - ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */ - @} - if (nr_printable_breakpoints > 0) - annotate_field (5); - ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */ - ui_out_table_body (uiout); - if (nr_printable_breakpoints > 0) - annotate_breakpoints_table (); -@end smallexample - -This example, from the @code{print_one_breakpoint} function, shows how -to produce the actual data for the table whose structure was defined -in the above example. The original code was: - -@smallexample - annotate_record (); - annotate_field (0); - printf_filtered ("%-3d ", b->number); - annotate_field (1); - if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0])) - || ((int) b->type != bptypes[(int) b->type].type)) - internal_error ("bptypes table does not describe type #%d.", - (int)b->type); - printf_filtered ("%-14s ", bptypes[(int)b->type].description); - annotate_field (2); - printf_filtered ("%-4s ", bpdisps[(int)b->disposition]); - annotate_field (3); - printf_filtered ("%-3c ", bpenables[(int)b->enable]); - @dots{} -@end smallexample - -This is the new version: - -@smallexample - annotate_record (); - ui_out_tuple_begin (uiout, "bkpt"); - annotate_field (0); - ui_out_field_int (uiout, "number", b->number); - annotate_field (1); - if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0]))) - || ((int) b->type != bptypes[(int) b->type].type)) - internal_error ("bptypes table does not describe type #%d.", - (int) b->type); - ui_out_field_string (uiout, "type", bptypes[(int)b->type].description); - annotate_field (2); - ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]); - annotate_field (3); - ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]); - @dots{} -@end smallexample - -This example, also from @code{print_one_breakpoint}, shows how to -produce a complicated output field using the @code{print_expression} -functions which requires a stream to be passed. It also shows how to -automate stream destruction with cleanups. The original code was: - -@smallexample - annotate_field (5); - print_expression (b->exp, gdb_stdout); -@end smallexample - -The new version is: - -@smallexample - struct ui_stream *stb = ui_out_stream_new (uiout); - struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb); - ... - annotate_field (5); - print_expression (b->exp, stb->stream); - ui_out_field_stream (uiout, "what", local_stream); -@end smallexample - -This example, also from @code{print_one_breakpoint}, shows how to use -@code{ui_out_text} and @code{ui_out_field_string}. The original code -was: - -@smallexample - annotate_field (5); - if (b->dll_pathname == NULL) - printf_filtered ("<any library> "); - else - printf_filtered ("library \"%s\" ", b->dll_pathname); -@end smallexample - -It became: - -@smallexample - annotate_field (5); - if (b->dll_pathname == NULL) - @{ - ui_out_field_string (uiout, "what", "<any library>"); - ui_out_spaces (uiout, 1); - @} - else - @{ - ui_out_text (uiout, "library \""); - ui_out_field_string (uiout, "what", b->dll_pathname); - ui_out_text (uiout, "\" "); - @} -@end smallexample - -The following example from @code{print_one_breakpoint} shows how to -use @code{ui_out_field_int} and @code{ui_out_spaces}. The original -code was: - -@smallexample - annotate_field (5); - if (b->forked_inferior_pid != 0) - printf_filtered ("process %d ", b->forked_inferior_pid); -@end smallexample - -It became: - -@smallexample - annotate_field (5); - if (b->forked_inferior_pid != 0) - @{ - ui_out_text (uiout, "process "); - ui_out_field_int (uiout, "what", b->forked_inferior_pid); - ui_out_spaces (uiout, 1); - @} -@end smallexample - -Here's an example of using @code{ui_out_field_string}. The original -code was: - -@smallexample - annotate_field (5); - if (b->exec_pathname != NULL) - printf_filtered ("program \"%s\" ", b->exec_pathname); -@end smallexample - -It became: - -@smallexample - annotate_field (5); - if (b->exec_pathname != NULL) - @{ - ui_out_text (uiout, "program \""); - ui_out_field_string (uiout, "what", b->exec_pathname); - ui_out_text (uiout, "\" "); - @} -@end smallexample - -Finally, here's an example of printing an address. The original code: - -@smallexample - annotate_field (4); - printf_filtered ("%s ", - hex_string_custom ((unsigned long) b->address, 8)); -@end smallexample - -It became: - -@smallexample - annotate_field (4); - ui_out_field_core_addr (uiout, "Address", b->address); -@end smallexample - - -@section Console Printing - -@section TUI - -@node libgdb - -@chapter libgdb - -@section libgdb 1.0 -@cindex @code{libgdb} -@code{libgdb} 1.0 was an abortive project of years ago. The theory was -to provide an API to @value{GDBN}'s functionality. - -@section libgdb 2.0 -@cindex @code{libgdb} -@code{libgdb} 2.0 is an ongoing effort to update @value{GDBN} so that is -better able to support graphical and other environments. - -Since @code{libgdb} development is on-going, its architecture is still -evolving. The following components have so far been identified: - -@itemize @bullet -@item -Observer - @file{gdb-events.h}. -@item -Builder - @file{ui-out.h} -@item -Event Loop - @file{event-loop.h} -@item -Library - @file{gdb.h} -@end itemize - -The model that ties these components together is described below. - -@section The @code{libgdb} Model - -A client of @code{libgdb} interacts with the library in two ways. - -@itemize @bullet -@item -As an observer (using @file{gdb-events}) receiving notifications from -@code{libgdb} of any internal state changes (break point changes, run -state, etc). -@item -As a client querying @code{libgdb} (using the @file{ui-out} builder) to -obtain various status values from @value{GDBN}. -@end itemize - -Since @code{libgdb} could have multiple clients (e.g., a GUI supporting -the existing @value{GDBN} CLI), those clients must co-operate when -controlling @code{libgdb}. In particular, a client must ensure that -@code{libgdb} is idle (i.e.@: no other client is using @code{libgdb}) -before responding to a @file{gdb-event} by making a query. - -@section CLI support - -At present @value{GDBN}'s CLI is very much entangled in with the core of -@code{libgdb}. Consequently, a client wishing to include the CLI in -their interface needs to carefully co-ordinate its own and the CLI's -requirements. - -It is suggested that the client set @code{libgdb} up to be bi-modal -(alternate between CLI and client query modes). The notes below sketch -out the theory: - -@itemize @bullet -@item -The client registers itself as an observer of @code{libgdb}. -@item -The client create and install @code{cli-out} builder using its own -versions of the @code{ui-file} @code{gdb_stderr}, @code{gdb_stdtarg} and -@code{gdb_stdout} streams. -@item -The client creates a separate custom @code{ui-out} builder that is only -used while making direct queries to @code{libgdb}. -@end itemize - -When the client receives input intended for the CLI, it simply passes it -along. Since the @code{cli-out} builder is installed by default, all -the CLI output in response to that command is routed (pronounced rooted) -through to the client controlled @code{gdb_stdout} et.@: al.@: streams. -At the same time, the client is kept abreast of internal changes by -virtue of being a @code{libgdb} observer. - -The only restriction on the client is that it must wait until -@code{libgdb} becomes idle before initiating any queries (using the -client's custom builder). - -@section @code{libgdb} components - -@subheading Observer - @file{gdb-events.h} -@file{gdb-events} provides the client with a very raw mechanism that can -be used to implement an observer. At present it only allows for one -observer and that observer must, internally, handle the need to delay -the processing of any event notifications until after @code{libgdb} has -finished the current command. - -@subheading Builder - @file{ui-out.h} -@file{ui-out} provides the infrastructure necessary for a client to -create a builder. That builder is then passed down to @code{libgdb} -when doing any queries. - -@subheading Event Loop - @file{event-loop.h} -@c There could be an entire section on the event-loop -@file{event-loop}, currently non-re-entrant, provides a simple event -loop. A client would need to either plug its self into this loop or, -implement a new event-loop that @value{GDBN} would use. - -The event-loop will eventually be made re-entrant. This is so that -@value{GDBN} can better handle the problem of some commands blocking -instead of returning. - -@subheading Library - @file{gdb.h} -@file{libgdb} is the most obvious component of this system. It provides -the query interface. Each function is parameterized by a @code{ui-out} -builder. The result of the query is constructed using that builder -before the query function returns. - -@node Values -@chapter Values -@section Values - -@cindex values -@cindex @code{value} structure -@value{GDBN} uses @code{struct value}, or @dfn{values}, as an internal -abstraction for the representation of a variety of inferior objects -and @value{GDBN} convenience objects. - -Values have an associated @code{struct type}, that describes a virtual -view of the raw data or object stored in or accessed through the -value. - -A value is in addition discriminated by its lvalue-ness, given its -@code{enum lval_type} enumeration type: - -@cindex @code{lval_type} enumeration, for values. -@table @code -@item @code{not_lval} -This value is not an lval. It can't be assigned to. - -@item @code{lval_memory} -This value represents an object in memory. - -@item @code{lval_register} -This value represents an object that lives in a register. - -@item @code{lval_internalvar} -Represents the value of an internal variable. - -@item @code{lval_internalvar_component} -Represents part of a @value{GDBN} internal variable. E.g., a -structure field. - -@cindex computed values -@item @code{lval_computed} -These are ``computed'' values. They allow creating specialized value -objects for specific purposes, all abstracted away from the core value -support code. The creator of such a value writes specialized -functions to handle the reading and writing to/from the value's -backend data, and optionally, a ``copy operator'' and a -``destructor''. - -Pointers to these functions are stored in a @code{struct lval_funcs} -instance (declared in @file{value.h}), and passed to the -@code{allocate_computed_value} function, as in the example below. - -@smallexample -static void -nil_value_read (struct value *v) -@{ - /* This callback reads data from some backend, and stores it in V. - In this case, we always read null data. You'll want to fill in - something more interesting. */ - - memset (value_contents_all_raw (v), - value_offset (v), - TYPE_LENGTH (value_type (v))); -@} - -static void -nil_value_write (struct value *v, struct value *fromval) -@{ - /* Takes the data from FROMVAL and stores it in the backend of V. */ - - to_oblivion (value_contents_all_raw (fromval), - value_offset (v), - TYPE_LENGTH (value_type (fromval))); -@} - -static struct lval_funcs nil_value_funcs = - @{ - nil_value_read, - nil_value_write - @}; - -struct value * -make_nil_value (void) -@{ - struct type *type; - struct value *v; - - type = make_nils_type (); - v = allocate_computed_value (type, &nil_value_funcs, NULL); - - return v; -@} -@end smallexample - -See the implementation of the @code{$_siginfo} convenience variable in -@file{infrun.c} as a real example use of lval_computed. - -@end table - -@node Stack Frames -@chapter Stack Frames - -@cindex frame -@cindex call stack frame -A frame is a construct that @value{GDBN} uses to keep track of calling -and called functions. - -@cindex unwind frame -@value{GDBN}'s frame model, a fresh design, was implemented with the -need to support @sc{dwarf}'s Call Frame Information in mind. In fact, -the term ``unwind'' is taken directly from that specification. -Developers wishing to learn more about unwinders, are encouraged to -read the @sc{dwarf} specification, available from -@url{http://www.dwarfstd.org}. - -@findex frame_register_unwind -@findex get_frame_register -@value{GDBN}'s model is that you find a frame's registers by -``unwinding'' them from the next younger frame. That is, -@samp{get_frame_register} which returns the value of a register in -frame #1 (the next-to-youngest frame), is implemented by calling frame -#0's @code{frame_register_unwind} (the youngest frame). But then the -obvious question is: how do you access the registers of the youngest -frame itself? - -@cindex sentinel frame -@findex get_frame_type -@vindex SENTINEL_FRAME -To answer this question, @value{GDBN} has the @dfn{sentinel} frame, the -``-1st'' frame. Unwinding registers from the sentinel frame gives you -the current values of the youngest real frame's registers. If @var{f} -is a sentinel frame, then @code{get_frame_type (@var{f}) @equiv{} -SENTINEL_FRAME}. - -@section Selecting an Unwinder - -@findex frame_unwind_prepend_unwinder -@findex frame_unwind_append_unwinder -The architecture registers a list of frame unwinders (@code{struct -frame_unwind}), using the functions -@code{frame_unwind_prepend_unwinder} and -@code{frame_unwind_append_unwinder}. Each unwinder includes a -sniffer. Whenever @value{GDBN} needs to unwind a frame (to fetch the -previous frame's registers or the current frame's ID), it calls -registered sniffers in order to find one which recognizes the frame. -The first time a sniffer returns non-zero, the corresponding unwinder -is assigned to the frame. - -@section Unwinding the Frame ID -@cindex frame ID - -Every frame has an associated ID, of type @code{struct frame_id}. -The ID includes the stack base and function start address for -the frame. The ID persists through the entire life of the frame, -including while other called frames are running; it is used to -locate an appropriate @code{struct frame_info} from the cache. - -Every time the inferior stops, and at various other times, the frame -cache is flushed. Because of this, parts of @value{GDBN} which need -to keep track of individual frames cannot use pointers to @code{struct -frame_info}. A frame ID provides a stable reference to a frame, even -when the unwinder must be run again to generate a new @code{struct -frame_info} for the same frame. - -The frame's unwinder's @code{this_id} method is called to find the ID. -Note that this is different from register unwinding, where the next -frame's @code{prev_register} is called to unwind this frame's -registers. - -Both stack base and function address are required to identify the -frame, because a recursive function has the same function address for -two consecutive frames and a leaf function may have the same stack -address as its caller. On some platforms, a third address is part of -the ID to further disambiguate frames---for instance, on IA-64 -the separate register stack address is included in the ID. - -An invalid frame ID (@code{outer_frame_id}) returned from the -@code{this_id} method means to stop unwinding after this frame. - -@code{null_frame_id} is another invalid frame ID which should be used -when there is no frame. For instance, certain breakpoints are attached -to a specific frame, and that frame is identified through its frame ID -(we use this to implement the "finish" command). Using -@code{null_frame_id} as the frame ID for a given breakpoint means -that the breakpoint is not specific to any frame. The @code{this_id} -method should never return @code{null_frame_id}. - -@section Unwinding Registers - -Each unwinder includes a @code{prev_register} method. This method -takes a frame, an associated cache pointer, and a register number. -It returns a @code{struct value *} describing the requested register, -as saved by this frame. This is the value of the register that is -current in this frame's caller. - -The returned value must have the same type as the register. It may -have any lvalue type. In most circumstances one of these routines -will generate the appropriate value: - -@table @code -@item frame_unwind_got_optimized -@findex frame_unwind_got_optimized -This register was not saved. - -@item frame_unwind_got_register -@findex frame_unwind_got_register -This register was copied into another register in this frame. This -is also used for unchanged registers; they are ``copied'' into the -same register. - -@item frame_unwind_got_memory -@findex frame_unwind_got_memory -This register was saved in memory. - -@item frame_unwind_got_constant -@findex frame_unwind_got_constant -This register was not saved, but the unwinder can compute the previous -value some other way. - -@item frame_unwind_got_address -@findex frame_unwind_got_address -Same as @code{frame_unwind_got_constant}, except that the value is a target -address. This is frequently used for the stack pointer, which is not -explicitly saved but has a known offset from this frame's stack -pointer. For architectures with a flat unified address space, this is -generally the same as @code{frame_unwind_got_constant}. -@end table - -@node Symbol Handling - -@chapter Symbol Handling - -Symbols are a key part of @value{GDBN}'s operation. Symbols include -variables, functions, and types. - -Symbol information for a large program can be truly massive, and -reading of symbol information is one of the major performance -bottlenecks in @value{GDBN}; it can take many minutes to process it -all. Studies have shown that nearly all the time spent is -computational, rather than file reading. - -One of the ways for @value{GDBN} to provide a good user experience is -to start up quickly, taking no more than a few seconds. It is simply -not possible to process all of a program's debugging info in that -time, and so we attempt to handle symbols incrementally. For instance, -we create @dfn{partial symbol tables} consisting of only selected -symbols, and only expand them to full symbol tables when necessary. - -@section Symbol Reading - -@cindex symbol reading -@cindex reading of symbols -@cindex symbol files -@value{GDBN} reads symbols from @dfn{symbol files}. The usual symbol -file is the file containing the program which @value{GDBN} is -debugging. @value{GDBN} can be directed to use a different file for -symbols (with the @samp{symbol-file} command), and it can also read -more symbols via the @samp{add-file} and @samp{load} commands. In -addition, it may bring in more symbols while loading shared -libraries. - -@findex find_sym_fns -Symbol files are initially opened by code in @file{symfile.c} using -the BFD library (@pxref{Support Libraries}). BFD identifies the type -of the file by examining its header. @code{find_sym_fns} then uses -this identification to locate a set of symbol-reading functions. - -@findex add_symtab_fns -@cindex @code{sym_fns} structure -@cindex adding a symbol-reading module -Symbol-reading modules identify themselves to @value{GDBN} by calling -@code{add_symtab_fns} during their module initialization. The argument -to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the -name (or name prefix) of the symbol format, the length of the prefix, -and pointers to four functions. These functions are called at various -times to process symbol files whose identification matches the specified -prefix. - -The functions supplied by each module are: - -@table @code -@item @var{xyz}_symfile_init(struct sym_fns *sf) - -@cindex secondary symbol file -Called from @code{symbol_file_add} when we are about to read a new -symbol file. This function should clean up any internal state (possibly -resulting from half-read previous files, for example) and prepare to -read a new symbol file. Note that the symbol file which we are reading -might be a new ``main'' symbol file, or might be a secondary symbol file -whose symbols are being added to the existing symbol table. - -The argument to @code{@var{xyz}_symfile_init} is a newly allocated -@code{struct sym_fns} whose @code{bfd} field contains the BFD for the -new symbol file being read. Its @code{private} field has been zeroed, -and can be modified as desired. Typically, a struct of private -information will be @code{malloc}'d, and a pointer to it will be placed -in the @code{private} field. - -There is no result from @code{@var{xyz}_symfile_init}, but it can call -@code{error} if it detects an unavoidable problem. - -@item @var{xyz}_new_init() - -Called from @code{symbol_file_add} when discarding existing symbols. -This function needs only handle the symbol-reading module's internal -state; the symbol table data structures visible to the rest of -@value{GDBN} will be discarded by @code{symbol_file_add}. It has no -arguments and no result. It may be called after -@code{@var{xyz}_symfile_init}, if a new symbol table is being read, or -may be called alone if all symbols are simply being discarded. - -@item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline) - -Called from @code{symbol_file_add} to actually read the symbols from a -symbol-file into a set of psymtabs or symtabs. - -@code{sf} points to the @code{struct sym_fns} originally passed to -@code{@var{xyz}_sym_init} for possible initialization. @code{addr} is -the offset between the file's specified start address and its true -address in memory. @code{mainline} is 1 if this is the main symbol -table being read, and 0 if a secondary symbol file (e.g., shared library -or dynamically loaded file) is being read.@refill -@end table - -In addition, if a symbol-reading module creates psymtabs when -@var{xyz}_symfile_read is called, these psymtabs will contain a pointer -to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called -from any point in the @value{GDBN} symbol-handling code. - -@table @code -@item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst) - -Called from @code{psymtab_to_symtab} (or the @code{PSYMTAB_TO_SYMTAB} macro) if -the psymtab has not already been read in and had its @code{pst->symtab} -pointer set. The argument is the psymtab to be fleshed-out into a -symtab. Upon return, @code{pst->readin} should have been set to 1, and -@code{pst->symtab} should contain a pointer to the new corresponding symtab, or -zero if there were no symbols in that part of the symbol file. -@end table - -@section Partial Symbol Tables - -@value{GDBN} has three types of symbol tables: - -@itemize @bullet -@cindex full symbol table -@cindex symtabs -@item -Full symbol tables (@dfn{symtabs}). These contain the main -information about symbols and addresses. - -@cindex psymtabs -@item -Partial symbol tables (@dfn{psymtabs}). These contain enough -information to know when to read the corresponding part of the full -symbol table. - -@cindex minimal symbol table -@cindex minsymtabs -@item -Minimal symbol tables (@dfn{msymtabs}). These contain information -gleaned from non-debugging symbols. -@end itemize - -@cindex partial symbol table -This section describes partial symbol tables. - -A psymtab is constructed by doing a very quick pass over an executable -file's debugging information. Small amounts of information are -extracted---enough to identify which parts of the symbol table will -need to be re-read and fully digested later, when the user needs the -information. The speed of this pass causes @value{GDBN} to start up very -quickly. Later, as the detailed rereading occurs, it occurs in small -pieces, at various times, and the delay therefrom is mostly invisible to -the user. -@c (@xref{Symbol Reading}.) - -The symbols that show up in a file's psymtab should be, roughly, those -visible to the debugger's user when the program is not running code from -that file. These include external symbols and types, static symbols and -types, and @code{enum} values declared at file scope. - -The psymtab also contains the range of instruction addresses that the -full symbol table would represent. - -@cindex finding a symbol -@cindex symbol lookup -The idea is that there are only two ways for the user (or much of the -code in the debugger) to reference a symbol: - -@itemize @bullet -@findex find_pc_function -@findex find_pc_line -@item -By its address (e.g., execution stops at some address which is inside a -function in this file). The address will be noticed to be in the -range of this psymtab, and the full symtab will be read in. -@code{find_pc_function}, @code{find_pc_line}, and other -@code{find_pc_@dots{}} functions handle this. - -@cindex lookup_symbol -@item -By its name -(e.g., the user asks to print a variable, or set a breakpoint on a -function). Global names and file-scope names will be found in the -psymtab, which will cause the symtab to be pulled in. Local names will -have to be qualified by a global name, or a file-scope name, in which -case we will have already read in the symtab as we evaluated the -qualifier. Or, a local symbol can be referenced when we are ``in'' a -local scope, in which case the first case applies. @code{lookup_symbol} -does most of the work here. -@end itemize - -The only reason that psymtabs exist is to cause a symtab to be read in -at the right moment. Any symbol that can be elided from a psymtab, -while still causing that to happen, should not appear in it. Since -psymtabs don't have the idea of scope, you can't put local symbols in -them anyway. Psymtabs don't have the idea of the type of a symbol, -either, so types need not appear, unless they will be referenced by -name. - -It is a bug for @value{GDBN} to behave one way when only a psymtab has -been read, and another way if the corresponding symtab has been read -in. Such bugs are typically caused by a psymtab that does not contain -all the visible symbols, or which has the wrong instruction address -ranges. - -The psymtab for a particular section of a symbol file (objfile) could be -thrown away after the symtab has been read in. The symtab should always -be searched before the psymtab, so the psymtab will never be used (in a -bug-free environment). Currently, psymtabs are allocated on an obstack, -and all the psymbols themselves are allocated in a pair of large arrays -on an obstack, so there is little to be gained by trying to free them -unless you want to do a lot more work. - -Whether or not psymtabs are created depends on the objfile's symbol -reader. The core of @value{GDBN} hides the details of partial symbols -and partial symbol tables behind a set of function pointers known as -the @dfn{quick symbol functions}. These are documented in -@file{symfile.h}. - -@section Types - -@unnumberedsubsec Fundamental Types (e.g., @code{FT_VOID}, @code{FT_BOOLEAN}). - -@cindex fundamental types -These are the fundamental types that @value{GDBN} uses internally. Fundamental -types from the various debugging formats (stabs, ELF, etc) are mapped -into one of these. They are basically a union of all fundamental types -that @value{GDBN} knows about for all the languages that @value{GDBN} -knows about. - -@unnumberedsubsec Type Codes (e.g., @code{TYPE_CODE_PTR}, @code{TYPE_CODE_ARRAY}). - -@cindex type codes -Each time @value{GDBN} builds an internal type, it marks it with one -of these types. The type may be a fundamental type, such as -@code{TYPE_CODE_INT}, or a derived type, such as @code{TYPE_CODE_PTR} -which is a pointer to another type. Typically, several @code{FT_*} -types map to one @code{TYPE_CODE_*} type, and are distinguished by -other members of the type struct, such as whether the type is signed -or unsigned, and how many bits it uses. - -@unnumberedsubsec Builtin Types (e.g., @code{builtin_type_void}, @code{builtin_type_char}). - -These are instances of type structs that roughly correspond to -fundamental types and are created as global types for @value{GDBN} to -use for various ugly historical reasons. We eventually want to -eliminate these. Note for example that @code{builtin_type_int} -initialized in @file{gdbtypes.c} is basically the same as a -@code{TYPE_CODE_INT} type that is initialized in @file{c-lang.c} for -an @code{FT_INTEGER} fundamental type. The difference is that the -@code{builtin_type} is not associated with any particular objfile, and -only one instance exists, while @file{c-lang.c} builds as many -@code{TYPE_CODE_INT} types as needed, with each one associated with -some particular objfile. - -@section Object File Formats -@cindex object file formats - -@subsection a.out - -@cindex @code{a.out} format -The @code{a.out} format is the original file format for Unix. It -consists of three sections: @code{text}, @code{data}, and @code{bss}, -which are for program code, initialized data, and uninitialized data, -respectively. - -The @code{a.out} format is so simple that it doesn't have any reserved -place for debugging information. (Hey, the original Unix hackers used -@samp{adb}, which is a machine-language debugger!) The only debugging -format for @code{a.out} is stabs, which is encoded as a set of normal -symbols with distinctive attributes. - -The basic @code{a.out} reader is in @file{dbxread.c}. - -@subsection COFF - -@cindex COFF format -The COFF format was introduced with System V Release 3 (SVR3) Unix. -COFF files may have multiple sections, each prefixed by a header. The -number of sections is limited. - -The COFF specification includes support for debugging. Although this -was a step forward, the debugging information was woefully limited. -For instance, it was not possible to represent code that came from an -included file. GNU's COFF-using configs often use stabs-type info, -encapsulated in special sections. - -The COFF reader is in @file{coffread.c}. - -@subsection ECOFF - -@cindex ECOFF format -ECOFF is an extended COFF originally introduced for Mips and Alpha -workstations. - -The basic ECOFF reader is in @file{mipsread.c}. - -@subsection XCOFF - -@cindex XCOFF format -The IBM RS/6000 running AIX uses an object file format called XCOFF. -The COFF sections, symbols, and line numbers are used, but debugging -symbols are @code{dbx}-style stabs whose strings are located in the -@code{.debug} section (rather than the string table). For more -information, see @ref{Top,,,stabs,The Stabs Debugging Format}. - -The shared library scheme has a clean interface for figuring out what -shared libraries are in use, but the catch is that everything which -refers to addresses (symbol tables and breakpoints at least) needs to be -relocated for both shared libraries and the main executable. At least -using the standard mechanism this can only be done once the program has -been run (or the core file has been read). - -@subsection PE - -@cindex PE-COFF format -Windows 95 and NT use the PE (@dfn{Portable Executable}) format for their -executables. PE is basically COFF with additional headers. - -While BFD includes special PE support, @value{GDBN} needs only the basic -COFF reader. - -@subsection ELF - -@cindex ELF format -The ELF format came with System V Release 4 (SVR4) Unix. ELF is -similar to COFF in being organized into a number of sections, but it -removes many of COFF's limitations. Debugging info may be either stabs -encapsulated in ELF sections, or more commonly these days, DWARF. - -The basic ELF reader is in @file{elfread.c}. - -@subsection SOM - -@cindex SOM format -SOM is HP's object file and debug format (not to be confused with IBM's -SOM, which is a cross-language ABI). - -The SOM reader is in @file{somread.c}. - -@section Debugging File Formats - -This section describes characteristics of debugging information that -are independent of the object file format. - -@subsection stabs - -@cindex stabs debugging info -@code{stabs} started out as special symbols within the @code{a.out} -format. Since then, it has been encapsulated into other file -formats, such as COFF and ELF. - -While @file{dbxread.c} does some of the basic stab processing, -including for encapsulated versions, @file{stabsread.c} does -the real work. - -@subsection COFF - -@cindex COFF debugging info -The basic COFF definition includes debugging information. The level -of support is minimal and non-extensible, and is not often used. - -@subsection Mips debug (Third Eye) - -@cindex ECOFF debugging info -ECOFF includes a definition of a special debug format. - -The file @file{mdebugread.c} implements reading for this format. - -@c mention DWARF 1 as a formerly-supported format - -@subsection DWARF 2 - -@cindex DWARF 2 debugging info -DWARF 2 is an improved but incompatible version of DWARF 1. - -The DWARF 2 reader is in @file{dwarf2read.c}. - -@subsection Compressed DWARF 2 - -@cindex Compressed DWARF 2 debugging info -Compressed DWARF 2 is not technically a separate debugging format, but -merely DWARF 2 debug information that has been compressed. In this -format, every object-file section holding DWARF 2 debugging -information is compressed and prepended with a header. (The section -is also typically renamed, so a section called @code{.debug_info} in a -DWARF 2 binary would be called @code{.zdebug_info} in a compressed -DWARF 2 binary.) The header is 12 bytes long: - -@itemize @bullet -@item -4 bytes: the literal string ``ZLIB'' -@item -8 bytes: the uncompressed size of the section, in big-endian byte -order. -@end itemize - -The same reader is used for both compressed an normal DWARF 2 info. -Section decompression is done in @code{zlib_decompress_section} in -@file{dwarf2read.c}. - -@subsection DWARF 3 - -@cindex DWARF 3 debugging info -DWARF 3 is an improved version of DWARF 2. - -@subsection SOM - -@cindex SOM debugging info -Like COFF, the SOM definition includes debugging information. - -@section Adding a New Symbol Reader to @value{GDBN} - -@cindex adding debugging info reader -If you are using an existing object file format (@code{a.out}, COFF, ELF, etc), -there is probably little to be done. - -If you need to add a new object file format, you must first add it to -BFD. This is beyond the scope of this document. - -You must then arrange for the BFD code to provide access to the -debugging symbols. Generally @value{GDBN} will have to call swapping -routines from BFD and a few other BFD internal routines to locate the -debugging information. As much as possible, @value{GDBN} should not -depend on the BFD internal data structures. - -For some targets (e.g., COFF), there is a special transfer vector used -to call swapping routines, since the external data structures on various -platforms have different sizes and layouts. Specialized routines that -will only ever be implemented by one object file format may be called -directly. This interface should be described in a file -@file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}. - -@section Memory Management for Symbol Files - -Most memory associated with a loaded symbol file is stored on -its @code{objfile_obstack}. This includes symbols, types, -namespace data, and other information produced by the symbol readers. - -Because this data lives on the objfile's obstack, it is automatically -released when the objfile is unloaded or reloaded. Therefore one -objfile must not reference symbol or type data from another objfile; -they could be unloaded at different times. - -User convenience variables, et cetera, have associated types. Normally -these types live in the associated objfile. However, when the objfile -is unloaded, those types are deep copied to global memory, so that -the values of the user variables and history items are not lost. - - -@node Language Support - -@chapter Language Support - -@cindex language support -@value{GDBN}'s language support is mainly driven by the symbol reader, -although it is possible for the user to set the source language -manually. - -@value{GDBN} chooses the source language by looking at the extension -of the file recorded in the debug info; @file{.c} means C, @file{.f} -means Fortran, etc. It may also use a special-purpose language -identifier if the debug format supports it, like with DWARF. - -@section Adding a Source Language to @value{GDBN} - -@cindex adding source language -To add other languages to @value{GDBN}'s expression parser, follow the -following steps: - -@table @emph -@item Create the expression parser. - -@cindex expression parser -This should reside in a file @file{@var{lang}-exp.y}. Routines for -building parsed expressions into a @code{union exp_element} list are in -@file{parse.c}. - -@cindex language parser -Since we can't depend upon everyone having Bison, and YACC produces -parsers that define a bunch of global names, the following lines -@strong{must} be included at the top of the YACC parser, to prevent the -various parsers from defining the same global names: - -@smallexample -#define yyparse @var{lang}_parse -#define yylex @var{lang}_lex -#define yyerror @var{lang}_error -#define yylval @var{lang}_lval -#define yychar @var{lang}_char -#define yydebug @var{lang}_debug -#define yypact @var{lang}_pact -#define yyr1 @var{lang}_r1 -#define yyr2 @var{lang}_r2 -#define yydef @var{lang}_def -#define yychk @var{lang}_chk -#define yypgo @var{lang}_pgo -#define yyact @var{lang}_act -#define yyexca @var{lang}_exca -#define yyerrflag @var{lang}_errflag -#define yynerrs @var{lang}_nerrs -@end smallexample - -At the bottom of your parser, define a @code{struct language_defn} and -initialize it with the right values for your language. Define an -@code{initialize_@var{lang}} routine and have it call -@samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN} -that your language exists. You'll need some other supporting variables -and functions, which will be used via pointers from your -@code{@var{lang}_language_defn}. See the declaration of @code{struct -language_defn} in @file{language.h}, and the other @file{*-exp.y} files, -for more information. - -@item Add any evaluation routines, if necessary - -@cindex expression evaluation routines -@findex evaluate_subexp -@findex prefixify_subexp -@findex length_of_subexp -If you need new opcodes (that represent the operations of the language), -add them to the enumerated type in @file{expression.h}. Add support -code for these operations in the @code{evaluate_subexp} function -defined in the file @file{eval.c}. Add cases -for new opcodes in two functions from @file{parse.c}: -@code{prefixify_subexp} and @code{length_of_subexp}. These compute -the number of @code{exp_element}s that a given operation takes up. - -@item Update some existing code - -Add an enumerated identifier for your language to the enumerated type -@code{enum language} in @file{defs.h}. - -Update the routines in @file{language.c} so your language is included. -These routines include type predicates and such, which (in some cases) -are language dependent. If your language does not appear in the switch -statement, an error is reported. - -@vindex current_language -Also included in @file{language.c} is the code that updates the variable -@code{current_language}, and the routines that translate the -@code{language_@var{lang}} enumerated identifier into a printable -string. - -@findex _initialize_language -Update the function @code{_initialize_language} to include your -language. This function picks the default language upon startup, so is -dependent upon which languages that @value{GDBN} is built for. - -@findex allocate_symtab -Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading -code so that the language of each symtab (source file) is set properly. -This is used to determine the language to use at each stack frame level. -Currently, the language is set based upon the extension of the source -file. If the language can be better inferred from the symbol -information, please set the language of the symtab in the symbol-reading -code. - -@findex print_subexp -@findex op_print_tab -Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new -expression opcodes you have added to @file{expression.h}. Also, add the -printed representations of your operators to @code{op_print_tab}. - -@item Add a place of call - -@findex parse_exp_1 -Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in -@code{parse_exp_1} (defined in @file{parse.c}). - -@item Edit @file{Makefile.in} - -Add dependencies in @file{Makefile.in}. Make sure you update the macro -variables such as @code{HFILES} and @code{OBJS}, otherwise your code may -not get linked in, or, worse yet, it may not get @code{tar}red into the -distribution! -@end table - - -@node Host Definition - -@chapter Host Definition - -With the advent of Autoconf, it's rarely necessary to have host -definition machinery anymore. The following information is provided, -mainly, as an historical reference. - -@section Adding a New Host - -@cindex adding a new host -@cindex host, adding -@value{GDBN}'s host configuration support normally happens via Autoconf. -New host-specific definitions should not be needed. Older hosts -@value{GDBN} still use the host-specific definitions and files listed -below, but these mostly exist for historical reasons, and will -eventually disappear. - -@table @file -@item gdb/config/@var{arch}/@var{xyz}.mh -This file is a Makefile fragment that once contained both host and -native configuration information (@pxref{Native Debugging}) for the -machine @var{xyz}. The host configuration information is now handled -by Autoconf. - -Host configuration information included definitions for @code{CC}, -@code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES}, -@code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}. - -New host-only configurations do not need this file. - -@end table - -(Files named @file{gdb/config/@var{arch}/xm-@var{xyz}.h} were once -used to define host-specific macros, but were no longer needed and -have all been removed.) - -@subheading Generic Host Support Files - -@cindex generic host support -There are some ``generic'' versions of routines that can be used by -various systems. - -@table @file -@cindex remote debugging support -@cindex serial line support -@item ser-unix.c -This contains serial line support for Unix systems. It is included by -default on all Unix-like hosts. - -@item ser-pipe.c -This contains serial pipe support for Unix systems. It is included by -default on all Unix-like hosts. - -@item ser-mingw.c -This contains serial line support for 32-bit programs running under -Windows using MinGW. - -@item ser-go32.c -This contains serial line support for 32-bit programs running under DOS, -using the DJGPP (a.k.a.@: GO32) execution environment. - -@cindex TCP remote support -@item ser-tcp.c -This contains generic TCP support using sockets. It is included by -default on all Unix-like hosts and with MinGW. -@end table - -@section Host Conditionals - -When @value{GDBN} is configured and compiled, various macros are -defined or left undefined, to control compilation based on the -attributes of the host system. While formerly they could be set in -host-specific header files, at present they can be changed only by -setting @code{CFLAGS} when building, or by editing the source code. - -These macros and their meanings (or if the meaning is not documented -here, then one of the source files where they are used is indicated) -are: - -@ftable @code -@item @value{GDBN}INIT_FILENAME -The default name of @value{GDBN}'s initialization file (normally -@file{.gdbinit}). - -@item CRLF_SOURCE_FILES -@cindex DOS text files -Define this if host files use @code{\r\n} rather than @code{\n} as a -line terminator. This will cause source file listings to omit @code{\r} -characters when printing and it will allow @code{\r\n} line endings of files -which are ``sourced'' by gdb. It must be possible to open files in binary -mode using @code{O_BINARY} or, for fopen, @code{"rb"}. - -@item DEFAULT_PROMPT -@cindex prompt -The default value of the prompt string (normally @code{"(gdb) "}). - -@item DEV_TTY -@cindex terminal device -The name of the generic TTY device, defaults to @code{"/dev/tty"}. - -@item ISATTY -Substitute for isatty, if not available. - -@item FOPEN_RB -Define this if binary files are opened the same way as text files. - -@item PRINTF_HAS_LONG_LONG -Define this if the host can handle printing of long long integers via -the printf format conversion specifier @code{ll}. This is set by the -@code{configure} script. - -@item LSEEK_NOT_LINEAR -Define this if @code{lseek (n)} does not necessarily move to byte number -@code{n} in the file. This is only used when reading source files. It -is normally faster to define @code{CRLF_SOURCE_FILES} when possible. - -@item lint -Define this to help placate @code{lint} in some situations. - -@item volatile -Define this to override the defaults of @code{__volatile__} or -@code{/**/}. -@end ftable - - -@node Target Architecture Definition - -@chapter Target Architecture Definition - -@cindex target architecture definition -@value{GDBN}'s target architecture defines what sort of -machine-language programs @value{GDBN} can work with, and how it works -with them. - -The target architecture object is implemented as the C structure -@code{struct gdbarch *}. The structure, and its methods, are generated -using the Bourne shell script @file{gdbarch.sh}. - -@menu -* OS ABI Variant Handling:: -* Initialize New Architecture:: -* Registers and Memory:: -* Pointers and Addresses:: -* Address Classes:: -* Register Representation:: -* Frame Interpretation:: -* Inferior Call Setup:: -* Adding support for debugging core files:: -* Defining Other Architecture Features:: -* Adding a New Target:: -@end menu - -@node OS ABI Variant Handling -@section Operating System ABI Variant Handling -@cindex OS ABI variants - -@value{GDBN} provides a mechanism for handling variations in OS -ABIs. An OS ABI variant may have influence over any number of -variables in the target architecture definition. There are two major -components in the OS ABI mechanism: sniffers and handlers. - -A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair -(the architecture may be wildcarded) in an attempt to determine the -OS ABI of that file. Sniffers with a wildcarded architecture are considered -to be @dfn{generic}, while sniffers for a specific architecture are -considered to be @dfn{specific}. A match from a specific sniffer -overrides a match from a generic sniffer. Multiple sniffers for an -architecture/flavour may exist, in order to differentiate between two -different operating systems which use the same basic file format. The -OS ABI framework provides a generic sniffer for ELF-format files which -examines the @code{EI_OSABI} field of the ELF header, as well as note -sections known to be used by several operating systems. - -@cindex fine-tuning @code{gdbarch} structure -A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the -selected OS ABI. There may be only one handler for a given OS ABI -for each BFD architecture. - -The following OS ABI variants are defined in @file{defs.h}: - -@table @code - -@findex GDB_OSABI_UNINITIALIZED -@item GDB_OSABI_UNINITIALIZED -Used for struct gdbarch_info if ABI is still uninitialized. - -@findex GDB_OSABI_UNKNOWN -@item GDB_OSABI_UNKNOWN -The ABI of the inferior is unknown. The default @code{gdbarch} -settings for the architecture will be used. - -@findex GDB_OSABI_SVR4 -@item GDB_OSABI_SVR4 -UNIX System V Release 4. - -@findex GDB_OSABI_HURD -@item GDB_OSABI_HURD -GNU using the Hurd kernel. - -@findex GDB_OSABI_SOLARIS -@item GDB_OSABI_SOLARIS -Sun Solaris. - -@findex GDB_OSABI_OSF1 -@item GDB_OSABI_OSF1 -OSF/1, including Digital UNIX and Compaq Tru64 UNIX. - -@findex GDB_OSABI_LINUX -@item GDB_OSABI_LINUX -GNU using the Linux kernel. - -@findex GDB_OSABI_FREEBSD_AOUT -@item GDB_OSABI_FREEBSD_AOUT -FreeBSD using the @code{a.out} executable format. - -@findex GDB_OSABI_FREEBSD_ELF -@item GDB_OSABI_FREEBSD_ELF -FreeBSD using the ELF executable format. - -@findex GDB_OSABI_NETBSD_AOUT -@item GDB_OSABI_NETBSD_AOUT -NetBSD using the @code{a.out} executable format. - -@findex GDB_OSABI_NETBSD_ELF -@item GDB_OSABI_NETBSD_ELF -NetBSD using the ELF executable format. - -@findex GDB_OSABI_OPENBSD_ELF -@item GDB_OSABI_OPENBSD_ELF -OpenBSD using the ELF executable format. - -@findex GDB_OSABI_WINCE -@item GDB_OSABI_WINCE -Windows CE. - -@findex GDB_OSABI_GO32 -@item GDB_OSABI_GO32 -DJGPP. - -@findex GDB_OSABI_IRIX -@item GDB_OSABI_IRIX -Irix. - -@findex GDB_OSABI_INTERIX -@item GDB_OSABI_INTERIX -Interix (Posix layer for MS-Windows systems). - -@findex GDB_OSABI_HPUX_ELF -@item GDB_OSABI_HPUX_ELF -HP/UX using the ELF executable format. - -@findex GDB_OSABI_HPUX_SOM -@item GDB_OSABI_HPUX_SOM -HP/UX using the SOM executable format. - -@findex GDB_OSABI_QNXNTO -@item GDB_OSABI_QNXNTO -QNX Neutrino. - -@findex GDB_OSABI_CYGWIN -@item GDB_OSABI_CYGWIN -Cygwin. - -@findex GDB_OSABI_AIX -@item GDB_OSABI_AIX -AIX. - -@end table - -Here are the functions that make up the OS ABI framework: - -@deftypefun {const char *} gdbarch_osabi_name (enum gdb_osabi @var{osabi}) -Return the name of the OS ABI corresponding to @var{osabi}. -@end deftypefun - -@deftypefun void gdbarch_register_osabi (enum bfd_architecture @var{arch}, unsigned long @var{machine}, enum gdb_osabi @var{osabi}, void (*@var{init_osabi})(struct gdbarch_info @var{info}, struct gdbarch *@var{gdbarch})) -Register the OS ABI handler specified by @var{init_osabi} for the -architecture, machine type and OS ABI specified by @var{arch}, -@var{machine} and @var{osabi}. In most cases, a value of zero for the -machine type, which implies the architecture's default machine type, -will suffice. -@end deftypefun - -@deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd})) -Register the OS ABI file sniffer specified by @var{sniffer} for the -BFD architecture/flavour pair specified by @var{arch} and @var{flavour}. -If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to -be generic, and is allowed to examine @var{flavour}-flavoured files for -any architecture. -@end deftypefun - -@deftypefun {enum gdb_osabi} gdbarch_lookup_osabi (bfd *@var{abfd}) -Examine the file described by @var{abfd} to determine its OS ABI. -The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot -be determined. -@end deftypefun - -@deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi}) -Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the -@code{gdbarch} structure specified by @var{gdbarch}. If a handler -corresponding to @var{osabi} has not been registered for @var{gdbarch}'s -architecture, a warning will be issued and the debugging session will continue -with the defaults already established for @var{gdbarch}. -@end deftypefun - -@deftypefun void generic_elf_osabi_sniff_abi_tag_sections (bfd *@var{abfd}, asection *@var{sect}, void *@var{obj}) -Helper routine for ELF file sniffers. Examine the file described by -@var{abfd} and look at ABI tag note sections to determine the OS ABI -from the note. This function should be called via -@code{bfd_map_over_sections}. -@end deftypefun - -@node Initialize New Architecture -@section Initializing a New Architecture - -@menu -* How an Architecture is Represented:: -* Looking Up an Existing Architecture:: -* Creating a New Architecture:: -@end menu - -@node How an Architecture is Represented -@subsection How an Architecture is Represented -@cindex architecture representation -@cindex representation of architecture - -Each @code{gdbarch} is associated with a single @sc{bfd} architecture, -via a @code{bfd_arch_@var{arch}} in the @code{bfd_architecture} -enumeration. The @code{gdbarch} is registered by a call to -@code{register_gdbarch_init}, usually from the file's -@code{_initialize_@var{filename}} routine, which will be automatically -called during @value{GDBN} startup. The arguments are a @sc{bfd} -architecture constant and an initialization function. - -@findex _initialize_@var{arch}_tdep -@cindex @file{@var{arch}-tdep.c} -A @value{GDBN} description for a new architecture, @var{arch} is created by -defining a global function @code{_initialize_@var{arch}_tdep}, by -convention in the source file @file{@var{arch}-tdep.c}. For example, -in the case of the OpenRISC 1000, this function is called -@code{_initialize_or1k_tdep} and is found in the file -@file{or1k-tdep.c}. - -@cindex @file{configure.tgt} -@cindex @code{gdbarch} -@findex gdbarch_register -The resulting object files containing the implementation of the -@code{_initialize_@var{arch}_tdep} function are specified in the @value{GDBN} -@file{configure.tgt} file, which includes a large case statement -pattern matching against the @code{--target} option of the -@code{configure} script. The new @code{struct gdbarch} is created -within the @code{_initialize_@var{arch}_tdep} function by calling -@code{gdbarch_register}: - -@smallexample -void gdbarch_register (enum bfd_architecture @var{architecture}, - gdbarch_init_ftype *@var{init_func}, - gdbarch_dump_tdep_ftype *@var{tdep_dump_func}); -@end smallexample - -The @var{architecture} will identify the unique @sc{bfd} to be -associated with this @code{gdbarch}. The @var{init_func} funciton is -called to create and return the new @code{struct gdbarch}. The -@var{tdep_dump_func} function will dump the target specific details -associated with this architecture. - -For example the function @code{_initialize_or1k_tdep} creates its -architecture for 32-bit OpenRISC 1000 architectures by calling: - -@smallexample -gdbarch_register (bfd_arch_or32, or1k_gdbarch_init, or1k_dump_tdep); -@end smallexample - -@node Looking Up an Existing Architecture -@subsection Looking Up an Existing Architecture -@cindex @code{gdbarch} lookup - -The initialization function has this prototype: - -@smallexample -static struct gdbarch * -@var{arch}_gdbarch_init (struct gdbarch_info @var{info}, - struct gdbarch_list *@var{arches}) -@end smallexample - -The @var{info} argument contains parameters used to select the correct -architecture, and @var{arches} is a list of architectures which -have already been created with the same @code{bfd_arch_@var{arch}} -value. - -The initialization function should first make sure that @var{info} -is acceptable, and return @code{NULL} if it is not. Then, it should -search through @var{arches} for an exact match to @var{info}, and -return one if found. Lastly, if no exact match was found, it should -create a new architecture based on @var{info} and return it. - -@findex gdbarch_list_lookup_by_info -@cindex @code{gdbarch_info} -The lookup is done using @code{gdbarch_list_lookup_by_info}. It is -passed the list of existing architectures, @var{arches}, and the -@code{struct gdbarch_info}, @var{info}, and returns the first matching -architecture it finds, or @code{NULL} if none are found. If an -architecture is found it can be returned as the result from the -initialization function, otherwise a new @code{struct gdbach} will need -to be created. - -The struct gdbarch_info has the following components: - -@smallexample -struct gdbarch_info -@{ - const struct bfd_arch_info *bfd_arch_info; - int byte_order; - bfd *abfd; - struct gdbarch_tdep_info *tdep_info; - enum gdb_osabi osabi; - const struct target_desc *target_desc; -@}; -@end smallexample - -@vindex bfd_arch_info -The @code{bfd_arch_info} member holds the key details about the -architecture. The @code{byte_order} member is a value in an -enumeration indicating the endianism. The @code{abfd} member is a -pointer to the full @sc{bfd}, the @code{tdep_info} member is -additional custom target specific information, @code{osabi} identifies -which (if any) of a number of operating specific ABIs are used by this -architecture and the @code{target_desc} member is a set of name-value -pairs with information about register usage in this target. - -When the @code{struct gdbarch} initialization function is called, not -all the fields are provided---only those which can be deduced from the -@sc{bfd}. The @code{struct gdbarch_info}, @var{info} is used as a -look-up key with the list of existing architectures, @var{arches} to -see if a suitable architecture already exists. The @var{tdep_info}, -@var{osabi} and @var{target_desc} fields may be added before this -lookup to refine the search. - -Only information in @var{info} should be used to choose the new -architecture. Historically, @var{info} could be sparse, and -defaults would be collected from the first element on @var{arches}. -However, @value{GDBN} now fills in @var{info} more thoroughly, -so new @code{gdbarch} initialization functions should not take -defaults from @var{arches}. - -@node Creating a New Architecture -@subsection Creating a New Architecture -@cindex @code{struct gdbarch} creation - -@findex gdbarch_alloc -@cindex @code{gdbarch_tdep} when allocating new @code{gdbarch} -If no architecture is found, then a new architecture must be created, -by calling @code{gdbarch_alloc} using the supplied @code{@w{struct -gdbarch_info}} and any additional custom target specific -information in a @code{struct gdbarch_tdep}. The prototype for -@code{gdbarch_alloc} is: - -@smallexample -struct gdbarch *gdbarch_alloc (const struct gdbarch_info *@var{info}, - struct gdbarch_tdep *@var{tdep}); -@end smallexample - -@cindex @code{set_gdbarch} functions -@cindex @code{gdbarch} accessor functions -The newly created struct gdbarch must then be populated. Although -there are default values, in most cases they are not what is -required. - -For each element, @var{X}, there is are a pair of corresponding accessor -functions, one to set the value of that element, -@code{set_gdbarch_@var{X}}, the second to either get the value of an -element (if it is a variable) or to apply the element (if it is a -function), @code{gdbarch_@var{X}}. Note that both accessor functions -take a pointer to the @code{@w{struct gdbarch}} as first -argument. Populating the new @code{gdbarch} should use the -@code{set_gdbarch} functions. - -The following sections identify the main elements that should be set -in this way. This is not the complete list, but represents the -functions and elements that must commonly be specified for a new -architecture. Many of the functions and variables are described in the -header file @file{gdbarch.h}. - -This is the main work in defining a new architecture. Implementing the -set of functions to populate the @code{struct gdbarch}. - -@cindex @code{gdbarch_tdep} definition -@code{struct gdbarch_tdep} is not defined within @value{GDBN}---it is up -to the user to define this struct if it is needed to hold custom target -information that is not covered by the standard @code{@w{struct -gdbarch}}. For example with the OpenRISC 1000 architecture it is used to -hold the number of matchpoints available in the target (along with other -information). - -If there is no additional target specific information, it can be set to -@code{NULL}. - -@node Registers and Memory -@section Registers and Memory - -@value{GDBN}'s model of the target machine is rather simple. -@value{GDBN} assumes the machine includes a bank of registers and a -block of memory. Each register may have a different size. - -@value{GDBN} does not have a magical way to match up with the -compiler's idea of which registers are which; however, it is critical -that they do match up accurately. The only way to make this work is -to get accurate information about the order that the compiler uses, -and to reflect that in the @code{gdbarch_register_name} and related functions. - -@value{GDBN} can handle big-endian, little-endian, and bi-endian architectures. - -@node Pointers and Addresses -@section Pointers Are Not Always Addresses -@cindex pointer representation -@cindex address representation -@cindex word-addressed machines -@cindex separate data and code address spaces -@cindex spaces, separate data and code address -@cindex address spaces, separate data and code -@cindex code pointers, word-addressed -@cindex converting between pointers and addresses -@cindex D10V addresses - -On almost all 32-bit architectures, the representation of a pointer is -indistinguishable from the representation of some fixed-length number -whose value is the byte address of the object pointed to. On such -machines, the words ``pointer'' and ``address'' can be used interchangeably. -However, architectures with smaller word sizes are often cramped for -address space, so they may choose a pointer representation that breaks this -identity, and allows a larger code address space. - -@c D10V is gone from sources - more current example? - -For example, the Renesas D10V is a 16-bit VLIW processor whose -instructions are 32 bits long@footnote{Some D10V instructions are -actually pairs of 16-bit sub-instructions. However, since you can't -jump into the middle of such a pair, code addresses can only refer to -full 32 bit instructions, which is what matters in this explanation.}. -If the D10V used ordinary byte addresses to refer to code locations, -then the processor would only be able to address 64kb of instructions. -However, since instructions must be aligned on four-byte boundaries, the -low two bits of any valid instruction's byte address are always -zero---byte addresses waste two bits. So instead of byte addresses, -the D10V uses word addresses---byte addresses shifted right two bits---to -refer to code. Thus, the D10V can use 16-bit words to address 256kb of -code space. - -However, this means that code pointers and data pointers have different -forms on the D10V. The 16-bit word @code{0xC020} refers to byte address -@code{0xC020} when used as a data address, but refers to byte address -@code{0x30080} when used as a code address. - -(The D10V also uses separate code and data address spaces, which also -affects the correspondence between pointers and addresses, but we're -going to ignore that here; this example is already too long.) - -To cope with architectures like this---the D10V is not the only -one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are -byte numbers, and @dfn{pointers}, which are the target's representation -of an address of a particular type of data. In the example above, -@code{0xC020} is the pointer, which refers to one of the addresses -@code{0xC020} or @code{0x30080}, depending on the type imposed upon it. -@value{GDBN} provides functions for turning a pointer into an address -and vice versa, in the appropriate way for the current architecture. - -Unfortunately, since addresses and pointers are identical on almost all -processors, this distinction tends to bit-rot pretty quickly. Thus, -each time you port @value{GDBN} to an architecture which does -distinguish between pointers and addresses, you'll probably need to -clean up some architecture-independent code. - -Here are functions which convert between pointers and addresses: - -@deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type}) -Treat the bytes at @var{buf} as a pointer or reference of type -@var{type}, and return the address it represents, in a manner -appropriate for the current architecture. This yields an address -@value{GDBN} can use to read target memory, disassemble, etc. Note that -@var{buf} refers to a buffer in @value{GDBN}'s memory, not the -inferior's. - -For example, if the current architecture is the Intel x86, this function -extracts a little-endian integer of the appropriate length from -@var{buf} and returns it. However, if the current architecture is the -D10V, this function will return a 16-bit integer extracted from -@var{buf}, multiplied by four if @var{type} is a pointer to a function. - -If @var{type} is not a pointer or reference type, then this function -will signal an internal error. -@end deftypefun - -@deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr}) -Store the address @var{addr} in @var{buf}, in the proper format for a -pointer of type @var{type} in the current architecture. Note that -@var{buf} refers to a buffer in @value{GDBN}'s memory, not the -inferior's. - -For example, if the current architecture is the Intel x86, this function -stores @var{addr} unmodified as a little-endian integer of the -appropriate length in @var{buf}. However, if the current architecture -is the D10V, this function divides @var{addr} by four if @var{type} is -a pointer to a function, and then stores it in @var{buf}. - -If @var{type} is not a pointer or reference type, then this function -will signal an internal error. -@end deftypefun - -@deftypefun CORE_ADDR value_as_address (struct value *@var{val}) -Assuming that @var{val} is a pointer, return the address it represents, -as appropriate for the current architecture. - -This function actually works on integral values, as well as pointers. -For pointers, it performs architecture-specific conversions as -described above for @code{extract_typed_address}. -@end deftypefun - -@deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr}) -Create and return a value representing a pointer of type @var{type} to -the address @var{addr}, as appropriate for the current architecture. -This function performs architecture-specific conversions as described -above for @code{store_typed_address}. -@end deftypefun - -Here are two functions which architectures can define to indicate the -relationship between pointers and addresses. These have default -definitions, appropriate for architectures on which all pointers are -simple unsigned byte addresses. - -@deftypefun CORE_ADDR gdbarch_pointer_to_address (struct gdbarch *@var{gdbarch}, struct type *@var{type}, char *@var{buf}) -Assume that @var{buf} holds a pointer of type @var{type}, in the -appropriate format for the current architecture. Return the byte -address the pointer refers to. - -This function may safely assume that @var{type} is either a pointer or a -C@t{++} reference type. -@end deftypefun - -@deftypefun void gdbarch_address_to_pointer (struct gdbarch *@var{gdbarch}, struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr}) -Store in @var{buf} a pointer of type @var{type} representing the address -@var{addr}, in the appropriate format for the current architecture. - -This function may safely assume that @var{type} is either a pointer or a -C@t{++} reference type. -@end deftypefun - -@node Address Classes -@section Address Classes -@cindex address classes -@cindex DW_AT_byte_size -@cindex DW_AT_address_class - -Sometimes information about different kinds of addresses is available -via the debug information. For example, some programming environments -define addresses of several different sizes. If the debug information -distinguishes these kinds of address classes through either the size -info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit -address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the -following macros should be defined in order to disambiguate these -types within @value{GDBN} as well as provide the added information to -a @value{GDBN} user when printing type expressions. - -@deftypefun int gdbarch_address_class_type_flags (struct gdbarch *@var{gdbarch}, int @var{byte_size}, int @var{dwarf2_addr_class}) -Returns the type flags needed to construct a pointer type whose size -is @var{byte_size} and whose address class is @var{dwarf2_addr_class}. -This function is normally called from within a symbol reader. See -@file{dwarf2read.c}. -@end deftypefun - -@deftypefun {char *} gdbarch_address_class_type_flags_to_name (struct gdbarch *@var{gdbarch}, int @var{type_flags}) -Given the type flags representing an address class qualifier, return -its name. -@end deftypefun -@deftypefun int gdbarch_address_class_name_to_type_flags (struct gdbarch *@var{gdbarch}, int @var{name}, int *@var{type_flags_ptr}) -Given an address qualifier name, set the @code{int} referenced by @var{type_flags_ptr} to the type flags -for that address class qualifier. -@end deftypefun - -Since the need for address classes is rather rare, none of -the address class functions are defined by default. Predicate -functions are provided to detect when they are defined. - -Consider a hypothetical architecture in which addresses are normally -32-bits wide, but 16-bit addresses are also supported. Furthermore, -suppose that the @w{DWARF 2} information for this architecture simply -uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one -of these "short" pointers. The following functions could be defined -to implement the address class functions: - -@smallexample -somearch_address_class_type_flags (int byte_size, - int dwarf2_addr_class) -@{ - if (byte_size == 2) - return TYPE_FLAG_ADDRESS_CLASS_1; - else - return 0; -@} - -static char * -somearch_address_class_type_flags_to_name (int type_flags) -@{ - if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1) - return "short"; - else - return NULL; -@} - -int -somearch_address_class_name_to_type_flags (char *name, - int *type_flags_ptr) -@{ - if (strcmp (name, "short") == 0) - @{ - *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1; - return 1; - @} - else - return 0; -@} -@end smallexample - -The qualifier @code{@@short} is used in @value{GDBN}'s type expressions -to indicate the presence of one of these ``short'' pointers. For -example if the debug information indicates that @code{short_ptr_var} is -one of these short pointers, @value{GDBN} might show the following -behavior: - -@smallexample -(gdb) ptype short_ptr_var -type = int * @@short -@end smallexample - - -@node Register Representation -@section Register Representation - -@menu -* Raw and Cooked Registers:: -* Register Architecture Functions & Variables:: -* Register Information Functions:: -* Register and Memory Data:: -* Register Caching:: -@end menu - -@node Raw and Cooked Registers -@subsection Raw and Cooked Registers -@cindex raw register representation -@cindex cooked register representation -@cindex representations, raw and cooked registers - -@value{GDBN} considers registers to be a set with members numbered -linearly from 0 upwards. The first part of that set corresponds to real -physical registers, the second part to any @dfn{pseudo-registers}. -Pseudo-registers have no independent physical existence, but are useful -representations of information within the architecture. For example the -OpenRISC 1000 architecture has up to 32 general purpose registers, which -are typically represented as 32-bit (or 64-bit) integers. However the -GPRs are also used as operands to the floating point operations, and it -could be convenient to define a set of pseudo-registers, to show the -GPRs represented as floating point values. - -For any architecture, the implementer will decide on a mapping from -hardware to @value{GDBN} register numbers. The registers corresponding to real -hardware are referred to as @dfn{raw} registers, the remaining registers are -@dfn{pseudo-registers}. The total register set (raw and pseudo) is called -the @dfn{cooked} register set. - - -@node Register Architecture Functions & Variables -@subsection Functions and Variables Specifying the Register Architecture -@cindex @code{gdbarch} register architecture functions - -These @code{struct gdbarch} functions and variables specify the number -and type of registers in the architecture. - -@deftypefn {Architecture Function} CORE_ADDR read_pc (struct regcache *@var{regcache}) -@end deftypefn -@deftypefn {Architecture Function} void write_pc (struct regcache *@var{regcache}, CORE_ADDR @var{val}) - -Read or write the program counter. The default value of both -functions is @code{NULL} (no function available). If the program -counter is just an ordinary register, it can be specified in -@code{struct gdbarch} instead (see @code{pc_regnum} below) and it will -be read or written using the standard routines to access registers. This -function need only be specified if the program counter is not an -ordinary register. - -Any register information can be obtained using the supplied register -cache, @var{regcache}. @xref{Register Caching, , Register Caching}. - -@end deftypefn - -@deftypefn {Architecture Function} void pseudo_register_read (struct gdbarch *@var{gdbarch}, struct regcache *@var{regcache}, int @var{regnum}, const gdb_byte *@var{buf}) -@end deftypefn -@deftypefn {Architecture Function} void pseudo_register_write (struct gdbarch *@var{gdbarch}, struct regcache *@var{regcache}, int @var{regnum}, const gdb_byte *@var{buf}) - -These functions should be defined if there are any pseudo-registers. -The default value is @code{NULL}. @var{regnum} is the number of the -register to read or write (which will be a @dfn{cooked} register -number) and @var{buf} is the buffer where the value read will be -placed, or from which the value to be written will be taken. The -value in the buffer may be converted to or from a signed or unsigned -integral value using one of the utility functions (@pxref{Register and -Memory Data, , Using Different Register and Memory Data -Representations}). - -The access should be for the specified architecture, -@var{gdbarch}. Any register information can be obtained using the -supplied register cache, @var{regcache}. @xref{Register Caching, , -Register Caching}. - -@end deftypefn - -@deftypevr {Architecture Variable} int sp_regnum -@vindex sp_regnum -@cindex stack pointer -@cindex @kbd{$sp} - -This specifies the register holding the stack pointer, which may be a -raw or pseudo-register. It defaults to -1 (not defined), but it is an -error for it not to be defined. - -The value of the stack pointer register can be accessed withing -@value{GDBN} as the variable @kbd{$sp}. - -@end deftypevr - -@deftypevr {Architecture Variable} int pc_regnum -@vindex pc_regnum -@cindex program counter -@cindex @kbd{$pc} - -This specifies the register holding the program counter, which may be a -raw or pseudo-register. It defaults to -1 (not defined). If -@code{pc_regnum} is not defined, then the functions @code{read_pc} and -@code{write_pc} (see above) must be defined. - -The value of the program counter (whether defined as a register, or -through @code{read_pc} and @code{write_pc}) can be accessed withing -@value{GDBN} as the variable @kbd{$pc}. - -@end deftypevr - -@deftypevr {Architecture Variable} int ps_regnum -@vindex ps_regnum -@cindex processor status register -@cindex status register -@cindex @kbd{$ps} - -This specifies the register holding the processor status (often called -the status register), which may be a raw or pseudo-register. It -defaults to -1 (not defined). - -If defined, the value of this register can be accessed withing -@value{GDBN} as the variable @kbd{$ps}. - -@end deftypevr - -@deftypevr {Architecture Variable} int fp0_regnum -@vindex fp0_regnum -@cindex first floating point register - -This specifies the first floating point register. It defaults to -0. @code{fp0_regnum} is not needed unless the target offers support -for floating point. - -@end deftypevr - -@node Register Information Functions -@subsection Functions Giving Register Information -@cindex @code{gdbarch} register information functions - -These functions return information about registers. - -@deftypefn {Architecture Function} {const char *} register_name (struct gdbarch *@var{gdbarch}, int @var{regnum}) - -This function should convert a register number (raw or pseudo) to a -register name (as a C @code{const char *}). This is used both to -determine the name of a register for output and to work out the meaning -of any register names used as input. The function may also return -@code{NULL}, to indicate that @var{regnum} is not a valid register. - -For example with the OpenRISC 1000, @value{GDBN} registers 0-31 are the -General Purpose Registers, register 32 is the program counter and -register 33 is the supervision register (i.e.@: the processor status -register), which map to the strings @code{"gpr00"} through -@code{"gpr31"}, @code{"pc"} and @code{"sr"} respectively. This means -that the @value{GDBN} command @kbd{print $gpr5} should print the value of -the OR1K general purpose register 5@footnote{ -@cindex frame pointer -@cindex @kbd{$fp} -Historically, @value{GDBN} always had a concept of a frame pointer -register, which could be accessed via the @value{GDBN} variable, -@kbd{$fp}. That concept is now deprecated, recognizing that not all -architectures have a frame pointer. However if an architecture does -have a frame pointer register, and defines a register or -pseudo-register with the name @code{"fp"}, then that register will be -used as the value of the @kbd{$fp} variable.}. - -The default value for this function is @code{NULL}, meaning -undefined. It should always be defined. - -The access should be for the specified architecture, @var{gdbarch}. - -@end deftypefn - -@deftypefn {Architecture Function} {struct type *} register_type (struct gdbarch *@var{gdbarch}, int @var{regnum}) - -Given a register number, this function identifies the type of data it -may be holding, specified as a @code{struct type}. @value{GDBN} allows -creation of arbitrary types, but a number of built in types are -provided (@code{builtin_type_void}, @code{builtin_type_int32} etc), -together with functions to derive types from these. - -Typically the program counter will have a type of ``pointer to -function'' (it points to code), the frame pointer and stack pointer -will have types of ``pointer to void'' (they point to data on the stack) -and all other integer registers will have a type of 32-bit integer or -64-bit integer. - -This information guides the formatting when displaying register -information. The default value is @code{NULL} meaning no information is -available to guide formatting when displaying registers. - -@end deftypefn - -@deftypefn {Architecture Function} void print_registers_info (struct gdbarch *@var{gdbarch}, struct ui_file *@var{file}, struct frame_info *@var{frame}, int @var{regnum}, int @var{all}) - -Define this function to print out one or all of the registers for the -@value{GDBN} @kbd{info registers} command. The default value is the -function @code{default_print_registers_info}, which uses the register -type information (see @code{register_type} above) to determine how each -register should be printed. Define a custom version of this function -for fuller control over how the registers are displayed. - -The access should be for the specified architecture, @var{gdbarch}, -with output to the file specified by the User Interface -Independent Output file handle, @var{file} (@pxref{UI-Independent -Output, , UI-Independent Output---the @code{ui_out} -Functions}). - -The registers should show their values in the frame specified by -@var{frame}. If @var{regnum} is -1 and @var{all} is zero, then all -the ``significant'' registers should be shown (the implementer should -decide which registers are ``significant''). Otherwise only the value of -the register specified by @var{regnum} should be output. If -@var{regnum} is -1 and @var{all} is non-zero (true), then the value of -all registers should be shown. - -By default @code{default_print_registers_info} prints one register per -line, and if @var{all} is zero omits floating-point registers. - -@end deftypefn - -@deftypefn {Architecture Function} void print_float_info (struct gdbarch *@var{gdbarch}, struct ui_file *@var{file}, struct frame_info *@var{frame}, const char *@var{args}) - -Define this function to provide output about the floating point unit and -registers for the @value{GDBN} @kbd{info float} command respectively. -The default value is @code{NULL} (not defined), meaning no information -will be provided. - -The @var{gdbarch} and @var{file} and @var{frame} arguments have the same -meaning as in the @code{print_registers_info} function above. The string -@var{args} contains any supplementary arguments to the @kbd{info float} -command. - -Define this function if the target supports floating point operations. - -@end deftypefn - -@deftypefn {Architecture Function} void print_vector_info (struct gdbarch *@var{gdbarch}, struct ui_file *@var{file}, struct frame_info *@var{frame}, const char *@var{args}) - -Define this function to provide output about the vector unit and -registers for the @value{GDBN} @kbd{info vector} command respectively. -The default value is @code{NULL} (not defined), meaning no information -will be provided. - -The @var{gdbarch}, @var{file} and @var{frame} arguments have the -same meaning as in the @code{print_registers_info} function above. The -string @var{args} contains any supplementary arguments to the @kbd{info -vector} command. - -Define this function if the target supports vector operations. - -@end deftypefn - -@deftypefn {Architecture Function} int register_reggroup_p (struct gdbarch *@var{gdbarch}, int @var{regnum}, struct reggroup *@var{group}) - -@value{GDBN} groups registers into different categories (general, -vector, floating point etc). This function, given a register, -@var{regnum}, and group, @var{group}, returns 1 (true) if the register -is in the group and 0 (false) otherwise. - -The information should be for the specified architecture, -@var{gdbarch} - -The default value is the function @code{default_register_reggroup_p} -which will do a reasonable job based on the type of the register (see -the function @code{register_type} above), with groups for general -purpose registers, floating point registers, vector registers and raw -(i.e not pseudo) registers. - -@end deftypefn - -@node Register and Memory Data -@subsection Using Different Register and Memory Data Representations -@cindex register representation -@cindex memory representation -@cindex representations, register and memory -@cindex register data formats, converting -@cindex @code{struct value}, converting register contents to - -Some architectures have different representations of data objects, -depending whether the object is held in a register or memory. For -example: - -@itemize @bullet - -@item -The Alpha architecture can represent 32 bit integer values in -floating-point registers. - -@item -The x86 architecture supports 80-bit floating-point registers. The -@code{long double} data type occupies 96 bits in memory but only 80 -bits when stored in a register. - -@end itemize - -In general, the register representation of a data type is determined by -the architecture, or @value{GDBN}'s interface to the architecture, while -the memory representation is determined by the Application Binary -Interface. - -For almost all data types on almost all architectures, the two -representations are identical, and no special handling is needed. -However, they do occasionally differ. An architecture may define the -following @code{struct gdbarch} functions to request conversions -between the register and memory representations of a data type: - -@deftypefn {Architecture Function} int gdbarch_convert_register_p (struct gdbarch *@var{gdbarch}, int @var{reg}) - -Return non-zero (true) if the representation of a data value stored in -this register may be different to the representation of that same data -value when stored in memory. The default value is @code{NULL} -(undefined). - -If this function is defined and returns non-zero, the @code{struct -gdbarch} functions @code{gdbarch_register_to_value} and -@code{gdbarch_value_to_register} (see below) should be used to perform -any necessary conversion. - -If defined, this function should return zero for the register's native -type, when no conversion is necessary. -@end deftypefn - -@deftypefn {Architecture Function} void gdbarch_register_to_value (struct gdbarch *@var{gdbarch}, int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to}) - -Convert the value of register number @var{reg} to a data object of -type @var{type}. The buffer at @var{from} holds the register's value -in raw format; the converted value should be placed in the buffer at -@var{to}. - -@quotation -@emph{Note:} @code{gdbarch_register_to_value} and -@code{gdbarch_value_to_register} take their @var{reg} and @var{type} -arguments in different orders. -@end quotation - -@code{gdbarch_register_to_value} should only be used with registers -for which the @code{gdbarch_convert_register_p} function returns a -non-zero value. - -@end deftypefn - -@deftypefn {Architecture Function} void gdbarch_value_to_register (struct gdbarch *@var{gdbarch}, struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to}) - -Convert a data value of type @var{type} to register number @var{reg}' -raw format. - -@quotation -@emph{Note:} @code{gdbarch_register_to_value} and -@code{gdbarch_value_to_register} take their @var{reg} and @var{type} -arguments in different orders. -@end quotation - -@code{gdbarch_value_to_register} should only be used with registers -for which the @code{gdbarch_convert_register_p} function returns a -non-zero value. - -@end deftypefn - -@node Register Caching -@subsection Register Caching -@cindex register caching - -Caching of registers is used, so that the target does not need to be -accessed and reanalyzed multiple times for each register in -circumstances where the register value cannot have changed. - -@cindex @code{struct regcache} -@value{GDBN} provides @code{struct regcache}, associated with a -particular @code{struct gdbarch} to hold the cached values of the raw -registers. A set of functions is provided to access both the raw -registers (with @code{raw} in their name) and the full set of cooked -registers (with @code{cooked} in their name). Functions are provided -to ensure the register cache is kept synchronized with the values of -the actual registers in the target. - -Accessing registers through the @code{struct regcache} routines will -ensure that the appropriate @code{struct gdbarch} functions are called -when necessary to access the underlying target architecture. In general -users should use the @dfn{cooked} functions, since these will map to the -@dfn{raw} functions automatically as appropriate. - -@findex regcache_cooked_read -@findex regcache_cooked_write -@cindex @code{gdb_byte} -@findex regcache_cooked_read_signed -@findex regcache_cooked_read_unsigned -@findex regcache_cooked_write_signed -@findex regcache_cooked_write_unsigned -The two key functions are @code{regcache_cooked_read} and -@code{regcache_cooked_write} which read or write a register from or to -a byte buffer (type @code{gdb_byte *}). For convenience the wrapper -functions @code{regcache_cooked_read_signed}, -@code{regcache_cooked_read_unsigned}, -@code{regcache_cooked_write_signed} and -@code{regcache_cooked_write_unsigned} are provided, which read or -write the value using the buffer and convert to or from an integral -value as appropriate. - -@node Frame Interpretation -@section Frame Interpretation - -@menu -* All About Stack Frames:: -* Frame Handling Terminology:: -* Prologue Caches:: -* Functions and Variable to Analyze Frames:: -* Functions to Access Frame Data:: -* Analyzing Stacks---Frame Sniffers:: -@end menu - -@node All About Stack Frames -@subsection All About Stack Frames - -@value{GDBN} needs to understand the stack on which local (automatic) -variables are stored. The area of the stack containing all the local -variables for a function invocation is known as the @dfn{stack frame} -for that function (or colloquially just as the @dfn{frame}). In turn the -function that called the function will have its stack frame, and so on -back through the chain of functions that have been called. - -Almost all architectures have one register dedicated to point to the -end of the stack (the @dfn{stack pointer}). Many have a second register -which points to the start of the currently active stack frame (the -@dfn{frame pointer}). The specific arrangements for an architecture are -a key part of the ABI. - -A diagram helps to explain this. Here is a simple program to compute -factorials: - -@smallexample -#include <stdio.h> -int fact (int n) -@{ - if (0 == n) - @{ - return 1; - @} - else - @{ - return n * fact (n - 1); - @} -@} - -main () -@{ - int i; - - for (i = 0; i < 10; i++) - @{ - int f = fact (i); - printf ("%d! = %d\n", i, f); - @} -@} -@end smallexample - -Consider the state of the stack when the code reaches line 6 after the -main program has called @code{fact@w{ }(3)}. The chain of function -calls will be @code{main ()}, @code{fact@w{ }(3)}, @code{fact@w{ -}(2)}, @code{@w{fact (1)}} and @code{fact@w{ }(0)}. - -In this illustration the stack is falling (as used for example by the -OpenRISC 1000 ABI). The stack pointer (SP) is at the end of the stack -(lowest address) and the frame pointer (FP) is at the highest address -in the current stack frame. The following diagram shows how the stack -looks. - -@center @image{stack_frame,14cm} - -In each stack frame, offset 0 from the stack pointer is the frame -pointer of the previous frame and offset 4 (this is illustrating a -32-bit architecture) from the stack pointer is the return address. -Local variables are indexed from the frame pointer, with negative -indexes. In the function @code{fact}, offset -4 from the frame -pointer is the argument @var{n}. In the @code{main} function, offset --4 from the frame pointer is the local variable @var{i} and offset -8 -from the frame pointer is the local variable @var{f}@footnote{This is -a simplified example for illustrative purposes only. Good optimizing -compilers would not put anything on the stack for such simple -functions. Indeed they might eliminate the recursion and use of the -stack entirely!}. - -It is very easy to get confused when examining stacks. @value{GDBN} -has terminology it uses rigorously throughout. The stack frame of the -function currently executing, or where execution stopped is numbered -zero. In this example frame #0 is the stack frame of the call to -@code{fact@w{ }(0)}. The stack frame of its calling function -(@code{fact@w{ }(1)} in this case) is numbered #1 and so on back -through the chain of calls. - -The main @value{GDBN} data structure describing frames is - @code{@w{struct frame_info}}. It is not used directly, but only via -its accessor functions. @code{frame_info} includes information about -the registers in the frame and a pointer to the code of the function -with which the frame is associated. The entire stack is represented as -a linked list of @code{frame_info} structs. - -@node Frame Handling Terminology -@subsection Frame Handling Terminology - -It is easy to get confused when referencing stack frames. @value{GDBN} -uses some precise terminology. - -@itemize @bullet - -@item -@cindex THIS frame -@cindex stack frame, definition of THIS frame -@cindex frame, definition of THIS frame -@dfn{THIS} frame is the frame currently under consideration. - -@item -@cindex NEXT frame -@cindex stack frame, definition of NEXT frame -@cindex frame, definition of NEXT frame -The @dfn{NEXT} frame, also sometimes called the inner or newer frame is the -frame of the function called by the function of THIS frame. - -@item -@cindex PREVIOUS frame -@cindex stack frame, definition of PREVIOUS frame -@cindex frame, definition of PREVIOUS frame -The @dfn{PREVIOUS} frame, also sometimes called the outer or older frame is -the frame of the function which called the function of THIS frame. - -@end itemize - -So in the example in the previous section (@pxref{All About Stack -Frames, , All About Stack Frames}), if THIS frame is #3 (the call to -@code{fact@w{ }(3)}), the NEXT frame is frame #2 (the call to -@code{fact@w{ }(2)}) and the PREVIOUS frame is frame #4 (the call to -@code{main@w{ }()}). - -@cindex innermost frame -@cindex stack frame, definition of innermost frame -@cindex frame, definition of innermost frame -The @dfn{innermost} frame is the frame of the current executing -function, or where the program stopped, in this example, in the middle -of the call to @code{@w{fact (0))}}. It is always numbered frame #0. - -@cindex base of a frame -@cindex stack frame, definition of base of a frame -@cindex frame, definition of base of a frame -The @dfn{base} of a frame is the address immediately before the start -of the NEXT frame. For a stack which grows down in memory (a -@dfn{falling} stack) this will be the lowest address and for a stack -which grows up in memory (a @dfn{rising} stack) this will be the -highest address in the frame. - -@value{GDBN} functions to analyze the stack are typically given a -pointer to the NEXT frame to determine information about THIS -frame. Information about THIS frame includes data on where the -registers of the PREVIOUS frame are stored in this stack frame. In -this example the frame pointer of the PREVIOUS frame is stored at -offset 0 from the stack pointer of THIS frame. - -@cindex unwinding -@cindex stack frame, definition of unwinding -@cindex frame, definition of unwinding -The process whereby a function is given a pointer to the NEXT -frame to work out information about THIS frame is referred to as -@dfn{unwinding}. The @value{GDBN} functions involved in this typically -include unwind in their name. - -@cindex sniffing -@cindex stack frame, definition of sniffing -@cindex frame, definition of sniffing -The process of analyzing a target to determine the information that -should go in struct frame_info is called @dfn{sniffing}. The functions -that carry this out are called sniffers and typically include sniffer -in their name. More than one sniffer may be required to extract all -the information for a particular frame. - -@cindex sentinel frame -@cindex stack frame, definition of sentinel frame -@cindex frame, definition of sentinel frame -Because so many functions work using the NEXT frame, there is an issue -about addressing the innermost frame---it has no NEXT frame. To solve -this @value{GDBN} creates a dummy frame #-1, known as the -@dfn{sentinel} frame. - -@node Prologue Caches -@subsection Prologue Caches - -@cindex function prologue -@cindex prologue of a function -All the frame sniffing functions typically examine the code at the -start of the corresponding function, to determine the state of -registers. The ABI will save old values and set new values of key -registers at the start of each function in what is known as the -function @dfn{prologue}. - -@cindex prologue cache -For any particular stack frame this data does not change, so all the -standard unwinding functions, in addition to receiving a pointer to -the NEXT frame as their first argument, receive a pointer to a -@dfn{prologue cache} as their second argument. This can be used to store -values associated with a particular frame, for reuse on subsequent -calls involving the same frame. - -It is up to the user to define the structure used (it is a -@code{void@w{ }*} pointer) and arrange allocation and deallocation of -storage. However for general use, @value{GDBN} provides -@code{@w{struct trad_frame_cache}}, with a set of accessor -routines. This structure holds the stack and code address of -THIS frame, the base address of the frame, a pointer to the -struct @code{frame_info} for the NEXT frame and details of -where the registers of the PREVIOUS frame may be found in THIS -frame. - -Typically the first time any sniffer function is called with NEXT -frame, the prologue sniffer for THIS frame will be @code{NULL}. The -sniffer will analyze the frame, allocate a prologue cache structure -and populate it. Subsequent calls using the same NEXT frame will -pass in this prologue cache, so the data can be returned with no -additional analysis. - -@node Functions and Variable to Analyze Frames -@subsection Functions and Variable to Analyze Frames - -These struct @code{gdbarch} functions and variable should be defined -to provide analysis of the stack frame and allow it to be adjusted as -required. - -@deftypefn {Architecture Function} CORE_ADDR skip_prologue (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{pc}) - -The prologue of a function is the code at the beginning of the -function which sets up the stack frame, saves the return address -etc. The code representing the behavior of the function starts after -the prologue. - -This function skips past the prologue of a function if the program -counter, @var{pc}, is within the prologue of a function. The result is -the program counter immediately after the prologue. With modern -optimizing compilers, this may be a far from trivial exercise. However -the required information may be within the binary as DWARF2 debugging -information, making the job much easier. - -The default value is @code{NULL} (not defined). This function should always -be provided, but can take advantage of DWARF2 debugging information, -if that is available. - -@end deftypefn - -@deftypefn {Architecture Function} int inner_than (CORE_ADDR @var{lhs}, CORE_ADDR @var{rhs}) -@findex core_addr_lessthan -@findex core_addr_greaterthan - -Given two frame or stack pointers, return non-zero (true) if the first -represents the @dfn{inner} stack frame and 0 (false) otherwise. This -is used to determine whether the target has a stack which grows up in -memory (rising stack) or grows down in memory (falling stack). -@xref{All About Stack Frames, , All About Stack Frames}, for an -explanation of @dfn{inner} frames. - -The default value of this function is @code{NULL} and it should always -be defined. However for almost all architectures one of the built-in -functions can be used: @code{core_addr_lessthan} (for stacks growing -down in memory) or @code{core_addr_greaterthan} (for stacks growing up -in memory). - -@end deftypefn - -@anchor{frame_align} -@deftypefn {Architecture Function} CORE_ADDR frame_align (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{address}) -@findex align_down -@findex align_up - -The architecture may have constraints on how its frames are -aligned. For example the OpenRISC 1000 ABI requires stack frames to be -double-word aligned, but 32-bit versions of the architecture allocate -single-word values to the stack. Thus extra padding may be needed at -the end of a stack frame. - -Given a proposed address for the stack pointer, this function -returns a suitably aligned address (by expanding the stack frame). - -The default value is @code{NULL} (undefined). This function should be defined -for any architecture where it is possible the stack could become -misaligned. The utility functions @code{align_down} (for falling -stacks) and @code{align_up} (for rising stacks) will facilitate the -implementation of this function. - -@end deftypefn - -@deftypevr {Architecture Variable} int frame_red_zone_size - -Some ABIs reserve space beyond the end of the stack for use by leaf -functions without prologue or epilogue or by exception handlers (for -example the OpenRISC 1000). - -This is known as a @dfn{red zone} (AMD terminology). The @sc{amd64} -(nee x86-64) ABI documentation refers to the @dfn{red zone} when -describing this scratch area. - -The default value is 0. Set this field if the architecture has such a -red zone. The value must be aligned as required by the ABI (see -@code{frame_align} above for an explanation of stack frame alignment). - -@end deftypevr - -@node Functions to Access Frame Data -@subsection Functions to Access Frame Data - -These functions provide access to key registers and arguments in the -stack frame. - -@deftypefn {Architecture Function} CORE_ADDR unwind_pc (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame}) - -This function is given a pointer to the NEXT stack frame (@pxref{All -About Stack Frames, , All About Stack Frames}, for how frames are -represented) and returns the value of the program counter in the -PREVIOUS frame (i.e.@: the frame of the function that called THIS -one). This is commonly referred to as the @dfn{return address}. - -The implementation, which must be frame agnostic (work with any frame), -is typically no more than: - -@smallexample -ULONGEST pc; -pc = frame_unwind_register_unsigned (next_frame, @var{ARCH}_PC_REGNUM); -return gdbarch_addr_bits_remove (gdbarch, pc); -@end smallexample - -@end deftypefn - -@deftypefn {Architecture Function} CORE_ADDR unwind_sp (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame}) - -This function is given a pointer to the NEXT stack frame -(@pxref{All About Stack Frames, , All About Stack Frames} for how -frames are represented) and returns the value of the stack pointer in -the PREVIOUS frame (i.e.@: the frame of the function that called -THIS one). - -The implementation, which must be frame agnostic (work with any frame), -is typically no more than: - -@smallexample -ULONGEST sp; -sp = frame_unwind_register_unsigned (next_frame, @var{ARCH}_SP_REGNUM); -return gdbarch_addr_bits_remove (gdbarch, sp); -@end smallexample - -@end deftypefn - -@deftypefn {Architecture Function} int frame_num_args (struct gdbarch *@var{gdbarch}, struct frame_info *@var{this_frame}) - -This function is given a pointer to THIS stack frame (@pxref{All -About Stack Frames, , All About Stack Frames} for how frames are -represented), and returns the number of arguments that are being -passed, or -1 if not known. - -The default value is @code{NULL} (undefined), in which case the number of -arguments passed on any stack frame is always unknown. For many -architectures this will be a suitable default. - -@end deftypefn - -@node Analyzing Stacks---Frame Sniffers -@subsection Analyzing Stacks---Frame Sniffers - -When a program stops, @value{GDBN} needs to construct the chain of -struct @code{frame_info} representing the state of the stack using -appropriate @dfn{sniffers}. - -Each architecture requires appropriate sniffers, but they do not form -entries in @code{@w{struct gdbarch}}, since more than one sniffer may -be required and a sniffer may be suitable for more than one -@code{@w{struct gdbarch}}. Instead sniffers are associated with -architectures using the following functions. - -@itemize @bullet - -@item -@findex frame_unwind_append_sniffer -@code{frame_unwind_append_sniffer} is used to add a new sniffer to -analyze THIS frame when given a pointer to the NEXT frame. - -@item -@findex frame_base_append_sniffer -@code{frame_base_append_sniffer} is used to add a new sniffer -which can determine information about the base of a stack frame. - -@item -@findex frame_base_set_default -@code{frame_base_set_default} is used to specify the default base -sniffer. - -@end itemize - -These functions all take a reference to @code{@w{struct gdbarch}}, so -they are associated with a specific architecture. They are usually -called in the @code{gdbarch} initialization function, after the -@code{gdbarch} struct has been set up. Unless a default has been set, the -most recently appended sniffer will be tried first. - -The main frame unwinding sniffer (as set by -@code{frame_unwind_append_sniffer)} returns a structure specifying -a set of sniffing functions: - -@cindex @code{frame_unwind} -@smallexample -struct frame_unwind -@{ - enum frame_type type; - frame_this_id_ftype *this_id; - frame_prev_register_ftype *prev_register; - const struct frame_data *unwind_data; - frame_sniffer_ftype *sniffer; - frame_prev_pc_ftype *prev_pc; - frame_dealloc_cache_ftype *dealloc_cache; -@}; -@end smallexample - -The @code{type} field indicates the type of frame this sniffer can -handle: normal, dummy (@pxref{Functions Creating Dummy Frames, , -Functions Creating Dummy Frames}), signal handler or sentinel. Signal -handlers sometimes have their own simplified stack structure for -efficiency, so may need their own handlers. - -The @code{unwind_data} field holds additional information which may be -relevant to particular types of frame. For example it may hold -additional information for signal handler frames. - -The remaining fields define functions that yield different types of -information when given a pointer to the NEXT stack frame. Not all -functions need be provided. If an entry is @code{NULL}, the next sniffer will -be tried instead. - -@itemize @bullet - -@item -@code{this_id} determines the stack pointer and function (code -entry point) for THIS stack frame. - -@item -@code{prev_register} determines where the values of registers for -the PREVIOUS stack frame are stored in THIS stack frame. - -@item -@code{sniffer} takes a look at THIS frame's registers to -determine if this is the appropriate unwinder. - -@item -@code{prev_pc} determines the program counter for THIS -frame. Only needed if the program counter is not an ordinary register -(@pxref{Register Architecture Functions & Variables, -, Functions and Variables Specifying the Register Architecture}). - -@item -@code{dealloc_cache} frees any additional memory associated with -the prologue cache for this frame (@pxref{Prologue Caches, , Prologue -Caches}). - -@end itemize - -In general it is only the @code{this_id} and @code{prev_register} -fields that need be defined for custom sniffers. - -The frame base sniffer is much simpler. It is a @code{@w{struct -frame_base}}, which refers to the corresponding @code{frame_unwind} -struct and whose fields refer to functions yielding various addresses -within the frame. - -@cindex @code{frame_base} -@smallexample -struct frame_base -@{ - const struct frame_unwind *unwind; - frame_this_base_ftype *this_base; - frame_this_locals_ftype *this_locals; - frame_this_args_ftype *this_args; -@}; -@end smallexample - -All the functions referred to take a pointer to the NEXT frame as -argument. The function referred to by @code{this_base} returns the -base address of THIS frame, the function referred to by -@code{this_locals} returns the base address of local variables in THIS -frame and the function referred to by @code{this_args} returns the -base address of the function arguments in this frame. - -As described above, the base address of a frame is the address -immediately before the start of the NEXT frame. For a falling -stack, this is the lowest address in the frame and for a rising stack -it is the highest address in the frame. For most architectures the -same address is also the base address for local variables and -arguments, in which case the same function can be used for all three -entries@footnote{It is worth noting that if it cannot be determined in any -other way (for example by there being a register with the name -@code{"fp"}), then the result of the @code{this_base} function will be -used as the value of the frame pointer variable @kbd{$fp} in -@value{GDBN}. This is very often not correct (for example with the -OpenRISC 1000, this value is the stack pointer, @kbd{$sp}). In this -case a register (raw or pseudo) with the name @code{"fp"} should be -defined. It will be used in preference as the value of @kbd{$fp}.}. - -@node Inferior Call Setup -@section Inferior Call Setup -@cindex calls to the inferior - -@menu -* About Dummy Frames:: -* Functions Creating Dummy Frames:: -@end menu - -@node About Dummy Frames -@subsection About Dummy Frames -@cindex dummy frames - -@value{GDBN} can call functions in the target code (for example by -using the @kbd{call} or @kbd{print} commands). These functions may be -breakpointed, and it is essential that if a function does hit a -breakpoint, commands like @kbd{backtrace} work correctly. - -This is achieved by making the stack look as though the function had -been called from the point where @value{GDBN} had previously stopped. -This requires that @value{GDBN} can set up stack frames appropriate for -such function calls. - -@node Functions Creating Dummy Frames -@subsection Functions Creating Dummy Frames - -The following functions provide the functionality to set up such -@dfn{dummy} stack frames. - -@deftypefn {Architecture Function} CORE_ADDR push_dummy_call (struct gdbarch *@var{gdbarch}, struct value *@var{function}, struct regcache *@var{regcache}, CORE_ADDR @var{bp_addr}, int @var{nargs}, struct value **@var{args}, CORE_ADDR @var{sp}, int @var{struct_return}, CORE_ADDR @var{struct_addr}) - -This function sets up a dummy stack frame for the function about to be -called. @code{push_dummy_call} is given the arguments to be passed -and must copy them into registers or push them on to the stack as -appropriate for the ABI. - -@var{function} is a pointer to the function -that will be called and @var{regcache} the register cache from which -values should be obtained. @var{bp_addr} is the address to which the -function should return (which is breakpointed, so @value{GDBN} can -regain control, hence the name). @var{nargs} is the number of -arguments to pass and @var{args} an array containing the argument -values. @var{struct_return} is non-zero (true) if the function returns -a structure, and if so @var{struct_addr} is the address in which the -structure should be returned. - - After calling this function, @value{GDBN} will pass control to the -target at the address of the function, which will find the stack and -registers set up just as expected. - -The default value of this function is @code{NULL} (undefined). If the -function is not defined, then @value{GDBN} will not allow the user to -call functions within the target being debugged. - -@end deftypefn - -@deftypefn {Architecture Function} {struct frame_id} unwind_dummy_id (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame}) - -This is the inverse of @code{push_dummy_call} which restores the stack -pointer and program counter after a call to evaluate a function using -a dummy stack frame. The result is a @code{@w{struct frame_id}}, which -contains the value of the stack pointer and program counter to be -used. - -The NEXT frame pointer is provided as argument, -@var{next_frame}. THIS frame is the frame of the dummy function, -which can be unwound, to yield the required stack pointer and program -counter from the PREVIOUS frame. - -The default value is @code{NULL} (undefined). If @code{push_dummy_call} is -defined, then this function should also be defined. - -@end deftypefn - -@deftypefn {Architecture Function} CORE_ADDR push_dummy_code (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{sp}, CORE_ADDR @var{funaddr}, struct value **@var{args}, int @var{nargs}, struct type *@var{value_type}, CORE_ADDR *@var{real_pc}, CORE_ADDR *@var{bp_addr}, struct regcache *@var{regcache}) - -If this function is not defined (its default value is @code{NULL}), a dummy -call will use the entry point of the currently loaded code on the -target as its return address. A temporary breakpoint will be set -there, so the location must be writable and have room for a -breakpoint. - -It is possible that this default is not suitable. It might not be -writable (in ROM possibly), or the ABI might require code to be -executed on return from a call to unwind the stack before the -breakpoint is encountered. - -If either of these is the case, then push_dummy_code should be defined -to push an instruction sequence onto the end of the stack to which the -dummy call should return. - -The arguments are essentially the same as those to -@code{push_dummy_call}. However the function is provided with the -type of the function result, @var{value_type}, @var{bp_addr} is used -to return a value (the address at which the breakpoint instruction -should be inserted) and @var{real pc} is used to specify the resume -address when starting the call sequence. The function should return -the updated innermost stack address. - -@quotation -@emph{Note:} This does require that code in the stack can be executed. -Some Harvard architectures may not allow this. -@end quotation - -@end deftypefn - -@node Adding support for debugging core files -@section Adding support for debugging core files -@cindex core files - -The prerequisite for adding core file support in @value{GDBN} is to have -core file support in BFD. - -Once BFD support is available, writing the apropriate -@code{regset_from_core_section} architecture function should be all -that is needed in order to add support for core files in @value{GDBN}. - -@node Defining Other Architecture Features -@section Defining Other Architecture Features - -This section describes other functions and values in @code{gdbarch}, -together with some useful macros, that you can use to define the -target architecture. - -@table @code - -@item CORE_ADDR gdbarch_addr_bits_remove (@var{gdbarch}, @var{addr}) -@findex gdbarch_addr_bits_remove -If a raw machine instruction address includes any bits that are not -really part of the address, then this function is used to zero those bits in -@var{addr}. This is only used for addresses of instructions, and even then not -in all contexts. - -For example, the two low-order bits of the PC on the Hewlett-Packard PA -2.0 architecture contain the privilege level of the corresponding -instruction. Since instructions must always be aligned on four-byte -boundaries, the processor masks out these bits to generate the actual -address of the instruction. @code{gdbarch_addr_bits_remove} would then for -example look like that: -@smallexample -arch_addr_bits_remove (CORE_ADDR addr) -@{ - return (addr &= ~0x3); -@} -@end smallexample - -@item int address_class_name_to_type_flags (@var{gdbarch}, @var{name}, @var{type_flags_ptr}) -@findex address_class_name_to_type_flags -If @var{name} is a valid address class qualifier name, set the @code{int} -referenced by @var{type_flags_ptr} to the mask representing the qualifier -and return 1. If @var{name} is not a valid address class qualifier name, -return 0. - -The value for @var{type_flags_ptr} should be one of -@code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or -possibly some combination of these values or'd together. -@xref{Target Architecture Definition, , Address Classes}. - -@item int address_class_name_to_type_flags_p (@var{gdbarch}) -@findex address_class_name_to_type_flags_p -Predicate which indicates whether @code{address_class_name_to_type_flags} -has been defined. - -@item int gdbarch_address_class_type_flags (@var{gdbarch}, @var{byte_size}, @var{dwarf2_addr_class}) -@findex gdbarch_address_class_type_flags -Given a pointers byte size (as described by the debug information) and -the possible @code{DW_AT_address_class} value, return the type flags -used by @value{GDBN} to represent this address class. The value -returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1}, -@code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these -values or'd together. -@xref{Target Architecture Definition, , Address Classes}. - -@item int gdbarch_address_class_type_flags_p (@var{gdbarch}) -@findex gdbarch_address_class_type_flags_p -Predicate which indicates whether @code{gdbarch_address_class_type_flags_p} has -been defined. - -@item const char *gdbarch_address_class_type_flags_to_name (@var{gdbarch}, @var{type_flags}) -@findex gdbarch_address_class_type_flags_to_name -Return the name of the address class qualifier associated with the type -flags given by @var{type_flags}. - -@item int gdbarch_address_class_type_flags_to_name_p (@var{gdbarch}) -@findex gdbarch_address_class_type_flags_to_name_p -Predicate which indicates whether @code{gdbarch_address_class_type_flags_to_name} has been defined. -@xref{Target Architecture Definition, , Address Classes}. - -@item void gdbarch_address_to_pointer (@var{gdbarch}, @var{type}, @var{buf}, @var{addr}) -@findex gdbarch_address_to_pointer -Store in @var{buf} a pointer of type @var{type} representing the address -@var{addr}, in the appropriate format for the current architecture. -This function may safely assume that @var{type} is either a pointer or a -C@t{++} reference type. -@xref{Target Architecture Definition, , Pointers Are Not Always Addresses}. - -@item int gdbarch_believe_pcc_promotion (@var{gdbarch}) -@findex gdbarch_believe_pcc_promotion -Used to notify if the compiler promotes a @code{short} or @code{char} -parameter to an @code{int}, but still reports the parameter as its -original type, rather than the promoted type. - -@item gdbarch_bits_big_endian (@var{gdbarch}) -@findex gdbarch_bits_big_endian -This is used if the numbering of bits in the targets does @strong{not} match -the endianism of the target byte order. A value of 1 means that the bits -are numbered in a big-endian bit order, 0 means little-endian. - -@item set_gdbarch_bits_big_endian (@var{gdbarch}, @var{bits_big_endian}) -@findex set_gdbarch_bits_big_endian -Calling set_gdbarch_bits_big_endian with a value of 1 indicates that the -bits in the target are numbered in a big-endian bit order, 0 indicates -little-endian. - -@item BREAKPOINT -@findex BREAKPOINT -This is the character array initializer for the bit pattern to put into -memory where a breakpoint is set. Although it's common to use a trap -instruction for a breakpoint, it's not required; for instance, the bit -pattern could be an invalid instruction. The breakpoint must be no -longer than the shortest instruction of the architecture. - -@code{BREAKPOINT} has been deprecated in favor of -@code{gdbarch_breakpoint_from_pc}. - -@item BIG_BREAKPOINT -@itemx LITTLE_BREAKPOINT -@findex LITTLE_BREAKPOINT -@findex BIG_BREAKPOINT -Similar to BREAKPOINT, but used for bi-endian targets. - -@code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in -favor of @code{gdbarch_breakpoint_from_pc}. - -@item const gdb_byte *gdbarch_breakpoint_from_pc (@var{gdbarch}, @var{pcptr}, @var{lenptr}) -@findex gdbarch_breakpoint_from_pc -@anchor{gdbarch_breakpoint_from_pc} Use the program counter to determine the -contents and size of a breakpoint instruction. It returns a pointer to -a static string of bytes that encode a breakpoint instruction, stores the -length of the string to @code{*@var{lenptr}}, and adjusts the program -counter (if necessary) to point to the actual memory location where the -breakpoint should be inserted. On input, the program counter -(@code{*@var{pcptr}} is the encoded inferior's PC register. If software -breakpoints are supported, the function sets this argument to the PC's -plain address. If software breakpoints are not supported, the function -returns NULL instead of the encoded breakpoint instruction. - -Although it is common to use a trap instruction for a breakpoint, it's -not required; for instance, the bit pattern could be an invalid -instruction. The breakpoint must be no longer than the shortest -instruction of the architecture. - -Provided breakpoint bytes can be also used by @code{bp_loc_is_permanent} to -detect permanent breakpoints. @code{gdbarch_breakpoint_from_pc} should return -an unchanged memory copy if it was called for a location with permanent -breakpoint as some architectures use breakpoint instructions containing -arbitrary parameter value. - -Replaces all the other @var{BREAKPOINT} macros. - -@item int gdbarch_memory_insert_breakpoint (@var{gdbarch}, @var{bp_tgt}) -@itemx gdbarch_memory_remove_breakpoint (@var{gdbarch}, @var{bp_tgt}) -@findex gdbarch_memory_remove_breakpoint -@findex gdbarch_memory_insert_breakpoint -Insert or remove memory based breakpoints. Reasonable defaults -(@code{default_memory_insert_breakpoint} and -@code{default_memory_remove_breakpoint} respectively) have been -provided so that it is not necessary to set these for most -architectures. Architectures which may want to set -@code{gdbarch_memory_insert_breakpoint} and @code{gdbarch_memory_remove_breakpoint} will likely have instructions that are oddly sized or are not stored in a -conventional manner. - -It may also be desirable (from an efficiency standpoint) to define -custom breakpoint insertion and removal routines if -@code{gdbarch_breakpoint_from_pc} needs to read the target's memory for some -reason. - -@item CORE_ADDR gdbarch_adjust_breakpoint_address (@var{gdbarch}, @var{bpaddr}) -@findex gdbarch_adjust_breakpoint_address -@cindex breakpoint address adjusted -Given an address at which a breakpoint is desired, return a breakpoint -address adjusted to account for architectural constraints on -breakpoint placement. This method is not needed by most targets. - -The FR-V target (see @file{frv-tdep.c}) requires this method. -The FR-V is a VLIW architecture in which a number of RISC-like -instructions are grouped (packed) together into an aggregate -instruction or instruction bundle. When the processor executes -one of these bundles, the component instructions are executed -in parallel. - -In the course of optimization, the compiler may group instructions -from distinct source statements into the same bundle. The line number -information associated with one of the latter statements will likely -refer to some instruction other than the first one in the bundle. So, -if the user attempts to place a breakpoint on one of these latter -statements, @value{GDBN} must be careful to @emph{not} place the break -instruction on any instruction other than the first one in the bundle. -(Remember though that the instructions within a bundle execute -in parallel, so the @emph{first} instruction is the instruction -at the lowest address and has nothing to do with execution order.) - -The FR-V's @code{gdbarch_adjust_breakpoint_address} method will adjust a -breakpoint's address by scanning backwards for the beginning of -the bundle, returning the address of the bundle. - -Since the adjustment of a breakpoint may significantly alter a user's -expectation, @value{GDBN} prints a warning when an adjusted breakpoint -is initially set and each time that that breakpoint is hit. - -@item int gdbarch_call_dummy_location (@var{gdbarch}) -@findex gdbarch_call_dummy_location -See the file @file{inferior.h}. - -This method has been replaced by @code{gdbarch_push_dummy_code} -(@pxref{gdbarch_push_dummy_code}). - -@item int gdbarch_cannot_fetch_register (@var{gdbarch}, @var{regum}) -@findex gdbarch_cannot_fetch_register -This function should return nonzero if @var{regno} cannot be fetched -from an inferior process. - -@item int gdbarch_cannot_store_register (@var{gdbarch}, @var{regnum}) -@findex gdbarch_cannot_store_register -This function should return nonzero if @var{regno} should not be -written to the target. This is often the case for program counters, -status words, and other special registers. This function returns 0 as -default so that @value{GDBN} will assume that all registers may be written. - -@item int gdbarch_convert_register_p (@var{gdbarch}, @var{regnum}, struct type *@var{type}) -@findex gdbarch_convert_register_p -Return non-zero if register @var{regnum} represents data values of type -@var{type} in a non-standard form. -@xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}. - -@item int gdbarch_fp0_regnum (@var{gdbarch}) -@findex gdbarch_fp0_regnum -This function returns the number of the first floating point register, -if the machine has such registers. Otherwise, it returns -1. - -@item CORE_ADDR gdbarch_decr_pc_after_break (@var{gdbarch}) -@findex gdbarch_decr_pc_after_break -This function shall return the amount by which to decrement the PC after the -program encounters a breakpoint. This is often the number of bytes in -@code{BREAKPOINT}, though not always. For most targets this value will be 0. - -@item DISABLE_UNSETTABLE_BREAK (@var{addr}) -@findex DISABLE_UNSETTABLE_BREAK -If defined, this should evaluate to 1 if @var{addr} is in a shared -library in which breakpoints cannot be set and so should be disabled. - -@item int gdbarch_dwarf2_reg_to_regnum (@var{gdbarch}, @var{dwarf2_regnr}) -@findex gdbarch_dwarf2_reg_to_regnum -Convert DWARF2 register number @var{dwarf2_regnr} into @value{GDBN} regnum. -If not defined, no conversion will be performed. - -@item int gdbarch_ecoff_reg_to_regnum (@var{gdbarch}, @var{ecoff_regnr}) -@findex gdbarch_ecoff_reg_to_regnum -Convert ECOFF register number @var{ecoff_regnr} into @value{GDBN} regnum. If -not defined, no conversion will be performed. - -@item GCC_COMPILED_FLAG_SYMBOL -@itemx GCC2_COMPILED_FLAG_SYMBOL -@findex GCC2_COMPILED_FLAG_SYMBOL -@findex GCC_COMPILED_FLAG_SYMBOL -If defined, these are the names of the symbols that @value{GDBN} will -look for to detect that GCC compiled the file. The default symbols -are @code{gcc_compiled.} and @code{gcc2_compiled.}, -respectively. (Currently only defined for the Delta 68.) - -@item gdbarch_get_longjmp_target -@findex gdbarch_get_longjmp_target -This function determines the target PC address that @code{longjmp} -will jump to, assuming that we have just stopped at a @code{longjmp} -breakpoint. It takes a @code{CORE_ADDR *} as argument, and stores the -target PC value through this pointer. It examines the current state -of the machine as needed, typically by using a manually-determined -offset into the @code{jmp_buf}. (While we might like to get the offset -from the target's @file{jmpbuf.h}, that header file cannot be assumed -to be available when building a cross-debugger.) - -@item DEPRECATED_IBM6000_TARGET -@findex DEPRECATED_IBM6000_TARGET -Shows that we are configured for an IBM RS/6000 system. This -conditional should be eliminated (FIXME) and replaced by -feature-specific macros. It was introduced in haste and we are -repenting at leisure. - -@item I386_USE_GENERIC_WATCHPOINTS -An x86-based target can define this to use the generic x86 watchpoint -support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}. - -@item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{addr}) -@findex gdbarch_in_function_epilogue_p -Returns non-zero if the given @var{addr} is in the epilogue of a function. -The epilogue of a function is defined as the part of a function where -the stack frame of the function already has been destroyed up to the -final `return from function call' instruction. - -@item int gdbarch_in_solib_return_trampoline (@var{gdbarch}, @var{pc}, @var{name}) -@findex gdbarch_in_solib_return_trampoline -Define this function to return nonzero if the program is stopped in the -trampoline that returns from a shared library. - -@item target_so_ops.in_dynsym_resolve_code (@var{pc}) -@findex in_dynsym_resolve_code -Define this to return nonzero if the program is stopped in the -dynamic linker. - -@item SKIP_SOLIB_RESOLVER (@var{pc}) -@findex SKIP_SOLIB_RESOLVER -Define this to evaluate to the (nonzero) address at which execution -should continue to get past the dynamic linker's symbol resolution -function. A zero value indicates that it is not important or necessary -to set a breakpoint to get through the dynamic linker and that single -stepping will suffice. - -@item CORE_ADDR gdbarch_integer_to_address (@var{gdbarch}, @var{type}, @var{buf}) -@findex gdbarch_integer_to_address -@cindex converting integers to addresses -Define this when the architecture needs to handle non-pointer to address -conversions specially. Converts that value to an address according to -the current architectures conventions. - -@emph{Pragmatics: When the user copies a well defined expression from -their source code and passes it, as a parameter, to @value{GDBN}'s -@code{print} command, they should get the same value as would have been -computed by the target program. Any deviation from this rule can cause -major confusion and annoyance, and needs to be justified carefully. In -other words, @value{GDBN} doesn't really have the freedom to do these -conversions in clever and useful ways. It has, however, been pointed -out that users aren't complaining about how @value{GDBN} casts integers -to pointers; they are complaining that they can't take an address from a -disassembly listing and give it to @code{x/i}. Adding an architecture -method like @code{gdbarch_integer_to_address} certainly makes it possible for -@value{GDBN} to ``get it right'' in all circumstances.} - -@xref{Target Architecture Definition, , Pointers Are Not Always -Addresses}. - -@item CORE_ADDR gdbarch_pointer_to_address (@var{gdbarch}, @var{type}, @var{buf}) -@findex gdbarch_pointer_to_address -Assume that @var{buf} holds a pointer of type @var{type}, in the -appropriate format for the current architecture. Return the byte -address the pointer refers to. -@xref{Target Architecture Definition, , Pointers Are Not Always Addresses}. - -@item void gdbarch_register_to_value(@var{gdbarch}, @var{frame}, @var{regnum}, @var{type}, @var{fur}) -@findex gdbarch_register_to_value -Convert the raw contents of register @var{regnum} into a value of type -@var{type}. -@xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}. - -@item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to}) -@findex REGISTER_CONVERT_TO_VIRTUAL -Convert the value of register @var{reg} from its raw form to its virtual -form. -@xref{Target Architecture Definition, , Raw and Virtual Register Representations}. - -@item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to}) -@findex REGISTER_CONVERT_TO_RAW -Convert the value of register @var{reg} from its virtual form to its raw -form. -@xref{Target Architecture Definition, , Raw and Virtual Register Representations}. - -@item const struct regset *regset_from_core_section (struct gdbarch * @var{gdbarch}, const char * @var{sect_name}, size_t @var{sect_size}) -@findex regset_from_core_section -Return the appropriate register set for a core file section with name -@var{sect_name} and size @var{sect_size}. - -@item SOFTWARE_SINGLE_STEP_P() -@findex SOFTWARE_SINGLE_STEP_P -Define this as 1 if the target does not have a hardware single-step -mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined. - -@item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breakpoints_p}) -@findex SOFTWARE_SINGLE_STEP -A function that inserts or removes (depending on -@var{insert_breakpoints_p}) breakpoints at each possible destinations of -the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c} -for examples. - -@item set_gdbarch_sofun_address_maybe_missing (@var{gdbarch}, @var{set}) -@findex set_gdbarch_sofun_address_maybe_missing -Somebody clever observed that, the more actual addresses you have in the -debug information, the more time the linker has to spend relocating -them. So whenever there's some other way the debugger could find the -address it needs, you should omit it from the debug info, to make -linking faster. - -Calling @code{set_gdbarch_sofun_address_maybe_missing} with a non-zero -argument @var{set} indicates that a particular set of hacks of this sort -are in use, affecting @code{N_SO} and @code{N_FUN} entries in stabs-format -debugging information. @code{N_SO} stabs mark the beginning and ending -addresses of compilation units in the text segment. @code{N_FUN} stabs -mark the starts and ends of functions. - -In this case, @value{GDBN} assumes two things: - -@itemize @bullet -@item -@code{N_FUN} stabs have an address of zero. Instead of using those -addresses, you should find the address where the function starts by -taking the function name from the stab, and then looking that up in the -minsyms (the linker/assembler symbol table). In other words, the stab -has the name, and the linker/assembler symbol table is the only place -that carries the address. - -@item -@code{N_SO} stabs have an address of zero, too. You just look at the -@code{N_FUN} stabs that appear before and after the @code{N_SO} stab, and -guess the starting and ending addresses of the compilation unit from them. -@end itemize - -@item int gdbarch_stabs_argument_has_addr (@var{gdbarch}, @var{type}) -@findex gdbarch_stabs_argument_has_addr -@anchor{gdbarch_stabs_argument_has_addr} Define this function to return -nonzero if a function argument of type @var{type} is passed by reference -instead of value. - -@item CORE_ADDR gdbarch_push_dummy_call (@var{gdbarch}, @var{function}, @var{regcache}, @var{bp_addr}, @var{nargs}, @var{args}, @var{sp}, @var{struct_return}, @var{struct_addr}) -@findex gdbarch_push_dummy_call -@anchor{gdbarch_push_dummy_call} Define this to push the dummy frame's call to -the inferior function onto the stack. In addition to pushing @var{nargs}, the -code should push @var{struct_addr} (when @var{struct_return} is non-zero), and -the return address (@var{bp_addr}, in inferior's PC register encoding). - -@var{function} is a pointer to a @code{struct value}; on architectures that use -function descriptors, this contains the function descriptor value. - -Returns the updated top-of-stack pointer. - -@item CORE_ADDR gdbarch_push_dummy_code (@var{gdbarch}, @var{sp}, @var{funaddr}, @var{using_gcc}, @var{args}, @var{nargs}, @var{value_type}, @var{real_pc}, @var{bp_addr}, @var{regcache}) -@findex gdbarch_push_dummy_code -@anchor{gdbarch_push_dummy_code} Given a stack based call dummy, push the -instruction sequence (including space for a breakpoint) to which the -called function should return. - -Set @var{bp_addr} to the address at which the breakpoint instruction -should be inserted (in inferior's PC register encoding), @var{real_pc} to the -resume address when starting the call sequence, and return the updated -inner-most stack address. - -By default, the stack is grown sufficient to hold a frame-aligned -(@pxref{frame_align}) breakpoint, @var{bp_addr} is set to the address -reserved for that breakpoint (in inferior's PC register encoding), and -@var{real_pc} set to @var{funaddr}. - -This method replaces @w{@code{gdbarch_call_dummy_location (@var{gdbarch})}}. - -@item int gdbarch_sdb_reg_to_regnum (@var{gdbarch}, @var{sdb_regnr}) -@findex gdbarch_sdb_reg_to_regnum -Use this function to convert sdb register @var{sdb_regnr} into @value{GDBN} -regnum. If not defined, no conversion will be done. - -@item enum return_value_convention gdbarch_return_value (struct gdbarch *@var{gdbarch}, struct type *@var{valtype}, struct regcache *@var{regcache}, void *@var{readbuf}, const void *@var{writebuf}) -@findex gdbarch_return_value -@anchor{gdbarch_return_value} Given a function with a return-value of -type @var{rettype}, return which return-value convention that function -would use. - -@value{GDBN} currently recognizes two function return-value conventions: -@code{RETURN_VALUE_REGISTER_CONVENTION} where the return value is found -in registers; and @code{RETURN_VALUE_STRUCT_CONVENTION} where the return -value is found in memory and the address of that memory location is -passed in as the function's first parameter. - -If the register convention is being used, and @var{writebuf} is -non-@code{NULL}, also copy the return-value in @var{writebuf} into -@var{regcache}. - -If the register convention is being used, and @var{readbuf} is -non-@code{NULL}, also copy the return value from @var{regcache} into -@var{readbuf} (@var{regcache} contains a copy of the registers from the -just returned function). - -@emph{Maintainer note: This method replaces separate predicate, extract, -store methods. By having only one method, the logic needed to determine -the return-value convention need only be implemented in one place. If -@value{GDBN} were written in an @sc{oo} language, this method would -instead return an object that knew how to perform the register -return-value extract and store.} - -@emph{Maintainer note: This method does not take a @var{gcc_p} -parameter, and such a parameter should not be added. If an architecture -that requires per-compiler or per-function information be identified, -then the replacement of @var{rettype} with @code{struct value} -@var{function} should be pursued.} - -@emph{Maintainer note: The @var{regcache} parameter limits this methods -to the inner most frame. While replacing @var{regcache} with a -@code{struct frame_info} @var{frame} parameter would remove that -limitation there has yet to be a demonstrated need for such a change.} - -@item void gdbarch_skip_permanent_breakpoint (@var{gdbarch}, @var{regcache}) -@findex gdbarch_skip_permanent_breakpoint -Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally -steps over a breakpoint by removing it, stepping one instruction, and -re-inserting the breakpoint. However, permanent breakpoints are -hardwired into the inferior, and can't be removed, so this strategy -doesn't work. Calling @code{gdbarch_skip_permanent_breakpoint} adjusts the -processor's state so that execution will resume just after the breakpoint. -This function does the right thing even when the breakpoint is in the delay slot -of a branch or jump. - -@item CORE_ADDR gdbarch_skip_trampoline_code (@var{gdbarch}, @var{frame}, @var{pc}) -@findex gdbarch_skip_trampoline_code -If the target machine has trampoline code that sits between callers and -the functions being called, then define this function to return a new PC -that is at the start of the real function. - -@item int gdbarch_deprecated_fp_regnum (@var{gdbarch}) -@findex gdbarch_deprecated_fp_regnum -If the frame pointer is in a register, use this function to return the -number of that register. - -@item int gdbarch_stab_reg_to_regnum (@var{gdbarch}, @var{stab_regnr}) -@findex gdbarch_stab_reg_to_regnum -Use this function to convert stab register @var{stab_regnr} into @value{GDBN} -regnum. If not defined, no conversion will be done. - -@item TARGET_CHAR_BIT -@findex TARGET_CHAR_BIT -Number of bits in a char; defaults to 8. - -@item int gdbarch_char_signed (@var{gdbarch}) -@findex gdbarch_char_signed -Non-zero if @code{char} is normally signed on this architecture; zero if -it should be unsigned. - -The ISO C standard requires the compiler to treat @code{char} as -equivalent to either @code{signed char} or @code{unsigned char}; any -character in the standard execution set is supposed to be positive. -Most compilers treat @code{char} as signed, but @code{char} is unsigned -on the IBM S/390, RS6000, and PowerPC targets. - -@item int gdbarch_double_bit (@var{gdbarch}) -@findex gdbarch_double_bit -Number of bits in a double float; defaults to @w{@code{8 * TARGET_CHAR_BIT}}. - -@item int gdbarch_float_bit (@var{gdbarch}) -@findex gdbarch_float_bit -Number of bits in a float; defaults to @w{@code{4 * TARGET_CHAR_BIT}}. - -@item int gdbarch_int_bit (@var{gdbarch}) -@findex gdbarch_int_bit -Number of bits in an integer; defaults to @w{@code{4 * TARGET_CHAR_BIT}}. - -@item int gdbarch_long_bit (@var{gdbarch}) -@findex gdbarch_long_bit -Number of bits in a long integer; defaults to @w{@code{4 * TARGET_CHAR_BIT}}. - -@item int gdbarch_long_double_bit (@var{gdbarch}) -@findex gdbarch_long_double_bit -Number of bits in a long double float; -defaults to @w{@code{2 * gdbarch_double_bit (@var{gdbarch})}}. - -@item int gdbarch_long_long_bit (@var{gdbarch}) -@findex gdbarch_long_long_bit -Number of bits in a long long integer; defaults to -@w{@code{2 * gdbarch_long_bit (@var{gdbarch})}}. - -@item int gdbarch_ptr_bit (@var{gdbarch}) -@findex gdbarch_ptr_bit -Number of bits in a pointer; defaults to -@w{@code{gdbarch_int_bit (@var{gdbarch})}}. - -@item int gdbarch_short_bit (@var{gdbarch}) -@findex gdbarch_short_bit -Number of bits in a short integer; defaults to @w{@code{2 * TARGET_CHAR_BIT}}. - -@item void gdbarch_virtual_frame_pointer (@var{gdbarch}, @var{pc}, @var{frame_regnum}, @var{frame_offset}) -@findex gdbarch_virtual_frame_pointer -Returns a @code{(@var{register}, @var{offset})} pair representing the virtual -frame pointer in use at the code address @var{pc}. If virtual frame -pointers are not used, a default definition simply returns -@code{gdbarch_deprecated_fp_regnum} (or @code{gdbarch_sp_regnum}, if -no frame pointer is defined), with an offset of zero. - -@c need to explain virtual frame pointers, they are recorded in agent -@c expressions for tracepoints - -@item TARGET_HAS_HARDWARE_WATCHPOINTS -If non-zero, the target has support for hardware-assisted -watchpoints. @xref{Algorithms, watchpoints}, for more details and -other related macros. - -@item int gdbarch_print_insn (@var{gdbarch}, @var{vma}, @var{info}) -@findex gdbarch_print_insn -This is the function used by @value{GDBN} to print an assembly -instruction. It prints the instruction at address @var{vma} in -debugged memory and returns the length of the instruction, in bytes. -This usually points to a function in the @code{opcodes} library -(@pxref{Support Libraries, ,Opcodes}). @var{info} is a structure (of -type @code{disassemble_info}) defined in the header file -@file{include/dis-asm.h}, and used to pass information to the -instruction decoding routine. - -@item frame_id gdbarch_dummy_id (@var{gdbarch}, @var{frame}) -@findex gdbarch_dummy_id -@anchor{gdbarch_dummy_id} Given @var{frame} return a @w{@code{struct -frame_id}} that uniquely identifies an inferior function call's dummy -frame. The value returned must match the dummy frame stack value -previously saved by @code{call_function_by_hand}. - -@item void gdbarch_value_to_register (@var{gdbarch}, @var{frame}, @var{type}, @var{buf}) -@findex gdbarch_value_to_register -Convert a value of type @var{type} into the raw contents of a register. -@xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}. - -@end table - -Motorola M68K target conditionals. - -@ftable @code -@item BPT_VECTOR -Define this to be the 4-bit location of the breakpoint trap vector. If -not defined, it will default to @code{0xf}. - -@item REMOTE_BPT_VECTOR -Defaults to @code{1}. - -@end ftable - -@node Adding a New Target -@section Adding a New Target - -@cindex adding a target -The following files add a target to @value{GDBN}: - -@table @file -@cindex target dependent files - -@item gdb/@var{ttt}-tdep.c -Contains any miscellaneous code required for this target machine. On -some machines it doesn't exist at all. - -@item gdb/@var{arch}-tdep.c -@itemx gdb/@var{arch}-tdep.h -This is required to describe the basic layout of the target machine's -processor chip (registers, stack, etc.). It can be shared among many -targets that use the same processor architecture. - -@end table - -(Target header files such as -@file{gdb/config/@var{arch}/tm-@var{ttt}.h}, -@file{gdb/config/@var{arch}/tm-@var{arch}.h}, and -@file{config/tm-@var{os}.h} are no longer used.) - -@findex _initialize_@var{arch}_tdep -A @value{GDBN} description for a new architecture, arch is created by -defining a global function @code{_initialize_@var{arch}_tdep}, by -convention in the source file @file{@var{arch}-tdep.c}. For -example, in the case of the OpenRISC 1000, this function is called -@code{_initialize_or1k_tdep} and is found in the file -@file{or1k-tdep.c}. - -The object file resulting from compiling this source file, which will -contain the implementation of the -@code{_initialize_@var{arch}_tdep} function is specified in the -@value{GDBN} @file{configure.tgt} file, which includes a large case -statement pattern matching against the @code{--target} option of the -@kbd{configure} script. - -@quotation -@emph{Note:} If the architecture requires multiple source files, the -corresponding binaries should be included in -@file{configure.tgt}. However if there are header files, the -dependencies on these will not be picked up from the entries in -@file{configure.tgt}. The @file{Makefile.in} file will need extending to -show these dependencies. -@end quotation - -@findex gdbarch_register -A new struct gdbarch, defining the new architecture, is created within -the @code{_initialize_@var{arch}_tdep} function by calling -@code{gdbarch_register}: - -@smallexample -void gdbarch_register (enum bfd_architecture architecture, - gdbarch_init_ftype *init_func, - gdbarch_dump_tdep_ftype *tdep_dump_func); -@end smallexample - -This function has been described fully in an earlier -section. @xref{How an Architecture is Represented, , How an -Architecture is Represented}. - -The new @code{@w{struct gdbarch}} should contain implementations of -the necessary functions (described in the previous sections) to -describe the basic layout of the target machine's processor chip -(registers, stack, etc.). It can be shared among many targets that use -the same processor architecture. - -@node Target Descriptions -@chapter Target Descriptions -@cindex target descriptions - -The target architecture definition (@pxref{Target Architecture Definition}) -contains @value{GDBN}'s hard-coded knowledge about an architecture. For -some platforms, it is handy to have more flexible knowledge about a specific -instance of the architecture---for instance, a processor or development board. -@dfn{Target descriptions} provide a mechanism for the user to tell @value{GDBN} -more about what their target supports, or for the target to tell @value{GDBN} -directly. - -For details on writing, automatically supplying, and manually selecting -target descriptions, see @ref{Target Descriptions, , , gdb, -Debugging with @value{GDBN}}. This section will cover some related -topics about the @value{GDBN} internals. - -@menu -* Target Descriptions Implementation:: -* Adding Target Described Register Support:: -@end menu - -@node Target Descriptions Implementation -@section Target Descriptions Implementation -@cindex target descriptions, implementation - -Before @value{GDBN} connects to a new target, or runs a new program on -an existing target, it discards any existing target description and -reverts to a default gdbarch. Then, after connecting, it looks for a -new target description by calling @code{target_find_description}. - -A description may come from a user specified file (XML), the remote -@samp{qXfer:features:read} packet (also XML), or from any custom -@code{to_read_description} routine in the target vector. For instance, -the remote target supports guessing whether a MIPS target is 32-bit or -64-bit based on the size of the @samp{g} packet. - -If any target description is found, @value{GDBN} creates a new gdbarch -incorporating the description by calling @code{gdbarch_update_p}. Any -@samp{<architecture>} element is handled first, to determine which -architecture's gdbarch initialization routine is called to create the -new architecture. Then the initialization routine is called, and has -a chance to adjust the constructed architecture based on the contents -of the target description. For instance, it can recognize any -properties set by a @code{to_read_description} routine. Also -see @ref{Adding Target Described Register Support}. - -@node Adding Target Described Register Support -@section Adding Target Described Register Support -@cindex target descriptions, adding register support - -Target descriptions can report additional registers specific to an -instance of the target. But it takes a little work in the architecture -specific routines to support this. - -A target description must either have no registers or a complete -set---this avoids complexity in trying to merge standard registers -with the target defined registers. It is the architecture's -responsibility to validate that a description with registers has -everything it needs. To keep architecture code simple, the same -mechanism is used to assign fixed internal register numbers to -standard registers. - -If @code{tdesc_has_registers} returns 1, the description contains -registers. The architecture's @code{gdbarch_init} routine should: - -@itemize @bullet - -@item -Call @code{tdesc_data_alloc} to allocate storage, early, before -searching for a matching gdbarch or allocating a new one. - -@item -Use @code{tdesc_find_feature} to locate standard features by name. - -@item -Use @code{tdesc_numbered_register} and @code{tdesc_numbered_register_choices} -to locate the expected registers in the standard features. - -@item -Return @code{NULL} if a required feature is missing, or if any standard -feature is missing expected registers. This will produce a warning that -the description was incomplete. - -@item -Free the allocated data before returning, unless @code{tdesc_use_registers} -is called. - -@item -Call @code{set_gdbarch_num_regs} as usual, with a number higher than any -fixed number passed to @code{tdesc_numbered_register}. - -@item -Call @code{tdesc_use_registers} after creating a new gdbarch, before -returning it. - -@end itemize - -After @code{tdesc_use_registers} has been called, the architecture's -@code{register_name}, @code{register_type}, and @code{register_reggroup_p} -routines will not be called; that information will be taken from -the target description. @code{num_regs} may be increased to account -for any additional registers in the description. - -Pseudo-registers require some extra care: - -@itemize @bullet - -@item -Using @code{tdesc_numbered_register} allows the architecture to give -constant register numbers to standard architectural registers, e.g.@: -as an @code{enum} in @file{@var{arch}-tdep.h}. But because -pseudo-registers are always numbered above @code{num_regs}, -which may be increased by the description, constant numbers -can not be used for pseudos. They must be numbered relative to -@code{num_regs} instead. - -@item -The description will not describe pseudo-registers, so the -architecture must call @code{set_tdesc_pseudo_register_name}, -@code{set_tdesc_pseudo_register_type}, and -@code{set_tdesc_pseudo_register_reggroup_p} to supply routines -describing pseudo registers. These routines will be passed -internal register numbers, so the same routines used for the -gdbarch equivalents are usually suitable. - -@end itemize - - -@node Target Vector Definition - -@chapter Target Vector Definition -@cindex target vector - -The target vector defines the interface between @value{GDBN}'s -abstract handling of target systems, and the nitty-gritty code that -actually exercises control over a process or a serial port. -@value{GDBN} includes some 30-40 different target vectors; however, -each configuration of @value{GDBN} includes only a few of them. - -@menu -* Managing Execution State:: -* Existing Targets:: -@end menu - -@node Managing Execution State -@section Managing Execution State -@cindex execution state - -A target vector can be completely inactive (not pushed on the target -stack), active but not running (pushed, but not connected to a fully -manifested inferior), or completely active (pushed, with an accessible -inferior). Most targets are only completely inactive or completely -active, but some support persistent connections to a target even -when the target has exited or not yet started. - -For example, connecting to the simulator using @code{target sim} does -not create a running program. Neither registers nor memory are -accessible until @code{run}. Similarly, after @code{kill}, the -program can not continue executing. But in both cases @value{GDBN} -remains connected to the simulator, and target-specific commands -are directed to the simulator. - -A target which only supports complete activation should push itself -onto the stack in its @code{to_open} routine (by calling -@code{push_target}), and unpush itself from the stack in its -@code{to_mourn_inferior} routine (by calling @code{unpush_target}). - -A target which supports both partial and complete activation should -still call @code{push_target} in @code{to_open}, but not call -@code{unpush_target} in @code{to_mourn_inferior}. Instead, it should -call either @code{target_mark_running} or @code{target_mark_exited} -in its @code{to_open}, depending on whether the target is fully active -after connection. It should also call @code{target_mark_running} any -time the inferior becomes fully active (e.g.@: in -@code{to_create_inferior} and @code{to_attach}), and -@code{target_mark_exited} when the inferior becomes inactive (in -@code{to_mourn_inferior}). The target should also make sure to call -@code{target_mourn_inferior} from its @code{to_kill}, to return the -target to inactive state. - -@node Existing Targets -@section Existing Targets -@cindex targets - -@subsection File Targets - -Both executables and core files have target vectors. - -@subsection Standard Protocol and Remote Stubs - -@value{GDBN}'s file @file{remote.c} talks a serial protocol to code that -runs in the target system. @value{GDBN} provides several sample -@dfn{stubs} that can be integrated into target programs or operating -systems for this purpose; they are named @file{@var{cpu}-stub.c}. Many -operating systems, embedded targets, emulators, and simulators already -have a @value{GDBN} stub built into them, and maintenance of the remote -protocol must be careful to preserve compatibility. - -The @value{GDBN} user's manual describes how to put such a stub into -your target code. What follows is a discussion of integrating the -SPARC stub into a complicated operating system (rather than a simple -program), by Stu Grossman, the author of this stub. - -The trap handling code in the stub assumes the following upon entry to -@code{trap_low}: - -@enumerate -@item -%l1 and %l2 contain pc and npc respectively at the time of the trap; - -@item -traps are disabled; - -@item -you are in the correct trap window. -@end enumerate - -As long as your trap handler can guarantee those conditions, then there -is no reason why you shouldn't be able to ``share'' traps with the stub. -The stub has no requirement that it be jumped to directly from the -hardware trap vector. That is why it calls @code{exceptionHandler()}, -which is provided by the external environment. For instance, this could -set up the hardware traps to actually execute code which calls the stub -first, and then transfers to its own trap handler. - -For the most point, there probably won't be much of an issue with -``sharing'' traps, as the traps we use are usually not used by the kernel, -and often indicate unrecoverable error conditions. Anyway, this is all -controlled by a table, and is trivial to modify. The most important -trap for us is for @code{ta 1}. Without that, we can't single step or -do breakpoints. Everything else is unnecessary for the proper operation -of the debugger/stub. - -From reading the stub, it's probably not obvious how breakpoints work. -They are simply done by deposit/examine operations from @value{GDBN}. - -@subsection ROM Monitor Interface - -@subsection Custom Protocols - -@subsection Transport Layer - -@subsection Builtin Simulator - - -@node Native Debugging - -@chapter Native Debugging -@cindex native debugging - -Several files control @value{GDBN}'s configuration for native support: - -@table @file -@vindex NATDEPFILES -@item gdb/config/@var{arch}/@var{xyz}.mh -Specifies Makefile fragments needed by a @emph{native} configuration on -machine @var{xyz}. In particular, this lists the required -native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}. -Also specifies the header file which describes native support on -@var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also -define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS}, -@samp{NAT_CDEPS}, @samp{NAT_GENERATED_FILES}, etc.; see @file{Makefile.in}. - -@emph{Maintainer's note: The @file{.mh} suffix is because this file -originally contained @file{Makefile} fragments for hosting @value{GDBN} -on machine @var{xyz}. While the file is no longer used for this -purpose, the @file{.mh} suffix remains. Perhaps someone will -eventually rename these fragments so that they have a @file{.mn} -suffix.} - -@item gdb/config/@var{arch}/nm-@var{xyz}.h -(@file{nm.h} is a link to this file, created by @code{configure}). Contains C -macro definitions describing the native system environment, such as -child process control and core file support. - -@item gdb/@var{xyz}-nat.c -Contains any miscellaneous C code required for this native support of -this machine. On some machines it doesn't exist at all. -@end table - -There are some ``generic'' versions of routines that can be used by -various systems. These can be customized in various ways by macros -defined in your @file{nm-@var{xyz}.h} file. If these routines work for -the @var{xyz} host, you can just include the generic file's name (with -@samp{.o}, not @samp{.c}) in @code{NATDEPFILES}. - -Otherwise, if your machine needs custom support routines, you will need -to write routines that perform the same functions as the generic file. -Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o} -into @code{NATDEPFILES}. - -@table @file -@item inftarg.c -This contains the @emph{target_ops vector} that supports Unix child -processes on systems which use ptrace and wait to control the child. - -@item procfs.c -This contains the @emph{target_ops vector} that supports Unix child -processes on systems which use /proc to control the child. - -@item fork-child.c -This does the low-level grunge that uses Unix system calls to do a ``fork -and exec'' to start up a child process. - -@item infptrace.c -This is the low level interface to inferior processes for systems using -the Unix @code{ptrace} call in a vanilla way. -@end table - -@section ptrace - -@section /proc - -@section win32 - -@section shared libraries - -@section Native Conditionals -@cindex native conditionals - -When @value{GDBN} is configured and compiled, various macros are -defined or left undefined, to control compilation when the host and -target systems are the same. These macros should be defined (or left -undefined) in @file{nm-@var{system}.h}. - -@table @code - -@item I386_USE_GENERIC_WATCHPOINTS -An x86-based machine can define this to use the generic x86 watchpoint -support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}. - -@item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms}) -@findex SOLIB_ADD -Define this to expand into an expression that will cause the symbols in -@var{filename} to be added to @value{GDBN}'s symbol table. If -@var{readsyms} is zero symbols are not read but any necessary low level -processing for @var{filename} is still done. - -@item SOLIB_CREATE_INFERIOR_HOOK -@findex SOLIB_CREATE_INFERIOR_HOOK -Define this to expand into any shared-library-relocation code that you -want to be run just after the child process has been forked. - -@item START_INFERIOR_TRAPS_EXPECTED -@findex START_INFERIOR_TRAPS_EXPECTED -When starting an inferior, @value{GDBN} normally expects to trap -twice; once when -the shell execs, and once when the program itself execs. If the actual -number of traps is something other than 2, then define this macro to -expand into the number expected. - -@end table - -@node Support Libraries - -@chapter Support Libraries - -@section BFD -@cindex BFD library - -BFD provides support for @value{GDBN} in several ways: - -@table @emph -@item identifying executable and core files -BFD will identify a variety of file types, including a.out, coff, and -several variants thereof, as well as several kinds of core files. - -@item access to sections of files -BFD parses the file headers to determine the names, virtual addresses, -sizes, and file locations of all the various named sections in files -(such as the text section or the data section). @value{GDBN} simply -calls BFD to read or write section @var{x} at byte offset @var{y} for -length @var{z}. - -@item specialized core file support -BFD provides routines to determine the failing command name stored in a -core file, the signal with which the program failed, and whether a core -file matches (i.e.@: could be a core dump of) a particular executable -file. - -@item locating the symbol information -@value{GDBN} uses an internal interface of BFD to determine where to find the -symbol information in an executable file or symbol-file. @value{GDBN} itself -handles the reading of symbols, since BFD does not ``understand'' debug -symbols, but @value{GDBN} uses BFD's cached information to find the symbols, -string table, etc. -@end table - -@section opcodes -@cindex opcodes library - -The opcodes library provides @value{GDBN}'s disassembler. (It's a separate -library because it's also used in binutils, for @file{objdump}). - -@section readline -@cindex readline library -The @code{readline} library provides a set of functions for use by applications -that allow users to edit command lines as they are typed in. - -@section libiberty -@cindex @code{libiberty} library - -The @code{libiberty} library provides a set of functions and features -that integrate and improve on functionality found in modern operating -systems. Broadly speaking, such features can be divided into three -groups: supplemental functions (functions that may be missing in some -environments and operating systems), replacement functions (providing -a uniform and easier to use interface for commonly used standard -functions), and extensions (which provide additional functionality -beyond standard functions). - -@value{GDBN} uses various features provided by the @code{libiberty} -library, for instance the C@t{++} demangler, the @acronym{IEEE} -floating format support functions, the input options parser -@samp{getopt}, the @samp{obstack} extension, and other functions. - -@subsection @code{obstacks} in @value{GDBN} -@cindex @code{obstacks} - -The obstack mechanism provides a convenient way to allocate and free -chunks of memory. Each obstack is a pool of memory that is managed -like a stack. Objects (of any nature, size and alignment) are -allocated and freed in a @acronym{LIFO} fashion on an obstack (see -@code{libiberty}'s documentation for a more detailed explanation of -@code{obstacks}). - -The most noticeable use of the @code{obstacks} in @value{GDBN} is in -object files. There is an obstack associated with each internal -representation of an object file. Lots of things get allocated on -these @code{obstacks}: dictionary entries, blocks, blockvectors, -symbols, minimal symbols, types, vectors of fundamental types, class -fields of types, object files section lists, object files section -offset lists, line tables, symbol tables, partial symbol tables, -string tables, symbol table private data, macros tables, debug -information sections and entries, import and export lists (som), -unwind information (hppa), dwarf2 location expressions data. Plus -various strings such as directory names strings, debug format strings, -names of types. - -An essential and convenient property of all data on @code{obstacks} is -that memory for it gets allocated (with @code{obstack_alloc}) at -various times during a debugging session, but it is released all at -once using the @code{obstack_free} function. The @code{obstack_free} -function takes a pointer to where in the stack it must start the -deletion from (much like the cleanup chains have a pointer to where to -start the cleanups). Because of the stack like structure of the -@code{obstacks}, this allows to free only a top portion of the -obstack. There are a few instances in @value{GDBN} where such thing -happens. Calls to @code{obstack_free} are done after some local data -is allocated to the obstack. Only the local data is deleted from the -obstack. Of course this assumes that nothing between the -@code{obstack_alloc} and the @code{obstack_free} allocates anything -else on the same obstack. For this reason it is best and safest to -use temporary @code{obstacks}. - -Releasing the whole obstack is also not safe per se. It is safe only -under the condition that we know the @code{obstacks} memory is no -longer needed. In @value{GDBN} we get rid of the @code{obstacks} only -when we get rid of the whole objfile(s), for instance upon reading a -new symbol file. - -@section gnu-regex -@cindex regular expressions library - -Regex conditionals. - -@table @code -@item C_ALLOCA - -@item NFAILURES - -@item RE_NREGS - -@item SIGN_EXTEND_CHAR - -@item SWITCH_ENUM_BUG - -@item SYNTAX_TABLE - -@item Sword - -@item sparc -@end table - -@section Array Containers -@cindex Array Containers -@cindex VEC - -Often it is necessary to manipulate a dynamic array of a set of -objects. C forces some bookkeeping on this, which can get cumbersome -and repetitive. The @file{vec.h} file contains macros for defining -and using a typesafe vector type. The functions defined will be -inlined when compiling, and so the abstraction cost should be zero. -Domain checks are added to detect programming errors. - -An example use would be an array of symbols or section information. -The array can be grown as symbols are read in (or preallocated), and -the accessor macros provided keep care of all the necessary -bookkeeping. Because the arrays are type safe, there is no danger of -accidentally mixing up the contents. Think of these as C++ templates, -but implemented in C. - -Because of the different behavior of structure objects, scalar objects -and of pointers, there are three flavors of vector, one for each of -these variants. Both the structure object and pointer variants pass -pointers to objects around --- in the former case the pointers are -stored into the vector and in the latter case the pointers are -dereferenced and the objects copied into the vector. The scalar -object variant is suitable for @code{int}-like objects, and the vector -elements are returned by value. - -There are both @code{index} and @code{iterate} accessors. The iterator -returns a boolean iteration condition and updates the iteration -variable passed by reference. Because the iterator will be inlined, -the address-of can be optimized away. - -The vectors are implemented using the trailing array idiom, thus they -are not resizeable without changing the address of the vector object -itself. This means you cannot have variables or fields of vector type ---- always use a pointer to a vector. The one exception is the final -field of a structure, which could be a vector type. You will have to -use the @code{embedded_size} & @code{embedded_init} calls to create -such objects, and they will probably not be resizeable (so don't use -the @dfn{safe} allocation variants). The trailing array idiom is used -(rather than a pointer to an array of data), because, if we allow -@code{NULL} to also represent an empty vector, empty vectors occupy -minimal space in the structure containing them. - -Each operation that increases the number of active elements is -available in @dfn{quick} and @dfn{safe} variants. The former presumes -that there is sufficient allocated space for the operation to succeed -(it dies if there is not). The latter will reallocate the vector, if -needed. Reallocation causes an exponential increase in vector size. -If you know you will be adding N elements, it would be more efficient -to use the reserve operation before adding the elements with the -@dfn{quick} operation. This will ensure there are at least as many -elements as you ask for, it will exponentially increase if there are -too few spare slots. If you want reserve a specific number of slots, -but do not want the exponential increase (for instance, you know this -is the last allocation), use a negative number for reservation. You -can also create a vector of a specific size from the get go. - -You should prefer the push and pop operations, as they append and -remove from the end of the vector. If you need to remove several items -in one go, use the truncate operation. The insert and remove -operations allow you to change elements in the middle of the vector. -There are two remove operations, one which preserves the element -ordering @code{ordered_remove}, and one which does not -@code{unordered_remove}. The latter function copies the end element -into the removed slot, rather than invoke a memmove operation. The -@code{lower_bound} function will determine where to place an item in -the array using insert that will maintain sorted order. - -If you need to directly manipulate a vector, then the @code{address} -accessor will return the address of the start of the vector. Also the -@code{space} predicate will tell you whether there is spare capacity in the -vector. You will not normally need to use these two functions. - -Vector types are defined using a -@code{DEF_VEC_@{O,P,I@}(@var{typename})} macro. Variables of vector -type are declared using a @code{VEC(@var{typename})} macro. The -characters @code{O}, @code{P} and @code{I} indicate whether -@var{typename} is an object (@code{O}), pointer (@code{P}) or integral -(@code{I}) type. Be careful to pick the correct one, as you'll get an -awkward and inefficient API if you use the wrong one. There is a -check, which results in a compile-time warning, for the @code{P} and -@code{I} versions, but there is no check for the @code{O} versions, as -that is not possible in plain C. - -An example of their use would be, - -@smallexample -DEF_VEC_P(tree); // non-managed tree vector. - -struct my_struct @{ - VEC(tree) *v; // A (pointer to) a vector of tree pointers. -@}; - -struct my_struct *s; - -if (VEC_length(tree, s->v)) @{ we have some contents @} -VEC_safe_push(tree, s->v, decl); // append some decl onto the end -for (ix = 0; VEC_iterate(tree, s->v, ix, elt); ix++) - @{ do something with elt @} - -@end smallexample - -The @file{vec.h} file provides details on how to invoke the various -accessors provided. They are enumerated here: - -@table @code -@item VEC_length -Return the number of items in the array, - -@item VEC_empty -Return true if the array has no elements. - -@item VEC_last -@itemx VEC_index -Return the last or arbitrary item in the array. - -@item VEC_iterate -Access an array element and indicate whether the array has been -traversed. - -@item VEC_alloc -@itemx VEC_free -Create and destroy an array. - -@item VEC_embedded_size -@itemx VEC_embedded_init -Helpers for embedding an array as the final element of another struct. - -@item VEC_copy -Duplicate an array. - -@item VEC_space -Return the amount of free space in an array. - -@item VEC_reserve -Ensure a certain amount of free space. - -@item VEC_quick_push -@itemx VEC_safe_push -Append to an array, either assuming the space is available, or making -sure that it is. - -@item VEC_pop -Remove the last item from an array. - -@item VEC_truncate -Remove several items from the end of an array. - -@item VEC_safe_grow -Add several items to the end of an array. - -@item VEC_replace -Overwrite an item in the array. - -@item VEC_quick_insert -@itemx VEC_safe_insert -Insert an item into the middle of the array. Either the space must -already exist, or the space is created. - -@item VEC_ordered_remove -@itemx VEC_unordered_remove -Remove an item from the array, preserving order or not. - -@item VEC_block_remove -Remove a set of items from the array. - -@item VEC_address -Provide the address of the first element. - -@item VEC_lower_bound -Binary search the array. - -@end table - -@section include - -@node Coding Standards - -@chapter Coding Standards -@cindex coding standards - -@section @value{GDBN} C Coding Standards - -@value{GDBN} follows the GNU coding standards, as described in -@file{etc/standards.texi}. This file is also available for anonymous -FTP from GNU archive sites. @value{GDBN} takes a strict interpretation -of the standard; in general, when the GNU standard recommends a practice -but does not require it, @value{GDBN} requires it. - -@value{GDBN} follows an additional set of coding standards specific to -@value{GDBN}, as described in the following sections. - -@subsection ISO C - -@value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant -compiler. - -@value{GDBN} does not assume an ISO C or POSIX compliant C library. - -@subsection Formatting - -@cindex source code formatting -The standard GNU recommendations for formatting must be followed -strictly. Any @value{GDBN}-specific deviation from GNU -recomendations is described below. - -A function declaration should not have its name in column zero. A -function definition should have its name in column zero. - -@smallexample -/* Declaration */ -static void foo (void); -/* Definition */ -void -foo (void) -@{ -@} -@end smallexample - -@emph{Pragmatics: This simplifies scripting. Function definitions can -be found using @samp{^function-name}.} - -There must be a space between a function or macro name and the opening -parenthesis of its argument list (except for macro definitions, as -required by C). There must not be a space after an open paren/bracket -or before a close paren/bracket. - -While additional whitespace is generally helpful for reading, do not use -more than one blank line to separate blocks, and avoid adding whitespace -after the end of a program line (as of 1/99, some 600 lines had -whitespace after the semicolon). Excess whitespace causes difficulties -for @code{diff} and @code{patch} utilities. - -Pointers are declared using the traditional K&R C style: - -@smallexample -void *foo; -@end smallexample - -@noindent -and not: - -@smallexample -void * foo; -void* foo; -@end smallexample - -In addition, whitespace around casts and unary operators should follow -the following guidelines: - -@multitable @columnfractions .2 .2 .8 -@item Use... @tab ...instead of @tab - -@item @code{!x} -@tab @code{! x} -@item @code{~x} -@tab @code{~ x} -@item @code{-x} -@tab @code{- x} -@tab (unary minus) -@item @code{(foo) x} -@tab @code{(foo)x} -@tab (cast) -@item @code{*x} -@tab @code{* x} -@tab (pointer dereference) -@end multitable - -Any two or more lines in code should be wrapped in braces, even if -they are comments, as they look like separate statements: - -@smallexample -if (i) - @{ - /* Return success. */ - return 0; - @} -@end smallexample - -@noindent -and not: - -@smallexample -if (i) - /* Return success. */ - return 0; -@end smallexample - -@subsection Comments - -@cindex comment formatting -The standard GNU requirements on comments must be followed strictly. - -Block comments must appear in the following form, with no @code{/*}- or -@code{*/}-only lines, and no leading @code{*}: - -@smallexample -/* Wait for control to return from inferior to debugger. If inferior - gets a signal, we may decide to start it up again instead of - returning. That is why there is a loop in this function. When - this function actually returns it means the inferior should be left - stopped and @value{GDBN} should read more commands. */ -@end smallexample - -(Note that this format is encouraged by Emacs; tabbing for a multi-line -comment works correctly, and @kbd{M-q} fills the block consistently.) - -Put a blank line between the block comments preceding function or -variable definitions, and the definition itself. - -In general, put function-body comments on lines by themselves, rather -than trying to fit them into the 20 characters left at the end of a -line, since either the comment or the code will inevitably get longer -than will fit, and then somebody will have to move it anyhow. - -@subsection C Usage - -@cindex C data types -Code must not depend on the sizes of C data types, the format of the -host's floating point numbers, the alignment of anything, or the order -of evaluation of expressions. - -@cindex function usage -Use functions freely. There are only a handful of compute-bound areas -in @value{GDBN} that might be affected by the overhead of a function -call, mainly in symbol reading. Most of @value{GDBN}'s performance is -limited by the target interface (whether serial line or system call). - -However, use functions with moderation. A thousand one-line functions -are just as hard to understand as a single thousand-line function. - -@emph{Macros are bad, M'kay.} -(But if you have to use a macro, make sure that the macro arguments are -protected with parentheses.) - -@cindex types - -Declarations like @samp{struct foo *} should be used in preference to -declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}. - -Zero constant (@code{0}) is not interchangeable with a null pointer -constant (@code{NULL}) anywhere. @sc{gcc} does not give a warning for -such interchange. Specifically: - -@multitable @columnfractions .2 .5 -@item incorrect -@tab @code{if (pointervar) @{@}} -@item incorrect -@tab @code{if (!pointervar) @{@}} -@item incorrect -@tab @code{if (pointervar != 0) @{@}} -@item incorrect -@tab @code{if (pointervar == 0) @{@}} -@item correct -@tab @code{if (pointervar != NULL) @{@}} -@item correct -@tab @code{if (pointervar == NULL) @{@}} -@end multitable - -@subsection Function Prototypes -@cindex function prototypes - -Prototypes must be used when both @emph{declaring} and @emph{defining} -a function. Prototypes for @value{GDBN} functions must include both the -argument type and name, with the name matching that used in the actual -function definition. - -All external functions should have a declaration in a header file that -callers include, that declaration should use the @code{extern} modifier. -The only exception concerns @code{_initialize_*} functions, which must -be external so that @file{init.c} construction works, but shouldn't be -visible to random source files. - -Where a source file needs a forward declaration of a static function, -that declaration must appear in a block near the top of the source file. - -@subsection File Names - -Any file used when building the core of @value{GDBN} must be in lower -case. Any file used when building the core of @value{GDBN} must be 8.3 -unique. These requirements apply to both source and generated files. - -@emph{Pragmatics: The core of @value{GDBN} must be buildable on many -platforms including DJGPP and MacOS/HFS. Every time an unfriendly file -is introduced to the build process both @file{Makefile.in} and -@file{configure.in} need to be modified accordingly. Compare the -convoluted conversion process needed to transform @file{COPYING} into -@file{copying.c} with the conversion needed to transform -@file{version.in} into @file{version.c}.} - -Any file non 8.3 compliant file (that is not used when building the core -of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}. - -@emph{Pragmatics: This is clearly a compromise.} - -When @value{GDBN} has a local version of a system header file (ex -@file{string.h}) the file name based on the POSIX header prefixed with -@file{gdb_} (@file{gdb_string.h}). These headers should be relatively -independent: they should use only macros defined by @file{configure}, -the compiler, or the host; they should include only system headers; they -should refer only to system types. They may be shared between multiple -programs, e.g.@: @value{GDBN} and @sc{gdbserver}. - -For other files @samp{-} is used as the separator. - -@subsection Include Files - -A @file{.c} file should include @file{defs.h} first. - -A @file{.c} file should directly include the @code{.h} file of every -declaration and/or definition it directly refers to. It cannot rely on -indirect inclusion. - -A @file{.h} file should directly include the @code{.h} file of every -declaration and/or definition it directly refers to. It cannot rely on -indirect inclusion. Exception: The file @file{defs.h} does not need to -be directly included. - -An external declaration should only appear in one include file. - -An external declaration should never appear in a @code{.c} file. -Exception: a declaration for the @code{_initialize} function that -pacifies @option{-Wmissing-declaration}. - -A @code{typedef} definition should only appear in one include file. - -An opaque @code{struct} declaration can appear in multiple @file{.h} -files. Where possible, a @file{.h} file should use an opaque -@code{struct} declaration instead of an include. - -All @file{.h} files should be wrapped in: - -@smallexample -#ifndef INCLUDE_FILE_NAME_H -#define INCLUDE_FILE_NAME_H -header body -#endif -@end smallexample - -@section @value{GDBN} Python Coding Standards - -@value{GDBN} follows the published @code{Python} coding standards in -@uref{http://www.python.org/dev/peps/pep-0008/, @code{PEP008}}. - -In addition, the guidelines in the -@uref{http://google-styleguide.googlecode.com/svn/trunk/pyguide.html, -Google Python Style Guide} are also followed where they do not -conflict with @code{PEP008}. - -@subsection @value{GDBN}-specific exceptions - -There are a few exceptions to the published standards. -They exist mainly for consistency with the @code{C} standards. - -@c It is expected that there are a few more exceptions, -@c so we use itemize here. - -@itemize @bullet - -@item -Use @code{FIXME} instead of @code{TODO}. - -@end itemize - -@node Misc Guidelines - -@chapter Misc Guidelines - -This chapter covers topics that are lower-level than the major -algorithms of @value{GDBN}. - -@section Cleanups -@cindex cleanups - -Cleanups are a structured way to deal with things that need to be done -later. - -When your code does something (e.g., @code{xmalloc} some memory, or -@code{open} a file) that needs to be undone later (e.g., @code{xfree} -the memory or @code{close} the file), it can make a cleanup. The -cleanup will be done at some future point: when the command is finished -and control returns to the top level; when an error occurs and the stack -is unwound; or when your code decides it's time to explicitly perform -cleanups. Alternatively you can elect to discard the cleanups you -created. - -Syntax: - -@table @code -@item struct cleanup *@var{old_chain}; -Declare a variable which will hold a cleanup chain handle. - -@findex make_cleanup -@item @var{old_chain} = make_cleanup (@var{function}, @var{arg}); -Make a cleanup which will cause @var{function} to be called with -@var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a -handle that can later be passed to @code{do_cleanups} or -@code{discard_cleanups}. Unless you are going to call -@code{do_cleanups} or @code{discard_cleanups}, you can ignore the result -from @code{make_cleanup}. - -@findex do_cleanups -@item do_cleanups (@var{old_chain}); -Do all cleanups added to the chain since the corresponding -@code{make_cleanup} call was made. - -@findex discard_cleanups -@item discard_cleanups (@var{old_chain}); -Same as @code{do_cleanups} except that it just removes the cleanups from -the chain and does not call the specified functions. -@end table - -Cleanups are implemented as a chain. The handle returned by -@code{make_cleanups} includes the cleanup passed to the call and any -later cleanups appended to the chain (but not yet discarded or -performed). E.g.: - -@smallexample -make_cleanup (a, 0); -@{ - struct cleanup *old = make_cleanup (b, 0); - make_cleanup (c, 0) - ... - do_cleanups (old); -@} -@end smallexample - -@noindent -will call @code{c()} and @code{b()} but will not call @code{a()}. The -cleanup that calls @code{a()} will remain in the cleanup chain, and will -be done later unless otherwise discarded.@refill - -Your function should explicitly do or discard the cleanups it creates. -Failing to do this leads to non-deterministic behavior since the caller -will arbitrarily do or discard your functions cleanups. This need leads -to two common cleanup styles. - -The first style is try/finally. Before it exits, your code-block calls -@code{do_cleanups} with the old cleanup chain and thus ensures that your -code-block's cleanups are always performed. For instance, the following -code-segment avoids a memory leak problem (even when @code{error} is -called and a forced stack unwind occurs) by ensuring that the -@code{xfree} will always be called: - -@smallexample -struct cleanup *old = make_cleanup (null_cleanup, 0); -data = xmalloc (sizeof blah); -make_cleanup (xfree, data); -... blah blah ... -do_cleanups (old); -@end smallexample - -The second style is try/except. Before it exits, your code-block calls -@code{discard_cleanups} with the old cleanup chain and thus ensures that -any created cleanups are not performed. For instance, the following -code segment, ensures that the file will be closed but only if there is -an error: - -@smallexample -FILE *file = fopen ("afile", "r"); -struct cleanup *old = make_cleanup (close_file, file); -... blah blah ... -discard_cleanups (old); -return file; -@end smallexample - -Some functions, e.g., @code{fputs_filtered()} or @code{error()}, specify -that they ``should not be called when cleanups are not in place''. This -means that any actions you need to reverse in the case of an error or -interruption must be on the cleanup chain before you call these -functions, since they might never return to your code (they -@samp{longjmp} instead). - -@section Per-architecture module data -@cindex per-architecture module data -@cindex multi-arch data -@cindex data-pointer, per-architecture/per-module - -The multi-arch framework includes a mechanism for adding module -specific per-architecture data-pointers to the @code{struct gdbarch} -architecture object. - -A module registers one or more per-architecture data-pointers using: - -@deftypefn {Architecture Function} {struct gdbarch_data *} gdbarch_data_register_pre_init (gdbarch_data_pre_init_ftype *@var{pre_init}) -@var{pre_init} is used to, on-demand, allocate an initial value for a -per-architecture data-pointer using the architecture's obstack (passed -in as a parameter). Since @var{pre_init} can be called during -architecture creation, it is not parameterized with the architecture. -and must not call modules that use per-architecture data. -@end deftypefn - -@deftypefn {Architecture Function} {struct gdbarch_data *} gdbarch_data_register_post_init (gdbarch_data_post_init_ftype *@var{post_init}) -@var{post_init} is used to obtain an initial value for a -per-architecture data-pointer @emph{after}. Since @var{post_init} is -always called after architecture creation, it both receives the fully -initialized architecture and is free to call modules that use -per-architecture data (care needs to be taken to ensure that those -other modules do not try to call back to this module as that will -create in cycles in the initialization call graph). -@end deftypefn - -These functions return a @code{struct gdbarch_data} that is used to -identify the per-architecture data-pointer added for that module. - -The per-architecture data-pointer is accessed using the function: - -@deftypefn {Architecture Function} {void *} gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle}) -Given the architecture @var{arch} and module data handle -@var{data_handle} (returned by @code{gdbarch_data_register_pre_init} -or @code{gdbarch_data_register_post_init}), this function returns the -current value of the per-architecture data-pointer. If the data -pointer is @code{NULL}, it is first initialized by calling the -corresponding @var{pre_init} or @var{post_init} method. -@end deftypefn - -The examples below assume the following definitions: - -@smallexample -struct nozel @{ int total; @}; -static struct gdbarch_data *nozel_handle; -@end smallexample - -A module can extend the architecture vector, adding additional -per-architecture data, using the @var{pre_init} method. The module's -per-architecture data is then initialized during architecture -creation. - -In the below, the module's per-architecture @emph{nozel} is added. An -architecture can specify its nozel by calling @code{set_gdbarch_nozel} -from @code{gdbarch_init}. - -@smallexample -static void * -nozel_pre_init (struct obstack *obstack) -@{ - struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel); - return data; -@} -@end smallexample - -@smallexample -extern void -set_gdbarch_nozel (struct gdbarch *gdbarch, int total) -@{ - struct nozel *data = gdbarch_data (gdbarch, nozel_handle); - data->total = nozel; -@} -@end smallexample - -A module can on-demand create architecture dependent data structures -using @code{post_init}. - -In the below, the nozel's total is computed on-demand by -@code{nozel_post_init} using information obtained from the -architecture. - -@smallexample -static void * -nozel_post_init (struct gdbarch *gdbarch) -@{ - struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel); - nozel->total = gdbarch@dots{} (gdbarch); - return data; -@} -@end smallexample - -@smallexample -extern int -nozel_total (struct gdbarch *gdbarch) -@{ - struct nozel *data = gdbarch_data (gdbarch, nozel_handle); - return data->total; -@} -@end smallexample - -@section Wrapping Output Lines -@cindex line wrap in output - -@findex wrap_here -Output that goes through @code{printf_filtered} or @code{fputs_filtered} -or @code{fputs_demangled} needs only to have calls to @code{wrap_here} -added in places that would be good breaking points. The utility -routines will take care of actually wrapping if the line width is -exceeded. - -The argument to @code{wrap_here} is an indentation string which is -printed @emph{only} if the line breaks there. This argument is saved -away and used later. It must remain valid until the next call to -@code{wrap_here} or until a newline has been printed through the -@code{*_filtered} functions. Don't pass in a local variable and then -return! - -It is usually best to call @code{wrap_here} after printing a comma or -space. If you call it before printing a space, make sure that your -indentation properly accounts for the leading space that will print if -the line wraps there. - -Any function or set of functions that produce filtered output must -finish by printing a newline, to flush the wrap buffer, before switching -to unfiltered (@code{printf}) output. Symbol reading routines that -print warnings are a good example. - -@section Memory Management - -@value{GDBN} does not use the functions @code{malloc}, @code{realloc}, -@code{calloc}, @code{free} and @code{asprintf}. - -@value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and -@code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@: -these functions do not return when the memory pool is empty. Instead, -they unwind the stack using cleanups. These functions return -@code{NULL} when requested to allocate a chunk of memory of size zero. - -@emph{Pragmatics: By using these functions, the need to check every -memory allocation is removed. These functions provide portable -behavior.} - -@value{GDBN} does not use the function @code{free}. - -@value{GDBN} uses the function @code{xfree} to return memory to the -memory pool. Consistent with ISO-C, this function ignores a request to -free a @code{NULL} pointer. - -@emph{Pragmatics: On some systems @code{free} fails when passed a -@code{NULL} pointer.} - -@value{GDBN} can use the non-portable function @code{alloca} for the -allocation of small temporary values (such as strings). - -@emph{Pragmatics: This function is very non-portable. Some systems -restrict the memory being allocated to no more than a few kilobytes.} - -@value{GDBN} uses the string function @code{xstrdup} and the print -function @code{xstrprintf}. - -@emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print -functions such as @code{sprintf} are very prone to buffer overflow -errors.} - - -@section Compiler Warnings -@cindex compiler warnings - -With few exceptions, developers should avoid the configuration option -@samp{--disable-werror} when building @value{GDBN}. The exceptions -are listed in the file @file{gdb/MAINTAINERS}. The default, when -building with @sc{gcc}, is @samp{--enable-werror}. - -This option causes @value{GDBN} (when built using GCC) to be compiled -with a carefully selected list of compiler warning flags. Any warnings -from those flags are treated as errors. - -The current list of warning flags includes: - -@table @samp -@item -Wall -Recommended @sc{gcc} warnings. - -@item -Wdeclaration-after-statement - -@sc{gcc} 3.x (and later) and @sc{c99} allow declarations mixed with -code, but @sc{gcc} 2.x and @sc{c89} do not. - -@item -Wpointer-arith - -@item -Wformat-nonliteral -Non-literal format strings, with a few exceptions, are bugs - they -might contain unintended user-supplied format specifiers. -Since @value{GDBN} uses the @code{format printf} attribute on all -@code{printf} like functions this checks not just @code{printf} calls -but also calls to functions such as @code{fprintf_unfiltered}. - -@item -Wno-pointer-sign -In version 4.0, GCC began warning about pointer argument passing or -assignment even when the source and destination differed only in -signedness. However, most @value{GDBN} code doesn't distinguish -carefully between @code{char} and @code{unsigned char}. In early 2006 -the @value{GDBN} developers decided correcting these warnings wasn't -worth the time it would take. - -@item -Wno-unused-parameter -Due to the way that @value{GDBN} is implemented many functions have -unused parameters. Consequently this warning is avoided. The macro -@code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives --- -it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that -is being used. - -@item -Wno-unused -@itemx -Wno-switch -@itemx -Wno-char-subscripts -These are warnings which might be useful for @value{GDBN}, but are -currently too noisy to enable with @samp{-Werror}. - -@end table - -@section Internal Error Recovery - -During its execution, @value{GDBN} can encounter two types of errors. -User errors and internal errors. User errors include not only a user -entering an incorrect command but also problems arising from corrupt -object files and system errors when interacting with the target. -Internal errors include situations where @value{GDBN} has detected, at -run time, a corrupt or erroneous situation. - -When reporting an internal error, @value{GDBN} uses -@code{internal_error} and @code{gdb_assert}. - -@value{GDBN} must not call @code{abort} or @code{assert}. - -@emph{Pragmatics: There is no @code{internal_warning} function. Either -the code detected a user error, recovered from it and issued a -@code{warning} or the code failed to correctly recover from the user -error and issued an @code{internal_error}.} - -@section Command Names - -GDB U/I commands are written @samp{foo-bar}, not @samp{foo_bar}. - -@section Clean Design and Portable Implementation - -@cindex design -In addition to getting the syntax right, there's the little question of -semantics. Some things are done in certain ways in @value{GDBN} because long -experience has shown that the more obvious ways caused various kinds of -trouble. - -@cindex assumptions about targets -You can't assume the byte order of anything that comes from a target -(including @var{value}s, object files, and instructions). Such things -must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in -@value{GDBN}, or one of the swap routines defined in @file{bfd.h}, -such as @code{bfd_get_32}. - -You can't assume that you know what interface is being used to talk to -the target system. All references to the target must go through the -current @code{target_ops} vector. - -You can't assume that the host and target machines are the same machine -(except in the ``native'' support modules). In particular, you can't -assume that the target machine's header files will be available on the -host machine. Target code must bring along its own header files -- -written from scratch or explicitly donated by their owner, to avoid -copyright problems. - -@cindex portability -Insertion of new @code{#ifdef}'s will be frowned upon. It's much better -to write the code portably than to conditionalize it for various -systems. - -@cindex system dependencies -New @code{#ifdef}'s which test for specific compilers or manufacturers -or operating systems are unacceptable. All @code{#ifdef}'s should test -for features. The information about which configurations contain which -features should be segregated into the configuration files. Experience -has proven far too often that a feature unique to one particular system -often creeps into other systems; and that a conditional based on some -predefined macro for your current system will become worthless over -time, as new versions of your system come out that behave differently -with regard to this feature. - -Adding code that handles specific architectures, operating systems, -target interfaces, or hosts, is not acceptable in generic code. - -@cindex portable file name handling -@cindex file names, portability -One particularly notorious area where system dependencies tend to -creep in is handling of file names. The mainline @value{GDBN} code -assumes Posix semantics of file names: absolute file names begin with -a forward slash @file{/}, slashes are used to separate leading -directories, case-sensitive file names. These assumptions are not -necessarily true on non-Posix systems such as MS-Windows. To avoid -system-dependent code where you need to take apart or construct a file -name, use the following portable macros: - -@table @code -@findex HAVE_DOS_BASED_FILE_SYSTEM -@item HAVE_DOS_BASED_FILE_SYSTEM -This preprocessing symbol is defined to a non-zero value on hosts -whose filesystems belong to the MS-DOS/MS-Windows family. Use this -symbol to write conditional code which should only be compiled for -such hosts. - -@findex IS_DIR_SEPARATOR -@item IS_DIR_SEPARATOR (@var{c}) -Evaluates to a non-zero value if @var{c} is a directory separator -character. On Unix and GNU/Linux systems, only a slash @file{/} is -such a character, but on Windows, both @file{/} and @file{\} will -pass. - -@findex IS_ABSOLUTE_PATH -@item IS_ABSOLUTE_PATH (@var{file}) -Evaluates to a non-zero value if @var{file} is an absolute file name. -For Unix and GNU/Linux hosts, a name which begins with a slash -@file{/} is absolute. On DOS and Windows, @file{d:/foo} and -@file{x:\bar} are also absolute file names. - -@findex FILENAME_CMP -@item FILENAME_CMP (@var{f1}, @var{f2}) -Calls a function which compares file names @var{f1} and @var{f2} as -appropriate for the underlying host filesystem. For Posix systems, -this simply calls @code{strcmp}; on case-insensitive filesystems it -will call @code{strcasecmp} instead. - -@findex DIRNAME_SEPARATOR -@item DIRNAME_SEPARATOR -Evaluates to a character which separates directories in -@code{PATH}-style lists, typically held in environment variables. -This character is @samp{:} on Unix, @samp{;} on DOS and Windows. - -@findex SLASH_STRING -@item SLASH_STRING -This evaluates to a constant string you should use to produce an -absolute filename from leading directories and the file's basename. -@code{SLASH_STRING} is @code{"/"} on most systems, but might be -@code{"\\"} for some Windows-based ports. -@end table - -In addition to using these macros, be sure to use portable library -functions whenever possible. For example, to extract a directory or a -basename part from a file name, use the @code{dirname} and -@code{basename} library functions (available in @code{libiberty} for -platforms which don't provide them), instead of searching for a slash -with @code{strrchr}. - -Another way to generalize @value{GDBN} along a particular interface is with an -attribute struct. For example, @value{GDBN} has been generalized to handle -multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but -by defining the @code{target_ops} structure and having a current target (as -well as a stack of targets below it, for memory references). Whenever -something needs to be done that depends on which remote interface we are -using, a flag in the current target_ops structure is tested (e.g., -@code{target_has_stack}), or a function is called through a pointer in the -current target_ops structure. In this way, when a new remote interface -is added, only one module needs to be touched---the one that actually -implements the new remote interface. Other examples of -attribute-structs are BFD access to multiple kinds of object file -formats, or @value{GDBN}'s access to multiple source languages. - -Please avoid duplicating code. For example, in @value{GDBN} 3.x all -the code interfacing between @code{ptrace} and the rest of -@value{GDBN} was duplicated in @file{*-dep.c}, and so changing -something was very painful. In @value{GDBN} 4.x, these have all been -consolidated into @file{infptrace.c}. @file{infptrace.c} can deal -with variations between systems the same way any system-independent -file would (hooks, @code{#if defined}, etc.), and machines which are -radically different don't need to use @file{infptrace.c} at all. - -All debugging code must be controllable using the @samp{set debug -@var{module}} command. Do not use @code{printf} to print trace -messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use -@code{#ifdef DEBUG}. - -@node Porting GDB - -@chapter Porting @value{GDBN} -@cindex porting to new machines - -Most of the work in making @value{GDBN} compile on a new machine is in -specifying the configuration of the machine. Porting a new -architecture to @value{GDBN} can be broken into a number of steps. - -@itemize @bullet - -@item -Ensure a @sc{bfd} exists for executables of the target architecture in -the @file{bfd} directory. If one does not exist, create one by -modifying an existing similar one. - -@item -Implement a disassembler for the target architecture in the @file{opcodes} -directory. - -@item -Define the target architecture in the @file{gdb} directory -(@pxref{Adding a New Target, , Adding a New Target}). Add the pattern -for the new target to @file{configure.tgt} with the names of the files -that contain the code. By convention the target architecture -definition for an architecture @var{arch} is placed in -@file{@var{arch}-tdep.c}. - -Within @file{@var{arch}-tdep.c} define the function -@code{_initialize_@var{arch}_tdep} which calls -@code{gdbarch_register} to create the new @code{@w{struct -gdbarch}} for the architecture. - -@item -If a new remote target is needed, consider adding a new remote target -by defining a function -@code{_initialize_remote_@var{arch}}. However if at all possible -use the @value{GDBN} @emph{Remote Serial Protocol} for this and implement -the server side protocol independently with the target. - -@item -If desired implement a simulator in the @file{sim} directory. This -should create the library @file{libsim.a} implementing the interface -in @file{remote-sim.h} (found in the @file{include} directory). - -@item -Build and test. If desired, lobby the @sc{gdb} steering group to -have the new port included in the main distribution! - -@item -Add a description of the new architecture to the main @value{GDBN} user -guide (@pxref{Configuration Specific Information, , Configuration -Specific Information, gdb, Debugging with @value{GDBN}}). - -@end itemize - -@node Versions and Branches -@chapter Versions and Branches - -@section Versions - -@value{GDBN}'s version is determined by the file -@file{gdb/version.in} and takes one of the following forms: - -@table @asis -@item @var{major}.@var{minor} -@itemx @var{major}.@var{minor}.@var{patchlevel} -an official release (e.g., 6.2 or 6.2.1) -@item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD} -a snapshot taken at @var{YYYY}-@var{MM}-@var{DD}-gmt (e.g., -6.1.50.20020302, 6.1.90.20020304, or 6.1.0.20020308) -@item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}-cvs -a @sc{cvs} check out drawn on @var{YYYY}-@var{MM}-@var{DD} (e.g., -6.1.50.20020302-cvs, 6.1.90.20020304-cvs, or 6.1.0.20020308-cvs) -@item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD} (@var{vendor}) -a vendor specific release of @value{GDBN}, that while based on@* -@var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}, -may include additional changes -@end table - -@value{GDBN}'s mainline uses the @var{major} and @var{minor} version -numbers from the most recent release branch, with a @var{patchlevel} -of 50. At the time each new release branch is created, the mainline's -@var{major} and @var{minor} version numbers are updated. - -@value{GDBN}'s release branch is similar. When the branch is cut, the -@var{patchlevel} is changed from 50 to 90. As draft releases are -drawn from the branch, the @var{patchlevel} is incremented. Once the -first release (@var{major}.@var{minor}) has been made, the -@var{patchlevel} is set to 0 and updates have an incremented -@var{patchlevel}. - -For snapshots, and @sc{cvs} check outs, it is also possible to -identify the @sc{cvs} origin: - -@table @asis -@item @var{major}.@var{minor}.50.@var{YYYY}@var{MM}@var{DD} -drawn from the @sc{head} of mainline @sc{cvs} (e.g., 6.1.50.20020302) -@item @var{major}.@var{minor}.90.@var{YYYY}@var{MM}@var{DD} -@itemx @var{major}.@var{minor}.91.@var{YYYY}@var{MM}@var{DD} @dots{} -drawn from a release branch prior to the release (e.g., -6.1.90.20020304) -@item @var{major}.@var{minor}.0.@var{YYYY}@var{MM}@var{DD} -@itemx @var{major}.@var{minor}.1.@var{YYYY}@var{MM}@var{DD} @dots{} -drawn from a release branch after the release (e.g., 6.2.0.20020308) -@end table - -If the previous @value{GDBN} version is 6.1 and the current version is -6.2, then, substituting 6 for @var{major} and 1 or 2 for @var{minor}, -here's an illustration of a typical sequence: - -@smallexample - <HEAD> - | -6.1.50.20020302-cvs - | - +--------------------------. - | <gdb_6_2-branch> - | | -6.2.50.20020303-cvs 6.1.90 (draft #1) - | | -6.2.50.20020304-cvs 6.1.90.20020304-cvs - | | -6.2.50.20020305-cvs 6.1.91 (draft #2) - | | -6.2.50.20020306-cvs 6.1.91.20020306-cvs - | | -6.2.50.20020307-cvs 6.2 (release) - | | -6.2.50.20020308-cvs 6.2.0.20020308-cvs - | | -6.2.50.20020309-cvs 6.2.1 (update) - | | -6.2.50.20020310-cvs <branch closed> - | -6.2.50.20020311-cvs - | - +--------------------------. - | <gdb_6_3-branch> - | | -6.3.50.20020312-cvs 6.2.90 (draft #1) - | | -@end smallexample - -@section Release Branches -@cindex Release Branches - -@value{GDBN} draws a release series (6.2, 6.2.1, @dots{}) from a -single release branch, and identifies that branch using the @sc{cvs} -branch tags: - -@smallexample -gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-branchpoint -gdb_@var{major}_@var{minor}-branch -gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-release -@end smallexample - -@emph{Pragmatics: To help identify the date at which a branch or -release is made, both the branchpoint and release tags include the -date that they are cut (@var{YYYY}@var{MM}@var{DD}) in the tag. The -branch tag, denoting the head of the branch, does not need this.} - -@section Vendor Branches -@cindex vendor branches - -To avoid version conflicts, vendors are expected to modify the file -@file{gdb/version.in} to include a vendor unique alphabetic identifier -(an official @value{GDBN} release never uses alphabetic characters in -its version identifier). E.g., @samp{6.2widgit2}, or @samp{6.2 (Widgit -Inc Patch 2)}. - -@section Experimental Branches -@cindex experimental branches - -@subsection Guidelines - -@value{GDBN} permits the creation of branches, cut from the @sc{cvs} -repository, for experimental development. Branches make it possible -for developers to share preliminary work, and maintainers to examine -significant new developments. - -The following are a set of guidelines for creating such branches: - -@table @emph - -@item a branch has an owner -The owner can set further policy for a branch, but may not change the -ground rules. In particular, they can set a policy for commits (be it -adding more reviewers or deciding who can commit). - -@item all commits are posted -All changes committed to a branch shall also be posted to -@email{gdb-patches@@sourceware.org, the @value{GDBN} patches -mailing list}. While commentary on such changes are encouraged, people -should remember that the changes only apply to a branch. - -@item all commits are covered by an assignment -This ensures that all changes belong to the Free Software Foundation, -and avoids the possibility that the branch may become contaminated. - -@item a branch is focused -A focused branch has a single objective or goal, and does not contain -unnecessary or irrelevant changes. Cleanups, where identified, being -be pushed into the mainline as soon as possible. - -@item a branch tracks mainline -This keeps the level of divergence under control. It also keeps the -pressure on developers to push cleanups and other stuff into the -mainline. - -@item a branch shall contain the entire @value{GDBN} module -The @value{GDBN} module @code{gdb} should be specified when creating a -branch (branches of individual files should be avoided). @xref{Tags}. - -@item a branch shall be branded using @file{version.in} -The file @file{gdb/version.in} shall be modified so that it identifies -the branch @var{owner} and branch @var{name}, e.g., -@samp{6.2.50.20030303_owner_name} or @samp{6.2 (Owner Name)}. - -@end table - -@subsection Tags -@anchor{Tags} - -To simplify the identification of @value{GDBN} branches, the following -branch tagging convention is strongly recommended: - -@table @code - -@item @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint -@itemx @var{owner}_@var{name}-@var{YYYYMMDD}-branch -The branch point and corresponding branch tag. @var{YYYYMMDD} is the -date that the branch was created. A branch is created using the -sequence: @anchor{experimental branch tags} -@smallexample -cvs rtag @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint gdb -cvs rtag -b -r @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint \ - @var{owner}_@var{name}-@var{YYYYMMDD}-branch gdb -@end smallexample - -@item @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint -The tagged point, on the mainline, that was used when merging the branch -on @var{yyyymmdd}. To merge in all changes since the branch was cut, -use a command sequence like: -@smallexample -cvs rtag @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint gdb -cvs update \ - -j@var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint - -j@var{owner}_@var{name}-@var{yyyymmdd}-mergepoint -@end smallexample -@noindent -Similar sequences can be used to just merge in changes since the last -merge. - -@end table - -@noindent -For further information on @sc{cvs}, see -@uref{http://www.gnu.org/software/cvs/, Concurrent Versions System}. - -@node Start of New Year Procedure -@chapter Start of New Year Procedure -@cindex new year procedure - -At the start of each new year, the following actions should be performed: - -@itemize @bullet -@item -Rotate the ChangeLog file - -The current @file{ChangeLog} file should be renamed into -@file{ChangeLog-YYYY} where YYYY is the year that has just passed. -A new @file{ChangeLog} file should be created, and its contents should -contain a reference to the previous ChangeLog. The following should -also be preserved at the end of the new ChangeLog, in order to provide -the appropriate settings when editing this file with Emacs: -@smallexample -Local Variables: -mode: change-log -left-margin: 8 -fill-column: 74 -version-control: never -coding: utf-8 -End: -@end smallexample - -@item -Add an entry for the newly created ChangeLog file (@file{ChangeLog-YYYY}) -in @file{gdb/config/djgpp/fnchange.lst}. - -@item -Update the copyright year in the startup message - -Update the copyright year in: -@itemize @bullet - @item - file @file{top.c}, function @code{print_gdb_version} - @item - file @file{gdbserver/server.c}, function @code{gdbserver_version} - @item - file @file{gdbserver/gdbreplay.c}, function @code{gdbreplay_version} -@end itemize - -@item -Run the @file{copyright.py} Python script to add the new year in the copyright -notices of most source files. This script has been tested with Python -2.6 and 2.7. - -@end itemize - -@node Releasing GDB - -@chapter Releasing @value{GDBN} -@cindex making a new release of gdb - -@section Branch Commit Policy - -The branch commit policy is pretty slack. @value{GDBN} releases 5.0, -5.1 and 5.2 all used the below: - -@itemize @bullet -@item -The @file{gdb/MAINTAINERS} file still holds. -@item -Don't fix something on the branch unless/until it is also fixed in the -trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS} -file is better than committing a hack. -@item -When considering a patch for the branch, suggested criteria include: -Does it fix a build? Does it fix the sequence @kbd{break main; run} -when debugging a static binary? -@item -The further a change is from the core of @value{GDBN}, the less likely -the change will worry anyone (e.g., target specific code). -@item -Only post a proposal to change the core of @value{GDBN} after you've -sent individual bribes to all the people listed in the -@file{MAINTAINERS} file @t{;-)} -@end itemize - -@emph{Pragmatics: Provided updates are restricted to non-core -functionality there is little chance that a broken change will be fatal. -This means that changes such as adding a new architectures or (within -reason) support for a new host are considered acceptable.} - - -@section Obsoleting code - -Before anything else, poke the other developers (and around the source -code) to see if there is anything that can be removed from @value{GDBN} -(an old target, an unused file). - -Obsolete code is identified by adding an @code{OBSOLETE} prefix to every -line. Doing this means that it is easy to identify something that has -been obsoleted when greping through the sources. - -The process is done in stages --- this is mainly to ensure that the -wider @value{GDBN} community has a reasonable opportunity to respond. -Remember, everything on the Internet takes a week. - -@enumerate -@item -Post the proposal on @email{gdb@@sourceware.org, the GDB mailing -list} Creating a bug report to track the task's state, is also highly -recommended. -@item -Wait a week or so. -@item -Post the proposal on @email{gdb-announce@@sourceware.org, the GDB -Announcement mailing list}. -@item -Wait a week or so. -@item -Go through and edit all relevant files and lines so that they are -prefixed with the word @code{OBSOLETE}. -@item -Wait until the next GDB version, containing this obsolete code, has been -released. -@item -Remove the obsolete code. -@end enumerate - -@noindent -@emph{Maintainer note: While removing old code is regrettable it is -hopefully better for @value{GDBN}'s long term development. Firstly it -helps the developers by removing code that is either no longer relevant -or simply wrong. Secondly since it removes any history associated with -the file (effectively clearing the slate) the developer has a much freer -hand when it comes to fixing broken files.} - - - -@section Before the Branch - -The most important objective at this stage is to find and fix simple -changes that become a pain to track once the branch is created. For -instance, configuration problems that stop @value{GDBN} from even -building. If you can't get the problem fixed, document it in the -@file{gdb/PROBLEMS} file. - -@subheading Prompt for @file{gdb/NEWS} - -People always forget. Send a post reminding them but also if you know -something interesting happened add it yourself. The @code{schedule} -script will mention this in its e-mail. - -@subheading Review @file{gdb/README} - -Grab one of the nightly snapshots and then walk through the -@file{gdb/README} looking for anything that can be improved. The -@code{schedule} script will mention this in its e-mail. - -@subheading Refresh any imported files. - -A number of files are taken from external repositories. They include: - -@itemize @bullet -@item -@file{texinfo/texinfo.tex} -@item -@file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS} -file) -@item -@file{etc/standards.texi}, @file{etc/make-stds.texi} -@end itemize - -@subheading Check the ARI - -@uref{http://sourceware.org/gdb/ari,,A.R.I.} is an @code{awk} script -(Awk Regression Index ;-) that checks for a number of errors and coding -conventions. The checks include things like using @code{malloc} instead -of @code{xmalloc} and file naming problems. There shouldn't be any -regressions. - -@subsection Review the bug data base - -Close anything obviously fixed. - -@subsection Check all cross targets build - -The targets are listed in @file{gdb/MAINTAINERS}. - - -@section Cut the Branch - -@subheading Create the branch - -@smallexample -$ u=5.1 -$ v=5.2 -$ V=`echo $v | sed 's/\./_/g'` -$ D=`date -u +%Y-%m-%d` -$ echo $u $V $D -5.1 5_2 2002-03-03 -$ echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \ --D $D-gmt gdb_$V-$D-branchpoint insight -cvs -f -d :ext:sourceware.org:/cvs/src rtag --D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight -$ ^echo ^^ -... -$ echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \ --b -r gdb_$V-$D-branchpoint gdb_$V-branch insight -cvs -f -d :ext:sourceware.org:/cvs/src rtag \ --b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight -$ ^echo ^^ -... -$ -@end smallexample - -@itemize @bullet -@item -By using @kbd{-D YYYY-MM-DD-gmt}, the branch is forced to an exact -date/time. -@item -The trunk is first tagged so that the branch point can easily be found. -@item -Insight, which includes @value{GDBN}, is tagged at the same time. -@item -@file{version.in} gets bumped to avoid version number conflicts. -@item -The reading of @file{.cvsrc} is disabled using @file{-f}. -@end itemize - -@subheading Update @file{version.in} - -@smallexample -$ u=5.1 -$ v=5.2 -$ V=`echo $v | sed 's/\./_/g'` -$ echo $u $v$V -5.1 5_2 -$ cd /tmp -$ echo cvs -f -d :ext:sourceware.org:/cvs/src co \ --r gdb_$V-branch src/gdb/version.in -cvs -f -d :ext:sourceware.org:/cvs/src co - -r gdb_5_2-branch src/gdb/version.in -$ ^echo ^^ -U src/gdb/version.in -$ cd src/gdb -$ echo $u.90-0000-00-00-cvs > version.in -$ cat version.in -5.1.90-0000-00-00-cvs -$ cvs -f commit version.in -@end smallexample - -@itemize @bullet -@item -@file{0000-00-00} is used as a date to pump prime the version.in update -mechanism. -@item -@file{.90} and the previous branch version are used as fairly arbitrary -initial branch version number. -@end itemize - - -@subheading Update the web and news pages - -Something? - -@subheading Tweak cron to track the new branch - -The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table. -This file needs to be updated so that: - -@itemize @bullet -@item -A daily timestamp is added to the file @file{version.in}. -@item -The new branch is included in the snapshot process. -@end itemize - -@noindent -See the file @file{gdbadmin/cron/README} for how to install the updated -cron table. - -The file @file{gdbadmin/ss/README} should also be reviewed to reflect -any changes. That file is copied to both the branch/ and current/ -snapshot directories. - - -@subheading Update the NEWS and README files - -The @file{NEWS} file needs to be updated so that on the branch it refers -to @emph{changes in the current release} while on the trunk it also -refers to @emph{changes since the current release}. - -The @file{README} file needs to be updated so that it refers to the -current release. - -@subheading Post the branch info - -Send an announcement to the mailing lists: - -@itemize @bullet -@item -@email{gdb-announce@@sourceware.org, GDB Announcement mailing list} -@item -@email{gdb@@sourceware.org, GDB Discussion mailing list} and -@email{gdb-testers@@sourceware.org, GDB Testers mailing list} -@end itemize - -@emph{Pragmatics: The branch creation is sent to the announce list to -ensure that people people not subscribed to the higher volume discussion -list are alerted.} - -The announcement should include: - -@itemize @bullet -@item -The branch tag. -@item -How to check out the branch using CVS. -@item -The date/number of weeks until the release. -@item -The branch commit policy still holds. -@end itemize - -@section Stabilize the branch - -Something goes here. - -@section Create a Release - -The process of creating and then making available a release is broken -down into a number of stages. The first part addresses the technical -process of creating a releasable tar ball. The later stages address the -process of releasing that tar ball. - -When making a release candidate just the first section is needed. - -@subsection Create a release candidate - -The objective at this stage is to create a set of tar balls that can be -made available as a formal release (or as a less formal release -candidate). - -@subsubheading Freeze the branch - -Send out an e-mail notifying everyone that the branch is frozen to -@email{gdb-patches@@sourceware.org}. - -@subsubheading Establish a few defaults. - -@smallexample -$ b=gdb_5_2-branch -$ v=5.2 -$ t=/sourceware/snapshot-tmp/gdbadmin-tmp -$ echo $t/$b/$v -/sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2 -$ mkdir -p $t/$b/$v -$ cd $t/$b/$v -$ pwd -/sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2 -$ which autoconf -/home/gdbadmin/bin/autoconf -$ -@end smallexample - -@noindent -Notes: - -@itemize @bullet -@item -Check the @code{autoconf} version carefully. You want to be using the -version documented in the toplevel @file{README-maintainer-mode} file. -It is very unlikely that the version of @code{autoconf} installed in -system directories (e.g., @file{/usr/bin/autoconf}) is correct. -@end itemize - -@subsubheading Check out the relevant modules: - -@smallexample -$ for m in gdb insight -do -( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m ) -done -$ -@end smallexample - -@noindent -Note: - -@itemize @bullet -@item -The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't -any confusion between what is written here and what your local -@code{cvs} really does. -@end itemize - -@subsubheading Update relevant files. - -@table @file - -@item gdb/NEWS - -Major releases get their comments added as part of the mainline. Minor -releases should probably mention any significant bugs that were fixed. - -Don't forget to include the @file{ChangeLog} entry. - -@smallexample -$ emacs gdb/src/gdb/NEWS -... -c-x 4 a -... -c-x c-s c-x c-c -$ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS -$ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog -@end smallexample - -@item gdb/README - -You'll need to update: - -@itemize @bullet -@item -The version. -@item -The update date. -@item -Who did it. -@end itemize - -@smallexample -$ emacs gdb/src/gdb/README -... -c-x 4 a -... -c-x c-s c-x c-c -$ cp gdb/src/gdb/README insight/src/gdb/README -$ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog -@end smallexample - -@emph{Maintainer note: Hopefully the @file{README} file was reviewed -before the initial branch was cut so just a simple substitute is needed -to get it updated.} - -@emph{Maintainer note: Other projects generate @file{README} and -@file{INSTALL} from the core documentation. This might be worth -pursuing.} - -@item gdb/version.in - -@smallexample -$ echo $v > gdb/src/gdb/version.in -$ cat gdb/src/gdb/version.in -5.2 -$ emacs gdb/src/gdb/version.in -... -c-x 4 a -... Bump to version ... -c-x c-s c-x c-c -$ cp gdb/src/gdb/version.in insight/src/gdb/version.in -$ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog -@end smallexample - -@end table - -@subsubheading Do the dirty work - -This is identical to the process used to create the daily snapshot. - -@smallexample -$ for m in gdb insight -do -( cd $m/src && gmake -f src-release $m.tar ) -done -@end smallexample - -If the top level source directory does not have @file{src-release} -(@value{GDBN} version 5.3.1 or earlier), try these commands instead: - -@smallexample -$ for m in gdb insight -do -( cd $m/src && gmake -f Makefile.in $m.tar ) -done -@end smallexample - -@subsubheading Check the source files - -You're looking for files that have mysteriously disappeared. -@kbd{distclean} has the habit of deleting files it shouldn't. Watch out -for the @file{version.in} update @kbd{cronjob}. - -@smallexample -$ ( cd gdb/src && cvs -f -q -n update ) -M djunpack.bat -? gdb-5.1.91.tar -? proto-toplev -@dots{} lots of generated files @dots{} -M gdb/ChangeLog -M gdb/NEWS -M gdb/README -M gdb/version.in -@dots{} lots of generated files @dots{} -$ -@end smallexample - -@noindent -@emph{Don't worry about the @file{gdb.info-??} or -@file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1} -was also generated only something strange with CVS means that they -didn't get suppressed). Fixing it would be nice though.} - -@subsubheading Create compressed versions of the release - -@smallexample -$ cp */src/*.tar . -$ cp */src/*.bz2 . -$ ls -F -gdb/ gdb-5.2.tar insight/ insight-5.2.tar -$ for m in gdb insight -do -bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2 -gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz -done -$ -@end smallexample - -@noindent -Note: - -@itemize @bullet -@item -A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since, -in that mode, @code{gzip} does not know the name of the file and, hence, -can not include it in the compressed file. This is also why the release -process runs @code{tar} and @code{bzip2} as separate passes. -@end itemize - -@subsection Sanity check the tar ball - -Pick a popular machine (Solaris/PPC?) and try the build on that. - -@smallexample -$ bunzip2 < gdb-5.2.tar.bz2 | tar xpf - -$ cd gdb-5.2 -$ ./configure -$ make -@dots{} -$ ./gdb/gdb ./gdb/gdb -GNU gdb 5.2 -@dots{} -(gdb) b main -Breakpoint 1 at 0x80732bc: file main.c, line 734. -(gdb) run -Starting program: /tmp/gdb-5.2/gdb/gdb - -Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734 -734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL); -(gdb) print args -$1 = @{argc = 136426532, argv = 0x821b7f0@} -(gdb) -@end smallexample - -@subsection Make a release candidate available - -If this is a release candidate then the only remaining steps are: - -@enumerate -@item -Commit @file{version.in} and @file{ChangeLog} -@item -Tweak @file{version.in} (and @file{ChangeLog} to read -@var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update -process can restart. -@item -Make the release candidate available in -@uref{ftp://sourceware.org/pub/gdb/snapshots/branch} -@item -Notify the relevant mailing lists ( @email{gdb@@sourceware.org} and -@email{gdb-testers@@sourceware.org} that the candidate is available. -@end enumerate - -@subsection Make a formal release available - -(And you thought all that was required was to post an e-mail.) - -@subsubheading Install on sware - -Copy the new files to both the release and the old release directory: - -@smallexample -$ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/ -$ cp *.bz2 *.gz ~ftp/pub/gdb/releases -@end smallexample - -@noindent -Clean up the releases directory so that only the most recent releases -are available (e.g.@: keep 5.2 and 5.2.1 but remove 5.1): - -@smallexample -$ cd ~ftp/pub/gdb/releases -$ rm @dots{} -@end smallexample - -@noindent -Update the file @file{README} and @file{.message} in the releases -directory: - -@smallexample -$ vi README -@dots{} -$ rm -f .message -$ ln README .message -@end smallexample - -@subsubheading Update the web pages. - -@table @file - -@item htdocs/download/ANNOUNCEMENT -This file, which is posted as the official announcement, includes: -@itemize @bullet -@item -General announcement. -@item -News. If making an @var{M}.@var{N}.1 release, retain the news from -earlier @var{M}.@var{N} release. -@item -Errata. -@end itemize - -@item htdocs/index.html -@itemx htdocs/news/index.html -@itemx htdocs/download/index.html -These files include: -@itemize @bullet -@item -Announcement of the most recent release. -@item -News entry (remember to update both the top level and the news directory). -@end itemize -These pages also need to be regenerate using @code{index.sh}. - -@item download/onlinedocs/ -You need to find the magic command that is used to generate the online -docs from the @file{.tar.bz2}. The best way is to look in the output -from one of the nightly @code{cron} jobs and then just edit accordingly. -Something like: - -@smallexample -$ ~/ss/update-web-docs \ - ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \ - $PWD/www \ - /www/sourceware/htdocs/gdb/download/onlinedocs \ - gdb -@end smallexample - -@item download/ari/ -Just like the online documentation. Something like: - -@smallexample -$ /bin/sh ~/ss/update-web-ari \ - ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \ - $PWD/www \ - /www/sourceware/htdocs/gdb/download/ari \ - gdb -@end smallexample - -@end table - -@subsubheading Shadow the pages onto gnu - -Something goes here. - - -@subsubheading Install the @value{GDBN} tar ball on GNU - -At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in -@file{~ftp/gnu/gdb}. - -@subsubheading Make the @file{ANNOUNCEMENT} - -Post the @file{ANNOUNCEMENT} file you created above to: - -@itemize @bullet -@item -@email{gdb-announce@@sourceware.org, GDB Announcement mailing list} -@item -@email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a -day or so to let things get out) -@item -@email{bug-gdb@@gnu.org, GDB Bug Report mailing list} -@end itemize - -@subsection Cleanup - -The release is out but you're still not finished. - -@subsubheading Commit outstanding changes - -In particular you'll need to commit any changes to: - -@itemize @bullet -@item -@file{gdb/ChangeLog} -@item -@file{gdb/version.in} -@item -@file{gdb/NEWS} -@item -@file{gdb/README} -@end itemize - -@subsubheading Tag the release - -Something like: - -@smallexample -$ d=`date -u +%Y-%m-%d` -$ echo $d -2002-01-24 -$ ( cd insight/src/gdb && cvs -f -q update ) -$ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release ) -@end smallexample - -Insight is used since that contains more of the release than -@value{GDBN}. - -@subsubheading Mention the release on the trunk - -Just put something in the @file{ChangeLog} so that the trunk also -indicates when the release was made. - -@subsubheading Restart @file{gdb/version.in} - -If @file{gdb/version.in} does not contain an ISO date such as -@kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having -committed all the release changes it can be set to -@file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_} -is important - it affects the snapshot process). - -Don't forget the @file{ChangeLog}. - -@subsubheading Merge into trunk - -The files committed to the branch may also need changes merged into the -trunk. - -@subsubheading Revise the release schedule - -Post a revised release schedule to @email{gdb@@sourceware.org, GDB -Discussion List} with an updated announcement. The schedule can be -generated by running: - -@smallexample -$ ~/ss/schedule `date +%s` schedule -@end smallexample - -@noindent -The first parameter is approximate date/time in seconds (from the epoch) -of the most recent release. - -Also update the schedule @code{cronjob}. - -@section Post release - -Remove any @code{OBSOLETE} code. - -@node Testsuite - -@chapter Testsuite -@cindex test suite - -The testsuite is an important component of the @value{GDBN} package. -While it is always worthwhile to encourage user testing, in practice -this is rarely sufficient; users typically use only a small subset of -the available commands, and it has proven all too common for a change -to cause a significant regression that went unnoticed for some time. - -The @value{GDBN} testsuite uses the DejaGNU testing framework. The -tests themselves are calls to various @code{Tcl} procs; the framework -runs all the procs and summarizes the passes and fails. - -@section Using the Testsuite - -@cindex running the test suite -To run the testsuite, simply go to the @value{GDBN} object directory (or to the -testsuite's objdir) and type @code{make check}. This just sets up some -environment variables and invokes DejaGNU's @code{runtest} script. While -the testsuite is running, you'll get mentions of which test file is in use, -and a mention of any unexpected passes or fails. When the testsuite is -finished, you'll get a summary that looks like this: - -@smallexample - === gdb Summary === - -# of expected passes 6016 -# of unexpected failures 58 -# of unexpected successes 5 -# of expected failures 183 -# of unresolved testcases 3 -# of untested testcases 5 -@end smallexample - -To run a specific test script, type: -@example -make check RUNTESTFLAGS='@var{tests}' -@end example -where @var{tests} is a list of test script file names, separated by -spaces. - -If you use GNU make, you can use its @option{-j} option to run the -testsuite in parallel. This can greatly reduce the amount of time it -takes for the testsuite to run. In this case, if you set -@code{RUNTESTFLAGS} then, by default, the tests will be run serially -even under @option{-j}. You can override this and force a parallel run -by setting the @code{make} variable @code{FORCE_PARALLEL} to any -non-empty value. Note that the parallel @kbd{make check} assumes -that you want to run the entire testsuite, so it is not compatible -with some dejagnu options, like @option{--directory}. - -The ideal test run consists of expected passes only; however, reality -conspires to keep us from this ideal. Unexpected failures indicate -real problems, whether in @value{GDBN} or in the testsuite. Expected -failures are still failures, but ones which have been decided are too -hard to deal with at the time; for instance, a test case might work -everywhere except on AIX, and there is no prospect of the AIX case -being fixed in the near future. Expected failures should not be added -lightly, since you may be masking serious bugs in @value{GDBN}. -Unexpected successes are expected fails that are passing for some -reason, while unresolved and untested cases often indicate some minor -catastrophe, such as the compiler being unable to deal with a test -program. - -When making any significant change to @value{GDBN}, you should run the -testsuite before and after the change, to confirm that there are no -regressions. Note that truly complete testing would require that you -run the testsuite with all supported configurations and a variety of -compilers; however this is more than really necessary. In many cases -testing with a single configuration is sufficient. Other useful -options are to test one big-endian (Sparc) and one little-endian (x86) -host, a cross config with a builtin simulator (powerpc-eabi, -mips-elf), or a 64-bit host (Alpha). - -If you add new functionality to @value{GDBN}, please consider adding -tests for it as well; this way future @value{GDBN} hackers can detect -and fix their changes that break the functionality you added. -Similarly, if you fix a bug that was not previously reported as a test -failure, please add a test case for it. Some cases are extremely -difficult to test, such as code that handles host OS failures or bugs -in particular versions of compilers, and it's OK not to try to write -tests for all of those. - -DejaGNU supports separate build, host, and target machines. However, -some @value{GDBN} test scripts do not work if the build machine and -the host machine are not the same. In such an environment, these scripts -will give a result of ``UNRESOLVED'', like this: - -@smallexample -UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host. -@end smallexample - -@section Testsuite Parameters - -Several variables exist to modify the behavior of the testsuite. - -@itemize @bullet - -@item @code{TRANSCRIPT} - -Sometimes it is convenient to get a transcript of the commands which -the testsuite sends to @value{GDBN}. For example, if @value{GDBN} -crashes during testing, a transcript can be used to more easily -reconstruct the failure when running @value{GDBN} under @value{GDBN}. - -You can instruct the @value{GDBN} testsuite to write transcripts by -setting the DejaGNU variable @code{TRANSCRIPT} (to any value) -before invoking @code{runtest} or @kbd{make check}. The transcripts -will be written into DejaGNU's output directory. One transcript will -be made for each invocation of @value{GDBN}; they will be named -@file{transcript.@var{n}}, where @var{n} is an integer. The first -line of the transcript file will show how @value{GDBN} was invoked; -each subsequent line is a command sent as input to @value{GDBN}. - -@smallexample -make check RUNTESTFLAGS=TRANSCRIPT=y -@end smallexample - -Note that the transcript is not always complete. In particular, tests -of completion can yield partial command lines. - -@item @code{GDB} - -Sometimes one wishes to test a different @value{GDBN} than the one in the build -directory. For example, one may wish to run the testsuite on -@file{/usr/bin/gdb}. - -@smallexample -make check RUNTESTFLAGS=GDB=/usr/bin/gdb -@end smallexample - -@item @code{GDBSERVER} - -When testing a different @value{GDBN}, it is often useful to also test a -different gdbserver. - -@smallexample -make check RUNTESTFLAGS="GDB=/usr/bin/gdb GDBSERVER=/usr/bin/gdbserver" -@end smallexample - -@item @code{INTERNAL_GDBFLAGS} - -When running the testsuite normally one doesn't want whatever is in -@file{~/.gdbinit} to interfere with the tests, therefore the test harness -passes @option{-nx} to @value{GDBN}. One also doesn't want any windowed -version of @value{GDBN}, e.g., @samp{gdb -tui}, to run. -This is achieved via @code{INTERNAL_GDBFLAGS}. - -@smallexample -set INTERNAL_GDBFLAGS "-nw -nx" -@end smallexample - -This is all well and good, except when testing an installed @value{GDBN} -that has been configured with @option{--with-system-gdbinit}. Here one -does not want @file{~/.gdbinit} loaded but one may want the system -@file{.gdbinit} file loaded. This can be achieved by pointing @code{$HOME} -at a directory without a @file{.gdbinit} and by overriding -@code{INTERNAL_GDBFLAGS} and removing @option{-nx}. - -@smallexample -cd testsuite -HOME=`pwd` runtest \ - GDB=/usr/bin/gdb \ - GDBSERVER=/usr/bin/gdbserver \ - INTERNAL_GDBFLAGS=-nw -@end smallexample - -@end itemize - -There are two ways to run the testsuite and pass additional parameters -to DejaGnu. The first is with @kbd{make check} and specifying the -makefile variable @samp{RUNTESTFLAGS}. - -@smallexample -make check RUNTESTFLAGS=TRANSCRIPT=y -@end smallexample - -The second is to cd to the @file{testsuite} directory and invoke the DejaGnu -@command{runtest} command directly. - -@smallexample -cd testsuite -make site.exp -runtest TRANSCRIPT=y -@end smallexample - -@section Testsuite Configuration -@cindex Testsuite Configuration - -It is possible to adjust the behavior of the testsuite by defining -the global variables listed below, either in a @file{site.exp} file, -or in a board file. - -@itemize @bullet - -@item @code{gdb_test_timeout} - -Defining this variable changes the default timeout duration used during -communication with @value{GDBN}. More specifically, the global variable -used during testing is @code{timeout}, but this variable gets reset to -@code{gdb_test_timeout} at the beginning of each testcase, making sure -that any local change to @code{timeout} in a testcase does not affect -subsequent testcases. - -This global variable comes in handy when the debugger is slower than -normal due to the testing environment, triggering unexpected @code{TIMEOUT} -test failures. Examples include when testing on a remote machine, or -against a system where communications are slow. - -If not specifically defined, this variable gets automatically defined -to the same value as @code{timeout} during the testsuite initialization. -The default value of the timeout is defined in the file -@file{gdb/testsuite/config/unix.exp} that is part of the @value{GDBN} -test suite@footnote{If you are using a board file, it could override -the test-suite default; search the board file for "timeout".}. - -@end itemize - -@section Testsuite Organization - -@cindex test suite organization -The testsuite is entirely contained in @file{gdb/testsuite}. While the -testsuite includes some makefiles and configury, these are very minimal, -and used for little besides cleaning up, since the tests themselves -handle the compilation of the programs that @value{GDBN} will run. The file -@file{testsuite/lib/gdb.exp} contains common utility procs useful for -all @value{GDBN} tests, while the directory @file{testsuite/config} contains -configuration-specific files, typically used for special-purpose -definitions of procs like @code{gdb_load} and @code{gdb_start}. - -The tests themselves are to be found in @file{testsuite/gdb.*} and -subdirectories of those. The names of the test files must always end -with @file{.exp}. DejaGNU collects the test files by wildcarding -in the test directories, so both subdirectories and individual files -get chosen and run in alphabetical order. - -The following table lists the main types of subdirectories and what they -are for. Since DejaGNU finds test files no matter where they are -located, and since each test file sets up its own compilation and -execution environment, this organization is simply for convenience and -intelligibility. - -@table @file -@item gdb.base -This is the base testsuite. The tests in it should apply to all -configurations of @value{GDBN} (but generic native-only tests may live here). -The test programs should be in the subset of C that is valid K&R, -ANSI/ISO, and C@t{++} (@code{#ifdef}s are allowed if necessary, for instance -for prototypes). - -@item gdb.@var{lang} -Language-specific tests for any language @var{lang} besides C. Examples are -@file{gdb.cp} and @file{gdb.java}. - -@item gdb.@var{platform} -Non-portable tests. The tests are specific to a specific configuration -(host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for -HP-UX. - -@item gdb.@var{compiler} -Tests specific to a particular compiler. As of this writing (June -1999), there aren't currently any groups of tests in this category that -couldn't just as sensibly be made platform-specific, but one could -imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC -extensions. - -@item gdb.@var{subsystem} -Tests that exercise a specific @value{GDBN} subsystem in more depth. For -instance, @file{gdb.disasm} exercises various disassemblers, while -@file{gdb.stabs} tests pathways through the stabs symbol reader. -@end table - -@section Writing Tests -@cindex writing tests - -In many areas, the @value{GDBN} tests are already quite comprehensive; you -should be able to copy existing tests to handle new cases. - -You should try to use @code{gdb_test} whenever possible, since it -includes cases to handle all the unexpected errors that might happen. -However, it doesn't cost anything to add new test procedures; for -instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that -calls @code{gdb_test} multiple times. - -Only use @code{send_gdb} and @code{gdb_expect} when absolutely -necessary. Even if @value{GDBN} has several valid responses to -a command, you can use @code{gdb_test_multiple}. Like @code{gdb_test}, -@code{gdb_test_multiple} recognizes internal errors and unexpected -prompts. - -Do not write tests which expect a literal tab character from @value{GDBN}. -On some operating systems (e.g.@: OpenBSD) the TTY layer expands tabs to -spaces, so by the time @value{GDBN}'s output reaches expect the tab is gone. - -The source language programs do @emph{not} need to be in a consistent -style. Since @value{GDBN} is used to debug programs written in many different -styles, it's worth having a mix of styles in the testsuite; for -instance, some @value{GDBN} bugs involving the display of source lines would -never manifest themselves if the programs used GNU coding style -uniformly. - -Some testcase results need more detailed explanation: - -@table @code -@item KFAIL -Known problem of @value{GDBN} itself. You must specify the @value{GDBN} bug -report number like in these sample tests: -@smallexample -kfail "gdb/13392" "continue to marker 2" -@end smallexample -or -@smallexample -setup_kfail gdb/13392 "*-*-*" -kfail "continue to marker 2" -@end smallexample - -@item XFAIL -Known problem of environment. This typically includes @value{NGCC} but it -includes also many other system components which cannot be fixed in the -@value{GDBN} project. Sample test with sanity check not knowing the specific -cause of the problem: -@smallexample -# On x86_64 it is commonly about 4MB. -if @{$stub_size > 25000000@} @{ - xfail "stub size $stub_size is too large" - return -@} -@end smallexample - -You should provide bug report number for the failing component of the -environment, if such bug report is available: -@smallexample -if @{[test_compiler_info @{gcc-[0-3]-*@}] - || [test_compiler_info @{gcc-4-[0-5]-*@}]@} @{ - setup_xfail "gcc/46955" *-*-* -@} -gdb_test "python print ttype.template_argument(2)" "&C::c" -@end smallexample -@end table - -@section Board settings -In @value{GDBN} testsuite, the tests can be configured or customized in the board -file by means of @dfn{Board Settings}. Each setting should be consulted by -test cases that depend on the corresponding feature. - -Here are the supported board settings: - -@table @code - -@item gdb,cannot_call_functions -The board does not support inferior call, that is, invoking inferior functions -in @value{GDBN}. -@item gdb,can_reverse -The board supports reverse execution. -@item gdb,no_hardware_watchpoints -The board does not support hardware watchpoints. -@item gdb,nofileio -@value{GDBN} is unable to intercept target file operations in remote and perform -them on the host. -@item gdb,noinferiorio -The board is unable to provide I/O capability to the inferior. -@c @item gdb,noresults -@c NEED DOCUMENT. -@item gdb,nosignals -The board does not support signals. -@item gdb,skip_huge_test -Skip time-consuming tests on the board with slow connection. -@item gdb,skip_float_tests -Skip tests related to float points on target board. -@item gdb,use_precord -The board supports process record. -@item gdb_server_prog -The location of GDBserver. If GDBserver somewhere other than its default -location is used in test, specify the location of GDBserver in this variable. -The location is a file name of GDBserver that can be either absolute or -relative to testsuite subdirectory in build directory. -@item in_proc_agent -The location of in-process agent. If in-process agent other than its default -location is used in test, specify the location of in-process agent in -this variable. The location is a file name of in-process agent that can be -either absolute or relative to testsuite subdirectory in build directory. -@item noargs -@value{GDBN} does not support argument passing for inferior. -@item no_long_long -The board does not support type @code{long long}. -@c @item use_cygmon -@c NEED DOCUMENT. -@item use_gdb_stub -The tests are running with gdb stub. -@end table - -@node Hints - -@chapter Hints - -Check the @file{README} file, it often has useful information that does not -appear anywhere else in the directory. - -@menu -* Getting Started:: Getting started working on @value{GDBN} -* Debugging GDB:: Debugging @value{GDBN} with itself -@end menu - -@node Getting Started - -@section Getting Started - -@value{GDBN} is a large and complicated program, and if you first starting to -work on it, it can be hard to know where to start. Fortunately, if you -know how to go about it, there are ways to figure out what is going on. - -This manual, the @value{GDBN} Internals manual, has information which applies -generally to many parts of @value{GDBN}. - -Information about particular functions or data structures are located in -comments with those functions or data structures. If you run across a -function or a global variable which does not have a comment correctly -explaining what is does, this can be thought of as a bug in @value{GDBN}; feel -free to submit a bug report, with a suggested comment if you can figure -out what the comment should say. If you find a comment which is -actually wrong, be especially sure to report that. - -Comments explaining the function of macros defined in host, target, or -native dependent files can be in several places. Sometimes they are -repeated every place the macro is defined. Sometimes they are where the -macro is used. Sometimes there is a header file which supplies a -default definition of the macro, and the comment is there. This manual -also documents all the available macros. -@c (@pxref{Host Conditionals}, @pxref{Target -@c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete -@c Conditionals}) - -Start with the header files. Once you have some idea of how -@value{GDBN}'s internal symbol tables are stored (see @file{symtab.h}, -@file{gdbtypes.h}), you will find it much easier to understand the -code which uses and creates those symbol tables. - -You may wish to process the information you are getting somehow, to -enhance your understanding of it. Summarize it, translate it to another -language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use -the code to predict what a test case would do and write the test case -and verify your prediction, etc. If you are reading code and your eyes -are starting to glaze over, this is a sign you need to use a more active -approach. - -Once you have a part of @value{GDBN} to start with, you can find more -specifically the part you are looking for by stepping through each -function with the @code{next} command. Do not use @code{step} or you -will quickly get distracted; when the function you are stepping through -calls another function try only to get a big-picture understanding -(perhaps using the comment at the beginning of the function being -called) of what it does. This way you can identify which of the -functions being called by the function you are stepping through is the -one which you are interested in. You may need to examine the data -structures generated at each stage, with reference to the comments in -the header files explaining what the data structures are supposed to -look like. - -Of course, this same technique can be used if you are just reading the -code, rather than actually stepping through it. The same general -principle applies---when the code you are looking at calls something -else, just try to understand generally what the code being called does, -rather than worrying about all its details. - -@cindex command implementation -A good place to start when tracking down some particular area is with -a command which invokes that feature. Suppose you want to know how -single-stepping works. As a @value{GDBN} user, you know that the -@code{step} command invokes single-stepping. The command is invoked -via command tables (see @file{command.h}); by convention the function -which actually performs the command is formed by taking the name of -the command and adding @samp{_command}, or in the case of an -@code{info} subcommand, @samp{_info}. For example, the @code{step} -command invokes the @code{step_command} function and the @code{info -display} command invokes @code{display_info}. When this convention is -not followed, you might have to use @code{grep} or @kbd{M-x -tags-search} in emacs, or run @value{GDBN} on itself and set a -breakpoint in @code{execute_command}. - -@cindex @code{bug-gdb} mailing list -If all of the above fail, it may be appropriate to ask for information -on @code{bug-gdb}. But @emph{never} post a generic question like ``I was -wondering if anyone could give me some tips about understanding -@value{GDBN}''---if we had some magic secret we would put it in this manual. -Suggestions for improving the manual are always welcome, of course. - -@node Debugging GDB - -@section Debugging @value{GDBN} with itself -@cindex debugging @value{GDBN} - -If @value{GDBN} is limping on your machine, this is the preferred way to get it -fully functional. Be warned that in some ancient Unix systems, like -Ultrix 4.2, a program can't be running in one process while it is being -debugged in another. Rather than typing the command @kbd{@w{./gdb -./gdb}}, which works on Suns and such, you can copy @file{gdb} to -@file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}. - -When you run @value{GDBN} in the @value{GDBN} source directory, it will read -@file{gdb-gdb.gdb} file (plus possibly @file{gdb-gdb.py} file) that sets up -some simple things to make debugging gdb easier. The @code{info} command, when -executed without a subcommand in a @value{GDBN} being debugged by gdb, will pop -you back up to the top level gdb. See @file{gdb-gdb.gdb} for details. - -If you use emacs, you will probably want to do a @code{make TAGS} after -you configure your distribution; this will put the machine dependent -routines for your local machine where they will be accessed first by -@kbd{M-.} - -Also, make sure that you've either compiled @value{GDBN} with your local cc, or -have run @code{fixincludes} if you are compiling with gcc. - -@section Submitting Patches - -@cindex submitting patches -Thanks for thinking of offering your changes back to the community of -@value{GDBN} users. In general we like to get well designed enhancements. -Thanks also for checking in advance about the best way to transfer the -changes. - -The @value{GDBN} maintainers will only install ``cleanly designed'' patches. -This manual summarizes what we believe to be clean design for @value{GDBN}. - -If the maintainers don't have time to put the patch in when it arrives, -or if there is any question about a patch, it goes into a large queue -with everyone else's patches and bug reports. - -@cindex legal papers for code contributions -The legal issue is that to incorporate substantial changes requires a -copyright assignment from you and/or your employer, granting ownership -of the changes to the Free Software Foundation. You can get the -standard documents for doing this by sending mail to @code{gnu@@gnu.org} -and asking for it. We recommend that people write in "All programs -owned by the Free Software Foundation" as "NAME OF PROGRAM", so that -changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC, -etc) can be -contributed with only one piece of legalese pushed through the -bureaucracy and filed with the FSF. We can't start merging changes until -this paperwork is received by the FSF (their rules, which we follow -since we maintain it for them). - -Technically, the easiest way to receive changes is to receive each -feature as a small context diff or unidiff, suitable for @code{patch}. -Each message sent to me should include the changes to C code and -header files for a single feature, plus @file{ChangeLog} entries for -each directory where files were modified, and diffs for any changes -needed to the manuals (@file{gdb/doc/gdb.texinfo} or -@file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a -single feature, they can be split down into multiple messages. - -In this way, if we read and like the feature, we can add it to the -sources with a single patch command, do some testing, and check it in. -If you leave out the @file{ChangeLog}, we have to write one. If you leave -out the doc, we have to puzzle out what needs documenting. Etc., etc. - -The reason to send each change in a separate message is that we will not -install some of the changes. They'll be returned to you with questions -or comments. If we're doing our job correctly, the message back to you -will say what you have to fix in order to make the change acceptable. -The reason to have separate messages for separate features is so that -the acceptable changes can be installed while one or more changes are -being reworked. If multiple features are sent in a single message, we -tend to not put in the effort to sort out the acceptable changes from -the unacceptable, so none of the features get installed until all are -acceptable. - -If this sounds painful or authoritarian, well, it is. But we get a lot -of bug reports and a lot of patches, and many of them don't get -installed because we don't have the time to finish the job that the bug -reporter or the contributor could have done. Patches that arrive -complete, working, and well designed, tend to get installed on the day -they arrive. The others go into a queue and get installed as time -permits, which, since the maintainers have many demands to meet, may not -be for quite some time. - -Please send patches directly to -@email{gdb-patches@@sourceware.org, the @value{GDBN} maintainers}. - -@section Build Script - -@cindex build script - -The script @file{gdb_buildall.sh} builds @value{GDBN} with flag -@option{--enable-targets=all} set. This builds @value{GDBN} with all supported -targets activated. This helps testing @value{GDBN} when doing changes that -affect more than one architecture and is much faster than using -@file{gdb_mbuild.sh}. - -After building @value{GDBN} the script checks which architectures are -supported and then switches the current architecture to each of those to get -information about the architecture. The test results are stored in log files -in the directory the script was called from. - -@include observer.texi - -@node GNU Free Documentation License -@appendix GNU Free Documentation License -@include fdl.texi - -@node Concept Index -@unnumbered Concept Index - -@printindex cp - -@node Function and Variable Index -@unnumbered Function and Variable Index - -@printindex fn - -@bye diff --git a/contrib/gdb-7/gdb/doc/gpl.texi b/contrib/gdb-7/gdb/doc/gpl.texi deleted file mode 100644 index ca6d72d99c..0000000000 --- a/contrib/gdb-7/gdb/doc/gpl.texi +++ /dev/null @@ -1,735 +0,0 @@ -@ignore -@c Set file name and title for man page. -@setfilename gpl -@settitle GNU General Public License -@c man begin SEEALSO -gfdl(7), fsf-funding(7). -@c man end -@c man begin COPYRIGHT -Copyright @copyright{} 2007 Free Software Foundation, Inc. @url{http://fsf.org/} - -Everyone is permitted to copy and distribute verbatim copies of this -license document, but changing it is not allowed. -@c man end -@end ignore -@node Copying -@c man begin DESCRIPTION -@appendix GNU GENERAL PUBLIC LICENSE -@c The GNU General Public License. -@center Version 3, 29 June 2007 - -@c This file is intended to be included within another document, -@c hence no sectioning command or @node. - -@display -Copyright @copyright{} 2007 Free Software Foundation, Inc. @url{http://fsf.org/} - -Everyone is permitted to copy and distribute verbatim copies of this -license document, but changing it is not allowed. -@end display - -@heading Preamble - -The GNU General Public License is a free, copyleft license for -software and other kinds of works. - -The licenses for most software and other practical works are designed -to take away your freedom to share and change the works. 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Of course, your -program's commands might be different; for a GUI interface, you would -use an ``about box''. - -You should also get your employer (if you work as a programmer) or school, -if any, to sign a ``copyright disclaimer'' for the program, if necessary. -For more information on this, and how to apply and follow the GNU GPL, see -@url{http://www.gnu.org/licenses/}. - -The GNU General Public License does not permit incorporating your -program into proprietary programs. If your program is a subroutine -library, you may consider it more useful to permit linking proprietary -applications with the library. If this is what you want to do, use -the GNU Lesser General Public License instead of this License. But -first, please read @url{http://www.gnu.org/philosophy/why-not-lgpl.html}. -@c man end diff --git a/contrib/gdb-7/gdb/doc/stabs.texinfo b/contrib/gdb-7/gdb/doc/stabs.texinfo deleted file mode 100644 index a81d0937e1..0000000000 --- a/contrib/gdb-7/gdb/doc/stabs.texinfo +++ /dev/null @@ -1,4125 +0,0 @@ -\input texinfo -@setfilename stabs.info -@setchapternewpage odd -@settitle STABS - -@c @finalout - -@c This is a dir.info fragment to support semi-automated addition of -@c manuals to an info tree. -@dircategory Software development -@direntry -* Stabs: (stabs). The "stabs" debugging information format. -@end direntry - -@copying -Copyright @copyright{} 1992-2013 Free Software Foundation, Inc. -Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon, -and David MacKenzie. - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, with no Front-Cover Texts, and with no Back-Cover -Texts. A copy of the license is included in the section entitled ``GNU -Free Documentation License''. -@end copying - -@ifnottex -This document describes the stabs debugging symbol tables. - -@insertcopying -@end ifnottex - -@titlepage -@title The ``stabs'' debug format -@author Julia Menapace, Jim Kingdon, David MacKenzie -@author Cygnus Support -@page -@tex -\def\$#1${{#1}} % Kluge: collect RCS revision info without $...$ -\xdef\manvers{\$Revision: 2.130 $} % For use in headers, footers too -{\parskip=0pt -\hfill Cygnus Support\par -\hfill \manvers\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex - -@vskip 0pt plus 1filll -@insertcopying -@end titlepage - -@ifnottex -@node Top -@top The "stabs" representation of debugging information - -This document describes the stabs debugging format. - -@menu -* Overview:: Overview of stabs -* Program Structure:: Encoding of the structure of the program -* Constants:: Constants -* Variables:: -* Types:: Type definitions -* Macro define and undefine:: Representation of #define and #undef -* Symbol Tables:: Symbol information in symbol tables -* Cplusplus:: Stabs specific to C++ -* Stab Types:: Symbol types in a.out files -* Symbol Descriptors:: Table of symbol descriptors -* Type Descriptors:: Table of type descriptors -* Expanded Reference:: Reference information by stab type -* Questions:: Questions and anomalies -* Stab Sections:: In some object file formats, stabs are - in sections. -* GNU Free Documentation License:: The license for this documentation -* Symbol Types Index:: Index of symbolic stab symbol type names. -@end menu -@end ifnottex - -@contents - -@node Overview -@chapter Overview of Stabs - -@dfn{Stabs} refers to a format for information that describes a program -to a debugger. This format was apparently invented by -Peter Kessler at -the University of California at Berkeley, for the @code{pdx} Pascal -debugger; the format has spread widely since then. - -This document is one of the few published sources of documentation on -stabs. It is believed to be comprehensive for stabs used by C. The -lists of symbol descriptors (@pxref{Symbol Descriptors}) and type -descriptors (@pxref{Type Descriptors}) are believed to be completely -comprehensive. Stabs for COBOL-specific features and for variant -records (used by Pascal and Modula-2) are poorly documented here. - -@c FIXME: Need to document all OS9000 stuff in GDB; see all references -@c to os9k_stabs in stabsread.c. - -Other sources of information on stabs are @cite{Dbx and Dbxtool -Interfaces}, 2nd edition, by Sun, 1988, and @cite{AIX Version 3.2 Files -Reference}, Fourth Edition, September 1992, "dbx Stabstring Grammar" in -the a.out section, page 2-31. This document is believed to incorporate -the information from those two sources except where it explicitly directs -you to them for more information. - -@menu -* Flow:: Overview of debugging information flow -* Stabs Format:: Overview of stab format -* String Field:: The string field -* C Example:: A simple example in C source -* Assembly Code:: The simple example at the assembly level -@end menu - -@node Flow -@section Overview of Debugging Information Flow - -The GNU C compiler compiles C source in a @file{.c} file into assembly -language in a @file{.s} file, which the assembler translates into -a @file{.o} file, which the linker combines with other @file{.o} files and -libraries to produce an executable file. - -With the @samp{-g} option, GCC puts in the @file{.s} file additional -debugging information, which is slightly transformed by the assembler -and linker, and carried through into the final executable. This -debugging information describes features of the source file like line -numbers, the types and scopes of variables, and function names, -parameters, and scopes. - -For some object file formats, the debugging information is encapsulated -in assembler directives known collectively as @dfn{stab} (symbol table) -directives, which are interspersed with the generated code. Stabs are -the native format for debugging information in the a.out and XCOFF -object file formats. The GNU tools can also emit stabs in the COFF and -ECOFF object file formats. - -The assembler adds the information from stabs to the symbol information -it places by default in the symbol table and the string table of the -@file{.o} file it is building. The linker consolidates the @file{.o} -files into one executable file, with one symbol table and one string -table. Debuggers use the symbol and string tables in the executable as -a source of debugging information about the program. - -@node Stabs Format -@section Overview of Stab Format - -There are three overall formats for stab assembler directives, -differentiated by the first word of the stab. The name of the directive -describes which combination of four possible data fields follows. It is -either @code{.stabs} (string), @code{.stabn} (number), or @code{.stabd} -(dot). IBM's XCOFF assembler uses @code{.stabx} (and some other -directives such as @code{.file} and @code{.bi}) instead of -@code{.stabs}, @code{.stabn} or @code{.stabd}. - -The overall format of each class of stab is: - -@example -.stabs "@var{string}",@var{type},@var{other},@var{desc},@var{value} -.stabn @var{type},@var{other},@var{desc},@var{value} -.stabd @var{type},@var{other},@var{desc} -.stabx "@var{string}",@var{value},@var{type},@var{sdb-type} -@end example - -@c what is the correct term for "current file location"? My AIX -@c assembler manual calls it "the value of the current location counter". -For @code{.stabn} and @code{.stabd}, there is no @var{string} (the -@code{n_strx} field is zero; see @ref{Symbol Tables}). For -@code{.stabd}, the @var{value} field is implicit and has the value of -the current file location. For @code{.stabx}, the @var{sdb-type} field -is unused for stabs and can always be set to zero. The @var{other} -field is almost always unused and can be set to zero. - -The number in the @var{type} field gives some basic information about -which type of stab this is (or whether it @emph{is} a stab, as opposed -to an ordinary symbol). Each valid type number defines a different stab -type; further, the stab type defines the exact interpretation of, and -possible values for, any remaining @var{string}, @var{desc}, or -@var{value} fields present in the stab. @xref{Stab Types}, for a list -in numeric order of the valid @var{type} field values for stab directives. - -@node String Field -@section The String Field - -For most stabs the string field holds the meat of the -debugging information. The flexible nature of this field -is what makes stabs extensible. For some stab types the string field -contains only a name. For other stab types the contents can be a great -deal more complex. - -The overall format of the string field for most stab types is: - -@example -"@var{name}:@var{symbol-descriptor} @var{type-information}" -@end example - -@var{name} is the name of the symbol represented by the stab; it can -contain a pair of colons (@pxref{Nested Symbols}). @var{name} can be -omitted, which means the stab represents an unnamed object. For -example, @samp{:t10=*2} defines type 10 as a pointer to type 2, but does -not give the type a name. Omitting the @var{name} field is supported by -AIX dbx and GDB after about version 4.8, but not other debuggers. GCC -sometimes uses a single space as the name instead of omitting the name -altogether; apparently that is supported by most debuggers. - -The @var{symbol-descriptor} following the @samp{:} is an alphabetic -character that tells more specifically what kind of symbol the stab -represents. If the @var{symbol-descriptor} is omitted, but type -information follows, then the stab represents a local variable. For a -list of symbol descriptors, see @ref{Symbol Descriptors}. The @samp{c} -symbol descriptor is an exception in that it is not followed by type -information. @xref{Constants}. - -@var{type-information} is either a @var{type-number}, or -@samp{@var{type-number}=}. A @var{type-number} alone is a type -reference, referring directly to a type that has already been defined. - -The @samp{@var{type-number}=} form is a type definition, where the -number represents a new type which is about to be defined. The type -definition may refer to other types by number, and those type numbers -may be followed by @samp{=} and nested definitions. Also, the Lucid -compiler will repeat @samp{@var{type-number}=} more than once if it -wants to define several type numbers at once. - -In a type definition, if the character that follows the equals sign is -non-numeric then it is a @var{type-descriptor}, and tells what kind of -type is about to be defined. Any other values following the -@var{type-descriptor} vary, depending on the @var{type-descriptor}. -@xref{Type Descriptors}, for a list of @var{type-descriptor} values. If -a number follows the @samp{=} then the number is a @var{type-reference}. -For a full description of types, @ref{Types}. - -A @var{type-number} is often a single number. The GNU and Sun tools -additionally permit a @var{type-number} to be a pair -(@var{file-number},@var{filetype-number}) (the parentheses appear in the -string, and serve to distinguish the two cases). The @var{file-number} -is 0 for the base source file, 1 for the first included file, 2 for the -next, and so on. The @var{filetype-number} is a number starting with -1 which is incremented for each new type defined in the file. -(Separating the file number and the type number permits the -@code{N_BINCL} optimization to succeed more often; see @ref{Include -Files}). - -There is an AIX extension for type attributes. Following the @samp{=} -are any number of type attributes. Each one starts with @samp{@@} and -ends with @samp{;}. Debuggers, including AIX's dbx and GDB 4.10, skip -any type attributes they do not recognize. GDB 4.9 and other versions -of dbx may not do this. Because of a conflict with C@t{++} -(@pxref{Cplusplus}), new attributes should not be defined which begin -with a digit, @samp{(}, or @samp{-}; GDB may be unable to distinguish -those from the C@t{++} type descriptor @samp{@@}. The attributes are: - -@table @code -@item a@var{boundary} -@var{boundary} is an integer specifying the alignment. I assume it -applies to all variables of this type. - -@item p@var{integer} -Pointer class (for checking). Not sure what this means, or how -@var{integer} is interpreted. - -@item P -Indicate this is a packed type, meaning that structure fields or array -elements are placed more closely in memory, to save memory at the -expense of speed. - -@item s@var{size} -Size in bits of a variable of this type. This is fully supported by GDB -4.11 and later. - -@item S -Indicate that this type is a string instead of an array of characters, -or a bitstring instead of a set. It doesn't change the layout of the -data being represented, but does enable the debugger to know which type -it is. - -@item V -Indicate that this type is a vector instead of an array. The only -major difference between vectors and arrays is that vectors are -passed by value instead of by reference (vector coprocessor extension). - -@end table - -All of this can make the string field quite long. All versions of GDB, -and some versions of dbx, can handle arbitrarily long strings. But many -versions of dbx (or assemblers or linkers, I'm not sure which) -cretinously limit the strings to about 80 characters, so compilers which -must work with such systems need to split the @code{.stabs} directive -into several @code{.stabs} directives. Each stab duplicates every field -except the string field. The string field of every stab except the last -is marked as continued with a backslash at the end (in the assembly code -this may be written as a double backslash, depending on the assembler). -Removing the backslashes and concatenating the string fields of each -stab produces the original, long string. Just to be incompatible (or so -they don't have to worry about what the assembler does with -backslashes), AIX can use @samp{?} instead of backslash. - -@node C Example -@section A Simple Example in C Source - -To get the flavor of how stabs describe source information for a C -program, let's look at the simple program: - -@example -main() -@{ - printf("Hello world"); -@} -@end example - -When compiled with @samp{-g}, the program above yields the following -@file{.s} file. Line numbers have been added to make it easier to refer -to parts of the @file{.s} file in the description of the stabs that -follows. - -@node Assembly Code -@section The Simple Example at the Assembly Level - -This simple ``hello world'' example demonstrates several of the stab -types used to describe C language source files. - -@example -1 gcc2_compiled.: -2 .stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 -3 .stabs "hello.c",100,0,0,Ltext0 -4 .text -5 Ltext0: -6 .stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 -7 .stabs "char:t2=r2;0;127;",128,0,0,0 -8 .stabs "long int:t3=r1;-2147483648;2147483647;",128,0,0,0 -9 .stabs "unsigned int:t4=r1;0;-1;",128,0,0,0 -10 .stabs "long unsigned int:t5=r1;0;-1;",128,0,0,0 -11 .stabs "short int:t6=r1;-32768;32767;",128,0,0,0 -12 .stabs "long long int:t7=r1;0;-1;",128,0,0,0 -13 .stabs "short unsigned int:t8=r1;0;65535;",128,0,0,0 -14 .stabs "long long unsigned int:t9=r1;0;-1;",128,0,0,0 -15 .stabs "signed char:t10=r1;-128;127;",128,0,0,0 -16 .stabs "unsigned char:t11=r1;0;255;",128,0,0,0 -17 .stabs "float:t12=r1;4;0;",128,0,0,0 -18 .stabs "double:t13=r1;8;0;",128,0,0,0 -19 .stabs "long double:t14=r1;8;0;",128,0,0,0 -20 .stabs "void:t15=15",128,0,0,0 -21 .align 4 -22 LC0: -23 .ascii "Hello, world!\12\0" -24 .align 4 -25 .global _main -26 .proc 1 -27 _main: -28 .stabn 68,0,4,LM1 -29 LM1: -30 !#PROLOGUE# 0 -31 save %sp,-136,%sp -32 !#PROLOGUE# 1 -33 call ___main,0 -34 nop -35 .stabn 68,0,5,LM2 -36 LM2: -37 LBB2: -38 sethi %hi(LC0),%o1 -39 or %o1,%lo(LC0),%o0 -40 call _printf,0 -41 nop -42 .stabn 68,0,6,LM3 -43 LM3: -44 LBE2: -45 .stabn 68,0,6,LM4 -46 LM4: -47 L1: -48 ret -49 restore -50 .stabs "main:F1",36,0,0,_main -51 .stabn 192,0,0,LBB2 -52 .stabn 224,0,0,LBE2 -@end example - -@node Program Structure -@chapter Encoding the Structure of the Program - -The elements of the program structure that stabs encode include the name -of the main function, the names of the source and include files, the -line numbers, procedure names and types, and the beginnings and ends of -blocks of code. - -@menu -* Main Program:: Indicate what the main program is -* Source Files:: The path and name of the source file -* Include Files:: Names of include files -* Line Numbers:: -* Procedures:: -* Nested Procedures:: -* Block Structure:: -* Alternate Entry Points:: Entering procedures except at the beginning. -@end menu - -@node Main Program -@section Main Program - -@findex N_MAIN -Most languages allow the main program to have any name. The -@code{N_MAIN} stab type tells the debugger the name that is used in this -program. Only the string field is significant; it is the name of -a function which is the main program. Most C compilers do not use this -stab (they expect the debugger to assume that the name is @code{main}), -but some C compilers emit an @code{N_MAIN} stab for the @code{main} -function. I'm not sure how XCOFF handles this. - -@node Source Files -@section Paths and Names of the Source Files - -@findex N_SO -Before any other stabs occur, there must be a stab specifying the source -file. This information is contained in a symbol of stab type -@code{N_SO}; the string field contains the name of the file. The -value of the symbol is the start address of the portion of the -text section corresponding to that file. - -Some compilers use the desc field to indicate the language of the -source file. Sun's compilers started this usage, and the first -constants are derived from their documentation. Languages added -by gcc/gdb start at 0x32 to avoid conflict with languages Sun may -add in the future. A desc field with a value 0 indicates that no -language has been specified via this mechanism. - -@table @asis -@item @code{N_SO_AS} (0x1) -Assembly language -@item @code{N_SO_C} (0x2) -K&R traditional C -@item @code{N_SO_ANSI_C} (0x3) -ANSI C -@item @code{N_SO_CC} (0x4) -C++ -@item @code{N_SO_FORTRAN} (0x5) -Fortran -@item @code{N_SO_PASCAL} (0x6) -Pascal -@item @code{N_SO_FORTRAN90} (0x7) -Fortran90 -@item @code{N_SO_OBJC} (0x32) -Objective-C -@item @code{N_SO_OBJCPLUS} (0x33) -Objective-C++ -@end table - -Some compilers (for example, GCC2 and SunOS4 @file{/bin/cc}) also -include the directory in which the source was compiled, in a second -@code{N_SO} symbol preceding the one containing the file name. This -symbol can be distinguished by the fact that it ends in a slash. Code -from the @code{cfront} C@t{++} compiler can have additional @code{N_SO} symbols for -nonexistent source files after the @code{N_SO} for the real source file; -these are believed to contain no useful information. - -For example: - -@example -.stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 # @r{100 is N_SO} -.stabs "hello.c",100,0,0,Ltext0 - .text -Ltext0: -@end example - -@findex C_FILE -Instead of @code{N_SO} symbols, XCOFF uses a @code{.file} assembler -directive which assembles to a @code{C_FILE} symbol; explaining this in -detail is outside the scope of this document. - -@c FIXME: Exactly when should the empty N_SO be used? Why? -If it is useful to indicate the end of a source file, this is done with -an @code{N_SO} symbol with an empty string for the name. The value is -the address of the end of the text section for the file. For some -systems, there is no indication of the end of a source file, and you -just need to figure it ended when you see an @code{N_SO} for a different -source file, or a symbol ending in @code{.o} (which at least some -linkers insert to mark the start of a new @code{.o} file). - -@node Include Files -@section Names of Include Files - -There are several schemes for dealing with include files: the -traditional @code{N_SOL} approach, Sun's @code{N_BINCL} approach, and the -XCOFF @code{C_BINCL} approach (which despite the similar name has little in -common with @code{N_BINCL}). - -@findex N_SOL -An @code{N_SOL} symbol specifies which include file subsequent symbols -refer to. The string field is the name of the file and the value is the -text address corresponding to the end of the previous include file and -the start of this one. To specify the main source file again, use an -@code{N_SOL} symbol with the name of the main source file. - -@findex N_BINCL -@findex N_EINCL -@findex N_EXCL -The @code{N_BINCL} approach works as follows. An @code{N_BINCL} symbol -specifies the start of an include file. In an object file, only the -string is significant; the linker puts data into some of the other -fields. The end of the include file is marked by an @code{N_EINCL} -symbol (which has no string field). In an object file, there is no -significant data in the @code{N_EINCL} symbol. @code{N_BINCL} and -@code{N_EINCL} can be nested. - -If the linker detects that two source files have identical stabs between -an @code{N_BINCL} and @code{N_EINCL} pair (as will generally be the case -for a header file), then it only puts out the stabs once. Each -additional occurrence is replaced by an @code{N_EXCL} symbol. I believe -the GNU linker and the Sun (both SunOS4 and Solaris) linker are the only -ones which supports this feature. - -A linker which supports this feature will set the value of a -@code{N_BINCL} symbol to the total of all the characters in the stabs -strings included in the header file, omitting any file numbers. The -value of an @code{N_EXCL} symbol is the same as the value of the -@code{N_BINCL} symbol it replaces. This information can be used to -match up @code{N_EXCL} and @code{N_BINCL} symbols which have the same -filename. The @code{N_EINCL} value, and the values of the other and -description fields for all three, appear to always be zero. - -@findex C_BINCL -@findex C_EINCL -For the start of an include file in XCOFF, use the @file{.bi} assembler -directive, which generates a @code{C_BINCL} symbol. A @file{.ei} -directive, which generates a @code{C_EINCL} symbol, denotes the end of -the include file. Both directives are followed by the name of the -source file in quotes, which becomes the string for the symbol. -The value of each symbol, produced automatically by the assembler -and linker, is the offset into the executable of the beginning -(inclusive, as you'd expect) or end (inclusive, as you would not expect) -of the portion of the COFF line table that corresponds to this include -file. @code{C_BINCL} and @code{C_EINCL} do not nest. - -@node Line Numbers -@section Line Numbers - -@findex N_SLINE -An @code{N_SLINE} symbol represents the start of a source line. The -desc field contains the line number and the value contains the code -address for the start of that source line. On most machines the address -is absolute; for stabs in sections (@pxref{Stab Sections}), it is -relative to the function in which the @code{N_SLINE} symbol occurs. - -@findex N_DSLINE -@findex N_BSLINE -GNU documents @code{N_DSLINE} and @code{N_BSLINE} symbols for line -numbers in the data or bss segments, respectively. They are identical -to @code{N_SLINE} but are relocated differently by the linker. They -were intended to be used to describe the source location of a variable -declaration, but I believe that GCC2 actually puts the line number in -the desc field of the stab for the variable itself. GDB has been -ignoring these symbols (unless they contain a string field) since -at least GDB 3.5. - -For single source lines that generate discontiguous code, such as flow -of control statements, there may be more than one line number entry for -the same source line. In this case there is a line number entry at the -start of each code range, each with the same line number. - -XCOFF does not use stabs for line numbers. Instead, it uses COFF line -numbers (which are outside the scope of this document). Standard COFF -line numbers cannot deal with include files, but in XCOFF this is fixed -with the @code{C_BINCL} method of marking include files (@pxref{Include -Files}). - -@node Procedures -@section Procedures - -@findex N_FUN, for functions -@findex N_FNAME -@findex N_STSYM, for functions (Sun acc) -@findex N_GSYM, for functions (Sun acc) -All of the following stabs normally use the @code{N_FUN} symbol type. -However, Sun's @code{acc} compiler on SunOS4 uses @code{N_GSYM} and -@code{N_STSYM}, which means that the value of the stab for the function -is useless and the debugger must get the address of the function from -the non-stab symbols instead. On systems where non-stab symbols have -leading underscores, the stabs will lack underscores and the debugger -needs to know about the leading underscore to match up the stab and the -non-stab symbol. BSD Fortran is said to use @code{N_FNAME} with the -same restriction; the value of the symbol is not useful (I'm not sure it -really does use this, because GDB doesn't handle this and no one has -complained). - -@findex C_FUN -A function is represented by an @samp{F} symbol descriptor for a global -(extern) function, and @samp{f} for a static (local) function. For -a.out, the value of the symbol is the address of the start of the -function; it is already relocated. For stabs in ELF, the SunPRO -compiler version 2.0.1 and GCC put out an address which gets relocated -by the linker. In a future release SunPRO is planning to put out zero, -in which case the address can be found from the ELF (non-stab) symbol. -Because looking things up in the ELF symbols would probably be slow, I'm -not sure how to find which symbol of that name is the right one, and -this doesn't provide any way to deal with nested functions, it would -probably be better to make the value of the stab an address relative to -the start of the file, or just absolute. See @ref{ELF Linker -Relocation} for more information on linker relocation of stabs in ELF -files. For XCOFF, the stab uses the @code{C_FUN} storage class and the -value of the stab is meaningless; the address of the function can be -found from the csect symbol (XTY_LD/XMC_PR). - -The type information of the stab represents the return type of the -function; thus @samp{foo:f5} means that foo is a function returning type -5. There is no need to try to get the line number of the start of the -function from the stab for the function; it is in the next -@code{N_SLINE} symbol. - -@c FIXME: verify whether the "I suspect" below is true or not. -Some compilers (such as Sun's Solaris compiler) support an extension for -specifying the types of the arguments. I suspect this extension is not -used for old (non-prototyped) function definitions in C. If the -extension is in use, the type information of the stab for the function -is followed by type information for each argument, with each argument -preceded by @samp{;}. An argument type of 0 means that additional -arguments are being passed, whose types and number may vary (@samp{...} -in ANSI C). GDB has tolerated this extension (parsed the syntax, if not -necessarily used the information) since at least version 4.8; I don't -know whether all versions of dbx tolerate it. The argument types given -here are not redundant with the symbols for the formal parameters -(@pxref{Parameters}); they are the types of the arguments as they are -passed, before any conversions might take place. For example, if a C -function which is declared without a prototype takes a @code{float} -argument, the value is passed as a @code{double} but then converted to a -@code{float}. Debuggers need to use the types given in the arguments -when printing values, but when calling the function they need to use the -types given in the symbol defining the function. - -If the return type and types of arguments of a function which is defined -in another source file are specified (i.e., a function prototype in ANSI -C), traditionally compilers emit no stab; the only way for the debugger -to find the information is if the source file where the function is -defined was also compiled with debugging symbols. As an extension the -Solaris compiler uses symbol descriptor @samp{P} followed by the return -type of the function, followed by the arguments, each preceded by -@samp{;}, as in a stab with symbol descriptor @samp{f} or @samp{F}. -This use of symbol descriptor @samp{P} can be distinguished from its use -for register parameters (@pxref{Register Parameters}) by the fact that it has -symbol type @code{N_FUN}. - -The AIX documentation also defines symbol descriptor @samp{J} as an -internal function. I assume this means a function nested within another -function. It also says symbol descriptor @samp{m} is a module in -Modula-2 or extended Pascal. - -Procedures (functions which do not return values) are represented as -functions returning the @code{void} type in C. I don't see why this couldn't -be used for all languages (inventing a @code{void} type for this purpose if -necessary), but the AIX documentation defines @samp{I}, @samp{P}, and -@samp{Q} for internal, global, and static procedures, respectively. -These symbol descriptors are unusual in that they are not followed by -type information. - -The following example shows a stab for a function @code{main} which -returns type number @code{1}. The @code{_main} specified for the value -is a reference to an assembler label which is used to fill in the start -address of the function. - -@example -.stabs "main:F1",36,0,0,_main # @r{36 is N_FUN} -@end example - -The stab representing a procedure is located immediately following the -code of the procedure. This stab is in turn directly followed by a -group of other stabs describing elements of the procedure. These other -stabs describe the procedure's parameters, its block local variables, and -its block structure. - -If functions can appear in different sections, then the debugger may not -be able to find the end of a function. Recent versions of GCC will mark -the end of a function with an @code{N_FUN} symbol with an empty string -for the name. The value is the address of the end of the current -function. Without such a symbol, there is no indication of the address -of the end of a function, and you must assume that it ended at the -starting address of the next function or at the end of the text section -for the program. - -@node Nested Procedures -@section Nested Procedures - -For any of the symbol descriptors representing procedures, after the -symbol descriptor and the type information is optionally a scope -specifier. This consists of a comma, the name of the procedure, another -comma, and the name of the enclosing procedure. The first name is local -to the scope specified, and seems to be redundant with the name of the -symbol (before the @samp{:}). This feature is used by GCC, and -presumably Pascal, Modula-2, etc., compilers, for nested functions. - -If procedures are nested more than one level deep, only the immediately -containing scope is specified. For example, this code: - -@example -int -foo (int x) -@{ - int bar (int y) - @{ - int baz (int z) - @{ - return x + y + z; - @} - return baz (x + 2 * y); - @} - return x + bar (3 * x); -@} -@end example - -@noindent -produces the stabs: - -@example -.stabs "baz:f1,baz,bar",36,0,0,_baz.15 # @r{36 is N_FUN} -.stabs "bar:f1,bar,foo",36,0,0,_bar.12 -.stabs "foo:F1",36,0,0,_foo -@end example - -@node Block Structure -@section Block Structure - -@findex N_LBRAC -@findex N_RBRAC -@c For GCC 2.5.8 or so stabs-in-coff, these are absolute instead of -@c function relative (as documented below). But GDB has never been able -@c to deal with that (it had wanted them to be relative to the file, but -@c I just fixed that (between GDB 4.12 and 4.13)), so it is function -@c relative just like ELF and SOM and the below documentation. -The program's block structure is represented by the @code{N_LBRAC} (left -brace) and the @code{N_RBRAC} (right brace) stab types. The variables -defined inside a block precede the @code{N_LBRAC} symbol for most -compilers, including GCC. Other compilers, such as the Convex, Acorn -RISC machine, and Sun @code{acc} compilers, put the variables after the -@code{N_LBRAC} symbol. The values of the @code{N_LBRAC} and -@code{N_RBRAC} symbols are the start and end addresses of the code of -the block, respectively. For most machines, they are relative to the -starting address of this source file. For the Gould NP1, they are -absolute. For stabs in sections (@pxref{Stab Sections}), they are -relative to the function in which they occur. - -The @code{N_LBRAC} and @code{N_RBRAC} stabs that describe the block -scope of a procedure are located after the @code{N_FUN} stab that -represents the procedure itself. - -Sun documents the desc field of @code{N_LBRAC} and -@code{N_RBRAC} symbols as containing the nesting level of the block. -However, dbx seems to not care, and GCC always sets desc to -zero. - -@findex .bb -@findex .be -@findex C_BLOCK -For XCOFF, block scope is indicated with @code{C_BLOCK} symbols. If the -name of the symbol is @samp{.bb}, then it is the beginning of the block; -if the name of the symbol is @samp{.be}; it is the end of the block. - -@node Alternate Entry Points -@section Alternate Entry Points - -@findex N_ENTRY -@findex C_ENTRY -Some languages, like Fortran, have the ability to enter procedures at -some place other than the beginning. One can declare an alternate entry -point. The @code{N_ENTRY} stab is for this; however, the Sun FORTRAN -compiler doesn't use it. According to AIX documentation, only the name -of a @code{C_ENTRY} stab is significant; the address of the alternate -entry point comes from the corresponding external symbol. A previous -revision of this document said that the value of an @code{N_ENTRY} stab -was the address of the alternate entry point, but I don't know the -source for that information. - -@node Constants -@chapter Constants - -The @samp{c} symbol descriptor indicates that this stab represents a -constant. This symbol descriptor is an exception to the general rule -that symbol descriptors are followed by type information. Instead, it -is followed by @samp{=} and one of the following: - -@table @code -@item b @var{value} -Boolean constant. @var{value} is a numeric value; I assume it is 0 for -false or 1 for true. - -@item c @var{value} -Character constant. @var{value} is the numeric value of the constant. - -@item e @var{type-information} , @var{value} -Constant whose value can be represented as integral. -@var{type-information} is the type of the constant, as it would appear -after a symbol descriptor (@pxref{String Field}). @var{value} is the -numeric value of the constant. GDB 4.9 does not actually get the right -value if @var{value} does not fit in a host @code{int}, but it does not -do anything violent, and future debuggers could be extended to accept -integers of any size (whether unsigned or not). This constant type is -usually documented as being only for enumeration constants, but GDB has -never imposed that restriction; I don't know about other debuggers. - -@item i @var{value} -Integer constant. @var{value} is the numeric value. The type is some -sort of generic integer type (for GDB, a host @code{int}); to specify -the type explicitly, use @samp{e} instead. - -@item r @var{value} -Real constant. @var{value} is the real value, which can be @samp{INF} -(optionally preceded by a sign) for infinity, @samp{QNAN} for a quiet -NaN (not-a-number), or @samp{SNAN} for a signalling NaN. If it is a -normal number the format is that accepted by the C library function -@code{atof}. - -@item s @var{string} -String constant. @var{string} is a string enclosed in either @samp{'} -(in which case @samp{'} characters within the string are represented as -@samp{\'} or @samp{"} (in which case @samp{"} characters within the -string are represented as @samp{\"}). - -@item S @var{type-information} , @var{elements} , @var{bits} , @var{pattern} -Set constant. @var{type-information} is the type of the constant, as it -would appear after a symbol descriptor (@pxref{String Field}). -@var{elements} is the number of elements in the set (does this means -how many bits of @var{pattern} are actually used, which would be -redundant with the type, or perhaps the number of bits set in -@var{pattern}? I don't get it), @var{bits} is the number of bits in the -constant (meaning it specifies the length of @var{pattern}, I think), -and @var{pattern} is a hexadecimal representation of the set. AIX -documentation refers to a limit of 32 bytes, but I see no reason why -this limit should exist. This form could probably be used for arbitrary -constants, not just sets; the only catch is that @var{pattern} should be -understood to be target, not host, byte order and format. -@end table - -The boolean, character, string, and set constants are not supported by -GDB 4.9, but it ignores them. GDB 4.8 and earlier gave an error -message and refused to read symbols from the file containing the -constants. - -The above information is followed by @samp{;}. - -@node Variables -@chapter Variables - -Different types of stabs describe the various ways that variables can be -allocated: on the stack, globally, in registers, in common blocks, -statically, or as arguments to a function. - -@menu -* Stack Variables:: Variables allocated on the stack. -* Global Variables:: Variables used by more than one source file. -* Register Variables:: Variables in registers. -* Common Blocks:: Variables statically allocated together. -* Statics:: Variables local to one source file. -* Based Variables:: Fortran pointer based variables. -* Parameters:: Variables for arguments to functions. -@end menu - -@node Stack Variables -@section Automatic Variables Allocated on the Stack - -If a variable's scope is local to a function and its lifetime is only as -long as that function executes (C calls such variables -@dfn{automatic}), it can be allocated in a register (@pxref{Register -Variables}) or on the stack. - -@findex N_LSYM, for stack variables -@findex C_LSYM -Each variable allocated on the stack has a stab with the symbol -descriptor omitted. Since type information should begin with a digit, -@samp{-}, or @samp{(}, only those characters precluded from being used -for symbol descriptors. However, the Acorn RISC machine (ARM) is said -to get this wrong: it puts out a mere type definition here, without the -preceding @samp{@var{type-number}=}. This is a bad idea; there is no -guarantee that type descriptors are distinct from symbol descriptors. -Stabs for stack variables use the @code{N_LSYM} stab type, or -@code{C_LSYM} for XCOFF. - -The value of the stab is the offset of the variable within the -local variables. On most machines this is an offset from the frame -pointer and is negative. The location of the stab specifies which block -it is defined in; see @ref{Block Structure}. - -For example, the following C code: - -@example -int -main () -@{ - int x; -@} -@end example - -produces the following stabs: - -@example -.stabs "main:F1",36,0,0,_main # @r{36 is N_FUN} -.stabs "x:1",128,0,0,-12 # @r{128 is N_LSYM} -.stabn 192,0,0,LBB2 # @r{192 is N_LBRAC} -.stabn 224,0,0,LBE2 # @r{224 is N_RBRAC} -@end example - -See @ref{Procedures} for more information on the @code{N_FUN} stab, and -@ref{Block Structure} for more information on the @code{N_LBRAC} and -@code{N_RBRAC} stabs. - -@node Global Variables -@section Global Variables - -@findex N_GSYM -@findex C_GSYM -@c FIXME: verify for sure that it really is C_GSYM on XCOFF -A variable whose scope is not specific to just one source file is -represented by the @samp{G} symbol descriptor. These stabs use the -@code{N_GSYM} stab type (C_GSYM for XCOFF). The type information for -the stab (@pxref{String Field}) gives the type of the variable. - -For example, the following source code: - -@example -char g_foo = 'c'; -@end example - -@noindent -yields the following assembly code: - -@example -.stabs "g_foo:G2",32,0,0,0 # @r{32 is N_GSYM} - .global _g_foo - .data -_g_foo: - .byte 99 -@end example - -The address of the variable represented by the @code{N_GSYM} is not -contained in the @code{N_GSYM} stab. The debugger gets this information -from the external symbol for the global variable. In the example above, -the @code{.global _g_foo} and @code{_g_foo:} lines tell the assembler to -produce an external symbol. - -Some compilers, like GCC, output @code{N_GSYM} stabs only once, where -the variable is defined. Other compilers, like SunOS4 /bin/cc, output a -@code{N_GSYM} stab for each compilation unit which references the -variable. - -@node Register Variables -@section Register Variables - -@findex N_RSYM -@findex C_RSYM -@c According to an old version of this manual, AIX uses C_RPSYM instead -@c of C_RSYM. I am skeptical; this should be verified. -Register variables have their own stab type, @code{N_RSYM} -(@code{C_RSYM} for XCOFF), and their own symbol descriptor, @samp{r}. -The stab's value is the number of the register where the variable data -will be stored. -@c .stabs "name:type",N_RSYM,0,RegSize,RegNumber (Sun doc) - -AIX defines a separate symbol descriptor @samp{d} for floating point -registers. This seems unnecessary; why not just just give floating -point registers different register numbers? I have not verified whether -the compiler actually uses @samp{d}. - -If the register is explicitly allocated to a global variable, but not -initialized, as in: - -@example -register int g_bar asm ("%g5"); -@end example - -@noindent -then the stab may be emitted at the end of the object file, with -the other bss symbols. - -@node Common Blocks -@section Common Blocks - -A common block is a statically allocated section of memory which can be -referred to by several source files. It may contain several variables. -I believe Fortran is the only language with this feature. - -@findex N_BCOMM -@findex N_ECOMM -@findex C_BCOMM -@findex C_ECOMM -A @code{N_BCOMM} stab begins a common block and an @code{N_ECOMM} stab -ends it. The only field that is significant in these two stabs is the -string, which names a normal (non-debugging) symbol that gives the -address of the common block. According to IBM documentation, only the -@code{N_BCOMM} has the name of the common block (even though their -compiler actually puts it both places). - -@findex N_ECOML -@findex C_ECOML -The stabs for the members of the common block are between the -@code{N_BCOMM} and the @code{N_ECOMM}; the value of each stab is the -offset within the common block of that variable. IBM uses the -@code{C_ECOML} stab type, and there is a corresponding @code{N_ECOML} -stab type, but Sun's Fortran compiler uses @code{N_GSYM} instead. The -variables within a common block use the @samp{V} symbol descriptor (I -believe this is true of all Fortran variables). Other stabs (at least -type declarations using @code{C_DECL}) can also be between the -@code{N_BCOMM} and the @code{N_ECOMM}. - -@node Statics -@section Static Variables - -Initialized static variables are represented by the @samp{S} and -@samp{V} symbol descriptors. @samp{S} means file scope static, and -@samp{V} means procedure scope static. One exception: in XCOFF, IBM's -xlc compiler always uses @samp{V}, and whether it is file scope or not -is distinguished by whether the stab is located within a function. - -@c This is probably not worth mentioning; it is only true on the sparc -@c for `double' variables which although declared const are actually in -@c the data segment (the text segment can't guarantee 8 byte alignment). -@c (although GCC -@c 2.4.5 has a bug in that it uses @code{N_FUN}, so neither dbx nor GDB can -@c find the variables) -@findex N_STSYM -@findex N_LCSYM -@findex N_FUN, for variables -@findex N_ROSYM -In a.out files, @code{N_STSYM} means the data section, @code{N_FUN} -means the text section, and @code{N_LCSYM} means the bss section. For -those systems with a read-only data section separate from the text -section (Solaris), @code{N_ROSYM} means the read-only data section. - -For example, the source lines: - -@example -static const int var_const = 5; -static int var_init = 2; -static int var_noinit; -@end example - -@noindent -yield the following stabs: - -@example -.stabs "var_const:S1",36,0,0,_var_const # @r{36 is N_FUN} -@dots{} -.stabs "var_init:S1",38,0,0,_var_init # @r{38 is N_STSYM} -@dots{} -.stabs "var_noinit:S1",40,0,0,_var_noinit # @r{40 is N_LCSYM} -@end example - -@findex C_STSYM -@findex C_BSTAT -@findex C_ESTAT -In XCOFF files, the stab type need not indicate the section; -@code{C_STSYM} can be used for all statics. Also, each static variable -is enclosed in a static block. A @code{C_BSTAT} (emitted with a -@samp{.bs} assembler directive) symbol begins the static block; its -value is the symbol number of the csect symbol whose value is the -address of the static block, its section is the section of the variables -in that static block, and its name is @samp{.bs}. A @code{C_ESTAT} -(emitted with a @samp{.es} assembler directive) symbol ends the static -block; its name is @samp{.es} and its value and section are ignored. - -In ECOFF files, the storage class is used to specify the section, so the -stab type need not indicate the section. - -In ELF files, for the SunPRO compiler version 2.0.1, symbol descriptor -@samp{S} means that the address is absolute (the linker relocates it) -and symbol descriptor @samp{V} means that the address is relative to the -start of the relevant section for that compilation unit. SunPRO has -plans to have the linker stop relocating stabs; I suspect that their the -debugger gets the address from the corresponding ELF (not stab) symbol. -I'm not sure how to find which symbol of that name is the right one. -The clean way to do all this would be to have the value of a symbol -descriptor @samp{S} symbol be an offset relative to the start of the -file, just like everything else, but that introduces obvious -compatibility problems. For more information on linker stab relocation, -@xref{ELF Linker Relocation}. - -@node Based Variables -@section Fortran Based Variables - -Fortran (at least, the Sun and SGI dialects of FORTRAN-77) has a feature -which allows allocating arrays with @code{malloc}, but which avoids -blurring the line between arrays and pointers the way that C does. In -stabs such a variable uses the @samp{b} symbol descriptor. - -For example, the Fortran declarations - -@example -real foo, foo10(10), foo10_5(10,5) -pointer (foop, foo) -pointer (foo10p, foo10) -pointer (foo105p, foo10_5) -@end example - -produce the stabs - -@example -foo:b6 -foo10:bar3;1;10;6 -foo10_5:bar3;1;5;ar3;1;10;6 -@end example - -In this example, @code{real} is type 6 and type 3 is an integral type -which is the type of the subscripts of the array (probably -@code{integer}). - -The @samp{b} symbol descriptor is like @samp{V} in that it denotes a -statically allocated symbol whose scope is local to a function; see -@xref{Statics}. The value of the symbol, instead of being the address -of the variable itself, is the address of a pointer to that variable. -So in the above example, the value of the @code{foo} stab is the address -of a pointer to a real, the value of the @code{foo10} stab is the -address of a pointer to a 10-element array of reals, and the value of -the @code{foo10_5} stab is the address of a pointer to a 5-element array -of 10-element arrays of reals. - -@node Parameters -@section Parameters - -Formal parameters to a function are represented by a stab (or sometimes -two; see below) for each parameter. The stabs are in the order in which -the debugger should print the parameters (i.e., the order in which the -parameters are declared in the source file). The exact form of the stab -depends on how the parameter is being passed. - -@findex N_PSYM -@findex C_PSYM -Parameters passed on the stack use the symbol descriptor @samp{p} and -the @code{N_PSYM} symbol type (or @code{C_PSYM} for XCOFF). The value -of the symbol is an offset used to locate the parameter on the stack; -its exact meaning is machine-dependent, but on most machines it is an -offset from the frame pointer. - -As a simple example, the code: - -@example -main (argc, argv) - int argc; - char **argv; -@end example - -produces the stabs: - -@example -.stabs "main:F1",36,0,0,_main # @r{36 is N_FUN} -.stabs "argc:p1",160,0,0,68 # @r{160 is N_PSYM} -.stabs "argv:p20=*21=*2",160,0,0,72 -@end example - -The type definition of @code{argv} is interesting because it contains -several type definitions. Type 21 is pointer to type 2 (char) and -@code{argv} (type 20) is pointer to type 21. - -@c FIXME: figure out what these mean and describe them coherently. -The following symbol descriptors are also said to go with @code{N_PSYM}. -The value of the symbol is said to be an offset from the argument -pointer (I'm not sure whether this is true or not). - -@example -pP (<<??>>) -pF Fortran function parameter -X (function result variable) -@end example - -@menu -* Register Parameters:: -* Local Variable Parameters:: -* Reference Parameters:: -* Conformant Arrays:: -@end menu - -@node Register Parameters -@subsection Passing Parameters in Registers - -If the parameter is passed in a register, then traditionally there are -two symbols for each argument: - -@example -.stabs "arg:p1" . . . ; N_PSYM -.stabs "arg:r1" . . . ; N_RSYM -@end example - -Debuggers use the second one to find the value, and the first one to -know that it is an argument. - -@findex C_RPSYM -@findex N_RSYM, for parameters -Because that approach is kind of ugly, some compilers use symbol -descriptor @samp{P} or @samp{R} to indicate an argument which is in a -register. Symbol type @code{C_RPSYM} is used in XCOFF and @code{N_RSYM} -is used otherwise. The symbol's value is the register number. @samp{P} -and @samp{R} mean the same thing; the difference is that @samp{P} is a -GNU invention and @samp{R} is an IBM (XCOFF) invention. As of version -4.9, GDB should handle either one. - -There is at least one case where GCC uses a @samp{p} and @samp{r} pair -rather than @samp{P}; this is where the argument is passed in the -argument list and then loaded into a register. - -According to the AIX documentation, symbol descriptor @samp{D} is for a -parameter passed in a floating point register. This seems -unnecessary---why not just use @samp{R} with a register number which -indicates that it's a floating point register? I haven't verified -whether the system actually does what the documentation indicates. - -@c FIXME: On the hppa this is for any type > 8 bytes, I think, and not -@c for small structures (investigate). -On the sparc and hppa, for a @samp{P} symbol whose type is a structure -or union, the register contains the address of the structure. On the -sparc, this is also true of a @samp{p} and @samp{r} pair (using Sun -@code{cc}) or a @samp{p} symbol. However, if a (small) structure is -really in a register, @samp{r} is used. And, to top it all off, on the -hppa it might be a structure which was passed on the stack and loaded -into a register and for which there is a @samp{p} and @samp{r} pair! I -believe that symbol descriptor @samp{i} is supposed to deal with this -case (it is said to mean "value parameter by reference, indirect -access"; I don't know the source for this information), but I don't know -details or what compilers or debuggers use it, if any (not GDB or GCC). -It is not clear to me whether this case needs to be dealt with -differently than parameters passed by reference (@pxref{Reference Parameters}). - -@node Local Variable Parameters -@subsection Storing Parameters as Local Variables - -There is a case similar to an argument in a register, which is an -argument that is actually stored as a local variable. Sometimes this -happens when the argument was passed in a register and then the compiler -stores it as a local variable. If possible, the compiler should claim -that it's in a register, but this isn't always done. - -If a parameter is passed as one type and converted to a smaller type by -the prologue (for example, the parameter is declared as a @code{float}, -but the calling conventions specify that it is passed as a -@code{double}), then GCC2 (sometimes) uses a pair of symbols. The first -symbol uses symbol descriptor @samp{p} and the type which is passed. -The second symbol has the type and location which the parameter actually -has after the prologue. For example, suppose the following C code -appears with no prototypes involved: - -@example -void -subr (f) - float f; -@{ -@end example - -if @code{f} is passed as a double at stack offset 8, and the prologue -converts it to a float in register number 0, then the stabs look like: - -@example -.stabs "f:p13",160,0,3,8 # @r{160 is @code{N_PSYM}, here 13 is @code{double}} -.stabs "f:r12",64,0,3,0 # @r{64 is @code{N_RSYM}, here 12 is @code{float}} -@end example - -In both stabs 3 is the line number where @code{f} is declared -(@pxref{Line Numbers}). - -@findex N_LSYM, for parameter -GCC, at least on the 960, has another solution to the same problem. It -uses a single @samp{p} symbol descriptor for an argument which is stored -as a local variable but uses @code{N_LSYM} instead of @code{N_PSYM}. In -this case, the value of the symbol is an offset relative to the local -variables for that function, not relative to the arguments; on some -machines those are the same thing, but not on all. - -@c This is mostly just background info; the part that logically belongs -@c here is the last sentence. -On the VAX or on other machines in which the calling convention includes -the number of words of arguments actually passed, the debugger (GDB at -least) uses the parameter symbols to keep track of whether it needs to -print nameless arguments in addition to the formal parameters which it -has printed because each one has a stab. For example, in - -@example -extern int fprintf (FILE *stream, char *format, @dots{}); -@dots{} -fprintf (stdout, "%d\n", x); -@end example - -there are stabs for @code{stream} and @code{format}. On most machines, -the debugger can only print those two arguments (because it has no way -of knowing that additional arguments were passed), but on the VAX or -other machines with a calling convention which indicates the number of -words of arguments, the debugger can print all three arguments. To do -so, the parameter symbol (symbol descriptor @samp{p}) (not necessarily -@samp{r} or symbol descriptor omitted symbols) needs to contain the -actual type as passed (for example, @code{double} not @code{float} if it -is passed as a double and converted to a float). - -@node Reference Parameters -@subsection Passing Parameters by Reference - -If the parameter is passed by reference (e.g., Pascal @code{VAR} -parameters), then the symbol descriptor is @samp{v} if it is in the -argument list, or @samp{a} if it in a register. Other than the fact -that these contain the address of the parameter rather than the -parameter itself, they are identical to @samp{p} and @samp{R}, -respectively. I believe @samp{a} is an AIX invention; @samp{v} is -supported by all stabs-using systems as far as I know. - -@node Conformant Arrays -@subsection Passing Conformant Array Parameters - -@c Is this paragraph correct? It is based on piecing together patchy -@c information and some guesswork -Conformant arrays are a feature of Modula-2, and perhaps other -languages, in which the size of an array parameter is not known to the -called function until run-time. Such parameters have two stabs: a -@samp{x} for the array itself, and a @samp{C}, which represents the size -of the array. The value of the @samp{x} stab is the offset in the -argument list where the address of the array is stored (it this right? -it is a guess); the value of the @samp{C} stab is the offset in the -argument list where the size of the array (in elements? in bytes?) is -stored. - -@node Types -@chapter Defining Types - -The examples so far have described types as references to previously -defined types, or defined in terms of subranges of or pointers to -previously defined types. This chapter describes the other type -descriptors that may follow the @samp{=} in a type definition. - -@menu -* Builtin Types:: Integers, floating point, void, etc. -* Miscellaneous Types:: Pointers, sets, files, etc. -* Cross-References:: Referring to a type not yet defined. -* Subranges:: A type with a specific range. -* Arrays:: An aggregate type of same-typed elements. -* Strings:: Like an array but also has a length. -* Enumerations:: Like an integer but the values have names. -* Structures:: An aggregate type of different-typed elements. -* Typedefs:: Giving a type a name. -* Unions:: Different types sharing storage. -* Function Types:: -@end menu - -@node Builtin Types -@section Builtin Types - -Certain types are built in (@code{int}, @code{short}, @code{void}, -@code{float}, etc.); the debugger recognizes these types and knows how -to handle them. Thus, don't be surprised if some of the following ways -of specifying builtin types do not specify everything that a debugger -would need to know about the type---in some cases they merely specify -enough information to distinguish the type from other types. - -The traditional way to define builtin types is convoluted, so new ways -have been invented to describe them. Sun's @code{acc} uses special -builtin type descriptors (@samp{b} and @samp{R}), and IBM uses negative -type numbers. GDB accepts all three ways, as of version 4.8; dbx just -accepts the traditional builtin types and perhaps one of the other two -formats. The following sections describe each of these formats. - -@menu -* Traditional Builtin Types:: Put on your seat belts and prepare for kludgery -* Builtin Type Descriptors:: Builtin types with special type descriptors -* Negative Type Numbers:: Builtin types using negative type numbers -@end menu - -@node Traditional Builtin Types -@subsection Traditional Builtin Types - -This is the traditional, convoluted method for defining builtin types. -There are several classes of such type definitions: integer, floating -point, and @code{void}. - -@menu -* Traditional Integer Types:: -* Traditional Other Types:: -@end menu - -@node Traditional Integer Types -@subsubsection Traditional Integer Types - -Often types are defined as subranges of themselves. If the bounding values -fit within an @code{int}, then they are given normally. For example: - -@example -.stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 # @r{128 is N_LSYM} -.stabs "char:t2=r2;0;127;",128,0,0,0 -@end example - -Builtin types can also be described as subranges of @code{int}: - -@example -.stabs "unsigned short:t6=r1;0;65535;",128,0,0,0 -@end example - -If the lower bound of a subrange is 0 and the upper bound is -1, -the type is an unsigned integral type whose bounds are too -big to describe in an @code{int}. Traditionally this is only used for -@code{unsigned int} and @code{unsigned long}: - -@example -.stabs "unsigned int:t4=r1;0;-1;",128,0,0,0 -@end example - -For larger types, GCC 2.4.5 puts out bounds in octal, with one or more -leading zeroes. In this case a negative bound consists of a number -which is a 1 bit (for the sign bit) followed by a 0 bit for each bit in -the number (except the sign bit), and a positive bound is one which is a -1 bit for each bit in the number (except possibly the sign bit). All -known versions of dbx and GDB version 4 accept this (at least in the -sense of not refusing to process the file), but GDB 3.5 refuses to read -the whole file containing such symbols. So GCC 2.3.3 did not output the -proper size for these types. As an example of octal bounds, the string -fields of the stabs for 64 bit integer types look like: - -@c .stabs directives, etc., omitted to make it fit on the page. -@example -long int:t3=r1;001000000000000000000000;000777777777777777777777; -long unsigned int:t5=r1;000000000000000000000000;001777777777777777777777; -@end example - -If the lower bound of a subrange is 0 and the upper bound is negative, -the type is an unsigned integral type whose size in bytes is the -absolute value of the upper bound. I believe this is a Convex -convention for @code{unsigned long long}. - -If the lower bound of a subrange is negative and the upper bound is 0, -the type is a signed integral type whose size in bytes is -the absolute value of the lower bound. I believe this is a Convex -convention for @code{long long}. To distinguish this from a legitimate -subrange, the type should be a subrange of itself. I'm not sure whether -this is the case for Convex. - -@node Traditional Other Types -@subsubsection Traditional Other Types - -If the upper bound of a subrange is 0 and the lower bound is positive, -the type is a floating point type, and the lower bound of the subrange -indicates the number of bytes in the type: - -@example -.stabs "float:t12=r1;4;0;",128,0,0,0 -.stabs "double:t13=r1;8;0;",128,0,0,0 -@end example - -However, GCC writes @code{long double} the same way it writes -@code{double}, so there is no way to distinguish. - -@example -.stabs "long double:t14=r1;8;0;",128,0,0,0 -@end example - -Complex types are defined the same way as floating-point types; there is -no way to distinguish a single-precision complex from a double-precision -floating-point type. - -The C @code{void} type is defined as itself: - -@example -.stabs "void:t15=15",128,0,0,0 -@end example - -I'm not sure how a boolean type is represented. - -@node Builtin Type Descriptors -@subsection Defining Builtin Types Using Builtin Type Descriptors - -This is the method used by Sun's @code{acc} for defining builtin types. -These are the type descriptors to define builtin types: - -@table @code -@c FIXME: clean up description of width and offset, once we figure out -@c what they mean -@item b @var{signed} @var{char-flag} @var{width} ; @var{offset} ; @var{nbits} ; -Define an integral type. @var{signed} is @samp{u} for unsigned or -@samp{s} for signed. @var{char-flag} is @samp{c} which indicates this -is a character type, or is omitted. I assume this is to distinguish an -integral type from a character type of the same size, for example it -might make sense to set it for the C type @code{wchar_t} so the debugger -can print such variables differently (Solaris does not do this). Sun -sets it on the C types @code{signed char} and @code{unsigned char} which -arguably is wrong. @var{width} and @var{offset} appear to be for small -objects stored in larger ones, for example a @code{short} in an -@code{int} register. @var{width} is normally the number of bytes in the -type. @var{offset} seems to always be zero. @var{nbits} is the number -of bits in the type. - -Note that type descriptor @samp{b} used for builtin types conflicts with -its use for Pascal space types (@pxref{Miscellaneous Types}); they can -be distinguished because the character following the type descriptor -will be a digit, @samp{(}, or @samp{-} for a Pascal space type, or -@samp{u} or @samp{s} for a builtin type. - -@item w -Documented by AIX to define a wide character type, but their compiler -actually uses negative type numbers (@pxref{Negative Type Numbers}). - -@item R @var{fp-type} ; @var{bytes} ; -Define a floating point type. @var{fp-type} has one of the following values: - -@table @code -@item 1 (NF_SINGLE) -IEEE 32-bit (single precision) floating point format. - -@item 2 (NF_DOUBLE) -IEEE 64-bit (double precision) floating point format. - -@item 3 (NF_COMPLEX) -@item 4 (NF_COMPLEX16) -@item 5 (NF_COMPLEX32) -@c "GDB source" really means @file{include/aout/stab_gnu.h}, but trying -@c to put that here got an overfull hbox. -These are for complex numbers. A comment in the GDB source describes -them as Fortran @code{complex}, @code{double complex}, and -@code{complex*16}, respectively, but what does that mean? (i.e., Single -precision? Double precision?). - -@item 6 (NF_LDOUBLE) -Long double. This should probably only be used for Sun format -@code{long double}, and new codes should be used for other floating -point formats (@code{NF_DOUBLE} can be used if a @code{long double} is -really just an IEEE double, of course). -@end table - -@var{bytes} is the number of bytes occupied by the type. This allows a -debugger to perform some operations with the type even if it doesn't -understand @var{fp-type}. - -@item g @var{type-information} ; @var{nbits} -Documented by AIX to define a floating type, but their compiler actually -uses negative type numbers (@pxref{Negative Type Numbers}). - -@item c @var{type-information} ; @var{nbits} -Documented by AIX to define a complex type, but their compiler actually -uses negative type numbers (@pxref{Negative Type Numbers}). -@end table - -The C @code{void} type is defined as a signed integral type 0 bits long: -@example -.stabs "void:t19=bs0;0;0",128,0,0,0 -@end example -The Solaris compiler seems to omit the trailing semicolon in this case. -Getting sloppy in this way is not a swift move because if a type is -embedded in a more complex expression it is necessary to be able to tell -where it ends. - -I'm not sure how a boolean type is represented. - -@node Negative Type Numbers -@subsection Negative Type Numbers - -This is the method used in XCOFF for defining builtin types. -Since the debugger knows about the builtin types anyway, the idea of -negative type numbers is simply to give a special type number which -indicates the builtin type. There is no stab defining these types. - -There are several subtle issues with negative type numbers. - -One is the size of the type. A builtin type (for example the C types -@code{int} or @code{long}) might have different sizes depending on -compiler options, the target architecture, the ABI, etc. This issue -doesn't come up for IBM tools since (so far) they just target the -RS/6000; the sizes indicated below for each size are what the IBM -RS/6000 tools use. To deal with differing sizes, either define separate -negative type numbers for each size (which works but requires changing -the debugger, and, unless you get both AIX dbx and GDB to accept the -change, introduces an incompatibility), or use a type attribute -(@pxref{String Field}) to define a new type with the appropriate size -(which merely requires a debugger which understands type attributes, -like AIX dbx or GDB). For example, - -@example -.stabs "boolean:t10=@@s8;-16",128,0,0,0 -@end example - -defines an 8-bit boolean type, and - -@example -.stabs "boolean:t10=@@s64;-16",128,0,0,0 -@end example - -defines a 64-bit boolean type. - -A similar issue is the format of the type. This comes up most often for -floating-point types, which could have various formats (particularly -extended doubles, which vary quite a bit even among IEEE systems). -Again, it is best to define a new negative type number for each -different format; changing the format based on the target system has -various problems. One such problem is that the Alpha has both VAX and -IEEE floating types. One can easily imagine one library using the VAX -types and another library in the same executable using the IEEE types. -Another example is that the interpretation of whether a boolean is true -or false can be based on the least significant bit, most significant -bit, whether it is zero, etc., and different compilers (or different -options to the same compiler) might provide different kinds of boolean. - -The last major issue is the names of the types. The name of a given -type depends @emph{only} on the negative type number given; these do not -vary depending on the language, the target system, or anything else. -One can always define separate type numbers---in the following list you -will see for example separate @code{int} and @code{integer*4} types -which are identical except for the name. But compatibility can be -maintained by not inventing new negative type numbers and instead just -defining a new type with a new name. For example: - -@example -.stabs "CARDINAL:t10=-8",128,0,0,0 -@end example - -Here is the list of negative type numbers. The phrase @dfn{integral -type} is used to mean twos-complement (I strongly suspect that all -machines which use stabs use twos-complement; most machines use -twos-complement these days). - -@table @code -@item -1 -@code{int}, 32 bit signed integral type. - -@item -2 -@code{char}, 8 bit type holding a character. Both GDB and dbx on AIX -treat this as signed. GCC uses this type whether @code{char} is signed -or not, which seems like a bad idea. The AIX compiler (@code{xlc}) seems to -avoid this type; it uses -5 instead for @code{char}. - -@item -3 -@code{short}, 16 bit signed integral type. - -@item -4 -@code{long}, 32 bit signed integral type. - -@item -5 -@code{unsigned char}, 8 bit unsigned integral type. - -@item -6 -@code{signed char}, 8 bit signed integral type. - -@item -7 -@code{unsigned short}, 16 bit unsigned integral type. - -@item -8 -@code{unsigned int}, 32 bit unsigned integral type. - -@item -9 -@code{unsigned}, 32 bit unsigned integral type. - -@item -10 -@code{unsigned long}, 32 bit unsigned integral type. - -@item -11 -@code{void}, type indicating the lack of a value. - -@item -12 -@code{float}, IEEE single precision. - -@item -13 -@code{double}, IEEE double precision. - -@item -14 -@code{long double}, IEEE double precision. The compiler claims the size -will increase in a future release, and for binary compatibility you have -to avoid using @code{long double}. I hope when they increase it they -use a new negative type number. - -@item -15 -@code{integer}. 32 bit signed integral type. - -@item -16 -@code{boolean}. 32 bit type. GDB and GCC assume that zero is false, -one is true, and other values have unspecified meaning. I hope this -agrees with how the IBM tools use the type. - -@item -17 -@code{short real}. IEEE single precision. - -@item -18 -@code{real}. IEEE double precision. - -@item -19 -@code{stringptr}. @xref{Strings}. - -@item -20 -@code{character}, 8 bit unsigned character type. - -@item -21 -@code{logical*1}, 8 bit type. This Fortran type has a split -personality in that it is used for boolean variables, but can also be -used for unsigned integers. 0 is false, 1 is true, and other values are -non-boolean. - -@item -22 -@code{logical*2}, 16 bit type. This Fortran type has a split -personality in that it is used for boolean variables, but can also be -used for unsigned integers. 0 is false, 1 is true, and other values are -non-boolean. - -@item -23 -@code{logical*4}, 32 bit type. This Fortran type has a split -personality in that it is used for boolean variables, but can also be -used for unsigned integers. 0 is false, 1 is true, and other values are -non-boolean. - -@item -24 -@code{logical}, 32 bit type. This Fortran type has a split -personality in that it is used for boolean variables, but can also be -used for unsigned integers. 0 is false, 1 is true, and other values are -non-boolean. - -@item -25 -@code{complex}. A complex type consisting of two IEEE single-precision -floating point values. - -@item -26 -@code{complex}. A complex type consisting of two IEEE double-precision -floating point values. - -@item -27 -@code{integer*1}, 8 bit signed integral type. - -@item -28 -@code{integer*2}, 16 bit signed integral type. - -@item -29 -@code{integer*4}, 32 bit signed integral type. - -@item -30 -@code{wchar}. Wide character, 16 bits wide, unsigned (what format? -Unicode?). - -@item -31 -@code{long long}, 64 bit signed integral type. - -@item -32 -@code{unsigned long long}, 64 bit unsigned integral type. - -@item -33 -@code{logical*8}, 64 bit unsigned integral type. - -@item -34 -@code{integer*8}, 64 bit signed integral type. -@end table - -@node Miscellaneous Types -@section Miscellaneous Types - -@table @code -@item b @var{type-information} ; @var{bytes} -Pascal space type. This is documented by IBM; what does it mean? - -This use of the @samp{b} type descriptor can be distinguished -from its use for builtin integral types (@pxref{Builtin Type -Descriptors}) because the character following the type descriptor is -always a digit, @samp{(}, or @samp{-}. - -@item B @var{type-information} -A volatile-qualified version of @var{type-information}. This is -a Sun extension. References and stores to a variable with a -volatile-qualified type must not be optimized or cached; they -must occur as the user specifies them. - -@item d @var{type-information} -File of type @var{type-information}. As far as I know this is only used -by Pascal. - -@item k @var{type-information} -A const-qualified version of @var{type-information}. This is a Sun -extension. A variable with a const-qualified type cannot be modified. - -@item M @var{type-information} ; @var{length} -Multiple instance type. The type seems to composed of @var{length} -repetitions of @var{type-information}, for example @code{character*3} is -represented by @samp{M-2;3}, where @samp{-2} is a reference to a -character type (@pxref{Negative Type Numbers}). I'm not sure how this -differs from an array. This appears to be a Fortran feature. -@var{length} is a bound, like those in range types; see @ref{Subranges}. - -@item S @var{type-information} -Pascal set type. @var{type-information} must be a small type such as an -enumeration or a subrange, and the type is a bitmask whose length is -specified by the number of elements in @var{type-information}. - -In CHILL, if it is a bitstring instead of a set, also use the @samp{S} -type attribute (@pxref{String Field}). - -@item * @var{type-information} -Pointer to @var{type-information}. -@end table - -@node Cross-References -@section Cross-References to Other Types - -A type can be used before it is defined; one common way to deal with -that situation is just to use a type reference to a type which has not -yet been defined. - -Another way is with the @samp{x} type descriptor, which is followed by -@samp{s} for a structure tag, @samp{u} for a union tag, or @samp{e} for -a enumerator tag, followed by the name of the tag, followed by @samp{:}. -If the name contains @samp{::} between a @samp{<} and @samp{>} pair (for -C@t{++} templates), such a @samp{::} does not end the name---only a single -@samp{:} ends the name; see @ref{Nested Symbols}. - -For example, the following C declarations: - -@example -struct foo; -struct foo *bar; -@end example - -@noindent -produce: - -@example -.stabs "bar:G16=*17=xsfoo:",32,0,0,0 -@end example - -Not all debuggers support the @samp{x} type descriptor, so on some -machines GCC does not use it. I believe that for the above example it -would just emit a reference to type 17 and never define it, but I -haven't verified that. - -Modula-2 imported types, at least on AIX, use the @samp{i} type -descriptor, which is followed by the name of the module from which the -type is imported, followed by @samp{:}, followed by the name of the -type. There is then optionally a comma followed by type information for -the type. This differs from merely naming the type (@pxref{Typedefs}) in -that it identifies the module; I don't understand whether the name of -the type given here is always just the same as the name we are giving -it, or whether this type descriptor is used with a nameless stab -(@pxref{String Field}), or what. The symbol ends with @samp{;}. - -@node Subranges -@section Subrange Types - -The @samp{r} type descriptor defines a type as a subrange of another -type. It is followed by type information for the type of which it is a -subrange, a semicolon, an integral lower bound, a semicolon, an -integral upper bound, and a semicolon. The AIX documentation does not -specify the trailing semicolon, in an effort to specify array indexes -more cleanly, but a subrange which is not an array index has always -included a trailing semicolon (@pxref{Arrays}). - -Instead of an integer, either bound can be one of the following: - -@table @code -@item A @var{offset} -The bound is passed by reference on the stack at offset @var{offset} -from the argument list. @xref{Parameters}, for more information on such -offsets. - -@item T @var{offset} -The bound is passed by value on the stack at offset @var{offset} from -the argument list. - -@item a @var{register-number} -The bound is passed by reference in register number -@var{register-number}. - -@item t @var{register-number} -The bound is passed by value in register number @var{register-number}. - -@item J -There is no bound. -@end table - -Subranges are also used for builtin types; see @ref{Traditional Builtin Types}. - -@node Arrays -@section Array Types - -Arrays use the @samp{a} type descriptor. Following the type descriptor -is the type of the index and the type of the array elements. If the -index type is a range type, it ends in a semicolon; otherwise -(for example, if it is a type reference), there does not -appear to be any way to tell where the types are separated. In an -effort to clean up this mess, IBM documents the two types as being -separated by a semicolon, and a range type as not ending in a semicolon -(but this is not right for range types which are not array indexes, -@pxref{Subranges}). I think probably the best solution is to specify -that a semicolon ends a range type, and that the index type and element -type of an array are separated by a semicolon, but that if the index -type is a range type, the extra semicolon can be omitted. GDB (at least -through version 4.9) doesn't support any kind of index type other than a -range anyway; I'm not sure about dbx. - -It is well established, and widely used, that the type of the index, -unlike most types found in the stabs, is merely a type definition, not -type information (@pxref{String Field}) (that is, it need not start with -@samp{@var{type-number}=} if it is defining a new type). According to a -comment in GDB, this is also true of the type of the array elements; it -gives @samp{ar1;1;10;ar1;1;10;4} as a legitimate way to express a two -dimensional array. According to AIX documentation, the element type -must be type information. GDB accepts either. - -The type of the index is often a range type, expressed as the type -descriptor @samp{r} and some parameters. It defines the size of the -array. In the example below, the range @samp{r1;0;2;} defines an index -type which is a subrange of type 1 (integer), with a lower bound of 0 -and an upper bound of 2. This defines the valid range of subscripts of -a three-element C array. - -For example, the definition: - -@example -char char_vec[3] = @{'a','b','c'@}; -@end example - -@noindent -produces the output: - -@example -.stabs "char_vec:G19=ar1;0;2;2",32,0,0,0 - .global _char_vec - .align 4 -_char_vec: - .byte 97 - .byte 98 - .byte 99 -@end example - -If an array is @dfn{packed}, the elements are spaced more -closely than normal, saving memory at the expense of speed. For -example, an array of 3-byte objects might, if unpacked, have each -element aligned on a 4-byte boundary, but if packed, have no padding. -One way to specify that something is packed is with type attributes -(@pxref{String Field}). In the case of arrays, another is to use the -@samp{P} type descriptor instead of @samp{a}. Other than specifying a -packed array, @samp{P} is identical to @samp{a}. - -@c FIXME-what is it? A pointer? -An open array is represented by the @samp{A} type descriptor followed by -type information specifying the type of the array elements. - -@c FIXME: what is the format of this type? A pointer to a vector of pointers? -An N-dimensional dynamic array is represented by - -@example -D @var{dimensions} ; @var{type-information} -@end example - -@c Does dimensions really have this meaning? The AIX documentation -@c doesn't say. -@var{dimensions} is the number of dimensions; @var{type-information} -specifies the type of the array elements. - -@c FIXME: what is the format of this type? A pointer to some offsets in -@c another array? -A subarray of an N-dimensional array is represented by - -@example -E @var{dimensions} ; @var{type-information} -@end example - -@c Does dimensions really have this meaning? The AIX documentation -@c doesn't say. -@var{dimensions} is the number of dimensions; @var{type-information} -specifies the type of the array elements. - -@node Strings -@section Strings - -Some languages, like C or the original Pascal, do not have string types, -they just have related things like arrays of characters. But most -Pascals and various other languages have string types, which are -indicated as follows: - -@table @code -@item n @var{type-information} ; @var{bytes} -@var{bytes} is the maximum length. I'm not sure what -@var{type-information} is; I suspect that it means that this is a string -of @var{type-information} (thus allowing a string of integers, a string -of wide characters, etc., as well as a string of characters). Not sure -what the format of this type is. This is an AIX feature. - -@item z @var{type-information} ; @var{bytes} -Just like @samp{n} except that this is a gstring, not an ordinary -string. I don't know the difference. - -@item N -Pascal Stringptr. What is this? This is an AIX feature. -@end table - -Languages, such as CHILL which have a string type which is basically -just an array of characters use the @samp{S} type attribute -(@pxref{String Field}). - -@node Enumerations -@section Enumerations - -Enumerations are defined with the @samp{e} type descriptor. - -@c FIXME: Where does this information properly go? Perhaps it is -@c redundant with something we already explain. -The source line below declares an enumeration type at file scope. -The type definition is located after the @code{N_RBRAC} that marks the end of -the previous procedure's block scope, and before the @code{N_FUN} that marks -the beginning of the next procedure's block scope. Therefore it does not -describe a block local symbol, but a file local one. - -The source line: - -@example -enum e_places @{first,second=3,last@}; -@end example - -@noindent -generates the following stab: - -@example -.stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0 -@end example - -The symbol descriptor (@samp{T}) says that the stab describes a -structure, enumeration, or union tag. The type descriptor @samp{e}, -following the @samp{22=} of the type definition narrows it down to an -enumeration type. Following the @samp{e} is a list of the elements of -the enumeration. The format is @samp{@var{name}:@var{value},}. The -list of elements ends with @samp{;}. The fact that @var{value} is -specified as an integer can cause problems if the value is large. GCC -2.5.2 tries to output it in octal in that case with a leading zero, -which is probably a good thing, although GDB 4.11 supports octal only in -cases where decimal is perfectly good. Negative decimal values are -supported by both GDB and dbx. - -There is no standard way to specify the size of an enumeration type; it -is determined by the architecture (normally all enumerations types are -32 bits). Type attributes can be used to specify an enumeration type of -another size for debuggers which support them; see @ref{String Field}. - -Enumeration types are unusual in that they define symbols for the -enumeration values (@code{first}, @code{second}, and @code{third} in the -above example), and even though these symbols are visible in the file as -a whole (rather than being in a more local namespace like structure -member names), they are defined in the type definition for the -enumeration type rather than each having their own symbol. In order to -be fast, GDB will only get symbols from such types (in its initial scan -of the stabs) if the type is the first thing defined after a @samp{T} or -@samp{t} symbol descriptor (the above example fulfills this -requirement). If the type does not have a name, the compiler should -emit it in a nameless stab (@pxref{String Field}); GCC does this. - -@node Structures -@section Structures - -The encoding of structures in stabs can be shown with an example. - -The following source code declares a structure tag and defines an -instance of the structure in global scope. Then a @code{typedef} equates the -structure tag with a new type. Separate stabs are generated for the -structure tag, the structure @code{typedef}, and the structure instance. The -stabs for the tag and the @code{typedef} are emitted when the definitions are -encountered. Since the structure elements are not initialized, the -stab and code for the structure variable itself is located at the end -of the program in the bss section. - -@example -struct s_tag @{ - int s_int; - float s_float; - char s_char_vec[8]; - struct s_tag* s_next; -@} g_an_s; - -typedef struct s_tag s_typedef; -@end example - -The structure tag has an @code{N_LSYM} stab type because, like the -enumeration, the symbol has file scope. Like the enumeration, the -symbol descriptor is @samp{T}, for enumeration, structure, or tag type. -The type descriptor @samp{s} following the @samp{16=} of the type -definition narrows the symbol type to structure. - -Following the @samp{s} type descriptor is the number of bytes the -structure occupies, followed by a description of each structure element. -The structure element descriptions are of the form -@samp{@var{name}:@var{type}, @var{bit offset from the start of the -struct}, @var{number of bits in the element}}. - -@c FIXME: phony line break. Can probably be fixed by using an example -@c with fewer fields. -@example -# @r{128 is N_LSYM} -.stabs "s_tag:T16=s20s_int:1,0,32;s_float:12,32,32; - s_char_vec:17=ar1;0;7;2,64,64;s_next:18=*16,128,32;;",128,0,0,0 -@end example - -In this example, the first two structure elements are previously defined -types. For these, the type following the @samp{@var{name}:} part of the -element description is a simple type reference. The other two structure -elements are new types. In this case there is a type definition -embedded after the @samp{@var{name}:}. The type definition for the -array element looks just like a type definition for a stand-alone array. -The @code{s_next} field is a pointer to the same kind of structure that -the field is an element of. So the definition of structure type 16 -contains a type definition for an element which is a pointer to type 16. - -If a field is a static member (this is a C@t{++} feature in which a single -variable appears to be a field of every structure of a given type) it -still starts out with the field name, a colon, and the type, but then -instead of a comma, bit position, comma, and bit size, there is a colon -followed by the name of the variable which each such field refers to. - -If the structure has methods (a C@t{++} feature), they follow the non-method -fields; see @ref{Cplusplus}. - -@node Typedefs -@section Giving a Type a Name - -@findex N_LSYM, for types -@findex C_DECL, for types -To give a type a name, use the @samp{t} symbol descriptor. The type -is specified by the type information (@pxref{String Field}) for the stab. -For example, - -@example -.stabs "s_typedef:t16",128,0,0,0 # @r{128 is N_LSYM} -@end example - -specifies that @code{s_typedef} refers to type number 16. Such stabs -have symbol type @code{N_LSYM} (or @code{C_DECL} for XCOFF). (The Sun -documentation mentions using @code{N_GSYM} in some cases). - -If you are specifying the tag name for a structure, union, or -enumeration, use the @samp{T} symbol descriptor instead. I believe C is -the only language with this feature. - -If the type is an opaque type (I believe this is a Modula-2 feature), -AIX provides a type descriptor to specify it. The type descriptor is -@samp{o} and is followed by a name. I don't know what the name -means---is it always the same as the name of the type, or is this type -descriptor used with a nameless stab (@pxref{String Field})? There -optionally follows a comma followed by type information which defines -the type of this type. If omitted, a semicolon is used in place of the -comma and the type information, and the type is much like a generic -pointer type---it has a known size but little else about it is -specified. - -@node Unions -@section Unions - -@example -union u_tag @{ - int u_int; - float u_float; - char* u_char; -@} an_u; -@end example - -This code generates a stab for a union tag and a stab for a union -variable. Both use the @code{N_LSYM} stab type. If a union variable is -scoped locally to the procedure in which it is defined, its stab is -located immediately preceding the @code{N_LBRAC} for the procedure's block -start. - -The stab for the union tag, however, is located preceding the code for -the procedure in which it is defined. The stab type is @code{N_LSYM}. This -would seem to imply that the union type is file scope, like the struct -type @code{s_tag}. This is not true. The contents and position of the stab -for @code{u_type} do not convey any information about its procedure local -scope. - -@c FIXME: phony line break. Can probably be fixed by using an example -@c with fewer fields. -@smallexample -# @r{128 is N_LSYM} -.stabs "u_tag:T23=u4u_int:1,0,32;u_float:12,0,32;u_char:21,0,32;;", - 128,0,0,0 -@end smallexample - -The symbol descriptor @samp{T}, following the @samp{name:} means that -the stab describes an enumeration, structure, or union tag. The type -descriptor @samp{u}, following the @samp{23=} of the type definition, -narrows it down to a union type definition. Following the @samp{u} is -the number of bytes in the union. After that is a list of union element -descriptions. Their format is @samp{@var{name}:@var{type}, @var{bit -offset into the union}, @var{number of bytes for the element};}. - -The stab for the union variable is: - -@example -.stabs "an_u:23",128,0,0,-20 # @r{128 is N_LSYM} -@end example - -@samp{-20} specifies where the variable is stored (@pxref{Stack -Variables}). - -@node Function Types -@section Function Types - -Various types can be defined for function variables. These types are -not used in defining functions (@pxref{Procedures}); they are used for -things like pointers to functions. - -The simple, traditional, type is type descriptor @samp{f} is followed by -type information for the return type of the function, followed by a -semicolon. - -This does not deal with functions for which the number and types of the -parameters are part of the type, as in Modula-2 or ANSI C. AIX provides -extensions to specify these, using the @samp{f}, @samp{F}, @samp{p}, and -@samp{R} type descriptors. - -First comes the type descriptor. If it is @samp{f} or @samp{F}, this -type involves a function rather than a procedure, and the type -information for the return type of the function follows, followed by a -comma. Then comes the number of parameters to the function and a -semicolon. Then, for each parameter, there is the name of the parameter -followed by a colon (this is only present for type descriptors @samp{R} -and @samp{F} which represent Pascal function or procedure parameters), -type information for the parameter, a comma, 0 if passed by reference or -1 if passed by value, and a semicolon. The type definition ends with a -semicolon. - -For example, this variable definition: - -@example -int (*g_pf)(); -@end example - -@noindent -generates the following code: - -@example -.stabs "g_pf:G24=*25=f1",32,0,0,0 - .common _g_pf,4,"bss" -@end example - -The variable defines a new type, 24, which is a pointer to another new -type, 25, which is a function returning @code{int}. - -@node Macro define and undefine -@chapter Representation of #define and #undef - -This section describes the stabs support for macro define and undefine -information, supported on some systems. (e.g., with @option{-g3} -@option{-gstabs} when using GCC). - -A @code{#define @var{macro-name} @var{macro-body}} is represented with -an @code{N_MAC_DEFINE} stab with a string field of -@code{@var{macro-name} @var{macro-body}}. -@findex N_MAC_DEFINE - -An @code{#undef @var{macro-name}} is represented with an -@code{N_MAC_UNDEF} stabs with a string field of simply -@code{@var{macro-name}}. -@findex N_MAC_UNDEF - -For both @code{N_MAC_DEFINE} and @code{N_MAC_UNDEF}, the desc field is -the line number within the file where the corresponding @code{#define} -or @code{#undef} occurred. - -For example, the following C code: - -@example - #define NONE 42 - #define TWO(a, b) (a + (a) + 2 * b) - #define ONE(c) (c + 19) - - main(int argc, char *argv[]) - @{ - func(NONE, TWO(10, 11)); - func(NONE, ONE(23)); - - #undef ONE - #define ONE(c) (c + 23) - - func(NONE, ONE(-23)); - - return (0); - @} - - int global; - - func(int arg1, int arg2) - @{ - global = arg1 + arg2; - @} -@end example - -@noindent -produces the following stabs (as well as many others): - -@example - .stabs "NONE 42",54,0,1,0 - .stabs "TWO(a,b) (a + (a) + 2 * b)",54,0,2,0 - .stabs "ONE(c) (c + 19)",54,0,3,0 - .stabs "ONE",58,0,10,0 - .stabs "ONE(c) (c + 23)",54,0,11,0 -@end example - -@noindent -NOTE: In the above example, @code{54} is @code{N_MAC_DEFINE} and -@code{58} is @code{N_MAC_UNDEF}. - -@node Symbol Tables -@chapter Symbol Information in Symbol Tables - -This chapter describes the format of symbol table entries -and how stab assembler directives map to them. It also describes the -transformations that the assembler and linker make on data from stabs. - -@menu -* Symbol Table Format:: -* Transformations On Symbol Tables:: -@end menu - -@node Symbol Table Format -@section Symbol Table Format - -Each time the assembler encounters a stab directive, it puts -each field of the stab into a corresponding field in a symbol table -entry of its output file. If the stab contains a string field, the -symbol table entry for that stab points to a string table entry -containing the string data from the stab. Assembler labels become -relocatable addresses. Symbol table entries in a.out have the format: - -@c FIXME: should refer to external, not internal. -@example -struct internal_nlist @{ - unsigned long n_strx; /* index into string table of name */ - unsigned char n_type; /* type of symbol */ - unsigned char n_other; /* misc info (usually empty) */ - unsigned short n_desc; /* description field */ - bfd_vma n_value; /* value of symbol */ -@}; -@end example - -If the stab has a string, the @code{n_strx} field holds the offset in -bytes of the string within the string table. The string is terminated -by a NUL character. If the stab lacks a string (for example, it was -produced by a @code{.stabn} or @code{.stabd} directive), the -@code{n_strx} field is zero. - -Symbol table entries with @code{n_type} field values greater than 0x1f -originated as stabs generated by the compiler (with one random -exception). The other entries were placed in the symbol table of the -executable by the assembler or the linker. - -@node Transformations On Symbol Tables -@section Transformations on Symbol Tables - -The linker concatenates object files and does fixups of externally -defined symbols. - -You can see the transformations made on stab data by the assembler and -linker by examining the symbol table after each pass of the build. To -do this, use @samp{nm -ap}, which dumps the symbol table, including -debugging information, unsorted. For stab entries the columns are: -@var{value}, @var{other}, @var{desc}, @var{type}, @var{string}. For -assembler and linker symbols, the columns are: @var{value}, @var{type}, -@var{string}. - -The low 5 bits of the stab type tell the linker how to relocate the -value of the stab. Thus for stab types like @code{N_RSYM} and -@code{N_LSYM}, where the value is an offset or a register number, the -low 5 bits are @code{N_ABS}, which tells the linker not to relocate the -value. - -Where the value of a stab contains an assembly language label, -it is transformed by each build step. The assembler turns it into a -relocatable address and the linker turns it into an absolute address. - -@menu -* Transformations On Static Variables:: -* Transformations On Global Variables:: -* Stab Section Transformations:: For some object file formats, - things are a bit different. -@end menu - -@node Transformations On Static Variables -@subsection Transformations on Static Variables - -This source line defines a static variable at file scope: - -@example -static int s_g_repeat -@end example - -@noindent -The following stab describes the symbol: - -@example -.stabs "s_g_repeat:S1",38,0,0,_s_g_repeat -@end example - -@noindent -The assembler transforms the stab into this symbol table entry in the -@file{.o} file. The location is expressed as a data segment offset. - -@example -00000084 - 00 0000 STSYM s_g_repeat:S1 -@end example - -@noindent -In the symbol table entry from the executable, the linker has made the -relocatable address absolute. - -@example -0000e00c - 00 0000 STSYM s_g_repeat:S1 -@end example - -@node Transformations On Global Variables -@subsection Transformations on Global Variables - -Stabs for global variables do not contain location information. In -this case, the debugger finds location information in the assembler or -linker symbol table entry describing the variable. The source line: - -@example -char g_foo = 'c'; -@end example - -@noindent -generates the stab: - -@example -.stabs "g_foo:G2",32,0,0,0 -@end example - -The variable is represented by two symbol table entries in the object -file (see below). The first one originated as a stab. The second one -is an external symbol. The upper case @samp{D} signifies that the -@code{n_type} field of the symbol table contains 7, @code{N_DATA} with -local linkage. The stab's value is zero since the value is not used for -@code{N_GSYM} stabs. The value of the linker symbol is the relocatable -address corresponding to the variable. - -@example -00000000 - 00 0000 GSYM g_foo:G2 -00000080 D _g_foo -@end example - -@noindent -These entries as transformed by the linker. The linker symbol table -entry now holds an absolute address: - -@example -00000000 - 00 0000 GSYM g_foo:G2 -@dots{} -0000e008 D _g_foo -@end example - -@node Stab Section Transformations -@subsection Transformations of Stabs in separate sections - -For object file formats using stabs in separate sections (@pxref{Stab -Sections}), use @code{objdump --stabs} instead of @code{nm} to show the -stabs in an object or executable file. @code{objdump} is a GNU utility; -Sun does not provide any equivalent. - -The following example is for a stab whose value is an address is -relative to the compilation unit (@pxref{ELF Linker Relocation}). For -example, if the source line - -@example -static int ld = 5; -@end example - -appears within a function, then the assembly language output from the -compiler contains: - -@example -.Ddata.data: -@dots{} - .stabs "ld:V(0,3)",0x26,0,4,.L18-Ddata.data # @r{0x26 is N_STSYM} -@dots{} -.L18: - .align 4 - .word 0x5 -@end example - -Because the value is formed by subtracting one symbol from another, the -value is absolute, not relocatable, and so the object file contains - -@example -Symnum n_type n_othr n_desc n_value n_strx String -31 STSYM 0 4 00000004 680 ld:V(0,3) -@end example - -without any relocations, and the executable file also contains - -@example -Symnum n_type n_othr n_desc n_value n_strx String -31 STSYM 0 4 00000004 680 ld:V(0,3) -@end example - -@node Cplusplus -@chapter GNU C@t{++} Stabs - -@menu -* Class Names:: C++ class names are both tags and typedefs. -* Nested Symbols:: C++ symbol names can be within other types. -* Basic Cplusplus Types:: -* Simple Classes:: -* Class Instance:: -* Methods:: Method definition -* Method Type Descriptor:: The @samp{#} type descriptor -* Member Type Descriptor:: The @samp{@@} type descriptor -* Protections:: -* Method Modifiers:: -* Virtual Methods:: -* Inheritance:: -* Virtual Base Classes:: -* Static Members:: -@end menu - -@node Class Names -@section C@t{++} Class Names - -In C@t{++}, a class name which is declared with @code{class}, @code{struct}, -or @code{union}, is not only a tag, as in C, but also a type name. Thus -there should be stabs with both @samp{t} and @samp{T} symbol descriptors -(@pxref{Typedefs}). - -To save space, there is a special abbreviation for this case. If the -@samp{T} symbol descriptor is followed by @samp{t}, then the stab -defines both a type name and a tag. - -For example, the C@t{++} code - -@example -struct foo @{int x;@}; -@end example - -can be represented as either - -@example -.stabs "foo:T19=s4x:1,0,32;;",128,0,0,0 # @r{128 is N_LSYM} -.stabs "foo:t19",128,0,0,0 -@end example - -or - -@example -.stabs "foo:Tt19=s4x:1,0,32;;",128,0,0,0 -@end example - -@node Nested Symbols -@section Defining a Symbol Within Another Type - -In C@t{++}, a symbol (such as a type name) can be defined within another type. -@c FIXME: Needs example. - -In stabs, this is sometimes represented by making the name of a symbol -which contains @samp{::}. Such a pair of colons does not end the name -of the symbol, the way a single colon would (@pxref{String Field}). I'm -not sure how consistently used or well thought out this mechanism is. -So that a pair of colons in this position always has this meaning, -@samp{:} cannot be used as a symbol descriptor. - -For example, if the string for a stab is @samp{foo::bar::baz:t5=*6}, -then @code{foo::bar::baz} is the name of the symbol, @samp{t} is the -symbol descriptor, and @samp{5=*6} is the type information. - -@node Basic Cplusplus Types -@section Basic Types For C@t{++} - -<< the examples that follow are based on a01.C >> - - -C@t{++} adds two more builtin types to the set defined for C. These are -the unknown type and the vtable record type. The unknown type, type -16, is defined in terms of itself like the void type. - -The vtable record type, type 17, is defined as a structure type and -then as a structure tag. The structure has four fields: delta, index, -pfn, and delta2. pfn is the function pointer. - -<< In boilerplate $vtbl_ptr_type, what are the fields delta, -index, and delta2 used for? >> - -This basic type is present in all C@t{++} programs even if there are no -virtual methods defined. - -@display -.stabs "struct_name:sym_desc(type)type_def(17)=type_desc(struct)struct_bytes(8) - elem_name(delta):type_ref(short int),bit_offset(0),field_bits(16); - elem_name(index):type_ref(short int),bit_offset(16),field_bits(16); - elem_name(pfn):type_def(18)=type_desc(ptr to)type_ref(void), - bit_offset(32),field_bits(32); - elem_name(delta2):type_def(short int);bit_offset(32),field_bits(16);;" - N_LSYM, NIL, NIL -@end display - -@smallexample -.stabs "$vtbl_ptr_type:t17=s8 - delta:6,0,16;index:6,16,16;pfn:18=*15,32,32;delta2:6,32,16;;" - ,128,0,0,0 -@end smallexample - -@display -.stabs "name:sym_dec(struct tag)type_ref($vtbl_ptr_type)",N_LSYM,NIL,NIL,NIL -@end display - -@example -.stabs "$vtbl_ptr_type:T17",128,0,0,0 -@end example - -@node Simple Classes -@section Simple Class Definition - -The stabs describing C@t{++} language features are an extension of the -stabs describing C. Stabs representing C@t{++} class types elaborate -extensively on the stab format used to describe structure types in C. -Stabs representing class type variables look just like stabs -representing C language variables. - -Consider the following very simple class definition. - -@example -class baseA @{ -public: - int Adat; - int Ameth(int in, char other); -@}; -@end example - -The class @code{baseA} is represented by two stabs. The first stab describes -the class as a structure type. The second stab describes a structure -tag of the class type. Both stabs are of stab type @code{N_LSYM}. Since the -stab is not located between an @code{N_FUN} and an @code{N_LBRAC} stab this indicates -that the class is defined at file scope. If it were, then the @code{N_LSYM} -would signify a local variable. - -A stab describing a C@t{++} class type is similar in format to a stab -describing a C struct, with each class member shown as a field in the -structure. The part of the struct format describing fields is -expanded to include extra information relevant to C@t{++} class members. -In addition, if the class has multiple base classes or virtual -functions the struct format outside of the field parts is also -augmented. - -In this simple example the field part of the C@t{++} class stab -representing member data looks just like the field part of a C struct -stab. The section on protections describes how its format is -sometimes extended for member data. - -The field part of a C@t{++} class stab representing a member function -differs substantially from the field part of a C struct stab. It -still begins with @samp{name:} but then goes on to define a new type number -for the member function, describe its return type, its argument types, -its protection level, any qualifiers applied to the method definition, -and whether the method is virtual or not. If the method is virtual -then the method description goes on to give the vtable index of the -method, and the type number of the first base class defining the -method. - -When the field name is a method name it is followed by two colons rather -than one. This is followed by a new type definition for the method. -This is a number followed by an equal sign and the type of the method. -Normally this will be a type declared using the @samp{#} type -descriptor; see @ref{Method Type Descriptor}; static member functions -are declared using the @samp{f} type descriptor instead; see -@ref{Function Types}. - -The format of an overloaded operator method name differs from that of -other methods. It is @samp{op$::@var{operator-name}.} where -@var{operator-name} is the operator name such as @samp{+} or @samp{+=}. -The name ends with a period, and any characters except the period can -occur in the @var{operator-name} string. - -The next part of the method description represents the arguments to the -method, preceded by a colon and ending with a semi-colon. The types of -the arguments are expressed in the same way argument types are expressed -in C@t{++} name mangling. In this example an @code{int} and a @code{char} -map to @samp{ic}. - -This is followed by a number, a letter, and an asterisk or period, -followed by another semicolon. The number indicates the protections -that apply to the member function. Here the 2 means public. The -letter encodes any qualifier applied to the method definition. In -this case, @samp{A} means that it is a normal function definition. The dot -shows that the method is not virtual. The sections that follow -elaborate further on these fields and describe the additional -information present for virtual methods. - - -@display -.stabs "class_name:sym_desc(type)type_def(20)=type_desc(struct)struct_bytes(4) - field_name(Adat):type(int),bit_offset(0),field_bits(32); - - method_name(Ameth)::type_def(21)=type_desc(method)return_type(int); - :arg_types(int char); - protection(public)qualifier(normal)virtual(no);;" - N_LSYM,NIL,NIL,NIL -@end display - -@smallexample -.stabs "baseA:t20=s4Adat:1,0,32;Ameth::21=##1;:ic;2A.;;",128,0,0,0 - -.stabs "class_name:sym_desc(struct tag)",N_LSYM,NIL,NIL,NIL - -.stabs "baseA:T20",128,0,0,0 -@end smallexample - -@node Class Instance -@section Class Instance - -As shown above, describing even a simple C@t{++} class definition is -accomplished by massively extending the stab format used in C to -describe structure types. However, once the class is defined, C stabs -with no modifications can be used to describe class instances. The -following source: - -@example -main () @{ - baseA AbaseA; -@} -@end example - -@noindent -yields the following stab describing the class instance. It looks no -different from a standard C stab describing a local variable. - -@display -.stabs "name:type_ref(baseA)", N_LSYM, NIL, NIL, frame_ptr_offset -@end display - -@example -.stabs "AbaseA:20",128,0,0,-20 -@end example - -@node Methods -@section Method Definition - -The class definition shown above declares Ameth. The C@t{++} source below -defines Ameth: - -@example -int -baseA::Ameth(int in, char other) -@{ - return in; -@}; -@end example - - -This method definition yields three stabs following the code of the -method. One stab describes the method itself and following two describe -its parameters. Although there is only one formal argument all methods -have an implicit argument which is the @code{this} pointer. The @code{this} -pointer is a pointer to the object on which the method was called. Note -that the method name is mangled to encode the class name and argument -types. Name mangling is described in the @sc{arm} (@cite{The Annotated -C++ Reference Manual}, by Ellis and Stroustrup, @sc{isbn} -0-201-51459-1); @file{gpcompare.texi} in Cygnus GCC distributions -describes the differences between GNU mangling and @sc{arm} -mangling. -@c FIXME: Use @xref, especially if this is generally installed in the -@c info tree. -@c FIXME: This information should be in a net release, either of GCC or -@c GDB. But gpcompare.texi doesn't seem to be in the FSF GCC. - -@example -.stabs "name:symbol_descriptor(global function)return_type(int)", - N_FUN, NIL, NIL, code_addr_of_method_start - -.stabs "Ameth__5baseAic:F1",36,0,0,_Ameth__5baseAic -@end example - -Here is the stab for the @code{this} pointer implicit argument. The -name of the @code{this} pointer is always @code{this}. Type 19, the -@code{this} pointer is defined as a pointer to type 20, @code{baseA}, -but a stab defining @code{baseA} has not yet been emitted. Since the -compiler knows it will be emitted shortly, here it just outputs a cross -reference to the undefined symbol, by prefixing the symbol name with -@samp{xs}. - -@example -.stabs "name:sym_desc(register param)type_def(19)= - type_desc(ptr to)type_ref(baseA)= - type_desc(cross-reference to)baseA:",N_RSYM,NIL,NIL,register_number - -.stabs "this:P19=*20=xsbaseA:",64,0,0,8 -@end example - -The stab for the explicit integer argument looks just like a parameter -to a C function. The last field of the stab is the offset from the -argument pointer, which in most systems is the same as the frame -pointer. - -@example -.stabs "name:sym_desc(value parameter)type_ref(int)", - N_PSYM,NIL,NIL,offset_from_arg_ptr - -.stabs "in:p1",160,0,0,72 -@end example - -<< The examples that follow are based on A1.C >> - -@node Method Type Descriptor -@section The @samp{#} Type Descriptor - -This is used to describe a class method. This is a function which takes -an extra argument as its first argument, for the @code{this} pointer. - -If the @samp{#} is immediately followed by another @samp{#}, the second -one will be followed by the return type and a semicolon. The class and -argument types are not specified, and must be determined by demangling -the name of the method if it is available. - -Otherwise, the single @samp{#} is followed by the class type, a comma, -the return type, a comma, and zero or more parameter types separated by -commas. The list of arguments is terminated by a semicolon. In the -debugging output generated by gcc, a final argument type of @code{void} -indicates a method which does not take a variable number of arguments. -If the final argument type of @code{void} does not appear, the method -was declared with an ellipsis. - -Note that although such a type will normally be used to describe fields -in structures, unions, or classes, for at least some versions of the -compiler it can also be used in other contexts. - -@node Member Type Descriptor -@section The @samp{@@} Type Descriptor - -The @samp{@@} type descriptor is used for a -pointer-to-non-static-member-data type. It is followed -by type information for the class (or union), a comma, and type -information for the member data. - -The following C@t{++} source: - -@smallexample -typedef int A::*int_in_a; -@end smallexample - -generates the following stab: - -@smallexample -.stabs "int_in_a:t20=21=@@19,1",128,0,0,0 -@end smallexample - -Note that there is a conflict between this and type attributes -(@pxref{String Field}); both use type descriptor @samp{@@}. -Fortunately, the @samp{@@} type descriptor used in this C@t{++} sense always -will be followed by a digit, @samp{(}, or @samp{-}, and type attributes -never start with those things. - -@node Protections -@section Protections - -In the simple class definition shown above all member data and -functions were publicly accessible. The example that follows -contrasts public, protected and privately accessible fields and shows -how these protections are encoded in C@t{++} stabs. - -If the character following the @samp{@var{field-name}:} part of the -string is @samp{/}, then the next character is the visibility. @samp{0} -means private, @samp{1} means protected, and @samp{2} means public. -Debuggers should ignore visibility characters they do not recognize, and -assume a reasonable default (such as public) (GDB 4.11 does not, but -this should be fixed in the next GDB release). If no visibility is -specified the field is public. The visibility @samp{9} means that the -field has been optimized out and is public (there is no way to specify -an optimized out field with a private or protected visibility). -Visibility @samp{9} is not supported by GDB 4.11; this should be fixed -in the next GDB release. - -The following C@t{++} source: - -@example -class vis @{ -private: - int priv; -protected: - char prot; -public: - float pub; -@}; -@end example - -@noindent -generates the following stab: - -@example -# @r{128 is N_LSYM} -.stabs "vis:T19=s12priv:/01,0,32;prot:/12,32,8;pub:12,64,32;;",128,0,0,0 -@end example - -@samp{vis:T19=s12} indicates that type number 19 is a 12 byte structure -named @code{vis} The @code{priv} field has public visibility -(@samp{/0}), type int (@samp{1}), and offset and size @samp{,0,32;}. -The @code{prot} field has protected visibility (@samp{/1}), type char -(@samp{2}) and offset and size @samp{,32,8;}. The @code{pub} field has -type float (@samp{12}), and offset and size @samp{,64,32;}. - -Protections for member functions are signified by one digit embedded in -the field part of the stab describing the method. The digit is 0 if -private, 1 if protected and 2 if public. Consider the C@t{++} class -definition below: - -@example -class all_methods @{ -private: - int priv_meth(int in)@{return in;@}; -protected: - char protMeth(char in)@{return in;@}; -public: - float pubMeth(float in)@{return in;@}; -@}; -@end example - -It generates the following stab. The digit in question is to the left -of an @samp{A} in each case. Notice also that in this case two symbol -descriptors apply to the class name struct tag and struct type. - -@display -.stabs "class_name:sym_desc(struct tag&type)type_def(21)= - sym_desc(struct)struct_bytes(1) - meth_name::type_def(22)=sym_desc(method)returning(int); - :args(int);protection(private)modifier(normal)virtual(no); - meth_name::type_def(23)=sym_desc(method)returning(char); - :args(char);protection(protected)modifier(normal)virtual(no); - meth_name::type_def(24)=sym_desc(method)returning(float); - :args(float);protection(public)modifier(normal)virtual(no);;", - N_LSYM,NIL,NIL,NIL -@end display - -@smallexample -.stabs "all_methods:Tt21=s1priv_meth::22=##1;:i;0A.;protMeth::23=##2;:c;1A.; - pubMeth::24=##12;:f;2A.;;",128,0,0,0 -@end smallexample - -@node Method Modifiers -@section Method Modifiers (@code{const}, @code{volatile}, @code{const volatile}) - -<< based on a6.C >> - -In the class example described above all the methods have the normal -modifier. This method modifier information is located just after the -protection information for the method. This field has four possible -character values. Normal methods use @samp{A}, const methods use -@samp{B}, volatile methods use @samp{C}, and const volatile methods use -@samp{D}. Consider the class definition below: - -@example -class A @{ -public: - int ConstMeth (int arg) const @{ return arg; @}; - char VolatileMeth (char arg) volatile @{ return arg; @}; - float ConstVolMeth (float arg) const volatile @{return arg; @}; -@}; -@end example - -This class is described by the following stab: - -@display -.stabs "class(A):sym_desc(struct)type_def(20)=type_desc(struct)struct_bytes(1) - meth_name(ConstMeth)::type_def(21)sym_desc(method) - returning(int);:arg(int);protection(public)modifier(const)virtual(no); - meth_name(VolatileMeth)::type_def(22)=sym_desc(method) - returning(char);:arg(char);protection(public)modifier(volatile)virt(no) - meth_name(ConstVolMeth)::type_def(23)=sym_desc(method) - returning(float);:arg(float);protection(public)modifier(const volatile) - virtual(no);;", @dots{} -@end display - -@example -.stabs "A:T20=s1ConstMeth::21=##1;:i;2B.;VolatileMeth::22=##2;:c;2C.; - ConstVolMeth::23=##12;:f;2D.;;",128,0,0,0 -@end example - -@node Virtual Methods -@section Virtual Methods - -<< The following examples are based on a4.C >> - -The presence of virtual methods in a class definition adds additional -data to the class description. The extra data is appended to the -description of the virtual method and to the end of the class -description. Consider the class definition below: - -@example -class A @{ -public: - int Adat; - virtual int A_virt (int arg) @{ return arg; @}; -@}; -@end example - -This results in the stab below describing class A. It defines a new -type (20) which is an 8 byte structure. The first field of the class -struct is @samp{Adat}, an integer, starting at structure offset 0 and -occupying 32 bits. - -The second field in the class struct is not explicitly defined by the -C@t{++} class definition but is implied by the fact that the class -contains a virtual method. This field is the vtable pointer. The -name of the vtable pointer field starts with @samp{$vf} and continues with a -type reference to the class it is part of. In this example the type -reference for class A is 20 so the name of its vtable pointer field is -@samp{$vf20}, followed by the usual colon. - -Next there is a type definition for the vtable pointer type (21). -This is in turn defined as a pointer to another new type (22). - -Type 22 is the vtable itself, which is defined as an array, indexed by -a range of integers between 0 and 1, and whose elements are of type -17. Type 17 was the vtable record type defined by the boilerplate C@t{++} -type definitions, as shown earlier. - -The bit offset of the vtable pointer field is 32. The number of bits -in the field are not specified when the field is a vtable pointer. - -Next is the method definition for the virtual member function @code{A_virt}. -Its description starts out using the same format as the non-virtual -member functions described above, except instead of a dot after the -@samp{A} there is an asterisk, indicating that the function is virtual. -Since is is virtual some addition information is appended to the end -of the method description. - -The first number represents the vtable index of the method. This is a -32 bit unsigned number with the high bit set, followed by a -semi-colon. - -The second number is a type reference to the first base class in the -inheritance hierarchy defining the virtual member function. In this -case the class stab describes a base class so the virtual function is -not overriding any other definition of the method. Therefore the -reference is to the type number of the class that the stab is -describing (20). - -This is followed by three semi-colons. One marks the end of the -current sub-section, one marks the end of the method field, and the -third marks the end of the struct definition. - -For classes containing virtual functions the very last section of the -string part of the stab holds a type reference to the first base -class. This is preceded by @samp{~%} and followed by a final semi-colon. - -@display -.stabs "class_name(A):type_def(20)=sym_desc(struct)struct_bytes(8) - field_name(Adat):type_ref(int),bit_offset(0),field_bits(32); - field_name(A virt func ptr):type_def(21)=type_desc(ptr to)type_def(22)= - sym_desc(array)index_type_ref(range of int from 0 to 1); - elem_type_ref(vtbl elem type), - bit_offset(32); - meth_name(A_virt)::typedef(23)=sym_desc(method)returning(int); - :arg_type(int),protection(public)normal(yes)virtual(yes) - vtable_index(1);class_first_defining(A);;;~%first_base(A);", - N_LSYM,NIL,NIL,NIL -@end display - -@c FIXME: bogus line break. -@example -.stabs "A:t20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32; - A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0 -@end example - -@node Inheritance -@section Inheritance - -Stabs describing C@t{++} derived classes include additional sections that -describe the inheritance hierarchy of the class. A derived class stab -also encodes the number of base classes. For each base class it tells -if the base class is virtual or not, and if the inheritance is private -or public. It also gives the offset into the object of the portion of -the object corresponding to each base class. - -This additional information is embedded in the class stab following the -number of bytes in the struct. First the number of base classes -appears bracketed by an exclamation point and a comma. - -Then for each base type there repeats a series: a virtual character, a -visibility character, a number, a comma, another number, and a -semi-colon. - -The virtual character is @samp{1} if the base class is virtual and -@samp{0} if not. The visibility character is @samp{2} if the derivation -is public, @samp{1} if it is protected, and @samp{0} if it is private. -Debuggers should ignore virtual or visibility characters they do not -recognize, and assume a reasonable default (such as public and -non-virtual) (GDB 4.11 does not, but this should be fixed in the next -GDB release). - -The number following the virtual and visibility characters is the offset -from the start of the object to the part of the object pertaining to the -base class. - -After the comma, the second number is a type_descriptor for the base -type. Finally a semi-colon ends the series, which repeats for each -base class. - -The source below defines three base classes @code{A}, @code{B}, and -@code{C} and the derived class @code{D}. - - -@example -class A @{ -public: - int Adat; - virtual int A_virt (int arg) @{ return arg; @}; -@}; - -class B @{ -public: - int B_dat; - virtual int B_virt (int arg) @{return arg; @}; -@}; - -class C @{ -public: - int Cdat; - virtual int C_virt (int arg) @{return arg; @}; -@}; - -class D : A, virtual B, public C @{ -public: - int Ddat; - virtual int A_virt (int arg ) @{ return arg+1; @}; - virtual int B_virt (int arg) @{ return arg+2; @}; - virtual int C_virt (int arg) @{ return arg+3; @}; - virtual int D_virt (int arg) @{ return arg; @}; -@}; -@end example - -Class stabs similar to the ones described earlier are generated for -each base class. - -@c FIXME!!! the linebreaks in the following example probably make the -@c examples literally unusable, but I don't know any other way to get -@c them on the page. -@c One solution would be to put some of the type definitions into -@c separate stabs, even if that's not exactly what the compiler actually -@c emits. -@smallexample -.stabs "A:T20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32; - A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0 - -.stabs "B:Tt25=s8Bdat:1,0,32;$vf25:21,32;B_virt::26=##1; - :i;2A*-2147483647;25;;;~%25;",128,0,0,0 - -.stabs "C:Tt28=s8Cdat:1,0,32;$vf28:21,32;C_virt::29=##1; - :i;2A*-2147483647;28;;;~%28;",128,0,0,0 -@end smallexample - -In the stab describing derived class @code{D} below, the information about -the derivation of this class is encoded as follows. - -@display -.stabs "derived_class_name:symbol_descriptors(struct tag&type)= - type_descriptor(struct)struct_bytes(32)!num_bases(3), - base_virtual(no)inheritance_public(no)base_offset(0), - base_class_type_ref(A); - base_virtual(yes)inheritance_public(no)base_offset(NIL), - base_class_type_ref(B); - base_virtual(no)inheritance_public(yes)base_offset(64), - base_class_type_ref(C); @dots{} -@end display - -@c FIXME! fake linebreaks. -@smallexample -.stabs "D:Tt31=s32!3,000,20;100,25;0264,28;$vb25:24,128;Ddat: - 1,160,32;A_virt::32=##1;:i;2A*-2147483647;20;;B_virt: - :32:i;2A*-2147483647;25;;C_virt::32:i;2A*-2147483647; - 28;;D_virt::32:i;2A*-2147483646;31;;;~%20;",128,0,0,0 -@end smallexample - -@node Virtual Base Classes -@section Virtual Base Classes - -A derived class object consists of a concatenation in memory of the data -areas defined by each base class, starting with the leftmost and ending -with the rightmost in the list of base classes. The exception to this -rule is for virtual inheritance. In the example above, class @code{D} -inherits virtually from base class @code{B}. This means that an -instance of a @code{D} object will not contain its own @code{B} part but -merely a pointer to a @code{B} part, known as a virtual base pointer. - -In a derived class stab, the base offset part of the derivation -information, described above, shows how the base class parts are -ordered. The base offset for a virtual base class is always given as 0. -Notice that the base offset for @code{B} is given as 0 even though -@code{B} is not the first base class. The first base class @code{A} -starts at offset 0. - -The field information part of the stab for class @code{D} describes the field -which is the pointer to the virtual base class @code{B}. The vbase pointer -name is @samp{$vb} followed by a type reference to the virtual base class. -Since the type id for @code{B} in this example is 25, the vbase pointer name -is @samp{$vb25}. - -@c FIXME!! fake linebreaks below -@smallexample -.stabs "D:Tt31=s32!3,000,20;100,25;0264,28;$vb25:24,128;Ddat:1, - 160,32;A_virt::32=##1;:i;2A*-2147483647;20;;B_virt::32:i; - 2A*-2147483647;25;;C_virt::32:i;2A*-2147483647;28;;D_virt: - :32:i;2A*-2147483646;31;;;~%20;",128,0,0,0 -@end smallexample - -Following the name and a semicolon is a type reference describing the -type of the virtual base class pointer, in this case 24. Type 24 was -defined earlier as the type of the @code{B} class @code{this} pointer. The -@code{this} pointer for a class is a pointer to the class type. - -@example -.stabs "this:P24=*25=xsB:",64,0,0,8 -@end example - -Finally the field offset part of the vbase pointer field description -shows that the vbase pointer is the first field in the @code{D} object, -before any data fields defined by the class. The layout of a @code{D} -class object is a follows, @code{Adat} at 0, the vtable pointer for -@code{A} at 32, @code{Cdat} at 64, the vtable pointer for C at 96, the -virtual base pointer for @code{B} at 128, and @code{Ddat} at 160. - - -@node Static Members -@section Static Members - -The data area for a class is a concatenation of the space used by the -data members of the class. If the class has virtual methods, a vtable -pointer follows the class data. The field offset part of each field -description in the class stab shows this ordering. - -<< How is this reflected in stabs? See Cygnus bug #677 for some info. >> - -@node Stab Types -@appendix Table of Stab Types - -The following are all the possible values for the stab type field, for -a.out files, in numeric order. This does not apply to XCOFF, but -it does apply to stabs in sections (@pxref{Stab Sections}). Stabs in -ECOFF use these values but add 0x8f300 to distinguish them from non-stab -symbols. - -The symbolic names are defined in the file @file{include/aout/stabs.def}. - -@menu -* Non-Stab Symbol Types:: Types from 0 to 0x1f -* Stab Symbol Types:: Types from 0x20 to 0xff -@end menu - -@node Non-Stab Symbol Types -@appendixsec Non-Stab Symbol Types - -The following types are used by the linker and assembler, not by stab -directives. Since this document does not attempt to describe aspects of -object file format other than the debugging format, no details are -given. - -@c Try to get most of these to fit on a single line. -@iftex -@tableindent=1.5in -@end iftex - -@table @code -@item 0x0 N_UNDF -Undefined symbol - -@item 0x2 N_ABS -File scope absolute symbol - -@item 0x3 N_ABS | N_EXT -External absolute symbol - -@item 0x4 N_TEXT -File scope text symbol - -@item 0x5 N_TEXT | N_EXT -External text symbol - -@item 0x6 N_DATA -File scope data symbol - -@item 0x7 N_DATA | N_EXT -External data symbol - -@item 0x8 N_BSS -File scope BSS symbol - -@item 0x9 N_BSS | N_EXT -External BSS symbol - -@item 0x0c N_FN_SEQ -Same as @code{N_FN}, for Sequent compilers - -@item 0x0a N_INDR -Symbol is indirected to another symbol - -@item 0x12 N_COMM -Common---visible after shared library dynamic link - -@item 0x14 N_SETA -@itemx 0x15 N_SETA | N_EXT -Absolute set element - -@item 0x16 N_SETT -@itemx 0x17 N_SETT | N_EXT -Text segment set element - -@item 0x18 N_SETD -@itemx 0x19 N_SETD | N_EXT -Data segment set element - -@item 0x1a N_SETB -@itemx 0x1b N_SETB | N_EXT -BSS segment set element - -@item 0x1c N_SETV -@itemx 0x1d N_SETV | N_EXT -Pointer to set vector - -@item 0x1e N_WARNING -Print a warning message during linking - -@item 0x1f N_FN -File name of a @file{.o} file -@end table - -@node Stab Symbol Types -@appendixsec Stab Symbol Types - -The following symbol types indicate that this is a stab. This is the -full list of stab numbers, including stab types that are used in -languages other than C. - -@table @code -@item 0x20 N_GSYM -Global symbol; see @ref{Global Variables}. - -@item 0x22 N_FNAME -Function name (for BSD Fortran); see @ref{Procedures}. - -@item 0x24 N_FUN -Function name (@pxref{Procedures}) or text segment variable -(@pxref{Statics}). - -@item 0x26 N_STSYM -Data segment file-scope variable; see @ref{Statics}. - -@item 0x28 N_LCSYM -BSS segment file-scope variable; see @ref{Statics}. - -@item 0x2a N_MAIN -Name of main routine; see @ref{Main Program}. - -@item 0x2c N_ROSYM -Variable in @code{.rodata} section; see @ref{Statics}. - -@item 0x30 N_PC -Global symbol (for Pascal); see @ref{N_PC}. - -@item 0x32 N_NSYMS -Number of symbols (according to Ultrix V4.0); see @ref{N_NSYMS}. - -@item 0x34 N_NOMAP -No DST map; see @ref{N_NOMAP}. - -@item 0x36 N_MAC_DEFINE -Name and body of a @code{#define}d macro; see @ref{Macro define and undefine}. - -@c FIXME: describe this solaris feature in the body of the text (see -@c comments in include/aout/stab.def). -@item 0x38 N_OBJ -Object file (Solaris2). - -@item 0x3a N_MAC_UNDEF -Name of an @code{#undef}ed macro; see @ref{Macro define and undefine}. - -@c See include/aout/stab.def for (a little) more info. -@item 0x3c N_OPT -Debugger options (Solaris2). - -@item 0x40 N_RSYM -Register variable; see @ref{Register Variables}. - -@item 0x42 N_M2C -Modula-2 compilation unit; see @ref{N_M2C}. - -@item 0x44 N_SLINE -Line number in text segment; see @ref{Line Numbers}. - -@item 0x46 N_DSLINE -Line number in data segment; see @ref{Line Numbers}. - -@item 0x48 N_BSLINE -Line number in bss segment; see @ref{Line Numbers}. - -@item 0x48 N_BROWS -Sun source code browser, path to @file{.cb} file; see @ref{N_BROWS}. - -@item 0x4a N_DEFD -GNU Modula2 definition module dependency; see @ref{N_DEFD}. - -@item 0x4c N_FLINE -Function start/body/end line numbers (Solaris2). - -@item 0x50 N_EHDECL -GNU C@t{++} exception variable; see @ref{N_EHDECL}. - -@item 0x50 N_MOD2 -Modula2 info "for imc" (according to Ultrix V4.0); see @ref{N_MOD2}. - -@item 0x54 N_CATCH -GNU C@t{++} @code{catch} clause; see @ref{N_CATCH}. - -@item 0x60 N_SSYM -Structure of union element; see @ref{N_SSYM}. - -@item 0x62 N_ENDM -Last stab for module (Solaris2). - -@item 0x64 N_SO -Path and name of source file; see @ref{Source Files}. - -@item 0x80 N_LSYM -Stack variable (@pxref{Stack Variables}) or type (@pxref{Typedefs}). - -@item 0x82 N_BINCL -Beginning of an include file (Sun only); see @ref{Include Files}. - -@item 0x84 N_SOL -Name of include file; see @ref{Include Files}. - -@item 0xa0 N_PSYM -Parameter variable; see @ref{Parameters}. - -@item 0xa2 N_EINCL -End of an include file; see @ref{Include Files}. - -@item 0xa4 N_ENTRY -Alternate entry point; see @ref{Alternate Entry Points}. - -@item 0xc0 N_LBRAC -Beginning of a lexical block; see @ref{Block Structure}. - -@item 0xc2 N_EXCL -Place holder for a deleted include file; see @ref{Include Files}. - -@item 0xc4 N_SCOPE -Modula2 scope information (Sun linker); see @ref{N_SCOPE}. - -@item 0xe0 N_RBRAC -End of a lexical block; see @ref{Block Structure}. - -@item 0xe2 N_BCOMM -Begin named common block; see @ref{Common Blocks}. - -@item 0xe4 N_ECOMM -End named common block; see @ref{Common Blocks}. - -@item 0xe8 N_ECOML -Member of a common block; see @ref{Common Blocks}. - -@c FIXME: How does this really work? Move it to main body of document. -@item 0xea N_WITH -Pascal @code{with} statement: type,,0,0,offset (Solaris2). - -@item 0xf0 N_NBTEXT -Gould non-base registers; see @ref{Gould}. - -@item 0xf2 N_NBDATA -Gould non-base registers; see @ref{Gould}. - -@item 0xf4 N_NBBSS -Gould non-base registers; see @ref{Gould}. - -@item 0xf6 N_NBSTS -Gould non-base registers; see @ref{Gould}. - -@item 0xf8 N_NBLCS -Gould non-base registers; see @ref{Gould}. -@end table - -@c Restore the default table indent -@iftex -@tableindent=.8in -@end iftex - -@node Symbol Descriptors -@appendix Table of Symbol Descriptors - -The symbol descriptor is the character which follows the colon in many -stabs, and which tells what kind of stab it is. @xref{String Field}, -for more information about their use. - -@c Please keep this alphabetical -@table @code -@c In TeX, this looks great, digit is in italics. But makeinfo insists -@c on putting it in `', not realizing that @var should override @code. -@c I don't know of any way to make makeinfo do the right thing. Seems -@c like a makeinfo bug to me. -@item @var{digit} -@itemx ( -@itemx - -Variable on the stack; see @ref{Stack Variables}. - -@item : -C@t{++} nested symbol; see @xref{Nested Symbols}. - -@item a -Parameter passed by reference in register; see @ref{Reference Parameters}. - -@item b -Based variable; see @ref{Based Variables}. - -@item c -Constant; see @ref{Constants}. - -@item C -Conformant array bound (Pascal, maybe other languages); @ref{Conformant -Arrays}. Name of a caught exception (GNU C@t{++}). These can be -distinguished because the latter uses @code{N_CATCH} and the former uses -another symbol type. - -@item d -Floating point register variable; see @ref{Register Variables}. - -@item D -Parameter in floating point register; see @ref{Register Parameters}. - -@item f -File scope function; see @ref{Procedures}. - -@item F -Global function; see @ref{Procedures}. - -@item G -Global variable; see @ref{Global Variables}. - -@item i -@xref{Register Parameters}. - -@item I -Internal (nested) procedure; see @ref{Nested Procedures}. - -@item J -Internal (nested) function; see @ref{Nested Procedures}. - -@item L -Label name (documented by AIX, no further information known). - -@item m -Module; see @ref{Procedures}. - -@item p -Argument list parameter; see @ref{Parameters}. - -@item pP -@xref{Parameters}. - -@item pF -Fortran Function parameter; see @ref{Parameters}. - -@item P -Unfortunately, three separate meanings have been independently invented -for this symbol descriptor. At least the GNU and Sun uses can be -distinguished by the symbol type. Global Procedure (AIX) (symbol type -used unknown); see @ref{Procedures}. Register parameter (GNU) (symbol -type @code{N_PSYM}); see @ref{Parameters}. Prototype of function -referenced by this file (Sun @code{acc}) (symbol type @code{N_FUN}). - -@item Q -Static Procedure; see @ref{Procedures}. - -@item R -Register parameter; see @ref{Register Parameters}. - -@item r -Register variable; see @ref{Register Variables}. - -@item S -File scope variable; see @ref{Statics}. - -@item s -Local variable (OS9000). - -@item t -Type name; see @ref{Typedefs}. - -@item T -Enumeration, structure, or union tag; see @ref{Typedefs}. - -@item v -Parameter passed by reference; see @ref{Reference Parameters}. - -@item V -Procedure scope static variable; see @ref{Statics}. - -@item x -Conformant array; see @ref{Conformant Arrays}. - -@item X -Function return variable; see @ref{Parameters}. -@end table - -@node Type Descriptors -@appendix Table of Type Descriptors - -The type descriptor is the character which follows the type number and -an equals sign. It specifies what kind of type is being defined. -@xref{String Field}, for more information about their use. - -@table @code -@item @var{digit} -@itemx ( -Type reference; see @ref{String Field}. - -@item - -Reference to builtin type; see @ref{Negative Type Numbers}. - -@item # -Method (C@t{++}); see @ref{Method Type Descriptor}. - -@item * -Pointer; see @ref{Miscellaneous Types}. - -@item & -Reference (C@t{++}). - -@item @@ -Type Attributes (AIX); see @ref{String Field}. Member (class and variable) -type (GNU C@t{++}); see @ref{Member Type Descriptor}. - -@item a -Array; see @ref{Arrays}. - -@item A -Open array; see @ref{Arrays}. - -@item b -Pascal space type (AIX); see @ref{Miscellaneous Types}. Builtin integer -type (Sun); see @ref{Builtin Type Descriptors}. Const and volatile -qualified type (OS9000). - -@item B -Volatile-qualified type; see @ref{Miscellaneous Types}. - -@item c -Complex builtin type (AIX); see @ref{Builtin Type Descriptors}. -Const-qualified type (OS9000). - -@item C -COBOL Picture type. See AIX documentation for details. - -@item d -File type; see @ref{Miscellaneous Types}. - -@item D -N-dimensional dynamic array; see @ref{Arrays}. - -@item e -Enumeration type; see @ref{Enumerations}. - -@item E -N-dimensional subarray; see @ref{Arrays}. - -@item f -Function type; see @ref{Function Types}. - -@item F -Pascal function parameter; see @ref{Function Types} - -@item g -Builtin floating point type; see @ref{Builtin Type Descriptors}. - -@item G -COBOL Group. See AIX documentation for details. - -@item i -Imported type (AIX); see @ref{Cross-References}. Volatile-qualified -type (OS9000). - -@item k -Const-qualified type; see @ref{Miscellaneous Types}. - -@item K -COBOL File Descriptor. See AIX documentation for details. - -@item M -Multiple instance type; see @ref{Miscellaneous Types}. - -@item n -String type; see @ref{Strings}. - -@item N -Stringptr; see @ref{Strings}. - -@item o -Opaque type; see @ref{Typedefs}. - -@item p -Procedure; see @ref{Function Types}. - -@item P -Packed array; see @ref{Arrays}. - -@item r -Range type; see @ref{Subranges}. - -@item R -Builtin floating type; see @ref{Builtin Type Descriptors} (Sun). Pascal -subroutine parameter; see @ref{Function Types} (AIX). Detecting this -conflict is possible with careful parsing (hint: a Pascal subroutine -parameter type will always contain a comma, and a builtin type -descriptor never will). - -@item s -Structure type; see @ref{Structures}. - -@item S -Set type; see @ref{Miscellaneous Types}. - -@item u -Union; see @ref{Unions}. - -@item v -Variant record. This is a Pascal and Modula-2 feature which is like a -union within a struct in C. See AIX documentation for details. - -@item w -Wide character; see @ref{Builtin Type Descriptors}. - -@item x -Cross-reference; see @ref{Cross-References}. - -@item Y -Used by IBM's xlC C@t{++} compiler (for structures, I think). - -@item z -gstring; see @ref{Strings}. -@end table - -@node Expanded Reference -@appendix Expanded Reference by Stab Type - -@c FIXME: This appendix should go away; see N_PSYM or N_SO for an example. - -For a full list of stab types, and cross-references to where they are -described, see @ref{Stab Types}. This appendix just covers certain -stabs which are not yet described in the main body of this document; -eventually the information will all be in one place. - -Format of an entry: - -The first line is the symbol type (see @file{include/aout/stab.def}). - -The second line describes the language constructs the symbol type -represents. - -The third line is the stab format with the significant stab fields -named and the rest NIL. - -Subsequent lines expand upon the meaning and possible values for each -significant stab field. - -Finally, any further information. - -@menu -* N_PC:: Pascal global symbol -* N_NSYMS:: Number of symbols -* N_NOMAP:: No DST map -* N_M2C:: Modula-2 compilation unit -* N_BROWS:: Path to .cb file for Sun source code browser -* N_DEFD:: GNU Modula2 definition module dependency -* N_EHDECL:: GNU C++ exception variable -* N_MOD2:: Modula2 information "for imc" -* N_CATCH:: GNU C++ "catch" clause -* N_SSYM:: Structure or union element -* N_SCOPE:: Modula2 scope information (Sun only) -* Gould:: non-base register symbols used on Gould systems -* N_LENG:: Length of preceding entry -@end menu - -@node N_PC -@section N_PC - -@deffn @code{.stabs} N_PC -@findex N_PC -Global symbol (for Pascal). - -@example -"name" -> "symbol_name" <<?>> -value -> supposedly the line number (stab.def is skeptical) -@end example - -@display -@file{stabdump.c} says: - -global pascal symbol: name,,0,subtype,line -<< subtype? >> -@end display -@end deffn - -@node N_NSYMS -@section N_NSYMS - -@deffn @code{.stabn} N_NSYMS -@findex N_NSYMS -Number of symbols (according to Ultrix V4.0). - -@display - 0, files,,funcs,lines (stab.def) -@end display -@end deffn - -@node N_NOMAP -@section N_NOMAP - -@deffn @code{.stabs} N_NOMAP -@findex N_NOMAP -No DST map for symbol (according to Ultrix V4.0). I think this means a -variable has been optimized out. - -@display - name, ,0,type,ignored (stab.def) -@end display -@end deffn - -@node N_M2C -@section N_M2C - -@deffn @code{.stabs} N_M2C -@findex N_M2C -Modula-2 compilation unit. - -@example -"string" -> "unit_name,unit_time_stamp[,code_time_stamp]" -desc -> unit_number -value -> 0 (main unit) - 1 (any other unit) -@end example - -See @cite{Dbx and Dbxtool Interfaces}, 2nd edition, by Sun, 1988, for -more information. - -@end deffn - -@node N_BROWS -@section N_BROWS - -@deffn @code{.stabs} N_BROWS -@findex N_BROWS -Sun source code browser, path to @file{.cb} file - -<<?>> -"path to associated @file{.cb} file" - -Note: N_BROWS has the same value as N_BSLINE. -@end deffn - -@node N_DEFD -@section N_DEFD - -@deffn @code{.stabn} N_DEFD -@findex N_DEFD -GNU Modula2 definition module dependency. - -GNU Modula-2 definition module dependency. The value is the -modification time of the definition file. The other field is non-zero -if it is imported with the GNU M2 keyword @code{%INITIALIZE}. Perhaps -@code{N_M2C} can be used if there are enough empty fields? -@end deffn - -@node N_EHDECL -@section N_EHDECL - -@deffn @code{.stabs} N_EHDECL -@findex N_EHDECL -GNU C@t{++} exception variable <<?>>. - -"@var{string} is variable name" - -Note: conflicts with @code{N_MOD2}. -@end deffn - -@node N_MOD2 -@section N_MOD2 - -@deffn @code{.stab?} N_MOD2 -@findex N_MOD2 -Modula2 info "for imc" (according to Ultrix V4.0) - -Note: conflicts with @code{N_EHDECL} <<?>> -@end deffn - -@node N_CATCH -@section N_CATCH - -@deffn @code{.stabn} N_CATCH -@findex N_CATCH -GNU C@t{++} @code{catch} clause - -GNU C@t{++} @code{catch} clause. The value is its address. The desc field -is nonzero if this entry is immediately followed by a @code{CAUGHT} stab -saying what exception was caught. Multiple @code{CAUGHT} stabs means -that multiple exceptions can be caught here. If desc is 0, it means all -exceptions are caught here. -@end deffn - -@node N_SSYM -@section N_SSYM - -@deffn @code{.stabn} N_SSYM -@findex N_SSYM -Structure or union element. - -The value is the offset in the structure. - -<<?looking at structs and unions in C I didn't see these>> -@end deffn - -@node N_SCOPE -@section N_SCOPE - -@deffn @code{.stab?} N_SCOPE -@findex N_SCOPE -Modula2 scope information (Sun linker) -<<?>> -@end deffn - -@node Gould -@section Non-base registers on Gould systems - -@deffn @code{.stab?} N_NBTEXT -@deffnx @code{.stab?} N_NBDATA -@deffnx @code{.stab?} N_NBBSS -@deffnx @code{.stab?} N_NBSTS -@deffnx @code{.stab?} N_NBLCS -@findex N_NBTEXT -@findex N_NBDATA -@findex N_NBBSS -@findex N_NBSTS -@findex N_NBLCS -These are used on Gould systems for non-base registers syms. - -However, the following values are not the values used by Gould; they are -the values which GNU has been documenting for these values for a long -time, without actually checking what Gould uses. I include these values -only because perhaps some someone actually did something with the GNU -information (I hope not, why GNU knowingly assigned wrong values to -these in the header file is a complete mystery to me). - -@example -240 0xf0 N_NBTEXT ?? -242 0xf2 N_NBDATA ?? -244 0xf4 N_NBBSS ?? -246 0xf6 N_NBSTS ?? -248 0xf8 N_NBLCS ?? -@end example -@end deffn - -@node N_LENG -@section N_LENG - -@deffn @code{.stabn} N_LENG -@findex N_LENG -Second symbol entry containing a length-value for the preceding entry. -The value is the length. -@end deffn - -@node Questions -@appendix Questions and Anomalies - -@itemize @bullet -@item -@c I think this is changed in GCC 2.4.5 to put the line number there. -For GNU C stabs defining local and global variables (@code{N_LSYM} and -@code{N_GSYM}), the desc field is supposed to contain the source -line number on which the variable is defined. In reality the desc -field is always 0. (This behavior is defined in @file{dbxout.c} and -putting a line number in desc is controlled by @samp{#ifdef -WINNING_GDB}, which defaults to false). GDB supposedly uses this -information if you say @samp{list @var{var}}. In reality, @var{var} can -be a variable defined in the program and GDB says @samp{function -@var{var} not defined}. - -@item -In GNU C stabs, there seems to be no way to differentiate tag types: -structures, unions, and enums (symbol descriptor @samp{T}) and typedefs -(symbol descriptor @samp{t}) defined at file scope from types defined locally -to a procedure or other more local scope. They all use the @code{N_LSYM} -stab type. Types defined at procedure scope are emitted after the -@code{N_RBRAC} of the preceding function and before the code of the -procedure in which they are defined. This is exactly the same as -types defined in the source file between the two procedure bodies. -GDB over-compensates by placing all types in block #1, the block for -symbols of file scope. This is true for default, @samp{-ansi} and -@samp{-traditional} compiler options. (Bugs gcc/1063, gdb/1066.) - -@item -What ends the procedure scope? Is it the proc block's @code{N_RBRAC} or the -next @code{N_FUN}? (I believe its the first.) -@end itemize - -@node Stab Sections -@appendix Using Stabs in Their Own Sections - -Many object file formats allow tools to create object files with custom -sections containing any arbitrary data. For any such object file -format, stabs can be embedded in special sections. This is how stabs -are used with ELF and SOM, and aside from ECOFF and XCOFF, is how stabs -are used with COFF. - -@menu -* Stab Section Basics:: How to embed stabs in sections -* ELF Linker Relocation:: Sun ELF hacks -@end menu - -@node Stab Section Basics -@appendixsec How to Embed Stabs in Sections - -The assembler creates two custom sections, a section named @code{.stab} -which contains an array of fixed length structures, one struct per stab, -and a section named @code{.stabstr} containing all the variable length -strings that are referenced by stabs in the @code{.stab} section. The -byte order of the stabs binary data depends on the object file format. -For ELF, it matches the byte order of the ELF file itself, as determined -from the @code{EI_DATA} field in the @code{e_ident} member of the ELF -header. For SOM, it is always big-endian (is this true??? FIXME). For -COFF, it matches the byte order of the COFF headers. The meaning of the -fields is the same as for a.out (@pxref{Symbol Table Format}), except -that the @code{n_strx} field is relative to the strings for the current -compilation unit (which can be found using the synthetic N_UNDF stab -described below), rather than the entire string table. - -The first stab in the @code{.stab} section for each compilation unit is -synthetic, generated entirely by the assembler, with no corresponding -@code{.stab} directive as input to the assembler. This stab contains -the following fields: - -@table @code -@item n_strx -Offset in the @code{.stabstr} section to the source filename. - -@item n_type -@code{N_UNDF}. - -@item n_other -Unused field, always zero. -This may eventually be used to hold overflows from the count in -the @code{n_desc} field. - -@item n_desc -Count of upcoming symbols, i.e., the number of remaining stabs for this -source file. - -@item n_value -Size of the string table fragment associated with this source file, in -bytes. -@end table - -The @code{.stabstr} section always starts with a null byte (so that string -offsets of zero reference a null string), followed by random length strings, -each of which is null byte terminated. - -The ELF section header for the @code{.stab} section has its -@code{sh_link} member set to the section number of the @code{.stabstr} -section, and the @code{.stabstr} section has its ELF section -header @code{sh_type} member set to @code{SHT_STRTAB} to mark it as a -string table. SOM and COFF have no way of linking the sections together -or marking them as string tables. - -For COFF, the @code{.stab} and @code{.stabstr} sections may be simply -concatenated by the linker. GDB then uses the @code{n_desc} fields to -figure out the extent of the original sections. Similarly, the -@code{n_value} fields of the header symbols are added together in order -to get the actual position of the strings in a desired @code{.stabstr} -section. Although this design obviates any need for the linker to -relocate or otherwise manipulate @code{.stab} and @code{.stabstr} -sections, it also requires some care to ensure that the offsets are -calculated correctly. For instance, if the linker were to pad in -between the @code{.stabstr} sections before concatenating, then the -offsets to strings in the middle of the executable's @code{.stabstr} -section would be wrong. - -The GNU linker is able to optimize stabs information by merging -duplicate strings and removing duplicate header file information -(@pxref{Include Files}). When some versions of the GNU linker optimize -stabs in sections, they remove the leading @code{N_UNDF} symbol and -arranges for all the @code{n_strx} fields to be relative to the start of -the @code{.stabstr} section. - -@node ELF Linker Relocation -@appendixsec Having the Linker Relocate Stabs in ELF - -This section describes some Sun hacks for Stabs in ELF; it does not -apply to COFF or SOM. - -To keep linking fast, you don't want the linker to have to relocate very -many stabs. Making sure this is done for @code{N_SLINE}, -@code{N_RBRAC}, and @code{N_LBRAC} stabs is the most important thing -(see the descriptions of those stabs for more information). But Sun's -stabs in ELF has taken this further, to make all addresses in the -@code{n_value} field (functions and static variables) relative to the -source file. For the @code{N_SO} symbol itself, Sun simply omits the -address. To find the address of each section corresponding to a given -source file, the compiler puts out symbols giving the address of each -section for a given source file. Since these are ELF (not stab) -symbols, the linker relocates them correctly without having to touch the -stabs section. They are named @code{Bbss.bss} for the bss section, -@code{Ddata.data} for the data section, and @code{Drodata.rodata} for -the rodata section. For the text section, there is no such symbol (but -there should be, see below). For an example of how these symbols work, -@xref{Stab Section Transformations}. GCC does not provide these symbols; -it instead relies on the stabs getting relocated. Thus addresses which -would normally be relative to @code{Bbss.bss}, etc., are already -relocated. The Sun linker provided with Solaris 2.2 and earlier -relocates stabs using normal ELF relocation information, as it would do -for any section. Sun has been threatening to kludge their linker to not -do this (to speed up linking), even though the correct way to avoid -having the linker do these relocations is to have the compiler no longer -output relocatable values. Last I heard they had been talked out of the -linker kludge. See Sun point patch 101052-01 and Sun bug 1142109. With -the Sun compiler this affects @samp{S} symbol descriptor stabs -(@pxref{Statics}) and functions (@pxref{Procedures}). In the latter -case, to adopt the clean solution (making the value of the stab relative -to the start of the compilation unit), it would be necessary to invent a -@code{Ttext.text} symbol, analogous to the @code{Bbss.bss}, etc., -symbols. I recommend this rather than using a zero value and getting -the address from the ELF symbols. - -Finding the correct @code{Bbss.bss}, etc., symbol is difficult, because -the linker simply concatenates the @code{.stab} sections from each -@file{.o} file without including any information about which part of a -@code{.stab} section comes from which @file{.o} file. The way GDB does -this is to look for an ELF @code{STT_FILE} symbol which has the same -name as the last component of the file name from the @code{N_SO} symbol -in the stabs (for example, if the file name is @file{../../gdb/main.c}, -it looks for an ELF @code{STT_FILE} symbol named @code{main.c}). This -loses if different files have the same name (they could be in different -directories, a library could have been copied from one system to -another, etc.). It would be much cleaner to have the @code{Bbss.bss} -symbols in the stabs themselves. Having the linker relocate them there -is no more work than having the linker relocate ELF symbols, and it -solves the problem of having to associate the ELF and stab symbols. -However, no one has yet designed or implemented such a scheme. - -@node GNU Free Documentation License -@appendix GNU Free Documentation License -@include fdl.texi - -@node Symbol Types Index -@unnumbered Symbol Types Index - -@printindex fn - -@bye diff --git a/contrib/gdb-7/gdb/doc/stack_frame.txt b/contrib/gdb-7/gdb/doc/stack_frame.txt deleted file mode 100644 index e6ff020b37..0000000000 --- a/contrib/gdb-7/gdb/doc/stack_frame.txt +++ /dev/null @@ -1,39 +0,0 @@ - ^ ->| | -Frame | | | | -Number - | | |============| int fact (int n) - | | | | i = 3 | { - | | | |------------| if (0 == n) { - | | | | f = ? | return 1; <-------- PC - #4 main() < | | |------------| } - | | | | | else { - | | -+->|------------| ---> return n * fact (n - 1); - | -+-+--+-----o | | } - = | | |============| | } - | | | | n = 3 | | - | | | |------------| | main () - #3 fact (3) < | | | o---------+- { - | -+-+->|------------| | | int i; - | | | --+-----o | | | - = | | |============| | | for (i = 0; i < 10; i++) { - | | | | n = 2 | | -> int f = fact (i); - | | | |------------| | printf ("%d! = %d\n", i , f); - #2 fact (2) < | | | o------+--| } - | | | ->|------------| | } - | | -+--+-----o | | - = | | |============| | - | | | | n = 1 | | - | | | |------------| | - #1 fact (1) < | | | o------+--| - | | | |------------| | - | ---|--+-----o |<-+------- FP - = | |============| | | - | | | n = 0 | | | - | | |------------| | | - #0 fact (0) < | | o--------- | - | | |------------| | - | --+-----o |<--------- SP | - = |============| | - | | Red Zone | v - | \/\/\/\/\/\/\/ Direction of - #-1 < \/\/\/\/\/\/\/ stack growth - | | | -- 2.41.0