1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
21 @c To avoid file-name clashes between index.html and Index.html, when
22 @c the manual is produced on a Posix host and then moved to a
23 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
24 @c indices into two: Concept Index and all the rest.
28 @c readline appendices use @vindex, @findex and @ftable,
29 @c annotate.texi and gdbmi use @findex.
32 @c !!set GDB manual's edition---not the same as GDB version!
33 @c This is updated by GNU Press.
36 @c !!set GDB edit command default editor
39 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
41 @c This is a dir.info fragment to support semi-automated addition of
42 @c manuals to an info tree.
43 @dircategory Software development
45 * Gdb: (gdb). The GNU debugger.
49 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.3 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
99 ISBN 978-0-9831592-3-0 @*
106 @node Top, Summary, (dir), (dir)
108 @top Debugging with @value{GDBN}
110 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
112 This is the @value{EDITION} Edition, for @value{GDBN}
113 @ifset VERSION_PACKAGE
114 @value{VERSION_PACKAGE}
116 Version @value{GDBVN}.
118 Copyright (C) 1988-2013 Free Software Foundation, Inc.
120 This edition of the GDB manual is dedicated to the memory of Fred
121 Fish. Fred was a long-standing contributor to GDB and to Free
122 software in general. We will miss him.
125 * Summary:: Summary of @value{GDBN}
126 * Sample Session:: A sample @value{GDBN} session
128 * Invocation:: Getting in and out of @value{GDBN}
129 * Commands:: @value{GDBN} commands
130 * Running:: Running programs under @value{GDBN}
131 * Stopping:: Stopping and continuing
132 * Reverse Execution:: Running programs backward
133 * Process Record and Replay:: Recording inferior's execution and replaying it
134 * Stack:: Examining the stack
135 * Source:: Examining source files
136 * Data:: Examining data
137 * Optimized Code:: Debugging optimized code
138 * Macros:: Preprocessor Macros
139 * Tracepoints:: Debugging remote targets non-intrusively
140 * Overlays:: Debugging programs that use overlays
142 * Languages:: Using @value{GDBN} with different languages
144 * Symbols:: Examining the symbol table
145 * Altering:: Altering execution
146 * GDB Files:: @value{GDBN} files
147 * Targets:: Specifying a debugging target
148 * Remote Debugging:: Debugging remote programs
149 * Configurations:: Configuration-specific information
150 * Controlling GDB:: Controlling @value{GDBN}
151 * Extending GDB:: Extending @value{GDBN}
152 * Interpreters:: Command Interpreters
153 * TUI:: @value{GDBN} Text User Interface
154 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
155 * GDB/MI:: @value{GDBN}'s Machine Interface.
156 * Annotations:: @value{GDBN}'s annotation interface.
157 * JIT Interface:: Using the JIT debugging interface.
158 * In-Process Agent:: In-Process Agent
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
185 * Concept Index:: Index of @value{GDBN} concepts
186 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
187 functions, and Python data types
195 @unnumbered Summary of @value{GDBN}
197 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
198 going on ``inside'' another program while it executes---or what another
199 program was doing at the moment it crashed.
201 @value{GDBN} can do four main kinds of things (plus other things in support of
202 these) to help you catch bugs in the act:
206 Start your program, specifying anything that might affect its behavior.
209 Make your program stop on specified conditions.
212 Examine what has happened, when your program has stopped.
215 Change things in your program, so you can experiment with correcting the
216 effects of one bug and go on to learn about another.
219 You can use @value{GDBN} to debug programs written in C and C@t{++}.
220 For more information, see @ref{Supported Languages,,Supported Languages}.
221 For more information, see @ref{C,,C and C++}.
223 Support for D is partial. For information on D, see
227 Support for Modula-2 is partial. For information on Modula-2, see
228 @ref{Modula-2,,Modula-2}.
230 Support for OpenCL C is partial. For information on OpenCL C, see
231 @ref{OpenCL C,,OpenCL C}.
234 Debugging Pascal programs which use sets, subranges, file variables, or
235 nested functions does not currently work. @value{GDBN} does not support
236 entering expressions, printing values, or similar features using Pascal
240 @value{GDBN} can be used to debug programs written in Fortran, although
241 it may be necessary to refer to some variables with a trailing
244 @value{GDBN} can be used to debug programs written in Objective-C,
245 using either the Apple/NeXT or the GNU Objective-C runtime.
248 * Free Software:: Freely redistributable software
249 * Free Documentation:: Free Software Needs Free Documentation
250 * Contributors:: Contributors to GDB
254 @unnumberedsec Free Software
256 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
257 General Public License
258 (GPL). The GPL gives you the freedom to copy or adapt a licensed
259 program---but every person getting a copy also gets with it the
260 freedom to modify that copy (which means that they must get access to
261 the source code), and the freedom to distribute further copies.
262 Typical software companies use copyrights to limit your freedoms; the
263 Free Software Foundation uses the GPL to preserve these freedoms.
265 Fundamentally, the General Public License is a license which says that
266 you have these freedoms and that you cannot take these freedoms away
269 @node Free Documentation
270 @unnumberedsec Free Software Needs Free Documentation
272 The biggest deficiency in the free software community today is not in
273 the software---it is the lack of good free documentation that we can
274 include with the free software. Many of our most important
275 programs do not come with free reference manuals and free introductory
276 texts. Documentation is an essential part of any software package;
277 when an important free software package does not come with a free
278 manual and a free tutorial, that is a major gap. We have many such
281 Consider Perl, for instance. The tutorial manuals that people
282 normally use are non-free. How did this come about? Because the
283 authors of those manuals published them with restrictive terms---no
284 copying, no modification, source files not available---which exclude
285 them from the free software world.
287 That wasn't the first time this sort of thing happened, and it was far
288 from the last. Many times we have heard a GNU user eagerly describe a
289 manual that he is writing, his intended contribution to the community,
290 only to learn that he had ruined everything by signing a publication
291 contract to make it non-free.
293 Free documentation, like free software, is a matter of freedom, not
294 price. The problem with the non-free manual is not that publishers
295 charge a price for printed copies---that in itself is fine. (The Free
296 Software Foundation sells printed copies of manuals, too.) The
297 problem is the restrictions on the use of the manual. Free manuals
298 are available in source code form, and give you permission to copy and
299 modify. Non-free manuals do not allow this.
301 The criteria of freedom for a free manual are roughly the same as for
302 free software. Redistribution (including the normal kinds of
303 commercial redistribution) must be permitted, so that the manual can
304 accompany every copy of the program, both on-line and on paper.
306 Permission for modification of the technical content is crucial too.
307 When people modify the software, adding or changing features, if they
308 are conscientious they will change the manual too---so they can
309 provide accurate and clear documentation for the modified program. A
310 manual that leaves you no choice but to write a new manual to document
311 a changed version of the program is not really available to our
314 Some kinds of limits on the way modification is handled are
315 acceptable. For example, requirements to preserve the original
316 author's copyright notice, the distribution terms, or the list of
317 authors, are ok. It is also no problem to require modified versions
318 to include notice that they were modified. Even entire sections that
319 may not be deleted or changed are acceptable, as long as they deal
320 with nontechnical topics (like this one). These kinds of restrictions
321 are acceptable because they don't obstruct the community's normal use
324 However, it must be possible to modify all the @emph{technical}
325 content of the manual, and then distribute the result in all the usual
326 media, through all the usual channels. Otherwise, the restrictions
327 obstruct the use of the manual, it is not free, and we need another
328 manual to replace it.
330 Please spread the word about this issue. Our community continues to
331 lose manuals to proprietary publishing. If we spread the word that
332 free software needs free reference manuals and free tutorials, perhaps
333 the next person who wants to contribute by writing documentation will
334 realize, before it is too late, that only free manuals contribute to
335 the free software community.
337 If you are writing documentation, please insist on publishing it under
338 the GNU Free Documentation License or another free documentation
339 license. Remember that this decision requires your approval---you
340 don't have to let the publisher decide. Some commercial publishers
341 will use a free license if you insist, but they will not propose the
342 option; it is up to you to raise the issue and say firmly that this is
343 what you want. If the publisher you are dealing with refuses, please
344 try other publishers. If you're not sure whether a proposed license
345 is free, write to @email{licensing@@gnu.org}.
347 You can encourage commercial publishers to sell more free, copylefted
348 manuals and tutorials by buying them, and particularly by buying
349 copies from the publishers that paid for their writing or for major
350 improvements. Meanwhile, try to avoid buying non-free documentation
351 at all. Check the distribution terms of a manual before you buy it,
352 and insist that whoever seeks your business must respect your freedom.
353 Check the history of the book, and try to reward the publishers that
354 have paid or pay the authors to work on it.
356 The Free Software Foundation maintains a list of free documentation
357 published by other publishers, at
358 @url{http://www.fsf.org/doc/other-free-books.html}.
361 @unnumberedsec Contributors to @value{GDBN}
363 Richard Stallman was the original author of @value{GDBN}, and of many
364 other @sc{gnu} programs. Many others have contributed to its
365 development. This section attempts to credit major contributors. One
366 of the virtues of free software is that everyone is free to contribute
367 to it; with regret, we cannot actually acknowledge everyone here. The
368 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
369 blow-by-blow account.
371 Changes much prior to version 2.0 are lost in the mists of time.
374 @emph{Plea:} Additions to this section are particularly welcome. If you
375 or your friends (or enemies, to be evenhanded) have been unfairly
376 omitted from this list, we would like to add your names!
379 So that they may not regard their many labors as thankless, we
380 particularly thank those who shepherded @value{GDBN} through major
382 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
383 Jim Blandy (release 4.18);
384 Jason Molenda (release 4.17);
385 Stan Shebs (release 4.14);
386 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
387 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
388 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
389 Jim Kingdon (releases 3.5, 3.4, and 3.3);
390 and Randy Smith (releases 3.2, 3.1, and 3.0).
392 Richard Stallman, assisted at various times by Peter TerMaat, Chris
393 Hanson, and Richard Mlynarik, handled releases through 2.8.
395 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
396 in @value{GDBN}, with significant additional contributions from Per
397 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
398 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
399 much general update work leading to release 3.0).
401 @value{GDBN} uses the BFD subroutine library to examine multiple
402 object-file formats; BFD was a joint project of David V.
403 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
405 David Johnson wrote the original COFF support; Pace Willison did
406 the original support for encapsulated COFF.
408 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
410 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
411 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
413 Jean-Daniel Fekete contributed Sun 386i support.
414 Chris Hanson improved the HP9000 support.
415 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
416 David Johnson contributed Encore Umax support.
417 Jyrki Kuoppala contributed Altos 3068 support.
418 Jeff Law contributed HP PA and SOM support.
419 Keith Packard contributed NS32K support.
420 Doug Rabson contributed Acorn Risc Machine support.
421 Bob Rusk contributed Harris Nighthawk CX-UX support.
422 Chris Smith contributed Convex support (and Fortran debugging).
423 Jonathan Stone contributed Pyramid support.
424 Michael Tiemann contributed SPARC support.
425 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
426 Pace Willison contributed Intel 386 support.
427 Jay Vosburgh contributed Symmetry support.
428 Marko Mlinar contributed OpenRISC 1000 support.
430 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
432 Rich Schaefer and Peter Schauer helped with support of SunOS shared
435 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
436 about several machine instruction sets.
438 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
439 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
440 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
441 and RDI targets, respectively.
443 Brian Fox is the author of the readline libraries providing
444 command-line editing and command history.
446 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
447 Modula-2 support, and contributed the Languages chapter of this manual.
449 Fred Fish wrote most of the support for Unix System Vr4.
450 He also enhanced the command-completion support to cover C@t{++} overloaded
453 Hitachi America (now Renesas America), Ltd. sponsored the support for
454 H8/300, H8/500, and Super-H processors.
456 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
458 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
461 Toshiba sponsored the support for the TX39 Mips processor.
463 Matsushita sponsored the support for the MN10200 and MN10300 processors.
465 Fujitsu sponsored the support for SPARClite and FR30 processors.
467 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
470 Michael Snyder added support for tracepoints.
472 Stu Grossman wrote gdbserver.
474 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
475 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
477 The following people at the Hewlett-Packard Company contributed
478 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
479 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
480 compiler, and the Text User Interface (nee Terminal User Interface):
481 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
482 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
483 provided HP-specific information in this manual.
485 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
486 Robert Hoehne made significant contributions to the DJGPP port.
488 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
489 development since 1991. Cygnus engineers who have worked on @value{GDBN}
490 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
491 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
492 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
493 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
494 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
495 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
496 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
497 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
498 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
499 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
500 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
501 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
502 Zuhn have made contributions both large and small.
504 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
505 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
507 Jim Blandy added support for preprocessor macros, while working for Red
510 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
511 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
512 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
513 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
514 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
515 with the migration of old architectures to this new framework.
517 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
518 unwinder framework, this consisting of a fresh new design featuring
519 frame IDs, independent frame sniffers, and the sentinel frame. Mark
520 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
521 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
522 trad unwinders. The architecture-specific changes, each involving a
523 complete rewrite of the architecture's frame code, were carried out by
524 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
525 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
526 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
527 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
530 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
531 Tensilica, Inc.@: contributed support for Xtensa processors. Others
532 who have worked on the Xtensa port of @value{GDBN} in the past include
533 Steve Tjiang, John Newlin, and Scott Foehner.
535 Michael Eager and staff of Xilinx, Inc., contributed support for the
536 Xilinx MicroBlaze architecture.
539 @chapter A Sample @value{GDBN} Session
541 You can use this manual at your leisure to read all about @value{GDBN}.
542 However, a handful of commands are enough to get started using the
543 debugger. This chapter illustrates those commands.
546 In this sample session, we emphasize user input like this: @b{input},
547 to make it easier to pick out from the surrounding output.
550 @c FIXME: this example may not be appropriate for some configs, where
551 @c FIXME...primary interest is in remote use.
553 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
554 processor) exhibits the following bug: sometimes, when we change its
555 quote strings from the default, the commands used to capture one macro
556 definition within another stop working. In the following short @code{m4}
557 session, we define a macro @code{foo} which expands to @code{0000}; we
558 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
559 same thing. However, when we change the open quote string to
560 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
561 procedure fails to define a new synonym @code{baz}:
570 @b{define(bar,defn(`foo'))}
574 @b{changequote(<QUOTE>,<UNQUOTE>)}
576 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
579 m4: End of input: 0: fatal error: EOF in string
583 Let us use @value{GDBN} to try to see what is going on.
586 $ @b{@value{GDBP} m4}
587 @c FIXME: this falsifies the exact text played out, to permit smallbook
588 @c FIXME... format to come out better.
589 @value{GDBN} is free software and you are welcome to distribute copies
590 of it under certain conditions; type "show copying" to see
592 There is absolutely no warranty for @value{GDBN}; type "show warranty"
595 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
600 @value{GDBN} reads only enough symbol data to know where to find the
601 rest when needed; as a result, the first prompt comes up very quickly.
602 We now tell @value{GDBN} to use a narrower display width than usual, so
603 that examples fit in this manual.
606 (@value{GDBP}) @b{set width 70}
610 We need to see how the @code{m4} built-in @code{changequote} works.
611 Having looked at the source, we know the relevant subroutine is
612 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
613 @code{break} command.
616 (@value{GDBP}) @b{break m4_changequote}
617 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
621 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
622 control; as long as control does not reach the @code{m4_changequote}
623 subroutine, the program runs as usual:
626 (@value{GDBP}) @b{run}
627 Starting program: /work/Editorial/gdb/gnu/m4/m4
635 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
636 suspends execution of @code{m4}, displaying information about the
637 context where it stops.
640 @b{changequote(<QUOTE>,<UNQUOTE>)}
642 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
644 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
648 Now we use the command @code{n} (@code{next}) to advance execution to
649 the next line of the current function.
653 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
658 @code{set_quotes} looks like a promising subroutine. We can go into it
659 by using the command @code{s} (@code{step}) instead of @code{next}.
660 @code{step} goes to the next line to be executed in @emph{any}
661 subroutine, so it steps into @code{set_quotes}.
665 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
667 530 if (lquote != def_lquote)
671 The display that shows the subroutine where @code{m4} is now
672 suspended (and its arguments) is called a stack frame display. It
673 shows a summary of the stack. We can use the @code{backtrace}
674 command (which can also be spelled @code{bt}), to see where we are
675 in the stack as a whole: the @code{backtrace} command displays a
676 stack frame for each active subroutine.
679 (@value{GDBP}) @b{bt}
680 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
682 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
684 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
685 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
687 #4 0x79dc in expand_input () at macro.c:40
688 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
692 We step through a few more lines to see what happens. The first two
693 times, we can use @samp{s}; the next two times we use @code{n} to avoid
694 falling into the @code{xstrdup} subroutine.
698 0x3b5c 532 if (rquote != def_rquote)
700 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
701 def_lquote : xstrdup(lq);
703 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
706 538 len_lquote = strlen(rquote);
710 The last line displayed looks a little odd; we can examine the variables
711 @code{lquote} and @code{rquote} to see if they are in fact the new left
712 and right quotes we specified. We use the command @code{p}
713 (@code{print}) to see their values.
716 (@value{GDBP}) @b{p lquote}
717 $1 = 0x35d40 "<QUOTE>"
718 (@value{GDBP}) @b{p rquote}
719 $2 = 0x35d50 "<UNQUOTE>"
723 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
724 To look at some context, we can display ten lines of source
725 surrounding the current line with the @code{l} (@code{list}) command.
731 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
733 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
736 538 len_lquote = strlen(rquote);
737 539 len_rquote = strlen(lquote);
744 Let us step past the two lines that set @code{len_lquote} and
745 @code{len_rquote}, and then examine the values of those variables.
749 539 len_rquote = strlen(lquote);
752 (@value{GDBP}) @b{p len_lquote}
754 (@value{GDBP}) @b{p len_rquote}
759 That certainly looks wrong, assuming @code{len_lquote} and
760 @code{len_rquote} are meant to be the lengths of @code{lquote} and
761 @code{rquote} respectively. We can set them to better values using
762 the @code{p} command, since it can print the value of
763 any expression---and that expression can include subroutine calls and
767 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
769 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
774 Is that enough to fix the problem of using the new quotes with the
775 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
776 executing with the @code{c} (@code{continue}) command, and then try the
777 example that caused trouble initially:
783 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
790 Success! The new quotes now work just as well as the default ones. The
791 problem seems to have been just the two typos defining the wrong
792 lengths. We allow @code{m4} exit by giving it an EOF as input:
796 Program exited normally.
800 The message @samp{Program exited normally.} is from @value{GDBN}; it
801 indicates @code{m4} has finished executing. We can end our @value{GDBN}
802 session with the @value{GDBN} @code{quit} command.
805 (@value{GDBP}) @b{quit}
809 @chapter Getting In and Out of @value{GDBN}
811 This chapter discusses how to start @value{GDBN}, and how to get out of it.
815 type @samp{@value{GDBP}} to start @value{GDBN}.
817 type @kbd{quit} or @kbd{Ctrl-d} to exit.
821 * Invoking GDB:: How to start @value{GDBN}
822 * Quitting GDB:: How to quit @value{GDBN}
823 * Shell Commands:: How to use shell commands inside @value{GDBN}
824 * Logging Output:: How to log @value{GDBN}'s output to a file
828 @section Invoking @value{GDBN}
830 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
831 @value{GDBN} reads commands from the terminal until you tell it to exit.
833 You can also run @code{@value{GDBP}} with a variety of arguments and options,
834 to specify more of your debugging environment at the outset.
836 The command-line options described here are designed
837 to cover a variety of situations; in some environments, some of these
838 options may effectively be unavailable.
840 The most usual way to start @value{GDBN} is with one argument,
841 specifying an executable program:
844 @value{GDBP} @var{program}
848 You can also start with both an executable program and a core file
852 @value{GDBP} @var{program} @var{core}
855 You can, instead, specify a process ID as a second argument, if you want
856 to debug a running process:
859 @value{GDBP} @var{program} 1234
863 would attach @value{GDBN} to process @code{1234} (unless you also have a file
864 named @file{1234}; @value{GDBN} does check for a core file first).
866 Taking advantage of the second command-line argument requires a fairly
867 complete operating system; when you use @value{GDBN} as a remote
868 debugger attached to a bare board, there may not be any notion of
869 ``process'', and there is often no way to get a core dump. @value{GDBN}
870 will warn you if it is unable to attach or to read core dumps.
872 You can optionally have @code{@value{GDBP}} pass any arguments after the
873 executable file to the inferior using @code{--args}. This option stops
876 @value{GDBP} --args gcc -O2 -c foo.c
878 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
879 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
881 You can run @code{@value{GDBP}} without printing the front material, which describes
882 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
889 You can further control how @value{GDBN} starts up by using command-line
890 options. @value{GDBN} itself can remind you of the options available.
900 to display all available options and briefly describe their use
901 (@samp{@value{GDBP} -h} is a shorter equivalent).
903 All options and command line arguments you give are processed
904 in sequential order. The order makes a difference when the
905 @samp{-x} option is used.
909 * File Options:: Choosing files
910 * Mode Options:: Choosing modes
911 * Startup:: What @value{GDBN} does during startup
915 @subsection Choosing Files
917 When @value{GDBN} starts, it reads any arguments other than options as
918 specifying an executable file and core file (or process ID). This is
919 the same as if the arguments were specified by the @samp{-se} and
920 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
921 first argument that does not have an associated option flag as
922 equivalent to the @samp{-se} option followed by that argument; and the
923 second argument that does not have an associated option flag, if any, as
924 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
925 If the second argument begins with a decimal digit, @value{GDBN} will
926 first attempt to attach to it as a process, and if that fails, attempt
927 to open it as a corefile. If you have a corefile whose name begins with
928 a digit, you can prevent @value{GDBN} from treating it as a pid by
929 prefixing it with @file{./}, e.g.@: @file{./12345}.
931 If @value{GDBN} has not been configured to included core file support,
932 such as for most embedded targets, then it will complain about a second
933 argument and ignore it.
935 Many options have both long and short forms; both are shown in the
936 following list. @value{GDBN} also recognizes the long forms if you truncate
937 them, so long as enough of the option is present to be unambiguous.
938 (If you prefer, you can flag option arguments with @samp{--} rather
939 than @samp{-}, though we illustrate the more usual convention.)
941 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
942 @c way, both those who look for -foo and --foo in the index, will find
946 @item -symbols @var{file}
948 @cindex @code{--symbols}
950 Read symbol table from file @var{file}.
952 @item -exec @var{file}
954 @cindex @code{--exec}
956 Use file @var{file} as the executable file to execute when appropriate,
957 and for examining pure data in conjunction with a core dump.
961 Read symbol table from file @var{file} and use it as the executable
964 @item -core @var{file}
966 @cindex @code{--core}
968 Use file @var{file} as a core dump to examine.
970 @item -pid @var{number}
971 @itemx -p @var{number}
974 Connect to process ID @var{number}, as with the @code{attach} command.
976 @item -command @var{file}
978 @cindex @code{--command}
980 Execute commands from file @var{file}. The contents of this file is
981 evaluated exactly as the @code{source} command would.
982 @xref{Command Files,, Command files}.
984 @item -eval-command @var{command}
985 @itemx -ex @var{command}
986 @cindex @code{--eval-command}
988 Execute a single @value{GDBN} command.
990 This option may be used multiple times to call multiple commands. It may
991 also be interleaved with @samp{-command} as required.
994 @value{GDBP} -ex 'target sim' -ex 'load' \
995 -x setbreakpoints -ex 'run' a.out
998 @item -init-command @var{file}
999 @itemx -ix @var{file}
1000 @cindex @code{--init-command}
1002 Execute commands from file @var{file} before loading the inferior (but
1003 after loading gdbinit files).
1006 @item -init-eval-command @var{command}
1007 @itemx -iex @var{command}
1008 @cindex @code{--init-eval-command}
1010 Execute a single @value{GDBN} command before loading the inferior (but
1011 after loading gdbinit files).
1014 @item -directory @var{directory}
1015 @itemx -d @var{directory}
1016 @cindex @code{--directory}
1018 Add @var{directory} to the path to search for source and script files.
1022 @cindex @code{--readnow}
1024 Read each symbol file's entire symbol table immediately, rather than
1025 the default, which is to read it incrementally as it is needed.
1026 This makes startup slower, but makes future operations faster.
1031 @subsection Choosing Modes
1033 You can run @value{GDBN} in various alternative modes---for example, in
1034 batch mode or quiet mode.
1042 Do not execute commands found in any initialization file.
1043 There are three init files, loaded in the following order:
1046 @item @file{system.gdbinit}
1047 This is the system-wide init file.
1048 Its location is specified with the @code{--with-system-gdbinit}
1049 configure option (@pxref{System-wide configuration}).
1050 It is loaded first when @value{GDBN} starts, before command line options
1051 have been processed.
1052 @item @file{~/.gdbinit}
1053 This is the init file in your home directory.
1054 It is loaded next, after @file{system.gdbinit}, and before
1055 command options have been processed.
1056 @item @file{./.gdbinit}
1057 This is the init file in the current directory.
1058 It is loaded last, after command line options other than @code{-x} and
1059 @code{-ex} have been processed. Command line options @code{-x} and
1060 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1063 For further documentation on startup processing, @xref{Startup}.
1064 For documentation on how to write command files,
1065 @xref{Command Files,,Command Files}.
1070 Do not execute commands found in @file{~/.gdbinit}, the init file
1071 in your home directory.
1077 @cindex @code{--quiet}
1078 @cindex @code{--silent}
1080 ``Quiet''. Do not print the introductory and copyright messages. These
1081 messages are also suppressed in batch mode.
1084 @cindex @code{--batch}
1085 Run in batch mode. Exit with status @code{0} after processing all the
1086 command files specified with @samp{-x} (and all commands from
1087 initialization files, if not inhibited with @samp{-n}). Exit with
1088 nonzero status if an error occurs in executing the @value{GDBN} commands
1089 in the command files. Batch mode also disables pagination, sets unlimited
1090 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1091 off} were in effect (@pxref{Messages/Warnings}).
1093 Batch mode may be useful for running @value{GDBN} as a filter, for
1094 example to download and run a program on another computer; in order to
1095 make this more useful, the message
1098 Program exited normally.
1102 (which is ordinarily issued whenever a program running under
1103 @value{GDBN} control terminates) is not issued when running in batch
1107 @cindex @code{--batch-silent}
1108 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1109 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1110 unaffected). This is much quieter than @samp{-silent} and would be useless
1111 for an interactive session.
1113 This is particularly useful when using targets that give @samp{Loading section}
1114 messages, for example.
1116 Note that targets that give their output via @value{GDBN}, as opposed to
1117 writing directly to @code{stdout}, will also be made silent.
1119 @item -return-child-result
1120 @cindex @code{--return-child-result}
1121 The return code from @value{GDBN} will be the return code from the child
1122 process (the process being debugged), with the following exceptions:
1126 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1127 internal error. In this case the exit code is the same as it would have been
1128 without @samp{-return-child-result}.
1130 The user quits with an explicit value. E.g., @samp{quit 1}.
1132 The child process never runs, or is not allowed to terminate, in which case
1133 the exit code will be -1.
1136 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1137 when @value{GDBN} is being used as a remote program loader or simulator
1142 @cindex @code{--nowindows}
1144 ``No windows''. If @value{GDBN} comes with a graphical user interface
1145 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1146 interface. If no GUI is available, this option has no effect.
1150 @cindex @code{--windows}
1152 If @value{GDBN} includes a GUI, then this option requires it to be
1155 @item -cd @var{directory}
1157 Run @value{GDBN} using @var{directory} as its working directory,
1158 instead of the current directory.
1160 @item -data-directory @var{directory}
1161 @cindex @code{--data-directory}
1162 Run @value{GDBN} using @var{directory} as its data directory.
1163 The data directory is where @value{GDBN} searches for its
1164 auxiliary files. @xref{Data Files}.
1168 @cindex @code{--fullname}
1170 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1171 subprocess. It tells @value{GDBN} to output the full file name and line
1172 number in a standard, recognizable fashion each time a stack frame is
1173 displayed (which includes each time your program stops). This
1174 recognizable format looks like two @samp{\032} characters, followed by
1175 the file name, line number and character position separated by colons,
1176 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1177 @samp{\032} characters as a signal to display the source code for the
1180 @item -annotate @var{level}
1181 @cindex @code{--annotate}
1182 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1183 effect is identical to using @samp{set annotate @var{level}}
1184 (@pxref{Annotations}). The annotation @var{level} controls how much
1185 information @value{GDBN} prints together with its prompt, values of
1186 expressions, source lines, and other types of output. Level 0 is the
1187 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1188 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1189 that control @value{GDBN}, and level 2 has been deprecated.
1191 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1195 @cindex @code{--args}
1196 Change interpretation of command line so that arguments following the
1197 executable file are passed as command line arguments to the inferior.
1198 This option stops option processing.
1200 @item -baud @var{bps}
1202 @cindex @code{--baud}
1204 Set the line speed (baud rate or bits per second) of any serial
1205 interface used by @value{GDBN} for remote debugging.
1207 @item -l @var{timeout}
1209 Set the timeout (in seconds) of any communication used by @value{GDBN}
1210 for remote debugging.
1212 @item -tty @var{device}
1213 @itemx -t @var{device}
1214 @cindex @code{--tty}
1216 Run using @var{device} for your program's standard input and output.
1217 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1219 @c resolve the situation of these eventually
1221 @cindex @code{--tui}
1222 Activate the @dfn{Text User Interface} when starting. The Text User
1223 Interface manages several text windows on the terminal, showing
1224 source, assembly, registers and @value{GDBN} command outputs
1225 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1226 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1227 Using @value{GDBN} under @sc{gnu} Emacs}).
1230 @c @cindex @code{--xdb}
1231 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1232 @c For information, see the file @file{xdb_trans.html}, which is usually
1233 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1236 @item -interpreter @var{interp}
1237 @cindex @code{--interpreter}
1238 Use the interpreter @var{interp} for interface with the controlling
1239 program or device. This option is meant to be set by programs which
1240 communicate with @value{GDBN} using it as a back end.
1241 @xref{Interpreters, , Command Interpreters}.
1243 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1244 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1245 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1246 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1247 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1248 @sc{gdb/mi} interfaces are no longer supported.
1251 @cindex @code{--write}
1252 Open the executable and core files for both reading and writing. This
1253 is equivalent to the @samp{set write on} command inside @value{GDBN}
1257 @cindex @code{--statistics}
1258 This option causes @value{GDBN} to print statistics about time and
1259 memory usage after it completes each command and returns to the prompt.
1262 @cindex @code{--version}
1263 This option causes @value{GDBN} to print its version number and
1264 no-warranty blurb, and exit.
1269 @subsection What @value{GDBN} Does During Startup
1270 @cindex @value{GDBN} startup
1272 Here's the description of what @value{GDBN} does during session startup:
1276 Sets up the command interpreter as specified by the command line
1277 (@pxref{Mode Options, interpreter}).
1281 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1282 used when building @value{GDBN}; @pxref{System-wide configuration,
1283 ,System-wide configuration and settings}) and executes all the commands in
1286 @anchor{Home Directory Init File}
1288 Reads the init file (if any) in your home directory@footnote{On
1289 DOS/Windows systems, the home directory is the one pointed to by the
1290 @code{HOME} environment variable.} and executes all the commands in
1293 @anchor{Option -init-eval-command}
1295 Executes commands and command files specified by the @samp{-iex} and
1296 @samp{-ix} options in their specified order. Usually you should use the
1297 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1298 settings before @value{GDBN} init files get executed and before inferior
1302 Processes command line options and operands.
1304 @anchor{Init File in the Current Directory during Startup}
1306 Reads and executes the commands from init file (if any) in the current
1307 working directory as long as @samp{set auto-load local-gdbinit} is set to
1308 @samp{on} (@pxref{Init File in the Current Directory}).
1309 This is only done if the current directory is
1310 different from your home directory. Thus, you can have more than one
1311 init file, one generic in your home directory, and another, specific
1312 to the program you are debugging, in the directory where you invoke
1316 If the command line specified a program to debug, or a process to
1317 attach to, or a core file, @value{GDBN} loads any auto-loaded
1318 scripts provided for the program or for its loaded shared libraries.
1319 @xref{Auto-loading}.
1321 If you wish to disable the auto-loading during startup,
1322 you must do something like the following:
1325 $ gdb -iex "set auto-load python-scripts off" myprogram
1328 Option @samp{-ex} does not work because the auto-loading is then turned
1332 Executes commands and command files specified by the @samp{-ex} and
1333 @samp{-x} options in their specified order. @xref{Command Files}, for
1334 more details about @value{GDBN} command files.
1337 Reads the command history recorded in the @dfn{history file}.
1338 @xref{Command History}, for more details about the command history and the
1339 files where @value{GDBN} records it.
1342 Init files use the same syntax as @dfn{command files} (@pxref{Command
1343 Files}) and are processed by @value{GDBN} in the same way. The init
1344 file in your home directory can set options (such as @samp{set
1345 complaints}) that affect subsequent processing of command line options
1346 and operands. Init files are not executed if you use the @samp{-nx}
1347 option (@pxref{Mode Options, ,Choosing Modes}).
1349 To display the list of init files loaded by gdb at startup, you
1350 can use @kbd{gdb --help}.
1352 @cindex init file name
1353 @cindex @file{.gdbinit}
1354 @cindex @file{gdb.ini}
1355 The @value{GDBN} init files are normally called @file{.gdbinit}.
1356 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1357 the limitations of file names imposed by DOS filesystems. The Windows
1358 port of @value{GDBN} uses the standard name, but if it finds a
1359 @file{gdb.ini} file in your home directory, it warns you about that
1360 and suggests to rename the file to the standard name.
1364 @section Quitting @value{GDBN}
1365 @cindex exiting @value{GDBN}
1366 @cindex leaving @value{GDBN}
1369 @kindex quit @r{[}@var{expression}@r{]}
1370 @kindex q @r{(@code{quit})}
1371 @item quit @r{[}@var{expression}@r{]}
1373 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1374 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1375 do not supply @var{expression}, @value{GDBN} will terminate normally;
1376 otherwise it will terminate using the result of @var{expression} as the
1381 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1382 terminates the action of any @value{GDBN} command that is in progress and
1383 returns to @value{GDBN} command level. It is safe to type the interrupt
1384 character at any time because @value{GDBN} does not allow it to take effect
1385 until a time when it is safe.
1387 If you have been using @value{GDBN} to control an attached process or
1388 device, you can release it with the @code{detach} command
1389 (@pxref{Attach, ,Debugging an Already-running Process}).
1391 @node Shell Commands
1392 @section Shell Commands
1394 If you need to execute occasional shell commands during your
1395 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1396 just use the @code{shell} command.
1401 @cindex shell escape
1402 @item shell @var{command-string}
1403 @itemx !@var{command-string}
1404 Invoke a standard shell to execute @var{command-string}.
1405 Note that no space is needed between @code{!} and @var{command-string}.
1406 If it exists, the environment variable @code{SHELL} determines which
1407 shell to run. Otherwise @value{GDBN} uses the default shell
1408 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1411 The utility @code{make} is often needed in development environments.
1412 You do not have to use the @code{shell} command for this purpose in
1417 @cindex calling make
1418 @item make @var{make-args}
1419 Execute the @code{make} program with the specified
1420 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1423 @node Logging Output
1424 @section Logging Output
1425 @cindex logging @value{GDBN} output
1426 @cindex save @value{GDBN} output to a file
1428 You may want to save the output of @value{GDBN} commands to a file.
1429 There are several commands to control @value{GDBN}'s logging.
1433 @item set logging on
1435 @item set logging off
1437 @cindex logging file name
1438 @item set logging file @var{file}
1439 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1440 @item set logging overwrite [on|off]
1441 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1442 you want @code{set logging on} to overwrite the logfile instead.
1443 @item set logging redirect [on|off]
1444 By default, @value{GDBN} output will go to both the terminal and the logfile.
1445 Set @code{redirect} if you want output to go only to the log file.
1446 @kindex show logging
1448 Show the current values of the logging settings.
1452 @chapter @value{GDBN} Commands
1454 You can abbreviate a @value{GDBN} command to the first few letters of the command
1455 name, if that abbreviation is unambiguous; and you can repeat certain
1456 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1457 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1458 show you the alternatives available, if there is more than one possibility).
1461 * Command Syntax:: How to give commands to @value{GDBN}
1462 * Completion:: Command completion
1463 * Help:: How to ask @value{GDBN} for help
1466 @node Command Syntax
1467 @section Command Syntax
1469 A @value{GDBN} command is a single line of input. There is no limit on
1470 how long it can be. It starts with a command name, which is followed by
1471 arguments whose meaning depends on the command name. For example, the
1472 command @code{step} accepts an argument which is the number of times to
1473 step, as in @samp{step 5}. You can also use the @code{step} command
1474 with no arguments. Some commands do not allow any arguments.
1476 @cindex abbreviation
1477 @value{GDBN} command names may always be truncated if that abbreviation is
1478 unambiguous. Other possible command abbreviations are listed in the
1479 documentation for individual commands. In some cases, even ambiguous
1480 abbreviations are allowed; for example, @code{s} is specially defined as
1481 equivalent to @code{step} even though there are other commands whose
1482 names start with @code{s}. You can test abbreviations by using them as
1483 arguments to the @code{help} command.
1485 @cindex repeating commands
1486 @kindex RET @r{(repeat last command)}
1487 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1488 repeat the previous command. Certain commands (for example, @code{run})
1489 will not repeat this way; these are commands whose unintentional
1490 repetition might cause trouble and which you are unlikely to want to
1491 repeat. User-defined commands can disable this feature; see
1492 @ref{Define, dont-repeat}.
1494 The @code{list} and @code{x} commands, when you repeat them with
1495 @key{RET}, construct new arguments rather than repeating
1496 exactly as typed. This permits easy scanning of source or memory.
1498 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1499 output, in a way similar to the common utility @code{more}
1500 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1501 @key{RET} too many in this situation, @value{GDBN} disables command
1502 repetition after any command that generates this sort of display.
1504 @kindex # @r{(a comment)}
1506 Any text from a @kbd{#} to the end of the line is a comment; it does
1507 nothing. This is useful mainly in command files (@pxref{Command
1508 Files,,Command Files}).
1510 @cindex repeating command sequences
1511 @kindex Ctrl-o @r{(operate-and-get-next)}
1512 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1513 commands. This command accepts the current line, like @key{RET}, and
1514 then fetches the next line relative to the current line from the history
1518 @section Command Completion
1521 @cindex word completion
1522 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1523 only one possibility; it can also show you what the valid possibilities
1524 are for the next word in a command, at any time. This works for @value{GDBN}
1525 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1527 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1528 of a word. If there is only one possibility, @value{GDBN} fills in the
1529 word, and waits for you to finish the command (or press @key{RET} to
1530 enter it). For example, if you type
1532 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1533 @c complete accuracy in these examples; space introduced for clarity.
1534 @c If texinfo enhancements make it unnecessary, it would be nice to
1535 @c replace " @key" by "@key" in the following...
1537 (@value{GDBP}) info bre @key{TAB}
1541 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1542 the only @code{info} subcommand beginning with @samp{bre}:
1545 (@value{GDBP}) info breakpoints
1549 You can either press @key{RET} at this point, to run the @code{info
1550 breakpoints} command, or backspace and enter something else, if
1551 @samp{breakpoints} does not look like the command you expected. (If you
1552 were sure you wanted @code{info breakpoints} in the first place, you
1553 might as well just type @key{RET} immediately after @samp{info bre},
1554 to exploit command abbreviations rather than command completion).
1556 If there is more than one possibility for the next word when you press
1557 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1558 characters and try again, or just press @key{TAB} a second time;
1559 @value{GDBN} displays all the possible completions for that word. For
1560 example, you might want to set a breakpoint on a subroutine whose name
1561 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1562 just sounds the bell. Typing @key{TAB} again displays all the
1563 function names in your program that begin with those characters, for
1567 (@value{GDBP}) b make_ @key{TAB}
1568 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1569 make_a_section_from_file make_environ
1570 make_abs_section make_function_type
1571 make_blockvector make_pointer_type
1572 make_cleanup make_reference_type
1573 make_command make_symbol_completion_list
1574 (@value{GDBP}) b make_
1578 After displaying the available possibilities, @value{GDBN} copies your
1579 partial input (@samp{b make_} in the example) so you can finish the
1582 If you just want to see the list of alternatives in the first place, you
1583 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1584 means @kbd{@key{META} ?}. You can type this either by holding down a
1585 key designated as the @key{META} shift on your keyboard (if there is
1586 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1588 @cindex quotes in commands
1589 @cindex completion of quoted strings
1590 Sometimes the string you need, while logically a ``word'', may contain
1591 parentheses or other characters that @value{GDBN} normally excludes from
1592 its notion of a word. To permit word completion to work in this
1593 situation, you may enclose words in @code{'} (single quote marks) in
1594 @value{GDBN} commands.
1596 The most likely situation where you might need this is in typing the
1597 name of a C@t{++} function. This is because C@t{++} allows function
1598 overloading (multiple definitions of the same function, distinguished
1599 by argument type). For example, when you want to set a breakpoint you
1600 may need to distinguish whether you mean the version of @code{name}
1601 that takes an @code{int} parameter, @code{name(int)}, or the version
1602 that takes a @code{float} parameter, @code{name(float)}. To use the
1603 word-completion facilities in this situation, type a single quote
1604 @code{'} at the beginning of the function name. This alerts
1605 @value{GDBN} that it may need to consider more information than usual
1606 when you press @key{TAB} or @kbd{M-?} to request word completion:
1609 (@value{GDBP}) b 'bubble( @kbd{M-?}
1610 bubble(double,double) bubble(int,int)
1611 (@value{GDBP}) b 'bubble(
1614 In some cases, @value{GDBN} can tell that completing a name requires using
1615 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1616 completing as much as it can) if you do not type the quote in the first
1620 (@value{GDBP}) b bub @key{TAB}
1621 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1622 (@value{GDBP}) b 'bubble(
1626 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1627 you have not yet started typing the argument list when you ask for
1628 completion on an overloaded symbol.
1630 For more information about overloaded functions, see @ref{C Plus Plus
1631 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1632 overload-resolution off} to disable overload resolution;
1633 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1635 @cindex completion of structure field names
1636 @cindex structure field name completion
1637 @cindex completion of union field names
1638 @cindex union field name completion
1639 When completing in an expression which looks up a field in a
1640 structure, @value{GDBN} also tries@footnote{The completer can be
1641 confused by certain kinds of invalid expressions. Also, it only
1642 examines the static type of the expression, not the dynamic type.} to
1643 limit completions to the field names available in the type of the
1647 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1648 magic to_fputs to_rewind
1649 to_data to_isatty to_write
1650 to_delete to_put to_write_async_safe
1655 This is because the @code{gdb_stdout} is a variable of the type
1656 @code{struct ui_file} that is defined in @value{GDBN} sources as
1663 ui_file_flush_ftype *to_flush;
1664 ui_file_write_ftype *to_write;
1665 ui_file_write_async_safe_ftype *to_write_async_safe;
1666 ui_file_fputs_ftype *to_fputs;
1667 ui_file_read_ftype *to_read;
1668 ui_file_delete_ftype *to_delete;
1669 ui_file_isatty_ftype *to_isatty;
1670 ui_file_rewind_ftype *to_rewind;
1671 ui_file_put_ftype *to_put;
1678 @section Getting Help
1679 @cindex online documentation
1682 You can always ask @value{GDBN} itself for information on its commands,
1683 using the command @code{help}.
1686 @kindex h @r{(@code{help})}
1689 You can use @code{help} (abbreviated @code{h}) with no arguments to
1690 display a short list of named classes of commands:
1694 List of classes of commands:
1696 aliases -- Aliases of other commands
1697 breakpoints -- Making program stop at certain points
1698 data -- Examining data
1699 files -- Specifying and examining files
1700 internals -- Maintenance commands
1701 obscure -- Obscure features
1702 running -- Running the program
1703 stack -- Examining the stack
1704 status -- Status inquiries
1705 support -- Support facilities
1706 tracepoints -- Tracing of program execution without
1707 stopping the program
1708 user-defined -- User-defined commands
1710 Type "help" followed by a class name for a list of
1711 commands in that class.
1712 Type "help" followed by command name for full
1714 Command name abbreviations are allowed if unambiguous.
1717 @c the above line break eliminates huge line overfull...
1719 @item help @var{class}
1720 Using one of the general help classes as an argument, you can get a
1721 list of the individual commands in that class. For example, here is the
1722 help display for the class @code{status}:
1725 (@value{GDBP}) help status
1730 @c Line break in "show" line falsifies real output, but needed
1731 @c to fit in smallbook page size.
1732 info -- Generic command for showing things
1733 about the program being debugged
1734 show -- Generic command for showing things
1737 Type "help" followed by command name for full
1739 Command name abbreviations are allowed if unambiguous.
1743 @item help @var{command}
1744 With a command name as @code{help} argument, @value{GDBN} displays a
1745 short paragraph on how to use that command.
1748 @item apropos @var{args}
1749 The @code{apropos} command searches through all of the @value{GDBN}
1750 commands, and their documentation, for the regular expression specified in
1751 @var{args}. It prints out all matches found. For example:
1762 alias -- Define a new command that is an alias of an existing command
1763 aliases -- Aliases of other commands
1764 d -- Delete some breakpoints or auto-display expressions
1765 del -- Delete some breakpoints or auto-display expressions
1766 delete -- Delete some breakpoints or auto-display expressions
1771 @item complete @var{args}
1772 The @code{complete @var{args}} command lists all the possible completions
1773 for the beginning of a command. Use @var{args} to specify the beginning of the
1774 command you want completed. For example:
1780 @noindent results in:
1791 @noindent This is intended for use by @sc{gnu} Emacs.
1794 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1795 and @code{show} to inquire about the state of your program, or the state
1796 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1797 manual introduces each of them in the appropriate context. The listings
1798 under @code{info} and under @code{show} in the Command, Variable, and
1799 Function Index point to all the sub-commands. @xref{Command and Variable
1805 @kindex i @r{(@code{info})}
1807 This command (abbreviated @code{i}) is for describing the state of your
1808 program. For example, you can show the arguments passed to a function
1809 with @code{info args}, list the registers currently in use with @code{info
1810 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1811 You can get a complete list of the @code{info} sub-commands with
1812 @w{@code{help info}}.
1816 You can assign the result of an expression to an environment variable with
1817 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1818 @code{set prompt $}.
1822 In contrast to @code{info}, @code{show} is for describing the state of
1823 @value{GDBN} itself.
1824 You can change most of the things you can @code{show}, by using the
1825 related command @code{set}; for example, you can control what number
1826 system is used for displays with @code{set radix}, or simply inquire
1827 which is currently in use with @code{show radix}.
1830 To display all the settable parameters and their current
1831 values, you can use @code{show} with no arguments; you may also use
1832 @code{info set}. Both commands produce the same display.
1833 @c FIXME: "info set" violates the rule that "info" is for state of
1834 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1835 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1839 Here are three miscellaneous @code{show} subcommands, all of which are
1840 exceptional in lacking corresponding @code{set} commands:
1843 @kindex show version
1844 @cindex @value{GDBN} version number
1846 Show what version of @value{GDBN} is running. You should include this
1847 information in @value{GDBN} bug-reports. If multiple versions of
1848 @value{GDBN} are in use at your site, you may need to determine which
1849 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1850 commands are introduced, and old ones may wither away. Also, many
1851 system vendors ship variant versions of @value{GDBN}, and there are
1852 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1853 The version number is the same as the one announced when you start
1856 @kindex show copying
1857 @kindex info copying
1858 @cindex display @value{GDBN} copyright
1861 Display information about permission for copying @value{GDBN}.
1863 @kindex show warranty
1864 @kindex info warranty
1866 @itemx info warranty
1867 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1868 if your version of @value{GDBN} comes with one.
1873 @chapter Running Programs Under @value{GDBN}
1875 When you run a program under @value{GDBN}, you must first generate
1876 debugging information when you compile it.
1878 You may start @value{GDBN} with its arguments, if any, in an environment
1879 of your choice. If you are doing native debugging, you may redirect
1880 your program's input and output, debug an already running process, or
1881 kill a child process.
1884 * Compilation:: Compiling for debugging
1885 * Starting:: Starting your program
1886 * Arguments:: Your program's arguments
1887 * Environment:: Your program's environment
1889 * Working Directory:: Your program's working directory
1890 * Input/Output:: Your program's input and output
1891 * Attach:: Debugging an already-running process
1892 * Kill Process:: Killing the child process
1894 * Inferiors and Programs:: Debugging multiple inferiors and programs
1895 * Threads:: Debugging programs with multiple threads
1896 * Forks:: Debugging forks
1897 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1901 @section Compiling for Debugging
1903 In order to debug a program effectively, you need to generate
1904 debugging information when you compile it. This debugging information
1905 is stored in the object file; it describes the data type of each
1906 variable or function and the correspondence between source line numbers
1907 and addresses in the executable code.
1909 To request debugging information, specify the @samp{-g} option when you run
1912 Programs that are to be shipped to your customers are compiled with
1913 optimizations, using the @samp{-O} compiler option. However, some
1914 compilers are unable to handle the @samp{-g} and @samp{-O} options
1915 together. Using those compilers, you cannot generate optimized
1916 executables containing debugging information.
1918 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1919 without @samp{-O}, making it possible to debug optimized code. We
1920 recommend that you @emph{always} use @samp{-g} whenever you compile a
1921 program. You may think your program is correct, but there is no sense
1922 in pushing your luck. For more information, see @ref{Optimized Code}.
1924 Older versions of the @sc{gnu} C compiler permitted a variant option
1925 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1926 format; if your @sc{gnu} C compiler has this option, do not use it.
1928 @value{GDBN} knows about preprocessor macros and can show you their
1929 expansion (@pxref{Macros}). Most compilers do not include information
1930 about preprocessor macros in the debugging information if you specify
1931 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1932 the @sc{gnu} C compiler, provides macro information if you are using
1933 the DWARF debugging format, and specify the option @option{-g3}.
1935 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1936 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1937 information on @value{NGCC} options affecting debug information.
1939 You will have the best debugging experience if you use the latest
1940 version of the DWARF debugging format that your compiler supports.
1941 DWARF is currently the most expressive and best supported debugging
1942 format in @value{GDBN}.
1946 @section Starting your Program
1952 @kindex r @r{(@code{run})}
1955 Use the @code{run} command to start your program under @value{GDBN}.
1956 You must first specify the program name (except on VxWorks) with an
1957 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1958 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1959 (@pxref{Files, ,Commands to Specify Files}).
1963 If you are running your program in an execution environment that
1964 supports processes, @code{run} creates an inferior process and makes
1965 that process run your program. In some environments without processes,
1966 @code{run} jumps to the start of your program. Other targets,
1967 like @samp{remote}, are always running. If you get an error
1968 message like this one:
1971 The "remote" target does not support "run".
1972 Try "help target" or "continue".
1976 then use @code{continue} to run your program. You may need @code{load}
1977 first (@pxref{load}).
1979 The execution of a program is affected by certain information it
1980 receives from its superior. @value{GDBN} provides ways to specify this
1981 information, which you must do @emph{before} starting your program. (You
1982 can change it after starting your program, but such changes only affect
1983 your program the next time you start it.) This information may be
1984 divided into four categories:
1987 @item The @emph{arguments.}
1988 Specify the arguments to give your program as the arguments of the
1989 @code{run} command. If a shell is available on your target, the shell
1990 is used to pass the arguments, so that you may use normal conventions
1991 (such as wildcard expansion or variable substitution) in describing
1993 In Unix systems, you can control which shell is used with the
1994 @code{SHELL} environment variable.
1995 @xref{Arguments, ,Your Program's Arguments}.
1997 @item The @emph{environment.}
1998 Your program normally inherits its environment from @value{GDBN}, but you can
1999 use the @value{GDBN} commands @code{set environment} and @code{unset
2000 environment} to change parts of the environment that affect
2001 your program. @xref{Environment, ,Your Program's Environment}.
2003 @item The @emph{working directory.}
2004 Your program inherits its working directory from @value{GDBN}. You can set
2005 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2006 @xref{Working Directory, ,Your Program's Working Directory}.
2008 @item The @emph{standard input and output.}
2009 Your program normally uses the same device for standard input and
2010 standard output as @value{GDBN} is using. You can redirect input and output
2011 in the @code{run} command line, or you can use the @code{tty} command to
2012 set a different device for your program.
2013 @xref{Input/Output, ,Your Program's Input and Output}.
2016 @emph{Warning:} While input and output redirection work, you cannot use
2017 pipes to pass the output of the program you are debugging to another
2018 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2022 When you issue the @code{run} command, your program begins to execute
2023 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2024 of how to arrange for your program to stop. Once your program has
2025 stopped, you may call functions in your program, using the @code{print}
2026 or @code{call} commands. @xref{Data, ,Examining Data}.
2028 If the modification time of your symbol file has changed since the last
2029 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2030 table, and reads it again. When it does this, @value{GDBN} tries to retain
2031 your current breakpoints.
2036 @cindex run to main procedure
2037 The name of the main procedure can vary from language to language.
2038 With C or C@t{++}, the main procedure name is always @code{main}, but
2039 other languages such as Ada do not require a specific name for their
2040 main procedure. The debugger provides a convenient way to start the
2041 execution of the program and to stop at the beginning of the main
2042 procedure, depending on the language used.
2044 The @samp{start} command does the equivalent of setting a temporary
2045 breakpoint at the beginning of the main procedure and then invoking
2046 the @samp{run} command.
2048 @cindex elaboration phase
2049 Some programs contain an @dfn{elaboration} phase where some startup code is
2050 executed before the main procedure is called. This depends on the
2051 languages used to write your program. In C@t{++}, for instance,
2052 constructors for static and global objects are executed before
2053 @code{main} is called. It is therefore possible that the debugger stops
2054 before reaching the main procedure. However, the temporary breakpoint
2055 will remain to halt execution.
2057 Specify the arguments to give to your program as arguments to the
2058 @samp{start} command. These arguments will be given verbatim to the
2059 underlying @samp{run} command. Note that the same arguments will be
2060 reused if no argument is provided during subsequent calls to
2061 @samp{start} or @samp{run}.
2063 It is sometimes necessary to debug the program during elaboration. In
2064 these cases, using the @code{start} command would stop the execution of
2065 your program too late, as the program would have already completed the
2066 elaboration phase. Under these circumstances, insert breakpoints in your
2067 elaboration code before running your program.
2069 @kindex set exec-wrapper
2070 @item set exec-wrapper @var{wrapper}
2071 @itemx show exec-wrapper
2072 @itemx unset exec-wrapper
2073 When @samp{exec-wrapper} is set, the specified wrapper is used to
2074 launch programs for debugging. @value{GDBN} starts your program
2075 with a shell command of the form @kbd{exec @var{wrapper}
2076 @var{program}}. Quoting is added to @var{program} and its
2077 arguments, but not to @var{wrapper}, so you should add quotes if
2078 appropriate for your shell. The wrapper runs until it executes
2079 your program, and then @value{GDBN} takes control.
2081 You can use any program that eventually calls @code{execve} with
2082 its arguments as a wrapper. Several standard Unix utilities do
2083 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2084 with @code{exec "$@@"} will also work.
2086 For example, you can use @code{env} to pass an environment variable to
2087 the debugged program, without setting the variable in your shell's
2091 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2095 This command is available when debugging locally on most targets, excluding
2096 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2098 @kindex set disable-randomization
2099 @item set disable-randomization
2100 @itemx set disable-randomization on
2101 This option (enabled by default in @value{GDBN}) will turn off the native
2102 randomization of the virtual address space of the started program. This option
2103 is useful for multiple debugging sessions to make the execution better
2104 reproducible and memory addresses reusable across debugging sessions.
2106 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2107 On @sc{gnu}/Linux you can get the same behavior using
2110 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2113 @item set disable-randomization off
2114 Leave the behavior of the started executable unchanged. Some bugs rear their
2115 ugly heads only when the program is loaded at certain addresses. If your bug
2116 disappears when you run the program under @value{GDBN}, that might be because
2117 @value{GDBN} by default disables the address randomization on platforms, such
2118 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2119 disable-randomization off} to try to reproduce such elusive bugs.
2121 On targets where it is available, virtual address space randomization
2122 protects the programs against certain kinds of security attacks. In these
2123 cases the attacker needs to know the exact location of a concrete executable
2124 code. Randomizing its location makes it impossible to inject jumps misusing
2125 a code at its expected addresses.
2127 Prelinking shared libraries provides a startup performance advantage but it
2128 makes addresses in these libraries predictable for privileged processes by
2129 having just unprivileged access at the target system. Reading the shared
2130 library binary gives enough information for assembling the malicious code
2131 misusing it. Still even a prelinked shared library can get loaded at a new
2132 random address just requiring the regular relocation process during the
2133 startup. Shared libraries not already prelinked are always loaded at
2134 a randomly chosen address.
2136 Position independent executables (PIE) contain position independent code
2137 similar to the shared libraries and therefore such executables get loaded at
2138 a randomly chosen address upon startup. PIE executables always load even
2139 already prelinked shared libraries at a random address. You can build such
2140 executable using @command{gcc -fPIE -pie}.
2142 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2143 (as long as the randomization is enabled).
2145 @item show disable-randomization
2146 Show the current setting of the explicit disable of the native randomization of
2147 the virtual address space of the started program.
2152 @section Your Program's Arguments
2154 @cindex arguments (to your program)
2155 The arguments to your program can be specified by the arguments of the
2157 They are passed to a shell, which expands wildcard characters and
2158 performs redirection of I/O, and thence to your program. Your
2159 @code{SHELL} environment variable (if it exists) specifies what shell
2160 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2161 the default shell (@file{/bin/sh} on Unix).
2163 On non-Unix systems, the program is usually invoked directly by
2164 @value{GDBN}, which emulates I/O redirection via the appropriate system
2165 calls, and the wildcard characters are expanded by the startup code of
2166 the program, not by the shell.
2168 @code{run} with no arguments uses the same arguments used by the previous
2169 @code{run}, or those set by the @code{set args} command.
2174 Specify the arguments to be used the next time your program is run. If
2175 @code{set args} has no arguments, @code{run} executes your program
2176 with no arguments. Once you have run your program with arguments,
2177 using @code{set args} before the next @code{run} is the only way to run
2178 it again without arguments.
2182 Show the arguments to give your program when it is started.
2186 @section Your Program's Environment
2188 @cindex environment (of your program)
2189 The @dfn{environment} consists of a set of environment variables and
2190 their values. Environment variables conventionally record such things as
2191 your user name, your home directory, your terminal type, and your search
2192 path for programs to run. Usually you set up environment variables with
2193 the shell and they are inherited by all the other programs you run. When
2194 debugging, it can be useful to try running your program with a modified
2195 environment without having to start @value{GDBN} over again.
2199 @item path @var{directory}
2200 Add @var{directory} to the front of the @code{PATH} environment variable
2201 (the search path for executables) that will be passed to your program.
2202 The value of @code{PATH} used by @value{GDBN} does not change.
2203 You may specify several directory names, separated by whitespace or by a
2204 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2205 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2206 is moved to the front, so it is searched sooner.
2208 You can use the string @samp{$cwd} to refer to whatever is the current
2209 working directory at the time @value{GDBN} searches the path. If you
2210 use @samp{.} instead, it refers to the directory where you executed the
2211 @code{path} command. @value{GDBN} replaces @samp{.} in the
2212 @var{directory} argument (with the current path) before adding
2213 @var{directory} to the search path.
2214 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2215 @c document that, since repeating it would be a no-op.
2219 Display the list of search paths for executables (the @code{PATH}
2220 environment variable).
2222 @kindex show environment
2223 @item show environment @r{[}@var{varname}@r{]}
2224 Print the value of environment variable @var{varname} to be given to
2225 your program when it starts. If you do not supply @var{varname},
2226 print the names and values of all environment variables to be given to
2227 your program. You can abbreviate @code{environment} as @code{env}.
2229 @kindex set environment
2230 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2231 Set environment variable @var{varname} to @var{value}. The value
2232 changes for your program only, not for @value{GDBN} itself. @var{value} may
2233 be any string; the values of environment variables are just strings, and
2234 any interpretation is supplied by your program itself. The @var{value}
2235 parameter is optional; if it is eliminated, the variable is set to a
2237 @c "any string" here does not include leading, trailing
2238 @c blanks. Gnu asks: does anyone care?
2240 For example, this command:
2247 tells the debugged program, when subsequently run, that its user is named
2248 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2249 are not actually required.)
2251 @kindex unset environment
2252 @item unset environment @var{varname}
2253 Remove variable @var{varname} from the environment to be passed to your
2254 program. This is different from @samp{set env @var{varname} =};
2255 @code{unset environment} removes the variable from the environment,
2256 rather than assigning it an empty value.
2259 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2261 by your @code{SHELL} environment variable if it exists (or
2262 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2263 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2264 @file{.bashrc} for BASH---any variables you set in that file affect
2265 your program. You may wish to move setting of environment variables to
2266 files that are only run when you sign on, such as @file{.login} or
2269 @node Working Directory
2270 @section Your Program's Working Directory
2272 @cindex working directory (of your program)
2273 Each time you start your program with @code{run}, it inherits its
2274 working directory from the current working directory of @value{GDBN}.
2275 The @value{GDBN} working directory is initially whatever it inherited
2276 from its parent process (typically the shell), but you can specify a new
2277 working directory in @value{GDBN} with the @code{cd} command.
2279 The @value{GDBN} working directory also serves as a default for the commands
2280 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2285 @cindex change working directory
2286 @item cd @r{[}@var{directory}@r{]}
2287 Set the @value{GDBN} working directory to @var{directory}. If not
2288 given, @var{directory} uses @file{'~'}.
2292 Print the @value{GDBN} working directory.
2295 It is generally impossible to find the current working directory of
2296 the process being debugged (since a program can change its directory
2297 during its run). If you work on a system where @value{GDBN} is
2298 configured with the @file{/proc} support, you can use the @code{info
2299 proc} command (@pxref{SVR4 Process Information}) to find out the
2300 current working directory of the debuggee.
2303 @section Your Program's Input and Output
2308 By default, the program you run under @value{GDBN} does input and output to
2309 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2310 to its own terminal modes to interact with you, but it records the terminal
2311 modes your program was using and switches back to them when you continue
2312 running your program.
2315 @kindex info terminal
2317 Displays information recorded by @value{GDBN} about the terminal modes your
2321 You can redirect your program's input and/or output using shell
2322 redirection with the @code{run} command. For example,
2329 starts your program, diverting its output to the file @file{outfile}.
2332 @cindex controlling terminal
2333 Another way to specify where your program should do input and output is
2334 with the @code{tty} command. This command accepts a file name as
2335 argument, and causes this file to be the default for future @code{run}
2336 commands. It also resets the controlling terminal for the child
2337 process, for future @code{run} commands. For example,
2344 directs that processes started with subsequent @code{run} commands
2345 default to do input and output on the terminal @file{/dev/ttyb} and have
2346 that as their controlling terminal.
2348 An explicit redirection in @code{run} overrides the @code{tty} command's
2349 effect on the input/output device, but not its effect on the controlling
2352 When you use the @code{tty} command or redirect input in the @code{run}
2353 command, only the input @emph{for your program} is affected. The input
2354 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2355 for @code{set inferior-tty}.
2357 @cindex inferior tty
2358 @cindex set inferior controlling terminal
2359 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2360 display the name of the terminal that will be used for future runs of your
2364 @item set inferior-tty /dev/ttyb
2365 @kindex set inferior-tty
2366 Set the tty for the program being debugged to /dev/ttyb.
2368 @item show inferior-tty
2369 @kindex show inferior-tty
2370 Show the current tty for the program being debugged.
2374 @section Debugging an Already-running Process
2379 @item attach @var{process-id}
2380 This command attaches to a running process---one that was started
2381 outside @value{GDBN}. (@code{info files} shows your active
2382 targets.) The command takes as argument a process ID. The usual way to
2383 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2384 or with the @samp{jobs -l} shell command.
2386 @code{attach} does not repeat if you press @key{RET} a second time after
2387 executing the command.
2390 To use @code{attach}, your program must be running in an environment
2391 which supports processes; for example, @code{attach} does not work for
2392 programs on bare-board targets that lack an operating system. You must
2393 also have permission to send the process a signal.
2395 When you use @code{attach}, the debugger finds the program running in
2396 the process first by looking in the current working directory, then (if
2397 the program is not found) by using the source file search path
2398 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2399 the @code{file} command to load the program. @xref{Files, ,Commands to
2402 The first thing @value{GDBN} does after arranging to debug the specified
2403 process is to stop it. You can examine and modify an attached process
2404 with all the @value{GDBN} commands that are ordinarily available when
2405 you start processes with @code{run}. You can insert breakpoints; you
2406 can step and continue; you can modify storage. If you would rather the
2407 process continue running, you may use the @code{continue} command after
2408 attaching @value{GDBN} to the process.
2413 When you have finished debugging the attached process, you can use the
2414 @code{detach} command to release it from @value{GDBN} control. Detaching
2415 the process continues its execution. After the @code{detach} command,
2416 that process and @value{GDBN} become completely independent once more, and you
2417 are ready to @code{attach} another process or start one with @code{run}.
2418 @code{detach} does not repeat if you press @key{RET} again after
2419 executing the command.
2422 If you exit @value{GDBN} while you have an attached process, you detach
2423 that process. If you use the @code{run} command, you kill that process.
2424 By default, @value{GDBN} asks for confirmation if you try to do either of these
2425 things; you can control whether or not you need to confirm by using the
2426 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2430 @section Killing the Child Process
2435 Kill the child process in which your program is running under @value{GDBN}.
2438 This command is useful if you wish to debug a core dump instead of a
2439 running process. @value{GDBN} ignores any core dump file while your program
2442 On some operating systems, a program cannot be executed outside @value{GDBN}
2443 while you have breakpoints set on it inside @value{GDBN}. You can use the
2444 @code{kill} command in this situation to permit running your program
2445 outside the debugger.
2447 The @code{kill} command is also useful if you wish to recompile and
2448 relink your program, since on many systems it is impossible to modify an
2449 executable file while it is running in a process. In this case, when you
2450 next type @code{run}, @value{GDBN} notices that the file has changed, and
2451 reads the symbol table again (while trying to preserve your current
2452 breakpoint settings).
2454 @node Inferiors and Programs
2455 @section Debugging Multiple Inferiors and Programs
2457 @value{GDBN} lets you run and debug multiple programs in a single
2458 session. In addition, @value{GDBN} on some systems may let you run
2459 several programs simultaneously (otherwise you have to exit from one
2460 before starting another). In the most general case, you can have
2461 multiple threads of execution in each of multiple processes, launched
2462 from multiple executables.
2465 @value{GDBN} represents the state of each program execution with an
2466 object called an @dfn{inferior}. An inferior typically corresponds to
2467 a process, but is more general and applies also to targets that do not
2468 have processes. Inferiors may be created before a process runs, and
2469 may be retained after a process exits. Inferiors have unique
2470 identifiers that are different from process ids. Usually each
2471 inferior will also have its own distinct address space, although some
2472 embedded targets may have several inferiors running in different parts
2473 of a single address space. Each inferior may in turn have multiple
2474 threads running in it.
2476 To find out what inferiors exist at any moment, use @w{@code{info
2480 @kindex info inferiors
2481 @item info inferiors
2482 Print a list of all inferiors currently being managed by @value{GDBN}.
2484 @value{GDBN} displays for each inferior (in this order):
2488 the inferior number assigned by @value{GDBN}
2491 the target system's inferior identifier
2494 the name of the executable the inferior is running.
2499 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2500 indicates the current inferior.
2504 @c end table here to get a little more width for example
2507 (@value{GDBP}) info inferiors
2508 Num Description Executable
2509 2 process 2307 hello
2510 * 1 process 3401 goodbye
2513 To switch focus between inferiors, use the @code{inferior} command:
2516 @kindex inferior @var{infno}
2517 @item inferior @var{infno}
2518 Make inferior number @var{infno} the current inferior. The argument
2519 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2520 in the first field of the @samp{info inferiors} display.
2524 You can get multiple executables into a debugging session via the
2525 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2526 systems @value{GDBN} can add inferiors to the debug session
2527 automatically by following calls to @code{fork} and @code{exec}. To
2528 remove inferiors from the debugging session use the
2529 @w{@code{remove-inferiors}} command.
2532 @kindex add-inferior
2533 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2534 Adds @var{n} inferiors to be run using @var{executable} as the
2535 executable. @var{n} defaults to 1. If no executable is specified,
2536 the inferiors begins empty, with no program. You can still assign or
2537 change the program assigned to the inferior at any time by using the
2538 @code{file} command with the executable name as its argument.
2540 @kindex clone-inferior
2541 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2542 Adds @var{n} inferiors ready to execute the same program as inferior
2543 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2544 number of the current inferior. This is a convenient command when you
2545 want to run another instance of the inferior you are debugging.
2548 (@value{GDBP}) info inferiors
2549 Num Description Executable
2550 * 1 process 29964 helloworld
2551 (@value{GDBP}) clone-inferior
2554 (@value{GDBP}) info inferiors
2555 Num Description Executable
2557 * 1 process 29964 helloworld
2560 You can now simply switch focus to inferior 2 and run it.
2562 @kindex remove-inferiors
2563 @item remove-inferiors @var{infno}@dots{}
2564 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2565 possible to remove an inferior that is running with this command. For
2566 those, use the @code{kill} or @code{detach} command first.
2570 To quit debugging one of the running inferiors that is not the current
2571 inferior, you can either detach from it by using the @w{@code{detach
2572 inferior}} command (allowing it to run independently), or kill it
2573 using the @w{@code{kill inferiors}} command:
2576 @kindex detach inferiors @var{infno}@dots{}
2577 @item detach inferior @var{infno}@dots{}
2578 Detach from the inferior or inferiors identified by @value{GDBN}
2579 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2580 still stays on the list of inferiors shown by @code{info inferiors},
2581 but its Description will show @samp{<null>}.
2583 @kindex kill inferiors @var{infno}@dots{}
2584 @item kill inferiors @var{infno}@dots{}
2585 Kill the inferior or inferiors identified by @value{GDBN} inferior
2586 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2587 stays on the list of inferiors shown by @code{info inferiors}, but its
2588 Description will show @samp{<null>}.
2591 After the successful completion of a command such as @code{detach},
2592 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2593 a normal process exit, the inferior is still valid and listed with
2594 @code{info inferiors}, ready to be restarted.
2597 To be notified when inferiors are started or exit under @value{GDBN}'s
2598 control use @w{@code{set print inferior-events}}:
2601 @kindex set print inferior-events
2602 @cindex print messages on inferior start and exit
2603 @item set print inferior-events
2604 @itemx set print inferior-events on
2605 @itemx set print inferior-events off
2606 The @code{set print inferior-events} command allows you to enable or
2607 disable printing of messages when @value{GDBN} notices that new
2608 inferiors have started or that inferiors have exited or have been
2609 detached. By default, these messages will not be printed.
2611 @kindex show print inferior-events
2612 @item show print inferior-events
2613 Show whether messages will be printed when @value{GDBN} detects that
2614 inferiors have started, exited or have been detached.
2617 Many commands will work the same with multiple programs as with a
2618 single program: e.g., @code{print myglobal} will simply display the
2619 value of @code{myglobal} in the current inferior.
2622 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2623 get more info about the relationship of inferiors, programs, address
2624 spaces in a debug session. You can do that with the @w{@code{maint
2625 info program-spaces}} command.
2628 @kindex maint info program-spaces
2629 @item maint info program-spaces
2630 Print a list of all program spaces currently being managed by
2633 @value{GDBN} displays for each program space (in this order):
2637 the program space number assigned by @value{GDBN}
2640 the name of the executable loaded into the program space, with e.g.,
2641 the @code{file} command.
2646 An asterisk @samp{*} preceding the @value{GDBN} program space number
2647 indicates the current program space.
2649 In addition, below each program space line, @value{GDBN} prints extra
2650 information that isn't suitable to display in tabular form. For
2651 example, the list of inferiors bound to the program space.
2654 (@value{GDBP}) maint info program-spaces
2657 Bound inferiors: ID 1 (process 21561)
2661 Here we can see that no inferior is running the program @code{hello},
2662 while @code{process 21561} is running the program @code{goodbye}. On
2663 some targets, it is possible that multiple inferiors are bound to the
2664 same program space. The most common example is that of debugging both
2665 the parent and child processes of a @code{vfork} call. For example,
2668 (@value{GDBP}) maint info program-spaces
2671 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2674 Here, both inferior 2 and inferior 1 are running in the same program
2675 space as a result of inferior 1 having executed a @code{vfork} call.
2679 @section Debugging Programs with Multiple Threads
2681 @cindex threads of execution
2682 @cindex multiple threads
2683 @cindex switching threads
2684 In some operating systems, such as HP-UX and Solaris, a single program
2685 may have more than one @dfn{thread} of execution. The precise semantics
2686 of threads differ from one operating system to another, but in general
2687 the threads of a single program are akin to multiple processes---except
2688 that they share one address space (that is, they can all examine and
2689 modify the same variables). On the other hand, each thread has its own
2690 registers and execution stack, and perhaps private memory.
2692 @value{GDBN} provides these facilities for debugging multi-thread
2696 @item automatic notification of new threads
2697 @item @samp{thread @var{threadno}}, a command to switch among threads
2698 @item @samp{info threads}, a command to inquire about existing threads
2699 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2700 a command to apply a command to a list of threads
2701 @item thread-specific breakpoints
2702 @item @samp{set print thread-events}, which controls printing of
2703 messages on thread start and exit.
2704 @item @samp{set libthread-db-search-path @var{path}}, which lets
2705 the user specify which @code{libthread_db} to use if the default choice
2706 isn't compatible with the program.
2710 @emph{Warning:} These facilities are not yet available on every
2711 @value{GDBN} configuration where the operating system supports threads.
2712 If your @value{GDBN} does not support threads, these commands have no
2713 effect. For example, a system without thread support shows no output
2714 from @samp{info threads}, and always rejects the @code{thread} command,
2718 (@value{GDBP}) info threads
2719 (@value{GDBP}) thread 1
2720 Thread ID 1 not known. Use the "info threads" command to
2721 see the IDs of currently known threads.
2723 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2724 @c doesn't support threads"?
2727 @cindex focus of debugging
2728 @cindex current thread
2729 The @value{GDBN} thread debugging facility allows you to observe all
2730 threads while your program runs---but whenever @value{GDBN} takes
2731 control, one thread in particular is always the focus of debugging.
2732 This thread is called the @dfn{current thread}. Debugging commands show
2733 program information from the perspective of the current thread.
2735 @cindex @code{New} @var{systag} message
2736 @cindex thread identifier (system)
2737 @c FIXME-implementors!! It would be more helpful if the [New...] message
2738 @c included GDB's numeric thread handle, so you could just go to that
2739 @c thread without first checking `info threads'.
2740 Whenever @value{GDBN} detects a new thread in your program, it displays
2741 the target system's identification for the thread with a message in the
2742 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2743 whose form varies depending on the particular system. For example, on
2744 @sc{gnu}/Linux, you might see
2747 [New Thread 0x41e02940 (LWP 25582)]
2751 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2752 the @var{systag} is simply something like @samp{process 368}, with no
2755 @c FIXME!! (1) Does the [New...] message appear even for the very first
2756 @c thread of a program, or does it only appear for the
2757 @c second---i.e.@: when it becomes obvious we have a multithread
2759 @c (2) *Is* there necessarily a first thread always? Or do some
2760 @c multithread systems permit starting a program with multiple
2761 @c threads ab initio?
2763 @cindex thread number
2764 @cindex thread identifier (GDB)
2765 For debugging purposes, @value{GDBN} associates its own thread
2766 number---always a single integer---with each thread in your program.
2769 @kindex info threads
2770 @item info threads @r{[}@var{id}@dots{}@r{]}
2771 Display a summary of all threads currently in your program. Optional
2772 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2773 means to print information only about the specified thread or threads.
2774 @value{GDBN} displays for each thread (in this order):
2778 the thread number assigned by @value{GDBN}
2781 the target system's thread identifier (@var{systag})
2784 the thread's name, if one is known. A thread can either be named by
2785 the user (see @code{thread name}, below), or, in some cases, by the
2789 the current stack frame summary for that thread
2793 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2794 indicates the current thread.
2798 @c end table here to get a little more width for example
2801 (@value{GDBP}) info threads
2803 3 process 35 thread 27 0x34e5 in sigpause ()
2804 2 process 35 thread 23 0x34e5 in sigpause ()
2805 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2809 On Solaris, you can display more information about user threads with a
2810 Solaris-specific command:
2813 @item maint info sol-threads
2814 @kindex maint info sol-threads
2815 @cindex thread info (Solaris)
2816 Display info on Solaris user threads.
2820 @kindex thread @var{threadno}
2821 @item thread @var{threadno}
2822 Make thread number @var{threadno} the current thread. The command
2823 argument @var{threadno} is the internal @value{GDBN} thread number, as
2824 shown in the first field of the @samp{info threads} display.
2825 @value{GDBN} responds by displaying the system identifier of the thread
2826 you selected, and its current stack frame summary:
2829 (@value{GDBP}) thread 2
2830 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2831 #0 some_function (ignore=0x0) at example.c:8
2832 8 printf ("hello\n");
2836 As with the @samp{[New @dots{}]} message, the form of the text after
2837 @samp{Switching to} depends on your system's conventions for identifying
2840 @vindex $_thread@r{, convenience variable}
2841 The debugger convenience variable @samp{$_thread} contains the number
2842 of the current thread. You may find this useful in writing breakpoint
2843 conditional expressions, command scripts, and so forth. See
2844 @xref{Convenience Vars,, Convenience Variables}, for general
2845 information on convenience variables.
2847 @kindex thread apply
2848 @cindex apply command to several threads
2849 @item thread apply [@var{threadno} | all] @var{command}
2850 The @code{thread apply} command allows you to apply the named
2851 @var{command} to one or more threads. Specify the numbers of the
2852 threads that you want affected with the command argument
2853 @var{threadno}. It can be a single thread number, one of the numbers
2854 shown in the first field of the @samp{info threads} display; or it
2855 could be a range of thread numbers, as in @code{2-4}. To apply a
2856 command to all threads, type @kbd{thread apply all @var{command}}.
2859 @cindex name a thread
2860 @item thread name [@var{name}]
2861 This command assigns a name to the current thread. If no argument is
2862 given, any existing user-specified name is removed. The thread name
2863 appears in the @samp{info threads} display.
2865 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2866 determine the name of the thread as given by the OS. On these
2867 systems, a name specified with @samp{thread name} will override the
2868 system-give name, and removing the user-specified name will cause
2869 @value{GDBN} to once again display the system-specified name.
2872 @cindex search for a thread
2873 @item thread find [@var{regexp}]
2874 Search for and display thread ids whose name or @var{systag}
2875 matches the supplied regular expression.
2877 As well as being the complement to the @samp{thread name} command,
2878 this command also allows you to identify a thread by its target
2879 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2883 (@value{GDBN}) thread find 26688
2884 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2885 (@value{GDBN}) info thread 4
2887 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2890 @kindex set print thread-events
2891 @cindex print messages on thread start and exit
2892 @item set print thread-events
2893 @itemx set print thread-events on
2894 @itemx set print thread-events off
2895 The @code{set print thread-events} command allows you to enable or
2896 disable printing of messages when @value{GDBN} notices that new threads have
2897 started or that threads have exited. By default, these messages will
2898 be printed if detection of these events is supported by the target.
2899 Note that these messages cannot be disabled on all targets.
2901 @kindex show print thread-events
2902 @item show print thread-events
2903 Show whether messages will be printed when @value{GDBN} detects that threads
2904 have started and exited.
2907 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2908 more information about how @value{GDBN} behaves when you stop and start
2909 programs with multiple threads.
2911 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2912 watchpoints in programs with multiple threads.
2914 @anchor{set libthread-db-search-path}
2916 @kindex set libthread-db-search-path
2917 @cindex search path for @code{libthread_db}
2918 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2919 If this variable is set, @var{path} is a colon-separated list of
2920 directories @value{GDBN} will use to search for @code{libthread_db}.
2921 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2922 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2923 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2926 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2927 @code{libthread_db} library to obtain information about threads in the
2928 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2929 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2930 specific thread debugging library loading is enabled
2931 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2933 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2934 refers to the default system directories that are
2935 normally searched for loading shared libraries. The @samp{$sdir} entry
2936 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2937 (@pxref{libthread_db.so.1 file}).
2939 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2940 refers to the directory from which @code{libpthread}
2941 was loaded in the inferior process.
2943 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2944 @value{GDBN} attempts to initialize it with the current inferior process.
2945 If this initialization fails (which could happen because of a version
2946 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2947 will unload @code{libthread_db}, and continue with the next directory.
2948 If none of @code{libthread_db} libraries initialize successfully,
2949 @value{GDBN} will issue a warning and thread debugging will be disabled.
2951 Setting @code{libthread-db-search-path} is currently implemented
2952 only on some platforms.
2954 @kindex show libthread-db-search-path
2955 @item show libthread-db-search-path
2956 Display current libthread_db search path.
2958 @kindex set debug libthread-db
2959 @kindex show debug libthread-db
2960 @cindex debugging @code{libthread_db}
2961 @item set debug libthread-db
2962 @itemx show debug libthread-db
2963 Turns on or off display of @code{libthread_db}-related events.
2964 Use @code{1} to enable, @code{0} to disable.
2968 @section Debugging Forks
2970 @cindex fork, debugging programs which call
2971 @cindex multiple processes
2972 @cindex processes, multiple
2973 On most systems, @value{GDBN} has no special support for debugging
2974 programs which create additional processes using the @code{fork}
2975 function. When a program forks, @value{GDBN} will continue to debug the
2976 parent process and the child process will run unimpeded. If you have
2977 set a breakpoint in any code which the child then executes, the child
2978 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2979 will cause it to terminate.
2981 However, if you want to debug the child process there is a workaround
2982 which isn't too painful. Put a call to @code{sleep} in the code which
2983 the child process executes after the fork. It may be useful to sleep
2984 only if a certain environment variable is set, or a certain file exists,
2985 so that the delay need not occur when you don't want to run @value{GDBN}
2986 on the child. While the child is sleeping, use the @code{ps} program to
2987 get its process ID. Then tell @value{GDBN} (a new invocation of
2988 @value{GDBN} if you are also debugging the parent process) to attach to
2989 the child process (@pxref{Attach}). From that point on you can debug
2990 the child process just like any other process which you attached to.
2992 On some systems, @value{GDBN} provides support for debugging programs that
2993 create additional processes using the @code{fork} or @code{vfork} functions.
2994 Currently, the only platforms with this feature are HP-UX (11.x and later
2995 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2997 By default, when a program forks, @value{GDBN} will continue to debug
2998 the parent process and the child process will run unimpeded.
3000 If you want to follow the child process instead of the parent process,
3001 use the command @w{@code{set follow-fork-mode}}.
3004 @kindex set follow-fork-mode
3005 @item set follow-fork-mode @var{mode}
3006 Set the debugger response to a program call of @code{fork} or
3007 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3008 process. The @var{mode} argument can be:
3012 The original process is debugged after a fork. The child process runs
3013 unimpeded. This is the default.
3016 The new process is debugged after a fork. The parent process runs
3021 @kindex show follow-fork-mode
3022 @item show follow-fork-mode
3023 Display the current debugger response to a @code{fork} or @code{vfork} call.
3026 @cindex debugging multiple processes
3027 On Linux, if you want to debug both the parent and child processes, use the
3028 command @w{@code{set detach-on-fork}}.
3031 @kindex set detach-on-fork
3032 @item set detach-on-fork @var{mode}
3033 Tells gdb whether to detach one of the processes after a fork, or
3034 retain debugger control over them both.
3038 The child process (or parent process, depending on the value of
3039 @code{follow-fork-mode}) will be detached and allowed to run
3040 independently. This is the default.
3043 Both processes will be held under the control of @value{GDBN}.
3044 One process (child or parent, depending on the value of
3045 @code{follow-fork-mode}) is debugged as usual, while the other
3050 @kindex show detach-on-fork
3051 @item show detach-on-fork
3052 Show whether detach-on-fork mode is on/off.
3055 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3056 will retain control of all forked processes (including nested forks).
3057 You can list the forked processes under the control of @value{GDBN} by
3058 using the @w{@code{info inferiors}} command, and switch from one fork
3059 to another by using the @code{inferior} command (@pxref{Inferiors and
3060 Programs, ,Debugging Multiple Inferiors and Programs}).
3062 To quit debugging one of the forked processes, you can either detach
3063 from it by using the @w{@code{detach inferiors}} command (allowing it
3064 to run independently), or kill it using the @w{@code{kill inferiors}}
3065 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3068 If you ask to debug a child process and a @code{vfork} is followed by an
3069 @code{exec}, @value{GDBN} executes the new target up to the first
3070 breakpoint in the new target. If you have a breakpoint set on
3071 @code{main} in your original program, the breakpoint will also be set on
3072 the child process's @code{main}.
3074 On some systems, when a child process is spawned by @code{vfork}, you
3075 cannot debug the child or parent until an @code{exec} call completes.
3077 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3078 call executes, the new target restarts. To restart the parent
3079 process, use the @code{file} command with the parent executable name
3080 as its argument. By default, after an @code{exec} call executes,
3081 @value{GDBN} discards the symbols of the previous executable image.
3082 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3086 @kindex set follow-exec-mode
3087 @item set follow-exec-mode @var{mode}
3089 Set debugger response to a program call of @code{exec}. An
3090 @code{exec} call replaces the program image of a process.
3092 @code{follow-exec-mode} can be:
3096 @value{GDBN} creates a new inferior and rebinds the process to this
3097 new inferior. The program the process was running before the
3098 @code{exec} call can be restarted afterwards by restarting the
3104 (@value{GDBP}) info inferiors
3106 Id Description Executable
3109 process 12020 is executing new program: prog2
3110 Program exited normally.
3111 (@value{GDBP}) info inferiors
3112 Id Description Executable
3118 @value{GDBN} keeps the process bound to the same inferior. The new
3119 executable image replaces the previous executable loaded in the
3120 inferior. Restarting the inferior after the @code{exec} call, with
3121 e.g., the @code{run} command, restarts the executable the process was
3122 running after the @code{exec} call. This is the default mode.
3127 (@value{GDBP}) info inferiors
3128 Id Description Executable
3131 process 12020 is executing new program: prog2
3132 Program exited normally.
3133 (@value{GDBP}) info inferiors
3134 Id Description Executable
3141 You can use the @code{catch} command to make @value{GDBN} stop whenever
3142 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3143 Catchpoints, ,Setting Catchpoints}.
3145 @node Checkpoint/Restart
3146 @section Setting a @emph{Bookmark} to Return to Later
3151 @cindex snapshot of a process
3152 @cindex rewind program state
3154 On certain operating systems@footnote{Currently, only
3155 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3156 program's state, called a @dfn{checkpoint}, and come back to it
3159 Returning to a checkpoint effectively undoes everything that has
3160 happened in the program since the @code{checkpoint} was saved. This
3161 includes changes in memory, registers, and even (within some limits)
3162 system state. Effectively, it is like going back in time to the
3163 moment when the checkpoint was saved.
3165 Thus, if you're stepping thru a program and you think you're
3166 getting close to the point where things go wrong, you can save
3167 a checkpoint. Then, if you accidentally go too far and miss
3168 the critical statement, instead of having to restart your program
3169 from the beginning, you can just go back to the checkpoint and
3170 start again from there.
3172 This can be especially useful if it takes a lot of time or
3173 steps to reach the point where you think the bug occurs.
3175 To use the @code{checkpoint}/@code{restart} method of debugging:
3180 Save a snapshot of the debugged program's current execution state.
3181 The @code{checkpoint} command takes no arguments, but each checkpoint
3182 is assigned a small integer id, similar to a breakpoint id.
3184 @kindex info checkpoints
3185 @item info checkpoints
3186 List the checkpoints that have been saved in the current debugging
3187 session. For each checkpoint, the following information will be
3194 @item Source line, or label
3197 @kindex restart @var{checkpoint-id}
3198 @item restart @var{checkpoint-id}
3199 Restore the program state that was saved as checkpoint number
3200 @var{checkpoint-id}. All program variables, registers, stack frames
3201 etc.@: will be returned to the values that they had when the checkpoint
3202 was saved. In essence, gdb will ``wind back the clock'' to the point
3203 in time when the checkpoint was saved.
3205 Note that breakpoints, @value{GDBN} variables, command history etc.
3206 are not affected by restoring a checkpoint. In general, a checkpoint
3207 only restores things that reside in the program being debugged, not in
3210 @kindex delete checkpoint @var{checkpoint-id}
3211 @item delete checkpoint @var{checkpoint-id}
3212 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3216 Returning to a previously saved checkpoint will restore the user state
3217 of the program being debugged, plus a significant subset of the system
3218 (OS) state, including file pointers. It won't ``un-write'' data from
3219 a file, but it will rewind the file pointer to the previous location,
3220 so that the previously written data can be overwritten. For files
3221 opened in read mode, the pointer will also be restored so that the
3222 previously read data can be read again.
3224 Of course, characters that have been sent to a printer (or other
3225 external device) cannot be ``snatched back'', and characters received
3226 from eg.@: a serial device can be removed from internal program buffers,
3227 but they cannot be ``pushed back'' into the serial pipeline, ready to
3228 be received again. Similarly, the actual contents of files that have
3229 been changed cannot be restored (at this time).
3231 However, within those constraints, you actually can ``rewind'' your
3232 program to a previously saved point in time, and begin debugging it
3233 again --- and you can change the course of events so as to debug a
3234 different execution path this time.
3236 @cindex checkpoints and process id
3237 Finally, there is one bit of internal program state that will be
3238 different when you return to a checkpoint --- the program's process
3239 id. Each checkpoint will have a unique process id (or @var{pid}),
3240 and each will be different from the program's original @var{pid}.
3241 If your program has saved a local copy of its process id, this could
3242 potentially pose a problem.
3244 @subsection A Non-obvious Benefit of Using Checkpoints
3246 On some systems such as @sc{gnu}/Linux, address space randomization
3247 is performed on new processes for security reasons. This makes it
3248 difficult or impossible to set a breakpoint, or watchpoint, on an
3249 absolute address if you have to restart the program, since the
3250 absolute location of a symbol will change from one execution to the
3253 A checkpoint, however, is an @emph{identical} copy of a process.
3254 Therefore if you create a checkpoint at (eg.@:) the start of main,
3255 and simply return to that checkpoint instead of restarting the
3256 process, you can avoid the effects of address randomization and
3257 your symbols will all stay in the same place.
3260 @chapter Stopping and Continuing
3262 The principal purposes of using a debugger are so that you can stop your
3263 program before it terminates; or so that, if your program runs into
3264 trouble, you can investigate and find out why.
3266 Inside @value{GDBN}, your program may stop for any of several reasons,
3267 such as a signal, a breakpoint, or reaching a new line after a
3268 @value{GDBN} command such as @code{step}. You may then examine and
3269 change variables, set new breakpoints or remove old ones, and then
3270 continue execution. Usually, the messages shown by @value{GDBN} provide
3271 ample explanation of the status of your program---but you can also
3272 explicitly request this information at any time.
3275 @kindex info program
3277 Display information about the status of your program: whether it is
3278 running or not, what process it is, and why it stopped.
3282 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3283 * Continuing and Stepping:: Resuming execution
3284 * Skipping Over Functions and Files::
3285 Skipping over functions and files
3287 * Thread Stops:: Stopping and starting multi-thread programs
3291 @section Breakpoints, Watchpoints, and Catchpoints
3294 A @dfn{breakpoint} makes your program stop whenever a certain point in
3295 the program is reached. For each breakpoint, you can add conditions to
3296 control in finer detail whether your program stops. You can set
3297 breakpoints with the @code{break} command and its variants (@pxref{Set
3298 Breaks, ,Setting Breakpoints}), to specify the place where your program
3299 should stop by line number, function name or exact address in the
3302 On some systems, you can set breakpoints in shared libraries before
3303 the executable is run. There is a minor limitation on HP-UX systems:
3304 you must wait until the executable is run in order to set breakpoints
3305 in shared library routines that are not called directly by the program
3306 (for example, routines that are arguments in a @code{pthread_create}
3310 @cindex data breakpoints
3311 @cindex memory tracing
3312 @cindex breakpoint on memory address
3313 @cindex breakpoint on variable modification
3314 A @dfn{watchpoint} is a special breakpoint that stops your program
3315 when the value of an expression changes. The expression may be a value
3316 of a variable, or it could involve values of one or more variables
3317 combined by operators, such as @samp{a + b}. This is sometimes called
3318 @dfn{data breakpoints}. You must use a different command to set
3319 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3320 from that, you can manage a watchpoint like any other breakpoint: you
3321 enable, disable, and delete both breakpoints and watchpoints using the
3324 You can arrange to have values from your program displayed automatically
3325 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3329 @cindex breakpoint on events
3330 A @dfn{catchpoint} is another special breakpoint that stops your program
3331 when a certain kind of event occurs, such as the throwing of a C@t{++}
3332 exception or the loading of a library. As with watchpoints, you use a
3333 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3334 Catchpoints}), but aside from that, you can manage a catchpoint like any
3335 other breakpoint. (To stop when your program receives a signal, use the
3336 @code{handle} command; see @ref{Signals, ,Signals}.)
3338 @cindex breakpoint numbers
3339 @cindex numbers for breakpoints
3340 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3341 catchpoint when you create it; these numbers are successive integers
3342 starting with one. In many of the commands for controlling various
3343 features of breakpoints you use the breakpoint number to say which
3344 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3345 @dfn{disabled}; if disabled, it has no effect on your program until you
3348 @cindex breakpoint ranges
3349 @cindex ranges of breakpoints
3350 Some @value{GDBN} commands accept a range of breakpoints on which to
3351 operate. A breakpoint range is either a single breakpoint number, like
3352 @samp{5}, or two such numbers, in increasing order, separated by a
3353 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3354 all breakpoints in that range are operated on.
3357 * Set Breaks:: Setting breakpoints
3358 * Set Watchpoints:: Setting watchpoints
3359 * Set Catchpoints:: Setting catchpoints
3360 * Delete Breaks:: Deleting breakpoints
3361 * Disabling:: Disabling breakpoints
3362 * Conditions:: Break conditions
3363 * Break Commands:: Breakpoint command lists
3364 * Dynamic Printf:: Dynamic printf
3365 * Save Breakpoints:: How to save breakpoints in a file
3366 * Static Probe Points:: Listing static probe points
3367 * Error in Breakpoints:: ``Cannot insert breakpoints''
3368 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3372 @subsection Setting Breakpoints
3374 @c FIXME LMB what does GDB do if no code on line of breakpt?
3375 @c consider in particular declaration with/without initialization.
3377 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3380 @kindex b @r{(@code{break})}
3381 @vindex $bpnum@r{, convenience variable}
3382 @cindex latest breakpoint
3383 Breakpoints are set with the @code{break} command (abbreviated
3384 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3385 number of the breakpoint you've set most recently; see @ref{Convenience
3386 Vars,, Convenience Variables}, for a discussion of what you can do with
3387 convenience variables.
3390 @item break @var{location}
3391 Set a breakpoint at the given @var{location}, which can specify a
3392 function name, a line number, or an address of an instruction.
3393 (@xref{Specify Location}, for a list of all the possible ways to
3394 specify a @var{location}.) The breakpoint will stop your program just
3395 before it executes any of the code in the specified @var{location}.
3397 When using source languages that permit overloading of symbols, such as
3398 C@t{++}, a function name may refer to more than one possible place to break.
3399 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3402 It is also possible to insert a breakpoint that will stop the program
3403 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3404 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3407 When called without any arguments, @code{break} sets a breakpoint at
3408 the next instruction to be executed in the selected stack frame
3409 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3410 innermost, this makes your program stop as soon as control
3411 returns to that frame. This is similar to the effect of a
3412 @code{finish} command in the frame inside the selected frame---except
3413 that @code{finish} does not leave an active breakpoint. If you use
3414 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3415 the next time it reaches the current location; this may be useful
3418 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3419 least one instruction has been executed. If it did not do this, you
3420 would be unable to proceed past a breakpoint without first disabling the
3421 breakpoint. This rule applies whether or not the breakpoint already
3422 existed when your program stopped.
3424 @item break @dots{} if @var{cond}
3425 Set a breakpoint with condition @var{cond}; evaluate the expression
3426 @var{cond} each time the breakpoint is reached, and stop only if the
3427 value is nonzero---that is, if @var{cond} evaluates as true.
3428 @samp{@dots{}} stands for one of the possible arguments described
3429 above (or no argument) specifying where to break. @xref{Conditions,
3430 ,Break Conditions}, for more information on breakpoint conditions.
3433 @item tbreak @var{args}
3434 Set a breakpoint enabled only for one stop. @var{args} are the
3435 same as for the @code{break} command, and the breakpoint is set in the same
3436 way, but the breakpoint is automatically deleted after the first time your
3437 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3440 @cindex hardware breakpoints
3441 @item hbreak @var{args}
3442 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3443 @code{break} command and the breakpoint is set in the same way, but the
3444 breakpoint requires hardware support and some target hardware may not
3445 have this support. The main purpose of this is EPROM/ROM code
3446 debugging, so you can set a breakpoint at an instruction without
3447 changing the instruction. This can be used with the new trap-generation
3448 provided by SPARClite DSU and most x86-based targets. These targets
3449 will generate traps when a program accesses some data or instruction
3450 address that is assigned to the debug registers. However the hardware
3451 breakpoint registers can take a limited number of breakpoints. For
3452 example, on the DSU, only two data breakpoints can be set at a time, and
3453 @value{GDBN} will reject this command if more than two are used. Delete
3454 or disable unused hardware breakpoints before setting new ones
3455 (@pxref{Disabling, ,Disabling Breakpoints}).
3456 @xref{Conditions, ,Break Conditions}.
3457 For remote targets, you can restrict the number of hardware
3458 breakpoints @value{GDBN} will use, see @ref{set remote
3459 hardware-breakpoint-limit}.
3462 @item thbreak @var{args}
3463 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3464 are the same as for the @code{hbreak} command and the breakpoint is set in
3465 the same way. However, like the @code{tbreak} command,
3466 the breakpoint is automatically deleted after the
3467 first time your program stops there. Also, like the @code{hbreak}
3468 command, the breakpoint requires hardware support and some target hardware
3469 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3470 See also @ref{Conditions, ,Break Conditions}.
3473 @cindex regular expression
3474 @cindex breakpoints at functions matching a regexp
3475 @cindex set breakpoints in many functions
3476 @item rbreak @var{regex}
3477 Set breakpoints on all functions matching the regular expression
3478 @var{regex}. This command sets an unconditional breakpoint on all
3479 matches, printing a list of all breakpoints it set. Once these
3480 breakpoints are set, they are treated just like the breakpoints set with
3481 the @code{break} command. You can delete them, disable them, or make
3482 them conditional the same way as any other breakpoint.
3484 The syntax of the regular expression is the standard one used with tools
3485 like @file{grep}. Note that this is different from the syntax used by
3486 shells, so for instance @code{foo*} matches all functions that include
3487 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3488 @code{.*} leading and trailing the regular expression you supply, so to
3489 match only functions that begin with @code{foo}, use @code{^foo}.
3491 @cindex non-member C@t{++} functions, set breakpoint in
3492 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3493 breakpoints on overloaded functions that are not members of any special
3496 @cindex set breakpoints on all functions
3497 The @code{rbreak} command can be used to set breakpoints in
3498 @strong{all} the functions in a program, like this:
3501 (@value{GDBP}) rbreak .
3504 @item rbreak @var{file}:@var{regex}
3505 If @code{rbreak} is called with a filename qualification, it limits
3506 the search for functions matching the given regular expression to the
3507 specified @var{file}. This can be used, for example, to set breakpoints on
3508 every function in a given file:
3511 (@value{GDBP}) rbreak file.c:.
3514 The colon separating the filename qualifier from the regex may
3515 optionally be surrounded by spaces.
3517 @kindex info breakpoints
3518 @cindex @code{$_} and @code{info breakpoints}
3519 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3520 @itemx info break @r{[}@var{n}@dots{}@r{]}
3521 Print a table of all breakpoints, watchpoints, and catchpoints set and
3522 not deleted. Optional argument @var{n} means print information only
3523 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3524 For each breakpoint, following columns are printed:
3527 @item Breakpoint Numbers
3529 Breakpoint, watchpoint, or catchpoint.
3531 Whether the breakpoint is marked to be disabled or deleted when hit.
3532 @item Enabled or Disabled
3533 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3534 that are not enabled.
3536 Where the breakpoint is in your program, as a memory address. For a
3537 pending breakpoint whose address is not yet known, this field will
3538 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3539 library that has the symbol or line referred by breakpoint is loaded.
3540 See below for details. A breakpoint with several locations will
3541 have @samp{<MULTIPLE>} in this field---see below for details.
3543 Where the breakpoint is in the source for your program, as a file and
3544 line number. For a pending breakpoint, the original string passed to
3545 the breakpoint command will be listed as it cannot be resolved until
3546 the appropriate shared library is loaded in the future.
3550 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3551 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3552 @value{GDBN} on the host's side. If it is ``target'', then the condition
3553 is evaluated by the target. The @code{info break} command shows
3554 the condition on the line following the affected breakpoint, together with
3555 its condition evaluation mode in between parentheses.
3557 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3558 allowed to have a condition specified for it. The condition is not parsed for
3559 validity until a shared library is loaded that allows the pending
3560 breakpoint to resolve to a valid location.
3563 @code{info break} with a breakpoint
3564 number @var{n} as argument lists only that breakpoint. The
3565 convenience variable @code{$_} and the default examining-address for
3566 the @code{x} command are set to the address of the last breakpoint
3567 listed (@pxref{Memory, ,Examining Memory}).
3570 @code{info break} displays a count of the number of times the breakpoint
3571 has been hit. This is especially useful in conjunction with the
3572 @code{ignore} command. You can ignore a large number of breakpoint
3573 hits, look at the breakpoint info to see how many times the breakpoint
3574 was hit, and then run again, ignoring one less than that number. This
3575 will get you quickly to the last hit of that breakpoint.
3578 For a breakpoints with an enable count (xref) greater than 1,
3579 @code{info break} also displays that count.
3583 @value{GDBN} allows you to set any number of breakpoints at the same place in
3584 your program. There is nothing silly or meaningless about this. When
3585 the breakpoints are conditional, this is even useful
3586 (@pxref{Conditions, ,Break Conditions}).
3588 @cindex multiple locations, breakpoints
3589 @cindex breakpoints, multiple locations
3590 It is possible that a breakpoint corresponds to several locations
3591 in your program. Examples of this situation are:
3595 Multiple functions in the program may have the same name.
3598 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3599 instances of the function body, used in different cases.
3602 For a C@t{++} template function, a given line in the function can
3603 correspond to any number of instantiations.
3606 For an inlined function, a given source line can correspond to
3607 several places where that function is inlined.
3610 In all those cases, @value{GDBN} will insert a breakpoint at all
3611 the relevant locations.
3613 A breakpoint with multiple locations is displayed in the breakpoint
3614 table using several rows---one header row, followed by one row for
3615 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3616 address column. The rows for individual locations contain the actual
3617 addresses for locations, and show the functions to which those
3618 locations belong. The number column for a location is of the form
3619 @var{breakpoint-number}.@var{location-number}.
3624 Num Type Disp Enb Address What
3625 1 breakpoint keep y <MULTIPLE>
3627 breakpoint already hit 1 time
3628 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3629 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3632 Each location can be individually enabled or disabled by passing
3633 @var{breakpoint-number}.@var{location-number} as argument to the
3634 @code{enable} and @code{disable} commands. Note that you cannot
3635 delete the individual locations from the list, you can only delete the
3636 entire list of locations that belong to their parent breakpoint (with
3637 the @kbd{delete @var{num}} command, where @var{num} is the number of
3638 the parent breakpoint, 1 in the above example). Disabling or enabling
3639 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3640 that belong to that breakpoint.
3642 @cindex pending breakpoints
3643 It's quite common to have a breakpoint inside a shared library.
3644 Shared libraries can be loaded and unloaded explicitly,
3645 and possibly repeatedly, as the program is executed. To support
3646 this use case, @value{GDBN} updates breakpoint locations whenever
3647 any shared library is loaded or unloaded. Typically, you would
3648 set a breakpoint in a shared library at the beginning of your
3649 debugging session, when the library is not loaded, and when the
3650 symbols from the library are not available. When you try to set
3651 breakpoint, @value{GDBN} will ask you if you want to set
3652 a so called @dfn{pending breakpoint}---breakpoint whose address
3653 is not yet resolved.
3655 After the program is run, whenever a new shared library is loaded,
3656 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3657 shared library contains the symbol or line referred to by some
3658 pending breakpoint, that breakpoint is resolved and becomes an
3659 ordinary breakpoint. When a library is unloaded, all breakpoints
3660 that refer to its symbols or source lines become pending again.
3662 This logic works for breakpoints with multiple locations, too. For
3663 example, if you have a breakpoint in a C@t{++} template function, and
3664 a newly loaded shared library has an instantiation of that template,
3665 a new location is added to the list of locations for the breakpoint.
3667 Except for having unresolved address, pending breakpoints do not
3668 differ from regular breakpoints. You can set conditions or commands,
3669 enable and disable them and perform other breakpoint operations.
3671 @value{GDBN} provides some additional commands for controlling what
3672 happens when the @samp{break} command cannot resolve breakpoint
3673 address specification to an address:
3675 @kindex set breakpoint pending
3676 @kindex show breakpoint pending
3678 @item set breakpoint pending auto
3679 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3680 location, it queries you whether a pending breakpoint should be created.
3682 @item set breakpoint pending on
3683 This indicates that an unrecognized breakpoint location should automatically
3684 result in a pending breakpoint being created.
3686 @item set breakpoint pending off
3687 This indicates that pending breakpoints are not to be created. Any
3688 unrecognized breakpoint location results in an error. This setting does
3689 not affect any pending breakpoints previously created.
3691 @item show breakpoint pending
3692 Show the current behavior setting for creating pending breakpoints.
3695 The settings above only affect the @code{break} command and its
3696 variants. Once breakpoint is set, it will be automatically updated
3697 as shared libraries are loaded and unloaded.
3699 @cindex automatic hardware breakpoints
3700 For some targets, @value{GDBN} can automatically decide if hardware or
3701 software breakpoints should be used, depending on whether the
3702 breakpoint address is read-only or read-write. This applies to
3703 breakpoints set with the @code{break} command as well as to internal
3704 breakpoints set by commands like @code{next} and @code{finish}. For
3705 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3708 You can control this automatic behaviour with the following commands::
3710 @kindex set breakpoint auto-hw
3711 @kindex show breakpoint auto-hw
3713 @item set breakpoint auto-hw on
3714 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3715 will try to use the target memory map to decide if software or hardware
3716 breakpoint must be used.
3718 @item set breakpoint auto-hw off
3719 This indicates @value{GDBN} should not automatically select breakpoint
3720 type. If the target provides a memory map, @value{GDBN} will warn when
3721 trying to set software breakpoint at a read-only address.
3724 @value{GDBN} normally implements breakpoints by replacing the program code
3725 at the breakpoint address with a special instruction, which, when
3726 executed, given control to the debugger. By default, the program
3727 code is so modified only when the program is resumed. As soon as
3728 the program stops, @value{GDBN} restores the original instructions. This
3729 behaviour guards against leaving breakpoints inserted in the
3730 target should gdb abrubptly disconnect. However, with slow remote
3731 targets, inserting and removing breakpoint can reduce the performance.
3732 This behavior can be controlled with the following commands::
3734 @kindex set breakpoint always-inserted
3735 @kindex show breakpoint always-inserted
3737 @item set breakpoint always-inserted off
3738 All breakpoints, including newly added by the user, are inserted in
3739 the target only when the target is resumed. All breakpoints are
3740 removed from the target when it stops.
3742 @item set breakpoint always-inserted on
3743 Causes all breakpoints to be inserted in the target at all times. If
3744 the user adds a new breakpoint, or changes an existing breakpoint, the
3745 breakpoints in the target are updated immediately. A breakpoint is
3746 removed from the target only when breakpoint itself is removed.
3748 @cindex non-stop mode, and @code{breakpoint always-inserted}
3749 @item set breakpoint always-inserted auto
3750 This is the default mode. If @value{GDBN} is controlling the inferior
3751 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3752 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3753 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3754 @code{breakpoint always-inserted} mode is off.
3757 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3758 when a breakpoint breaks. If the condition is true, then the process being
3759 debugged stops, otherwise the process is resumed.
3761 If the target supports evaluating conditions on its end, @value{GDBN} may
3762 download the breakpoint, together with its conditions, to it.
3764 This feature can be controlled via the following commands:
3766 @kindex set breakpoint condition-evaluation
3767 @kindex show breakpoint condition-evaluation
3769 @item set breakpoint condition-evaluation host
3770 This option commands @value{GDBN} to evaluate the breakpoint
3771 conditions on the host's side. Unconditional breakpoints are sent to
3772 the target which in turn receives the triggers and reports them back to GDB
3773 for condition evaluation. This is the standard evaluation mode.
3775 @item set breakpoint condition-evaluation target
3776 This option commands @value{GDBN} to download breakpoint conditions
3777 to the target at the moment of their insertion. The target
3778 is responsible for evaluating the conditional expression and reporting
3779 breakpoint stop events back to @value{GDBN} whenever the condition
3780 is true. Due to limitations of target-side evaluation, some conditions
3781 cannot be evaluated there, e.g., conditions that depend on local data
3782 that is only known to the host. Examples include
3783 conditional expressions involving convenience variables, complex types
3784 that cannot be handled by the agent expression parser and expressions
3785 that are too long to be sent over to the target, specially when the
3786 target is a remote system. In these cases, the conditions will be
3787 evaluated by @value{GDBN}.
3789 @item set breakpoint condition-evaluation auto
3790 This is the default mode. If the target supports evaluating breakpoint
3791 conditions on its end, @value{GDBN} will download breakpoint conditions to
3792 the target (limitations mentioned previously apply). If the target does
3793 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3794 to evaluating all these conditions on the host's side.
3798 @cindex negative breakpoint numbers
3799 @cindex internal @value{GDBN} breakpoints
3800 @value{GDBN} itself sometimes sets breakpoints in your program for
3801 special purposes, such as proper handling of @code{longjmp} (in C
3802 programs). These internal breakpoints are assigned negative numbers,
3803 starting with @code{-1}; @samp{info breakpoints} does not display them.
3804 You can see these breakpoints with the @value{GDBN} maintenance command
3805 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3808 @node Set Watchpoints
3809 @subsection Setting Watchpoints
3811 @cindex setting watchpoints
3812 You can use a watchpoint to stop execution whenever the value of an
3813 expression changes, without having to predict a particular place where
3814 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3815 The expression may be as simple as the value of a single variable, or
3816 as complex as many variables combined by operators. Examples include:
3820 A reference to the value of a single variable.
3823 An address cast to an appropriate data type. For example,
3824 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3825 address (assuming an @code{int} occupies 4 bytes).
3828 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3829 expression can use any operators valid in the program's native
3830 language (@pxref{Languages}).
3833 You can set a watchpoint on an expression even if the expression can
3834 not be evaluated yet. For instance, you can set a watchpoint on
3835 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3836 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3837 the expression produces a valid value. If the expression becomes
3838 valid in some other way than changing a variable (e.g.@: if the memory
3839 pointed to by @samp{*global_ptr} becomes readable as the result of a
3840 @code{malloc} call), @value{GDBN} may not stop until the next time
3841 the expression changes.
3843 @cindex software watchpoints
3844 @cindex hardware watchpoints
3845 Depending on your system, watchpoints may be implemented in software or
3846 hardware. @value{GDBN} does software watchpointing by single-stepping your
3847 program and testing the variable's value each time, which is hundreds of
3848 times slower than normal execution. (But this may still be worth it, to
3849 catch errors where you have no clue what part of your program is the
3852 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3853 x86-based targets, @value{GDBN} includes support for hardware
3854 watchpoints, which do not slow down the running of your program.
3858 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3859 Set a watchpoint for an expression. @value{GDBN} will break when the
3860 expression @var{expr} is written into by the program and its value
3861 changes. The simplest (and the most popular) use of this command is
3862 to watch the value of a single variable:
3865 (@value{GDBP}) watch foo
3868 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3869 argument, @value{GDBN} breaks only when the thread identified by
3870 @var{threadnum} changes the value of @var{expr}. If any other threads
3871 change the value of @var{expr}, @value{GDBN} will not break. Note
3872 that watchpoints restricted to a single thread in this way only work
3873 with Hardware Watchpoints.
3875 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3876 (see below). The @code{-location} argument tells @value{GDBN} to
3877 instead watch the memory referred to by @var{expr}. In this case,
3878 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3879 and watch the memory at that address. The type of the result is used
3880 to determine the size of the watched memory. If the expression's
3881 result does not have an address, then @value{GDBN} will print an
3884 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3885 of masked watchpoints, if the current architecture supports this
3886 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3887 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3888 to an address to watch. The mask specifies that some bits of an address
3889 (the bits which are reset in the mask) should be ignored when matching
3890 the address accessed by the inferior against the watchpoint address.
3891 Thus, a masked watchpoint watches many addresses simultaneously---those
3892 addresses whose unmasked bits are identical to the unmasked bits in the
3893 watchpoint address. The @code{mask} argument implies @code{-location}.
3897 (@value{GDBP}) watch foo mask 0xffff00ff
3898 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3902 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3903 Set a watchpoint that will break when the value of @var{expr} is read
3907 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3908 Set a watchpoint that will break when @var{expr} is either read from
3909 or written into by the program.
3911 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3912 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3913 This command prints a list of watchpoints, using the same format as
3914 @code{info break} (@pxref{Set Breaks}).
3917 If you watch for a change in a numerically entered address you need to
3918 dereference it, as the address itself is just a constant number which will
3919 never change. @value{GDBN} refuses to create a watchpoint that watches
3920 a never-changing value:
3923 (@value{GDBP}) watch 0x600850
3924 Cannot watch constant value 0x600850.
3925 (@value{GDBP}) watch *(int *) 0x600850
3926 Watchpoint 1: *(int *) 6293584
3929 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3930 watchpoints execute very quickly, and the debugger reports a change in
3931 value at the exact instruction where the change occurs. If @value{GDBN}
3932 cannot set a hardware watchpoint, it sets a software watchpoint, which
3933 executes more slowly and reports the change in value at the next
3934 @emph{statement}, not the instruction, after the change occurs.
3936 @cindex use only software watchpoints
3937 You can force @value{GDBN} to use only software watchpoints with the
3938 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3939 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3940 the underlying system supports them. (Note that hardware-assisted
3941 watchpoints that were set @emph{before} setting
3942 @code{can-use-hw-watchpoints} to zero will still use the hardware
3943 mechanism of watching expression values.)
3946 @item set can-use-hw-watchpoints
3947 @kindex set can-use-hw-watchpoints
3948 Set whether or not to use hardware watchpoints.
3950 @item show can-use-hw-watchpoints
3951 @kindex show can-use-hw-watchpoints
3952 Show the current mode of using hardware watchpoints.
3955 For remote targets, you can restrict the number of hardware
3956 watchpoints @value{GDBN} will use, see @ref{set remote
3957 hardware-breakpoint-limit}.
3959 When you issue the @code{watch} command, @value{GDBN} reports
3962 Hardware watchpoint @var{num}: @var{expr}
3966 if it was able to set a hardware watchpoint.
3968 Currently, the @code{awatch} and @code{rwatch} commands can only set
3969 hardware watchpoints, because accesses to data that don't change the
3970 value of the watched expression cannot be detected without examining
3971 every instruction as it is being executed, and @value{GDBN} does not do
3972 that currently. If @value{GDBN} finds that it is unable to set a
3973 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3974 will print a message like this:
3977 Expression cannot be implemented with read/access watchpoint.
3980 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3981 data type of the watched expression is wider than what a hardware
3982 watchpoint on the target machine can handle. For example, some systems
3983 can only watch regions that are up to 4 bytes wide; on such systems you
3984 cannot set hardware watchpoints for an expression that yields a
3985 double-precision floating-point number (which is typically 8 bytes
3986 wide). As a work-around, it might be possible to break the large region
3987 into a series of smaller ones and watch them with separate watchpoints.
3989 If you set too many hardware watchpoints, @value{GDBN} might be unable
3990 to insert all of them when you resume the execution of your program.
3991 Since the precise number of active watchpoints is unknown until such
3992 time as the program is about to be resumed, @value{GDBN} might not be
3993 able to warn you about this when you set the watchpoints, and the
3994 warning will be printed only when the program is resumed:
3997 Hardware watchpoint @var{num}: Could not insert watchpoint
4001 If this happens, delete or disable some of the watchpoints.
4003 Watching complex expressions that reference many variables can also
4004 exhaust the resources available for hardware-assisted watchpoints.
4005 That's because @value{GDBN} needs to watch every variable in the
4006 expression with separately allocated resources.
4008 If you call a function interactively using @code{print} or @code{call},
4009 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4010 kind of breakpoint or the call completes.
4012 @value{GDBN} automatically deletes watchpoints that watch local
4013 (automatic) variables, or expressions that involve such variables, when
4014 they go out of scope, that is, when the execution leaves the block in
4015 which these variables were defined. In particular, when the program
4016 being debugged terminates, @emph{all} local variables go out of scope,
4017 and so only watchpoints that watch global variables remain set. If you
4018 rerun the program, you will need to set all such watchpoints again. One
4019 way of doing that would be to set a code breakpoint at the entry to the
4020 @code{main} function and when it breaks, set all the watchpoints.
4022 @cindex watchpoints and threads
4023 @cindex threads and watchpoints
4024 In multi-threaded programs, watchpoints will detect changes to the
4025 watched expression from every thread.
4028 @emph{Warning:} In multi-threaded programs, software watchpoints
4029 have only limited usefulness. If @value{GDBN} creates a software
4030 watchpoint, it can only watch the value of an expression @emph{in a
4031 single thread}. If you are confident that the expression can only
4032 change due to the current thread's activity (and if you are also
4033 confident that no other thread can become current), then you can use
4034 software watchpoints as usual. However, @value{GDBN} may not notice
4035 when a non-current thread's activity changes the expression. (Hardware
4036 watchpoints, in contrast, watch an expression in all threads.)
4039 @xref{set remote hardware-watchpoint-limit}.
4041 @node Set Catchpoints
4042 @subsection Setting Catchpoints
4043 @cindex catchpoints, setting
4044 @cindex exception handlers
4045 @cindex event handling
4047 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4048 kinds of program events, such as C@t{++} exceptions or the loading of a
4049 shared library. Use the @code{catch} command to set a catchpoint.
4053 @item catch @var{event}
4054 Stop when @var{event} occurs. @var{event} can be any of the following:
4057 @cindex stop on C@t{++} exceptions
4058 The throwing of a C@t{++} exception.
4061 The catching of a C@t{++} exception.
4064 @cindex Ada exception catching
4065 @cindex catch Ada exceptions
4066 An Ada exception being raised. If an exception name is specified
4067 at the end of the command (eg @code{catch exception Program_Error}),
4068 the debugger will stop only when this specific exception is raised.
4069 Otherwise, the debugger stops execution when any Ada exception is raised.
4071 When inserting an exception catchpoint on a user-defined exception whose
4072 name is identical to one of the exceptions defined by the language, the
4073 fully qualified name must be used as the exception name. Otherwise,
4074 @value{GDBN} will assume that it should stop on the pre-defined exception
4075 rather than the user-defined one. For instance, assuming an exception
4076 called @code{Constraint_Error} is defined in package @code{Pck}, then
4077 the command to use to catch such exceptions is @kbd{catch exception
4078 Pck.Constraint_Error}.
4080 @item exception unhandled
4081 An exception that was raised but is not handled by the program.
4084 A failed Ada assertion.
4087 @cindex break on fork/exec
4088 A call to @code{exec}. This is currently only available for HP-UX
4092 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4093 @cindex break on a system call.
4094 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4095 syscall is a mechanism for application programs to request a service
4096 from the operating system (OS) or one of the OS system services.
4097 @value{GDBN} can catch some or all of the syscalls issued by the
4098 debuggee, and show the related information for each syscall. If no
4099 argument is specified, calls to and returns from all system calls
4102 @var{name} can be any system call name that is valid for the
4103 underlying OS. Just what syscalls are valid depends on the OS. On
4104 GNU and Unix systems, you can find the full list of valid syscall
4105 names on @file{/usr/include/asm/unistd.h}.
4107 @c For MS-Windows, the syscall names and the corresponding numbers
4108 @c can be found, e.g., on this URL:
4109 @c http://www.metasploit.com/users/opcode/syscalls.html
4110 @c but we don't support Windows syscalls yet.
4112 Normally, @value{GDBN} knows in advance which syscalls are valid for
4113 each OS, so you can use the @value{GDBN} command-line completion
4114 facilities (@pxref{Completion,, command completion}) to list the
4117 You may also specify the system call numerically. A syscall's
4118 number is the value passed to the OS's syscall dispatcher to
4119 identify the requested service. When you specify the syscall by its
4120 name, @value{GDBN} uses its database of syscalls to convert the name
4121 into the corresponding numeric code, but using the number directly
4122 may be useful if @value{GDBN}'s database does not have the complete
4123 list of syscalls on your system (e.g., because @value{GDBN} lags
4124 behind the OS upgrades).
4126 The example below illustrates how this command works if you don't provide
4130 (@value{GDBP}) catch syscall
4131 Catchpoint 1 (syscall)
4133 Starting program: /tmp/catch-syscall
4135 Catchpoint 1 (call to syscall 'close'), \
4136 0xffffe424 in __kernel_vsyscall ()
4140 Catchpoint 1 (returned from syscall 'close'), \
4141 0xffffe424 in __kernel_vsyscall ()
4145 Here is an example of catching a system call by name:
4148 (@value{GDBP}) catch syscall chroot
4149 Catchpoint 1 (syscall 'chroot' [61])
4151 Starting program: /tmp/catch-syscall
4153 Catchpoint 1 (call to syscall 'chroot'), \
4154 0xffffe424 in __kernel_vsyscall ()
4158 Catchpoint 1 (returned from syscall 'chroot'), \
4159 0xffffe424 in __kernel_vsyscall ()
4163 An example of specifying a system call numerically. In the case
4164 below, the syscall number has a corresponding entry in the XML
4165 file, so @value{GDBN} finds its name and prints it:
4168 (@value{GDBP}) catch syscall 252
4169 Catchpoint 1 (syscall(s) 'exit_group')
4171 Starting program: /tmp/catch-syscall
4173 Catchpoint 1 (call to syscall 'exit_group'), \
4174 0xffffe424 in __kernel_vsyscall ()
4178 Program exited normally.
4182 However, there can be situations when there is no corresponding name
4183 in XML file for that syscall number. In this case, @value{GDBN} prints
4184 a warning message saying that it was not able to find the syscall name,
4185 but the catchpoint will be set anyway. See the example below:
4188 (@value{GDBP}) catch syscall 764
4189 warning: The number '764' does not represent a known syscall.
4190 Catchpoint 2 (syscall 764)
4194 If you configure @value{GDBN} using the @samp{--without-expat} option,
4195 it will not be able to display syscall names. Also, if your
4196 architecture does not have an XML file describing its system calls,
4197 you will not be able to see the syscall names. It is important to
4198 notice that these two features are used for accessing the syscall
4199 name database. In either case, you will see a warning like this:
4202 (@value{GDBP}) catch syscall
4203 warning: Could not open "syscalls/i386-linux.xml"
4204 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4205 GDB will not be able to display syscall names.
4206 Catchpoint 1 (syscall)
4210 Of course, the file name will change depending on your architecture and system.
4212 Still using the example above, you can also try to catch a syscall by its
4213 number. In this case, you would see something like:
4216 (@value{GDBP}) catch syscall 252
4217 Catchpoint 1 (syscall(s) 252)
4220 Again, in this case @value{GDBN} would not be able to display syscall's names.
4223 A call to @code{fork}. This is currently only available for HP-UX
4227 A call to @code{vfork}. This is currently only available for HP-UX
4230 @item load @r{[}regexp@r{]}
4231 @itemx unload @r{[}regexp@r{]}
4232 The loading or unloading of a shared library. If @var{regexp} is
4233 given, then the catchpoint will stop only if the regular expression
4234 matches one of the affected libraries.
4236 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4237 The delivery of a signal.
4239 With no arguments, this catchpoint will catch any signal that is not
4240 used internally by @value{GDBN}, specifically, all signals except
4241 @samp{SIGTRAP} and @samp{SIGINT}.
4243 With the argument @samp{all}, all signals, including those used by
4244 @value{GDBN}, will be caught. This argument cannot be used with other
4247 Otherwise, the arguments are a list of signal names as given to
4248 @code{handle} (@pxref{Signals}). Only signals specified in this list
4251 One reason that @code{catch signal} can be more useful than
4252 @code{handle} is that you can attach commands and conditions to the
4255 When a signal is caught by a catchpoint, the signal's @code{stop} and
4256 @code{print} settings, as specified by @code{handle}, are ignored.
4257 However, whether the signal is still delivered to the inferior depends
4258 on the @code{pass} setting; this can be changed in the catchpoint's
4263 @item tcatch @var{event}
4264 Set a catchpoint that is enabled only for one stop. The catchpoint is
4265 automatically deleted after the first time the event is caught.
4269 Use the @code{info break} command to list the current catchpoints.
4271 There are currently some limitations to C@t{++} exception handling
4272 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4276 If you call a function interactively, @value{GDBN} normally returns
4277 control to you when the function has finished executing. If the call
4278 raises an exception, however, the call may bypass the mechanism that
4279 returns control to you and cause your program either to abort or to
4280 simply continue running until it hits a breakpoint, catches a signal
4281 that @value{GDBN} is listening for, or exits. This is the case even if
4282 you set a catchpoint for the exception; catchpoints on exceptions are
4283 disabled within interactive calls.
4286 You cannot raise an exception interactively.
4289 You cannot install an exception handler interactively.
4292 @cindex raise exceptions
4293 Sometimes @code{catch} is not the best way to debug exception handling:
4294 if you need to know exactly where an exception is raised, it is better to
4295 stop @emph{before} the exception handler is called, since that way you
4296 can see the stack before any unwinding takes place. If you set a
4297 breakpoint in an exception handler instead, it may not be easy to find
4298 out where the exception was raised.
4300 To stop just before an exception handler is called, you need some
4301 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4302 raised by calling a library function named @code{__raise_exception}
4303 which has the following ANSI C interface:
4306 /* @var{addr} is where the exception identifier is stored.
4307 @var{id} is the exception identifier. */
4308 void __raise_exception (void **addr, void *id);
4312 To make the debugger catch all exceptions before any stack
4313 unwinding takes place, set a breakpoint on @code{__raise_exception}
4314 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4316 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4317 that depends on the value of @var{id}, you can stop your program when
4318 a specific exception is raised. You can use multiple conditional
4319 breakpoints to stop your program when any of a number of exceptions are
4324 @subsection Deleting Breakpoints
4326 @cindex clearing breakpoints, watchpoints, catchpoints
4327 @cindex deleting breakpoints, watchpoints, catchpoints
4328 It is often necessary to eliminate a breakpoint, watchpoint, or
4329 catchpoint once it has done its job and you no longer want your program
4330 to stop there. This is called @dfn{deleting} the breakpoint. A
4331 breakpoint that has been deleted no longer exists; it is forgotten.
4333 With the @code{clear} command you can delete breakpoints according to
4334 where they are in your program. With the @code{delete} command you can
4335 delete individual breakpoints, watchpoints, or catchpoints by specifying
4336 their breakpoint numbers.
4338 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4339 automatically ignores breakpoints on the first instruction to be executed
4340 when you continue execution without changing the execution address.
4345 Delete any breakpoints at the next instruction to be executed in the
4346 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4347 the innermost frame is selected, this is a good way to delete a
4348 breakpoint where your program just stopped.
4350 @item clear @var{location}
4351 Delete any breakpoints set at the specified @var{location}.
4352 @xref{Specify Location}, for the various forms of @var{location}; the
4353 most useful ones are listed below:
4356 @item clear @var{function}
4357 @itemx clear @var{filename}:@var{function}
4358 Delete any breakpoints set at entry to the named @var{function}.
4360 @item clear @var{linenum}
4361 @itemx clear @var{filename}:@var{linenum}
4362 Delete any breakpoints set at or within the code of the specified
4363 @var{linenum} of the specified @var{filename}.
4366 @cindex delete breakpoints
4368 @kindex d @r{(@code{delete})}
4369 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4370 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4371 ranges specified as arguments. If no argument is specified, delete all
4372 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4373 confirm off}). You can abbreviate this command as @code{d}.
4377 @subsection Disabling Breakpoints
4379 @cindex enable/disable a breakpoint
4380 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4381 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4382 it had been deleted, but remembers the information on the breakpoint so
4383 that you can @dfn{enable} it again later.
4385 You disable and enable breakpoints, watchpoints, and catchpoints with
4386 the @code{enable} and @code{disable} commands, optionally specifying
4387 one or more breakpoint numbers as arguments. Use @code{info break} to
4388 print a list of all breakpoints, watchpoints, and catchpoints if you
4389 do not know which numbers to use.
4391 Disabling and enabling a breakpoint that has multiple locations
4392 affects all of its locations.
4394 A breakpoint, watchpoint, or catchpoint can have any of several
4395 different states of enablement:
4399 Enabled. The breakpoint stops your program. A breakpoint set
4400 with the @code{break} command starts out in this state.
4402 Disabled. The breakpoint has no effect on your program.
4404 Enabled once. The breakpoint stops your program, but then becomes
4407 Enabled for a count. The breakpoint stops your program for the next
4408 N times, then becomes disabled.
4410 Enabled for deletion. The breakpoint stops your program, but
4411 immediately after it does so it is deleted permanently. A breakpoint
4412 set with the @code{tbreak} command starts out in this state.
4415 You can use the following commands to enable or disable breakpoints,
4416 watchpoints, and catchpoints:
4420 @kindex dis @r{(@code{disable})}
4421 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4422 Disable the specified breakpoints---or all breakpoints, if none are
4423 listed. A disabled breakpoint has no effect but is not forgotten. All
4424 options such as ignore-counts, conditions and commands are remembered in
4425 case the breakpoint is enabled again later. You may abbreviate
4426 @code{disable} as @code{dis}.
4429 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4430 Enable the specified breakpoints (or all defined breakpoints). They
4431 become effective once again in stopping your program.
4433 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4434 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4435 of these breakpoints immediately after stopping your program.
4437 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4438 Enable the specified breakpoints temporarily. @value{GDBN} records
4439 @var{count} with each of the specified breakpoints, and decrements a
4440 breakpoint's count when it is hit. When any count reaches 0,
4441 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4442 count (@pxref{Conditions, ,Break Conditions}), that will be
4443 decremented to 0 before @var{count} is affected.
4445 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4446 Enable the specified breakpoints to work once, then die. @value{GDBN}
4447 deletes any of these breakpoints as soon as your program stops there.
4448 Breakpoints set by the @code{tbreak} command start out in this state.
4451 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4452 @c confusing: tbreak is also initially enabled.
4453 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4454 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4455 subsequently, they become disabled or enabled only when you use one of
4456 the commands above. (The command @code{until} can set and delete a
4457 breakpoint of its own, but it does not change the state of your other
4458 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4462 @subsection Break Conditions
4463 @cindex conditional breakpoints
4464 @cindex breakpoint conditions
4466 @c FIXME what is scope of break condition expr? Context where wanted?
4467 @c in particular for a watchpoint?
4468 The simplest sort of breakpoint breaks every time your program reaches a
4469 specified place. You can also specify a @dfn{condition} for a
4470 breakpoint. A condition is just a Boolean expression in your
4471 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4472 a condition evaluates the expression each time your program reaches it,
4473 and your program stops only if the condition is @emph{true}.
4475 This is the converse of using assertions for program validation; in that
4476 situation, you want to stop when the assertion is violated---that is,
4477 when the condition is false. In C, if you want to test an assertion expressed
4478 by the condition @var{assert}, you should set the condition
4479 @samp{! @var{assert}} on the appropriate breakpoint.
4481 Conditions are also accepted for watchpoints; you may not need them,
4482 since a watchpoint is inspecting the value of an expression anyhow---but
4483 it might be simpler, say, to just set a watchpoint on a variable name,
4484 and specify a condition that tests whether the new value is an interesting
4487 Break conditions can have side effects, and may even call functions in
4488 your program. This can be useful, for example, to activate functions
4489 that log program progress, or to use your own print functions to
4490 format special data structures. The effects are completely predictable
4491 unless there is another enabled breakpoint at the same address. (In
4492 that case, @value{GDBN} might see the other breakpoint first and stop your
4493 program without checking the condition of this one.) Note that
4494 breakpoint commands are usually more convenient and flexible than break
4496 purpose of performing side effects when a breakpoint is reached
4497 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4499 Breakpoint conditions can also be evaluated on the target's side if
4500 the target supports it. Instead of evaluating the conditions locally,
4501 @value{GDBN} encodes the expression into an agent expression
4502 (@pxref{Agent Expressions}) suitable for execution on the target,
4503 independently of @value{GDBN}. Global variables become raw memory
4504 locations, locals become stack accesses, and so forth.
4506 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4507 when its condition evaluates to true. This mechanism may provide faster
4508 response times depending on the performance characteristics of the target
4509 since it does not need to keep @value{GDBN} informed about
4510 every breakpoint trigger, even those with false conditions.
4512 Break conditions can be specified when a breakpoint is set, by using
4513 @samp{if} in the arguments to the @code{break} command. @xref{Set
4514 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4515 with the @code{condition} command.
4517 You can also use the @code{if} keyword with the @code{watch} command.
4518 The @code{catch} command does not recognize the @code{if} keyword;
4519 @code{condition} is the only way to impose a further condition on a
4524 @item condition @var{bnum} @var{expression}
4525 Specify @var{expression} as the break condition for breakpoint,
4526 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4527 breakpoint @var{bnum} stops your program only if the value of
4528 @var{expression} is true (nonzero, in C). When you use
4529 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4530 syntactic correctness, and to determine whether symbols in it have
4531 referents in the context of your breakpoint. If @var{expression} uses
4532 symbols not referenced in the context of the breakpoint, @value{GDBN}
4533 prints an error message:
4536 No symbol "foo" in current context.
4541 not actually evaluate @var{expression} at the time the @code{condition}
4542 command (or a command that sets a breakpoint with a condition, like
4543 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4545 @item condition @var{bnum}
4546 Remove the condition from breakpoint number @var{bnum}. It becomes
4547 an ordinary unconditional breakpoint.
4550 @cindex ignore count (of breakpoint)
4551 A special case of a breakpoint condition is to stop only when the
4552 breakpoint has been reached a certain number of times. This is so
4553 useful that there is a special way to do it, using the @dfn{ignore
4554 count} of the breakpoint. Every breakpoint has an ignore count, which
4555 is an integer. Most of the time, the ignore count is zero, and
4556 therefore has no effect. But if your program reaches a breakpoint whose
4557 ignore count is positive, then instead of stopping, it just decrements
4558 the ignore count by one and continues. As a result, if the ignore count
4559 value is @var{n}, the breakpoint does not stop the next @var{n} times
4560 your program reaches it.
4564 @item ignore @var{bnum} @var{count}
4565 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4566 The next @var{count} times the breakpoint is reached, your program's
4567 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4570 To make the breakpoint stop the next time it is reached, specify
4573 When you use @code{continue} to resume execution of your program from a
4574 breakpoint, you can specify an ignore count directly as an argument to
4575 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4576 Stepping,,Continuing and Stepping}.
4578 If a breakpoint has a positive ignore count and a condition, the
4579 condition is not checked. Once the ignore count reaches zero,
4580 @value{GDBN} resumes checking the condition.
4582 You could achieve the effect of the ignore count with a condition such
4583 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4584 is decremented each time. @xref{Convenience Vars, ,Convenience
4588 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4591 @node Break Commands
4592 @subsection Breakpoint Command Lists
4594 @cindex breakpoint commands
4595 You can give any breakpoint (or watchpoint or catchpoint) a series of
4596 commands to execute when your program stops due to that breakpoint. For
4597 example, you might want to print the values of certain expressions, or
4598 enable other breakpoints.
4602 @kindex end@r{ (breakpoint commands)}
4603 @item commands @r{[}@var{range}@dots{}@r{]}
4604 @itemx @dots{} @var{command-list} @dots{}
4606 Specify a list of commands for the given breakpoints. The commands
4607 themselves appear on the following lines. Type a line containing just
4608 @code{end} to terminate the commands.
4610 To remove all commands from a breakpoint, type @code{commands} and
4611 follow it immediately with @code{end}; that is, give no commands.
4613 With no argument, @code{commands} refers to the last breakpoint,
4614 watchpoint, or catchpoint set (not to the breakpoint most recently
4615 encountered). If the most recent breakpoints were set with a single
4616 command, then the @code{commands} will apply to all the breakpoints
4617 set by that command. This applies to breakpoints set by
4618 @code{rbreak}, and also applies when a single @code{break} command
4619 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4623 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4624 disabled within a @var{command-list}.
4626 You can use breakpoint commands to start your program up again. Simply
4627 use the @code{continue} command, or @code{step}, or any other command
4628 that resumes execution.
4630 Any other commands in the command list, after a command that resumes
4631 execution, are ignored. This is because any time you resume execution
4632 (even with a simple @code{next} or @code{step}), you may encounter
4633 another breakpoint---which could have its own command list, leading to
4634 ambiguities about which list to execute.
4637 If the first command you specify in a command list is @code{silent}, the
4638 usual message about stopping at a breakpoint is not printed. This may
4639 be desirable for breakpoints that are to print a specific message and
4640 then continue. If none of the remaining commands print anything, you
4641 see no sign that the breakpoint was reached. @code{silent} is
4642 meaningful only at the beginning of a breakpoint command list.
4644 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4645 print precisely controlled output, and are often useful in silent
4646 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4648 For example, here is how you could use breakpoint commands to print the
4649 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4655 printf "x is %d\n",x
4660 One application for breakpoint commands is to compensate for one bug so
4661 you can test for another. Put a breakpoint just after the erroneous line
4662 of code, give it a condition to detect the case in which something
4663 erroneous has been done, and give it commands to assign correct values
4664 to any variables that need them. End with the @code{continue} command
4665 so that your program does not stop, and start with the @code{silent}
4666 command so that no output is produced. Here is an example:
4677 @node Dynamic Printf
4678 @subsection Dynamic Printf
4680 @cindex dynamic printf
4682 The dynamic printf command @code{dprintf} combines a breakpoint with
4683 formatted printing of your program's data to give you the effect of
4684 inserting @code{printf} calls into your program on-the-fly, without
4685 having to recompile it.
4687 In its most basic form, the output goes to the GDB console. However,
4688 you can set the variable @code{dprintf-style} for alternate handling.
4689 For instance, you can ask to format the output by calling your
4690 program's @code{printf} function. This has the advantage that the
4691 characters go to the program's output device, so they can recorded in
4692 redirects to files and so forth.
4694 If you are doing remote debugging with a stub or agent, you can also
4695 ask to have the printf handled by the remote agent. In addition to
4696 ensuring that the output goes to the remote program's device along
4697 with any other output the program might produce, you can also ask that
4698 the dprintf remain active even after disconnecting from the remote
4699 target. Using the stub/agent is also more efficient, as it can do
4700 everything without needing to communicate with @value{GDBN}.
4704 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4705 Whenever execution reaches @var{location}, print the values of one or
4706 more @var{expressions} under the control of the string @var{template}.
4707 To print several values, separate them with commas.
4709 @item set dprintf-style @var{style}
4710 Set the dprintf output to be handled in one of several different
4711 styles enumerated below. A change of style affects all existing
4712 dynamic printfs immediately. (If you need individual control over the
4713 print commands, simply define normal breakpoints with
4714 explicitly-supplied command lists.)
4717 @kindex dprintf-style gdb
4718 Handle the output using the @value{GDBN} @code{printf} command.
4721 @kindex dprintf-style call
4722 Handle the output by calling a function in your program (normally
4726 @kindex dprintf-style agent
4727 Have the remote debugging agent (such as @code{gdbserver}) handle
4728 the output itself. This style is only available for agents that
4729 support running commands on the target.
4731 @item set dprintf-function @var{function}
4732 Set the function to call if the dprintf style is @code{call}. By
4733 default its value is @code{printf}. You may set it to any expression.
4734 that @value{GDBN} can evaluate to a function, as per the @code{call}
4737 @item set dprintf-channel @var{channel}
4738 Set a ``channel'' for dprintf. If set to a non-empty value,
4739 @value{GDBN} will evaluate it as an expression and pass the result as
4740 a first argument to the @code{dprintf-function}, in the manner of
4741 @code{fprintf} and similar functions. Otherwise, the dprintf format
4742 string will be the first argument, in the manner of @code{printf}.
4744 As an example, if you wanted @code{dprintf} output to go to a logfile
4745 that is a standard I/O stream assigned to the variable @code{mylog},
4746 you could do the following:
4749 (gdb) set dprintf-style call
4750 (gdb) set dprintf-function fprintf
4751 (gdb) set dprintf-channel mylog
4752 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4753 Dprintf 1 at 0x123456: file main.c, line 25.
4755 1 dprintf keep y 0x00123456 in main at main.c:25
4756 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4761 Note that the @code{info break} displays the dynamic printf commands
4762 as normal breakpoint commands; you can thus easily see the effect of
4763 the variable settings.
4765 @item set disconnected-dprintf on
4766 @itemx set disconnected-dprintf off
4767 @kindex set disconnected-dprintf
4768 Choose whether @code{dprintf} commands should continue to run if
4769 @value{GDBN} has disconnected from the target. This only applies
4770 if the @code{dprintf-style} is @code{agent}.
4772 @item show disconnected-dprintf off
4773 @kindex show disconnected-dprintf
4774 Show the current choice for disconnected @code{dprintf}.
4778 @value{GDBN} does not check the validity of function and channel,
4779 relying on you to supply values that are meaningful for the contexts
4780 in which they are being used. For instance, the function and channel
4781 may be the values of local variables, but if that is the case, then
4782 all enabled dynamic prints must be at locations within the scope of
4783 those locals. If evaluation fails, @value{GDBN} will report an error.
4785 @node Save Breakpoints
4786 @subsection How to save breakpoints to a file
4788 To save breakpoint definitions to a file use the @w{@code{save
4789 breakpoints}} command.
4792 @kindex save breakpoints
4793 @cindex save breakpoints to a file for future sessions
4794 @item save breakpoints [@var{filename}]
4795 This command saves all current breakpoint definitions together with
4796 their commands and ignore counts, into a file @file{@var{filename}}
4797 suitable for use in a later debugging session. This includes all
4798 types of breakpoints (breakpoints, watchpoints, catchpoints,
4799 tracepoints). To read the saved breakpoint definitions, use the
4800 @code{source} command (@pxref{Command Files}). Note that watchpoints
4801 with expressions involving local variables may fail to be recreated
4802 because it may not be possible to access the context where the
4803 watchpoint is valid anymore. Because the saved breakpoint definitions
4804 are simply a sequence of @value{GDBN} commands that recreate the
4805 breakpoints, you can edit the file in your favorite editing program,
4806 and remove the breakpoint definitions you're not interested in, or
4807 that can no longer be recreated.
4810 @node Static Probe Points
4811 @subsection Static Probe Points
4813 @cindex static probe point, SystemTap
4814 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4815 for Statically Defined Tracing, and the probes are designed to have a tiny
4816 runtime code and data footprint, and no dynamic relocations. They are
4817 usable from assembly, C and C@t{++} languages. See
4818 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4819 for a good reference on how the @acronym{SDT} probes are implemented.
4821 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4822 @acronym{SDT} probes are supported on ELF-compatible systems. See
4823 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4824 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4825 in your applications.
4827 @cindex semaphores on static probe points
4828 Some probes have an associated semaphore variable; for instance, this
4829 happens automatically if you defined your probe using a DTrace-style
4830 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4831 automatically enable it when you specify a breakpoint using the
4832 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4833 location by some other method (e.g., @code{break file:line}), then
4834 @value{GDBN} will not automatically set the semaphore.
4836 You can examine the available static static probes using @code{info
4837 probes}, with optional arguments:
4841 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4842 If given, @var{provider} is a regular expression used to match against provider
4843 names when selecting which probes to list. If omitted, probes by all
4844 probes from all providers are listed.
4846 If given, @var{name} is a regular expression to match against probe names
4847 when selecting which probes to list. If omitted, probe names are not
4848 considered when deciding whether to display them.
4850 If given, @var{objfile} is a regular expression used to select which
4851 object files (executable or shared libraries) to examine. If not
4852 given, all object files are considered.
4854 @item info probes all
4855 List the available static probes, from all types.
4858 @vindex $_probe_arg@r{, convenience variable}
4859 A probe may specify up to twelve arguments. These are available at the
4860 point at which the probe is defined---that is, when the current PC is
4861 at the probe's location. The arguments are available using the
4862 convenience variables (@pxref{Convenience Vars})
4863 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4864 an integer of the appropriate size; types are not preserved. The
4865 convenience variable @code{$_probe_argc} holds the number of arguments
4866 at the current probe point.
4868 These variables are always available, but attempts to access them at
4869 any location other than a probe point will cause @value{GDBN} to give
4873 @c @ifclear BARETARGET
4874 @node Error in Breakpoints
4875 @subsection ``Cannot insert breakpoints''
4877 If you request too many active hardware-assisted breakpoints and
4878 watchpoints, you will see this error message:
4880 @c FIXME: the precise wording of this message may change; the relevant
4881 @c source change is not committed yet (Sep 3, 1999).
4883 Stopped; cannot insert breakpoints.
4884 You may have requested too many hardware breakpoints and watchpoints.
4888 This message is printed when you attempt to resume the program, since
4889 only then @value{GDBN} knows exactly how many hardware breakpoints and
4890 watchpoints it needs to insert.
4892 When this message is printed, you need to disable or remove some of the
4893 hardware-assisted breakpoints and watchpoints, and then continue.
4895 @node Breakpoint-related Warnings
4896 @subsection ``Breakpoint address adjusted...''
4897 @cindex breakpoint address adjusted
4899 Some processor architectures place constraints on the addresses at
4900 which breakpoints may be placed. For architectures thus constrained,
4901 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4902 with the constraints dictated by the architecture.
4904 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4905 a VLIW architecture in which a number of RISC-like instructions may be
4906 bundled together for parallel execution. The FR-V architecture
4907 constrains the location of a breakpoint instruction within such a
4908 bundle to the instruction with the lowest address. @value{GDBN}
4909 honors this constraint by adjusting a breakpoint's address to the
4910 first in the bundle.
4912 It is not uncommon for optimized code to have bundles which contain
4913 instructions from different source statements, thus it may happen that
4914 a breakpoint's address will be adjusted from one source statement to
4915 another. Since this adjustment may significantly alter @value{GDBN}'s
4916 breakpoint related behavior from what the user expects, a warning is
4917 printed when the breakpoint is first set and also when the breakpoint
4920 A warning like the one below is printed when setting a breakpoint
4921 that's been subject to address adjustment:
4924 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4927 Such warnings are printed both for user settable and @value{GDBN}'s
4928 internal breakpoints. If you see one of these warnings, you should
4929 verify that a breakpoint set at the adjusted address will have the
4930 desired affect. If not, the breakpoint in question may be removed and
4931 other breakpoints may be set which will have the desired behavior.
4932 E.g., it may be sufficient to place the breakpoint at a later
4933 instruction. A conditional breakpoint may also be useful in some
4934 cases to prevent the breakpoint from triggering too often.
4936 @value{GDBN} will also issue a warning when stopping at one of these
4937 adjusted breakpoints:
4940 warning: Breakpoint 1 address previously adjusted from 0x00010414
4944 When this warning is encountered, it may be too late to take remedial
4945 action except in cases where the breakpoint is hit earlier or more
4946 frequently than expected.
4948 @node Continuing and Stepping
4949 @section Continuing and Stepping
4953 @cindex resuming execution
4954 @dfn{Continuing} means resuming program execution until your program
4955 completes normally. In contrast, @dfn{stepping} means executing just
4956 one more ``step'' of your program, where ``step'' may mean either one
4957 line of source code, or one machine instruction (depending on what
4958 particular command you use). Either when continuing or when stepping,
4959 your program may stop even sooner, due to a breakpoint or a signal. (If
4960 it stops due to a signal, you may want to use @code{handle}, or use
4961 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4965 @kindex c @r{(@code{continue})}
4966 @kindex fg @r{(resume foreground execution)}
4967 @item continue @r{[}@var{ignore-count}@r{]}
4968 @itemx c @r{[}@var{ignore-count}@r{]}
4969 @itemx fg @r{[}@var{ignore-count}@r{]}
4970 Resume program execution, at the address where your program last stopped;
4971 any breakpoints set at that address are bypassed. The optional argument
4972 @var{ignore-count} allows you to specify a further number of times to
4973 ignore a breakpoint at this location; its effect is like that of
4974 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4976 The argument @var{ignore-count} is meaningful only when your program
4977 stopped due to a breakpoint. At other times, the argument to
4978 @code{continue} is ignored.
4980 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4981 debugged program is deemed to be the foreground program) are provided
4982 purely for convenience, and have exactly the same behavior as
4986 To resume execution at a different place, you can use @code{return}
4987 (@pxref{Returning, ,Returning from a Function}) to go back to the
4988 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4989 Different Address}) to go to an arbitrary location in your program.
4991 A typical technique for using stepping is to set a breakpoint
4992 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4993 beginning of the function or the section of your program where a problem
4994 is believed to lie, run your program until it stops at that breakpoint,
4995 and then step through the suspect area, examining the variables that are
4996 interesting, until you see the problem happen.
5000 @kindex s @r{(@code{step})}
5002 Continue running your program until control reaches a different source
5003 line, then stop it and return control to @value{GDBN}. This command is
5004 abbreviated @code{s}.
5007 @c "without debugging information" is imprecise; actually "without line
5008 @c numbers in the debugging information". (gcc -g1 has debugging info but
5009 @c not line numbers). But it seems complex to try to make that
5010 @c distinction here.
5011 @emph{Warning:} If you use the @code{step} command while control is
5012 within a function that was compiled without debugging information,
5013 execution proceeds until control reaches a function that does have
5014 debugging information. Likewise, it will not step into a function which
5015 is compiled without debugging information. To step through functions
5016 without debugging information, use the @code{stepi} command, described
5020 The @code{step} command only stops at the first instruction of a source
5021 line. This prevents the multiple stops that could otherwise occur in
5022 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5023 to stop if a function that has debugging information is called within
5024 the line. In other words, @code{step} @emph{steps inside} any functions
5025 called within the line.
5027 Also, the @code{step} command only enters a function if there is line
5028 number information for the function. Otherwise it acts like the
5029 @code{next} command. This avoids problems when using @code{cc -gl}
5030 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5031 was any debugging information about the routine.
5033 @item step @var{count}
5034 Continue running as in @code{step}, but do so @var{count} times. If a
5035 breakpoint is reached, or a signal not related to stepping occurs before
5036 @var{count} steps, stepping stops right away.
5039 @kindex n @r{(@code{next})}
5040 @item next @r{[}@var{count}@r{]}
5041 Continue to the next source line in the current (innermost) stack frame.
5042 This is similar to @code{step}, but function calls that appear within
5043 the line of code are executed without stopping. Execution stops when
5044 control reaches a different line of code at the original stack level
5045 that was executing when you gave the @code{next} command. This command
5046 is abbreviated @code{n}.
5048 An argument @var{count} is a repeat count, as for @code{step}.
5051 @c FIX ME!! Do we delete this, or is there a way it fits in with
5052 @c the following paragraph? --- Vctoria
5054 @c @code{next} within a function that lacks debugging information acts like
5055 @c @code{step}, but any function calls appearing within the code of the
5056 @c function are executed without stopping.
5058 The @code{next} command only stops at the first instruction of a
5059 source line. This prevents multiple stops that could otherwise occur in
5060 @code{switch} statements, @code{for} loops, etc.
5062 @kindex set step-mode
5064 @cindex functions without line info, and stepping
5065 @cindex stepping into functions with no line info
5066 @itemx set step-mode on
5067 The @code{set step-mode on} command causes the @code{step} command to
5068 stop at the first instruction of a function which contains no debug line
5069 information rather than stepping over it.
5071 This is useful in cases where you may be interested in inspecting the
5072 machine instructions of a function which has no symbolic info and do not
5073 want @value{GDBN} to automatically skip over this function.
5075 @item set step-mode off
5076 Causes the @code{step} command to step over any functions which contains no
5077 debug information. This is the default.
5079 @item show step-mode
5080 Show whether @value{GDBN} will stop in or step over functions without
5081 source line debug information.
5084 @kindex fin @r{(@code{finish})}
5086 Continue running until just after function in the selected stack frame
5087 returns. Print the returned value (if any). This command can be
5088 abbreviated as @code{fin}.
5090 Contrast this with the @code{return} command (@pxref{Returning,
5091 ,Returning from a Function}).
5094 @kindex u @r{(@code{until})}
5095 @cindex run until specified location
5098 Continue running until a source line past the current line, in the
5099 current stack frame, is reached. This command is used to avoid single
5100 stepping through a loop more than once. It is like the @code{next}
5101 command, except that when @code{until} encounters a jump, it
5102 automatically continues execution until the program counter is greater
5103 than the address of the jump.
5105 This means that when you reach the end of a loop after single stepping
5106 though it, @code{until} makes your program continue execution until it
5107 exits the loop. In contrast, a @code{next} command at the end of a loop
5108 simply steps back to the beginning of the loop, which forces you to step
5109 through the next iteration.
5111 @code{until} always stops your program if it attempts to exit the current
5114 @code{until} may produce somewhat counterintuitive results if the order
5115 of machine code does not match the order of the source lines. For
5116 example, in the following excerpt from a debugging session, the @code{f}
5117 (@code{frame}) command shows that execution is stopped at line
5118 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5122 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5124 (@value{GDBP}) until
5125 195 for ( ; argc > 0; NEXTARG) @{
5128 This happened because, for execution efficiency, the compiler had
5129 generated code for the loop closure test at the end, rather than the
5130 start, of the loop---even though the test in a C @code{for}-loop is
5131 written before the body of the loop. The @code{until} command appeared
5132 to step back to the beginning of the loop when it advanced to this
5133 expression; however, it has not really gone to an earlier
5134 statement---not in terms of the actual machine code.
5136 @code{until} with no argument works by means of single
5137 instruction stepping, and hence is slower than @code{until} with an
5140 @item until @var{location}
5141 @itemx u @var{location}
5142 Continue running your program until either the specified location is
5143 reached, or the current stack frame returns. @var{location} is any of
5144 the forms described in @ref{Specify Location}.
5145 This form of the command uses temporary breakpoints, and
5146 hence is quicker than @code{until} without an argument. The specified
5147 location is actually reached only if it is in the current frame. This
5148 implies that @code{until} can be used to skip over recursive function
5149 invocations. For instance in the code below, if the current location is
5150 line @code{96}, issuing @code{until 99} will execute the program up to
5151 line @code{99} in the same invocation of factorial, i.e., after the inner
5152 invocations have returned.
5155 94 int factorial (int value)
5157 96 if (value > 1) @{
5158 97 value *= factorial (value - 1);
5165 @kindex advance @var{location}
5166 @item advance @var{location}
5167 Continue running the program up to the given @var{location}. An argument is
5168 required, which should be of one of the forms described in
5169 @ref{Specify Location}.
5170 Execution will also stop upon exit from the current stack
5171 frame. This command is similar to @code{until}, but @code{advance} will
5172 not skip over recursive function calls, and the target location doesn't
5173 have to be in the same frame as the current one.
5177 @kindex si @r{(@code{stepi})}
5179 @itemx stepi @var{arg}
5181 Execute one machine instruction, then stop and return to the debugger.
5183 It is often useful to do @samp{display/i $pc} when stepping by machine
5184 instructions. This makes @value{GDBN} automatically display the next
5185 instruction to be executed, each time your program stops. @xref{Auto
5186 Display,, Automatic Display}.
5188 An argument is a repeat count, as in @code{step}.
5192 @kindex ni @r{(@code{nexti})}
5194 @itemx nexti @var{arg}
5196 Execute one machine instruction, but if it is a function call,
5197 proceed until the function returns.
5199 An argument is a repeat count, as in @code{next}.
5202 @node Skipping Over Functions and Files
5203 @section Skipping Over Functions and Files
5204 @cindex skipping over functions and files
5206 The program you are debugging may contain some functions which are
5207 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5208 skip a function or all functions in a file when stepping.
5210 For example, consider the following C function:
5221 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5222 are not interested in stepping through @code{boring}. If you run @code{step}
5223 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5224 step over both @code{foo} and @code{boring}!
5226 One solution is to @code{step} into @code{boring} and use the @code{finish}
5227 command to immediately exit it. But this can become tedious if @code{boring}
5228 is called from many places.
5230 A more flexible solution is to execute @kbd{skip boring}. This instructs
5231 @value{GDBN} never to step into @code{boring}. Now when you execute
5232 @code{step} at line 103, you'll step over @code{boring} and directly into
5235 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5236 example, @code{skip file boring.c}.
5239 @kindex skip function
5240 @item skip @r{[}@var{linespec}@r{]}
5241 @itemx skip function @r{[}@var{linespec}@r{]}
5242 After running this command, the function named by @var{linespec} or the
5243 function containing the line named by @var{linespec} will be skipped over when
5244 stepping. @xref{Specify Location}.
5246 If you do not specify @var{linespec}, the function you're currently debugging
5249 (If you have a function called @code{file} that you want to skip, use
5250 @kbd{skip function file}.)
5253 @item skip file @r{[}@var{filename}@r{]}
5254 After running this command, any function whose source lives in @var{filename}
5255 will be skipped over when stepping.
5257 If you do not specify @var{filename}, functions whose source lives in the file
5258 you're currently debugging will be skipped.
5261 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5262 These are the commands for managing your list of skips:
5266 @item info skip @r{[}@var{range}@r{]}
5267 Print details about the specified skip(s). If @var{range} is not specified,
5268 print a table with details about all functions and files marked for skipping.
5269 @code{info skip} prints the following information about each skip:
5273 A number identifying this skip.
5275 The type of this skip, either @samp{function} or @samp{file}.
5276 @item Enabled or Disabled
5277 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5279 For function skips, this column indicates the address in memory of the function
5280 being skipped. If you've set a function skip on a function which has not yet
5281 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5282 which has the function is loaded, @code{info skip} will show the function's
5285 For file skips, this field contains the filename being skipped. For functions
5286 skips, this field contains the function name and its line number in the file
5287 where it is defined.
5291 @item skip delete @r{[}@var{range}@r{]}
5292 Delete the specified skip(s). If @var{range} is not specified, delete all
5296 @item skip enable @r{[}@var{range}@r{]}
5297 Enable the specified skip(s). If @var{range} is not specified, enable all
5300 @kindex skip disable
5301 @item skip disable @r{[}@var{range}@r{]}
5302 Disable the specified skip(s). If @var{range} is not specified, disable all
5311 A signal is an asynchronous event that can happen in a program. The
5312 operating system defines the possible kinds of signals, and gives each
5313 kind a name and a number. For example, in Unix @code{SIGINT} is the
5314 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5315 @code{SIGSEGV} is the signal a program gets from referencing a place in
5316 memory far away from all the areas in use; @code{SIGALRM} occurs when
5317 the alarm clock timer goes off (which happens only if your program has
5318 requested an alarm).
5320 @cindex fatal signals
5321 Some signals, including @code{SIGALRM}, are a normal part of the
5322 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5323 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5324 program has not specified in advance some other way to handle the signal.
5325 @code{SIGINT} does not indicate an error in your program, but it is normally
5326 fatal so it can carry out the purpose of the interrupt: to kill the program.
5328 @value{GDBN} has the ability to detect any occurrence of a signal in your
5329 program. You can tell @value{GDBN} in advance what to do for each kind of
5332 @cindex handling signals
5333 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5334 @code{SIGALRM} be silently passed to your program
5335 (so as not to interfere with their role in the program's functioning)
5336 but to stop your program immediately whenever an error signal happens.
5337 You can change these settings with the @code{handle} command.
5340 @kindex info signals
5344 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5345 handle each one. You can use this to see the signal numbers of all
5346 the defined types of signals.
5348 @item info signals @var{sig}
5349 Similar, but print information only about the specified signal number.
5351 @code{info handle} is an alias for @code{info signals}.
5353 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5354 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5355 for details about this command.
5358 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5359 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5360 can be the number of a signal or its name (with or without the
5361 @samp{SIG} at the beginning); a list of signal numbers of the form
5362 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5363 known signals. Optional arguments @var{keywords}, described below,
5364 say what change to make.
5368 The keywords allowed by the @code{handle} command can be abbreviated.
5369 Their full names are:
5373 @value{GDBN} should not stop your program when this signal happens. It may
5374 still print a message telling you that the signal has come in.
5377 @value{GDBN} should stop your program when this signal happens. This implies
5378 the @code{print} keyword as well.
5381 @value{GDBN} should print a message when this signal happens.
5384 @value{GDBN} should not mention the occurrence of the signal at all. This
5385 implies the @code{nostop} keyword as well.
5389 @value{GDBN} should allow your program to see this signal; your program
5390 can handle the signal, or else it may terminate if the signal is fatal
5391 and not handled. @code{pass} and @code{noignore} are synonyms.
5395 @value{GDBN} should not allow your program to see this signal.
5396 @code{nopass} and @code{ignore} are synonyms.
5400 When a signal stops your program, the signal is not visible to the
5402 continue. Your program sees the signal then, if @code{pass} is in
5403 effect for the signal in question @emph{at that time}. In other words,
5404 after @value{GDBN} reports a signal, you can use the @code{handle}
5405 command with @code{pass} or @code{nopass} to control whether your
5406 program sees that signal when you continue.
5408 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5409 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5410 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5413 You can also use the @code{signal} command to prevent your program from
5414 seeing a signal, or cause it to see a signal it normally would not see,
5415 or to give it any signal at any time. For example, if your program stopped
5416 due to some sort of memory reference error, you might store correct
5417 values into the erroneous variables and continue, hoping to see more
5418 execution; but your program would probably terminate immediately as
5419 a result of the fatal signal once it saw the signal. To prevent this,
5420 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5423 @cindex extra signal information
5424 @anchor{extra signal information}
5426 On some targets, @value{GDBN} can inspect extra signal information
5427 associated with the intercepted signal, before it is actually
5428 delivered to the program being debugged. This information is exported
5429 by the convenience variable @code{$_siginfo}, and consists of data
5430 that is passed by the kernel to the signal handler at the time of the
5431 receipt of a signal. The data type of the information itself is
5432 target dependent. You can see the data type using the @code{ptype
5433 $_siginfo} command. On Unix systems, it typically corresponds to the
5434 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5437 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5438 referenced address that raised a segmentation fault.
5442 (@value{GDBP}) continue
5443 Program received signal SIGSEGV, Segmentation fault.
5444 0x0000000000400766 in main ()
5446 (@value{GDBP}) ptype $_siginfo
5453 struct @{...@} _kill;
5454 struct @{...@} _timer;
5456 struct @{...@} _sigchld;
5457 struct @{...@} _sigfault;
5458 struct @{...@} _sigpoll;
5461 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5465 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5466 $1 = (void *) 0x7ffff7ff7000
5470 Depending on target support, @code{$_siginfo} may also be writable.
5473 @section Stopping and Starting Multi-thread Programs
5475 @cindex stopped threads
5476 @cindex threads, stopped
5478 @cindex continuing threads
5479 @cindex threads, continuing
5481 @value{GDBN} supports debugging programs with multiple threads
5482 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5483 are two modes of controlling execution of your program within the
5484 debugger. In the default mode, referred to as @dfn{all-stop mode},
5485 when any thread in your program stops (for example, at a breakpoint
5486 or while being stepped), all other threads in the program are also stopped by
5487 @value{GDBN}. On some targets, @value{GDBN} also supports
5488 @dfn{non-stop mode}, in which other threads can continue to run freely while
5489 you examine the stopped thread in the debugger.
5492 * All-Stop Mode:: All threads stop when GDB takes control
5493 * Non-Stop Mode:: Other threads continue to execute
5494 * Background Execution:: Running your program asynchronously
5495 * Thread-Specific Breakpoints:: Controlling breakpoints
5496 * Interrupted System Calls:: GDB may interfere with system calls
5497 * Observer Mode:: GDB does not alter program behavior
5501 @subsection All-Stop Mode
5503 @cindex all-stop mode
5505 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5506 @emph{all} threads of execution stop, not just the current thread. This
5507 allows you to examine the overall state of the program, including
5508 switching between threads, without worrying that things may change
5511 Conversely, whenever you restart the program, @emph{all} threads start
5512 executing. @emph{This is true even when single-stepping} with commands
5513 like @code{step} or @code{next}.
5515 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5516 Since thread scheduling is up to your debugging target's operating
5517 system (not controlled by @value{GDBN}), other threads may
5518 execute more than one statement while the current thread completes a
5519 single step. Moreover, in general other threads stop in the middle of a
5520 statement, rather than at a clean statement boundary, when the program
5523 You might even find your program stopped in another thread after
5524 continuing or even single-stepping. This happens whenever some other
5525 thread runs into a breakpoint, a signal, or an exception before the
5526 first thread completes whatever you requested.
5528 @cindex automatic thread selection
5529 @cindex switching threads automatically
5530 @cindex threads, automatic switching
5531 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5532 signal, it automatically selects the thread where that breakpoint or
5533 signal happened. @value{GDBN} alerts you to the context switch with a
5534 message such as @samp{[Switching to Thread @var{n}]} to identify the
5537 On some OSes, you can modify @value{GDBN}'s default behavior by
5538 locking the OS scheduler to allow only a single thread to run.
5541 @item set scheduler-locking @var{mode}
5542 @cindex scheduler locking mode
5543 @cindex lock scheduler
5544 Set the scheduler locking mode. If it is @code{off}, then there is no
5545 locking and any thread may run at any time. If @code{on}, then only the
5546 current thread may run when the inferior is resumed. The @code{step}
5547 mode optimizes for single-stepping; it prevents other threads
5548 from preempting the current thread while you are stepping, so that
5549 the focus of debugging does not change unexpectedly.
5550 Other threads only rarely (or never) get a chance to run
5551 when you step. They are more likely to run when you @samp{next} over a
5552 function call, and they are completely free to run when you use commands
5553 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5554 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5555 the current thread away from the thread that you are debugging.
5557 @item show scheduler-locking
5558 Display the current scheduler locking mode.
5561 @cindex resume threads of multiple processes simultaneously
5562 By default, when you issue one of the execution commands such as
5563 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5564 threads of the current inferior to run. For example, if @value{GDBN}
5565 is attached to two inferiors, each with two threads, the
5566 @code{continue} command resumes only the two threads of the current
5567 inferior. This is useful, for example, when you debug a program that
5568 forks and you want to hold the parent stopped (so that, for instance,
5569 it doesn't run to exit), while you debug the child. In other
5570 situations, you may not be interested in inspecting the current state
5571 of any of the processes @value{GDBN} is attached to, and you may want
5572 to resume them all until some breakpoint is hit. In the latter case,
5573 you can instruct @value{GDBN} to allow all threads of all the
5574 inferiors to run with the @w{@code{set schedule-multiple}} command.
5577 @kindex set schedule-multiple
5578 @item set schedule-multiple
5579 Set the mode for allowing threads of multiple processes to be resumed
5580 when an execution command is issued. When @code{on}, all threads of
5581 all processes are allowed to run. When @code{off}, only the threads
5582 of the current process are resumed. The default is @code{off}. The
5583 @code{scheduler-locking} mode takes precedence when set to @code{on},
5584 or while you are stepping and set to @code{step}.
5586 @item show schedule-multiple
5587 Display the current mode for resuming the execution of threads of
5592 @subsection Non-Stop Mode
5594 @cindex non-stop mode
5596 @c This section is really only a place-holder, and needs to be expanded
5597 @c with more details.
5599 For some multi-threaded targets, @value{GDBN} supports an optional
5600 mode of operation in which you can examine stopped program threads in
5601 the debugger while other threads continue to execute freely. This
5602 minimizes intrusion when debugging live systems, such as programs
5603 where some threads have real-time constraints or must continue to
5604 respond to external events. This is referred to as @dfn{non-stop} mode.
5606 In non-stop mode, when a thread stops to report a debugging event,
5607 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5608 threads as well, in contrast to the all-stop mode behavior. Additionally,
5609 execution commands such as @code{continue} and @code{step} apply by default
5610 only to the current thread in non-stop mode, rather than all threads as
5611 in all-stop mode. This allows you to control threads explicitly in
5612 ways that are not possible in all-stop mode --- for example, stepping
5613 one thread while allowing others to run freely, stepping
5614 one thread while holding all others stopped, or stepping several threads
5615 independently and simultaneously.
5617 To enter non-stop mode, use this sequence of commands before you run
5618 or attach to your program:
5621 # Enable the async interface.
5624 # If using the CLI, pagination breaks non-stop.
5627 # Finally, turn it on!
5631 You can use these commands to manipulate the non-stop mode setting:
5634 @kindex set non-stop
5635 @item set non-stop on
5636 Enable selection of non-stop mode.
5637 @item set non-stop off
5638 Disable selection of non-stop mode.
5639 @kindex show non-stop
5641 Show the current non-stop enablement setting.
5644 Note these commands only reflect whether non-stop mode is enabled,
5645 not whether the currently-executing program is being run in non-stop mode.
5646 In particular, the @code{set non-stop} preference is only consulted when
5647 @value{GDBN} starts or connects to the target program, and it is generally
5648 not possible to switch modes once debugging has started. Furthermore,
5649 since not all targets support non-stop mode, even when you have enabled
5650 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5653 In non-stop mode, all execution commands apply only to the current thread
5654 by default. That is, @code{continue} only continues one thread.
5655 To continue all threads, issue @code{continue -a} or @code{c -a}.
5657 You can use @value{GDBN}'s background execution commands
5658 (@pxref{Background Execution}) to run some threads in the background
5659 while you continue to examine or step others from @value{GDBN}.
5660 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5661 always executed asynchronously in non-stop mode.
5663 Suspending execution is done with the @code{interrupt} command when
5664 running in the background, or @kbd{Ctrl-c} during foreground execution.
5665 In all-stop mode, this stops the whole process;
5666 but in non-stop mode the interrupt applies only to the current thread.
5667 To stop the whole program, use @code{interrupt -a}.
5669 Other execution commands do not currently support the @code{-a} option.
5671 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5672 that thread current, as it does in all-stop mode. This is because the
5673 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5674 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5675 changed to a different thread just as you entered a command to operate on the
5676 previously current thread.
5678 @node Background Execution
5679 @subsection Background Execution
5681 @cindex foreground execution
5682 @cindex background execution
5683 @cindex asynchronous execution
5684 @cindex execution, foreground, background and asynchronous
5686 @value{GDBN}'s execution commands have two variants: the normal
5687 foreground (synchronous) behavior, and a background
5688 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5689 the program to report that some thread has stopped before prompting for
5690 another command. In background execution, @value{GDBN} immediately gives
5691 a command prompt so that you can issue other commands while your program runs.
5693 You need to explicitly enable asynchronous mode before you can use
5694 background execution commands. You can use these commands to
5695 manipulate the asynchronous mode setting:
5698 @kindex set target-async
5699 @item set target-async on
5700 Enable asynchronous mode.
5701 @item set target-async off
5702 Disable asynchronous mode.
5703 @kindex show target-async
5704 @item show target-async
5705 Show the current target-async setting.
5708 If the target doesn't support async mode, @value{GDBN} issues an error
5709 message if you attempt to use the background execution commands.
5711 To specify background execution, add a @code{&} to the command. For example,
5712 the background form of the @code{continue} command is @code{continue&}, or
5713 just @code{c&}. The execution commands that accept background execution
5719 @xref{Starting, , Starting your Program}.
5723 @xref{Attach, , Debugging an Already-running Process}.
5727 @xref{Continuing and Stepping, step}.
5731 @xref{Continuing and Stepping, stepi}.
5735 @xref{Continuing and Stepping, next}.
5739 @xref{Continuing and Stepping, nexti}.
5743 @xref{Continuing and Stepping, continue}.
5747 @xref{Continuing and Stepping, finish}.
5751 @xref{Continuing and Stepping, until}.
5755 Background execution is especially useful in conjunction with non-stop
5756 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5757 However, you can also use these commands in the normal all-stop mode with
5758 the restriction that you cannot issue another execution command until the
5759 previous one finishes. Examples of commands that are valid in all-stop
5760 mode while the program is running include @code{help} and @code{info break}.
5762 You can interrupt your program while it is running in the background by
5763 using the @code{interrupt} command.
5770 Suspend execution of the running program. In all-stop mode,
5771 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5772 only the current thread. To stop the whole program in non-stop mode,
5773 use @code{interrupt -a}.
5776 @node Thread-Specific Breakpoints
5777 @subsection Thread-Specific Breakpoints
5779 When your program has multiple threads (@pxref{Threads,, Debugging
5780 Programs with Multiple Threads}), you can choose whether to set
5781 breakpoints on all threads, or on a particular thread.
5784 @cindex breakpoints and threads
5785 @cindex thread breakpoints
5786 @kindex break @dots{} thread @var{threadno}
5787 @item break @var{linespec} thread @var{threadno}
5788 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5789 @var{linespec} specifies source lines; there are several ways of
5790 writing them (@pxref{Specify Location}), but the effect is always to
5791 specify some source line.
5793 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5794 to specify that you only want @value{GDBN} to stop the program when a
5795 particular thread reaches this breakpoint. @var{threadno} is one of the
5796 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5797 column of the @samp{info threads} display.
5799 If you do not specify @samp{thread @var{threadno}} when you set a
5800 breakpoint, the breakpoint applies to @emph{all} threads of your
5803 You can use the @code{thread} qualifier on conditional breakpoints as
5804 well; in this case, place @samp{thread @var{threadno}} before or
5805 after the breakpoint condition, like this:
5808 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5813 @node Interrupted System Calls
5814 @subsection Interrupted System Calls
5816 @cindex thread breakpoints and system calls
5817 @cindex system calls and thread breakpoints
5818 @cindex premature return from system calls
5819 There is an unfortunate side effect when using @value{GDBN} to debug
5820 multi-threaded programs. If one thread stops for a
5821 breakpoint, or for some other reason, and another thread is blocked in a
5822 system call, then the system call may return prematurely. This is a
5823 consequence of the interaction between multiple threads and the signals
5824 that @value{GDBN} uses to implement breakpoints and other events that
5827 To handle this problem, your program should check the return value of
5828 each system call and react appropriately. This is good programming
5831 For example, do not write code like this:
5837 The call to @code{sleep} will return early if a different thread stops
5838 at a breakpoint or for some other reason.
5840 Instead, write this:
5845 unslept = sleep (unslept);
5848 A system call is allowed to return early, so the system is still
5849 conforming to its specification. But @value{GDBN} does cause your
5850 multi-threaded program to behave differently than it would without
5853 Also, @value{GDBN} uses internal breakpoints in the thread library to
5854 monitor certain events such as thread creation and thread destruction.
5855 When such an event happens, a system call in another thread may return
5856 prematurely, even though your program does not appear to stop.
5859 @subsection Observer Mode
5861 If you want to build on non-stop mode and observe program behavior
5862 without any chance of disruption by @value{GDBN}, you can set
5863 variables to disable all of the debugger's attempts to modify state,
5864 whether by writing memory, inserting breakpoints, etc. These operate
5865 at a low level, intercepting operations from all commands.
5867 When all of these are set to @code{off}, then @value{GDBN} is said to
5868 be @dfn{observer mode}. As a convenience, the variable
5869 @code{observer} can be set to disable these, plus enable non-stop
5872 Note that @value{GDBN} will not prevent you from making nonsensical
5873 combinations of these settings. For instance, if you have enabled
5874 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5875 then breakpoints that work by writing trap instructions into the code
5876 stream will still not be able to be placed.
5881 @item set observer on
5882 @itemx set observer off
5883 When set to @code{on}, this disables all the permission variables
5884 below (except for @code{insert-fast-tracepoints}), plus enables
5885 non-stop debugging. Setting this to @code{off} switches back to
5886 normal debugging, though remaining in non-stop mode.
5889 Show whether observer mode is on or off.
5891 @kindex may-write-registers
5892 @item set may-write-registers on
5893 @itemx set may-write-registers off
5894 This controls whether @value{GDBN} will attempt to alter the values of
5895 registers, such as with assignment expressions in @code{print}, or the
5896 @code{jump} command. It defaults to @code{on}.
5898 @item show may-write-registers
5899 Show the current permission to write registers.
5901 @kindex may-write-memory
5902 @item set may-write-memory on
5903 @itemx set may-write-memory off
5904 This controls whether @value{GDBN} will attempt to alter the contents
5905 of memory, such as with assignment expressions in @code{print}. It
5906 defaults to @code{on}.
5908 @item show may-write-memory
5909 Show the current permission to write memory.
5911 @kindex may-insert-breakpoints
5912 @item set may-insert-breakpoints on
5913 @itemx set may-insert-breakpoints off
5914 This controls whether @value{GDBN} will attempt to insert breakpoints.
5915 This affects all breakpoints, including internal breakpoints defined
5916 by @value{GDBN}. It defaults to @code{on}.
5918 @item show may-insert-breakpoints
5919 Show the current permission to insert breakpoints.
5921 @kindex may-insert-tracepoints
5922 @item set may-insert-tracepoints on
5923 @itemx set may-insert-tracepoints off
5924 This controls whether @value{GDBN} will attempt to insert (regular)
5925 tracepoints at the beginning of a tracing experiment. It affects only
5926 non-fast tracepoints, fast tracepoints being under the control of
5927 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5929 @item show may-insert-tracepoints
5930 Show the current permission to insert tracepoints.
5932 @kindex may-insert-fast-tracepoints
5933 @item set may-insert-fast-tracepoints on
5934 @itemx set may-insert-fast-tracepoints off
5935 This controls whether @value{GDBN} will attempt to insert fast
5936 tracepoints at the beginning of a tracing experiment. It affects only
5937 fast tracepoints, regular (non-fast) tracepoints being under the
5938 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5940 @item show may-insert-fast-tracepoints
5941 Show the current permission to insert fast tracepoints.
5943 @kindex may-interrupt
5944 @item set may-interrupt on
5945 @itemx set may-interrupt off
5946 This controls whether @value{GDBN} will attempt to interrupt or stop
5947 program execution. When this variable is @code{off}, the
5948 @code{interrupt} command will have no effect, nor will
5949 @kbd{Ctrl-c}. It defaults to @code{on}.
5951 @item show may-interrupt
5952 Show the current permission to interrupt or stop the program.
5956 @node Reverse Execution
5957 @chapter Running programs backward
5958 @cindex reverse execution
5959 @cindex running programs backward
5961 When you are debugging a program, it is not unusual to realize that
5962 you have gone too far, and some event of interest has already happened.
5963 If the target environment supports it, @value{GDBN} can allow you to
5964 ``rewind'' the program by running it backward.
5966 A target environment that supports reverse execution should be able
5967 to ``undo'' the changes in machine state that have taken place as the
5968 program was executing normally. Variables, registers etc.@: should
5969 revert to their previous values. Obviously this requires a great
5970 deal of sophistication on the part of the target environment; not
5971 all target environments can support reverse execution.
5973 When a program is executed in reverse, the instructions that
5974 have most recently been executed are ``un-executed'', in reverse
5975 order. The program counter runs backward, following the previous
5976 thread of execution in reverse. As each instruction is ``un-executed'',
5977 the values of memory and/or registers that were changed by that
5978 instruction are reverted to their previous states. After executing
5979 a piece of source code in reverse, all side effects of that code
5980 should be ``undone'', and all variables should be returned to their
5981 prior values@footnote{
5982 Note that some side effects are easier to undo than others. For instance,
5983 memory and registers are relatively easy, but device I/O is hard. Some
5984 targets may be able undo things like device I/O, and some may not.
5986 The contract between @value{GDBN} and the reverse executing target
5987 requires only that the target do something reasonable when
5988 @value{GDBN} tells it to execute backwards, and then report the
5989 results back to @value{GDBN}. Whatever the target reports back to
5990 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5991 assumes that the memory and registers that the target reports are in a
5992 consistant state, but @value{GDBN} accepts whatever it is given.
5995 If you are debugging in a target environment that supports
5996 reverse execution, @value{GDBN} provides the following commands.
5999 @kindex reverse-continue
6000 @kindex rc @r{(@code{reverse-continue})}
6001 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6002 @itemx rc @r{[}@var{ignore-count}@r{]}
6003 Beginning at the point where your program last stopped, start executing
6004 in reverse. Reverse execution will stop for breakpoints and synchronous
6005 exceptions (signals), just like normal execution. Behavior of
6006 asynchronous signals depends on the target environment.
6008 @kindex reverse-step
6009 @kindex rs @r{(@code{step})}
6010 @item reverse-step @r{[}@var{count}@r{]}
6011 Run the program backward until control reaches the start of a
6012 different source line; then stop it, and return control to @value{GDBN}.
6014 Like the @code{step} command, @code{reverse-step} will only stop
6015 at the beginning of a source line. It ``un-executes'' the previously
6016 executed source line. If the previous source line included calls to
6017 debuggable functions, @code{reverse-step} will step (backward) into
6018 the called function, stopping at the beginning of the @emph{last}
6019 statement in the called function (typically a return statement).
6021 Also, as with the @code{step} command, if non-debuggable functions are
6022 called, @code{reverse-step} will run thru them backward without stopping.
6024 @kindex reverse-stepi
6025 @kindex rsi @r{(@code{reverse-stepi})}
6026 @item reverse-stepi @r{[}@var{count}@r{]}
6027 Reverse-execute one machine instruction. Note that the instruction
6028 to be reverse-executed is @emph{not} the one pointed to by the program
6029 counter, but the instruction executed prior to that one. For instance,
6030 if the last instruction was a jump, @code{reverse-stepi} will take you
6031 back from the destination of the jump to the jump instruction itself.
6033 @kindex reverse-next
6034 @kindex rn @r{(@code{reverse-next})}
6035 @item reverse-next @r{[}@var{count}@r{]}
6036 Run backward to the beginning of the previous line executed in
6037 the current (innermost) stack frame. If the line contains function
6038 calls, they will be ``un-executed'' without stopping. Starting from
6039 the first line of a function, @code{reverse-next} will take you back
6040 to the caller of that function, @emph{before} the function was called,
6041 just as the normal @code{next} command would take you from the last
6042 line of a function back to its return to its caller
6043 @footnote{Unless the code is too heavily optimized.}.
6045 @kindex reverse-nexti
6046 @kindex rni @r{(@code{reverse-nexti})}
6047 @item reverse-nexti @r{[}@var{count}@r{]}
6048 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6049 in reverse, except that called functions are ``un-executed'' atomically.
6050 That is, if the previously executed instruction was a return from
6051 another function, @code{reverse-nexti} will continue to execute
6052 in reverse until the call to that function (from the current stack
6055 @kindex reverse-finish
6056 @item reverse-finish
6057 Just as the @code{finish} command takes you to the point where the
6058 current function returns, @code{reverse-finish} takes you to the point
6059 where it was called. Instead of ending up at the end of the current
6060 function invocation, you end up at the beginning.
6062 @kindex set exec-direction
6063 @item set exec-direction
6064 Set the direction of target execution.
6065 @item set exec-direction reverse
6066 @cindex execute forward or backward in time
6067 @value{GDBN} will perform all execution commands in reverse, until the
6068 exec-direction mode is changed to ``forward''. Affected commands include
6069 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6070 command cannot be used in reverse mode.
6071 @item set exec-direction forward
6072 @value{GDBN} will perform all execution commands in the normal fashion.
6073 This is the default.
6077 @node Process Record and Replay
6078 @chapter Recording Inferior's Execution and Replaying It
6079 @cindex process record and replay
6080 @cindex recording inferior's execution and replaying it
6082 On some platforms, @value{GDBN} provides a special @dfn{process record
6083 and replay} target that can record a log of the process execution, and
6084 replay it later with both forward and reverse execution commands.
6087 When this target is in use, if the execution log includes the record
6088 for the next instruction, @value{GDBN} will debug in @dfn{replay
6089 mode}. In the replay mode, the inferior does not really execute code
6090 instructions. Instead, all the events that normally happen during
6091 code execution are taken from the execution log. While code is not
6092 really executed in replay mode, the values of registers (including the
6093 program counter register) and the memory of the inferior are still
6094 changed as they normally would. Their contents are taken from the
6098 If the record for the next instruction is not in the execution log,
6099 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6100 inferior executes normally, and @value{GDBN} records the execution log
6103 The process record and replay target supports reverse execution
6104 (@pxref{Reverse Execution}), even if the platform on which the
6105 inferior runs does not. However, the reverse execution is limited in
6106 this case by the range of the instructions recorded in the execution
6107 log. In other words, reverse execution on platforms that don't
6108 support it directly can only be done in the replay mode.
6110 When debugging in the reverse direction, @value{GDBN} will work in
6111 replay mode as long as the execution log includes the record for the
6112 previous instruction; otherwise, it will work in record mode, if the
6113 platform supports reverse execution, or stop if not.
6115 For architecture environments that support process record and replay,
6116 @value{GDBN} provides the following commands:
6119 @kindex target record
6120 @kindex target record-full
6121 @kindex target record-btrace
6124 @kindex record btrace
6128 @item record @var{method}
6129 This command starts the process record and replay target. The
6130 recording method can be specified as parameter. Without a parameter
6131 the command uses the @code{full} recording method. The following
6132 recording methods are available:
6136 Full record/replay recording using @value{GDBN}'s software record and
6137 replay implementation. This method allows replaying and reverse
6141 Hardware-supported instruction recording. This method does not allow
6142 replaying and reverse execution.
6144 This recording method may not be available on all processors.
6147 The process record and replay target can only debug a process that is
6148 already running. Therefore, you need first to start the process with
6149 the @kbd{run} or @kbd{start} commands, and then start the recording
6150 with the @kbd{record @var{method}} command.
6152 Both @code{record @var{method}} and @code{rec @var{method}} are
6153 aliases of @code{target record-@var{method}}.
6155 @cindex displaced stepping, and process record and replay
6156 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6157 will be automatically disabled when process record and replay target
6158 is started. That's because the process record and replay target
6159 doesn't support displaced stepping.
6161 @cindex non-stop mode, and process record and replay
6162 @cindex asynchronous execution, and process record and replay
6163 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6164 the asynchronous execution mode (@pxref{Background Execution}), not
6165 all recording methods are available. The @code{full} recording method
6166 does not support these two modes.
6171 Stop the process record and replay target. When process record and
6172 replay target stops, the entire execution log will be deleted and the
6173 inferior will either be terminated, or will remain in its final state.
6175 When you stop the process record and replay target in record mode (at
6176 the end of the execution log), the inferior will be stopped at the
6177 next instruction that would have been recorded. In other words, if
6178 you record for a while and then stop recording, the inferior process
6179 will be left in the same state as if the recording never happened.
6181 On the other hand, if the process record and replay target is stopped
6182 while in replay mode (that is, not at the end of the execution log,
6183 but at some earlier point), the inferior process will become ``live''
6184 at that earlier state, and it will then be possible to continue the
6185 usual ``live'' debugging of the process from that state.
6187 When the inferior process exits, or @value{GDBN} detaches from it,
6188 process record and replay target will automatically stop itself.
6191 @item record save @var{filename}
6192 Save the execution log to a file @file{@var{filename}}.
6193 Default filename is @file{gdb_record.@var{process_id}}, where
6194 @var{process_id} is the process ID of the inferior.
6196 This command may not be available for all recording methods.
6198 @kindex record restore
6199 @item record restore @var{filename}
6200 Restore the execution log from a file @file{@var{filename}}.
6201 File must have been created with @code{record save}.
6203 @kindex set record full
6204 @item set record full insn-number-max @var{limit}
6205 Set the limit of instructions to be recorded for the @code{full}
6206 recording method. Default value is 200000.
6208 If @var{limit} is a positive number, then @value{GDBN} will start
6209 deleting instructions from the log once the number of the record
6210 instructions becomes greater than @var{limit}. For every new recorded
6211 instruction, @value{GDBN} will delete the earliest recorded
6212 instruction to keep the number of recorded instructions at the limit.
6213 (Since deleting recorded instructions loses information, @value{GDBN}
6214 lets you control what happens when the limit is reached, by means of
6215 the @code{stop-at-limit} option, described below.)
6217 If @var{limit} is zero, @value{GDBN} will never delete recorded
6218 instructions from the execution log. The number of recorded
6219 instructions is unlimited in this case.
6221 @kindex show record full
6222 @item show record full insn-number-max
6223 Show the limit of instructions to be recorded with the @code{full}
6226 @item set record full stop-at-limit
6227 Control the behavior of the @code{full} recording method when the
6228 number of recorded instructions reaches the limit. If ON (the
6229 default), @value{GDBN} will stop when the limit is reached for the
6230 first time and ask you whether you want to stop the inferior or
6231 continue running it and recording the execution log. If you decide
6232 to continue recording, each new recorded instruction will cause the
6233 oldest one to be deleted.
6235 If this option is OFF, @value{GDBN} will automatically delete the
6236 oldest record to make room for each new one, without asking.
6238 @item show record full stop-at-limit
6239 Show the current setting of @code{stop-at-limit}.
6241 @item set record full memory-query
6242 Control the behavior when @value{GDBN} is unable to record memory
6243 changes caused by an instruction for the @code{full} recording method.
6244 If ON, @value{GDBN} will query whether to stop the inferior in that
6247 If this option is OFF (the default), @value{GDBN} will automatically
6248 ignore the effect of such instructions on memory. Later, when
6249 @value{GDBN} replays this execution log, it will mark the log of this
6250 instruction as not accessible, and it will not affect the replay
6253 @item show record full memory-query
6254 Show the current setting of @code{memory-query}.
6258 Show various statistics about the recording depending on the recording
6263 For the @code{full} recording method, it shows the state of process
6264 record and its in-memory execution log buffer, including:
6268 Whether in record mode or replay mode.
6270 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6272 Highest recorded instruction number.
6274 Current instruction about to be replayed (if in replay mode).
6276 Number of instructions contained in the execution log.
6278 Maximum number of instructions that may be contained in the execution log.
6282 For the @code{btrace} recording method, it shows the number of
6283 instructions that have been recorded and the number of blocks of
6284 sequential control-flow that is formed by the recorded instructions.
6287 @kindex record delete
6290 When record target runs in replay mode (``in the past''), delete the
6291 subsequent execution log and begin to record a new execution log starting
6292 from the current address. This means you will abandon the previously
6293 recorded ``future'' and begin recording a new ``future''.
6295 @kindex record instruction-history
6296 @kindex rec instruction-history
6297 @item record instruction-history
6298 Disassembles instructions from the recorded execution log. By
6299 default, ten instructions are disassembled. This can be changed using
6300 the @code{set record instruction-history-size} command. Instructions
6301 are printed in execution order. There are several ways to specify
6302 what part of the execution log to disassemble:
6305 @item record instruction-history @var{insn}
6306 Disassembles ten instructions starting from instruction number
6309 @item record instruction-history @var{insn}, +/-@var{n}
6310 Disassembles @var{n} instructions around instruction number
6311 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6312 @var{n} instructions after instruction number @var{insn}. If
6313 @var{n} is preceded with @code{-}, disassembles @var{n}
6314 instructions before instruction number @var{insn}.
6316 @item record instruction-history
6317 Disassembles ten more instructions after the last disassembly.
6319 @item record instruction-history -
6320 Disassembles ten more instructions before the last disassembly.
6322 @item record instruction-history @var{begin} @var{end}
6323 Disassembles instructions beginning with instruction number
6324 @var{begin} until instruction number @var{end}. The instruction
6325 number @var{end} is not included.
6328 This command may not be available for all recording methods.
6331 @item set record instruction-history-size
6332 Define how many instructions to disassemble in the @code{record
6333 instruction-history} command. The default value is 10.
6336 @item show record instruction-history-size
6337 Show how many instructions to disassemble in the @code{record
6338 instruction-history} command.
6340 @kindex record function-call-history
6341 @kindex rec function-call-history
6342 @item record function-call-history
6343 Prints the execution history at function granularity. It prints one
6344 line for each sequence of instructions that belong to the same
6345 function giving the name of that function, the source lines
6346 for this instruction sequence (if the @code{/l} modifier is
6347 specified), and the instructions numbers that form the sequence (if
6348 the @code{/i} modifier is specified).
6351 (@value{GDBP}) @b{list 1, 10}
6362 (@value{GDBP}) @b{record function-call-history /l}
6368 By default, ten lines are printed. This can be changed using the
6369 @code{set record function-call-history-size} command. Functions are
6370 printed in execution order. There are several ways to specify what
6374 @item record function-call-history @var{func}
6375 Prints ten functions starting from function number @var{func}.
6377 @item record function-call-history @var{func}, +/-@var{n}
6378 Prints @var{n} functions around function number @var{func}. If
6379 @var{n} is preceded with @code{+}, prints @var{n} functions after
6380 function number @var{func}. If @var{n} is preceded with @code{-},
6381 prints @var{n} functions before function number @var{func}.
6383 @item record function-call-history
6384 Prints ten more functions after the last ten-line print.
6386 @item record function-call-history -
6387 Prints ten more functions before the last ten-line print.
6389 @item record function-call-history @var{begin} @var{end}
6390 Prints functions beginning with function number @var{begin} until
6391 function number @var{end}. The function number @var{end} is not
6395 This command may not be available for all recording methods.
6397 @item set record function-call-history-size
6398 Define how many lines to print in the
6399 @code{record function-call-history} command. The default value is 10.
6401 @item show record function-call-history-size
6402 Show how many lines to print in the
6403 @code{record function-call-history} command.
6408 @chapter Examining the Stack
6410 When your program has stopped, the first thing you need to know is where it
6411 stopped and how it got there.
6414 Each time your program performs a function call, information about the call
6416 That information includes the location of the call in your program,
6417 the arguments of the call,
6418 and the local variables of the function being called.
6419 The information is saved in a block of data called a @dfn{stack frame}.
6420 The stack frames are allocated in a region of memory called the @dfn{call
6423 When your program stops, the @value{GDBN} commands for examining the
6424 stack allow you to see all of this information.
6426 @cindex selected frame
6427 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6428 @value{GDBN} commands refer implicitly to the selected frame. In
6429 particular, whenever you ask @value{GDBN} for the value of a variable in
6430 your program, the value is found in the selected frame. There are
6431 special @value{GDBN} commands to select whichever frame you are
6432 interested in. @xref{Selection, ,Selecting a Frame}.
6434 When your program stops, @value{GDBN} automatically selects the
6435 currently executing frame and describes it briefly, similar to the
6436 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6439 * Frames:: Stack frames
6440 * Backtrace:: Backtraces
6441 * Selection:: Selecting a frame
6442 * Frame Info:: Information on a frame
6447 @section Stack Frames
6449 @cindex frame, definition
6451 The call stack is divided up into contiguous pieces called @dfn{stack
6452 frames}, or @dfn{frames} for short; each frame is the data associated
6453 with one call to one function. The frame contains the arguments given
6454 to the function, the function's local variables, and the address at
6455 which the function is executing.
6457 @cindex initial frame
6458 @cindex outermost frame
6459 @cindex innermost frame
6460 When your program is started, the stack has only one frame, that of the
6461 function @code{main}. This is called the @dfn{initial} frame or the
6462 @dfn{outermost} frame. Each time a function is called, a new frame is
6463 made. Each time a function returns, the frame for that function invocation
6464 is eliminated. If a function is recursive, there can be many frames for
6465 the same function. The frame for the function in which execution is
6466 actually occurring is called the @dfn{innermost} frame. This is the most
6467 recently created of all the stack frames that still exist.
6469 @cindex frame pointer
6470 Inside your program, stack frames are identified by their addresses. A
6471 stack frame consists of many bytes, each of which has its own address; each
6472 kind of computer has a convention for choosing one byte whose
6473 address serves as the address of the frame. Usually this address is kept
6474 in a register called the @dfn{frame pointer register}
6475 (@pxref{Registers, $fp}) while execution is going on in that frame.
6477 @cindex frame number
6478 @value{GDBN} assigns numbers to all existing stack frames, starting with
6479 zero for the innermost frame, one for the frame that called it,
6480 and so on upward. These numbers do not really exist in your program;
6481 they are assigned by @value{GDBN} to give you a way of designating stack
6482 frames in @value{GDBN} commands.
6484 @c The -fomit-frame-pointer below perennially causes hbox overflow
6485 @c underflow problems.
6486 @cindex frameless execution
6487 Some compilers provide a way to compile functions so that they operate
6488 without stack frames. (For example, the @value{NGCC} option
6490 @samp{-fomit-frame-pointer}
6492 generates functions without a frame.)
6493 This is occasionally done with heavily used library functions to save
6494 the frame setup time. @value{GDBN} has limited facilities for dealing
6495 with these function invocations. If the innermost function invocation
6496 has no stack frame, @value{GDBN} nevertheless regards it as though
6497 it had a separate frame, which is numbered zero as usual, allowing
6498 correct tracing of the function call chain. However, @value{GDBN} has
6499 no provision for frameless functions elsewhere in the stack.
6502 @kindex frame@r{, command}
6503 @cindex current stack frame
6504 @item frame @var{args}
6505 The @code{frame} command allows you to move from one stack frame to another,
6506 and to print the stack frame you select. @var{args} may be either the
6507 address of the frame or the stack frame number. Without an argument,
6508 @code{frame} prints the current stack frame.
6510 @kindex select-frame
6511 @cindex selecting frame silently
6513 The @code{select-frame} command allows you to move from one stack frame
6514 to another without printing the frame. This is the silent version of
6522 @cindex call stack traces
6523 A backtrace is a summary of how your program got where it is. It shows one
6524 line per frame, for many frames, starting with the currently executing
6525 frame (frame zero), followed by its caller (frame one), and on up the
6530 @kindex bt @r{(@code{backtrace})}
6533 Print a backtrace of the entire stack: one line per frame for all
6534 frames in the stack.
6536 You can stop the backtrace at any time by typing the system interrupt
6537 character, normally @kbd{Ctrl-c}.
6539 @item backtrace @var{n}
6541 Similar, but print only the innermost @var{n} frames.
6543 @item backtrace -@var{n}
6545 Similar, but print only the outermost @var{n} frames.
6547 @item backtrace full
6549 @itemx bt full @var{n}
6550 @itemx bt full -@var{n}
6551 Print the values of the local variables also. @var{n} specifies the
6552 number of frames to print, as described above.
6557 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6558 are additional aliases for @code{backtrace}.
6560 @cindex multiple threads, backtrace
6561 In a multi-threaded program, @value{GDBN} by default shows the
6562 backtrace only for the current thread. To display the backtrace for
6563 several or all of the threads, use the command @code{thread apply}
6564 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6565 apply all backtrace}, @value{GDBN} will display the backtrace for all
6566 the threads; this is handy when you debug a core dump of a
6567 multi-threaded program.
6569 Each line in the backtrace shows the frame number and the function name.
6570 The program counter value is also shown---unless you use @code{set
6571 print address off}. The backtrace also shows the source file name and
6572 line number, as well as the arguments to the function. The program
6573 counter value is omitted if it is at the beginning of the code for that
6576 Here is an example of a backtrace. It was made with the command
6577 @samp{bt 3}, so it shows the innermost three frames.
6581 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6583 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6584 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6586 (More stack frames follow...)
6591 The display for frame zero does not begin with a program counter
6592 value, indicating that your program has stopped at the beginning of the
6593 code for line @code{993} of @code{builtin.c}.
6596 The value of parameter @code{data} in frame 1 has been replaced by
6597 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6598 only if it is a scalar (integer, pointer, enumeration, etc). See command
6599 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6600 on how to configure the way function parameter values are printed.
6602 @cindex optimized out, in backtrace
6603 @cindex function call arguments, optimized out
6604 If your program was compiled with optimizations, some compilers will
6605 optimize away arguments passed to functions if those arguments are
6606 never used after the call. Such optimizations generate code that
6607 passes arguments through registers, but doesn't store those arguments
6608 in the stack frame. @value{GDBN} has no way of displaying such
6609 arguments in stack frames other than the innermost one. Here's what
6610 such a backtrace might look like:
6614 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6616 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6617 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6619 (More stack frames follow...)
6624 The values of arguments that were not saved in their stack frames are
6625 shown as @samp{<optimized out>}.
6627 If you need to display the values of such optimized-out arguments,
6628 either deduce that from other variables whose values depend on the one
6629 you are interested in, or recompile without optimizations.
6631 @cindex backtrace beyond @code{main} function
6632 @cindex program entry point
6633 @cindex startup code, and backtrace
6634 Most programs have a standard user entry point---a place where system
6635 libraries and startup code transition into user code. For C this is
6636 @code{main}@footnote{
6637 Note that embedded programs (the so-called ``free-standing''
6638 environment) are not required to have a @code{main} function as the
6639 entry point. They could even have multiple entry points.}.
6640 When @value{GDBN} finds the entry function in a backtrace
6641 it will terminate the backtrace, to avoid tracing into highly
6642 system-specific (and generally uninteresting) code.
6644 If you need to examine the startup code, or limit the number of levels
6645 in a backtrace, you can change this behavior:
6648 @item set backtrace past-main
6649 @itemx set backtrace past-main on
6650 @kindex set backtrace
6651 Backtraces will continue past the user entry point.
6653 @item set backtrace past-main off
6654 Backtraces will stop when they encounter the user entry point. This is the
6657 @item show backtrace past-main
6658 @kindex show backtrace
6659 Display the current user entry point backtrace policy.
6661 @item set backtrace past-entry
6662 @itemx set backtrace past-entry on
6663 Backtraces will continue past the internal entry point of an application.
6664 This entry point is encoded by the linker when the application is built,
6665 and is likely before the user entry point @code{main} (or equivalent) is called.
6667 @item set backtrace past-entry off
6668 Backtraces will stop when they encounter the internal entry point of an
6669 application. This is the default.
6671 @item show backtrace past-entry
6672 Display the current internal entry point backtrace policy.
6674 @item set backtrace limit @var{n}
6675 @itemx set backtrace limit 0
6676 @cindex backtrace limit
6677 Limit the backtrace to @var{n} levels. A value of zero means
6680 @item show backtrace limit
6681 Display the current limit on backtrace levels.
6684 You can control how file names are displayed.
6687 @item set filename-display
6688 @itemx set filename-display relative
6689 @cindex filename-display
6690 Display file names relative to the compilation directory. This is the default.
6692 @item set filename-display basename
6693 Display only basename of a filename.
6695 @item set filename-display absolute
6696 Display an absolute filename.
6698 @item show filename-display
6699 Show the current way to display filenames.
6703 @section Selecting a Frame
6705 Most commands for examining the stack and other data in your program work on
6706 whichever stack frame is selected at the moment. Here are the commands for
6707 selecting a stack frame; all of them finish by printing a brief description
6708 of the stack frame just selected.
6711 @kindex frame@r{, selecting}
6712 @kindex f @r{(@code{frame})}
6715 Select frame number @var{n}. Recall that frame zero is the innermost
6716 (currently executing) frame, frame one is the frame that called the
6717 innermost one, and so on. The highest-numbered frame is the one for
6720 @item frame @var{addr}
6722 Select the frame at address @var{addr}. This is useful mainly if the
6723 chaining of stack frames has been damaged by a bug, making it
6724 impossible for @value{GDBN} to assign numbers properly to all frames. In
6725 addition, this can be useful when your program has multiple stacks and
6726 switches between them.
6728 On the SPARC architecture, @code{frame} needs two addresses to
6729 select an arbitrary frame: a frame pointer and a stack pointer.
6731 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6732 pointer and a program counter.
6734 On the 29k architecture, it needs three addresses: a register stack
6735 pointer, a program counter, and a memory stack pointer.
6739 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6740 advances toward the outermost frame, to higher frame numbers, to frames
6741 that have existed longer. @var{n} defaults to one.
6744 @kindex do @r{(@code{down})}
6746 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6747 advances toward the innermost frame, to lower frame numbers, to frames
6748 that were created more recently. @var{n} defaults to one. You may
6749 abbreviate @code{down} as @code{do}.
6752 All of these commands end by printing two lines of output describing the
6753 frame. The first line shows the frame number, the function name, the
6754 arguments, and the source file and line number of execution in that
6755 frame. The second line shows the text of that source line.
6763 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6765 10 read_input_file (argv[i]);
6769 After such a printout, the @code{list} command with no arguments
6770 prints ten lines centered on the point of execution in the frame.
6771 You can also edit the program at the point of execution with your favorite
6772 editing program by typing @code{edit}.
6773 @xref{List, ,Printing Source Lines},
6777 @kindex down-silently
6779 @item up-silently @var{n}
6780 @itemx down-silently @var{n}
6781 These two commands are variants of @code{up} and @code{down},
6782 respectively; they differ in that they do their work silently, without
6783 causing display of the new frame. They are intended primarily for use
6784 in @value{GDBN} command scripts, where the output might be unnecessary and
6789 @section Information About a Frame
6791 There are several other commands to print information about the selected
6797 When used without any argument, this command does not change which
6798 frame is selected, but prints a brief description of the currently
6799 selected stack frame. It can be abbreviated @code{f}. With an
6800 argument, this command is used to select a stack frame.
6801 @xref{Selection, ,Selecting a Frame}.
6804 @kindex info f @r{(@code{info frame})}
6807 This command prints a verbose description of the selected stack frame,
6812 the address of the frame
6814 the address of the next frame down (called by this frame)
6816 the address of the next frame up (caller of this frame)
6818 the language in which the source code corresponding to this frame is written
6820 the address of the frame's arguments
6822 the address of the frame's local variables
6824 the program counter saved in it (the address of execution in the caller frame)
6826 which registers were saved in the frame
6829 @noindent The verbose description is useful when
6830 something has gone wrong that has made the stack format fail to fit
6831 the usual conventions.
6833 @item info frame @var{addr}
6834 @itemx info f @var{addr}
6835 Print a verbose description of the frame at address @var{addr}, without
6836 selecting that frame. The selected frame remains unchanged by this
6837 command. This requires the same kind of address (more than one for some
6838 architectures) that you specify in the @code{frame} command.
6839 @xref{Selection, ,Selecting a Frame}.
6843 Print the arguments of the selected frame, each on a separate line.
6847 Print the local variables of the selected frame, each on a separate
6848 line. These are all variables (declared either static or automatic)
6849 accessible at the point of execution of the selected frame.
6855 @chapter Examining Source Files
6857 @value{GDBN} can print parts of your program's source, since the debugging
6858 information recorded in the program tells @value{GDBN} what source files were
6859 used to build it. When your program stops, @value{GDBN} spontaneously prints
6860 the line where it stopped. Likewise, when you select a stack frame
6861 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6862 execution in that frame has stopped. You can print other portions of
6863 source files by explicit command.
6865 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6866 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6867 @value{GDBN} under @sc{gnu} Emacs}.
6870 * List:: Printing source lines
6871 * Specify Location:: How to specify code locations
6872 * Edit:: Editing source files
6873 * Search:: Searching source files
6874 * Source Path:: Specifying source directories
6875 * Machine Code:: Source and machine code
6879 @section Printing Source Lines
6882 @kindex l @r{(@code{list})}
6883 To print lines from a source file, use the @code{list} command
6884 (abbreviated @code{l}). By default, ten lines are printed.
6885 There are several ways to specify what part of the file you want to
6886 print; see @ref{Specify Location}, for the full list.
6888 Here are the forms of the @code{list} command most commonly used:
6891 @item list @var{linenum}
6892 Print lines centered around line number @var{linenum} in the
6893 current source file.
6895 @item list @var{function}
6896 Print lines centered around the beginning of function
6900 Print more lines. If the last lines printed were printed with a
6901 @code{list} command, this prints lines following the last lines
6902 printed; however, if the last line printed was a solitary line printed
6903 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6904 Stack}), this prints lines centered around that line.
6907 Print lines just before the lines last printed.
6910 @cindex @code{list}, how many lines to display
6911 By default, @value{GDBN} prints ten source lines with any of these forms of
6912 the @code{list} command. You can change this using @code{set listsize}:
6915 @kindex set listsize
6916 @item set listsize @var{count}
6917 Make the @code{list} command display @var{count} source lines (unless
6918 the @code{list} argument explicitly specifies some other number).
6919 Setting @var{count} to 0 means there's no limit.
6921 @kindex show listsize
6923 Display the number of lines that @code{list} prints.
6926 Repeating a @code{list} command with @key{RET} discards the argument,
6927 so it is equivalent to typing just @code{list}. This is more useful
6928 than listing the same lines again. An exception is made for an
6929 argument of @samp{-}; that argument is preserved in repetition so that
6930 each repetition moves up in the source file.
6932 In general, the @code{list} command expects you to supply zero, one or two
6933 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6934 of writing them (@pxref{Specify Location}), but the effect is always
6935 to specify some source line.
6937 Here is a complete description of the possible arguments for @code{list}:
6940 @item list @var{linespec}
6941 Print lines centered around the line specified by @var{linespec}.
6943 @item list @var{first},@var{last}
6944 Print lines from @var{first} to @var{last}. Both arguments are
6945 linespecs. When a @code{list} command has two linespecs, and the
6946 source file of the second linespec is omitted, this refers to
6947 the same source file as the first linespec.
6949 @item list ,@var{last}
6950 Print lines ending with @var{last}.
6952 @item list @var{first},
6953 Print lines starting with @var{first}.
6956 Print lines just after the lines last printed.
6959 Print lines just before the lines last printed.
6962 As described in the preceding table.
6965 @node Specify Location
6966 @section Specifying a Location
6967 @cindex specifying location
6970 Several @value{GDBN} commands accept arguments that specify a location
6971 of your program's code. Since @value{GDBN} is a source-level
6972 debugger, a location usually specifies some line in the source code;
6973 for that reason, locations are also known as @dfn{linespecs}.
6975 Here are all the different ways of specifying a code location that
6976 @value{GDBN} understands:
6980 Specifies the line number @var{linenum} of the current source file.
6983 @itemx +@var{offset}
6984 Specifies the line @var{offset} lines before or after the @dfn{current
6985 line}. For the @code{list} command, the current line is the last one
6986 printed; for the breakpoint commands, this is the line at which
6987 execution stopped in the currently selected @dfn{stack frame}
6988 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6989 used as the second of the two linespecs in a @code{list} command,
6990 this specifies the line @var{offset} lines up or down from the first
6993 @item @var{filename}:@var{linenum}
6994 Specifies the line @var{linenum} in the source file @var{filename}.
6995 If @var{filename} is a relative file name, then it will match any
6996 source file name with the same trailing components. For example, if
6997 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6998 name of @file{/build/trunk/gcc/expr.c}, but not
6999 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7001 @item @var{function}
7002 Specifies the line that begins the body of the function @var{function}.
7003 For example, in C, this is the line with the open brace.
7005 @item @var{function}:@var{label}
7006 Specifies the line where @var{label} appears in @var{function}.
7008 @item @var{filename}:@var{function}
7009 Specifies the line that begins the body of the function @var{function}
7010 in the file @var{filename}. You only need the file name with a
7011 function name to avoid ambiguity when there are identically named
7012 functions in different source files.
7015 Specifies the line at which the label named @var{label} appears.
7016 @value{GDBN} searches for the label in the function corresponding to
7017 the currently selected stack frame. If there is no current selected
7018 stack frame (for instance, if the inferior is not running), then
7019 @value{GDBN} will not search for a label.
7021 @item *@var{address}
7022 Specifies the program address @var{address}. For line-oriented
7023 commands, such as @code{list} and @code{edit}, this specifies a source
7024 line that contains @var{address}. For @code{break} and other
7025 breakpoint oriented commands, this can be used to set breakpoints in
7026 parts of your program which do not have debugging information or
7029 Here @var{address} may be any expression valid in the current working
7030 language (@pxref{Languages, working language}) that specifies a code
7031 address. In addition, as a convenience, @value{GDBN} extends the
7032 semantics of expressions used in locations to cover the situations
7033 that frequently happen during debugging. Here are the various forms
7037 @item @var{expression}
7038 Any expression valid in the current working language.
7040 @item @var{funcaddr}
7041 An address of a function or procedure derived from its name. In C,
7042 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7043 simply the function's name @var{function} (and actually a special case
7044 of a valid expression). In Pascal and Modula-2, this is
7045 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7046 (although the Pascal form also works).
7048 This form specifies the address of the function's first instruction,
7049 before the stack frame and arguments have been set up.
7051 @item '@var{filename}'::@var{funcaddr}
7052 Like @var{funcaddr} above, but also specifies the name of the source
7053 file explicitly. This is useful if the name of the function does not
7054 specify the function unambiguously, e.g., if there are several
7055 functions with identical names in different source files.
7058 @cindex breakpoint at static probe point
7059 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7060 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7061 applications to embed static probes. @xref{Static Probe Points}, for more
7062 information on finding and using static probes. This form of linespec
7063 specifies the location of such a static probe.
7065 If @var{objfile} is given, only probes coming from that shared library
7066 or executable matching @var{objfile} as a regular expression are considered.
7067 If @var{provider} is given, then only probes from that provider are considered.
7068 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7069 each one of those probes.
7075 @section Editing Source Files
7076 @cindex editing source files
7079 @kindex e @r{(@code{edit})}
7080 To edit the lines in a source file, use the @code{edit} command.
7081 The editing program of your choice
7082 is invoked with the current line set to
7083 the active line in the program.
7084 Alternatively, there are several ways to specify what part of the file you
7085 want to print if you want to see other parts of the program:
7088 @item edit @var{location}
7089 Edit the source file specified by @code{location}. Editing starts at
7090 that @var{location}, e.g., at the specified source line of the
7091 specified file. @xref{Specify Location}, for all the possible forms
7092 of the @var{location} argument; here are the forms of the @code{edit}
7093 command most commonly used:
7096 @item edit @var{number}
7097 Edit the current source file with @var{number} as the active line number.
7099 @item edit @var{function}
7100 Edit the file containing @var{function} at the beginning of its definition.
7105 @subsection Choosing your Editor
7106 You can customize @value{GDBN} to use any editor you want
7108 The only restriction is that your editor (say @code{ex}), recognizes the
7109 following command-line syntax:
7111 ex +@var{number} file
7113 The optional numeric value +@var{number} specifies the number of the line in
7114 the file where to start editing.}.
7115 By default, it is @file{@value{EDITOR}}, but you can change this
7116 by setting the environment variable @code{EDITOR} before using
7117 @value{GDBN}. For example, to configure @value{GDBN} to use the
7118 @code{vi} editor, you could use these commands with the @code{sh} shell:
7124 or in the @code{csh} shell,
7126 setenv EDITOR /usr/bin/vi
7131 @section Searching Source Files
7132 @cindex searching source files
7134 There are two commands for searching through the current source file for a
7139 @kindex forward-search
7140 @kindex fo @r{(@code{forward-search})}
7141 @item forward-search @var{regexp}
7142 @itemx search @var{regexp}
7143 The command @samp{forward-search @var{regexp}} checks each line,
7144 starting with the one following the last line listed, for a match for
7145 @var{regexp}. It lists the line that is found. You can use the
7146 synonym @samp{search @var{regexp}} or abbreviate the command name as
7149 @kindex reverse-search
7150 @item reverse-search @var{regexp}
7151 The command @samp{reverse-search @var{regexp}} checks each line, starting
7152 with the one before the last line listed and going backward, for a match
7153 for @var{regexp}. It lists the line that is found. You can abbreviate
7154 this command as @code{rev}.
7158 @section Specifying Source Directories
7161 @cindex directories for source files
7162 Executable programs sometimes do not record the directories of the source
7163 files from which they were compiled, just the names. Even when they do,
7164 the directories could be moved between the compilation and your debugging
7165 session. @value{GDBN} has a list of directories to search for source files;
7166 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7167 it tries all the directories in the list, in the order they are present
7168 in the list, until it finds a file with the desired name.
7170 For example, suppose an executable references the file
7171 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7172 @file{/mnt/cross}. The file is first looked up literally; if this
7173 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7174 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7175 message is printed. @value{GDBN} does not look up the parts of the
7176 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7177 Likewise, the subdirectories of the source path are not searched: if
7178 the source path is @file{/mnt/cross}, and the binary refers to
7179 @file{foo.c}, @value{GDBN} would not find it under
7180 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7182 Plain file names, relative file names with leading directories, file
7183 names containing dots, etc.@: are all treated as described above; for
7184 instance, if the source path is @file{/mnt/cross}, and the source file
7185 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7186 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7187 that---@file{/mnt/cross/foo.c}.
7189 Note that the executable search path is @emph{not} used to locate the
7192 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7193 any information it has cached about where source files are found and where
7194 each line is in the file.
7198 When you start @value{GDBN}, its source path includes only @samp{cdir}
7199 and @samp{cwd}, in that order.
7200 To add other directories, use the @code{directory} command.
7202 The search path is used to find both program source files and @value{GDBN}
7203 script files (read using the @samp{-command} option and @samp{source} command).
7205 In addition to the source path, @value{GDBN} provides a set of commands
7206 that manage a list of source path substitution rules. A @dfn{substitution
7207 rule} specifies how to rewrite source directories stored in the program's
7208 debug information in case the sources were moved to a different
7209 directory between compilation and debugging. A rule is made of
7210 two strings, the first specifying what needs to be rewritten in
7211 the path, and the second specifying how it should be rewritten.
7212 In @ref{set substitute-path}, we name these two parts @var{from} and
7213 @var{to} respectively. @value{GDBN} does a simple string replacement
7214 of @var{from} with @var{to} at the start of the directory part of the
7215 source file name, and uses that result instead of the original file
7216 name to look up the sources.
7218 Using the previous example, suppose the @file{foo-1.0} tree has been
7219 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7220 @value{GDBN} to replace @file{/usr/src} in all source path names with
7221 @file{/mnt/cross}. The first lookup will then be
7222 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7223 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7224 substitution rule, use the @code{set substitute-path} command
7225 (@pxref{set substitute-path}).
7227 To avoid unexpected substitution results, a rule is applied only if the
7228 @var{from} part of the directory name ends at a directory separator.
7229 For instance, a rule substituting @file{/usr/source} into
7230 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7231 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7232 is applied only at the beginning of the directory name, this rule will
7233 not be applied to @file{/root/usr/source/baz.c} either.
7235 In many cases, you can achieve the same result using the @code{directory}
7236 command. However, @code{set substitute-path} can be more efficient in
7237 the case where the sources are organized in a complex tree with multiple
7238 subdirectories. With the @code{directory} command, you need to add each
7239 subdirectory of your project. If you moved the entire tree while
7240 preserving its internal organization, then @code{set substitute-path}
7241 allows you to direct the debugger to all the sources with one single
7244 @code{set substitute-path} is also more than just a shortcut command.
7245 The source path is only used if the file at the original location no
7246 longer exists. On the other hand, @code{set substitute-path} modifies
7247 the debugger behavior to look at the rewritten location instead. So, if
7248 for any reason a source file that is not relevant to your executable is
7249 located at the original location, a substitution rule is the only
7250 method available to point @value{GDBN} at the new location.
7252 @cindex @samp{--with-relocated-sources}
7253 @cindex default source path substitution
7254 You can configure a default source path substitution rule by
7255 configuring @value{GDBN} with the
7256 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7257 should be the name of a directory under @value{GDBN}'s configured
7258 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7259 directory names in debug information under @var{dir} will be adjusted
7260 automatically if the installed @value{GDBN} is moved to a new
7261 location. This is useful if @value{GDBN}, libraries or executables
7262 with debug information and corresponding source code are being moved
7266 @item directory @var{dirname} @dots{}
7267 @item dir @var{dirname} @dots{}
7268 Add directory @var{dirname} to the front of the source path. Several
7269 directory names may be given to this command, separated by @samp{:}
7270 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7271 part of absolute file names) or
7272 whitespace. You may specify a directory that is already in the source
7273 path; this moves it forward, so @value{GDBN} searches it sooner.
7277 @vindex $cdir@r{, convenience variable}
7278 @vindex $cwd@r{, convenience variable}
7279 @cindex compilation directory
7280 @cindex current directory
7281 @cindex working directory
7282 @cindex directory, current
7283 @cindex directory, compilation
7284 You can use the string @samp{$cdir} to refer to the compilation
7285 directory (if one is recorded), and @samp{$cwd} to refer to the current
7286 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7287 tracks the current working directory as it changes during your @value{GDBN}
7288 session, while the latter is immediately expanded to the current
7289 directory at the time you add an entry to the source path.
7292 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7294 @c RET-repeat for @code{directory} is explicitly disabled, but since
7295 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7297 @item set directories @var{path-list}
7298 @kindex set directories
7299 Set the source path to @var{path-list}.
7300 @samp{$cdir:$cwd} are added if missing.
7302 @item show directories
7303 @kindex show directories
7304 Print the source path: show which directories it contains.
7306 @anchor{set substitute-path}
7307 @item set substitute-path @var{from} @var{to}
7308 @kindex set substitute-path
7309 Define a source path substitution rule, and add it at the end of the
7310 current list of existing substitution rules. If a rule with the same
7311 @var{from} was already defined, then the old rule is also deleted.
7313 For example, if the file @file{/foo/bar/baz.c} was moved to
7314 @file{/mnt/cross/baz.c}, then the command
7317 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7321 will tell @value{GDBN} to replace @samp{/usr/src} with
7322 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7323 @file{baz.c} even though it was moved.
7325 In the case when more than one substitution rule have been defined,
7326 the rules are evaluated one by one in the order where they have been
7327 defined. The first one matching, if any, is selected to perform
7330 For instance, if we had entered the following commands:
7333 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7334 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7338 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7339 @file{/mnt/include/defs.h} by using the first rule. However, it would
7340 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7341 @file{/mnt/src/lib/foo.c}.
7344 @item unset substitute-path [path]
7345 @kindex unset substitute-path
7346 If a path is specified, search the current list of substitution rules
7347 for a rule that would rewrite that path. Delete that rule if found.
7348 A warning is emitted by the debugger if no rule could be found.
7350 If no path is specified, then all substitution rules are deleted.
7352 @item show substitute-path [path]
7353 @kindex show substitute-path
7354 If a path is specified, then print the source path substitution rule
7355 which would rewrite that path, if any.
7357 If no path is specified, then print all existing source path substitution
7362 If your source path is cluttered with directories that are no longer of
7363 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7364 versions of source. You can correct the situation as follows:
7368 Use @code{directory} with no argument to reset the source path to its default value.
7371 Use @code{directory} with suitable arguments to reinstall the
7372 directories you want in the source path. You can add all the
7373 directories in one command.
7377 @section Source and Machine Code
7378 @cindex source line and its code address
7380 You can use the command @code{info line} to map source lines to program
7381 addresses (and vice versa), and the command @code{disassemble} to display
7382 a range of addresses as machine instructions. You can use the command
7383 @code{set disassemble-next-line} to set whether to disassemble next
7384 source line when execution stops. When run under @sc{gnu} Emacs
7385 mode, the @code{info line} command causes the arrow to point to the
7386 line specified. Also, @code{info line} prints addresses in symbolic form as
7391 @item info line @var{linespec}
7392 Print the starting and ending addresses of the compiled code for
7393 source line @var{linespec}. You can specify source lines in any of
7394 the ways documented in @ref{Specify Location}.
7397 For example, we can use @code{info line} to discover the location of
7398 the object code for the first line of function
7399 @code{m4_changequote}:
7401 @c FIXME: I think this example should also show the addresses in
7402 @c symbolic form, as they usually would be displayed.
7404 (@value{GDBP}) info line m4_changequote
7405 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7409 @cindex code address and its source line
7410 We can also inquire (using @code{*@var{addr}} as the form for
7411 @var{linespec}) what source line covers a particular address:
7413 (@value{GDBP}) info line *0x63ff
7414 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7417 @cindex @code{$_} and @code{info line}
7418 @cindex @code{x} command, default address
7419 @kindex x@r{(examine), and} info line
7420 After @code{info line}, the default address for the @code{x} command
7421 is changed to the starting address of the line, so that @samp{x/i} is
7422 sufficient to begin examining the machine code (@pxref{Memory,
7423 ,Examining Memory}). Also, this address is saved as the value of the
7424 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7429 @cindex assembly instructions
7430 @cindex instructions, assembly
7431 @cindex machine instructions
7432 @cindex listing machine instructions
7434 @itemx disassemble /m
7435 @itemx disassemble /r
7436 This specialized command dumps a range of memory as machine
7437 instructions. It can also print mixed source+disassembly by specifying
7438 the @code{/m} modifier and print the raw instructions in hex as well as
7439 in symbolic form by specifying the @code{/r}.
7440 The default memory range is the function surrounding the
7441 program counter of the selected frame. A single argument to this
7442 command is a program counter value; @value{GDBN} dumps the function
7443 surrounding this value. When two arguments are given, they should
7444 be separated by a comma, possibly surrounded by whitespace. The
7445 arguments specify a range of addresses to dump, in one of two forms:
7448 @item @var{start},@var{end}
7449 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7450 @item @var{start},+@var{length}
7451 the addresses from @var{start} (inclusive) to
7452 @code{@var{start}+@var{length}} (exclusive).
7456 When 2 arguments are specified, the name of the function is also
7457 printed (since there could be several functions in the given range).
7459 The argument(s) can be any expression yielding a numeric value, such as
7460 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7462 If the range of memory being disassembled contains current program counter,
7463 the instruction at that location is shown with a @code{=>} marker.
7466 The following example shows the disassembly of a range of addresses of
7467 HP PA-RISC 2.0 code:
7470 (@value{GDBP}) disas 0x32c4, 0x32e4
7471 Dump of assembler code from 0x32c4 to 0x32e4:
7472 0x32c4 <main+204>: addil 0,dp
7473 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7474 0x32cc <main+212>: ldil 0x3000,r31
7475 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7476 0x32d4 <main+220>: ldo 0(r31),rp
7477 0x32d8 <main+224>: addil -0x800,dp
7478 0x32dc <main+228>: ldo 0x588(r1),r26
7479 0x32e0 <main+232>: ldil 0x3000,r31
7480 End of assembler dump.
7483 Here is an example showing mixed source+assembly for Intel x86, when the
7484 program is stopped just after function prologue:
7487 (@value{GDBP}) disas /m main
7488 Dump of assembler code for function main:
7490 0x08048330 <+0>: push %ebp
7491 0x08048331 <+1>: mov %esp,%ebp
7492 0x08048333 <+3>: sub $0x8,%esp
7493 0x08048336 <+6>: and $0xfffffff0,%esp
7494 0x08048339 <+9>: sub $0x10,%esp
7496 6 printf ("Hello.\n");
7497 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7498 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7502 0x08048348 <+24>: mov $0x0,%eax
7503 0x0804834d <+29>: leave
7504 0x0804834e <+30>: ret
7506 End of assembler dump.
7509 Here is another example showing raw instructions in hex for AMD x86-64,
7512 (gdb) disas /r 0x400281,+10
7513 Dump of assembler code from 0x400281 to 0x40028b:
7514 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7515 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7516 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7517 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7518 End of assembler dump.
7521 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7522 So, for example, if you want to disassemble function @code{bar}
7523 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7524 and not @samp{disassemble foo.c:bar}.
7526 Some architectures have more than one commonly-used set of instruction
7527 mnemonics or other syntax.
7529 For programs that were dynamically linked and use shared libraries,
7530 instructions that call functions or branch to locations in the shared
7531 libraries might show a seemingly bogus location---it's actually a
7532 location of the relocation table. On some architectures, @value{GDBN}
7533 might be able to resolve these to actual function names.
7536 @kindex set disassembly-flavor
7537 @cindex Intel disassembly flavor
7538 @cindex AT&T disassembly flavor
7539 @item set disassembly-flavor @var{instruction-set}
7540 Select the instruction set to use when disassembling the
7541 program via the @code{disassemble} or @code{x/i} commands.
7543 Currently this command is only defined for the Intel x86 family. You
7544 can set @var{instruction-set} to either @code{intel} or @code{att}.
7545 The default is @code{att}, the AT&T flavor used by default by Unix
7546 assemblers for x86-based targets.
7548 @kindex show disassembly-flavor
7549 @item show disassembly-flavor
7550 Show the current setting of the disassembly flavor.
7554 @kindex set disassemble-next-line
7555 @kindex show disassemble-next-line
7556 @item set disassemble-next-line
7557 @itemx show disassemble-next-line
7558 Control whether or not @value{GDBN} will disassemble the next source
7559 line or instruction when execution stops. If ON, @value{GDBN} will
7560 display disassembly of the next source line when execution of the
7561 program being debugged stops. This is @emph{in addition} to
7562 displaying the source line itself, which @value{GDBN} always does if
7563 possible. If the next source line cannot be displayed for some reason
7564 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7565 info in the debug info), @value{GDBN} will display disassembly of the
7566 next @emph{instruction} instead of showing the next source line. If
7567 AUTO, @value{GDBN} will display disassembly of next instruction only
7568 if the source line cannot be displayed. This setting causes
7569 @value{GDBN} to display some feedback when you step through a function
7570 with no line info or whose source file is unavailable. The default is
7571 OFF, which means never display the disassembly of the next line or
7577 @chapter Examining Data
7579 @cindex printing data
7580 @cindex examining data
7583 The usual way to examine data in your program is with the @code{print}
7584 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7585 evaluates and prints the value of an expression of the language your
7586 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7587 Different Languages}). It may also print the expression using a
7588 Python-based pretty-printer (@pxref{Pretty Printing}).
7591 @item print @var{expr}
7592 @itemx print /@var{f} @var{expr}
7593 @var{expr} is an expression (in the source language). By default the
7594 value of @var{expr} is printed in a format appropriate to its data type;
7595 you can choose a different format by specifying @samp{/@var{f}}, where
7596 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7600 @itemx print /@var{f}
7601 @cindex reprint the last value
7602 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7603 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7604 conveniently inspect the same value in an alternative format.
7607 A more low-level way of examining data is with the @code{x} command.
7608 It examines data in memory at a specified address and prints it in a
7609 specified format. @xref{Memory, ,Examining Memory}.
7611 If you are interested in information about types, or about how the
7612 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7613 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7616 @cindex exploring hierarchical data structures
7618 Another way of examining values of expressions and type information is
7619 through the Python extension command @code{explore} (available only if
7620 the @value{GDBN} build is configured with @code{--with-python}). It
7621 offers an interactive way to start at the highest level (or, the most
7622 abstract level) of the data type of an expression (or, the data type
7623 itself) and explore all the way down to leaf scalar values/fields
7624 embedded in the higher level data types.
7627 @item explore @var{arg}
7628 @var{arg} is either an expression (in the source language), or a type
7629 visible in the current context of the program being debugged.
7632 The working of the @code{explore} command can be illustrated with an
7633 example. If a data type @code{struct ComplexStruct} is defined in your
7643 struct ComplexStruct
7645 struct SimpleStruct *ss_p;
7651 followed by variable declarations as
7654 struct SimpleStruct ss = @{ 10, 1.11 @};
7655 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7659 then, the value of the variable @code{cs} can be explored using the
7660 @code{explore} command as follows.
7664 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7665 the following fields:
7667 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7668 arr = <Enter 1 to explore this field of type `int [10]'>
7670 Enter the field number of choice:
7674 Since the fields of @code{cs} are not scalar values, you are being
7675 prompted to chose the field you want to explore. Let's say you choose
7676 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7677 pointer, you will be asked if it is pointing to a single value. From
7678 the declaration of @code{cs} above, it is indeed pointing to a single
7679 value, hence you enter @code{y}. If you enter @code{n}, then you will
7680 be asked if it were pointing to an array of values, in which case this
7681 field will be explored as if it were an array.
7684 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7685 Continue exploring it as a pointer to a single value [y/n]: y
7686 The value of `*(cs.ss_p)' is a struct/class of type `struct
7687 SimpleStruct' with the following fields:
7689 i = 10 .. (Value of type `int')
7690 d = 1.1100000000000001 .. (Value of type `double')
7692 Press enter to return to parent value:
7696 If the field @code{arr} of @code{cs} was chosen for exploration by
7697 entering @code{1} earlier, then since it is as array, you will be
7698 prompted to enter the index of the element in the array that you want
7702 `cs.arr' is an array of `int'.
7703 Enter the index of the element you want to explore in `cs.arr': 5
7705 `(cs.arr)[5]' is a scalar value of type `int'.
7709 Press enter to return to parent value:
7712 In general, at any stage of exploration, you can go deeper towards the
7713 leaf values by responding to the prompts appropriately, or hit the
7714 return key to return to the enclosing data structure (the @i{higher}
7715 level data structure).
7717 Similar to exploring values, you can use the @code{explore} command to
7718 explore types. Instead of specifying a value (which is typically a
7719 variable name or an expression valid in the current context of the
7720 program being debugged), you specify a type name. If you consider the
7721 same example as above, your can explore the type
7722 @code{struct ComplexStruct} by passing the argument
7723 @code{struct ComplexStruct} to the @code{explore} command.
7726 (gdb) explore struct ComplexStruct
7730 By responding to the prompts appropriately in the subsequent interactive
7731 session, you can explore the type @code{struct ComplexStruct} in a
7732 manner similar to how the value @code{cs} was explored in the above
7735 The @code{explore} command also has two sub-commands,
7736 @code{explore value} and @code{explore type}. The former sub-command is
7737 a way to explicitly specify that value exploration of the argument is
7738 being invoked, while the latter is a way to explicitly specify that type
7739 exploration of the argument is being invoked.
7742 @item explore value @var{expr}
7743 @cindex explore value
7744 This sub-command of @code{explore} explores the value of the
7745 expression @var{expr} (if @var{expr} is an expression valid in the
7746 current context of the program being debugged). The behavior of this
7747 command is identical to that of the behavior of the @code{explore}
7748 command being passed the argument @var{expr}.
7750 @item explore type @var{arg}
7751 @cindex explore type
7752 This sub-command of @code{explore} explores the type of @var{arg} (if
7753 @var{arg} is a type visible in the current context of program being
7754 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7755 is an expression valid in the current context of the program being
7756 debugged). If @var{arg} is a type, then the behavior of this command is
7757 identical to that of the @code{explore} command being passed the
7758 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7759 this command will be identical to that of the @code{explore} command
7760 being passed the type of @var{arg} as the argument.
7764 * Expressions:: Expressions
7765 * Ambiguous Expressions:: Ambiguous Expressions
7766 * Variables:: Program variables
7767 * Arrays:: Artificial arrays
7768 * Output Formats:: Output formats
7769 * Memory:: Examining memory
7770 * Auto Display:: Automatic display
7771 * Print Settings:: Print settings
7772 * Pretty Printing:: Python pretty printing
7773 * Value History:: Value history
7774 * Convenience Vars:: Convenience variables
7775 * Convenience Funs:: Convenience functions
7776 * Registers:: Registers
7777 * Floating Point Hardware:: Floating point hardware
7778 * Vector Unit:: Vector Unit
7779 * OS Information:: Auxiliary data provided by operating system
7780 * Memory Region Attributes:: Memory region attributes
7781 * Dump/Restore Files:: Copy between memory and a file
7782 * Core File Generation:: Cause a program dump its core
7783 * Character Sets:: Debugging programs that use a different
7784 character set than GDB does
7785 * Caching Remote Data:: Data caching for remote targets
7786 * Searching Memory:: Searching memory for a sequence of bytes
7790 @section Expressions
7793 @code{print} and many other @value{GDBN} commands accept an expression and
7794 compute its value. Any kind of constant, variable or operator defined
7795 by the programming language you are using is valid in an expression in
7796 @value{GDBN}. This includes conditional expressions, function calls,
7797 casts, and string constants. It also includes preprocessor macros, if
7798 you compiled your program to include this information; see
7801 @cindex arrays in expressions
7802 @value{GDBN} supports array constants in expressions input by
7803 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7804 you can use the command @code{print @{1, 2, 3@}} to create an array
7805 of three integers. If you pass an array to a function or assign it
7806 to a program variable, @value{GDBN} copies the array to memory that
7807 is @code{malloc}ed in the target program.
7809 Because C is so widespread, most of the expressions shown in examples in
7810 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7811 Languages}, for information on how to use expressions in other
7814 In this section, we discuss operators that you can use in @value{GDBN}
7815 expressions regardless of your programming language.
7817 @cindex casts, in expressions
7818 Casts are supported in all languages, not just in C, because it is so
7819 useful to cast a number into a pointer in order to examine a structure
7820 at that address in memory.
7821 @c FIXME: casts supported---Mod2 true?
7823 @value{GDBN} supports these operators, in addition to those common
7824 to programming languages:
7828 @samp{@@} is a binary operator for treating parts of memory as arrays.
7829 @xref{Arrays, ,Artificial Arrays}, for more information.
7832 @samp{::} allows you to specify a variable in terms of the file or
7833 function where it is defined. @xref{Variables, ,Program Variables}.
7835 @cindex @{@var{type}@}
7836 @cindex type casting memory
7837 @cindex memory, viewing as typed object
7838 @cindex casts, to view memory
7839 @item @{@var{type}@} @var{addr}
7840 Refers to an object of type @var{type} stored at address @var{addr} in
7841 memory. @var{addr} may be any expression whose value is an integer or
7842 pointer (but parentheses are required around binary operators, just as in
7843 a cast). This construct is allowed regardless of what kind of data is
7844 normally supposed to reside at @var{addr}.
7847 @node Ambiguous Expressions
7848 @section Ambiguous Expressions
7849 @cindex ambiguous expressions
7851 Expressions can sometimes contain some ambiguous elements. For instance,
7852 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7853 a single function name to be defined several times, for application in
7854 different contexts. This is called @dfn{overloading}. Another example
7855 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7856 templates and is typically instantiated several times, resulting in
7857 the same function name being defined in different contexts.
7859 In some cases and depending on the language, it is possible to adjust
7860 the expression to remove the ambiguity. For instance in C@t{++}, you
7861 can specify the signature of the function you want to break on, as in
7862 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7863 qualified name of your function often makes the expression unambiguous
7866 When an ambiguity that needs to be resolved is detected, the debugger
7867 has the capability to display a menu of numbered choices for each
7868 possibility, and then waits for the selection with the prompt @samp{>}.
7869 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7870 aborts the current command. If the command in which the expression was
7871 used allows more than one choice to be selected, the next option in the
7872 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7875 For example, the following session excerpt shows an attempt to set a
7876 breakpoint at the overloaded symbol @code{String::after}.
7877 We choose three particular definitions of that function name:
7879 @c FIXME! This is likely to change to show arg type lists, at least
7882 (@value{GDBP}) b String::after
7885 [2] file:String.cc; line number:867
7886 [3] file:String.cc; line number:860
7887 [4] file:String.cc; line number:875
7888 [5] file:String.cc; line number:853
7889 [6] file:String.cc; line number:846
7890 [7] file:String.cc; line number:735
7892 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7893 Breakpoint 2 at 0xb344: file String.cc, line 875.
7894 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7895 Multiple breakpoints were set.
7896 Use the "delete" command to delete unwanted
7903 @kindex set multiple-symbols
7904 @item set multiple-symbols @var{mode}
7905 @cindex multiple-symbols menu
7907 This option allows you to adjust the debugger behavior when an expression
7910 By default, @var{mode} is set to @code{all}. If the command with which
7911 the expression is used allows more than one choice, then @value{GDBN}
7912 automatically selects all possible choices. For instance, inserting
7913 a breakpoint on a function using an ambiguous name results in a breakpoint
7914 inserted on each possible match. However, if a unique choice must be made,
7915 then @value{GDBN} uses the menu to help you disambiguate the expression.
7916 For instance, printing the address of an overloaded function will result
7917 in the use of the menu.
7919 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7920 when an ambiguity is detected.
7922 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7923 an error due to the ambiguity and the command is aborted.
7925 @kindex show multiple-symbols
7926 @item show multiple-symbols
7927 Show the current value of the @code{multiple-symbols} setting.
7931 @section Program Variables
7933 The most common kind of expression to use is the name of a variable
7936 Variables in expressions are understood in the selected stack frame
7937 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7941 global (or file-static)
7948 visible according to the scope rules of the
7949 programming language from the point of execution in that frame
7952 @noindent This means that in the function
7967 you can examine and use the variable @code{a} whenever your program is
7968 executing within the function @code{foo}, but you can only use or
7969 examine the variable @code{b} while your program is executing inside
7970 the block where @code{b} is declared.
7972 @cindex variable name conflict
7973 There is an exception: you can refer to a variable or function whose
7974 scope is a single source file even if the current execution point is not
7975 in this file. But it is possible to have more than one such variable or
7976 function with the same name (in different source files). If that
7977 happens, referring to that name has unpredictable effects. If you wish,
7978 you can specify a static variable in a particular function or file by
7979 using the colon-colon (@code{::}) notation:
7981 @cindex colon-colon, context for variables/functions
7983 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7984 @cindex @code{::}, context for variables/functions
7987 @var{file}::@var{variable}
7988 @var{function}::@var{variable}
7992 Here @var{file} or @var{function} is the name of the context for the
7993 static @var{variable}. In the case of file names, you can use quotes to
7994 make sure @value{GDBN} parses the file name as a single word---for example,
7995 to print a global value of @code{x} defined in @file{f2.c}:
7998 (@value{GDBP}) p 'f2.c'::x
8001 The @code{::} notation is normally used for referring to
8002 static variables, since you typically disambiguate uses of local variables
8003 in functions by selecting the appropriate frame and using the
8004 simple name of the variable. However, you may also use this notation
8005 to refer to local variables in frames enclosing the selected frame:
8014 process (a); /* Stop here */
8025 For example, if there is a breakpoint at the commented line,
8026 here is what you might see
8027 when the program stops after executing the call @code{bar(0)}:
8032 (@value{GDBP}) p bar::a
8035 #2 0x080483d0 in foo (a=5) at foobar.c:12
8038 (@value{GDBP}) p bar::a
8042 @cindex C@t{++} scope resolution
8043 These uses of @samp{::} are very rarely in conflict with the very similar
8044 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8045 scope resolution operator in @value{GDBN} expressions.
8046 @c FIXME: Um, so what happens in one of those rare cases where it's in
8049 @cindex wrong values
8050 @cindex variable values, wrong
8051 @cindex function entry/exit, wrong values of variables
8052 @cindex optimized code, wrong values of variables
8054 @emph{Warning:} Occasionally, a local variable may appear to have the
8055 wrong value at certain points in a function---just after entry to a new
8056 scope, and just before exit.
8058 You may see this problem when you are stepping by machine instructions.
8059 This is because, on most machines, it takes more than one instruction to
8060 set up a stack frame (including local variable definitions); if you are
8061 stepping by machine instructions, variables may appear to have the wrong
8062 values until the stack frame is completely built. On exit, it usually
8063 also takes more than one machine instruction to destroy a stack frame;
8064 after you begin stepping through that group of instructions, local
8065 variable definitions may be gone.
8067 This may also happen when the compiler does significant optimizations.
8068 To be sure of always seeing accurate values, turn off all optimization
8071 @cindex ``No symbol "foo" in current context''
8072 Another possible effect of compiler optimizations is to optimize
8073 unused variables out of existence, or assign variables to registers (as
8074 opposed to memory addresses). Depending on the support for such cases
8075 offered by the debug info format used by the compiler, @value{GDBN}
8076 might not be able to display values for such local variables. If that
8077 happens, @value{GDBN} will print a message like this:
8080 No symbol "foo" in current context.
8083 To solve such problems, either recompile without optimizations, or use a
8084 different debug info format, if the compiler supports several such
8085 formats. @xref{Compilation}, for more information on choosing compiler
8086 options. @xref{C, ,C and C@t{++}}, for more information about debug
8087 info formats that are best suited to C@t{++} programs.
8089 If you ask to print an object whose contents are unknown to
8090 @value{GDBN}, e.g., because its data type is not completely specified
8091 by the debug information, @value{GDBN} will say @samp{<incomplete
8092 type>}. @xref{Symbols, incomplete type}, for more about this.
8094 If you append @kbd{@@entry} string to a function parameter name you get its
8095 value at the time the function got called. If the value is not available an
8096 error message is printed. Entry values are available only with some compilers.
8097 Entry values are normally also printed at the function parameter list according
8098 to @ref{set print entry-values}.
8101 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8107 (gdb) print i@@entry
8111 Strings are identified as arrays of @code{char} values without specified
8112 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8113 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8114 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8115 defines literal string type @code{"char"} as @code{char} without a sign.
8120 signed char var1[] = "A";
8123 You get during debugging
8128 $2 = @{65 'A', 0 '\0'@}
8132 @section Artificial Arrays
8134 @cindex artificial array
8136 @kindex @@@r{, referencing memory as an array}
8137 It is often useful to print out several successive objects of the
8138 same type in memory; a section of an array, or an array of
8139 dynamically determined size for which only a pointer exists in the
8142 You can do this by referring to a contiguous span of memory as an
8143 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8144 operand of @samp{@@} should be the first element of the desired array
8145 and be an individual object. The right operand should be the desired length
8146 of the array. The result is an array value whose elements are all of
8147 the type of the left argument. The first element is actually the left
8148 argument; the second element comes from bytes of memory immediately
8149 following those that hold the first element, and so on. Here is an
8150 example. If a program says
8153 int *array = (int *) malloc (len * sizeof (int));
8157 you can print the contents of @code{array} with
8163 The left operand of @samp{@@} must reside in memory. Array values made
8164 with @samp{@@} in this way behave just like other arrays in terms of
8165 subscripting, and are coerced to pointers when used in expressions.
8166 Artificial arrays most often appear in expressions via the value history
8167 (@pxref{Value History, ,Value History}), after printing one out.
8169 Another way to create an artificial array is to use a cast.
8170 This re-interprets a value as if it were an array.
8171 The value need not be in memory:
8173 (@value{GDBP}) p/x (short[2])0x12345678
8174 $1 = @{0x1234, 0x5678@}
8177 As a convenience, if you leave the array length out (as in
8178 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8179 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8181 (@value{GDBP}) p/x (short[])0x12345678
8182 $2 = @{0x1234, 0x5678@}
8185 Sometimes the artificial array mechanism is not quite enough; in
8186 moderately complex data structures, the elements of interest may not
8187 actually be adjacent---for example, if you are interested in the values
8188 of pointers in an array. One useful work-around in this situation is
8189 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8190 Variables}) as a counter in an expression that prints the first
8191 interesting value, and then repeat that expression via @key{RET}. For
8192 instance, suppose you have an array @code{dtab} of pointers to
8193 structures, and you are interested in the values of a field @code{fv}
8194 in each structure. Here is an example of what you might type:
8204 @node Output Formats
8205 @section Output Formats
8207 @cindex formatted output
8208 @cindex output formats
8209 By default, @value{GDBN} prints a value according to its data type. Sometimes
8210 this is not what you want. For example, you might want to print a number
8211 in hex, or a pointer in decimal. Or you might want to view data in memory
8212 at a certain address as a character string or as an instruction. To do
8213 these things, specify an @dfn{output format} when you print a value.
8215 The simplest use of output formats is to say how to print a value
8216 already computed. This is done by starting the arguments of the
8217 @code{print} command with a slash and a format letter. The format
8218 letters supported are:
8222 Regard the bits of the value as an integer, and print the integer in
8226 Print as integer in signed decimal.
8229 Print as integer in unsigned decimal.
8232 Print as integer in octal.
8235 Print as integer in binary. The letter @samp{t} stands for ``two''.
8236 @footnote{@samp{b} cannot be used because these format letters are also
8237 used with the @code{x} command, where @samp{b} stands for ``byte'';
8238 see @ref{Memory,,Examining Memory}.}
8241 @cindex unknown address, locating
8242 @cindex locate address
8243 Print as an address, both absolute in hexadecimal and as an offset from
8244 the nearest preceding symbol. You can use this format used to discover
8245 where (in what function) an unknown address is located:
8248 (@value{GDBP}) p/a 0x54320
8249 $3 = 0x54320 <_initialize_vx+396>
8253 The command @code{info symbol 0x54320} yields similar results.
8254 @xref{Symbols, info symbol}.
8257 Regard as an integer and print it as a character constant. This
8258 prints both the numerical value and its character representation. The
8259 character representation is replaced with the octal escape @samp{\nnn}
8260 for characters outside the 7-bit @sc{ascii} range.
8262 Without this format, @value{GDBN} displays @code{char},
8263 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8264 constants. Single-byte members of vectors are displayed as integer
8268 Regard the bits of the value as a floating point number and print
8269 using typical floating point syntax.
8272 @cindex printing strings
8273 @cindex printing byte arrays
8274 Regard as a string, if possible. With this format, pointers to single-byte
8275 data are displayed as null-terminated strings and arrays of single-byte data
8276 are displayed as fixed-length strings. Other values are displayed in their
8279 Without this format, @value{GDBN} displays pointers to and arrays of
8280 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8281 strings. Single-byte members of a vector are displayed as an integer
8285 @cindex raw printing
8286 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8287 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8288 Printing}). This typically results in a higher-level display of the
8289 value's contents. The @samp{r} format bypasses any Python
8290 pretty-printer which might exist.
8293 For example, to print the program counter in hex (@pxref{Registers}), type
8300 Note that no space is required before the slash; this is because command
8301 names in @value{GDBN} cannot contain a slash.
8303 To reprint the last value in the value history with a different format,
8304 you can use the @code{print} command with just a format and no
8305 expression. For example, @samp{p/x} reprints the last value in hex.
8308 @section Examining Memory
8310 You can use the command @code{x} (for ``examine'') to examine memory in
8311 any of several formats, independently of your program's data types.
8313 @cindex examining memory
8315 @kindex x @r{(examine memory)}
8316 @item x/@var{nfu} @var{addr}
8319 Use the @code{x} command to examine memory.
8322 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8323 much memory to display and how to format it; @var{addr} is an
8324 expression giving the address where you want to start displaying memory.
8325 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8326 Several commands set convenient defaults for @var{addr}.
8329 @item @var{n}, the repeat count
8330 The repeat count is a decimal integer; the default is 1. It specifies
8331 how much memory (counting by units @var{u}) to display.
8332 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8335 @item @var{f}, the display format
8336 The display format is one of the formats used by @code{print}
8337 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8338 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8339 The default is @samp{x} (hexadecimal) initially. The default changes
8340 each time you use either @code{x} or @code{print}.
8342 @item @var{u}, the unit size
8343 The unit size is any of
8349 Halfwords (two bytes).
8351 Words (four bytes). This is the initial default.
8353 Giant words (eight bytes).
8356 Each time you specify a unit size with @code{x}, that size becomes the
8357 default unit the next time you use @code{x}. For the @samp{i} format,
8358 the unit size is ignored and is normally not written. For the @samp{s} format,
8359 the unit size defaults to @samp{b}, unless it is explicitly given.
8360 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8361 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8362 Note that the results depend on the programming language of the
8363 current compilation unit. If the language is C, the @samp{s}
8364 modifier will use the UTF-16 encoding while @samp{w} will use
8365 UTF-32. The encoding is set by the programming language and cannot
8368 @item @var{addr}, starting display address
8369 @var{addr} is the address where you want @value{GDBN} to begin displaying
8370 memory. The expression need not have a pointer value (though it may);
8371 it is always interpreted as an integer address of a byte of memory.
8372 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8373 @var{addr} is usually just after the last address examined---but several
8374 other commands also set the default address: @code{info breakpoints} (to
8375 the address of the last breakpoint listed), @code{info line} (to the
8376 starting address of a line), and @code{print} (if you use it to display
8377 a value from memory).
8380 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8381 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8382 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8383 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8384 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8386 Since the letters indicating unit sizes are all distinct from the
8387 letters specifying output formats, you do not have to remember whether
8388 unit size or format comes first; either order works. The output
8389 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8390 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8392 Even though the unit size @var{u} is ignored for the formats @samp{s}
8393 and @samp{i}, you might still want to use a count @var{n}; for example,
8394 @samp{3i} specifies that you want to see three machine instructions,
8395 including any operands. For convenience, especially when used with
8396 the @code{display} command, the @samp{i} format also prints branch delay
8397 slot instructions, if any, beyond the count specified, which immediately
8398 follow the last instruction that is within the count. The command
8399 @code{disassemble} gives an alternative way of inspecting machine
8400 instructions; see @ref{Machine Code,,Source and Machine Code}.
8402 All the defaults for the arguments to @code{x} are designed to make it
8403 easy to continue scanning memory with minimal specifications each time
8404 you use @code{x}. For example, after you have inspected three machine
8405 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8406 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8407 the repeat count @var{n} is used again; the other arguments default as
8408 for successive uses of @code{x}.
8410 When examining machine instructions, the instruction at current program
8411 counter is shown with a @code{=>} marker. For example:
8414 (@value{GDBP}) x/5i $pc-6
8415 0x804837f <main+11>: mov %esp,%ebp
8416 0x8048381 <main+13>: push %ecx
8417 0x8048382 <main+14>: sub $0x4,%esp
8418 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8419 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8422 @cindex @code{$_}, @code{$__}, and value history
8423 The addresses and contents printed by the @code{x} command are not saved
8424 in the value history because there is often too much of them and they
8425 would get in the way. Instead, @value{GDBN} makes these values available for
8426 subsequent use in expressions as values of the convenience variables
8427 @code{$_} and @code{$__}. After an @code{x} command, the last address
8428 examined is available for use in expressions in the convenience variable
8429 @code{$_}. The contents of that address, as examined, are available in
8430 the convenience variable @code{$__}.
8432 If the @code{x} command has a repeat count, the address and contents saved
8433 are from the last memory unit printed; this is not the same as the last
8434 address printed if several units were printed on the last line of output.
8436 @cindex remote memory comparison
8437 @cindex verify remote memory image
8438 When you are debugging a program running on a remote target machine
8439 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8440 remote machine's memory against the executable file you downloaded to
8441 the target. The @code{compare-sections} command is provided for such
8445 @kindex compare-sections
8446 @item compare-sections @r{[}@var{section-name}@r{]}
8447 Compare the data of a loadable section @var{section-name} in the
8448 executable file of the program being debugged with the same section in
8449 the remote machine's memory, and report any mismatches. With no
8450 arguments, compares all loadable sections. This command's
8451 availability depends on the target's support for the @code{"qCRC"}
8456 @section Automatic Display
8457 @cindex automatic display
8458 @cindex display of expressions
8460 If you find that you want to print the value of an expression frequently
8461 (to see how it changes), you might want to add it to the @dfn{automatic
8462 display list} so that @value{GDBN} prints its value each time your program stops.
8463 Each expression added to the list is given a number to identify it;
8464 to remove an expression from the list, you specify that number.
8465 The automatic display looks like this:
8469 3: bar[5] = (struct hack *) 0x3804
8473 This display shows item numbers, expressions and their current values. As with
8474 displays you request manually using @code{x} or @code{print}, you can
8475 specify the output format you prefer; in fact, @code{display} decides
8476 whether to use @code{print} or @code{x} depending your format
8477 specification---it uses @code{x} if you specify either the @samp{i}
8478 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8482 @item display @var{expr}
8483 Add the expression @var{expr} to the list of expressions to display
8484 each time your program stops. @xref{Expressions, ,Expressions}.
8486 @code{display} does not repeat if you press @key{RET} again after using it.
8488 @item display/@var{fmt} @var{expr}
8489 For @var{fmt} specifying only a display format and not a size or
8490 count, add the expression @var{expr} to the auto-display list but
8491 arrange to display it each time in the specified format @var{fmt}.
8492 @xref{Output Formats,,Output Formats}.
8494 @item display/@var{fmt} @var{addr}
8495 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8496 number of units, add the expression @var{addr} as a memory address to
8497 be examined each time your program stops. Examining means in effect
8498 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8501 For example, @samp{display/i $pc} can be helpful, to see the machine
8502 instruction about to be executed each time execution stops (@samp{$pc}
8503 is a common name for the program counter; @pxref{Registers, ,Registers}).
8506 @kindex delete display
8508 @item undisplay @var{dnums}@dots{}
8509 @itemx delete display @var{dnums}@dots{}
8510 Remove items from the list of expressions to display. Specify the
8511 numbers of the displays that you want affected with the command
8512 argument @var{dnums}. It can be a single display number, one of the
8513 numbers shown in the first field of the @samp{info display} display;
8514 or it could be a range of display numbers, as in @code{2-4}.
8516 @code{undisplay} does not repeat if you press @key{RET} after using it.
8517 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8519 @kindex disable display
8520 @item disable display @var{dnums}@dots{}
8521 Disable the display of item numbers @var{dnums}. A disabled display
8522 item is not printed automatically, but is not forgotten. It may be
8523 enabled again later. Specify the numbers of the displays that you
8524 want affected with the command argument @var{dnums}. It can be a
8525 single display number, one of the numbers shown in the first field of
8526 the @samp{info display} display; or it could be a range of display
8527 numbers, as in @code{2-4}.
8529 @kindex enable display
8530 @item enable display @var{dnums}@dots{}
8531 Enable display of item numbers @var{dnums}. It becomes effective once
8532 again in auto display of its expression, until you specify otherwise.
8533 Specify the numbers of the displays that you want affected with the
8534 command argument @var{dnums}. It can be a single display number, one
8535 of the numbers shown in the first field of the @samp{info display}
8536 display; or it could be a range of display numbers, as in @code{2-4}.
8539 Display the current values of the expressions on the list, just as is
8540 done when your program stops.
8542 @kindex info display
8544 Print the list of expressions previously set up to display
8545 automatically, each one with its item number, but without showing the
8546 values. This includes disabled expressions, which are marked as such.
8547 It also includes expressions which would not be displayed right now
8548 because they refer to automatic variables not currently available.
8551 @cindex display disabled out of scope
8552 If a display expression refers to local variables, then it does not make
8553 sense outside the lexical context for which it was set up. Such an
8554 expression is disabled when execution enters a context where one of its
8555 variables is not defined. For example, if you give the command
8556 @code{display last_char} while inside a function with an argument
8557 @code{last_char}, @value{GDBN} displays this argument while your program
8558 continues to stop inside that function. When it stops elsewhere---where
8559 there is no variable @code{last_char}---the display is disabled
8560 automatically. The next time your program stops where @code{last_char}
8561 is meaningful, you can enable the display expression once again.
8563 @node Print Settings
8564 @section Print Settings
8566 @cindex format options
8567 @cindex print settings
8568 @value{GDBN} provides the following ways to control how arrays, structures,
8569 and symbols are printed.
8572 These settings are useful for debugging programs in any language:
8576 @item set print address
8577 @itemx set print address on
8578 @cindex print/don't print memory addresses
8579 @value{GDBN} prints memory addresses showing the location of stack
8580 traces, structure values, pointer values, breakpoints, and so forth,
8581 even when it also displays the contents of those addresses. The default
8582 is @code{on}. For example, this is what a stack frame display looks like with
8583 @code{set print address on}:
8588 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8590 530 if (lquote != def_lquote)
8594 @item set print address off
8595 Do not print addresses when displaying their contents. For example,
8596 this is the same stack frame displayed with @code{set print address off}:
8600 (@value{GDBP}) set print addr off
8602 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8603 530 if (lquote != def_lquote)
8607 You can use @samp{set print address off} to eliminate all machine
8608 dependent displays from the @value{GDBN} interface. For example, with
8609 @code{print address off}, you should get the same text for backtraces on
8610 all machines---whether or not they involve pointer arguments.
8613 @item show print address
8614 Show whether or not addresses are to be printed.
8617 When @value{GDBN} prints a symbolic address, it normally prints the
8618 closest earlier symbol plus an offset. If that symbol does not uniquely
8619 identify the address (for example, it is a name whose scope is a single
8620 source file), you may need to clarify. One way to do this is with
8621 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8622 you can set @value{GDBN} to print the source file and line number when
8623 it prints a symbolic address:
8626 @item set print symbol-filename on
8627 @cindex source file and line of a symbol
8628 @cindex symbol, source file and line
8629 Tell @value{GDBN} to print the source file name and line number of a
8630 symbol in the symbolic form of an address.
8632 @item set print symbol-filename off
8633 Do not print source file name and line number of a symbol. This is the
8636 @item show print symbol-filename
8637 Show whether or not @value{GDBN} will print the source file name and
8638 line number of a symbol in the symbolic form of an address.
8641 Another situation where it is helpful to show symbol filenames and line
8642 numbers is when disassembling code; @value{GDBN} shows you the line
8643 number and source file that corresponds to each instruction.
8645 Also, you may wish to see the symbolic form only if the address being
8646 printed is reasonably close to the closest earlier symbol:
8649 @item set print max-symbolic-offset @var{max-offset}
8650 @cindex maximum value for offset of closest symbol
8651 Tell @value{GDBN} to only display the symbolic form of an address if the
8652 offset between the closest earlier symbol and the address is less than
8653 @var{max-offset}. The default is 0, which tells @value{GDBN}
8654 to always print the symbolic form of an address if any symbol precedes it.
8656 @item show print max-symbolic-offset
8657 Ask how large the maximum offset is that @value{GDBN} prints in a
8661 @cindex wild pointer, interpreting
8662 @cindex pointer, finding referent
8663 If you have a pointer and you are not sure where it points, try
8664 @samp{set print symbol-filename on}. Then you can determine the name
8665 and source file location of the variable where it points, using
8666 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8667 For example, here @value{GDBN} shows that a variable @code{ptt} points
8668 at another variable @code{t}, defined in @file{hi2.c}:
8671 (@value{GDBP}) set print symbol-filename on
8672 (@value{GDBP}) p/a ptt
8673 $4 = 0xe008 <t in hi2.c>
8677 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8678 does not show the symbol name and filename of the referent, even with
8679 the appropriate @code{set print} options turned on.
8682 You can also enable @samp{/a}-like formatting all the time using
8683 @samp{set print symbol on}:
8686 @item set print symbol on
8687 Tell @value{GDBN} to print the symbol corresponding to an address, if
8690 @item set print symbol off
8691 Tell @value{GDBN} not to print the symbol corresponding to an
8692 address. In this mode, @value{GDBN} will still print the symbol
8693 corresponding to pointers to functions. This is the default.
8695 @item show print symbol
8696 Show whether @value{GDBN} will display the symbol corresponding to an
8700 Other settings control how different kinds of objects are printed:
8703 @item set print array
8704 @itemx set print array on
8705 @cindex pretty print arrays
8706 Pretty print arrays. This format is more convenient to read,
8707 but uses more space. The default is off.
8709 @item set print array off
8710 Return to compressed format for arrays.
8712 @item show print array
8713 Show whether compressed or pretty format is selected for displaying
8716 @cindex print array indexes
8717 @item set print array-indexes
8718 @itemx set print array-indexes on
8719 Print the index of each element when displaying arrays. May be more
8720 convenient to locate a given element in the array or quickly find the
8721 index of a given element in that printed array. The default is off.
8723 @item set print array-indexes off
8724 Stop printing element indexes when displaying arrays.
8726 @item show print array-indexes
8727 Show whether the index of each element is printed when displaying
8730 @item set print elements @var{number-of-elements}
8731 @cindex number of array elements to print
8732 @cindex limit on number of printed array elements
8733 Set a limit on how many elements of an array @value{GDBN} will print.
8734 If @value{GDBN} is printing a large array, it stops printing after it has
8735 printed the number of elements set by the @code{set print elements} command.
8736 This limit also applies to the display of strings.
8737 When @value{GDBN} starts, this limit is set to 200.
8738 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8740 @item show print elements
8741 Display the number of elements of a large array that @value{GDBN} will print.
8742 If the number is 0, then the printing is unlimited.
8744 @item set print frame-arguments @var{value}
8745 @kindex set print frame-arguments
8746 @cindex printing frame argument values
8747 @cindex print all frame argument values
8748 @cindex print frame argument values for scalars only
8749 @cindex do not print frame argument values
8750 This command allows to control how the values of arguments are printed
8751 when the debugger prints a frame (@pxref{Frames}). The possible
8756 The values of all arguments are printed.
8759 Print the value of an argument only if it is a scalar. The value of more
8760 complex arguments such as arrays, structures, unions, etc, is replaced
8761 by @code{@dots{}}. This is the default. Here is an example where
8762 only scalar arguments are shown:
8765 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8770 None of the argument values are printed. Instead, the value of each argument
8771 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8774 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8779 By default, only scalar arguments are printed. This command can be used
8780 to configure the debugger to print the value of all arguments, regardless
8781 of their type. However, it is often advantageous to not print the value
8782 of more complex parameters. For instance, it reduces the amount of
8783 information printed in each frame, making the backtrace more readable.
8784 Also, it improves performance when displaying Ada frames, because
8785 the computation of large arguments can sometimes be CPU-intensive,
8786 especially in large applications. Setting @code{print frame-arguments}
8787 to @code{scalars} (the default) or @code{none} avoids this computation,
8788 thus speeding up the display of each Ada frame.
8790 @item show print frame-arguments
8791 Show how the value of arguments should be displayed when printing a frame.
8793 @anchor{set print entry-values}
8794 @item set print entry-values @var{value}
8795 @kindex set print entry-values
8796 Set printing of frame argument values at function entry. In some cases
8797 @value{GDBN} can determine the value of function argument which was passed by
8798 the function caller, even if the value was modified inside the called function
8799 and therefore is different. With optimized code, the current value could be
8800 unavailable, but the entry value may still be known.
8802 The default value is @code{default} (see below for its description). Older
8803 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8804 this feature will behave in the @code{default} setting the same way as with the
8807 This functionality is currently supported only by DWARF 2 debugging format and
8808 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8809 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8812 The @var{value} parameter can be one of the following:
8816 Print only actual parameter values, never print values from function entry
8820 #0 different (val=6)
8821 #0 lost (val=<optimized out>)
8823 #0 invalid (val=<optimized out>)
8827 Print only parameter values from function entry point. The actual parameter
8828 values are never printed.
8830 #0 equal (val@@entry=5)
8831 #0 different (val@@entry=5)
8832 #0 lost (val@@entry=5)
8833 #0 born (val@@entry=<optimized out>)
8834 #0 invalid (val@@entry=<optimized out>)
8838 Print only parameter values from function entry point. If value from function
8839 entry point is not known while the actual value is known, print the actual
8840 value for such parameter.
8842 #0 equal (val@@entry=5)
8843 #0 different (val@@entry=5)
8844 #0 lost (val@@entry=5)
8846 #0 invalid (val@@entry=<optimized out>)
8850 Print actual parameter values. If actual parameter value is not known while
8851 value from function entry point is known, print the entry point value for such
8855 #0 different (val=6)
8856 #0 lost (val@@entry=5)
8858 #0 invalid (val=<optimized out>)
8862 Always print both the actual parameter value and its value from function entry
8863 point, even if values of one or both are not available due to compiler
8866 #0 equal (val=5, val@@entry=5)
8867 #0 different (val=6, val@@entry=5)
8868 #0 lost (val=<optimized out>, val@@entry=5)
8869 #0 born (val=10, val@@entry=<optimized out>)
8870 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8874 Print the actual parameter value if it is known and also its value from
8875 function entry point if it is known. If neither is known, print for the actual
8876 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8877 values are known and identical, print the shortened
8878 @code{param=param@@entry=VALUE} notation.
8880 #0 equal (val=val@@entry=5)
8881 #0 different (val=6, val@@entry=5)
8882 #0 lost (val@@entry=5)
8884 #0 invalid (val=<optimized out>)
8888 Always print the actual parameter value. Print also its value from function
8889 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8890 if both values are known and identical, print the shortened
8891 @code{param=param@@entry=VALUE} notation.
8893 #0 equal (val=val@@entry=5)
8894 #0 different (val=6, val@@entry=5)
8895 #0 lost (val=<optimized out>, val@@entry=5)
8897 #0 invalid (val=<optimized out>)
8901 For analysis messages on possible failures of frame argument values at function
8902 entry resolution see @ref{set debug entry-values}.
8904 @item show print entry-values
8905 Show the method being used for printing of frame argument values at function
8908 @item set print repeats
8909 @cindex repeated array elements
8910 Set the threshold for suppressing display of repeated array
8911 elements. When the number of consecutive identical elements of an
8912 array exceeds the threshold, @value{GDBN} prints the string
8913 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8914 identical repetitions, instead of displaying the identical elements
8915 themselves. Setting the threshold to zero will cause all elements to
8916 be individually printed. The default threshold is 10.
8918 @item show print repeats
8919 Display the current threshold for printing repeated identical
8922 @item set print null-stop
8923 @cindex @sc{null} elements in arrays
8924 Cause @value{GDBN} to stop printing the characters of an array when the first
8925 @sc{null} is encountered. This is useful when large arrays actually
8926 contain only short strings.
8929 @item show print null-stop
8930 Show whether @value{GDBN} stops printing an array on the first
8931 @sc{null} character.
8933 @item set print pretty on
8934 @cindex print structures in indented form
8935 @cindex indentation in structure display
8936 Cause @value{GDBN} to print structures in an indented format with one member
8937 per line, like this:
8952 @item set print pretty off
8953 Cause @value{GDBN} to print structures in a compact format, like this:
8957 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8958 meat = 0x54 "Pork"@}
8963 This is the default format.
8965 @item show print pretty
8966 Show which format @value{GDBN} is using to print structures.
8968 @item set print sevenbit-strings on
8969 @cindex eight-bit characters in strings
8970 @cindex octal escapes in strings
8971 Print using only seven-bit characters; if this option is set,
8972 @value{GDBN} displays any eight-bit characters (in strings or
8973 character values) using the notation @code{\}@var{nnn}. This setting is
8974 best if you are working in English (@sc{ascii}) and you use the
8975 high-order bit of characters as a marker or ``meta'' bit.
8977 @item set print sevenbit-strings off
8978 Print full eight-bit characters. This allows the use of more
8979 international character sets, and is the default.
8981 @item show print sevenbit-strings
8982 Show whether or not @value{GDBN} is printing only seven-bit characters.
8984 @item set print union on
8985 @cindex unions in structures, printing
8986 Tell @value{GDBN} to print unions which are contained in structures
8987 and other unions. This is the default setting.
8989 @item set print union off
8990 Tell @value{GDBN} not to print unions which are contained in
8991 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8994 @item show print union
8995 Ask @value{GDBN} whether or not it will print unions which are contained in
8996 structures and other unions.
8998 For example, given the declarations
9001 typedef enum @{Tree, Bug@} Species;
9002 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9003 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9014 struct thing foo = @{Tree, @{Acorn@}@};
9018 with @code{set print union on} in effect @samp{p foo} would print
9021 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9025 and with @code{set print union off} in effect it would print
9028 $1 = @{it = Tree, form = @{...@}@}
9032 @code{set print union} affects programs written in C-like languages
9038 These settings are of interest when debugging C@t{++} programs:
9041 @cindex demangling C@t{++} names
9042 @item set print demangle
9043 @itemx set print demangle on
9044 Print C@t{++} names in their source form rather than in the encoded
9045 (``mangled'') form passed to the assembler and linker for type-safe
9046 linkage. The default is on.
9048 @item show print demangle
9049 Show whether C@t{++} names are printed in mangled or demangled form.
9051 @item set print asm-demangle
9052 @itemx set print asm-demangle on
9053 Print C@t{++} names in their source form rather than their mangled form, even
9054 in assembler code printouts such as instruction disassemblies.
9057 @item show print asm-demangle
9058 Show whether C@t{++} names in assembly listings are printed in mangled
9061 @cindex C@t{++} symbol decoding style
9062 @cindex symbol decoding style, C@t{++}
9063 @kindex set demangle-style
9064 @item set demangle-style @var{style}
9065 Choose among several encoding schemes used by different compilers to
9066 represent C@t{++} names. The choices for @var{style} are currently:
9070 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9071 This is the default.
9074 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9077 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9080 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9083 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9084 @strong{Warning:} this setting alone is not sufficient to allow
9085 debugging @code{cfront}-generated executables. @value{GDBN} would
9086 require further enhancement to permit that.
9089 If you omit @var{style}, you will see a list of possible formats.
9091 @item show demangle-style
9092 Display the encoding style currently in use for decoding C@t{++} symbols.
9094 @item set print object
9095 @itemx set print object on
9096 @cindex derived type of an object, printing
9097 @cindex display derived types
9098 When displaying a pointer to an object, identify the @emph{actual}
9099 (derived) type of the object rather than the @emph{declared} type, using
9100 the virtual function table. Note that the virtual function table is
9101 required---this feature can only work for objects that have run-time
9102 type identification; a single virtual method in the object's declared
9103 type is sufficient. Note that this setting is also taken into account when
9104 working with variable objects via MI (@pxref{GDB/MI}).
9106 @item set print object off
9107 Display only the declared type of objects, without reference to the
9108 virtual function table. This is the default setting.
9110 @item show print object
9111 Show whether actual, or declared, object types are displayed.
9113 @item set print static-members
9114 @itemx set print static-members on
9115 @cindex static members of C@t{++} objects
9116 Print static members when displaying a C@t{++} object. The default is on.
9118 @item set print static-members off
9119 Do not print static members when displaying a C@t{++} object.
9121 @item show print static-members
9122 Show whether C@t{++} static members are printed or not.
9124 @item set print pascal_static-members
9125 @itemx set print pascal_static-members on
9126 @cindex static members of Pascal objects
9127 @cindex Pascal objects, static members display
9128 Print static members when displaying a Pascal object. The default is on.
9130 @item set print pascal_static-members off
9131 Do not print static members when displaying a Pascal object.
9133 @item show print pascal_static-members
9134 Show whether Pascal static members are printed or not.
9136 @c These don't work with HP ANSI C++ yet.
9137 @item set print vtbl
9138 @itemx set print vtbl on
9139 @cindex pretty print C@t{++} virtual function tables
9140 @cindex virtual functions (C@t{++}) display
9141 @cindex VTBL display
9142 Pretty print C@t{++} virtual function tables. The default is off.
9143 (The @code{vtbl} commands do not work on programs compiled with the HP
9144 ANSI C@t{++} compiler (@code{aCC}).)
9146 @item set print vtbl off
9147 Do not pretty print C@t{++} virtual function tables.
9149 @item show print vtbl
9150 Show whether C@t{++} virtual function tables are pretty printed, or not.
9153 @node Pretty Printing
9154 @section Pretty Printing
9156 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9157 Python code. It greatly simplifies the display of complex objects. This
9158 mechanism works for both MI and the CLI.
9161 * Pretty-Printer Introduction:: Introduction to pretty-printers
9162 * Pretty-Printer Example:: An example pretty-printer
9163 * Pretty-Printer Commands:: Pretty-printer commands
9166 @node Pretty-Printer Introduction
9167 @subsection Pretty-Printer Introduction
9169 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9170 registered for the value. If there is then @value{GDBN} invokes the
9171 pretty-printer to print the value. Otherwise the value is printed normally.
9173 Pretty-printers are normally named. This makes them easy to manage.
9174 The @samp{info pretty-printer} command will list all the installed
9175 pretty-printers with their names.
9176 If a pretty-printer can handle multiple data types, then its
9177 @dfn{subprinters} are the printers for the individual data types.
9178 Each such subprinter has its own name.
9179 The format of the name is @var{printer-name};@var{subprinter-name}.
9181 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9182 Typically they are automatically loaded and registered when the corresponding
9183 debug information is loaded, thus making them available without having to
9184 do anything special.
9186 There are three places where a pretty-printer can be registered.
9190 Pretty-printers registered globally are available when debugging
9194 Pretty-printers registered with a program space are available only
9195 when debugging that program.
9196 @xref{Progspaces In Python}, for more details on program spaces in Python.
9199 Pretty-printers registered with an objfile are loaded and unloaded
9200 with the corresponding objfile (e.g., shared library).
9201 @xref{Objfiles In Python}, for more details on objfiles in Python.
9204 @xref{Selecting Pretty-Printers}, for further information on how
9205 pretty-printers are selected,
9207 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9210 @node Pretty-Printer Example
9211 @subsection Pretty-Printer Example
9213 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9216 (@value{GDBP}) print s
9218 static npos = 4294967295,
9220 <std::allocator<char>> = @{
9221 <__gnu_cxx::new_allocator<char>> = @{
9222 <No data fields>@}, <No data fields>
9224 members of std::basic_string<char, std::char_traits<char>,
9225 std::allocator<char> >::_Alloc_hider:
9226 _M_p = 0x804a014 "abcd"
9231 With a pretty-printer for @code{std::string} only the contents are printed:
9234 (@value{GDBP}) print s
9238 @node Pretty-Printer Commands
9239 @subsection Pretty-Printer Commands
9240 @cindex pretty-printer commands
9243 @kindex info pretty-printer
9244 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9245 Print the list of installed pretty-printers.
9246 This includes disabled pretty-printers, which are marked as such.
9248 @var{object-regexp} is a regular expression matching the objects
9249 whose pretty-printers to list.
9250 Objects can be @code{global}, the program space's file
9251 (@pxref{Progspaces In Python}),
9252 and the object files within that program space (@pxref{Objfiles In Python}).
9253 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9254 looks up a printer from these three objects.
9256 @var{name-regexp} is a regular expression matching the name of the printers
9259 @kindex disable pretty-printer
9260 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9261 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9262 A disabled pretty-printer is not forgotten, it may be enabled again later.
9264 @kindex enable pretty-printer
9265 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9266 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9271 Suppose we have three pretty-printers installed: one from library1.so
9272 named @code{foo} that prints objects of type @code{foo}, and
9273 another from library2.so named @code{bar} that prints two types of objects,
9274 @code{bar1} and @code{bar2}.
9277 (gdb) info pretty-printer
9284 (gdb) info pretty-printer library2
9289 (gdb) disable pretty-printer library1
9291 2 of 3 printers enabled
9292 (gdb) info pretty-printer
9299 (gdb) disable pretty-printer library2 bar:bar1
9301 1 of 3 printers enabled
9302 (gdb) info pretty-printer library2
9309 (gdb) disable pretty-printer library2 bar
9311 0 of 3 printers enabled
9312 (gdb) info pretty-printer library2
9321 Note that for @code{bar} the entire printer can be disabled,
9322 as can each individual subprinter.
9325 @section Value History
9327 @cindex value history
9328 @cindex history of values printed by @value{GDBN}
9329 Values printed by the @code{print} command are saved in the @value{GDBN}
9330 @dfn{value history}. This allows you to refer to them in other expressions.
9331 Values are kept until the symbol table is re-read or discarded
9332 (for example with the @code{file} or @code{symbol-file} commands).
9333 When the symbol table changes, the value history is discarded,
9334 since the values may contain pointers back to the types defined in the
9339 @cindex history number
9340 The values printed are given @dfn{history numbers} by which you can
9341 refer to them. These are successive integers starting with one.
9342 @code{print} shows you the history number assigned to a value by
9343 printing @samp{$@var{num} = } before the value; here @var{num} is the
9346 To refer to any previous value, use @samp{$} followed by the value's
9347 history number. The way @code{print} labels its output is designed to
9348 remind you of this. Just @code{$} refers to the most recent value in
9349 the history, and @code{$$} refers to the value before that.
9350 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9351 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9352 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9354 For example, suppose you have just printed a pointer to a structure and
9355 want to see the contents of the structure. It suffices to type
9361 If you have a chain of structures where the component @code{next} points
9362 to the next one, you can print the contents of the next one with this:
9369 You can print successive links in the chain by repeating this
9370 command---which you can do by just typing @key{RET}.
9372 Note that the history records values, not expressions. If the value of
9373 @code{x} is 4 and you type these commands:
9381 then the value recorded in the value history by the @code{print} command
9382 remains 4 even though the value of @code{x} has changed.
9387 Print the last ten values in the value history, with their item numbers.
9388 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9389 values} does not change the history.
9391 @item show values @var{n}
9392 Print ten history values centered on history item number @var{n}.
9395 Print ten history values just after the values last printed. If no more
9396 values are available, @code{show values +} produces no display.
9399 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9400 same effect as @samp{show values +}.
9402 @node Convenience Vars
9403 @section Convenience Variables
9405 @cindex convenience variables
9406 @cindex user-defined variables
9407 @value{GDBN} provides @dfn{convenience variables} that you can use within
9408 @value{GDBN} to hold on to a value and refer to it later. These variables
9409 exist entirely within @value{GDBN}; they are not part of your program, and
9410 setting a convenience variable has no direct effect on further execution
9411 of your program. That is why you can use them freely.
9413 Convenience variables are prefixed with @samp{$}. Any name preceded by
9414 @samp{$} can be used for a convenience variable, unless it is one of
9415 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9416 (Value history references, in contrast, are @emph{numbers} preceded
9417 by @samp{$}. @xref{Value History, ,Value History}.)
9419 You can save a value in a convenience variable with an assignment
9420 expression, just as you would set a variable in your program.
9424 set $foo = *object_ptr
9428 would save in @code{$foo} the value contained in the object pointed to by
9431 Using a convenience variable for the first time creates it, but its
9432 value is @code{void} until you assign a new value. You can alter the
9433 value with another assignment at any time.
9435 Convenience variables have no fixed types. You can assign a convenience
9436 variable any type of value, including structures and arrays, even if
9437 that variable already has a value of a different type. The convenience
9438 variable, when used as an expression, has the type of its current value.
9441 @kindex show convenience
9442 @cindex show all user variables and functions
9443 @item show convenience
9444 Print a list of convenience variables used so far, and their values,
9445 as well as a list of the convenience functions.
9446 Abbreviated @code{show conv}.
9448 @kindex init-if-undefined
9449 @cindex convenience variables, initializing
9450 @item init-if-undefined $@var{variable} = @var{expression}
9451 Set a convenience variable if it has not already been set. This is useful
9452 for user-defined commands that keep some state. It is similar, in concept,
9453 to using local static variables with initializers in C (except that
9454 convenience variables are global). It can also be used to allow users to
9455 override default values used in a command script.
9457 If the variable is already defined then the expression is not evaluated so
9458 any side-effects do not occur.
9461 One of the ways to use a convenience variable is as a counter to be
9462 incremented or a pointer to be advanced. For example, to print
9463 a field from successive elements of an array of structures:
9467 print bar[$i++]->contents
9471 Repeat that command by typing @key{RET}.
9473 Some convenience variables are created automatically by @value{GDBN} and given
9474 values likely to be useful.
9477 @vindex $_@r{, convenience variable}
9479 The variable @code{$_} is automatically set by the @code{x} command to
9480 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9481 commands which provide a default address for @code{x} to examine also
9482 set @code{$_} to that address; these commands include @code{info line}
9483 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9484 except when set by the @code{x} command, in which case it is a pointer
9485 to the type of @code{$__}.
9487 @vindex $__@r{, convenience variable}
9489 The variable @code{$__} is automatically set by the @code{x} command
9490 to the value found in the last address examined. Its type is chosen
9491 to match the format in which the data was printed.
9494 @vindex $_exitcode@r{, convenience variable}
9495 The variable @code{$_exitcode} is automatically set to the exit code when
9496 the program being debugged terminates.
9499 @itemx $_probe_arg0@dots{}$_probe_arg11
9500 Arguments to a static probe. @xref{Static Probe Points}.
9503 @vindex $_sdata@r{, inspect, convenience variable}
9504 The variable @code{$_sdata} contains extra collected static tracepoint
9505 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9506 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9507 if extra static tracepoint data has not been collected.
9510 @vindex $_siginfo@r{, convenience variable}
9511 The variable @code{$_siginfo} contains extra signal information
9512 (@pxref{extra signal information}). Note that @code{$_siginfo}
9513 could be empty, if the application has not yet received any signals.
9514 For example, it will be empty before you execute the @code{run} command.
9517 @vindex $_tlb@r{, convenience variable}
9518 The variable @code{$_tlb} is automatically set when debugging
9519 applications running on MS-Windows in native mode or connected to
9520 gdbserver that supports the @code{qGetTIBAddr} request.
9521 @xref{General Query Packets}.
9522 This variable contains the address of the thread information block.
9526 On HP-UX systems, if you refer to a function or variable name that
9527 begins with a dollar sign, @value{GDBN} searches for a user or system
9528 name first, before it searches for a convenience variable.
9530 @node Convenience Funs
9531 @section Convenience Functions
9533 @cindex convenience functions
9534 @value{GDBN} also supplies some @dfn{convenience functions}. These
9535 have a syntax similar to convenience variables. A convenience
9536 function can be used in an expression just like an ordinary function;
9537 however, a convenience function is implemented internally to
9540 These functions require @value{GDBN} to be configured with
9541 @code{Python} support.
9545 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9546 @findex $_memeq@r{, convenience function}
9547 Returns one if the @var{length} bytes at the addresses given by
9548 @var{buf1} and @var{buf2} are equal.
9549 Otherwise it returns zero.
9551 @item $_regex(@var{str}, @var{regex})
9552 @findex $_regex@r{, convenience function}
9553 Returns one if the string @var{str} matches the regular expression
9554 @var{regex}. Otherwise it returns zero.
9555 The syntax of the regular expression is that specified by @code{Python}'s
9556 regular expression support.
9558 @item $_streq(@var{str1}, @var{str2})
9559 @findex $_streq@r{, convenience function}
9560 Returns one if the strings @var{str1} and @var{str2} are equal.
9561 Otherwise it returns zero.
9563 @item $_strlen(@var{str})
9564 @findex $_strlen@r{, convenience function}
9565 Returns the length of string @var{str}.
9569 @value{GDBN} provides the ability to list and get help on
9570 convenience functions.
9574 @kindex help function
9575 @cindex show all convenience functions
9576 Print a list of all convenience functions.
9583 You can refer to machine register contents, in expressions, as variables
9584 with names starting with @samp{$}. The names of registers are different
9585 for each machine; use @code{info registers} to see the names used on
9589 @kindex info registers
9590 @item info registers
9591 Print the names and values of all registers except floating-point
9592 and vector registers (in the selected stack frame).
9594 @kindex info all-registers
9595 @cindex floating point registers
9596 @item info all-registers
9597 Print the names and values of all registers, including floating-point
9598 and vector registers (in the selected stack frame).
9600 @item info registers @var{regname} @dots{}
9601 Print the @dfn{relativized} value of each specified register @var{regname}.
9602 As discussed in detail below, register values are normally relative to
9603 the selected stack frame. @var{regname} may be any register name valid on
9604 the machine you are using, with or without the initial @samp{$}.
9607 @cindex stack pointer register
9608 @cindex program counter register
9609 @cindex process status register
9610 @cindex frame pointer register
9611 @cindex standard registers
9612 @value{GDBN} has four ``standard'' register names that are available (in
9613 expressions) on most machines---whenever they do not conflict with an
9614 architecture's canonical mnemonics for registers. The register names
9615 @code{$pc} and @code{$sp} are used for the program counter register and
9616 the stack pointer. @code{$fp} is used for a register that contains a
9617 pointer to the current stack frame, and @code{$ps} is used for a
9618 register that contains the processor status. For example,
9619 you could print the program counter in hex with
9626 or print the instruction to be executed next with
9633 or add four to the stack pointer@footnote{This is a way of removing
9634 one word from the stack, on machines where stacks grow downward in
9635 memory (most machines, nowadays). This assumes that the innermost
9636 stack frame is selected; setting @code{$sp} is not allowed when other
9637 stack frames are selected. To pop entire frames off the stack,
9638 regardless of machine architecture, use @code{return};
9639 see @ref{Returning, ,Returning from a Function}.} with
9645 Whenever possible, these four standard register names are available on
9646 your machine even though the machine has different canonical mnemonics,
9647 so long as there is no conflict. The @code{info registers} command
9648 shows the canonical names. For example, on the SPARC, @code{info
9649 registers} displays the processor status register as @code{$psr} but you
9650 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9651 is an alias for the @sc{eflags} register.
9653 @value{GDBN} always considers the contents of an ordinary register as an
9654 integer when the register is examined in this way. Some machines have
9655 special registers which can hold nothing but floating point; these
9656 registers are considered to have floating point values. There is no way
9657 to refer to the contents of an ordinary register as floating point value
9658 (although you can @emph{print} it as a floating point value with
9659 @samp{print/f $@var{regname}}).
9661 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9662 means that the data format in which the register contents are saved by
9663 the operating system is not the same one that your program normally
9664 sees. For example, the registers of the 68881 floating point
9665 coprocessor are always saved in ``extended'' (raw) format, but all C
9666 programs expect to work with ``double'' (virtual) format. In such
9667 cases, @value{GDBN} normally works with the virtual format only (the format
9668 that makes sense for your program), but the @code{info registers} command
9669 prints the data in both formats.
9671 @cindex SSE registers (x86)
9672 @cindex MMX registers (x86)
9673 Some machines have special registers whose contents can be interpreted
9674 in several different ways. For example, modern x86-based machines
9675 have SSE and MMX registers that can hold several values packed
9676 together in several different formats. @value{GDBN} refers to such
9677 registers in @code{struct} notation:
9680 (@value{GDBP}) print $xmm1
9682 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9683 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9684 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9685 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9686 v4_int32 = @{0, 20657912, 11, 13@},
9687 v2_int64 = @{88725056443645952, 55834574859@},
9688 uint128 = 0x0000000d0000000b013b36f800000000
9693 To set values of such registers, you need to tell @value{GDBN} which
9694 view of the register you wish to change, as if you were assigning
9695 value to a @code{struct} member:
9698 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9701 Normally, register values are relative to the selected stack frame
9702 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9703 value that the register would contain if all stack frames farther in
9704 were exited and their saved registers restored. In order to see the
9705 true contents of hardware registers, you must select the innermost
9706 frame (with @samp{frame 0}).
9708 However, @value{GDBN} must deduce where registers are saved, from the machine
9709 code generated by your compiler. If some registers are not saved, or if
9710 @value{GDBN} is unable to locate the saved registers, the selected stack
9711 frame makes no difference.
9713 @node Floating Point Hardware
9714 @section Floating Point Hardware
9715 @cindex floating point
9717 Depending on the configuration, @value{GDBN} may be able to give
9718 you more information about the status of the floating point hardware.
9723 Display hardware-dependent information about the floating
9724 point unit. The exact contents and layout vary depending on the
9725 floating point chip. Currently, @samp{info float} is supported on
9726 the ARM and x86 machines.
9730 @section Vector Unit
9733 Depending on the configuration, @value{GDBN} may be able to give you
9734 more information about the status of the vector unit.
9739 Display information about the vector unit. The exact contents and
9740 layout vary depending on the hardware.
9743 @node OS Information
9744 @section Operating System Auxiliary Information
9745 @cindex OS information
9747 @value{GDBN} provides interfaces to useful OS facilities that can help
9748 you debug your program.
9750 @cindex auxiliary vector
9751 @cindex vector, auxiliary
9752 Some operating systems supply an @dfn{auxiliary vector} to programs at
9753 startup. This is akin to the arguments and environment that you
9754 specify for a program, but contains a system-dependent variety of
9755 binary values that tell system libraries important details about the
9756 hardware, operating system, and process. Each value's purpose is
9757 identified by an integer tag; the meanings are well-known but system-specific.
9758 Depending on the configuration and operating system facilities,
9759 @value{GDBN} may be able to show you this information. For remote
9760 targets, this functionality may further depend on the remote stub's
9761 support of the @samp{qXfer:auxv:read} packet, see
9762 @ref{qXfer auxiliary vector read}.
9767 Display the auxiliary vector of the inferior, which can be either a
9768 live process or a core dump file. @value{GDBN} prints each tag value
9769 numerically, and also shows names and text descriptions for recognized
9770 tags. Some values in the vector are numbers, some bit masks, and some
9771 pointers to strings or other data. @value{GDBN} displays each value in the
9772 most appropriate form for a recognized tag, and in hexadecimal for
9773 an unrecognized tag.
9776 On some targets, @value{GDBN} can access operating system-specific
9777 information and show it to you. The types of information available
9778 will differ depending on the type of operating system running on the
9779 target. The mechanism used to fetch the data is described in
9780 @ref{Operating System Information}. For remote targets, this
9781 functionality depends on the remote stub's support of the
9782 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9786 @item info os @var{infotype}
9788 Display OS information of the requested type.
9790 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9792 @anchor{linux info os infotypes}
9794 @kindex info os processes
9796 Display the list of processes on the target. For each process,
9797 @value{GDBN} prints the process identifier, the name of the user, the
9798 command corresponding to the process, and the list of processor cores
9799 that the process is currently running on. (To understand what these
9800 properties mean, for this and the following info types, please consult
9801 the general @sc{gnu}/Linux documentation.)
9803 @kindex info os procgroups
9805 Display the list of process groups on the target. For each process,
9806 @value{GDBN} prints the identifier of the process group that it belongs
9807 to, the command corresponding to the process group leader, the process
9808 identifier, and the command line of the process. The list is sorted
9809 first by the process group identifier, then by the process identifier,
9810 so that processes belonging to the same process group are grouped together
9811 and the process group leader is listed first.
9813 @kindex info os threads
9815 Display the list of threads running on the target. For each thread,
9816 @value{GDBN} prints the identifier of the process that the thread
9817 belongs to, the command of the process, the thread identifier, and the
9818 processor core that it is currently running on. The main thread of a
9819 process is not listed.
9821 @kindex info os files
9823 Display the list of open file descriptors on the target. For each
9824 file descriptor, @value{GDBN} prints the identifier of the process
9825 owning the descriptor, the command of the owning process, the value
9826 of the descriptor, and the target of the descriptor.
9828 @kindex info os sockets
9830 Display the list of Internet-domain sockets on the target. For each
9831 socket, @value{GDBN} prints the address and port of the local and
9832 remote endpoints, the current state of the connection, the creator of
9833 the socket, the IP address family of the socket, and the type of the
9838 Display the list of all System V shared-memory regions on the target.
9839 For each shared-memory region, @value{GDBN} prints the region key,
9840 the shared-memory identifier, the access permissions, the size of the
9841 region, the process that created the region, the process that last
9842 attached to or detached from the region, the current number of live
9843 attaches to the region, and the times at which the region was last
9844 attached to, detach from, and changed.
9846 @kindex info os semaphores
9848 Display the list of all System V semaphore sets on the target. For each
9849 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9850 set identifier, the access permissions, the number of semaphores in the
9851 set, the user and group of the owner and creator of the semaphore set,
9852 and the times at which the semaphore set was operated upon and changed.
9856 Display the list of all System V message queues on the target. For each
9857 message queue, @value{GDBN} prints the message queue key, the message
9858 queue identifier, the access permissions, the current number of bytes
9859 on the queue, the current number of messages on the queue, the processes
9860 that last sent and received a message on the queue, the user and group
9861 of the owner and creator of the message queue, the times at which a
9862 message was last sent and received on the queue, and the time at which
9863 the message queue was last changed.
9865 @kindex info os modules
9867 Display the list of all loaded kernel modules on the target. For each
9868 module, @value{GDBN} prints the module name, the size of the module in
9869 bytes, the number of times the module is used, the dependencies of the
9870 module, the status of the module, and the address of the loaded module
9875 If @var{infotype} is omitted, then list the possible values for
9876 @var{infotype} and the kind of OS information available for each
9877 @var{infotype}. If the target does not return a list of possible
9878 types, this command will report an error.
9881 @node Memory Region Attributes
9882 @section Memory Region Attributes
9883 @cindex memory region attributes
9885 @dfn{Memory region attributes} allow you to describe special handling
9886 required by regions of your target's memory. @value{GDBN} uses
9887 attributes to determine whether to allow certain types of memory
9888 accesses; whether to use specific width accesses; and whether to cache
9889 target memory. By default the description of memory regions is
9890 fetched from the target (if the current target supports this), but the
9891 user can override the fetched regions.
9893 Defined memory regions can be individually enabled and disabled. When a
9894 memory region is disabled, @value{GDBN} uses the default attributes when
9895 accessing memory in that region. Similarly, if no memory regions have
9896 been defined, @value{GDBN} uses the default attributes when accessing
9899 When a memory region is defined, it is given a number to identify it;
9900 to enable, disable, or remove a memory region, you specify that number.
9904 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9905 Define a memory region bounded by @var{lower} and @var{upper} with
9906 attributes @var{attributes}@dots{}, and add it to the list of regions
9907 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9908 case: it is treated as the target's maximum memory address.
9909 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9912 Discard any user changes to the memory regions and use target-supplied
9913 regions, if available, or no regions if the target does not support.
9916 @item delete mem @var{nums}@dots{}
9917 Remove memory regions @var{nums}@dots{} from the list of regions
9918 monitored by @value{GDBN}.
9921 @item disable mem @var{nums}@dots{}
9922 Disable monitoring of memory regions @var{nums}@dots{}.
9923 A disabled memory region is not forgotten.
9924 It may be enabled again later.
9927 @item enable mem @var{nums}@dots{}
9928 Enable monitoring of memory regions @var{nums}@dots{}.
9932 Print a table of all defined memory regions, with the following columns
9936 @item Memory Region Number
9937 @item Enabled or Disabled.
9938 Enabled memory regions are marked with @samp{y}.
9939 Disabled memory regions are marked with @samp{n}.
9942 The address defining the inclusive lower bound of the memory region.
9945 The address defining the exclusive upper bound of the memory region.
9948 The list of attributes set for this memory region.
9953 @subsection Attributes
9955 @subsubsection Memory Access Mode
9956 The access mode attributes set whether @value{GDBN} may make read or
9957 write accesses to a memory region.
9959 While these attributes prevent @value{GDBN} from performing invalid
9960 memory accesses, they do nothing to prevent the target system, I/O DMA,
9961 etc.@: from accessing memory.
9965 Memory is read only.
9967 Memory is write only.
9969 Memory is read/write. This is the default.
9972 @subsubsection Memory Access Size
9973 The access size attribute tells @value{GDBN} to use specific sized
9974 accesses in the memory region. Often memory mapped device registers
9975 require specific sized accesses. If no access size attribute is
9976 specified, @value{GDBN} may use accesses of any size.
9980 Use 8 bit memory accesses.
9982 Use 16 bit memory accesses.
9984 Use 32 bit memory accesses.
9986 Use 64 bit memory accesses.
9989 @c @subsubsection Hardware/Software Breakpoints
9990 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9991 @c will use hardware or software breakpoints for the internal breakpoints
9992 @c used by the step, next, finish, until, etc. commands.
9996 @c Always use hardware breakpoints
9997 @c @item swbreak (default)
10000 @subsubsection Data Cache
10001 The data cache attributes set whether @value{GDBN} will cache target
10002 memory. While this generally improves performance by reducing debug
10003 protocol overhead, it can lead to incorrect results because @value{GDBN}
10004 does not know about volatile variables or memory mapped device
10009 Enable @value{GDBN} to cache target memory.
10011 Disable @value{GDBN} from caching target memory. This is the default.
10014 @subsection Memory Access Checking
10015 @value{GDBN} can be instructed to refuse accesses to memory that is
10016 not explicitly described. This can be useful if accessing such
10017 regions has undesired effects for a specific target, or to provide
10018 better error checking. The following commands control this behaviour.
10021 @kindex set mem inaccessible-by-default
10022 @item set mem inaccessible-by-default [on|off]
10023 If @code{on} is specified, make @value{GDBN} treat memory not
10024 explicitly described by the memory ranges as non-existent and refuse accesses
10025 to such memory. The checks are only performed if there's at least one
10026 memory range defined. If @code{off} is specified, make @value{GDBN}
10027 treat the memory not explicitly described by the memory ranges as RAM.
10028 The default value is @code{on}.
10029 @kindex show mem inaccessible-by-default
10030 @item show mem inaccessible-by-default
10031 Show the current handling of accesses to unknown memory.
10035 @c @subsubsection Memory Write Verification
10036 @c The memory write verification attributes set whether @value{GDBN}
10037 @c will re-reads data after each write to verify the write was successful.
10041 @c @item noverify (default)
10044 @node Dump/Restore Files
10045 @section Copy Between Memory and a File
10046 @cindex dump/restore files
10047 @cindex append data to a file
10048 @cindex dump data to a file
10049 @cindex restore data from a file
10051 You can use the commands @code{dump}, @code{append}, and
10052 @code{restore} to copy data between target memory and a file. The
10053 @code{dump} and @code{append} commands write data to a file, and the
10054 @code{restore} command reads data from a file back into the inferior's
10055 memory. Files may be in binary, Motorola S-record, Intel hex, or
10056 Tektronix Hex format; however, @value{GDBN} can only append to binary
10062 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10063 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10064 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10065 or the value of @var{expr}, to @var{filename} in the given format.
10067 The @var{format} parameter may be any one of:
10074 Motorola S-record format.
10076 Tektronix Hex format.
10079 @value{GDBN} uses the same definitions of these formats as the
10080 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10081 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10085 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10086 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10087 Append the contents of memory from @var{start_addr} to @var{end_addr},
10088 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10089 (@value{GDBN} can only append data to files in raw binary form.)
10092 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10093 Restore the contents of file @var{filename} into memory. The
10094 @code{restore} command can automatically recognize any known @sc{bfd}
10095 file format, except for raw binary. To restore a raw binary file you
10096 must specify the optional keyword @code{binary} after the filename.
10098 If @var{bias} is non-zero, its value will be added to the addresses
10099 contained in the file. Binary files always start at address zero, so
10100 they will be restored at address @var{bias}. Other bfd files have
10101 a built-in location; they will be restored at offset @var{bias}
10102 from that location.
10104 If @var{start} and/or @var{end} are non-zero, then only data between
10105 file offset @var{start} and file offset @var{end} will be restored.
10106 These offsets are relative to the addresses in the file, before
10107 the @var{bias} argument is applied.
10111 @node Core File Generation
10112 @section How to Produce a Core File from Your Program
10113 @cindex dump core from inferior
10115 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10116 image of a running process and its process status (register values
10117 etc.). Its primary use is post-mortem debugging of a program that
10118 crashed while it ran outside a debugger. A program that crashes
10119 automatically produces a core file, unless this feature is disabled by
10120 the user. @xref{Files}, for information on invoking @value{GDBN} in
10121 the post-mortem debugging mode.
10123 Occasionally, you may wish to produce a core file of the program you
10124 are debugging in order to preserve a snapshot of its state.
10125 @value{GDBN} has a special command for that.
10129 @kindex generate-core-file
10130 @item generate-core-file [@var{file}]
10131 @itemx gcore [@var{file}]
10132 Produce a core dump of the inferior process. The optional argument
10133 @var{file} specifies the file name where to put the core dump. If not
10134 specified, the file name defaults to @file{core.@var{pid}}, where
10135 @var{pid} is the inferior process ID.
10137 Note that this command is implemented only for some systems (as of
10138 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10141 @node Character Sets
10142 @section Character Sets
10143 @cindex character sets
10145 @cindex translating between character sets
10146 @cindex host character set
10147 @cindex target character set
10149 If the program you are debugging uses a different character set to
10150 represent characters and strings than the one @value{GDBN} uses itself,
10151 @value{GDBN} can automatically translate between the character sets for
10152 you. The character set @value{GDBN} uses we call the @dfn{host
10153 character set}; the one the inferior program uses we call the
10154 @dfn{target character set}.
10156 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10157 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10158 remote protocol (@pxref{Remote Debugging}) to debug a program
10159 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10160 then the host character set is Latin-1, and the target character set is
10161 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10162 target-charset EBCDIC-US}, then @value{GDBN} translates between
10163 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10164 character and string literals in expressions.
10166 @value{GDBN} has no way to automatically recognize which character set
10167 the inferior program uses; you must tell it, using the @code{set
10168 target-charset} command, described below.
10170 Here are the commands for controlling @value{GDBN}'s character set
10174 @item set target-charset @var{charset}
10175 @kindex set target-charset
10176 Set the current target character set to @var{charset}. To display the
10177 list of supported target character sets, type
10178 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10180 @item set host-charset @var{charset}
10181 @kindex set host-charset
10182 Set the current host character set to @var{charset}.
10184 By default, @value{GDBN} uses a host character set appropriate to the
10185 system it is running on; you can override that default using the
10186 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10187 automatically determine the appropriate host character set. In this
10188 case, @value{GDBN} uses @samp{UTF-8}.
10190 @value{GDBN} can only use certain character sets as its host character
10191 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10192 @value{GDBN} will list the host character sets it supports.
10194 @item set charset @var{charset}
10195 @kindex set charset
10196 Set the current host and target character sets to @var{charset}. As
10197 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10198 @value{GDBN} will list the names of the character sets that can be used
10199 for both host and target.
10202 @kindex show charset
10203 Show the names of the current host and target character sets.
10205 @item show host-charset
10206 @kindex show host-charset
10207 Show the name of the current host character set.
10209 @item show target-charset
10210 @kindex show target-charset
10211 Show the name of the current target character set.
10213 @item set target-wide-charset @var{charset}
10214 @kindex set target-wide-charset
10215 Set the current target's wide character set to @var{charset}. This is
10216 the character set used by the target's @code{wchar_t} type. To
10217 display the list of supported wide character sets, type
10218 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10220 @item show target-wide-charset
10221 @kindex show target-wide-charset
10222 Show the name of the current target's wide character set.
10225 Here is an example of @value{GDBN}'s character set support in action.
10226 Assume that the following source code has been placed in the file
10227 @file{charset-test.c}:
10233 = @{72, 101, 108, 108, 111, 44, 32, 119,
10234 111, 114, 108, 100, 33, 10, 0@};
10235 char ibm1047_hello[]
10236 = @{200, 133, 147, 147, 150, 107, 64, 166,
10237 150, 153, 147, 132, 90, 37, 0@};
10241 printf ("Hello, world!\n");
10245 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10246 containing the string @samp{Hello, world!} followed by a newline,
10247 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10249 We compile the program, and invoke the debugger on it:
10252 $ gcc -g charset-test.c -o charset-test
10253 $ gdb -nw charset-test
10254 GNU gdb 2001-12-19-cvs
10255 Copyright 2001 Free Software Foundation, Inc.
10260 We can use the @code{show charset} command to see what character sets
10261 @value{GDBN} is currently using to interpret and display characters and
10265 (@value{GDBP}) show charset
10266 The current host and target character set is `ISO-8859-1'.
10270 For the sake of printing this manual, let's use @sc{ascii} as our
10271 initial character set:
10273 (@value{GDBP}) set charset ASCII
10274 (@value{GDBP}) show charset
10275 The current host and target character set is `ASCII'.
10279 Let's assume that @sc{ascii} is indeed the correct character set for our
10280 host system --- in other words, let's assume that if @value{GDBN} prints
10281 characters using the @sc{ascii} character set, our terminal will display
10282 them properly. Since our current target character set is also
10283 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10286 (@value{GDBP}) print ascii_hello
10287 $1 = 0x401698 "Hello, world!\n"
10288 (@value{GDBP}) print ascii_hello[0]
10293 @value{GDBN} uses the target character set for character and string
10294 literals you use in expressions:
10297 (@value{GDBP}) print '+'
10302 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10305 @value{GDBN} relies on the user to tell it which character set the
10306 target program uses. If we print @code{ibm1047_hello} while our target
10307 character set is still @sc{ascii}, we get jibberish:
10310 (@value{GDBP}) print ibm1047_hello
10311 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10312 (@value{GDBP}) print ibm1047_hello[0]
10317 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10318 @value{GDBN} tells us the character sets it supports:
10321 (@value{GDBP}) set target-charset
10322 ASCII EBCDIC-US IBM1047 ISO-8859-1
10323 (@value{GDBP}) set target-charset
10326 We can select @sc{ibm1047} as our target character set, and examine the
10327 program's strings again. Now the @sc{ascii} string is wrong, but
10328 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10329 target character set, @sc{ibm1047}, to the host character set,
10330 @sc{ascii}, and they display correctly:
10333 (@value{GDBP}) set target-charset IBM1047
10334 (@value{GDBP}) show charset
10335 The current host character set is `ASCII'.
10336 The current target character set is `IBM1047'.
10337 (@value{GDBP}) print ascii_hello
10338 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10339 (@value{GDBP}) print ascii_hello[0]
10341 (@value{GDBP}) print ibm1047_hello
10342 $8 = 0x4016a8 "Hello, world!\n"
10343 (@value{GDBP}) print ibm1047_hello[0]
10348 As above, @value{GDBN} uses the target character set for character and
10349 string literals you use in expressions:
10352 (@value{GDBP}) print '+'
10357 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10360 @node Caching Remote Data
10361 @section Caching Data of Remote Targets
10362 @cindex caching data of remote targets
10364 @value{GDBN} caches data exchanged between the debugger and a
10365 remote target (@pxref{Remote Debugging}). Such caching generally improves
10366 performance, because it reduces the overhead of the remote protocol by
10367 bundling memory reads and writes into large chunks. Unfortunately, simply
10368 caching everything would lead to incorrect results, since @value{GDBN}
10369 does not necessarily know anything about volatile values, memory-mapped I/O
10370 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10371 memory can be changed @emph{while} a gdb command is executing.
10372 Therefore, by default, @value{GDBN} only caches data
10373 known to be on the stack@footnote{In non-stop mode, it is moderately
10374 rare for a running thread to modify the stack of a stopped thread
10375 in a way that would interfere with a backtrace, and caching of
10376 stack reads provides a significant speed up of remote backtraces.}.
10377 Other regions of memory can be explicitly marked as
10378 cacheable; see @pxref{Memory Region Attributes}.
10381 @kindex set remotecache
10382 @item set remotecache on
10383 @itemx set remotecache off
10384 This option no longer does anything; it exists for compatibility
10387 @kindex show remotecache
10388 @item show remotecache
10389 Show the current state of the obsolete remotecache flag.
10391 @kindex set stack-cache
10392 @item set stack-cache on
10393 @itemx set stack-cache off
10394 Enable or disable caching of stack accesses. When @code{ON}, use
10395 caching. By default, this option is @code{ON}.
10397 @kindex show stack-cache
10398 @item show stack-cache
10399 Show the current state of data caching for memory accesses.
10401 @kindex info dcache
10402 @item info dcache @r{[}line@r{]}
10403 Print the information about the data cache performance. The
10404 information displayed includes the dcache width and depth, and for
10405 each cache line, its number, address, and how many times it was
10406 referenced. This command is useful for debugging the data cache
10409 If a line number is specified, the contents of that line will be
10412 @item set dcache size @var{size}
10413 @cindex dcache size
10414 @kindex set dcache size
10415 Set maximum number of entries in dcache (dcache depth above).
10417 @item set dcache line-size @var{line-size}
10418 @cindex dcache line-size
10419 @kindex set dcache line-size
10420 Set number of bytes each dcache entry caches (dcache width above).
10421 Must be a power of 2.
10423 @item show dcache size
10424 @kindex show dcache size
10425 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10427 @item show dcache line-size
10428 @kindex show dcache line-size
10429 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10433 @node Searching Memory
10434 @section Search Memory
10435 @cindex searching memory
10437 Memory can be searched for a particular sequence of bytes with the
10438 @code{find} command.
10442 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10443 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10444 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10445 etc. The search begins at address @var{start_addr} and continues for either
10446 @var{len} bytes or through to @var{end_addr} inclusive.
10449 @var{s} and @var{n} are optional parameters.
10450 They may be specified in either order, apart or together.
10453 @item @var{s}, search query size
10454 The size of each search query value.
10460 halfwords (two bytes)
10464 giant words (eight bytes)
10467 All values are interpreted in the current language.
10468 This means, for example, that if the current source language is C/C@t{++}
10469 then searching for the string ``hello'' includes the trailing '\0'.
10471 If the value size is not specified, it is taken from the
10472 value's type in the current language.
10473 This is useful when one wants to specify the search
10474 pattern as a mixture of types.
10475 Note that this means, for example, that in the case of C-like languages
10476 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10477 which is typically four bytes.
10479 @item @var{n}, maximum number of finds
10480 The maximum number of matches to print. The default is to print all finds.
10483 You can use strings as search values. Quote them with double-quotes
10485 The string value is copied into the search pattern byte by byte,
10486 regardless of the endianness of the target and the size specification.
10488 The address of each match found is printed as well as a count of the
10489 number of matches found.
10491 The address of the last value found is stored in convenience variable
10493 A count of the number of matches is stored in @samp{$numfound}.
10495 For example, if stopped at the @code{printf} in this function:
10501 static char hello[] = "hello-hello";
10502 static struct @{ char c; short s; int i; @}
10503 __attribute__ ((packed)) mixed
10504 = @{ 'c', 0x1234, 0x87654321 @};
10505 printf ("%s\n", hello);
10510 you get during debugging:
10513 (gdb) find &hello[0], +sizeof(hello), "hello"
10514 0x804956d <hello.1620+6>
10516 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10517 0x8049567 <hello.1620>
10518 0x804956d <hello.1620+6>
10520 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10521 0x8049567 <hello.1620>
10523 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10524 0x8049560 <mixed.1625>
10526 (gdb) print $numfound
10529 $2 = (void *) 0x8049560
10532 @node Optimized Code
10533 @chapter Debugging Optimized Code
10534 @cindex optimized code, debugging
10535 @cindex debugging optimized code
10537 Almost all compilers support optimization. With optimization
10538 disabled, the compiler generates assembly code that corresponds
10539 directly to your source code, in a simplistic way. As the compiler
10540 applies more powerful optimizations, the generated assembly code
10541 diverges from your original source code. With help from debugging
10542 information generated by the compiler, @value{GDBN} can map from
10543 the running program back to constructs from your original source.
10545 @value{GDBN} is more accurate with optimization disabled. If you
10546 can recompile without optimization, it is easier to follow the
10547 progress of your program during debugging. But, there are many cases
10548 where you may need to debug an optimized version.
10550 When you debug a program compiled with @samp{-g -O}, remember that the
10551 optimizer has rearranged your code; the debugger shows you what is
10552 really there. Do not be too surprised when the execution path does not
10553 exactly match your source file! An extreme example: if you define a
10554 variable, but never use it, @value{GDBN} never sees that
10555 variable---because the compiler optimizes it out of existence.
10557 Some things do not work as well with @samp{-g -O} as with just
10558 @samp{-g}, particularly on machines with instruction scheduling. If in
10559 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10560 please report it to us as a bug (including a test case!).
10561 @xref{Variables}, for more information about debugging optimized code.
10564 * Inline Functions:: How @value{GDBN} presents inlining
10565 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10568 @node Inline Functions
10569 @section Inline Functions
10570 @cindex inline functions, debugging
10572 @dfn{Inlining} is an optimization that inserts a copy of the function
10573 body directly at each call site, instead of jumping to a shared
10574 routine. @value{GDBN} displays inlined functions just like
10575 non-inlined functions. They appear in backtraces. You can view their
10576 arguments and local variables, step into them with @code{step}, skip
10577 them with @code{next}, and escape from them with @code{finish}.
10578 You can check whether a function was inlined by using the
10579 @code{info frame} command.
10581 For @value{GDBN} to support inlined functions, the compiler must
10582 record information about inlining in the debug information ---
10583 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10584 other compilers do also. @value{GDBN} only supports inlined functions
10585 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10586 do not emit two required attributes (@samp{DW_AT_call_file} and
10587 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10588 function calls with earlier versions of @value{NGCC}. It instead
10589 displays the arguments and local variables of inlined functions as
10590 local variables in the caller.
10592 The body of an inlined function is directly included at its call site;
10593 unlike a non-inlined function, there are no instructions devoted to
10594 the call. @value{GDBN} still pretends that the call site and the
10595 start of the inlined function are different instructions. Stepping to
10596 the call site shows the call site, and then stepping again shows
10597 the first line of the inlined function, even though no additional
10598 instructions are executed.
10600 This makes source-level debugging much clearer; you can see both the
10601 context of the call and then the effect of the call. Only stepping by
10602 a single instruction using @code{stepi} or @code{nexti} does not do
10603 this; single instruction steps always show the inlined body.
10605 There are some ways that @value{GDBN} does not pretend that inlined
10606 function calls are the same as normal calls:
10610 Setting breakpoints at the call site of an inlined function may not
10611 work, because the call site does not contain any code. @value{GDBN}
10612 may incorrectly move the breakpoint to the next line of the enclosing
10613 function, after the call. This limitation will be removed in a future
10614 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10615 or inside the inlined function instead.
10618 @value{GDBN} cannot locate the return value of inlined calls after
10619 using the @code{finish} command. This is a limitation of compiler-generated
10620 debugging information; after @code{finish}, you can step to the next line
10621 and print a variable where your program stored the return value.
10625 @node Tail Call Frames
10626 @section Tail Call Frames
10627 @cindex tail call frames, debugging
10629 Function @code{B} can call function @code{C} in its very last statement. In
10630 unoptimized compilation the call of @code{C} is immediately followed by return
10631 instruction at the end of @code{B} code. Optimizing compiler may replace the
10632 call and return in function @code{B} into one jump to function @code{C}
10633 instead. Such use of a jump instruction is called @dfn{tail call}.
10635 During execution of function @code{C}, there will be no indication in the
10636 function call stack frames that it was tail-called from @code{B}. If function
10637 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10638 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10639 some cases @value{GDBN} can determine that @code{C} was tail-called from
10640 @code{B}, and it will then create fictitious call frame for that, with the
10641 return address set up as if @code{B} called @code{C} normally.
10643 This functionality is currently supported only by DWARF 2 debugging format and
10644 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10645 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10648 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10649 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10653 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10655 Stack level 1, frame at 0x7fffffffda30:
10656 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10657 tail call frame, caller of frame at 0x7fffffffda30
10658 source language c++.
10659 Arglist at unknown address.
10660 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10663 The detection of all the possible code path executions can find them ambiguous.
10664 There is no execution history stored (possible @ref{Reverse Execution} is never
10665 used for this purpose) and the last known caller could have reached the known
10666 callee by multiple different jump sequences. In such case @value{GDBN} still
10667 tries to show at least all the unambiguous top tail callers and all the
10668 unambiguous bottom tail calees, if any.
10671 @anchor{set debug entry-values}
10672 @item set debug entry-values
10673 @kindex set debug entry-values
10674 When set to on, enables printing of analysis messages for both frame argument
10675 values at function entry and tail calls. It will show all the possible valid
10676 tail calls code paths it has considered. It will also print the intersection
10677 of them with the final unambiguous (possibly partial or even empty) code path
10680 @item show debug entry-values
10681 @kindex show debug entry-values
10682 Show the current state of analysis messages printing for both frame argument
10683 values at function entry and tail calls.
10686 The analysis messages for tail calls can for example show why the virtual tail
10687 call frame for function @code{c} has not been recognized (due to the indirect
10688 reference by variable @code{x}):
10691 static void __attribute__((noinline, noclone)) c (void);
10692 void (*x) (void) = c;
10693 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10694 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10695 int main (void) @{ x (); return 0; @}
10697 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10698 DW_TAG_GNU_call_site 0x40039a in main
10700 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10703 #1 0x000000000040039a in main () at t.c:5
10706 Another possibility is an ambiguous virtual tail call frames resolution:
10710 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10711 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10712 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10713 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10714 static void __attribute__((noinline, noclone)) b (void)
10715 @{ if (i) c (); else e (); @}
10716 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10717 int main (void) @{ a (); return 0; @}
10719 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10720 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10721 tailcall: reduced: 0x4004d2(a) |
10724 #1 0x00000000004004d2 in a () at t.c:8
10725 #2 0x0000000000400395 in main () at t.c:9
10728 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10729 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10731 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10732 @ifset HAVE_MAKEINFO_CLICK
10733 @set ARROW @click{}
10734 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10735 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10737 @ifclear HAVE_MAKEINFO_CLICK
10739 @set CALLSEQ1B @value{CALLSEQ1A}
10740 @set CALLSEQ2B @value{CALLSEQ2A}
10743 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10744 The code can have possible execution paths @value{CALLSEQ1B} or
10745 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10747 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10748 has found. It then finds another possible calling sequcen - that one is
10749 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10750 printed as the @code{reduced:} calling sequence. That one could have many
10751 futher @code{compare:} and @code{reduced:} statements as long as there remain
10752 any non-ambiguous sequence entries.
10754 For the frame of function @code{b} in both cases there are different possible
10755 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10756 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10757 therefore this one is displayed to the user while the ambiguous frames are
10760 There can be also reasons why printing of frame argument values at function
10765 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10766 static void __attribute__((noinline, noclone)) a (int i);
10767 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10768 static void __attribute__((noinline, noclone)) a (int i)
10769 @{ if (i) b (i - 1); else c (0); @}
10770 int main (void) @{ a (5); return 0; @}
10773 #0 c (i=i@@entry=0) at t.c:2
10774 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10775 function "a" at 0x400420 can call itself via tail calls
10776 i=<optimized out>) at t.c:6
10777 #2 0x000000000040036e in main () at t.c:7
10780 @value{GDBN} cannot find out from the inferior state if and how many times did
10781 function @code{a} call itself (via function @code{b}) as these calls would be
10782 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10783 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10784 prints @code{<optimized out>} instead.
10787 @chapter C Preprocessor Macros
10789 Some languages, such as C and C@t{++}, provide a way to define and invoke
10790 ``preprocessor macros'' which expand into strings of tokens.
10791 @value{GDBN} can evaluate expressions containing macro invocations, show
10792 the result of macro expansion, and show a macro's definition, including
10793 where it was defined.
10795 You may need to compile your program specially to provide @value{GDBN}
10796 with information about preprocessor macros. Most compilers do not
10797 include macros in their debugging information, even when you compile
10798 with the @option{-g} flag. @xref{Compilation}.
10800 A program may define a macro at one point, remove that definition later,
10801 and then provide a different definition after that. Thus, at different
10802 points in the program, a macro may have different definitions, or have
10803 no definition at all. If there is a current stack frame, @value{GDBN}
10804 uses the macros in scope at that frame's source code line. Otherwise,
10805 @value{GDBN} uses the macros in scope at the current listing location;
10808 Whenever @value{GDBN} evaluates an expression, it always expands any
10809 macro invocations present in the expression. @value{GDBN} also provides
10810 the following commands for working with macros explicitly.
10814 @kindex macro expand
10815 @cindex macro expansion, showing the results of preprocessor
10816 @cindex preprocessor macro expansion, showing the results of
10817 @cindex expanding preprocessor macros
10818 @item macro expand @var{expression}
10819 @itemx macro exp @var{expression}
10820 Show the results of expanding all preprocessor macro invocations in
10821 @var{expression}. Since @value{GDBN} simply expands macros, but does
10822 not parse the result, @var{expression} need not be a valid expression;
10823 it can be any string of tokens.
10826 @item macro expand-once @var{expression}
10827 @itemx macro exp1 @var{expression}
10828 @cindex expand macro once
10829 @i{(This command is not yet implemented.)} Show the results of
10830 expanding those preprocessor macro invocations that appear explicitly in
10831 @var{expression}. Macro invocations appearing in that expansion are
10832 left unchanged. This command allows you to see the effect of a
10833 particular macro more clearly, without being confused by further
10834 expansions. Since @value{GDBN} simply expands macros, but does not
10835 parse the result, @var{expression} need not be a valid expression; it
10836 can be any string of tokens.
10839 @cindex macro definition, showing
10840 @cindex definition of a macro, showing
10841 @cindex macros, from debug info
10842 @item info macro [-a|-all] [--] @var{macro}
10843 Show the current definition or all definitions of the named @var{macro},
10844 and describe the source location or compiler command-line where that
10845 definition was established. The optional double dash is to signify the end of
10846 argument processing and the beginning of @var{macro} for non C-like macros where
10847 the macro may begin with a hyphen.
10849 @kindex info macros
10850 @item info macros @var{linespec}
10851 Show all macro definitions that are in effect at the location specified
10852 by @var{linespec}, and describe the source location or compiler
10853 command-line where those definitions were established.
10855 @kindex macro define
10856 @cindex user-defined macros
10857 @cindex defining macros interactively
10858 @cindex macros, user-defined
10859 @item macro define @var{macro} @var{replacement-list}
10860 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10861 Introduce a definition for a preprocessor macro named @var{macro},
10862 invocations of which are replaced by the tokens given in
10863 @var{replacement-list}. The first form of this command defines an
10864 ``object-like'' macro, which takes no arguments; the second form
10865 defines a ``function-like'' macro, which takes the arguments given in
10868 A definition introduced by this command is in scope in every
10869 expression evaluated in @value{GDBN}, until it is removed with the
10870 @code{macro undef} command, described below. The definition overrides
10871 all definitions for @var{macro} present in the program being debugged,
10872 as well as any previous user-supplied definition.
10874 @kindex macro undef
10875 @item macro undef @var{macro}
10876 Remove any user-supplied definition for the macro named @var{macro}.
10877 This command only affects definitions provided with the @code{macro
10878 define} command, described above; it cannot remove definitions present
10879 in the program being debugged.
10883 List all the macros defined using the @code{macro define} command.
10886 @cindex macros, example of debugging with
10887 Here is a transcript showing the above commands in action. First, we
10888 show our source files:
10893 #include "sample.h"
10896 #define ADD(x) (M + x)
10901 printf ("Hello, world!\n");
10903 printf ("We're so creative.\n");
10905 printf ("Goodbye, world!\n");
10912 Now, we compile the program using the @sc{gnu} C compiler,
10913 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10914 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10915 and @option{-gdwarf-4}; we recommend always choosing the most recent
10916 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10917 includes information about preprocessor macros in the debugging
10921 $ gcc -gdwarf-2 -g3 sample.c -o sample
10925 Now, we start @value{GDBN} on our sample program:
10929 GNU gdb 2002-05-06-cvs
10930 Copyright 2002 Free Software Foundation, Inc.
10931 GDB is free software, @dots{}
10935 We can expand macros and examine their definitions, even when the
10936 program is not running. @value{GDBN} uses the current listing position
10937 to decide which macro definitions are in scope:
10940 (@value{GDBP}) list main
10943 5 #define ADD(x) (M + x)
10948 10 printf ("Hello, world!\n");
10950 12 printf ("We're so creative.\n");
10951 (@value{GDBP}) info macro ADD
10952 Defined at /home/jimb/gdb/macros/play/sample.c:5
10953 #define ADD(x) (M + x)
10954 (@value{GDBP}) info macro Q
10955 Defined at /home/jimb/gdb/macros/play/sample.h:1
10956 included at /home/jimb/gdb/macros/play/sample.c:2
10958 (@value{GDBP}) macro expand ADD(1)
10959 expands to: (42 + 1)
10960 (@value{GDBP}) macro expand-once ADD(1)
10961 expands to: once (M + 1)
10965 In the example above, note that @code{macro expand-once} expands only
10966 the macro invocation explicit in the original text --- the invocation of
10967 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10968 which was introduced by @code{ADD}.
10970 Once the program is running, @value{GDBN} uses the macro definitions in
10971 force at the source line of the current stack frame:
10974 (@value{GDBP}) break main
10975 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10977 Starting program: /home/jimb/gdb/macros/play/sample
10979 Breakpoint 1, main () at sample.c:10
10980 10 printf ("Hello, world!\n");
10984 At line 10, the definition of the macro @code{N} at line 9 is in force:
10987 (@value{GDBP}) info macro N
10988 Defined at /home/jimb/gdb/macros/play/sample.c:9
10990 (@value{GDBP}) macro expand N Q M
10991 expands to: 28 < 42
10992 (@value{GDBP}) print N Q M
10997 As we step over directives that remove @code{N}'s definition, and then
10998 give it a new definition, @value{GDBN} finds the definition (or lack
10999 thereof) in force at each point:
11002 (@value{GDBP}) next
11004 12 printf ("We're so creative.\n");
11005 (@value{GDBP}) info macro N
11006 The symbol `N' has no definition as a C/C++ preprocessor macro
11007 at /home/jimb/gdb/macros/play/sample.c:12
11008 (@value{GDBP}) next
11010 14 printf ("Goodbye, world!\n");
11011 (@value{GDBP}) info macro N
11012 Defined at /home/jimb/gdb/macros/play/sample.c:13
11014 (@value{GDBP}) macro expand N Q M
11015 expands to: 1729 < 42
11016 (@value{GDBP}) print N Q M
11021 In addition to source files, macros can be defined on the compilation command
11022 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11023 such a way, @value{GDBN} displays the location of their definition as line zero
11024 of the source file submitted to the compiler.
11027 (@value{GDBP}) info macro __STDC__
11028 Defined at /home/jimb/gdb/macros/play/sample.c:0
11035 @chapter Tracepoints
11036 @c This chapter is based on the documentation written by Michael
11037 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11039 @cindex tracepoints
11040 In some applications, it is not feasible for the debugger to interrupt
11041 the program's execution long enough for the developer to learn
11042 anything helpful about its behavior. If the program's correctness
11043 depends on its real-time behavior, delays introduced by a debugger
11044 might cause the program to change its behavior drastically, or perhaps
11045 fail, even when the code itself is correct. It is useful to be able
11046 to observe the program's behavior without interrupting it.
11048 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11049 specify locations in the program, called @dfn{tracepoints}, and
11050 arbitrary expressions to evaluate when those tracepoints are reached.
11051 Later, using the @code{tfind} command, you can examine the values
11052 those expressions had when the program hit the tracepoints. The
11053 expressions may also denote objects in memory---structures or arrays,
11054 for example---whose values @value{GDBN} should record; while visiting
11055 a particular tracepoint, you may inspect those objects as if they were
11056 in memory at that moment. However, because @value{GDBN} records these
11057 values without interacting with you, it can do so quickly and
11058 unobtrusively, hopefully not disturbing the program's behavior.
11060 The tracepoint facility is currently available only for remote
11061 targets. @xref{Targets}. In addition, your remote target must know
11062 how to collect trace data. This functionality is implemented in the
11063 remote stub; however, none of the stubs distributed with @value{GDBN}
11064 support tracepoints as of this writing. The format of the remote
11065 packets used to implement tracepoints are described in @ref{Tracepoint
11068 It is also possible to get trace data from a file, in a manner reminiscent
11069 of corefiles; you specify the filename, and use @code{tfind} to search
11070 through the file. @xref{Trace Files}, for more details.
11072 This chapter describes the tracepoint commands and features.
11075 * Set Tracepoints::
11076 * Analyze Collected Data::
11077 * Tracepoint Variables::
11081 @node Set Tracepoints
11082 @section Commands to Set Tracepoints
11084 Before running such a @dfn{trace experiment}, an arbitrary number of
11085 tracepoints can be set. A tracepoint is actually a special type of
11086 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11087 standard breakpoint commands. For instance, as with breakpoints,
11088 tracepoint numbers are successive integers starting from one, and many
11089 of the commands associated with tracepoints take the tracepoint number
11090 as their argument, to identify which tracepoint to work on.
11092 For each tracepoint, you can specify, in advance, some arbitrary set
11093 of data that you want the target to collect in the trace buffer when
11094 it hits that tracepoint. The collected data can include registers,
11095 local variables, or global data. Later, you can use @value{GDBN}
11096 commands to examine the values these data had at the time the
11097 tracepoint was hit.
11099 Tracepoints do not support every breakpoint feature. Ignore counts on
11100 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11101 commands when they are hit. Tracepoints may not be thread-specific
11104 @cindex fast tracepoints
11105 Some targets may support @dfn{fast tracepoints}, which are inserted in
11106 a different way (such as with a jump instead of a trap), that is
11107 faster but possibly restricted in where they may be installed.
11109 @cindex static tracepoints
11110 @cindex markers, static tracepoints
11111 @cindex probing markers, static tracepoints
11112 Regular and fast tracepoints are dynamic tracing facilities, meaning
11113 that they can be used to insert tracepoints at (almost) any location
11114 in the target. Some targets may also support controlling @dfn{static
11115 tracepoints} from @value{GDBN}. With static tracing, a set of
11116 instrumentation points, also known as @dfn{markers}, are embedded in
11117 the target program, and can be activated or deactivated by name or
11118 address. These are usually placed at locations which facilitate
11119 investigating what the target is actually doing. @value{GDBN}'s
11120 support for static tracing includes being able to list instrumentation
11121 points, and attach them with @value{GDBN} defined high level
11122 tracepoints that expose the whole range of convenience of
11123 @value{GDBN}'s tracepoints support. Namely, support for collecting
11124 registers values and values of global or local (to the instrumentation
11125 point) variables; tracepoint conditions and trace state variables.
11126 The act of installing a @value{GDBN} static tracepoint on an
11127 instrumentation point, or marker, is referred to as @dfn{probing} a
11128 static tracepoint marker.
11130 @code{gdbserver} supports tracepoints on some target systems.
11131 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11133 This section describes commands to set tracepoints and associated
11134 conditions and actions.
11137 * Create and Delete Tracepoints::
11138 * Enable and Disable Tracepoints::
11139 * Tracepoint Passcounts::
11140 * Tracepoint Conditions::
11141 * Trace State Variables::
11142 * Tracepoint Actions::
11143 * Listing Tracepoints::
11144 * Listing Static Tracepoint Markers::
11145 * Starting and Stopping Trace Experiments::
11146 * Tracepoint Restrictions::
11149 @node Create and Delete Tracepoints
11150 @subsection Create and Delete Tracepoints
11153 @cindex set tracepoint
11155 @item trace @var{location}
11156 The @code{trace} command is very similar to the @code{break} command.
11157 Its argument @var{location} can be a source line, a function name, or
11158 an address in the target program. @xref{Specify Location}. The
11159 @code{trace} command defines a tracepoint, which is a point in the
11160 target program where the debugger will briefly stop, collect some
11161 data, and then allow the program to continue. Setting a tracepoint or
11162 changing its actions takes effect immediately if the remote stub
11163 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11165 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11166 these changes don't take effect until the next @code{tstart}
11167 command, and once a trace experiment is running, further changes will
11168 not have any effect until the next trace experiment starts. In addition,
11169 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11170 address is not yet resolved. (This is similar to pending breakpoints.)
11171 Pending tracepoints are not downloaded to the target and not installed
11172 until they are resolved. The resolution of pending tracepoints requires
11173 @value{GDBN} support---when debugging with the remote target, and
11174 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11175 tracing}), pending tracepoints can not be resolved (and downloaded to
11176 the remote stub) while @value{GDBN} is disconnected.
11178 Here are some examples of using the @code{trace} command:
11181 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11183 (@value{GDBP}) @b{trace +2} // 2 lines forward
11185 (@value{GDBP}) @b{trace my_function} // first source line of function
11187 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11189 (@value{GDBP}) @b{trace *0x2117c4} // an address
11193 You can abbreviate @code{trace} as @code{tr}.
11195 @item trace @var{location} if @var{cond}
11196 Set a tracepoint with condition @var{cond}; evaluate the expression
11197 @var{cond} each time the tracepoint is reached, and collect data only
11198 if the value is nonzero---that is, if @var{cond} evaluates as true.
11199 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11200 information on tracepoint conditions.
11202 @item ftrace @var{location} [ if @var{cond} ]
11203 @cindex set fast tracepoint
11204 @cindex fast tracepoints, setting
11206 The @code{ftrace} command sets a fast tracepoint. For targets that
11207 support them, fast tracepoints will use a more efficient but possibly
11208 less general technique to trigger data collection, such as a jump
11209 instruction instead of a trap, or some sort of hardware support. It
11210 may not be possible to create a fast tracepoint at the desired
11211 location, in which case the command will exit with an explanatory
11214 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11217 On 32-bit x86-architecture systems, fast tracepoints normally need to
11218 be placed at an instruction that is 5 bytes or longer, but can be
11219 placed at 4-byte instructions if the low 64K of memory of the target
11220 program is available to install trampolines. Some Unix-type systems,
11221 such as @sc{gnu}/Linux, exclude low addresses from the program's
11222 address space; but for instance with the Linux kernel it is possible
11223 to let @value{GDBN} use this area by doing a @command{sysctl} command
11224 to set the @code{mmap_min_addr} kernel parameter, as in
11227 sudo sysctl -w vm.mmap_min_addr=32768
11231 which sets the low address to 32K, which leaves plenty of room for
11232 trampolines. The minimum address should be set to a page boundary.
11234 @item strace @var{location} [ if @var{cond} ]
11235 @cindex set static tracepoint
11236 @cindex static tracepoints, setting
11237 @cindex probe static tracepoint marker
11239 The @code{strace} command sets a static tracepoint. For targets that
11240 support it, setting a static tracepoint probes a static
11241 instrumentation point, or marker, found at @var{location}. It may not
11242 be possible to set a static tracepoint at the desired location, in
11243 which case the command will exit with an explanatory message.
11245 @value{GDBN} handles arguments to @code{strace} exactly as for
11246 @code{trace}, with the addition that the user can also specify
11247 @code{-m @var{marker}} as @var{location}. This probes the marker
11248 identified by the @var{marker} string identifier. This identifier
11249 depends on the static tracepoint backend library your program is
11250 using. You can find all the marker identifiers in the @samp{ID} field
11251 of the @code{info static-tracepoint-markers} command output.
11252 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11253 Markers}. For example, in the following small program using the UST
11259 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11264 the marker id is composed of joining the first two arguments to the
11265 @code{trace_mark} call with a slash, which translates to:
11268 (@value{GDBP}) info static-tracepoint-markers
11269 Cnt Enb ID Address What
11270 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11276 so you may probe the marker above with:
11279 (@value{GDBP}) strace -m ust/bar33
11282 Static tracepoints accept an extra collect action --- @code{collect
11283 $_sdata}. This collects arbitrary user data passed in the probe point
11284 call to the tracing library. In the UST example above, you'll see
11285 that the third argument to @code{trace_mark} is a printf-like format
11286 string. The user data is then the result of running that formating
11287 string against the following arguments. Note that @code{info
11288 static-tracepoint-markers} command output lists that format string in
11289 the @samp{Data:} field.
11291 You can inspect this data when analyzing the trace buffer, by printing
11292 the $_sdata variable like any other variable available to
11293 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11296 @cindex last tracepoint number
11297 @cindex recent tracepoint number
11298 @cindex tracepoint number
11299 The convenience variable @code{$tpnum} records the tracepoint number
11300 of the most recently set tracepoint.
11302 @kindex delete tracepoint
11303 @cindex tracepoint deletion
11304 @item delete tracepoint @r{[}@var{num}@r{]}
11305 Permanently delete one or more tracepoints. With no argument, the
11306 default is to delete all tracepoints. Note that the regular
11307 @code{delete} command can remove tracepoints also.
11312 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11314 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11318 You can abbreviate this command as @code{del tr}.
11321 @node Enable and Disable Tracepoints
11322 @subsection Enable and Disable Tracepoints
11324 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11327 @kindex disable tracepoint
11328 @item disable tracepoint @r{[}@var{num}@r{]}
11329 Disable tracepoint @var{num}, or all tracepoints if no argument
11330 @var{num} is given. A disabled tracepoint will have no effect during
11331 a trace experiment, but it is not forgotten. You can re-enable
11332 a disabled tracepoint using the @code{enable tracepoint} command.
11333 If the command is issued during a trace experiment and the debug target
11334 has support for disabling tracepoints during a trace experiment, then the
11335 change will be effective immediately. Otherwise, it will be applied to the
11336 next trace experiment.
11338 @kindex enable tracepoint
11339 @item enable tracepoint @r{[}@var{num}@r{]}
11340 Enable tracepoint @var{num}, or all tracepoints. If this command is
11341 issued during a trace experiment and the debug target supports enabling
11342 tracepoints during a trace experiment, then the enabled tracepoints will
11343 become effective immediately. Otherwise, they will become effective the
11344 next time a trace experiment is run.
11347 @node Tracepoint Passcounts
11348 @subsection Tracepoint Passcounts
11352 @cindex tracepoint pass count
11353 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11354 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11355 automatically stop a trace experiment. If a tracepoint's passcount is
11356 @var{n}, then the trace experiment will be automatically stopped on
11357 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11358 @var{num} is not specified, the @code{passcount} command sets the
11359 passcount of the most recently defined tracepoint. If no passcount is
11360 given, the trace experiment will run until stopped explicitly by the
11366 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11367 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11369 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11370 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11371 (@value{GDBP}) @b{trace foo}
11372 (@value{GDBP}) @b{pass 3}
11373 (@value{GDBP}) @b{trace bar}
11374 (@value{GDBP}) @b{pass 2}
11375 (@value{GDBP}) @b{trace baz}
11376 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11377 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11378 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11379 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11383 @node Tracepoint Conditions
11384 @subsection Tracepoint Conditions
11385 @cindex conditional tracepoints
11386 @cindex tracepoint conditions
11388 The simplest sort of tracepoint collects data every time your program
11389 reaches a specified place. You can also specify a @dfn{condition} for
11390 a tracepoint. A condition is just a Boolean expression in your
11391 programming language (@pxref{Expressions, ,Expressions}). A
11392 tracepoint with a condition evaluates the expression each time your
11393 program reaches it, and data collection happens only if the condition
11396 Tracepoint conditions can be specified when a tracepoint is set, by
11397 using @samp{if} in the arguments to the @code{trace} command.
11398 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11399 also be set or changed at any time with the @code{condition} command,
11400 just as with breakpoints.
11402 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11403 the conditional expression itself. Instead, @value{GDBN} encodes the
11404 expression into an agent expression (@pxref{Agent Expressions})
11405 suitable for execution on the target, independently of @value{GDBN}.
11406 Global variables become raw memory locations, locals become stack
11407 accesses, and so forth.
11409 For instance, suppose you have a function that is usually called
11410 frequently, but should not be called after an error has occurred. You
11411 could use the following tracepoint command to collect data about calls
11412 of that function that happen while the error code is propagating
11413 through the program; an unconditional tracepoint could end up
11414 collecting thousands of useless trace frames that you would have to
11418 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11421 @node Trace State Variables
11422 @subsection Trace State Variables
11423 @cindex trace state variables
11425 A @dfn{trace state variable} is a special type of variable that is
11426 created and managed by target-side code. The syntax is the same as
11427 that for GDB's convenience variables (a string prefixed with ``$''),
11428 but they are stored on the target. They must be created explicitly,
11429 using a @code{tvariable} command. They are always 64-bit signed
11432 Trace state variables are remembered by @value{GDBN}, and downloaded
11433 to the target along with tracepoint information when the trace
11434 experiment starts. There are no intrinsic limits on the number of
11435 trace state variables, beyond memory limitations of the target.
11437 @cindex convenience variables, and trace state variables
11438 Although trace state variables are managed by the target, you can use
11439 them in print commands and expressions as if they were convenience
11440 variables; @value{GDBN} will get the current value from the target
11441 while the trace experiment is running. Trace state variables share
11442 the same namespace as other ``$'' variables, which means that you
11443 cannot have trace state variables with names like @code{$23} or
11444 @code{$pc}, nor can you have a trace state variable and a convenience
11445 variable with the same name.
11449 @item tvariable $@var{name} [ = @var{expression} ]
11451 The @code{tvariable} command creates a new trace state variable named
11452 @code{$@var{name}}, and optionally gives it an initial value of
11453 @var{expression}. @var{expression} is evaluated when this command is
11454 entered; the result will be converted to an integer if possible,
11455 otherwise @value{GDBN} will report an error. A subsequent
11456 @code{tvariable} command specifying the same name does not create a
11457 variable, but instead assigns the supplied initial value to the
11458 existing variable of that name, overwriting any previous initial
11459 value. The default initial value is 0.
11461 @item info tvariables
11462 @kindex info tvariables
11463 List all the trace state variables along with their initial values.
11464 Their current values may also be displayed, if the trace experiment is
11467 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11468 @kindex delete tvariable
11469 Delete the given trace state variables, or all of them if no arguments
11474 @node Tracepoint Actions
11475 @subsection Tracepoint Action Lists
11479 @cindex tracepoint actions
11480 @item actions @r{[}@var{num}@r{]}
11481 This command will prompt for a list of actions to be taken when the
11482 tracepoint is hit. If the tracepoint number @var{num} is not
11483 specified, this command sets the actions for the one that was most
11484 recently defined (so that you can define a tracepoint and then say
11485 @code{actions} without bothering about its number). You specify the
11486 actions themselves on the following lines, one action at a time, and
11487 terminate the actions list with a line containing just @code{end}. So
11488 far, the only defined actions are @code{collect}, @code{teval}, and
11489 @code{while-stepping}.
11491 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11492 Commands, ,Breakpoint Command Lists}), except that only the defined
11493 actions are allowed; any other @value{GDBN} command is rejected.
11495 @cindex remove actions from a tracepoint
11496 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11497 and follow it immediately with @samp{end}.
11500 (@value{GDBP}) @b{collect @var{data}} // collect some data
11502 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11504 (@value{GDBP}) @b{end} // signals the end of actions.
11507 In the following example, the action list begins with @code{collect}
11508 commands indicating the things to be collected when the tracepoint is
11509 hit. Then, in order to single-step and collect additional data
11510 following the tracepoint, a @code{while-stepping} command is used,
11511 followed by the list of things to be collected after each step in a
11512 sequence of single steps. The @code{while-stepping} command is
11513 terminated by its own separate @code{end} command. Lastly, the action
11514 list is terminated by an @code{end} command.
11517 (@value{GDBP}) @b{trace foo}
11518 (@value{GDBP}) @b{actions}
11519 Enter actions for tracepoint 1, one per line:
11522 > while-stepping 12
11523 > collect $pc, arr[i]
11528 @kindex collect @r{(tracepoints)}
11529 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11530 Collect values of the given expressions when the tracepoint is hit.
11531 This command accepts a comma-separated list of any valid expressions.
11532 In addition to global, static, or local variables, the following
11533 special arguments are supported:
11537 Collect all registers.
11540 Collect all function arguments.
11543 Collect all local variables.
11546 Collect the return address. This is helpful if you want to see more
11550 Collects the number of arguments from the static probe at which the
11551 tracepoint is located.
11552 @xref{Static Probe Points}.
11554 @item $_probe_arg@var{n}
11555 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11556 from the static probe at which the tracepoint is located.
11557 @xref{Static Probe Points}.
11560 @vindex $_sdata@r{, collect}
11561 Collect static tracepoint marker specific data. Only available for
11562 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11563 Lists}. On the UST static tracepoints library backend, an
11564 instrumentation point resembles a @code{printf} function call. The
11565 tracing library is able to collect user specified data formatted to a
11566 character string using the format provided by the programmer that
11567 instrumented the program. Other backends have similar mechanisms.
11568 Here's an example of a UST marker call:
11571 const char master_name[] = "$your_name";
11572 trace_mark(channel1, marker1, "hello %s", master_name)
11575 In this case, collecting @code{$_sdata} collects the string
11576 @samp{hello $yourname}. When analyzing the trace buffer, you can
11577 inspect @samp{$_sdata} like any other variable available to
11581 You can give several consecutive @code{collect} commands, each one
11582 with a single argument, or one @code{collect} command with several
11583 arguments separated by commas; the effect is the same.
11585 The optional @var{mods} changes the usual handling of the arguments.
11586 @code{s} requests that pointers to chars be handled as strings, in
11587 particular collecting the contents of the memory being pointed at, up
11588 to the first zero. The upper bound is by default the value of the
11589 @code{print elements} variable; if @code{s} is followed by a decimal
11590 number, that is the upper bound instead. So for instance
11591 @samp{collect/s25 mystr} collects as many as 25 characters at
11594 The command @code{info scope} (@pxref{Symbols, info scope}) is
11595 particularly useful for figuring out what data to collect.
11597 @kindex teval @r{(tracepoints)}
11598 @item teval @var{expr1}, @var{expr2}, @dots{}
11599 Evaluate the given expressions when the tracepoint is hit. This
11600 command accepts a comma-separated list of expressions. The results
11601 are discarded, so this is mainly useful for assigning values to trace
11602 state variables (@pxref{Trace State Variables}) without adding those
11603 values to the trace buffer, as would be the case if the @code{collect}
11606 @kindex while-stepping @r{(tracepoints)}
11607 @item while-stepping @var{n}
11608 Perform @var{n} single-step instruction traces after the tracepoint,
11609 collecting new data after each step. The @code{while-stepping}
11610 command is followed by the list of what to collect while stepping
11611 (followed by its own @code{end} command):
11614 > while-stepping 12
11615 > collect $regs, myglobal
11621 Note that @code{$pc} is not automatically collected by
11622 @code{while-stepping}; you need to explicitly collect that register if
11623 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11626 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11627 @kindex set default-collect
11628 @cindex default collection action
11629 This variable is a list of expressions to collect at each tracepoint
11630 hit. It is effectively an additional @code{collect} action prepended
11631 to every tracepoint action list. The expressions are parsed
11632 individually for each tracepoint, so for instance a variable named
11633 @code{xyz} may be interpreted as a global for one tracepoint, and a
11634 local for another, as appropriate to the tracepoint's location.
11636 @item show default-collect
11637 @kindex show default-collect
11638 Show the list of expressions that are collected by default at each
11643 @node Listing Tracepoints
11644 @subsection Listing Tracepoints
11647 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11648 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11649 @cindex information about tracepoints
11650 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11651 Display information about the tracepoint @var{num}. If you don't
11652 specify a tracepoint number, displays information about all the
11653 tracepoints defined so far. The format is similar to that used for
11654 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11655 command, simply restricting itself to tracepoints.
11657 A tracepoint's listing may include additional information specific to
11662 its passcount as given by the @code{passcount @var{n}} command
11665 the state about installed on target of each location
11669 (@value{GDBP}) @b{info trace}
11670 Num Type Disp Enb Address What
11671 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11673 collect globfoo, $regs
11678 2 tracepoint keep y <MULTIPLE>
11680 2.1 y 0x0804859c in func4 at change-loc.h:35
11681 installed on target
11682 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11683 installed on target
11684 2.3 y <PENDING> set_tracepoint
11685 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11686 not installed on target
11691 This command can be abbreviated @code{info tp}.
11694 @node Listing Static Tracepoint Markers
11695 @subsection Listing Static Tracepoint Markers
11698 @kindex info static-tracepoint-markers
11699 @cindex information about static tracepoint markers
11700 @item info static-tracepoint-markers
11701 Display information about all static tracepoint markers defined in the
11704 For each marker, the following columns are printed:
11708 An incrementing counter, output to help readability. This is not a
11711 The marker ID, as reported by the target.
11712 @item Enabled or Disabled
11713 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11714 that are not enabled.
11716 Where the marker is in your program, as a memory address.
11718 Where the marker is in the source for your program, as a file and line
11719 number. If the debug information included in the program does not
11720 allow @value{GDBN} to locate the source of the marker, this column
11721 will be left blank.
11725 In addition, the following information may be printed for each marker:
11729 User data passed to the tracing library by the marker call. In the
11730 UST backend, this is the format string passed as argument to the
11732 @item Static tracepoints probing the marker
11733 The list of static tracepoints attached to the marker.
11737 (@value{GDBP}) info static-tracepoint-markers
11738 Cnt ID Enb Address What
11739 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11740 Data: number1 %d number2 %d
11741 Probed by static tracepoints: #2
11742 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11748 @node Starting and Stopping Trace Experiments
11749 @subsection Starting and Stopping Trace Experiments
11752 @kindex tstart [ @var{notes} ]
11753 @cindex start a new trace experiment
11754 @cindex collected data discarded
11756 This command starts the trace experiment, and begins collecting data.
11757 It has the side effect of discarding all the data collected in the
11758 trace buffer during the previous trace experiment. If any arguments
11759 are supplied, they are taken as a note and stored with the trace
11760 experiment's state. The notes may be arbitrary text, and are
11761 especially useful with disconnected tracing in a multi-user context;
11762 the notes can explain what the trace is doing, supply user contact
11763 information, and so forth.
11765 @kindex tstop [ @var{notes} ]
11766 @cindex stop a running trace experiment
11768 This command stops the trace experiment. If any arguments are
11769 supplied, they are recorded with the experiment as a note. This is
11770 useful if you are stopping a trace started by someone else, for
11771 instance if the trace is interfering with the system's behavior and
11772 needs to be stopped quickly.
11774 @strong{Note}: a trace experiment and data collection may stop
11775 automatically if any tracepoint's passcount is reached
11776 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11779 @cindex status of trace data collection
11780 @cindex trace experiment, status of
11782 This command displays the status of the current trace data
11786 Here is an example of the commands we described so far:
11789 (@value{GDBP}) @b{trace gdb_c_test}
11790 (@value{GDBP}) @b{actions}
11791 Enter actions for tracepoint #1, one per line.
11792 > collect $regs,$locals,$args
11793 > while-stepping 11
11797 (@value{GDBP}) @b{tstart}
11798 [time passes @dots{}]
11799 (@value{GDBP}) @b{tstop}
11802 @anchor{disconnected tracing}
11803 @cindex disconnected tracing
11804 You can choose to continue running the trace experiment even if
11805 @value{GDBN} disconnects from the target, voluntarily or
11806 involuntarily. For commands such as @code{detach}, the debugger will
11807 ask what you want to do with the trace. But for unexpected
11808 terminations (@value{GDBN} crash, network outage), it would be
11809 unfortunate to lose hard-won trace data, so the variable
11810 @code{disconnected-tracing} lets you decide whether the trace should
11811 continue running without @value{GDBN}.
11814 @item set disconnected-tracing on
11815 @itemx set disconnected-tracing off
11816 @kindex set disconnected-tracing
11817 Choose whether a tracing run should continue to run if @value{GDBN}
11818 has disconnected from the target. Note that @code{detach} or
11819 @code{quit} will ask you directly what to do about a running trace no
11820 matter what this variable's setting, so the variable is mainly useful
11821 for handling unexpected situations, such as loss of the network.
11823 @item show disconnected-tracing
11824 @kindex show disconnected-tracing
11825 Show the current choice for disconnected tracing.
11829 When you reconnect to the target, the trace experiment may or may not
11830 still be running; it might have filled the trace buffer in the
11831 meantime, or stopped for one of the other reasons. If it is running,
11832 it will continue after reconnection.
11834 Upon reconnection, the target will upload information about the
11835 tracepoints in effect. @value{GDBN} will then compare that
11836 information to the set of tracepoints currently defined, and attempt
11837 to match them up, allowing for the possibility that the numbers may
11838 have changed due to creation and deletion in the meantime. If one of
11839 the target's tracepoints does not match any in @value{GDBN}, the
11840 debugger will create a new tracepoint, so that you have a number with
11841 which to specify that tracepoint. This matching-up process is
11842 necessarily heuristic, and it may result in useless tracepoints being
11843 created; you may simply delete them if they are of no use.
11845 @cindex circular trace buffer
11846 If your target agent supports a @dfn{circular trace buffer}, then you
11847 can run a trace experiment indefinitely without filling the trace
11848 buffer; when space runs out, the agent deletes already-collected trace
11849 frames, oldest first, until there is enough room to continue
11850 collecting. This is especially useful if your tracepoints are being
11851 hit too often, and your trace gets terminated prematurely because the
11852 buffer is full. To ask for a circular trace buffer, simply set
11853 @samp{circular-trace-buffer} to on. You can set this at any time,
11854 including during tracing; if the agent can do it, it will change
11855 buffer handling on the fly, otherwise it will not take effect until
11859 @item set circular-trace-buffer on
11860 @itemx set circular-trace-buffer off
11861 @kindex set circular-trace-buffer
11862 Choose whether a tracing run should use a linear or circular buffer
11863 for trace data. A linear buffer will not lose any trace data, but may
11864 fill up prematurely, while a circular buffer will discard old trace
11865 data, but it will have always room for the latest tracepoint hits.
11867 @item show circular-trace-buffer
11868 @kindex show circular-trace-buffer
11869 Show the current choice for the trace buffer. Note that this may not
11870 match the agent's current buffer handling, nor is it guaranteed to
11871 match the setting that might have been in effect during a past run,
11872 for instance if you are looking at frames from a trace file.
11877 @item set trace-buffer-size @var{n}
11878 @kindex set trace-buffer-size
11879 Request that the target use a trace buffer of @var{n} bytes. Not all
11880 targets will honor the request; they may have a compiled-in size for
11881 the trace buffer, or some other limitation. Set to a value of
11882 @code{-1} to let the target use whatever size it likes. This is also
11885 @item show trace-buffer-size
11886 @kindex show trace-buffer-size
11887 Show the current requested size for the trace buffer. Note that this
11888 will only match the actual size if the target supports size-setting,
11889 and was able to handle the requested size. For instance, if the
11890 target can only change buffer size between runs, this variable will
11891 not reflect the change until the next run starts. Use @code{tstatus}
11892 to get a report of the actual buffer size.
11896 @item set trace-user @var{text}
11897 @kindex set trace-user
11899 @item show trace-user
11900 @kindex show trace-user
11902 @item set trace-notes @var{text}
11903 @kindex set trace-notes
11904 Set the trace run's notes.
11906 @item show trace-notes
11907 @kindex show trace-notes
11908 Show the trace run's notes.
11910 @item set trace-stop-notes @var{text}
11911 @kindex set trace-stop-notes
11912 Set the trace run's stop notes. The handling of the note is as for
11913 @code{tstop} arguments; the set command is convenient way to fix a
11914 stop note that is mistaken or incomplete.
11916 @item show trace-stop-notes
11917 @kindex show trace-stop-notes
11918 Show the trace run's stop notes.
11922 @node Tracepoint Restrictions
11923 @subsection Tracepoint Restrictions
11925 @cindex tracepoint restrictions
11926 There are a number of restrictions on the use of tracepoints. As
11927 described above, tracepoint data gathering occurs on the target
11928 without interaction from @value{GDBN}. Thus the full capabilities of
11929 the debugger are not available during data gathering, and then at data
11930 examination time, you will be limited by only having what was
11931 collected. The following items describe some common problems, but it
11932 is not exhaustive, and you may run into additional difficulties not
11938 Tracepoint expressions are intended to gather objects (lvalues). Thus
11939 the full flexibility of GDB's expression evaluator is not available.
11940 You cannot call functions, cast objects to aggregate types, access
11941 convenience variables or modify values (except by assignment to trace
11942 state variables). Some language features may implicitly call
11943 functions (for instance Objective-C fields with accessors), and therefore
11944 cannot be collected either.
11947 Collection of local variables, either individually or in bulk with
11948 @code{$locals} or @code{$args}, during @code{while-stepping} may
11949 behave erratically. The stepping action may enter a new scope (for
11950 instance by stepping into a function), or the location of the variable
11951 may change (for instance it is loaded into a register). The
11952 tracepoint data recorded uses the location information for the
11953 variables that is correct for the tracepoint location. When the
11954 tracepoint is created, it is not possible, in general, to determine
11955 where the steps of a @code{while-stepping} sequence will advance the
11956 program---particularly if a conditional branch is stepped.
11959 Collection of an incompletely-initialized or partially-destroyed object
11960 may result in something that @value{GDBN} cannot display, or displays
11961 in a misleading way.
11964 When @value{GDBN} displays a pointer to character it automatically
11965 dereferences the pointer to also display characters of the string
11966 being pointed to. However, collecting the pointer during tracing does
11967 not automatically collect the string. You need to explicitly
11968 dereference the pointer and provide size information if you want to
11969 collect not only the pointer, but the memory pointed to. For example,
11970 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11974 It is not possible to collect a complete stack backtrace at a
11975 tracepoint. Instead, you may collect the registers and a few hundred
11976 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11977 (adjust to use the name of the actual stack pointer register on your
11978 target architecture, and the amount of stack you wish to capture).
11979 Then the @code{backtrace} command will show a partial backtrace when
11980 using a trace frame. The number of stack frames that can be examined
11981 depends on the sizes of the frames in the collected stack. Note that
11982 if you ask for a block so large that it goes past the bottom of the
11983 stack, the target agent may report an error trying to read from an
11987 If you do not collect registers at a tracepoint, @value{GDBN} can
11988 infer that the value of @code{$pc} must be the same as the address of
11989 the tracepoint and use that when you are looking at a trace frame
11990 for that tracepoint. However, this cannot work if the tracepoint has
11991 multiple locations (for instance if it was set in a function that was
11992 inlined), or if it has a @code{while-stepping} loop. In those cases
11993 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11998 @node Analyze Collected Data
11999 @section Using the Collected Data
12001 After the tracepoint experiment ends, you use @value{GDBN} commands
12002 for examining the trace data. The basic idea is that each tracepoint
12003 collects a trace @dfn{snapshot} every time it is hit and another
12004 snapshot every time it single-steps. All these snapshots are
12005 consecutively numbered from zero and go into a buffer, and you can
12006 examine them later. The way you examine them is to @dfn{focus} on a
12007 specific trace snapshot. When the remote stub is focused on a trace
12008 snapshot, it will respond to all @value{GDBN} requests for memory and
12009 registers by reading from the buffer which belongs to that snapshot,
12010 rather than from @emph{real} memory or registers of the program being
12011 debugged. This means that @strong{all} @value{GDBN} commands
12012 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12013 behave as if we were currently debugging the program state as it was
12014 when the tracepoint occurred. Any requests for data that are not in
12015 the buffer will fail.
12018 * tfind:: How to select a trace snapshot
12019 * tdump:: How to display all data for a snapshot
12020 * save tracepoints:: How to save tracepoints for a future run
12024 @subsection @code{tfind @var{n}}
12027 @cindex select trace snapshot
12028 @cindex find trace snapshot
12029 The basic command for selecting a trace snapshot from the buffer is
12030 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12031 counting from zero. If no argument @var{n} is given, the next
12032 snapshot is selected.
12034 Here are the various forms of using the @code{tfind} command.
12038 Find the first snapshot in the buffer. This is a synonym for
12039 @code{tfind 0} (since 0 is the number of the first snapshot).
12042 Stop debugging trace snapshots, resume @emph{live} debugging.
12045 Same as @samp{tfind none}.
12048 No argument means find the next trace snapshot.
12051 Find the previous trace snapshot before the current one. This permits
12052 retracing earlier steps.
12054 @item tfind tracepoint @var{num}
12055 Find the next snapshot associated with tracepoint @var{num}. Search
12056 proceeds forward from the last examined trace snapshot. If no
12057 argument @var{num} is given, it means find the next snapshot collected
12058 for the same tracepoint as the current snapshot.
12060 @item tfind pc @var{addr}
12061 Find the next snapshot associated with the value @var{addr} of the
12062 program counter. Search proceeds forward from the last examined trace
12063 snapshot. If no argument @var{addr} is given, it means find the next
12064 snapshot with the same value of PC as the current snapshot.
12066 @item tfind outside @var{addr1}, @var{addr2}
12067 Find the next snapshot whose PC is outside the given range of
12068 addresses (exclusive).
12070 @item tfind range @var{addr1}, @var{addr2}
12071 Find the next snapshot whose PC is between @var{addr1} and
12072 @var{addr2} (inclusive).
12074 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12075 Find the next snapshot associated with the source line @var{n}. If
12076 the optional argument @var{file} is given, refer to line @var{n} in
12077 that source file. Search proceeds forward from the last examined
12078 trace snapshot. If no argument @var{n} is given, it means find the
12079 next line other than the one currently being examined; thus saying
12080 @code{tfind line} repeatedly can appear to have the same effect as
12081 stepping from line to line in a @emph{live} debugging session.
12084 The default arguments for the @code{tfind} commands are specifically
12085 designed to make it easy to scan through the trace buffer. For
12086 instance, @code{tfind} with no argument selects the next trace
12087 snapshot, and @code{tfind -} with no argument selects the previous
12088 trace snapshot. So, by giving one @code{tfind} command, and then
12089 simply hitting @key{RET} repeatedly you can examine all the trace
12090 snapshots in order. Or, by saying @code{tfind -} and then hitting
12091 @key{RET} repeatedly you can examine the snapshots in reverse order.
12092 The @code{tfind line} command with no argument selects the snapshot
12093 for the next source line executed. The @code{tfind pc} command with
12094 no argument selects the next snapshot with the same program counter
12095 (PC) as the current frame. The @code{tfind tracepoint} command with
12096 no argument selects the next trace snapshot collected by the same
12097 tracepoint as the current one.
12099 In addition to letting you scan through the trace buffer manually,
12100 these commands make it easy to construct @value{GDBN} scripts that
12101 scan through the trace buffer and print out whatever collected data
12102 you are interested in. Thus, if we want to examine the PC, FP, and SP
12103 registers from each trace frame in the buffer, we can say this:
12106 (@value{GDBP}) @b{tfind start}
12107 (@value{GDBP}) @b{while ($trace_frame != -1)}
12108 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12109 $trace_frame, $pc, $sp, $fp
12113 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12114 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12115 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12116 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12117 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12118 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12119 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12120 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12121 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12122 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12123 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12126 Or, if we want to examine the variable @code{X} at each source line in
12130 (@value{GDBP}) @b{tfind start}
12131 (@value{GDBP}) @b{while ($trace_frame != -1)}
12132 > printf "Frame %d, X == %d\n", $trace_frame, X
12142 @subsection @code{tdump}
12144 @cindex dump all data collected at tracepoint
12145 @cindex tracepoint data, display
12147 This command takes no arguments. It prints all the data collected at
12148 the current trace snapshot.
12151 (@value{GDBP}) @b{trace 444}
12152 (@value{GDBP}) @b{actions}
12153 Enter actions for tracepoint #2, one per line:
12154 > collect $regs, $locals, $args, gdb_long_test
12157 (@value{GDBP}) @b{tstart}
12159 (@value{GDBP}) @b{tfind line 444}
12160 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12162 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12164 (@value{GDBP}) @b{tdump}
12165 Data collected at tracepoint 2, trace frame 1:
12166 d0 0xc4aa0085 -995491707
12170 d4 0x71aea3d 119204413
12173 d7 0x380035 3670069
12174 a0 0x19e24a 1696330
12175 a1 0x3000668 50333288
12177 a3 0x322000 3284992
12178 a4 0x3000698 50333336
12179 a5 0x1ad3cc 1758156
12180 fp 0x30bf3c 0x30bf3c
12181 sp 0x30bf34 0x30bf34
12183 pc 0x20b2c8 0x20b2c8
12187 p = 0x20e5b4 "gdb-test"
12194 gdb_long_test = 17 '\021'
12199 @code{tdump} works by scanning the tracepoint's current collection
12200 actions and printing the value of each expression listed. So
12201 @code{tdump} can fail, if after a run, you change the tracepoint's
12202 actions to mention variables that were not collected during the run.
12204 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12205 uses the collected value of @code{$pc} to distinguish between trace
12206 frames that were collected at the tracepoint hit, and frames that were
12207 collected while stepping. This allows it to correctly choose whether
12208 to display the basic list of collections, or the collections from the
12209 body of the while-stepping loop. However, if @code{$pc} was not collected,
12210 then @code{tdump} will always attempt to dump using the basic collection
12211 list, and may fail if a while-stepping frame does not include all the
12212 same data that is collected at the tracepoint hit.
12213 @c This is getting pretty arcane, example would be good.
12215 @node save tracepoints
12216 @subsection @code{save tracepoints @var{filename}}
12217 @kindex save tracepoints
12218 @kindex save-tracepoints
12219 @cindex save tracepoints for future sessions
12221 This command saves all current tracepoint definitions together with
12222 their actions and passcounts, into a file @file{@var{filename}}
12223 suitable for use in a later debugging session. To read the saved
12224 tracepoint definitions, use the @code{source} command (@pxref{Command
12225 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12226 alias for @w{@code{save tracepoints}}
12228 @node Tracepoint Variables
12229 @section Convenience Variables for Tracepoints
12230 @cindex tracepoint variables
12231 @cindex convenience variables for tracepoints
12234 @vindex $trace_frame
12235 @item (int) $trace_frame
12236 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12237 snapshot is selected.
12239 @vindex $tracepoint
12240 @item (int) $tracepoint
12241 The tracepoint for the current trace snapshot.
12243 @vindex $trace_line
12244 @item (int) $trace_line
12245 The line number for the current trace snapshot.
12247 @vindex $trace_file
12248 @item (char []) $trace_file
12249 The source file for the current trace snapshot.
12251 @vindex $trace_func
12252 @item (char []) $trace_func
12253 The name of the function containing @code{$tracepoint}.
12256 Note: @code{$trace_file} is not suitable for use in @code{printf},
12257 use @code{output} instead.
12259 Here's a simple example of using these convenience variables for
12260 stepping through all the trace snapshots and printing some of their
12261 data. Note that these are not the same as trace state variables,
12262 which are managed by the target.
12265 (@value{GDBP}) @b{tfind start}
12267 (@value{GDBP}) @b{while $trace_frame != -1}
12268 > output $trace_file
12269 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12275 @section Using Trace Files
12276 @cindex trace files
12278 In some situations, the target running a trace experiment may no
12279 longer be available; perhaps it crashed, or the hardware was needed
12280 for a different activity. To handle these cases, you can arrange to
12281 dump the trace data into a file, and later use that file as a source
12282 of trace data, via the @code{target tfile} command.
12287 @item tsave [ -r ] @var{filename}
12288 Save the trace data to @var{filename}. By default, this command
12289 assumes that @var{filename} refers to the host filesystem, so if
12290 necessary @value{GDBN} will copy raw trace data up from the target and
12291 then save it. If the target supports it, you can also supply the
12292 optional argument @code{-r} (``remote'') to direct the target to save
12293 the data directly into @var{filename} in its own filesystem, which may be
12294 more efficient if the trace buffer is very large. (Note, however, that
12295 @code{target tfile} can only read from files accessible to the host.)
12297 @kindex target tfile
12299 @item target tfile @var{filename}
12300 Use the file named @var{filename} as a source of trace data. Commands
12301 that examine data work as they do with a live target, but it is not
12302 possible to run any new trace experiments. @code{tstatus} will report
12303 the state of the trace run at the moment the data was saved, as well
12304 as the current trace frame you are examining. @var{filename} must be
12305 on a filesystem accessible to the host.
12310 @chapter Debugging Programs That Use Overlays
12313 If your program is too large to fit completely in your target system's
12314 memory, you can sometimes use @dfn{overlays} to work around this
12315 problem. @value{GDBN} provides some support for debugging programs that
12319 * How Overlays Work:: A general explanation of overlays.
12320 * Overlay Commands:: Managing overlays in @value{GDBN}.
12321 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12322 mapped by asking the inferior.
12323 * Overlay Sample Program:: A sample program using overlays.
12326 @node How Overlays Work
12327 @section How Overlays Work
12328 @cindex mapped overlays
12329 @cindex unmapped overlays
12330 @cindex load address, overlay's
12331 @cindex mapped address
12332 @cindex overlay area
12334 Suppose you have a computer whose instruction address space is only 64
12335 kilobytes long, but which has much more memory which can be accessed by
12336 other means: special instructions, segment registers, or memory
12337 management hardware, for example. Suppose further that you want to
12338 adapt a program which is larger than 64 kilobytes to run on this system.
12340 One solution is to identify modules of your program which are relatively
12341 independent, and need not call each other directly; call these modules
12342 @dfn{overlays}. Separate the overlays from the main program, and place
12343 their machine code in the larger memory. Place your main program in
12344 instruction memory, but leave at least enough space there to hold the
12345 largest overlay as well.
12347 Now, to call a function located in an overlay, you must first copy that
12348 overlay's machine code from the large memory into the space set aside
12349 for it in the instruction memory, and then jump to its entry point
12352 @c NB: In the below the mapped area's size is greater or equal to the
12353 @c size of all overlays. This is intentional to remind the developer
12354 @c that overlays don't necessarily need to be the same size.
12358 Data Instruction Larger
12359 Address Space Address Space Address Space
12360 +-----------+ +-----------+ +-----------+
12362 +-----------+ +-----------+ +-----------+<-- overlay 1
12363 | program | | main | .----| overlay 1 | load address
12364 | variables | | program | | +-----------+
12365 | and heap | | | | | |
12366 +-----------+ | | | +-----------+<-- overlay 2
12367 | | +-----------+ | | | load address
12368 +-----------+ | | | .-| overlay 2 |
12370 mapped --->+-----------+ | | +-----------+
12371 address | | | | | |
12372 | overlay | <-' | | |
12373 | area | <---' +-----------+<-- overlay 3
12374 | | <---. | | load address
12375 +-----------+ `--| overlay 3 |
12382 @anchor{A code overlay}A code overlay
12386 The diagram (@pxref{A code overlay}) shows a system with separate data
12387 and instruction address spaces. To map an overlay, the program copies
12388 its code from the larger address space to the instruction address space.
12389 Since the overlays shown here all use the same mapped address, only one
12390 may be mapped at a time. For a system with a single address space for
12391 data and instructions, the diagram would be similar, except that the
12392 program variables and heap would share an address space with the main
12393 program and the overlay area.
12395 An overlay loaded into instruction memory and ready for use is called a
12396 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12397 instruction memory. An overlay not present (or only partially present)
12398 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12399 is its address in the larger memory. The mapped address is also called
12400 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12401 called the @dfn{load memory address}, or @dfn{LMA}.
12403 Unfortunately, overlays are not a completely transparent way to adapt a
12404 program to limited instruction memory. They introduce a new set of
12405 global constraints you must keep in mind as you design your program:
12410 Before calling or returning to a function in an overlay, your program
12411 must make sure that overlay is actually mapped. Otherwise, the call or
12412 return will transfer control to the right address, but in the wrong
12413 overlay, and your program will probably crash.
12416 If the process of mapping an overlay is expensive on your system, you
12417 will need to choose your overlays carefully to minimize their effect on
12418 your program's performance.
12421 The executable file you load onto your system must contain each
12422 overlay's instructions, appearing at the overlay's load address, not its
12423 mapped address. However, each overlay's instructions must be relocated
12424 and its symbols defined as if the overlay were at its mapped address.
12425 You can use GNU linker scripts to specify different load and relocation
12426 addresses for pieces of your program; see @ref{Overlay Description,,,
12427 ld.info, Using ld: the GNU linker}.
12430 The procedure for loading executable files onto your system must be able
12431 to load their contents into the larger address space as well as the
12432 instruction and data spaces.
12436 The overlay system described above is rather simple, and could be
12437 improved in many ways:
12442 If your system has suitable bank switch registers or memory management
12443 hardware, you could use those facilities to make an overlay's load area
12444 contents simply appear at their mapped address in instruction space.
12445 This would probably be faster than copying the overlay to its mapped
12446 area in the usual way.
12449 If your overlays are small enough, you could set aside more than one
12450 overlay area, and have more than one overlay mapped at a time.
12453 You can use overlays to manage data, as well as instructions. In
12454 general, data overlays are even less transparent to your design than
12455 code overlays: whereas code overlays only require care when you call or
12456 return to functions, data overlays require care every time you access
12457 the data. Also, if you change the contents of a data overlay, you
12458 must copy its contents back out to its load address before you can copy a
12459 different data overlay into the same mapped area.
12464 @node Overlay Commands
12465 @section Overlay Commands
12467 To use @value{GDBN}'s overlay support, each overlay in your program must
12468 correspond to a separate section of the executable file. The section's
12469 virtual memory address and load memory address must be the overlay's
12470 mapped and load addresses. Identifying overlays with sections allows
12471 @value{GDBN} to determine the appropriate address of a function or
12472 variable, depending on whether the overlay is mapped or not.
12474 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12475 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12480 Disable @value{GDBN}'s overlay support. When overlay support is
12481 disabled, @value{GDBN} assumes that all functions and variables are
12482 always present at their mapped addresses. By default, @value{GDBN}'s
12483 overlay support is disabled.
12485 @item overlay manual
12486 @cindex manual overlay debugging
12487 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12488 relies on you to tell it which overlays are mapped, and which are not,
12489 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12490 commands described below.
12492 @item overlay map-overlay @var{overlay}
12493 @itemx overlay map @var{overlay}
12494 @cindex map an overlay
12495 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12496 be the name of the object file section containing the overlay. When an
12497 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12498 functions and variables at their mapped addresses. @value{GDBN} assumes
12499 that any other overlays whose mapped ranges overlap that of
12500 @var{overlay} are now unmapped.
12502 @item overlay unmap-overlay @var{overlay}
12503 @itemx overlay unmap @var{overlay}
12504 @cindex unmap an overlay
12505 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12506 must be the name of the object file section containing the overlay.
12507 When an overlay is unmapped, @value{GDBN} assumes it can find the
12508 overlay's functions and variables at their load addresses.
12511 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12512 consults a data structure the overlay manager maintains in the inferior
12513 to see which overlays are mapped. For details, see @ref{Automatic
12514 Overlay Debugging}.
12516 @item overlay load-target
12517 @itemx overlay load
12518 @cindex reloading the overlay table
12519 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12520 re-reads the table @value{GDBN} automatically each time the inferior
12521 stops, so this command should only be necessary if you have changed the
12522 overlay mapping yourself using @value{GDBN}. This command is only
12523 useful when using automatic overlay debugging.
12525 @item overlay list-overlays
12526 @itemx overlay list
12527 @cindex listing mapped overlays
12528 Display a list of the overlays currently mapped, along with their mapped
12529 addresses, load addresses, and sizes.
12533 Normally, when @value{GDBN} prints a code address, it includes the name
12534 of the function the address falls in:
12537 (@value{GDBP}) print main
12538 $3 = @{int ()@} 0x11a0 <main>
12541 When overlay debugging is enabled, @value{GDBN} recognizes code in
12542 unmapped overlays, and prints the names of unmapped functions with
12543 asterisks around them. For example, if @code{foo} is a function in an
12544 unmapped overlay, @value{GDBN} prints it this way:
12547 (@value{GDBP}) overlay list
12548 No sections are mapped.
12549 (@value{GDBP}) print foo
12550 $5 = @{int (int)@} 0x100000 <*foo*>
12553 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12557 (@value{GDBP}) overlay list
12558 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12559 mapped at 0x1016 - 0x104a
12560 (@value{GDBP}) print foo
12561 $6 = @{int (int)@} 0x1016 <foo>
12564 When overlay debugging is enabled, @value{GDBN} can find the correct
12565 address for functions and variables in an overlay, whether or not the
12566 overlay is mapped. This allows most @value{GDBN} commands, like
12567 @code{break} and @code{disassemble}, to work normally, even on unmapped
12568 code. However, @value{GDBN}'s breakpoint support has some limitations:
12572 @cindex breakpoints in overlays
12573 @cindex overlays, setting breakpoints in
12574 You can set breakpoints in functions in unmapped overlays, as long as
12575 @value{GDBN} can write to the overlay at its load address.
12577 @value{GDBN} can not set hardware or simulator-based breakpoints in
12578 unmapped overlays. However, if you set a breakpoint at the end of your
12579 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12580 you are using manual overlay management), @value{GDBN} will re-set its
12581 breakpoints properly.
12585 @node Automatic Overlay Debugging
12586 @section Automatic Overlay Debugging
12587 @cindex automatic overlay debugging
12589 @value{GDBN} can automatically track which overlays are mapped and which
12590 are not, given some simple co-operation from the overlay manager in the
12591 inferior. If you enable automatic overlay debugging with the
12592 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12593 looks in the inferior's memory for certain variables describing the
12594 current state of the overlays.
12596 Here are the variables your overlay manager must define to support
12597 @value{GDBN}'s automatic overlay debugging:
12601 @item @code{_ovly_table}:
12602 This variable must be an array of the following structures:
12607 /* The overlay's mapped address. */
12610 /* The size of the overlay, in bytes. */
12611 unsigned long size;
12613 /* The overlay's load address. */
12616 /* Non-zero if the overlay is currently mapped;
12618 unsigned long mapped;
12622 @item @code{_novlys}:
12623 This variable must be a four-byte signed integer, holding the total
12624 number of elements in @code{_ovly_table}.
12628 To decide whether a particular overlay is mapped or not, @value{GDBN}
12629 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12630 @code{lma} members equal the VMA and LMA of the overlay's section in the
12631 executable file. When @value{GDBN} finds a matching entry, it consults
12632 the entry's @code{mapped} member to determine whether the overlay is
12635 In addition, your overlay manager may define a function called
12636 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12637 will silently set a breakpoint there. If the overlay manager then
12638 calls this function whenever it has changed the overlay table, this
12639 will enable @value{GDBN} to accurately keep track of which overlays
12640 are in program memory, and update any breakpoints that may be set
12641 in overlays. This will allow breakpoints to work even if the
12642 overlays are kept in ROM or other non-writable memory while they
12643 are not being executed.
12645 @node Overlay Sample Program
12646 @section Overlay Sample Program
12647 @cindex overlay example program
12649 When linking a program which uses overlays, you must place the overlays
12650 at their load addresses, while relocating them to run at their mapped
12651 addresses. To do this, you must write a linker script (@pxref{Overlay
12652 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12653 since linker scripts are specific to a particular host system, target
12654 architecture, and target memory layout, this manual cannot provide
12655 portable sample code demonstrating @value{GDBN}'s overlay support.
12657 However, the @value{GDBN} source distribution does contain an overlaid
12658 program, with linker scripts for a few systems, as part of its test
12659 suite. The program consists of the following files from
12660 @file{gdb/testsuite/gdb.base}:
12664 The main program file.
12666 A simple overlay manager, used by @file{overlays.c}.
12671 Overlay modules, loaded and used by @file{overlays.c}.
12674 Linker scripts for linking the test program on the @code{d10v-elf}
12675 and @code{m32r-elf} targets.
12678 You can build the test program using the @code{d10v-elf} GCC
12679 cross-compiler like this:
12682 $ d10v-elf-gcc -g -c overlays.c
12683 $ d10v-elf-gcc -g -c ovlymgr.c
12684 $ d10v-elf-gcc -g -c foo.c
12685 $ d10v-elf-gcc -g -c bar.c
12686 $ d10v-elf-gcc -g -c baz.c
12687 $ d10v-elf-gcc -g -c grbx.c
12688 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12689 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12692 The build process is identical for any other architecture, except that
12693 you must substitute the appropriate compiler and linker script for the
12694 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12698 @chapter Using @value{GDBN} with Different Languages
12701 Although programming languages generally have common aspects, they are
12702 rarely expressed in the same manner. For instance, in ANSI C,
12703 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12704 Modula-2, it is accomplished by @code{p^}. Values can also be
12705 represented (and displayed) differently. Hex numbers in C appear as
12706 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12708 @cindex working language
12709 Language-specific information is built into @value{GDBN} for some languages,
12710 allowing you to express operations like the above in your program's
12711 native language, and allowing @value{GDBN} to output values in a manner
12712 consistent with the syntax of your program's native language. The
12713 language you use to build expressions is called the @dfn{working
12717 * Setting:: Switching between source languages
12718 * Show:: Displaying the language
12719 * Checks:: Type and range checks
12720 * Supported Languages:: Supported languages
12721 * Unsupported Languages:: Unsupported languages
12725 @section Switching Between Source Languages
12727 There are two ways to control the working language---either have @value{GDBN}
12728 set it automatically, or select it manually yourself. You can use the
12729 @code{set language} command for either purpose. On startup, @value{GDBN}
12730 defaults to setting the language automatically. The working language is
12731 used to determine how expressions you type are interpreted, how values
12734 In addition to the working language, every source file that
12735 @value{GDBN} knows about has its own working language. For some object
12736 file formats, the compiler might indicate which language a particular
12737 source file is in. However, most of the time @value{GDBN} infers the
12738 language from the name of the file. The language of a source file
12739 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12740 show each frame appropriately for its own language. There is no way to
12741 set the language of a source file from within @value{GDBN}, but you can
12742 set the language associated with a filename extension. @xref{Show, ,
12743 Displaying the Language}.
12745 This is most commonly a problem when you use a program, such
12746 as @code{cfront} or @code{f2c}, that generates C but is written in
12747 another language. In that case, make the
12748 program use @code{#line} directives in its C output; that way
12749 @value{GDBN} will know the correct language of the source code of the original
12750 program, and will display that source code, not the generated C code.
12753 * Filenames:: Filename extensions and languages.
12754 * Manually:: Setting the working language manually
12755 * Automatically:: Having @value{GDBN} infer the source language
12759 @subsection List of Filename Extensions and Languages
12761 If a source file name ends in one of the following extensions, then
12762 @value{GDBN} infers that its language is the one indicated.
12780 C@t{++} source file
12786 Objective-C source file
12790 Fortran source file
12793 Modula-2 source file
12797 Assembler source file. This actually behaves almost like C, but
12798 @value{GDBN} does not skip over function prologues when stepping.
12801 In addition, you may set the language associated with a filename
12802 extension. @xref{Show, , Displaying the Language}.
12805 @subsection Setting the Working Language
12807 If you allow @value{GDBN} to set the language automatically,
12808 expressions are interpreted the same way in your debugging session and
12811 @kindex set language
12812 If you wish, you may set the language manually. To do this, issue the
12813 command @samp{set language @var{lang}}, where @var{lang} is the name of
12814 a language, such as
12815 @code{c} or @code{modula-2}.
12816 For a list of the supported languages, type @samp{set language}.
12818 Setting the language manually prevents @value{GDBN} from updating the working
12819 language automatically. This can lead to confusion if you try
12820 to debug a program when the working language is not the same as the
12821 source language, when an expression is acceptable to both
12822 languages---but means different things. For instance, if the current
12823 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12831 might not have the effect you intended. In C, this means to add
12832 @code{b} and @code{c} and place the result in @code{a}. The result
12833 printed would be the value of @code{a}. In Modula-2, this means to compare
12834 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12836 @node Automatically
12837 @subsection Having @value{GDBN} Infer the Source Language
12839 To have @value{GDBN} set the working language automatically, use
12840 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12841 then infers the working language. That is, when your program stops in a
12842 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12843 working language to the language recorded for the function in that
12844 frame. If the language for a frame is unknown (that is, if the function
12845 or block corresponding to the frame was defined in a source file that
12846 does not have a recognized extension), the current working language is
12847 not changed, and @value{GDBN} issues a warning.
12849 This may not seem necessary for most programs, which are written
12850 entirely in one source language. However, program modules and libraries
12851 written in one source language can be used by a main program written in
12852 a different source language. Using @samp{set language auto} in this
12853 case frees you from having to set the working language manually.
12856 @section Displaying the Language
12858 The following commands help you find out which language is the
12859 working language, and also what language source files were written in.
12862 @item show language
12863 @kindex show language
12864 Display the current working language. This is the
12865 language you can use with commands such as @code{print} to
12866 build and compute expressions that may involve variables in your program.
12869 @kindex info frame@r{, show the source language}
12870 Display the source language for this frame. This language becomes the
12871 working language if you use an identifier from this frame.
12872 @xref{Frame Info, ,Information about a Frame}, to identify the other
12873 information listed here.
12876 @kindex info source@r{, show the source language}
12877 Display the source language of this source file.
12878 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12879 information listed here.
12882 In unusual circumstances, you may have source files with extensions
12883 not in the standard list. You can then set the extension associated
12884 with a language explicitly:
12887 @item set extension-language @var{ext} @var{language}
12888 @kindex set extension-language
12889 Tell @value{GDBN} that source files with extension @var{ext} are to be
12890 assumed as written in the source language @var{language}.
12892 @item info extensions
12893 @kindex info extensions
12894 List all the filename extensions and the associated languages.
12898 @section Type and Range Checking
12900 Some languages are designed to guard you against making seemingly common
12901 errors through a series of compile- and run-time checks. These include
12902 checking the type of arguments to functions and operators and making
12903 sure mathematical overflows are caught at run time. Checks such as
12904 these help to ensure a program's correctness once it has been compiled
12905 by eliminating type mismatches and providing active checks for range
12906 errors when your program is running.
12908 By default @value{GDBN} checks for these errors according to the
12909 rules of the current source language. Although @value{GDBN} does not check
12910 the statements in your program, it can check expressions entered directly
12911 into @value{GDBN} for evaluation via the @code{print} command, for example.
12914 * Type Checking:: An overview of type checking
12915 * Range Checking:: An overview of range checking
12918 @cindex type checking
12919 @cindex checks, type
12920 @node Type Checking
12921 @subsection An Overview of Type Checking
12923 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12924 arguments to operators and functions have to be of the correct type,
12925 otherwise an error occurs. These checks prevent type mismatch
12926 errors from ever causing any run-time problems. For example,
12929 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12931 (@value{GDBP}) print obj.my_method (0)
12934 (@value{GDBP}) print obj.my_method (0x1234)
12935 Cannot resolve method klass::my_method to any overloaded instance
12938 The second example fails because in C@t{++} the integer constant
12939 @samp{0x1234} is not type-compatible with the pointer parameter type.
12941 For the expressions you use in @value{GDBN} commands, you can tell
12942 @value{GDBN} to not enforce strict type checking or
12943 to treat any mismatches as errors and abandon the expression;
12944 When type checking is disabled, @value{GDBN} successfully evaluates
12945 expressions like the second example above.
12947 Even if type checking is off, there may be other reasons
12948 related to type that prevent @value{GDBN} from evaluating an expression.
12949 For instance, @value{GDBN} does not know how to add an @code{int} and
12950 a @code{struct foo}. These particular type errors have nothing to do
12951 with the language in use and usually arise from expressions which make
12952 little sense to evaluate anyway.
12954 @value{GDBN} provides some additional commands for controlling type checking:
12956 @kindex set check type
12957 @kindex show check type
12959 @item set check type on
12960 @itemx set check type off
12961 Set strict type checking on or off. If any type mismatches occur in
12962 evaluating an expression while type checking is on, @value{GDBN} prints a
12963 message and aborts evaluation of the expression.
12965 @item show check type
12966 Show the current setting of type checking and whether @value{GDBN}
12967 is enforcing strict type checking rules.
12970 @cindex range checking
12971 @cindex checks, range
12972 @node Range Checking
12973 @subsection An Overview of Range Checking
12975 In some languages (such as Modula-2), it is an error to exceed the
12976 bounds of a type; this is enforced with run-time checks. Such range
12977 checking is meant to ensure program correctness by making sure
12978 computations do not overflow, or indices on an array element access do
12979 not exceed the bounds of the array.
12981 For expressions you use in @value{GDBN} commands, you can tell
12982 @value{GDBN} to treat range errors in one of three ways: ignore them,
12983 always treat them as errors and abandon the expression, or issue
12984 warnings but evaluate the expression anyway.
12986 A range error can result from numerical overflow, from exceeding an
12987 array index bound, or when you type a constant that is not a member
12988 of any type. Some languages, however, do not treat overflows as an
12989 error. In many implementations of C, mathematical overflow causes the
12990 result to ``wrap around'' to lower values---for example, if @var{m} is
12991 the largest integer value, and @var{s} is the smallest, then
12994 @var{m} + 1 @result{} @var{s}
12997 This, too, is specific to individual languages, and in some cases
12998 specific to individual compilers or machines. @xref{Supported Languages, ,
12999 Supported Languages}, for further details on specific languages.
13001 @value{GDBN} provides some additional commands for controlling the range checker:
13003 @kindex set check range
13004 @kindex show check range
13006 @item set check range auto
13007 Set range checking on or off based on the current working language.
13008 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13011 @item set check range on
13012 @itemx set check range off
13013 Set range checking on or off, overriding the default setting for the
13014 current working language. A warning is issued if the setting does not
13015 match the language default. If a range error occurs and range checking is on,
13016 then a message is printed and evaluation of the expression is aborted.
13018 @item set check range warn
13019 Output messages when the @value{GDBN} range checker detects a range error,
13020 but attempt to evaluate the expression anyway. Evaluating the
13021 expression may still be impossible for other reasons, such as accessing
13022 memory that the process does not own (a typical example from many Unix
13026 Show the current setting of the range checker, and whether or not it is
13027 being set automatically by @value{GDBN}.
13030 @node Supported Languages
13031 @section Supported Languages
13033 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13034 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13035 @c This is false ...
13036 Some @value{GDBN} features may be used in expressions regardless of the
13037 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13038 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13039 ,Expressions}) can be used with the constructs of any supported
13042 The following sections detail to what degree each source language is
13043 supported by @value{GDBN}. These sections are not meant to be language
13044 tutorials or references, but serve only as a reference guide to what the
13045 @value{GDBN} expression parser accepts, and what input and output
13046 formats should look like for different languages. There are many good
13047 books written on each of these languages; please look to these for a
13048 language reference or tutorial.
13051 * C:: C and C@t{++}
13054 * Objective-C:: Objective-C
13055 * OpenCL C:: OpenCL C
13056 * Fortran:: Fortran
13058 * Modula-2:: Modula-2
13063 @subsection C and C@t{++}
13065 @cindex C and C@t{++}
13066 @cindex expressions in C or C@t{++}
13068 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13069 to both languages. Whenever this is the case, we discuss those languages
13073 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13074 @cindex @sc{gnu} C@t{++}
13075 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13076 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13077 effectively, you must compile your C@t{++} programs with a supported
13078 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13079 compiler (@code{aCC}).
13082 * C Operators:: C and C@t{++} operators
13083 * C Constants:: C and C@t{++} constants
13084 * C Plus Plus Expressions:: C@t{++} expressions
13085 * C Defaults:: Default settings for C and C@t{++}
13086 * C Checks:: C and C@t{++} type and range checks
13087 * Debugging C:: @value{GDBN} and C
13088 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13089 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13093 @subsubsection C and C@t{++} Operators
13095 @cindex C and C@t{++} operators
13097 Operators must be defined on values of specific types. For instance,
13098 @code{+} is defined on numbers, but not on structures. Operators are
13099 often defined on groups of types.
13101 For the purposes of C and C@t{++}, the following definitions hold:
13106 @emph{Integral types} include @code{int} with any of its storage-class
13107 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13110 @emph{Floating-point types} include @code{float}, @code{double}, and
13111 @code{long double} (if supported by the target platform).
13114 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13117 @emph{Scalar types} include all of the above.
13122 The following operators are supported. They are listed here
13123 in order of increasing precedence:
13127 The comma or sequencing operator. Expressions in a comma-separated list
13128 are evaluated from left to right, with the result of the entire
13129 expression being the last expression evaluated.
13132 Assignment. The value of an assignment expression is the value
13133 assigned. Defined on scalar types.
13136 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13137 and translated to @w{@code{@var{a} = @var{a op b}}}.
13138 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13139 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13140 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13143 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13144 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13148 Logical @sc{or}. Defined on integral types.
13151 Logical @sc{and}. Defined on integral types.
13154 Bitwise @sc{or}. Defined on integral types.
13157 Bitwise exclusive-@sc{or}. Defined on integral types.
13160 Bitwise @sc{and}. Defined on integral types.
13163 Equality and inequality. Defined on scalar types. The value of these
13164 expressions is 0 for false and non-zero for true.
13166 @item <@r{, }>@r{, }<=@r{, }>=
13167 Less than, greater than, less than or equal, greater than or equal.
13168 Defined on scalar types. The value of these expressions is 0 for false
13169 and non-zero for true.
13172 left shift, and right shift. Defined on integral types.
13175 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13178 Addition and subtraction. Defined on integral types, floating-point types and
13181 @item *@r{, }/@r{, }%
13182 Multiplication, division, and modulus. Multiplication and division are
13183 defined on integral and floating-point types. Modulus is defined on
13187 Increment and decrement. When appearing before a variable, the
13188 operation is performed before the variable is used in an expression;
13189 when appearing after it, the variable's value is used before the
13190 operation takes place.
13193 Pointer dereferencing. Defined on pointer types. Same precedence as
13197 Address operator. Defined on variables. Same precedence as @code{++}.
13199 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13200 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13201 to examine the address
13202 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13206 Negative. Defined on integral and floating-point types. Same
13207 precedence as @code{++}.
13210 Logical negation. Defined on integral types. Same precedence as
13214 Bitwise complement operator. Defined on integral types. Same precedence as
13219 Structure member, and pointer-to-structure member. For convenience,
13220 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13221 pointer based on the stored type information.
13222 Defined on @code{struct} and @code{union} data.
13225 Dereferences of pointers to members.
13228 Array indexing. @code{@var{a}[@var{i}]} is defined as
13229 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13232 Function parameter list. Same precedence as @code{->}.
13235 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13236 and @code{class} types.
13239 Doubled colons also represent the @value{GDBN} scope operator
13240 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13244 If an operator is redefined in the user code, @value{GDBN} usually
13245 attempts to invoke the redefined version instead of using the operator's
13246 predefined meaning.
13249 @subsubsection C and C@t{++} Constants
13251 @cindex C and C@t{++} constants
13253 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13258 Integer constants are a sequence of digits. Octal constants are
13259 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13260 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13261 @samp{l}, specifying that the constant should be treated as a
13265 Floating point constants are a sequence of digits, followed by a decimal
13266 point, followed by a sequence of digits, and optionally followed by an
13267 exponent. An exponent is of the form:
13268 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13269 sequence of digits. The @samp{+} is optional for positive exponents.
13270 A floating-point constant may also end with a letter @samp{f} or
13271 @samp{F}, specifying that the constant should be treated as being of
13272 the @code{float} (as opposed to the default @code{double}) type; or with
13273 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13277 Enumerated constants consist of enumerated identifiers, or their
13278 integral equivalents.
13281 Character constants are a single character surrounded by single quotes
13282 (@code{'}), or a number---the ordinal value of the corresponding character
13283 (usually its @sc{ascii} value). Within quotes, the single character may
13284 be represented by a letter or by @dfn{escape sequences}, which are of
13285 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13286 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13287 @samp{@var{x}} is a predefined special character---for example,
13288 @samp{\n} for newline.
13290 Wide character constants can be written by prefixing a character
13291 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13292 form of @samp{x}. The target wide character set is used when
13293 computing the value of this constant (@pxref{Character Sets}).
13296 String constants are a sequence of character constants surrounded by
13297 double quotes (@code{"}). Any valid character constant (as described
13298 above) may appear. Double quotes within the string must be preceded by
13299 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13302 Wide string constants can be written by prefixing a string constant
13303 with @samp{L}, as in C. The target wide character set is used when
13304 computing the value of this constant (@pxref{Character Sets}).
13307 Pointer constants are an integral value. You can also write pointers
13308 to constants using the C operator @samp{&}.
13311 Array constants are comma-separated lists surrounded by braces @samp{@{}
13312 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13313 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13314 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13317 @node C Plus Plus Expressions
13318 @subsubsection C@t{++} Expressions
13320 @cindex expressions in C@t{++}
13321 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13323 @cindex debugging C@t{++} programs
13324 @cindex C@t{++} compilers
13325 @cindex debug formats and C@t{++}
13326 @cindex @value{NGCC} and C@t{++}
13328 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13329 the proper compiler and the proper debug format. Currently,
13330 @value{GDBN} works best when debugging C@t{++} code that is compiled
13331 with the most recent version of @value{NGCC} possible. The DWARF
13332 debugging format is preferred; @value{NGCC} defaults to this on most
13333 popular platforms. Other compilers and/or debug formats are likely to
13334 work badly or not at all when using @value{GDBN} to debug C@t{++}
13335 code. @xref{Compilation}.
13340 @cindex member functions
13342 Member function calls are allowed; you can use expressions like
13345 count = aml->GetOriginal(x, y)
13348 @vindex this@r{, inside C@t{++} member functions}
13349 @cindex namespace in C@t{++}
13351 While a member function is active (in the selected stack frame), your
13352 expressions have the same namespace available as the member function;
13353 that is, @value{GDBN} allows implicit references to the class instance
13354 pointer @code{this} following the same rules as C@t{++}. @code{using}
13355 declarations in the current scope are also respected by @value{GDBN}.
13357 @cindex call overloaded functions
13358 @cindex overloaded functions, calling
13359 @cindex type conversions in C@t{++}
13361 You can call overloaded functions; @value{GDBN} resolves the function
13362 call to the right definition, with some restrictions. @value{GDBN} does not
13363 perform overload resolution involving user-defined type conversions,
13364 calls to constructors, or instantiations of templates that do not exist
13365 in the program. It also cannot handle ellipsis argument lists or
13368 It does perform integral conversions and promotions, floating-point
13369 promotions, arithmetic conversions, pointer conversions, conversions of
13370 class objects to base classes, and standard conversions such as those of
13371 functions or arrays to pointers; it requires an exact match on the
13372 number of function arguments.
13374 Overload resolution is always performed, unless you have specified
13375 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13376 ,@value{GDBN} Features for C@t{++}}.
13378 You must specify @code{set overload-resolution off} in order to use an
13379 explicit function signature to call an overloaded function, as in
13381 p 'foo(char,int)'('x', 13)
13384 The @value{GDBN} command-completion facility can simplify this;
13385 see @ref{Completion, ,Command Completion}.
13387 @cindex reference declarations
13389 @value{GDBN} understands variables declared as C@t{++} references; you can use
13390 them in expressions just as you do in C@t{++} source---they are automatically
13393 In the parameter list shown when @value{GDBN} displays a frame, the values of
13394 reference variables are not displayed (unlike other variables); this
13395 avoids clutter, since references are often used for large structures.
13396 The @emph{address} of a reference variable is always shown, unless
13397 you have specified @samp{set print address off}.
13400 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13401 expressions can use it just as expressions in your program do. Since
13402 one scope may be defined in another, you can use @code{::} repeatedly if
13403 necessary, for example in an expression like
13404 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13405 resolving name scope by reference to source files, in both C and C@t{++}
13406 debugging (@pxref{Variables, ,Program Variables}).
13409 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13414 @subsubsection C and C@t{++} Defaults
13416 @cindex C and C@t{++} defaults
13418 If you allow @value{GDBN} to set range checking automatically, it
13419 defaults to @code{off} whenever the working language changes to
13420 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13421 selects the working language.
13423 If you allow @value{GDBN} to set the language automatically, it
13424 recognizes source files whose names end with @file{.c}, @file{.C}, or
13425 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13426 these files, it sets the working language to C or C@t{++}.
13427 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13428 for further details.
13431 @subsubsection C and C@t{++} Type and Range Checks
13433 @cindex C and C@t{++} checks
13435 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13436 checking is used. However, if you turn type checking off, @value{GDBN}
13437 will allow certain non-standard conversions, such as promoting integer
13438 constants to pointers.
13440 Range checking, if turned on, is done on mathematical operations. Array
13441 indices are not checked, since they are often used to index a pointer
13442 that is not itself an array.
13445 @subsubsection @value{GDBN} and C
13447 The @code{set print union} and @code{show print union} commands apply to
13448 the @code{union} type. When set to @samp{on}, any @code{union} that is
13449 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13450 appears as @samp{@{...@}}.
13452 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13453 with pointers and a memory allocation function. @xref{Expressions,
13456 @node Debugging C Plus Plus
13457 @subsubsection @value{GDBN} Features for C@t{++}
13459 @cindex commands for C@t{++}
13461 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13462 designed specifically for use with C@t{++}. Here is a summary:
13465 @cindex break in overloaded functions
13466 @item @r{breakpoint menus}
13467 When you want a breakpoint in a function whose name is overloaded,
13468 @value{GDBN} has the capability to display a menu of possible breakpoint
13469 locations to help you specify which function definition you want.
13470 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13472 @cindex overloading in C@t{++}
13473 @item rbreak @var{regex}
13474 Setting breakpoints using regular expressions is helpful for setting
13475 breakpoints on overloaded functions that are not members of any special
13477 @xref{Set Breaks, ,Setting Breakpoints}.
13479 @cindex C@t{++} exception handling
13482 Debug C@t{++} exception handling using these commands. @xref{Set
13483 Catchpoints, , Setting Catchpoints}.
13485 @cindex inheritance
13486 @item ptype @var{typename}
13487 Print inheritance relationships as well as other information for type
13489 @xref{Symbols, ,Examining the Symbol Table}.
13491 @item info vtbl @var{expression}.
13492 The @code{info vtbl} command can be used to display the virtual
13493 method tables of the object computed by @var{expression}. This shows
13494 one entry per virtual table; there may be multiple virtual tables when
13495 multiple inheritance is in use.
13497 @cindex C@t{++} symbol display
13498 @item set print demangle
13499 @itemx show print demangle
13500 @itemx set print asm-demangle
13501 @itemx show print asm-demangle
13502 Control whether C@t{++} symbols display in their source form, both when
13503 displaying code as C@t{++} source and when displaying disassemblies.
13504 @xref{Print Settings, ,Print Settings}.
13506 @item set print object
13507 @itemx show print object
13508 Choose whether to print derived (actual) or declared types of objects.
13509 @xref{Print Settings, ,Print Settings}.
13511 @item set print vtbl
13512 @itemx show print vtbl
13513 Control the format for printing virtual function tables.
13514 @xref{Print Settings, ,Print Settings}.
13515 (The @code{vtbl} commands do not work on programs compiled with the HP
13516 ANSI C@t{++} compiler (@code{aCC}).)
13518 @kindex set overload-resolution
13519 @cindex overloaded functions, overload resolution
13520 @item set overload-resolution on
13521 Enable overload resolution for C@t{++} expression evaluation. The default
13522 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13523 and searches for a function whose signature matches the argument types,
13524 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13525 Expressions, ,C@t{++} Expressions}, for details).
13526 If it cannot find a match, it emits a message.
13528 @item set overload-resolution off
13529 Disable overload resolution for C@t{++} expression evaluation. For
13530 overloaded functions that are not class member functions, @value{GDBN}
13531 chooses the first function of the specified name that it finds in the
13532 symbol table, whether or not its arguments are of the correct type. For
13533 overloaded functions that are class member functions, @value{GDBN}
13534 searches for a function whose signature @emph{exactly} matches the
13537 @kindex show overload-resolution
13538 @item show overload-resolution
13539 Show the current setting of overload resolution.
13541 @item @r{Overloaded symbol names}
13542 You can specify a particular definition of an overloaded symbol, using
13543 the same notation that is used to declare such symbols in C@t{++}: type
13544 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13545 also use the @value{GDBN} command-line word completion facilities to list the
13546 available choices, or to finish the type list for you.
13547 @xref{Completion,, Command Completion}, for details on how to do this.
13550 @node Decimal Floating Point
13551 @subsubsection Decimal Floating Point format
13552 @cindex decimal floating point format
13554 @value{GDBN} can examine, set and perform computations with numbers in
13555 decimal floating point format, which in the C language correspond to the
13556 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13557 specified by the extension to support decimal floating-point arithmetic.
13559 There are two encodings in use, depending on the architecture: BID (Binary
13560 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13561 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13564 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13565 to manipulate decimal floating point numbers, it is not possible to convert
13566 (using a cast, for example) integers wider than 32-bit to decimal float.
13568 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13569 point computations, error checking in decimal float operations ignores
13570 underflow, overflow and divide by zero exceptions.
13572 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13573 to inspect @code{_Decimal128} values stored in floating point registers.
13574 See @ref{PowerPC,,PowerPC} for more details.
13580 @value{GDBN} can be used to debug programs written in D and compiled with
13581 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13582 specific feature --- dynamic arrays.
13587 @cindex Go (programming language)
13588 @value{GDBN} can be used to debug programs written in Go and compiled with
13589 @file{gccgo} or @file{6g} compilers.
13591 Here is a summary of the Go-specific features and restrictions:
13594 @cindex current Go package
13595 @item The current Go package
13596 The name of the current package does not need to be specified when
13597 specifying global variables and functions.
13599 For example, given the program:
13603 var myglob = "Shall we?"
13609 When stopped inside @code{main} either of these work:
13613 (gdb) p main.myglob
13616 @cindex builtin Go types
13617 @item Builtin Go types
13618 The @code{string} type is recognized by @value{GDBN} and is printed
13621 @cindex builtin Go functions
13622 @item Builtin Go functions
13623 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13624 function and handles it internally.
13626 @cindex restrictions on Go expressions
13627 @item Restrictions on Go expressions
13628 All Go operators are supported except @code{&^}.
13629 The Go @code{_} ``blank identifier'' is not supported.
13630 Automatic dereferencing of pointers is not supported.
13634 @subsection Objective-C
13636 @cindex Objective-C
13637 This section provides information about some commands and command
13638 options that are useful for debugging Objective-C code. See also
13639 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13640 few more commands specific to Objective-C support.
13643 * Method Names in Commands::
13644 * The Print Command with Objective-C::
13647 @node Method Names in Commands
13648 @subsubsection Method Names in Commands
13650 The following commands have been extended to accept Objective-C method
13651 names as line specifications:
13653 @kindex clear@r{, and Objective-C}
13654 @kindex break@r{, and Objective-C}
13655 @kindex info line@r{, and Objective-C}
13656 @kindex jump@r{, and Objective-C}
13657 @kindex list@r{, and Objective-C}
13661 @item @code{info line}
13666 A fully qualified Objective-C method name is specified as
13669 -[@var{Class} @var{methodName}]
13672 where the minus sign is used to indicate an instance method and a
13673 plus sign (not shown) is used to indicate a class method. The class
13674 name @var{Class} and method name @var{methodName} are enclosed in
13675 brackets, similar to the way messages are specified in Objective-C
13676 source code. For example, to set a breakpoint at the @code{create}
13677 instance method of class @code{Fruit} in the program currently being
13681 break -[Fruit create]
13684 To list ten program lines around the @code{initialize} class method,
13688 list +[NSText initialize]
13691 In the current version of @value{GDBN}, the plus or minus sign is
13692 required. In future versions of @value{GDBN}, the plus or minus
13693 sign will be optional, but you can use it to narrow the search. It
13694 is also possible to specify just a method name:
13700 You must specify the complete method name, including any colons. If
13701 your program's source files contain more than one @code{create} method,
13702 you'll be presented with a numbered list of classes that implement that
13703 method. Indicate your choice by number, or type @samp{0} to exit if
13706 As another example, to clear a breakpoint established at the
13707 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13710 clear -[NSWindow makeKeyAndOrderFront:]
13713 @node The Print Command with Objective-C
13714 @subsubsection The Print Command With Objective-C
13715 @cindex Objective-C, print objects
13716 @kindex print-object
13717 @kindex po @r{(@code{print-object})}
13719 The print command has also been extended to accept methods. For example:
13722 print -[@var{object} hash]
13725 @cindex print an Objective-C object description
13726 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13728 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13729 and print the result. Also, an additional command has been added,
13730 @code{print-object} or @code{po} for short, which is meant to print
13731 the description of an object. However, this command may only work
13732 with certain Objective-C libraries that have a particular hook
13733 function, @code{_NSPrintForDebugger}, defined.
13736 @subsection OpenCL C
13739 This section provides information about @value{GDBN}s OpenCL C support.
13742 * OpenCL C Datatypes::
13743 * OpenCL C Expressions::
13744 * OpenCL C Operators::
13747 @node OpenCL C Datatypes
13748 @subsubsection OpenCL C Datatypes
13750 @cindex OpenCL C Datatypes
13751 @value{GDBN} supports the builtin scalar and vector datatypes specified
13752 by OpenCL 1.1. In addition the half- and double-precision floating point
13753 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13754 extensions are also known to @value{GDBN}.
13756 @node OpenCL C Expressions
13757 @subsubsection OpenCL C Expressions
13759 @cindex OpenCL C Expressions
13760 @value{GDBN} supports accesses to vector components including the access as
13761 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13762 supported by @value{GDBN} can be used as well.
13764 @node OpenCL C Operators
13765 @subsubsection OpenCL C Operators
13767 @cindex OpenCL C Operators
13768 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13772 @subsection Fortran
13773 @cindex Fortran-specific support in @value{GDBN}
13775 @value{GDBN} can be used to debug programs written in Fortran, but it
13776 currently supports only the features of Fortran 77 language.
13778 @cindex trailing underscore, in Fortran symbols
13779 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13780 among them) append an underscore to the names of variables and
13781 functions. When you debug programs compiled by those compilers, you
13782 will need to refer to variables and functions with a trailing
13786 * Fortran Operators:: Fortran operators and expressions
13787 * Fortran Defaults:: Default settings for Fortran
13788 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13791 @node Fortran Operators
13792 @subsubsection Fortran Operators and Expressions
13794 @cindex Fortran operators and expressions
13796 Operators must be defined on values of specific types. For instance,
13797 @code{+} is defined on numbers, but not on characters or other non-
13798 arithmetic types. Operators are often defined on groups of types.
13802 The exponentiation operator. It raises the first operand to the power
13806 The range operator. Normally used in the form of array(low:high) to
13807 represent a section of array.
13810 The access component operator. Normally used to access elements in derived
13811 types. Also suitable for unions. As unions aren't part of regular Fortran,
13812 this can only happen when accessing a register that uses a gdbarch-defined
13816 @node Fortran Defaults
13817 @subsubsection Fortran Defaults
13819 @cindex Fortran Defaults
13821 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13822 default uses case-insensitive matches for Fortran symbols. You can
13823 change that with the @samp{set case-insensitive} command, see
13824 @ref{Symbols}, for the details.
13826 @node Special Fortran Commands
13827 @subsubsection Special Fortran Commands
13829 @cindex Special Fortran commands
13831 @value{GDBN} has some commands to support Fortran-specific features,
13832 such as displaying common blocks.
13835 @cindex @code{COMMON} blocks, Fortran
13836 @kindex info common
13837 @item info common @r{[}@var{common-name}@r{]}
13838 This command prints the values contained in the Fortran @code{COMMON}
13839 block whose name is @var{common-name}. With no argument, the names of
13840 all @code{COMMON} blocks visible at the current program location are
13847 @cindex Pascal support in @value{GDBN}, limitations
13848 Debugging Pascal programs which use sets, subranges, file variables, or
13849 nested functions does not currently work. @value{GDBN} does not support
13850 entering expressions, printing values, or similar features using Pascal
13853 The Pascal-specific command @code{set print pascal_static-members}
13854 controls whether static members of Pascal objects are displayed.
13855 @xref{Print Settings, pascal_static-members}.
13858 @subsection Modula-2
13860 @cindex Modula-2, @value{GDBN} support
13862 The extensions made to @value{GDBN} to support Modula-2 only support
13863 output from the @sc{gnu} Modula-2 compiler (which is currently being
13864 developed). Other Modula-2 compilers are not currently supported, and
13865 attempting to debug executables produced by them is most likely
13866 to give an error as @value{GDBN} reads in the executable's symbol
13869 @cindex expressions in Modula-2
13871 * M2 Operators:: Built-in operators
13872 * Built-In Func/Proc:: Built-in functions and procedures
13873 * M2 Constants:: Modula-2 constants
13874 * M2 Types:: Modula-2 types
13875 * M2 Defaults:: Default settings for Modula-2
13876 * Deviations:: Deviations from standard Modula-2
13877 * M2 Checks:: Modula-2 type and range checks
13878 * M2 Scope:: The scope operators @code{::} and @code{.}
13879 * GDB/M2:: @value{GDBN} and Modula-2
13883 @subsubsection Operators
13884 @cindex Modula-2 operators
13886 Operators must be defined on values of specific types. For instance,
13887 @code{+} is defined on numbers, but not on structures. Operators are
13888 often defined on groups of types. For the purposes of Modula-2, the
13889 following definitions hold:
13894 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13898 @emph{Character types} consist of @code{CHAR} and its subranges.
13901 @emph{Floating-point types} consist of @code{REAL}.
13904 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13908 @emph{Scalar types} consist of all of the above.
13911 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13914 @emph{Boolean types} consist of @code{BOOLEAN}.
13918 The following operators are supported, and appear in order of
13919 increasing precedence:
13923 Function argument or array index separator.
13926 Assignment. The value of @var{var} @code{:=} @var{value} is
13930 Less than, greater than on integral, floating-point, or enumerated
13934 Less than or equal to, greater than or equal to
13935 on integral, floating-point and enumerated types, or set inclusion on
13936 set types. Same precedence as @code{<}.
13938 @item =@r{, }<>@r{, }#
13939 Equality and two ways of expressing inequality, valid on scalar types.
13940 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13941 available for inequality, since @code{#} conflicts with the script
13945 Set membership. Defined on set types and the types of their members.
13946 Same precedence as @code{<}.
13949 Boolean disjunction. Defined on boolean types.
13952 Boolean conjunction. Defined on boolean types.
13955 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13958 Addition and subtraction on integral and floating-point types, or union
13959 and difference on set types.
13962 Multiplication on integral and floating-point types, or set intersection
13966 Division on floating-point types, or symmetric set difference on set
13967 types. Same precedence as @code{*}.
13970 Integer division and remainder. Defined on integral types. Same
13971 precedence as @code{*}.
13974 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13977 Pointer dereferencing. Defined on pointer types.
13980 Boolean negation. Defined on boolean types. Same precedence as
13984 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13985 precedence as @code{^}.
13988 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13991 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13995 @value{GDBN} and Modula-2 scope operators.
13999 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14000 treats the use of the operator @code{IN}, or the use of operators
14001 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14002 @code{<=}, and @code{>=} on sets as an error.
14006 @node Built-In Func/Proc
14007 @subsubsection Built-in Functions and Procedures
14008 @cindex Modula-2 built-ins
14010 Modula-2 also makes available several built-in procedures and functions.
14011 In describing these, the following metavariables are used:
14016 represents an @code{ARRAY} variable.
14019 represents a @code{CHAR} constant or variable.
14022 represents a variable or constant of integral type.
14025 represents an identifier that belongs to a set. Generally used in the
14026 same function with the metavariable @var{s}. The type of @var{s} should
14027 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14030 represents a variable or constant of integral or floating-point type.
14033 represents a variable or constant of floating-point type.
14039 represents a variable.
14042 represents a variable or constant of one of many types. See the
14043 explanation of the function for details.
14046 All Modula-2 built-in procedures also return a result, described below.
14050 Returns the absolute value of @var{n}.
14053 If @var{c} is a lower case letter, it returns its upper case
14054 equivalent, otherwise it returns its argument.
14057 Returns the character whose ordinal value is @var{i}.
14060 Decrements the value in the variable @var{v} by one. Returns the new value.
14062 @item DEC(@var{v},@var{i})
14063 Decrements the value in the variable @var{v} by @var{i}. Returns the
14066 @item EXCL(@var{m},@var{s})
14067 Removes the element @var{m} from the set @var{s}. Returns the new
14070 @item FLOAT(@var{i})
14071 Returns the floating point equivalent of the integer @var{i}.
14073 @item HIGH(@var{a})
14074 Returns the index of the last member of @var{a}.
14077 Increments the value in the variable @var{v} by one. Returns the new value.
14079 @item INC(@var{v},@var{i})
14080 Increments the value in the variable @var{v} by @var{i}. Returns the
14083 @item INCL(@var{m},@var{s})
14084 Adds the element @var{m} to the set @var{s} if it is not already
14085 there. Returns the new set.
14088 Returns the maximum value of the type @var{t}.
14091 Returns the minimum value of the type @var{t}.
14094 Returns boolean TRUE if @var{i} is an odd number.
14097 Returns the ordinal value of its argument. For example, the ordinal
14098 value of a character is its @sc{ascii} value (on machines supporting the
14099 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14100 integral, character and enumerated types.
14102 @item SIZE(@var{x})
14103 Returns the size of its argument. @var{x} can be a variable or a type.
14105 @item TRUNC(@var{r})
14106 Returns the integral part of @var{r}.
14108 @item TSIZE(@var{x})
14109 Returns the size of its argument. @var{x} can be a variable or a type.
14111 @item VAL(@var{t},@var{i})
14112 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14116 @emph{Warning:} Sets and their operations are not yet supported, so
14117 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14121 @cindex Modula-2 constants
14123 @subsubsection Constants
14125 @value{GDBN} allows you to express the constants of Modula-2 in the following
14131 Integer constants are simply a sequence of digits. When used in an
14132 expression, a constant is interpreted to be type-compatible with the
14133 rest of the expression. Hexadecimal integers are specified by a
14134 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14137 Floating point constants appear as a sequence of digits, followed by a
14138 decimal point and another sequence of digits. An optional exponent can
14139 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14140 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14141 digits of the floating point constant must be valid decimal (base 10)
14145 Character constants consist of a single character enclosed by a pair of
14146 like quotes, either single (@code{'}) or double (@code{"}). They may
14147 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14148 followed by a @samp{C}.
14151 String constants consist of a sequence of characters enclosed by a
14152 pair of like quotes, either single (@code{'}) or double (@code{"}).
14153 Escape sequences in the style of C are also allowed. @xref{C
14154 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14158 Enumerated constants consist of an enumerated identifier.
14161 Boolean constants consist of the identifiers @code{TRUE} and
14165 Pointer constants consist of integral values only.
14168 Set constants are not yet supported.
14172 @subsubsection Modula-2 Types
14173 @cindex Modula-2 types
14175 Currently @value{GDBN} can print the following data types in Modula-2
14176 syntax: array types, record types, set types, pointer types, procedure
14177 types, enumerated types, subrange types and base types. You can also
14178 print the contents of variables declared using these type.
14179 This section gives a number of simple source code examples together with
14180 sample @value{GDBN} sessions.
14182 The first example contains the following section of code:
14191 and you can request @value{GDBN} to interrogate the type and value of
14192 @code{r} and @code{s}.
14195 (@value{GDBP}) print s
14197 (@value{GDBP}) ptype s
14199 (@value{GDBP}) print r
14201 (@value{GDBP}) ptype r
14206 Likewise if your source code declares @code{s} as:
14210 s: SET ['A'..'Z'] ;
14214 then you may query the type of @code{s} by:
14217 (@value{GDBP}) ptype s
14218 type = SET ['A'..'Z']
14222 Note that at present you cannot interactively manipulate set
14223 expressions using the debugger.
14225 The following example shows how you might declare an array in Modula-2
14226 and how you can interact with @value{GDBN} to print its type and contents:
14230 s: ARRAY [-10..10] OF CHAR ;
14234 (@value{GDBP}) ptype s
14235 ARRAY [-10..10] OF CHAR
14238 Note that the array handling is not yet complete and although the type
14239 is printed correctly, expression handling still assumes that all
14240 arrays have a lower bound of zero and not @code{-10} as in the example
14243 Here are some more type related Modula-2 examples:
14247 colour = (blue, red, yellow, green) ;
14248 t = [blue..yellow] ;
14256 The @value{GDBN} interaction shows how you can query the data type
14257 and value of a variable.
14260 (@value{GDBP}) print s
14262 (@value{GDBP}) ptype t
14263 type = [blue..yellow]
14267 In this example a Modula-2 array is declared and its contents
14268 displayed. Observe that the contents are written in the same way as
14269 their @code{C} counterparts.
14273 s: ARRAY [1..5] OF CARDINAL ;
14279 (@value{GDBP}) print s
14280 $1 = @{1, 0, 0, 0, 0@}
14281 (@value{GDBP}) ptype s
14282 type = ARRAY [1..5] OF CARDINAL
14285 The Modula-2 language interface to @value{GDBN} also understands
14286 pointer types as shown in this example:
14290 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14297 and you can request that @value{GDBN} describes the type of @code{s}.
14300 (@value{GDBP}) ptype s
14301 type = POINTER TO ARRAY [1..5] OF CARDINAL
14304 @value{GDBN} handles compound types as we can see in this example.
14305 Here we combine array types, record types, pointer types and subrange
14316 myarray = ARRAY myrange OF CARDINAL ;
14317 myrange = [-2..2] ;
14319 s: POINTER TO ARRAY myrange OF foo ;
14323 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14327 (@value{GDBP}) ptype s
14328 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14331 f3 : ARRAY [-2..2] OF CARDINAL;
14336 @subsubsection Modula-2 Defaults
14337 @cindex Modula-2 defaults
14339 If type and range checking are set automatically by @value{GDBN}, they
14340 both default to @code{on} whenever the working language changes to
14341 Modula-2. This happens regardless of whether you or @value{GDBN}
14342 selected the working language.
14344 If you allow @value{GDBN} to set the language automatically, then entering
14345 code compiled from a file whose name ends with @file{.mod} sets the
14346 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14347 Infer the Source Language}, for further details.
14350 @subsubsection Deviations from Standard Modula-2
14351 @cindex Modula-2, deviations from
14353 A few changes have been made to make Modula-2 programs easier to debug.
14354 This is done primarily via loosening its type strictness:
14358 Unlike in standard Modula-2, pointer constants can be formed by
14359 integers. This allows you to modify pointer variables during
14360 debugging. (In standard Modula-2, the actual address contained in a
14361 pointer variable is hidden from you; it can only be modified
14362 through direct assignment to another pointer variable or expression that
14363 returned a pointer.)
14366 C escape sequences can be used in strings and characters to represent
14367 non-printable characters. @value{GDBN} prints out strings with these
14368 escape sequences embedded. Single non-printable characters are
14369 printed using the @samp{CHR(@var{nnn})} format.
14372 The assignment operator (@code{:=}) returns the value of its right-hand
14376 All built-in procedures both modify @emph{and} return their argument.
14380 @subsubsection Modula-2 Type and Range Checks
14381 @cindex Modula-2 checks
14384 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14387 @c FIXME remove warning when type/range checks added
14389 @value{GDBN} considers two Modula-2 variables type equivalent if:
14393 They are of types that have been declared equivalent via a @code{TYPE
14394 @var{t1} = @var{t2}} statement
14397 They have been declared on the same line. (Note: This is true of the
14398 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14401 As long as type checking is enabled, any attempt to combine variables
14402 whose types are not equivalent is an error.
14404 Range checking is done on all mathematical operations, assignment, array
14405 index bounds, and all built-in functions and procedures.
14408 @subsubsection The Scope Operators @code{::} and @code{.}
14410 @cindex @code{.}, Modula-2 scope operator
14411 @cindex colon, doubled as scope operator
14413 @vindex colon-colon@r{, in Modula-2}
14414 @c Info cannot handle :: but TeX can.
14417 @vindex ::@r{, in Modula-2}
14420 There are a few subtle differences between the Modula-2 scope operator
14421 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14426 @var{module} . @var{id}
14427 @var{scope} :: @var{id}
14431 where @var{scope} is the name of a module or a procedure,
14432 @var{module} the name of a module, and @var{id} is any declared
14433 identifier within your program, except another module.
14435 Using the @code{::} operator makes @value{GDBN} search the scope
14436 specified by @var{scope} for the identifier @var{id}. If it is not
14437 found in the specified scope, then @value{GDBN} searches all scopes
14438 enclosing the one specified by @var{scope}.
14440 Using the @code{.} operator makes @value{GDBN} search the current scope for
14441 the identifier specified by @var{id} that was imported from the
14442 definition module specified by @var{module}. With this operator, it is
14443 an error if the identifier @var{id} was not imported from definition
14444 module @var{module}, or if @var{id} is not an identifier in
14448 @subsubsection @value{GDBN} and Modula-2
14450 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14451 Five subcommands of @code{set print} and @code{show print} apply
14452 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14453 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14454 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14455 analogue in Modula-2.
14457 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14458 with any language, is not useful with Modula-2. Its
14459 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14460 created in Modula-2 as they can in C or C@t{++}. However, because an
14461 address can be specified by an integral constant, the construct
14462 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14464 @cindex @code{#} in Modula-2
14465 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14466 interpreted as the beginning of a comment. Use @code{<>} instead.
14472 The extensions made to @value{GDBN} for Ada only support
14473 output from the @sc{gnu} Ada (GNAT) compiler.
14474 Other Ada compilers are not currently supported, and
14475 attempting to debug executables produced by them is most likely
14479 @cindex expressions in Ada
14481 * Ada Mode Intro:: General remarks on the Ada syntax
14482 and semantics supported by Ada mode
14484 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14485 * Additions to Ada:: Extensions of the Ada expression syntax.
14486 * Stopping Before Main Program:: Debugging the program during elaboration.
14487 * Ada Tasks:: Listing and setting breakpoints in tasks.
14488 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14489 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14491 * Ada Glitches:: Known peculiarities of Ada mode.
14494 @node Ada Mode Intro
14495 @subsubsection Introduction
14496 @cindex Ada mode, general
14498 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14499 syntax, with some extensions.
14500 The philosophy behind the design of this subset is
14504 That @value{GDBN} should provide basic literals and access to operations for
14505 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14506 leaving more sophisticated computations to subprograms written into the
14507 program (which therefore may be called from @value{GDBN}).
14510 That type safety and strict adherence to Ada language restrictions
14511 are not particularly important to the @value{GDBN} user.
14514 That brevity is important to the @value{GDBN} user.
14517 Thus, for brevity, the debugger acts as if all names declared in
14518 user-written packages are directly visible, even if they are not visible
14519 according to Ada rules, thus making it unnecessary to fully qualify most
14520 names with their packages, regardless of context. Where this causes
14521 ambiguity, @value{GDBN} asks the user's intent.
14523 The debugger will start in Ada mode if it detects an Ada main program.
14524 As for other languages, it will enter Ada mode when stopped in a program that
14525 was translated from an Ada source file.
14527 While in Ada mode, you may use `@t{--}' for comments. This is useful
14528 mostly for documenting command files. The standard @value{GDBN} comment
14529 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14530 middle (to allow based literals).
14532 The debugger supports limited overloading. Given a subprogram call in which
14533 the function symbol has multiple definitions, it will use the number of
14534 actual parameters and some information about their types to attempt to narrow
14535 the set of definitions. It also makes very limited use of context, preferring
14536 procedures to functions in the context of the @code{call} command, and
14537 functions to procedures elsewhere.
14539 @node Omissions from Ada
14540 @subsubsection Omissions from Ada
14541 @cindex Ada, omissions from
14543 Here are the notable omissions from the subset:
14547 Only a subset of the attributes are supported:
14551 @t{'First}, @t{'Last}, and @t{'Length}
14552 on array objects (not on types and subtypes).
14555 @t{'Min} and @t{'Max}.
14558 @t{'Pos} and @t{'Val}.
14564 @t{'Range} on array objects (not subtypes), but only as the right
14565 operand of the membership (@code{in}) operator.
14568 @t{'Access}, @t{'Unchecked_Access}, and
14569 @t{'Unrestricted_Access} (a GNAT extension).
14577 @code{Characters.Latin_1} are not available and
14578 concatenation is not implemented. Thus, escape characters in strings are
14579 not currently available.
14582 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14583 equality of representations. They will generally work correctly
14584 for strings and arrays whose elements have integer or enumeration types.
14585 They may not work correctly for arrays whose element
14586 types have user-defined equality, for arrays of real values
14587 (in particular, IEEE-conformant floating point, because of negative
14588 zeroes and NaNs), and for arrays whose elements contain unused bits with
14589 indeterminate values.
14592 The other component-by-component array operations (@code{and}, @code{or},
14593 @code{xor}, @code{not}, and relational tests other than equality)
14594 are not implemented.
14597 @cindex array aggregates (Ada)
14598 @cindex record aggregates (Ada)
14599 @cindex aggregates (Ada)
14600 There is limited support for array and record aggregates. They are
14601 permitted only on the right sides of assignments, as in these examples:
14604 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14605 (@value{GDBP}) set An_Array := (1, others => 0)
14606 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14607 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14608 (@value{GDBP}) set A_Record := (1, "Peter", True);
14609 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14613 discriminant's value by assigning an aggregate has an
14614 undefined effect if that discriminant is used within the record.
14615 However, you can first modify discriminants by directly assigning to
14616 them (which normally would not be allowed in Ada), and then performing an
14617 aggregate assignment. For example, given a variable @code{A_Rec}
14618 declared to have a type such as:
14621 type Rec (Len : Small_Integer := 0) is record
14623 Vals : IntArray (1 .. Len);
14627 you can assign a value with a different size of @code{Vals} with two
14631 (@value{GDBP}) set A_Rec.Len := 4
14632 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14635 As this example also illustrates, @value{GDBN} is very loose about the usual
14636 rules concerning aggregates. You may leave out some of the
14637 components of an array or record aggregate (such as the @code{Len}
14638 component in the assignment to @code{A_Rec} above); they will retain their
14639 original values upon assignment. You may freely use dynamic values as
14640 indices in component associations. You may even use overlapping or
14641 redundant component associations, although which component values are
14642 assigned in such cases is not defined.
14645 Calls to dispatching subprograms are not implemented.
14648 The overloading algorithm is much more limited (i.e., less selective)
14649 than that of real Ada. It makes only limited use of the context in
14650 which a subexpression appears to resolve its meaning, and it is much
14651 looser in its rules for allowing type matches. As a result, some
14652 function calls will be ambiguous, and the user will be asked to choose
14653 the proper resolution.
14656 The @code{new} operator is not implemented.
14659 Entry calls are not implemented.
14662 Aside from printing, arithmetic operations on the native VAX floating-point
14663 formats are not supported.
14666 It is not possible to slice a packed array.
14669 The names @code{True} and @code{False}, when not part of a qualified name,
14670 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14672 Should your program
14673 redefine these names in a package or procedure (at best a dubious practice),
14674 you will have to use fully qualified names to access their new definitions.
14677 @node Additions to Ada
14678 @subsubsection Additions to Ada
14679 @cindex Ada, deviations from
14681 As it does for other languages, @value{GDBN} makes certain generic
14682 extensions to Ada (@pxref{Expressions}):
14686 If the expression @var{E} is a variable residing in memory (typically
14687 a local variable or array element) and @var{N} is a positive integer,
14688 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14689 @var{N}-1 adjacent variables following it in memory as an array. In
14690 Ada, this operator is generally not necessary, since its prime use is
14691 in displaying parts of an array, and slicing will usually do this in
14692 Ada. However, there are occasional uses when debugging programs in
14693 which certain debugging information has been optimized away.
14696 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14697 appears in function or file @var{B}.'' When @var{B} is a file name,
14698 you must typically surround it in single quotes.
14701 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14702 @var{type} that appears at address @var{addr}.''
14705 A name starting with @samp{$} is a convenience variable
14706 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14709 In addition, @value{GDBN} provides a few other shortcuts and outright
14710 additions specific to Ada:
14714 The assignment statement is allowed as an expression, returning
14715 its right-hand operand as its value. Thus, you may enter
14718 (@value{GDBP}) set x := y + 3
14719 (@value{GDBP}) print A(tmp := y + 1)
14723 The semicolon is allowed as an ``operator,'' returning as its value
14724 the value of its right-hand operand.
14725 This allows, for example,
14726 complex conditional breaks:
14729 (@value{GDBP}) break f
14730 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14734 Rather than use catenation and symbolic character names to introduce special
14735 characters into strings, one may instead use a special bracket notation,
14736 which is also used to print strings. A sequence of characters of the form
14737 @samp{["@var{XX}"]} within a string or character literal denotes the
14738 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14739 sequence of characters @samp{["""]} also denotes a single quotation mark
14740 in strings. For example,
14742 "One line.["0a"]Next line.["0a"]"
14745 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14749 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14750 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14754 (@value{GDBP}) print 'max(x, y)
14758 When printing arrays, @value{GDBN} uses positional notation when the
14759 array has a lower bound of 1, and uses a modified named notation otherwise.
14760 For example, a one-dimensional array of three integers with a lower bound
14761 of 3 might print as
14768 That is, in contrast to valid Ada, only the first component has a @code{=>}
14772 You may abbreviate attributes in expressions with any unique,
14773 multi-character subsequence of
14774 their names (an exact match gets preference).
14775 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14776 in place of @t{a'length}.
14779 @cindex quoting Ada internal identifiers
14780 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14781 to lower case. The GNAT compiler uses upper-case characters for
14782 some of its internal identifiers, which are normally of no interest to users.
14783 For the rare occasions when you actually have to look at them,
14784 enclose them in angle brackets to avoid the lower-case mapping.
14787 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14791 Printing an object of class-wide type or dereferencing an
14792 access-to-class-wide value will display all the components of the object's
14793 specific type (as indicated by its run-time tag). Likewise, component
14794 selection on such a value will operate on the specific type of the
14799 @node Stopping Before Main Program
14800 @subsubsection Stopping at the Very Beginning
14802 @cindex breakpointing Ada elaboration code
14803 It is sometimes necessary to debug the program during elaboration, and
14804 before reaching the main procedure.
14805 As defined in the Ada Reference
14806 Manual, the elaboration code is invoked from a procedure called
14807 @code{adainit}. To run your program up to the beginning of
14808 elaboration, simply use the following two commands:
14809 @code{tbreak adainit} and @code{run}.
14812 @subsubsection Extensions for Ada Tasks
14813 @cindex Ada, tasking
14815 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14816 @value{GDBN} provides the following task-related commands:
14821 This command shows a list of current Ada tasks, as in the following example:
14828 (@value{GDBP}) info tasks
14829 ID TID P-ID Pri State Name
14830 1 8088000 0 15 Child Activation Wait main_task
14831 2 80a4000 1 15 Accept Statement b
14832 3 809a800 1 15 Child Activation Wait a
14833 * 4 80ae800 3 15 Runnable c
14838 In this listing, the asterisk before the last task indicates it to be the
14839 task currently being inspected.
14843 Represents @value{GDBN}'s internal task number.
14849 The parent's task ID (@value{GDBN}'s internal task number).
14852 The base priority of the task.
14855 Current state of the task.
14859 The task has been created but has not been activated. It cannot be
14863 The task is not blocked for any reason known to Ada. (It may be waiting
14864 for a mutex, though.) It is conceptually "executing" in normal mode.
14867 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14868 that were waiting on terminate alternatives have been awakened and have
14869 terminated themselves.
14871 @item Child Activation Wait
14872 The task is waiting for created tasks to complete activation.
14874 @item Accept Statement
14875 The task is waiting on an accept or selective wait statement.
14877 @item Waiting on entry call
14878 The task is waiting on an entry call.
14880 @item Async Select Wait
14881 The task is waiting to start the abortable part of an asynchronous
14885 The task is waiting on a select statement with only a delay
14888 @item Child Termination Wait
14889 The task is sleeping having completed a master within itself, and is
14890 waiting for the tasks dependent on that master to become terminated or
14891 waiting on a terminate Phase.
14893 @item Wait Child in Term Alt
14894 The task is sleeping waiting for tasks on terminate alternatives to
14895 finish terminating.
14897 @item Accepting RV with @var{taskno}
14898 The task is accepting a rendez-vous with the task @var{taskno}.
14902 Name of the task in the program.
14906 @kindex info task @var{taskno}
14907 @item info task @var{taskno}
14908 This command shows detailled informations on the specified task, as in
14909 the following example:
14914 (@value{GDBP}) info tasks
14915 ID TID P-ID Pri State Name
14916 1 8077880 0 15 Child Activation Wait main_task
14917 * 2 807c468 1 15 Runnable task_1
14918 (@value{GDBP}) info task 2
14919 Ada Task: 0x807c468
14922 Parent: 1 (main_task)
14928 @kindex task@r{ (Ada)}
14929 @cindex current Ada task ID
14930 This command prints the ID of the current task.
14936 (@value{GDBP}) info tasks
14937 ID TID P-ID Pri State Name
14938 1 8077870 0 15 Child Activation Wait main_task
14939 * 2 807c458 1 15 Runnable t
14940 (@value{GDBP}) task
14941 [Current task is 2]
14944 @item task @var{taskno}
14945 @cindex Ada task switching
14946 This command is like the @code{thread @var{threadno}}
14947 command (@pxref{Threads}). It switches the context of debugging
14948 from the current task to the given task.
14954 (@value{GDBP}) info tasks
14955 ID TID P-ID Pri State Name
14956 1 8077870 0 15 Child Activation Wait main_task
14957 * 2 807c458 1 15 Runnable t
14958 (@value{GDBP}) task 1
14959 [Switching to task 1]
14960 #0 0x8067726 in pthread_cond_wait ()
14962 #0 0x8067726 in pthread_cond_wait ()
14963 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14964 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14965 #3 0x806153e in system.tasking.stages.activate_tasks ()
14966 #4 0x804aacc in un () at un.adb:5
14969 @item break @var{linespec} task @var{taskno}
14970 @itemx break @var{linespec} task @var{taskno} if @dots{}
14971 @cindex breakpoints and tasks, in Ada
14972 @cindex task breakpoints, in Ada
14973 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14974 These commands are like the @code{break @dots{} thread @dots{}}
14975 command (@pxref{Thread Stops}).
14976 @var{linespec} specifies source lines, as described
14977 in @ref{Specify Location}.
14979 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14980 to specify that you only want @value{GDBN} to stop the program when a
14981 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14982 numeric task identifiers assigned by @value{GDBN}, shown in the first
14983 column of the @samp{info tasks} display.
14985 If you do not specify @samp{task @var{taskno}} when you set a
14986 breakpoint, the breakpoint applies to @emph{all} tasks of your
14989 You can use the @code{task} qualifier on conditional breakpoints as
14990 well; in this case, place @samp{task @var{taskno}} before the
14991 breakpoint condition (before the @code{if}).
14999 (@value{GDBP}) info tasks
15000 ID TID P-ID Pri State Name
15001 1 140022020 0 15 Child Activation Wait main_task
15002 2 140045060 1 15 Accept/Select Wait t2
15003 3 140044840 1 15 Runnable t1
15004 * 4 140056040 1 15 Runnable t3
15005 (@value{GDBP}) b 15 task 2
15006 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15007 (@value{GDBP}) cont
15012 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15014 (@value{GDBP}) info tasks
15015 ID TID P-ID Pri State Name
15016 1 140022020 0 15 Child Activation Wait main_task
15017 * 2 140045060 1 15 Runnable t2
15018 3 140044840 1 15 Runnable t1
15019 4 140056040 1 15 Delay Sleep t3
15023 @node Ada Tasks and Core Files
15024 @subsubsection Tasking Support when Debugging Core Files
15025 @cindex Ada tasking and core file debugging
15027 When inspecting a core file, as opposed to debugging a live program,
15028 tasking support may be limited or even unavailable, depending on
15029 the platform being used.
15030 For instance, on x86-linux, the list of tasks is available, but task
15031 switching is not supported. On Tru64, however, task switching will work
15034 On certain platforms, including Tru64, the debugger needs to perform some
15035 memory writes in order to provide Ada tasking support. When inspecting
15036 a core file, this means that the core file must be opened with read-write
15037 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15038 Under these circumstances, you should make a backup copy of the core
15039 file before inspecting it with @value{GDBN}.
15041 @node Ravenscar Profile
15042 @subsubsection Tasking Support when using the Ravenscar Profile
15043 @cindex Ravenscar Profile
15045 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15046 specifically designed for systems with safety-critical real-time
15050 @kindex set ravenscar task-switching on
15051 @cindex task switching with program using Ravenscar Profile
15052 @item set ravenscar task-switching on
15053 Allows task switching when debugging a program that uses the Ravenscar
15054 Profile. This is the default.
15056 @kindex set ravenscar task-switching off
15057 @item set ravenscar task-switching off
15058 Turn off task switching when debugging a program that uses the Ravenscar
15059 Profile. This is mostly intended to disable the code that adds support
15060 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15061 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15062 To be effective, this command should be run before the program is started.
15064 @kindex show ravenscar task-switching
15065 @item show ravenscar task-switching
15066 Show whether it is possible to switch from task to task in a program
15067 using the Ravenscar Profile.
15072 @subsubsection Known Peculiarities of Ada Mode
15073 @cindex Ada, problems
15075 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15076 we know of several problems with and limitations of Ada mode in
15078 some of which will be fixed with planned future releases of the debugger
15079 and the GNU Ada compiler.
15083 Static constants that the compiler chooses not to materialize as objects in
15084 storage are invisible to the debugger.
15087 Named parameter associations in function argument lists are ignored (the
15088 argument lists are treated as positional).
15091 Many useful library packages are currently invisible to the debugger.
15094 Fixed-point arithmetic, conversions, input, and output is carried out using
15095 floating-point arithmetic, and may give results that only approximate those on
15099 The GNAT compiler never generates the prefix @code{Standard} for any of
15100 the standard symbols defined by the Ada language. @value{GDBN} knows about
15101 this: it will strip the prefix from names when you use it, and will never
15102 look for a name you have so qualified among local symbols, nor match against
15103 symbols in other packages or subprograms. If you have
15104 defined entities anywhere in your program other than parameters and
15105 local variables whose simple names match names in @code{Standard},
15106 GNAT's lack of qualification here can cause confusion. When this happens,
15107 you can usually resolve the confusion
15108 by qualifying the problematic names with package
15109 @code{Standard} explicitly.
15112 Older versions of the compiler sometimes generate erroneous debugging
15113 information, resulting in the debugger incorrectly printing the value
15114 of affected entities. In some cases, the debugger is able to work
15115 around an issue automatically. In other cases, the debugger is able
15116 to work around the issue, but the work-around has to be specifically
15119 @kindex set ada trust-PAD-over-XVS
15120 @kindex show ada trust-PAD-over-XVS
15123 @item set ada trust-PAD-over-XVS on
15124 Configure GDB to strictly follow the GNAT encoding when computing the
15125 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15126 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15127 a complete description of the encoding used by the GNAT compiler).
15128 This is the default.
15130 @item set ada trust-PAD-over-XVS off
15131 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15132 sometimes prints the wrong value for certain entities, changing @code{ada
15133 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15134 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15135 @code{off}, but this incurs a slight performance penalty, so it is
15136 recommended to leave this setting to @code{on} unless necessary.
15140 @node Unsupported Languages
15141 @section Unsupported Languages
15143 @cindex unsupported languages
15144 @cindex minimal language
15145 In addition to the other fully-supported programming languages,
15146 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15147 It does not represent a real programming language, but provides a set
15148 of capabilities close to what the C or assembly languages provide.
15149 This should allow most simple operations to be performed while debugging
15150 an application that uses a language currently not supported by @value{GDBN}.
15152 If the language is set to @code{auto}, @value{GDBN} will automatically
15153 select this language if the current frame corresponds to an unsupported
15157 @chapter Examining the Symbol Table
15159 The commands described in this chapter allow you to inquire about the
15160 symbols (names of variables, functions and types) defined in your
15161 program. This information is inherent in the text of your program and
15162 does not change as your program executes. @value{GDBN} finds it in your
15163 program's symbol table, in the file indicated when you started @value{GDBN}
15164 (@pxref{File Options, ,Choosing Files}), or by one of the
15165 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15167 @cindex symbol names
15168 @cindex names of symbols
15169 @cindex quoting names
15170 Occasionally, you may need to refer to symbols that contain unusual
15171 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15172 most frequent case is in referring to static variables in other
15173 source files (@pxref{Variables,,Program Variables}). File names
15174 are recorded in object files as debugging symbols, but @value{GDBN} would
15175 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15176 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15177 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15184 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15187 @cindex case-insensitive symbol names
15188 @cindex case sensitivity in symbol names
15189 @kindex set case-sensitive
15190 @item set case-sensitive on
15191 @itemx set case-sensitive off
15192 @itemx set case-sensitive auto
15193 Normally, when @value{GDBN} looks up symbols, it matches their names
15194 with case sensitivity determined by the current source language.
15195 Occasionally, you may wish to control that. The command @code{set
15196 case-sensitive} lets you do that by specifying @code{on} for
15197 case-sensitive matches or @code{off} for case-insensitive ones. If
15198 you specify @code{auto}, case sensitivity is reset to the default
15199 suitable for the source language. The default is case-sensitive
15200 matches for all languages except for Fortran, for which the default is
15201 case-insensitive matches.
15203 @kindex show case-sensitive
15204 @item show case-sensitive
15205 This command shows the current setting of case sensitivity for symbols
15208 @kindex set print type methods
15209 @item set print type methods
15210 @itemx set print type methods on
15211 @itemx set print type methods off
15212 Normally, when @value{GDBN} prints a class, it displays any methods
15213 declared in that class. You can control this behavior either by
15214 passing the appropriate flag to @code{ptype}, or using @command{set
15215 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15216 display the methods; this is the default. Specifying @code{off} will
15217 cause @value{GDBN} to omit the methods.
15219 @kindex show print type methods
15220 @item show print type methods
15221 This command shows the current setting of method display when printing
15224 @kindex set print type typedefs
15225 @item set print type typedefs
15226 @itemx set print type typedefs on
15227 @itemx set print type typedefs off
15229 Normally, when @value{GDBN} prints a class, it displays any typedefs
15230 defined in that class. You can control this behavior either by
15231 passing the appropriate flag to @code{ptype}, or using @command{set
15232 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15233 display the typedef definitions; this is the default. Specifying
15234 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15235 Note that this controls whether the typedef definition itself is
15236 printed, not whether typedef names are substituted when printing other
15239 @kindex show print type typedefs
15240 @item show print type typedefs
15241 This command shows the current setting of typedef display when
15244 @kindex info address
15245 @cindex address of a symbol
15246 @item info address @var{symbol}
15247 Describe where the data for @var{symbol} is stored. For a register
15248 variable, this says which register it is kept in. For a non-register
15249 local variable, this prints the stack-frame offset at which the variable
15252 Note the contrast with @samp{print &@var{symbol}}, which does not work
15253 at all for a register variable, and for a stack local variable prints
15254 the exact address of the current instantiation of the variable.
15256 @kindex info symbol
15257 @cindex symbol from address
15258 @cindex closest symbol and offset for an address
15259 @item info symbol @var{addr}
15260 Print the name of a symbol which is stored at the address @var{addr}.
15261 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15262 nearest symbol and an offset from it:
15265 (@value{GDBP}) info symbol 0x54320
15266 _initialize_vx + 396 in section .text
15270 This is the opposite of the @code{info address} command. You can use
15271 it to find out the name of a variable or a function given its address.
15273 For dynamically linked executables, the name of executable or shared
15274 library containing the symbol is also printed:
15277 (@value{GDBP}) info symbol 0x400225
15278 _start + 5 in section .text of /tmp/a.out
15279 (@value{GDBP}) info symbol 0x2aaaac2811cf
15280 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15284 @item whatis[/@var{flags}] [@var{arg}]
15285 Print the data type of @var{arg}, which can be either an expression
15286 or a name of a data type. With no argument, print the data type of
15287 @code{$}, the last value in the value history.
15289 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15290 is not actually evaluated, and any side-effecting operations (such as
15291 assignments or function calls) inside it do not take place.
15293 If @var{arg} is a variable or an expression, @code{whatis} prints its
15294 literal type as it is used in the source code. If the type was
15295 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15296 the data type underlying the @code{typedef}. If the type of the
15297 variable or the expression is a compound data type, such as
15298 @code{struct} or @code{class}, @code{whatis} never prints their
15299 fields or methods. It just prints the @code{struct}/@code{class}
15300 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15301 such a compound data type, use @code{ptype}.
15303 If @var{arg} is a type name that was defined using @code{typedef},
15304 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15305 Unrolling means that @code{whatis} will show the underlying type used
15306 in the @code{typedef} declaration of @var{arg}. However, if that
15307 underlying type is also a @code{typedef}, @code{whatis} will not
15310 For C code, the type names may also have the form @samp{class
15311 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15312 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15314 @var{flags} can be used to modify how the type is displayed.
15315 Available flags are:
15319 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15320 parameters and typedefs defined in a class when printing the class'
15321 members. The @code{/r} flag disables this.
15324 Do not print methods defined in the class.
15327 Print methods defined in the class. This is the default, but the flag
15328 exists in case you change the default with @command{set print type methods}.
15331 Do not print typedefs defined in the class. Note that this controls
15332 whether the typedef definition itself is printed, not whether typedef
15333 names are substituted when printing other types.
15336 Print typedefs defined in the class. This is the default, but the flag
15337 exists in case you change the default with @command{set print type typedefs}.
15341 @item ptype[/@var{flags}] [@var{arg}]
15342 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15343 detailed description of the type, instead of just the name of the type.
15344 @xref{Expressions, ,Expressions}.
15346 Contrary to @code{whatis}, @code{ptype} always unrolls any
15347 @code{typedef}s in its argument declaration, whether the argument is
15348 a variable, expression, or a data type. This means that @code{ptype}
15349 of a variable or an expression will not print literally its type as
15350 present in the source code---use @code{whatis} for that. @code{typedef}s at
15351 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15352 fields, methods and inner @code{class typedef}s of @code{struct}s,
15353 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15355 For example, for this variable declaration:
15358 typedef double real_t;
15359 struct complex @{ real_t real; double imag; @};
15360 typedef struct complex complex_t;
15362 real_t *real_pointer_var;
15366 the two commands give this output:
15370 (@value{GDBP}) whatis var
15372 (@value{GDBP}) ptype var
15373 type = struct complex @{
15377 (@value{GDBP}) whatis complex_t
15378 type = struct complex
15379 (@value{GDBP}) whatis struct complex
15380 type = struct complex
15381 (@value{GDBP}) ptype struct complex
15382 type = struct complex @{
15386 (@value{GDBP}) whatis real_pointer_var
15388 (@value{GDBP}) ptype real_pointer_var
15394 As with @code{whatis}, using @code{ptype} without an argument refers to
15395 the type of @code{$}, the last value in the value history.
15397 @cindex incomplete type
15398 Sometimes, programs use opaque data types or incomplete specifications
15399 of complex data structure. If the debug information included in the
15400 program does not allow @value{GDBN} to display a full declaration of
15401 the data type, it will say @samp{<incomplete type>}. For example,
15402 given these declarations:
15406 struct foo *fooptr;
15410 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15413 (@value{GDBP}) ptype foo
15414 $1 = <incomplete type>
15418 ``Incomplete type'' is C terminology for data types that are not
15419 completely specified.
15422 @item info types @var{regexp}
15424 Print a brief description of all types whose names match the regular
15425 expression @var{regexp} (or all types in your program, if you supply
15426 no argument). Each complete typename is matched as though it were a
15427 complete line; thus, @samp{i type value} gives information on all
15428 types in your program whose names include the string @code{value}, but
15429 @samp{i type ^value$} gives information only on types whose complete
15430 name is @code{value}.
15432 This command differs from @code{ptype} in two ways: first, like
15433 @code{whatis}, it does not print a detailed description; second, it
15434 lists all source files where a type is defined.
15436 @kindex info type-printers
15437 @item info type-printers
15438 Versions of @value{GDBN} that ship with Python scripting enabled may
15439 have ``type printers'' available. When using @command{ptype} or
15440 @command{whatis}, these printers are consulted when the name of a type
15441 is needed. @xref{Type Printing API}, for more information on writing
15444 @code{info type-printers} displays all the available type printers.
15446 @kindex enable type-printer
15447 @kindex disable type-printer
15448 @item enable type-printer @var{name}@dots{}
15449 @item disable type-printer @var{name}@dots{}
15450 These commands can be used to enable or disable type printers.
15453 @cindex local variables
15454 @item info scope @var{location}
15455 List all the variables local to a particular scope. This command
15456 accepts a @var{location} argument---a function name, a source line, or
15457 an address preceded by a @samp{*}, and prints all the variables local
15458 to the scope defined by that location. (@xref{Specify Location}, for
15459 details about supported forms of @var{location}.) For example:
15462 (@value{GDBP}) @b{info scope command_line_handler}
15463 Scope for command_line_handler:
15464 Symbol rl is an argument at stack/frame offset 8, length 4.
15465 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15466 Symbol linelength is in static storage at address 0x150a1c, length 4.
15467 Symbol p is a local variable in register $esi, length 4.
15468 Symbol p1 is a local variable in register $ebx, length 4.
15469 Symbol nline is a local variable in register $edx, length 4.
15470 Symbol repeat is a local variable at frame offset -8, length 4.
15474 This command is especially useful for determining what data to collect
15475 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15478 @kindex info source
15480 Show information about the current source file---that is, the source file for
15481 the function containing the current point of execution:
15484 the name of the source file, and the directory containing it,
15486 the directory it was compiled in,
15488 its length, in lines,
15490 which programming language it is written in,
15492 whether the executable includes debugging information for that file, and
15493 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15495 whether the debugging information includes information about
15496 preprocessor macros.
15500 @kindex info sources
15502 Print the names of all source files in your program for which there is
15503 debugging information, organized into two lists: files whose symbols
15504 have already been read, and files whose symbols will be read when needed.
15506 @kindex info functions
15507 @item info functions
15508 Print the names and data types of all defined functions.
15510 @item info functions @var{regexp}
15511 Print the names and data types of all defined functions
15512 whose names contain a match for regular expression @var{regexp}.
15513 Thus, @samp{info fun step} finds all functions whose names
15514 include @code{step}; @samp{info fun ^step} finds those whose names
15515 start with @code{step}. If a function name contains characters
15516 that conflict with the regular expression language (e.g.@:
15517 @samp{operator*()}), they may be quoted with a backslash.
15519 @kindex info variables
15520 @item info variables
15521 Print the names and data types of all variables that are defined
15522 outside of functions (i.e.@: excluding local variables).
15524 @item info variables @var{regexp}
15525 Print the names and data types of all variables (except for local
15526 variables) whose names contain a match for regular expression
15529 @kindex info classes
15530 @cindex Objective-C, classes and selectors
15532 @itemx info classes @var{regexp}
15533 Display all Objective-C classes in your program, or
15534 (with the @var{regexp} argument) all those matching a particular regular
15537 @kindex info selectors
15538 @item info selectors
15539 @itemx info selectors @var{regexp}
15540 Display all Objective-C selectors in your program, or
15541 (with the @var{regexp} argument) all those matching a particular regular
15545 This was never implemented.
15546 @kindex info methods
15548 @itemx info methods @var{regexp}
15549 The @code{info methods} command permits the user to examine all defined
15550 methods within C@t{++} program, or (with the @var{regexp} argument) a
15551 specific set of methods found in the various C@t{++} classes. Many
15552 C@t{++} classes provide a large number of methods. Thus, the output
15553 from the @code{ptype} command can be overwhelming and hard to use. The
15554 @code{info-methods} command filters the methods, printing only those
15555 which match the regular-expression @var{regexp}.
15558 @cindex opaque data types
15559 @kindex set opaque-type-resolution
15560 @item set opaque-type-resolution on
15561 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15562 declared as a pointer to a @code{struct}, @code{class}, or
15563 @code{union}---for example, @code{struct MyType *}---that is used in one
15564 source file although the full declaration of @code{struct MyType} is in
15565 another source file. The default is on.
15567 A change in the setting of this subcommand will not take effect until
15568 the next time symbols for a file are loaded.
15570 @item set opaque-type-resolution off
15571 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15572 is printed as follows:
15574 @{<no data fields>@}
15577 @kindex show opaque-type-resolution
15578 @item show opaque-type-resolution
15579 Show whether opaque types are resolved or not.
15581 @kindex maint print symbols
15582 @cindex symbol dump
15583 @kindex maint print psymbols
15584 @cindex partial symbol dump
15585 @item maint print symbols @var{filename}
15586 @itemx maint print psymbols @var{filename}
15587 @itemx maint print msymbols @var{filename}
15588 Write a dump of debugging symbol data into the file @var{filename}.
15589 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15590 symbols with debugging data are included. If you use @samp{maint print
15591 symbols}, @value{GDBN} includes all the symbols for which it has already
15592 collected full details: that is, @var{filename} reflects symbols for
15593 only those files whose symbols @value{GDBN} has read. You can use the
15594 command @code{info sources} to find out which files these are. If you
15595 use @samp{maint print psymbols} instead, the dump shows information about
15596 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15597 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15598 @samp{maint print msymbols} dumps just the minimal symbol information
15599 required for each object file from which @value{GDBN} has read some symbols.
15600 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15601 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15603 @kindex maint info symtabs
15604 @kindex maint info psymtabs
15605 @cindex listing @value{GDBN}'s internal symbol tables
15606 @cindex symbol tables, listing @value{GDBN}'s internal
15607 @cindex full symbol tables, listing @value{GDBN}'s internal
15608 @cindex partial symbol tables, listing @value{GDBN}'s internal
15609 @item maint info symtabs @r{[} @var{regexp} @r{]}
15610 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15612 List the @code{struct symtab} or @code{struct partial_symtab}
15613 structures whose names match @var{regexp}. If @var{regexp} is not
15614 given, list them all. The output includes expressions which you can
15615 copy into a @value{GDBN} debugging this one to examine a particular
15616 structure in more detail. For example:
15619 (@value{GDBP}) maint info psymtabs dwarf2read
15620 @{ objfile /home/gnu/build/gdb/gdb
15621 ((struct objfile *) 0x82e69d0)
15622 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15623 ((struct partial_symtab *) 0x8474b10)
15626 text addresses 0x814d3c8 -- 0x8158074
15627 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15628 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15629 dependencies (none)
15632 (@value{GDBP}) maint info symtabs
15636 We see that there is one partial symbol table whose filename contains
15637 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15638 and we see that @value{GDBN} has not read in any symtabs yet at all.
15639 If we set a breakpoint on a function, that will cause @value{GDBN} to
15640 read the symtab for the compilation unit containing that function:
15643 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15644 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15646 (@value{GDBP}) maint info symtabs
15647 @{ objfile /home/gnu/build/gdb/gdb
15648 ((struct objfile *) 0x82e69d0)
15649 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15650 ((struct symtab *) 0x86c1f38)
15653 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15654 linetable ((struct linetable *) 0x8370fa0)
15655 debugformat DWARF 2
15664 @chapter Altering Execution
15666 Once you think you have found an error in your program, you might want to
15667 find out for certain whether correcting the apparent error would lead to
15668 correct results in the rest of the run. You can find the answer by
15669 experiment, using the @value{GDBN} features for altering execution of the
15672 For example, you can store new values into variables or memory
15673 locations, give your program a signal, restart it at a different
15674 address, or even return prematurely from a function.
15677 * Assignment:: Assignment to variables
15678 * Jumping:: Continuing at a different address
15679 * Signaling:: Giving your program a signal
15680 * Returning:: Returning from a function
15681 * Calling:: Calling your program's functions
15682 * Patching:: Patching your program
15686 @section Assignment to Variables
15689 @cindex setting variables
15690 To alter the value of a variable, evaluate an assignment expression.
15691 @xref{Expressions, ,Expressions}. For example,
15698 stores the value 4 into the variable @code{x}, and then prints the
15699 value of the assignment expression (which is 4).
15700 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15701 information on operators in supported languages.
15703 @kindex set variable
15704 @cindex variables, setting
15705 If you are not interested in seeing the value of the assignment, use the
15706 @code{set} command instead of the @code{print} command. @code{set} is
15707 really the same as @code{print} except that the expression's value is
15708 not printed and is not put in the value history (@pxref{Value History,
15709 ,Value History}). The expression is evaluated only for its effects.
15711 If the beginning of the argument string of the @code{set} command
15712 appears identical to a @code{set} subcommand, use the @code{set
15713 variable} command instead of just @code{set}. This command is identical
15714 to @code{set} except for its lack of subcommands. For example, if your
15715 program has a variable @code{width}, you get an error if you try to set
15716 a new value with just @samp{set width=13}, because @value{GDBN} has the
15717 command @code{set width}:
15720 (@value{GDBP}) whatis width
15722 (@value{GDBP}) p width
15724 (@value{GDBP}) set width=47
15725 Invalid syntax in expression.
15729 The invalid expression, of course, is @samp{=47}. In
15730 order to actually set the program's variable @code{width}, use
15733 (@value{GDBP}) set var width=47
15736 Because the @code{set} command has many subcommands that can conflict
15737 with the names of program variables, it is a good idea to use the
15738 @code{set variable} command instead of just @code{set}. For example, if
15739 your program has a variable @code{g}, you run into problems if you try
15740 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15741 the command @code{set gnutarget}, abbreviated @code{set g}:
15745 (@value{GDBP}) whatis g
15749 (@value{GDBP}) set g=4
15753 The program being debugged has been started already.
15754 Start it from the beginning? (y or n) y
15755 Starting program: /home/smith/cc_progs/a.out
15756 "/home/smith/cc_progs/a.out": can't open to read symbols:
15757 Invalid bfd target.
15758 (@value{GDBP}) show g
15759 The current BFD target is "=4".
15764 The program variable @code{g} did not change, and you silently set the
15765 @code{gnutarget} to an invalid value. In order to set the variable
15769 (@value{GDBP}) set var g=4
15772 @value{GDBN} allows more implicit conversions in assignments than C; you can
15773 freely store an integer value into a pointer variable or vice versa,
15774 and you can convert any structure to any other structure that is the
15775 same length or shorter.
15776 @comment FIXME: how do structs align/pad in these conversions?
15777 @comment /doc@cygnus.com 18dec1990
15779 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15780 construct to generate a value of specified type at a specified address
15781 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15782 to memory location @code{0x83040} as an integer (which implies a certain size
15783 and representation in memory), and
15786 set @{int@}0x83040 = 4
15790 stores the value 4 into that memory location.
15793 @section Continuing at a Different Address
15795 Ordinarily, when you continue your program, you do so at the place where
15796 it stopped, with the @code{continue} command. You can instead continue at
15797 an address of your own choosing, with the following commands:
15801 @kindex j @r{(@code{jump})}
15802 @item jump @var{linespec}
15803 @itemx j @var{linespec}
15804 @itemx jump @var{location}
15805 @itemx j @var{location}
15806 Resume execution at line @var{linespec} or at address given by
15807 @var{location}. Execution stops again immediately if there is a
15808 breakpoint there. @xref{Specify Location}, for a description of the
15809 different forms of @var{linespec} and @var{location}. It is common
15810 practice to use the @code{tbreak} command in conjunction with
15811 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15813 The @code{jump} command does not change the current stack frame, or
15814 the stack pointer, or the contents of any memory location or any
15815 register other than the program counter. If line @var{linespec} is in
15816 a different function from the one currently executing, the results may
15817 be bizarre if the two functions expect different patterns of arguments or
15818 of local variables. For this reason, the @code{jump} command requests
15819 confirmation if the specified line is not in the function currently
15820 executing. However, even bizarre results are predictable if you are
15821 well acquainted with the machine-language code of your program.
15824 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15825 On many systems, you can get much the same effect as the @code{jump}
15826 command by storing a new value into the register @code{$pc}. The
15827 difference is that this does not start your program running; it only
15828 changes the address of where it @emph{will} run when you continue. For
15836 makes the next @code{continue} command or stepping command execute at
15837 address @code{0x485}, rather than at the address where your program stopped.
15838 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15840 The most common occasion to use the @code{jump} command is to back
15841 up---perhaps with more breakpoints set---over a portion of a program
15842 that has already executed, in order to examine its execution in more
15847 @section Giving your Program a Signal
15848 @cindex deliver a signal to a program
15852 @item signal @var{signal}
15853 Resume execution where your program stopped, but immediately give it the
15854 signal @var{signal}. @var{signal} can be the name or the number of a
15855 signal. For example, on many systems @code{signal 2} and @code{signal
15856 SIGINT} are both ways of sending an interrupt signal.
15858 Alternatively, if @var{signal} is zero, continue execution without
15859 giving a signal. This is useful when your program stopped on account of
15860 a signal and would ordinarily see the signal when resumed with the
15861 @code{continue} command; @samp{signal 0} causes it to resume without a
15864 @code{signal} does not repeat when you press @key{RET} a second time
15865 after executing the command.
15869 Invoking the @code{signal} command is not the same as invoking the
15870 @code{kill} utility from the shell. Sending a signal with @code{kill}
15871 causes @value{GDBN} to decide what to do with the signal depending on
15872 the signal handling tables (@pxref{Signals}). The @code{signal} command
15873 passes the signal directly to your program.
15877 @section Returning from a Function
15880 @cindex returning from a function
15883 @itemx return @var{expression}
15884 You can cancel execution of a function call with the @code{return}
15885 command. If you give an
15886 @var{expression} argument, its value is used as the function's return
15890 When you use @code{return}, @value{GDBN} discards the selected stack frame
15891 (and all frames within it). You can think of this as making the
15892 discarded frame return prematurely. If you wish to specify a value to
15893 be returned, give that value as the argument to @code{return}.
15895 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15896 Frame}), and any other frames inside of it, leaving its caller as the
15897 innermost remaining frame. That frame becomes selected. The
15898 specified value is stored in the registers used for returning values
15901 The @code{return} command does not resume execution; it leaves the
15902 program stopped in the state that would exist if the function had just
15903 returned. In contrast, the @code{finish} command (@pxref{Continuing
15904 and Stepping, ,Continuing and Stepping}) resumes execution until the
15905 selected stack frame returns naturally.
15907 @value{GDBN} needs to know how the @var{expression} argument should be set for
15908 the inferior. The concrete registers assignment depends on the OS ABI and the
15909 type being returned by the selected stack frame. For example it is common for
15910 OS ABI to return floating point values in FPU registers while integer values in
15911 CPU registers. Still some ABIs return even floating point values in CPU
15912 registers. Larger integer widths (such as @code{long long int}) also have
15913 specific placement rules. @value{GDBN} already knows the OS ABI from its
15914 current target so it needs to find out also the type being returned to make the
15915 assignment into the right register(s).
15917 Normally, the selected stack frame has debug info. @value{GDBN} will always
15918 use the debug info instead of the implicit type of @var{expression} when the
15919 debug info is available. For example, if you type @kbd{return -1}, and the
15920 function in the current stack frame is declared to return a @code{long long
15921 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15922 into a @code{long long int}:
15925 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15927 (@value{GDBP}) return -1
15928 Make func return now? (y or n) y
15929 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15930 43 printf ("result=%lld\n", func ());
15934 However, if the selected stack frame does not have a debug info, e.g., if the
15935 function was compiled without debug info, @value{GDBN} has to find out the type
15936 to return from user. Specifying a different type by mistake may set the value
15937 in different inferior registers than the caller code expects. For example,
15938 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15939 of a @code{long long int} result for a debug info less function (on 32-bit
15940 architectures). Therefore the user is required to specify the return type by
15941 an appropriate cast explicitly:
15944 Breakpoint 2, 0x0040050b in func ()
15945 (@value{GDBP}) return -1
15946 Return value type not available for selected stack frame.
15947 Please use an explicit cast of the value to return.
15948 (@value{GDBP}) return (long long int) -1
15949 Make selected stack frame return now? (y or n) y
15950 #0 0x00400526 in main ()
15955 @section Calling Program Functions
15958 @cindex calling functions
15959 @cindex inferior functions, calling
15960 @item print @var{expr}
15961 Evaluate the expression @var{expr} and display the resulting value.
15962 @var{expr} may include calls to functions in the program being
15966 @item call @var{expr}
15967 Evaluate the expression @var{expr} without displaying @code{void}
15970 You can use this variant of the @code{print} command if you want to
15971 execute a function from your program that does not return anything
15972 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15973 with @code{void} returned values that @value{GDBN} will otherwise
15974 print. If the result is not void, it is printed and saved in the
15978 It is possible for the function you call via the @code{print} or
15979 @code{call} command to generate a signal (e.g., if there's a bug in
15980 the function, or if you passed it incorrect arguments). What happens
15981 in that case is controlled by the @code{set unwindonsignal} command.
15983 Similarly, with a C@t{++} program it is possible for the function you
15984 call via the @code{print} or @code{call} command to generate an
15985 exception that is not handled due to the constraints of the dummy
15986 frame. In this case, any exception that is raised in the frame, but has
15987 an out-of-frame exception handler will not be found. GDB builds a
15988 dummy-frame for the inferior function call, and the unwinder cannot
15989 seek for exception handlers outside of this dummy-frame. What happens
15990 in that case is controlled by the
15991 @code{set unwind-on-terminating-exception} command.
15994 @item set unwindonsignal
15995 @kindex set unwindonsignal
15996 @cindex unwind stack in called functions
15997 @cindex call dummy stack unwinding
15998 Set unwinding of the stack if a signal is received while in a function
15999 that @value{GDBN} called in the program being debugged. If set to on,
16000 @value{GDBN} unwinds the stack it created for the call and restores
16001 the context to what it was before the call. If set to off (the
16002 default), @value{GDBN} stops in the frame where the signal was
16005 @item show unwindonsignal
16006 @kindex show unwindonsignal
16007 Show the current setting of stack unwinding in the functions called by
16010 @item set unwind-on-terminating-exception
16011 @kindex set unwind-on-terminating-exception
16012 @cindex unwind stack in called functions with unhandled exceptions
16013 @cindex call dummy stack unwinding on unhandled exception.
16014 Set unwinding of the stack if a C@t{++} exception is raised, but left
16015 unhandled while in a function that @value{GDBN} called in the program being
16016 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16017 it created for the call and restores the context to what it was before
16018 the call. If set to off, @value{GDBN} the exception is delivered to
16019 the default C@t{++} exception handler and the inferior terminated.
16021 @item show unwind-on-terminating-exception
16022 @kindex show unwind-on-terminating-exception
16023 Show the current setting of stack unwinding in the functions called by
16028 @cindex weak alias functions
16029 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16030 for another function. In such case, @value{GDBN} might not pick up
16031 the type information, including the types of the function arguments,
16032 which causes @value{GDBN} to call the inferior function incorrectly.
16033 As a result, the called function will function erroneously and may
16034 even crash. A solution to that is to use the name of the aliased
16038 @section Patching Programs
16040 @cindex patching binaries
16041 @cindex writing into executables
16042 @cindex writing into corefiles
16044 By default, @value{GDBN} opens the file containing your program's
16045 executable code (or the corefile) read-only. This prevents accidental
16046 alterations to machine code; but it also prevents you from intentionally
16047 patching your program's binary.
16049 If you'd like to be able to patch the binary, you can specify that
16050 explicitly with the @code{set write} command. For example, you might
16051 want to turn on internal debugging flags, or even to make emergency
16057 @itemx set write off
16058 If you specify @samp{set write on}, @value{GDBN} opens executable and
16059 core files for both reading and writing; if you specify @kbd{set write
16060 off} (the default), @value{GDBN} opens them read-only.
16062 If you have already loaded a file, you must load it again (using the
16063 @code{exec-file} or @code{core-file} command) after changing @code{set
16064 write}, for your new setting to take effect.
16068 Display whether executable files and core files are opened for writing
16069 as well as reading.
16073 @chapter @value{GDBN} Files
16075 @value{GDBN} needs to know the file name of the program to be debugged,
16076 both in order to read its symbol table and in order to start your
16077 program. To debug a core dump of a previous run, you must also tell
16078 @value{GDBN} the name of the core dump file.
16081 * Files:: Commands to specify files
16082 * Separate Debug Files:: Debugging information in separate files
16083 * MiniDebugInfo:: Debugging information in a special section
16084 * Index Files:: Index files speed up GDB
16085 * Symbol Errors:: Errors reading symbol files
16086 * Data Files:: GDB data files
16090 @section Commands to Specify Files
16092 @cindex symbol table
16093 @cindex core dump file
16095 You may want to specify executable and core dump file names. The usual
16096 way to do this is at start-up time, using the arguments to
16097 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16098 Out of @value{GDBN}}).
16100 Occasionally it is necessary to change to a different file during a
16101 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16102 specify a file you want to use. Or you are debugging a remote target
16103 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16104 Program}). In these situations the @value{GDBN} commands to specify
16105 new files are useful.
16108 @cindex executable file
16110 @item file @var{filename}
16111 Use @var{filename} as the program to be debugged. It is read for its
16112 symbols and for the contents of pure memory. It is also the program
16113 executed when you use the @code{run} command. If you do not specify a
16114 directory and the file is not found in the @value{GDBN} working directory,
16115 @value{GDBN} uses the environment variable @code{PATH} as a list of
16116 directories to search, just as the shell does when looking for a program
16117 to run. You can change the value of this variable, for both @value{GDBN}
16118 and your program, using the @code{path} command.
16120 @cindex unlinked object files
16121 @cindex patching object files
16122 You can load unlinked object @file{.o} files into @value{GDBN} using
16123 the @code{file} command. You will not be able to ``run'' an object
16124 file, but you can disassemble functions and inspect variables. Also,
16125 if the underlying BFD functionality supports it, you could use
16126 @kbd{gdb -write} to patch object files using this technique. Note
16127 that @value{GDBN} can neither interpret nor modify relocations in this
16128 case, so branches and some initialized variables will appear to go to
16129 the wrong place. But this feature is still handy from time to time.
16132 @code{file} with no argument makes @value{GDBN} discard any information it
16133 has on both executable file and the symbol table.
16136 @item exec-file @r{[} @var{filename} @r{]}
16137 Specify that the program to be run (but not the symbol table) is found
16138 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16139 if necessary to locate your program. Omitting @var{filename} means to
16140 discard information on the executable file.
16142 @kindex symbol-file
16143 @item symbol-file @r{[} @var{filename} @r{]}
16144 Read symbol table information from file @var{filename}. @code{PATH} is
16145 searched when necessary. Use the @code{file} command to get both symbol
16146 table and program to run from the same file.
16148 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16149 program's symbol table.
16151 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16152 some breakpoints and auto-display expressions. This is because they may
16153 contain pointers to the internal data recording symbols and data types,
16154 which are part of the old symbol table data being discarded inside
16157 @code{symbol-file} does not repeat if you press @key{RET} again after
16160 When @value{GDBN} is configured for a particular environment, it
16161 understands debugging information in whatever format is the standard
16162 generated for that environment; you may use either a @sc{gnu} compiler, or
16163 other compilers that adhere to the local conventions.
16164 Best results are usually obtained from @sc{gnu} compilers; for example,
16165 using @code{@value{NGCC}} you can generate debugging information for
16168 For most kinds of object files, with the exception of old SVR3 systems
16169 using COFF, the @code{symbol-file} command does not normally read the
16170 symbol table in full right away. Instead, it scans the symbol table
16171 quickly to find which source files and which symbols are present. The
16172 details are read later, one source file at a time, as they are needed.
16174 The purpose of this two-stage reading strategy is to make @value{GDBN}
16175 start up faster. For the most part, it is invisible except for
16176 occasional pauses while the symbol table details for a particular source
16177 file are being read. (The @code{set verbose} command can turn these
16178 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16179 Warnings and Messages}.)
16181 We have not implemented the two-stage strategy for COFF yet. When the
16182 symbol table is stored in COFF format, @code{symbol-file} reads the
16183 symbol table data in full right away. Note that ``stabs-in-COFF''
16184 still does the two-stage strategy, since the debug info is actually
16188 @cindex reading symbols immediately
16189 @cindex symbols, reading immediately
16190 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16191 @itemx file @r{[} -readnow @r{]} @var{filename}
16192 You can override the @value{GDBN} two-stage strategy for reading symbol
16193 tables by using the @samp{-readnow} option with any of the commands that
16194 load symbol table information, if you want to be sure @value{GDBN} has the
16195 entire symbol table available.
16197 @c FIXME: for now no mention of directories, since this seems to be in
16198 @c flux. 13mar1992 status is that in theory GDB would look either in
16199 @c current dir or in same dir as myprog; but issues like competing
16200 @c GDB's, or clutter in system dirs, mean that in practice right now
16201 @c only current dir is used. FFish says maybe a special GDB hierarchy
16202 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16206 @item core-file @r{[}@var{filename}@r{]}
16208 Specify the whereabouts of a core dump file to be used as the ``contents
16209 of memory''. Traditionally, core files contain only some parts of the
16210 address space of the process that generated them; @value{GDBN} can access the
16211 executable file itself for other parts.
16213 @code{core-file} with no argument specifies that no core file is
16216 Note that the core file is ignored when your program is actually running
16217 under @value{GDBN}. So, if you have been running your program and you
16218 wish to debug a core file instead, you must kill the subprocess in which
16219 the program is running. To do this, use the @code{kill} command
16220 (@pxref{Kill Process, ,Killing the Child Process}).
16222 @kindex add-symbol-file
16223 @cindex dynamic linking
16224 @item add-symbol-file @var{filename} @var{address}
16225 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16226 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16227 The @code{add-symbol-file} command reads additional symbol table
16228 information from the file @var{filename}. You would use this command
16229 when @var{filename} has been dynamically loaded (by some other means)
16230 into the program that is running. @var{address} should be the memory
16231 address at which the file has been loaded; @value{GDBN} cannot figure
16232 this out for itself. You can additionally specify an arbitrary number
16233 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16234 section name and base address for that section. You can specify any
16235 @var{address} as an expression.
16237 The symbol table of the file @var{filename} is added to the symbol table
16238 originally read with the @code{symbol-file} command. You can use the
16239 @code{add-symbol-file} command any number of times; the new symbol data
16240 thus read keeps adding to the old. To discard all old symbol data
16241 instead, use the @code{symbol-file} command without any arguments.
16243 @cindex relocatable object files, reading symbols from
16244 @cindex object files, relocatable, reading symbols from
16245 @cindex reading symbols from relocatable object files
16246 @cindex symbols, reading from relocatable object files
16247 @cindex @file{.o} files, reading symbols from
16248 Although @var{filename} is typically a shared library file, an
16249 executable file, or some other object file which has been fully
16250 relocated for loading into a process, you can also load symbolic
16251 information from relocatable @file{.o} files, as long as:
16255 the file's symbolic information refers only to linker symbols defined in
16256 that file, not to symbols defined by other object files,
16258 every section the file's symbolic information refers to has actually
16259 been loaded into the inferior, as it appears in the file, and
16261 you can determine the address at which every section was loaded, and
16262 provide these to the @code{add-symbol-file} command.
16266 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16267 relocatable files into an already running program; such systems
16268 typically make the requirements above easy to meet. However, it's
16269 important to recognize that many native systems use complex link
16270 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16271 assembly, for example) that make the requirements difficult to meet. In
16272 general, one cannot assume that using @code{add-symbol-file} to read a
16273 relocatable object file's symbolic information will have the same effect
16274 as linking the relocatable object file into the program in the normal
16277 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16279 @kindex add-symbol-file-from-memory
16280 @cindex @code{syscall DSO}
16281 @cindex load symbols from memory
16282 @item add-symbol-file-from-memory @var{address}
16283 Load symbols from the given @var{address} in a dynamically loaded
16284 object file whose image is mapped directly into the inferior's memory.
16285 For example, the Linux kernel maps a @code{syscall DSO} into each
16286 process's address space; this DSO provides kernel-specific code for
16287 some system calls. The argument can be any expression whose
16288 evaluation yields the address of the file's shared object file header.
16289 For this command to work, you must have used @code{symbol-file} or
16290 @code{exec-file} commands in advance.
16292 @kindex add-shared-symbol-files
16294 @item add-shared-symbol-files @var{library-file}
16295 @itemx assf @var{library-file}
16296 The @code{add-shared-symbol-files} command can currently be used only
16297 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16298 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16299 @value{GDBN} automatically looks for shared libraries, however if
16300 @value{GDBN} does not find yours, you can invoke
16301 @code{add-shared-symbol-files}. It takes one argument: the shared
16302 library's file name. @code{assf} is a shorthand alias for
16303 @code{add-shared-symbol-files}.
16306 @item section @var{section} @var{addr}
16307 The @code{section} command changes the base address of the named
16308 @var{section} of the exec file to @var{addr}. This can be used if the
16309 exec file does not contain section addresses, (such as in the
16310 @code{a.out} format), or when the addresses specified in the file
16311 itself are wrong. Each section must be changed separately. The
16312 @code{info files} command, described below, lists all the sections and
16316 @kindex info target
16319 @code{info files} and @code{info target} are synonymous; both print the
16320 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16321 including the names of the executable and core dump files currently in
16322 use by @value{GDBN}, and the files from which symbols were loaded. The
16323 command @code{help target} lists all possible targets rather than
16326 @kindex maint info sections
16327 @item maint info sections
16328 Another command that can give you extra information about program sections
16329 is @code{maint info sections}. In addition to the section information
16330 displayed by @code{info files}, this command displays the flags and file
16331 offset of each section in the executable and core dump files. In addition,
16332 @code{maint info sections} provides the following command options (which
16333 may be arbitrarily combined):
16337 Display sections for all loaded object files, including shared libraries.
16338 @item @var{sections}
16339 Display info only for named @var{sections}.
16340 @item @var{section-flags}
16341 Display info only for sections for which @var{section-flags} are true.
16342 The section flags that @value{GDBN} currently knows about are:
16345 Section will have space allocated in the process when loaded.
16346 Set for all sections except those containing debug information.
16348 Section will be loaded from the file into the child process memory.
16349 Set for pre-initialized code and data, clear for @code{.bss} sections.
16351 Section needs to be relocated before loading.
16353 Section cannot be modified by the child process.
16355 Section contains executable code only.
16357 Section contains data only (no executable code).
16359 Section will reside in ROM.
16361 Section contains data for constructor/destructor lists.
16363 Section is not empty.
16365 An instruction to the linker to not output the section.
16366 @item COFF_SHARED_LIBRARY
16367 A notification to the linker that the section contains
16368 COFF shared library information.
16370 Section contains common symbols.
16373 @kindex set trust-readonly-sections
16374 @cindex read-only sections
16375 @item set trust-readonly-sections on
16376 Tell @value{GDBN} that readonly sections in your object file
16377 really are read-only (i.e.@: that their contents will not change).
16378 In that case, @value{GDBN} can fetch values from these sections
16379 out of the object file, rather than from the target program.
16380 For some targets (notably embedded ones), this can be a significant
16381 enhancement to debugging performance.
16383 The default is off.
16385 @item set trust-readonly-sections off
16386 Tell @value{GDBN} not to trust readonly sections. This means that
16387 the contents of the section might change while the program is running,
16388 and must therefore be fetched from the target when needed.
16390 @item show trust-readonly-sections
16391 Show the current setting of trusting readonly sections.
16394 All file-specifying commands allow both absolute and relative file names
16395 as arguments. @value{GDBN} always converts the file name to an absolute file
16396 name and remembers it that way.
16398 @cindex shared libraries
16399 @anchor{Shared Libraries}
16400 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16401 and IBM RS/6000 AIX shared libraries.
16403 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16404 shared libraries. @xref{Expat}.
16406 @value{GDBN} automatically loads symbol definitions from shared libraries
16407 when you use the @code{run} command, or when you examine a core file.
16408 (Before you issue the @code{run} command, @value{GDBN} does not understand
16409 references to a function in a shared library, however---unless you are
16410 debugging a core file).
16412 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16413 automatically loads the symbols at the time of the @code{shl_load} call.
16415 @c FIXME: some @value{GDBN} release may permit some refs to undef
16416 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16417 @c FIXME...lib; check this from time to time when updating manual
16419 There are times, however, when you may wish to not automatically load
16420 symbol definitions from shared libraries, such as when they are
16421 particularly large or there are many of them.
16423 To control the automatic loading of shared library symbols, use the
16427 @kindex set auto-solib-add
16428 @item set auto-solib-add @var{mode}
16429 If @var{mode} is @code{on}, symbols from all shared object libraries
16430 will be loaded automatically when the inferior begins execution, you
16431 attach to an independently started inferior, or when the dynamic linker
16432 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16433 is @code{off}, symbols must be loaded manually, using the
16434 @code{sharedlibrary} command. The default value is @code{on}.
16436 @cindex memory used for symbol tables
16437 If your program uses lots of shared libraries with debug info that
16438 takes large amounts of memory, you can decrease the @value{GDBN}
16439 memory footprint by preventing it from automatically loading the
16440 symbols from shared libraries. To that end, type @kbd{set
16441 auto-solib-add off} before running the inferior, then load each
16442 library whose debug symbols you do need with @kbd{sharedlibrary
16443 @var{regexp}}, where @var{regexp} is a regular expression that matches
16444 the libraries whose symbols you want to be loaded.
16446 @kindex show auto-solib-add
16447 @item show auto-solib-add
16448 Display the current autoloading mode.
16451 @cindex load shared library
16452 To explicitly load shared library symbols, use the @code{sharedlibrary}
16456 @kindex info sharedlibrary
16458 @item info share @var{regex}
16459 @itemx info sharedlibrary @var{regex}
16460 Print the names of the shared libraries which are currently loaded
16461 that match @var{regex}. If @var{regex} is omitted then print
16462 all shared libraries that are loaded.
16464 @kindex sharedlibrary
16466 @item sharedlibrary @var{regex}
16467 @itemx share @var{regex}
16468 Load shared object library symbols for files matching a
16469 Unix regular expression.
16470 As with files loaded automatically, it only loads shared libraries
16471 required by your program for a core file or after typing @code{run}. If
16472 @var{regex} is omitted all shared libraries required by your program are
16475 @item nosharedlibrary
16476 @kindex nosharedlibrary
16477 @cindex unload symbols from shared libraries
16478 Unload all shared object library symbols. This discards all symbols
16479 that have been loaded from all shared libraries. Symbols from shared
16480 libraries that were loaded by explicit user requests are not
16484 Sometimes you may wish that @value{GDBN} stops and gives you control
16485 when any of shared library events happen. The best way to do this is
16486 to use @code{catch load} and @code{catch unload} (@pxref{Set
16489 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16490 command for this. This command exists for historical reasons. It is
16491 less useful than setting a catchpoint, because it does not allow for
16492 conditions or commands as a catchpoint does.
16495 @item set stop-on-solib-events
16496 @kindex set stop-on-solib-events
16497 This command controls whether @value{GDBN} should give you control
16498 when the dynamic linker notifies it about some shared library event.
16499 The most common event of interest is loading or unloading of a new
16502 @item show stop-on-solib-events
16503 @kindex show stop-on-solib-events
16504 Show whether @value{GDBN} stops and gives you control when shared
16505 library events happen.
16508 Shared libraries are also supported in many cross or remote debugging
16509 configurations. @value{GDBN} needs to have access to the target's libraries;
16510 this can be accomplished either by providing copies of the libraries
16511 on the host system, or by asking @value{GDBN} to automatically retrieve the
16512 libraries from the target. If copies of the target libraries are
16513 provided, they need to be the same as the target libraries, although the
16514 copies on the target can be stripped as long as the copies on the host are
16517 @cindex where to look for shared libraries
16518 For remote debugging, you need to tell @value{GDBN} where the target
16519 libraries are, so that it can load the correct copies---otherwise, it
16520 may try to load the host's libraries. @value{GDBN} has two variables
16521 to specify the search directories for target libraries.
16524 @cindex prefix for shared library file names
16525 @cindex system root, alternate
16526 @kindex set solib-absolute-prefix
16527 @kindex set sysroot
16528 @item set sysroot @var{path}
16529 Use @var{path} as the system root for the program being debugged. Any
16530 absolute shared library paths will be prefixed with @var{path}; many
16531 runtime loaders store the absolute paths to the shared library in the
16532 target program's memory. If you use @code{set sysroot} to find shared
16533 libraries, they need to be laid out in the same way that they are on
16534 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16537 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16538 retrieve the target libraries from the remote system. This is only
16539 supported when using a remote target that supports the @code{remote get}
16540 command (@pxref{File Transfer,,Sending files to a remote system}).
16541 The part of @var{path} following the initial @file{remote:}
16542 (if present) is used as system root prefix on the remote file system.
16543 @footnote{If you want to specify a local system root using a directory
16544 that happens to be named @file{remote:}, you need to use some equivalent
16545 variant of the name like @file{./remote:}.}
16547 For targets with an MS-DOS based filesystem, such as MS-Windows and
16548 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16549 absolute file name with @var{path}. But first, on Unix hosts,
16550 @value{GDBN} converts all backslash directory separators into forward
16551 slashes, because the backslash is not a directory separator on Unix:
16554 c:\foo\bar.dll @result{} c:/foo/bar.dll
16557 Then, @value{GDBN} attempts prefixing the target file name with
16558 @var{path}, and looks for the resulting file name in the host file
16562 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16565 If that does not find the shared library, @value{GDBN} tries removing
16566 the @samp{:} character from the drive spec, both for convenience, and,
16567 for the case of the host file system not supporting file names with
16571 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16574 This makes it possible to have a system root that mirrors a target
16575 with more than one drive. E.g., you may want to setup your local
16576 copies of the target system shared libraries like so (note @samp{c} vs
16580 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16581 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16582 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16586 and point the system root at @file{/path/to/sysroot}, so that
16587 @value{GDBN} can find the correct copies of both
16588 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16590 If that still does not find the shared library, @value{GDBN} tries
16591 removing the whole drive spec from the target file name:
16594 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16597 This last lookup makes it possible to not care about the drive name,
16598 if you don't want or need to.
16600 The @code{set solib-absolute-prefix} command is an alias for @code{set
16603 @cindex default system root
16604 @cindex @samp{--with-sysroot}
16605 You can set the default system root by using the configure-time
16606 @samp{--with-sysroot} option. If the system root is inside
16607 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16608 @samp{--exec-prefix}), then the default system root will be updated
16609 automatically if the installed @value{GDBN} is moved to a new
16612 @kindex show sysroot
16614 Display the current shared library prefix.
16616 @kindex set solib-search-path
16617 @item set solib-search-path @var{path}
16618 If this variable is set, @var{path} is a colon-separated list of
16619 directories to search for shared libraries. @samp{solib-search-path}
16620 is used after @samp{sysroot} fails to locate the library, or if the
16621 path to the library is relative instead of absolute. If you want to
16622 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16623 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16624 finding your host's libraries. @samp{sysroot} is preferred; setting
16625 it to a nonexistent directory may interfere with automatic loading
16626 of shared library symbols.
16628 @kindex show solib-search-path
16629 @item show solib-search-path
16630 Display the current shared library search path.
16632 @cindex DOS file-name semantics of file names.
16633 @kindex set target-file-system-kind (unix|dos-based|auto)
16634 @kindex show target-file-system-kind
16635 @item set target-file-system-kind @var{kind}
16636 Set assumed file system kind for target reported file names.
16638 Shared library file names as reported by the target system may not
16639 make sense as is on the system @value{GDBN} is running on. For
16640 example, when remote debugging a target that has MS-DOS based file
16641 system semantics, from a Unix host, the target may be reporting to
16642 @value{GDBN} a list of loaded shared libraries with file names such as
16643 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16644 drive letters, so the @samp{c:\} prefix is not normally understood as
16645 indicating an absolute file name, and neither is the backslash
16646 normally considered a directory separator character. In that case,
16647 the native file system would interpret this whole absolute file name
16648 as a relative file name with no directory components. This would make
16649 it impossible to point @value{GDBN} at a copy of the remote target's
16650 shared libraries on the host using @code{set sysroot}, and impractical
16651 with @code{set solib-search-path}. Setting
16652 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16653 to interpret such file names similarly to how the target would, and to
16654 map them to file names valid on @value{GDBN}'s native file system
16655 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16656 to one of the supported file system kinds. In that case, @value{GDBN}
16657 tries to determine the appropriate file system variant based on the
16658 current target's operating system (@pxref{ABI, ,Configuring the
16659 Current ABI}). The supported file system settings are:
16663 Instruct @value{GDBN} to assume the target file system is of Unix
16664 kind. Only file names starting the forward slash (@samp{/}) character
16665 are considered absolute, and the directory separator character is also
16669 Instruct @value{GDBN} to assume the target file system is DOS based.
16670 File names starting with either a forward slash, or a drive letter
16671 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16672 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16673 considered directory separators.
16676 Instruct @value{GDBN} to use the file system kind associated with the
16677 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16678 This is the default.
16682 @cindex file name canonicalization
16683 @cindex base name differences
16684 When processing file names provided by the user, @value{GDBN}
16685 frequently needs to compare them to the file names recorded in the
16686 program's debug info. Normally, @value{GDBN} compares just the
16687 @dfn{base names} of the files as strings, which is reasonably fast
16688 even for very large programs. (The base name of a file is the last
16689 portion of its name, after stripping all the leading directories.)
16690 This shortcut in comparison is based upon the assumption that files
16691 cannot have more than one base name. This is usually true, but
16692 references to files that use symlinks or similar filesystem
16693 facilities violate that assumption. If your program records files
16694 using such facilities, or if you provide file names to @value{GDBN}
16695 using symlinks etc., you can set @code{basenames-may-differ} to
16696 @code{true} to instruct @value{GDBN} to completely canonicalize each
16697 pair of file names it needs to compare. This will make file-name
16698 comparisons accurate, but at a price of a significant slowdown.
16701 @item set basenames-may-differ
16702 @kindex set basenames-may-differ
16703 Set whether a source file may have multiple base names.
16705 @item show basenames-may-differ
16706 @kindex show basenames-may-differ
16707 Show whether a source file may have multiple base names.
16710 @node Separate Debug Files
16711 @section Debugging Information in Separate Files
16712 @cindex separate debugging information files
16713 @cindex debugging information in separate files
16714 @cindex @file{.debug} subdirectories
16715 @cindex debugging information directory, global
16716 @cindex global debugging information directories
16717 @cindex build ID, and separate debugging files
16718 @cindex @file{.build-id} directory
16720 @value{GDBN} allows you to put a program's debugging information in a
16721 file separate from the executable itself, in a way that allows
16722 @value{GDBN} to find and load the debugging information automatically.
16723 Since debugging information can be very large---sometimes larger
16724 than the executable code itself---some systems distribute debugging
16725 information for their executables in separate files, which users can
16726 install only when they need to debug a problem.
16728 @value{GDBN} supports two ways of specifying the separate debug info
16733 The executable contains a @dfn{debug link} that specifies the name of
16734 the separate debug info file. The separate debug file's name is
16735 usually @file{@var{executable}.debug}, where @var{executable} is the
16736 name of the corresponding executable file without leading directories
16737 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16738 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16739 checksum for the debug file, which @value{GDBN} uses to validate that
16740 the executable and the debug file came from the same build.
16743 The executable contains a @dfn{build ID}, a unique bit string that is
16744 also present in the corresponding debug info file. (This is supported
16745 only on some operating systems, notably those which use the ELF format
16746 for binary files and the @sc{gnu} Binutils.) For more details about
16747 this feature, see the description of the @option{--build-id}
16748 command-line option in @ref{Options, , Command Line Options, ld.info,
16749 The GNU Linker}. The debug info file's name is not specified
16750 explicitly by the build ID, but can be computed from the build ID, see
16754 Depending on the way the debug info file is specified, @value{GDBN}
16755 uses two different methods of looking for the debug file:
16759 For the ``debug link'' method, @value{GDBN} looks up the named file in
16760 the directory of the executable file, then in a subdirectory of that
16761 directory named @file{.debug}, and finally under each one of the global debug
16762 directories, in a subdirectory whose name is identical to the leading
16763 directories of the executable's absolute file name.
16766 For the ``build ID'' method, @value{GDBN} looks in the
16767 @file{.build-id} subdirectory of each one of the global debug directories for
16768 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16769 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16770 are the rest of the bit string. (Real build ID strings are 32 or more
16771 hex characters, not 10.)
16774 So, for example, suppose you ask @value{GDBN} to debug
16775 @file{/usr/bin/ls}, which has a debug link that specifies the
16776 file @file{ls.debug}, and a build ID whose value in hex is
16777 @code{abcdef1234}. If the list of the global debug directories includes
16778 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16779 debug information files, in the indicated order:
16783 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16785 @file{/usr/bin/ls.debug}
16787 @file{/usr/bin/.debug/ls.debug}
16789 @file{/usr/lib/debug/usr/bin/ls.debug}.
16792 @anchor{debug-file-directory}
16793 Global debugging info directories default to what is set by @value{GDBN}
16794 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16795 you can also set the global debugging info directories, and view the list
16796 @value{GDBN} is currently using.
16800 @kindex set debug-file-directory
16801 @item set debug-file-directory @var{directories}
16802 Set the directories which @value{GDBN} searches for separate debugging
16803 information files to @var{directory}. Multiple path components can be set
16804 concatenating them by a path separator.
16806 @kindex show debug-file-directory
16807 @item show debug-file-directory
16808 Show the directories @value{GDBN} searches for separate debugging
16813 @cindex @code{.gnu_debuglink} sections
16814 @cindex debug link sections
16815 A debug link is a special section of the executable file named
16816 @code{.gnu_debuglink}. The section must contain:
16820 A filename, with any leading directory components removed, followed by
16823 zero to three bytes of padding, as needed to reach the next four-byte
16824 boundary within the section, and
16826 a four-byte CRC checksum, stored in the same endianness used for the
16827 executable file itself. The checksum is computed on the debugging
16828 information file's full contents by the function given below, passing
16829 zero as the @var{crc} argument.
16832 Any executable file format can carry a debug link, as long as it can
16833 contain a section named @code{.gnu_debuglink} with the contents
16836 @cindex @code{.note.gnu.build-id} sections
16837 @cindex build ID sections
16838 The build ID is a special section in the executable file (and in other
16839 ELF binary files that @value{GDBN} may consider). This section is
16840 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16841 It contains unique identification for the built files---the ID remains
16842 the same across multiple builds of the same build tree. The default
16843 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16844 content for the build ID string. The same section with an identical
16845 value is present in the original built binary with symbols, in its
16846 stripped variant, and in the separate debugging information file.
16848 The debugging information file itself should be an ordinary
16849 executable, containing a full set of linker symbols, sections, and
16850 debugging information. The sections of the debugging information file
16851 should have the same names, addresses, and sizes as the original file,
16852 but they need not contain any data---much like a @code{.bss} section
16853 in an ordinary executable.
16855 The @sc{gnu} binary utilities (Binutils) package includes the
16856 @samp{objcopy} utility that can produce
16857 the separated executable / debugging information file pairs using the
16858 following commands:
16861 @kbd{objcopy --only-keep-debug foo foo.debug}
16866 These commands remove the debugging
16867 information from the executable file @file{foo} and place it in the file
16868 @file{foo.debug}. You can use the first, second or both methods to link the
16873 The debug link method needs the following additional command to also leave
16874 behind a debug link in @file{foo}:
16877 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16880 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16881 a version of the @code{strip} command such that the command @kbd{strip foo -f
16882 foo.debug} has the same functionality as the two @code{objcopy} commands and
16883 the @code{ln -s} command above, together.
16886 Build ID gets embedded into the main executable using @code{ld --build-id} or
16887 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16888 compatibility fixes for debug files separation are present in @sc{gnu} binary
16889 utilities (Binutils) package since version 2.18.
16894 @cindex CRC algorithm definition
16895 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16896 IEEE 802.3 using the polynomial:
16898 @c TexInfo requires naked braces for multi-digit exponents for Tex
16899 @c output, but this causes HTML output to barf. HTML has to be set using
16900 @c raw commands. So we end up having to specify this equation in 2
16905 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
16906 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
16912 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16913 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16917 The function is computed byte at a time, taking the least
16918 significant bit of each byte first. The initial pattern
16919 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16920 the final result is inverted to ensure trailing zeros also affect the
16923 @emph{Note:} This is the same CRC polynomial as used in handling the
16924 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16925 , @value{GDBN} Remote Serial Protocol}). However in the
16926 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16927 significant bit first, and the result is not inverted, so trailing
16928 zeros have no effect on the CRC value.
16930 To complete the description, we show below the code of the function
16931 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16932 initially supplied @code{crc} argument means that an initial call to
16933 this function passing in zero will start computing the CRC using
16936 @kindex gnu_debuglink_crc32
16939 gnu_debuglink_crc32 (unsigned long crc,
16940 unsigned char *buf, size_t len)
16942 static const unsigned long crc32_table[256] =
16944 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16945 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16946 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16947 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16948 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16949 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16950 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16951 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16952 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16953 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16954 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16955 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16956 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16957 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16958 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16959 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16960 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16961 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16962 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16963 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16964 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16965 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16966 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16967 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16968 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16969 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16970 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16971 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16972 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16973 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16974 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16975 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16976 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16977 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16978 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16979 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16980 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16981 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16982 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16983 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16984 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16985 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16986 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16987 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16988 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16989 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16990 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16991 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16992 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16993 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16994 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16997 unsigned char *end;
16999 crc = ~crc & 0xffffffff;
17000 for (end = buf + len; buf < end; ++buf)
17001 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17002 return ~crc & 0xffffffff;
17007 This computation does not apply to the ``build ID'' method.
17009 @node MiniDebugInfo
17010 @section Debugging information in a special section
17011 @cindex separate debug sections
17012 @cindex @samp{.gnu_debugdata} section
17014 Some systems ship pre-built executables and libraries that have a
17015 special @samp{.gnu_debugdata} section. This feature is called
17016 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17017 is used to supply extra symbols for backtraces.
17019 The intent of this section is to provide extra minimal debugging
17020 information for use in simple backtraces. It is not intended to be a
17021 replacement for full separate debugging information (@pxref{Separate
17022 Debug Files}). The example below shows the intended use; however,
17023 @value{GDBN} does not currently put restrictions on what sort of
17024 debugging information might be included in the section.
17026 @value{GDBN} has support for this extension. If the section exists,
17027 then it is used provided that no other source of debugging information
17028 can be found, and that @value{GDBN} was configured with LZMA support.
17030 This section can be easily created using @command{objcopy} and other
17031 standard utilities:
17034 # Extract the dynamic symbols from the main binary, there is no need
17035 # to also have these in the normal symbol table
17036 nm -D @var{binary} --format=posix --defined-only \
17037 | awk '@{ print $1 @}' | sort > dynsyms
17039 # Extract all the text (i.e. function) symbols from the debuginfo .
17040 nm @var{binary} --format=posix --defined-only \
17041 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17044 # Keep all the function symbols not already in the dynamic symbol
17046 comm -13 dynsyms funcsyms > keep_symbols
17048 # Copy the full debuginfo, keeping only a minimal set of symbols and
17049 # removing some unnecessary sections.
17050 objcopy -S --remove-section .gdb_index --remove-section .comment \
17051 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17053 # Inject the compressed data into the .gnu_debugdata section of the
17056 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17060 @section Index Files Speed Up @value{GDBN}
17061 @cindex index files
17062 @cindex @samp{.gdb_index} section
17064 When @value{GDBN} finds a symbol file, it scans the symbols in the
17065 file in order to construct an internal symbol table. This lets most
17066 @value{GDBN} operations work quickly---at the cost of a delay early
17067 on. For large programs, this delay can be quite lengthy, so
17068 @value{GDBN} provides a way to build an index, which speeds up
17071 The index is stored as a section in the symbol file. @value{GDBN} can
17072 write the index to a file, then you can put it into the symbol file
17073 using @command{objcopy}.
17075 To create an index file, use the @code{save gdb-index} command:
17078 @item save gdb-index @var{directory}
17079 @kindex save gdb-index
17080 Create an index file for each symbol file currently known by
17081 @value{GDBN}. Each file is named after its corresponding symbol file,
17082 with @samp{.gdb-index} appended, and is written into the given
17086 Once you have created an index file you can merge it into your symbol
17087 file, here named @file{symfile}, using @command{objcopy}:
17090 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17091 --set-section-flags .gdb_index=readonly symfile symfile
17094 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17095 sections that have been deprecated. Usually they are deprecated because
17096 they are missing a new feature or have performance issues.
17097 To tell @value{GDBN} to use a deprecated index section anyway
17098 specify @code{set use-deprecated-index-sections on}.
17099 The default is @code{off}.
17100 This can speed up startup, but may result in some functionality being lost.
17101 @xref{Index Section Format}.
17103 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17104 must be done before gdb reads the file. The following will not work:
17107 $ gdb -ex "set use-deprecated-index-sections on" <program>
17110 Instead you must do, for example,
17113 $ gdb -iex "set use-deprecated-index-sections on" <program>
17116 There are currently some limitation on indices. They only work when
17117 for DWARF debugging information, not stabs. And, they do not
17118 currently work for programs using Ada.
17120 @node Symbol Errors
17121 @section Errors Reading Symbol Files
17123 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17124 such as symbol types it does not recognize, or known bugs in compiler
17125 output. By default, @value{GDBN} does not notify you of such problems, since
17126 they are relatively common and primarily of interest to people
17127 debugging compilers. If you are interested in seeing information
17128 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17129 only one message about each such type of problem, no matter how many
17130 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17131 to see how many times the problems occur, with the @code{set
17132 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17135 The messages currently printed, and their meanings, include:
17138 @item inner block not inside outer block in @var{symbol}
17140 The symbol information shows where symbol scopes begin and end
17141 (such as at the start of a function or a block of statements). This
17142 error indicates that an inner scope block is not fully contained
17143 in its outer scope blocks.
17145 @value{GDBN} circumvents the problem by treating the inner block as if it had
17146 the same scope as the outer block. In the error message, @var{symbol}
17147 may be shown as ``@code{(don't know)}'' if the outer block is not a
17150 @item block at @var{address} out of order
17152 The symbol information for symbol scope blocks should occur in
17153 order of increasing addresses. This error indicates that it does not
17156 @value{GDBN} does not circumvent this problem, and has trouble
17157 locating symbols in the source file whose symbols it is reading. (You
17158 can often determine what source file is affected by specifying
17159 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17162 @item bad block start address patched
17164 The symbol information for a symbol scope block has a start address
17165 smaller than the address of the preceding source line. This is known
17166 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17168 @value{GDBN} circumvents the problem by treating the symbol scope block as
17169 starting on the previous source line.
17171 @item bad string table offset in symbol @var{n}
17174 Symbol number @var{n} contains a pointer into the string table which is
17175 larger than the size of the string table.
17177 @value{GDBN} circumvents the problem by considering the symbol to have the
17178 name @code{foo}, which may cause other problems if many symbols end up
17181 @item unknown symbol type @code{0x@var{nn}}
17183 The symbol information contains new data types that @value{GDBN} does
17184 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17185 uncomprehended information, in hexadecimal.
17187 @value{GDBN} circumvents the error by ignoring this symbol information.
17188 This usually allows you to debug your program, though certain symbols
17189 are not accessible. If you encounter such a problem and feel like
17190 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17191 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17192 and examine @code{*bufp} to see the symbol.
17194 @item stub type has NULL name
17196 @value{GDBN} could not find the full definition for a struct or class.
17198 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17199 The symbol information for a C@t{++} member function is missing some
17200 information that recent versions of the compiler should have output for
17203 @item info mismatch between compiler and debugger
17205 @value{GDBN} could not parse a type specification output by the compiler.
17210 @section GDB Data Files
17212 @cindex prefix for data files
17213 @value{GDBN} will sometimes read an auxiliary data file. These files
17214 are kept in a directory known as the @dfn{data directory}.
17216 You can set the data directory's name, and view the name @value{GDBN}
17217 is currently using.
17220 @kindex set data-directory
17221 @item set data-directory @var{directory}
17222 Set the directory which @value{GDBN} searches for auxiliary data files
17223 to @var{directory}.
17225 @kindex show data-directory
17226 @item show data-directory
17227 Show the directory @value{GDBN} searches for auxiliary data files.
17230 @cindex default data directory
17231 @cindex @samp{--with-gdb-datadir}
17232 You can set the default data directory by using the configure-time
17233 @samp{--with-gdb-datadir} option. If the data directory is inside
17234 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17235 @samp{--exec-prefix}), then the default data directory will be updated
17236 automatically if the installed @value{GDBN} is moved to a new
17239 The data directory may also be specified with the
17240 @code{--data-directory} command line option.
17241 @xref{Mode Options}.
17244 @chapter Specifying a Debugging Target
17246 @cindex debugging target
17247 A @dfn{target} is the execution environment occupied by your program.
17249 Often, @value{GDBN} runs in the same host environment as your program;
17250 in that case, the debugging target is specified as a side effect when
17251 you use the @code{file} or @code{core} commands. When you need more
17252 flexibility---for example, running @value{GDBN} on a physically separate
17253 host, or controlling a standalone system over a serial port or a
17254 realtime system over a TCP/IP connection---you can use the @code{target}
17255 command to specify one of the target types configured for @value{GDBN}
17256 (@pxref{Target Commands, ,Commands for Managing Targets}).
17258 @cindex target architecture
17259 It is possible to build @value{GDBN} for several different @dfn{target
17260 architectures}. When @value{GDBN} is built like that, you can choose
17261 one of the available architectures with the @kbd{set architecture}
17265 @kindex set architecture
17266 @kindex show architecture
17267 @item set architecture @var{arch}
17268 This command sets the current target architecture to @var{arch}. The
17269 value of @var{arch} can be @code{"auto"}, in addition to one of the
17270 supported architectures.
17272 @item show architecture
17273 Show the current target architecture.
17275 @item set processor
17277 @kindex set processor
17278 @kindex show processor
17279 These are alias commands for, respectively, @code{set architecture}
17280 and @code{show architecture}.
17284 * Active Targets:: Active targets
17285 * Target Commands:: Commands for managing targets
17286 * Byte Order:: Choosing target byte order
17289 @node Active Targets
17290 @section Active Targets
17292 @cindex stacking targets
17293 @cindex active targets
17294 @cindex multiple targets
17296 There are multiple classes of targets such as: processes, executable files or
17297 recording sessions. Core files belong to the process class, making core file
17298 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17299 on multiple active targets, one in each class. This allows you to (for
17300 example) start a process and inspect its activity, while still having access to
17301 the executable file after the process finishes. Or if you start process
17302 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17303 presented a virtual layer of the recording target, while the process target
17304 remains stopped at the chronologically last point of the process execution.
17306 Use the @code{core-file} and @code{exec-file} commands to select a new core
17307 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17308 specify as a target a process that is already running, use the @code{attach}
17309 command (@pxref{Attach, ,Debugging an Already-running Process}).
17311 @node Target Commands
17312 @section Commands for Managing Targets
17315 @item target @var{type} @var{parameters}
17316 Connects the @value{GDBN} host environment to a target machine or
17317 process. A target is typically a protocol for talking to debugging
17318 facilities. You use the argument @var{type} to specify the type or
17319 protocol of the target machine.
17321 Further @var{parameters} are interpreted by the target protocol, but
17322 typically include things like device names or host names to connect
17323 with, process numbers, and baud rates.
17325 The @code{target} command does not repeat if you press @key{RET} again
17326 after executing the command.
17328 @kindex help target
17330 Displays the names of all targets available. To display targets
17331 currently selected, use either @code{info target} or @code{info files}
17332 (@pxref{Files, ,Commands to Specify Files}).
17334 @item help target @var{name}
17335 Describe a particular target, including any parameters necessary to
17338 @kindex set gnutarget
17339 @item set gnutarget @var{args}
17340 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17341 knows whether it is reading an @dfn{executable},
17342 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17343 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17344 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17347 @emph{Warning:} To specify a file format with @code{set gnutarget},
17348 you must know the actual BFD name.
17352 @xref{Files, , Commands to Specify Files}.
17354 @kindex show gnutarget
17355 @item show gnutarget
17356 Use the @code{show gnutarget} command to display what file format
17357 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17358 @value{GDBN} will determine the file format for each file automatically,
17359 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17362 @cindex common targets
17363 Here are some common targets (available, or not, depending on the GDB
17368 @item target exec @var{program}
17369 @cindex executable file target
17370 An executable file. @samp{target exec @var{program}} is the same as
17371 @samp{exec-file @var{program}}.
17373 @item target core @var{filename}
17374 @cindex core dump file target
17375 A core dump file. @samp{target core @var{filename}} is the same as
17376 @samp{core-file @var{filename}}.
17378 @item target remote @var{medium}
17379 @cindex remote target
17380 A remote system connected to @value{GDBN} via a serial line or network
17381 connection. This command tells @value{GDBN} to use its own remote
17382 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17384 For example, if you have a board connected to @file{/dev/ttya} on the
17385 machine running @value{GDBN}, you could say:
17388 target remote /dev/ttya
17391 @code{target remote} supports the @code{load} command. This is only
17392 useful if you have some other way of getting the stub to the target
17393 system, and you can put it somewhere in memory where it won't get
17394 clobbered by the download.
17396 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17397 @cindex built-in simulator target
17398 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17406 works; however, you cannot assume that a specific memory map, device
17407 drivers, or even basic I/O is available, although some simulators do
17408 provide these. For info about any processor-specific simulator details,
17409 see the appropriate section in @ref{Embedded Processors, ,Embedded
17414 Some configurations may include these targets as well:
17418 @item target nrom @var{dev}
17419 @cindex NetROM ROM emulator target
17420 NetROM ROM emulator. This target only supports downloading.
17424 Different targets are available on different configurations of @value{GDBN};
17425 your configuration may have more or fewer targets.
17427 Many remote targets require you to download the executable's code once
17428 you've successfully established a connection. You may wish to control
17429 various aspects of this process.
17434 @kindex set hash@r{, for remote monitors}
17435 @cindex hash mark while downloading
17436 This command controls whether a hash mark @samp{#} is displayed while
17437 downloading a file to the remote monitor. If on, a hash mark is
17438 displayed after each S-record is successfully downloaded to the
17442 @kindex show hash@r{, for remote monitors}
17443 Show the current status of displaying the hash mark.
17445 @item set debug monitor
17446 @kindex set debug monitor
17447 @cindex display remote monitor communications
17448 Enable or disable display of communications messages between
17449 @value{GDBN} and the remote monitor.
17451 @item show debug monitor
17452 @kindex show debug monitor
17453 Show the current status of displaying communications between
17454 @value{GDBN} and the remote monitor.
17459 @kindex load @var{filename}
17460 @item load @var{filename}
17462 Depending on what remote debugging facilities are configured into
17463 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17464 is meant to make @var{filename} (an executable) available for debugging
17465 on the remote system---by downloading, or dynamic linking, for example.
17466 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17467 the @code{add-symbol-file} command.
17469 If your @value{GDBN} does not have a @code{load} command, attempting to
17470 execute it gets the error message ``@code{You can't do that when your
17471 target is @dots{}}''
17473 The file is loaded at whatever address is specified in the executable.
17474 For some object file formats, you can specify the load address when you
17475 link the program; for other formats, like a.out, the object file format
17476 specifies a fixed address.
17477 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17479 Depending on the remote side capabilities, @value{GDBN} may be able to
17480 load programs into flash memory.
17482 @code{load} does not repeat if you press @key{RET} again after using it.
17486 @section Choosing Target Byte Order
17488 @cindex choosing target byte order
17489 @cindex target byte order
17491 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17492 offer the ability to run either big-endian or little-endian byte
17493 orders. Usually the executable or symbol will include a bit to
17494 designate the endian-ness, and you will not need to worry about
17495 which to use. However, you may still find it useful to adjust
17496 @value{GDBN}'s idea of processor endian-ness manually.
17500 @item set endian big
17501 Instruct @value{GDBN} to assume the target is big-endian.
17503 @item set endian little
17504 Instruct @value{GDBN} to assume the target is little-endian.
17506 @item set endian auto
17507 Instruct @value{GDBN} to use the byte order associated with the
17511 Display @value{GDBN}'s current idea of the target byte order.
17515 Note that these commands merely adjust interpretation of symbolic
17516 data on the host, and that they have absolutely no effect on the
17520 @node Remote Debugging
17521 @chapter Debugging Remote Programs
17522 @cindex remote debugging
17524 If you are trying to debug a program running on a machine that cannot run
17525 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17526 For example, you might use remote debugging on an operating system kernel,
17527 or on a small system which does not have a general purpose operating system
17528 powerful enough to run a full-featured debugger.
17530 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17531 to make this work with particular debugging targets. In addition,
17532 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17533 but not specific to any particular target system) which you can use if you
17534 write the remote stubs---the code that runs on the remote system to
17535 communicate with @value{GDBN}.
17537 Other remote targets may be available in your
17538 configuration of @value{GDBN}; use @code{help target} to list them.
17541 * Connecting:: Connecting to a remote target
17542 * File Transfer:: Sending files to a remote system
17543 * Server:: Using the gdbserver program
17544 * Remote Configuration:: Remote configuration
17545 * Remote Stub:: Implementing a remote stub
17549 @section Connecting to a Remote Target
17551 On the @value{GDBN} host machine, you will need an unstripped copy of
17552 your program, since @value{GDBN} needs symbol and debugging information.
17553 Start up @value{GDBN} as usual, using the name of the local copy of your
17554 program as the first argument.
17556 @cindex @code{target remote}
17557 @value{GDBN} can communicate with the target over a serial line, or
17558 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17559 each case, @value{GDBN} uses the same protocol for debugging your
17560 program; only the medium carrying the debugging packets varies. The
17561 @code{target remote} command establishes a connection to the target.
17562 Its arguments indicate which medium to use:
17566 @item target remote @var{serial-device}
17567 @cindex serial line, @code{target remote}
17568 Use @var{serial-device} to communicate with the target. For example,
17569 to use a serial line connected to the device named @file{/dev/ttyb}:
17572 target remote /dev/ttyb
17575 If you're using a serial line, you may want to give @value{GDBN} the
17576 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17577 (@pxref{Remote Configuration, set remotebaud}) before the
17578 @code{target} command.
17580 @item target remote @code{@var{host}:@var{port}}
17581 @itemx target remote @code{tcp:@var{host}:@var{port}}
17582 @cindex @acronym{TCP} port, @code{target remote}
17583 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17584 The @var{host} may be either a host name or a numeric @acronym{IP}
17585 address; @var{port} must be a decimal number. The @var{host} could be
17586 the target machine itself, if it is directly connected to the net, or
17587 it might be a terminal server which in turn has a serial line to the
17590 For example, to connect to port 2828 on a terminal server named
17594 target remote manyfarms:2828
17597 If your remote target is actually running on the same machine as your
17598 debugger session (e.g.@: a simulator for your target running on the
17599 same host), you can omit the hostname. For example, to connect to
17600 port 1234 on your local machine:
17603 target remote :1234
17607 Note that the colon is still required here.
17609 @item target remote @code{udp:@var{host}:@var{port}}
17610 @cindex @acronym{UDP} port, @code{target remote}
17611 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17612 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17615 target remote udp:manyfarms:2828
17618 When using a @acronym{UDP} connection for remote debugging, you should
17619 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17620 can silently drop packets on busy or unreliable networks, which will
17621 cause havoc with your debugging session.
17623 @item target remote | @var{command}
17624 @cindex pipe, @code{target remote} to
17625 Run @var{command} in the background and communicate with it using a
17626 pipe. The @var{command} is a shell command, to be parsed and expanded
17627 by the system's command shell, @code{/bin/sh}; it should expect remote
17628 protocol packets on its standard input, and send replies on its
17629 standard output. You could use this to run a stand-alone simulator
17630 that speaks the remote debugging protocol, to make net connections
17631 using programs like @code{ssh}, or for other similar tricks.
17633 If @var{command} closes its standard output (perhaps by exiting),
17634 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17635 program has already exited, this will have no effect.)
17639 Once the connection has been established, you can use all the usual
17640 commands to examine and change data. The remote program is already
17641 running; you can use @kbd{step} and @kbd{continue}, and you do not
17642 need to use @kbd{run}.
17644 @cindex interrupting remote programs
17645 @cindex remote programs, interrupting
17646 Whenever @value{GDBN} is waiting for the remote program, if you type the
17647 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17648 program. This may or may not succeed, depending in part on the hardware
17649 and the serial drivers the remote system uses. If you type the
17650 interrupt character once again, @value{GDBN} displays this prompt:
17653 Interrupted while waiting for the program.
17654 Give up (and stop debugging it)? (y or n)
17657 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17658 (If you decide you want to try again later, you can use @samp{target
17659 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17660 goes back to waiting.
17663 @kindex detach (remote)
17665 When you have finished debugging the remote program, you can use the
17666 @code{detach} command to release it from @value{GDBN} control.
17667 Detaching from the target normally resumes its execution, but the results
17668 will depend on your particular remote stub. After the @code{detach}
17669 command, @value{GDBN} is free to connect to another target.
17673 The @code{disconnect} command behaves like @code{detach}, except that
17674 the target is generally not resumed. It will wait for @value{GDBN}
17675 (this instance or another one) to connect and continue debugging. After
17676 the @code{disconnect} command, @value{GDBN} is again free to connect to
17679 @cindex send command to remote monitor
17680 @cindex extend @value{GDBN} for remote targets
17681 @cindex add new commands for external monitor
17683 @item monitor @var{cmd}
17684 This command allows you to send arbitrary commands directly to the
17685 remote monitor. Since @value{GDBN} doesn't care about the commands it
17686 sends like this, this command is the way to extend @value{GDBN}---you
17687 can add new commands that only the external monitor will understand
17691 @node File Transfer
17692 @section Sending files to a remote system
17693 @cindex remote target, file transfer
17694 @cindex file transfer
17695 @cindex sending files to remote systems
17697 Some remote targets offer the ability to transfer files over the same
17698 connection used to communicate with @value{GDBN}. This is convenient
17699 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17700 running @code{gdbserver} over a network interface. For other targets,
17701 e.g.@: embedded devices with only a single serial port, this may be
17702 the only way to upload or download files.
17704 Not all remote targets support these commands.
17708 @item remote put @var{hostfile} @var{targetfile}
17709 Copy file @var{hostfile} from the host system (the machine running
17710 @value{GDBN}) to @var{targetfile} on the target system.
17713 @item remote get @var{targetfile} @var{hostfile}
17714 Copy file @var{targetfile} from the target system to @var{hostfile}
17715 on the host system.
17717 @kindex remote delete
17718 @item remote delete @var{targetfile}
17719 Delete @var{targetfile} from the target system.
17724 @section Using the @code{gdbserver} Program
17727 @cindex remote connection without stubs
17728 @code{gdbserver} is a control program for Unix-like systems, which
17729 allows you to connect your program with a remote @value{GDBN} via
17730 @code{target remote}---but without linking in the usual debugging stub.
17732 @code{gdbserver} is not a complete replacement for the debugging stubs,
17733 because it requires essentially the same operating-system facilities
17734 that @value{GDBN} itself does. In fact, a system that can run
17735 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17736 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17737 because it is a much smaller program than @value{GDBN} itself. It is
17738 also easier to port than all of @value{GDBN}, so you may be able to get
17739 started more quickly on a new system by using @code{gdbserver}.
17740 Finally, if you develop code for real-time systems, you may find that
17741 the tradeoffs involved in real-time operation make it more convenient to
17742 do as much development work as possible on another system, for example
17743 by cross-compiling. You can use @code{gdbserver} to make a similar
17744 choice for debugging.
17746 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17747 or a TCP connection, using the standard @value{GDBN} remote serial
17751 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17752 Do not run @code{gdbserver} connected to any public network; a
17753 @value{GDBN} connection to @code{gdbserver} provides access to the
17754 target system with the same privileges as the user running
17758 @subsection Running @code{gdbserver}
17759 @cindex arguments, to @code{gdbserver}
17760 @cindex @code{gdbserver}, command-line arguments
17762 Run @code{gdbserver} on the target system. You need a copy of the
17763 program you want to debug, including any libraries it requires.
17764 @code{gdbserver} does not need your program's symbol table, so you can
17765 strip the program if necessary to save space. @value{GDBN} on the host
17766 system does all the symbol handling.
17768 To use the server, you must tell it how to communicate with @value{GDBN};
17769 the name of your program; and the arguments for your program. The usual
17773 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17776 @var{comm} is either a device name (to use a serial line), or a TCP
17777 hostname and portnumber, or @code{-} or @code{stdio} to use
17778 stdin/stdout of @code{gdbserver}.
17779 For example, to debug Emacs with the argument
17780 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17784 target> gdbserver /dev/com1 emacs foo.txt
17787 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17790 To use a TCP connection instead of a serial line:
17793 target> gdbserver host:2345 emacs foo.txt
17796 The only difference from the previous example is the first argument,
17797 specifying that you are communicating with the host @value{GDBN} via
17798 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17799 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17800 (Currently, the @samp{host} part is ignored.) You can choose any number
17801 you want for the port number as long as it does not conflict with any
17802 TCP ports already in use on the target system (for example, @code{23} is
17803 reserved for @code{telnet}).@footnote{If you choose a port number that
17804 conflicts with another service, @code{gdbserver} prints an error message
17805 and exits.} You must use the same port number with the host @value{GDBN}
17806 @code{target remote} command.
17808 The @code{stdio} connection is useful when starting @code{gdbserver}
17812 (gdb) target remote | ssh -T hostname gdbserver - hello
17815 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17816 and we don't want escape-character handling. Ssh does this by default when
17817 a command is provided, the flag is provided to make it explicit.
17818 You could elide it if you want to.
17820 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17821 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17822 display through a pipe connected to gdbserver.
17823 Both @code{stdout} and @code{stderr} use the same pipe.
17825 @subsubsection Attaching to a Running Program
17826 @cindex attach to a program, @code{gdbserver}
17827 @cindex @option{--attach}, @code{gdbserver} option
17829 On some targets, @code{gdbserver} can also attach to running programs.
17830 This is accomplished via the @code{--attach} argument. The syntax is:
17833 target> gdbserver --attach @var{comm} @var{pid}
17836 @var{pid} is the process ID of a currently running process. It isn't necessary
17837 to point @code{gdbserver} at a binary for the running process.
17840 You can debug processes by name instead of process ID if your target has the
17841 @code{pidof} utility:
17844 target> gdbserver --attach @var{comm} `pidof @var{program}`
17847 In case more than one copy of @var{program} is running, or @var{program}
17848 has multiple threads, most versions of @code{pidof} support the
17849 @code{-s} option to only return the first process ID.
17851 @subsubsection Multi-Process Mode for @code{gdbserver}
17852 @cindex @code{gdbserver}, multiple processes
17853 @cindex multiple processes with @code{gdbserver}
17855 When you connect to @code{gdbserver} using @code{target remote},
17856 @code{gdbserver} debugs the specified program only once. When the
17857 program exits, or you detach from it, @value{GDBN} closes the connection
17858 and @code{gdbserver} exits.
17860 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17861 enters multi-process mode. When the debugged program exits, or you
17862 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17863 though no program is running. The @code{run} and @code{attach}
17864 commands instruct @code{gdbserver} to run or attach to a new program.
17865 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17866 remote exec-file}) to select the program to run. Command line
17867 arguments are supported, except for wildcard expansion and I/O
17868 redirection (@pxref{Arguments}).
17870 @cindex @option{--multi}, @code{gdbserver} option
17871 To start @code{gdbserver} without supplying an initial command to run
17872 or process ID to attach, use the @option{--multi} command line option.
17873 Then you can connect using @kbd{target extended-remote} and start
17874 the program you want to debug.
17876 In multi-process mode @code{gdbserver} does not automatically exit unless you
17877 use the option @option{--once}. You can terminate it by using
17878 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17879 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17880 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17881 @option{--multi} option to @code{gdbserver} has no influence on that.
17883 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17885 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17887 @code{gdbserver} normally terminates after all of its debugged processes have
17888 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17889 extended-remote}, @code{gdbserver} stays running even with no processes left.
17890 @value{GDBN} normally terminates the spawned debugged process on its exit,
17891 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17892 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17893 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17894 stays running even in the @kbd{target remote} mode.
17896 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17897 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17898 completeness, at most one @value{GDBN} can be connected at a time.
17900 @cindex @option{--once}, @code{gdbserver} option
17901 By default, @code{gdbserver} keeps the listening TCP port open, so that
17902 additional connections are possible. However, if you start @code{gdbserver}
17903 with the @option{--once} option, it will stop listening for any further
17904 connection attempts after connecting to the first @value{GDBN} session. This
17905 means no further connections to @code{gdbserver} will be possible after the
17906 first one. It also means @code{gdbserver} will terminate after the first
17907 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17908 connections and even in the @kbd{target extended-remote} mode. The
17909 @option{--once} option allows reusing the same port number for connecting to
17910 multiple instances of @code{gdbserver} running on the same host, since each
17911 instance closes its port after the first connection.
17913 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17915 @cindex @option{--debug}, @code{gdbserver} option
17916 The @option{--debug} option tells @code{gdbserver} to display extra
17917 status information about the debugging process.
17918 @cindex @option{--remote-debug}, @code{gdbserver} option
17919 The @option{--remote-debug} option tells @code{gdbserver} to display
17920 remote protocol debug output. These options are intended for
17921 @code{gdbserver} development and for bug reports to the developers.
17923 @cindex @option{--wrapper}, @code{gdbserver} option
17924 The @option{--wrapper} option specifies a wrapper to launch programs
17925 for debugging. The option should be followed by the name of the
17926 wrapper, then any command-line arguments to pass to the wrapper, then
17927 @kbd{--} indicating the end of the wrapper arguments.
17929 @code{gdbserver} runs the specified wrapper program with a combined
17930 command line including the wrapper arguments, then the name of the
17931 program to debug, then any arguments to the program. The wrapper
17932 runs until it executes your program, and then @value{GDBN} gains control.
17934 You can use any program that eventually calls @code{execve} with
17935 its arguments as a wrapper. Several standard Unix utilities do
17936 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17937 with @code{exec "$@@"} will also work.
17939 For example, you can use @code{env} to pass an environment variable to
17940 the debugged program, without setting the variable in @code{gdbserver}'s
17944 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17947 @subsection Connecting to @code{gdbserver}
17949 Run @value{GDBN} on the host system.
17951 First make sure you have the necessary symbol files. Load symbols for
17952 your application using the @code{file} command before you connect. Use
17953 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17954 was compiled with the correct sysroot using @code{--with-sysroot}).
17956 The symbol file and target libraries must exactly match the executable
17957 and libraries on the target, with one exception: the files on the host
17958 system should not be stripped, even if the files on the target system
17959 are. Mismatched or missing files will lead to confusing results
17960 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17961 files may also prevent @code{gdbserver} from debugging multi-threaded
17964 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17965 For TCP connections, you must start up @code{gdbserver} prior to using
17966 the @code{target remote} command. Otherwise you may get an error whose
17967 text depends on the host system, but which usually looks something like
17968 @samp{Connection refused}. Don't use the @code{load}
17969 command in @value{GDBN} when using @code{gdbserver}, since the program is
17970 already on the target.
17972 @subsection Monitor Commands for @code{gdbserver}
17973 @cindex monitor commands, for @code{gdbserver}
17974 @anchor{Monitor Commands for gdbserver}
17976 During a @value{GDBN} session using @code{gdbserver}, you can use the
17977 @code{monitor} command to send special requests to @code{gdbserver}.
17978 Here are the available commands.
17982 List the available monitor commands.
17984 @item monitor set debug 0
17985 @itemx monitor set debug 1
17986 Disable or enable general debugging messages.
17988 @item monitor set remote-debug 0
17989 @itemx monitor set remote-debug 1
17990 Disable or enable specific debugging messages associated with the remote
17991 protocol (@pxref{Remote Protocol}).
17993 @item monitor set libthread-db-search-path [PATH]
17994 @cindex gdbserver, search path for @code{libthread_db}
17995 When this command is issued, @var{path} is a colon-separated list of
17996 directories to search for @code{libthread_db} (@pxref{Threads,,set
17997 libthread-db-search-path}). If you omit @var{path},
17998 @samp{libthread-db-search-path} will be reset to its default value.
18000 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18001 not supported in @code{gdbserver}.
18004 Tell gdbserver to exit immediately. This command should be followed by
18005 @code{disconnect} to close the debugging session. @code{gdbserver} will
18006 detach from any attached processes and kill any processes it created.
18007 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18008 of a multi-process mode debug session.
18012 @subsection Tracepoints support in @code{gdbserver}
18013 @cindex tracepoints support in @code{gdbserver}
18015 On some targets, @code{gdbserver} supports tracepoints, fast
18016 tracepoints and static tracepoints.
18018 For fast or static tracepoints to work, a special library called the
18019 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18020 This library is built and distributed as an integral part of
18021 @code{gdbserver}. In addition, support for static tracepoints
18022 requires building the in-process agent library with static tracepoints
18023 support. At present, the UST (LTTng Userspace Tracer,
18024 @url{http://lttng.org/ust}) tracing engine is supported. This support
18025 is automatically available if UST development headers are found in the
18026 standard include path when @code{gdbserver} is built, or if
18027 @code{gdbserver} was explicitly configured using @option{--with-ust}
18028 to point at such headers. You can explicitly disable the support
18029 using @option{--with-ust=no}.
18031 There are several ways to load the in-process agent in your program:
18034 @item Specifying it as dependency at link time
18036 You can link your program dynamically with the in-process agent
18037 library. On most systems, this is accomplished by adding
18038 @code{-linproctrace} to the link command.
18040 @item Using the system's preloading mechanisms
18042 You can force loading the in-process agent at startup time by using
18043 your system's support for preloading shared libraries. Many Unixes
18044 support the concept of preloading user defined libraries. In most
18045 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18046 in the environment. See also the description of @code{gdbserver}'s
18047 @option{--wrapper} command line option.
18049 @item Using @value{GDBN} to force loading the agent at run time
18051 On some systems, you can force the inferior to load a shared library,
18052 by calling a dynamic loader function in the inferior that takes care
18053 of dynamically looking up and loading a shared library. On most Unix
18054 systems, the function is @code{dlopen}. You'll use the @code{call}
18055 command for that. For example:
18058 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18061 Note that on most Unix systems, for the @code{dlopen} function to be
18062 available, the program needs to be linked with @code{-ldl}.
18065 On systems that have a userspace dynamic loader, like most Unix
18066 systems, when you connect to @code{gdbserver} using @code{target
18067 remote}, you'll find that the program is stopped at the dynamic
18068 loader's entry point, and no shared library has been loaded in the
18069 program's address space yet, including the in-process agent. In that
18070 case, before being able to use any of the fast or static tracepoints
18071 features, you need to let the loader run and load the shared
18072 libraries. The simplest way to do that is to run the program to the
18073 main procedure. E.g., if debugging a C or C@t{++} program, start
18074 @code{gdbserver} like so:
18077 $ gdbserver :9999 myprogram
18080 Start GDB and connect to @code{gdbserver} like so, and run to main:
18084 (@value{GDBP}) target remote myhost:9999
18085 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18086 (@value{GDBP}) b main
18087 (@value{GDBP}) continue
18090 The in-process tracing agent library should now be loaded into the
18091 process; you can confirm it with the @code{info sharedlibrary}
18092 command, which will list @file{libinproctrace.so} as loaded in the
18093 process. You are now ready to install fast tracepoints, list static
18094 tracepoint markers, probe static tracepoints markers, and start
18097 @node Remote Configuration
18098 @section Remote Configuration
18101 @kindex show remote
18102 This section documents the configuration options available when
18103 debugging remote programs. For the options related to the File I/O
18104 extensions of the remote protocol, see @ref{system,
18105 system-call-allowed}.
18108 @item set remoteaddresssize @var{bits}
18109 @cindex address size for remote targets
18110 @cindex bits in remote address
18111 Set the maximum size of address in a memory packet to the specified
18112 number of bits. @value{GDBN} will mask off the address bits above
18113 that number, when it passes addresses to the remote target. The
18114 default value is the number of bits in the target's address.
18116 @item show remoteaddresssize
18117 Show the current value of remote address size in bits.
18119 @item set remotebaud @var{n}
18120 @cindex baud rate for remote targets
18121 Set the baud rate for the remote serial I/O to @var{n} baud. The
18122 value is used to set the speed of the serial port used for debugging
18125 @item show remotebaud
18126 Show the current speed of the remote connection.
18128 @item set remotebreak
18129 @cindex interrupt remote programs
18130 @cindex BREAK signal instead of Ctrl-C
18131 @anchor{set remotebreak}
18132 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18133 when you type @kbd{Ctrl-c} to interrupt the program running
18134 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18135 character instead. The default is off, since most remote systems
18136 expect to see @samp{Ctrl-C} as the interrupt signal.
18138 @item show remotebreak
18139 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18140 interrupt the remote program.
18142 @item set remoteflow on
18143 @itemx set remoteflow off
18144 @kindex set remoteflow
18145 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18146 on the serial port used to communicate to the remote target.
18148 @item show remoteflow
18149 @kindex show remoteflow
18150 Show the current setting of hardware flow control.
18152 @item set remotelogbase @var{base}
18153 Set the base (a.k.a.@: radix) of logging serial protocol
18154 communications to @var{base}. Supported values of @var{base} are:
18155 @code{ascii}, @code{octal}, and @code{hex}. The default is
18158 @item show remotelogbase
18159 Show the current setting of the radix for logging remote serial
18162 @item set remotelogfile @var{file}
18163 @cindex record serial communications on file
18164 Record remote serial communications on the named @var{file}. The
18165 default is not to record at all.
18167 @item show remotelogfile.
18168 Show the current setting of the file name on which to record the
18169 serial communications.
18171 @item set remotetimeout @var{num}
18172 @cindex timeout for serial communications
18173 @cindex remote timeout
18174 Set the timeout limit to wait for the remote target to respond to
18175 @var{num} seconds. The default is 2 seconds.
18177 @item show remotetimeout
18178 Show the current number of seconds to wait for the remote target
18181 @cindex limit hardware breakpoints and watchpoints
18182 @cindex remote target, limit break- and watchpoints
18183 @anchor{set remote hardware-watchpoint-limit}
18184 @anchor{set remote hardware-breakpoint-limit}
18185 @item set remote hardware-watchpoint-limit @var{limit}
18186 @itemx set remote hardware-breakpoint-limit @var{limit}
18187 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18188 watchpoints. A limit of -1, the default, is treated as unlimited.
18190 @cindex limit hardware watchpoints length
18191 @cindex remote target, limit watchpoints length
18192 @anchor{set remote hardware-watchpoint-length-limit}
18193 @item set remote hardware-watchpoint-length-limit @var{limit}
18194 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18195 a remote hardware watchpoint. A limit of -1, the default, is treated
18198 @item show remote hardware-watchpoint-length-limit
18199 Show the current limit (in bytes) of the maximum length of
18200 a remote hardware watchpoint.
18202 @item set remote exec-file @var{filename}
18203 @itemx show remote exec-file
18204 @anchor{set remote exec-file}
18205 @cindex executable file, for remote target
18206 Select the file used for @code{run} with @code{target
18207 extended-remote}. This should be set to a filename valid on the
18208 target system. If it is not set, the target will use a default
18209 filename (e.g.@: the last program run).
18211 @item set remote interrupt-sequence
18212 @cindex interrupt remote programs
18213 @cindex select Ctrl-C, BREAK or BREAK-g
18214 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18215 @samp{BREAK-g} as the
18216 sequence to the remote target in order to interrupt the execution.
18217 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18218 is high level of serial line for some certain time.
18219 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18220 It is @code{BREAK} signal followed by character @code{g}.
18222 @item show interrupt-sequence
18223 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18224 is sent by @value{GDBN} to interrupt the remote program.
18225 @code{BREAK-g} is BREAK signal followed by @code{g} and
18226 also known as Magic SysRq g.
18228 @item set remote interrupt-on-connect
18229 @cindex send interrupt-sequence on start
18230 Specify whether interrupt-sequence is sent to remote target when
18231 @value{GDBN} connects to it. This is mostly needed when you debug
18232 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18233 which is known as Magic SysRq g in order to connect @value{GDBN}.
18235 @item show interrupt-on-connect
18236 Show whether interrupt-sequence is sent
18237 to remote target when @value{GDBN} connects to it.
18241 @item set tcp auto-retry on
18242 @cindex auto-retry, for remote TCP target
18243 Enable auto-retry for remote TCP connections. This is useful if the remote
18244 debugging agent is launched in parallel with @value{GDBN}; there is a race
18245 condition because the agent may not become ready to accept the connection
18246 before @value{GDBN} attempts to connect. When auto-retry is
18247 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18248 to establish the connection using the timeout specified by
18249 @code{set tcp connect-timeout}.
18251 @item set tcp auto-retry off
18252 Do not auto-retry failed TCP connections.
18254 @item show tcp auto-retry
18255 Show the current auto-retry setting.
18257 @item set tcp connect-timeout @var{seconds}
18258 @cindex connection timeout, for remote TCP target
18259 @cindex timeout, for remote target connection
18260 Set the timeout for establishing a TCP connection to the remote target to
18261 @var{seconds}. The timeout affects both polling to retry failed connections
18262 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18263 that are merely slow to complete, and represents an approximate cumulative
18266 @item show tcp connect-timeout
18267 Show the current connection timeout setting.
18270 @cindex remote packets, enabling and disabling
18271 The @value{GDBN} remote protocol autodetects the packets supported by
18272 your debugging stub. If you need to override the autodetection, you
18273 can use these commands to enable or disable individual packets. Each
18274 packet can be set to @samp{on} (the remote target supports this
18275 packet), @samp{off} (the remote target does not support this packet),
18276 or @samp{auto} (detect remote target support for this packet). They
18277 all default to @samp{auto}. For more information about each packet,
18278 see @ref{Remote Protocol}.
18280 During normal use, you should not have to use any of these commands.
18281 If you do, that may be a bug in your remote debugging stub, or a bug
18282 in @value{GDBN}. You may want to report the problem to the
18283 @value{GDBN} developers.
18285 For each packet @var{name}, the command to enable or disable the
18286 packet is @code{set remote @var{name}-packet}. The available settings
18289 @multitable @columnfractions 0.28 0.32 0.25
18292 @tab Related Features
18294 @item @code{fetch-register}
18296 @tab @code{info registers}
18298 @item @code{set-register}
18302 @item @code{binary-download}
18304 @tab @code{load}, @code{set}
18306 @item @code{read-aux-vector}
18307 @tab @code{qXfer:auxv:read}
18308 @tab @code{info auxv}
18310 @item @code{symbol-lookup}
18311 @tab @code{qSymbol}
18312 @tab Detecting multiple threads
18314 @item @code{attach}
18315 @tab @code{vAttach}
18318 @item @code{verbose-resume}
18320 @tab Stepping or resuming multiple threads
18326 @item @code{software-breakpoint}
18330 @item @code{hardware-breakpoint}
18334 @item @code{write-watchpoint}
18338 @item @code{read-watchpoint}
18342 @item @code{access-watchpoint}
18346 @item @code{target-features}
18347 @tab @code{qXfer:features:read}
18348 @tab @code{set architecture}
18350 @item @code{library-info}
18351 @tab @code{qXfer:libraries:read}
18352 @tab @code{info sharedlibrary}
18354 @item @code{memory-map}
18355 @tab @code{qXfer:memory-map:read}
18356 @tab @code{info mem}
18358 @item @code{read-sdata-object}
18359 @tab @code{qXfer:sdata:read}
18360 @tab @code{print $_sdata}
18362 @item @code{read-spu-object}
18363 @tab @code{qXfer:spu:read}
18364 @tab @code{info spu}
18366 @item @code{write-spu-object}
18367 @tab @code{qXfer:spu:write}
18368 @tab @code{info spu}
18370 @item @code{read-siginfo-object}
18371 @tab @code{qXfer:siginfo:read}
18372 @tab @code{print $_siginfo}
18374 @item @code{write-siginfo-object}
18375 @tab @code{qXfer:siginfo:write}
18376 @tab @code{set $_siginfo}
18378 @item @code{threads}
18379 @tab @code{qXfer:threads:read}
18380 @tab @code{info threads}
18382 @item @code{get-thread-local-@*storage-address}
18383 @tab @code{qGetTLSAddr}
18384 @tab Displaying @code{__thread} variables
18386 @item @code{get-thread-information-block-address}
18387 @tab @code{qGetTIBAddr}
18388 @tab Display MS-Windows Thread Information Block.
18390 @item @code{search-memory}
18391 @tab @code{qSearch:memory}
18394 @item @code{supported-packets}
18395 @tab @code{qSupported}
18396 @tab Remote communications parameters
18398 @item @code{pass-signals}
18399 @tab @code{QPassSignals}
18400 @tab @code{handle @var{signal}}
18402 @item @code{program-signals}
18403 @tab @code{QProgramSignals}
18404 @tab @code{handle @var{signal}}
18406 @item @code{hostio-close-packet}
18407 @tab @code{vFile:close}
18408 @tab @code{remote get}, @code{remote put}
18410 @item @code{hostio-open-packet}
18411 @tab @code{vFile:open}
18412 @tab @code{remote get}, @code{remote put}
18414 @item @code{hostio-pread-packet}
18415 @tab @code{vFile:pread}
18416 @tab @code{remote get}, @code{remote put}
18418 @item @code{hostio-pwrite-packet}
18419 @tab @code{vFile:pwrite}
18420 @tab @code{remote get}, @code{remote put}
18422 @item @code{hostio-unlink-packet}
18423 @tab @code{vFile:unlink}
18424 @tab @code{remote delete}
18426 @item @code{hostio-readlink-packet}
18427 @tab @code{vFile:readlink}
18430 @item @code{noack-packet}
18431 @tab @code{QStartNoAckMode}
18432 @tab Packet acknowledgment
18434 @item @code{osdata}
18435 @tab @code{qXfer:osdata:read}
18436 @tab @code{info os}
18438 @item @code{query-attached}
18439 @tab @code{qAttached}
18440 @tab Querying remote process attach state.
18442 @item @code{trace-buffer-size}
18443 @tab @code{QTBuffer:size}
18444 @tab @code{set trace-buffer-size}
18446 @item @code{traceframe-info}
18447 @tab @code{qXfer:traceframe-info:read}
18448 @tab Traceframe info
18450 @item @code{install-in-trace}
18451 @tab @code{InstallInTrace}
18452 @tab Install tracepoint in tracing
18454 @item @code{disable-randomization}
18455 @tab @code{QDisableRandomization}
18456 @tab @code{set disable-randomization}
18458 @item @code{conditional-breakpoints-packet}
18459 @tab @code{Z0 and Z1}
18460 @tab @code{Support for target-side breakpoint condition evaluation}
18464 @section Implementing a Remote Stub
18466 @cindex debugging stub, example
18467 @cindex remote stub, example
18468 @cindex stub example, remote debugging
18469 The stub files provided with @value{GDBN} implement the target side of the
18470 communication protocol, and the @value{GDBN} side is implemented in the
18471 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18472 these subroutines to communicate, and ignore the details. (If you're
18473 implementing your own stub file, you can still ignore the details: start
18474 with one of the existing stub files. @file{sparc-stub.c} is the best
18475 organized, and therefore the easiest to read.)
18477 @cindex remote serial debugging, overview
18478 To debug a program running on another machine (the debugging
18479 @dfn{target} machine), you must first arrange for all the usual
18480 prerequisites for the program to run by itself. For example, for a C
18485 A startup routine to set up the C runtime environment; these usually
18486 have a name like @file{crt0}. The startup routine may be supplied by
18487 your hardware supplier, or you may have to write your own.
18490 A C subroutine library to support your program's
18491 subroutine calls, notably managing input and output.
18494 A way of getting your program to the other machine---for example, a
18495 download program. These are often supplied by the hardware
18496 manufacturer, but you may have to write your own from hardware
18500 The next step is to arrange for your program to use a serial port to
18501 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18502 machine). In general terms, the scheme looks like this:
18506 @value{GDBN} already understands how to use this protocol; when everything
18507 else is set up, you can simply use the @samp{target remote} command
18508 (@pxref{Targets,,Specifying a Debugging Target}).
18510 @item On the target,
18511 you must link with your program a few special-purpose subroutines that
18512 implement the @value{GDBN} remote serial protocol. The file containing these
18513 subroutines is called a @dfn{debugging stub}.
18515 On certain remote targets, you can use an auxiliary program
18516 @code{gdbserver} instead of linking a stub into your program.
18517 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18520 The debugging stub is specific to the architecture of the remote
18521 machine; for example, use @file{sparc-stub.c} to debug programs on
18524 @cindex remote serial stub list
18525 These working remote stubs are distributed with @value{GDBN}:
18530 @cindex @file{i386-stub.c}
18533 For Intel 386 and compatible architectures.
18536 @cindex @file{m68k-stub.c}
18537 @cindex Motorola 680x0
18539 For Motorola 680x0 architectures.
18542 @cindex @file{sh-stub.c}
18545 For Renesas SH architectures.
18548 @cindex @file{sparc-stub.c}
18550 For @sc{sparc} architectures.
18552 @item sparcl-stub.c
18553 @cindex @file{sparcl-stub.c}
18556 For Fujitsu @sc{sparclite} architectures.
18560 The @file{README} file in the @value{GDBN} distribution may list other
18561 recently added stubs.
18564 * Stub Contents:: What the stub can do for you
18565 * Bootstrapping:: What you must do for the stub
18566 * Debug Session:: Putting it all together
18569 @node Stub Contents
18570 @subsection What the Stub Can Do for You
18572 @cindex remote serial stub
18573 The debugging stub for your architecture supplies these three
18577 @item set_debug_traps
18578 @findex set_debug_traps
18579 @cindex remote serial stub, initialization
18580 This routine arranges for @code{handle_exception} to run when your
18581 program stops. You must call this subroutine explicitly in your
18582 program's startup code.
18584 @item handle_exception
18585 @findex handle_exception
18586 @cindex remote serial stub, main routine
18587 This is the central workhorse, but your program never calls it
18588 explicitly---the setup code arranges for @code{handle_exception} to
18589 run when a trap is triggered.
18591 @code{handle_exception} takes control when your program stops during
18592 execution (for example, on a breakpoint), and mediates communications
18593 with @value{GDBN} on the host machine. This is where the communications
18594 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18595 representative on the target machine. It begins by sending summary
18596 information on the state of your program, then continues to execute,
18597 retrieving and transmitting any information @value{GDBN} needs, until you
18598 execute a @value{GDBN} command that makes your program resume; at that point,
18599 @code{handle_exception} returns control to your own code on the target
18603 @cindex @code{breakpoint} subroutine, remote
18604 Use this auxiliary subroutine to make your program contain a
18605 breakpoint. Depending on the particular situation, this may be the only
18606 way for @value{GDBN} to get control. For instance, if your target
18607 machine has some sort of interrupt button, you won't need to call this;
18608 pressing the interrupt button transfers control to
18609 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18610 simply receiving characters on the serial port may also trigger a trap;
18611 again, in that situation, you don't need to call @code{breakpoint} from
18612 your own program---simply running @samp{target remote} from the host
18613 @value{GDBN} session gets control.
18615 Call @code{breakpoint} if none of these is true, or if you simply want
18616 to make certain your program stops at a predetermined point for the
18617 start of your debugging session.
18620 @node Bootstrapping
18621 @subsection What You Must Do for the Stub
18623 @cindex remote stub, support routines
18624 The debugging stubs that come with @value{GDBN} are set up for a particular
18625 chip architecture, but they have no information about the rest of your
18626 debugging target machine.
18628 First of all you need to tell the stub how to communicate with the
18632 @item int getDebugChar()
18633 @findex getDebugChar
18634 Write this subroutine to read a single character from the serial port.
18635 It may be identical to @code{getchar} for your target system; a
18636 different name is used to allow you to distinguish the two if you wish.
18638 @item void putDebugChar(int)
18639 @findex putDebugChar
18640 Write this subroutine to write a single character to the serial port.
18641 It may be identical to @code{putchar} for your target system; a
18642 different name is used to allow you to distinguish the two if you wish.
18645 @cindex control C, and remote debugging
18646 @cindex interrupting remote targets
18647 If you want @value{GDBN} to be able to stop your program while it is
18648 running, you need to use an interrupt-driven serial driver, and arrange
18649 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18650 character). That is the character which @value{GDBN} uses to tell the
18651 remote system to stop.
18653 Getting the debugging target to return the proper status to @value{GDBN}
18654 probably requires changes to the standard stub; one quick and dirty way
18655 is to just execute a breakpoint instruction (the ``dirty'' part is that
18656 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18658 Other routines you need to supply are:
18661 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18662 @findex exceptionHandler
18663 Write this function to install @var{exception_address} in the exception
18664 handling tables. You need to do this because the stub does not have any
18665 way of knowing what the exception handling tables on your target system
18666 are like (for example, the processor's table might be in @sc{rom},
18667 containing entries which point to a table in @sc{ram}).
18668 @var{exception_number} is the exception number which should be changed;
18669 its meaning is architecture-dependent (for example, different numbers
18670 might represent divide by zero, misaligned access, etc). When this
18671 exception occurs, control should be transferred directly to
18672 @var{exception_address}, and the processor state (stack, registers,
18673 and so on) should be just as it is when a processor exception occurs. So if
18674 you want to use a jump instruction to reach @var{exception_address}, it
18675 should be a simple jump, not a jump to subroutine.
18677 For the 386, @var{exception_address} should be installed as an interrupt
18678 gate so that interrupts are masked while the handler runs. The gate
18679 should be at privilege level 0 (the most privileged level). The
18680 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18681 help from @code{exceptionHandler}.
18683 @item void flush_i_cache()
18684 @findex flush_i_cache
18685 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18686 instruction cache, if any, on your target machine. If there is no
18687 instruction cache, this subroutine may be a no-op.
18689 On target machines that have instruction caches, @value{GDBN} requires this
18690 function to make certain that the state of your program is stable.
18694 You must also make sure this library routine is available:
18697 @item void *memset(void *, int, int)
18699 This is the standard library function @code{memset} that sets an area of
18700 memory to a known value. If you have one of the free versions of
18701 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18702 either obtain it from your hardware manufacturer, or write your own.
18705 If you do not use the GNU C compiler, you may need other standard
18706 library subroutines as well; this varies from one stub to another,
18707 but in general the stubs are likely to use any of the common library
18708 subroutines which @code{@value{NGCC}} generates as inline code.
18711 @node Debug Session
18712 @subsection Putting it All Together
18714 @cindex remote serial debugging summary
18715 In summary, when your program is ready to debug, you must follow these
18720 Make sure you have defined the supporting low-level routines
18721 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18723 @code{getDebugChar}, @code{putDebugChar},
18724 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18728 Insert these lines in your program's startup code, before the main
18729 procedure is called:
18736 On some machines, when a breakpoint trap is raised, the hardware
18737 automatically makes the PC point to the instruction after the
18738 breakpoint. If your machine doesn't do that, you may need to adjust
18739 @code{handle_exception} to arrange for it to return to the instruction
18740 after the breakpoint on this first invocation, so that your program
18741 doesn't keep hitting the initial breakpoint instead of making
18745 For the 680x0 stub only, you need to provide a variable called
18746 @code{exceptionHook}. Normally you just use:
18749 void (*exceptionHook)() = 0;
18753 but if before calling @code{set_debug_traps}, you set it to point to a
18754 function in your program, that function is called when
18755 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18756 error). The function indicated by @code{exceptionHook} is called with
18757 one parameter: an @code{int} which is the exception number.
18760 Compile and link together: your program, the @value{GDBN} debugging stub for
18761 your target architecture, and the supporting subroutines.
18764 Make sure you have a serial connection between your target machine and
18765 the @value{GDBN} host, and identify the serial port on the host.
18768 @c The "remote" target now provides a `load' command, so we should
18769 @c document that. FIXME.
18770 Download your program to your target machine (or get it there by
18771 whatever means the manufacturer provides), and start it.
18774 Start @value{GDBN} on the host, and connect to the target
18775 (@pxref{Connecting,,Connecting to a Remote Target}).
18779 @node Configurations
18780 @chapter Configuration-Specific Information
18782 While nearly all @value{GDBN} commands are available for all native and
18783 cross versions of the debugger, there are some exceptions. This chapter
18784 describes things that are only available in certain configurations.
18786 There are three major categories of configurations: native
18787 configurations, where the host and target are the same, embedded
18788 operating system configurations, which are usually the same for several
18789 different processor architectures, and bare embedded processors, which
18790 are quite different from each other.
18795 * Embedded Processors::
18802 This section describes details specific to particular native
18807 * BSD libkvm Interface:: Debugging BSD kernel memory images
18808 * SVR4 Process Information:: SVR4 process information
18809 * DJGPP Native:: Features specific to the DJGPP port
18810 * Cygwin Native:: Features specific to the Cygwin port
18811 * Hurd Native:: Features specific to @sc{gnu} Hurd
18812 * Darwin:: Features specific to Darwin
18818 On HP-UX systems, if you refer to a function or variable name that
18819 begins with a dollar sign, @value{GDBN} searches for a user or system
18820 name first, before it searches for a convenience variable.
18823 @node BSD libkvm Interface
18824 @subsection BSD libkvm Interface
18827 @cindex kernel memory image
18828 @cindex kernel crash dump
18830 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18831 interface that provides a uniform interface for accessing kernel virtual
18832 memory images, including live systems and crash dumps. @value{GDBN}
18833 uses this interface to allow you to debug live kernels and kernel crash
18834 dumps on many native BSD configurations. This is implemented as a
18835 special @code{kvm} debugging target. For debugging a live system, load
18836 the currently running kernel into @value{GDBN} and connect to the
18840 (@value{GDBP}) @b{target kvm}
18843 For debugging crash dumps, provide the file name of the crash dump as an
18847 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18850 Once connected to the @code{kvm} target, the following commands are
18856 Set current context from the @dfn{Process Control Block} (PCB) address.
18859 Set current context from proc address. This command isn't available on
18860 modern FreeBSD systems.
18863 @node SVR4 Process Information
18864 @subsection SVR4 Process Information
18866 @cindex examine process image
18867 @cindex process info via @file{/proc}
18869 Many versions of SVR4 and compatible systems provide a facility called
18870 @samp{/proc} that can be used to examine the image of a running
18871 process using file-system subroutines.
18873 If @value{GDBN} is configured for an operating system with this
18874 facility, the command @code{info proc} is available to report
18875 information about the process running your program, or about any
18876 process running on your system. This includes, as of this writing,
18877 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18878 not HP-UX, for example.
18880 This command may also work on core files that were created on a system
18881 that has the @samp{/proc} facility.
18887 @itemx info proc @var{process-id}
18888 Summarize available information about any running process. If a
18889 process ID is specified by @var{process-id}, display information about
18890 that process; otherwise display information about the program being
18891 debugged. The summary includes the debugged process ID, the command
18892 line used to invoke it, its current working directory, and its
18893 executable file's absolute file name.
18895 On some systems, @var{process-id} can be of the form
18896 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18897 within a process. If the optional @var{pid} part is missing, it means
18898 a thread from the process being debugged (the leading @samp{/} still
18899 needs to be present, or else @value{GDBN} will interpret the number as
18900 a process ID rather than a thread ID).
18902 @item info proc cmdline
18903 @cindex info proc cmdline
18904 Show the original command line of the process. This command is
18905 specific to @sc{gnu}/Linux.
18907 @item info proc cwd
18908 @cindex info proc cwd
18909 Show the current working directory of the process. This command is
18910 specific to @sc{gnu}/Linux.
18912 @item info proc exe
18913 @cindex info proc exe
18914 Show the name of executable of the process. This command is specific
18917 @item info proc mappings
18918 @cindex memory address space mappings
18919 Report the memory address space ranges accessible in the program, with
18920 information on whether the process has read, write, or execute access
18921 rights to each range. On @sc{gnu}/Linux systems, each memory range
18922 includes the object file which is mapped to that range, instead of the
18923 memory access rights to that range.
18925 @item info proc stat
18926 @itemx info proc status
18927 @cindex process detailed status information
18928 These subcommands are specific to @sc{gnu}/Linux systems. They show
18929 the process-related information, including the user ID and group ID;
18930 how many threads are there in the process; its virtual memory usage;
18931 the signals that are pending, blocked, and ignored; its TTY; its
18932 consumption of system and user time; its stack size; its @samp{nice}
18933 value; etc. For more information, see the @samp{proc} man page
18934 (type @kbd{man 5 proc} from your shell prompt).
18936 @item info proc all
18937 Show all the information about the process described under all of the
18938 above @code{info proc} subcommands.
18941 @comment These sub-options of 'info proc' were not included when
18942 @comment procfs.c was re-written. Keep their descriptions around
18943 @comment against the day when someone finds the time to put them back in.
18944 @kindex info proc times
18945 @item info proc times
18946 Starting time, user CPU time, and system CPU time for your program and
18949 @kindex info proc id
18951 Report on the process IDs related to your program: its own process ID,
18952 the ID of its parent, the process group ID, and the session ID.
18955 @item set procfs-trace
18956 @kindex set procfs-trace
18957 @cindex @code{procfs} API calls
18958 This command enables and disables tracing of @code{procfs} API calls.
18960 @item show procfs-trace
18961 @kindex show procfs-trace
18962 Show the current state of @code{procfs} API call tracing.
18964 @item set procfs-file @var{file}
18965 @kindex set procfs-file
18966 Tell @value{GDBN} to write @code{procfs} API trace to the named
18967 @var{file}. @value{GDBN} appends the trace info to the previous
18968 contents of the file. The default is to display the trace on the
18971 @item show procfs-file
18972 @kindex show procfs-file
18973 Show the file to which @code{procfs} API trace is written.
18975 @item proc-trace-entry
18976 @itemx proc-trace-exit
18977 @itemx proc-untrace-entry
18978 @itemx proc-untrace-exit
18979 @kindex proc-trace-entry
18980 @kindex proc-trace-exit
18981 @kindex proc-untrace-entry
18982 @kindex proc-untrace-exit
18983 These commands enable and disable tracing of entries into and exits
18984 from the @code{syscall} interface.
18987 @kindex info pidlist
18988 @cindex process list, QNX Neutrino
18989 For QNX Neutrino only, this command displays the list of all the
18990 processes and all the threads within each process.
18993 @kindex info meminfo
18994 @cindex mapinfo list, QNX Neutrino
18995 For QNX Neutrino only, this command displays the list of all mapinfos.
18999 @subsection Features for Debugging @sc{djgpp} Programs
19000 @cindex @sc{djgpp} debugging
19001 @cindex native @sc{djgpp} debugging
19002 @cindex MS-DOS-specific commands
19005 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19006 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19007 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19008 top of real-mode DOS systems and their emulations.
19010 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19011 defines a few commands specific to the @sc{djgpp} port. This
19012 subsection describes those commands.
19017 This is a prefix of @sc{djgpp}-specific commands which print
19018 information about the target system and important OS structures.
19021 @cindex MS-DOS system info
19022 @cindex free memory information (MS-DOS)
19023 @item info dos sysinfo
19024 This command displays assorted information about the underlying
19025 platform: the CPU type and features, the OS version and flavor, the
19026 DPMI version, and the available conventional and DPMI memory.
19031 @cindex segment descriptor tables
19032 @cindex descriptor tables display
19034 @itemx info dos ldt
19035 @itemx info dos idt
19036 These 3 commands display entries from, respectively, Global, Local,
19037 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19038 tables are data structures which store a descriptor for each segment
19039 that is currently in use. The segment's selector is an index into a
19040 descriptor table; the table entry for that index holds the
19041 descriptor's base address and limit, and its attributes and access
19044 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19045 segment (used for both data and the stack), and a DOS segment (which
19046 allows access to DOS/BIOS data structures and absolute addresses in
19047 conventional memory). However, the DPMI host will usually define
19048 additional segments in order to support the DPMI environment.
19050 @cindex garbled pointers
19051 These commands allow to display entries from the descriptor tables.
19052 Without an argument, all entries from the specified table are
19053 displayed. An argument, which should be an integer expression, means
19054 display a single entry whose index is given by the argument. For
19055 example, here's a convenient way to display information about the
19056 debugged program's data segment:
19059 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19060 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19064 This comes in handy when you want to see whether a pointer is outside
19065 the data segment's limit (i.e.@: @dfn{garbled}).
19067 @cindex page tables display (MS-DOS)
19069 @itemx info dos pte
19070 These two commands display entries from, respectively, the Page
19071 Directory and the Page Tables. Page Directories and Page Tables are
19072 data structures which control how virtual memory addresses are mapped
19073 into physical addresses. A Page Table includes an entry for every
19074 page of memory that is mapped into the program's address space; there
19075 may be several Page Tables, each one holding up to 4096 entries. A
19076 Page Directory has up to 4096 entries, one each for every Page Table
19077 that is currently in use.
19079 Without an argument, @kbd{info dos pde} displays the entire Page
19080 Directory, and @kbd{info dos pte} displays all the entries in all of
19081 the Page Tables. An argument, an integer expression, given to the
19082 @kbd{info dos pde} command means display only that entry from the Page
19083 Directory table. An argument given to the @kbd{info dos pte} command
19084 means display entries from a single Page Table, the one pointed to by
19085 the specified entry in the Page Directory.
19087 @cindex direct memory access (DMA) on MS-DOS
19088 These commands are useful when your program uses @dfn{DMA} (Direct
19089 Memory Access), which needs physical addresses to program the DMA
19092 These commands are supported only with some DPMI servers.
19094 @cindex physical address from linear address
19095 @item info dos address-pte @var{addr}
19096 This command displays the Page Table entry for a specified linear
19097 address. The argument @var{addr} is a linear address which should
19098 already have the appropriate segment's base address added to it,
19099 because this command accepts addresses which may belong to @emph{any}
19100 segment. For example, here's how to display the Page Table entry for
19101 the page where a variable @code{i} is stored:
19104 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19105 @exdent @code{Page Table entry for address 0x11a00d30:}
19106 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19110 This says that @code{i} is stored at offset @code{0xd30} from the page
19111 whose physical base address is @code{0x02698000}, and shows all the
19112 attributes of that page.
19114 Note that you must cast the addresses of variables to a @code{char *},
19115 since otherwise the value of @code{__djgpp_base_address}, the base
19116 address of all variables and functions in a @sc{djgpp} program, will
19117 be added using the rules of C pointer arithmetics: if @code{i} is
19118 declared an @code{int}, @value{GDBN} will add 4 times the value of
19119 @code{__djgpp_base_address} to the address of @code{i}.
19121 Here's another example, it displays the Page Table entry for the
19125 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19126 @exdent @code{Page Table entry for address 0x29110:}
19127 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19131 (The @code{+ 3} offset is because the transfer buffer's address is the
19132 3rd member of the @code{_go32_info_block} structure.) The output
19133 clearly shows that this DPMI server maps the addresses in conventional
19134 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19135 linear (@code{0x29110}) addresses are identical.
19137 This command is supported only with some DPMI servers.
19140 @cindex DOS serial data link, remote debugging
19141 In addition to native debugging, the DJGPP port supports remote
19142 debugging via a serial data link. The following commands are specific
19143 to remote serial debugging in the DJGPP port of @value{GDBN}.
19146 @kindex set com1base
19147 @kindex set com1irq
19148 @kindex set com2base
19149 @kindex set com2irq
19150 @kindex set com3base
19151 @kindex set com3irq
19152 @kindex set com4base
19153 @kindex set com4irq
19154 @item set com1base @var{addr}
19155 This command sets the base I/O port address of the @file{COM1} serial
19158 @item set com1irq @var{irq}
19159 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19160 for the @file{COM1} serial port.
19162 There are similar commands @samp{set com2base}, @samp{set com3irq},
19163 etc.@: for setting the port address and the @code{IRQ} lines for the
19166 @kindex show com1base
19167 @kindex show com1irq
19168 @kindex show com2base
19169 @kindex show com2irq
19170 @kindex show com3base
19171 @kindex show com3irq
19172 @kindex show com4base
19173 @kindex show com4irq
19174 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19175 display the current settings of the base address and the @code{IRQ}
19176 lines used by the COM ports.
19179 @kindex info serial
19180 @cindex DOS serial port status
19181 This command prints the status of the 4 DOS serial ports. For each
19182 port, it prints whether it's active or not, its I/O base address and
19183 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19184 counts of various errors encountered so far.
19188 @node Cygwin Native
19189 @subsection Features for Debugging MS Windows PE Executables
19190 @cindex MS Windows debugging
19191 @cindex native Cygwin debugging
19192 @cindex Cygwin-specific commands
19194 @value{GDBN} supports native debugging of MS Windows programs, including
19195 DLLs with and without symbolic debugging information.
19197 @cindex Ctrl-BREAK, MS-Windows
19198 @cindex interrupt debuggee on MS-Windows
19199 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19200 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19201 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19202 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19203 sequence, which can be used to interrupt the debuggee even if it
19206 There are various additional Cygwin-specific commands, described in
19207 this section. Working with DLLs that have no debugging symbols is
19208 described in @ref{Non-debug DLL Symbols}.
19213 This is a prefix of MS Windows-specific commands which print
19214 information about the target system and important OS structures.
19216 @item info w32 selector
19217 This command displays information returned by
19218 the Win32 API @code{GetThreadSelectorEntry} function.
19219 It takes an optional argument that is evaluated to
19220 a long value to give the information about this given selector.
19221 Without argument, this command displays information
19222 about the six segment registers.
19224 @item info w32 thread-information-block
19225 This command displays thread specific information stored in the
19226 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19227 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19231 This is a Cygwin-specific alias of @code{info shared}.
19233 @kindex dll-symbols
19235 This command loads symbols from a dll similarly to
19236 add-sym command but without the need to specify a base address.
19238 @kindex set cygwin-exceptions
19239 @cindex debugging the Cygwin DLL
19240 @cindex Cygwin DLL, debugging
19241 @item set cygwin-exceptions @var{mode}
19242 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19243 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19244 @value{GDBN} will delay recognition of exceptions, and may ignore some
19245 exceptions which seem to be caused by internal Cygwin DLL
19246 ``bookkeeping''. This option is meant primarily for debugging the
19247 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19248 @value{GDBN} users with false @code{SIGSEGV} signals.
19250 @kindex show cygwin-exceptions
19251 @item show cygwin-exceptions
19252 Displays whether @value{GDBN} will break on exceptions that happen
19253 inside the Cygwin DLL itself.
19255 @kindex set new-console
19256 @item set new-console @var{mode}
19257 If @var{mode} is @code{on} the debuggee will
19258 be started in a new console on next start.
19259 If @var{mode} is @code{off}, the debuggee will
19260 be started in the same console as the debugger.
19262 @kindex show new-console
19263 @item show new-console
19264 Displays whether a new console is used
19265 when the debuggee is started.
19267 @kindex set new-group
19268 @item set new-group @var{mode}
19269 This boolean value controls whether the debuggee should
19270 start a new group or stay in the same group as the debugger.
19271 This affects the way the Windows OS handles
19274 @kindex show new-group
19275 @item show new-group
19276 Displays current value of new-group boolean.
19278 @kindex set debugevents
19279 @item set debugevents
19280 This boolean value adds debug output concerning kernel events related
19281 to the debuggee seen by the debugger. This includes events that
19282 signal thread and process creation and exit, DLL loading and
19283 unloading, console interrupts, and debugging messages produced by the
19284 Windows @code{OutputDebugString} API call.
19286 @kindex set debugexec
19287 @item set debugexec
19288 This boolean value adds debug output concerning execute events
19289 (such as resume thread) seen by the debugger.
19291 @kindex set debugexceptions
19292 @item set debugexceptions
19293 This boolean value adds debug output concerning exceptions in the
19294 debuggee seen by the debugger.
19296 @kindex set debugmemory
19297 @item set debugmemory
19298 This boolean value adds debug output concerning debuggee memory reads
19299 and writes by the debugger.
19303 This boolean values specifies whether the debuggee is called
19304 via a shell or directly (default value is on).
19308 Displays if the debuggee will be started with a shell.
19313 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19316 @node Non-debug DLL Symbols
19317 @subsubsection Support for DLLs without Debugging Symbols
19318 @cindex DLLs with no debugging symbols
19319 @cindex Minimal symbols and DLLs
19321 Very often on windows, some of the DLLs that your program relies on do
19322 not include symbolic debugging information (for example,
19323 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19324 symbols in a DLL, it relies on the minimal amount of symbolic
19325 information contained in the DLL's export table. This section
19326 describes working with such symbols, known internally to @value{GDBN} as
19327 ``minimal symbols''.
19329 Note that before the debugged program has started execution, no DLLs
19330 will have been loaded. The easiest way around this problem is simply to
19331 start the program --- either by setting a breakpoint or letting the
19332 program run once to completion. It is also possible to force
19333 @value{GDBN} to load a particular DLL before starting the executable ---
19334 see the shared library information in @ref{Files}, or the
19335 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19336 explicitly loading symbols from a DLL with no debugging information will
19337 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19338 which may adversely affect symbol lookup performance.
19340 @subsubsection DLL Name Prefixes
19342 In keeping with the naming conventions used by the Microsoft debugging
19343 tools, DLL export symbols are made available with a prefix based on the
19344 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19345 also entered into the symbol table, so @code{CreateFileA} is often
19346 sufficient. In some cases there will be name clashes within a program
19347 (particularly if the executable itself includes full debugging symbols)
19348 necessitating the use of the fully qualified name when referring to the
19349 contents of the DLL. Use single-quotes around the name to avoid the
19350 exclamation mark (``!'') being interpreted as a language operator.
19352 Note that the internal name of the DLL may be all upper-case, even
19353 though the file name of the DLL is lower-case, or vice-versa. Since
19354 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19355 some confusion. If in doubt, try the @code{info functions} and
19356 @code{info variables} commands or even @code{maint print msymbols}
19357 (@pxref{Symbols}). Here's an example:
19360 (@value{GDBP}) info function CreateFileA
19361 All functions matching regular expression "CreateFileA":
19363 Non-debugging symbols:
19364 0x77e885f4 CreateFileA
19365 0x77e885f4 KERNEL32!CreateFileA
19369 (@value{GDBP}) info function !
19370 All functions matching regular expression "!":
19372 Non-debugging symbols:
19373 0x6100114c cygwin1!__assert
19374 0x61004034 cygwin1!_dll_crt0@@0
19375 0x61004240 cygwin1!dll_crt0(per_process *)
19379 @subsubsection Working with Minimal Symbols
19381 Symbols extracted from a DLL's export table do not contain very much
19382 type information. All that @value{GDBN} can do is guess whether a symbol
19383 refers to a function or variable depending on the linker section that
19384 contains the symbol. Also note that the actual contents of the memory
19385 contained in a DLL are not available unless the program is running. This
19386 means that you cannot examine the contents of a variable or disassemble
19387 a function within a DLL without a running program.
19389 Variables are generally treated as pointers and dereferenced
19390 automatically. For this reason, it is often necessary to prefix a
19391 variable name with the address-of operator (``&'') and provide explicit
19392 type information in the command. Here's an example of the type of
19396 (@value{GDBP}) print 'cygwin1!__argv'
19401 (@value{GDBP}) x 'cygwin1!__argv'
19402 0x10021610: "\230y\""
19405 And two possible solutions:
19408 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19409 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19413 (@value{GDBP}) x/2x &'cygwin1!__argv'
19414 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19415 (@value{GDBP}) x/x 0x10021608
19416 0x10021608: 0x0022fd98
19417 (@value{GDBP}) x/s 0x0022fd98
19418 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19421 Setting a break point within a DLL is possible even before the program
19422 starts execution. However, under these circumstances, @value{GDBN} can't
19423 examine the initial instructions of the function in order to skip the
19424 function's frame set-up code. You can work around this by using ``*&''
19425 to set the breakpoint at a raw memory address:
19428 (@value{GDBP}) break *&'python22!PyOS_Readline'
19429 Breakpoint 1 at 0x1e04eff0
19432 The author of these extensions is not entirely convinced that setting a
19433 break point within a shared DLL like @file{kernel32.dll} is completely
19437 @subsection Commands Specific to @sc{gnu} Hurd Systems
19438 @cindex @sc{gnu} Hurd debugging
19440 This subsection describes @value{GDBN} commands specific to the
19441 @sc{gnu} Hurd native debugging.
19446 @kindex set signals@r{, Hurd command}
19447 @kindex set sigs@r{, Hurd command}
19448 This command toggles the state of inferior signal interception by
19449 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19450 affected by this command. @code{sigs} is a shorthand alias for
19455 @kindex show signals@r{, Hurd command}
19456 @kindex show sigs@r{, Hurd command}
19457 Show the current state of intercepting inferior's signals.
19459 @item set signal-thread
19460 @itemx set sigthread
19461 @kindex set signal-thread
19462 @kindex set sigthread
19463 This command tells @value{GDBN} which thread is the @code{libc} signal
19464 thread. That thread is run when a signal is delivered to a running
19465 process. @code{set sigthread} is the shorthand alias of @code{set
19468 @item show signal-thread
19469 @itemx show sigthread
19470 @kindex show signal-thread
19471 @kindex show sigthread
19472 These two commands show which thread will run when the inferior is
19473 delivered a signal.
19476 @kindex set stopped@r{, Hurd command}
19477 This commands tells @value{GDBN} that the inferior process is stopped,
19478 as with the @code{SIGSTOP} signal. The stopped process can be
19479 continued by delivering a signal to it.
19482 @kindex show stopped@r{, Hurd command}
19483 This command shows whether @value{GDBN} thinks the debuggee is
19486 @item set exceptions
19487 @kindex set exceptions@r{, Hurd command}
19488 Use this command to turn off trapping of exceptions in the inferior.
19489 When exception trapping is off, neither breakpoints nor
19490 single-stepping will work. To restore the default, set exception
19493 @item show exceptions
19494 @kindex show exceptions@r{, Hurd command}
19495 Show the current state of trapping exceptions in the inferior.
19497 @item set task pause
19498 @kindex set task@r{, Hurd commands}
19499 @cindex task attributes (@sc{gnu} Hurd)
19500 @cindex pause current task (@sc{gnu} Hurd)
19501 This command toggles task suspension when @value{GDBN} has control.
19502 Setting it to on takes effect immediately, and the task is suspended
19503 whenever @value{GDBN} gets control. Setting it to off will take
19504 effect the next time the inferior is continued. If this option is set
19505 to off, you can use @code{set thread default pause on} or @code{set
19506 thread pause on} (see below) to pause individual threads.
19508 @item show task pause
19509 @kindex show task@r{, Hurd commands}
19510 Show the current state of task suspension.
19512 @item set task detach-suspend-count
19513 @cindex task suspend count
19514 @cindex detach from task, @sc{gnu} Hurd
19515 This command sets the suspend count the task will be left with when
19516 @value{GDBN} detaches from it.
19518 @item show task detach-suspend-count
19519 Show the suspend count the task will be left with when detaching.
19521 @item set task exception-port
19522 @itemx set task excp
19523 @cindex task exception port, @sc{gnu} Hurd
19524 This command sets the task exception port to which @value{GDBN} will
19525 forward exceptions. The argument should be the value of the @dfn{send
19526 rights} of the task. @code{set task excp} is a shorthand alias.
19528 @item set noninvasive
19529 @cindex noninvasive task options
19530 This command switches @value{GDBN} to a mode that is the least
19531 invasive as far as interfering with the inferior is concerned. This
19532 is the same as using @code{set task pause}, @code{set exceptions}, and
19533 @code{set signals} to values opposite to the defaults.
19535 @item info send-rights
19536 @itemx info receive-rights
19537 @itemx info port-rights
19538 @itemx info port-sets
19539 @itemx info dead-names
19542 @cindex send rights, @sc{gnu} Hurd
19543 @cindex receive rights, @sc{gnu} Hurd
19544 @cindex port rights, @sc{gnu} Hurd
19545 @cindex port sets, @sc{gnu} Hurd
19546 @cindex dead names, @sc{gnu} Hurd
19547 These commands display information about, respectively, send rights,
19548 receive rights, port rights, port sets, and dead names of a task.
19549 There are also shorthand aliases: @code{info ports} for @code{info
19550 port-rights} and @code{info psets} for @code{info port-sets}.
19552 @item set thread pause
19553 @kindex set thread@r{, Hurd command}
19554 @cindex thread properties, @sc{gnu} Hurd
19555 @cindex pause current thread (@sc{gnu} Hurd)
19556 This command toggles current thread suspension when @value{GDBN} has
19557 control. Setting it to on takes effect immediately, and the current
19558 thread is suspended whenever @value{GDBN} gets control. Setting it to
19559 off will take effect the next time the inferior is continued.
19560 Normally, this command has no effect, since when @value{GDBN} has
19561 control, the whole task is suspended. However, if you used @code{set
19562 task pause off} (see above), this command comes in handy to suspend
19563 only the current thread.
19565 @item show thread pause
19566 @kindex show thread@r{, Hurd command}
19567 This command shows the state of current thread suspension.
19569 @item set thread run
19570 This command sets whether the current thread is allowed to run.
19572 @item show thread run
19573 Show whether the current thread is allowed to run.
19575 @item set thread detach-suspend-count
19576 @cindex thread suspend count, @sc{gnu} Hurd
19577 @cindex detach from thread, @sc{gnu} Hurd
19578 This command sets the suspend count @value{GDBN} will leave on a
19579 thread when detaching. This number is relative to the suspend count
19580 found by @value{GDBN} when it notices the thread; use @code{set thread
19581 takeover-suspend-count} to force it to an absolute value.
19583 @item show thread detach-suspend-count
19584 Show the suspend count @value{GDBN} will leave on the thread when
19587 @item set thread exception-port
19588 @itemx set thread excp
19589 Set the thread exception port to which to forward exceptions. This
19590 overrides the port set by @code{set task exception-port} (see above).
19591 @code{set thread excp} is the shorthand alias.
19593 @item set thread takeover-suspend-count
19594 Normally, @value{GDBN}'s thread suspend counts are relative to the
19595 value @value{GDBN} finds when it notices each thread. This command
19596 changes the suspend counts to be absolute instead.
19598 @item set thread default
19599 @itemx show thread default
19600 @cindex thread default settings, @sc{gnu} Hurd
19601 Each of the above @code{set thread} commands has a @code{set thread
19602 default} counterpart (e.g., @code{set thread default pause}, @code{set
19603 thread default exception-port}, etc.). The @code{thread default}
19604 variety of commands sets the default thread properties for all
19605 threads; you can then change the properties of individual threads with
19606 the non-default commands.
19613 @value{GDBN} provides the following commands specific to the Darwin target:
19616 @item set debug darwin @var{num}
19617 @kindex set debug darwin
19618 When set to a non zero value, enables debugging messages specific to
19619 the Darwin support. Higher values produce more verbose output.
19621 @item show debug darwin
19622 @kindex show debug darwin
19623 Show the current state of Darwin messages.
19625 @item set debug mach-o @var{num}
19626 @kindex set debug mach-o
19627 When set to a non zero value, enables debugging messages while
19628 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19629 file format used on Darwin for object and executable files.) Higher
19630 values produce more verbose output. This is a command to diagnose
19631 problems internal to @value{GDBN} and should not be needed in normal
19634 @item show debug mach-o
19635 @kindex show debug mach-o
19636 Show the current state of Mach-O file messages.
19638 @item set mach-exceptions on
19639 @itemx set mach-exceptions off
19640 @kindex set mach-exceptions
19641 On Darwin, faults are first reported as a Mach exception and are then
19642 mapped to a Posix signal. Use this command to turn on trapping of
19643 Mach exceptions in the inferior. This might be sometimes useful to
19644 better understand the cause of a fault. The default is off.
19646 @item show mach-exceptions
19647 @kindex show mach-exceptions
19648 Show the current state of exceptions trapping.
19653 @section Embedded Operating Systems
19655 This section describes configurations involving the debugging of
19656 embedded operating systems that are available for several different
19660 * VxWorks:: Using @value{GDBN} with VxWorks
19663 @value{GDBN} includes the ability to debug programs running on
19664 various real-time operating systems.
19667 @subsection Using @value{GDBN} with VxWorks
19673 @kindex target vxworks
19674 @item target vxworks @var{machinename}
19675 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19676 is the target system's machine name or IP address.
19680 On VxWorks, @code{load} links @var{filename} dynamically on the
19681 current target system as well as adding its symbols in @value{GDBN}.
19683 @value{GDBN} enables developers to spawn and debug tasks running on networked
19684 VxWorks targets from a Unix host. Already-running tasks spawned from
19685 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19686 both the Unix host and on the VxWorks target. The program
19687 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19688 installed with the name @code{vxgdb}, to distinguish it from a
19689 @value{GDBN} for debugging programs on the host itself.)
19692 @item VxWorks-timeout @var{args}
19693 @kindex vxworks-timeout
19694 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19695 This option is set by the user, and @var{args} represents the number of
19696 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19697 your VxWorks target is a slow software simulator or is on the far side
19698 of a thin network line.
19701 The following information on connecting to VxWorks was current when
19702 this manual was produced; newer releases of VxWorks may use revised
19705 @findex INCLUDE_RDB
19706 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19707 to include the remote debugging interface routines in the VxWorks
19708 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19709 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19710 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19711 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19712 information on configuring and remaking VxWorks, see the manufacturer's
19714 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19716 Once you have included @file{rdb.a} in your VxWorks system image and set
19717 your Unix execution search path to find @value{GDBN}, you are ready to
19718 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19719 @code{vxgdb}, depending on your installation).
19721 @value{GDBN} comes up showing the prompt:
19728 * VxWorks Connection:: Connecting to VxWorks
19729 * VxWorks Download:: VxWorks download
19730 * VxWorks Attach:: Running tasks
19733 @node VxWorks Connection
19734 @subsubsection Connecting to VxWorks
19736 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19737 network. To connect to a target whose host name is ``@code{tt}'', type:
19740 (vxgdb) target vxworks tt
19744 @value{GDBN} displays messages like these:
19747 Attaching remote machine across net...
19752 @value{GDBN} then attempts to read the symbol tables of any object modules
19753 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19754 these files by searching the directories listed in the command search
19755 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19756 to find an object file, it displays a message such as:
19759 prog.o: No such file or directory.
19762 When this happens, add the appropriate directory to the search path with
19763 the @value{GDBN} command @code{path}, and execute the @code{target}
19766 @node VxWorks Download
19767 @subsubsection VxWorks Download
19769 @cindex download to VxWorks
19770 If you have connected to the VxWorks target and you want to debug an
19771 object that has not yet been loaded, you can use the @value{GDBN}
19772 @code{load} command to download a file from Unix to VxWorks
19773 incrementally. The object file given as an argument to the @code{load}
19774 command is actually opened twice: first by the VxWorks target in order
19775 to download the code, then by @value{GDBN} in order to read the symbol
19776 table. This can lead to problems if the current working directories on
19777 the two systems differ. If both systems have NFS mounted the same
19778 filesystems, you can avoid these problems by using absolute paths.
19779 Otherwise, it is simplest to set the working directory on both systems
19780 to the directory in which the object file resides, and then to reference
19781 the file by its name, without any path. For instance, a program
19782 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19783 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19784 program, type this on VxWorks:
19787 -> cd "@var{vxpath}/vw/demo/rdb"
19791 Then, in @value{GDBN}, type:
19794 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19795 (vxgdb) load prog.o
19798 @value{GDBN} displays a response similar to this:
19801 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19804 You can also use the @code{load} command to reload an object module
19805 after editing and recompiling the corresponding source file. Note that
19806 this makes @value{GDBN} delete all currently-defined breakpoints,
19807 auto-displays, and convenience variables, and to clear the value
19808 history. (This is necessary in order to preserve the integrity of
19809 debugger's data structures that reference the target system's symbol
19812 @node VxWorks Attach
19813 @subsubsection Running Tasks
19815 @cindex running VxWorks tasks
19816 You can also attach to an existing task using the @code{attach} command as
19820 (vxgdb) attach @var{task}
19824 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19825 or suspended when you attach to it. Running tasks are suspended at
19826 the time of attachment.
19828 @node Embedded Processors
19829 @section Embedded Processors
19831 This section goes into details specific to particular embedded
19834 @cindex send command to simulator
19835 Whenever a specific embedded processor has a simulator, @value{GDBN}
19836 allows to send an arbitrary command to the simulator.
19839 @item sim @var{command}
19840 @kindex sim@r{, a command}
19841 Send an arbitrary @var{command} string to the simulator. Consult the
19842 documentation for the specific simulator in use for information about
19843 acceptable commands.
19849 * M32R/D:: Renesas M32R/D
19850 * M68K:: Motorola M68K
19851 * MicroBlaze:: Xilinx MicroBlaze
19852 * MIPS Embedded:: MIPS Embedded
19853 * OpenRISC 1000:: OpenRisc 1000
19854 * PowerPC Embedded:: PowerPC Embedded
19855 * PA:: HP PA Embedded
19856 * Sparclet:: Tsqware Sparclet
19857 * Sparclite:: Fujitsu Sparclite
19858 * Z8000:: Zilog Z8000
19861 * Super-H:: Renesas Super-H
19870 @item target rdi @var{dev}
19871 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19872 use this target to communicate with both boards running the Angel
19873 monitor, or with the EmbeddedICE JTAG debug device.
19876 @item target rdp @var{dev}
19881 @value{GDBN} provides the following ARM-specific commands:
19884 @item set arm disassembler
19886 This commands selects from a list of disassembly styles. The
19887 @code{"std"} style is the standard style.
19889 @item show arm disassembler
19891 Show the current disassembly style.
19893 @item set arm apcs32
19894 @cindex ARM 32-bit mode
19895 This command toggles ARM operation mode between 32-bit and 26-bit.
19897 @item show arm apcs32
19898 Display the current usage of the ARM 32-bit mode.
19900 @item set arm fpu @var{fputype}
19901 This command sets the ARM floating-point unit (FPU) type. The
19902 argument @var{fputype} can be one of these:
19906 Determine the FPU type by querying the OS ABI.
19908 Software FPU, with mixed-endian doubles on little-endian ARM
19911 GCC-compiled FPA co-processor.
19913 Software FPU with pure-endian doubles.
19919 Show the current type of the FPU.
19922 This command forces @value{GDBN} to use the specified ABI.
19925 Show the currently used ABI.
19927 @item set arm fallback-mode (arm|thumb|auto)
19928 @value{GDBN} uses the symbol table, when available, to determine
19929 whether instructions are ARM or Thumb. This command controls
19930 @value{GDBN}'s default behavior when the symbol table is not
19931 available. The default is @samp{auto}, which causes @value{GDBN} to
19932 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19935 @item show arm fallback-mode
19936 Show the current fallback instruction mode.
19938 @item set arm force-mode (arm|thumb|auto)
19939 This command overrides use of the symbol table to determine whether
19940 instructions are ARM or Thumb. The default is @samp{auto}, which
19941 causes @value{GDBN} to use the symbol table and then the setting
19942 of @samp{set arm fallback-mode}.
19944 @item show arm force-mode
19945 Show the current forced instruction mode.
19947 @item set debug arm
19948 Toggle whether to display ARM-specific debugging messages from the ARM
19949 target support subsystem.
19951 @item show debug arm
19952 Show whether ARM-specific debugging messages are enabled.
19955 The following commands are available when an ARM target is debugged
19956 using the RDI interface:
19959 @item rdilogfile @r{[}@var{file}@r{]}
19961 @cindex ADP (Angel Debugger Protocol) logging
19962 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19963 With an argument, sets the log file to the specified @var{file}. With
19964 no argument, show the current log file name. The default log file is
19967 @item rdilogenable @r{[}@var{arg}@r{]}
19968 @kindex rdilogenable
19969 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19970 enables logging, with an argument 0 or @code{"no"} disables it. With
19971 no arguments displays the current setting. When logging is enabled,
19972 ADP packets exchanged between @value{GDBN} and the RDI target device
19973 are logged to a file.
19975 @item set rdiromatzero
19976 @kindex set rdiromatzero
19977 @cindex ROM at zero address, RDI
19978 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19979 vector catching is disabled, so that zero address can be used. If off
19980 (the default), vector catching is enabled. For this command to take
19981 effect, it needs to be invoked prior to the @code{target rdi} command.
19983 @item show rdiromatzero
19984 @kindex show rdiromatzero
19985 Show the current setting of ROM at zero address.
19987 @item set rdiheartbeat
19988 @kindex set rdiheartbeat
19989 @cindex RDI heartbeat
19990 Enable or disable RDI heartbeat packets. It is not recommended to
19991 turn on this option, since it confuses ARM and EPI JTAG interface, as
19992 well as the Angel monitor.
19994 @item show rdiheartbeat
19995 @kindex show rdiheartbeat
19996 Show the setting of RDI heartbeat packets.
20000 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20001 The @value{GDBN} ARM simulator accepts the following optional arguments.
20004 @item --swi-support=@var{type}
20005 Tell the simulator which SWI interfaces to support.
20006 @var{type} may be a comma separated list of the following values.
20007 The default value is @code{all}.
20020 @subsection Renesas M32R/D and M32R/SDI
20023 @kindex target m32r
20024 @item target m32r @var{dev}
20025 Renesas M32R/D ROM monitor.
20027 @kindex target m32rsdi
20028 @item target m32rsdi @var{dev}
20029 Renesas M32R SDI server, connected via parallel port to the board.
20032 The following @value{GDBN} commands are specific to the M32R monitor:
20035 @item set download-path @var{path}
20036 @kindex set download-path
20037 @cindex find downloadable @sc{srec} files (M32R)
20038 Set the default path for finding downloadable @sc{srec} files.
20040 @item show download-path
20041 @kindex show download-path
20042 Show the default path for downloadable @sc{srec} files.
20044 @item set board-address @var{addr}
20045 @kindex set board-address
20046 @cindex M32-EVA target board address
20047 Set the IP address for the M32R-EVA target board.
20049 @item show board-address
20050 @kindex show board-address
20051 Show the current IP address of the target board.
20053 @item set server-address @var{addr}
20054 @kindex set server-address
20055 @cindex download server address (M32R)
20056 Set the IP address for the download server, which is the @value{GDBN}'s
20059 @item show server-address
20060 @kindex show server-address
20061 Display the IP address of the download server.
20063 @item upload @r{[}@var{file}@r{]}
20064 @kindex upload@r{, M32R}
20065 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20066 upload capability. If no @var{file} argument is given, the current
20067 executable file is uploaded.
20069 @item tload @r{[}@var{file}@r{]}
20070 @kindex tload@r{, M32R}
20071 Test the @code{upload} command.
20074 The following commands are available for M32R/SDI:
20079 @cindex reset SDI connection, M32R
20080 This command resets the SDI connection.
20084 This command shows the SDI connection status.
20087 @kindex debug_chaos
20088 @cindex M32R/Chaos debugging
20089 Instructs the remote that M32R/Chaos debugging is to be used.
20091 @item use_debug_dma
20092 @kindex use_debug_dma
20093 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20096 @kindex use_mon_code
20097 Instructs the remote to use the MON_CODE method of accessing memory.
20100 @kindex use_ib_break
20101 Instructs the remote to set breakpoints by IB break.
20103 @item use_dbt_break
20104 @kindex use_dbt_break
20105 Instructs the remote to set breakpoints by DBT.
20111 The Motorola m68k configuration includes ColdFire support, and a
20112 target command for the following ROM monitor.
20116 @kindex target dbug
20117 @item target dbug @var{dev}
20118 dBUG ROM monitor for Motorola ColdFire.
20123 @subsection MicroBlaze
20124 @cindex Xilinx MicroBlaze
20125 @cindex XMD, Xilinx Microprocessor Debugger
20127 The MicroBlaze is a soft-core processor supported on various Xilinx
20128 FPGAs, such as Spartan or Virtex series. Boards with these processors
20129 usually have JTAG ports which connect to a host system running the Xilinx
20130 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20131 This host system is used to download the configuration bitstream to
20132 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20133 communicates with the target board using the JTAG interface and
20134 presents a @code{gdbserver} interface to the board. By default
20135 @code{xmd} uses port @code{1234}. (While it is possible to change
20136 this default port, it requires the use of undocumented @code{xmd}
20137 commands. Contact Xilinx support if you need to do this.)
20139 Use these GDB commands to connect to the MicroBlaze target processor.
20142 @item target remote :1234
20143 Use this command to connect to the target if you are running @value{GDBN}
20144 on the same system as @code{xmd}.
20146 @item target remote @var{xmd-host}:1234
20147 Use this command to connect to the target if it is connected to @code{xmd}
20148 running on a different system named @var{xmd-host}.
20151 Use this command to download a program to the MicroBlaze target.
20153 @item set debug microblaze @var{n}
20154 Enable MicroBlaze-specific debugging messages if non-zero.
20156 @item show debug microblaze @var{n}
20157 Show MicroBlaze-specific debugging level.
20160 @node MIPS Embedded
20161 @subsection @acronym{MIPS} Embedded
20163 @cindex @acronym{MIPS} boards
20164 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20165 @acronym{MIPS} board attached to a serial line. This is available when
20166 you configure @value{GDBN} with @samp{--target=mips-elf}.
20169 Use these @value{GDBN} commands to specify the connection to your target board:
20172 @item target mips @var{port}
20173 @kindex target mips @var{port}
20174 To run a program on the board, start up @code{@value{GDBP}} with the
20175 name of your program as the argument. To connect to the board, use the
20176 command @samp{target mips @var{port}}, where @var{port} is the name of
20177 the serial port connected to the board. If the program has not already
20178 been downloaded to the board, you may use the @code{load} command to
20179 download it. You can then use all the usual @value{GDBN} commands.
20181 For example, this sequence connects to the target board through a serial
20182 port, and loads and runs a program called @var{prog} through the
20186 host$ @value{GDBP} @var{prog}
20187 @value{GDBN} is free software and @dots{}
20188 (@value{GDBP}) target mips /dev/ttyb
20189 (@value{GDBP}) load @var{prog}
20193 @item target mips @var{hostname}:@var{portnumber}
20194 On some @value{GDBN} host configurations, you can specify a TCP
20195 connection (for instance, to a serial line managed by a terminal
20196 concentrator) instead of a serial port, using the syntax
20197 @samp{@var{hostname}:@var{portnumber}}.
20199 @item target pmon @var{port}
20200 @kindex target pmon @var{port}
20203 @item target ddb @var{port}
20204 @kindex target ddb @var{port}
20205 NEC's DDB variant of PMON for Vr4300.
20207 @item target lsi @var{port}
20208 @kindex target lsi @var{port}
20209 LSI variant of PMON.
20211 @kindex target r3900
20212 @item target r3900 @var{dev}
20213 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20215 @kindex target array
20216 @item target array @var{dev}
20217 Array Tech LSI33K RAID controller board.
20223 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20226 @item set mipsfpu double
20227 @itemx set mipsfpu single
20228 @itemx set mipsfpu none
20229 @itemx set mipsfpu auto
20230 @itemx show mipsfpu
20231 @kindex set mipsfpu
20232 @kindex show mipsfpu
20233 @cindex @acronym{MIPS} remote floating point
20234 @cindex floating point, @acronym{MIPS} remote
20235 If your target board does not support the @acronym{MIPS} floating point
20236 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20237 need this, you may wish to put the command in your @value{GDBN} init
20238 file). This tells @value{GDBN} how to find the return value of
20239 functions which return floating point values. It also allows
20240 @value{GDBN} to avoid saving the floating point registers when calling
20241 functions on the board. If you are using a floating point coprocessor
20242 with only single precision floating point support, as on the @sc{r4650}
20243 processor, use the command @samp{set mipsfpu single}. The default
20244 double precision floating point coprocessor may be selected using
20245 @samp{set mipsfpu double}.
20247 In previous versions the only choices were double precision or no
20248 floating point, so @samp{set mipsfpu on} will select double precision
20249 and @samp{set mipsfpu off} will select no floating point.
20251 As usual, you can inquire about the @code{mipsfpu} variable with
20252 @samp{show mipsfpu}.
20254 @item set timeout @var{seconds}
20255 @itemx set retransmit-timeout @var{seconds}
20256 @itemx show timeout
20257 @itemx show retransmit-timeout
20258 @cindex @code{timeout}, @acronym{MIPS} protocol
20259 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20260 @kindex set timeout
20261 @kindex show timeout
20262 @kindex set retransmit-timeout
20263 @kindex show retransmit-timeout
20264 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20265 remote protocol, with the @code{set timeout @var{seconds}} command. The
20266 default is 5 seconds. Similarly, you can control the timeout used while
20267 waiting for an acknowledgment of a packet with the @code{set
20268 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20269 You can inspect both values with @code{show timeout} and @code{show
20270 retransmit-timeout}. (These commands are @emph{only} available when
20271 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20273 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20274 is waiting for your program to stop. In that case, @value{GDBN} waits
20275 forever because it has no way of knowing how long the program is going
20276 to run before stopping.
20278 @item set syn-garbage-limit @var{num}
20279 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20280 @cindex synchronize with remote @acronym{MIPS} target
20281 Limit the maximum number of characters @value{GDBN} should ignore when
20282 it tries to synchronize with the remote target. The default is 10
20283 characters. Setting the limit to -1 means there's no limit.
20285 @item show syn-garbage-limit
20286 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20287 Show the current limit on the number of characters to ignore when
20288 trying to synchronize with the remote system.
20290 @item set monitor-prompt @var{prompt}
20291 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20292 @cindex remote monitor prompt
20293 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20294 remote monitor. The default depends on the target:
20304 @item show monitor-prompt
20305 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20306 Show the current strings @value{GDBN} expects as the prompt from the
20309 @item set monitor-warnings
20310 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20311 Enable or disable monitor warnings about hardware breakpoints. This
20312 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20313 display warning messages whose codes are returned by the @code{lsi}
20314 PMON monitor for breakpoint commands.
20316 @item show monitor-warnings
20317 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20318 Show the current setting of printing monitor warnings.
20320 @item pmon @var{command}
20321 @kindex pmon@r{, @acronym{MIPS} remote}
20322 @cindex send PMON command
20323 This command allows sending an arbitrary @var{command} string to the
20324 monitor. The monitor must be in debug mode for this to work.
20327 @node OpenRISC 1000
20328 @subsection OpenRISC 1000
20329 @cindex OpenRISC 1000
20331 @cindex or1k boards
20332 See OR1k Architecture document (@uref{www.opencores.org}) for more information
20333 about platform and commands.
20337 @kindex target jtag
20338 @item target jtag jtag://@var{host}:@var{port}
20340 Connects to remote JTAG server.
20341 JTAG remote server can be either an or1ksim or JTAG server,
20342 connected via parallel port to the board.
20344 Example: @code{target jtag jtag://localhost:9999}
20347 @item or1ksim @var{command}
20348 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20349 Simulator, proprietary commands can be executed.
20351 @kindex info or1k spr
20352 @item info or1k spr
20353 Displays spr groups.
20355 @item info or1k spr @var{group}
20356 @itemx info or1k spr @var{groupno}
20357 Displays register names in selected group.
20359 @item info or1k spr @var{group} @var{register}
20360 @itemx info or1k spr @var{register}
20361 @itemx info or1k spr @var{groupno} @var{registerno}
20362 @itemx info or1k spr @var{registerno}
20363 Shows information about specified spr register.
20366 @item spr @var{group} @var{register} @var{value}
20367 @itemx spr @var{register @var{value}}
20368 @itemx spr @var{groupno} @var{registerno @var{value}}
20369 @itemx spr @var{registerno @var{value}}
20370 Writes @var{value} to specified spr register.
20373 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20374 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20375 program execution and is thus much faster. Hardware breakpoints/watchpoint
20376 triggers can be set using:
20379 Load effective address/data
20381 Store effective address/data
20383 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20388 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20389 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20391 @code{htrace} commands:
20392 @cindex OpenRISC 1000 htrace
20395 @item hwatch @var{conditional}
20396 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20397 or Data. For example:
20399 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20401 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20405 Display information about current HW trace configuration.
20407 @item htrace trigger @var{conditional}
20408 Set starting criteria for HW trace.
20410 @item htrace qualifier @var{conditional}
20411 Set acquisition qualifier for HW trace.
20413 @item htrace stop @var{conditional}
20414 Set HW trace stopping criteria.
20416 @item htrace record [@var{data}]*
20417 Selects the data to be recorded, when qualifier is met and HW trace was
20420 @item htrace enable
20421 @itemx htrace disable
20422 Enables/disables the HW trace.
20424 @item htrace rewind [@var{filename}]
20425 Clears currently recorded trace data.
20427 If filename is specified, new trace file is made and any newly collected data
20428 will be written there.
20430 @item htrace print [@var{start} [@var{len}]]
20431 Prints trace buffer, using current record configuration.
20433 @item htrace mode continuous
20434 Set continuous trace mode.
20436 @item htrace mode suspend
20437 Set suspend trace mode.
20441 @node PowerPC Embedded
20442 @subsection PowerPC Embedded
20444 @cindex DVC register
20445 @value{GDBN} supports using the DVC (Data Value Compare) register to
20446 implement in hardware simple hardware watchpoint conditions of the form:
20449 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20450 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20453 The DVC register will be automatically used when @value{GDBN} detects
20454 such pattern in a condition expression, and the created watchpoint uses one
20455 debug register (either the @code{exact-watchpoints} option is on and the
20456 variable is scalar, or the variable has a length of one byte). This feature
20457 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20460 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20461 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20462 in which case watchpoints using only one debug register are created when
20463 watching variables of scalar types.
20465 You can create an artificial array to watch an arbitrary memory
20466 region using one of the following commands (@pxref{Expressions}):
20469 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20470 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20473 PowerPC embedded processors support masked watchpoints. See the discussion
20474 about the @code{mask} argument in @ref{Set Watchpoints}.
20476 @cindex ranged breakpoint
20477 PowerPC embedded processors support hardware accelerated
20478 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20479 the inferior whenever it executes an instruction at any address within
20480 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20481 use the @code{break-range} command.
20483 @value{GDBN} provides the following PowerPC-specific commands:
20486 @kindex break-range
20487 @item break-range @var{start-location}, @var{end-location}
20488 Set a breakpoint for an address range.
20489 @var{start-location} and @var{end-location} can specify a function name,
20490 a line number, an offset of lines from the current line or from the start
20491 location, or an address of an instruction (see @ref{Specify Location},
20492 for a list of all the possible ways to specify a @var{location}.)
20493 The breakpoint will stop execution of the inferior whenever it
20494 executes an instruction at any address within the specified range,
20495 (including @var{start-location} and @var{end-location}.)
20497 @kindex set powerpc
20498 @item set powerpc soft-float
20499 @itemx show powerpc soft-float
20500 Force @value{GDBN} to use (or not use) a software floating point calling
20501 convention. By default, @value{GDBN} selects the calling convention based
20502 on the selected architecture and the provided executable file.
20504 @item set powerpc vector-abi
20505 @itemx show powerpc vector-abi
20506 Force @value{GDBN} to use the specified calling convention for vector
20507 arguments and return values. The valid options are @samp{auto};
20508 @samp{generic}, to avoid vector registers even if they are present;
20509 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20510 registers. By default, @value{GDBN} selects the calling convention
20511 based on the selected architecture and the provided executable file.
20513 @item set powerpc exact-watchpoints
20514 @itemx show powerpc exact-watchpoints
20515 Allow @value{GDBN} to use only one debug register when watching a variable
20516 of scalar type, thus assuming that the variable is accessed through the
20517 address of its first byte.
20519 @kindex target dink32
20520 @item target dink32 @var{dev}
20521 DINK32 ROM monitor.
20523 @kindex target ppcbug
20524 @item target ppcbug @var{dev}
20525 @kindex target ppcbug1
20526 @item target ppcbug1 @var{dev}
20527 PPCBUG ROM monitor for PowerPC.
20530 @item target sds @var{dev}
20531 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20534 @cindex SDS protocol
20535 The following commands specific to the SDS protocol are supported
20539 @item set sdstimeout @var{nsec}
20540 @kindex set sdstimeout
20541 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20542 default is 2 seconds.
20544 @item show sdstimeout
20545 @kindex show sdstimeout
20546 Show the current value of the SDS timeout.
20548 @item sds @var{command}
20549 @kindex sds@r{, a command}
20550 Send the specified @var{command} string to the SDS monitor.
20555 @subsection HP PA Embedded
20559 @kindex target op50n
20560 @item target op50n @var{dev}
20561 OP50N monitor, running on an OKI HPPA board.
20563 @kindex target w89k
20564 @item target w89k @var{dev}
20565 W89K monitor, running on a Winbond HPPA board.
20570 @subsection Tsqware Sparclet
20574 @value{GDBN} enables developers to debug tasks running on
20575 Sparclet targets from a Unix host.
20576 @value{GDBN} uses code that runs on
20577 both the Unix host and on the Sparclet target. The program
20578 @code{@value{GDBP}} is installed and executed on the Unix host.
20581 @item remotetimeout @var{args}
20582 @kindex remotetimeout
20583 @value{GDBN} supports the option @code{remotetimeout}.
20584 This option is set by the user, and @var{args} represents the number of
20585 seconds @value{GDBN} waits for responses.
20588 @cindex compiling, on Sparclet
20589 When compiling for debugging, include the options @samp{-g} to get debug
20590 information and @samp{-Ttext} to relocate the program to where you wish to
20591 load it on the target. You may also want to add the options @samp{-n} or
20592 @samp{-N} in order to reduce the size of the sections. Example:
20595 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20598 You can use @code{objdump} to verify that the addresses are what you intended:
20601 sparclet-aout-objdump --headers --syms prog
20604 @cindex running, on Sparclet
20606 your Unix execution search path to find @value{GDBN}, you are ready to
20607 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20608 (or @code{sparclet-aout-gdb}, depending on your installation).
20610 @value{GDBN} comes up showing the prompt:
20617 * Sparclet File:: Setting the file to debug
20618 * Sparclet Connection:: Connecting to Sparclet
20619 * Sparclet Download:: Sparclet download
20620 * Sparclet Execution:: Running and debugging
20623 @node Sparclet File
20624 @subsubsection Setting File to Debug
20626 The @value{GDBN} command @code{file} lets you choose with program to debug.
20629 (gdbslet) file prog
20633 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20634 @value{GDBN} locates
20635 the file by searching the directories listed in the command search
20637 If the file was compiled with debug information (option @samp{-g}), source
20638 files will be searched as well.
20639 @value{GDBN} locates
20640 the source files by searching the directories listed in the directory search
20641 path (@pxref{Environment, ,Your Program's Environment}).
20643 to find a file, it displays a message such as:
20646 prog: No such file or directory.
20649 When this happens, add the appropriate directories to the search paths with
20650 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20651 @code{target} command again.
20653 @node Sparclet Connection
20654 @subsubsection Connecting to Sparclet
20656 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20657 To connect to a target on serial port ``@code{ttya}'', type:
20660 (gdbslet) target sparclet /dev/ttya
20661 Remote target sparclet connected to /dev/ttya
20662 main () at ../prog.c:3
20666 @value{GDBN} displays messages like these:
20672 @node Sparclet Download
20673 @subsubsection Sparclet Download
20675 @cindex download to Sparclet
20676 Once connected to the Sparclet target,
20677 you can use the @value{GDBN}
20678 @code{load} command to download the file from the host to the target.
20679 The file name and load offset should be given as arguments to the @code{load}
20681 Since the file format is aout, the program must be loaded to the starting
20682 address. You can use @code{objdump} to find out what this value is. The load
20683 offset is an offset which is added to the VMA (virtual memory address)
20684 of each of the file's sections.
20685 For instance, if the program
20686 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20687 and bss at 0x12010170, in @value{GDBN}, type:
20690 (gdbslet) load prog 0x12010000
20691 Loading section .text, size 0xdb0 vma 0x12010000
20694 If the code is loaded at a different address then what the program was linked
20695 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20696 to tell @value{GDBN} where to map the symbol table.
20698 @node Sparclet Execution
20699 @subsubsection Running and Debugging
20701 @cindex running and debugging Sparclet programs
20702 You can now begin debugging the task using @value{GDBN}'s execution control
20703 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20704 manual for the list of commands.
20708 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20710 Starting program: prog
20711 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20712 3 char *symarg = 0;
20714 4 char *execarg = "hello!";
20719 @subsection Fujitsu Sparclite
20723 @kindex target sparclite
20724 @item target sparclite @var{dev}
20725 Fujitsu sparclite boards, used only for the purpose of loading.
20726 You must use an additional command to debug the program.
20727 For example: target remote @var{dev} using @value{GDBN} standard
20733 @subsection Zilog Z8000
20736 @cindex simulator, Z8000
20737 @cindex Zilog Z8000 simulator
20739 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20742 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20743 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20744 segmented variant). The simulator recognizes which architecture is
20745 appropriate by inspecting the object code.
20748 @item target sim @var{args}
20750 @kindex target sim@r{, with Z8000}
20751 Debug programs on a simulated CPU. If the simulator supports setup
20752 options, specify them via @var{args}.
20756 After specifying this target, you can debug programs for the simulated
20757 CPU in the same style as programs for your host computer; use the
20758 @code{file} command to load a new program image, the @code{run} command
20759 to run your program, and so on.
20761 As well as making available all the usual machine registers
20762 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20763 additional items of information as specially named registers:
20768 Counts clock-ticks in the simulator.
20771 Counts instructions run in the simulator.
20774 Execution time in 60ths of a second.
20778 You can refer to these values in @value{GDBN} expressions with the usual
20779 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20780 conditional breakpoint that suspends only after at least 5000
20781 simulated clock ticks.
20784 @subsection Atmel AVR
20787 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20788 following AVR-specific commands:
20791 @item info io_registers
20792 @kindex info io_registers@r{, AVR}
20793 @cindex I/O registers (Atmel AVR)
20794 This command displays information about the AVR I/O registers. For
20795 each register, @value{GDBN} prints its number and value.
20802 When configured for debugging CRIS, @value{GDBN} provides the
20803 following CRIS-specific commands:
20806 @item set cris-version @var{ver}
20807 @cindex CRIS version
20808 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20809 The CRIS version affects register names and sizes. This command is useful in
20810 case autodetection of the CRIS version fails.
20812 @item show cris-version
20813 Show the current CRIS version.
20815 @item set cris-dwarf2-cfi
20816 @cindex DWARF-2 CFI and CRIS
20817 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20818 Change to @samp{off} when using @code{gcc-cris} whose version is below
20821 @item show cris-dwarf2-cfi
20822 Show the current state of using DWARF-2 CFI.
20824 @item set cris-mode @var{mode}
20826 Set the current CRIS mode to @var{mode}. It should only be changed when
20827 debugging in guru mode, in which case it should be set to
20828 @samp{guru} (the default is @samp{normal}).
20830 @item show cris-mode
20831 Show the current CRIS mode.
20835 @subsection Renesas Super-H
20838 For the Renesas Super-H processor, @value{GDBN} provides these
20842 @item set sh calling-convention @var{convention}
20843 @kindex set sh calling-convention
20844 Set the calling-convention used when calling functions from @value{GDBN}.
20845 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20846 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20847 convention. If the DWARF-2 information of the called function specifies
20848 that the function follows the Renesas calling convention, the function
20849 is called using the Renesas calling convention. If the calling convention
20850 is set to @samp{renesas}, the Renesas calling convention is always used,
20851 regardless of the DWARF-2 information. This can be used to override the
20852 default of @samp{gcc} if debug information is missing, or the compiler
20853 does not emit the DWARF-2 calling convention entry for a function.
20855 @item show sh calling-convention
20856 @kindex show sh calling-convention
20857 Show the current calling convention setting.
20862 @node Architectures
20863 @section Architectures
20865 This section describes characteristics of architectures that affect
20866 all uses of @value{GDBN} with the architecture, both native and cross.
20873 * HPPA:: HP PA architecture
20874 * SPU:: Cell Broadband Engine SPU architecture
20879 @subsection AArch64
20880 @cindex AArch64 support
20882 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20883 following special commands:
20886 @item set debug aarch64
20887 @kindex set debug aarch64
20888 This command determines whether AArch64 architecture-specific debugging
20889 messages are to be displayed.
20891 @item show debug aarch64
20892 Show whether AArch64 debugging messages are displayed.
20897 @subsection x86 Architecture-specific Issues
20900 @item set struct-convention @var{mode}
20901 @kindex set struct-convention
20902 @cindex struct return convention
20903 @cindex struct/union returned in registers
20904 Set the convention used by the inferior to return @code{struct}s and
20905 @code{union}s from functions to @var{mode}. Possible values of
20906 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20907 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20908 are returned on the stack, while @code{"reg"} means that a
20909 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20910 be returned in a register.
20912 @item show struct-convention
20913 @kindex show struct-convention
20914 Show the current setting of the convention to return @code{struct}s
20921 See the following section.
20924 @subsection @acronym{MIPS}
20926 @cindex stack on Alpha
20927 @cindex stack on @acronym{MIPS}
20928 @cindex Alpha stack
20929 @cindex @acronym{MIPS} stack
20930 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20931 sometimes requires @value{GDBN} to search backward in the object code to
20932 find the beginning of a function.
20934 @cindex response time, @acronym{MIPS} debugging
20935 To improve response time (especially for embedded applications, where
20936 @value{GDBN} may be restricted to a slow serial line for this search)
20937 you may want to limit the size of this search, using one of these
20941 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20942 @item set heuristic-fence-post @var{limit}
20943 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20944 search for the beginning of a function. A value of @var{0} (the
20945 default) means there is no limit. However, except for @var{0}, the
20946 larger the limit the more bytes @code{heuristic-fence-post} must search
20947 and therefore the longer it takes to run. You should only need to use
20948 this command when debugging a stripped executable.
20950 @item show heuristic-fence-post
20951 Display the current limit.
20955 These commands are available @emph{only} when @value{GDBN} is configured
20956 for debugging programs on Alpha or @acronym{MIPS} processors.
20958 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20962 @item set mips abi @var{arg}
20963 @kindex set mips abi
20964 @cindex set ABI for @acronym{MIPS}
20965 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20966 values of @var{arg} are:
20970 The default ABI associated with the current binary (this is the
20980 @item show mips abi
20981 @kindex show mips abi
20982 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20984 @item set mips compression @var{arg}
20985 @kindex set mips compression
20986 @cindex code compression, @acronym{MIPS}
20987 Tell @value{GDBN} which @acronym{MIPS} compressed
20988 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20989 inferior. @value{GDBN} uses this for code disassembly and other
20990 internal interpretation purposes. This setting is only referred to
20991 when no executable has been associated with the debugging session or
20992 the executable does not provide information about the encoding it uses.
20993 Otherwise this setting is automatically updated from information
20994 provided by the executable.
20996 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20997 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20998 executables containing @acronym{MIPS16} code frequently are not
20999 identified as such.
21001 This setting is ``sticky''; that is, it retains its value across
21002 debugging sessions until reset either explicitly with this command or
21003 implicitly from an executable.
21005 The compiler and/or assembler typically add symbol table annotations to
21006 identify functions compiled for the @acronym{MIPS16} or
21007 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21008 are present, @value{GDBN} uses them in preference to the global
21009 compressed @acronym{ISA} encoding setting.
21011 @item show mips compression
21012 @kindex show mips compression
21013 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21014 @value{GDBN} to debug the inferior.
21017 @itemx show mipsfpu
21018 @xref{MIPS Embedded, set mipsfpu}.
21020 @item set mips mask-address @var{arg}
21021 @kindex set mips mask-address
21022 @cindex @acronym{MIPS} addresses, masking
21023 This command determines whether the most-significant 32 bits of 64-bit
21024 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21025 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21026 setting, which lets @value{GDBN} determine the correct value.
21028 @item show mips mask-address
21029 @kindex show mips mask-address
21030 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21033 @item set remote-mips64-transfers-32bit-regs
21034 @kindex set remote-mips64-transfers-32bit-regs
21035 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21036 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21037 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21038 and 64 bits for other registers, set this option to @samp{on}.
21040 @item show remote-mips64-transfers-32bit-regs
21041 @kindex show remote-mips64-transfers-32bit-regs
21042 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21044 @item set debug mips
21045 @kindex set debug mips
21046 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21047 target code in @value{GDBN}.
21049 @item show debug mips
21050 @kindex show debug mips
21051 Show the current setting of @acronym{MIPS} debugging messages.
21057 @cindex HPPA support
21059 When @value{GDBN} is debugging the HP PA architecture, it provides the
21060 following special commands:
21063 @item set debug hppa
21064 @kindex set debug hppa
21065 This command determines whether HPPA architecture-specific debugging
21066 messages are to be displayed.
21068 @item show debug hppa
21069 Show whether HPPA debugging messages are displayed.
21071 @item maint print unwind @var{address}
21072 @kindex maint print unwind@r{, HPPA}
21073 This command displays the contents of the unwind table entry at the
21074 given @var{address}.
21080 @subsection Cell Broadband Engine SPU architecture
21081 @cindex Cell Broadband Engine
21084 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21085 it provides the following special commands:
21088 @item info spu event
21090 Display SPU event facility status. Shows current event mask
21091 and pending event status.
21093 @item info spu signal
21094 Display SPU signal notification facility status. Shows pending
21095 signal-control word and signal notification mode of both signal
21096 notification channels.
21098 @item info spu mailbox
21099 Display SPU mailbox facility status. Shows all pending entries,
21100 in order of processing, in each of the SPU Write Outbound,
21101 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21104 Display MFC DMA status. Shows all pending commands in the MFC
21105 DMA queue. For each entry, opcode, tag, class IDs, effective
21106 and local store addresses and transfer size are shown.
21108 @item info spu proxydma
21109 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21110 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21111 and local store addresses and transfer size are shown.
21115 When @value{GDBN} is debugging a combined PowerPC/SPU application
21116 on the Cell Broadband Engine, it provides in addition the following
21120 @item set spu stop-on-load @var{arg}
21122 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21123 will give control to the user when a new SPE thread enters its @code{main}
21124 function. The default is @code{off}.
21126 @item show spu stop-on-load
21128 Show whether to stop for new SPE threads.
21130 @item set spu auto-flush-cache @var{arg}
21131 Set whether to automatically flush the software-managed cache. When set to
21132 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21133 cache to be flushed whenever SPE execution stops. This provides a consistent
21134 view of PowerPC memory that is accessed via the cache. If an application
21135 does not use the software-managed cache, this option has no effect.
21137 @item show spu auto-flush-cache
21138 Show whether to automatically flush the software-managed cache.
21143 @subsection PowerPC
21144 @cindex PowerPC architecture
21146 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21147 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21148 numbers stored in the floating point registers. These values must be stored
21149 in two consecutive registers, always starting at an even register like
21150 @code{f0} or @code{f2}.
21152 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21153 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21154 @code{f2} and @code{f3} for @code{$dl1} and so on.
21156 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21157 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21160 @node Controlling GDB
21161 @chapter Controlling @value{GDBN}
21163 You can alter the way @value{GDBN} interacts with you by using the
21164 @code{set} command. For commands controlling how @value{GDBN} displays
21165 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21170 * Editing:: Command editing
21171 * Command History:: Command history
21172 * Screen Size:: Screen size
21173 * Numbers:: Numbers
21174 * ABI:: Configuring the current ABI
21175 * Auto-loading:: Automatically loading associated files
21176 * Messages/Warnings:: Optional warnings and messages
21177 * Debugging Output:: Optional messages about internal happenings
21178 * Other Misc Settings:: Other Miscellaneous Settings
21186 @value{GDBN} indicates its readiness to read a command by printing a string
21187 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21188 can change the prompt string with the @code{set prompt} command. For
21189 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21190 the prompt in one of the @value{GDBN} sessions so that you can always tell
21191 which one you are talking to.
21193 @emph{Note:} @code{set prompt} does not add a space for you after the
21194 prompt you set. This allows you to set a prompt which ends in a space
21195 or a prompt that does not.
21199 @item set prompt @var{newprompt}
21200 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21202 @kindex show prompt
21204 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21207 Versions of @value{GDBN} that ship with Python scripting enabled have
21208 prompt extensions. The commands for interacting with these extensions
21212 @kindex set extended-prompt
21213 @item set extended-prompt @var{prompt}
21214 Set an extended prompt that allows for substitutions.
21215 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21216 substitution. Any escape sequences specified as part of the prompt
21217 string are replaced with the corresponding strings each time the prompt
21223 set extended-prompt Current working directory: \w (gdb)
21226 Note that when an extended-prompt is set, it takes control of the
21227 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21229 @kindex show extended-prompt
21230 @item show extended-prompt
21231 Prints the extended prompt. Any escape sequences specified as part of
21232 the prompt string with @code{set extended-prompt}, are replaced with the
21233 corresponding strings each time the prompt is displayed.
21237 @section Command Editing
21239 @cindex command line editing
21241 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21242 @sc{gnu} library provides consistent behavior for programs which provide a
21243 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21244 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21245 substitution, and a storage and recall of command history across
21246 debugging sessions.
21248 You may control the behavior of command line editing in @value{GDBN} with the
21249 command @code{set}.
21252 @kindex set editing
21255 @itemx set editing on
21256 Enable command line editing (enabled by default).
21258 @item set editing off
21259 Disable command line editing.
21261 @kindex show editing
21263 Show whether command line editing is enabled.
21266 @ifset SYSTEM_READLINE
21267 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21269 @ifclear SYSTEM_READLINE
21270 @xref{Command Line Editing},
21272 for more details about the Readline
21273 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21274 encouraged to read that chapter.
21276 @node Command History
21277 @section Command History
21278 @cindex command history
21280 @value{GDBN} can keep track of the commands you type during your
21281 debugging sessions, so that you can be certain of precisely what
21282 happened. Use these commands to manage the @value{GDBN} command
21285 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21286 package, to provide the history facility.
21287 @ifset SYSTEM_READLINE
21288 @xref{Using History Interactively, , , history, GNU History Library},
21290 @ifclear SYSTEM_READLINE
21291 @xref{Using History Interactively},
21293 for the detailed description of the History library.
21295 To issue a command to @value{GDBN} without affecting certain aspects of
21296 the state which is seen by users, prefix it with @samp{server }
21297 (@pxref{Server Prefix}). This
21298 means that this command will not affect the command history, nor will it
21299 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21300 pressed on a line by itself.
21302 @cindex @code{server}, command prefix
21303 The server prefix does not affect the recording of values into the value
21304 history; to print a value without recording it into the value history,
21305 use the @code{output} command instead of the @code{print} command.
21307 Here is the description of @value{GDBN} commands related to command
21311 @cindex history substitution
21312 @cindex history file
21313 @kindex set history filename
21314 @cindex @env{GDBHISTFILE}, environment variable
21315 @item set history filename @var{fname}
21316 Set the name of the @value{GDBN} command history file to @var{fname}.
21317 This is the file where @value{GDBN} reads an initial command history
21318 list, and where it writes the command history from this session when it
21319 exits. You can access this list through history expansion or through
21320 the history command editing characters listed below. This file defaults
21321 to the value of the environment variable @code{GDBHISTFILE}, or to
21322 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21325 @cindex save command history
21326 @kindex set history save
21327 @item set history save
21328 @itemx set history save on
21329 Record command history in a file, whose name may be specified with the
21330 @code{set history filename} command. By default, this option is disabled.
21332 @item set history save off
21333 Stop recording command history in a file.
21335 @cindex history size
21336 @kindex set history size
21337 @cindex @env{HISTSIZE}, environment variable
21338 @item set history size @var{size}
21339 Set the number of commands which @value{GDBN} keeps in its history list.
21340 This defaults to the value of the environment variable
21341 @code{HISTSIZE}, or to 256 if this variable is not set.
21344 History expansion assigns special meaning to the character @kbd{!}.
21345 @ifset SYSTEM_READLINE
21346 @xref{Event Designators, , , history, GNU History Library},
21348 @ifclear SYSTEM_READLINE
21349 @xref{Event Designators},
21353 @cindex history expansion, turn on/off
21354 Since @kbd{!} is also the logical not operator in C, history expansion
21355 is off by default. If you decide to enable history expansion with the
21356 @code{set history expansion on} command, you may sometimes need to
21357 follow @kbd{!} (when it is used as logical not, in an expression) with
21358 a space or a tab to prevent it from being expanded. The readline
21359 history facilities do not attempt substitution on the strings
21360 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21362 The commands to control history expansion are:
21365 @item set history expansion on
21366 @itemx set history expansion
21367 @kindex set history expansion
21368 Enable history expansion. History expansion is off by default.
21370 @item set history expansion off
21371 Disable history expansion.
21374 @kindex show history
21376 @itemx show history filename
21377 @itemx show history save
21378 @itemx show history size
21379 @itemx show history expansion
21380 These commands display the state of the @value{GDBN} history parameters.
21381 @code{show history} by itself displays all four states.
21386 @kindex show commands
21387 @cindex show last commands
21388 @cindex display command history
21389 @item show commands
21390 Display the last ten commands in the command history.
21392 @item show commands @var{n}
21393 Print ten commands centered on command number @var{n}.
21395 @item show commands +
21396 Print ten commands just after the commands last printed.
21400 @section Screen Size
21401 @cindex size of screen
21402 @cindex pauses in output
21404 Certain commands to @value{GDBN} may produce large amounts of
21405 information output to the screen. To help you read all of it,
21406 @value{GDBN} pauses and asks you for input at the end of each page of
21407 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21408 to discard the remaining output. Also, the screen width setting
21409 determines when to wrap lines of output. Depending on what is being
21410 printed, @value{GDBN} tries to break the line at a readable place,
21411 rather than simply letting it overflow onto the following line.
21413 Normally @value{GDBN} knows the size of the screen from the terminal
21414 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21415 together with the value of the @code{TERM} environment variable and the
21416 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21417 you can override it with the @code{set height} and @code{set
21424 @kindex show height
21425 @item set height @var{lpp}
21427 @itemx set width @var{cpl}
21429 These @code{set} commands specify a screen height of @var{lpp} lines and
21430 a screen width of @var{cpl} characters. The associated @code{show}
21431 commands display the current settings.
21433 If you specify a height of zero lines, @value{GDBN} does not pause during
21434 output no matter how long the output is. This is useful if output is to a
21435 file or to an editor buffer.
21437 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21438 from wrapping its output.
21440 @item set pagination on
21441 @itemx set pagination off
21442 @kindex set pagination
21443 Turn the output pagination on or off; the default is on. Turning
21444 pagination off is the alternative to @code{set height 0}. Note that
21445 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21446 Options, -batch}) also automatically disables pagination.
21448 @item show pagination
21449 @kindex show pagination
21450 Show the current pagination mode.
21455 @cindex number representation
21456 @cindex entering numbers
21458 You can always enter numbers in octal, decimal, or hexadecimal in
21459 @value{GDBN} by the usual conventions: octal numbers begin with
21460 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21461 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21462 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21463 10; likewise, the default display for numbers---when no particular
21464 format is specified---is base 10. You can change the default base for
21465 both input and output with the commands described below.
21468 @kindex set input-radix
21469 @item set input-radix @var{base}
21470 Set the default base for numeric input. Supported choices
21471 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21472 specified either unambiguously or using the current input radix; for
21476 set input-radix 012
21477 set input-radix 10.
21478 set input-radix 0xa
21482 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21483 leaves the input radix unchanged, no matter what it was, since
21484 @samp{10}, being without any leading or trailing signs of its base, is
21485 interpreted in the current radix. Thus, if the current radix is 16,
21486 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21489 @kindex set output-radix
21490 @item set output-radix @var{base}
21491 Set the default base for numeric display. Supported choices
21492 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21493 specified either unambiguously or using the current input radix.
21495 @kindex show input-radix
21496 @item show input-radix
21497 Display the current default base for numeric input.
21499 @kindex show output-radix
21500 @item show output-radix
21501 Display the current default base for numeric display.
21503 @item set radix @r{[}@var{base}@r{]}
21507 These commands set and show the default base for both input and output
21508 of numbers. @code{set radix} sets the radix of input and output to
21509 the same base; without an argument, it resets the radix back to its
21510 default value of 10.
21515 @section Configuring the Current ABI
21517 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21518 application automatically. However, sometimes you need to override its
21519 conclusions. Use these commands to manage @value{GDBN}'s view of the
21525 @cindex Newlib OS ABI and its influence on the longjmp handling
21527 One @value{GDBN} configuration can debug binaries for multiple operating
21528 system targets, either via remote debugging or native emulation.
21529 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21530 but you can override its conclusion using the @code{set osabi} command.
21531 One example where this is useful is in debugging of binaries which use
21532 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21533 not have the same identifying marks that the standard C library for your
21536 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21537 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21538 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21539 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21543 Show the OS ABI currently in use.
21546 With no argument, show the list of registered available OS ABI's.
21548 @item set osabi @var{abi}
21549 Set the current OS ABI to @var{abi}.
21552 @cindex float promotion
21554 Generally, the way that an argument of type @code{float} is passed to a
21555 function depends on whether the function is prototyped. For a prototyped
21556 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21557 according to the architecture's convention for @code{float}. For unprototyped
21558 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21559 @code{double} and then passed.
21561 Unfortunately, some forms of debug information do not reliably indicate whether
21562 a function is prototyped. If @value{GDBN} calls a function that is not marked
21563 as prototyped, it consults @kbd{set coerce-float-to-double}.
21566 @kindex set coerce-float-to-double
21567 @item set coerce-float-to-double
21568 @itemx set coerce-float-to-double on
21569 Arguments of type @code{float} will be promoted to @code{double} when passed
21570 to an unprototyped function. This is the default setting.
21572 @item set coerce-float-to-double off
21573 Arguments of type @code{float} will be passed directly to unprototyped
21576 @kindex show coerce-float-to-double
21577 @item show coerce-float-to-double
21578 Show the current setting of promoting @code{float} to @code{double}.
21582 @kindex show cp-abi
21583 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21584 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21585 used to build your application. @value{GDBN} only fully supports
21586 programs with a single C@t{++} ABI; if your program contains code using
21587 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21588 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21589 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21590 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21591 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21592 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21597 Show the C@t{++} ABI currently in use.
21600 With no argument, show the list of supported C@t{++} ABI's.
21602 @item set cp-abi @var{abi}
21603 @itemx set cp-abi auto
21604 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21608 @section Automatically loading associated files
21609 @cindex auto-loading
21611 @value{GDBN} sometimes reads files with commands and settings automatically,
21612 without being explicitly told so by the user. We call this feature
21613 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21614 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21615 results or introduce security risks (e.g., if the file comes from untrusted
21618 Note that loading of these associated files (including the local @file{.gdbinit}
21619 file) requires accordingly configured @code{auto-load safe-path}
21620 (@pxref{Auto-loading safe path}).
21622 For these reasons, @value{GDBN} includes commands and options to let you
21623 control when to auto-load files and which files should be auto-loaded.
21626 @anchor{set auto-load off}
21627 @kindex set auto-load off
21628 @item set auto-load off
21629 Globally disable loading of all auto-loaded files.
21630 You may want to use this command with the @samp{-iex} option
21631 (@pxref{Option -init-eval-command}) such as:
21633 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21636 Be aware that system init file (@pxref{System-wide configuration})
21637 and init files from your home directory (@pxref{Home Directory Init File})
21638 still get read (as they come from generally trusted directories).
21639 To prevent @value{GDBN} from auto-loading even those init files, use the
21640 @option{-nx} option (@pxref{Mode Options}), in addition to
21641 @code{set auto-load no}.
21643 @anchor{show auto-load}
21644 @kindex show auto-load
21645 @item show auto-load
21646 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21650 (gdb) show auto-load
21651 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21652 libthread-db: Auto-loading of inferior specific libthread_db is on.
21653 local-gdbinit: Auto-loading of .gdbinit script from current directory
21655 python-scripts: Auto-loading of Python scripts is on.
21656 safe-path: List of directories from which it is safe to auto-load files
21657 is $debugdir:$datadir/auto-load.
21658 scripts-directory: List of directories from which to load auto-loaded scripts
21659 is $debugdir:$datadir/auto-load.
21662 @anchor{info auto-load}
21663 @kindex info auto-load
21664 @item info auto-load
21665 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21669 (gdb) info auto-load
21672 Yes /home/user/gdb/gdb-gdb.gdb
21673 libthread-db: No auto-loaded libthread-db.
21674 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21678 Yes /home/user/gdb/gdb-gdb.py
21682 These are various kinds of files @value{GDBN} can automatically load:
21686 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21688 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21690 @xref{dotdebug_gdb_scripts section},
21691 controlled by @ref{set auto-load python-scripts}.
21693 @xref{Init File in the Current Directory},
21694 controlled by @ref{set auto-load local-gdbinit}.
21696 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21699 These are @value{GDBN} control commands for the auto-loading:
21701 @multitable @columnfractions .5 .5
21702 @item @xref{set auto-load off}.
21703 @tab Disable auto-loading globally.
21704 @item @xref{show auto-load}.
21705 @tab Show setting of all kinds of files.
21706 @item @xref{info auto-load}.
21707 @tab Show state of all kinds of files.
21708 @item @xref{set auto-load gdb-scripts}.
21709 @tab Control for @value{GDBN} command scripts.
21710 @item @xref{show auto-load gdb-scripts}.
21711 @tab Show setting of @value{GDBN} command scripts.
21712 @item @xref{info auto-load gdb-scripts}.
21713 @tab Show state of @value{GDBN} command scripts.
21714 @item @xref{set auto-load python-scripts}.
21715 @tab Control for @value{GDBN} Python scripts.
21716 @item @xref{show auto-load python-scripts}.
21717 @tab Show setting of @value{GDBN} Python scripts.
21718 @item @xref{info auto-load python-scripts}.
21719 @tab Show state of @value{GDBN} Python scripts.
21720 @item @xref{set auto-load scripts-directory}.
21721 @tab Control for @value{GDBN} auto-loaded scripts location.
21722 @item @xref{show auto-load scripts-directory}.
21723 @tab Show @value{GDBN} auto-loaded scripts location.
21724 @item @xref{set auto-load local-gdbinit}.
21725 @tab Control for init file in the current directory.
21726 @item @xref{show auto-load local-gdbinit}.
21727 @tab Show setting of init file in the current directory.
21728 @item @xref{info auto-load local-gdbinit}.
21729 @tab Show state of init file in the current directory.
21730 @item @xref{set auto-load libthread-db}.
21731 @tab Control for thread debugging library.
21732 @item @xref{show auto-load libthread-db}.
21733 @tab Show setting of thread debugging library.
21734 @item @xref{info auto-load libthread-db}.
21735 @tab Show state of thread debugging library.
21736 @item @xref{set auto-load safe-path}.
21737 @tab Control directories trusted for automatic loading.
21738 @item @xref{show auto-load safe-path}.
21739 @tab Show directories trusted for automatic loading.
21740 @item @xref{add-auto-load-safe-path}.
21741 @tab Add directory trusted for automatic loading.
21745 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21746 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21747 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21748 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21749 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21750 @xref{Python Auto-loading}.
21753 @node Init File in the Current Directory
21754 @subsection Automatically loading init file in the current directory
21755 @cindex auto-loading init file in the current directory
21757 By default, @value{GDBN} reads and executes the canned sequences of commands
21758 from init file (if any) in the current working directory,
21759 see @ref{Init File in the Current Directory during Startup}.
21761 Note that loading of this local @file{.gdbinit} file also requires accordingly
21762 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21765 @anchor{set auto-load local-gdbinit}
21766 @kindex set auto-load local-gdbinit
21767 @item set auto-load local-gdbinit [on|off]
21768 Enable or disable the auto-loading of canned sequences of commands
21769 (@pxref{Sequences}) found in init file in the current directory.
21771 @anchor{show auto-load local-gdbinit}
21772 @kindex show auto-load local-gdbinit
21773 @item show auto-load local-gdbinit
21774 Show whether auto-loading of canned sequences of commands from init file in the
21775 current directory is enabled or disabled.
21777 @anchor{info auto-load local-gdbinit}
21778 @kindex info auto-load local-gdbinit
21779 @item info auto-load local-gdbinit
21780 Print whether canned sequences of commands from init file in the
21781 current directory have been auto-loaded.
21784 @node libthread_db.so.1 file
21785 @subsection Automatically loading thread debugging library
21786 @cindex auto-loading libthread_db.so.1
21788 This feature is currently present only on @sc{gnu}/Linux native hosts.
21790 @value{GDBN} reads in some cases thread debugging library from places specific
21791 to the inferior (@pxref{set libthread-db-search-path}).
21793 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21794 without checking this @samp{set auto-load libthread-db} switch as system
21795 libraries have to be trusted in general. In all other cases of
21796 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21797 auto-load libthread-db} is enabled before trying to open such thread debugging
21800 Note that loading of this debugging library also requires accordingly configured
21801 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21804 @anchor{set auto-load libthread-db}
21805 @kindex set auto-load libthread-db
21806 @item set auto-load libthread-db [on|off]
21807 Enable or disable the auto-loading of inferior specific thread debugging library.
21809 @anchor{show auto-load libthread-db}
21810 @kindex show auto-load libthread-db
21811 @item show auto-load libthread-db
21812 Show whether auto-loading of inferior specific thread debugging library is
21813 enabled or disabled.
21815 @anchor{info auto-load libthread-db}
21816 @kindex info auto-load libthread-db
21817 @item info auto-load libthread-db
21818 Print the list of all loaded inferior specific thread debugging libraries and
21819 for each such library print list of inferior @var{pid}s using it.
21822 @node objfile-gdb.gdb file
21823 @subsection The @file{@var{objfile}-gdb.gdb} file
21824 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21826 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21827 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21828 auto-load gdb-scripts} is set to @samp{on}.
21830 Note that loading of this script file also requires accordingly configured
21831 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21833 For more background refer to the similar Python scripts auto-loading
21834 description (@pxref{objfile-gdb.py file}).
21837 @anchor{set auto-load gdb-scripts}
21838 @kindex set auto-load gdb-scripts
21839 @item set auto-load gdb-scripts [on|off]
21840 Enable or disable the auto-loading of canned sequences of commands scripts.
21842 @anchor{show auto-load gdb-scripts}
21843 @kindex show auto-load gdb-scripts
21844 @item show auto-load gdb-scripts
21845 Show whether auto-loading of canned sequences of commands scripts is enabled or
21848 @anchor{info auto-load gdb-scripts}
21849 @kindex info auto-load gdb-scripts
21850 @cindex print list of auto-loaded canned sequences of commands scripts
21851 @item info auto-load gdb-scripts [@var{regexp}]
21852 Print the list of all canned sequences of commands scripts that @value{GDBN}
21856 If @var{regexp} is supplied only canned sequences of commands scripts with
21857 matching names are printed.
21859 @node Auto-loading safe path
21860 @subsection Security restriction for auto-loading
21861 @cindex auto-loading safe-path
21863 As the files of inferior can come from untrusted source (such as submitted by
21864 an application user) @value{GDBN} does not always load any files automatically.
21865 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21866 directories trusted for loading files not explicitly requested by user.
21867 Each directory can also be a shell wildcard pattern.
21869 If the path is not set properly you will see a warning and the file will not
21874 Reading symbols from /home/user/gdb/gdb...done.
21875 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21876 declined by your `auto-load safe-path' set
21877 to "$debugdir:$datadir/auto-load".
21878 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21879 declined by your `auto-load safe-path' set
21880 to "$debugdir:$datadir/auto-load".
21884 To instruct @value{GDBN} to go ahead and use the init files anyway,
21885 invoke @value{GDBN} like this:
21888 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
21891 The list of trusted directories is controlled by the following commands:
21894 @anchor{set auto-load safe-path}
21895 @kindex set auto-load safe-path
21896 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21897 Set the list of directories (and their subdirectories) trusted for automatic
21898 loading and execution of scripts. You can also enter a specific trusted file.
21899 Each directory can also be a shell wildcard pattern; wildcards do not match
21900 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21901 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21902 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21903 its default value as specified during @value{GDBN} compilation.
21905 The list of directories uses path separator (@samp{:} on GNU and Unix
21906 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21907 to the @env{PATH} environment variable.
21909 @anchor{show auto-load safe-path}
21910 @kindex show auto-load safe-path
21911 @item show auto-load safe-path
21912 Show the list of directories trusted for automatic loading and execution of
21915 @anchor{add-auto-load-safe-path}
21916 @kindex add-auto-load-safe-path
21917 @item add-auto-load-safe-path
21918 Add an entry (or list of entries) the list of directories trusted for automatic
21919 loading and execution of scripts. Multiple entries may be delimited by the
21920 host platform path separator in use.
21923 This variable defaults to what @code{--with-auto-load-dir} has been configured
21924 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21925 substitution applies the same as for @ref{set auto-load scripts-directory}.
21926 The default @code{set auto-load safe-path} value can be also overriden by
21927 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21929 Setting this variable to @file{/} disables this security protection,
21930 corresponding @value{GDBN} configuration option is
21931 @option{--without-auto-load-safe-path}.
21932 This variable is supposed to be set to the system directories writable by the
21933 system superuser only. Users can add their source directories in init files in
21934 their home directories (@pxref{Home Directory Init File}). See also deprecated
21935 init file in the current directory
21936 (@pxref{Init File in the Current Directory during Startup}).
21938 To force @value{GDBN} to load the files it declined to load in the previous
21939 example, you could use one of the following ways:
21942 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21943 Specify this trusted directory (or a file) as additional component of the list.
21944 You have to specify also any existing directories displayed by
21945 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21947 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21948 Specify this directory as in the previous case but just for a single
21949 @value{GDBN} session.
21951 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21952 Disable auto-loading safety for a single @value{GDBN} session.
21953 This assumes all the files you debug during this @value{GDBN} session will come
21954 from trusted sources.
21956 @item @kbd{./configure --without-auto-load-safe-path}
21957 During compilation of @value{GDBN} you may disable any auto-loading safety.
21958 This assumes all the files you will ever debug with this @value{GDBN} come from
21962 On the other hand you can also explicitly forbid automatic files loading which
21963 also suppresses any such warning messages:
21966 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21967 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21969 @item @file{~/.gdbinit}: @samp{set auto-load no}
21970 Disable auto-loading globally for the user
21971 (@pxref{Home Directory Init File}). While it is improbable, you could also
21972 use system init file instead (@pxref{System-wide configuration}).
21975 This setting applies to the file names as entered by user. If no entry matches
21976 @value{GDBN} tries as a last resort to also resolve all the file names into
21977 their canonical form (typically resolving symbolic links) and compare the
21978 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21979 own before starting the comparison so a canonical form of directories is
21980 recommended to be entered.
21982 @node Auto-loading verbose mode
21983 @subsection Displaying files tried for auto-load
21984 @cindex auto-loading verbose mode
21986 For better visibility of all the file locations where you can place scripts to
21987 be auto-loaded with inferior --- or to protect yourself against accidental
21988 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21989 all the files attempted to be loaded. Both existing and non-existing files may
21992 For example the list of directories from which it is safe to auto-load files
21993 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21994 may not be too obvious while setting it up.
21997 (gdb) set debug auto-load on
21998 (gdb) file ~/src/t/true
21999 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22000 for objfile "/tmp/true".
22001 auto-load: Updating directories of "/usr:/opt".
22002 auto-load: Using directory "/usr".
22003 auto-load: Using directory "/opt".
22004 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22005 by your `auto-load safe-path' set to "/usr:/opt".
22009 @anchor{set debug auto-load}
22010 @kindex set debug auto-load
22011 @item set debug auto-load [on|off]
22012 Set whether to print the filenames attempted to be auto-loaded.
22014 @anchor{show debug auto-load}
22015 @kindex show debug auto-load
22016 @item show debug auto-load
22017 Show whether printing of the filenames attempted to be auto-loaded is turned
22021 @node Messages/Warnings
22022 @section Optional Warnings and Messages
22024 @cindex verbose operation
22025 @cindex optional warnings
22026 By default, @value{GDBN} is silent about its inner workings. If you are
22027 running on a slow machine, you may want to use the @code{set verbose}
22028 command. This makes @value{GDBN} tell you when it does a lengthy
22029 internal operation, so you will not think it has crashed.
22031 Currently, the messages controlled by @code{set verbose} are those
22032 which announce that the symbol table for a source file is being read;
22033 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22036 @kindex set verbose
22037 @item set verbose on
22038 Enables @value{GDBN} output of certain informational messages.
22040 @item set verbose off
22041 Disables @value{GDBN} output of certain informational messages.
22043 @kindex show verbose
22045 Displays whether @code{set verbose} is on or off.
22048 By default, if @value{GDBN} encounters bugs in the symbol table of an
22049 object file, it is silent; but if you are debugging a compiler, you may
22050 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22055 @kindex set complaints
22056 @item set complaints @var{limit}
22057 Permits @value{GDBN} to output @var{limit} complaints about each type of
22058 unusual symbols before becoming silent about the problem. Set
22059 @var{limit} to zero to suppress all complaints; set it to a large number
22060 to prevent complaints from being suppressed.
22062 @kindex show complaints
22063 @item show complaints
22064 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22068 @anchor{confirmation requests}
22069 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22070 lot of stupid questions to confirm certain commands. For example, if
22071 you try to run a program which is already running:
22075 The program being debugged has been started already.
22076 Start it from the beginning? (y or n)
22079 If you are willing to unflinchingly face the consequences of your own
22080 commands, you can disable this ``feature'':
22084 @kindex set confirm
22086 @cindex confirmation
22087 @cindex stupid questions
22088 @item set confirm off
22089 Disables confirmation requests. Note that running @value{GDBN} with
22090 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22091 automatically disables confirmation requests.
22093 @item set confirm on
22094 Enables confirmation requests (the default).
22096 @kindex show confirm
22098 Displays state of confirmation requests.
22102 @cindex command tracing
22103 If you need to debug user-defined commands or sourced files you may find it
22104 useful to enable @dfn{command tracing}. In this mode each command will be
22105 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22106 quantity denoting the call depth of each command.
22109 @kindex set trace-commands
22110 @cindex command scripts, debugging
22111 @item set trace-commands on
22112 Enable command tracing.
22113 @item set trace-commands off
22114 Disable command tracing.
22115 @item show trace-commands
22116 Display the current state of command tracing.
22119 @node Debugging Output
22120 @section Optional Messages about Internal Happenings
22121 @cindex optional debugging messages
22123 @value{GDBN} has commands that enable optional debugging messages from
22124 various @value{GDBN} subsystems; normally these commands are of
22125 interest to @value{GDBN} maintainers, or when reporting a bug. This
22126 section documents those commands.
22129 @kindex set exec-done-display
22130 @item set exec-done-display
22131 Turns on or off the notification of asynchronous commands'
22132 completion. When on, @value{GDBN} will print a message when an
22133 asynchronous command finishes its execution. The default is off.
22134 @kindex show exec-done-display
22135 @item show exec-done-display
22136 Displays the current setting of asynchronous command completion
22139 @cindex ARM AArch64
22140 @item set debug aarch64
22141 Turns on or off display of debugging messages related to ARM AArch64.
22142 The default is off.
22144 @item show debug aarch64
22145 Displays the current state of displaying debugging messages related to
22147 @cindex gdbarch debugging info
22148 @cindex architecture debugging info
22149 @item set debug arch
22150 Turns on or off display of gdbarch debugging info. The default is off
22151 @item show debug arch
22152 Displays the current state of displaying gdbarch debugging info.
22153 @item set debug aix-thread
22154 @cindex AIX threads
22155 Display debugging messages about inner workings of the AIX thread
22157 @item show debug aix-thread
22158 Show the current state of AIX thread debugging info display.
22159 @item set debug check-physname
22161 Check the results of the ``physname'' computation. When reading DWARF
22162 debugging information for C@t{++}, @value{GDBN} attempts to compute
22163 each entity's name. @value{GDBN} can do this computation in two
22164 different ways, depending on exactly what information is present.
22165 When enabled, this setting causes @value{GDBN} to compute the names
22166 both ways and display any discrepancies.
22167 @item show debug check-physname
22168 Show the current state of ``physname'' checking.
22169 @item set debug coff-pe-read
22170 @cindex COFF/PE exported symbols
22171 Control display of debugging messages related to reading of COFF/PE
22172 exported symbols. The default is off.
22173 @item show debug coff-pe-read
22174 Displays the current state of displaying debugging messages related to
22175 reading of COFF/PE exported symbols.
22176 @item set debug dwarf2-die
22177 @cindex DWARF2 DIEs
22178 Dump DWARF2 DIEs after they are read in.
22179 The value is the number of nesting levels to print.
22180 A value of zero turns off the display.
22181 @item show debug dwarf2-die
22182 Show the current state of DWARF2 DIE debugging.
22183 @item set debug dwarf2-read
22184 @cindex DWARF2 Reading
22185 Turns on or off display of debugging messages related to reading
22186 DWARF debug info. The default is off.
22187 @item show debug dwarf2-read
22188 Show the current state of DWARF2 reader debugging.
22189 @item set debug displaced
22190 @cindex displaced stepping debugging info
22191 Turns on or off display of @value{GDBN} debugging info for the
22192 displaced stepping support. The default is off.
22193 @item show debug displaced
22194 Displays the current state of displaying @value{GDBN} debugging info
22195 related to displaced stepping.
22196 @item set debug event
22197 @cindex event debugging info
22198 Turns on or off display of @value{GDBN} event debugging info. The
22200 @item show debug event
22201 Displays the current state of displaying @value{GDBN} event debugging
22203 @item set debug expression
22204 @cindex expression debugging info
22205 Turns on or off display of debugging info about @value{GDBN}
22206 expression parsing. The default is off.
22207 @item show debug expression
22208 Displays the current state of displaying debugging info about
22209 @value{GDBN} expression parsing.
22210 @item set debug frame
22211 @cindex frame debugging info
22212 Turns on or off display of @value{GDBN} frame debugging info. The
22214 @item show debug frame
22215 Displays the current state of displaying @value{GDBN} frame debugging
22217 @item set debug gnu-nat
22218 @cindex @sc{gnu}/Hurd debug messages
22219 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22220 @item show debug gnu-nat
22221 Show the current state of @sc{gnu}/Hurd debugging messages.
22222 @item set debug infrun
22223 @cindex inferior debugging info
22224 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22225 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22226 for implementing operations such as single-stepping the inferior.
22227 @item show debug infrun
22228 Displays the current state of @value{GDBN} inferior debugging.
22229 @item set debug jit
22230 @cindex just-in-time compilation, debugging messages
22231 Turns on or off debugging messages from JIT debug support.
22232 @item show debug jit
22233 Displays the current state of @value{GDBN} JIT debugging.
22234 @item set debug lin-lwp
22235 @cindex @sc{gnu}/Linux LWP debug messages
22236 @cindex Linux lightweight processes
22237 Turns on or off debugging messages from the Linux LWP debug support.
22238 @item show debug lin-lwp
22239 Show the current state of Linux LWP debugging messages.
22240 @item set debug mach-o
22241 @cindex Mach-O symbols processing
22242 Control display of debugging messages related to Mach-O symbols
22243 processing. The default is off.
22244 @item show debug mach-o
22245 Displays the current state of displaying debugging messages related to
22246 reading of COFF/PE exported symbols.
22247 @item set debug notification
22248 @cindex remote async notification debugging info
22249 Turns on or off debugging messages about remote async notification.
22250 The default is off.
22251 @item show debug notification
22252 Displays the current state of remote async notification debugging messages.
22253 @item set debug observer
22254 @cindex observer debugging info
22255 Turns on or off display of @value{GDBN} observer debugging. This
22256 includes info such as the notification of observable events.
22257 @item show debug observer
22258 Displays the current state of observer debugging.
22259 @item set debug overload
22260 @cindex C@t{++} overload debugging info
22261 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22262 info. This includes info such as ranking of functions, etc. The default
22264 @item show debug overload
22265 Displays the current state of displaying @value{GDBN} C@t{++} overload
22267 @cindex expression parser, debugging info
22268 @cindex debug expression parser
22269 @item set debug parser
22270 Turns on or off the display of expression parser debugging output.
22271 Internally, this sets the @code{yydebug} variable in the expression
22272 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22273 details. The default is off.
22274 @item show debug parser
22275 Show the current state of expression parser debugging.
22276 @cindex packets, reporting on stdout
22277 @cindex serial connections, debugging
22278 @cindex debug remote protocol
22279 @cindex remote protocol debugging
22280 @cindex display remote packets
22281 @item set debug remote
22282 Turns on or off display of reports on all packets sent back and forth across
22283 the serial line to the remote machine. The info is printed on the
22284 @value{GDBN} standard output stream. The default is off.
22285 @item show debug remote
22286 Displays the state of display of remote packets.
22287 @item set debug serial
22288 Turns on or off display of @value{GDBN} serial debugging info. The
22290 @item show debug serial
22291 Displays the current state of displaying @value{GDBN} serial debugging
22293 @item set debug solib-frv
22294 @cindex FR-V shared-library debugging
22295 Turns on or off debugging messages for FR-V shared-library code.
22296 @item show debug solib-frv
22297 Display the current state of FR-V shared-library code debugging
22299 @item set debug symtab-create
22300 @cindex symbol table creation
22301 Turns on or off display of debugging messages related to symbol table creation.
22302 The default is off.
22303 @item show debug symtab-create
22304 Show the current state of symbol table creation debugging.
22305 @item set debug target
22306 @cindex target debugging info
22307 Turns on or off display of @value{GDBN} target debugging info. This info
22308 includes what is going on at the target level of GDB, as it happens. The
22309 default is 0. Set it to 1 to track events, and to 2 to also track the
22310 value of large memory transfers. Changes to this flag do not take effect
22311 until the next time you connect to a target or use the @code{run} command.
22312 @item show debug target
22313 Displays the current state of displaying @value{GDBN} target debugging
22315 @item set debug timestamp
22316 @cindex timestampping debugging info
22317 Turns on or off display of timestamps with @value{GDBN} debugging info.
22318 When enabled, seconds and microseconds are displayed before each debugging
22320 @item show debug timestamp
22321 Displays the current state of displaying timestamps with @value{GDBN}
22323 @item set debugvarobj
22324 @cindex variable object debugging info
22325 Turns on or off display of @value{GDBN} variable object debugging
22326 info. The default is off.
22327 @item show debugvarobj
22328 Displays the current state of displaying @value{GDBN} variable object
22330 @item set debug xml
22331 @cindex XML parser debugging
22332 Turns on or off debugging messages for built-in XML parsers.
22333 @item show debug xml
22334 Displays the current state of XML debugging messages.
22337 @node Other Misc Settings
22338 @section Other Miscellaneous Settings
22339 @cindex miscellaneous settings
22342 @kindex set interactive-mode
22343 @item set interactive-mode
22344 If @code{on}, forces @value{GDBN} to assume that GDB was started
22345 in a terminal. In practice, this means that @value{GDBN} should wait
22346 for the user to answer queries generated by commands entered at
22347 the command prompt. If @code{off}, forces @value{GDBN} to operate
22348 in the opposite mode, and it uses the default answers to all queries.
22349 If @code{auto} (the default), @value{GDBN} tries to determine whether
22350 its standard input is a terminal, and works in interactive-mode if it
22351 is, non-interactively otherwise.
22353 In the vast majority of cases, the debugger should be able to guess
22354 correctly which mode should be used. But this setting can be useful
22355 in certain specific cases, such as running a MinGW @value{GDBN}
22356 inside a cygwin window.
22358 @kindex show interactive-mode
22359 @item show interactive-mode
22360 Displays whether the debugger is operating in interactive mode or not.
22363 @node Extending GDB
22364 @chapter Extending @value{GDBN}
22365 @cindex extending GDB
22367 @value{GDBN} provides three mechanisms for extension. The first is based
22368 on composition of @value{GDBN} commands, the second is based on the
22369 Python scripting language, and the third is for defining new aliases of
22372 To facilitate the use of the first two extensions, @value{GDBN} is capable
22373 of evaluating the contents of a file. When doing so, @value{GDBN}
22374 can recognize which scripting language is being used by looking at
22375 the filename extension. Files with an unrecognized filename extension
22376 are always treated as a @value{GDBN} Command Files.
22377 @xref{Command Files,, Command files}.
22379 You can control how @value{GDBN} evaluates these files with the following
22383 @kindex set script-extension
22384 @kindex show script-extension
22385 @item set script-extension off
22386 All scripts are always evaluated as @value{GDBN} Command Files.
22388 @item set script-extension soft
22389 The debugger determines the scripting language based on filename
22390 extension. If this scripting language is supported, @value{GDBN}
22391 evaluates the script using that language. Otherwise, it evaluates
22392 the file as a @value{GDBN} Command File.
22394 @item set script-extension strict
22395 The debugger determines the scripting language based on filename
22396 extension, and evaluates the script using that language. If the
22397 language is not supported, then the evaluation fails.
22399 @item show script-extension
22400 Display the current value of the @code{script-extension} option.
22405 * Sequences:: Canned Sequences of Commands
22406 * Python:: Scripting @value{GDBN} using Python
22407 * Aliases:: Creating new spellings of existing commands
22411 @section Canned Sequences of Commands
22413 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22414 Command Lists}), @value{GDBN} provides two ways to store sequences of
22415 commands for execution as a unit: user-defined commands and command
22419 * Define:: How to define your own commands
22420 * Hooks:: Hooks for user-defined commands
22421 * Command Files:: How to write scripts of commands to be stored in a file
22422 * Output:: Commands for controlled output
22426 @subsection User-defined Commands
22428 @cindex user-defined command
22429 @cindex arguments, to user-defined commands
22430 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22431 which you assign a new name as a command. This is done with the
22432 @code{define} command. User commands may accept up to 10 arguments
22433 separated by whitespace. Arguments are accessed within the user command
22434 via @code{$arg0@dots{}$arg9}. A trivial example:
22438 print $arg0 + $arg1 + $arg2
22443 To execute the command use:
22450 This defines the command @code{adder}, which prints the sum of
22451 its three arguments. Note the arguments are text substitutions, so they may
22452 reference variables, use complex expressions, or even perform inferior
22455 @cindex argument count in user-defined commands
22456 @cindex how many arguments (user-defined commands)
22457 In addition, @code{$argc} may be used to find out how many arguments have
22458 been passed. This expands to a number in the range 0@dots{}10.
22463 print $arg0 + $arg1
22466 print $arg0 + $arg1 + $arg2
22474 @item define @var{commandname}
22475 Define a command named @var{commandname}. If there is already a command
22476 by that name, you are asked to confirm that you want to redefine it.
22477 @var{commandname} may be a bare command name consisting of letters,
22478 numbers, dashes, and underscores. It may also start with any predefined
22479 prefix command. For example, @samp{define target my-target} creates
22480 a user-defined @samp{target my-target} command.
22482 The definition of the command is made up of other @value{GDBN} command lines,
22483 which are given following the @code{define} command. The end of these
22484 commands is marked by a line containing @code{end}.
22487 @kindex end@r{ (user-defined commands)}
22488 @item document @var{commandname}
22489 Document the user-defined command @var{commandname}, so that it can be
22490 accessed by @code{help}. The command @var{commandname} must already be
22491 defined. This command reads lines of documentation just as @code{define}
22492 reads the lines of the command definition, ending with @code{end}.
22493 After the @code{document} command is finished, @code{help} on command
22494 @var{commandname} displays the documentation you have written.
22496 You may use the @code{document} command again to change the
22497 documentation of a command. Redefining the command with @code{define}
22498 does not change the documentation.
22500 @kindex dont-repeat
22501 @cindex don't repeat command
22503 Used inside a user-defined command, this tells @value{GDBN} that this
22504 command should not be repeated when the user hits @key{RET}
22505 (@pxref{Command Syntax, repeat last command}).
22507 @kindex help user-defined
22508 @item help user-defined
22509 List all user-defined commands and all python commands defined in class
22510 COMAND_USER. The first line of the documentation or docstring is
22515 @itemx show user @var{commandname}
22516 Display the @value{GDBN} commands used to define @var{commandname} (but
22517 not its documentation). If no @var{commandname} is given, display the
22518 definitions for all user-defined commands.
22519 This does not work for user-defined python commands.
22521 @cindex infinite recursion in user-defined commands
22522 @kindex show max-user-call-depth
22523 @kindex set max-user-call-depth
22524 @item show max-user-call-depth
22525 @itemx set max-user-call-depth
22526 The value of @code{max-user-call-depth} controls how many recursion
22527 levels are allowed in user-defined commands before @value{GDBN} suspects an
22528 infinite recursion and aborts the command.
22529 This does not apply to user-defined python commands.
22532 In addition to the above commands, user-defined commands frequently
22533 use control flow commands, described in @ref{Command Files}.
22535 When user-defined commands are executed, the
22536 commands of the definition are not printed. An error in any command
22537 stops execution of the user-defined command.
22539 If used interactively, commands that would ask for confirmation proceed
22540 without asking when used inside a user-defined command. Many @value{GDBN}
22541 commands that normally print messages to say what they are doing omit the
22542 messages when used in a user-defined command.
22545 @subsection User-defined Command Hooks
22546 @cindex command hooks
22547 @cindex hooks, for commands
22548 @cindex hooks, pre-command
22551 You may define @dfn{hooks}, which are a special kind of user-defined
22552 command. Whenever you run the command @samp{foo}, if the user-defined
22553 command @samp{hook-foo} exists, it is executed (with no arguments)
22554 before that command.
22556 @cindex hooks, post-command
22558 A hook may also be defined which is run after the command you executed.
22559 Whenever you run the command @samp{foo}, if the user-defined command
22560 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22561 that command. Post-execution hooks may exist simultaneously with
22562 pre-execution hooks, for the same command.
22564 It is valid for a hook to call the command which it hooks. If this
22565 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22567 @c It would be nice if hookpost could be passed a parameter indicating
22568 @c if the command it hooks executed properly or not. FIXME!
22570 @kindex stop@r{, a pseudo-command}
22571 In addition, a pseudo-command, @samp{stop} exists. Defining
22572 (@samp{hook-stop}) makes the associated commands execute every time
22573 execution stops in your program: before breakpoint commands are run,
22574 displays are printed, or the stack frame is printed.
22576 For example, to ignore @code{SIGALRM} signals while
22577 single-stepping, but treat them normally during normal execution,
22582 handle SIGALRM nopass
22586 handle SIGALRM pass
22589 define hook-continue
22590 handle SIGALRM pass
22594 As a further example, to hook at the beginning and end of the @code{echo}
22595 command, and to add extra text to the beginning and end of the message,
22603 define hookpost-echo
22607 (@value{GDBP}) echo Hello World
22608 <<<---Hello World--->>>
22613 You can define a hook for any single-word command in @value{GDBN}, but
22614 not for command aliases; you should define a hook for the basic command
22615 name, e.g.@: @code{backtrace} rather than @code{bt}.
22616 @c FIXME! So how does Joe User discover whether a command is an alias
22618 You can hook a multi-word command by adding @code{hook-} or
22619 @code{hookpost-} to the last word of the command, e.g.@:
22620 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22622 If an error occurs during the execution of your hook, execution of
22623 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22624 (before the command that you actually typed had a chance to run).
22626 If you try to define a hook which does not match any known command, you
22627 get a warning from the @code{define} command.
22629 @node Command Files
22630 @subsection Command Files
22632 @cindex command files
22633 @cindex scripting commands
22634 A command file for @value{GDBN} is a text file made of lines that are
22635 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22636 also be included. An empty line in a command file does nothing; it
22637 does not mean to repeat the last command, as it would from the
22640 You can request the execution of a command file with the @code{source}
22641 command. Note that the @code{source} command is also used to evaluate
22642 scripts that are not Command Files. The exact behavior can be configured
22643 using the @code{script-extension} setting.
22644 @xref{Extending GDB,, Extending GDB}.
22648 @cindex execute commands from a file
22649 @item source [-s] [-v] @var{filename}
22650 Execute the command file @var{filename}.
22653 The lines in a command file are generally executed sequentially,
22654 unless the order of execution is changed by one of the
22655 @emph{flow-control commands} described below. The commands are not
22656 printed as they are executed. An error in any command terminates
22657 execution of the command file and control is returned to the console.
22659 @value{GDBN} first searches for @var{filename} in the current directory.
22660 If the file is not found there, and @var{filename} does not specify a
22661 directory, then @value{GDBN} also looks for the file on the source search path
22662 (specified with the @samp{directory} command);
22663 except that @file{$cdir} is not searched because the compilation directory
22664 is not relevant to scripts.
22666 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22667 on the search path even if @var{filename} specifies a directory.
22668 The search is done by appending @var{filename} to each element of the
22669 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22670 and the search path contains @file{/home/user} then @value{GDBN} will
22671 look for the script @file{/home/user/mylib/myscript}.
22672 The search is also done if @var{filename} is an absolute path.
22673 For example, if @var{filename} is @file{/tmp/myscript} and
22674 the search path contains @file{/home/user} then @value{GDBN} will
22675 look for the script @file{/home/user/tmp/myscript}.
22676 For DOS-like systems, if @var{filename} contains a drive specification,
22677 it is stripped before concatenation. For example, if @var{filename} is
22678 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22679 will look for the script @file{c:/tmp/myscript}.
22681 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22682 each command as it is executed. The option must be given before
22683 @var{filename}, and is interpreted as part of the filename anywhere else.
22685 Commands that would ask for confirmation if used interactively proceed
22686 without asking when used in a command file. Many @value{GDBN} commands that
22687 normally print messages to say what they are doing omit the messages
22688 when called from command files.
22690 @value{GDBN} also accepts command input from standard input. In this
22691 mode, normal output goes to standard output and error output goes to
22692 standard error. Errors in a command file supplied on standard input do
22693 not terminate execution of the command file---execution continues with
22697 gdb < cmds > log 2>&1
22700 (The syntax above will vary depending on the shell used.) This example
22701 will execute commands from the file @file{cmds}. All output and errors
22702 would be directed to @file{log}.
22704 Since commands stored on command files tend to be more general than
22705 commands typed interactively, they frequently need to deal with
22706 complicated situations, such as different or unexpected values of
22707 variables and symbols, changes in how the program being debugged is
22708 built, etc. @value{GDBN} provides a set of flow-control commands to
22709 deal with these complexities. Using these commands, you can write
22710 complex scripts that loop over data structures, execute commands
22711 conditionally, etc.
22718 This command allows to include in your script conditionally executed
22719 commands. The @code{if} command takes a single argument, which is an
22720 expression to evaluate. It is followed by a series of commands that
22721 are executed only if the expression is true (its value is nonzero).
22722 There can then optionally be an @code{else} line, followed by a series
22723 of commands that are only executed if the expression was false. The
22724 end of the list is marked by a line containing @code{end}.
22728 This command allows to write loops. Its syntax is similar to
22729 @code{if}: the command takes a single argument, which is an expression
22730 to evaluate, and must be followed by the commands to execute, one per
22731 line, terminated by an @code{end}. These commands are called the
22732 @dfn{body} of the loop. The commands in the body of @code{while} are
22733 executed repeatedly as long as the expression evaluates to true.
22737 This command exits the @code{while} loop in whose body it is included.
22738 Execution of the script continues after that @code{while}s @code{end}
22741 @kindex loop_continue
22742 @item loop_continue
22743 This command skips the execution of the rest of the body of commands
22744 in the @code{while} loop in whose body it is included. Execution
22745 branches to the beginning of the @code{while} loop, where it evaluates
22746 the controlling expression.
22748 @kindex end@r{ (if/else/while commands)}
22750 Terminate the block of commands that are the body of @code{if},
22751 @code{else}, or @code{while} flow-control commands.
22756 @subsection Commands for Controlled Output
22758 During the execution of a command file or a user-defined command, normal
22759 @value{GDBN} output is suppressed; the only output that appears is what is
22760 explicitly printed by the commands in the definition. This section
22761 describes three commands useful for generating exactly the output you
22766 @item echo @var{text}
22767 @c I do not consider backslash-space a standard C escape sequence
22768 @c because it is not in ANSI.
22769 Print @var{text}. Nonprinting characters can be included in
22770 @var{text} using C escape sequences, such as @samp{\n} to print a
22771 newline. @strong{No newline is printed unless you specify one.}
22772 In addition to the standard C escape sequences, a backslash followed
22773 by a space stands for a space. This is useful for displaying a
22774 string with spaces at the beginning or the end, since leading and
22775 trailing spaces are otherwise trimmed from all arguments.
22776 To print @samp{@w{ }and foo =@w{ }}, use the command
22777 @samp{echo \@w{ }and foo = \@w{ }}.
22779 A backslash at the end of @var{text} can be used, as in C, to continue
22780 the command onto subsequent lines. For example,
22783 echo This is some text\n\
22784 which is continued\n\
22785 onto several lines.\n
22788 produces the same output as
22791 echo This is some text\n
22792 echo which is continued\n
22793 echo onto several lines.\n
22797 @item output @var{expression}
22798 Print the value of @var{expression} and nothing but that value: no
22799 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22800 value history either. @xref{Expressions, ,Expressions}, for more information
22803 @item output/@var{fmt} @var{expression}
22804 Print the value of @var{expression} in format @var{fmt}. You can use
22805 the same formats as for @code{print}. @xref{Output Formats,,Output
22806 Formats}, for more information.
22809 @item printf @var{template}, @var{expressions}@dots{}
22810 Print the values of one or more @var{expressions} under the control of
22811 the string @var{template}. To print several values, make
22812 @var{expressions} be a comma-separated list of individual expressions,
22813 which may be either numbers or pointers. Their values are printed as
22814 specified by @var{template}, exactly as a C program would do by
22815 executing the code below:
22818 printf (@var{template}, @var{expressions}@dots{});
22821 As in @code{C} @code{printf}, ordinary characters in @var{template}
22822 are printed verbatim, while @dfn{conversion specification} introduced
22823 by the @samp{%} character cause subsequent @var{expressions} to be
22824 evaluated, their values converted and formatted according to type and
22825 style information encoded in the conversion specifications, and then
22828 For example, you can print two values in hex like this:
22831 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22834 @code{printf} supports all the standard @code{C} conversion
22835 specifications, including the flags and modifiers between the @samp{%}
22836 character and the conversion letter, with the following exceptions:
22840 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22843 The modifier @samp{*} is not supported for specifying precision or
22847 The @samp{'} flag (for separation of digits into groups according to
22848 @code{LC_NUMERIC'}) is not supported.
22851 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22855 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22858 The conversion letters @samp{a} and @samp{A} are not supported.
22862 Note that the @samp{ll} type modifier is supported only if the
22863 underlying @code{C} implementation used to build @value{GDBN} supports
22864 the @code{long long int} type, and the @samp{L} type modifier is
22865 supported only if @code{long double} type is available.
22867 As in @code{C}, @code{printf} supports simple backslash-escape
22868 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22869 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22870 single character. Octal and hexadecimal escape sequences are not
22873 Additionally, @code{printf} supports conversion specifications for DFP
22874 (@dfn{Decimal Floating Point}) types using the following length modifiers
22875 together with a floating point specifier.
22880 @samp{H} for printing @code{Decimal32} types.
22883 @samp{D} for printing @code{Decimal64} types.
22886 @samp{DD} for printing @code{Decimal128} types.
22889 If the underlying @code{C} implementation used to build @value{GDBN} has
22890 support for the three length modifiers for DFP types, other modifiers
22891 such as width and precision will also be available for @value{GDBN} to use.
22893 In case there is no such @code{C} support, no additional modifiers will be
22894 available and the value will be printed in the standard way.
22896 Here's an example of printing DFP types using the above conversion letters:
22898 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22902 @item eval @var{template}, @var{expressions}@dots{}
22903 Convert the values of one or more @var{expressions} under the control of
22904 the string @var{template} to a command line, and call it.
22909 @section Scripting @value{GDBN} using Python
22910 @cindex python scripting
22911 @cindex scripting with python
22913 You can script @value{GDBN} using the @uref{http://www.python.org/,
22914 Python programming language}. This feature is available only if
22915 @value{GDBN} was configured using @option{--with-python}.
22917 @cindex python directory
22918 Python scripts used by @value{GDBN} should be installed in
22919 @file{@var{data-directory}/python}, where @var{data-directory} is
22920 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22921 This directory, known as the @dfn{python directory},
22922 is automatically added to the Python Search Path in order to allow
22923 the Python interpreter to locate all scripts installed at this location.
22925 Additionally, @value{GDBN} commands and convenience functions which
22926 are written in Python and are located in the
22927 @file{@var{data-directory}/python/gdb/command} or
22928 @file{@var{data-directory}/python/gdb/function} directories are
22929 automatically imported when @value{GDBN} starts.
22932 * Python Commands:: Accessing Python from @value{GDBN}.
22933 * Python API:: Accessing @value{GDBN} from Python.
22934 * Python Auto-loading:: Automatically loading Python code.
22935 * Python modules:: Python modules provided by @value{GDBN}.
22938 @node Python Commands
22939 @subsection Python Commands
22940 @cindex python commands
22941 @cindex commands to access python
22943 @value{GDBN} provides two commands for accessing the Python interpreter,
22944 and one related setting:
22947 @kindex python-interactive
22949 @item python-interactive @r{[}@var{command}@r{]}
22950 @itemx pi @r{[}@var{command}@r{]}
22951 Without an argument, the @code{python-interactive} command can be used
22952 to start an interactive Python prompt. To return to @value{GDBN},
22953 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22955 Alternatively, a single-line Python command can be given as an
22956 argument and evaluated. If the command is an expression, the result
22957 will be printed; otherwise, nothing will be printed. For example:
22960 (@value{GDBP}) python-interactive 2 + 3
22966 @item python @r{[}@var{command}@r{]}
22967 @itemx py @r{[}@var{command}@r{]}
22968 The @code{python} command can be used to evaluate Python code.
22970 If given an argument, the @code{python} command will evaluate the
22971 argument as a Python command. For example:
22974 (@value{GDBP}) python print 23
22978 If you do not provide an argument to @code{python}, it will act as a
22979 multi-line command, like @code{define}. In this case, the Python
22980 script is made up of subsequent command lines, given after the
22981 @code{python} command. This command list is terminated using a line
22982 containing @code{end}. For example:
22985 (@value{GDBP}) python
22987 End with a line saying just "end".
22993 @kindex set python print-stack
22994 @item set python print-stack
22995 By default, @value{GDBN} will print only the message component of a
22996 Python exception when an error occurs in a Python script. This can be
22997 controlled using @code{set python print-stack}: if @code{full}, then
22998 full Python stack printing is enabled; if @code{none}, then Python stack
22999 and message printing is disabled; if @code{message}, the default, only
23000 the message component of the error is printed.
23003 It is also possible to execute a Python script from the @value{GDBN}
23007 @item source @file{script-name}
23008 The script name must end with @samp{.py} and @value{GDBN} must be configured
23009 to recognize the script language based on filename extension using
23010 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23012 @item python execfile ("script-name")
23013 This method is based on the @code{execfile} Python built-in function,
23014 and thus is always available.
23018 @subsection Python API
23020 @cindex programming in python
23022 @cindex python stdout
23023 @cindex python pagination
23024 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23025 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23026 A Python program which outputs to one of these streams may have its
23027 output interrupted by the user (@pxref{Screen Size}). In this
23028 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23031 * Basic Python:: Basic Python Functions.
23032 * Exception Handling:: How Python exceptions are translated.
23033 * Values From Inferior:: Python representation of values.
23034 * Types In Python:: Python representation of types.
23035 * Pretty Printing API:: Pretty-printing values.
23036 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23037 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23038 * Type Printing API:: Pretty-printing types.
23039 * Inferiors In Python:: Python representation of inferiors (processes)
23040 * Events In Python:: Listening for events from @value{GDBN}.
23041 * Threads In Python:: Accessing inferior threads from Python.
23042 * Commands In Python:: Implementing new commands in Python.
23043 * Parameters In Python:: Adding new @value{GDBN} parameters.
23044 * Functions In Python:: Writing new convenience functions.
23045 * Progspaces In Python:: Program spaces.
23046 * Objfiles In Python:: Object files.
23047 * Frames In Python:: Accessing inferior stack frames from Python.
23048 * Blocks In Python:: Accessing frame blocks from Python.
23049 * Symbols In Python:: Python representation of symbols.
23050 * Symbol Tables In Python:: Python representation of symbol tables.
23051 * Breakpoints In Python:: Manipulating breakpoints using Python.
23052 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23054 * Lazy Strings In Python:: Python representation of lazy strings.
23055 * Architectures In Python:: Python representation of architectures.
23059 @subsubsection Basic Python
23061 @cindex python functions
23062 @cindex python module
23064 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23065 methods and classes added by @value{GDBN} are placed in this module.
23066 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23067 use in all scripts evaluated by the @code{python} command.
23069 @findex gdb.PYTHONDIR
23070 @defvar gdb.PYTHONDIR
23071 A string containing the python directory (@pxref{Python}).
23074 @findex gdb.execute
23075 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23076 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23077 If a GDB exception happens while @var{command} runs, it is
23078 translated as described in @ref{Exception Handling,,Exception Handling}.
23080 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23081 command as having originated from the user invoking it interactively.
23082 It must be a boolean value. If omitted, it defaults to @code{False}.
23084 By default, any output produced by @var{command} is sent to
23085 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23086 @code{True}, then output will be collected by @code{gdb.execute} and
23087 returned as a string. The default is @code{False}, in which case the
23088 return value is @code{None}. If @var{to_string} is @code{True}, the
23089 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23090 and height, and its pagination will be disabled; @pxref{Screen Size}.
23093 @findex gdb.breakpoints
23094 @defun gdb.breakpoints ()
23095 Return a sequence holding all of @value{GDBN}'s breakpoints.
23096 @xref{Breakpoints In Python}, for more information.
23099 @findex gdb.parameter
23100 @defun gdb.parameter (parameter)
23101 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23102 string naming the parameter to look up; @var{parameter} may contain
23103 spaces if the parameter has a multi-part name. For example,
23104 @samp{print object} is a valid parameter name.
23106 If the named parameter does not exist, this function throws a
23107 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23108 parameter's value is converted to a Python value of the appropriate
23109 type, and returned.
23112 @findex gdb.history
23113 @defun gdb.history (number)
23114 Return a value from @value{GDBN}'s value history (@pxref{Value
23115 History}). @var{number} indicates which history element to return.
23116 If @var{number} is negative, then @value{GDBN} will take its absolute value
23117 and count backward from the last element (i.e., the most recent element) to
23118 find the value to return. If @var{number} is zero, then @value{GDBN} will
23119 return the most recent element. If the element specified by @var{number}
23120 doesn't exist in the value history, a @code{gdb.error} exception will be
23123 If no exception is raised, the return value is always an instance of
23124 @code{gdb.Value} (@pxref{Values From Inferior}).
23127 @findex gdb.parse_and_eval
23128 @defun gdb.parse_and_eval (expression)
23129 Parse @var{expression} as an expression in the current language,
23130 evaluate it, and return the result as a @code{gdb.Value}.
23131 @var{expression} must be a string.
23133 This function can be useful when implementing a new command
23134 (@pxref{Commands In Python}), as it provides a way to parse the
23135 command's argument as an expression. It is also useful simply to
23136 compute values, for example, it is the only way to get the value of a
23137 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23140 @findex gdb.find_pc_line
23141 @defun gdb.find_pc_line (pc)
23142 Return the @code{gdb.Symtab_and_line} object corresponding to the
23143 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23144 value of @var{pc} is passed as an argument, then the @code{symtab} and
23145 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23146 will be @code{None} and 0 respectively.
23149 @findex gdb.post_event
23150 @defun gdb.post_event (event)
23151 Put @var{event}, a callable object taking no arguments, into
23152 @value{GDBN}'s internal event queue. This callable will be invoked at
23153 some later point, during @value{GDBN}'s event processing. Events
23154 posted using @code{post_event} will be run in the order in which they
23155 were posted; however, there is no way to know when they will be
23156 processed relative to other events inside @value{GDBN}.
23158 @value{GDBN} is not thread-safe. If your Python program uses multiple
23159 threads, you must be careful to only call @value{GDBN}-specific
23160 functions in the main @value{GDBN} thread. @code{post_event} ensures
23164 (@value{GDBP}) python
23168 > def __init__(self, message):
23169 > self.message = message;
23170 > def __call__(self):
23171 > gdb.write(self.message)
23173 >class MyThread1 (threading.Thread):
23175 > gdb.post_event(Writer("Hello "))
23177 >class MyThread2 (threading.Thread):
23179 > gdb.post_event(Writer("World\n"))
23181 >MyThread1().start()
23182 >MyThread2().start()
23184 (@value{GDBP}) Hello World
23189 @defun gdb.write (string @r{[}, stream{]})
23190 Print a string to @value{GDBN}'s paginated output stream. The
23191 optional @var{stream} determines the stream to print to. The default
23192 stream is @value{GDBN}'s standard output stream. Possible stream
23199 @value{GDBN}'s standard output stream.
23204 @value{GDBN}'s standard error stream.
23209 @value{GDBN}'s log stream (@pxref{Logging Output}).
23212 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23213 call this function and will automatically direct the output to the
23218 @defun gdb.flush ()
23219 Flush the buffer of a @value{GDBN} paginated stream so that the
23220 contents are displayed immediately. @value{GDBN} will flush the
23221 contents of a stream automatically when it encounters a newline in the
23222 buffer. The optional @var{stream} determines the stream to flush. The
23223 default stream is @value{GDBN}'s standard output stream. Possible
23230 @value{GDBN}'s standard output stream.
23235 @value{GDBN}'s standard error stream.
23240 @value{GDBN}'s log stream (@pxref{Logging Output}).
23244 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23245 call this function for the relevant stream.
23248 @findex gdb.target_charset
23249 @defun gdb.target_charset ()
23250 Return the name of the current target character set (@pxref{Character
23251 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23252 that @samp{auto} is never returned.
23255 @findex gdb.target_wide_charset
23256 @defun gdb.target_wide_charset ()
23257 Return the name of the current target wide character set
23258 (@pxref{Character Sets}). This differs from
23259 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23263 @findex gdb.solib_name
23264 @defun gdb.solib_name (address)
23265 Return the name of the shared library holding the given @var{address}
23266 as a string, or @code{None}.
23269 @findex gdb.decode_line
23270 @defun gdb.decode_line @r{[}expression@r{]}
23271 Return locations of the line specified by @var{expression}, or of the
23272 current line if no argument was given. This function returns a Python
23273 tuple containing two elements. The first element contains a string
23274 holding any unparsed section of @var{expression} (or @code{None} if
23275 the expression has been fully parsed). The second element contains
23276 either @code{None} or another tuple that contains all the locations
23277 that match the expression represented as @code{gdb.Symtab_and_line}
23278 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23279 provided, it is decoded the way that @value{GDBN}'s inbuilt
23280 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23283 @defun gdb.prompt_hook (current_prompt)
23284 @anchor{prompt_hook}
23286 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23287 assigned to this operation before a prompt is displayed by
23290 The parameter @code{current_prompt} contains the current @value{GDBN}
23291 prompt. This method must return a Python string, or @code{None}. If
23292 a string is returned, the @value{GDBN} prompt will be set to that
23293 string. If @code{None} is returned, @value{GDBN} will continue to use
23294 the current prompt.
23296 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23297 such as those used by readline for command input, and annotation
23298 related prompts are prohibited from being changed.
23301 @node Exception Handling
23302 @subsubsection Exception Handling
23303 @cindex python exceptions
23304 @cindex exceptions, python
23306 When executing the @code{python} command, Python exceptions
23307 uncaught within the Python code are translated to calls to
23308 @value{GDBN} error-reporting mechanism. If the command that called
23309 @code{python} does not handle the error, @value{GDBN} will
23310 terminate it and print an error message containing the Python
23311 exception name, the associated value, and the Python call stack
23312 backtrace at the point where the exception was raised. Example:
23315 (@value{GDBP}) python print foo
23316 Traceback (most recent call last):
23317 File "<string>", line 1, in <module>
23318 NameError: name 'foo' is not defined
23321 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23322 Python code are converted to Python exceptions. The type of the
23323 Python exception depends on the error.
23327 This is the base class for most exceptions generated by @value{GDBN}.
23328 It is derived from @code{RuntimeError}, for compatibility with earlier
23329 versions of @value{GDBN}.
23331 If an error occurring in @value{GDBN} does not fit into some more
23332 specific category, then the generated exception will have this type.
23334 @item gdb.MemoryError
23335 This is a subclass of @code{gdb.error} which is thrown when an
23336 operation tried to access invalid memory in the inferior.
23338 @item KeyboardInterrupt
23339 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23340 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23343 In all cases, your exception handler will see the @value{GDBN} error
23344 message as its value and the Python call stack backtrace at the Python
23345 statement closest to where the @value{GDBN} error occured as the
23348 @findex gdb.GdbError
23349 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23350 it is useful to be able to throw an exception that doesn't cause a
23351 traceback to be printed. For example, the user may have invoked the
23352 command incorrectly. Use the @code{gdb.GdbError} exception
23353 to handle this case. Example:
23357 >class HelloWorld (gdb.Command):
23358 > """Greet the whole world."""
23359 > def __init__ (self):
23360 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23361 > def invoke (self, args, from_tty):
23362 > argv = gdb.string_to_argv (args)
23363 > if len (argv) != 0:
23364 > raise gdb.GdbError ("hello-world takes no arguments")
23365 > print "Hello, World!"
23368 (gdb) hello-world 42
23369 hello-world takes no arguments
23372 @node Values From Inferior
23373 @subsubsection Values From Inferior
23374 @cindex values from inferior, with Python
23375 @cindex python, working with values from inferior
23377 @cindex @code{gdb.Value}
23378 @value{GDBN} provides values it obtains from the inferior program in
23379 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23380 for its internal bookkeeping of the inferior's values, and for
23381 fetching values when necessary.
23383 Inferior values that are simple scalars can be used directly in
23384 Python expressions that are valid for the value's data type. Here's
23385 an example for an integer or floating-point value @code{some_val}:
23392 As result of this, @code{bar} will also be a @code{gdb.Value} object
23393 whose values are of the same type as those of @code{some_val}.
23395 Inferior values that are structures or instances of some class can
23396 be accessed using the Python @dfn{dictionary syntax}. For example, if
23397 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23398 can access its @code{foo} element with:
23401 bar = some_val['foo']
23404 Again, @code{bar} will also be a @code{gdb.Value} object.
23406 A @code{gdb.Value} that represents a function can be executed via
23407 inferior function call. Any arguments provided to the call must match
23408 the function's prototype, and must be provided in the order specified
23411 For example, @code{some_val} is a @code{gdb.Value} instance
23412 representing a function that takes two integers as arguments. To
23413 execute this function, call it like so:
23416 result = some_val (10,20)
23419 Any values returned from a function call will be stored as a
23422 The following attributes are provided:
23424 @defvar Value.address
23425 If this object is addressable, this read-only attribute holds a
23426 @code{gdb.Value} object representing the address. Otherwise,
23427 this attribute holds @code{None}.
23430 @cindex optimized out value in Python
23431 @defvar Value.is_optimized_out
23432 This read-only boolean attribute is true if the compiler optimized out
23433 this value, thus it is not available for fetching from the inferior.
23437 The type of this @code{gdb.Value}. The value of this attribute is a
23438 @code{gdb.Type} object (@pxref{Types In Python}).
23441 @defvar Value.dynamic_type
23442 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23443 type information (@acronym{RTTI}) to determine the dynamic type of the
23444 value. If this value is of class type, it will return the class in
23445 which the value is embedded, if any. If this value is of pointer or
23446 reference to a class type, it will compute the dynamic type of the
23447 referenced object, and return a pointer or reference to that type,
23448 respectively. In all other cases, it will return the value's static
23451 Note that this feature will only work when debugging a C@t{++} program
23452 that includes @acronym{RTTI} for the object in question. Otherwise,
23453 it will just return the static type of the value as in @kbd{ptype foo}
23454 (@pxref{Symbols, ptype}).
23457 @defvar Value.is_lazy
23458 The value of this read-only boolean attribute is @code{True} if this
23459 @code{gdb.Value} has not yet been fetched from the inferior.
23460 @value{GDBN} does not fetch values until necessary, for efficiency.
23464 myval = gdb.parse_and_eval ('somevar')
23467 The value of @code{somevar} is not fetched at this time. It will be
23468 fetched when the value is needed, or when the @code{fetch_lazy}
23472 The following methods are provided:
23474 @defun Value.__init__ (@var{val})
23475 Many Python values can be converted directly to a @code{gdb.Value} via
23476 this object initializer. Specifically:
23479 @item Python boolean
23480 A Python boolean is converted to the boolean type from the current
23483 @item Python integer
23484 A Python integer is converted to the C @code{long} type for the
23485 current architecture.
23488 A Python long is converted to the C @code{long long} type for the
23489 current architecture.
23492 A Python float is converted to the C @code{double} type for the
23493 current architecture.
23495 @item Python string
23496 A Python string is converted to a target string, using the current
23499 @item @code{gdb.Value}
23500 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23502 @item @code{gdb.LazyString}
23503 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23504 Python}), then the lazy string's @code{value} method is called, and
23505 its result is used.
23509 @defun Value.cast (type)
23510 Return a new instance of @code{gdb.Value} that is the result of
23511 casting this instance to the type described by @var{type}, which must
23512 be a @code{gdb.Type} object. If the cast cannot be performed for some
23513 reason, this method throws an exception.
23516 @defun Value.dereference ()
23517 For pointer data types, this method returns a new @code{gdb.Value} object
23518 whose contents is the object pointed to by the pointer. For example, if
23519 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23526 then you can use the corresponding @code{gdb.Value} to access what
23527 @code{foo} points to like this:
23530 bar = foo.dereference ()
23533 The result @code{bar} will be a @code{gdb.Value} object holding the
23534 value pointed to by @code{foo}.
23536 A similar function @code{Value.referenced_value} exists which also
23537 returns @code{gdb.Value} objects corresonding to the values pointed to
23538 by pointer values (and additionally, values referenced by reference
23539 values). However, the behavior of @code{Value.dereference}
23540 differs from @code{Value.referenced_value} by the fact that the
23541 behavior of @code{Value.dereference} is identical to applying the C
23542 unary operator @code{*} on a given value. For example, consider a
23543 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23547 typedef int *intptr;
23551 intptr &ptrref = ptr;
23554 Though @code{ptrref} is a reference value, one can apply the method
23555 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23556 to it and obtain a @code{gdb.Value} which is identical to that
23557 corresponding to @code{val}. However, if you apply the method
23558 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23559 object identical to that corresponding to @code{ptr}.
23562 py_ptrref = gdb.parse_and_eval ("ptrref")
23563 py_val = py_ptrref.dereference ()
23564 py_ptr = py_ptrref.referenced_value ()
23567 The @code{gdb.Value} object @code{py_val} is identical to that
23568 corresponding to @code{val}, and @code{py_ptr} is identical to that
23569 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23570 be applied whenever the C unary operator @code{*} can be applied
23571 to the corresponding C value. For those cases where applying both
23572 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23573 the results obtained need not be identical (as we have seen in the above
23574 example). The results are however identical when applied on
23575 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23576 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23579 @defun Value.referenced_value ()
23580 For pointer or reference data types, this method returns a new
23581 @code{gdb.Value} object corresponding to the value referenced by the
23582 pointer/reference value. For pointer data types,
23583 @code{Value.dereference} and @code{Value.referenced_value} produce
23584 identical results. The difference between these methods is that
23585 @code{Value.dereference} cannot get the values referenced by reference
23586 values. For example, consider a reference to an @code{int}, declared
23587 in your C@t{++} program as
23595 then applying @code{Value.dereference} to the @code{gdb.Value} object
23596 corresponding to @code{ref} will result in an error, while applying
23597 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23598 identical to that corresponding to @code{val}.
23601 py_ref = gdb.parse_and_eval ("ref")
23602 er_ref = py_ref.dereference () # Results in error
23603 py_val = py_ref.referenced_value () # Returns the referenced value
23606 The @code{gdb.Value} object @code{py_val} is identical to that
23607 corresponding to @code{val}.
23610 @defun Value.dynamic_cast (type)
23611 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23612 operator were used. Consult a C@t{++} reference for details.
23615 @defun Value.reinterpret_cast (type)
23616 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23617 operator were used. Consult a C@t{++} reference for details.
23620 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23621 If this @code{gdb.Value} represents a string, then this method
23622 converts the contents to a Python string. Otherwise, this method will
23623 throw an exception.
23625 Strings are recognized in a language-specific way; whether a given
23626 @code{gdb.Value} represents a string is determined by the current
23629 For C-like languages, a value is a string if it is a pointer to or an
23630 array of characters or ints. The string is assumed to be terminated
23631 by a zero of the appropriate width. However if the optional length
23632 argument is given, the string will be converted to that given length,
23633 ignoring any embedded zeros that the string may contain.
23635 If the optional @var{encoding} argument is given, it must be a string
23636 naming the encoding of the string in the @code{gdb.Value}, such as
23637 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23638 the same encodings as the corresponding argument to Python's
23639 @code{string.decode} method, and the Python codec machinery will be used
23640 to convert the string. If @var{encoding} is not given, or if
23641 @var{encoding} is the empty string, then either the @code{target-charset}
23642 (@pxref{Character Sets}) will be used, or a language-specific encoding
23643 will be used, if the current language is able to supply one.
23645 The optional @var{errors} argument is the same as the corresponding
23646 argument to Python's @code{string.decode} method.
23648 If the optional @var{length} argument is given, the string will be
23649 fetched and converted to the given length.
23652 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23653 If this @code{gdb.Value} represents a string, then this method
23654 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23655 In Python}). Otherwise, this method will throw an exception.
23657 If the optional @var{encoding} argument is given, it must be a string
23658 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23659 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23660 @var{encoding} argument is an encoding that @value{GDBN} does
23661 recognize, @value{GDBN} will raise an error.
23663 When a lazy string is printed, the @value{GDBN} encoding machinery is
23664 used to convert the string during printing. If the optional
23665 @var{encoding} argument is not provided, or is an empty string,
23666 @value{GDBN} will automatically select the encoding most suitable for
23667 the string type. For further information on encoding in @value{GDBN}
23668 please see @ref{Character Sets}.
23670 If the optional @var{length} argument is given, the string will be
23671 fetched and encoded to the length of characters specified. If
23672 the @var{length} argument is not provided, the string will be fetched
23673 and encoded until a null of appropriate width is found.
23676 @defun Value.fetch_lazy ()
23677 If the @code{gdb.Value} object is currently a lazy value
23678 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23679 fetched from the inferior. Any errors that occur in the process
23680 will produce a Python exception.
23682 If the @code{gdb.Value} object is not a lazy value, this method
23685 This method does not return a value.
23689 @node Types In Python
23690 @subsubsection Types In Python
23691 @cindex types in Python
23692 @cindex Python, working with types
23695 @value{GDBN} represents types from the inferior using the class
23698 The following type-related functions are available in the @code{gdb}
23701 @findex gdb.lookup_type
23702 @defun gdb.lookup_type (name @r{[}, block@r{]})
23703 This function looks up a type by name. @var{name} is the name of the
23704 type to look up. It must be a string.
23706 If @var{block} is given, then @var{name} is looked up in that scope.
23707 Otherwise, it is searched for globally.
23709 Ordinarily, this function will return an instance of @code{gdb.Type}.
23710 If the named type cannot be found, it will throw an exception.
23713 If the type is a structure or class type, or an enum type, the fields
23714 of that type can be accessed using the Python @dfn{dictionary syntax}.
23715 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23716 a structure type, you can access its @code{foo} field with:
23719 bar = some_type['foo']
23722 @code{bar} will be a @code{gdb.Field} object; see below under the
23723 description of the @code{Type.fields} method for a description of the
23724 @code{gdb.Field} class.
23726 An instance of @code{Type} has the following attributes:
23729 The type code for this type. The type code will be one of the
23730 @code{TYPE_CODE_} constants defined below.
23733 @defvar Type.sizeof
23734 The size of this type, in target @code{char} units. Usually, a
23735 target's @code{char} type will be an 8-bit byte. However, on some
23736 unusual platforms, this type may have a different size.
23740 The tag name for this type. The tag name is the name after
23741 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23742 languages have this concept. If this type has no tag name, then
23743 @code{None} is returned.
23746 The following methods are provided:
23748 @defun Type.fields ()
23749 For structure and union types, this method returns the fields. Range
23750 types have two fields, the minimum and maximum values. Enum types
23751 have one field per enum constant. Function and method types have one
23752 field per parameter. The base types of C@t{++} classes are also
23753 represented as fields. If the type has no fields, or does not fit
23754 into one of these categories, an empty sequence will be returned.
23756 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23759 This attribute is not available for @code{static} fields (as in
23760 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23761 position of the field. For @code{enum} fields, the value is the
23762 enumeration member's integer representation.
23765 The name of the field, or @code{None} for anonymous fields.
23768 This is @code{True} if the field is artificial, usually meaning that
23769 it was provided by the compiler and not the user. This attribute is
23770 always provided, and is @code{False} if the field is not artificial.
23772 @item is_base_class
23773 This is @code{True} if the field represents a base class of a C@t{++}
23774 structure. This attribute is always provided, and is @code{False}
23775 if the field is not a base class of the type that is the argument of
23776 @code{fields}, or if that type was not a C@t{++} class.
23779 If the field is packed, or is a bitfield, then this will have a
23780 non-zero value, which is the size of the field in bits. Otherwise,
23781 this will be zero; in this case the field's size is given by its type.
23784 The type of the field. This is usually an instance of @code{Type},
23785 but it can be @code{None} in some situations.
23789 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23790 Return a new @code{gdb.Type} object which represents an array of this
23791 type. If one argument is given, it is the inclusive upper bound of
23792 the array; in this case the lower bound is zero. If two arguments are
23793 given, the first argument is the lower bound of the array, and the
23794 second argument is the upper bound of the array. An array's length
23795 must not be negative, but the bounds can be.
23798 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23799 Return a new @code{gdb.Type} object which represents a vector of this
23800 type. If one argument is given, it is the inclusive upper bound of
23801 the vector; in this case the lower bound is zero. If two arguments are
23802 given, the first argument is the lower bound of the vector, and the
23803 second argument is the upper bound of the vector. A vector's length
23804 must not be negative, but the bounds can be.
23806 The difference between an @code{array} and a @code{vector} is that
23807 arrays behave like in C: when used in expressions they decay to a pointer
23808 to the first element whereas vectors are treated as first class values.
23811 @defun Type.const ()
23812 Return a new @code{gdb.Type} object which represents a
23813 @code{const}-qualified variant of this type.
23816 @defun Type.volatile ()
23817 Return a new @code{gdb.Type} object which represents a
23818 @code{volatile}-qualified variant of this type.
23821 @defun Type.unqualified ()
23822 Return a new @code{gdb.Type} object which represents an unqualified
23823 variant of this type. That is, the result is neither @code{const} nor
23827 @defun Type.range ()
23828 Return a Python @code{Tuple} object that contains two elements: the
23829 low bound of the argument type and the high bound of that type. If
23830 the type does not have a range, @value{GDBN} will raise a
23831 @code{gdb.error} exception (@pxref{Exception Handling}).
23834 @defun Type.reference ()
23835 Return a new @code{gdb.Type} object which represents a reference to this
23839 @defun Type.pointer ()
23840 Return a new @code{gdb.Type} object which represents a pointer to this
23844 @defun Type.strip_typedefs ()
23845 Return a new @code{gdb.Type} that represents the real type,
23846 after removing all layers of typedefs.
23849 @defun Type.target ()
23850 Return a new @code{gdb.Type} object which represents the target type
23853 For a pointer type, the target type is the type of the pointed-to
23854 object. For an array type (meaning C-like arrays), the target type is
23855 the type of the elements of the array. For a function or method type,
23856 the target type is the type of the return value. For a complex type,
23857 the target type is the type of the elements. For a typedef, the
23858 target type is the aliased type.
23860 If the type does not have a target, this method will throw an
23864 @defun Type.template_argument (n @r{[}, block@r{]})
23865 If this @code{gdb.Type} is an instantiation of a template, this will
23866 return a new @code{gdb.Type} which represents the type of the
23867 @var{n}th template argument.
23869 If this @code{gdb.Type} is not a template type, this will throw an
23870 exception. Ordinarily, only C@t{++} code will have template types.
23872 If @var{block} is given, then @var{name} is looked up in that scope.
23873 Otherwise, it is searched for globally.
23877 Each type has a code, which indicates what category this type falls
23878 into. The available type categories are represented by constants
23879 defined in the @code{gdb} module:
23882 @findex TYPE_CODE_PTR
23883 @findex gdb.TYPE_CODE_PTR
23884 @item gdb.TYPE_CODE_PTR
23885 The type is a pointer.
23887 @findex TYPE_CODE_ARRAY
23888 @findex gdb.TYPE_CODE_ARRAY
23889 @item gdb.TYPE_CODE_ARRAY
23890 The type is an array.
23892 @findex TYPE_CODE_STRUCT
23893 @findex gdb.TYPE_CODE_STRUCT
23894 @item gdb.TYPE_CODE_STRUCT
23895 The type is a structure.
23897 @findex TYPE_CODE_UNION
23898 @findex gdb.TYPE_CODE_UNION
23899 @item gdb.TYPE_CODE_UNION
23900 The type is a union.
23902 @findex TYPE_CODE_ENUM
23903 @findex gdb.TYPE_CODE_ENUM
23904 @item gdb.TYPE_CODE_ENUM
23905 The type is an enum.
23907 @findex TYPE_CODE_FLAGS
23908 @findex gdb.TYPE_CODE_FLAGS
23909 @item gdb.TYPE_CODE_FLAGS
23910 A bit flags type, used for things such as status registers.
23912 @findex TYPE_CODE_FUNC
23913 @findex gdb.TYPE_CODE_FUNC
23914 @item gdb.TYPE_CODE_FUNC
23915 The type is a function.
23917 @findex TYPE_CODE_INT
23918 @findex gdb.TYPE_CODE_INT
23919 @item gdb.TYPE_CODE_INT
23920 The type is an integer type.
23922 @findex TYPE_CODE_FLT
23923 @findex gdb.TYPE_CODE_FLT
23924 @item gdb.TYPE_CODE_FLT
23925 A floating point type.
23927 @findex TYPE_CODE_VOID
23928 @findex gdb.TYPE_CODE_VOID
23929 @item gdb.TYPE_CODE_VOID
23930 The special type @code{void}.
23932 @findex TYPE_CODE_SET
23933 @findex gdb.TYPE_CODE_SET
23934 @item gdb.TYPE_CODE_SET
23937 @findex TYPE_CODE_RANGE
23938 @findex gdb.TYPE_CODE_RANGE
23939 @item gdb.TYPE_CODE_RANGE
23940 A range type, that is, an integer type with bounds.
23942 @findex TYPE_CODE_STRING
23943 @findex gdb.TYPE_CODE_STRING
23944 @item gdb.TYPE_CODE_STRING
23945 A string type. Note that this is only used for certain languages with
23946 language-defined string types; C strings are not represented this way.
23948 @findex TYPE_CODE_BITSTRING
23949 @findex gdb.TYPE_CODE_BITSTRING
23950 @item gdb.TYPE_CODE_BITSTRING
23951 A string of bits. It is deprecated.
23953 @findex TYPE_CODE_ERROR
23954 @findex gdb.TYPE_CODE_ERROR
23955 @item gdb.TYPE_CODE_ERROR
23956 An unknown or erroneous type.
23958 @findex TYPE_CODE_METHOD
23959 @findex gdb.TYPE_CODE_METHOD
23960 @item gdb.TYPE_CODE_METHOD
23961 A method type, as found in C@t{++} or Java.
23963 @findex TYPE_CODE_METHODPTR
23964 @findex gdb.TYPE_CODE_METHODPTR
23965 @item gdb.TYPE_CODE_METHODPTR
23966 A pointer-to-member-function.
23968 @findex TYPE_CODE_MEMBERPTR
23969 @findex gdb.TYPE_CODE_MEMBERPTR
23970 @item gdb.TYPE_CODE_MEMBERPTR
23971 A pointer-to-member.
23973 @findex TYPE_CODE_REF
23974 @findex gdb.TYPE_CODE_REF
23975 @item gdb.TYPE_CODE_REF
23978 @findex TYPE_CODE_CHAR
23979 @findex gdb.TYPE_CODE_CHAR
23980 @item gdb.TYPE_CODE_CHAR
23983 @findex TYPE_CODE_BOOL
23984 @findex gdb.TYPE_CODE_BOOL
23985 @item gdb.TYPE_CODE_BOOL
23988 @findex TYPE_CODE_COMPLEX
23989 @findex gdb.TYPE_CODE_COMPLEX
23990 @item gdb.TYPE_CODE_COMPLEX
23991 A complex float type.
23993 @findex TYPE_CODE_TYPEDEF
23994 @findex gdb.TYPE_CODE_TYPEDEF
23995 @item gdb.TYPE_CODE_TYPEDEF
23996 A typedef to some other type.
23998 @findex TYPE_CODE_NAMESPACE
23999 @findex gdb.TYPE_CODE_NAMESPACE
24000 @item gdb.TYPE_CODE_NAMESPACE
24001 A C@t{++} namespace.
24003 @findex TYPE_CODE_DECFLOAT
24004 @findex gdb.TYPE_CODE_DECFLOAT
24005 @item gdb.TYPE_CODE_DECFLOAT
24006 A decimal floating point type.
24008 @findex TYPE_CODE_INTERNAL_FUNCTION
24009 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24010 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24011 A function internal to @value{GDBN}. This is the type used to represent
24012 convenience functions.
24015 Further support for types is provided in the @code{gdb.types}
24016 Python module (@pxref{gdb.types}).
24018 @node Pretty Printing API
24019 @subsubsection Pretty Printing API
24021 An example output is provided (@pxref{Pretty Printing}).
24023 A pretty-printer is just an object that holds a value and implements a
24024 specific interface, defined here.
24026 @defun pretty_printer.children (self)
24027 @value{GDBN} will call this method on a pretty-printer to compute the
24028 children of the pretty-printer's value.
24030 This method must return an object conforming to the Python iterator
24031 protocol. Each item returned by the iterator must be a tuple holding
24032 two elements. The first element is the ``name'' of the child; the
24033 second element is the child's value. The value can be any Python
24034 object which is convertible to a @value{GDBN} value.
24036 This method is optional. If it does not exist, @value{GDBN} will act
24037 as though the value has no children.
24040 @defun pretty_printer.display_hint (self)
24041 The CLI may call this method and use its result to change the
24042 formatting of a value. The result will also be supplied to an MI
24043 consumer as a @samp{displayhint} attribute of the variable being
24046 This method is optional. If it does exist, this method must return a
24049 Some display hints are predefined by @value{GDBN}:
24053 Indicate that the object being printed is ``array-like''. The CLI
24054 uses this to respect parameters such as @code{set print elements} and
24055 @code{set print array}.
24058 Indicate that the object being printed is ``map-like'', and that the
24059 children of this value can be assumed to alternate between keys and
24063 Indicate that the object being printed is ``string-like''. If the
24064 printer's @code{to_string} method returns a Python string of some
24065 kind, then @value{GDBN} will call its internal language-specific
24066 string-printing function to format the string. For the CLI this means
24067 adding quotation marks, possibly escaping some characters, respecting
24068 @code{set print elements}, and the like.
24072 @defun pretty_printer.to_string (self)
24073 @value{GDBN} will call this method to display the string
24074 representation of the value passed to the object's constructor.
24076 When printing from the CLI, if the @code{to_string} method exists,
24077 then @value{GDBN} will prepend its result to the values returned by
24078 @code{children}. Exactly how this formatting is done is dependent on
24079 the display hint, and may change as more hints are added. Also,
24080 depending on the print settings (@pxref{Print Settings}), the CLI may
24081 print just the result of @code{to_string} in a stack trace, omitting
24082 the result of @code{children}.
24084 If this method returns a string, it is printed verbatim.
24086 Otherwise, if this method returns an instance of @code{gdb.Value},
24087 then @value{GDBN} prints this value. This may result in a call to
24088 another pretty-printer.
24090 If instead the method returns a Python value which is convertible to a
24091 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24092 the resulting value. Again, this may result in a call to another
24093 pretty-printer. Python scalars (integers, floats, and booleans) and
24094 strings are convertible to @code{gdb.Value}; other types are not.
24096 Finally, if this method returns @code{None} then no further operations
24097 are peformed in this method and nothing is printed.
24099 If the result is not one of these types, an exception is raised.
24102 @value{GDBN} provides a function which can be used to look up the
24103 default pretty-printer for a @code{gdb.Value}:
24105 @findex gdb.default_visualizer
24106 @defun gdb.default_visualizer (value)
24107 This function takes a @code{gdb.Value} object as an argument. If a
24108 pretty-printer for this value exists, then it is returned. If no such
24109 printer exists, then this returns @code{None}.
24112 @node Selecting Pretty-Printers
24113 @subsubsection Selecting Pretty-Printers
24115 The Python list @code{gdb.pretty_printers} contains an array of
24116 functions or callable objects that have been registered via addition
24117 as a pretty-printer. Printers in this list are called @code{global}
24118 printers, they're available when debugging all inferiors.
24119 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24120 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24123 Each function on these lists is passed a single @code{gdb.Value}
24124 argument and should return a pretty-printer object conforming to the
24125 interface definition above (@pxref{Pretty Printing API}). If a function
24126 cannot create a pretty-printer for the value, it should return
24129 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24130 @code{gdb.Objfile} in the current program space and iteratively calls
24131 each enabled lookup routine in the list for that @code{gdb.Objfile}
24132 until it receives a pretty-printer object.
24133 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24134 searches the pretty-printer list of the current program space,
24135 calling each enabled function until an object is returned.
24136 After these lists have been exhausted, it tries the global
24137 @code{gdb.pretty_printers} list, again calling each enabled function until an
24138 object is returned.
24140 The order in which the objfiles are searched is not specified. For a
24141 given list, functions are always invoked from the head of the list,
24142 and iterated over sequentially until the end of the list, or a printer
24143 object is returned.
24145 For various reasons a pretty-printer may not work.
24146 For example, the underlying data structure may have changed and
24147 the pretty-printer is out of date.
24149 The consequences of a broken pretty-printer are severe enough that
24150 @value{GDBN} provides support for enabling and disabling individual
24151 printers. For example, if @code{print frame-arguments} is on,
24152 a backtrace can become highly illegible if any argument is printed
24153 with a broken printer.
24155 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24156 attribute to the registered function or callable object. If this attribute
24157 is present and its value is @code{False}, the printer is disabled, otherwise
24158 the printer is enabled.
24160 @node Writing a Pretty-Printer
24161 @subsubsection Writing a Pretty-Printer
24162 @cindex writing a pretty-printer
24164 A pretty-printer consists of two parts: a lookup function to detect
24165 if the type is supported, and the printer itself.
24167 Here is an example showing how a @code{std::string} printer might be
24168 written. @xref{Pretty Printing API}, for details on the API this class
24172 class StdStringPrinter(object):
24173 "Print a std::string"
24175 def __init__(self, val):
24178 def to_string(self):
24179 return self.val['_M_dataplus']['_M_p']
24181 def display_hint(self):
24185 And here is an example showing how a lookup function for the printer
24186 example above might be written.
24189 def str_lookup_function(val):
24190 lookup_tag = val.type.tag
24191 if lookup_tag == None:
24193 regex = re.compile("^std::basic_string<char,.*>$")
24194 if regex.match(lookup_tag):
24195 return StdStringPrinter(val)
24199 The example lookup function extracts the value's type, and attempts to
24200 match it to a type that it can pretty-print. If it is a type the
24201 printer can pretty-print, it will return a printer object. If not, it
24202 returns @code{None}.
24204 We recommend that you put your core pretty-printers into a Python
24205 package. If your pretty-printers are for use with a library, we
24206 further recommend embedding a version number into the package name.
24207 This practice will enable @value{GDBN} to load multiple versions of
24208 your pretty-printers at the same time, because they will have
24211 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24212 can be evaluated multiple times without changing its meaning. An
24213 ideal auto-load file will consist solely of @code{import}s of your
24214 printer modules, followed by a call to a register pretty-printers with
24215 the current objfile.
24217 Taken as a whole, this approach will scale nicely to multiple
24218 inferiors, each potentially using a different library version.
24219 Embedding a version number in the Python package name will ensure that
24220 @value{GDBN} is able to load both sets of printers simultaneously.
24221 Then, because the search for pretty-printers is done by objfile, and
24222 because your auto-loaded code took care to register your library's
24223 printers with a specific objfile, @value{GDBN} will find the correct
24224 printers for the specific version of the library used by each
24227 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24228 this code might appear in @code{gdb.libstdcxx.v6}:
24231 def register_printers(objfile):
24232 objfile.pretty_printers.append(str_lookup_function)
24236 And then the corresponding contents of the auto-load file would be:
24239 import gdb.libstdcxx.v6
24240 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24243 The previous example illustrates a basic pretty-printer.
24244 There are a few things that can be improved on.
24245 The printer doesn't have a name, making it hard to identify in a
24246 list of installed printers. The lookup function has a name, but
24247 lookup functions can have arbitrary, even identical, names.
24249 Second, the printer only handles one type, whereas a library typically has
24250 several types. One could install a lookup function for each desired type
24251 in the library, but one could also have a single lookup function recognize
24252 several types. The latter is the conventional way this is handled.
24253 If a pretty-printer can handle multiple data types, then its
24254 @dfn{subprinters} are the printers for the individual data types.
24256 The @code{gdb.printing} module provides a formal way of solving these
24257 problems (@pxref{gdb.printing}).
24258 Here is another example that handles multiple types.
24260 These are the types we are going to pretty-print:
24263 struct foo @{ int a, b; @};
24264 struct bar @{ struct foo x, y; @};
24267 Here are the printers:
24271 """Print a foo object."""
24273 def __init__(self, val):
24276 def to_string(self):
24277 return ("a=<" + str(self.val["a"]) +
24278 "> b=<" + str(self.val["b"]) + ">")
24281 """Print a bar object."""
24283 def __init__(self, val):
24286 def to_string(self):
24287 return ("x=<" + str(self.val["x"]) +
24288 "> y=<" + str(self.val["y"]) + ">")
24291 This example doesn't need a lookup function, that is handled by the
24292 @code{gdb.printing} module. Instead a function is provided to build up
24293 the object that handles the lookup.
24296 import gdb.printing
24298 def build_pretty_printer():
24299 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24301 pp.add_printer('foo', '^foo$', fooPrinter)
24302 pp.add_printer('bar', '^bar$', barPrinter)
24306 And here is the autoload support:
24309 import gdb.printing
24311 gdb.printing.register_pretty_printer(
24312 gdb.current_objfile(),
24313 my_library.build_pretty_printer())
24316 Finally, when this printer is loaded into @value{GDBN}, here is the
24317 corresponding output of @samp{info pretty-printer}:
24320 (gdb) info pretty-printer
24327 @node Type Printing API
24328 @subsubsection Type Printing API
24329 @cindex type printing API for Python
24331 @value{GDBN} provides a way for Python code to customize type display.
24332 This is mainly useful for substituting canonical typedef names for
24335 @cindex type printer
24336 A @dfn{type printer} is just a Python object conforming to a certain
24337 protocol. A simple base class implementing the protocol is provided;
24338 see @ref{gdb.types}. A type printer must supply at least:
24340 @defivar type_printer enabled
24341 A boolean which is True if the printer is enabled, and False
24342 otherwise. This is manipulated by the @code{enable type-printer}
24343 and @code{disable type-printer} commands.
24346 @defivar type_printer name
24347 The name of the type printer. This must be a string. This is used by
24348 the @code{enable type-printer} and @code{disable type-printer}
24352 @defmethod type_printer instantiate (self)
24353 This is called by @value{GDBN} at the start of type-printing. It is
24354 only called if the type printer is enabled. This method must return a
24355 new object that supplies a @code{recognize} method, as described below.
24359 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24360 will compute a list of type recognizers. This is done by iterating
24361 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24362 followed by the per-progspace type printers (@pxref{Progspaces In
24363 Python}), and finally the global type printers.
24365 @value{GDBN} will call the @code{instantiate} method of each enabled
24366 type printer. If this method returns @code{None}, then the result is
24367 ignored; otherwise, it is appended to the list of recognizers.
24369 Then, when @value{GDBN} is going to display a type name, it iterates
24370 over the list of recognizers. For each one, it calls the recognition
24371 function, stopping if the function returns a non-@code{None} value.
24372 The recognition function is defined as:
24374 @defmethod type_recognizer recognize (self, type)
24375 If @var{type} is not recognized, return @code{None}. Otherwise,
24376 return a string which is to be printed as the name of @var{type}.
24377 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24381 @value{GDBN} uses this two-pass approach so that type printers can
24382 efficiently cache information without holding on to it too long. For
24383 example, it can be convenient to look up type information in a type
24384 printer and hold it for a recognizer's lifetime; if a single pass were
24385 done then type printers would have to make use of the event system in
24386 order to avoid holding information that could become stale as the
24389 @node Inferiors In Python
24390 @subsubsection Inferiors In Python
24391 @cindex inferiors in Python
24393 @findex gdb.Inferior
24394 Programs which are being run under @value{GDBN} are called inferiors
24395 (@pxref{Inferiors and Programs}). Python scripts can access
24396 information about and manipulate inferiors controlled by @value{GDBN}
24397 via objects of the @code{gdb.Inferior} class.
24399 The following inferior-related functions are available in the @code{gdb}
24402 @defun gdb.inferiors ()
24403 Return a tuple containing all inferior objects.
24406 @defun gdb.selected_inferior ()
24407 Return an object representing the current inferior.
24410 A @code{gdb.Inferior} object has the following attributes:
24412 @defvar Inferior.num
24413 ID of inferior, as assigned by GDB.
24416 @defvar Inferior.pid
24417 Process ID of the inferior, as assigned by the underlying operating
24421 @defvar Inferior.was_attached
24422 Boolean signaling whether the inferior was created using `attach', or
24423 started by @value{GDBN} itself.
24426 A @code{gdb.Inferior} object has the following methods:
24428 @defun Inferior.is_valid ()
24429 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24430 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24431 if the inferior no longer exists within @value{GDBN}. All other
24432 @code{gdb.Inferior} methods will throw an exception if it is invalid
24433 at the time the method is called.
24436 @defun Inferior.threads ()
24437 This method returns a tuple holding all the threads which are valid
24438 when it is called. If there are no valid threads, the method will
24439 return an empty tuple.
24442 @findex Inferior.read_memory
24443 @defun Inferior.read_memory (address, length)
24444 Read @var{length} bytes of memory from the inferior, starting at
24445 @var{address}. Returns a buffer object, which behaves much like an array
24446 or a string. It can be modified and given to the
24447 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24448 value is a @code{memoryview} object.
24451 @findex Inferior.write_memory
24452 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24453 Write the contents of @var{buffer} to the inferior, starting at
24454 @var{address}. The @var{buffer} parameter must be a Python object
24455 which supports the buffer protocol, i.e., a string, an array or the
24456 object returned from @code{Inferior.read_memory}. If given, @var{length}
24457 determines the number of bytes from @var{buffer} to be written.
24460 @findex gdb.search_memory
24461 @defun Inferior.search_memory (address, length, pattern)
24462 Search a region of the inferior memory starting at @var{address} with
24463 the given @var{length} using the search pattern supplied in
24464 @var{pattern}. The @var{pattern} parameter must be a Python object
24465 which supports the buffer protocol, i.e., a string, an array or the
24466 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24467 containing the address where the pattern was found, or @code{None} if
24468 the pattern could not be found.
24471 @node Events In Python
24472 @subsubsection Events In Python
24473 @cindex inferior events in Python
24475 @value{GDBN} provides a general event facility so that Python code can be
24476 notified of various state changes, particularly changes that occur in
24479 An @dfn{event} is just an object that describes some state change. The
24480 type of the object and its attributes will vary depending on the details
24481 of the change. All the existing events are described below.
24483 In order to be notified of an event, you must register an event handler
24484 with an @dfn{event registry}. An event registry is an object in the
24485 @code{gdb.events} module which dispatches particular events. A registry
24486 provides methods to register and unregister event handlers:
24488 @defun EventRegistry.connect (object)
24489 Add the given callable @var{object} to the registry. This object will be
24490 called when an event corresponding to this registry occurs.
24493 @defun EventRegistry.disconnect (object)
24494 Remove the given @var{object} from the registry. Once removed, the object
24495 will no longer receive notifications of events.
24498 Here is an example:
24501 def exit_handler (event):
24502 print "event type: exit"
24503 print "exit code: %d" % (event.exit_code)
24505 gdb.events.exited.connect (exit_handler)
24508 In the above example we connect our handler @code{exit_handler} to the
24509 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24510 called when the inferior exits. The argument @dfn{event} in this example is
24511 of type @code{gdb.ExitedEvent}. As you can see in the example the
24512 @code{ExitedEvent} object has an attribute which indicates the exit code of
24515 The following is a listing of the event registries that are available and
24516 details of the events they emit:
24521 Emits @code{gdb.ThreadEvent}.
24523 Some events can be thread specific when @value{GDBN} is running in non-stop
24524 mode. When represented in Python, these events all extend
24525 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24526 events which are emitted by this or other modules might extend this event.
24527 Examples of these events are @code{gdb.BreakpointEvent} and
24528 @code{gdb.ContinueEvent}.
24530 @defvar ThreadEvent.inferior_thread
24531 In non-stop mode this attribute will be set to the specific thread which was
24532 involved in the emitted event. Otherwise, it will be set to @code{None}.
24535 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24537 This event indicates that the inferior has been continued after a stop. For
24538 inherited attribute refer to @code{gdb.ThreadEvent} above.
24540 @item events.exited
24541 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24542 @code{events.ExitedEvent} has two attributes:
24543 @defvar ExitedEvent.exit_code
24544 An integer representing the exit code, if available, which the inferior
24545 has returned. (The exit code could be unavailable if, for example,
24546 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24547 the attribute does not exist.
24549 @defvar ExitedEvent inferior
24550 A reference to the inferior which triggered the @code{exited} event.
24554 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24556 Indicates that the inferior has stopped. All events emitted by this registry
24557 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24558 will indicate the stopped thread when @value{GDBN} is running in non-stop
24559 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24561 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24563 This event indicates that the inferior or one of its threads has received as
24564 signal. @code{gdb.SignalEvent} has the following attributes:
24566 @defvar SignalEvent.stop_signal
24567 A string representing the signal received by the inferior. A list of possible
24568 signal values can be obtained by running the command @code{info signals} in
24569 the @value{GDBN} command prompt.
24572 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24574 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24575 been hit, and has the following attributes:
24577 @defvar BreakpointEvent.breakpoints
24578 A sequence containing references to all the breakpoints (type
24579 @code{gdb.Breakpoint}) that were hit.
24580 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24582 @defvar BreakpointEvent.breakpoint
24583 A reference to the first breakpoint that was hit.
24584 This function is maintained for backward compatibility and is now deprecated
24585 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24588 @item events.new_objfile
24589 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24590 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24592 @defvar NewObjFileEvent.new_objfile
24593 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24594 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24599 @node Threads In Python
24600 @subsubsection Threads In Python
24601 @cindex threads in python
24603 @findex gdb.InferiorThread
24604 Python scripts can access information about, and manipulate inferior threads
24605 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24607 The following thread-related functions are available in the @code{gdb}
24610 @findex gdb.selected_thread
24611 @defun gdb.selected_thread ()
24612 This function returns the thread object for the selected thread. If there
24613 is no selected thread, this will return @code{None}.
24616 A @code{gdb.InferiorThread} object has the following attributes:
24618 @defvar InferiorThread.name
24619 The name of the thread. If the user specified a name using
24620 @code{thread name}, then this returns that name. Otherwise, if an
24621 OS-supplied name is available, then it is returned. Otherwise, this
24622 returns @code{None}.
24624 This attribute can be assigned to. The new value must be a string
24625 object, which sets the new name, or @code{None}, which removes any
24626 user-specified thread name.
24629 @defvar InferiorThread.num
24630 ID of the thread, as assigned by GDB.
24633 @defvar InferiorThread.ptid
24634 ID of the thread, as assigned by the operating system. This attribute is a
24635 tuple containing three integers. The first is the Process ID (PID); the second
24636 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24637 Either the LWPID or TID may be 0, which indicates that the operating system
24638 does not use that identifier.
24641 A @code{gdb.InferiorThread} object has the following methods:
24643 @defun InferiorThread.is_valid ()
24644 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24645 @code{False} if not. A @code{gdb.InferiorThread} object will become
24646 invalid if the thread exits, or the inferior that the thread belongs
24647 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24648 exception if it is invalid at the time the method is called.
24651 @defun InferiorThread.switch ()
24652 This changes @value{GDBN}'s currently selected thread to the one represented
24656 @defun InferiorThread.is_stopped ()
24657 Return a Boolean indicating whether the thread is stopped.
24660 @defun InferiorThread.is_running ()
24661 Return a Boolean indicating whether the thread is running.
24664 @defun InferiorThread.is_exited ()
24665 Return a Boolean indicating whether the thread is exited.
24668 @node Commands In Python
24669 @subsubsection Commands In Python
24671 @cindex commands in python
24672 @cindex python commands
24673 You can implement new @value{GDBN} CLI commands in Python. A CLI
24674 command is implemented using an instance of the @code{gdb.Command}
24675 class, most commonly using a subclass.
24677 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24678 The object initializer for @code{Command} registers the new command
24679 with @value{GDBN}. This initializer is normally invoked from the
24680 subclass' own @code{__init__} method.
24682 @var{name} is the name of the command. If @var{name} consists of
24683 multiple words, then the initial words are looked for as prefix
24684 commands. In this case, if one of the prefix commands does not exist,
24685 an exception is raised.
24687 There is no support for multi-line commands.
24689 @var{command_class} should be one of the @samp{COMMAND_} constants
24690 defined below. This argument tells @value{GDBN} how to categorize the
24691 new command in the help system.
24693 @var{completer_class} is an optional argument. If given, it should be
24694 one of the @samp{COMPLETE_} constants defined below. This argument
24695 tells @value{GDBN} how to perform completion for this command. If not
24696 given, @value{GDBN} will attempt to complete using the object's
24697 @code{complete} method (see below); if no such method is found, an
24698 error will occur when completion is attempted.
24700 @var{prefix} is an optional argument. If @code{True}, then the new
24701 command is a prefix command; sub-commands of this command may be
24704 The help text for the new command is taken from the Python
24705 documentation string for the command's class, if there is one. If no
24706 documentation string is provided, the default value ``This command is
24707 not documented.'' is used.
24710 @cindex don't repeat Python command
24711 @defun Command.dont_repeat ()
24712 By default, a @value{GDBN} command is repeated when the user enters a
24713 blank line at the command prompt. A command can suppress this
24714 behavior by invoking the @code{dont_repeat} method. This is similar
24715 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24718 @defun Command.invoke (argument, from_tty)
24719 This method is called by @value{GDBN} when this command is invoked.
24721 @var{argument} is a string. It is the argument to the command, after
24722 leading and trailing whitespace has been stripped.
24724 @var{from_tty} is a boolean argument. When true, this means that the
24725 command was entered by the user at the terminal; when false it means
24726 that the command came from elsewhere.
24728 If this method throws an exception, it is turned into a @value{GDBN}
24729 @code{error} call. Otherwise, the return value is ignored.
24731 @findex gdb.string_to_argv
24732 To break @var{argument} up into an argv-like string use
24733 @code{gdb.string_to_argv}. This function behaves identically to
24734 @value{GDBN}'s internal argument lexer @code{buildargv}.
24735 It is recommended to use this for consistency.
24736 Arguments are separated by spaces and may be quoted.
24740 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24741 ['1', '2 "3', '4 "5', "6 '7"]
24746 @cindex completion of Python commands
24747 @defun Command.complete (text, word)
24748 This method is called by @value{GDBN} when the user attempts
24749 completion on this command. All forms of completion are handled by
24750 this method, that is, the @key{TAB} and @key{M-?} key bindings
24751 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24754 The arguments @var{text} and @var{word} are both strings. @var{text}
24755 holds the complete command line up to the cursor's location.
24756 @var{word} holds the last word of the command line; this is computed
24757 using a word-breaking heuristic.
24759 The @code{complete} method can return several values:
24762 If the return value is a sequence, the contents of the sequence are
24763 used as the completions. It is up to @code{complete} to ensure that the
24764 contents actually do complete the word. A zero-length sequence is
24765 allowed, it means that there were no completions available. Only
24766 string elements of the sequence are used; other elements in the
24767 sequence are ignored.
24770 If the return value is one of the @samp{COMPLETE_} constants defined
24771 below, then the corresponding @value{GDBN}-internal completion
24772 function is invoked, and its result is used.
24775 All other results are treated as though there were no available
24780 When a new command is registered, it must be declared as a member of
24781 some general class of commands. This is used to classify top-level
24782 commands in the on-line help system; note that prefix commands are not
24783 listed under their own category but rather that of their top-level
24784 command. The available classifications are represented by constants
24785 defined in the @code{gdb} module:
24788 @findex COMMAND_NONE
24789 @findex gdb.COMMAND_NONE
24790 @item gdb.COMMAND_NONE
24791 The command does not belong to any particular class. A command in
24792 this category will not be displayed in any of the help categories.
24794 @findex COMMAND_RUNNING
24795 @findex gdb.COMMAND_RUNNING
24796 @item gdb.COMMAND_RUNNING
24797 The command is related to running the inferior. For example,
24798 @code{start}, @code{step}, and @code{continue} are in this category.
24799 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24800 commands in this category.
24802 @findex COMMAND_DATA
24803 @findex gdb.COMMAND_DATA
24804 @item gdb.COMMAND_DATA
24805 The command is related to data or variables. For example,
24806 @code{call}, @code{find}, and @code{print} are in this category. Type
24807 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24810 @findex COMMAND_STACK
24811 @findex gdb.COMMAND_STACK
24812 @item gdb.COMMAND_STACK
24813 The command has to do with manipulation of the stack. For example,
24814 @code{backtrace}, @code{frame}, and @code{return} are in this
24815 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24816 list of commands in this category.
24818 @findex COMMAND_FILES
24819 @findex gdb.COMMAND_FILES
24820 @item gdb.COMMAND_FILES
24821 This class is used for file-related commands. For example,
24822 @code{file}, @code{list} and @code{section} are in this category.
24823 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24824 commands in this category.
24826 @findex COMMAND_SUPPORT
24827 @findex gdb.COMMAND_SUPPORT
24828 @item gdb.COMMAND_SUPPORT
24829 This should be used for ``support facilities'', generally meaning
24830 things that are useful to the user when interacting with @value{GDBN},
24831 but not related to the state of the inferior. For example,
24832 @code{help}, @code{make}, and @code{shell} are in this category. Type
24833 @kbd{help support} at the @value{GDBN} prompt to see a list of
24834 commands in this category.
24836 @findex COMMAND_STATUS
24837 @findex gdb.COMMAND_STATUS
24838 @item gdb.COMMAND_STATUS
24839 The command is an @samp{info}-related command, that is, related to the
24840 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24841 and @code{show} are in this category. Type @kbd{help status} at the
24842 @value{GDBN} prompt to see a list of commands in this category.
24844 @findex COMMAND_BREAKPOINTS
24845 @findex gdb.COMMAND_BREAKPOINTS
24846 @item gdb.COMMAND_BREAKPOINTS
24847 The command has to do with breakpoints. For example, @code{break},
24848 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24849 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24852 @findex COMMAND_TRACEPOINTS
24853 @findex gdb.COMMAND_TRACEPOINTS
24854 @item gdb.COMMAND_TRACEPOINTS
24855 The command has to do with tracepoints. For example, @code{trace},
24856 @code{actions}, and @code{tfind} are in this category. Type
24857 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24858 commands in this category.
24860 @findex COMMAND_USER
24861 @findex gdb.COMMAND_USER
24862 @item gdb.COMMAND_USER
24863 The command is a general purpose command for the user, and typically
24864 does not fit in one of the other categories.
24865 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24866 a list of commands in this category, as well as the list of gdb macros
24867 (@pxref{Sequences}).
24869 @findex COMMAND_OBSCURE
24870 @findex gdb.COMMAND_OBSCURE
24871 @item gdb.COMMAND_OBSCURE
24872 The command is only used in unusual circumstances, or is not of
24873 general interest to users. For example, @code{checkpoint},
24874 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24875 obscure} at the @value{GDBN} prompt to see a list of commands in this
24878 @findex COMMAND_MAINTENANCE
24879 @findex gdb.COMMAND_MAINTENANCE
24880 @item gdb.COMMAND_MAINTENANCE
24881 The command is only useful to @value{GDBN} maintainers. The
24882 @code{maintenance} and @code{flushregs} commands are in this category.
24883 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24884 commands in this category.
24887 A new command can use a predefined completion function, either by
24888 specifying it via an argument at initialization, or by returning it
24889 from the @code{complete} method. These predefined completion
24890 constants are all defined in the @code{gdb} module:
24893 @findex COMPLETE_NONE
24894 @findex gdb.COMPLETE_NONE
24895 @item gdb.COMPLETE_NONE
24896 This constant means that no completion should be done.
24898 @findex COMPLETE_FILENAME
24899 @findex gdb.COMPLETE_FILENAME
24900 @item gdb.COMPLETE_FILENAME
24901 This constant means that filename completion should be performed.
24903 @findex COMPLETE_LOCATION
24904 @findex gdb.COMPLETE_LOCATION
24905 @item gdb.COMPLETE_LOCATION
24906 This constant means that location completion should be done.
24907 @xref{Specify Location}.
24909 @findex COMPLETE_COMMAND
24910 @findex gdb.COMPLETE_COMMAND
24911 @item gdb.COMPLETE_COMMAND
24912 This constant means that completion should examine @value{GDBN}
24915 @findex COMPLETE_SYMBOL
24916 @findex gdb.COMPLETE_SYMBOL
24917 @item gdb.COMPLETE_SYMBOL
24918 This constant means that completion should be done using symbol names
24922 The following code snippet shows how a trivial CLI command can be
24923 implemented in Python:
24926 class HelloWorld (gdb.Command):
24927 """Greet the whole world."""
24929 def __init__ (self):
24930 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24932 def invoke (self, arg, from_tty):
24933 print "Hello, World!"
24938 The last line instantiates the class, and is necessary to trigger the
24939 registration of the command with @value{GDBN}. Depending on how the
24940 Python code is read into @value{GDBN}, you may need to import the
24941 @code{gdb} module explicitly.
24943 @node Parameters In Python
24944 @subsubsection Parameters In Python
24946 @cindex parameters in python
24947 @cindex python parameters
24948 @tindex gdb.Parameter
24950 You can implement new @value{GDBN} parameters using Python. A new
24951 parameter is implemented as an instance of the @code{gdb.Parameter}
24954 Parameters are exposed to the user via the @code{set} and
24955 @code{show} commands. @xref{Help}.
24957 There are many parameters that already exist and can be set in
24958 @value{GDBN}. Two examples are: @code{set follow fork} and
24959 @code{set charset}. Setting these parameters influences certain
24960 behavior in @value{GDBN}. Similarly, you can define parameters that
24961 can be used to influence behavior in custom Python scripts and commands.
24963 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24964 The object initializer for @code{Parameter} registers the new
24965 parameter with @value{GDBN}. This initializer is normally invoked
24966 from the subclass' own @code{__init__} method.
24968 @var{name} is the name of the new parameter. If @var{name} consists
24969 of multiple words, then the initial words are looked for as prefix
24970 parameters. An example of this can be illustrated with the
24971 @code{set print} set of parameters. If @var{name} is
24972 @code{print foo}, then @code{print} will be searched as the prefix
24973 parameter. In this case the parameter can subsequently be accessed in
24974 @value{GDBN} as @code{set print foo}.
24976 If @var{name} consists of multiple words, and no prefix parameter group
24977 can be found, an exception is raised.
24979 @var{command-class} should be one of the @samp{COMMAND_} constants
24980 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24981 categorize the new parameter in the help system.
24983 @var{parameter-class} should be one of the @samp{PARAM_} constants
24984 defined below. This argument tells @value{GDBN} the type of the new
24985 parameter; this information is used for input validation and
24988 If @var{parameter-class} is @code{PARAM_ENUM}, then
24989 @var{enum-sequence} must be a sequence of strings. These strings
24990 represent the possible values for the parameter.
24992 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24993 of a fourth argument will cause an exception to be thrown.
24995 The help text for the new parameter is taken from the Python
24996 documentation string for the parameter's class, if there is one. If
24997 there is no documentation string, a default value is used.
25000 @defvar Parameter.set_doc
25001 If this attribute exists, and is a string, then its value is used as
25002 the help text for this parameter's @code{set} command. The value is
25003 examined when @code{Parameter.__init__} is invoked; subsequent changes
25007 @defvar Parameter.show_doc
25008 If this attribute exists, and is a string, then its value is used as
25009 the help text for this parameter's @code{show} command. The value is
25010 examined when @code{Parameter.__init__} is invoked; subsequent changes
25014 @defvar Parameter.value
25015 The @code{value} attribute holds the underlying value of the
25016 parameter. It can be read and assigned to just as any other
25017 attribute. @value{GDBN} does validation when assignments are made.
25020 There are two methods that should be implemented in any
25021 @code{Parameter} class. These are:
25023 @defun Parameter.get_set_string (self)
25024 @value{GDBN} will call this method when a @var{parameter}'s value has
25025 been changed via the @code{set} API (for example, @kbd{set foo off}).
25026 The @code{value} attribute has already been populated with the new
25027 value and may be used in output. This method must return a string.
25030 @defun Parameter.get_show_string (self, svalue)
25031 @value{GDBN} will call this method when a @var{parameter}'s
25032 @code{show} API has been invoked (for example, @kbd{show foo}). The
25033 argument @code{svalue} receives the string representation of the
25034 current value. This method must return a string.
25037 When a new parameter is defined, its type must be specified. The
25038 available types are represented by constants defined in the @code{gdb}
25042 @findex PARAM_BOOLEAN
25043 @findex gdb.PARAM_BOOLEAN
25044 @item gdb.PARAM_BOOLEAN
25045 The value is a plain boolean. The Python boolean values, @code{True}
25046 and @code{False} are the only valid values.
25048 @findex PARAM_AUTO_BOOLEAN
25049 @findex gdb.PARAM_AUTO_BOOLEAN
25050 @item gdb.PARAM_AUTO_BOOLEAN
25051 The value has three possible states: true, false, and @samp{auto}. In
25052 Python, true and false are represented using boolean constants, and
25053 @samp{auto} is represented using @code{None}.
25055 @findex PARAM_UINTEGER
25056 @findex gdb.PARAM_UINTEGER
25057 @item gdb.PARAM_UINTEGER
25058 The value is an unsigned integer. The value of 0 should be
25059 interpreted to mean ``unlimited''.
25061 @findex PARAM_INTEGER
25062 @findex gdb.PARAM_INTEGER
25063 @item gdb.PARAM_INTEGER
25064 The value is a signed integer. The value of 0 should be interpreted
25065 to mean ``unlimited''.
25067 @findex PARAM_STRING
25068 @findex gdb.PARAM_STRING
25069 @item gdb.PARAM_STRING
25070 The value is a string. When the user modifies the string, any escape
25071 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25072 translated into corresponding characters and encoded into the current
25075 @findex PARAM_STRING_NOESCAPE
25076 @findex gdb.PARAM_STRING_NOESCAPE
25077 @item gdb.PARAM_STRING_NOESCAPE
25078 The value is a string. When the user modifies the string, escapes are
25079 passed through untranslated.
25081 @findex PARAM_OPTIONAL_FILENAME
25082 @findex gdb.PARAM_OPTIONAL_FILENAME
25083 @item gdb.PARAM_OPTIONAL_FILENAME
25084 The value is a either a filename (a string), or @code{None}.
25086 @findex PARAM_FILENAME
25087 @findex gdb.PARAM_FILENAME
25088 @item gdb.PARAM_FILENAME
25089 The value is a filename. This is just like
25090 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25092 @findex PARAM_ZINTEGER
25093 @findex gdb.PARAM_ZINTEGER
25094 @item gdb.PARAM_ZINTEGER
25095 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25096 is interpreted as itself.
25099 @findex gdb.PARAM_ENUM
25100 @item gdb.PARAM_ENUM
25101 The value is a string, which must be one of a collection string
25102 constants provided when the parameter is created.
25105 @node Functions In Python
25106 @subsubsection Writing new convenience functions
25108 @cindex writing convenience functions
25109 @cindex convenience functions in python
25110 @cindex python convenience functions
25111 @tindex gdb.Function
25113 You can implement new convenience functions (@pxref{Convenience Vars})
25114 in Python. A convenience function is an instance of a subclass of the
25115 class @code{gdb.Function}.
25117 @defun Function.__init__ (name)
25118 The initializer for @code{Function} registers the new function with
25119 @value{GDBN}. The argument @var{name} is the name of the function,
25120 a string. The function will be visible to the user as a convenience
25121 variable of type @code{internal function}, whose name is the same as
25122 the given @var{name}.
25124 The documentation for the new function is taken from the documentation
25125 string for the new class.
25128 @defun Function.invoke (@var{*args})
25129 When a convenience function is evaluated, its arguments are converted
25130 to instances of @code{gdb.Value}, and then the function's
25131 @code{invoke} method is called. Note that @value{GDBN} does not
25132 predetermine the arity of convenience functions. Instead, all
25133 available arguments are passed to @code{invoke}, following the
25134 standard Python calling convention. In particular, a convenience
25135 function can have default values for parameters without ill effect.
25137 The return value of this method is used as its value in the enclosing
25138 expression. If an ordinary Python value is returned, it is converted
25139 to a @code{gdb.Value} following the usual rules.
25142 The following code snippet shows how a trivial convenience function can
25143 be implemented in Python:
25146 class Greet (gdb.Function):
25147 """Return string to greet someone.
25148 Takes a name as argument."""
25150 def __init__ (self):
25151 super (Greet, self).__init__ ("greet")
25153 def invoke (self, name):
25154 return "Hello, %s!" % name.string ()
25159 The last line instantiates the class, and is necessary to trigger the
25160 registration of the function with @value{GDBN}. Depending on how the
25161 Python code is read into @value{GDBN}, you may need to import the
25162 @code{gdb} module explicitly.
25164 Now you can use the function in an expression:
25167 (gdb) print $greet("Bob")
25171 @node Progspaces In Python
25172 @subsubsection Program Spaces In Python
25174 @cindex progspaces in python
25175 @tindex gdb.Progspace
25177 A program space, or @dfn{progspace}, represents a symbolic view
25178 of an address space.
25179 It consists of all of the objfiles of the program.
25180 @xref{Objfiles In Python}.
25181 @xref{Inferiors and Programs, program spaces}, for more details
25182 about program spaces.
25184 The following progspace-related functions are available in the
25187 @findex gdb.current_progspace
25188 @defun gdb.current_progspace ()
25189 This function returns the program space of the currently selected inferior.
25190 @xref{Inferiors and Programs}.
25193 @findex gdb.progspaces
25194 @defun gdb.progspaces ()
25195 Return a sequence of all the progspaces currently known to @value{GDBN}.
25198 Each progspace is represented by an instance of the @code{gdb.Progspace}
25201 @defvar Progspace.filename
25202 The file name of the progspace as a string.
25205 @defvar Progspace.pretty_printers
25206 The @code{pretty_printers} attribute is a list of functions. It is
25207 used to look up pretty-printers. A @code{Value} is passed to each
25208 function in order; if the function returns @code{None}, then the
25209 search continues. Otherwise, the return value should be an object
25210 which is used to format the value. @xref{Pretty Printing API}, for more
25214 @defvar Progspace.type_printers
25215 The @code{type_printers} attribute is a list of type printer objects.
25216 @xref{Type Printing API}, for more information.
25219 @node Objfiles In Python
25220 @subsubsection Objfiles In Python
25222 @cindex objfiles in python
25223 @tindex gdb.Objfile
25225 @value{GDBN} loads symbols for an inferior from various
25226 symbol-containing files (@pxref{Files}). These include the primary
25227 executable file, any shared libraries used by the inferior, and any
25228 separate debug info files (@pxref{Separate Debug Files}).
25229 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25231 The following objfile-related functions are available in the
25234 @findex gdb.current_objfile
25235 @defun gdb.current_objfile ()
25236 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25237 sets the ``current objfile'' to the corresponding objfile. This
25238 function returns the current objfile. If there is no current objfile,
25239 this function returns @code{None}.
25242 @findex gdb.objfiles
25243 @defun gdb.objfiles ()
25244 Return a sequence of all the objfiles current known to @value{GDBN}.
25245 @xref{Objfiles In Python}.
25248 Each objfile is represented by an instance of the @code{gdb.Objfile}
25251 @defvar Objfile.filename
25252 The file name of the objfile as a string.
25255 @defvar Objfile.pretty_printers
25256 The @code{pretty_printers} attribute is a list of functions. It is
25257 used to look up pretty-printers. A @code{Value} is passed to each
25258 function in order; if the function returns @code{None}, then the
25259 search continues. Otherwise, the return value should be an object
25260 which is used to format the value. @xref{Pretty Printing API}, for more
25264 @defvar Objfile.type_printers
25265 The @code{type_printers} attribute is a list of type printer objects.
25266 @xref{Type Printing API}, for more information.
25269 A @code{gdb.Objfile} object has the following methods:
25271 @defun Objfile.is_valid ()
25272 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25273 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25274 if the object file it refers to is not loaded in @value{GDBN} any
25275 longer. All other @code{gdb.Objfile} methods will throw an exception
25276 if it is invalid at the time the method is called.
25279 @node Frames In Python
25280 @subsubsection Accessing inferior stack frames from Python.
25282 @cindex frames in python
25283 When the debugged program stops, @value{GDBN} is able to analyze its call
25284 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25285 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25286 while its corresponding frame exists in the inferior's stack. If you try
25287 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25288 exception (@pxref{Exception Handling}).
25290 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25294 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25298 The following frame-related functions are available in the @code{gdb} module:
25300 @findex gdb.selected_frame
25301 @defun gdb.selected_frame ()
25302 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25305 @findex gdb.newest_frame
25306 @defun gdb.newest_frame ()
25307 Return the newest frame object for the selected thread.
25310 @defun gdb.frame_stop_reason_string (reason)
25311 Return a string explaining the reason why @value{GDBN} stopped unwinding
25312 frames, as expressed by the given @var{reason} code (an integer, see the
25313 @code{unwind_stop_reason} method further down in this section).
25316 A @code{gdb.Frame} object has the following methods:
25318 @defun Frame.is_valid ()
25319 Returns true if the @code{gdb.Frame} object is valid, false if not.
25320 A frame object can become invalid if the frame it refers to doesn't
25321 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25322 an exception if it is invalid at the time the method is called.
25325 @defun Frame.name ()
25326 Returns the function name of the frame, or @code{None} if it can't be
25330 @defun Frame.architecture ()
25331 Returns the @code{gdb.Architecture} object corresponding to the frame's
25332 architecture. @xref{Architectures In Python}.
25335 @defun Frame.type ()
25336 Returns the type of the frame. The value can be one of:
25338 @item gdb.NORMAL_FRAME
25339 An ordinary stack frame.
25341 @item gdb.DUMMY_FRAME
25342 A fake stack frame that was created by @value{GDBN} when performing an
25343 inferior function call.
25345 @item gdb.INLINE_FRAME
25346 A frame representing an inlined function. The function was inlined
25347 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25349 @item gdb.TAILCALL_FRAME
25350 A frame representing a tail call. @xref{Tail Call Frames}.
25352 @item gdb.SIGTRAMP_FRAME
25353 A signal trampoline frame. This is the frame created by the OS when
25354 it calls into a signal handler.
25356 @item gdb.ARCH_FRAME
25357 A fake stack frame representing a cross-architecture call.
25359 @item gdb.SENTINEL_FRAME
25360 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25365 @defun Frame.unwind_stop_reason ()
25366 Return an integer representing the reason why it's not possible to find
25367 more frames toward the outermost frame. Use
25368 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25369 function to a string. The value can be one of:
25372 @item gdb.FRAME_UNWIND_NO_REASON
25373 No particular reason (older frames should be available).
25375 @item gdb.FRAME_UNWIND_NULL_ID
25376 The previous frame's analyzer returns an invalid result.
25378 @item gdb.FRAME_UNWIND_OUTERMOST
25379 This frame is the outermost.
25381 @item gdb.FRAME_UNWIND_UNAVAILABLE
25382 Cannot unwind further, because that would require knowing the
25383 values of registers or memory that have not been collected.
25385 @item gdb.FRAME_UNWIND_INNER_ID
25386 This frame ID looks like it ought to belong to a NEXT frame,
25387 but we got it for a PREV frame. Normally, this is a sign of
25388 unwinder failure. It could also indicate stack corruption.
25390 @item gdb.FRAME_UNWIND_SAME_ID
25391 This frame has the same ID as the previous one. That means
25392 that unwinding further would almost certainly give us another
25393 frame with exactly the same ID, so break the chain. Normally,
25394 this is a sign of unwinder failure. It could also indicate
25397 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25398 The frame unwinder did not find any saved PC, but we needed
25399 one to unwind further.
25401 @item gdb.FRAME_UNWIND_FIRST_ERROR
25402 Any stop reason greater or equal to this value indicates some kind
25403 of error. This special value facilitates writing code that tests
25404 for errors in unwinding in a way that will work correctly even if
25405 the list of the other values is modified in future @value{GDBN}
25406 versions. Using it, you could write:
25408 reason = gdb.selected_frame().unwind_stop_reason ()
25409 reason_str = gdb.frame_stop_reason_string (reason)
25410 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25411 print "An error occured: %s" % reason_str
25418 Returns the frame's resume address.
25421 @defun Frame.block ()
25422 Return the frame's code block. @xref{Blocks In Python}.
25425 @defun Frame.function ()
25426 Return the symbol for the function corresponding to this frame.
25427 @xref{Symbols In Python}.
25430 @defun Frame.older ()
25431 Return the frame that called this frame.
25434 @defun Frame.newer ()
25435 Return the frame called by this frame.
25438 @defun Frame.find_sal ()
25439 Return the frame's symtab and line object.
25440 @xref{Symbol Tables In Python}.
25443 @defun Frame.read_var (variable @r{[}, block@r{]})
25444 Return the value of @var{variable} in this frame. If the optional
25445 argument @var{block} is provided, search for the variable from that
25446 block; otherwise start at the frame's current block (which is
25447 determined by the frame's current program counter). @var{variable}
25448 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25449 @code{gdb.Block} object.
25452 @defun Frame.select ()
25453 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25457 @node Blocks In Python
25458 @subsubsection Accessing frame blocks from Python.
25460 @cindex blocks in python
25463 Within each frame, @value{GDBN} maintains information on each block
25464 stored in that frame. These blocks are organized hierarchically, and
25465 are represented individually in Python as a @code{gdb.Block}.
25466 Please see @ref{Frames In Python}, for a more in-depth discussion on
25467 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25468 detailed technical information on @value{GDBN}'s book-keeping of the
25471 A @code{gdb.Block} is iterable. The iterator returns the symbols
25472 (@pxref{Symbols In Python}) local to the block. Python programs
25473 should not assume that a specific block object will always contain a
25474 given symbol, since changes in @value{GDBN} features and
25475 infrastructure may cause symbols move across blocks in a symbol
25478 The following block-related functions are available in the @code{gdb}
25481 @findex gdb.block_for_pc
25482 @defun gdb.block_for_pc (pc)
25483 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25484 block cannot be found for the @var{pc} value specified, the function
25485 will return @code{None}.
25488 A @code{gdb.Block} object has the following methods:
25490 @defun Block.is_valid ()
25491 Returns @code{True} if the @code{gdb.Block} object is valid,
25492 @code{False} if not. A block object can become invalid if the block it
25493 refers to doesn't exist anymore in the inferior. All other
25494 @code{gdb.Block} methods will throw an exception if it is invalid at
25495 the time the method is called. The block's validity is also checked
25496 during iteration over symbols of the block.
25499 A @code{gdb.Block} object has the following attributes:
25501 @defvar Block.start
25502 The start address of the block. This attribute is not writable.
25506 The end address of the block. This attribute is not writable.
25509 @defvar Block.function
25510 The name of the block represented as a @code{gdb.Symbol}. If the
25511 block is not named, then this attribute holds @code{None}. This
25512 attribute is not writable.
25515 @defvar Block.superblock
25516 The block containing this block. If this parent block does not exist,
25517 this attribute holds @code{None}. This attribute is not writable.
25520 @defvar Block.global_block
25521 The global block associated with this block. This attribute is not
25525 @defvar Block.static_block
25526 The static block associated with this block. This attribute is not
25530 @defvar Block.is_global
25531 @code{True} if the @code{gdb.Block} object is a global block,
25532 @code{False} if not. This attribute is not
25536 @defvar Block.is_static
25537 @code{True} if the @code{gdb.Block} object is a static block,
25538 @code{False} if not. This attribute is not writable.
25541 @node Symbols In Python
25542 @subsubsection Python representation of Symbols.
25544 @cindex symbols in python
25547 @value{GDBN} represents every variable, function and type as an
25548 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25549 Similarly, Python represents these symbols in @value{GDBN} with the
25550 @code{gdb.Symbol} object.
25552 The following symbol-related functions are available in the @code{gdb}
25555 @findex gdb.lookup_symbol
25556 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25557 This function searches for a symbol by name. The search scope can be
25558 restricted to the parameters defined in the optional domain and block
25561 @var{name} is the name of the symbol. It must be a string. The
25562 optional @var{block} argument restricts the search to symbols visible
25563 in that @var{block}. The @var{block} argument must be a
25564 @code{gdb.Block} object. If omitted, the block for the current frame
25565 is used. The optional @var{domain} argument restricts
25566 the search to the domain type. The @var{domain} argument must be a
25567 domain constant defined in the @code{gdb} module and described later
25570 The result is a tuple of two elements.
25571 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25573 If the symbol is found, the second element is @code{True} if the symbol
25574 is a field of a method's object (e.g., @code{this} in C@t{++}),
25575 otherwise it is @code{False}.
25576 If the symbol is not found, the second element is @code{False}.
25579 @findex gdb.lookup_global_symbol
25580 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25581 This function searches for a global symbol by name.
25582 The search scope can be restricted to by the domain argument.
25584 @var{name} is the name of the symbol. It must be a string.
25585 The optional @var{domain} argument restricts the search to the domain type.
25586 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25587 module and described later in this chapter.
25589 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25593 A @code{gdb.Symbol} object has the following attributes:
25595 @defvar Symbol.type
25596 The type of the symbol or @code{None} if no type is recorded.
25597 This attribute is represented as a @code{gdb.Type} object.
25598 @xref{Types In Python}. This attribute is not writable.
25601 @defvar Symbol.symtab
25602 The symbol table in which the symbol appears. This attribute is
25603 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25604 Python}. This attribute is not writable.
25607 @defvar Symbol.line
25608 The line number in the source code at which the symbol was defined.
25609 This is an integer.
25612 @defvar Symbol.name
25613 The name of the symbol as a string. This attribute is not writable.
25616 @defvar Symbol.linkage_name
25617 The name of the symbol, as used by the linker (i.e., may be mangled).
25618 This attribute is not writable.
25621 @defvar Symbol.print_name
25622 The name of the symbol in a form suitable for output. This is either
25623 @code{name} or @code{linkage_name}, depending on whether the user
25624 asked @value{GDBN} to display demangled or mangled names.
25627 @defvar Symbol.addr_class
25628 The address class of the symbol. This classifies how to find the value
25629 of a symbol. Each address class is a constant defined in the
25630 @code{gdb} module and described later in this chapter.
25633 @defvar Symbol.needs_frame
25634 This is @code{True} if evaluating this symbol's value requires a frame
25635 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25636 local variables will require a frame, but other symbols will not.
25639 @defvar Symbol.is_argument
25640 @code{True} if the symbol is an argument of a function.
25643 @defvar Symbol.is_constant
25644 @code{True} if the symbol is a constant.
25647 @defvar Symbol.is_function
25648 @code{True} if the symbol is a function or a method.
25651 @defvar Symbol.is_variable
25652 @code{True} if the symbol is a variable.
25655 A @code{gdb.Symbol} object has the following methods:
25657 @defun Symbol.is_valid ()
25658 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25659 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25660 the symbol it refers to does not exist in @value{GDBN} any longer.
25661 All other @code{gdb.Symbol} methods will throw an exception if it is
25662 invalid at the time the method is called.
25665 @defun Symbol.value (@r{[}frame@r{]})
25666 Compute the value of the symbol, as a @code{gdb.Value}. For
25667 functions, this computes the address of the function, cast to the
25668 appropriate type. If the symbol requires a frame in order to compute
25669 its value, then @var{frame} must be given. If @var{frame} is not
25670 given, or if @var{frame} is invalid, then this method will throw an
25674 The available domain categories in @code{gdb.Symbol} are represented
25675 as constants in the @code{gdb} module:
25678 @findex SYMBOL_UNDEF_DOMAIN
25679 @findex gdb.SYMBOL_UNDEF_DOMAIN
25680 @item gdb.SYMBOL_UNDEF_DOMAIN
25681 This is used when a domain has not been discovered or none of the
25682 following domains apply. This usually indicates an error either
25683 in the symbol information or in @value{GDBN}'s handling of symbols.
25684 @findex SYMBOL_VAR_DOMAIN
25685 @findex gdb.SYMBOL_VAR_DOMAIN
25686 @item gdb.SYMBOL_VAR_DOMAIN
25687 This domain contains variables, function names, typedef names and enum
25689 @findex SYMBOL_STRUCT_DOMAIN
25690 @findex gdb.SYMBOL_STRUCT_DOMAIN
25691 @item gdb.SYMBOL_STRUCT_DOMAIN
25692 This domain holds struct, union and enum type names.
25693 @findex SYMBOL_LABEL_DOMAIN
25694 @findex gdb.SYMBOL_LABEL_DOMAIN
25695 @item gdb.SYMBOL_LABEL_DOMAIN
25696 This domain contains names of labels (for gotos).
25697 @findex SYMBOL_VARIABLES_DOMAIN
25698 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25699 @item gdb.SYMBOL_VARIABLES_DOMAIN
25700 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25701 contains everything minus functions and types.
25702 @findex SYMBOL_FUNCTIONS_DOMAIN
25703 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25704 @item gdb.SYMBOL_FUNCTION_DOMAIN
25705 This domain contains all functions.
25706 @findex SYMBOL_TYPES_DOMAIN
25707 @findex gdb.SYMBOL_TYPES_DOMAIN
25708 @item gdb.SYMBOL_TYPES_DOMAIN
25709 This domain contains all types.
25712 The available address class categories in @code{gdb.Symbol} are represented
25713 as constants in the @code{gdb} module:
25716 @findex SYMBOL_LOC_UNDEF
25717 @findex gdb.SYMBOL_LOC_UNDEF
25718 @item gdb.SYMBOL_LOC_UNDEF
25719 If this is returned by address class, it indicates an error either in
25720 the symbol information or in @value{GDBN}'s handling of symbols.
25721 @findex SYMBOL_LOC_CONST
25722 @findex gdb.SYMBOL_LOC_CONST
25723 @item gdb.SYMBOL_LOC_CONST
25724 Value is constant int.
25725 @findex SYMBOL_LOC_STATIC
25726 @findex gdb.SYMBOL_LOC_STATIC
25727 @item gdb.SYMBOL_LOC_STATIC
25728 Value is at a fixed address.
25729 @findex SYMBOL_LOC_REGISTER
25730 @findex gdb.SYMBOL_LOC_REGISTER
25731 @item gdb.SYMBOL_LOC_REGISTER
25732 Value is in a register.
25733 @findex SYMBOL_LOC_ARG
25734 @findex gdb.SYMBOL_LOC_ARG
25735 @item gdb.SYMBOL_LOC_ARG
25736 Value is an argument. This value is at the offset stored within the
25737 symbol inside the frame's argument list.
25738 @findex SYMBOL_LOC_REF_ARG
25739 @findex gdb.SYMBOL_LOC_REF_ARG
25740 @item gdb.SYMBOL_LOC_REF_ARG
25741 Value address is stored in the frame's argument list. Just like
25742 @code{LOC_ARG} except that the value's address is stored at the
25743 offset, not the value itself.
25744 @findex SYMBOL_LOC_REGPARM_ADDR
25745 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25746 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25747 Value is a specified register. Just like @code{LOC_REGISTER} except
25748 the register holds the address of the argument instead of the argument
25750 @findex SYMBOL_LOC_LOCAL
25751 @findex gdb.SYMBOL_LOC_LOCAL
25752 @item gdb.SYMBOL_LOC_LOCAL
25753 Value is a local variable.
25754 @findex SYMBOL_LOC_TYPEDEF
25755 @findex gdb.SYMBOL_LOC_TYPEDEF
25756 @item gdb.SYMBOL_LOC_TYPEDEF
25757 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25759 @findex SYMBOL_LOC_BLOCK
25760 @findex gdb.SYMBOL_LOC_BLOCK
25761 @item gdb.SYMBOL_LOC_BLOCK
25763 @findex SYMBOL_LOC_CONST_BYTES
25764 @findex gdb.SYMBOL_LOC_CONST_BYTES
25765 @item gdb.SYMBOL_LOC_CONST_BYTES
25766 Value is a byte-sequence.
25767 @findex SYMBOL_LOC_UNRESOLVED
25768 @findex gdb.SYMBOL_LOC_UNRESOLVED
25769 @item gdb.SYMBOL_LOC_UNRESOLVED
25770 Value is at a fixed address, but the address of the variable has to be
25771 determined from the minimal symbol table whenever the variable is
25773 @findex SYMBOL_LOC_OPTIMIZED_OUT
25774 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25775 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25776 The value does not actually exist in the program.
25777 @findex SYMBOL_LOC_COMPUTED
25778 @findex gdb.SYMBOL_LOC_COMPUTED
25779 @item gdb.SYMBOL_LOC_COMPUTED
25780 The value's address is a computed location.
25783 @node Symbol Tables In Python
25784 @subsubsection Symbol table representation in Python.
25786 @cindex symbol tables in python
25788 @tindex gdb.Symtab_and_line
25790 Access to symbol table data maintained by @value{GDBN} on the inferior
25791 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25792 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25793 from the @code{find_sal} method in @code{gdb.Frame} object.
25794 @xref{Frames In Python}.
25796 For more information on @value{GDBN}'s symbol table management, see
25797 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25799 A @code{gdb.Symtab_and_line} object has the following attributes:
25801 @defvar Symtab_and_line.symtab
25802 The symbol table object (@code{gdb.Symtab}) for this frame.
25803 This attribute is not writable.
25806 @defvar Symtab_and_line.pc
25807 Indicates the start of the address range occupied by code for the
25808 current source line. This attribute is not writable.
25811 @defvar Symtab_and_line.last
25812 Indicates the end of the address range occupied by code for the current
25813 source line. This attribute is not writable.
25816 @defvar Symtab_and_line.line
25817 Indicates the current line number for this object. This
25818 attribute is not writable.
25821 A @code{gdb.Symtab_and_line} object has the following methods:
25823 @defun Symtab_and_line.is_valid ()
25824 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25825 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25826 invalid if the Symbol table and line object it refers to does not
25827 exist in @value{GDBN} any longer. All other
25828 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25829 invalid at the time the method is called.
25832 A @code{gdb.Symtab} object has the following attributes:
25834 @defvar Symtab.filename
25835 The symbol table's source filename. This attribute is not writable.
25838 @defvar Symtab.objfile
25839 The symbol table's backing object file. @xref{Objfiles In Python}.
25840 This attribute is not writable.
25843 A @code{gdb.Symtab} object has the following methods:
25845 @defun Symtab.is_valid ()
25846 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25847 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25848 the symbol table it refers to does not exist in @value{GDBN} any
25849 longer. All other @code{gdb.Symtab} methods will throw an exception
25850 if it is invalid at the time the method is called.
25853 @defun Symtab.fullname ()
25854 Return the symbol table's source absolute file name.
25857 @defun Symtab.global_block ()
25858 Return the global block of the underlying symbol table.
25859 @xref{Blocks In Python}.
25862 @defun Symtab.static_block ()
25863 Return the static block of the underlying symbol table.
25864 @xref{Blocks In Python}.
25867 @node Breakpoints In Python
25868 @subsubsection Manipulating breakpoints using Python
25870 @cindex breakpoints in python
25871 @tindex gdb.Breakpoint
25873 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25876 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25877 Create a new breakpoint. @var{spec} is a string naming the
25878 location of the breakpoint, or an expression that defines a
25879 watchpoint. The contents can be any location recognized by the
25880 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25881 command. The optional @var{type} denotes the breakpoint to create
25882 from the types defined later in this chapter. This argument can be
25883 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25884 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25885 allows the breakpoint to become invisible to the user. The breakpoint
25886 will neither be reported when created, nor will it be listed in the
25887 output from @code{info breakpoints} (but will be listed with the
25888 @code{maint info breakpoints} command). The optional @var{wp_class}
25889 argument defines the class of watchpoint to create, if @var{type} is
25890 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25891 assumed to be a @code{gdb.WP_WRITE} class.
25894 @defun Breakpoint.stop (self)
25895 The @code{gdb.Breakpoint} class can be sub-classed and, in
25896 particular, you may choose to implement the @code{stop} method.
25897 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25898 it will be called when the inferior reaches any location of a
25899 breakpoint which instantiates that sub-class. If the method returns
25900 @code{True}, the inferior will be stopped at the location of the
25901 breakpoint, otherwise the inferior will continue.
25903 If there are multiple breakpoints at the same location with a
25904 @code{stop} method, each one will be called regardless of the
25905 return status of the previous. This ensures that all @code{stop}
25906 methods have a chance to execute at that location. In this scenario
25907 if one of the methods returns @code{True} but the others return
25908 @code{False}, the inferior will still be stopped.
25910 You should not alter the execution state of the inferior (i.e.@:, step,
25911 next, etc.), alter the current frame context (i.e.@:, change the current
25912 active frame), or alter, add or delete any breakpoint. As a general
25913 rule, you should not alter any data within @value{GDBN} or the inferior
25916 Example @code{stop} implementation:
25919 class MyBreakpoint (gdb.Breakpoint):
25921 inf_val = gdb.parse_and_eval("foo")
25928 The available watchpoint types represented by constants are defined in the
25933 @findex gdb.WP_READ
25935 Read only watchpoint.
25938 @findex gdb.WP_WRITE
25940 Write only watchpoint.
25943 @findex gdb.WP_ACCESS
25944 @item gdb.WP_ACCESS
25945 Read/Write watchpoint.
25948 @defun Breakpoint.is_valid ()
25949 Return @code{True} if this @code{Breakpoint} object is valid,
25950 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25951 if the user deletes the breakpoint. In this case, the object still
25952 exists, but the underlying breakpoint does not. In the cases of
25953 watchpoint scope, the watchpoint remains valid even if execution of the
25954 inferior leaves the scope of that watchpoint.
25957 @defun Breakpoint.delete
25958 Permanently deletes the @value{GDBN} breakpoint. This also
25959 invalidates the Python @code{Breakpoint} object. Any further access
25960 to this object's attributes or methods will raise an error.
25963 @defvar Breakpoint.enabled
25964 This attribute is @code{True} if the breakpoint is enabled, and
25965 @code{False} otherwise. This attribute is writable.
25968 @defvar Breakpoint.silent
25969 This attribute is @code{True} if the breakpoint is silent, and
25970 @code{False} otherwise. This attribute is writable.
25972 Note that a breakpoint can also be silent if it has commands and the
25973 first command is @code{silent}. This is not reported by the
25974 @code{silent} attribute.
25977 @defvar Breakpoint.thread
25978 If the breakpoint is thread-specific, this attribute holds the thread
25979 id. If the breakpoint is not thread-specific, this attribute is
25980 @code{None}. This attribute is writable.
25983 @defvar Breakpoint.task
25984 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25985 id. If the breakpoint is not task-specific (or the underlying
25986 language is not Ada), this attribute is @code{None}. This attribute
25990 @defvar Breakpoint.ignore_count
25991 This attribute holds the ignore count for the breakpoint, an integer.
25992 This attribute is writable.
25995 @defvar Breakpoint.number
25996 This attribute holds the breakpoint's number --- the identifier used by
25997 the user to manipulate the breakpoint. This attribute is not writable.
26000 @defvar Breakpoint.type
26001 This attribute holds the breakpoint's type --- the identifier used to
26002 determine the actual breakpoint type or use-case. This attribute is not
26006 @defvar Breakpoint.visible
26007 This attribute tells whether the breakpoint is visible to the user
26008 when set, or when the @samp{info breakpoints} command is run. This
26009 attribute is not writable.
26012 The available types are represented by constants defined in the @code{gdb}
26016 @findex BP_BREAKPOINT
26017 @findex gdb.BP_BREAKPOINT
26018 @item gdb.BP_BREAKPOINT
26019 Normal code breakpoint.
26021 @findex BP_WATCHPOINT
26022 @findex gdb.BP_WATCHPOINT
26023 @item gdb.BP_WATCHPOINT
26024 Watchpoint breakpoint.
26026 @findex BP_HARDWARE_WATCHPOINT
26027 @findex gdb.BP_HARDWARE_WATCHPOINT
26028 @item gdb.BP_HARDWARE_WATCHPOINT
26029 Hardware assisted watchpoint.
26031 @findex BP_READ_WATCHPOINT
26032 @findex gdb.BP_READ_WATCHPOINT
26033 @item gdb.BP_READ_WATCHPOINT
26034 Hardware assisted read watchpoint.
26036 @findex BP_ACCESS_WATCHPOINT
26037 @findex gdb.BP_ACCESS_WATCHPOINT
26038 @item gdb.BP_ACCESS_WATCHPOINT
26039 Hardware assisted access watchpoint.
26042 @defvar Breakpoint.hit_count
26043 This attribute holds the hit count for the breakpoint, an integer.
26044 This attribute is writable, but currently it can only be set to zero.
26047 @defvar Breakpoint.location
26048 This attribute holds the location of the breakpoint, as specified by
26049 the user. It is a string. If the breakpoint does not have a location
26050 (that is, it is a watchpoint) the attribute's value is @code{None}. This
26051 attribute is not writable.
26054 @defvar Breakpoint.expression
26055 This attribute holds a breakpoint expression, as specified by
26056 the user. It is a string. If the breakpoint does not have an
26057 expression (the breakpoint is not a watchpoint) the attribute's value
26058 is @code{None}. This attribute is not writable.
26061 @defvar Breakpoint.condition
26062 This attribute holds the condition of the breakpoint, as specified by
26063 the user. It is a string. If there is no condition, this attribute's
26064 value is @code{None}. This attribute is writable.
26067 @defvar Breakpoint.commands
26068 This attribute holds the commands attached to the breakpoint. If
26069 there are commands, this attribute's value is a string holding all the
26070 commands, separated by newlines. If there are no commands, this
26071 attribute is @code{None}. This attribute is not writable.
26074 @node Finish Breakpoints in Python
26075 @subsubsection Finish Breakpoints
26077 @cindex python finish breakpoints
26078 @tindex gdb.FinishBreakpoint
26080 A finish breakpoint is a temporary breakpoint set at the return address of
26081 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26082 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26083 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26084 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26085 Finish breakpoints are thread specific and must be create with the right
26088 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26089 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26090 object @var{frame}. If @var{frame} is not provided, this defaults to the
26091 newest frame. The optional @var{internal} argument allows the breakpoint to
26092 become invisible to the user. @xref{Breakpoints In Python}, for further
26093 details about this argument.
26096 @defun FinishBreakpoint.out_of_scope (self)
26097 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26098 @code{return} command, @dots{}), a function may not properly terminate, and
26099 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26100 situation, the @code{out_of_scope} callback will be triggered.
26102 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26106 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26108 print "normal finish"
26111 def out_of_scope ():
26112 print "abnormal finish"
26116 @defvar FinishBreakpoint.return_value
26117 When @value{GDBN} is stopped at a finish breakpoint and the frame
26118 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26119 attribute will contain a @code{gdb.Value} object corresponding to the return
26120 value of the function. The value will be @code{None} if the function return
26121 type is @code{void} or if the return value was not computable. This attribute
26125 @node Lazy Strings In Python
26126 @subsubsection Python representation of lazy strings.
26128 @cindex lazy strings in python
26129 @tindex gdb.LazyString
26131 A @dfn{lazy string} is a string whose contents is not retrieved or
26132 encoded until it is needed.
26134 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26135 @code{address} that points to a region of memory, an @code{encoding}
26136 that will be used to encode that region of memory, and a @code{length}
26137 to delimit the region of memory that represents the string. The
26138 difference between a @code{gdb.LazyString} and a string wrapped within
26139 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26140 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26141 retrieved and encoded during printing, while a @code{gdb.Value}
26142 wrapping a string is immediately retrieved and encoded on creation.
26144 A @code{gdb.LazyString} object has the following functions:
26146 @defun LazyString.value ()
26147 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26148 will point to the string in memory, but will lose all the delayed
26149 retrieval, encoding and handling that @value{GDBN} applies to a
26150 @code{gdb.LazyString}.
26153 @defvar LazyString.address
26154 This attribute holds the address of the string. This attribute is not
26158 @defvar LazyString.length
26159 This attribute holds the length of the string in characters. If the
26160 length is -1, then the string will be fetched and encoded up to the
26161 first null of appropriate width. This attribute is not writable.
26164 @defvar LazyString.encoding
26165 This attribute holds the encoding that will be applied to the string
26166 when the string is printed by @value{GDBN}. If the encoding is not
26167 set, or contains an empty string, then @value{GDBN} will select the
26168 most appropriate encoding when the string is printed. This attribute
26172 @defvar LazyString.type
26173 This attribute holds the type that is represented by the lazy string's
26174 type. For a lazy string this will always be a pointer type. To
26175 resolve this to the lazy string's character type, use the type's
26176 @code{target} method. @xref{Types In Python}. This attribute is not
26180 @node Architectures In Python
26181 @subsubsection Python representation of architectures
26182 @cindex Python architectures
26184 @value{GDBN} uses architecture specific parameters and artifacts in a
26185 number of its various computations. An architecture is represented
26186 by an instance of the @code{gdb.Architecture} class.
26188 A @code{gdb.Architecture} class has the following methods:
26190 @defun Architecture.name ()
26191 Return the name (string value) of the architecture.
26194 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26195 Return a list of disassembled instructions starting from the memory
26196 address @var{start_pc}. The optional arguments @var{end_pc} and
26197 @var{count} determine the number of instructions in the returned list.
26198 If both the optional arguments @var{end_pc} and @var{count} are
26199 specified, then a list of at most @var{count} disassembled instructions
26200 whose start address falls in the closed memory address interval from
26201 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26202 specified, but @var{count} is specified, then @var{count} number of
26203 instructions starting from the address @var{start_pc} are returned. If
26204 @var{count} is not specified but @var{end_pc} is specified, then all
26205 instructions whose start address falls in the closed memory address
26206 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26207 @var{end_pc} nor @var{count} are specified, then a single instruction at
26208 @var{start_pc} is returned. For all of these cases, each element of the
26209 returned list is a Python @code{dict} with the following string keys:
26214 The value corresponding to this key is a Python long integer capturing
26215 the memory address of the instruction.
26218 The value corresponding to this key is a string value which represents
26219 the instruction with assembly language mnemonics. The assembly
26220 language flavor used is the same as that specified by the current CLI
26221 variable @code{disassembly-flavor}. @xref{Machine Code}.
26224 The value corresponding to this key is the length (integer value) of the
26225 instruction in bytes.
26230 @node Python Auto-loading
26231 @subsection Python Auto-loading
26232 @cindex Python auto-loading
26234 When a new object file is read (for example, due to the @code{file}
26235 command, or because the inferior has loaded a shared library),
26236 @value{GDBN} will look for Python support scripts in several ways:
26237 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26238 and @code{.debug_gdb_scripts} section
26239 (@pxref{dotdebug_gdb_scripts section}).
26241 The auto-loading feature is useful for supplying application-specific
26242 debugging commands and scripts.
26244 Auto-loading can be enabled or disabled,
26245 and the list of auto-loaded scripts can be printed.
26248 @anchor{set auto-load python-scripts}
26249 @kindex set auto-load python-scripts
26250 @item set auto-load python-scripts [on|off]
26251 Enable or disable the auto-loading of Python scripts.
26253 @anchor{show auto-load python-scripts}
26254 @kindex show auto-load python-scripts
26255 @item show auto-load python-scripts
26256 Show whether auto-loading of Python scripts is enabled or disabled.
26258 @anchor{info auto-load python-scripts}
26259 @kindex info auto-load python-scripts
26260 @cindex print list of auto-loaded Python scripts
26261 @item info auto-load python-scripts [@var{regexp}]
26262 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26264 Also printed is the list of Python scripts that were mentioned in
26265 the @code{.debug_gdb_scripts} section and were not found
26266 (@pxref{dotdebug_gdb_scripts section}).
26267 This is useful because their names are not printed when @value{GDBN}
26268 tries to load them and fails. There may be many of them, and printing
26269 an error message for each one is problematic.
26271 If @var{regexp} is supplied only Python scripts with matching names are printed.
26276 (gdb) info auto-load python-scripts
26278 Yes py-section-script.py
26279 full name: /tmp/py-section-script.py
26280 No my-foo-pretty-printers.py
26284 When reading an auto-loaded file, @value{GDBN} sets the
26285 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26286 function (@pxref{Objfiles In Python}). This can be useful for
26287 registering objfile-specific pretty-printers.
26290 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26291 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26292 * Which flavor to choose?::
26295 @node objfile-gdb.py file
26296 @subsubsection The @file{@var{objfile}-gdb.py} file
26297 @cindex @file{@var{objfile}-gdb.py}
26299 When a new object file is read, @value{GDBN} looks for
26300 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26301 where @var{objfile} is the object file's real name, formed by ensuring
26302 that the file name is absolute, following all symlinks, and resolving
26303 @code{.} and @code{..} components. If this file exists and is
26304 readable, @value{GDBN} will evaluate it as a Python script.
26306 If this file does not exist, then @value{GDBN} will look for
26307 @var{script-name} file in all of the directories as specified below.
26309 Note that loading of this script file also requires accordingly configured
26310 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26312 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26313 scripts normally according to its @file{.exe} filename. But if no scripts are
26314 found @value{GDBN} also tries script filenames matching the object file without
26315 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26316 is attempted on any platform. This makes the script filenames compatible
26317 between Unix and MS-Windows hosts.
26320 @anchor{set auto-load scripts-directory}
26321 @kindex set auto-load scripts-directory
26322 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26323 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26324 may be delimited by the host platform path separator in use
26325 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26327 Each entry here needs to be covered also by the security setting
26328 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26330 @anchor{with-auto-load-dir}
26331 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26332 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26333 configuration option @option{--with-auto-load-dir}.
26335 Any reference to @file{$debugdir} will get replaced by
26336 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26337 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26338 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26339 @file{$datadir} must be placed as a directory component --- either alone or
26340 delimited by @file{/} or @file{\} directory separators, depending on the host
26343 The list of directories uses path separator (@samp{:} on GNU and Unix
26344 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26345 to the @env{PATH} environment variable.
26347 @anchor{show auto-load scripts-directory}
26348 @kindex show auto-load scripts-directory
26349 @item show auto-load scripts-directory
26350 Show @value{GDBN} auto-loaded scripts location.
26353 @value{GDBN} does not track which files it has already auto-loaded this way.
26354 @value{GDBN} will load the associated script every time the corresponding
26355 @var{objfile} is opened.
26356 So your @file{-gdb.py} file should be careful to avoid errors if it
26357 is evaluated more than once.
26359 @node dotdebug_gdb_scripts section
26360 @subsubsection The @code{.debug_gdb_scripts} section
26361 @cindex @code{.debug_gdb_scripts} section
26363 For systems using file formats like ELF and COFF,
26364 when @value{GDBN} loads a new object file
26365 it will look for a special section named @samp{.debug_gdb_scripts}.
26366 If this section exists, its contents is a list of names of scripts to load.
26368 @value{GDBN} will look for each specified script file first in the
26369 current directory and then along the source search path
26370 (@pxref{Source Path, ,Specifying Source Directories}),
26371 except that @file{$cdir} is not searched, since the compilation
26372 directory is not relevant to scripts.
26374 Entries can be placed in section @code{.debug_gdb_scripts} with,
26375 for example, this GCC macro:
26378 /* Note: The "MS" section flags are to remove duplicates. */
26379 #define DEFINE_GDB_SCRIPT(script_name) \
26381 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26383 .asciz \"" script_name "\"\n\
26389 Then one can reference the macro in a header or source file like this:
26392 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26395 The script name may include directories if desired.
26397 Note that loading of this script file also requires accordingly configured
26398 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26400 If the macro is put in a header, any application or library
26401 using this header will get a reference to the specified script.
26403 @node Which flavor to choose?
26404 @subsubsection Which flavor to choose?
26406 Given the multiple ways of auto-loading Python scripts, it might not always
26407 be clear which one to choose. This section provides some guidance.
26409 Benefits of the @file{-gdb.py} way:
26413 Can be used with file formats that don't support multiple sections.
26416 Ease of finding scripts for public libraries.
26418 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26419 in the source search path.
26420 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26421 isn't a source directory in which to find the script.
26424 Doesn't require source code additions.
26427 Benefits of the @code{.debug_gdb_scripts} way:
26431 Works with static linking.
26433 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26434 trigger their loading. When an application is statically linked the only
26435 objfile available is the executable, and it is cumbersome to attach all the
26436 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26439 Works with classes that are entirely inlined.
26441 Some classes can be entirely inlined, and thus there may not be an associated
26442 shared library to attach a @file{-gdb.py} script to.
26445 Scripts needn't be copied out of the source tree.
26447 In some circumstances, apps can be built out of large collections of internal
26448 libraries, and the build infrastructure necessary to install the
26449 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26450 cumbersome. It may be easier to specify the scripts in the
26451 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26452 top of the source tree to the source search path.
26455 @node Python modules
26456 @subsection Python modules
26457 @cindex python modules
26459 @value{GDBN} comes with several modules to assist writing Python code.
26462 * gdb.printing:: Building and registering pretty-printers.
26463 * gdb.types:: Utilities for working with types.
26464 * gdb.prompt:: Utilities for prompt value substitution.
26468 @subsubsection gdb.printing
26469 @cindex gdb.printing
26471 This module provides a collection of utilities for working with
26475 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26476 This class specifies the API that makes @samp{info pretty-printer},
26477 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26478 Pretty-printers should generally inherit from this class.
26480 @item SubPrettyPrinter (@var{name})
26481 For printers that handle multiple types, this class specifies the
26482 corresponding API for the subprinters.
26484 @item RegexpCollectionPrettyPrinter (@var{name})
26485 Utility class for handling multiple printers, all recognized via
26486 regular expressions.
26487 @xref{Writing a Pretty-Printer}, for an example.
26489 @item FlagEnumerationPrinter (@var{name})
26490 A pretty-printer which handles printing of @code{enum} values. Unlike
26491 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26492 work properly when there is some overlap between the enumeration
26493 constants. @var{name} is the name of the printer and also the name of
26494 the @code{enum} type to look up.
26496 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26497 Register @var{printer} with the pretty-printer list of @var{obj}.
26498 If @var{replace} is @code{True} then any existing copy of the printer
26499 is replaced. Otherwise a @code{RuntimeError} exception is raised
26500 if a printer with the same name already exists.
26504 @subsubsection gdb.types
26507 This module provides a collection of utilities for working with
26508 @code{gdb.Type} objects.
26511 @item get_basic_type (@var{type})
26512 Return @var{type} with const and volatile qualifiers stripped,
26513 and with typedefs and C@t{++} references converted to the underlying type.
26518 typedef const int const_int;
26520 const_int& foo_ref (foo);
26521 int main () @{ return 0; @}
26528 (gdb) python import gdb.types
26529 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26530 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26534 @item has_field (@var{type}, @var{field})
26535 Return @code{True} if @var{type}, assumed to be a type with fields
26536 (e.g., a structure or union), has field @var{field}.
26538 @item make_enum_dict (@var{enum_type})
26539 Return a Python @code{dictionary} type produced from @var{enum_type}.
26541 @item deep_items (@var{type})
26542 Returns a Python iterator similar to the standard
26543 @code{gdb.Type.iteritems} method, except that the iterator returned
26544 by @code{deep_items} will recursively traverse anonymous struct or
26545 union fields. For example:
26559 Then in @value{GDBN}:
26561 (@value{GDBP}) python import gdb.types
26562 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26563 (@value{GDBP}) python print struct_a.keys ()
26565 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26566 @{['a', 'b0', 'b1']@}
26569 @item get_type_recognizers ()
26570 Return a list of the enabled type recognizers for the current context.
26571 This is called by @value{GDBN} during the type-printing process
26572 (@pxref{Type Printing API}).
26574 @item apply_type_recognizers (recognizers, type_obj)
26575 Apply the type recognizers, @var{recognizers}, to the type object
26576 @var{type_obj}. If any recognizer returns a string, return that
26577 string. Otherwise, return @code{None}. This is called by
26578 @value{GDBN} during the type-printing process (@pxref{Type Printing
26581 @item register_type_printer (locus, printer)
26582 This is a convenience function to register a type printer.
26583 @var{printer} is the type printer to register. It must implement the
26584 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26585 which case the printer is registered with that objfile; a
26586 @code{gdb.Progspace}, in which case the printer is registered with
26587 that progspace; or @code{None}, in which case the printer is
26588 registered globally.
26591 This is a base class that implements the type printer protocol. Type
26592 printers are encouraged, but not required, to derive from this class.
26593 It defines a constructor:
26595 @defmethod TypePrinter __init__ (self, name)
26596 Initialize the type printer with the given name. The new printer
26597 starts in the enabled state.
26603 @subsubsection gdb.prompt
26606 This module provides a method for prompt value-substitution.
26609 @item substitute_prompt (@var{string})
26610 Return @var{string} with escape sequences substituted by values. Some
26611 escape sequences take arguments. You can specify arguments inside
26612 ``@{@}'' immediately following the escape sequence.
26614 The escape sequences you can pass to this function are:
26618 Substitute a backslash.
26620 Substitute an ESC character.
26622 Substitute the selected frame; an argument names a frame parameter.
26624 Substitute a newline.
26626 Substitute a parameter's value; the argument names the parameter.
26628 Substitute a carriage return.
26630 Substitute the selected thread; an argument names a thread parameter.
26632 Substitute the version of GDB.
26634 Substitute the current working directory.
26636 Begin a sequence of non-printing characters. These sequences are
26637 typically used with the ESC character, and are not counted in the string
26638 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26639 blue-colored ``(gdb)'' prompt where the length is five.
26641 End a sequence of non-printing characters.
26647 substitute_prompt (``frame: \f,
26648 print arguments: \p@{print frame-arguments@}'')
26651 @exdent will return the string:
26654 "frame: main, print arguments: scalars"
26659 @section Creating new spellings of existing commands
26660 @cindex aliases for commands
26662 It is often useful to define alternate spellings of existing commands.
26663 For example, if a new @value{GDBN} command defined in Python has
26664 a long name to type, it is handy to have an abbreviated version of it
26665 that involves less typing.
26667 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26668 of the @samp{step} command even though it is otherwise an ambiguous
26669 abbreviation of other commands like @samp{set} and @samp{show}.
26671 Aliases are also used to provide shortened or more common versions
26672 of multi-word commands. For example, @value{GDBN} provides the
26673 @samp{tty} alias of the @samp{set inferior-tty} command.
26675 You can define a new alias with the @samp{alias} command.
26680 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26684 @var{ALIAS} specifies the name of the new alias.
26685 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26688 @var{COMMAND} specifies the name of an existing command
26689 that is being aliased.
26691 The @samp{-a} option specifies that the new alias is an abbreviation
26692 of the command. Abbreviations are not shown in command
26693 lists displayed by the @samp{help} command.
26695 The @samp{--} option specifies the end of options,
26696 and is useful when @var{ALIAS} begins with a dash.
26698 Here is a simple example showing how to make an abbreviation
26699 of a command so that there is less to type.
26700 Suppose you were tired of typing @samp{disas}, the current
26701 shortest unambiguous abbreviation of the @samp{disassemble} command
26702 and you wanted an even shorter version named @samp{di}.
26703 The following will accomplish this.
26706 (gdb) alias -a di = disas
26709 Note that aliases are different from user-defined commands.
26710 With a user-defined command, you also need to write documentation
26711 for it with the @samp{document} command.
26712 An alias automatically picks up the documentation of the existing command.
26714 Here is an example where we make @samp{elms} an abbreviation of
26715 @samp{elements} in the @samp{set print elements} command.
26716 This is to show that you can make an abbreviation of any part
26720 (gdb) alias -a set print elms = set print elements
26721 (gdb) alias -a show print elms = show print elements
26722 (gdb) set p elms 20
26724 Limit on string chars or array elements to print is 200.
26727 Note that if you are defining an alias of a @samp{set} command,
26728 and you want to have an alias for the corresponding @samp{show}
26729 command, then you need to define the latter separately.
26731 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26732 @var{ALIAS}, just as they are normally.
26735 (gdb) alias -a set pr elms = set p ele
26738 Finally, here is an example showing the creation of a one word
26739 alias for a more complex command.
26740 This creates alias @samp{spe} of the command @samp{set print elements}.
26743 (gdb) alias spe = set print elements
26748 @chapter Command Interpreters
26749 @cindex command interpreters
26751 @value{GDBN} supports multiple command interpreters, and some command
26752 infrastructure to allow users or user interface writers to switch
26753 between interpreters or run commands in other interpreters.
26755 @value{GDBN} currently supports two command interpreters, the console
26756 interpreter (sometimes called the command-line interpreter or @sc{cli})
26757 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26758 describes both of these interfaces in great detail.
26760 By default, @value{GDBN} will start with the console interpreter.
26761 However, the user may choose to start @value{GDBN} with another
26762 interpreter by specifying the @option{-i} or @option{--interpreter}
26763 startup options. Defined interpreters include:
26767 @cindex console interpreter
26768 The traditional console or command-line interpreter. This is the most often
26769 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26770 @value{GDBN} will use this interpreter.
26773 @cindex mi interpreter
26774 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26775 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26776 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26780 @cindex mi2 interpreter
26781 The current @sc{gdb/mi} interface.
26784 @cindex mi1 interpreter
26785 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26789 @cindex invoke another interpreter
26790 The interpreter being used by @value{GDBN} may not be dynamically
26791 switched at runtime. Although possible, this could lead to a very
26792 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26793 enters the command "interpreter-set console" in a console view,
26794 @value{GDBN} would switch to using the console interpreter, rendering
26795 the IDE inoperable!
26797 @kindex interpreter-exec
26798 Although you may only choose a single interpreter at startup, you may execute
26799 commands in any interpreter from the current interpreter using the appropriate
26800 command. If you are running the console interpreter, simply use the
26801 @code{interpreter-exec} command:
26804 interpreter-exec mi "-data-list-register-names"
26807 @sc{gdb/mi} has a similar command, although it is only available in versions of
26808 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26811 @chapter @value{GDBN} Text User Interface
26813 @cindex Text User Interface
26816 * TUI Overview:: TUI overview
26817 * TUI Keys:: TUI key bindings
26818 * TUI Single Key Mode:: TUI single key mode
26819 * TUI Commands:: TUI-specific commands
26820 * TUI Configuration:: TUI configuration variables
26823 The @value{GDBN} Text User Interface (TUI) is a terminal
26824 interface which uses the @code{curses} library to show the source
26825 file, the assembly output, the program registers and @value{GDBN}
26826 commands in separate text windows. The TUI mode is supported only
26827 on platforms where a suitable version of the @code{curses} library
26830 The TUI mode is enabled by default when you invoke @value{GDBN} as
26831 @samp{@value{GDBP} -tui}.
26832 You can also switch in and out of TUI mode while @value{GDBN} runs by
26833 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26834 @xref{TUI Keys, ,TUI Key Bindings}.
26837 @section TUI Overview
26839 In TUI mode, @value{GDBN} can display several text windows:
26843 This window is the @value{GDBN} command window with the @value{GDBN}
26844 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26845 managed using readline.
26848 The source window shows the source file of the program. The current
26849 line and active breakpoints are displayed in this window.
26852 The assembly window shows the disassembly output of the program.
26855 This window shows the processor registers. Registers are highlighted
26856 when their values change.
26859 The source and assembly windows show the current program position
26860 by highlighting the current line and marking it with a @samp{>} marker.
26861 Breakpoints are indicated with two markers. The first marker
26862 indicates the breakpoint type:
26866 Breakpoint which was hit at least once.
26869 Breakpoint which was never hit.
26872 Hardware breakpoint which was hit at least once.
26875 Hardware breakpoint which was never hit.
26878 The second marker indicates whether the breakpoint is enabled or not:
26882 Breakpoint is enabled.
26885 Breakpoint is disabled.
26888 The source, assembly and register windows are updated when the current
26889 thread changes, when the frame changes, or when the program counter
26892 These windows are not all visible at the same time. The command
26893 window is always visible. The others can be arranged in several
26904 source and assembly,
26907 source and registers, or
26910 assembly and registers.
26913 A status line above the command window shows the following information:
26917 Indicates the current @value{GDBN} target.
26918 (@pxref{Targets, ,Specifying a Debugging Target}).
26921 Gives the current process or thread number.
26922 When no process is being debugged, this field is set to @code{No process}.
26925 Gives the current function name for the selected frame.
26926 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26927 When there is no symbol corresponding to the current program counter,
26928 the string @code{??} is displayed.
26931 Indicates the current line number for the selected frame.
26932 When the current line number is not known, the string @code{??} is displayed.
26935 Indicates the current program counter address.
26939 @section TUI Key Bindings
26940 @cindex TUI key bindings
26942 The TUI installs several key bindings in the readline keymaps
26943 @ifset SYSTEM_READLINE
26944 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26946 @ifclear SYSTEM_READLINE
26947 (@pxref{Command Line Editing}).
26949 The following key bindings are installed for both TUI mode and the
26950 @value{GDBN} standard mode.
26959 Enter or leave the TUI mode. When leaving the TUI mode,
26960 the curses window management stops and @value{GDBN} operates using
26961 its standard mode, writing on the terminal directly. When reentering
26962 the TUI mode, control is given back to the curses windows.
26963 The screen is then refreshed.
26967 Use a TUI layout with only one window. The layout will
26968 either be @samp{source} or @samp{assembly}. When the TUI mode
26969 is not active, it will switch to the TUI mode.
26971 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26975 Use a TUI layout with at least two windows. When the current
26976 layout already has two windows, the next layout with two windows is used.
26977 When a new layout is chosen, one window will always be common to the
26978 previous layout and the new one.
26980 Think of it as the Emacs @kbd{C-x 2} binding.
26984 Change the active window. The TUI associates several key bindings
26985 (like scrolling and arrow keys) with the active window. This command
26986 gives the focus to the next TUI window.
26988 Think of it as the Emacs @kbd{C-x o} binding.
26992 Switch in and out of the TUI SingleKey mode that binds single
26993 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26996 The following key bindings only work in the TUI mode:
27001 Scroll the active window one page up.
27005 Scroll the active window one page down.
27009 Scroll the active window one line up.
27013 Scroll the active window one line down.
27017 Scroll the active window one column left.
27021 Scroll the active window one column right.
27025 Refresh the screen.
27028 Because the arrow keys scroll the active window in the TUI mode, they
27029 are not available for their normal use by readline unless the command
27030 window has the focus. When another window is active, you must use
27031 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27032 and @kbd{C-f} to control the command window.
27034 @node TUI Single Key Mode
27035 @section TUI Single Key Mode
27036 @cindex TUI single key mode
27038 The TUI also provides a @dfn{SingleKey} mode, which binds several
27039 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27040 switch into this mode, where the following key bindings are used:
27043 @kindex c @r{(SingleKey TUI key)}
27047 @kindex d @r{(SingleKey TUI key)}
27051 @kindex f @r{(SingleKey TUI key)}
27055 @kindex n @r{(SingleKey TUI key)}
27059 @kindex q @r{(SingleKey TUI key)}
27061 exit the SingleKey mode.
27063 @kindex r @r{(SingleKey TUI key)}
27067 @kindex s @r{(SingleKey TUI key)}
27071 @kindex u @r{(SingleKey TUI key)}
27075 @kindex v @r{(SingleKey TUI key)}
27079 @kindex w @r{(SingleKey TUI key)}
27084 Other keys temporarily switch to the @value{GDBN} command prompt.
27085 The key that was pressed is inserted in the editing buffer so that
27086 it is possible to type most @value{GDBN} commands without interaction
27087 with the TUI SingleKey mode. Once the command is entered the TUI
27088 SingleKey mode is restored. The only way to permanently leave
27089 this mode is by typing @kbd{q} or @kbd{C-x s}.
27093 @section TUI-specific Commands
27094 @cindex TUI commands
27096 The TUI has specific commands to control the text windows.
27097 These commands are always available, even when @value{GDBN} is not in
27098 the TUI mode. When @value{GDBN} is in the standard mode, most
27099 of these commands will automatically switch to the TUI mode.
27101 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27102 terminal, or @value{GDBN} has been started with the machine interface
27103 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27104 these commands will fail with an error, because it would not be
27105 possible or desirable to enable curses window management.
27110 List and give the size of all displayed windows.
27114 Display the next layout.
27117 Display the previous layout.
27120 Display the source window only.
27123 Display the assembly window only.
27126 Display the source and assembly window.
27129 Display the register window together with the source or assembly window.
27133 Make the next window active for scrolling.
27136 Make the previous window active for scrolling.
27139 Make the source window active for scrolling.
27142 Make the assembly window active for scrolling.
27145 Make the register window active for scrolling.
27148 Make the command window active for scrolling.
27152 Refresh the screen. This is similar to typing @kbd{C-L}.
27154 @item tui reg float
27156 Show the floating point registers in the register window.
27158 @item tui reg general
27159 Show the general registers in the register window.
27162 Show the next register group. The list of register groups as well as
27163 their order is target specific. The predefined register groups are the
27164 following: @code{general}, @code{float}, @code{system}, @code{vector},
27165 @code{all}, @code{save}, @code{restore}.
27167 @item tui reg system
27168 Show the system registers in the register window.
27172 Update the source window and the current execution point.
27174 @item winheight @var{name} +@var{count}
27175 @itemx winheight @var{name} -@var{count}
27177 Change the height of the window @var{name} by @var{count}
27178 lines. Positive counts increase the height, while negative counts
27181 @item tabset @var{nchars}
27183 Set the width of tab stops to be @var{nchars} characters.
27186 @node TUI Configuration
27187 @section TUI Configuration Variables
27188 @cindex TUI configuration variables
27190 Several configuration variables control the appearance of TUI windows.
27193 @item set tui border-kind @var{kind}
27194 @kindex set tui border-kind
27195 Select the border appearance for the source, assembly and register windows.
27196 The possible values are the following:
27199 Use a space character to draw the border.
27202 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27205 Use the Alternate Character Set to draw the border. The border is
27206 drawn using character line graphics if the terminal supports them.
27209 @item set tui border-mode @var{mode}
27210 @kindex set tui border-mode
27211 @itemx set tui active-border-mode @var{mode}
27212 @kindex set tui active-border-mode
27213 Select the display attributes for the borders of the inactive windows
27214 or the active window. The @var{mode} can be one of the following:
27217 Use normal attributes to display the border.
27223 Use reverse video mode.
27226 Use half bright mode.
27228 @item half-standout
27229 Use half bright and standout mode.
27232 Use extra bright or bold mode.
27234 @item bold-standout
27235 Use extra bright or bold and standout mode.
27240 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27243 @cindex @sc{gnu} Emacs
27244 A special interface allows you to use @sc{gnu} Emacs to view (and
27245 edit) the source files for the program you are debugging with
27248 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27249 executable file you want to debug as an argument. This command starts
27250 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27251 created Emacs buffer.
27252 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27254 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27259 All ``terminal'' input and output goes through an Emacs buffer, called
27262 This applies both to @value{GDBN} commands and their output, and to the input
27263 and output done by the program you are debugging.
27265 This is useful because it means that you can copy the text of previous
27266 commands and input them again; you can even use parts of the output
27269 All the facilities of Emacs' Shell mode are available for interacting
27270 with your program. In particular, you can send signals the usual
27271 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27275 @value{GDBN} displays source code through Emacs.
27277 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27278 source file for that frame and puts an arrow (@samp{=>}) at the
27279 left margin of the current line. Emacs uses a separate buffer for
27280 source display, and splits the screen to show both your @value{GDBN} session
27283 Explicit @value{GDBN} @code{list} or search commands still produce output as
27284 usual, but you probably have no reason to use them from Emacs.
27287 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27288 a graphical mode, enabled by default, which provides further buffers
27289 that can control the execution and describe the state of your program.
27290 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27292 If you specify an absolute file name when prompted for the @kbd{M-x
27293 gdb} argument, then Emacs sets your current working directory to where
27294 your program resides. If you only specify the file name, then Emacs
27295 sets your current working directory to the directory associated
27296 with the previous buffer. In this case, @value{GDBN} may find your
27297 program by searching your environment's @code{PATH} variable, but on
27298 some operating systems it might not find the source. So, although the
27299 @value{GDBN} input and output session proceeds normally, the auxiliary
27300 buffer does not display the current source and line of execution.
27302 The initial working directory of @value{GDBN} is printed on the top
27303 line of the GUD buffer and this serves as a default for the commands
27304 that specify files for @value{GDBN} to operate on. @xref{Files,
27305 ,Commands to Specify Files}.
27307 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27308 need to call @value{GDBN} by a different name (for example, if you
27309 keep several configurations around, with different names) you can
27310 customize the Emacs variable @code{gud-gdb-command-name} to run the
27313 In the GUD buffer, you can use these special Emacs commands in
27314 addition to the standard Shell mode commands:
27318 Describe the features of Emacs' GUD Mode.
27321 Execute to another source line, like the @value{GDBN} @code{step} command; also
27322 update the display window to show the current file and location.
27325 Execute to next source line in this function, skipping all function
27326 calls, like the @value{GDBN} @code{next} command. Then update the display window
27327 to show the current file and location.
27330 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27331 display window accordingly.
27334 Execute until exit from the selected stack frame, like the @value{GDBN}
27335 @code{finish} command.
27338 Continue execution of your program, like the @value{GDBN} @code{continue}
27342 Go up the number of frames indicated by the numeric argument
27343 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27344 like the @value{GDBN} @code{up} command.
27347 Go down the number of frames indicated by the numeric argument, like the
27348 @value{GDBN} @code{down} command.
27351 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27352 tells @value{GDBN} to set a breakpoint on the source line point is on.
27354 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27355 separate frame which shows a backtrace when the GUD buffer is current.
27356 Move point to any frame in the stack and type @key{RET} to make it
27357 become the current frame and display the associated source in the
27358 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27359 selected frame become the current one. In graphical mode, the
27360 speedbar displays watch expressions.
27362 If you accidentally delete the source-display buffer, an easy way to get
27363 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27364 request a frame display; when you run under Emacs, this recreates
27365 the source buffer if necessary to show you the context of the current
27368 The source files displayed in Emacs are in ordinary Emacs buffers
27369 which are visiting the source files in the usual way. You can edit
27370 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27371 communicates with Emacs in terms of line numbers. If you add or
27372 delete lines from the text, the line numbers that @value{GDBN} knows cease
27373 to correspond properly with the code.
27375 A more detailed description of Emacs' interaction with @value{GDBN} is
27376 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27380 @chapter The @sc{gdb/mi} Interface
27382 @unnumberedsec Function and Purpose
27384 @cindex @sc{gdb/mi}, its purpose
27385 @sc{gdb/mi} is a line based machine oriented text interface to
27386 @value{GDBN} and is activated by specifying using the
27387 @option{--interpreter} command line option (@pxref{Mode Options}). It
27388 is specifically intended to support the development of systems which
27389 use the debugger as just one small component of a larger system.
27391 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27392 in the form of a reference manual.
27394 Note that @sc{gdb/mi} is still under construction, so some of the
27395 features described below are incomplete and subject to change
27396 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27398 @unnumberedsec Notation and Terminology
27400 @cindex notational conventions, for @sc{gdb/mi}
27401 This chapter uses the following notation:
27405 @code{|} separates two alternatives.
27408 @code{[ @var{something} ]} indicates that @var{something} is optional:
27409 it may or may not be given.
27412 @code{( @var{group} )*} means that @var{group} inside the parentheses
27413 may repeat zero or more times.
27416 @code{( @var{group} )+} means that @var{group} inside the parentheses
27417 may repeat one or more times.
27420 @code{"@var{string}"} means a literal @var{string}.
27424 @heading Dependencies
27428 * GDB/MI General Design::
27429 * GDB/MI Command Syntax::
27430 * GDB/MI Compatibility with CLI::
27431 * GDB/MI Development and Front Ends::
27432 * GDB/MI Output Records::
27433 * GDB/MI Simple Examples::
27434 * GDB/MI Command Description Format::
27435 * GDB/MI Breakpoint Commands::
27436 * GDB/MI Catchpoint Commands::
27437 * GDB/MI Program Context::
27438 * GDB/MI Thread Commands::
27439 * GDB/MI Ada Tasking Commands::
27440 * GDB/MI Program Execution::
27441 * GDB/MI Stack Manipulation::
27442 * GDB/MI Variable Objects::
27443 * GDB/MI Data Manipulation::
27444 * GDB/MI Tracepoint Commands::
27445 * GDB/MI Symbol Query::
27446 * GDB/MI File Commands::
27448 * GDB/MI Kod Commands::
27449 * GDB/MI Memory Overlay Commands::
27450 * GDB/MI Signal Handling Commands::
27452 * GDB/MI Target Manipulation::
27453 * GDB/MI File Transfer Commands::
27454 * GDB/MI Miscellaneous Commands::
27457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27458 @node GDB/MI General Design
27459 @section @sc{gdb/mi} General Design
27460 @cindex GDB/MI General Design
27462 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27463 parts---commands sent to @value{GDBN}, responses to those commands
27464 and notifications. Each command results in exactly one response,
27465 indicating either successful completion of the command, or an error.
27466 For the commands that do not resume the target, the response contains the
27467 requested information. For the commands that resume the target, the
27468 response only indicates whether the target was successfully resumed.
27469 Notifications is the mechanism for reporting changes in the state of the
27470 target, or in @value{GDBN} state, that cannot conveniently be associated with
27471 a command and reported as part of that command response.
27473 The important examples of notifications are:
27477 Exec notifications. These are used to report changes in
27478 target state---when a target is resumed, or stopped. It would not
27479 be feasible to include this information in response of resuming
27480 commands, because one resume commands can result in multiple events in
27481 different threads. Also, quite some time may pass before any event
27482 happens in the target, while a frontend needs to know whether the resuming
27483 command itself was successfully executed.
27486 Console output, and status notifications. Console output
27487 notifications are used to report output of CLI commands, as well as
27488 diagnostics for other commands. Status notifications are used to
27489 report the progress of a long-running operation. Naturally, including
27490 this information in command response would mean no output is produced
27491 until the command is finished, which is undesirable.
27494 General notifications. Commands may have various side effects on
27495 the @value{GDBN} or target state beyond their official purpose. For example,
27496 a command may change the selected thread. Although such changes can
27497 be included in command response, using notification allows for more
27498 orthogonal frontend design.
27502 There's no guarantee that whenever an MI command reports an error,
27503 @value{GDBN} or the target are in any specific state, and especially,
27504 the state is not reverted to the state before the MI command was
27505 processed. Therefore, whenever an MI command results in an error,
27506 we recommend that the frontend refreshes all the information shown in
27507 the user interface.
27511 * Context management::
27512 * Asynchronous and non-stop modes::
27516 @node Context management
27517 @subsection Context management
27519 In most cases when @value{GDBN} accesses the target, this access is
27520 done in context of a specific thread and frame (@pxref{Frames}).
27521 Often, even when accessing global data, the target requires that a thread
27522 be specified. The CLI interface maintains the selected thread and frame,
27523 and supplies them to target on each command. This is convenient,
27524 because a command line user would not want to specify that information
27525 explicitly on each command, and because user interacts with
27526 @value{GDBN} via a single terminal, so no confusion is possible as
27527 to what thread and frame are the current ones.
27529 In the case of MI, the concept of selected thread and frame is less
27530 useful. First, a frontend can easily remember this information
27531 itself. Second, a graphical frontend can have more than one window,
27532 each one used for debugging a different thread, and the frontend might
27533 want to access additional threads for internal purposes. This
27534 increases the risk that by relying on implicitly selected thread, the
27535 frontend may be operating on a wrong one. Therefore, each MI command
27536 should explicitly specify which thread and frame to operate on. To
27537 make it possible, each MI command accepts the @samp{--thread} and
27538 @samp{--frame} options, the value to each is @value{GDBN} identifier
27539 for thread and frame to operate on.
27541 Usually, each top-level window in a frontend allows the user to select
27542 a thread and a frame, and remembers the user selection for further
27543 operations. However, in some cases @value{GDBN} may suggest that the
27544 current thread be changed. For example, when stopping on a breakpoint
27545 it is reasonable to switch to the thread where breakpoint is hit. For
27546 another example, if the user issues the CLI @samp{thread} command via
27547 the frontend, it is desirable to change the frontend's selected thread to the
27548 one specified by user. @value{GDBN} communicates the suggestion to
27549 change current thread using the @samp{=thread-selected} notification.
27550 No such notification is available for the selected frame at the moment.
27552 Note that historically, MI shares the selected thread with CLI, so
27553 frontends used the @code{-thread-select} to execute commands in the
27554 right context. However, getting this to work right is cumbersome. The
27555 simplest way is for frontend to emit @code{-thread-select} command
27556 before every command. This doubles the number of commands that need
27557 to be sent. The alternative approach is to suppress @code{-thread-select}
27558 if the selected thread in @value{GDBN} is supposed to be identical to the
27559 thread the frontend wants to operate on. However, getting this
27560 optimization right can be tricky. In particular, if the frontend
27561 sends several commands to @value{GDBN}, and one of the commands changes the
27562 selected thread, then the behaviour of subsequent commands will
27563 change. So, a frontend should either wait for response from such
27564 problematic commands, or explicitly add @code{-thread-select} for
27565 all subsequent commands. No frontend is known to do this exactly
27566 right, so it is suggested to just always pass the @samp{--thread} and
27567 @samp{--frame} options.
27569 @node Asynchronous and non-stop modes
27570 @subsection Asynchronous command execution and non-stop mode
27572 On some targets, @value{GDBN} is capable of processing MI commands
27573 even while the target is running. This is called @dfn{asynchronous
27574 command execution} (@pxref{Background Execution}). The frontend may
27575 specify a preferrence for asynchronous execution using the
27576 @code{-gdb-set target-async 1} command, which should be emitted before
27577 either running the executable or attaching to the target. After the
27578 frontend has started the executable or attached to the target, it can
27579 find if asynchronous execution is enabled using the
27580 @code{-list-target-features} command.
27582 Even if @value{GDBN} can accept a command while target is running,
27583 many commands that access the target do not work when the target is
27584 running. Therefore, asynchronous command execution is most useful
27585 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27586 it is possible to examine the state of one thread, while other threads
27589 When a given thread is running, MI commands that try to access the
27590 target in the context of that thread may not work, or may work only on
27591 some targets. In particular, commands that try to operate on thread's
27592 stack will not work, on any target. Commands that read memory, or
27593 modify breakpoints, may work or not work, depending on the target. Note
27594 that even commands that operate on global state, such as @code{print},
27595 @code{set}, and breakpoint commands, still access the target in the
27596 context of a specific thread, so frontend should try to find a
27597 stopped thread and perform the operation on that thread (using the
27598 @samp{--thread} option).
27600 Which commands will work in the context of a running thread is
27601 highly target dependent. However, the two commands
27602 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27603 to find the state of a thread, will always work.
27605 @node Thread groups
27606 @subsection Thread groups
27607 @value{GDBN} may be used to debug several processes at the same time.
27608 On some platfroms, @value{GDBN} may support debugging of several
27609 hardware systems, each one having several cores with several different
27610 processes running on each core. This section describes the MI
27611 mechanism to support such debugging scenarios.
27613 The key observation is that regardless of the structure of the
27614 target, MI can have a global list of threads, because most commands that
27615 accept the @samp{--thread} option do not need to know what process that
27616 thread belongs to. Therefore, it is not necessary to introduce
27617 neither additional @samp{--process} option, nor an notion of the
27618 current process in the MI interface. The only strictly new feature
27619 that is required is the ability to find how the threads are grouped
27622 To allow the user to discover such grouping, and to support arbitrary
27623 hierarchy of machines/cores/processes, MI introduces the concept of a
27624 @dfn{thread group}. Thread group is a collection of threads and other
27625 thread groups. A thread group always has a string identifier, a type,
27626 and may have additional attributes specific to the type. A new
27627 command, @code{-list-thread-groups}, returns the list of top-level
27628 thread groups, which correspond to processes that @value{GDBN} is
27629 debugging at the moment. By passing an identifier of a thread group
27630 to the @code{-list-thread-groups} command, it is possible to obtain
27631 the members of specific thread group.
27633 To allow the user to easily discover processes, and other objects, he
27634 wishes to debug, a concept of @dfn{available thread group} is
27635 introduced. Available thread group is an thread group that
27636 @value{GDBN} is not debugging, but that can be attached to, using the
27637 @code{-target-attach} command. The list of available top-level thread
27638 groups can be obtained using @samp{-list-thread-groups --available}.
27639 In general, the content of a thread group may be only retrieved only
27640 after attaching to that thread group.
27642 Thread groups are related to inferiors (@pxref{Inferiors and
27643 Programs}). Each inferior corresponds to a thread group of a special
27644 type @samp{process}, and some additional operations are permitted on
27645 such thread groups.
27647 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27648 @node GDB/MI Command Syntax
27649 @section @sc{gdb/mi} Command Syntax
27652 * GDB/MI Input Syntax::
27653 * GDB/MI Output Syntax::
27656 @node GDB/MI Input Syntax
27657 @subsection @sc{gdb/mi} Input Syntax
27659 @cindex input syntax for @sc{gdb/mi}
27660 @cindex @sc{gdb/mi}, input syntax
27662 @item @var{command} @expansion{}
27663 @code{@var{cli-command} | @var{mi-command}}
27665 @item @var{cli-command} @expansion{}
27666 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27667 @var{cli-command} is any existing @value{GDBN} CLI command.
27669 @item @var{mi-command} @expansion{}
27670 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27671 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27673 @item @var{token} @expansion{}
27674 "any sequence of digits"
27676 @item @var{option} @expansion{}
27677 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27679 @item @var{parameter} @expansion{}
27680 @code{@var{non-blank-sequence} | @var{c-string}}
27682 @item @var{operation} @expansion{}
27683 @emph{any of the operations described in this chapter}
27685 @item @var{non-blank-sequence} @expansion{}
27686 @emph{anything, provided it doesn't contain special characters such as
27687 "-", @var{nl}, """ and of course " "}
27689 @item @var{c-string} @expansion{}
27690 @code{""" @var{seven-bit-iso-c-string-content} """}
27692 @item @var{nl} @expansion{}
27701 The CLI commands are still handled by the @sc{mi} interpreter; their
27702 output is described below.
27705 The @code{@var{token}}, when present, is passed back when the command
27709 Some @sc{mi} commands accept optional arguments as part of the parameter
27710 list. Each option is identified by a leading @samp{-} (dash) and may be
27711 followed by an optional argument parameter. Options occur first in the
27712 parameter list and can be delimited from normal parameters using
27713 @samp{--} (this is useful when some parameters begin with a dash).
27720 We want easy access to the existing CLI syntax (for debugging).
27723 We want it to be easy to spot a @sc{mi} operation.
27726 @node GDB/MI Output Syntax
27727 @subsection @sc{gdb/mi} Output Syntax
27729 @cindex output syntax of @sc{gdb/mi}
27730 @cindex @sc{gdb/mi}, output syntax
27731 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27732 followed, optionally, by a single result record. This result record
27733 is for the most recent command. The sequence of output records is
27734 terminated by @samp{(gdb)}.
27736 If an input command was prefixed with a @code{@var{token}} then the
27737 corresponding output for that command will also be prefixed by that same
27741 @item @var{output} @expansion{}
27742 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27744 @item @var{result-record} @expansion{}
27745 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27747 @item @var{out-of-band-record} @expansion{}
27748 @code{@var{async-record} | @var{stream-record}}
27750 @item @var{async-record} @expansion{}
27751 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27753 @item @var{exec-async-output} @expansion{}
27754 @code{[ @var{token} ] "*" @var{async-output}}
27756 @item @var{status-async-output} @expansion{}
27757 @code{[ @var{token} ] "+" @var{async-output}}
27759 @item @var{notify-async-output} @expansion{}
27760 @code{[ @var{token} ] "=" @var{async-output}}
27762 @item @var{async-output} @expansion{}
27763 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27765 @item @var{result-class} @expansion{}
27766 @code{"done" | "running" | "connected" | "error" | "exit"}
27768 @item @var{async-class} @expansion{}
27769 @code{"stopped" | @var{others}} (where @var{others} will be added
27770 depending on the needs---this is still in development).
27772 @item @var{result} @expansion{}
27773 @code{ @var{variable} "=" @var{value}}
27775 @item @var{variable} @expansion{}
27776 @code{ @var{string} }
27778 @item @var{value} @expansion{}
27779 @code{ @var{const} | @var{tuple} | @var{list} }
27781 @item @var{const} @expansion{}
27782 @code{@var{c-string}}
27784 @item @var{tuple} @expansion{}
27785 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27787 @item @var{list} @expansion{}
27788 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27789 @var{result} ( "," @var{result} )* "]" }
27791 @item @var{stream-record} @expansion{}
27792 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27794 @item @var{console-stream-output} @expansion{}
27795 @code{"~" @var{c-string}}
27797 @item @var{target-stream-output} @expansion{}
27798 @code{"@@" @var{c-string}}
27800 @item @var{log-stream-output} @expansion{}
27801 @code{"&" @var{c-string}}
27803 @item @var{nl} @expansion{}
27806 @item @var{token} @expansion{}
27807 @emph{any sequence of digits}.
27815 All output sequences end in a single line containing a period.
27818 The @code{@var{token}} is from the corresponding request. Note that
27819 for all async output, while the token is allowed by the grammar and
27820 may be output by future versions of @value{GDBN} for select async
27821 output messages, it is generally omitted. Frontends should treat
27822 all async output as reporting general changes in the state of the
27823 target and there should be no need to associate async output to any
27827 @cindex status output in @sc{gdb/mi}
27828 @var{status-async-output} contains on-going status information about the
27829 progress of a slow operation. It can be discarded. All status output is
27830 prefixed by @samp{+}.
27833 @cindex async output in @sc{gdb/mi}
27834 @var{exec-async-output} contains asynchronous state change on the target
27835 (stopped, started, disappeared). All async output is prefixed by
27839 @cindex notify output in @sc{gdb/mi}
27840 @var{notify-async-output} contains supplementary information that the
27841 client should handle (e.g., a new breakpoint information). All notify
27842 output is prefixed by @samp{=}.
27845 @cindex console output in @sc{gdb/mi}
27846 @var{console-stream-output} is output that should be displayed as is in the
27847 console. It is the textual response to a CLI command. All the console
27848 output is prefixed by @samp{~}.
27851 @cindex target output in @sc{gdb/mi}
27852 @var{target-stream-output} is the output produced by the target program.
27853 All the target output is prefixed by @samp{@@}.
27856 @cindex log output in @sc{gdb/mi}
27857 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27858 instance messages that should be displayed as part of an error log. All
27859 the log output is prefixed by @samp{&}.
27862 @cindex list output in @sc{gdb/mi}
27863 New @sc{gdb/mi} commands should only output @var{lists} containing
27869 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27870 details about the various output records.
27872 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27873 @node GDB/MI Compatibility with CLI
27874 @section @sc{gdb/mi} Compatibility with CLI
27876 @cindex compatibility, @sc{gdb/mi} and CLI
27877 @cindex @sc{gdb/mi}, compatibility with CLI
27879 For the developers convenience CLI commands can be entered directly,
27880 but there may be some unexpected behaviour. For example, commands
27881 that query the user will behave as if the user replied yes, breakpoint
27882 command lists are not executed and some CLI commands, such as
27883 @code{if}, @code{when} and @code{define}, prompt for further input with
27884 @samp{>}, which is not valid MI output.
27886 This feature may be removed at some stage in the future and it is
27887 recommended that front ends use the @code{-interpreter-exec} command
27888 (@pxref{-interpreter-exec}).
27890 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27891 @node GDB/MI Development and Front Ends
27892 @section @sc{gdb/mi} Development and Front Ends
27893 @cindex @sc{gdb/mi} development
27895 The application which takes the MI output and presents the state of the
27896 program being debugged to the user is called a @dfn{front end}.
27898 Although @sc{gdb/mi} is still incomplete, it is currently being used
27899 by a variety of front ends to @value{GDBN}. This makes it difficult
27900 to introduce new functionality without breaking existing usage. This
27901 section tries to minimize the problems by describing how the protocol
27904 Some changes in MI need not break a carefully designed front end, and
27905 for these the MI version will remain unchanged. The following is a
27906 list of changes that may occur within one level, so front ends should
27907 parse MI output in a way that can handle them:
27911 New MI commands may be added.
27914 New fields may be added to the output of any MI command.
27917 The range of values for fields with specified values, e.g.,
27918 @code{in_scope} (@pxref{-var-update}) may be extended.
27920 @c The format of field's content e.g type prefix, may change so parse it
27921 @c at your own risk. Yes, in general?
27923 @c The order of fields may change? Shouldn't really matter but it might
27924 @c resolve inconsistencies.
27927 If the changes are likely to break front ends, the MI version level
27928 will be increased by one. This will allow the front end to parse the
27929 output according to the MI version. Apart from mi0, new versions of
27930 @value{GDBN} will not support old versions of MI and it will be the
27931 responsibility of the front end to work with the new one.
27933 @c Starting with mi3, add a new command -mi-version that prints the MI
27936 The best way to avoid unexpected changes in MI that might break your front
27937 end is to make your project known to @value{GDBN} developers and
27938 follow development on @email{gdb@@sourceware.org} and
27939 @email{gdb-patches@@sourceware.org}.
27940 @cindex mailing lists
27942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27943 @node GDB/MI Output Records
27944 @section @sc{gdb/mi} Output Records
27947 * GDB/MI Result Records::
27948 * GDB/MI Stream Records::
27949 * GDB/MI Async Records::
27950 * GDB/MI Breakpoint Information::
27951 * GDB/MI Frame Information::
27952 * GDB/MI Thread Information::
27953 * GDB/MI Ada Exception Information::
27956 @node GDB/MI Result Records
27957 @subsection @sc{gdb/mi} Result Records
27959 @cindex result records in @sc{gdb/mi}
27960 @cindex @sc{gdb/mi}, result records
27961 In addition to a number of out-of-band notifications, the response to a
27962 @sc{gdb/mi} command includes one of the following result indications:
27966 @item "^done" [ "," @var{results} ]
27967 The synchronous operation was successful, @code{@var{results}} are the return
27972 This result record is equivalent to @samp{^done}. Historically, it
27973 was output instead of @samp{^done} if the command has resumed the
27974 target. This behaviour is maintained for backward compatibility, but
27975 all frontends should treat @samp{^done} and @samp{^running}
27976 identically and rely on the @samp{*running} output record to determine
27977 which threads are resumed.
27981 @value{GDBN} has connected to a remote target.
27983 @item "^error" "," @var{c-string}
27985 The operation failed. The @code{@var{c-string}} contains the corresponding
27990 @value{GDBN} has terminated.
27994 @node GDB/MI Stream Records
27995 @subsection @sc{gdb/mi} Stream Records
27997 @cindex @sc{gdb/mi}, stream records
27998 @cindex stream records in @sc{gdb/mi}
27999 @value{GDBN} internally maintains a number of output streams: the console, the
28000 target, and the log. The output intended for each of these streams is
28001 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28003 Each stream record begins with a unique @dfn{prefix character} which
28004 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28005 Syntax}). In addition to the prefix, each stream record contains a
28006 @code{@var{string-output}}. This is either raw text (with an implicit new
28007 line) or a quoted C string (which does not contain an implicit newline).
28010 @item "~" @var{string-output}
28011 The console output stream contains text that should be displayed in the
28012 CLI console window. It contains the textual responses to CLI commands.
28014 @item "@@" @var{string-output}
28015 The target output stream contains any textual output from the running
28016 target. This is only present when GDB's event loop is truly
28017 asynchronous, which is currently only the case for remote targets.
28019 @item "&" @var{string-output}
28020 The log stream contains debugging messages being produced by @value{GDBN}'s
28024 @node GDB/MI Async Records
28025 @subsection @sc{gdb/mi} Async Records
28027 @cindex async records in @sc{gdb/mi}
28028 @cindex @sc{gdb/mi}, async records
28029 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28030 additional changes that have occurred. Those changes can either be a
28031 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28032 target activity (e.g., target stopped).
28034 The following is the list of possible async records:
28038 @item *running,thread-id="@var{thread}"
28039 The target is now running. The @var{thread} field tells which
28040 specific thread is now running, and can be @samp{all} if all threads
28041 are running. The frontend should assume that no interaction with a
28042 running thread is possible after this notification is produced.
28043 The frontend should not assume that this notification is output
28044 only once for any command. @value{GDBN} may emit this notification
28045 several times, either for different threads, because it cannot resume
28046 all threads together, or even for a single thread, if the thread must
28047 be stepped though some code before letting it run freely.
28049 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28050 The target has stopped. The @var{reason} field can have one of the
28054 @item breakpoint-hit
28055 A breakpoint was reached.
28056 @item watchpoint-trigger
28057 A watchpoint was triggered.
28058 @item read-watchpoint-trigger
28059 A read watchpoint was triggered.
28060 @item access-watchpoint-trigger
28061 An access watchpoint was triggered.
28062 @item function-finished
28063 An -exec-finish or similar CLI command was accomplished.
28064 @item location-reached
28065 An -exec-until or similar CLI command was accomplished.
28066 @item watchpoint-scope
28067 A watchpoint has gone out of scope.
28068 @item end-stepping-range
28069 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28070 similar CLI command was accomplished.
28071 @item exited-signalled
28072 The inferior exited because of a signal.
28074 The inferior exited.
28075 @item exited-normally
28076 The inferior exited normally.
28077 @item signal-received
28078 A signal was received by the inferior.
28080 The inferior has stopped due to a library being loaded or unloaded.
28081 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28082 set or when a @code{catch load} or @code{catch unload} catchpoint is
28083 in use (@pxref{Set Catchpoints}).
28085 The inferior has forked. This is reported when @code{catch fork}
28086 (@pxref{Set Catchpoints}) has been used.
28088 The inferior has vforked. This is reported in when @code{catch vfork}
28089 (@pxref{Set Catchpoints}) has been used.
28090 @item syscall-entry
28091 The inferior entered a system call. This is reported when @code{catch
28092 syscall} (@pxref{Set Catchpoints}) has been used.
28093 @item syscall-entry
28094 The inferior returned from a system call. This is reported when
28095 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28097 The inferior called @code{exec}. This is reported when @code{catch exec}
28098 (@pxref{Set Catchpoints}) has been used.
28101 The @var{id} field identifies the thread that directly caused the stop
28102 -- for example by hitting a breakpoint. Depending on whether all-stop
28103 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28104 stop all threads, or only the thread that directly triggered the stop.
28105 If all threads are stopped, the @var{stopped} field will have the
28106 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28107 field will be a list of thread identifiers. Presently, this list will
28108 always include a single thread, but frontend should be prepared to see
28109 several threads in the list. The @var{core} field reports the
28110 processor core on which the stop event has happened. This field may be absent
28111 if such information is not available.
28113 @item =thread-group-added,id="@var{id}"
28114 @itemx =thread-group-removed,id="@var{id}"
28115 A thread group was either added or removed. The @var{id} field
28116 contains the @value{GDBN} identifier of the thread group. When a thread
28117 group is added, it generally might not be associated with a running
28118 process. When a thread group is removed, its id becomes invalid and
28119 cannot be used in any way.
28121 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28122 A thread group became associated with a running program,
28123 either because the program was just started or the thread group
28124 was attached to a program. The @var{id} field contains the
28125 @value{GDBN} identifier of the thread group. The @var{pid} field
28126 contains process identifier, specific to the operating system.
28128 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28129 A thread group is no longer associated with a running program,
28130 either because the program has exited, or because it was detached
28131 from. The @var{id} field contains the @value{GDBN} identifier of the
28132 thread group. @var{code} is the exit code of the inferior; it exists
28133 only when the inferior exited with some code.
28135 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28136 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28137 A thread either was created, or has exited. The @var{id} field
28138 contains the @value{GDBN} identifier of the thread. The @var{gid}
28139 field identifies the thread group this thread belongs to.
28141 @item =thread-selected,id="@var{id}"
28142 Informs that the selected thread was changed as result of the last
28143 command. This notification is not emitted as result of @code{-thread-select}
28144 command but is emitted whenever an MI command that is not documented
28145 to change the selected thread actually changes it. In particular,
28146 invoking, directly or indirectly (via user-defined command), the CLI
28147 @code{thread} command, will generate this notification.
28149 We suggest that in response to this notification, front ends
28150 highlight the selected thread and cause subsequent commands to apply to
28153 @item =library-loaded,...
28154 Reports that a new library file was loaded by the program. This
28155 notification has 4 fields---@var{id}, @var{target-name},
28156 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28157 opaque identifier of the library. For remote debugging case,
28158 @var{target-name} and @var{host-name} fields give the name of the
28159 library file on the target, and on the host respectively. For native
28160 debugging, both those fields have the same value. The
28161 @var{symbols-loaded} field is emitted only for backward compatibility
28162 and should not be relied on to convey any useful information. The
28163 @var{thread-group} field, if present, specifies the id of the thread
28164 group in whose context the library was loaded. If the field is
28165 absent, it means the library was loaded in the context of all present
28168 @item =library-unloaded,...
28169 Reports that a library was unloaded by the program. This notification
28170 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28171 the same meaning as for the @code{=library-loaded} notification.
28172 The @var{thread-group} field, if present, specifies the id of the
28173 thread group in whose context the library was unloaded. If the field is
28174 absent, it means the library was unloaded in the context of all present
28177 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28178 @itemx =traceframe-changed,end
28179 Reports that the trace frame was changed and its new number is
28180 @var{tfnum}. The number of the tracepoint associated with this trace
28181 frame is @var{tpnum}.
28183 @item =tsv-created,name=@var{name},initial=@var{initial}
28184 Reports that the new trace state variable @var{name} is created with
28185 initial value @var{initial}.
28187 @item =tsv-deleted,name=@var{name}
28188 @itemx =tsv-deleted
28189 Reports that the trace state variable @var{name} is deleted or all
28190 trace state variables are deleted.
28192 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28193 Reports that the trace state variable @var{name} is modified with
28194 the initial value @var{initial}. The current value @var{current} of
28195 trace state variable is optional and is reported if the current
28196 value of trace state variable is known.
28198 @item =breakpoint-created,bkpt=@{...@}
28199 @itemx =breakpoint-modified,bkpt=@{...@}
28200 @itemx =breakpoint-deleted,id=@var{number}
28201 Reports that a breakpoint was created, modified, or deleted,
28202 respectively. Only user-visible breakpoints are reported to the MI
28205 The @var{bkpt} argument is of the same form as returned by the various
28206 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28207 @var{number} is the ordinal number of the breakpoint.
28209 Note that if a breakpoint is emitted in the result record of a
28210 command, then it will not also be emitted in an async record.
28212 @item =record-started,thread-group="@var{id}"
28213 @itemx =record-stopped,thread-group="@var{id}"
28214 Execution log recording was either started or stopped on an
28215 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28216 group corresponding to the affected inferior.
28218 @item =cmd-param-changed,param=@var{param},value=@var{value}
28219 Reports that a parameter of the command @code{set @var{param}} is
28220 changed to @var{value}. In the multi-word @code{set} command,
28221 the @var{param} is the whole parameter list to @code{set} command.
28222 For example, In command @code{set check type on}, @var{param}
28223 is @code{check type} and @var{value} is @code{on}.
28225 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28226 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28227 written in an inferior. The @var{id} is the identifier of the
28228 thread group corresponding to the affected inferior. The optional
28229 @code{type="code"} part is reported if the memory written to holds
28233 @node GDB/MI Breakpoint Information
28234 @subsection @sc{gdb/mi} Breakpoint Information
28236 When @value{GDBN} reports information about a breakpoint, a
28237 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28242 The breakpoint number. For a breakpoint that represents one location
28243 of a multi-location breakpoint, this will be a dotted pair, like
28247 The type of the breakpoint. For ordinary breakpoints this will be
28248 @samp{breakpoint}, but many values are possible.
28251 If the type of the breakpoint is @samp{catchpoint}, then this
28252 indicates the exact type of catchpoint.
28255 This is the breakpoint disposition---either @samp{del}, meaning that
28256 the breakpoint will be deleted at the next stop, or @samp{keep},
28257 meaning that the breakpoint will not be deleted.
28260 This indicates whether the breakpoint is enabled, in which case the
28261 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28262 Note that this is not the same as the field @code{enable}.
28265 The address of the breakpoint. This may be a hexidecimal number,
28266 giving the address; or the string @samp{<PENDING>}, for a pending
28267 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28268 multiple locations. This field will not be present if no address can
28269 be determined. For example, a watchpoint does not have an address.
28272 If known, the function in which the breakpoint appears.
28273 If not known, this field is not present.
28276 The name of the source file which contains this function, if known.
28277 If not known, this field is not present.
28280 The full file name of the source file which contains this function, if
28281 known. If not known, this field is not present.
28284 The line number at which this breakpoint appears, if known.
28285 If not known, this field is not present.
28288 If the source file is not known, this field may be provided. If
28289 provided, this holds the address of the breakpoint, possibly followed
28293 If this breakpoint is pending, this field is present and holds the
28294 text used to set the breakpoint, as entered by the user.
28297 Where this breakpoint's condition is evaluated, either @samp{host} or
28301 If this is a thread-specific breakpoint, then this identifies the
28302 thread in which the breakpoint can trigger.
28305 If this breakpoint is restricted to a particular Ada task, then this
28306 field will hold the task identifier.
28309 If the breakpoint is conditional, this is the condition expression.
28312 The ignore count of the breakpoint.
28315 The enable count of the breakpoint.
28317 @item traceframe-usage
28320 @item static-tracepoint-marker-string-id
28321 For a static tracepoint, the name of the static tracepoint marker.
28324 For a masked watchpoint, this is the mask.
28327 A tracepoint's pass count.
28329 @item original-location
28330 The location of the breakpoint as originally specified by the user.
28331 This field is optional.
28334 The number of times the breakpoint has been hit.
28337 This field is only given for tracepoints. This is either @samp{y},
28338 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28342 Some extra data, the exact contents of which are type-dependent.
28346 For example, here is what the output of @code{-break-insert}
28347 (@pxref{GDB/MI Breakpoint Commands}) might be:
28350 -> -break-insert main
28351 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28352 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28353 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28358 @node GDB/MI Frame Information
28359 @subsection @sc{gdb/mi} Frame Information
28361 Response from many MI commands includes an information about stack
28362 frame. This information is a tuple that may have the following
28367 The level of the stack frame. The innermost frame has the level of
28368 zero. This field is always present.
28371 The name of the function corresponding to the frame. This field may
28372 be absent if @value{GDBN} is unable to determine the function name.
28375 The code address for the frame. This field is always present.
28378 The name of the source files that correspond to the frame's code
28379 address. This field may be absent.
28382 The source line corresponding to the frames' code address. This field
28386 The name of the binary file (either executable or shared library) the
28387 corresponds to the frame's code address. This field may be absent.
28391 @node GDB/MI Thread Information
28392 @subsection @sc{gdb/mi} Thread Information
28394 Whenever @value{GDBN} has to report an information about a thread, it
28395 uses a tuple with the following fields:
28399 The numeric id assigned to the thread by @value{GDBN}. This field is
28403 Target-specific string identifying the thread. This field is always present.
28406 Additional information about the thread provided by the target.
28407 It is supposed to be human-readable and not interpreted by the
28408 frontend. This field is optional.
28411 Either @samp{stopped} or @samp{running}, depending on whether the
28412 thread is presently running. This field is always present.
28415 The value of this field is an integer number of the processor core the
28416 thread was last seen on. This field is optional.
28419 @node GDB/MI Ada Exception Information
28420 @subsection @sc{gdb/mi} Ada Exception Information
28422 Whenever a @code{*stopped} record is emitted because the program
28423 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28424 @value{GDBN} provides the name of the exception that was raised via
28425 the @code{exception-name} field.
28427 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28428 @node GDB/MI Simple Examples
28429 @section Simple Examples of @sc{gdb/mi} Interaction
28430 @cindex @sc{gdb/mi}, simple examples
28432 This subsection presents several simple examples of interaction using
28433 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28434 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28435 the output received from @sc{gdb/mi}.
28437 Note the line breaks shown in the examples are here only for
28438 readability, they don't appear in the real output.
28440 @subheading Setting a Breakpoint
28442 Setting a breakpoint generates synchronous output which contains detailed
28443 information of the breakpoint.
28446 -> -break-insert main
28447 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28448 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28449 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28454 @subheading Program Execution
28456 Program execution generates asynchronous records and MI gives the
28457 reason that execution stopped.
28463 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28464 frame=@{addr="0x08048564",func="main",
28465 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28466 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28471 <- *stopped,reason="exited-normally"
28475 @subheading Quitting @value{GDBN}
28477 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28485 Please note that @samp{^exit} is printed immediately, but it might
28486 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28487 performs necessary cleanups, including killing programs being debugged
28488 or disconnecting from debug hardware, so the frontend should wait till
28489 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28490 fails to exit in reasonable time.
28492 @subheading A Bad Command
28494 Here's what happens if you pass a non-existent command:
28498 <- ^error,msg="Undefined MI command: rubbish"
28503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28504 @node GDB/MI Command Description Format
28505 @section @sc{gdb/mi} Command Description Format
28507 The remaining sections describe blocks of commands. Each block of
28508 commands is laid out in a fashion similar to this section.
28510 @subheading Motivation
28512 The motivation for this collection of commands.
28514 @subheading Introduction
28516 A brief introduction to this collection of commands as a whole.
28518 @subheading Commands
28520 For each command in the block, the following is described:
28522 @subsubheading Synopsis
28525 -command @var{args}@dots{}
28528 @subsubheading Result
28530 @subsubheading @value{GDBN} Command
28532 The corresponding @value{GDBN} CLI command(s), if any.
28534 @subsubheading Example
28536 Example(s) formatted for readability. Some of the described commands have
28537 not been implemented yet and these are labeled N.A.@: (not available).
28540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28541 @node GDB/MI Breakpoint Commands
28542 @section @sc{gdb/mi} Breakpoint Commands
28544 @cindex breakpoint commands for @sc{gdb/mi}
28545 @cindex @sc{gdb/mi}, breakpoint commands
28546 This section documents @sc{gdb/mi} commands for manipulating
28549 @subheading The @code{-break-after} Command
28550 @findex -break-after
28552 @subsubheading Synopsis
28555 -break-after @var{number} @var{count}
28558 The breakpoint number @var{number} is not in effect until it has been
28559 hit @var{count} times. To see how this is reflected in the output of
28560 the @samp{-break-list} command, see the description of the
28561 @samp{-break-list} command below.
28563 @subsubheading @value{GDBN} Command
28565 The corresponding @value{GDBN} command is @samp{ignore}.
28567 @subsubheading Example
28572 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28573 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28574 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28582 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28589 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28590 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28591 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28596 @subheading The @code{-break-catch} Command
28597 @findex -break-catch
28600 @subheading The @code{-break-commands} Command
28601 @findex -break-commands
28603 @subsubheading Synopsis
28606 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28609 Specifies the CLI commands that should be executed when breakpoint
28610 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28611 are the commands. If no command is specified, any previously-set
28612 commands are cleared. @xref{Break Commands}. Typical use of this
28613 functionality is tracing a program, that is, printing of values of
28614 some variables whenever breakpoint is hit and then continuing.
28616 @subsubheading @value{GDBN} Command
28618 The corresponding @value{GDBN} command is @samp{commands}.
28620 @subsubheading Example
28625 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28626 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28627 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28630 -break-commands 1 "print v" "continue"
28635 @subheading The @code{-break-condition} Command
28636 @findex -break-condition
28638 @subsubheading Synopsis
28641 -break-condition @var{number} @var{expr}
28644 Breakpoint @var{number} will stop the program only if the condition in
28645 @var{expr} is true. The condition becomes part of the
28646 @samp{-break-list} output (see the description of the @samp{-break-list}
28649 @subsubheading @value{GDBN} Command
28651 The corresponding @value{GDBN} command is @samp{condition}.
28653 @subsubheading Example
28657 -break-condition 1 1
28661 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28662 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28663 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28664 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28665 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28666 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28667 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28668 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28669 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28670 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28674 @subheading The @code{-break-delete} Command
28675 @findex -break-delete
28677 @subsubheading Synopsis
28680 -break-delete ( @var{breakpoint} )+
28683 Delete the breakpoint(s) whose number(s) are specified in the argument
28684 list. This is obviously reflected in the breakpoint list.
28686 @subsubheading @value{GDBN} Command
28688 The corresponding @value{GDBN} command is @samp{delete}.
28690 @subsubheading Example
28698 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28699 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28700 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28701 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28702 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28703 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28704 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28709 @subheading The @code{-break-disable} Command
28710 @findex -break-disable
28712 @subsubheading Synopsis
28715 -break-disable ( @var{breakpoint} )+
28718 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28719 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28721 @subsubheading @value{GDBN} Command
28723 The corresponding @value{GDBN} command is @samp{disable}.
28725 @subsubheading Example
28733 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28740 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28741 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28742 line="5",thread-groups=["i1"],times="0"@}]@}
28746 @subheading The @code{-break-enable} Command
28747 @findex -break-enable
28749 @subsubheading Synopsis
28752 -break-enable ( @var{breakpoint} )+
28755 Enable (previously disabled) @var{breakpoint}(s).
28757 @subsubheading @value{GDBN} Command
28759 The corresponding @value{GDBN} command is @samp{enable}.
28761 @subsubheading Example
28769 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28770 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28771 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28772 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28773 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28774 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28775 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28776 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28777 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28778 line="5",thread-groups=["i1"],times="0"@}]@}
28782 @subheading The @code{-break-info} Command
28783 @findex -break-info
28785 @subsubheading Synopsis
28788 -break-info @var{breakpoint}
28792 Get information about a single breakpoint.
28794 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28795 Information}, for details on the format of each breakpoint in the
28798 @subsubheading @value{GDBN} Command
28800 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28802 @subsubheading Example
28805 @subheading The @code{-break-insert} Command
28806 @findex -break-insert
28808 @subsubheading Synopsis
28811 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28812 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28813 [ -p @var{thread-id} ] [ @var{location} ]
28817 If specified, @var{location}, can be one of:
28824 @item filename:linenum
28825 @item filename:function
28829 The possible optional parameters of this command are:
28833 Insert a temporary breakpoint.
28835 Insert a hardware breakpoint.
28837 If @var{location} cannot be parsed (for example if it
28838 refers to unknown files or functions), create a pending
28839 breakpoint. Without this flag, @value{GDBN} will report
28840 an error, and won't create a breakpoint, if @var{location}
28843 Create a disabled breakpoint.
28845 Create a tracepoint. @xref{Tracepoints}. When this parameter
28846 is used together with @samp{-h}, a fast tracepoint is created.
28847 @item -c @var{condition}
28848 Make the breakpoint conditional on @var{condition}.
28849 @item -i @var{ignore-count}
28850 Initialize the @var{ignore-count}.
28851 @item -p @var{thread-id}
28852 Restrict the breakpoint to the specified @var{thread-id}.
28855 @subsubheading Result
28857 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28858 resulting breakpoint.
28860 Note: this format is open to change.
28861 @c An out-of-band breakpoint instead of part of the result?
28863 @subsubheading @value{GDBN} Command
28865 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28866 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28868 @subsubheading Example
28873 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28874 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28877 -break-insert -t foo
28878 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28879 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28883 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28884 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28885 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28886 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28887 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28888 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28889 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28890 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28891 addr="0x0001072c", func="main",file="recursive2.c",
28892 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28894 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28895 addr="0x00010774",func="foo",file="recursive2.c",
28896 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28899 @c -break-insert -r foo.*
28900 @c ~int foo(int, int);
28901 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28902 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28907 @subheading The @code{-break-list} Command
28908 @findex -break-list
28910 @subsubheading Synopsis
28916 Displays the list of inserted breakpoints, showing the following fields:
28920 number of the breakpoint
28922 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28924 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28927 is the breakpoint enabled or no: @samp{y} or @samp{n}
28929 memory location at which the breakpoint is set
28931 logical location of the breakpoint, expressed by function name, file
28933 @item Thread-groups
28934 list of thread groups to which this breakpoint applies
28936 number of times the breakpoint has been hit
28939 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28940 @code{body} field is an empty list.
28942 @subsubheading @value{GDBN} Command
28944 The corresponding @value{GDBN} command is @samp{info break}.
28946 @subsubheading Example
28951 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28952 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28953 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28954 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28955 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28956 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28957 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28958 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28959 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28961 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28962 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28963 line="13",thread-groups=["i1"],times="0"@}]@}
28967 Here's an example of the result when there are no breakpoints:
28972 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28973 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28974 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28975 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28976 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28977 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28978 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28983 @subheading The @code{-break-passcount} Command
28984 @findex -break-passcount
28986 @subsubheading Synopsis
28989 -break-passcount @var{tracepoint-number} @var{passcount}
28992 Set the passcount for tracepoint @var{tracepoint-number} to
28993 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28994 is not a tracepoint, error is emitted. This corresponds to CLI
28995 command @samp{passcount}.
28997 @subheading The @code{-break-watch} Command
28998 @findex -break-watch
29000 @subsubheading Synopsis
29003 -break-watch [ -a | -r ]
29006 Create a watchpoint. With the @samp{-a} option it will create an
29007 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29008 read from or on a write to the memory location. With the @samp{-r}
29009 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29010 trigger only when the memory location is accessed for reading. Without
29011 either of the options, the watchpoint created is a regular watchpoint,
29012 i.e., it will trigger when the memory location is accessed for writing.
29013 @xref{Set Watchpoints, , Setting Watchpoints}.
29015 Note that @samp{-break-list} will report a single list of watchpoints and
29016 breakpoints inserted.
29018 @subsubheading @value{GDBN} Command
29020 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29023 @subsubheading Example
29025 Setting a watchpoint on a variable in the @code{main} function:
29030 ^done,wpt=@{number="2",exp="x"@}
29035 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29036 value=@{old="-268439212",new="55"@},
29037 frame=@{func="main",args=[],file="recursive2.c",
29038 fullname="/home/foo/bar/recursive2.c",line="5"@}
29042 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29043 the program execution twice: first for the variable changing value, then
29044 for the watchpoint going out of scope.
29049 ^done,wpt=@{number="5",exp="C"@}
29054 *stopped,reason="watchpoint-trigger",
29055 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29056 frame=@{func="callee4",args=[],
29057 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29058 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29063 *stopped,reason="watchpoint-scope",wpnum="5",
29064 frame=@{func="callee3",args=[@{name="strarg",
29065 value="0x11940 \"A string argument.\""@}],
29066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29067 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29071 Listing breakpoints and watchpoints, at different points in the program
29072 execution. Note that once the watchpoint goes out of scope, it is
29078 ^done,wpt=@{number="2",exp="C"@}
29081 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29082 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29083 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29084 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29085 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29086 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29087 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29088 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29089 addr="0x00010734",func="callee4",
29090 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29091 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29093 bkpt=@{number="2",type="watchpoint",disp="keep",
29094 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29099 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29100 value=@{old="-276895068",new="3"@},
29101 frame=@{func="callee4",args=[],
29102 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29103 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29106 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29107 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29108 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29109 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29110 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29111 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29112 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29113 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29114 addr="0x00010734",func="callee4",
29115 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29116 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29118 bkpt=@{number="2",type="watchpoint",disp="keep",
29119 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29123 ^done,reason="watchpoint-scope",wpnum="2",
29124 frame=@{func="callee3",args=[@{name="strarg",
29125 value="0x11940 \"A string argument.\""@}],
29126 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29127 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29130 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29131 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29132 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29133 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29134 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29135 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29136 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29137 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29138 addr="0x00010734",func="callee4",
29139 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29140 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29141 thread-groups=["i1"],times="1"@}]@}
29146 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29147 @node GDB/MI Catchpoint Commands
29148 @section @sc{gdb/mi} Catchpoint Commands
29150 This section documents @sc{gdb/mi} commands for manipulating
29153 @subheading The @code{-catch-load} Command
29154 @findex -catch-load
29156 @subsubheading Synopsis
29159 -catch-load [ -t ] [ -d ] @var{regexp}
29162 Add a catchpoint for library load events. If the @samp{-t} option is used,
29163 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29164 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29165 in a disabled state. The @samp{regexp} argument is a regular
29166 expression used to match the name of the loaded library.
29169 @subsubheading @value{GDBN} Command
29171 The corresponding @value{GDBN} command is @samp{catch load}.
29173 @subsubheading Example
29176 -catch-load -t foo.so
29177 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29178 what="load of library matching foo.so",catch-type="load",times="0"@}
29183 @subheading The @code{-catch-unload} Command
29184 @findex -catch-unload
29186 @subsubheading Synopsis
29189 -catch-unload [ -t ] [ -d ] @var{regexp}
29192 Add a catchpoint for library unload events. If the @samp{-t} option is
29193 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29194 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29195 created in a disabled state. The @samp{regexp} argument is a regular
29196 expression used to match the name of the unloaded library.
29198 @subsubheading @value{GDBN} Command
29200 The corresponding @value{GDBN} command is @samp{catch unload}.
29202 @subsubheading Example
29205 -catch-unload -d bar.so
29206 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29207 what="load of library matching bar.so",catch-type="unload",times="0"@}
29212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29213 @node GDB/MI Program Context
29214 @section @sc{gdb/mi} Program Context
29216 @subheading The @code{-exec-arguments} Command
29217 @findex -exec-arguments
29220 @subsubheading Synopsis
29223 -exec-arguments @var{args}
29226 Set the inferior program arguments, to be used in the next
29229 @subsubheading @value{GDBN} Command
29231 The corresponding @value{GDBN} command is @samp{set args}.
29233 @subsubheading Example
29237 -exec-arguments -v word
29244 @subheading The @code{-exec-show-arguments} Command
29245 @findex -exec-show-arguments
29247 @subsubheading Synopsis
29250 -exec-show-arguments
29253 Print the arguments of the program.
29255 @subsubheading @value{GDBN} Command
29257 The corresponding @value{GDBN} command is @samp{show args}.
29259 @subsubheading Example
29264 @subheading The @code{-environment-cd} Command
29265 @findex -environment-cd
29267 @subsubheading Synopsis
29270 -environment-cd @var{pathdir}
29273 Set @value{GDBN}'s working directory.
29275 @subsubheading @value{GDBN} Command
29277 The corresponding @value{GDBN} command is @samp{cd}.
29279 @subsubheading Example
29283 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29289 @subheading The @code{-environment-directory} Command
29290 @findex -environment-directory
29292 @subsubheading Synopsis
29295 -environment-directory [ -r ] [ @var{pathdir} ]+
29298 Add directories @var{pathdir} to beginning of search path for source files.
29299 If the @samp{-r} option is used, the search path is reset to the default
29300 search path. If directories @var{pathdir} are supplied in addition to the
29301 @samp{-r} option, the search path is first reset and then addition
29303 Multiple directories may be specified, separated by blanks. Specifying
29304 multiple directories in a single command
29305 results in the directories added to the beginning of the
29306 search path in the same order they were presented in the command.
29307 If blanks are needed as
29308 part of a directory name, double-quotes should be used around
29309 the name. In the command output, the path will show up separated
29310 by the system directory-separator character. The directory-separator
29311 character must not be used
29312 in any directory name.
29313 If no directories are specified, the current search path is displayed.
29315 @subsubheading @value{GDBN} Command
29317 The corresponding @value{GDBN} command is @samp{dir}.
29319 @subsubheading Example
29323 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29324 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29326 -environment-directory ""
29327 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29329 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29330 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29332 -environment-directory -r
29333 ^done,source-path="$cdir:$cwd"
29338 @subheading The @code{-environment-path} Command
29339 @findex -environment-path
29341 @subsubheading Synopsis
29344 -environment-path [ -r ] [ @var{pathdir} ]+
29347 Add directories @var{pathdir} to beginning of search path for object files.
29348 If the @samp{-r} option is used, the search path is reset to the original
29349 search path that existed at gdb start-up. If directories @var{pathdir} are
29350 supplied in addition to the
29351 @samp{-r} option, the search path is first reset and then addition
29353 Multiple directories may be specified, separated by blanks. Specifying
29354 multiple directories in a single command
29355 results in the directories added to the beginning of the
29356 search path in the same order they were presented in the command.
29357 If blanks are needed as
29358 part of a directory name, double-quotes should be used around
29359 the name. In the command output, the path will show up separated
29360 by the system directory-separator character. The directory-separator
29361 character must not be used
29362 in any directory name.
29363 If no directories are specified, the current path is displayed.
29366 @subsubheading @value{GDBN} Command
29368 The corresponding @value{GDBN} command is @samp{path}.
29370 @subsubheading Example
29375 ^done,path="/usr/bin"
29377 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29378 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29380 -environment-path -r /usr/local/bin
29381 ^done,path="/usr/local/bin:/usr/bin"
29386 @subheading The @code{-environment-pwd} Command
29387 @findex -environment-pwd
29389 @subsubheading Synopsis
29395 Show the current working directory.
29397 @subsubheading @value{GDBN} Command
29399 The corresponding @value{GDBN} command is @samp{pwd}.
29401 @subsubheading Example
29406 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29410 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29411 @node GDB/MI Thread Commands
29412 @section @sc{gdb/mi} Thread Commands
29415 @subheading The @code{-thread-info} Command
29416 @findex -thread-info
29418 @subsubheading Synopsis
29421 -thread-info [ @var{thread-id} ]
29424 Reports information about either a specific thread, if
29425 the @var{thread-id} parameter is present, or about all
29426 threads. When printing information about all threads,
29427 also reports the current thread.
29429 @subsubheading @value{GDBN} Command
29431 The @samp{info thread} command prints the same information
29434 @subsubheading Result
29436 The result is a list of threads. The following attributes are
29437 defined for a given thread:
29441 This field exists only for the current thread. It has the value @samp{*}.
29444 The identifier that @value{GDBN} uses to refer to the thread.
29447 The identifier that the target uses to refer to the thread.
29450 Extra information about the thread, in a target-specific format. This
29454 The name of the thread. If the user specified a name using the
29455 @code{thread name} command, then this name is given. Otherwise, if
29456 @value{GDBN} can extract the thread name from the target, then that
29457 name is given. If @value{GDBN} cannot find the thread name, then this
29461 The stack frame currently executing in the thread.
29464 The thread's state. The @samp{state} field may have the following
29469 The thread is stopped. Frame information is available for stopped
29473 The thread is running. There's no frame information for running
29479 If @value{GDBN} can find the CPU core on which this thread is running,
29480 then this field is the core identifier. This field is optional.
29484 @subsubheading Example
29489 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29490 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29491 args=[]@},state="running"@},
29492 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29493 frame=@{level="0",addr="0x0804891f",func="foo",
29494 args=[@{name="i",value="10"@}],
29495 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29496 state="running"@}],
29497 current-thread-id="1"
29501 @subheading The @code{-thread-list-ids} Command
29502 @findex -thread-list-ids
29504 @subsubheading Synopsis
29510 Produces a list of the currently known @value{GDBN} thread ids. At the
29511 end of the list it also prints the total number of such threads.
29513 This command is retained for historical reasons, the
29514 @code{-thread-info} command should be used instead.
29516 @subsubheading @value{GDBN} Command
29518 Part of @samp{info threads} supplies the same information.
29520 @subsubheading Example
29525 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29526 current-thread-id="1",number-of-threads="3"
29531 @subheading The @code{-thread-select} Command
29532 @findex -thread-select
29534 @subsubheading Synopsis
29537 -thread-select @var{threadnum}
29540 Make @var{threadnum} the current thread. It prints the number of the new
29541 current thread, and the topmost frame for that thread.
29543 This command is deprecated in favor of explicitly using the
29544 @samp{--thread} option to each command.
29546 @subsubheading @value{GDBN} Command
29548 The corresponding @value{GDBN} command is @samp{thread}.
29550 @subsubheading Example
29557 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29558 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29562 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29563 number-of-threads="3"
29566 ^done,new-thread-id="3",
29567 frame=@{level="0",func="vprintf",
29568 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29569 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29573 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29574 @node GDB/MI Ada Tasking Commands
29575 @section @sc{gdb/mi} Ada Tasking Commands
29577 @subheading The @code{-ada-task-info} Command
29578 @findex -ada-task-info
29580 @subsubheading Synopsis
29583 -ada-task-info [ @var{task-id} ]
29586 Reports information about either a specific Ada task, if the
29587 @var{task-id} parameter is present, or about all Ada tasks.
29589 @subsubheading @value{GDBN} Command
29591 The @samp{info tasks} command prints the same information
29592 about all Ada tasks (@pxref{Ada Tasks}).
29594 @subsubheading Result
29596 The result is a table of Ada tasks. The following columns are
29597 defined for each Ada task:
29601 This field exists only for the current thread. It has the value @samp{*}.
29604 The identifier that @value{GDBN} uses to refer to the Ada task.
29607 The identifier that the target uses to refer to the Ada task.
29610 The identifier of the thread corresponding to the Ada task.
29612 This field should always exist, as Ada tasks are always implemented
29613 on top of a thread. But if @value{GDBN} cannot find this corresponding
29614 thread for any reason, the field is omitted.
29617 This field exists only when the task was created by another task.
29618 In this case, it provides the ID of the parent task.
29621 The base priority of the task.
29624 The current state of the task. For a detailed description of the
29625 possible states, see @ref{Ada Tasks}.
29628 The name of the task.
29632 @subsubheading Example
29636 ^done,tasks=@{nr_rows="3",nr_cols="8",
29637 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29638 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29639 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29640 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29641 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29642 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29643 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29644 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29645 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29646 state="Child Termination Wait",name="main_task"@}]@}
29650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29651 @node GDB/MI Program Execution
29652 @section @sc{gdb/mi} Program Execution
29654 These are the asynchronous commands which generate the out-of-band
29655 record @samp{*stopped}. Currently @value{GDBN} only really executes
29656 asynchronously with remote targets and this interaction is mimicked in
29659 @subheading The @code{-exec-continue} Command
29660 @findex -exec-continue
29662 @subsubheading Synopsis
29665 -exec-continue [--reverse] [--all|--thread-group N]
29668 Resumes the execution of the inferior program, which will continue
29669 to execute until it reaches a debugger stop event. If the
29670 @samp{--reverse} option is specified, execution resumes in reverse until
29671 it reaches a stop event. Stop events may include
29674 breakpoints or watchpoints
29676 signals or exceptions
29678 the end of the process (or its beginning under @samp{--reverse})
29680 the end or beginning of a replay log if one is being used.
29682 In all-stop mode (@pxref{All-Stop
29683 Mode}), may resume only one thread, or all threads, depending on the
29684 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29685 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29686 ignored in all-stop mode. If the @samp{--thread-group} options is
29687 specified, then all threads in that thread group are resumed.
29689 @subsubheading @value{GDBN} Command
29691 The corresponding @value{GDBN} corresponding is @samp{continue}.
29693 @subsubheading Example
29700 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29701 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29707 @subheading The @code{-exec-finish} Command
29708 @findex -exec-finish
29710 @subsubheading Synopsis
29713 -exec-finish [--reverse]
29716 Resumes the execution of the inferior program until the current
29717 function is exited. Displays the results returned by the function.
29718 If the @samp{--reverse} option is specified, resumes the reverse
29719 execution of the inferior program until the point where current
29720 function was called.
29722 @subsubheading @value{GDBN} Command
29724 The corresponding @value{GDBN} command is @samp{finish}.
29726 @subsubheading Example
29728 Function returning @code{void}.
29735 *stopped,reason="function-finished",frame=@{func="main",args=[],
29736 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29740 Function returning other than @code{void}. The name of the internal
29741 @value{GDBN} variable storing the result is printed, together with the
29748 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29749 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29750 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29751 gdb-result-var="$1",return-value="0"
29756 @subheading The @code{-exec-interrupt} Command
29757 @findex -exec-interrupt
29759 @subsubheading Synopsis
29762 -exec-interrupt [--all|--thread-group N]
29765 Interrupts the background execution of the target. Note how the token
29766 associated with the stop message is the one for the execution command
29767 that has been interrupted. The token for the interrupt itself only
29768 appears in the @samp{^done} output. If the user is trying to
29769 interrupt a non-running program, an error message will be printed.
29771 Note that when asynchronous execution is enabled, this command is
29772 asynchronous just like other execution commands. That is, first the
29773 @samp{^done} response will be printed, and the target stop will be
29774 reported after that using the @samp{*stopped} notification.
29776 In non-stop mode, only the context thread is interrupted by default.
29777 All threads (in all inferiors) will be interrupted if the
29778 @samp{--all} option is specified. If the @samp{--thread-group}
29779 option is specified, all threads in that group will be interrupted.
29781 @subsubheading @value{GDBN} Command
29783 The corresponding @value{GDBN} command is @samp{interrupt}.
29785 @subsubheading Example
29796 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29797 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29798 fullname="/home/foo/bar/try.c",line="13"@}
29803 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29807 @subheading The @code{-exec-jump} Command
29810 @subsubheading Synopsis
29813 -exec-jump @var{location}
29816 Resumes execution of the inferior program at the location specified by
29817 parameter. @xref{Specify Location}, for a description of the
29818 different forms of @var{location}.
29820 @subsubheading @value{GDBN} Command
29822 The corresponding @value{GDBN} command is @samp{jump}.
29824 @subsubheading Example
29827 -exec-jump foo.c:10
29828 *running,thread-id="all"
29833 @subheading The @code{-exec-next} Command
29836 @subsubheading Synopsis
29839 -exec-next [--reverse]
29842 Resumes execution of the inferior program, stopping when the beginning
29843 of the next source line is reached.
29845 If the @samp{--reverse} option is specified, resumes reverse execution
29846 of the inferior program, stopping at the beginning of the previous
29847 source line. If you issue this command on the first line of a
29848 function, it will take you back to the caller of that function, to the
29849 source line where the function was called.
29852 @subsubheading @value{GDBN} Command
29854 The corresponding @value{GDBN} command is @samp{next}.
29856 @subsubheading Example
29862 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29867 @subheading The @code{-exec-next-instruction} Command
29868 @findex -exec-next-instruction
29870 @subsubheading Synopsis
29873 -exec-next-instruction [--reverse]
29876 Executes one machine instruction. If the instruction is a function
29877 call, continues until the function returns. If the program stops at an
29878 instruction in the middle of a source line, the address will be
29881 If the @samp{--reverse} option is specified, resumes reverse execution
29882 of the inferior program, stopping at the previous instruction. If the
29883 previously executed instruction was a return from another function,
29884 it will continue to execute in reverse until the call to that function
29885 (from the current stack frame) is reached.
29887 @subsubheading @value{GDBN} Command
29889 The corresponding @value{GDBN} command is @samp{nexti}.
29891 @subsubheading Example
29895 -exec-next-instruction
29899 *stopped,reason="end-stepping-range",
29900 addr="0x000100d4",line="5",file="hello.c"
29905 @subheading The @code{-exec-return} Command
29906 @findex -exec-return
29908 @subsubheading Synopsis
29914 Makes current function return immediately. Doesn't execute the inferior.
29915 Displays the new current frame.
29917 @subsubheading @value{GDBN} Command
29919 The corresponding @value{GDBN} command is @samp{return}.
29921 @subsubheading Example
29925 200-break-insert callee4
29926 200^done,bkpt=@{number="1",addr="0x00010734",
29927 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29932 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29933 frame=@{func="callee4",args=[],
29934 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29935 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29941 111^done,frame=@{level="0",func="callee3",
29942 args=[@{name="strarg",
29943 value="0x11940 \"A string argument.\""@}],
29944 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29945 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29950 @subheading The @code{-exec-run} Command
29953 @subsubheading Synopsis
29956 -exec-run [--all | --thread-group N]
29959 Starts execution of the inferior from the beginning. The inferior
29960 executes until either a breakpoint is encountered or the program
29961 exits. In the latter case the output will include an exit code, if
29962 the program has exited exceptionally.
29964 When no option is specified, the current inferior is started. If the
29965 @samp{--thread-group} option is specified, it should refer to a thread
29966 group of type @samp{process}, and that thread group will be started.
29967 If the @samp{--all} option is specified, then all inferiors will be started.
29969 @subsubheading @value{GDBN} Command
29971 The corresponding @value{GDBN} command is @samp{run}.
29973 @subsubheading Examples
29978 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29983 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29984 frame=@{func="main",args=[],file="recursive2.c",
29985 fullname="/home/foo/bar/recursive2.c",line="4"@}
29990 Program exited normally:
29998 *stopped,reason="exited-normally"
30003 Program exited exceptionally:
30011 *stopped,reason="exited",exit-code="01"
30015 Another way the program can terminate is if it receives a signal such as
30016 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30020 *stopped,reason="exited-signalled",signal-name="SIGINT",
30021 signal-meaning="Interrupt"
30025 @c @subheading -exec-signal
30028 @subheading The @code{-exec-step} Command
30031 @subsubheading Synopsis
30034 -exec-step [--reverse]
30037 Resumes execution of the inferior program, stopping when the beginning
30038 of the next source line is reached, if the next source line is not a
30039 function call. If it is, stop at the first instruction of the called
30040 function. If the @samp{--reverse} option is specified, resumes reverse
30041 execution of the inferior program, stopping at the beginning of the
30042 previously executed source line.
30044 @subsubheading @value{GDBN} Command
30046 The corresponding @value{GDBN} command is @samp{step}.
30048 @subsubheading Example
30050 Stepping into a function:
30056 *stopped,reason="end-stepping-range",
30057 frame=@{func="foo",args=[@{name="a",value="10"@},
30058 @{name="b",value="0"@}],file="recursive2.c",
30059 fullname="/home/foo/bar/recursive2.c",line="11"@}
30069 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30074 @subheading The @code{-exec-step-instruction} Command
30075 @findex -exec-step-instruction
30077 @subsubheading Synopsis
30080 -exec-step-instruction [--reverse]
30083 Resumes the inferior which executes one machine instruction. If the
30084 @samp{--reverse} option is specified, resumes reverse execution of the
30085 inferior program, stopping at the previously executed instruction.
30086 The output, once @value{GDBN} has stopped, will vary depending on
30087 whether we have stopped in the middle of a source line or not. In the
30088 former case, the address at which the program stopped will be printed
30091 @subsubheading @value{GDBN} Command
30093 The corresponding @value{GDBN} command is @samp{stepi}.
30095 @subsubheading Example
30099 -exec-step-instruction
30103 *stopped,reason="end-stepping-range",
30104 frame=@{func="foo",args=[],file="try.c",
30105 fullname="/home/foo/bar/try.c",line="10"@}
30107 -exec-step-instruction
30111 *stopped,reason="end-stepping-range",
30112 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30113 fullname="/home/foo/bar/try.c",line="10"@}
30118 @subheading The @code{-exec-until} Command
30119 @findex -exec-until
30121 @subsubheading Synopsis
30124 -exec-until [ @var{location} ]
30127 Executes the inferior until the @var{location} specified in the
30128 argument is reached. If there is no argument, the inferior executes
30129 until a source line greater than the current one is reached. The
30130 reason for stopping in this case will be @samp{location-reached}.
30132 @subsubheading @value{GDBN} Command
30134 The corresponding @value{GDBN} command is @samp{until}.
30136 @subsubheading Example
30140 -exec-until recursive2.c:6
30144 *stopped,reason="location-reached",frame=@{func="main",args=[],
30145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30150 @subheading -file-clear
30151 Is this going away????
30154 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30155 @node GDB/MI Stack Manipulation
30156 @section @sc{gdb/mi} Stack Manipulation Commands
30159 @subheading The @code{-stack-info-frame} Command
30160 @findex -stack-info-frame
30162 @subsubheading Synopsis
30168 Get info on the selected frame.
30170 @subsubheading @value{GDBN} Command
30172 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30173 (without arguments).
30175 @subsubheading Example
30180 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30181 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30182 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30186 @subheading The @code{-stack-info-depth} Command
30187 @findex -stack-info-depth
30189 @subsubheading Synopsis
30192 -stack-info-depth [ @var{max-depth} ]
30195 Return the depth of the stack. If the integer argument @var{max-depth}
30196 is specified, do not count beyond @var{max-depth} frames.
30198 @subsubheading @value{GDBN} Command
30200 There's no equivalent @value{GDBN} command.
30202 @subsubheading Example
30204 For a stack with frame levels 0 through 11:
30211 -stack-info-depth 4
30214 -stack-info-depth 12
30217 -stack-info-depth 11
30220 -stack-info-depth 13
30225 @subheading The @code{-stack-list-arguments} Command
30226 @findex -stack-list-arguments
30228 @subsubheading Synopsis
30231 -stack-list-arguments @var{print-values}
30232 [ @var{low-frame} @var{high-frame} ]
30235 Display a list of the arguments for the frames between @var{low-frame}
30236 and @var{high-frame} (inclusive). If @var{low-frame} and
30237 @var{high-frame} are not provided, list the arguments for the whole
30238 call stack. If the two arguments are equal, show the single frame
30239 at the corresponding level. It is an error if @var{low-frame} is
30240 larger than the actual number of frames. On the other hand,
30241 @var{high-frame} may be larger than the actual number of frames, in
30242 which case only existing frames will be returned.
30244 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30245 the variables; if it is 1 or @code{--all-values}, print also their
30246 values; and if it is 2 or @code{--simple-values}, print the name,
30247 type and value for simple data types, and the name and type for arrays,
30248 structures and unions.
30250 Use of this command to obtain arguments in a single frame is
30251 deprecated in favor of the @samp{-stack-list-variables} command.
30253 @subsubheading @value{GDBN} Command
30255 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30256 @samp{gdb_get_args} command which partially overlaps with the
30257 functionality of @samp{-stack-list-arguments}.
30259 @subsubheading Example
30266 frame=@{level="0",addr="0x00010734",func="callee4",
30267 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30268 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30269 frame=@{level="1",addr="0x0001076c",func="callee3",
30270 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30271 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30272 frame=@{level="2",addr="0x0001078c",func="callee2",
30273 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30274 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30275 frame=@{level="3",addr="0x000107b4",func="callee1",
30276 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30277 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30278 frame=@{level="4",addr="0x000107e0",func="main",
30279 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30280 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30282 -stack-list-arguments 0
30285 frame=@{level="0",args=[]@},
30286 frame=@{level="1",args=[name="strarg"]@},
30287 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30288 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30289 frame=@{level="4",args=[]@}]
30291 -stack-list-arguments 1
30294 frame=@{level="0",args=[]@},
30296 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30297 frame=@{level="2",args=[
30298 @{name="intarg",value="2"@},
30299 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30300 @{frame=@{level="3",args=[
30301 @{name="intarg",value="2"@},
30302 @{name="strarg",value="0x11940 \"A string argument.\""@},
30303 @{name="fltarg",value="3.5"@}]@},
30304 frame=@{level="4",args=[]@}]
30306 -stack-list-arguments 0 2 2
30307 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30309 -stack-list-arguments 1 2 2
30310 ^done,stack-args=[frame=@{level="2",
30311 args=[@{name="intarg",value="2"@},
30312 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30316 @c @subheading -stack-list-exception-handlers
30319 @subheading The @code{-stack-list-frames} Command
30320 @findex -stack-list-frames
30322 @subsubheading Synopsis
30325 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30328 List the frames currently on the stack. For each frame it displays the
30333 The frame number, 0 being the topmost frame, i.e., the innermost function.
30335 The @code{$pc} value for that frame.
30339 File name of the source file where the function lives.
30340 @item @var{fullname}
30341 The full file name of the source file where the function lives.
30343 Line number corresponding to the @code{$pc}.
30345 The shared library where this function is defined. This is only given
30346 if the frame's function is not known.
30349 If invoked without arguments, this command prints a backtrace for the
30350 whole stack. If given two integer arguments, it shows the frames whose
30351 levels are between the two arguments (inclusive). If the two arguments
30352 are equal, it shows the single frame at the corresponding level. It is
30353 an error if @var{low-frame} is larger than the actual number of
30354 frames. On the other hand, @var{high-frame} may be larger than the
30355 actual number of frames, in which case only existing frames will be returned.
30357 @subsubheading @value{GDBN} Command
30359 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30361 @subsubheading Example
30363 Full stack backtrace:
30369 [frame=@{level="0",addr="0x0001076c",func="foo",
30370 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30371 frame=@{level="1",addr="0x000107a4",func="foo",
30372 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30373 frame=@{level="2",addr="0x000107a4",func="foo",
30374 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30375 frame=@{level="3",addr="0x000107a4",func="foo",
30376 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30377 frame=@{level="4",addr="0x000107a4",func="foo",
30378 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30379 frame=@{level="5",addr="0x000107a4",func="foo",
30380 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30381 frame=@{level="6",addr="0x000107a4",func="foo",
30382 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30383 frame=@{level="7",addr="0x000107a4",func="foo",
30384 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30385 frame=@{level="8",addr="0x000107a4",func="foo",
30386 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30387 frame=@{level="9",addr="0x000107a4",func="foo",
30388 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30389 frame=@{level="10",addr="0x000107a4",func="foo",
30390 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30391 frame=@{level="11",addr="0x00010738",func="main",
30392 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30396 Show frames between @var{low_frame} and @var{high_frame}:
30400 -stack-list-frames 3 5
30402 [frame=@{level="3",addr="0x000107a4",func="foo",
30403 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30404 frame=@{level="4",addr="0x000107a4",func="foo",
30405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30406 frame=@{level="5",addr="0x000107a4",func="foo",
30407 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30411 Show a single frame:
30415 -stack-list-frames 3 3
30417 [frame=@{level="3",addr="0x000107a4",func="foo",
30418 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30423 @subheading The @code{-stack-list-locals} Command
30424 @findex -stack-list-locals
30426 @subsubheading Synopsis
30429 -stack-list-locals @var{print-values}
30432 Display the local variable names for the selected frame. If
30433 @var{print-values} is 0 or @code{--no-values}, print only the names of
30434 the variables; if it is 1 or @code{--all-values}, print also their
30435 values; and if it is 2 or @code{--simple-values}, print the name,
30436 type and value for simple data types, and the name and type for arrays,
30437 structures and unions. In this last case, a frontend can immediately
30438 display the value of simple data types and create variable objects for
30439 other data types when the user wishes to explore their values in
30442 This command is deprecated in favor of the
30443 @samp{-stack-list-variables} command.
30445 @subsubheading @value{GDBN} Command
30447 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30449 @subsubheading Example
30453 -stack-list-locals 0
30454 ^done,locals=[name="A",name="B",name="C"]
30456 -stack-list-locals --all-values
30457 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30458 @{name="C",value="@{1, 2, 3@}"@}]
30459 -stack-list-locals --simple-values
30460 ^done,locals=[@{name="A",type="int",value="1"@},
30461 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30465 @subheading The @code{-stack-list-variables} Command
30466 @findex -stack-list-variables
30468 @subsubheading Synopsis
30471 -stack-list-variables @var{print-values}
30474 Display the names of local variables and function arguments for the selected frame. If
30475 @var{print-values} is 0 or @code{--no-values}, print only the names of
30476 the variables; if it is 1 or @code{--all-values}, print also their
30477 values; and if it is 2 or @code{--simple-values}, print the name,
30478 type and value for simple data types, and the name and type for arrays,
30479 structures and unions.
30481 @subsubheading Example
30485 -stack-list-variables --thread 1 --frame 0 --all-values
30486 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30491 @subheading The @code{-stack-select-frame} Command
30492 @findex -stack-select-frame
30494 @subsubheading Synopsis
30497 -stack-select-frame @var{framenum}
30500 Change the selected frame. Select a different frame @var{framenum} on
30503 This command in deprecated in favor of passing the @samp{--frame}
30504 option to every command.
30506 @subsubheading @value{GDBN} Command
30508 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30509 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30511 @subsubheading Example
30515 -stack-select-frame 2
30520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30521 @node GDB/MI Variable Objects
30522 @section @sc{gdb/mi} Variable Objects
30526 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30528 For the implementation of a variable debugger window (locals, watched
30529 expressions, etc.), we are proposing the adaptation of the existing code
30530 used by @code{Insight}.
30532 The two main reasons for that are:
30536 It has been proven in practice (it is already on its second generation).
30539 It will shorten development time (needless to say how important it is
30543 The original interface was designed to be used by Tcl code, so it was
30544 slightly changed so it could be used through @sc{gdb/mi}. This section
30545 describes the @sc{gdb/mi} operations that will be available and gives some
30546 hints about their use.
30548 @emph{Note}: In addition to the set of operations described here, we
30549 expect the @sc{gui} implementation of a variable window to require, at
30550 least, the following operations:
30553 @item @code{-gdb-show} @code{output-radix}
30554 @item @code{-stack-list-arguments}
30555 @item @code{-stack-list-locals}
30556 @item @code{-stack-select-frame}
30561 @subheading Introduction to Variable Objects
30563 @cindex variable objects in @sc{gdb/mi}
30565 Variable objects are "object-oriented" MI interface for examining and
30566 changing values of expressions. Unlike some other MI interfaces that
30567 work with expressions, variable objects are specifically designed for
30568 simple and efficient presentation in the frontend. A variable object
30569 is identified by string name. When a variable object is created, the
30570 frontend specifies the expression for that variable object. The
30571 expression can be a simple variable, or it can be an arbitrary complex
30572 expression, and can even involve CPU registers. After creating a
30573 variable object, the frontend can invoke other variable object
30574 operations---for example to obtain or change the value of a variable
30575 object, or to change display format.
30577 Variable objects have hierarchical tree structure. Any variable object
30578 that corresponds to a composite type, such as structure in C, has
30579 a number of child variable objects, for example corresponding to each
30580 element of a structure. A child variable object can itself have
30581 children, recursively. Recursion ends when we reach
30582 leaf variable objects, which always have built-in types. Child variable
30583 objects are created only by explicit request, so if a frontend
30584 is not interested in the children of a particular variable object, no
30585 child will be created.
30587 For a leaf variable object it is possible to obtain its value as a
30588 string, or set the value from a string. String value can be also
30589 obtained for a non-leaf variable object, but it's generally a string
30590 that only indicates the type of the object, and does not list its
30591 contents. Assignment to a non-leaf variable object is not allowed.
30593 A frontend does not need to read the values of all variable objects each time
30594 the program stops. Instead, MI provides an update command that lists all
30595 variable objects whose values has changed since the last update
30596 operation. This considerably reduces the amount of data that must
30597 be transferred to the frontend. As noted above, children variable
30598 objects are created on demand, and only leaf variable objects have a
30599 real value. As result, gdb will read target memory only for leaf
30600 variables that frontend has created.
30602 The automatic update is not always desirable. For example, a frontend
30603 might want to keep a value of some expression for future reference,
30604 and never update it. For another example, fetching memory is
30605 relatively slow for embedded targets, so a frontend might want
30606 to disable automatic update for the variables that are either not
30607 visible on the screen, or ``closed''. This is possible using so
30608 called ``frozen variable objects''. Such variable objects are never
30609 implicitly updated.
30611 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30612 fixed variable object, the expression is parsed when the variable
30613 object is created, including associating identifiers to specific
30614 variables. The meaning of expression never changes. For a floating
30615 variable object the values of variables whose names appear in the
30616 expressions are re-evaluated every time in the context of the current
30617 frame. Consider this example:
30622 struct work_state state;
30629 If a fixed variable object for the @code{state} variable is created in
30630 this function, and we enter the recursive call, the variable
30631 object will report the value of @code{state} in the top-level
30632 @code{do_work} invocation. On the other hand, a floating variable
30633 object will report the value of @code{state} in the current frame.
30635 If an expression specified when creating a fixed variable object
30636 refers to a local variable, the variable object becomes bound to the
30637 thread and frame in which the variable object is created. When such
30638 variable object is updated, @value{GDBN} makes sure that the
30639 thread/frame combination the variable object is bound to still exists,
30640 and re-evaluates the variable object in context of that thread/frame.
30642 The following is the complete set of @sc{gdb/mi} operations defined to
30643 access this functionality:
30645 @multitable @columnfractions .4 .6
30646 @item @strong{Operation}
30647 @tab @strong{Description}
30649 @item @code{-enable-pretty-printing}
30650 @tab enable Python-based pretty-printing
30651 @item @code{-var-create}
30652 @tab create a variable object
30653 @item @code{-var-delete}
30654 @tab delete the variable object and/or its children
30655 @item @code{-var-set-format}
30656 @tab set the display format of this variable
30657 @item @code{-var-show-format}
30658 @tab show the display format of this variable
30659 @item @code{-var-info-num-children}
30660 @tab tells how many children this object has
30661 @item @code{-var-list-children}
30662 @tab return a list of the object's children
30663 @item @code{-var-info-type}
30664 @tab show the type of this variable object
30665 @item @code{-var-info-expression}
30666 @tab print parent-relative expression that this variable object represents
30667 @item @code{-var-info-path-expression}
30668 @tab print full expression that this variable object represents
30669 @item @code{-var-show-attributes}
30670 @tab is this variable editable? does it exist here?
30671 @item @code{-var-evaluate-expression}
30672 @tab get the value of this variable
30673 @item @code{-var-assign}
30674 @tab set the value of this variable
30675 @item @code{-var-update}
30676 @tab update the variable and its children
30677 @item @code{-var-set-frozen}
30678 @tab set frozeness attribute
30679 @item @code{-var-set-update-range}
30680 @tab set range of children to display on update
30683 In the next subsection we describe each operation in detail and suggest
30684 how it can be used.
30686 @subheading Description And Use of Operations on Variable Objects
30688 @subheading The @code{-enable-pretty-printing} Command
30689 @findex -enable-pretty-printing
30692 -enable-pretty-printing
30695 @value{GDBN} allows Python-based visualizers to affect the output of the
30696 MI variable object commands. However, because there was no way to
30697 implement this in a fully backward-compatible way, a front end must
30698 request that this functionality be enabled.
30700 Once enabled, this feature cannot be disabled.
30702 Note that if Python support has not been compiled into @value{GDBN},
30703 this command will still succeed (and do nothing).
30705 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30706 may work differently in future versions of @value{GDBN}.
30708 @subheading The @code{-var-create} Command
30709 @findex -var-create
30711 @subsubheading Synopsis
30714 -var-create @{@var{name} | "-"@}
30715 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30718 This operation creates a variable object, which allows the monitoring of
30719 a variable, the result of an expression, a memory cell or a CPU
30722 The @var{name} parameter is the string by which the object can be
30723 referenced. It must be unique. If @samp{-} is specified, the varobj
30724 system will generate a string ``varNNNNNN'' automatically. It will be
30725 unique provided that one does not specify @var{name} of that format.
30726 The command fails if a duplicate name is found.
30728 The frame under which the expression should be evaluated can be
30729 specified by @var{frame-addr}. A @samp{*} indicates that the current
30730 frame should be used. A @samp{@@} indicates that a floating variable
30731 object must be created.
30733 @var{expression} is any expression valid on the current language set (must not
30734 begin with a @samp{*}), or one of the following:
30738 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30741 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30744 @samp{$@var{regname}} --- a CPU register name
30747 @cindex dynamic varobj
30748 A varobj's contents may be provided by a Python-based pretty-printer. In this
30749 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30750 have slightly different semantics in some cases. If the
30751 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30752 will never create a dynamic varobj. This ensures backward
30753 compatibility for existing clients.
30755 @subsubheading Result
30757 This operation returns attributes of the newly-created varobj. These
30762 The name of the varobj.
30765 The number of children of the varobj. This number is not necessarily
30766 reliable for a dynamic varobj. Instead, you must examine the
30767 @samp{has_more} attribute.
30770 The varobj's scalar value. For a varobj whose type is some sort of
30771 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30772 will not be interesting.
30775 The varobj's type. This is a string representation of the type, as
30776 would be printed by the @value{GDBN} CLI. If @samp{print object}
30777 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30778 @emph{actual} (derived) type of the object is shown rather than the
30779 @emph{declared} one.
30782 If a variable object is bound to a specific thread, then this is the
30783 thread's identifier.
30786 For a dynamic varobj, this indicates whether there appear to be any
30787 children available. For a non-dynamic varobj, this will be 0.
30790 This attribute will be present and have the value @samp{1} if the
30791 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30792 then this attribute will not be present.
30795 A dynamic varobj can supply a display hint to the front end. The
30796 value comes directly from the Python pretty-printer object's
30797 @code{display_hint} method. @xref{Pretty Printing API}.
30800 Typical output will look like this:
30803 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30804 has_more="@var{has_more}"
30808 @subheading The @code{-var-delete} Command
30809 @findex -var-delete
30811 @subsubheading Synopsis
30814 -var-delete [ -c ] @var{name}
30817 Deletes a previously created variable object and all of its children.
30818 With the @samp{-c} option, just deletes the children.
30820 Returns an error if the object @var{name} is not found.
30823 @subheading The @code{-var-set-format} Command
30824 @findex -var-set-format
30826 @subsubheading Synopsis
30829 -var-set-format @var{name} @var{format-spec}
30832 Sets the output format for the value of the object @var{name} to be
30835 @anchor{-var-set-format}
30836 The syntax for the @var{format-spec} is as follows:
30839 @var{format-spec} @expansion{}
30840 @{binary | decimal | hexadecimal | octal | natural@}
30843 The natural format is the default format choosen automatically
30844 based on the variable type (like decimal for an @code{int}, hex
30845 for pointers, etc.).
30847 For a variable with children, the format is set only on the
30848 variable itself, and the children are not affected.
30850 @subheading The @code{-var-show-format} Command
30851 @findex -var-show-format
30853 @subsubheading Synopsis
30856 -var-show-format @var{name}
30859 Returns the format used to display the value of the object @var{name}.
30862 @var{format} @expansion{}
30867 @subheading The @code{-var-info-num-children} Command
30868 @findex -var-info-num-children
30870 @subsubheading Synopsis
30873 -var-info-num-children @var{name}
30876 Returns the number of children of a variable object @var{name}:
30882 Note that this number is not completely reliable for a dynamic varobj.
30883 It will return the current number of children, but more children may
30887 @subheading The @code{-var-list-children} Command
30888 @findex -var-list-children
30890 @subsubheading Synopsis
30893 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30895 @anchor{-var-list-children}
30897 Return a list of the children of the specified variable object and
30898 create variable objects for them, if they do not already exist. With
30899 a single argument or if @var{print-values} has a value of 0 or
30900 @code{--no-values}, print only the names of the variables; if
30901 @var{print-values} is 1 or @code{--all-values}, also print their
30902 values; and if it is 2 or @code{--simple-values} print the name and
30903 value for simple data types and just the name for arrays, structures
30906 @var{from} and @var{to}, if specified, indicate the range of children
30907 to report. If @var{from} or @var{to} is less than zero, the range is
30908 reset and all children will be reported. Otherwise, children starting
30909 at @var{from} (zero-based) and up to and excluding @var{to} will be
30912 If a child range is requested, it will only affect the current call to
30913 @code{-var-list-children}, but not future calls to @code{-var-update}.
30914 For this, you must instead use @code{-var-set-update-range}. The
30915 intent of this approach is to enable a front end to implement any
30916 update approach it likes; for example, scrolling a view may cause the
30917 front end to request more children with @code{-var-list-children}, and
30918 then the front end could call @code{-var-set-update-range} with a
30919 different range to ensure that future updates are restricted to just
30922 For each child the following results are returned:
30927 Name of the variable object created for this child.
30930 The expression to be shown to the user by the front end to designate this child.
30931 For example this may be the name of a structure member.
30933 For a dynamic varobj, this value cannot be used to form an
30934 expression. There is no way to do this at all with a dynamic varobj.
30936 For C/C@t{++} structures there are several pseudo children returned to
30937 designate access qualifiers. For these pseudo children @var{exp} is
30938 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30939 type and value are not present.
30941 A dynamic varobj will not report the access qualifying
30942 pseudo-children, regardless of the language. This information is not
30943 available at all with a dynamic varobj.
30946 Number of children this child has. For a dynamic varobj, this will be
30950 The type of the child. If @samp{print object}
30951 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30952 @emph{actual} (derived) type of the object is shown rather than the
30953 @emph{declared} one.
30956 If values were requested, this is the value.
30959 If this variable object is associated with a thread, this is the thread id.
30960 Otherwise this result is not present.
30963 If the variable object is frozen, this variable will be present with a value of 1.
30966 The result may have its own attributes:
30970 A dynamic varobj can supply a display hint to the front end. The
30971 value comes directly from the Python pretty-printer object's
30972 @code{display_hint} method. @xref{Pretty Printing API}.
30975 This is an integer attribute which is nonzero if there are children
30976 remaining after the end of the selected range.
30979 @subsubheading Example
30983 -var-list-children n
30984 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30985 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30987 -var-list-children --all-values n
30988 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30989 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30993 @subheading The @code{-var-info-type} Command
30994 @findex -var-info-type
30996 @subsubheading Synopsis
30999 -var-info-type @var{name}
31002 Returns the type of the specified variable @var{name}. The type is
31003 returned as a string in the same format as it is output by the
31007 type=@var{typename}
31011 @subheading The @code{-var-info-expression} Command
31012 @findex -var-info-expression
31014 @subsubheading Synopsis
31017 -var-info-expression @var{name}
31020 Returns a string that is suitable for presenting this
31021 variable object in user interface. The string is generally
31022 not valid expression in the current language, and cannot be evaluated.
31024 For example, if @code{a} is an array, and variable object
31025 @code{A} was created for @code{a}, then we'll get this output:
31028 (gdb) -var-info-expression A.1
31029 ^done,lang="C",exp="1"
31033 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
31035 Note that the output of the @code{-var-list-children} command also
31036 includes those expressions, so the @code{-var-info-expression} command
31039 @subheading The @code{-var-info-path-expression} Command
31040 @findex -var-info-path-expression
31042 @subsubheading Synopsis
31045 -var-info-path-expression @var{name}
31048 Returns an expression that can be evaluated in the current
31049 context and will yield the same value that a variable object has.
31050 Compare this with the @code{-var-info-expression} command, which
31051 result can be used only for UI presentation. Typical use of
31052 the @code{-var-info-path-expression} command is creating a
31053 watchpoint from a variable object.
31055 This command is currently not valid for children of a dynamic varobj,
31056 and will give an error when invoked on one.
31058 For example, suppose @code{C} is a C@t{++} class, derived from class
31059 @code{Base}, and that the @code{Base} class has a member called
31060 @code{m_size}. Assume a variable @code{c} is has the type of
31061 @code{C} and a variable object @code{C} was created for variable
31062 @code{c}. Then, we'll get this output:
31064 (gdb) -var-info-path-expression C.Base.public.m_size
31065 ^done,path_expr=((Base)c).m_size)
31068 @subheading The @code{-var-show-attributes} Command
31069 @findex -var-show-attributes
31071 @subsubheading Synopsis
31074 -var-show-attributes @var{name}
31077 List attributes of the specified variable object @var{name}:
31080 status=@var{attr} [ ( ,@var{attr} )* ]
31084 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31086 @subheading The @code{-var-evaluate-expression} Command
31087 @findex -var-evaluate-expression
31089 @subsubheading Synopsis
31092 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31095 Evaluates the expression that is represented by the specified variable
31096 object and returns its value as a string. The format of the string
31097 can be specified with the @samp{-f} option. The possible values of
31098 this option are the same as for @code{-var-set-format}
31099 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31100 the current display format will be used. The current display format
31101 can be changed using the @code{-var-set-format} command.
31107 Note that one must invoke @code{-var-list-children} for a variable
31108 before the value of a child variable can be evaluated.
31110 @subheading The @code{-var-assign} Command
31111 @findex -var-assign
31113 @subsubheading Synopsis
31116 -var-assign @var{name} @var{expression}
31119 Assigns the value of @var{expression} to the variable object specified
31120 by @var{name}. The object must be @samp{editable}. If the variable's
31121 value is altered by the assign, the variable will show up in any
31122 subsequent @code{-var-update} list.
31124 @subsubheading Example
31132 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31136 @subheading The @code{-var-update} Command
31137 @findex -var-update
31139 @subsubheading Synopsis
31142 -var-update [@var{print-values}] @{@var{name} | "*"@}
31145 Reevaluate the expressions corresponding to the variable object
31146 @var{name} and all its direct and indirect children, and return the
31147 list of variable objects whose values have changed; @var{name} must
31148 be a root variable object. Here, ``changed'' means that the result of
31149 @code{-var-evaluate-expression} before and after the
31150 @code{-var-update} is different. If @samp{*} is used as the variable
31151 object names, all existing variable objects are updated, except
31152 for frozen ones (@pxref{-var-set-frozen}). The option
31153 @var{print-values} determines whether both names and values, or just
31154 names are printed. The possible values of this option are the same
31155 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31156 recommended to use the @samp{--all-values} option, to reduce the
31157 number of MI commands needed on each program stop.
31159 With the @samp{*} parameter, if a variable object is bound to a
31160 currently running thread, it will not be updated, without any
31163 If @code{-var-set-update-range} was previously used on a varobj, then
31164 only the selected range of children will be reported.
31166 @code{-var-update} reports all the changed varobjs in a tuple named
31169 Each item in the change list is itself a tuple holding:
31173 The name of the varobj.
31176 If values were requested for this update, then this field will be
31177 present and will hold the value of the varobj.
31180 @anchor{-var-update}
31181 This field is a string which may take one of three values:
31185 The variable object's current value is valid.
31188 The variable object does not currently hold a valid value but it may
31189 hold one in the future if its associated expression comes back into
31193 The variable object no longer holds a valid value.
31194 This can occur when the executable file being debugged has changed,
31195 either through recompilation or by using the @value{GDBN} @code{file}
31196 command. The front end should normally choose to delete these variable
31200 In the future new values may be added to this list so the front should
31201 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31204 This is only present if the varobj is still valid. If the type
31205 changed, then this will be the string @samp{true}; otherwise it will
31208 When a varobj's type changes, its children are also likely to have
31209 become incorrect. Therefore, the varobj's children are automatically
31210 deleted when this attribute is @samp{true}. Also, the varobj's update
31211 range, when set using the @code{-var-set-update-range} command, is
31215 If the varobj's type changed, then this field will be present and will
31218 @item new_num_children
31219 For a dynamic varobj, if the number of children changed, or if the
31220 type changed, this will be the new number of children.
31222 The @samp{numchild} field in other varobj responses is generally not
31223 valid for a dynamic varobj -- it will show the number of children that
31224 @value{GDBN} knows about, but because dynamic varobjs lazily
31225 instantiate their children, this will not reflect the number of
31226 children which may be available.
31228 The @samp{new_num_children} attribute only reports changes to the
31229 number of children known by @value{GDBN}. This is the only way to
31230 detect whether an update has removed children (which necessarily can
31231 only happen at the end of the update range).
31234 The display hint, if any.
31237 This is an integer value, which will be 1 if there are more children
31238 available outside the varobj's update range.
31241 This attribute will be present and have the value @samp{1} if the
31242 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31243 then this attribute will not be present.
31246 If new children were added to a dynamic varobj within the selected
31247 update range (as set by @code{-var-set-update-range}), then they will
31248 be listed in this attribute.
31251 @subsubheading Example
31258 -var-update --all-values var1
31259 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31260 type_changed="false"@}]
31264 @subheading The @code{-var-set-frozen} Command
31265 @findex -var-set-frozen
31266 @anchor{-var-set-frozen}
31268 @subsubheading Synopsis
31271 -var-set-frozen @var{name} @var{flag}
31274 Set the frozenness flag on the variable object @var{name}. The
31275 @var{flag} parameter should be either @samp{1} to make the variable
31276 frozen or @samp{0} to make it unfrozen. If a variable object is
31277 frozen, then neither itself, nor any of its children, are
31278 implicitly updated by @code{-var-update} of
31279 a parent variable or by @code{-var-update *}. Only
31280 @code{-var-update} of the variable itself will update its value and
31281 values of its children. After a variable object is unfrozen, it is
31282 implicitly updated by all subsequent @code{-var-update} operations.
31283 Unfreezing a variable does not update it, only subsequent
31284 @code{-var-update} does.
31286 @subsubheading Example
31290 -var-set-frozen V 1
31295 @subheading The @code{-var-set-update-range} command
31296 @findex -var-set-update-range
31297 @anchor{-var-set-update-range}
31299 @subsubheading Synopsis
31302 -var-set-update-range @var{name} @var{from} @var{to}
31305 Set the range of children to be returned by future invocations of
31306 @code{-var-update}.
31308 @var{from} and @var{to} indicate the range of children to report. If
31309 @var{from} or @var{to} is less than zero, the range is reset and all
31310 children will be reported. Otherwise, children starting at @var{from}
31311 (zero-based) and up to and excluding @var{to} will be reported.
31313 @subsubheading Example
31317 -var-set-update-range V 1 2
31321 @subheading The @code{-var-set-visualizer} command
31322 @findex -var-set-visualizer
31323 @anchor{-var-set-visualizer}
31325 @subsubheading Synopsis
31328 -var-set-visualizer @var{name} @var{visualizer}
31331 Set a visualizer for the variable object @var{name}.
31333 @var{visualizer} is the visualizer to use. The special value
31334 @samp{None} means to disable any visualizer in use.
31336 If not @samp{None}, @var{visualizer} must be a Python expression.
31337 This expression must evaluate to a callable object which accepts a
31338 single argument. @value{GDBN} will call this object with the value of
31339 the varobj @var{name} as an argument (this is done so that the same
31340 Python pretty-printing code can be used for both the CLI and MI).
31341 When called, this object must return an object which conforms to the
31342 pretty-printing interface (@pxref{Pretty Printing API}).
31344 The pre-defined function @code{gdb.default_visualizer} may be used to
31345 select a visualizer by following the built-in process
31346 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31347 a varobj is created, and so ordinarily is not needed.
31349 This feature is only available if Python support is enabled. The MI
31350 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31351 can be used to check this.
31353 @subsubheading Example
31355 Resetting the visualizer:
31359 -var-set-visualizer V None
31363 Reselecting the default (type-based) visualizer:
31367 -var-set-visualizer V gdb.default_visualizer
31371 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31372 can be used to instantiate this class for a varobj:
31376 -var-set-visualizer V "lambda val: SomeClass()"
31380 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31381 @node GDB/MI Data Manipulation
31382 @section @sc{gdb/mi} Data Manipulation
31384 @cindex data manipulation, in @sc{gdb/mi}
31385 @cindex @sc{gdb/mi}, data manipulation
31386 This section describes the @sc{gdb/mi} commands that manipulate data:
31387 examine memory and registers, evaluate expressions, etc.
31389 @c REMOVED FROM THE INTERFACE.
31390 @c @subheading -data-assign
31391 @c Change the value of a program variable. Plenty of side effects.
31392 @c @subsubheading GDB Command
31394 @c @subsubheading Example
31397 @subheading The @code{-data-disassemble} Command
31398 @findex -data-disassemble
31400 @subsubheading Synopsis
31404 [ -s @var{start-addr} -e @var{end-addr} ]
31405 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31413 @item @var{start-addr}
31414 is the beginning address (or @code{$pc})
31415 @item @var{end-addr}
31417 @item @var{filename}
31418 is the name of the file to disassemble
31419 @item @var{linenum}
31420 is the line number to disassemble around
31422 is the number of disassembly lines to be produced. If it is -1,
31423 the whole function will be disassembled, in case no @var{end-addr} is
31424 specified. If @var{end-addr} is specified as a non-zero value, and
31425 @var{lines} is lower than the number of disassembly lines between
31426 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31427 displayed; if @var{lines} is higher than the number of lines between
31428 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31431 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31432 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31433 mixed source and disassembly with raw opcodes).
31436 @subsubheading Result
31438 The result of the @code{-data-disassemble} command will be a list named
31439 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31440 used with the @code{-data-disassemble} command.
31442 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31447 The address at which this instruction was disassembled.
31450 The name of the function this instruction is within.
31453 The decimal offset in bytes from the start of @samp{func-name}.
31456 The text disassembly for this @samp{address}.
31459 This field is only present for mode 2. This contains the raw opcode
31460 bytes for the @samp{inst} field.
31464 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31465 @samp{src_and_asm_line}, each of which has the following fields:
31469 The line number within @samp{file}.
31472 The file name from the compilation unit. This might be an absolute
31473 file name or a relative file name depending on the compile command
31477 Absolute file name of @samp{file}. It is converted to a canonical form
31478 using the source file search path
31479 (@pxref{Source Path, ,Specifying Source Directories})
31480 and after resolving all the symbolic links.
31482 If the source file is not found this field will contain the path as
31483 present in the debug information.
31485 @item line_asm_insn
31486 This is a list of tuples containing the disassembly for @samp{line} in
31487 @samp{file}. The fields of each tuple are the same as for
31488 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31489 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31494 Note that whatever included in the @samp{inst} field, is not
31495 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31498 @subsubheading @value{GDBN} Command
31500 The corresponding @value{GDBN} command is @samp{disassemble}.
31502 @subsubheading Example
31504 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31508 -data-disassemble -s $pc -e "$pc + 20" -- 0
31511 @{address="0x000107c0",func-name="main",offset="4",
31512 inst="mov 2, %o0"@},
31513 @{address="0x000107c4",func-name="main",offset="8",
31514 inst="sethi %hi(0x11800), %o2"@},
31515 @{address="0x000107c8",func-name="main",offset="12",
31516 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31517 @{address="0x000107cc",func-name="main",offset="16",
31518 inst="sethi %hi(0x11800), %o2"@},
31519 @{address="0x000107d0",func-name="main",offset="20",
31520 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31524 Disassemble the whole @code{main} function. Line 32 is part of
31528 -data-disassemble -f basics.c -l 32 -- 0
31530 @{address="0x000107bc",func-name="main",offset="0",
31531 inst="save %sp, -112, %sp"@},
31532 @{address="0x000107c0",func-name="main",offset="4",
31533 inst="mov 2, %o0"@},
31534 @{address="0x000107c4",func-name="main",offset="8",
31535 inst="sethi %hi(0x11800), %o2"@},
31537 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31538 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31542 Disassemble 3 instructions from the start of @code{main}:
31546 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31548 @{address="0x000107bc",func-name="main",offset="0",
31549 inst="save %sp, -112, %sp"@},
31550 @{address="0x000107c0",func-name="main",offset="4",
31551 inst="mov 2, %o0"@},
31552 @{address="0x000107c4",func-name="main",offset="8",
31553 inst="sethi %hi(0x11800), %o2"@}]
31557 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31561 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31563 src_and_asm_line=@{line="31",
31564 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31565 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31566 line_asm_insn=[@{address="0x000107bc",
31567 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31568 src_and_asm_line=@{line="32",
31569 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31570 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31571 line_asm_insn=[@{address="0x000107c0",
31572 func-name="main",offset="4",inst="mov 2, %o0"@},
31573 @{address="0x000107c4",func-name="main",offset="8",
31574 inst="sethi %hi(0x11800), %o2"@}]@}]
31579 @subheading The @code{-data-evaluate-expression} Command
31580 @findex -data-evaluate-expression
31582 @subsubheading Synopsis
31585 -data-evaluate-expression @var{expr}
31588 Evaluate @var{expr} as an expression. The expression could contain an
31589 inferior function call. The function call will execute synchronously.
31590 If the expression contains spaces, it must be enclosed in double quotes.
31592 @subsubheading @value{GDBN} Command
31594 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31595 @samp{call}. In @code{gdbtk} only, there's a corresponding
31596 @samp{gdb_eval} command.
31598 @subsubheading Example
31600 In the following example, the numbers that precede the commands are the
31601 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31602 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31606 211-data-evaluate-expression A
31609 311-data-evaluate-expression &A
31610 311^done,value="0xefffeb7c"
31612 411-data-evaluate-expression A+3
31615 511-data-evaluate-expression "A + 3"
31621 @subheading The @code{-data-list-changed-registers} Command
31622 @findex -data-list-changed-registers
31624 @subsubheading Synopsis
31627 -data-list-changed-registers
31630 Display a list of the registers that have changed.
31632 @subsubheading @value{GDBN} Command
31634 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31635 has the corresponding command @samp{gdb_changed_register_list}.
31637 @subsubheading Example
31639 On a PPC MBX board:
31647 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31648 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31651 -data-list-changed-registers
31652 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31653 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31654 "24","25","26","27","28","30","31","64","65","66","67","69"]
31659 @subheading The @code{-data-list-register-names} Command
31660 @findex -data-list-register-names
31662 @subsubheading Synopsis
31665 -data-list-register-names [ ( @var{regno} )+ ]
31668 Show a list of register names for the current target. If no arguments
31669 are given, it shows a list of the names of all the registers. If
31670 integer numbers are given as arguments, it will print a list of the
31671 names of the registers corresponding to the arguments. To ensure
31672 consistency between a register name and its number, the output list may
31673 include empty register names.
31675 @subsubheading @value{GDBN} Command
31677 @value{GDBN} does not have a command which corresponds to
31678 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31679 corresponding command @samp{gdb_regnames}.
31681 @subsubheading Example
31683 For the PPC MBX board:
31686 -data-list-register-names
31687 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31688 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31689 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31690 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31691 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31692 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31693 "", "pc","ps","cr","lr","ctr","xer"]
31695 -data-list-register-names 1 2 3
31696 ^done,register-names=["r1","r2","r3"]
31700 @subheading The @code{-data-list-register-values} Command
31701 @findex -data-list-register-values
31703 @subsubheading Synopsis
31706 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31709 Display the registers' contents. @var{fmt} is the format according to
31710 which the registers' contents are to be returned, followed by an optional
31711 list of numbers specifying the registers to display. A missing list of
31712 numbers indicates that the contents of all the registers must be returned.
31714 Allowed formats for @var{fmt} are:
31731 @subsubheading @value{GDBN} Command
31733 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31734 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31736 @subsubheading Example
31738 For a PPC MBX board (note: line breaks are for readability only, they
31739 don't appear in the actual output):
31743 -data-list-register-values r 64 65
31744 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31745 @{number="65",value="0x00029002"@}]
31747 -data-list-register-values x
31748 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31749 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31750 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31751 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31752 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31753 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31754 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31755 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31756 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31757 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31758 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31759 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31760 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31761 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31762 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31763 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31764 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31765 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31766 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31767 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31768 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31769 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31770 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31771 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31772 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31773 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31774 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31775 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31776 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31777 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31778 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31779 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31780 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31781 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31782 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31783 @{number="69",value="0x20002b03"@}]
31788 @subheading The @code{-data-read-memory} Command
31789 @findex -data-read-memory
31791 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31793 @subsubheading Synopsis
31796 -data-read-memory [ -o @var{byte-offset} ]
31797 @var{address} @var{word-format} @var{word-size}
31798 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31805 @item @var{address}
31806 An expression specifying the address of the first memory word to be
31807 read. Complex expressions containing embedded white space should be
31808 quoted using the C convention.
31810 @item @var{word-format}
31811 The format to be used to print the memory words. The notation is the
31812 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31815 @item @var{word-size}
31816 The size of each memory word in bytes.
31818 @item @var{nr-rows}
31819 The number of rows in the output table.
31821 @item @var{nr-cols}
31822 The number of columns in the output table.
31825 If present, indicates that each row should include an @sc{ascii} dump. The
31826 value of @var{aschar} is used as a padding character when a byte is not a
31827 member of the printable @sc{ascii} character set (printable @sc{ascii}
31828 characters are those whose code is between 32 and 126, inclusively).
31830 @item @var{byte-offset}
31831 An offset to add to the @var{address} before fetching memory.
31834 This command displays memory contents as a table of @var{nr-rows} by
31835 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31836 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31837 (returned as @samp{total-bytes}). Should less than the requested number
31838 of bytes be returned by the target, the missing words are identified
31839 using @samp{N/A}. The number of bytes read from the target is returned
31840 in @samp{nr-bytes} and the starting address used to read memory in
31843 The address of the next/previous row or page is available in
31844 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31847 @subsubheading @value{GDBN} Command
31849 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31850 @samp{gdb_get_mem} memory read command.
31852 @subsubheading Example
31854 Read six bytes of memory starting at @code{bytes+6} but then offset by
31855 @code{-6} bytes. Format as three rows of two columns. One byte per
31856 word. Display each word in hex.
31860 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31861 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31862 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31863 prev-page="0x0000138a",memory=[
31864 @{addr="0x00001390",data=["0x00","0x01"]@},
31865 @{addr="0x00001392",data=["0x02","0x03"]@},
31866 @{addr="0x00001394",data=["0x04","0x05"]@}]
31870 Read two bytes of memory starting at address @code{shorts + 64} and
31871 display as a single word formatted in decimal.
31875 5-data-read-memory shorts+64 d 2 1 1
31876 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31877 next-row="0x00001512",prev-row="0x0000150e",
31878 next-page="0x00001512",prev-page="0x0000150e",memory=[
31879 @{addr="0x00001510",data=["128"]@}]
31883 Read thirty two bytes of memory starting at @code{bytes+16} and format
31884 as eight rows of four columns. Include a string encoding with @samp{x}
31885 used as the non-printable character.
31889 4-data-read-memory bytes+16 x 1 8 4 x
31890 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31891 next-row="0x000013c0",prev-row="0x0000139c",
31892 next-page="0x000013c0",prev-page="0x00001380",memory=[
31893 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31894 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31895 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31896 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31897 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31898 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31899 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31900 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31904 @subheading The @code{-data-read-memory-bytes} Command
31905 @findex -data-read-memory-bytes
31907 @subsubheading Synopsis
31910 -data-read-memory-bytes [ -o @var{byte-offset} ]
31911 @var{address} @var{count}
31918 @item @var{address}
31919 An expression specifying the address of the first memory word to be
31920 read. Complex expressions containing embedded white space should be
31921 quoted using the C convention.
31924 The number of bytes to read. This should be an integer literal.
31926 @item @var{byte-offset}
31927 The offsets in bytes relative to @var{address} at which to start
31928 reading. This should be an integer literal. This option is provided
31929 so that a frontend is not required to first evaluate address and then
31930 perform address arithmetics itself.
31934 This command attempts to read all accessible memory regions in the
31935 specified range. First, all regions marked as unreadable in the memory
31936 map (if one is defined) will be skipped. @xref{Memory Region
31937 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31938 regions. For each one, if reading full region results in an errors,
31939 @value{GDBN} will try to read a subset of the region.
31941 In general, every single byte in the region may be readable or not,
31942 and the only way to read every readable byte is to try a read at
31943 every address, which is not practical. Therefore, @value{GDBN} will
31944 attempt to read all accessible bytes at either beginning or the end
31945 of the region, using a binary division scheme. This heuristic works
31946 well for reading accross a memory map boundary. Note that if a region
31947 has a readable range that is neither at the beginning or the end,
31948 @value{GDBN} will not read it.
31950 The result record (@pxref{GDB/MI Result Records}) that is output of
31951 the command includes a field named @samp{memory} whose content is a
31952 list of tuples. Each tuple represent a successfully read memory block
31953 and has the following fields:
31957 The start address of the memory block, as hexadecimal literal.
31960 The end address of the memory block, as hexadecimal literal.
31963 The offset of the memory block, as hexadecimal literal, relative to
31964 the start address passed to @code{-data-read-memory-bytes}.
31967 The contents of the memory block, in hex.
31973 @subsubheading @value{GDBN} Command
31975 The corresponding @value{GDBN} command is @samp{x}.
31977 @subsubheading Example
31981 -data-read-memory-bytes &a 10
31982 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31984 contents="01000000020000000300"@}]
31989 @subheading The @code{-data-write-memory-bytes} Command
31990 @findex -data-write-memory-bytes
31992 @subsubheading Synopsis
31995 -data-write-memory-bytes @var{address} @var{contents}
31996 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32003 @item @var{address}
32004 An expression specifying the address of the first memory word to be
32005 read. Complex expressions containing embedded white space should be
32006 quoted using the C convention.
32008 @item @var{contents}
32009 The hex-encoded bytes to write.
32012 Optional argument indicating the number of bytes to be written. If @var{count}
32013 is greater than @var{contents}' length, @value{GDBN} will repeatedly
32014 write @var{contents} until it fills @var{count} bytes.
32018 @subsubheading @value{GDBN} Command
32020 There's no corresponding @value{GDBN} command.
32022 @subsubheading Example
32026 -data-write-memory-bytes &a "aabbccdd"
32033 -data-write-memory-bytes &a "aabbccdd" 16e
32038 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32039 @node GDB/MI Tracepoint Commands
32040 @section @sc{gdb/mi} Tracepoint Commands
32042 The commands defined in this section implement MI support for
32043 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32045 @subheading The @code{-trace-find} Command
32046 @findex -trace-find
32048 @subsubheading Synopsis
32051 -trace-find @var{mode} [@var{parameters}@dots{}]
32054 Find a trace frame using criteria defined by @var{mode} and
32055 @var{parameters}. The following table lists permissible
32056 modes and their parameters. For details of operation, see @ref{tfind}.
32061 No parameters are required. Stops examining trace frames.
32064 An integer is required as parameter. Selects tracepoint frame with
32067 @item tracepoint-number
32068 An integer is required as parameter. Finds next
32069 trace frame that corresponds to tracepoint with the specified number.
32072 An address is required as parameter. Finds
32073 next trace frame that corresponds to any tracepoint at the specified
32076 @item pc-inside-range
32077 Two addresses are required as parameters. Finds next trace
32078 frame that corresponds to a tracepoint at an address inside the
32079 specified range. Both bounds are considered to be inside the range.
32081 @item pc-outside-range
32082 Two addresses are required as parameters. Finds
32083 next trace frame that corresponds to a tracepoint at an address outside
32084 the specified range. Both bounds are considered to be inside the range.
32087 Line specification is required as parameter. @xref{Specify Location}.
32088 Finds next trace frame that corresponds to a tracepoint at
32089 the specified location.
32093 If @samp{none} was passed as @var{mode}, the response does not
32094 have fields. Otherwise, the response may have the following fields:
32098 This field has either @samp{0} or @samp{1} as the value, depending
32099 on whether a matching tracepoint was found.
32102 The index of the found traceframe. This field is present iff
32103 the @samp{found} field has value of @samp{1}.
32106 The index of the found tracepoint. This field is present iff
32107 the @samp{found} field has value of @samp{1}.
32110 The information about the frame corresponding to the found trace
32111 frame. This field is present only if a trace frame was found.
32112 @xref{GDB/MI Frame Information}, for description of this field.
32116 @subsubheading @value{GDBN} Command
32118 The corresponding @value{GDBN} command is @samp{tfind}.
32120 @subheading -trace-define-variable
32121 @findex -trace-define-variable
32123 @subsubheading Synopsis
32126 -trace-define-variable @var{name} [ @var{value} ]
32129 Create trace variable @var{name} if it does not exist. If
32130 @var{value} is specified, sets the initial value of the specified
32131 trace variable to that value. Note that the @var{name} should start
32132 with the @samp{$} character.
32134 @subsubheading @value{GDBN} Command
32136 The corresponding @value{GDBN} command is @samp{tvariable}.
32138 @subheading -trace-list-variables
32139 @findex -trace-list-variables
32141 @subsubheading Synopsis
32144 -trace-list-variables
32147 Return a table of all defined trace variables. Each element of the
32148 table has the following fields:
32152 The name of the trace variable. This field is always present.
32155 The initial value. This is a 64-bit signed integer. This
32156 field is always present.
32159 The value the trace variable has at the moment. This is a 64-bit
32160 signed integer. This field is absent iff current value is
32161 not defined, for example if the trace was never run, or is
32166 @subsubheading @value{GDBN} Command
32168 The corresponding @value{GDBN} command is @samp{tvariables}.
32170 @subsubheading Example
32174 -trace-list-variables
32175 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32176 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32177 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32178 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32179 body=[variable=@{name="$trace_timestamp",initial="0"@}
32180 variable=@{name="$foo",initial="10",current="15"@}]@}
32184 @subheading -trace-save
32185 @findex -trace-save
32187 @subsubheading Synopsis
32190 -trace-save [-r ] @var{filename}
32193 Saves the collected trace data to @var{filename}. Without the
32194 @samp{-r} option, the data is downloaded from the target and saved
32195 in a local file. With the @samp{-r} option the target is asked
32196 to perform the save.
32198 @subsubheading @value{GDBN} Command
32200 The corresponding @value{GDBN} command is @samp{tsave}.
32203 @subheading -trace-start
32204 @findex -trace-start
32206 @subsubheading Synopsis
32212 Starts a tracing experiments. The result of this command does not
32215 @subsubheading @value{GDBN} Command
32217 The corresponding @value{GDBN} command is @samp{tstart}.
32219 @subheading -trace-status
32220 @findex -trace-status
32222 @subsubheading Synopsis
32228 Obtains the status of a tracing experiment. The result may include
32229 the following fields:
32234 May have a value of either @samp{0}, when no tracing operations are
32235 supported, @samp{1}, when all tracing operations are supported, or
32236 @samp{file} when examining trace file. In the latter case, examining
32237 of trace frame is possible but new tracing experiement cannot be
32238 started. This field is always present.
32241 May have a value of either @samp{0} or @samp{1} depending on whether
32242 tracing experiement is in progress on target. This field is present
32243 if @samp{supported} field is not @samp{0}.
32246 Report the reason why the tracing was stopped last time. This field
32247 may be absent iff tracing was never stopped on target yet. The
32248 value of @samp{request} means the tracing was stopped as result of
32249 the @code{-trace-stop} command. The value of @samp{overflow} means
32250 the tracing buffer is full. The value of @samp{disconnection} means
32251 tracing was automatically stopped when @value{GDBN} has disconnected.
32252 The value of @samp{passcount} means tracing was stopped when a
32253 tracepoint was passed a maximal number of times for that tracepoint.
32254 This field is present if @samp{supported} field is not @samp{0}.
32256 @item stopping-tracepoint
32257 The number of tracepoint whose passcount as exceeded. This field is
32258 present iff the @samp{stop-reason} field has the value of
32262 @itemx frames-created
32263 The @samp{frames} field is a count of the total number of trace frames
32264 in the trace buffer, while @samp{frames-created} is the total created
32265 during the run, including ones that were discarded, such as when a
32266 circular trace buffer filled up. Both fields are optional.
32270 These fields tell the current size of the tracing buffer and the
32271 remaining space. These fields are optional.
32274 The value of the circular trace buffer flag. @code{1} means that the
32275 trace buffer is circular and old trace frames will be discarded if
32276 necessary to make room, @code{0} means that the trace buffer is linear
32280 The value of the disconnected tracing flag. @code{1} means that
32281 tracing will continue after @value{GDBN} disconnects, @code{0} means
32282 that the trace run will stop.
32285 The filename of the trace file being examined. This field is
32286 optional, and only present when examining a trace file.
32290 @subsubheading @value{GDBN} Command
32292 The corresponding @value{GDBN} command is @samp{tstatus}.
32294 @subheading -trace-stop
32295 @findex -trace-stop
32297 @subsubheading Synopsis
32303 Stops a tracing experiment. The result of this command has the same
32304 fields as @code{-trace-status}, except that the @samp{supported} and
32305 @samp{running} fields are not output.
32307 @subsubheading @value{GDBN} Command
32309 The corresponding @value{GDBN} command is @samp{tstop}.
32312 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32313 @node GDB/MI Symbol Query
32314 @section @sc{gdb/mi} Symbol Query Commands
32318 @subheading The @code{-symbol-info-address} Command
32319 @findex -symbol-info-address
32321 @subsubheading Synopsis
32324 -symbol-info-address @var{symbol}
32327 Describe where @var{symbol} is stored.
32329 @subsubheading @value{GDBN} Command
32331 The corresponding @value{GDBN} command is @samp{info address}.
32333 @subsubheading Example
32337 @subheading The @code{-symbol-info-file} Command
32338 @findex -symbol-info-file
32340 @subsubheading Synopsis
32346 Show the file for the symbol.
32348 @subsubheading @value{GDBN} Command
32350 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32351 @samp{gdb_find_file}.
32353 @subsubheading Example
32357 @subheading The @code{-symbol-info-function} Command
32358 @findex -symbol-info-function
32360 @subsubheading Synopsis
32363 -symbol-info-function
32366 Show which function the symbol lives in.
32368 @subsubheading @value{GDBN} Command
32370 @samp{gdb_get_function} in @code{gdbtk}.
32372 @subsubheading Example
32376 @subheading The @code{-symbol-info-line} Command
32377 @findex -symbol-info-line
32379 @subsubheading Synopsis
32385 Show the core addresses of the code for a source line.
32387 @subsubheading @value{GDBN} Command
32389 The corresponding @value{GDBN} command is @samp{info line}.
32390 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32392 @subsubheading Example
32396 @subheading The @code{-symbol-info-symbol} Command
32397 @findex -symbol-info-symbol
32399 @subsubheading Synopsis
32402 -symbol-info-symbol @var{addr}
32405 Describe what symbol is at location @var{addr}.
32407 @subsubheading @value{GDBN} Command
32409 The corresponding @value{GDBN} command is @samp{info symbol}.
32411 @subsubheading Example
32415 @subheading The @code{-symbol-list-functions} Command
32416 @findex -symbol-list-functions
32418 @subsubheading Synopsis
32421 -symbol-list-functions
32424 List the functions in the executable.
32426 @subsubheading @value{GDBN} Command
32428 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32429 @samp{gdb_search} in @code{gdbtk}.
32431 @subsubheading Example
32436 @subheading The @code{-symbol-list-lines} Command
32437 @findex -symbol-list-lines
32439 @subsubheading Synopsis
32442 -symbol-list-lines @var{filename}
32445 Print the list of lines that contain code and their associated program
32446 addresses for the given source filename. The entries are sorted in
32447 ascending PC order.
32449 @subsubheading @value{GDBN} Command
32451 There is no corresponding @value{GDBN} command.
32453 @subsubheading Example
32456 -symbol-list-lines basics.c
32457 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32463 @subheading The @code{-symbol-list-types} Command
32464 @findex -symbol-list-types
32466 @subsubheading Synopsis
32472 List all the type names.
32474 @subsubheading @value{GDBN} Command
32476 The corresponding commands are @samp{info types} in @value{GDBN},
32477 @samp{gdb_search} in @code{gdbtk}.
32479 @subsubheading Example
32483 @subheading The @code{-symbol-list-variables} Command
32484 @findex -symbol-list-variables
32486 @subsubheading Synopsis
32489 -symbol-list-variables
32492 List all the global and static variable names.
32494 @subsubheading @value{GDBN} Command
32496 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32498 @subsubheading Example
32502 @subheading The @code{-symbol-locate} Command
32503 @findex -symbol-locate
32505 @subsubheading Synopsis
32511 @subsubheading @value{GDBN} Command
32513 @samp{gdb_loc} in @code{gdbtk}.
32515 @subsubheading Example
32519 @subheading The @code{-symbol-type} Command
32520 @findex -symbol-type
32522 @subsubheading Synopsis
32525 -symbol-type @var{variable}
32528 Show type of @var{variable}.
32530 @subsubheading @value{GDBN} Command
32532 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32533 @samp{gdb_obj_variable}.
32535 @subsubheading Example
32540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32541 @node GDB/MI File Commands
32542 @section @sc{gdb/mi} File Commands
32544 This section describes the GDB/MI commands to specify executable file names
32545 and to read in and obtain symbol table information.
32547 @subheading The @code{-file-exec-and-symbols} Command
32548 @findex -file-exec-and-symbols
32550 @subsubheading Synopsis
32553 -file-exec-and-symbols @var{file}
32556 Specify the executable file to be debugged. This file is the one from
32557 which the symbol table is also read. If no file is specified, the
32558 command clears the executable and symbol information. If breakpoints
32559 are set when using this command with no arguments, @value{GDBN} will produce
32560 error messages. Otherwise, no output is produced, except a completion
32563 @subsubheading @value{GDBN} Command
32565 The corresponding @value{GDBN} command is @samp{file}.
32567 @subsubheading Example
32571 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32577 @subheading The @code{-file-exec-file} Command
32578 @findex -file-exec-file
32580 @subsubheading Synopsis
32583 -file-exec-file @var{file}
32586 Specify the executable file to be debugged. Unlike
32587 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32588 from this file. If used without argument, @value{GDBN} clears the information
32589 about the executable file. No output is produced, except a completion
32592 @subsubheading @value{GDBN} Command
32594 The corresponding @value{GDBN} command is @samp{exec-file}.
32596 @subsubheading Example
32600 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32607 @subheading The @code{-file-list-exec-sections} Command
32608 @findex -file-list-exec-sections
32610 @subsubheading Synopsis
32613 -file-list-exec-sections
32616 List the sections of the current executable file.
32618 @subsubheading @value{GDBN} Command
32620 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32621 information as this command. @code{gdbtk} has a corresponding command
32622 @samp{gdb_load_info}.
32624 @subsubheading Example
32629 @subheading The @code{-file-list-exec-source-file} Command
32630 @findex -file-list-exec-source-file
32632 @subsubheading Synopsis
32635 -file-list-exec-source-file
32638 List the line number, the current source file, and the absolute path
32639 to the current source file for the current executable. The macro
32640 information field has a value of @samp{1} or @samp{0} depending on
32641 whether or not the file includes preprocessor macro information.
32643 @subsubheading @value{GDBN} Command
32645 The @value{GDBN} equivalent is @samp{info source}
32647 @subsubheading Example
32651 123-file-list-exec-source-file
32652 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32657 @subheading The @code{-file-list-exec-source-files} Command
32658 @findex -file-list-exec-source-files
32660 @subsubheading Synopsis
32663 -file-list-exec-source-files
32666 List the source files for the current executable.
32668 It will always output both the filename and fullname (absolute file
32669 name) of a source file.
32671 @subsubheading @value{GDBN} Command
32673 The @value{GDBN} equivalent is @samp{info sources}.
32674 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32676 @subsubheading Example
32679 -file-list-exec-source-files
32681 @{file=foo.c,fullname=/home/foo.c@},
32682 @{file=/home/bar.c,fullname=/home/bar.c@},
32683 @{file=gdb_could_not_find_fullpath.c@}]
32688 @subheading The @code{-file-list-shared-libraries} Command
32689 @findex -file-list-shared-libraries
32691 @subsubheading Synopsis
32694 -file-list-shared-libraries
32697 List the shared libraries in the program.
32699 @subsubheading @value{GDBN} Command
32701 The corresponding @value{GDBN} command is @samp{info shared}.
32703 @subsubheading Example
32707 @subheading The @code{-file-list-symbol-files} Command
32708 @findex -file-list-symbol-files
32710 @subsubheading Synopsis
32713 -file-list-symbol-files
32718 @subsubheading @value{GDBN} Command
32720 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32722 @subsubheading Example
32727 @subheading The @code{-file-symbol-file} Command
32728 @findex -file-symbol-file
32730 @subsubheading Synopsis
32733 -file-symbol-file @var{file}
32736 Read symbol table info from the specified @var{file} argument. When
32737 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32738 produced, except for a completion notification.
32740 @subsubheading @value{GDBN} Command
32742 The corresponding @value{GDBN} command is @samp{symbol-file}.
32744 @subsubheading Example
32748 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32754 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32755 @node GDB/MI Memory Overlay Commands
32756 @section @sc{gdb/mi} Memory Overlay Commands
32758 The memory overlay commands are not implemented.
32760 @c @subheading -overlay-auto
32762 @c @subheading -overlay-list-mapping-state
32764 @c @subheading -overlay-list-overlays
32766 @c @subheading -overlay-map
32768 @c @subheading -overlay-off
32770 @c @subheading -overlay-on
32772 @c @subheading -overlay-unmap
32774 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32775 @node GDB/MI Signal Handling Commands
32776 @section @sc{gdb/mi} Signal Handling Commands
32778 Signal handling commands are not implemented.
32780 @c @subheading -signal-handle
32782 @c @subheading -signal-list-handle-actions
32784 @c @subheading -signal-list-signal-types
32788 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32789 @node GDB/MI Target Manipulation
32790 @section @sc{gdb/mi} Target Manipulation Commands
32793 @subheading The @code{-target-attach} Command
32794 @findex -target-attach
32796 @subsubheading Synopsis
32799 -target-attach @var{pid} | @var{gid} | @var{file}
32802 Attach to a process @var{pid} or a file @var{file} outside of
32803 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32804 group, the id previously returned by
32805 @samp{-list-thread-groups --available} must be used.
32807 @subsubheading @value{GDBN} Command
32809 The corresponding @value{GDBN} command is @samp{attach}.
32811 @subsubheading Example
32815 =thread-created,id="1"
32816 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32822 @subheading The @code{-target-compare-sections} Command
32823 @findex -target-compare-sections
32825 @subsubheading Synopsis
32828 -target-compare-sections [ @var{section} ]
32831 Compare data of section @var{section} on target to the exec file.
32832 Without the argument, all sections are compared.
32834 @subsubheading @value{GDBN} Command
32836 The @value{GDBN} equivalent is @samp{compare-sections}.
32838 @subsubheading Example
32843 @subheading The @code{-target-detach} Command
32844 @findex -target-detach
32846 @subsubheading Synopsis
32849 -target-detach [ @var{pid} | @var{gid} ]
32852 Detach from the remote target which normally resumes its execution.
32853 If either @var{pid} or @var{gid} is specified, detaches from either
32854 the specified process, or specified thread group. There's no output.
32856 @subsubheading @value{GDBN} Command
32858 The corresponding @value{GDBN} command is @samp{detach}.
32860 @subsubheading Example
32870 @subheading The @code{-target-disconnect} Command
32871 @findex -target-disconnect
32873 @subsubheading Synopsis
32879 Disconnect from the remote target. There's no output and the target is
32880 generally not resumed.
32882 @subsubheading @value{GDBN} Command
32884 The corresponding @value{GDBN} command is @samp{disconnect}.
32886 @subsubheading Example
32896 @subheading The @code{-target-download} Command
32897 @findex -target-download
32899 @subsubheading Synopsis
32905 Loads the executable onto the remote target.
32906 It prints out an update message every half second, which includes the fields:
32910 The name of the section.
32912 The size of what has been sent so far for that section.
32914 The size of the section.
32916 The total size of what was sent so far (the current and the previous sections).
32918 The size of the overall executable to download.
32922 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32923 @sc{gdb/mi} Output Syntax}).
32925 In addition, it prints the name and size of the sections, as they are
32926 downloaded. These messages include the following fields:
32930 The name of the section.
32932 The size of the section.
32934 The size of the overall executable to download.
32938 At the end, a summary is printed.
32940 @subsubheading @value{GDBN} Command
32942 The corresponding @value{GDBN} command is @samp{load}.
32944 @subsubheading Example
32946 Note: each status message appears on a single line. Here the messages
32947 have been broken down so that they can fit onto a page.
32952 +download,@{section=".text",section-size="6668",total-size="9880"@}
32953 +download,@{section=".text",section-sent="512",section-size="6668",
32954 total-sent="512",total-size="9880"@}
32955 +download,@{section=".text",section-sent="1024",section-size="6668",
32956 total-sent="1024",total-size="9880"@}
32957 +download,@{section=".text",section-sent="1536",section-size="6668",
32958 total-sent="1536",total-size="9880"@}
32959 +download,@{section=".text",section-sent="2048",section-size="6668",
32960 total-sent="2048",total-size="9880"@}
32961 +download,@{section=".text",section-sent="2560",section-size="6668",
32962 total-sent="2560",total-size="9880"@}
32963 +download,@{section=".text",section-sent="3072",section-size="6668",
32964 total-sent="3072",total-size="9880"@}
32965 +download,@{section=".text",section-sent="3584",section-size="6668",
32966 total-sent="3584",total-size="9880"@}
32967 +download,@{section=".text",section-sent="4096",section-size="6668",
32968 total-sent="4096",total-size="9880"@}
32969 +download,@{section=".text",section-sent="4608",section-size="6668",
32970 total-sent="4608",total-size="9880"@}
32971 +download,@{section=".text",section-sent="5120",section-size="6668",
32972 total-sent="5120",total-size="9880"@}
32973 +download,@{section=".text",section-sent="5632",section-size="6668",
32974 total-sent="5632",total-size="9880"@}
32975 +download,@{section=".text",section-sent="6144",section-size="6668",
32976 total-sent="6144",total-size="9880"@}
32977 +download,@{section=".text",section-sent="6656",section-size="6668",
32978 total-sent="6656",total-size="9880"@}
32979 +download,@{section=".init",section-size="28",total-size="9880"@}
32980 +download,@{section=".fini",section-size="28",total-size="9880"@}
32981 +download,@{section=".data",section-size="3156",total-size="9880"@}
32982 +download,@{section=".data",section-sent="512",section-size="3156",
32983 total-sent="7236",total-size="9880"@}
32984 +download,@{section=".data",section-sent="1024",section-size="3156",
32985 total-sent="7748",total-size="9880"@}
32986 +download,@{section=".data",section-sent="1536",section-size="3156",
32987 total-sent="8260",total-size="9880"@}
32988 +download,@{section=".data",section-sent="2048",section-size="3156",
32989 total-sent="8772",total-size="9880"@}
32990 +download,@{section=".data",section-sent="2560",section-size="3156",
32991 total-sent="9284",total-size="9880"@}
32992 +download,@{section=".data",section-sent="3072",section-size="3156",
32993 total-sent="9796",total-size="9880"@}
32994 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33001 @subheading The @code{-target-exec-status} Command
33002 @findex -target-exec-status
33004 @subsubheading Synopsis
33007 -target-exec-status
33010 Provide information on the state of the target (whether it is running or
33011 not, for instance).
33013 @subsubheading @value{GDBN} Command
33015 There's no equivalent @value{GDBN} command.
33017 @subsubheading Example
33021 @subheading The @code{-target-list-available-targets} Command
33022 @findex -target-list-available-targets
33024 @subsubheading Synopsis
33027 -target-list-available-targets
33030 List the possible targets to connect to.
33032 @subsubheading @value{GDBN} Command
33034 The corresponding @value{GDBN} command is @samp{help target}.
33036 @subsubheading Example
33040 @subheading The @code{-target-list-current-targets} Command
33041 @findex -target-list-current-targets
33043 @subsubheading Synopsis
33046 -target-list-current-targets
33049 Describe the current target.
33051 @subsubheading @value{GDBN} Command
33053 The corresponding information is printed by @samp{info file} (among
33056 @subsubheading Example
33060 @subheading The @code{-target-list-parameters} Command
33061 @findex -target-list-parameters
33063 @subsubheading Synopsis
33066 -target-list-parameters
33072 @subsubheading @value{GDBN} Command
33076 @subsubheading Example
33080 @subheading The @code{-target-select} Command
33081 @findex -target-select
33083 @subsubheading Synopsis
33086 -target-select @var{type} @var{parameters @dots{}}
33089 Connect @value{GDBN} to the remote target. This command takes two args:
33093 The type of target, for instance @samp{remote}, etc.
33094 @item @var{parameters}
33095 Device names, host names and the like. @xref{Target Commands, ,
33096 Commands for Managing Targets}, for more details.
33099 The output is a connection notification, followed by the address at
33100 which the target program is, in the following form:
33103 ^connected,addr="@var{address}",func="@var{function name}",
33104 args=[@var{arg list}]
33107 @subsubheading @value{GDBN} Command
33109 The corresponding @value{GDBN} command is @samp{target}.
33111 @subsubheading Example
33115 -target-select remote /dev/ttya
33116 ^connected,addr="0xfe00a300",func="??",args=[]
33120 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33121 @node GDB/MI File Transfer Commands
33122 @section @sc{gdb/mi} File Transfer Commands
33125 @subheading The @code{-target-file-put} Command
33126 @findex -target-file-put
33128 @subsubheading Synopsis
33131 -target-file-put @var{hostfile} @var{targetfile}
33134 Copy file @var{hostfile} from the host system (the machine running
33135 @value{GDBN}) to @var{targetfile} on the target system.
33137 @subsubheading @value{GDBN} Command
33139 The corresponding @value{GDBN} command is @samp{remote put}.
33141 @subsubheading Example
33145 -target-file-put localfile remotefile
33151 @subheading The @code{-target-file-get} Command
33152 @findex -target-file-get
33154 @subsubheading Synopsis
33157 -target-file-get @var{targetfile} @var{hostfile}
33160 Copy file @var{targetfile} from the target system to @var{hostfile}
33161 on the host system.
33163 @subsubheading @value{GDBN} Command
33165 The corresponding @value{GDBN} command is @samp{remote get}.
33167 @subsubheading Example
33171 -target-file-get remotefile localfile
33177 @subheading The @code{-target-file-delete} Command
33178 @findex -target-file-delete
33180 @subsubheading Synopsis
33183 -target-file-delete @var{targetfile}
33186 Delete @var{targetfile} from the target system.
33188 @subsubheading @value{GDBN} Command
33190 The corresponding @value{GDBN} command is @samp{remote delete}.
33192 @subsubheading Example
33196 -target-file-delete remotefile
33202 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33203 @node GDB/MI Miscellaneous Commands
33204 @section Miscellaneous @sc{gdb/mi} Commands
33206 @c @subheading -gdb-complete
33208 @subheading The @code{-gdb-exit} Command
33211 @subsubheading Synopsis
33217 Exit @value{GDBN} immediately.
33219 @subsubheading @value{GDBN} Command
33221 Approximately corresponds to @samp{quit}.
33223 @subsubheading Example
33233 @subheading The @code{-exec-abort} Command
33234 @findex -exec-abort
33236 @subsubheading Synopsis
33242 Kill the inferior running program.
33244 @subsubheading @value{GDBN} Command
33246 The corresponding @value{GDBN} command is @samp{kill}.
33248 @subsubheading Example
33253 @subheading The @code{-gdb-set} Command
33256 @subsubheading Synopsis
33262 Set an internal @value{GDBN} variable.
33263 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33265 @subsubheading @value{GDBN} Command
33267 The corresponding @value{GDBN} command is @samp{set}.
33269 @subsubheading Example
33279 @subheading The @code{-gdb-show} Command
33282 @subsubheading Synopsis
33288 Show the current value of a @value{GDBN} variable.
33290 @subsubheading @value{GDBN} Command
33292 The corresponding @value{GDBN} command is @samp{show}.
33294 @subsubheading Example
33303 @c @subheading -gdb-source
33306 @subheading The @code{-gdb-version} Command
33307 @findex -gdb-version
33309 @subsubheading Synopsis
33315 Show version information for @value{GDBN}. Used mostly in testing.
33317 @subsubheading @value{GDBN} Command
33319 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33320 default shows this information when you start an interactive session.
33322 @subsubheading Example
33324 @c This example modifies the actual output from GDB to avoid overfull
33330 ~Copyright 2000 Free Software Foundation, Inc.
33331 ~GDB is free software, covered by the GNU General Public License, and
33332 ~you are welcome to change it and/or distribute copies of it under
33333 ~ certain conditions.
33334 ~Type "show copying" to see the conditions.
33335 ~There is absolutely no warranty for GDB. Type "show warranty" for
33337 ~This GDB was configured as
33338 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33343 @subheading The @code{-list-features} Command
33344 @findex -list-features
33346 Returns a list of particular features of the MI protocol that
33347 this version of gdb implements. A feature can be a command,
33348 or a new field in an output of some command, or even an
33349 important bugfix. While a frontend can sometimes detect presence
33350 of a feature at runtime, it is easier to perform detection at debugger
33353 The command returns a list of strings, with each string naming an
33354 available feature. Each returned string is just a name, it does not
33355 have any internal structure. The list of possible feature names
33361 (gdb) -list-features
33362 ^done,result=["feature1","feature2"]
33365 The current list of features is:
33368 @item frozen-varobjs
33369 Indicates support for the @code{-var-set-frozen} command, as well
33370 as possible presense of the @code{frozen} field in the output
33371 of @code{-varobj-create}.
33372 @item pending-breakpoints
33373 Indicates support for the @option{-f} option to the @code{-break-insert}
33376 Indicates Python scripting support, Python-based
33377 pretty-printing commands, and possible presence of the
33378 @samp{display_hint} field in the output of @code{-var-list-children}
33380 Indicates support for the @code{-thread-info} command.
33381 @item data-read-memory-bytes
33382 Indicates support for the @code{-data-read-memory-bytes} and the
33383 @code{-data-write-memory-bytes} commands.
33384 @item breakpoint-notifications
33385 Indicates that changes to breakpoints and breakpoints created via the
33386 CLI will be announced via async records.
33387 @item ada-task-info
33388 Indicates support for the @code{-ada-task-info} command.
33391 @subheading The @code{-list-target-features} Command
33392 @findex -list-target-features
33394 Returns a list of particular features that are supported by the
33395 target. Those features affect the permitted MI commands, but
33396 unlike the features reported by the @code{-list-features} command, the
33397 features depend on which target GDB is using at the moment. Whenever
33398 a target can change, due to commands such as @code{-target-select},
33399 @code{-target-attach} or @code{-exec-run}, the list of target features
33400 may change, and the frontend should obtain it again.
33404 (gdb) -list-features
33405 ^done,result=["async"]
33408 The current list of features is:
33412 Indicates that the target is capable of asynchronous command
33413 execution, which means that @value{GDBN} will accept further commands
33414 while the target is running.
33417 Indicates that the target is capable of reverse execution.
33418 @xref{Reverse Execution}, for more information.
33422 @subheading The @code{-list-thread-groups} Command
33423 @findex -list-thread-groups
33425 @subheading Synopsis
33428 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33431 Lists thread groups (@pxref{Thread groups}). When a single thread
33432 group is passed as the argument, lists the children of that group.
33433 When several thread group are passed, lists information about those
33434 thread groups. Without any parameters, lists information about all
33435 top-level thread groups.
33437 Normally, thread groups that are being debugged are reported.
33438 With the @samp{--available} option, @value{GDBN} reports thread groups
33439 available on the target.
33441 The output of this command may have either a @samp{threads} result or
33442 a @samp{groups} result. The @samp{thread} result has a list of tuples
33443 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33444 Information}). The @samp{groups} result has a list of tuples as value,
33445 each tuple describing a thread group. If top-level groups are
33446 requested (that is, no parameter is passed), or when several groups
33447 are passed, the output always has a @samp{groups} result. The format
33448 of the @samp{group} result is described below.
33450 To reduce the number of roundtrips it's possible to list thread groups
33451 together with their children, by passing the @samp{--recurse} option
33452 and the recursion depth. Presently, only recursion depth of 1 is
33453 permitted. If this option is present, then every reported thread group
33454 will also include its children, either as @samp{group} or
33455 @samp{threads} field.
33457 In general, any combination of option and parameters is permitted, with
33458 the following caveats:
33462 When a single thread group is passed, the output will typically
33463 be the @samp{threads} result. Because threads may not contain
33464 anything, the @samp{recurse} option will be ignored.
33467 When the @samp{--available} option is passed, limited information may
33468 be available. In particular, the list of threads of a process might
33469 be inaccessible. Further, specifying specific thread groups might
33470 not give any performance advantage over listing all thread groups.
33471 The frontend should assume that @samp{-list-thread-groups --available}
33472 is always an expensive operation and cache the results.
33476 The @samp{groups} result is a list of tuples, where each tuple may
33477 have the following fields:
33481 Identifier of the thread group. This field is always present.
33482 The identifier is an opaque string; frontends should not try to
33483 convert it to an integer, even though it might look like one.
33486 The type of the thread group. At present, only @samp{process} is a
33490 The target-specific process identifier. This field is only present
33491 for thread groups of type @samp{process} and only if the process exists.
33494 The number of children this thread group has. This field may be
33495 absent for an available thread group.
33498 This field has a list of tuples as value, each tuple describing a
33499 thread. It may be present if the @samp{--recurse} option is
33500 specified, and it's actually possible to obtain the threads.
33503 This field is a list of integers, each identifying a core that one
33504 thread of the group is running on. This field may be absent if
33505 such information is not available.
33508 The name of the executable file that corresponds to this thread group.
33509 The field is only present for thread groups of type @samp{process},
33510 and only if there is a corresponding executable file.
33514 @subheading Example
33518 -list-thread-groups
33519 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33520 -list-thread-groups 17
33521 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33522 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33523 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33524 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33525 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33526 -list-thread-groups --available
33527 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33528 -list-thread-groups --available --recurse 1
33529 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33530 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33531 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33532 -list-thread-groups --available --recurse 1 17 18
33533 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33534 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33535 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33538 @subheading The @code{-info-os} Command
33541 @subsubheading Synopsis
33544 -info-os [ @var{type} ]
33547 If no argument is supplied, the command returns a table of available
33548 operating-system-specific information types. If one of these types is
33549 supplied as an argument @var{type}, then the command returns a table
33550 of data of that type.
33552 The types of information available depend on the target operating
33555 @subsubheading @value{GDBN} Command
33557 The corresponding @value{GDBN} command is @samp{info os}.
33559 @subsubheading Example
33561 When run on a @sc{gnu}/Linux system, the output will look something
33567 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33568 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33569 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33570 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33571 body=[item=@{col0="processes",col1="Listing of all processes",
33572 col2="Processes"@},
33573 item=@{col0="procgroups",col1="Listing of all process groups",
33574 col2="Process groups"@},
33575 item=@{col0="threads",col1="Listing of all threads",
33577 item=@{col0="files",col1="Listing of all file descriptors",
33578 col2="File descriptors"@},
33579 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33581 item=@{col0="shm",col1="Listing of all shared-memory regions",
33582 col2="Shared-memory regions"@},
33583 item=@{col0="semaphores",col1="Listing of all semaphores",
33584 col2="Semaphores"@},
33585 item=@{col0="msg",col1="Listing of all message queues",
33586 col2="Message queues"@},
33587 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33588 col2="Kernel modules"@}]@}
33591 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33592 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33593 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33594 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33595 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33596 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33597 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33598 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33600 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33601 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33605 (Note that the MI output here includes a @code{"Title"} column that
33606 does not appear in command-line @code{info os}; this column is useful
33607 for MI clients that want to enumerate the types of data, such as in a
33608 popup menu, but is needless clutter on the command line, and
33609 @code{info os} omits it.)
33611 @subheading The @code{-add-inferior} Command
33612 @findex -add-inferior
33614 @subheading Synopsis
33620 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33621 inferior is not associated with any executable. Such association may
33622 be established with the @samp{-file-exec-and-symbols} command
33623 (@pxref{GDB/MI File Commands}). The command response has a single
33624 field, @samp{thread-group}, whose value is the identifier of the
33625 thread group corresponding to the new inferior.
33627 @subheading Example
33632 ^done,thread-group="i3"
33635 @subheading The @code{-interpreter-exec} Command
33636 @findex -interpreter-exec
33638 @subheading Synopsis
33641 -interpreter-exec @var{interpreter} @var{command}
33643 @anchor{-interpreter-exec}
33645 Execute the specified @var{command} in the given @var{interpreter}.
33647 @subheading @value{GDBN} Command
33649 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33651 @subheading Example
33655 -interpreter-exec console "break main"
33656 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33657 &"During symbol reading, bad structure-type format.\n"
33658 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33663 @subheading The @code{-inferior-tty-set} Command
33664 @findex -inferior-tty-set
33666 @subheading Synopsis
33669 -inferior-tty-set /dev/pts/1
33672 Set terminal for future runs of the program being debugged.
33674 @subheading @value{GDBN} Command
33676 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33678 @subheading Example
33682 -inferior-tty-set /dev/pts/1
33687 @subheading The @code{-inferior-tty-show} Command
33688 @findex -inferior-tty-show
33690 @subheading Synopsis
33696 Show terminal for future runs of program being debugged.
33698 @subheading @value{GDBN} Command
33700 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33702 @subheading Example
33706 -inferior-tty-set /dev/pts/1
33710 ^done,inferior_tty_terminal="/dev/pts/1"
33714 @subheading The @code{-enable-timings} Command
33715 @findex -enable-timings
33717 @subheading Synopsis
33720 -enable-timings [yes | no]
33723 Toggle the printing of the wallclock, user and system times for an MI
33724 command as a field in its output. This command is to help frontend
33725 developers optimize the performance of their code. No argument is
33726 equivalent to @samp{yes}.
33728 @subheading @value{GDBN} Command
33732 @subheading Example
33740 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33741 addr="0x080484ed",func="main",file="myprog.c",
33742 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33744 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33752 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33753 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33754 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33755 fullname="/home/nickrob/myprog.c",line="73"@}
33760 @chapter @value{GDBN} Annotations
33762 This chapter describes annotations in @value{GDBN}. Annotations were
33763 designed to interface @value{GDBN} to graphical user interfaces or other
33764 similar programs which want to interact with @value{GDBN} at a
33765 relatively high level.
33767 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33771 This is Edition @value{EDITION}, @value{DATE}.
33775 * Annotations Overview:: What annotations are; the general syntax.
33776 * Server Prefix:: Issuing a command without affecting user state.
33777 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33778 * Errors:: Annotations for error messages.
33779 * Invalidation:: Some annotations describe things now invalid.
33780 * Annotations for Running::
33781 Whether the program is running, how it stopped, etc.
33782 * Source Annotations:: Annotations describing source code.
33785 @node Annotations Overview
33786 @section What is an Annotation?
33787 @cindex annotations
33789 Annotations start with a newline character, two @samp{control-z}
33790 characters, and the name of the annotation. If there is no additional
33791 information associated with this annotation, the name of the annotation
33792 is followed immediately by a newline. If there is additional
33793 information, the name of the annotation is followed by a space, the
33794 additional information, and a newline. The additional information
33795 cannot contain newline characters.
33797 Any output not beginning with a newline and two @samp{control-z}
33798 characters denotes literal output from @value{GDBN}. Currently there is
33799 no need for @value{GDBN} to output a newline followed by two
33800 @samp{control-z} characters, but if there was such a need, the
33801 annotations could be extended with an @samp{escape} annotation which
33802 means those three characters as output.
33804 The annotation @var{level}, which is specified using the
33805 @option{--annotate} command line option (@pxref{Mode Options}), controls
33806 how much information @value{GDBN} prints together with its prompt,
33807 values of expressions, source lines, and other types of output. Level 0
33808 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33809 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33810 for programs that control @value{GDBN}, and level 2 annotations have
33811 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33812 Interface, annotate, GDB's Obsolete Annotations}).
33815 @kindex set annotate
33816 @item set annotate @var{level}
33817 The @value{GDBN} command @code{set annotate} sets the level of
33818 annotations to the specified @var{level}.
33820 @item show annotate
33821 @kindex show annotate
33822 Show the current annotation level.
33825 This chapter describes level 3 annotations.
33827 A simple example of starting up @value{GDBN} with annotations is:
33830 $ @kbd{gdb --annotate=3}
33832 Copyright 2003 Free Software Foundation, Inc.
33833 GDB is free software, covered by the GNU General Public License,
33834 and you are welcome to change it and/or distribute copies of it
33835 under certain conditions.
33836 Type "show copying" to see the conditions.
33837 There is absolutely no warranty for GDB. Type "show warranty"
33839 This GDB was configured as "i386-pc-linux-gnu"
33850 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33851 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33852 denotes a @samp{control-z} character) are annotations; the rest is
33853 output from @value{GDBN}.
33855 @node Server Prefix
33856 @section The Server Prefix
33857 @cindex server prefix
33859 If you prefix a command with @samp{server } then it will not affect
33860 the command history, nor will it affect @value{GDBN}'s notion of which
33861 command to repeat if @key{RET} is pressed on a line by itself. This
33862 means that commands can be run behind a user's back by a front-end in
33863 a transparent manner.
33865 The @code{server } prefix does not affect the recording of values into
33866 the value history; to print a value without recording it into the
33867 value history, use the @code{output} command instead of the
33868 @code{print} command.
33870 Using this prefix also disables confirmation requests
33871 (@pxref{confirmation requests}).
33874 @section Annotation for @value{GDBN} Input
33876 @cindex annotations for prompts
33877 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33878 to know when to send output, when the output from a given command is
33881 Different kinds of input each have a different @dfn{input type}. Each
33882 input type has three annotations: a @code{pre-} annotation, which
33883 denotes the beginning of any prompt which is being output, a plain
33884 annotation, which denotes the end of the prompt, and then a @code{post-}
33885 annotation which denotes the end of any echo which may (or may not) be
33886 associated with the input. For example, the @code{prompt} input type
33887 features the following annotations:
33895 The input types are
33898 @findex pre-prompt annotation
33899 @findex prompt annotation
33900 @findex post-prompt annotation
33902 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33904 @findex pre-commands annotation
33905 @findex commands annotation
33906 @findex post-commands annotation
33908 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33909 command. The annotations are repeated for each command which is input.
33911 @findex pre-overload-choice annotation
33912 @findex overload-choice annotation
33913 @findex post-overload-choice annotation
33914 @item overload-choice
33915 When @value{GDBN} wants the user to select between various overloaded functions.
33917 @findex pre-query annotation
33918 @findex query annotation
33919 @findex post-query annotation
33921 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33923 @findex pre-prompt-for-continue annotation
33924 @findex prompt-for-continue annotation
33925 @findex post-prompt-for-continue annotation
33926 @item prompt-for-continue
33927 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33928 expect this to work well; instead use @code{set height 0} to disable
33929 prompting. This is because the counting of lines is buggy in the
33930 presence of annotations.
33935 @cindex annotations for errors, warnings and interrupts
33937 @findex quit annotation
33942 This annotation occurs right before @value{GDBN} responds to an interrupt.
33944 @findex error annotation
33949 This annotation occurs right before @value{GDBN} responds to an error.
33951 Quit and error annotations indicate that any annotations which @value{GDBN} was
33952 in the middle of may end abruptly. For example, if a
33953 @code{value-history-begin} annotation is followed by a @code{error}, one
33954 cannot expect to receive the matching @code{value-history-end}. One
33955 cannot expect not to receive it either, however; an error annotation
33956 does not necessarily mean that @value{GDBN} is immediately returning all the way
33959 @findex error-begin annotation
33960 A quit or error annotation may be preceded by
33966 Any output between that and the quit or error annotation is the error
33969 Warning messages are not yet annotated.
33970 @c If we want to change that, need to fix warning(), type_error(),
33971 @c range_error(), and possibly other places.
33974 @section Invalidation Notices
33976 @cindex annotations for invalidation messages
33977 The following annotations say that certain pieces of state may have
33981 @findex frames-invalid annotation
33982 @item ^Z^Zframes-invalid
33984 The frames (for example, output from the @code{backtrace} command) may
33987 @findex breakpoints-invalid annotation
33988 @item ^Z^Zbreakpoints-invalid
33990 The breakpoints may have changed. For example, the user just added or
33991 deleted a breakpoint.
33994 @node Annotations for Running
33995 @section Running the Program
33996 @cindex annotations for running programs
33998 @findex starting annotation
33999 @findex stopping annotation
34000 When the program starts executing due to a @value{GDBN} command such as
34001 @code{step} or @code{continue},
34007 is output. When the program stops,
34013 is output. Before the @code{stopped} annotation, a variety of
34014 annotations describe how the program stopped.
34017 @findex exited annotation
34018 @item ^Z^Zexited @var{exit-status}
34019 The program exited, and @var{exit-status} is the exit status (zero for
34020 successful exit, otherwise nonzero).
34022 @findex signalled annotation
34023 @findex signal-name annotation
34024 @findex signal-name-end annotation
34025 @findex signal-string annotation
34026 @findex signal-string-end annotation
34027 @item ^Z^Zsignalled
34028 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34029 annotation continues:
34035 ^Z^Zsignal-name-end
34039 ^Z^Zsignal-string-end
34044 where @var{name} is the name of the signal, such as @code{SIGILL} or
34045 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34046 as @code{Illegal Instruction} or @code{Segmentation fault}.
34047 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34048 user's benefit and have no particular format.
34050 @findex signal annotation
34052 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34053 just saying that the program received the signal, not that it was
34054 terminated with it.
34056 @findex breakpoint annotation
34057 @item ^Z^Zbreakpoint @var{number}
34058 The program hit breakpoint number @var{number}.
34060 @findex watchpoint annotation
34061 @item ^Z^Zwatchpoint @var{number}
34062 The program hit watchpoint number @var{number}.
34065 @node Source Annotations
34066 @section Displaying Source
34067 @cindex annotations for source display
34069 @findex source annotation
34070 The following annotation is used instead of displaying source code:
34073 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34076 where @var{filename} is an absolute file name indicating which source
34077 file, @var{line} is the line number within that file (where 1 is the
34078 first line in the file), @var{character} is the character position
34079 within the file (where 0 is the first character in the file) (for most
34080 debug formats this will necessarily point to the beginning of a line),
34081 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34082 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34083 @var{addr} is the address in the target program associated with the
34084 source which is being displayed. @var{addr} is in the form @samp{0x}
34085 followed by one or more lowercase hex digits (note that this does not
34086 depend on the language).
34088 @node JIT Interface
34089 @chapter JIT Compilation Interface
34090 @cindex just-in-time compilation
34091 @cindex JIT compilation interface
34093 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34094 interface. A JIT compiler is a program or library that generates native
34095 executable code at runtime and executes it, usually in order to achieve good
34096 performance while maintaining platform independence.
34098 Programs that use JIT compilation are normally difficult to debug because
34099 portions of their code are generated at runtime, instead of being loaded from
34100 object files, which is where @value{GDBN} normally finds the program's symbols
34101 and debug information. In order to debug programs that use JIT compilation,
34102 @value{GDBN} has an interface that allows the program to register in-memory
34103 symbol files with @value{GDBN} at runtime.
34105 If you are using @value{GDBN} to debug a program that uses this interface, then
34106 it should work transparently so long as you have not stripped the binary. If
34107 you are developing a JIT compiler, then the interface is documented in the rest
34108 of this chapter. At this time, the only known client of this interface is the
34111 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34112 JIT compiler communicates with @value{GDBN} by writing data into a global
34113 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34114 attaches, it reads a linked list of symbol files from the global variable to
34115 find existing code, and puts a breakpoint in the function so that it can find
34116 out about additional code.
34119 * Declarations:: Relevant C struct declarations
34120 * Registering Code:: Steps to register code
34121 * Unregistering Code:: Steps to unregister code
34122 * Custom Debug Info:: Emit debug information in a custom format
34126 @section JIT Declarations
34128 These are the relevant struct declarations that a C program should include to
34129 implement the interface:
34139 struct jit_code_entry
34141 struct jit_code_entry *next_entry;
34142 struct jit_code_entry *prev_entry;
34143 const char *symfile_addr;
34144 uint64_t symfile_size;
34147 struct jit_descriptor
34150 /* This type should be jit_actions_t, but we use uint32_t
34151 to be explicit about the bitwidth. */
34152 uint32_t action_flag;
34153 struct jit_code_entry *relevant_entry;
34154 struct jit_code_entry *first_entry;
34157 /* GDB puts a breakpoint in this function. */
34158 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34160 /* Make sure to specify the version statically, because the
34161 debugger may check the version before we can set it. */
34162 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34165 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34166 modifications to this global data properly, which can easily be done by putting
34167 a global mutex around modifications to these structures.
34169 @node Registering Code
34170 @section Registering Code
34172 To register code with @value{GDBN}, the JIT should follow this protocol:
34176 Generate an object file in memory with symbols and other desired debug
34177 information. The file must include the virtual addresses of the sections.
34180 Create a code entry for the file, which gives the start and size of the symbol
34184 Add it to the linked list in the JIT descriptor.
34187 Point the relevant_entry field of the descriptor at the entry.
34190 Set @code{action_flag} to @code{JIT_REGISTER} and call
34191 @code{__jit_debug_register_code}.
34194 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34195 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34196 new code. However, the linked list must still be maintained in order to allow
34197 @value{GDBN} to attach to a running process and still find the symbol files.
34199 @node Unregistering Code
34200 @section Unregistering Code
34202 If code is freed, then the JIT should use the following protocol:
34206 Remove the code entry corresponding to the code from the linked list.
34209 Point the @code{relevant_entry} field of the descriptor at the code entry.
34212 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34213 @code{__jit_debug_register_code}.
34216 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34217 and the JIT will leak the memory used for the associated symbol files.
34219 @node Custom Debug Info
34220 @section Custom Debug Info
34221 @cindex custom JIT debug info
34222 @cindex JIT debug info reader
34224 Generating debug information in platform-native file formats (like ELF
34225 or COFF) may be an overkill for JIT compilers; especially if all the
34226 debug info is used for is displaying a meaningful backtrace. The
34227 issue can be resolved by having the JIT writers decide on a debug info
34228 format and also provide a reader that parses the debug info generated
34229 by the JIT compiler. This section gives a brief overview on writing
34230 such a parser. More specific details can be found in the source file
34231 @file{gdb/jit-reader.in}, which is also installed as a header at
34232 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34234 The reader is implemented as a shared object (so this functionality is
34235 not available on platforms which don't allow loading shared objects at
34236 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34237 @code{jit-reader-unload} are provided, to be used to load and unload
34238 the readers from a preconfigured directory. Once loaded, the shared
34239 object is used the parse the debug information emitted by the JIT
34243 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34244 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34247 @node Using JIT Debug Info Readers
34248 @subsection Using JIT Debug Info Readers
34249 @kindex jit-reader-load
34250 @kindex jit-reader-unload
34252 Readers can be loaded and unloaded using the @code{jit-reader-load}
34253 and @code{jit-reader-unload} commands.
34256 @item jit-reader-load @var{reader}
34257 Load the JIT reader named @var{reader}. @var{reader} is a shared
34258 object specified as either an absolute or a relative file name. In
34259 the latter case, @value{GDBN} will try to load the reader from a
34260 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34261 system (here @var{libdir} is the system library directory, often
34262 @file{/usr/local/lib}).
34264 Only one reader can be active at a time; trying to load a second
34265 reader when one is already loaded will result in @value{GDBN}
34266 reporting an error. A new JIT reader can be loaded by first unloading
34267 the current one using @code{jit-reader-unload} and then invoking
34268 @code{jit-reader-load}.
34270 @item jit-reader-unload
34271 Unload the currently loaded JIT reader.
34275 @node Writing JIT Debug Info Readers
34276 @subsection Writing JIT Debug Info Readers
34277 @cindex writing JIT debug info readers
34279 As mentioned, a reader is essentially a shared object conforming to a
34280 certain ABI. This ABI is described in @file{jit-reader.h}.
34282 @file{jit-reader.h} defines the structures, macros and functions
34283 required to write a reader. It is installed (along with
34284 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34285 the system include directory.
34287 Readers need to be released under a GPL compatible license. A reader
34288 can be declared as released under such a license by placing the macro
34289 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34291 The entry point for readers is the symbol @code{gdb_init_reader},
34292 which is expected to be a function with the prototype
34294 @findex gdb_init_reader
34296 extern struct gdb_reader_funcs *gdb_init_reader (void);
34299 @cindex @code{struct gdb_reader_funcs}
34301 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34302 functions. These functions are executed to read the debug info
34303 generated by the JIT compiler (@code{read}), to unwind stack frames
34304 (@code{unwind}) and to create canonical frame IDs
34305 (@code{get_Frame_id}). It also has a callback that is called when the
34306 reader is being unloaded (@code{destroy}). The struct looks like this
34309 struct gdb_reader_funcs
34311 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34312 int reader_version;
34314 /* For use by the reader. */
34317 gdb_read_debug_info *read;
34318 gdb_unwind_frame *unwind;
34319 gdb_get_frame_id *get_frame_id;
34320 gdb_destroy_reader *destroy;
34324 @cindex @code{struct gdb_symbol_callbacks}
34325 @cindex @code{struct gdb_unwind_callbacks}
34327 The callbacks are provided with another set of callbacks by
34328 @value{GDBN} to do their job. For @code{read}, these callbacks are
34329 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34330 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34331 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34332 files and new symbol tables inside those object files. @code{struct
34333 gdb_unwind_callbacks} has callbacks to read registers off the current
34334 frame and to write out the values of the registers in the previous
34335 frame. Both have a callback (@code{target_read}) to read bytes off the
34336 target's address space.
34338 @node In-Process Agent
34339 @chapter In-Process Agent
34340 @cindex debugging agent
34341 The traditional debugging model is conceptually low-speed, but works fine,
34342 because most bugs can be reproduced in debugging-mode execution. However,
34343 as multi-core or many-core processors are becoming mainstream, and
34344 multi-threaded programs become more and more popular, there should be more
34345 and more bugs that only manifest themselves at normal-mode execution, for
34346 example, thread races, because debugger's interference with the program's
34347 timing may conceal the bugs. On the other hand, in some applications,
34348 it is not feasible for the debugger to interrupt the program's execution
34349 long enough for the developer to learn anything helpful about its behavior.
34350 If the program's correctness depends on its real-time behavior, delays
34351 introduced by a debugger might cause the program to fail, even when the
34352 code itself is correct. It is useful to be able to observe the program's
34353 behavior without interrupting it.
34355 Therefore, traditional debugging model is too intrusive to reproduce
34356 some bugs. In order to reduce the interference with the program, we can
34357 reduce the number of operations performed by debugger. The
34358 @dfn{In-Process Agent}, a shared library, is running within the same
34359 process with inferior, and is able to perform some debugging operations
34360 itself. As a result, debugger is only involved when necessary, and
34361 performance of debugging can be improved accordingly. Note that
34362 interference with program can be reduced but can't be removed completely,
34363 because the in-process agent will still stop or slow down the program.
34365 The in-process agent can interpret and execute Agent Expressions
34366 (@pxref{Agent Expressions}) during performing debugging operations. The
34367 agent expressions can be used for different purposes, such as collecting
34368 data in tracepoints, and condition evaluation in breakpoints.
34370 @anchor{Control Agent}
34371 You can control whether the in-process agent is used as an aid for
34372 debugging with the following commands:
34375 @kindex set agent on
34377 Causes the in-process agent to perform some operations on behalf of the
34378 debugger. Just which operations requested by the user will be done
34379 by the in-process agent depends on the its capabilities. For example,
34380 if you request to evaluate breakpoint conditions in the in-process agent,
34381 and the in-process agent has such capability as well, then breakpoint
34382 conditions will be evaluated in the in-process agent.
34384 @kindex set agent off
34385 @item set agent off
34386 Disables execution of debugging operations by the in-process agent. All
34387 of the operations will be performed by @value{GDBN}.
34391 Display the current setting of execution of debugging operations by
34392 the in-process agent.
34396 * In-Process Agent Protocol::
34399 @node In-Process Agent Protocol
34400 @section In-Process Agent Protocol
34401 @cindex in-process agent protocol
34403 The in-process agent is able to communicate with both @value{GDBN} and
34404 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34405 used for communications between @value{GDBN} or GDBserver and the IPA.
34406 In general, @value{GDBN} or GDBserver sends commands
34407 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34408 in-process agent replies back with the return result of the command, or
34409 some other information. The data sent to in-process agent is composed
34410 of primitive data types, such as 4-byte or 8-byte type, and composite
34411 types, which are called objects (@pxref{IPA Protocol Objects}).
34414 * IPA Protocol Objects::
34415 * IPA Protocol Commands::
34418 @node IPA Protocol Objects
34419 @subsection IPA Protocol Objects
34420 @cindex ipa protocol objects
34422 The commands sent to and results received from agent may contain some
34423 complex data types called @dfn{objects}.
34425 The in-process agent is running on the same machine with @value{GDBN}
34426 or GDBserver, so it doesn't have to handle as much differences between
34427 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34428 However, there are still some differences of two ends in two processes:
34432 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34433 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34435 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34436 GDBserver is compiled with one, and in-process agent is compiled with
34440 Here are the IPA Protocol Objects:
34444 agent expression object. It represents an agent expression
34445 (@pxref{Agent Expressions}).
34446 @anchor{agent expression object}
34448 tracepoint action object. It represents a tracepoint action
34449 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34450 memory, static trace data and to evaluate expression.
34451 @anchor{tracepoint action object}
34453 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34454 @anchor{tracepoint object}
34458 The following table describes important attributes of each IPA protocol
34461 @multitable @columnfractions .30 .20 .50
34462 @headitem Name @tab Size @tab Description
34463 @item @emph{agent expression object} @tab @tab
34464 @item length @tab 4 @tab length of bytes code
34465 @item byte code @tab @var{length} @tab contents of byte code
34466 @item @emph{tracepoint action for collecting memory} @tab @tab
34467 @item 'M' @tab 1 @tab type of tracepoint action
34468 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34469 address of the lowest byte to collect, otherwise @var{addr} is the offset
34470 of @var{basereg} for memory collecting.
34471 @item len @tab 8 @tab length of memory for collecting
34472 @item basereg @tab 4 @tab the register number containing the starting
34473 memory address for collecting.
34474 @item @emph{tracepoint action for collecting registers} @tab @tab
34475 @item 'R' @tab 1 @tab type of tracepoint action
34476 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34477 @item 'L' @tab 1 @tab type of tracepoint action
34478 @item @emph{tracepoint action for expression evaluation} @tab @tab
34479 @item 'X' @tab 1 @tab type of tracepoint action
34480 @item agent expression @tab length of @tab @ref{agent expression object}
34481 @item @emph{tracepoint object} @tab @tab
34482 @item number @tab 4 @tab number of tracepoint
34483 @item address @tab 8 @tab address of tracepoint inserted on
34484 @item type @tab 4 @tab type of tracepoint
34485 @item enabled @tab 1 @tab enable or disable of tracepoint
34486 @item step_count @tab 8 @tab step
34487 @item pass_count @tab 8 @tab pass
34488 @item numactions @tab 4 @tab number of tracepoint actions
34489 @item hit count @tab 8 @tab hit count
34490 @item trace frame usage @tab 8 @tab trace frame usage
34491 @item compiled_cond @tab 8 @tab compiled condition
34492 @item orig_size @tab 8 @tab orig size
34493 @item condition @tab 4 if condition is NULL otherwise length of
34494 @ref{agent expression object}
34495 @tab zero if condition is NULL, otherwise is
34496 @ref{agent expression object}
34497 @item actions @tab variable
34498 @tab numactions number of @ref{tracepoint action object}
34501 @node IPA Protocol Commands
34502 @subsection IPA Protocol Commands
34503 @cindex ipa protocol commands
34505 The spaces in each command are delimiters to ease reading this commands
34506 specification. They don't exist in real commands.
34510 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34511 Installs a new fast tracepoint described by @var{tracepoint_object}
34512 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34513 head of @dfn{jumppad}, which is used to jump to data collection routine
34518 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34519 @var{target_address} is address of tracepoint in the inferior.
34520 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34521 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34522 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34523 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34530 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34531 is about to kill inferiors.
34539 @item probe_marker_at:@var{address}
34540 Asks in-process agent to probe the marker at @var{address}.
34547 @item unprobe_marker_at:@var{address}
34548 Asks in-process agent to unprobe the marker at @var{address}.
34552 @chapter Reporting Bugs in @value{GDBN}
34553 @cindex bugs in @value{GDBN}
34554 @cindex reporting bugs in @value{GDBN}
34556 Your bug reports play an essential role in making @value{GDBN} reliable.
34558 Reporting a bug may help you by bringing a solution to your problem, or it
34559 may not. But in any case the principal function of a bug report is to help
34560 the entire community by making the next version of @value{GDBN} work better. Bug
34561 reports are your contribution to the maintenance of @value{GDBN}.
34563 In order for a bug report to serve its purpose, you must include the
34564 information that enables us to fix the bug.
34567 * Bug Criteria:: Have you found a bug?
34568 * Bug Reporting:: How to report bugs
34572 @section Have You Found a Bug?
34573 @cindex bug criteria
34575 If you are not sure whether you have found a bug, here are some guidelines:
34578 @cindex fatal signal
34579 @cindex debugger crash
34580 @cindex crash of debugger
34582 If the debugger gets a fatal signal, for any input whatever, that is a
34583 @value{GDBN} bug. Reliable debuggers never crash.
34585 @cindex error on valid input
34587 If @value{GDBN} produces an error message for valid input, that is a
34588 bug. (Note that if you're cross debugging, the problem may also be
34589 somewhere in the connection to the target.)
34591 @cindex invalid input
34593 If @value{GDBN} does not produce an error message for invalid input,
34594 that is a bug. However, you should note that your idea of
34595 ``invalid input'' might be our idea of ``an extension'' or ``support
34596 for traditional practice''.
34599 If you are an experienced user of debugging tools, your suggestions
34600 for improvement of @value{GDBN} are welcome in any case.
34603 @node Bug Reporting
34604 @section How to Report Bugs
34605 @cindex bug reports
34606 @cindex @value{GDBN} bugs, reporting
34608 A number of companies and individuals offer support for @sc{gnu} products.
34609 If you obtained @value{GDBN} from a support organization, we recommend you
34610 contact that organization first.
34612 You can find contact information for many support companies and
34613 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34615 @c should add a web page ref...
34618 @ifset BUGURL_DEFAULT
34619 In any event, we also recommend that you submit bug reports for
34620 @value{GDBN}. The preferred method is to submit them directly using
34621 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34622 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34625 @strong{Do not send bug reports to @samp{info-gdb}, or to
34626 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34627 not want to receive bug reports. Those that do have arranged to receive
34630 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34631 serves as a repeater. The mailing list and the newsgroup carry exactly
34632 the same messages. Often people think of posting bug reports to the
34633 newsgroup instead of mailing them. This appears to work, but it has one
34634 problem which can be crucial: a newsgroup posting often lacks a mail
34635 path back to the sender. Thus, if we need to ask for more information,
34636 we may be unable to reach you. For this reason, it is better to send
34637 bug reports to the mailing list.
34639 @ifclear BUGURL_DEFAULT
34640 In any event, we also recommend that you submit bug reports for
34641 @value{GDBN} to @value{BUGURL}.
34645 The fundamental principle of reporting bugs usefully is this:
34646 @strong{report all the facts}. If you are not sure whether to state a
34647 fact or leave it out, state it!
34649 Often people omit facts because they think they know what causes the
34650 problem and assume that some details do not matter. Thus, you might
34651 assume that the name of the variable you use in an example does not matter.
34652 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34653 stray memory reference which happens to fetch from the location where that
34654 name is stored in memory; perhaps, if the name were different, the contents
34655 of that location would fool the debugger into doing the right thing despite
34656 the bug. Play it safe and give a specific, complete example. That is the
34657 easiest thing for you to do, and the most helpful.
34659 Keep in mind that the purpose of a bug report is to enable us to fix the
34660 bug. It may be that the bug has been reported previously, but neither
34661 you nor we can know that unless your bug report is complete and
34664 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34665 bell?'' Those bug reports are useless, and we urge everyone to
34666 @emph{refuse to respond to them} except to chide the sender to report
34669 To enable us to fix the bug, you should include all these things:
34673 The version of @value{GDBN}. @value{GDBN} announces it if you start
34674 with no arguments; you can also print it at any time using @code{show
34677 Without this, we will not know whether there is any point in looking for
34678 the bug in the current version of @value{GDBN}.
34681 The type of machine you are using, and the operating system name and
34685 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34686 ``@value{GCC}--2.8.1''.
34689 What compiler (and its version) was used to compile the program you are
34690 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34691 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34692 to get this information; for other compilers, see the documentation for
34696 The command arguments you gave the compiler to compile your example and
34697 observe the bug. For example, did you use @samp{-O}? To guarantee
34698 you will not omit something important, list them all. A copy of the
34699 Makefile (or the output from make) is sufficient.
34701 If we were to try to guess the arguments, we would probably guess wrong
34702 and then we might not encounter the bug.
34705 A complete input script, and all necessary source files, that will
34709 A description of what behavior you observe that you believe is
34710 incorrect. For example, ``It gets a fatal signal.''
34712 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34713 will certainly notice it. But if the bug is incorrect output, we might
34714 not notice unless it is glaringly wrong. You might as well not give us
34715 a chance to make a mistake.
34717 Even if the problem you experience is a fatal signal, you should still
34718 say so explicitly. Suppose something strange is going on, such as, your
34719 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34720 the C library on your system. (This has happened!) Your copy might
34721 crash and ours would not. If you told us to expect a crash, then when
34722 ours fails to crash, we would know that the bug was not happening for
34723 us. If you had not told us to expect a crash, then we would not be able
34724 to draw any conclusion from our observations.
34727 @cindex recording a session script
34728 To collect all this information, you can use a session recording program
34729 such as @command{script}, which is available on many Unix systems.
34730 Just run your @value{GDBN} session inside @command{script} and then
34731 include the @file{typescript} file with your bug report.
34733 Another way to record a @value{GDBN} session is to run @value{GDBN}
34734 inside Emacs and then save the entire buffer to a file.
34737 If you wish to suggest changes to the @value{GDBN} source, send us context
34738 diffs. If you even discuss something in the @value{GDBN} source, refer to
34739 it by context, not by line number.
34741 The line numbers in our development sources will not match those in your
34742 sources. Your line numbers would convey no useful information to us.
34746 Here are some things that are not necessary:
34750 A description of the envelope of the bug.
34752 Often people who encounter a bug spend a lot of time investigating
34753 which changes to the input file will make the bug go away and which
34754 changes will not affect it.
34756 This is often time consuming and not very useful, because the way we
34757 will find the bug is by running a single example under the debugger
34758 with breakpoints, not by pure deduction from a series of examples.
34759 We recommend that you save your time for something else.
34761 Of course, if you can find a simpler example to report @emph{instead}
34762 of the original one, that is a convenience for us. Errors in the
34763 output will be easier to spot, running under the debugger will take
34764 less time, and so on.
34766 However, simplification is not vital; if you do not want to do this,
34767 report the bug anyway and send us the entire test case you used.
34770 A patch for the bug.
34772 A patch for the bug does help us if it is a good one. But do not omit
34773 the necessary information, such as the test case, on the assumption that
34774 a patch is all we need. We might see problems with your patch and decide
34775 to fix the problem another way, or we might not understand it at all.
34777 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34778 construct an example that will make the program follow a certain path
34779 through the code. If you do not send us the example, we will not be able
34780 to construct one, so we will not be able to verify that the bug is fixed.
34782 And if we cannot understand what bug you are trying to fix, or why your
34783 patch should be an improvement, we will not install it. A test case will
34784 help us to understand.
34787 A guess about what the bug is or what it depends on.
34789 Such guesses are usually wrong. Even we cannot guess right about such
34790 things without first using the debugger to find the facts.
34793 @c The readline documentation is distributed with the readline code
34794 @c and consists of the two following files:
34797 @c Use -I with makeinfo to point to the appropriate directory,
34798 @c environment var TEXINPUTS with TeX.
34799 @ifclear SYSTEM_READLINE
34800 @include rluser.texi
34801 @include hsuser.texi
34805 @appendix In Memoriam
34807 The @value{GDBN} project mourns the loss of the following long-time
34812 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34813 to Free Software in general. Outside of @value{GDBN}, he was known in
34814 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34816 @item Michael Snyder
34817 Michael was one of the Global Maintainers of the @value{GDBN} project,
34818 with contributions recorded as early as 1996, until 2011. In addition
34819 to his day to day participation, he was a large driving force behind
34820 adding Reverse Debugging to @value{GDBN}.
34823 Beyond their technical contributions to the project, they were also
34824 enjoyable members of the Free Software Community. We will miss them.
34826 @node Formatting Documentation
34827 @appendix Formatting Documentation
34829 @cindex @value{GDBN} reference card
34830 @cindex reference card
34831 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34832 for printing with PostScript or Ghostscript, in the @file{gdb}
34833 subdirectory of the main source directory@footnote{In
34834 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34835 release.}. If you can use PostScript or Ghostscript with your printer,
34836 you can print the reference card immediately with @file{refcard.ps}.
34838 The release also includes the source for the reference card. You
34839 can format it, using @TeX{}, by typing:
34845 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34846 mode on US ``letter'' size paper;
34847 that is, on a sheet 11 inches wide by 8.5 inches
34848 high. You will need to specify this form of printing as an option to
34849 your @sc{dvi} output program.
34851 @cindex documentation
34853 All the documentation for @value{GDBN} comes as part of the machine-readable
34854 distribution. The documentation is written in Texinfo format, which is
34855 a documentation system that uses a single source file to produce both
34856 on-line information and a printed manual. You can use one of the Info
34857 formatting commands to create the on-line version of the documentation
34858 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34860 @value{GDBN} includes an already formatted copy of the on-line Info
34861 version of this manual in the @file{gdb} subdirectory. The main Info
34862 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34863 subordinate files matching @samp{gdb.info*} in the same directory. If
34864 necessary, you can print out these files, or read them with any editor;
34865 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34866 Emacs or the standalone @code{info} program, available as part of the
34867 @sc{gnu} Texinfo distribution.
34869 If you want to format these Info files yourself, you need one of the
34870 Info formatting programs, such as @code{texinfo-format-buffer} or
34873 If you have @code{makeinfo} installed, and are in the top level
34874 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34875 version @value{GDBVN}), you can make the Info file by typing:
34882 If you want to typeset and print copies of this manual, you need @TeX{},
34883 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34884 Texinfo definitions file.
34886 @TeX{} is a typesetting program; it does not print files directly, but
34887 produces output files called @sc{dvi} files. To print a typeset
34888 document, you need a program to print @sc{dvi} files. If your system
34889 has @TeX{} installed, chances are it has such a program. The precise
34890 command to use depends on your system; @kbd{lpr -d} is common; another
34891 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34892 require a file name without any extension or a @samp{.dvi} extension.
34894 @TeX{} also requires a macro definitions file called
34895 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34896 written in Texinfo format. On its own, @TeX{} cannot either read or
34897 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34898 and is located in the @file{gdb-@var{version-number}/texinfo}
34901 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34902 typeset and print this manual. First switch to the @file{gdb}
34903 subdirectory of the main source directory (for example, to
34904 @file{gdb-@value{GDBVN}/gdb}) and type:
34910 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34912 @node Installing GDB
34913 @appendix Installing @value{GDBN}
34914 @cindex installation
34917 * Requirements:: Requirements for building @value{GDBN}
34918 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34919 * Separate Objdir:: Compiling @value{GDBN} in another directory
34920 * Config Names:: Specifying names for hosts and targets
34921 * Configure Options:: Summary of options for configure
34922 * System-wide configuration:: Having a system-wide init file
34926 @section Requirements for Building @value{GDBN}
34927 @cindex building @value{GDBN}, requirements for
34929 Building @value{GDBN} requires various tools and packages to be available.
34930 Other packages will be used only if they are found.
34932 @heading Tools/Packages Necessary for Building @value{GDBN}
34934 @item ISO C90 compiler
34935 @value{GDBN} is written in ISO C90. It should be buildable with any
34936 working C90 compiler, e.g.@: GCC.
34940 @heading Tools/Packages Optional for Building @value{GDBN}
34944 @value{GDBN} can use the Expat XML parsing library. This library may be
34945 included with your operating system distribution; if it is not, you
34946 can get the latest version from @url{http://expat.sourceforge.net}.
34947 The @file{configure} script will search for this library in several
34948 standard locations; if it is installed in an unusual path, you can
34949 use the @option{--with-libexpat-prefix} option to specify its location.
34955 Remote protocol memory maps (@pxref{Memory Map Format})
34957 Target descriptions (@pxref{Target Descriptions})
34959 Remote shared library lists (@xref{Library List Format},
34960 or alternatively @pxref{Library List Format for SVR4 Targets})
34962 MS-Windows shared libraries (@pxref{Shared Libraries})
34964 Traceframe info (@pxref{Traceframe Info Format})
34966 Branch trace (@pxref{Branch Trace Format})
34970 @cindex compressed debug sections
34971 @value{GDBN} will use the @samp{zlib} library, if available, to read
34972 compressed debug sections. Some linkers, such as GNU gold, are capable
34973 of producing binaries with compressed debug sections. If @value{GDBN}
34974 is compiled with @samp{zlib}, it will be able to read the debug
34975 information in such binaries.
34977 The @samp{zlib} library is likely included with your operating system
34978 distribution; if it is not, you can get the latest version from
34979 @url{http://zlib.net}.
34982 @value{GDBN}'s features related to character sets (@pxref{Character
34983 Sets}) require a functioning @code{iconv} implementation. If you are
34984 on a GNU system, then this is provided by the GNU C Library. Some
34985 other systems also provide a working @code{iconv}.
34987 If @value{GDBN} is using the @code{iconv} program which is installed
34988 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34989 This is done with @option{--with-iconv-bin} which specifies the
34990 directory that contains the @code{iconv} program.
34992 On systems without @code{iconv}, you can install GNU Libiconv. If you
34993 have previously installed Libiconv, you can use the
34994 @option{--with-libiconv-prefix} option to configure.
34996 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34997 arrange to build Libiconv if a directory named @file{libiconv} appears
34998 in the top-most source directory. If Libiconv is built this way, and
34999 if the operating system does not provide a suitable @code{iconv}
35000 implementation, then the just-built library will automatically be used
35001 by @value{GDBN}. One easy way to set this up is to download GNU
35002 Libiconv, unpack it, and then rename the directory holding the
35003 Libiconv source code to @samp{libiconv}.
35006 @node Running Configure
35007 @section Invoking the @value{GDBN} @file{configure} Script
35008 @cindex configuring @value{GDBN}
35009 @value{GDBN} comes with a @file{configure} script that automates the process
35010 of preparing @value{GDBN} for installation; you can then use @code{make} to
35011 build the @code{gdb} program.
35013 @c irrelevant in info file; it's as current as the code it lives with.
35014 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35015 look at the @file{README} file in the sources; we may have improved the
35016 installation procedures since publishing this manual.}
35019 The @value{GDBN} distribution includes all the source code you need for
35020 @value{GDBN} in a single directory, whose name is usually composed by
35021 appending the version number to @samp{gdb}.
35023 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35024 @file{gdb-@value{GDBVN}} directory. That directory contains:
35027 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35028 script for configuring @value{GDBN} and all its supporting libraries
35030 @item gdb-@value{GDBVN}/gdb
35031 the source specific to @value{GDBN} itself
35033 @item gdb-@value{GDBVN}/bfd
35034 source for the Binary File Descriptor library
35036 @item gdb-@value{GDBVN}/include
35037 @sc{gnu} include files
35039 @item gdb-@value{GDBVN}/libiberty
35040 source for the @samp{-liberty} free software library
35042 @item gdb-@value{GDBVN}/opcodes
35043 source for the library of opcode tables and disassemblers
35045 @item gdb-@value{GDBVN}/readline
35046 source for the @sc{gnu} command-line interface
35048 @item gdb-@value{GDBVN}/glob
35049 source for the @sc{gnu} filename pattern-matching subroutine
35051 @item gdb-@value{GDBVN}/mmalloc
35052 source for the @sc{gnu} memory-mapped malloc package
35055 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35056 from the @file{gdb-@var{version-number}} source directory, which in
35057 this example is the @file{gdb-@value{GDBVN}} directory.
35059 First switch to the @file{gdb-@var{version-number}} source directory
35060 if you are not already in it; then run @file{configure}. Pass the
35061 identifier for the platform on which @value{GDBN} will run as an
35067 cd gdb-@value{GDBVN}
35068 ./configure @var{host}
35073 where @var{host} is an identifier such as @samp{sun4} or
35074 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35075 (You can often leave off @var{host}; @file{configure} tries to guess the
35076 correct value by examining your system.)
35078 Running @samp{configure @var{host}} and then running @code{make} builds the
35079 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35080 libraries, then @code{gdb} itself. The configured source files, and the
35081 binaries, are left in the corresponding source directories.
35084 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35085 system does not recognize this automatically when you run a different
35086 shell, you may need to run @code{sh} on it explicitly:
35089 sh configure @var{host}
35092 If you run @file{configure} from a directory that contains source
35093 directories for multiple libraries or programs, such as the
35094 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35096 creates configuration files for every directory level underneath (unless
35097 you tell it not to, with the @samp{--norecursion} option).
35099 You should run the @file{configure} script from the top directory in the
35100 source tree, the @file{gdb-@var{version-number}} directory. If you run
35101 @file{configure} from one of the subdirectories, you will configure only
35102 that subdirectory. That is usually not what you want. In particular,
35103 if you run the first @file{configure} from the @file{gdb} subdirectory
35104 of the @file{gdb-@var{version-number}} directory, you will omit the
35105 configuration of @file{bfd}, @file{readline}, and other sibling
35106 directories of the @file{gdb} subdirectory. This leads to build errors
35107 about missing include files such as @file{bfd/bfd.h}.
35109 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35110 However, you should make sure that the shell on your path (named by
35111 the @samp{SHELL} environment variable) is publicly readable. Remember
35112 that @value{GDBN} uses the shell to start your program---some systems refuse to
35113 let @value{GDBN} debug child processes whose programs are not readable.
35115 @node Separate Objdir
35116 @section Compiling @value{GDBN} in Another Directory
35118 If you want to run @value{GDBN} versions for several host or target machines,
35119 you need a different @code{gdb} compiled for each combination of
35120 host and target. @file{configure} is designed to make this easy by
35121 allowing you to generate each configuration in a separate subdirectory,
35122 rather than in the source directory. If your @code{make} program
35123 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35124 @code{make} in each of these directories builds the @code{gdb}
35125 program specified there.
35127 To build @code{gdb} in a separate directory, run @file{configure}
35128 with the @samp{--srcdir} option to specify where to find the source.
35129 (You also need to specify a path to find @file{configure}
35130 itself from your working directory. If the path to @file{configure}
35131 would be the same as the argument to @samp{--srcdir}, you can leave out
35132 the @samp{--srcdir} option; it is assumed.)
35134 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35135 separate directory for a Sun 4 like this:
35139 cd gdb-@value{GDBVN}
35142 ../gdb-@value{GDBVN}/configure sun4
35147 When @file{configure} builds a configuration using a remote source
35148 directory, it creates a tree for the binaries with the same structure
35149 (and using the same names) as the tree under the source directory. In
35150 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35151 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35152 @file{gdb-sun4/gdb}.
35154 Make sure that your path to the @file{configure} script has just one
35155 instance of @file{gdb} in it. If your path to @file{configure} looks
35156 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35157 one subdirectory of @value{GDBN}, not the whole package. This leads to
35158 build errors about missing include files such as @file{bfd/bfd.h}.
35160 One popular reason to build several @value{GDBN} configurations in separate
35161 directories is to configure @value{GDBN} for cross-compiling (where
35162 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35163 programs that run on another machine---the @dfn{target}).
35164 You specify a cross-debugging target by
35165 giving the @samp{--target=@var{target}} option to @file{configure}.
35167 When you run @code{make} to build a program or library, you must run
35168 it in a configured directory---whatever directory you were in when you
35169 called @file{configure} (or one of its subdirectories).
35171 The @code{Makefile} that @file{configure} generates in each source
35172 directory also runs recursively. If you type @code{make} in a source
35173 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35174 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35175 will build all the required libraries, and then build GDB.
35177 When you have multiple hosts or targets configured in separate
35178 directories, you can run @code{make} on them in parallel (for example,
35179 if they are NFS-mounted on each of the hosts); they will not interfere
35183 @section Specifying Names for Hosts and Targets
35185 The specifications used for hosts and targets in the @file{configure}
35186 script are based on a three-part naming scheme, but some short predefined
35187 aliases are also supported. The full naming scheme encodes three pieces
35188 of information in the following pattern:
35191 @var{architecture}-@var{vendor}-@var{os}
35194 For example, you can use the alias @code{sun4} as a @var{host} argument,
35195 or as the value for @var{target} in a @code{--target=@var{target}}
35196 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35198 The @file{configure} script accompanying @value{GDBN} does not provide
35199 any query facility to list all supported host and target names or
35200 aliases. @file{configure} calls the Bourne shell script
35201 @code{config.sub} to map abbreviations to full names; you can read the
35202 script, if you wish, or you can use it to test your guesses on
35203 abbreviations---for example:
35206 % sh config.sub i386-linux
35208 % sh config.sub alpha-linux
35209 alpha-unknown-linux-gnu
35210 % sh config.sub hp9k700
35212 % sh config.sub sun4
35213 sparc-sun-sunos4.1.1
35214 % sh config.sub sun3
35215 m68k-sun-sunos4.1.1
35216 % sh config.sub i986v
35217 Invalid configuration `i986v': machine `i986v' not recognized
35221 @code{config.sub} is also distributed in the @value{GDBN} source
35222 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35224 @node Configure Options
35225 @section @file{configure} Options
35227 Here is a summary of the @file{configure} options and arguments that
35228 are most often useful for building @value{GDBN}. @file{configure} also has
35229 several other options not listed here. @inforef{What Configure
35230 Does,,configure.info}, for a full explanation of @file{configure}.
35233 configure @r{[}--help@r{]}
35234 @r{[}--prefix=@var{dir}@r{]}
35235 @r{[}--exec-prefix=@var{dir}@r{]}
35236 @r{[}--srcdir=@var{dirname}@r{]}
35237 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35238 @r{[}--target=@var{target}@r{]}
35243 You may introduce options with a single @samp{-} rather than
35244 @samp{--} if you prefer; but you may abbreviate option names if you use
35249 Display a quick summary of how to invoke @file{configure}.
35251 @item --prefix=@var{dir}
35252 Configure the source to install programs and files under directory
35255 @item --exec-prefix=@var{dir}
35256 Configure the source to install programs under directory
35259 @c avoid splitting the warning from the explanation:
35261 @item --srcdir=@var{dirname}
35262 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35263 @code{make} that implements the @code{VPATH} feature.}@*
35264 Use this option to make configurations in directories separate from the
35265 @value{GDBN} source directories. Among other things, you can use this to
35266 build (or maintain) several configurations simultaneously, in separate
35267 directories. @file{configure} writes configuration-specific files in
35268 the current directory, but arranges for them to use the source in the
35269 directory @var{dirname}. @file{configure} creates directories under
35270 the working directory in parallel to the source directories below
35273 @item --norecursion
35274 Configure only the directory level where @file{configure} is executed; do not
35275 propagate configuration to subdirectories.
35277 @item --target=@var{target}
35278 Configure @value{GDBN} for cross-debugging programs running on the specified
35279 @var{target}. Without this option, @value{GDBN} is configured to debug
35280 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35282 There is no convenient way to generate a list of all available targets.
35284 @item @var{host} @dots{}
35285 Configure @value{GDBN} to run on the specified @var{host}.
35287 There is no convenient way to generate a list of all available hosts.
35290 There are many other options available as well, but they are generally
35291 needed for special purposes only.
35293 @node System-wide configuration
35294 @section System-wide configuration and settings
35295 @cindex system-wide init file
35297 @value{GDBN} can be configured to have a system-wide init file;
35298 this file will be read and executed at startup (@pxref{Startup, , What
35299 @value{GDBN} does during startup}).
35301 Here is the corresponding configure option:
35304 @item --with-system-gdbinit=@var{file}
35305 Specify that the default location of the system-wide init file is
35309 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35310 it may be subject to relocation. Two possible cases:
35314 If the default location of this init file contains @file{$prefix},
35315 it will be subject to relocation. Suppose that the configure options
35316 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35317 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35318 init file is looked for as @file{$install/etc/gdbinit} instead of
35319 @file{$prefix/etc/gdbinit}.
35322 By contrast, if the default location does not contain the prefix,
35323 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35324 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35325 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35326 wherever @value{GDBN} is installed.
35329 If the configured location of the system-wide init file (as given by the
35330 @option{--with-system-gdbinit} option at configure time) is in the
35331 data-directory (as specified by @option{--with-gdb-datadir} at configure
35332 time) or in one of its subdirectories, then @value{GDBN} will look for the
35333 system-wide init file in the directory specified by the
35334 @option{--data-directory} command-line option.
35335 Note that the system-wide init file is only read once, during @value{GDBN}
35336 initialization. If the data-directory is changed after @value{GDBN} has
35337 started with the @code{set data-directory} command, the file will not be
35340 @node Maintenance Commands
35341 @appendix Maintenance Commands
35342 @cindex maintenance commands
35343 @cindex internal commands
35345 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35346 includes a number of commands intended for @value{GDBN} developers,
35347 that are not documented elsewhere in this manual. These commands are
35348 provided here for reference. (For commands that turn on debugging
35349 messages, see @ref{Debugging Output}.)
35352 @kindex maint agent
35353 @kindex maint agent-eval
35354 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35355 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35356 Translate the given @var{expression} into remote agent bytecodes.
35357 This command is useful for debugging the Agent Expression mechanism
35358 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35359 expression useful for data collection, such as by tracepoints, while
35360 @samp{maint agent-eval} produces an expression that evaluates directly
35361 to a result. For instance, a collection expression for @code{globa +
35362 globb} will include bytecodes to record four bytes of memory at each
35363 of the addresses of @code{globa} and @code{globb}, while discarding
35364 the result of the addition, while an evaluation expression will do the
35365 addition and return the sum.
35366 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35367 If not, generate remote agent bytecode for current frame PC address.
35369 @kindex maint agent-printf
35370 @item maint agent-printf @var{format},@var{expr},...
35371 Translate the given format string and list of argument expressions
35372 into remote agent bytecodes and display them as a disassembled list.
35373 This command is useful for debugging the agent version of dynamic
35374 printf (@pxref{Dynamic Printf}.
35376 @kindex maint info breakpoints
35377 @item @anchor{maint info breakpoints}maint info breakpoints
35378 Using the same format as @samp{info breakpoints}, display both the
35379 breakpoints you've set explicitly, and those @value{GDBN} is using for
35380 internal purposes. Internal breakpoints are shown with negative
35381 breakpoint numbers. The type column identifies what kind of breakpoint
35386 Normal, explicitly set breakpoint.
35389 Normal, explicitly set watchpoint.
35392 Internal breakpoint, used to handle correctly stepping through
35393 @code{longjmp} calls.
35395 @item longjmp resume
35396 Internal breakpoint at the target of a @code{longjmp}.
35399 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35402 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35405 Shared library events.
35409 @kindex maint info bfds
35410 @item maint info bfds
35411 This prints information about each @code{bfd} object that is known to
35412 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35414 @kindex set displaced-stepping
35415 @kindex show displaced-stepping
35416 @cindex displaced stepping support
35417 @cindex out-of-line single-stepping
35418 @item set displaced-stepping
35419 @itemx show displaced-stepping
35420 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35421 if the target supports it. Displaced stepping is a way to single-step
35422 over breakpoints without removing them from the inferior, by executing
35423 an out-of-line copy of the instruction that was originally at the
35424 breakpoint location. It is also known as out-of-line single-stepping.
35427 @item set displaced-stepping on
35428 If the target architecture supports it, @value{GDBN} will use
35429 displaced stepping to step over breakpoints.
35431 @item set displaced-stepping off
35432 @value{GDBN} will not use displaced stepping to step over breakpoints,
35433 even if such is supported by the target architecture.
35435 @cindex non-stop mode, and @samp{set displaced-stepping}
35436 @item set displaced-stepping auto
35437 This is the default mode. @value{GDBN} will use displaced stepping
35438 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35439 architecture supports displaced stepping.
35442 @kindex maint check-symtabs
35443 @item maint check-symtabs
35444 Check the consistency of psymtabs and symtabs.
35446 @kindex maint cplus first_component
35447 @item maint cplus first_component @var{name}
35448 Print the first C@t{++} class/namespace component of @var{name}.
35450 @kindex maint cplus namespace
35451 @item maint cplus namespace
35452 Print the list of possible C@t{++} namespaces.
35454 @kindex maint demangle
35455 @item maint demangle @var{name}
35456 Demangle a C@t{++} or Objective-C mangled @var{name}.
35458 @kindex maint deprecate
35459 @kindex maint undeprecate
35460 @cindex deprecated commands
35461 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35462 @itemx maint undeprecate @var{command}
35463 Deprecate or undeprecate the named @var{command}. Deprecated commands
35464 cause @value{GDBN} to issue a warning when you use them. The optional
35465 argument @var{replacement} says which newer command should be used in
35466 favor of the deprecated one; if it is given, @value{GDBN} will mention
35467 the replacement as part of the warning.
35469 @kindex maint dump-me
35470 @item maint dump-me
35471 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35472 Cause a fatal signal in the debugger and force it to dump its core.
35473 This is supported only on systems which support aborting a program
35474 with the @code{SIGQUIT} signal.
35476 @kindex maint internal-error
35477 @kindex maint internal-warning
35478 @item maint internal-error @r{[}@var{message-text}@r{]}
35479 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35480 Cause @value{GDBN} to call the internal function @code{internal_error}
35481 or @code{internal_warning} and hence behave as though an internal error
35482 or internal warning has been detected. In addition to reporting the
35483 internal problem, these functions give the user the opportunity to
35484 either quit @value{GDBN} or create a core file of the current
35485 @value{GDBN} session.
35487 These commands take an optional parameter @var{message-text} that is
35488 used as the text of the error or warning message.
35490 Here's an example of using @code{internal-error}:
35493 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35494 @dots{}/maint.c:121: internal-error: testing, 1, 2
35495 A problem internal to GDB has been detected. Further
35496 debugging may prove unreliable.
35497 Quit this debugging session? (y or n) @kbd{n}
35498 Create a core file? (y or n) @kbd{n}
35502 @cindex @value{GDBN} internal error
35503 @cindex internal errors, control of @value{GDBN} behavior
35505 @kindex maint set internal-error
35506 @kindex maint show internal-error
35507 @kindex maint set internal-warning
35508 @kindex maint show internal-warning
35509 @item maint set internal-error @var{action} [ask|yes|no]
35510 @itemx maint show internal-error @var{action}
35511 @itemx maint set internal-warning @var{action} [ask|yes|no]
35512 @itemx maint show internal-warning @var{action}
35513 When @value{GDBN} reports an internal problem (error or warning) it
35514 gives the user the opportunity to both quit @value{GDBN} and create a
35515 core file of the current @value{GDBN} session. These commands let you
35516 override the default behaviour for each particular @var{action},
35517 described in the table below.
35521 You can specify that @value{GDBN} should always (yes) or never (no)
35522 quit. The default is to ask the user what to do.
35525 You can specify that @value{GDBN} should always (yes) or never (no)
35526 create a core file. The default is to ask the user what to do.
35529 @kindex maint packet
35530 @item maint packet @var{text}
35531 If @value{GDBN} is talking to an inferior via the serial protocol,
35532 then this command sends the string @var{text} to the inferior, and
35533 displays the response packet. @value{GDBN} supplies the initial
35534 @samp{$} character, the terminating @samp{#} character, and the
35537 @kindex maint print architecture
35538 @item maint print architecture @r{[}@var{file}@r{]}
35539 Print the entire architecture configuration. The optional argument
35540 @var{file} names the file where the output goes.
35542 @kindex maint print c-tdesc
35543 @item maint print c-tdesc
35544 Print the current target description (@pxref{Target Descriptions}) as
35545 a C source file. The created source file can be used in @value{GDBN}
35546 when an XML parser is not available to parse the description.
35548 @kindex maint print dummy-frames
35549 @item maint print dummy-frames
35550 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35553 (@value{GDBP}) @kbd{b add}
35555 (@value{GDBP}) @kbd{print add(2,3)}
35556 Breakpoint 2, add (a=2, b=3) at @dots{}
35558 The program being debugged stopped while in a function called from GDB.
35560 (@value{GDBP}) @kbd{maint print dummy-frames}
35561 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35562 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35563 call_lo=0x01014000 call_hi=0x01014001
35567 Takes an optional file parameter.
35569 @kindex maint print registers
35570 @kindex maint print raw-registers
35571 @kindex maint print cooked-registers
35572 @kindex maint print register-groups
35573 @kindex maint print remote-registers
35574 @item maint print registers @r{[}@var{file}@r{]}
35575 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35576 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35577 @itemx maint print register-groups @r{[}@var{file}@r{]}
35578 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35579 Print @value{GDBN}'s internal register data structures.
35581 The command @code{maint print raw-registers} includes the contents of
35582 the raw register cache; the command @code{maint print
35583 cooked-registers} includes the (cooked) value of all registers,
35584 including registers which aren't available on the target nor visible
35585 to user; the command @code{maint print register-groups} includes the
35586 groups that each register is a member of; and the command @code{maint
35587 print remote-registers} includes the remote target's register numbers
35588 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35589 @value{GDBN} Internals}.
35591 These commands take an optional parameter, a file name to which to
35592 write the information.
35594 @kindex maint print reggroups
35595 @item maint print reggroups @r{[}@var{file}@r{]}
35596 Print @value{GDBN}'s internal register group data structures. The
35597 optional argument @var{file} tells to what file to write the
35600 The register groups info looks like this:
35603 (@value{GDBP}) @kbd{maint print reggroups}
35616 This command forces @value{GDBN} to flush its internal register cache.
35618 @kindex maint print objfiles
35619 @cindex info for known object files
35620 @item maint print objfiles
35621 Print a dump of all known object files. For each object file, this
35622 command prints its name, address in memory, and all of its psymtabs
35625 @kindex maint print section-scripts
35626 @cindex info for known .debug_gdb_scripts-loaded scripts
35627 @item maint print section-scripts [@var{regexp}]
35628 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35629 If @var{regexp} is specified, only print scripts loaded by object files
35630 matching @var{regexp}.
35631 For each script, this command prints its name as specified in the objfile,
35632 and the full path if known.
35633 @xref{dotdebug_gdb_scripts section}.
35635 @kindex maint print statistics
35636 @cindex bcache statistics
35637 @item maint print statistics
35638 This command prints, for each object file in the program, various data
35639 about that object file followed by the byte cache (@dfn{bcache})
35640 statistics for the object file. The objfile data includes the number
35641 of minimal, partial, full, and stabs symbols, the number of types
35642 defined by the objfile, the number of as yet unexpanded psym tables,
35643 the number of line tables and string tables, and the amount of memory
35644 used by the various tables. The bcache statistics include the counts,
35645 sizes, and counts of duplicates of all and unique objects, max,
35646 average, and median entry size, total memory used and its overhead and
35647 savings, and various measures of the hash table size and chain
35650 @kindex maint print target-stack
35651 @cindex target stack description
35652 @item maint print target-stack
35653 A @dfn{target} is an interface between the debugger and a particular
35654 kind of file or process. Targets can be stacked in @dfn{strata},
35655 so that more than one target can potentially respond to a request.
35656 In particular, memory accesses will walk down the stack of targets
35657 until they find a target that is interested in handling that particular
35660 This command prints a short description of each layer that was pushed on
35661 the @dfn{target stack}, starting from the top layer down to the bottom one.
35663 @kindex maint print type
35664 @cindex type chain of a data type
35665 @item maint print type @var{expr}
35666 Print the type chain for a type specified by @var{expr}. The argument
35667 can be either a type name or a symbol. If it is a symbol, the type of
35668 that symbol is described. The type chain produced by this command is
35669 a recursive definition of the data type as stored in @value{GDBN}'s
35670 data structures, including its flags and contained types.
35672 @kindex maint set dwarf2 always-disassemble
35673 @kindex maint show dwarf2 always-disassemble
35674 @item maint set dwarf2 always-disassemble
35675 @item maint show dwarf2 always-disassemble
35676 Control the behavior of @code{info address} when using DWARF debugging
35679 The default is @code{off}, which means that @value{GDBN} should try to
35680 describe a variable's location in an easily readable format. When
35681 @code{on}, @value{GDBN} will instead display the DWARF location
35682 expression in an assembly-like format. Note that some locations are
35683 too complex for @value{GDBN} to describe simply; in this case you will
35684 always see the disassembly form.
35686 Here is an example of the resulting disassembly:
35689 (gdb) info addr argc
35690 Symbol "argc" is a complex DWARF expression:
35694 For more information on these expressions, see
35695 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35697 @kindex maint set dwarf2 max-cache-age
35698 @kindex maint show dwarf2 max-cache-age
35699 @item maint set dwarf2 max-cache-age
35700 @itemx maint show dwarf2 max-cache-age
35701 Control the DWARF 2 compilation unit cache.
35703 @cindex DWARF 2 compilation units cache
35704 In object files with inter-compilation-unit references, such as those
35705 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35706 reader needs to frequently refer to previously read compilation units.
35707 This setting controls how long a compilation unit will remain in the
35708 cache if it is not referenced. A higher limit means that cached
35709 compilation units will be stored in memory longer, and more total
35710 memory will be used. Setting it to zero disables caching, which will
35711 slow down @value{GDBN} startup, but reduce memory consumption.
35713 @kindex maint set profile
35714 @kindex maint show profile
35715 @cindex profiling GDB
35716 @item maint set profile
35717 @itemx maint show profile
35718 Control profiling of @value{GDBN}.
35720 Profiling will be disabled until you use the @samp{maint set profile}
35721 command to enable it. When you enable profiling, the system will begin
35722 collecting timing and execution count data; when you disable profiling or
35723 exit @value{GDBN}, the results will be written to a log file. Remember that
35724 if you use profiling, @value{GDBN} will overwrite the profiling log file
35725 (often called @file{gmon.out}). If you have a record of important profiling
35726 data in a @file{gmon.out} file, be sure to move it to a safe location.
35728 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35729 compiled with the @samp{-pg} compiler option.
35731 @kindex maint set show-debug-regs
35732 @kindex maint show show-debug-regs
35733 @cindex hardware debug registers
35734 @item maint set show-debug-regs
35735 @itemx maint show show-debug-regs
35736 Control whether to show variables that mirror the hardware debug
35737 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35738 enabled, the debug registers values are shown when @value{GDBN} inserts or
35739 removes a hardware breakpoint or watchpoint, and when the inferior
35740 triggers a hardware-assisted breakpoint or watchpoint.
35742 @kindex maint set show-all-tib
35743 @kindex maint show show-all-tib
35744 @item maint set show-all-tib
35745 @itemx maint show show-all-tib
35746 Control whether to show all non zero areas within a 1k block starting
35747 at thread local base, when using the @samp{info w32 thread-information-block}
35750 @kindex maint space
35751 @cindex memory used by commands
35753 Control whether to display memory usage for each command. If set to a
35754 nonzero value, @value{GDBN} will display how much memory each command
35755 took, following the command's own output. This can also be requested
35756 by invoking @value{GDBN} with the @option{--statistics} command-line
35757 switch (@pxref{Mode Options}).
35760 @cindex time of command execution
35762 Control whether to display the execution time of @value{GDBN} for each command.
35763 If set to a nonzero value, @value{GDBN} will display how much time it
35764 took to execute each command, following the command's own output.
35765 Both CPU time and wallclock time are printed.
35766 Printing both is useful when trying to determine whether the cost is
35767 CPU or, e.g., disk/network, latency.
35768 Note that the CPU time printed is for @value{GDBN} only, it does not include
35769 the execution time of the inferior because there's no mechanism currently
35770 to compute how much time was spent by @value{GDBN} and how much time was
35771 spent by the program been debugged.
35772 This can also be requested by invoking @value{GDBN} with the
35773 @option{--statistics} command-line switch (@pxref{Mode Options}).
35775 @kindex maint translate-address
35776 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35777 Find the symbol stored at the location specified by the address
35778 @var{addr} and an optional section name @var{section}. If found,
35779 @value{GDBN} prints the name of the closest symbol and an offset from
35780 the symbol's location to the specified address. This is similar to
35781 the @code{info address} command (@pxref{Symbols}), except that this
35782 command also allows to find symbols in other sections.
35784 If section was not specified, the section in which the symbol was found
35785 is also printed. For dynamically linked executables, the name of
35786 executable or shared library containing the symbol is printed as well.
35790 The following command is useful for non-interactive invocations of
35791 @value{GDBN}, such as in the test suite.
35794 @item set watchdog @var{nsec}
35795 @kindex set watchdog
35796 @cindex watchdog timer
35797 @cindex timeout for commands
35798 Set the maximum number of seconds @value{GDBN} will wait for the
35799 target operation to finish. If this time expires, @value{GDBN}
35800 reports and error and the command is aborted.
35802 @item show watchdog
35803 Show the current setting of the target wait timeout.
35806 @node Remote Protocol
35807 @appendix @value{GDBN} Remote Serial Protocol
35812 * Stop Reply Packets::
35813 * General Query Packets::
35814 * Architecture-Specific Protocol Details::
35815 * Tracepoint Packets::
35816 * Host I/O Packets::
35818 * Notification Packets::
35819 * Remote Non-Stop::
35820 * Packet Acknowledgment::
35822 * File-I/O Remote Protocol Extension::
35823 * Library List Format::
35824 * Library List Format for SVR4 Targets::
35825 * Memory Map Format::
35826 * Thread List Format::
35827 * Traceframe Info Format::
35828 * Branch Trace Format::
35834 There may be occasions when you need to know something about the
35835 protocol---for example, if there is only one serial port to your target
35836 machine, you might want your program to do something special if it
35837 recognizes a packet meant for @value{GDBN}.
35839 In the examples below, @samp{->} and @samp{<-} are used to indicate
35840 transmitted and received data, respectively.
35842 @cindex protocol, @value{GDBN} remote serial
35843 @cindex serial protocol, @value{GDBN} remote
35844 @cindex remote serial protocol
35845 All @value{GDBN} commands and responses (other than acknowledgments
35846 and notifications, see @ref{Notification Packets}) are sent as a
35847 @var{packet}. A @var{packet} is introduced with the character
35848 @samp{$}, the actual @var{packet-data}, and the terminating character
35849 @samp{#} followed by a two-digit @var{checksum}:
35852 @code{$}@var{packet-data}@code{#}@var{checksum}
35856 @cindex checksum, for @value{GDBN} remote
35858 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35859 characters between the leading @samp{$} and the trailing @samp{#} (an
35860 eight bit unsigned checksum).
35862 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35863 specification also included an optional two-digit @var{sequence-id}:
35866 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35869 @cindex sequence-id, for @value{GDBN} remote
35871 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35872 has never output @var{sequence-id}s. Stubs that handle packets added
35873 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35875 When either the host or the target machine receives a packet, the first
35876 response expected is an acknowledgment: either @samp{+} (to indicate
35877 the package was received correctly) or @samp{-} (to request
35881 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35886 The @samp{+}/@samp{-} acknowledgments can be disabled
35887 once a connection is established.
35888 @xref{Packet Acknowledgment}, for details.
35890 The host (@value{GDBN}) sends @var{command}s, and the target (the
35891 debugging stub incorporated in your program) sends a @var{response}. In
35892 the case of step and continue @var{command}s, the response is only sent
35893 when the operation has completed, and the target has again stopped all
35894 threads in all attached processes. This is the default all-stop mode
35895 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35896 execution mode; see @ref{Remote Non-Stop}, for details.
35898 @var{packet-data} consists of a sequence of characters with the
35899 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35902 @cindex remote protocol, field separator
35903 Fields within the packet should be separated using @samp{,} @samp{;} or
35904 @samp{:}. Except where otherwise noted all numbers are represented in
35905 @sc{hex} with leading zeros suppressed.
35907 Implementors should note that prior to @value{GDBN} 5.0, the character
35908 @samp{:} could not appear as the third character in a packet (as it
35909 would potentially conflict with the @var{sequence-id}).
35911 @cindex remote protocol, binary data
35912 @anchor{Binary Data}
35913 Binary data in most packets is encoded either as two hexadecimal
35914 digits per byte of binary data. This allowed the traditional remote
35915 protocol to work over connections which were only seven-bit clean.
35916 Some packets designed more recently assume an eight-bit clean
35917 connection, and use a more efficient encoding to send and receive
35920 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35921 as an escape character. Any escaped byte is transmitted as the escape
35922 character followed by the original character XORed with @code{0x20}.
35923 For example, the byte @code{0x7d} would be transmitted as the two
35924 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35925 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35926 @samp{@}}) must always be escaped. Responses sent by the stub
35927 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35928 is not interpreted as the start of a run-length encoded sequence
35931 Response @var{data} can be run-length encoded to save space.
35932 Run-length encoding replaces runs of identical characters with one
35933 instance of the repeated character, followed by a @samp{*} and a
35934 repeat count. The repeat count is itself sent encoded, to avoid
35935 binary characters in @var{data}: a value of @var{n} is sent as
35936 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35937 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35938 code 32) for a repeat count of 3. (This is because run-length
35939 encoding starts to win for counts 3 or more.) Thus, for example,
35940 @samp{0* } is a run-length encoding of ``0000'': the space character
35941 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35944 The printable characters @samp{#} and @samp{$} or with a numeric value
35945 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35946 seven repeats (@samp{$}) can be expanded using a repeat count of only
35947 five (@samp{"}). For example, @samp{00000000} can be encoded as
35950 The error response returned for some packets includes a two character
35951 error number. That number is not well defined.
35953 @cindex empty response, for unsupported packets
35954 For any @var{command} not supported by the stub, an empty response
35955 (@samp{$#00}) should be returned. That way it is possible to extend the
35956 protocol. A newer @value{GDBN} can tell if a packet is supported based
35959 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35960 commands for register access, and the @samp{m} and @samp{M} commands
35961 for memory access. Stubs that only control single-threaded targets
35962 can implement run control with the @samp{c} (continue), and @samp{s}
35963 (step) commands. Stubs that support multi-threading targets should
35964 support the @samp{vCont} command. All other commands are optional.
35969 The following table provides a complete list of all currently defined
35970 @var{command}s and their corresponding response @var{data}.
35971 @xref{File-I/O Remote Protocol Extension}, for details about the File
35972 I/O extension of the remote protocol.
35974 Each packet's description has a template showing the packet's overall
35975 syntax, followed by an explanation of the packet's meaning. We
35976 include spaces in some of the templates for clarity; these are not
35977 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35978 separate its components. For example, a template like @samp{foo
35979 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35980 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35981 @var{baz}. @value{GDBN} does not transmit a space character between the
35982 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35985 @cindex @var{thread-id}, in remote protocol
35986 @anchor{thread-id syntax}
35987 Several packets and replies include a @var{thread-id} field to identify
35988 a thread. Normally these are positive numbers with a target-specific
35989 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35990 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35993 In addition, the remote protocol supports a multiprocess feature in
35994 which the @var{thread-id} syntax is extended to optionally include both
35995 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35996 The @var{pid} (process) and @var{tid} (thread) components each have the
35997 format described above: a positive number with target-specific
35998 interpretation formatted as a big-endian hex string, literal @samp{-1}
35999 to indicate all processes or threads (respectively), or @samp{0} to
36000 indicate an arbitrary process or thread. Specifying just a process, as
36001 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36002 error to specify all processes but a specific thread, such as
36003 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36004 for those packets and replies explicitly documented to include a process
36005 ID, rather than a @var{thread-id}.
36007 The multiprocess @var{thread-id} syntax extensions are only used if both
36008 @value{GDBN} and the stub report support for the @samp{multiprocess}
36009 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36012 Note that all packet forms beginning with an upper- or lower-case
36013 letter, other than those described here, are reserved for future use.
36015 Here are the packet descriptions.
36020 @cindex @samp{!} packet
36021 @anchor{extended mode}
36022 Enable extended mode. In extended mode, the remote server is made
36023 persistent. The @samp{R} packet is used to restart the program being
36029 The remote target both supports and has enabled extended mode.
36033 @cindex @samp{?} packet
36034 Indicate the reason the target halted. The reply is the same as for
36035 step and continue. This packet has a special interpretation when the
36036 target is in non-stop mode; see @ref{Remote Non-Stop}.
36039 @xref{Stop Reply Packets}, for the reply specifications.
36041 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36042 @cindex @samp{A} packet
36043 Initialized @code{argv[]} array passed into program. @var{arglen}
36044 specifies the number of bytes in the hex encoded byte stream
36045 @var{arg}. See @code{gdbserver} for more details.
36050 The arguments were set.
36056 @cindex @samp{b} packet
36057 (Don't use this packet; its behavior is not well-defined.)
36058 Change the serial line speed to @var{baud}.
36060 JTC: @emph{When does the transport layer state change? When it's
36061 received, or after the ACK is transmitted. In either case, there are
36062 problems if the command or the acknowledgment packet is dropped.}
36064 Stan: @emph{If people really wanted to add something like this, and get
36065 it working for the first time, they ought to modify ser-unix.c to send
36066 some kind of out-of-band message to a specially-setup stub and have the
36067 switch happen "in between" packets, so that from remote protocol's point
36068 of view, nothing actually happened.}
36070 @item B @var{addr},@var{mode}
36071 @cindex @samp{B} packet
36072 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36073 breakpoint at @var{addr}.
36075 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36076 (@pxref{insert breakpoint or watchpoint packet}).
36078 @cindex @samp{bc} packet
36081 Backward continue. Execute the target system in reverse. No parameter.
36082 @xref{Reverse Execution}, for more information.
36085 @xref{Stop Reply Packets}, for the reply specifications.
36087 @cindex @samp{bs} packet
36090 Backward single step. Execute one instruction in reverse. No parameter.
36091 @xref{Reverse Execution}, for more information.
36094 @xref{Stop Reply Packets}, for the reply specifications.
36096 @item c @r{[}@var{addr}@r{]}
36097 @cindex @samp{c} packet
36098 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36099 resume at current address.
36101 This packet is deprecated for multi-threading support. @xref{vCont
36105 @xref{Stop Reply Packets}, for the reply specifications.
36107 @item C @var{sig}@r{[};@var{addr}@r{]}
36108 @cindex @samp{C} packet
36109 Continue with signal @var{sig} (hex signal number). If
36110 @samp{;@var{addr}} is omitted, resume at same address.
36112 This packet is deprecated for multi-threading support. @xref{vCont
36116 @xref{Stop Reply Packets}, for the reply specifications.
36119 @cindex @samp{d} packet
36122 Don't use this packet; instead, define a general set packet
36123 (@pxref{General Query Packets}).
36127 @cindex @samp{D} packet
36128 The first form of the packet is used to detach @value{GDBN} from the
36129 remote system. It is sent to the remote target
36130 before @value{GDBN} disconnects via the @code{detach} command.
36132 The second form, including a process ID, is used when multiprocess
36133 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36134 detach only a specific process. The @var{pid} is specified as a
36135 big-endian hex string.
36145 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36146 @cindex @samp{F} packet
36147 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36148 This is part of the File-I/O protocol extension. @xref{File-I/O
36149 Remote Protocol Extension}, for the specification.
36152 @anchor{read registers packet}
36153 @cindex @samp{g} packet
36154 Read general registers.
36158 @item @var{XX@dots{}}
36159 Each byte of register data is described by two hex digits. The bytes
36160 with the register are transmitted in target byte order. The size of
36161 each register and their position within the @samp{g} packet are
36162 determined by the @value{GDBN} internal gdbarch functions
36163 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36164 specification of several standard @samp{g} packets is specified below.
36166 When reading registers from a trace frame (@pxref{Analyze Collected
36167 Data,,Using the Collected Data}), the stub may also return a string of
36168 literal @samp{x}'s in place of the register data digits, to indicate
36169 that the corresponding register has not been collected, thus its value
36170 is unavailable. For example, for an architecture with 4 registers of
36171 4 bytes each, the following reply indicates to @value{GDBN} that
36172 registers 0 and 2 have not been collected, while registers 1 and 3
36173 have been collected, and both have zero value:
36177 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36184 @item G @var{XX@dots{}}
36185 @cindex @samp{G} packet
36186 Write general registers. @xref{read registers packet}, for a
36187 description of the @var{XX@dots{}} data.
36197 @item H @var{op} @var{thread-id}
36198 @cindex @samp{H} packet
36199 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36200 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36201 it should be @samp{c} for step and continue operations (note that this
36202 is deprecated, supporting the @samp{vCont} command is a better
36203 option), @samp{g} for other operations. The thread designator
36204 @var{thread-id} has the format and interpretation described in
36205 @ref{thread-id syntax}.
36216 @c 'H': How restrictive (or permissive) is the thread model. If a
36217 @c thread is selected and stopped, are other threads allowed
36218 @c to continue to execute? As I mentioned above, I think the
36219 @c semantics of each command when a thread is selected must be
36220 @c described. For example:
36222 @c 'g': If the stub supports threads and a specific thread is
36223 @c selected, returns the register block from that thread;
36224 @c otherwise returns current registers.
36226 @c 'G' If the stub supports threads and a specific thread is
36227 @c selected, sets the registers of the register block of
36228 @c that thread; otherwise sets current registers.
36230 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36231 @anchor{cycle step packet}
36232 @cindex @samp{i} packet
36233 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36234 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36235 step starting at that address.
36238 @cindex @samp{I} packet
36239 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36243 @cindex @samp{k} packet
36246 FIXME: @emph{There is no description of how to operate when a specific
36247 thread context has been selected (i.e.@: does 'k' kill only that
36250 @item m @var{addr},@var{length}
36251 @cindex @samp{m} packet
36252 Read @var{length} bytes of memory starting at address @var{addr}.
36253 Note that @var{addr} may not be aligned to any particular boundary.
36255 The stub need not use any particular size or alignment when gathering
36256 data from memory for the response; even if @var{addr} is word-aligned
36257 and @var{length} is a multiple of the word size, the stub is free to
36258 use byte accesses, or not. For this reason, this packet may not be
36259 suitable for accessing memory-mapped I/O devices.
36260 @cindex alignment of remote memory accesses
36261 @cindex size of remote memory accesses
36262 @cindex memory, alignment and size of remote accesses
36266 @item @var{XX@dots{}}
36267 Memory contents; each byte is transmitted as a two-digit hexadecimal
36268 number. The reply may contain fewer bytes than requested if the
36269 server was able to read only part of the region of memory.
36274 @item M @var{addr},@var{length}:@var{XX@dots{}}
36275 @cindex @samp{M} packet
36276 Write @var{length} bytes of memory starting at address @var{addr}.
36277 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36278 hexadecimal number.
36285 for an error (this includes the case where only part of the data was
36290 @cindex @samp{p} packet
36291 Read the value of register @var{n}; @var{n} is in hex.
36292 @xref{read registers packet}, for a description of how the returned
36293 register value is encoded.
36297 @item @var{XX@dots{}}
36298 the register's value
36302 Indicating an unrecognized @var{query}.
36305 @item P @var{n@dots{}}=@var{r@dots{}}
36306 @anchor{write register packet}
36307 @cindex @samp{P} packet
36308 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36309 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36310 digits for each byte in the register (target byte order).
36320 @item q @var{name} @var{params}@dots{}
36321 @itemx Q @var{name} @var{params}@dots{}
36322 @cindex @samp{q} packet
36323 @cindex @samp{Q} packet
36324 General query (@samp{q}) and set (@samp{Q}). These packets are
36325 described fully in @ref{General Query Packets}.
36328 @cindex @samp{r} packet
36329 Reset the entire system.
36331 Don't use this packet; use the @samp{R} packet instead.
36334 @cindex @samp{R} packet
36335 Restart the program being debugged. @var{XX}, while needed, is ignored.
36336 This packet is only available in extended mode (@pxref{extended mode}).
36338 The @samp{R} packet has no reply.
36340 @item s @r{[}@var{addr}@r{]}
36341 @cindex @samp{s} packet
36342 Single step. @var{addr} is the address at which to resume. If
36343 @var{addr} is omitted, resume at same address.
36345 This packet is deprecated for multi-threading support. @xref{vCont
36349 @xref{Stop Reply Packets}, for the reply specifications.
36351 @item S @var{sig}@r{[};@var{addr}@r{]}
36352 @anchor{step with signal packet}
36353 @cindex @samp{S} packet
36354 Step with signal. This is analogous to the @samp{C} packet, but
36355 requests a single-step, rather than a normal resumption of execution.
36357 This packet is deprecated for multi-threading support. @xref{vCont
36361 @xref{Stop Reply Packets}, for the reply specifications.
36363 @item t @var{addr}:@var{PP},@var{MM}
36364 @cindex @samp{t} packet
36365 Search backwards starting at address @var{addr} for a match with pattern
36366 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36367 @var{addr} must be at least 3 digits.
36369 @item T @var{thread-id}
36370 @cindex @samp{T} packet
36371 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36376 thread is still alive
36382 Packets starting with @samp{v} are identified by a multi-letter name,
36383 up to the first @samp{;} or @samp{?} (or the end of the packet).
36385 @item vAttach;@var{pid}
36386 @cindex @samp{vAttach} packet
36387 Attach to a new process with the specified process ID @var{pid}.
36388 The process ID is a
36389 hexadecimal integer identifying the process. In all-stop mode, all
36390 threads in the attached process are stopped; in non-stop mode, it may be
36391 attached without being stopped if that is supported by the target.
36393 @c In non-stop mode, on a successful vAttach, the stub should set the
36394 @c current thread to a thread of the newly-attached process. After
36395 @c attaching, GDB queries for the attached process's thread ID with qC.
36396 @c Also note that, from a user perspective, whether or not the
36397 @c target is stopped on attach in non-stop mode depends on whether you
36398 @c use the foreground or background version of the attach command, not
36399 @c on what vAttach does; GDB does the right thing with respect to either
36400 @c stopping or restarting threads.
36402 This packet is only available in extended mode (@pxref{extended mode}).
36408 @item @r{Any stop packet}
36409 for success in all-stop mode (@pxref{Stop Reply Packets})
36411 for success in non-stop mode (@pxref{Remote Non-Stop})
36414 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36415 @cindex @samp{vCont} packet
36416 @anchor{vCont packet}
36417 Resume the inferior, specifying different actions for each thread.
36418 If an action is specified with no @var{thread-id}, then it is applied to any
36419 threads that don't have a specific action specified; if no default action is
36420 specified then other threads should remain stopped in all-stop mode and
36421 in their current state in non-stop mode.
36422 Specifying multiple
36423 default actions is an error; specifying no actions is also an error.
36424 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36426 Currently supported actions are:
36432 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36436 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36441 The optional argument @var{addr} normally associated with the
36442 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36443 not supported in @samp{vCont}.
36445 The @samp{t} action is only relevant in non-stop mode
36446 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36447 A stop reply should be generated for any affected thread not already stopped.
36448 When a thread is stopped by means of a @samp{t} action,
36449 the corresponding stop reply should indicate that the thread has stopped with
36450 signal @samp{0}, regardless of whether the target uses some other signal
36451 as an implementation detail.
36453 The stub must support @samp{vCont} if it reports support for
36454 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36455 this case @samp{vCont} actions can be specified to apply to all threads
36456 in a process by using the @samp{p@var{pid}.-1} form of the
36460 @xref{Stop Reply Packets}, for the reply specifications.
36463 @cindex @samp{vCont?} packet
36464 Request a list of actions supported by the @samp{vCont} packet.
36468 @item vCont@r{[};@var{action}@dots{}@r{]}
36469 The @samp{vCont} packet is supported. Each @var{action} is a supported
36470 command in the @samp{vCont} packet.
36472 The @samp{vCont} packet is not supported.
36475 @item vFile:@var{operation}:@var{parameter}@dots{}
36476 @cindex @samp{vFile} packet
36477 Perform a file operation on the target system. For details,
36478 see @ref{Host I/O Packets}.
36480 @item vFlashErase:@var{addr},@var{length}
36481 @cindex @samp{vFlashErase} packet
36482 Direct the stub to erase @var{length} bytes of flash starting at
36483 @var{addr}. The region may enclose any number of flash blocks, but
36484 its start and end must fall on block boundaries, as indicated by the
36485 flash block size appearing in the memory map (@pxref{Memory Map
36486 Format}). @value{GDBN} groups flash memory programming operations
36487 together, and sends a @samp{vFlashDone} request after each group; the
36488 stub is allowed to delay erase operation until the @samp{vFlashDone}
36489 packet is received.
36499 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36500 @cindex @samp{vFlashWrite} packet
36501 Direct the stub to write data to flash address @var{addr}. The data
36502 is passed in binary form using the same encoding as for the @samp{X}
36503 packet (@pxref{Binary Data}). The memory ranges specified by
36504 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36505 not overlap, and must appear in order of increasing addresses
36506 (although @samp{vFlashErase} packets for higher addresses may already
36507 have been received; the ordering is guaranteed only between
36508 @samp{vFlashWrite} packets). If a packet writes to an address that was
36509 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36510 target-specific method, the results are unpredictable.
36518 for vFlashWrite addressing non-flash memory
36524 @cindex @samp{vFlashDone} packet
36525 Indicate to the stub that flash programming operation is finished.
36526 The stub is permitted to delay or batch the effects of a group of
36527 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36528 @samp{vFlashDone} packet is received. The contents of the affected
36529 regions of flash memory are unpredictable until the @samp{vFlashDone}
36530 request is completed.
36532 @item vKill;@var{pid}
36533 @cindex @samp{vKill} packet
36534 Kill the process with the specified process ID. @var{pid} is a
36535 hexadecimal integer identifying the process. This packet is used in
36536 preference to @samp{k} when multiprocess protocol extensions are
36537 supported; see @ref{multiprocess extensions}.
36547 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36548 @cindex @samp{vRun} packet
36549 Run the program @var{filename}, passing it each @var{argument} on its
36550 command line. The file and arguments are hex-encoded strings. If
36551 @var{filename} is an empty string, the stub may use a default program
36552 (e.g.@: the last program run). The program is created in the stopped
36555 @c FIXME: What about non-stop mode?
36557 This packet is only available in extended mode (@pxref{extended mode}).
36563 @item @r{Any stop packet}
36564 for success (@pxref{Stop Reply Packets})
36568 @cindex @samp{vStopped} packet
36569 @xref{Notification Packets}.
36571 @item X @var{addr},@var{length}:@var{XX@dots{}}
36573 @cindex @samp{X} packet
36574 Write data to memory, where the data is transmitted in binary.
36575 @var{addr} is address, @var{length} is number of bytes,
36576 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36586 @item z @var{type},@var{addr},@var{kind}
36587 @itemx Z @var{type},@var{addr},@var{kind}
36588 @anchor{insert breakpoint or watchpoint packet}
36589 @cindex @samp{z} packet
36590 @cindex @samp{Z} packets
36591 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36592 watchpoint starting at address @var{address} of kind @var{kind}.
36594 Each breakpoint and watchpoint packet @var{type} is documented
36597 @emph{Implementation notes: A remote target shall return an empty string
36598 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36599 remote target shall support either both or neither of a given
36600 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36601 avoid potential problems with duplicate packets, the operations should
36602 be implemented in an idempotent way.}
36604 @item z0,@var{addr},@var{kind}
36605 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36606 @cindex @samp{z0} packet
36607 @cindex @samp{Z0} packet
36608 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36609 @var{addr} of type @var{kind}.
36611 A memory breakpoint is implemented by replacing the instruction at
36612 @var{addr} with a software breakpoint or trap instruction. The
36613 @var{kind} is target-specific and typically indicates the size of
36614 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36615 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36616 architectures have additional meanings for @var{kind};
36617 @var{cond_list} is an optional list of conditional expressions in bytecode
36618 form that should be evaluated on the target's side. These are the
36619 conditions that should be taken into consideration when deciding if
36620 the breakpoint trigger should be reported back to @var{GDBN}.
36622 The @var{cond_list} parameter is comprised of a series of expressions,
36623 concatenated without separators. Each expression has the following form:
36627 @item X @var{len},@var{expr}
36628 @var{len} is the length of the bytecode expression and @var{expr} is the
36629 actual conditional expression in bytecode form.
36633 The optional @var{cmd_list} parameter introduces commands that may be
36634 run on the target, rather than being reported back to @value{GDBN}.
36635 The parameter starts with a numeric flag @var{persist}; if the flag is
36636 nonzero, then the breakpoint may remain active and the commands
36637 continue to be run even when @value{GDBN} disconnects from the target.
36638 Following this flag is a series of expressions concatenated with no
36639 separators. Each expression has the following form:
36643 @item X @var{len},@var{expr}
36644 @var{len} is the length of the bytecode expression and @var{expr} is the
36645 actual conditional expression in bytecode form.
36649 see @ref{Architecture-Specific Protocol Details}.
36651 @emph{Implementation note: It is possible for a target to copy or move
36652 code that contains memory breakpoints (e.g., when implementing
36653 overlays). The behavior of this packet, in the presence of such a
36654 target, is not defined.}
36666 @item z1,@var{addr},@var{kind}
36667 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36668 @cindex @samp{z1} packet
36669 @cindex @samp{Z1} packet
36670 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36671 address @var{addr}.
36673 A hardware breakpoint is implemented using a mechanism that is not
36674 dependant on being able to modify the target's memory. @var{kind}
36675 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36677 @emph{Implementation note: A hardware breakpoint is not affected by code
36690 @item z2,@var{addr},@var{kind}
36691 @itemx Z2,@var{addr},@var{kind}
36692 @cindex @samp{z2} packet
36693 @cindex @samp{Z2} packet
36694 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36695 @var{kind} is interpreted as the number of bytes to watch.
36707 @item z3,@var{addr},@var{kind}
36708 @itemx Z3,@var{addr},@var{kind}
36709 @cindex @samp{z3} packet
36710 @cindex @samp{Z3} packet
36711 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36712 @var{kind} is interpreted as the number of bytes to watch.
36724 @item z4,@var{addr},@var{kind}
36725 @itemx Z4,@var{addr},@var{kind}
36726 @cindex @samp{z4} packet
36727 @cindex @samp{Z4} packet
36728 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36729 @var{kind} is interpreted as the number of bytes to watch.
36743 @node Stop Reply Packets
36744 @section Stop Reply Packets
36745 @cindex stop reply packets
36747 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36748 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36749 receive any of the below as a reply. Except for @samp{?}
36750 and @samp{vStopped}, that reply is only returned
36751 when the target halts. In the below the exact meaning of @dfn{signal
36752 number} is defined by the header @file{include/gdb/signals.h} in the
36753 @value{GDBN} source code.
36755 As in the description of request packets, we include spaces in the
36756 reply templates for clarity; these are not part of the reply packet's
36757 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36763 The program received signal number @var{AA} (a two-digit hexadecimal
36764 number). This is equivalent to a @samp{T} response with no
36765 @var{n}:@var{r} pairs.
36767 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36768 @cindex @samp{T} packet reply
36769 The program received signal number @var{AA} (a two-digit hexadecimal
36770 number). This is equivalent to an @samp{S} response, except that the
36771 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36772 and other information directly in the stop reply packet, reducing
36773 round-trip latency. Single-step and breakpoint traps are reported
36774 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36778 If @var{n} is a hexadecimal number, it is a register number, and the
36779 corresponding @var{r} gives that register's value. @var{r} is a
36780 series of bytes in target byte order, with each byte given by a
36781 two-digit hex number.
36784 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36785 the stopped thread, as specified in @ref{thread-id syntax}.
36788 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36789 the core on which the stop event was detected.
36792 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36793 specific event that stopped the target. The currently defined stop
36794 reasons are listed below. @var{aa} should be @samp{05}, the trap
36795 signal. At most one stop reason should be present.
36798 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36799 and go on to the next; this allows us to extend the protocol in the
36803 The currently defined stop reasons are:
36809 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36812 @cindex shared library events, remote reply
36814 The packet indicates that the loaded libraries have changed.
36815 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36816 list of loaded libraries. @var{r} is ignored.
36818 @cindex replay log events, remote reply
36820 The packet indicates that the target cannot continue replaying
36821 logged execution events, because it has reached the end (or the
36822 beginning when executing backward) of the log. The value of @var{r}
36823 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36824 for more information.
36828 @itemx W @var{AA} ; process:@var{pid}
36829 The process exited, and @var{AA} is the exit status. This is only
36830 applicable to certain targets.
36832 The second form of the response, including the process ID of the exited
36833 process, can be used only when @value{GDBN} has reported support for
36834 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36835 The @var{pid} is formatted as a big-endian hex string.
36838 @itemx X @var{AA} ; process:@var{pid}
36839 The process terminated with signal @var{AA}.
36841 The second form of the response, including the process ID of the
36842 terminated process, can be used only when @value{GDBN} has reported
36843 support for multiprocess protocol extensions; see @ref{multiprocess
36844 extensions}. The @var{pid} is formatted as a big-endian hex string.
36846 @item O @var{XX}@dots{}
36847 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36848 written as the program's console output. This can happen at any time
36849 while the program is running and the debugger should continue to wait
36850 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36852 @item F @var{call-id},@var{parameter}@dots{}
36853 @var{call-id} is the identifier which says which host system call should
36854 be called. This is just the name of the function. Translation into the
36855 correct system call is only applicable as it's defined in @value{GDBN}.
36856 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36859 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36860 this very system call.
36862 The target replies with this packet when it expects @value{GDBN} to
36863 call a host system call on behalf of the target. @value{GDBN} replies
36864 with an appropriate @samp{F} packet and keeps up waiting for the next
36865 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36866 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36867 Protocol Extension}, for more details.
36871 @node General Query Packets
36872 @section General Query Packets
36873 @cindex remote query requests
36875 Packets starting with @samp{q} are @dfn{general query packets};
36876 packets starting with @samp{Q} are @dfn{general set packets}. General
36877 query and set packets are a semi-unified form for retrieving and
36878 sending information to and from the stub.
36880 The initial letter of a query or set packet is followed by a name
36881 indicating what sort of thing the packet applies to. For example,
36882 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36883 definitions with the stub. These packet names follow some
36888 The name must not contain commas, colons or semicolons.
36890 Most @value{GDBN} query and set packets have a leading upper case
36893 The names of custom vendor packets should use a company prefix, in
36894 lower case, followed by a period. For example, packets designed at
36895 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36896 foos) or @samp{Qacme.bar} (for setting bars).
36899 The name of a query or set packet should be separated from any
36900 parameters by a @samp{:}; the parameters themselves should be
36901 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36902 full packet name, and check for a separator or the end of the packet,
36903 in case two packet names share a common prefix. New packets should not begin
36904 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36905 packets predate these conventions, and have arguments without any terminator
36906 for the packet name; we suspect they are in widespread use in places that
36907 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36908 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36911 Like the descriptions of the other packets, each description here
36912 has a template showing the packet's overall syntax, followed by an
36913 explanation of the packet's meaning. We include spaces in some of the
36914 templates for clarity; these are not part of the packet's syntax. No
36915 @value{GDBN} packet uses spaces to separate its components.
36917 Here are the currently defined query and set packets:
36923 Turn on or off the agent as a helper to perform some debugging operations
36924 delegated from @value{GDBN} (@pxref{Control Agent}).
36926 @item QAllow:@var{op}:@var{val}@dots{}
36927 @cindex @samp{QAllow} packet
36928 Specify which operations @value{GDBN} expects to request of the
36929 target, as a semicolon-separated list of operation name and value
36930 pairs. Possible values for @var{op} include @samp{WriteReg},
36931 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36932 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36933 indicating that @value{GDBN} will not request the operation, or 1,
36934 indicating that it may. (The target can then use this to set up its
36935 own internals optimally, for instance if the debugger never expects to
36936 insert breakpoints, it may not need to install its own trap handler.)
36939 @cindex current thread, remote request
36940 @cindex @samp{qC} packet
36941 Return the current thread ID.
36945 @item QC @var{thread-id}
36946 Where @var{thread-id} is a thread ID as documented in
36947 @ref{thread-id syntax}.
36948 @item @r{(anything else)}
36949 Any other reply implies the old thread ID.
36952 @item qCRC:@var{addr},@var{length}
36953 @cindex CRC of memory block, remote request
36954 @cindex @samp{qCRC} packet
36955 Compute the CRC checksum of a block of memory using CRC-32 defined in
36956 IEEE 802.3. The CRC is computed byte at a time, taking the most
36957 significant bit of each byte first. The initial pattern code
36958 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36960 @emph{Note:} This is the same CRC used in validating separate debug
36961 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36962 Files}). However the algorithm is slightly different. When validating
36963 separate debug files, the CRC is computed taking the @emph{least}
36964 significant bit of each byte first, and the final result is inverted to
36965 detect trailing zeros.
36970 An error (such as memory fault)
36971 @item C @var{crc32}
36972 The specified memory region's checksum is @var{crc32}.
36975 @item QDisableRandomization:@var{value}
36976 @cindex disable address space randomization, remote request
36977 @cindex @samp{QDisableRandomization} packet
36978 Some target operating systems will randomize the virtual address space
36979 of the inferior process as a security feature, but provide a feature
36980 to disable such randomization, e.g.@: to allow for a more deterministic
36981 debugging experience. On such systems, this packet with a @var{value}
36982 of 1 directs the target to disable address space randomization for
36983 processes subsequently started via @samp{vRun} packets, while a packet
36984 with a @var{value} of 0 tells the target to enable address space
36987 This packet is only available in extended mode (@pxref{extended mode}).
36992 The request succeeded.
36995 An error occurred. @var{nn} are hex digits.
36998 An empty reply indicates that @samp{QDisableRandomization} is not supported
37002 This packet is not probed by default; the remote stub must request it,
37003 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37004 This should only be done on targets that actually support disabling
37005 address space randomization.
37008 @itemx qsThreadInfo
37009 @cindex list active threads, remote request
37010 @cindex @samp{qfThreadInfo} packet
37011 @cindex @samp{qsThreadInfo} packet
37012 Obtain a list of all active thread IDs from the target (OS). Since there
37013 may be too many active threads to fit into one reply packet, this query
37014 works iteratively: it may require more than one query/reply sequence to
37015 obtain the entire list of threads. The first query of the sequence will
37016 be the @samp{qfThreadInfo} query; subsequent queries in the
37017 sequence will be the @samp{qsThreadInfo} query.
37019 NOTE: This packet replaces the @samp{qL} query (see below).
37023 @item m @var{thread-id}
37025 @item m @var{thread-id},@var{thread-id}@dots{}
37026 a comma-separated list of thread IDs
37028 (lower case letter @samp{L}) denotes end of list.
37031 In response to each query, the target will reply with a list of one or
37032 more thread IDs, separated by commas.
37033 @value{GDBN} will respond to each reply with a request for more thread
37034 ids (using the @samp{qs} form of the query), until the target responds
37035 with @samp{l} (lower-case ell, for @dfn{last}).
37036 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37039 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37040 @cindex get thread-local storage address, remote request
37041 @cindex @samp{qGetTLSAddr} packet
37042 Fetch the address associated with thread local storage specified
37043 by @var{thread-id}, @var{offset}, and @var{lm}.
37045 @var{thread-id} is the thread ID associated with the
37046 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37048 @var{offset} is the (big endian, hex encoded) offset associated with the
37049 thread local variable. (This offset is obtained from the debug
37050 information associated with the variable.)
37052 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37053 load module associated with the thread local storage. For example,
37054 a @sc{gnu}/Linux system will pass the link map address of the shared
37055 object associated with the thread local storage under consideration.
37056 Other operating environments may choose to represent the load module
37057 differently, so the precise meaning of this parameter will vary.
37061 @item @var{XX}@dots{}
37062 Hex encoded (big endian) bytes representing the address of the thread
37063 local storage requested.
37066 An error occurred. @var{nn} are hex digits.
37069 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37072 @item qGetTIBAddr:@var{thread-id}
37073 @cindex get thread information block address
37074 @cindex @samp{qGetTIBAddr} packet
37075 Fetch address of the Windows OS specific Thread Information Block.
37077 @var{thread-id} is the thread ID associated with the thread.
37081 @item @var{XX}@dots{}
37082 Hex encoded (big endian) bytes representing the linear address of the
37083 thread information block.
37086 An error occured. This means that either the thread was not found, or the
37087 address could not be retrieved.
37090 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37093 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37094 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37095 digit) is one to indicate the first query and zero to indicate a
37096 subsequent query; @var{threadcount} (two hex digits) is the maximum
37097 number of threads the response packet can contain; and @var{nextthread}
37098 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37099 returned in the response as @var{argthread}.
37101 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37105 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37106 Where: @var{count} (two hex digits) is the number of threads being
37107 returned; @var{done} (one hex digit) is zero to indicate more threads
37108 and one indicates no further threads; @var{argthreadid} (eight hex
37109 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37110 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37111 digits). See @code{remote.c:parse_threadlist_response()}.
37115 @cindex section offsets, remote request
37116 @cindex @samp{qOffsets} packet
37117 Get section offsets that the target used when relocating the downloaded
37122 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37123 Relocate the @code{Text} section by @var{xxx} from its original address.
37124 Relocate the @code{Data} section by @var{yyy} from its original address.
37125 If the object file format provides segment information (e.g.@: @sc{elf}
37126 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37127 segments by the supplied offsets.
37129 @emph{Note: while a @code{Bss} offset may be included in the response,
37130 @value{GDBN} ignores this and instead applies the @code{Data} offset
37131 to the @code{Bss} section.}
37133 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37134 Relocate the first segment of the object file, which conventionally
37135 contains program code, to a starting address of @var{xxx}. If
37136 @samp{DataSeg} is specified, relocate the second segment, which
37137 conventionally contains modifiable data, to a starting address of
37138 @var{yyy}. @value{GDBN} will report an error if the object file
37139 does not contain segment information, or does not contain at least
37140 as many segments as mentioned in the reply. Extra segments are
37141 kept at fixed offsets relative to the last relocated segment.
37144 @item qP @var{mode} @var{thread-id}
37145 @cindex thread information, remote request
37146 @cindex @samp{qP} packet
37147 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37148 encoded 32 bit mode; @var{thread-id} is a thread ID
37149 (@pxref{thread-id syntax}).
37151 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37154 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37158 @cindex non-stop mode, remote request
37159 @cindex @samp{QNonStop} packet
37161 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37162 @xref{Remote Non-Stop}, for more information.
37167 The request succeeded.
37170 An error occurred. @var{nn} are hex digits.
37173 An empty reply indicates that @samp{QNonStop} is not supported by
37177 This packet is not probed by default; the remote stub must request it,
37178 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37179 Use of this packet is controlled by the @code{set non-stop} command;
37180 @pxref{Non-Stop Mode}.
37182 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37183 @cindex pass signals to inferior, remote request
37184 @cindex @samp{QPassSignals} packet
37185 @anchor{QPassSignals}
37186 Each listed @var{signal} should be passed directly to the inferior process.
37187 Signals are numbered identically to continue packets and stop replies
37188 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37189 strictly greater than the previous item. These signals do not need to stop
37190 the inferior, or be reported to @value{GDBN}. All other signals should be
37191 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37192 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37193 new list. This packet improves performance when using @samp{handle
37194 @var{signal} nostop noprint pass}.
37199 The request succeeded.
37202 An error occurred. @var{nn} are hex digits.
37205 An empty reply indicates that @samp{QPassSignals} is not supported by
37209 Use of this packet is controlled by the @code{set remote pass-signals}
37210 command (@pxref{Remote Configuration, set remote pass-signals}).
37211 This packet is not probed by default; the remote stub must request it,
37212 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37214 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37215 @cindex signals the inferior may see, remote request
37216 @cindex @samp{QProgramSignals} packet
37217 @anchor{QProgramSignals}
37218 Each listed @var{signal} may be delivered to the inferior process.
37219 Others should be silently discarded.
37221 In some cases, the remote stub may need to decide whether to deliver a
37222 signal to the program or not without @value{GDBN} involvement. One
37223 example of that is while detaching --- the program's threads may have
37224 stopped for signals that haven't yet had a chance of being reported to
37225 @value{GDBN}, and so the remote stub can use the signal list specified
37226 by this packet to know whether to deliver or ignore those pending
37229 This does not influence whether to deliver a signal as requested by a
37230 resumption packet (@pxref{vCont packet}).
37232 Signals are numbered identically to continue packets and stop replies
37233 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37234 strictly greater than the previous item. Multiple
37235 @samp{QProgramSignals} packets do not combine; any earlier
37236 @samp{QProgramSignals} list is completely replaced by the new list.
37241 The request succeeded.
37244 An error occurred. @var{nn} are hex digits.
37247 An empty reply indicates that @samp{QProgramSignals} is not supported
37251 Use of this packet is controlled by the @code{set remote program-signals}
37252 command (@pxref{Remote Configuration, set remote program-signals}).
37253 This packet is not probed by default; the remote stub must request it,
37254 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37256 @item qRcmd,@var{command}
37257 @cindex execute remote command, remote request
37258 @cindex @samp{qRcmd} packet
37259 @var{command} (hex encoded) is passed to the local interpreter for
37260 execution. Invalid commands should be reported using the output
37261 string. Before the final result packet, the target may also respond
37262 with a number of intermediate @samp{O@var{output}} console output
37263 packets. @emph{Implementors should note that providing access to a
37264 stubs's interpreter may have security implications}.
37269 A command response with no output.
37271 A command response with the hex encoded output string @var{OUTPUT}.
37273 Indicate a badly formed request.
37275 An empty reply indicates that @samp{qRcmd} is not recognized.
37278 (Note that the @code{qRcmd} packet's name is separated from the
37279 command by a @samp{,}, not a @samp{:}, contrary to the naming
37280 conventions above. Please don't use this packet as a model for new
37283 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37284 @cindex searching memory, in remote debugging
37286 @cindex @samp{qSearch:memory} packet
37288 @cindex @samp{qSearch memory} packet
37289 @anchor{qSearch memory}
37290 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37291 @var{address} and @var{length} are encoded in hex.
37292 @var{search-pattern} is a sequence of bytes, hex encoded.
37297 The pattern was not found.
37299 The pattern was found at @var{address}.
37301 A badly formed request or an error was encountered while searching memory.
37303 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37306 @item QStartNoAckMode
37307 @cindex @samp{QStartNoAckMode} packet
37308 @anchor{QStartNoAckMode}
37309 Request that the remote stub disable the normal @samp{+}/@samp{-}
37310 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37315 The stub has switched to no-acknowledgment mode.
37316 @value{GDBN} acknowledges this reponse,
37317 but neither the stub nor @value{GDBN} shall send or expect further
37318 @samp{+}/@samp{-} acknowledgments in the current connection.
37320 An empty reply indicates that the stub does not support no-acknowledgment mode.
37323 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37324 @cindex supported packets, remote query
37325 @cindex features of the remote protocol
37326 @cindex @samp{qSupported} packet
37327 @anchor{qSupported}
37328 Tell the remote stub about features supported by @value{GDBN}, and
37329 query the stub for features it supports. This packet allows
37330 @value{GDBN} and the remote stub to take advantage of each others'
37331 features. @samp{qSupported} also consolidates multiple feature probes
37332 at startup, to improve @value{GDBN} performance---a single larger
37333 packet performs better than multiple smaller probe packets on
37334 high-latency links. Some features may enable behavior which must not
37335 be on by default, e.g.@: because it would confuse older clients or
37336 stubs. Other features may describe packets which could be
37337 automatically probed for, but are not. These features must be
37338 reported before @value{GDBN} will use them. This ``default
37339 unsupported'' behavior is not appropriate for all packets, but it
37340 helps to keep the initial connection time under control with new
37341 versions of @value{GDBN} which support increasing numbers of packets.
37345 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37346 The stub supports or does not support each returned @var{stubfeature},
37347 depending on the form of each @var{stubfeature} (see below for the
37350 An empty reply indicates that @samp{qSupported} is not recognized,
37351 or that no features needed to be reported to @value{GDBN}.
37354 The allowed forms for each feature (either a @var{gdbfeature} in the
37355 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37359 @item @var{name}=@var{value}
37360 The remote protocol feature @var{name} is supported, and associated
37361 with the specified @var{value}. The format of @var{value} depends
37362 on the feature, but it must not include a semicolon.
37364 The remote protocol feature @var{name} is supported, and does not
37365 need an associated value.
37367 The remote protocol feature @var{name} is not supported.
37369 The remote protocol feature @var{name} may be supported, and
37370 @value{GDBN} should auto-detect support in some other way when it is
37371 needed. This form will not be used for @var{gdbfeature} notifications,
37372 but may be used for @var{stubfeature} responses.
37375 Whenever the stub receives a @samp{qSupported} request, the
37376 supplied set of @value{GDBN} features should override any previous
37377 request. This allows @value{GDBN} to put the stub in a known
37378 state, even if the stub had previously been communicating with
37379 a different version of @value{GDBN}.
37381 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37386 This feature indicates whether @value{GDBN} supports multiprocess
37387 extensions to the remote protocol. @value{GDBN} does not use such
37388 extensions unless the stub also reports that it supports them by
37389 including @samp{multiprocess+} in its @samp{qSupported} reply.
37390 @xref{multiprocess extensions}, for details.
37393 This feature indicates that @value{GDBN} supports the XML target
37394 description. If the stub sees @samp{xmlRegisters=} with target
37395 specific strings separated by a comma, it will report register
37399 This feature indicates whether @value{GDBN} supports the
37400 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37401 instruction reply packet}).
37404 Stubs should ignore any unknown values for
37405 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37406 packet supports receiving packets of unlimited length (earlier
37407 versions of @value{GDBN} may reject overly long responses). Additional values
37408 for @var{gdbfeature} may be defined in the future to let the stub take
37409 advantage of new features in @value{GDBN}, e.g.@: incompatible
37410 improvements in the remote protocol---the @samp{multiprocess} feature is
37411 an example of such a feature. The stub's reply should be independent
37412 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37413 describes all the features it supports, and then the stub replies with
37414 all the features it supports.
37416 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37417 responses, as long as each response uses one of the standard forms.
37419 Some features are flags. A stub which supports a flag feature
37420 should respond with a @samp{+} form response. Other features
37421 require values, and the stub should respond with an @samp{=}
37424 Each feature has a default value, which @value{GDBN} will use if
37425 @samp{qSupported} is not available or if the feature is not mentioned
37426 in the @samp{qSupported} response. The default values are fixed; a
37427 stub is free to omit any feature responses that match the defaults.
37429 Not all features can be probed, but for those which can, the probing
37430 mechanism is useful: in some cases, a stub's internal
37431 architecture may not allow the protocol layer to know some information
37432 about the underlying target in advance. This is especially common in
37433 stubs which may be configured for multiple targets.
37435 These are the currently defined stub features and their properties:
37437 @multitable @columnfractions 0.35 0.2 0.12 0.2
37438 @c NOTE: The first row should be @headitem, but we do not yet require
37439 @c a new enough version of Texinfo (4.7) to use @headitem.
37441 @tab Value Required
37445 @item @samp{PacketSize}
37450 @item @samp{qXfer:auxv:read}
37455 @item @samp{qXfer:btrace:read}
37460 @item @samp{qXfer:features:read}
37465 @item @samp{qXfer:libraries:read}
37470 @item @samp{qXfer:memory-map:read}
37475 @item @samp{qXfer:sdata:read}
37480 @item @samp{qXfer:spu:read}
37485 @item @samp{qXfer:spu:write}
37490 @item @samp{qXfer:siginfo:read}
37495 @item @samp{qXfer:siginfo:write}
37500 @item @samp{qXfer:threads:read}
37505 @item @samp{qXfer:traceframe-info:read}
37510 @item @samp{qXfer:uib:read}
37515 @item @samp{qXfer:fdpic:read}
37520 @item @samp{Qbtrace:off}
37525 @item @samp{Qbtrace:bts}
37530 @item @samp{QNonStop}
37535 @item @samp{QPassSignals}
37540 @item @samp{QStartNoAckMode}
37545 @item @samp{multiprocess}
37550 @item @samp{ConditionalBreakpoints}
37555 @item @samp{ConditionalTracepoints}
37560 @item @samp{ReverseContinue}
37565 @item @samp{ReverseStep}
37570 @item @samp{TracepointSource}
37575 @item @samp{QAgent}
37580 @item @samp{QAllow}
37585 @item @samp{QDisableRandomization}
37590 @item @samp{EnableDisableTracepoints}
37595 @item @samp{QTBuffer:size}
37600 @item @samp{tracenz}
37605 @item @samp{BreakpointCommands}
37612 These are the currently defined stub features, in more detail:
37615 @cindex packet size, remote protocol
37616 @item PacketSize=@var{bytes}
37617 The remote stub can accept packets up to at least @var{bytes} in
37618 length. @value{GDBN} will send packets up to this size for bulk
37619 transfers, and will never send larger packets. This is a limit on the
37620 data characters in the packet, including the frame and checksum.
37621 There is no trailing NUL byte in a remote protocol packet; if the stub
37622 stores packets in a NUL-terminated format, it should allow an extra
37623 byte in its buffer for the NUL. If this stub feature is not supported,
37624 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37626 @item qXfer:auxv:read
37627 The remote stub understands the @samp{qXfer:auxv:read} packet
37628 (@pxref{qXfer auxiliary vector read}).
37630 @item qXfer:btrace:read
37631 The remote stub understands the @samp{qXfer:btrace:read}
37632 packet (@pxref{qXfer btrace read}).
37634 @item qXfer:features:read
37635 The remote stub understands the @samp{qXfer:features:read} packet
37636 (@pxref{qXfer target description read}).
37638 @item qXfer:libraries:read
37639 The remote stub understands the @samp{qXfer:libraries:read} packet
37640 (@pxref{qXfer library list read}).
37642 @item qXfer:libraries-svr4:read
37643 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37644 (@pxref{qXfer svr4 library list read}).
37646 @item qXfer:memory-map:read
37647 The remote stub understands the @samp{qXfer:memory-map:read} packet
37648 (@pxref{qXfer memory map read}).
37650 @item qXfer:sdata:read
37651 The remote stub understands the @samp{qXfer:sdata:read} packet
37652 (@pxref{qXfer sdata read}).
37654 @item qXfer:spu:read
37655 The remote stub understands the @samp{qXfer:spu:read} packet
37656 (@pxref{qXfer spu read}).
37658 @item qXfer:spu:write
37659 The remote stub understands the @samp{qXfer:spu:write} packet
37660 (@pxref{qXfer spu write}).
37662 @item qXfer:siginfo:read
37663 The remote stub understands the @samp{qXfer:siginfo:read} packet
37664 (@pxref{qXfer siginfo read}).
37666 @item qXfer:siginfo:write
37667 The remote stub understands the @samp{qXfer:siginfo:write} packet
37668 (@pxref{qXfer siginfo write}).
37670 @item qXfer:threads:read
37671 The remote stub understands the @samp{qXfer:threads:read} packet
37672 (@pxref{qXfer threads read}).
37674 @item qXfer:traceframe-info:read
37675 The remote stub understands the @samp{qXfer:traceframe-info:read}
37676 packet (@pxref{qXfer traceframe info read}).
37678 @item qXfer:uib:read
37679 The remote stub understands the @samp{qXfer:uib:read}
37680 packet (@pxref{qXfer unwind info block}).
37682 @item qXfer:fdpic:read
37683 The remote stub understands the @samp{qXfer:fdpic:read}
37684 packet (@pxref{qXfer fdpic loadmap read}).
37687 The remote stub understands the @samp{QNonStop} packet
37688 (@pxref{QNonStop}).
37691 The remote stub understands the @samp{QPassSignals} packet
37692 (@pxref{QPassSignals}).
37694 @item QStartNoAckMode
37695 The remote stub understands the @samp{QStartNoAckMode} packet and
37696 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37699 @anchor{multiprocess extensions}
37700 @cindex multiprocess extensions, in remote protocol
37701 The remote stub understands the multiprocess extensions to the remote
37702 protocol syntax. The multiprocess extensions affect the syntax of
37703 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37704 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37705 replies. Note that reporting this feature indicates support for the
37706 syntactic extensions only, not that the stub necessarily supports
37707 debugging of more than one process at a time. The stub must not use
37708 multiprocess extensions in packet replies unless @value{GDBN} has also
37709 indicated it supports them in its @samp{qSupported} request.
37711 @item qXfer:osdata:read
37712 The remote stub understands the @samp{qXfer:osdata:read} packet
37713 ((@pxref{qXfer osdata read}).
37715 @item ConditionalBreakpoints
37716 The target accepts and implements evaluation of conditional expressions
37717 defined for breakpoints. The target will only report breakpoint triggers
37718 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37720 @item ConditionalTracepoints
37721 The remote stub accepts and implements conditional expressions defined
37722 for tracepoints (@pxref{Tracepoint Conditions}).
37724 @item ReverseContinue
37725 The remote stub accepts and implements the reverse continue packet
37729 The remote stub accepts and implements the reverse step packet
37732 @item TracepointSource
37733 The remote stub understands the @samp{QTDPsrc} packet that supplies
37734 the source form of tracepoint definitions.
37737 The remote stub understands the @samp{QAgent} packet.
37740 The remote stub understands the @samp{QAllow} packet.
37742 @item QDisableRandomization
37743 The remote stub understands the @samp{QDisableRandomization} packet.
37745 @item StaticTracepoint
37746 @cindex static tracepoints, in remote protocol
37747 The remote stub supports static tracepoints.
37749 @item InstallInTrace
37750 @anchor{install tracepoint in tracing}
37751 The remote stub supports installing tracepoint in tracing.
37753 @item EnableDisableTracepoints
37754 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37755 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37756 to be enabled and disabled while a trace experiment is running.
37758 @item QTBuffer:size
37759 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37760 packet that allows to change the size of the trace buffer.
37763 @cindex string tracing, in remote protocol
37764 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37765 See @ref{Bytecode Descriptions} for details about the bytecode.
37767 @item BreakpointCommands
37768 @cindex breakpoint commands, in remote protocol
37769 The remote stub supports running a breakpoint's command list itself,
37770 rather than reporting the hit to @value{GDBN}.
37773 The remote stub understands the @samp{Qbtrace:off} packet.
37776 The remote stub understands the @samp{Qbtrace:bts} packet.
37781 @cindex symbol lookup, remote request
37782 @cindex @samp{qSymbol} packet
37783 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37784 requests. Accept requests from the target for the values of symbols.
37789 The target does not need to look up any (more) symbols.
37790 @item qSymbol:@var{sym_name}
37791 The target requests the value of symbol @var{sym_name} (hex encoded).
37792 @value{GDBN} may provide the value by using the
37793 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37797 @item qSymbol:@var{sym_value}:@var{sym_name}
37798 Set the value of @var{sym_name} to @var{sym_value}.
37800 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37801 target has previously requested.
37803 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37804 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37810 The target does not need to look up any (more) symbols.
37811 @item qSymbol:@var{sym_name}
37812 The target requests the value of a new symbol @var{sym_name} (hex
37813 encoded). @value{GDBN} will continue to supply the values of symbols
37814 (if available), until the target ceases to request them.
37819 @itemx QTDisconnected
37826 @itemx qTMinFTPILen
37828 @xref{Tracepoint Packets}.
37830 @item qThreadExtraInfo,@var{thread-id}
37831 @cindex thread attributes info, remote request
37832 @cindex @samp{qThreadExtraInfo} packet
37833 Obtain a printable string description of a thread's attributes from
37834 the target OS. @var{thread-id} is a thread ID;
37835 see @ref{thread-id syntax}. This
37836 string may contain anything that the target OS thinks is interesting
37837 for @value{GDBN} to tell the user about the thread. The string is
37838 displayed in @value{GDBN}'s @code{info threads} display. Some
37839 examples of possible thread extra info strings are @samp{Runnable}, or
37840 @samp{Blocked on Mutex}.
37844 @item @var{XX}@dots{}
37845 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37846 comprising the printable string containing the extra information about
37847 the thread's attributes.
37850 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37851 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37852 conventions above. Please don't use this packet as a model for new
37871 @xref{Tracepoint Packets}.
37873 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37874 @cindex read special object, remote request
37875 @cindex @samp{qXfer} packet
37876 @anchor{qXfer read}
37877 Read uninterpreted bytes from the target's special data area
37878 identified by the keyword @var{object}. Request @var{length} bytes
37879 starting at @var{offset} bytes into the data. The content and
37880 encoding of @var{annex} is specific to @var{object}; it can supply
37881 additional details about what data to access.
37883 Here are the specific requests of this form defined so far. All
37884 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37885 formats, listed below.
37888 @item qXfer:auxv:read::@var{offset},@var{length}
37889 @anchor{qXfer auxiliary vector read}
37890 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37891 auxiliary vector}. Note @var{annex} must be empty.
37893 This packet is not probed by default; the remote stub must request it,
37894 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37896 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37897 @anchor{qXfer btrace read}
37899 Return a description of the current branch trace.
37900 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37901 packet may have one of the following values:
37905 Returns all available branch trace.
37908 Returns all available branch trace if the branch trace changed since
37909 the last read request.
37912 This packet is not probed by default; the remote stub must request it
37913 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37915 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37916 @anchor{qXfer target description read}
37917 Access the @dfn{target description}. @xref{Target Descriptions}. The
37918 annex specifies which XML document to access. The main description is
37919 always loaded from the @samp{target.xml} annex.
37921 This packet is not probed by default; the remote stub must request it,
37922 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37924 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37925 @anchor{qXfer library list read}
37926 Access the target's list of loaded libraries. @xref{Library List Format}.
37927 The annex part of the generic @samp{qXfer} packet must be empty
37928 (@pxref{qXfer read}).
37930 Targets which maintain a list of libraries in the program's memory do
37931 not need to implement this packet; it is designed for platforms where
37932 the operating system manages the list of loaded libraries.
37934 This packet is not probed by default; the remote stub must request it,
37935 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37937 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37938 @anchor{qXfer svr4 library list read}
37939 Access the target's list of loaded libraries when the target is an SVR4
37940 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37941 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37943 This packet is optional for better performance on SVR4 targets.
37944 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37946 This packet is not probed by default; the remote stub must request it,
37947 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37949 @item qXfer:memory-map:read::@var{offset},@var{length}
37950 @anchor{qXfer memory map read}
37951 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37952 annex part of the generic @samp{qXfer} packet must be empty
37953 (@pxref{qXfer read}).
37955 This packet is not probed by default; the remote stub must request it,
37956 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37958 @item qXfer:sdata:read::@var{offset},@var{length}
37959 @anchor{qXfer sdata read}
37961 Read contents of the extra collected static tracepoint marker
37962 information. The annex part of the generic @samp{qXfer} packet must
37963 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37966 This packet is not probed by default; the remote stub must request it,
37967 by supplying an appropriate @samp{qSupported} response
37968 (@pxref{qSupported}).
37970 @item qXfer:siginfo:read::@var{offset},@var{length}
37971 @anchor{qXfer siginfo read}
37972 Read contents of the extra signal information on the target
37973 system. The annex part of the generic @samp{qXfer} packet must be
37974 empty (@pxref{qXfer read}).
37976 This packet is not probed by default; the remote stub must request it,
37977 by supplying an appropriate @samp{qSupported} response
37978 (@pxref{qSupported}).
37980 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37981 @anchor{qXfer spu read}
37982 Read contents of an @code{spufs} file on the target system. The
37983 annex specifies which file to read; it must be of the form
37984 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37985 in the target process, and @var{name} identifes the @code{spufs} file
37986 in that context to be accessed.
37988 This packet is not probed by default; the remote stub must request it,
37989 by supplying an appropriate @samp{qSupported} response
37990 (@pxref{qSupported}).
37992 @item qXfer:threads:read::@var{offset},@var{length}
37993 @anchor{qXfer threads read}
37994 Access the list of threads on target. @xref{Thread List Format}. The
37995 annex part of the generic @samp{qXfer} packet must be empty
37996 (@pxref{qXfer read}).
37998 This packet is not probed by default; the remote stub must request it,
37999 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38001 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38002 @anchor{qXfer traceframe info read}
38004 Return a description of the current traceframe's contents.
38005 @xref{Traceframe Info Format}. The annex part of the generic
38006 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38008 This packet is not probed by default; the remote stub must request it,
38009 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38011 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38012 @anchor{qXfer unwind info block}
38014 Return the unwind information block for @var{pc}. This packet is used
38015 on OpenVMS/ia64 to ask the kernel unwind information.
38017 This packet is not probed by default.
38019 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38020 @anchor{qXfer fdpic loadmap read}
38021 Read contents of @code{loadmap}s on the target system. The
38022 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38023 executable @code{loadmap} or interpreter @code{loadmap} to read.
38025 This packet is not probed by default; the remote stub must request it,
38026 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38028 @item qXfer:osdata:read::@var{offset},@var{length}
38029 @anchor{qXfer osdata read}
38030 Access the target's @dfn{operating system information}.
38031 @xref{Operating System Information}.
38038 Data @var{data} (@pxref{Binary Data}) has been read from the
38039 target. There may be more data at a higher address (although
38040 it is permitted to return @samp{m} even for the last valid
38041 block of data, as long as at least one byte of data was read).
38042 @var{data} may have fewer bytes than the @var{length} in the
38046 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38047 There is no more data to be read. @var{data} may have fewer bytes
38048 than the @var{length} in the request.
38051 The @var{offset} in the request is at the end of the data.
38052 There is no more data to be read.
38055 The request was malformed, or @var{annex} was invalid.
38058 The offset was invalid, or there was an error encountered reading the data.
38059 @var{nn} is a hex-encoded @code{errno} value.
38062 An empty reply indicates the @var{object} string was not recognized by
38063 the stub, or that the object does not support reading.
38066 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38067 @cindex write data into object, remote request
38068 @anchor{qXfer write}
38069 Write uninterpreted bytes into the target's special data area
38070 identified by the keyword @var{object}, starting at @var{offset} bytes
38071 into the data. @var{data}@dots{} is the binary-encoded data
38072 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38073 is specific to @var{object}; it can supply additional details about what data
38076 Here are the specific requests of this form defined so far. All
38077 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38078 formats, listed below.
38081 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38082 @anchor{qXfer siginfo write}
38083 Write @var{data} to the extra signal information on the target system.
38084 The annex part of the generic @samp{qXfer} packet must be
38085 empty (@pxref{qXfer write}).
38087 This packet is not probed by default; the remote stub must request it,
38088 by supplying an appropriate @samp{qSupported} response
38089 (@pxref{qSupported}).
38091 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38092 @anchor{qXfer spu write}
38093 Write @var{data} to an @code{spufs} file on the target system. The
38094 annex specifies which file to write; it must be of the form
38095 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38096 in the target process, and @var{name} identifes the @code{spufs} file
38097 in that context to be accessed.
38099 This packet is not probed by default; the remote stub must request it,
38100 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38106 @var{nn} (hex encoded) is the number of bytes written.
38107 This may be fewer bytes than supplied in the request.
38110 The request was malformed, or @var{annex} was invalid.
38113 The offset was invalid, or there was an error encountered writing the data.
38114 @var{nn} is a hex-encoded @code{errno} value.
38117 An empty reply indicates the @var{object} string was not
38118 recognized by the stub, or that the object does not support writing.
38121 @item qXfer:@var{object}:@var{operation}:@dots{}
38122 Requests of this form may be added in the future. When a stub does
38123 not recognize the @var{object} keyword, or its support for
38124 @var{object} does not recognize the @var{operation} keyword, the stub
38125 must respond with an empty packet.
38127 @item qAttached:@var{pid}
38128 @cindex query attached, remote request
38129 @cindex @samp{qAttached} packet
38130 Return an indication of whether the remote server attached to an
38131 existing process or created a new process. When the multiprocess
38132 protocol extensions are supported (@pxref{multiprocess extensions}),
38133 @var{pid} is an integer in hexadecimal format identifying the target
38134 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38135 the query packet will be simplified as @samp{qAttached}.
38137 This query is used, for example, to know whether the remote process
38138 should be detached or killed when a @value{GDBN} session is ended with
38139 the @code{quit} command.
38144 The remote server attached to an existing process.
38146 The remote server created a new process.
38148 A badly formed request or an error was encountered.
38152 Enable branch tracing for the current thread using bts tracing.
38157 Branch tracing has been enabled.
38159 A badly formed request or an error was encountered.
38163 Disable branch tracing for the current thread.
38168 Branch tracing has been disabled.
38170 A badly formed request or an error was encountered.
38175 @node Architecture-Specific Protocol Details
38176 @section Architecture-Specific Protocol Details
38178 This section describes how the remote protocol is applied to specific
38179 target architectures. Also see @ref{Standard Target Features}, for
38180 details of XML target descriptions for each architecture.
38183 * ARM-Specific Protocol Details::
38184 * MIPS-Specific Protocol Details::
38187 @node ARM-Specific Protocol Details
38188 @subsection @acronym{ARM}-specific Protocol Details
38191 * ARM Breakpoint Kinds::
38194 @node ARM Breakpoint Kinds
38195 @subsubsection @acronym{ARM} Breakpoint Kinds
38196 @cindex breakpoint kinds, @acronym{ARM}
38198 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38203 16-bit Thumb mode breakpoint.
38206 32-bit Thumb mode (Thumb-2) breakpoint.
38209 32-bit @acronym{ARM} mode breakpoint.
38213 @node MIPS-Specific Protocol Details
38214 @subsection @acronym{MIPS}-specific Protocol Details
38217 * MIPS Register packet Format::
38218 * MIPS Breakpoint Kinds::
38221 @node MIPS Register packet Format
38222 @subsubsection @acronym{MIPS} Register Packet Format
38223 @cindex register packet format, @acronym{MIPS}
38225 The following @code{g}/@code{G} packets have previously been defined.
38226 In the below, some thirty-two bit registers are transferred as
38227 sixty-four bits. Those registers should be zero/sign extended (which?)
38228 to fill the space allocated. Register bytes are transferred in target
38229 byte order. The two nibbles within a register byte are transferred
38230 most-significant -- least-significant.
38235 All registers are transferred as thirty-two bit quantities in the order:
38236 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38237 registers; fsr; fir; fp.
38240 All registers are transferred as sixty-four bit quantities (including
38241 thirty-two bit registers such as @code{sr}). The ordering is the same
38246 @node MIPS Breakpoint Kinds
38247 @subsubsection @acronym{MIPS} Breakpoint Kinds
38248 @cindex breakpoint kinds, @acronym{MIPS}
38250 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38255 16-bit @acronym{MIPS16} mode breakpoint.
38258 16-bit @acronym{microMIPS} mode breakpoint.
38261 32-bit standard @acronym{MIPS} mode breakpoint.
38264 32-bit @acronym{microMIPS} mode breakpoint.
38268 @node Tracepoint Packets
38269 @section Tracepoint Packets
38270 @cindex tracepoint packets
38271 @cindex packets, tracepoint
38273 Here we describe the packets @value{GDBN} uses to implement
38274 tracepoints (@pxref{Tracepoints}).
38278 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38279 @cindex @samp{QTDP} packet
38280 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38281 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38282 the tracepoint is disabled. @var{step} is the tracepoint's step
38283 count, and @var{pass} is its pass count. If an @samp{F} is present,
38284 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38285 the number of bytes that the target should copy elsewhere to make room
38286 for the tracepoint. If an @samp{X} is present, it introduces a
38287 tracepoint condition, which consists of a hexadecimal length, followed
38288 by a comma and hex-encoded bytes, in a manner similar to action
38289 encodings as described below. If the trailing @samp{-} is present,
38290 further @samp{QTDP} packets will follow to specify this tracepoint's
38296 The packet was understood and carried out.
38298 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38300 The packet was not recognized.
38303 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38304 Define actions to be taken when a tracepoint is hit. @var{n} and
38305 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38306 this tracepoint. This packet may only be sent immediately after
38307 another @samp{QTDP} packet that ended with a @samp{-}. If the
38308 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38309 specifying more actions for this tracepoint.
38311 In the series of action packets for a given tracepoint, at most one
38312 can have an @samp{S} before its first @var{action}. If such a packet
38313 is sent, it and the following packets define ``while-stepping''
38314 actions. Any prior packets define ordinary actions --- that is, those
38315 taken when the tracepoint is first hit. If no action packet has an
38316 @samp{S}, then all the packets in the series specify ordinary
38317 tracepoint actions.
38319 The @samp{@var{action}@dots{}} portion of the packet is a series of
38320 actions, concatenated without separators. Each action has one of the
38326 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38327 a hexadecimal number whose @var{i}'th bit is set if register number
38328 @var{i} should be collected. (The least significant bit is numbered
38329 zero.) Note that @var{mask} may be any number of digits long; it may
38330 not fit in a 32-bit word.
38332 @item M @var{basereg},@var{offset},@var{len}
38333 Collect @var{len} bytes of memory starting at the address in register
38334 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38335 @samp{-1}, then the range has a fixed address: @var{offset} is the
38336 address of the lowest byte to collect. The @var{basereg},
38337 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38338 values (the @samp{-1} value for @var{basereg} is a special case).
38340 @item X @var{len},@var{expr}
38341 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38342 it directs. @var{expr} is an agent expression, as described in
38343 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38344 two-digit hex number in the packet; @var{len} is the number of bytes
38345 in the expression (and thus one-half the number of hex digits in the
38350 Any number of actions may be packed together in a single @samp{QTDP}
38351 packet, as long as the packet does not exceed the maximum packet
38352 length (400 bytes, for many stubs). There may be only one @samp{R}
38353 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38354 actions. Any registers referred to by @samp{M} and @samp{X} actions
38355 must be collected by a preceding @samp{R} action. (The
38356 ``while-stepping'' actions are treated as if they were attached to a
38357 separate tracepoint, as far as these restrictions are concerned.)
38362 The packet was understood and carried out.
38364 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38366 The packet was not recognized.
38369 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38370 @cindex @samp{QTDPsrc} packet
38371 Specify a source string of tracepoint @var{n} at address @var{addr}.
38372 This is useful to get accurate reproduction of the tracepoints
38373 originally downloaded at the beginning of the trace run. @var{type}
38374 is the name of the tracepoint part, such as @samp{cond} for the
38375 tracepoint's conditional expression (see below for a list of types), while
38376 @var{bytes} is the string, encoded in hexadecimal.
38378 @var{start} is the offset of the @var{bytes} within the overall source
38379 string, while @var{slen} is the total length of the source string.
38380 This is intended for handling source strings that are longer than will
38381 fit in a single packet.
38382 @c Add detailed example when this info is moved into a dedicated
38383 @c tracepoint descriptions section.
38385 The available string types are @samp{at} for the location,
38386 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38387 @value{GDBN} sends a separate packet for each command in the action
38388 list, in the same order in which the commands are stored in the list.
38390 The target does not need to do anything with source strings except
38391 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38394 Although this packet is optional, and @value{GDBN} will only send it
38395 if the target replies with @samp{TracepointSource} @xref{General
38396 Query Packets}, it makes both disconnected tracing and trace files
38397 much easier to use. Otherwise the user must be careful that the
38398 tracepoints in effect while looking at trace frames are identical to
38399 the ones in effect during the trace run; even a small discrepancy
38400 could cause @samp{tdump} not to work, or a particular trace frame not
38403 @item QTDV:@var{n}:@var{value}
38404 @cindex define trace state variable, remote request
38405 @cindex @samp{QTDV} packet
38406 Create a new trace state variable, number @var{n}, with an initial
38407 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38408 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38409 the option of not using this packet for initial values of zero; the
38410 target should simply create the trace state variables as they are
38411 mentioned in expressions.
38413 @item QTFrame:@var{n}
38414 @cindex @samp{QTFrame} packet
38415 Select the @var{n}'th tracepoint frame from the buffer, and use the
38416 register and memory contents recorded there to answer subsequent
38417 request packets from @value{GDBN}.
38419 A successful reply from the stub indicates that the stub has found the
38420 requested frame. The response is a series of parts, concatenated
38421 without separators, describing the frame we selected. Each part has
38422 one of the following forms:
38426 The selected frame is number @var{n} in the trace frame buffer;
38427 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38428 was no frame matching the criteria in the request packet.
38431 The selected trace frame records a hit of tracepoint number @var{t};
38432 @var{t} is a hexadecimal number.
38436 @item QTFrame:pc:@var{addr}
38437 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38438 currently selected frame whose PC is @var{addr};
38439 @var{addr} is a hexadecimal number.
38441 @item QTFrame:tdp:@var{t}
38442 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38443 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38444 is a hexadecimal number.
38446 @item QTFrame:range:@var{start}:@var{end}
38447 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38448 currently selected frame whose PC is between @var{start} (inclusive)
38449 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38452 @item QTFrame:outside:@var{start}:@var{end}
38453 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38454 frame @emph{outside} the given range of addresses (exclusive).
38457 @cindex @samp{qTMinFTPILen} packet
38458 This packet requests the minimum length of instruction at which a fast
38459 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38460 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38461 it depends on the target system being able to create trampolines in
38462 the first 64K of memory, which might or might not be possible for that
38463 system. So the reply to this packet will be 4 if it is able to
38470 The minimum instruction length is currently unknown.
38472 The minimum instruction length is @var{length}, where @var{length} is greater
38473 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38474 that a fast tracepoint may be placed on any instruction regardless of size.
38476 An error has occurred.
38478 An empty reply indicates that the request is not supported by the stub.
38482 @cindex @samp{QTStart} packet
38483 Begin the tracepoint experiment. Begin collecting data from
38484 tracepoint hits in the trace frame buffer. This packet supports the
38485 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38486 instruction reply packet}).
38489 @cindex @samp{QTStop} packet
38490 End the tracepoint experiment. Stop collecting trace frames.
38492 @item QTEnable:@var{n}:@var{addr}
38494 @cindex @samp{QTEnable} packet
38495 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38496 experiment. If the tracepoint was previously disabled, then collection
38497 of data from it will resume.
38499 @item QTDisable:@var{n}:@var{addr}
38501 @cindex @samp{QTDisable} packet
38502 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38503 experiment. No more data will be collected from the tracepoint unless
38504 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38507 @cindex @samp{QTinit} packet
38508 Clear the table of tracepoints, and empty the trace frame buffer.
38510 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38511 @cindex @samp{QTro} packet
38512 Establish the given ranges of memory as ``transparent''. The stub
38513 will answer requests for these ranges from memory's current contents,
38514 if they were not collected as part of the tracepoint hit.
38516 @value{GDBN} uses this to mark read-only regions of memory, like those
38517 containing program code. Since these areas never change, they should
38518 still have the same contents they did when the tracepoint was hit, so
38519 there's no reason for the stub to refuse to provide their contents.
38521 @item QTDisconnected:@var{value}
38522 @cindex @samp{QTDisconnected} packet
38523 Set the choice to what to do with the tracing run when @value{GDBN}
38524 disconnects from the target. A @var{value} of 1 directs the target to
38525 continue the tracing run, while 0 tells the target to stop tracing if
38526 @value{GDBN} is no longer in the picture.
38529 @cindex @samp{qTStatus} packet
38530 Ask the stub if there is a trace experiment running right now.
38532 The reply has the form:
38536 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38537 @var{running} is a single digit @code{1} if the trace is presently
38538 running, or @code{0} if not. It is followed by semicolon-separated
38539 optional fields that an agent may use to report additional status.
38543 If the trace is not running, the agent may report any of several
38544 explanations as one of the optional fields:
38549 No trace has been run yet.
38551 @item tstop[:@var{text}]:0
38552 The trace was stopped by a user-originated stop command. The optional
38553 @var{text} field is a user-supplied string supplied as part of the
38554 stop command (for instance, an explanation of why the trace was
38555 stopped manually). It is hex-encoded.
38558 The trace stopped because the trace buffer filled up.
38560 @item tdisconnected:0
38561 The trace stopped because @value{GDBN} disconnected from the target.
38563 @item tpasscount:@var{tpnum}
38564 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38566 @item terror:@var{text}:@var{tpnum}
38567 The trace stopped because tracepoint @var{tpnum} had an error. The
38568 string @var{text} is available to describe the nature of the error
38569 (for instance, a divide by zero in the condition expression).
38570 @var{text} is hex encoded.
38573 The trace stopped for some other reason.
38577 Additional optional fields supply statistical and other information.
38578 Although not required, they are extremely useful for users monitoring
38579 the progress of a trace run. If a trace has stopped, and these
38580 numbers are reported, they must reflect the state of the just-stopped
38585 @item tframes:@var{n}
38586 The number of trace frames in the buffer.
38588 @item tcreated:@var{n}
38589 The total number of trace frames created during the run. This may
38590 be larger than the trace frame count, if the buffer is circular.
38592 @item tsize:@var{n}
38593 The total size of the trace buffer, in bytes.
38595 @item tfree:@var{n}
38596 The number of bytes still unused in the buffer.
38598 @item circular:@var{n}
38599 The value of the circular trace buffer flag. @code{1} means that the
38600 trace buffer is circular and old trace frames will be discarded if
38601 necessary to make room, @code{0} means that the trace buffer is linear
38604 @item disconn:@var{n}
38605 The value of the disconnected tracing flag. @code{1} means that
38606 tracing will continue after @value{GDBN} disconnects, @code{0} means
38607 that the trace run will stop.
38611 @item qTP:@var{tp}:@var{addr}
38612 @cindex tracepoint status, remote request
38613 @cindex @samp{qTP} packet
38614 Ask the stub for the current state of tracepoint number @var{tp} at
38615 address @var{addr}.
38619 @item V@var{hits}:@var{usage}
38620 The tracepoint has been hit @var{hits} times so far during the trace
38621 run, and accounts for @var{usage} in the trace buffer. Note that
38622 @code{while-stepping} steps are not counted as separate hits, but the
38623 steps' space consumption is added into the usage number.
38627 @item qTV:@var{var}
38628 @cindex trace state variable value, remote request
38629 @cindex @samp{qTV} packet
38630 Ask the stub for the value of the trace state variable number @var{var}.
38635 The value of the variable is @var{value}. This will be the current
38636 value of the variable if the user is examining a running target, or a
38637 saved value if the variable was collected in the trace frame that the
38638 user is looking at. Note that multiple requests may result in
38639 different reply values, such as when requesting values while the
38640 program is running.
38643 The value of the variable is unknown. This would occur, for example,
38644 if the user is examining a trace frame in which the requested variable
38649 @cindex @samp{qTfP} packet
38651 @cindex @samp{qTsP} packet
38652 These packets request data about tracepoints that are being used by
38653 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38654 of data, and multiple @code{qTsP} to get additional pieces. Replies
38655 to these packets generally take the form of the @code{QTDP} packets
38656 that define tracepoints. (FIXME add detailed syntax)
38659 @cindex @samp{qTfV} packet
38661 @cindex @samp{qTsV} packet
38662 These packets request data about trace state variables that are on the
38663 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38664 and multiple @code{qTsV} to get additional variables. Replies to
38665 these packets follow the syntax of the @code{QTDV} packets that define
38666 trace state variables.
38672 @cindex @samp{qTfSTM} packet
38673 @cindex @samp{qTsSTM} packet
38674 These packets request data about static tracepoint markers that exist
38675 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38676 first piece of data, and multiple @code{qTsSTM} to get additional
38677 pieces. Replies to these packets take the following form:
38681 @item m @var{address}:@var{id}:@var{extra}
38683 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38684 a comma-separated list of markers
38686 (lower case letter @samp{L}) denotes end of list.
38688 An error occurred. @var{nn} are hex digits.
38690 An empty reply indicates that the request is not supported by the
38694 @var{address} is encoded in hex.
38695 @var{id} and @var{extra} are strings encoded in hex.
38697 In response to each query, the target will reply with a list of one or
38698 more markers, separated by commas. @value{GDBN} will respond to each
38699 reply with a request for more markers (using the @samp{qs} form of the
38700 query), until the target responds with @samp{l} (lower-case ell, for
38703 @item qTSTMat:@var{address}
38705 @cindex @samp{qTSTMat} packet
38706 This packets requests data about static tracepoint markers in the
38707 target program at @var{address}. Replies to this packet follow the
38708 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38709 tracepoint markers.
38711 @item QTSave:@var{filename}
38712 @cindex @samp{QTSave} packet
38713 This packet directs the target to save trace data to the file name
38714 @var{filename} in the target's filesystem. @var{filename} is encoded
38715 as a hex string; the interpretation of the file name (relative vs
38716 absolute, wild cards, etc) is up to the target.
38718 @item qTBuffer:@var{offset},@var{len}
38719 @cindex @samp{qTBuffer} packet
38720 Return up to @var{len} bytes of the current contents of trace buffer,
38721 starting at @var{offset}. The trace buffer is treated as if it were
38722 a contiguous collection of traceframes, as per the trace file format.
38723 The reply consists as many hex-encoded bytes as the target can deliver
38724 in a packet; it is not an error to return fewer than were asked for.
38725 A reply consisting of just @code{l} indicates that no bytes are
38728 @item QTBuffer:circular:@var{value}
38729 This packet directs the target to use a circular trace buffer if
38730 @var{value} is 1, or a linear buffer if the value is 0.
38732 @item QTBuffer:size:@var{size}
38733 @anchor{QTBuffer-size}
38734 @cindex @samp{QTBuffer size} packet
38735 This packet directs the target to make the trace buffer be of size
38736 @var{size} if possible. A value of @code{-1} tells the target to
38737 use whatever size it prefers.
38739 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38740 @cindex @samp{QTNotes} packet
38741 This packet adds optional textual notes to the trace run. Allowable
38742 types include @code{user}, @code{notes}, and @code{tstop}, the
38743 @var{text} fields are arbitrary strings, hex-encoded.
38747 @subsection Relocate instruction reply packet
38748 When installing fast tracepoints in memory, the target may need to
38749 relocate the instruction currently at the tracepoint address to a
38750 different address in memory. For most instructions, a simple copy is
38751 enough, but, for example, call instructions that implicitly push the
38752 return address on the stack, and relative branches or other
38753 PC-relative instructions require offset adjustment, so that the effect
38754 of executing the instruction at a different address is the same as if
38755 it had executed in the original location.
38757 In response to several of the tracepoint packets, the target may also
38758 respond with a number of intermediate @samp{qRelocInsn} request
38759 packets before the final result packet, to have @value{GDBN} handle
38760 this relocation operation. If a packet supports this mechanism, its
38761 documentation will explicitly say so. See for example the above
38762 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38763 format of the request is:
38766 @item qRelocInsn:@var{from};@var{to}
38768 This requests @value{GDBN} to copy instruction at address @var{from}
38769 to address @var{to}, possibly adjusted so that executing the
38770 instruction at @var{to} has the same effect as executing it at
38771 @var{from}. @value{GDBN} writes the adjusted instruction to target
38772 memory starting at @var{to}.
38777 @item qRelocInsn:@var{adjusted_size}
38778 Informs the stub the relocation is complete. @var{adjusted_size} is
38779 the length in bytes of resulting relocated instruction sequence.
38781 A badly formed request was detected, or an error was encountered while
38782 relocating the instruction.
38785 @node Host I/O Packets
38786 @section Host I/O Packets
38787 @cindex Host I/O, remote protocol
38788 @cindex file transfer, remote protocol
38790 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38791 operations on the far side of a remote link. For example, Host I/O is
38792 used to upload and download files to a remote target with its own
38793 filesystem. Host I/O uses the same constant values and data structure
38794 layout as the target-initiated File-I/O protocol. However, the
38795 Host I/O packets are structured differently. The target-initiated
38796 protocol relies on target memory to store parameters and buffers.
38797 Host I/O requests are initiated by @value{GDBN}, and the
38798 target's memory is not involved. @xref{File-I/O Remote Protocol
38799 Extension}, for more details on the target-initiated protocol.
38801 The Host I/O request packets all encode a single operation along with
38802 its arguments. They have this format:
38806 @item vFile:@var{operation}: @var{parameter}@dots{}
38807 @var{operation} is the name of the particular request; the target
38808 should compare the entire packet name up to the second colon when checking
38809 for a supported operation. The format of @var{parameter} depends on
38810 the operation. Numbers are always passed in hexadecimal. Negative
38811 numbers have an explicit minus sign (i.e.@: two's complement is not
38812 used). Strings (e.g.@: filenames) are encoded as a series of
38813 hexadecimal bytes. The last argument to a system call may be a
38814 buffer of escaped binary data (@pxref{Binary Data}).
38818 The valid responses to Host I/O packets are:
38822 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38823 @var{result} is the integer value returned by this operation, usually
38824 non-negative for success and -1 for errors. If an error has occured,
38825 @var{errno} will be included in the result. @var{errno} will have a
38826 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38827 operations which return data, @var{attachment} supplies the data as a
38828 binary buffer. Binary buffers in response packets are escaped in the
38829 normal way (@pxref{Binary Data}). See the individual packet
38830 documentation for the interpretation of @var{result} and
38834 An empty response indicates that this operation is not recognized.
38838 These are the supported Host I/O operations:
38841 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38842 Open a file at @var{pathname} and return a file descriptor for it, or
38843 return -1 if an error occurs. @var{pathname} is a string,
38844 @var{flags} is an integer indicating a mask of open flags
38845 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38846 of mode bits to use if the file is created (@pxref{mode_t Values}).
38847 @xref{open}, for details of the open flags and mode values.
38849 @item vFile:close: @var{fd}
38850 Close the open file corresponding to @var{fd} and return 0, or
38851 -1 if an error occurs.
38853 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38854 Read data from the open file corresponding to @var{fd}. Up to
38855 @var{count} bytes will be read from the file, starting at @var{offset}
38856 relative to the start of the file. The target may read fewer bytes;
38857 common reasons include packet size limits and an end-of-file
38858 condition. The number of bytes read is returned. Zero should only be
38859 returned for a successful read at the end of the file, or if
38860 @var{count} was zero.
38862 The data read should be returned as a binary attachment on success.
38863 If zero bytes were read, the response should include an empty binary
38864 attachment (i.e.@: a trailing semicolon). The return value is the
38865 number of target bytes read; the binary attachment may be longer if
38866 some characters were escaped.
38868 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38869 Write @var{data} (a binary buffer) to the open file corresponding
38870 to @var{fd}. Start the write at @var{offset} from the start of the
38871 file. Unlike many @code{write} system calls, there is no
38872 separate @var{count} argument; the length of @var{data} in the
38873 packet is used. @samp{vFile:write} returns the number of bytes written,
38874 which may be shorter than the length of @var{data}, or -1 if an
38877 @item vFile:unlink: @var{pathname}
38878 Delete the file at @var{pathname} on the target. Return 0,
38879 or -1 if an error occurs. @var{pathname} is a string.
38881 @item vFile:readlink: @var{filename}
38882 Read value of symbolic link @var{filename} on the target. Return
38883 the number of bytes read, or -1 if an error occurs.
38885 The data read should be returned as a binary attachment on success.
38886 If zero bytes were read, the response should include an empty binary
38887 attachment (i.e.@: a trailing semicolon). The return value is the
38888 number of target bytes read; the binary attachment may be longer if
38889 some characters were escaped.
38894 @section Interrupts
38895 @cindex interrupts (remote protocol)
38897 When a program on the remote target is running, @value{GDBN} may
38898 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38899 a @code{BREAK} followed by @code{g},
38900 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38902 The precise meaning of @code{BREAK} is defined by the transport
38903 mechanism and may, in fact, be undefined. @value{GDBN} does not
38904 currently define a @code{BREAK} mechanism for any of the network
38905 interfaces except for TCP, in which case @value{GDBN} sends the
38906 @code{telnet} BREAK sequence.
38908 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38909 transport mechanisms. It is represented by sending the single byte
38910 @code{0x03} without any of the usual packet overhead described in
38911 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38912 transmitted as part of a packet, it is considered to be packet data
38913 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38914 (@pxref{X packet}), used for binary downloads, may include an unescaped
38915 @code{0x03} as part of its packet.
38917 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38918 When Linux kernel receives this sequence from serial port,
38919 it stops execution and connects to gdb.
38921 Stubs are not required to recognize these interrupt mechanisms and the
38922 precise meaning associated with receipt of the interrupt is
38923 implementation defined. If the target supports debugging of multiple
38924 threads and/or processes, it should attempt to interrupt all
38925 currently-executing threads and processes.
38926 If the stub is successful at interrupting the
38927 running program, it should send one of the stop
38928 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38929 of successfully stopping the program in all-stop mode, and a stop reply
38930 for each stopped thread in non-stop mode.
38931 Interrupts received while the
38932 program is stopped are discarded.
38934 @node Notification Packets
38935 @section Notification Packets
38936 @cindex notification packets
38937 @cindex packets, notification
38939 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38940 packets that require no acknowledgment. Both the GDB and the stub
38941 may send notifications (although the only notifications defined at
38942 present are sent by the stub). Notifications carry information
38943 without incurring the round-trip latency of an acknowledgment, and so
38944 are useful for low-impact communications where occasional packet loss
38947 A notification packet has the form @samp{% @var{data} #
38948 @var{checksum}}, where @var{data} is the content of the notification,
38949 and @var{checksum} is a checksum of @var{data}, computed and formatted
38950 as for ordinary @value{GDBN} packets. A notification's @var{data}
38951 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38952 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38953 to acknowledge the notification's receipt or to report its corruption.
38955 Every notification's @var{data} begins with a name, which contains no
38956 colon characters, followed by a colon character.
38958 Recipients should silently ignore corrupted notifications and
38959 notifications they do not understand. Recipients should restart
38960 timeout periods on receipt of a well-formed notification, whether or
38961 not they understand it.
38963 Senders should only send the notifications described here when this
38964 protocol description specifies that they are permitted. In the
38965 future, we may extend the protocol to permit existing notifications in
38966 new contexts; this rule helps older senders avoid confusing newer
38969 (Older versions of @value{GDBN} ignore bytes received until they see
38970 the @samp{$} byte that begins an ordinary packet, so new stubs may
38971 transmit notifications without fear of confusing older clients. There
38972 are no notifications defined for @value{GDBN} to send at the moment, but we
38973 assume that most older stubs would ignore them, as well.)
38975 Each notification is comprised of three parts:
38977 @item @var{name}:@var{event}
38978 The notification packet is sent by the side that initiates the
38979 exchange (currently, only the stub does that), with @var{event}
38980 carrying the specific information about the notification.
38981 @var{name} is the name of the notification.
38983 The acknowledge sent by the other side, usually @value{GDBN}, to
38984 acknowledge the exchange and request the event.
38987 The purpose of an asynchronous notification mechanism is to report to
38988 @value{GDBN} that something interesting happened in the remote stub.
38990 The remote stub may send notification @var{name}:@var{event}
38991 at any time, but @value{GDBN} acknowledges the notification when
38992 appropriate. The notification event is pending before @value{GDBN}
38993 acknowledges. Only one notification at a time may be pending; if
38994 additional events occur before @value{GDBN} has acknowledged the
38995 previous notification, they must be queued by the stub for later
38996 synchronous transmission in response to @var{ack} packets from
38997 @value{GDBN}. Because the notification mechanism is unreliable,
38998 the stub is permitted to resend a notification if it believes
38999 @value{GDBN} may not have received it.
39001 Specifically, notifications may appear when @value{GDBN} is not
39002 otherwise reading input from the stub, or when @value{GDBN} is
39003 expecting to read a normal synchronous response or a
39004 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39005 Notification packets are distinct from any other communication from
39006 the stub so there is no ambiguity.
39008 After receiving a notification, @value{GDBN} shall acknowledge it by
39009 sending a @var{ack} packet as a regular, synchronous request to the
39010 stub. Such acknowledgment is not required to happen immediately, as
39011 @value{GDBN} is permitted to send other, unrelated packets to the
39012 stub first, which the stub should process normally.
39014 Upon receiving a @var{ack} packet, if the stub has other queued
39015 events to report to @value{GDBN}, it shall respond by sending a
39016 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39017 packet to solicit further responses; again, it is permitted to send
39018 other, unrelated packets as well which the stub should process
39021 If the stub receives a @var{ack} packet and there are no additional
39022 @var{event} to report, the stub shall return an @samp{OK} response.
39023 At this point, @value{GDBN} has finished processing a notification
39024 and the stub has completed sending any queued events. @value{GDBN}
39025 won't accept any new notifications until the final @samp{OK} is
39026 received . If further notification events occur, the stub shall send
39027 a new notification, @value{GDBN} shall accept the notification, and
39028 the process shall be repeated.
39030 The process of asynchronous notification can be illustrated by the
39033 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39036 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39038 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39043 The following notifications are defined:
39044 @multitable @columnfractions 0.12 0.12 0.38 0.38
39053 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39054 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39055 for information on how these notifications are acknowledged by
39057 @tab Report an asynchronous stop event in non-stop mode.
39061 @node Remote Non-Stop
39062 @section Remote Protocol Support for Non-Stop Mode
39064 @value{GDBN}'s remote protocol supports non-stop debugging of
39065 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39066 supports non-stop mode, it should report that to @value{GDBN} by including
39067 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39069 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39070 establishing a new connection with the stub. Entering non-stop mode
39071 does not alter the state of any currently-running threads, but targets
39072 must stop all threads in any already-attached processes when entering
39073 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39074 probe the target state after a mode change.
39076 In non-stop mode, when an attached process encounters an event that
39077 would otherwise be reported with a stop reply, it uses the
39078 asynchronous notification mechanism (@pxref{Notification Packets}) to
39079 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39080 in all processes are stopped when a stop reply is sent, in non-stop
39081 mode only the thread reporting the stop event is stopped. That is,
39082 when reporting a @samp{S} or @samp{T} response to indicate completion
39083 of a step operation, hitting a breakpoint, or a fault, only the
39084 affected thread is stopped; any other still-running threads continue
39085 to run. When reporting a @samp{W} or @samp{X} response, all running
39086 threads belonging to other attached processes continue to run.
39088 In non-stop mode, the target shall respond to the @samp{?} packet as
39089 follows. First, any incomplete stop reply notification/@samp{vStopped}
39090 sequence in progress is abandoned. The target must begin a new
39091 sequence reporting stop events for all stopped threads, whether or not
39092 it has previously reported those events to @value{GDBN}. The first
39093 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39094 subsequent stop replies are sent as responses to @samp{vStopped} packets
39095 using the mechanism described above. The target must not send
39096 asynchronous stop reply notifications until the sequence is complete.
39097 If all threads are running when the target receives the @samp{?} packet,
39098 or if the target is not attached to any process, it shall respond
39101 @node Packet Acknowledgment
39102 @section Packet Acknowledgment
39104 @cindex acknowledgment, for @value{GDBN} remote
39105 @cindex packet acknowledgment, for @value{GDBN} remote
39106 By default, when either the host or the target machine receives a packet,
39107 the first response expected is an acknowledgment: either @samp{+} (to indicate
39108 the package was received correctly) or @samp{-} (to request retransmission).
39109 This mechanism allows the @value{GDBN} remote protocol to operate over
39110 unreliable transport mechanisms, such as a serial line.
39112 In cases where the transport mechanism is itself reliable (such as a pipe or
39113 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39114 It may be desirable to disable them in that case to reduce communication
39115 overhead, or for other reasons. This can be accomplished by means of the
39116 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39118 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39119 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39120 and response format still includes the normal checksum, as described in
39121 @ref{Overview}, but the checksum may be ignored by the receiver.
39123 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39124 no-acknowledgment mode, it should report that to @value{GDBN}
39125 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39126 @pxref{qSupported}.
39127 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39128 disabled via the @code{set remote noack-packet off} command
39129 (@pxref{Remote Configuration}),
39130 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39131 Only then may the stub actually turn off packet acknowledgments.
39132 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39133 response, which can be safely ignored by the stub.
39135 Note that @code{set remote noack-packet} command only affects negotiation
39136 between @value{GDBN} and the stub when subsequent connections are made;
39137 it does not affect the protocol acknowledgment state for any current
39139 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39140 new connection is established,
39141 there is also no protocol request to re-enable the acknowledgments
39142 for the current connection, once disabled.
39147 Example sequence of a target being re-started. Notice how the restart
39148 does not get any direct output:
39153 @emph{target restarts}
39156 <- @code{T001:1234123412341234}
39160 Example sequence of a target being stepped by a single instruction:
39163 -> @code{G1445@dots{}}
39168 <- @code{T001:1234123412341234}
39172 <- @code{1455@dots{}}
39176 @node File-I/O Remote Protocol Extension
39177 @section File-I/O Remote Protocol Extension
39178 @cindex File-I/O remote protocol extension
39181 * File-I/O Overview::
39182 * Protocol Basics::
39183 * The F Request Packet::
39184 * The F Reply Packet::
39185 * The Ctrl-C Message::
39187 * List of Supported Calls::
39188 * Protocol-specific Representation of Datatypes::
39190 * File-I/O Examples::
39193 @node File-I/O Overview
39194 @subsection File-I/O Overview
39195 @cindex file-i/o overview
39197 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39198 target to use the host's file system and console I/O to perform various
39199 system calls. System calls on the target system are translated into a
39200 remote protocol packet to the host system, which then performs the needed
39201 actions and returns a response packet to the target system.
39202 This simulates file system operations even on targets that lack file systems.
39204 The protocol is defined to be independent of both the host and target systems.
39205 It uses its own internal representation of datatypes and values. Both
39206 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39207 translating the system-dependent value representations into the internal
39208 protocol representations when data is transmitted.
39210 The communication is synchronous. A system call is possible only when
39211 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39212 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39213 the target is stopped to allow deterministic access to the target's
39214 memory. Therefore File-I/O is not interruptible by target signals. On
39215 the other hand, it is possible to interrupt File-I/O by a user interrupt
39216 (@samp{Ctrl-C}) within @value{GDBN}.
39218 The target's request to perform a host system call does not finish
39219 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39220 after finishing the system call, the target returns to continuing the
39221 previous activity (continue, step). No additional continue or step
39222 request from @value{GDBN} is required.
39225 (@value{GDBP}) continue
39226 <- target requests 'system call X'
39227 target is stopped, @value{GDBN} executes system call
39228 -> @value{GDBN} returns result
39229 ... target continues, @value{GDBN} returns to wait for the target
39230 <- target hits breakpoint and sends a Txx packet
39233 The protocol only supports I/O on the console and to regular files on
39234 the host file system. Character or block special devices, pipes,
39235 named pipes, sockets or any other communication method on the host
39236 system are not supported by this protocol.
39238 File I/O is not supported in non-stop mode.
39240 @node Protocol Basics
39241 @subsection Protocol Basics
39242 @cindex protocol basics, file-i/o
39244 The File-I/O protocol uses the @code{F} packet as the request as well
39245 as reply packet. Since a File-I/O system call can only occur when
39246 @value{GDBN} is waiting for a response from the continuing or stepping target,
39247 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39248 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39249 This @code{F} packet contains all information needed to allow @value{GDBN}
39250 to call the appropriate host system call:
39254 A unique identifier for the requested system call.
39257 All parameters to the system call. Pointers are given as addresses
39258 in the target memory address space. Pointers to strings are given as
39259 pointer/length pair. Numerical values are given as they are.
39260 Numerical control flags are given in a protocol-specific representation.
39264 At this point, @value{GDBN} has to perform the following actions.
39268 If the parameters include pointer values to data needed as input to a
39269 system call, @value{GDBN} requests this data from the target with a
39270 standard @code{m} packet request. This additional communication has to be
39271 expected by the target implementation and is handled as any other @code{m}
39275 @value{GDBN} translates all value from protocol representation to host
39276 representation as needed. Datatypes are coerced into the host types.
39279 @value{GDBN} calls the system call.
39282 It then coerces datatypes back to protocol representation.
39285 If the system call is expected to return data in buffer space specified
39286 by pointer parameters to the call, the data is transmitted to the
39287 target using a @code{M} or @code{X} packet. This packet has to be expected
39288 by the target implementation and is handled as any other @code{M} or @code{X}
39293 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39294 necessary information for the target to continue. This at least contains
39301 @code{errno}, if has been changed by the system call.
39308 After having done the needed type and value coercion, the target continues
39309 the latest continue or step action.
39311 @node The F Request Packet
39312 @subsection The @code{F} Request Packet
39313 @cindex file-i/o request packet
39314 @cindex @code{F} request packet
39316 The @code{F} request packet has the following format:
39319 @item F@var{call-id},@var{parameter@dots{}}
39321 @var{call-id} is the identifier to indicate the host system call to be called.
39322 This is just the name of the function.
39324 @var{parameter@dots{}} are the parameters to the system call.
39325 Parameters are hexadecimal integer values, either the actual values in case
39326 of scalar datatypes, pointers to target buffer space in case of compound
39327 datatypes and unspecified memory areas, or pointer/length pairs in case
39328 of string parameters. These are appended to the @var{call-id} as a
39329 comma-delimited list. All values are transmitted in ASCII
39330 string representation, pointer/length pairs separated by a slash.
39336 @node The F Reply Packet
39337 @subsection The @code{F} Reply Packet
39338 @cindex file-i/o reply packet
39339 @cindex @code{F} reply packet
39341 The @code{F} reply packet has the following format:
39345 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39347 @var{retcode} is the return code of the system call as hexadecimal value.
39349 @var{errno} is the @code{errno} set by the call, in protocol-specific
39351 This parameter can be omitted if the call was successful.
39353 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39354 case, @var{errno} must be sent as well, even if the call was successful.
39355 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39362 or, if the call was interrupted before the host call has been performed:
39369 assuming 4 is the protocol-specific representation of @code{EINTR}.
39374 @node The Ctrl-C Message
39375 @subsection The @samp{Ctrl-C} Message
39376 @cindex ctrl-c message, in file-i/o protocol
39378 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39379 reply packet (@pxref{The F Reply Packet}),
39380 the target should behave as if it had
39381 gotten a break message. The meaning for the target is ``system call
39382 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39383 (as with a break message) and return to @value{GDBN} with a @code{T02}
39386 It's important for the target to know in which
39387 state the system call was interrupted. There are two possible cases:
39391 The system call hasn't been performed on the host yet.
39394 The system call on the host has been finished.
39398 These two states can be distinguished by the target by the value of the
39399 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39400 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39401 on POSIX systems. In any other case, the target may presume that the
39402 system call has been finished --- successfully or not --- and should behave
39403 as if the break message arrived right after the system call.
39405 @value{GDBN} must behave reliably. If the system call has not been called
39406 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39407 @code{errno} in the packet. If the system call on the host has been finished
39408 before the user requests a break, the full action must be finished by
39409 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39410 The @code{F} packet may only be sent when either nothing has happened
39411 or the full action has been completed.
39414 @subsection Console I/O
39415 @cindex console i/o as part of file-i/o
39417 By default and if not explicitly closed by the target system, the file
39418 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39419 on the @value{GDBN} console is handled as any other file output operation
39420 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39421 by @value{GDBN} so that after the target read request from file descriptor
39422 0 all following typing is buffered until either one of the following
39427 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39429 system call is treated as finished.
39432 The user presses @key{RET}. This is treated as end of input with a trailing
39436 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39437 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39441 If the user has typed more characters than fit in the buffer given to
39442 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39443 either another @code{read(0, @dots{})} is requested by the target, or debugging
39444 is stopped at the user's request.
39447 @node List of Supported Calls
39448 @subsection List of Supported Calls
39449 @cindex list of supported file-i/o calls
39466 @unnumberedsubsubsec open
39467 @cindex open, file-i/o system call
39472 int open(const char *pathname, int flags);
39473 int open(const char *pathname, int flags, mode_t mode);
39477 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39480 @var{flags} is the bitwise @code{OR} of the following values:
39484 If the file does not exist it will be created. The host
39485 rules apply as far as file ownership and time stamps
39489 When used with @code{O_CREAT}, if the file already exists it is
39490 an error and open() fails.
39493 If the file already exists and the open mode allows
39494 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39495 truncated to zero length.
39498 The file is opened in append mode.
39501 The file is opened for reading only.
39504 The file is opened for writing only.
39507 The file is opened for reading and writing.
39511 Other bits are silently ignored.
39515 @var{mode} is the bitwise @code{OR} of the following values:
39519 User has read permission.
39522 User has write permission.
39525 Group has read permission.
39528 Group has write permission.
39531 Others have read permission.
39534 Others have write permission.
39538 Other bits are silently ignored.
39541 @item Return value:
39542 @code{open} returns the new file descriptor or -1 if an error
39549 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39552 @var{pathname} refers to a directory.
39555 The requested access is not allowed.
39558 @var{pathname} was too long.
39561 A directory component in @var{pathname} does not exist.
39564 @var{pathname} refers to a device, pipe, named pipe or socket.
39567 @var{pathname} refers to a file on a read-only filesystem and
39568 write access was requested.
39571 @var{pathname} is an invalid pointer value.
39574 No space on device to create the file.
39577 The process already has the maximum number of files open.
39580 The limit on the total number of files open on the system
39584 The call was interrupted by the user.
39590 @unnumberedsubsubsec close
39591 @cindex close, file-i/o system call
39600 @samp{Fclose,@var{fd}}
39602 @item Return value:
39603 @code{close} returns zero on success, or -1 if an error occurred.
39609 @var{fd} isn't a valid open file descriptor.
39612 The call was interrupted by the user.
39618 @unnumberedsubsubsec read
39619 @cindex read, file-i/o system call
39624 int read(int fd, void *buf, unsigned int count);
39628 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39630 @item Return value:
39631 On success, the number of bytes read is returned.
39632 Zero indicates end of file. If count is zero, read
39633 returns zero as well. On error, -1 is returned.
39639 @var{fd} is not a valid file descriptor or is not open for
39643 @var{bufptr} is an invalid pointer value.
39646 The call was interrupted by the user.
39652 @unnumberedsubsubsec write
39653 @cindex write, file-i/o system call
39658 int write(int fd, const void *buf, unsigned int count);
39662 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39664 @item Return value:
39665 On success, the number of bytes written are returned.
39666 Zero indicates nothing was written. On error, -1
39673 @var{fd} is not a valid file descriptor or is not open for
39677 @var{bufptr} is an invalid pointer value.
39680 An attempt was made to write a file that exceeds the
39681 host-specific maximum file size allowed.
39684 No space on device to write the data.
39687 The call was interrupted by the user.
39693 @unnumberedsubsubsec lseek
39694 @cindex lseek, file-i/o system call
39699 long lseek (int fd, long offset, int flag);
39703 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39705 @var{flag} is one of:
39709 The offset is set to @var{offset} bytes.
39712 The offset is set to its current location plus @var{offset}
39716 The offset is set to the size of the file plus @var{offset}
39720 @item Return value:
39721 On success, the resulting unsigned offset in bytes from
39722 the beginning of the file is returned. Otherwise, a
39723 value of -1 is returned.
39729 @var{fd} is not a valid open file descriptor.
39732 @var{fd} is associated with the @value{GDBN} console.
39735 @var{flag} is not a proper value.
39738 The call was interrupted by the user.
39744 @unnumberedsubsubsec rename
39745 @cindex rename, file-i/o system call
39750 int rename(const char *oldpath, const char *newpath);
39754 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39756 @item Return value:
39757 On success, zero is returned. On error, -1 is returned.
39763 @var{newpath} is an existing directory, but @var{oldpath} is not a
39767 @var{newpath} is a non-empty directory.
39770 @var{oldpath} or @var{newpath} is a directory that is in use by some
39774 An attempt was made to make a directory a subdirectory
39778 A component used as a directory in @var{oldpath} or new
39779 path is not a directory. Or @var{oldpath} is a directory
39780 and @var{newpath} exists but is not a directory.
39783 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39786 No access to the file or the path of the file.
39790 @var{oldpath} or @var{newpath} was too long.
39793 A directory component in @var{oldpath} or @var{newpath} does not exist.
39796 The file is on a read-only filesystem.
39799 The device containing the file has no room for the new
39803 The call was interrupted by the user.
39809 @unnumberedsubsubsec unlink
39810 @cindex unlink, file-i/o system call
39815 int unlink(const char *pathname);
39819 @samp{Funlink,@var{pathnameptr}/@var{len}}
39821 @item Return value:
39822 On success, zero is returned. On error, -1 is returned.
39828 No access to the file or the path of the file.
39831 The system does not allow unlinking of directories.
39834 The file @var{pathname} cannot be unlinked because it's
39835 being used by another process.
39838 @var{pathnameptr} is an invalid pointer value.
39841 @var{pathname} was too long.
39844 A directory component in @var{pathname} does not exist.
39847 A component of the path is not a directory.
39850 The file is on a read-only filesystem.
39853 The call was interrupted by the user.
39859 @unnumberedsubsubsec stat/fstat
39860 @cindex fstat, file-i/o system call
39861 @cindex stat, file-i/o system call
39866 int stat(const char *pathname, struct stat *buf);
39867 int fstat(int fd, struct stat *buf);
39871 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39872 @samp{Ffstat,@var{fd},@var{bufptr}}
39874 @item Return value:
39875 On success, zero is returned. On error, -1 is returned.
39881 @var{fd} is not a valid open file.
39884 A directory component in @var{pathname} does not exist or the
39885 path is an empty string.
39888 A component of the path is not a directory.
39891 @var{pathnameptr} is an invalid pointer value.
39894 No access to the file or the path of the file.
39897 @var{pathname} was too long.
39900 The call was interrupted by the user.
39906 @unnumberedsubsubsec gettimeofday
39907 @cindex gettimeofday, file-i/o system call
39912 int gettimeofday(struct timeval *tv, void *tz);
39916 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39918 @item Return value:
39919 On success, 0 is returned, -1 otherwise.
39925 @var{tz} is a non-NULL pointer.
39928 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39934 @unnumberedsubsubsec isatty
39935 @cindex isatty, file-i/o system call
39940 int isatty(int fd);
39944 @samp{Fisatty,@var{fd}}
39946 @item Return value:
39947 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39953 The call was interrupted by the user.
39958 Note that the @code{isatty} call is treated as a special case: it returns
39959 1 to the target if the file descriptor is attached
39960 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39961 would require implementing @code{ioctl} and would be more complex than
39966 @unnumberedsubsubsec system
39967 @cindex system, file-i/o system call
39972 int system(const char *command);
39976 @samp{Fsystem,@var{commandptr}/@var{len}}
39978 @item Return value:
39979 If @var{len} is zero, the return value indicates whether a shell is
39980 available. A zero return value indicates a shell is not available.
39981 For non-zero @var{len}, the value returned is -1 on error and the
39982 return status of the command otherwise. Only the exit status of the
39983 command is returned, which is extracted from the host's @code{system}
39984 return value by calling @code{WEXITSTATUS(retval)}. In case
39985 @file{/bin/sh} could not be executed, 127 is returned.
39991 The call was interrupted by the user.
39996 @value{GDBN} takes over the full task of calling the necessary host calls
39997 to perform the @code{system} call. The return value of @code{system} on
39998 the host is simplified before it's returned
39999 to the target. Any termination signal information from the child process
40000 is discarded, and the return value consists
40001 entirely of the exit status of the called command.
40003 Due to security concerns, the @code{system} call is by default refused
40004 by @value{GDBN}. The user has to allow this call explicitly with the
40005 @code{set remote system-call-allowed 1} command.
40008 @item set remote system-call-allowed
40009 @kindex set remote system-call-allowed
40010 Control whether to allow the @code{system} calls in the File I/O
40011 protocol for the remote target. The default is zero (disabled).
40013 @item show remote system-call-allowed
40014 @kindex show remote system-call-allowed
40015 Show whether the @code{system} calls are allowed in the File I/O
40019 @node Protocol-specific Representation of Datatypes
40020 @subsection Protocol-specific Representation of Datatypes
40021 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40024 * Integral Datatypes::
40026 * Memory Transfer::
40031 @node Integral Datatypes
40032 @unnumberedsubsubsec Integral Datatypes
40033 @cindex integral datatypes, in file-i/o protocol
40035 The integral datatypes used in the system calls are @code{int},
40036 @code{unsigned int}, @code{long}, @code{unsigned long},
40037 @code{mode_t}, and @code{time_t}.
40039 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40040 implemented as 32 bit values in this protocol.
40042 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40044 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40045 in @file{limits.h}) to allow range checking on host and target.
40047 @code{time_t} datatypes are defined as seconds since the Epoch.
40049 All integral datatypes transferred as part of a memory read or write of a
40050 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40053 @node Pointer Values
40054 @unnumberedsubsubsec Pointer Values
40055 @cindex pointer values, in file-i/o protocol
40057 Pointers to target data are transmitted as they are. An exception
40058 is made for pointers to buffers for which the length isn't
40059 transmitted as part of the function call, namely strings. Strings
40060 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40067 which is a pointer to data of length 18 bytes at position 0x1aaf.
40068 The length is defined as the full string length in bytes, including
40069 the trailing null byte. For example, the string @code{"hello world"}
40070 at address 0x123456 is transmitted as
40076 @node Memory Transfer
40077 @unnumberedsubsubsec Memory Transfer
40078 @cindex memory transfer, in file-i/o protocol
40080 Structured data which is transferred using a memory read or write (for
40081 example, a @code{struct stat}) is expected to be in a protocol-specific format
40082 with all scalar multibyte datatypes being big endian. Translation to
40083 this representation needs to be done both by the target before the @code{F}
40084 packet is sent, and by @value{GDBN} before
40085 it transfers memory to the target. Transferred pointers to structured
40086 data should point to the already-coerced data at any time.
40090 @unnumberedsubsubsec struct stat
40091 @cindex struct stat, in file-i/o protocol
40093 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40094 is defined as follows:
40098 unsigned int st_dev; /* device */
40099 unsigned int st_ino; /* inode */
40100 mode_t st_mode; /* protection */
40101 unsigned int st_nlink; /* number of hard links */
40102 unsigned int st_uid; /* user ID of owner */
40103 unsigned int st_gid; /* group ID of owner */
40104 unsigned int st_rdev; /* device type (if inode device) */
40105 unsigned long st_size; /* total size, in bytes */
40106 unsigned long st_blksize; /* blocksize for filesystem I/O */
40107 unsigned long st_blocks; /* number of blocks allocated */
40108 time_t st_atime; /* time of last access */
40109 time_t st_mtime; /* time of last modification */
40110 time_t st_ctime; /* time of last change */
40114 The integral datatypes conform to the definitions given in the
40115 appropriate section (see @ref{Integral Datatypes}, for details) so this
40116 structure is of size 64 bytes.
40118 The values of several fields have a restricted meaning and/or
40124 A value of 0 represents a file, 1 the console.
40127 No valid meaning for the target. Transmitted unchanged.
40130 Valid mode bits are described in @ref{Constants}. Any other
40131 bits have currently no meaning for the target.
40136 No valid meaning for the target. Transmitted unchanged.
40141 These values have a host and file system dependent
40142 accuracy. Especially on Windows hosts, the file system may not
40143 support exact timing values.
40146 The target gets a @code{struct stat} of the above representation and is
40147 responsible for coercing it to the target representation before
40150 Note that due to size differences between the host, target, and protocol
40151 representations of @code{struct stat} members, these members could eventually
40152 get truncated on the target.
40154 @node struct timeval
40155 @unnumberedsubsubsec struct timeval
40156 @cindex struct timeval, in file-i/o protocol
40158 The buffer of type @code{struct timeval} used by the File-I/O protocol
40159 is defined as follows:
40163 time_t tv_sec; /* second */
40164 long tv_usec; /* microsecond */
40168 The integral datatypes conform to the definitions given in the
40169 appropriate section (see @ref{Integral Datatypes}, for details) so this
40170 structure is of size 8 bytes.
40173 @subsection Constants
40174 @cindex constants, in file-i/o protocol
40176 The following values are used for the constants inside of the
40177 protocol. @value{GDBN} and target are responsible for translating these
40178 values before and after the call as needed.
40189 @unnumberedsubsubsec Open Flags
40190 @cindex open flags, in file-i/o protocol
40192 All values are given in hexadecimal representation.
40204 @node mode_t Values
40205 @unnumberedsubsubsec mode_t Values
40206 @cindex mode_t values, in file-i/o protocol
40208 All values are given in octal representation.
40225 @unnumberedsubsubsec Errno Values
40226 @cindex errno values, in file-i/o protocol
40228 All values are given in decimal representation.
40253 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40254 any error value not in the list of supported error numbers.
40257 @unnumberedsubsubsec Lseek Flags
40258 @cindex lseek flags, in file-i/o protocol
40267 @unnumberedsubsubsec Limits
40268 @cindex limits, in file-i/o protocol
40270 All values are given in decimal representation.
40273 INT_MIN -2147483648
40275 UINT_MAX 4294967295
40276 LONG_MIN -9223372036854775808
40277 LONG_MAX 9223372036854775807
40278 ULONG_MAX 18446744073709551615
40281 @node File-I/O Examples
40282 @subsection File-I/O Examples
40283 @cindex file-i/o examples
40285 Example sequence of a write call, file descriptor 3, buffer is at target
40286 address 0x1234, 6 bytes should be written:
40289 <- @code{Fwrite,3,1234,6}
40290 @emph{request memory read from target}
40293 @emph{return "6 bytes written"}
40297 Example sequence of a read call, file descriptor 3, buffer is at target
40298 address 0x1234, 6 bytes should be read:
40301 <- @code{Fread,3,1234,6}
40302 @emph{request memory write to target}
40303 -> @code{X1234,6:XXXXXX}
40304 @emph{return "6 bytes read"}
40308 Example sequence of a read call, call fails on the host due to invalid
40309 file descriptor (@code{EBADF}):
40312 <- @code{Fread,3,1234,6}
40316 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40320 <- @code{Fread,3,1234,6}
40325 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40329 <- @code{Fread,3,1234,6}
40330 -> @code{X1234,6:XXXXXX}
40334 @node Library List Format
40335 @section Library List Format
40336 @cindex library list format, remote protocol
40338 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40339 same process as your application to manage libraries. In this case,
40340 @value{GDBN} can use the loader's symbol table and normal memory
40341 operations to maintain a list of shared libraries. On other
40342 platforms, the operating system manages loaded libraries.
40343 @value{GDBN} can not retrieve the list of currently loaded libraries
40344 through memory operations, so it uses the @samp{qXfer:libraries:read}
40345 packet (@pxref{qXfer library list read}) instead. The remote stub
40346 queries the target's operating system and reports which libraries
40349 The @samp{qXfer:libraries:read} packet returns an XML document which
40350 lists loaded libraries and their offsets. Each library has an
40351 associated name and one or more segment or section base addresses,
40352 which report where the library was loaded in memory.
40354 For the common case of libraries that are fully linked binaries, the
40355 library should have a list of segments. If the target supports
40356 dynamic linking of a relocatable object file, its library XML element
40357 should instead include a list of allocated sections. The segment or
40358 section bases are start addresses, not relocation offsets; they do not
40359 depend on the library's link-time base addresses.
40361 @value{GDBN} must be linked with the Expat library to support XML
40362 library lists. @xref{Expat}.
40364 A simple memory map, with one loaded library relocated by a single
40365 offset, looks like this:
40369 <library name="/lib/libc.so.6">
40370 <segment address="0x10000000"/>
40375 Another simple memory map, with one loaded library with three
40376 allocated sections (.text, .data, .bss), looks like this:
40380 <library name="sharedlib.o">
40381 <section address="0x10000000"/>
40382 <section address="0x20000000"/>
40383 <section address="0x30000000"/>
40388 The format of a library list is described by this DTD:
40391 <!-- library-list: Root element with versioning -->
40392 <!ELEMENT library-list (library)*>
40393 <!ATTLIST library-list version CDATA #FIXED "1.0">
40394 <!ELEMENT library (segment*, section*)>
40395 <!ATTLIST library name CDATA #REQUIRED>
40396 <!ELEMENT segment EMPTY>
40397 <!ATTLIST segment address CDATA #REQUIRED>
40398 <!ELEMENT section EMPTY>
40399 <!ATTLIST section address CDATA #REQUIRED>
40402 In addition, segments and section descriptors cannot be mixed within a
40403 single library element, and you must supply at least one segment or
40404 section for each library.
40406 @node Library List Format for SVR4 Targets
40407 @section Library List Format for SVR4 Targets
40408 @cindex library list format, remote protocol
40410 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40411 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40412 shared libraries. Still a special library list provided by this packet is
40413 more efficient for the @value{GDBN} remote protocol.
40415 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40416 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40417 target, the following parameters are reported:
40421 @code{name}, the absolute file name from the @code{l_name} field of
40422 @code{struct link_map}.
40424 @code{lm} with address of @code{struct link_map} used for TLS
40425 (Thread Local Storage) access.
40427 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40428 @code{struct link_map}. For prelinked libraries this is not an absolute
40429 memory address. It is a displacement of absolute memory address against
40430 address the file was prelinked to during the library load.
40432 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40435 Additionally the single @code{main-lm} attribute specifies address of
40436 @code{struct link_map} used for the main executable. This parameter is used
40437 for TLS access and its presence is optional.
40439 @value{GDBN} must be linked with the Expat library to support XML
40440 SVR4 library lists. @xref{Expat}.
40442 A simple memory map, with two loaded libraries (which do not use prelink),
40446 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40447 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40449 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40451 </library-list-svr>
40454 The format of an SVR4 library list is described by this DTD:
40457 <!-- library-list-svr4: Root element with versioning -->
40458 <!ELEMENT library-list-svr4 (library)*>
40459 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40460 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40461 <!ELEMENT library EMPTY>
40462 <!ATTLIST library name CDATA #REQUIRED>
40463 <!ATTLIST library lm CDATA #REQUIRED>
40464 <!ATTLIST library l_addr CDATA #REQUIRED>
40465 <!ATTLIST library l_ld CDATA #REQUIRED>
40468 @node Memory Map Format
40469 @section Memory Map Format
40470 @cindex memory map format
40472 To be able to write into flash memory, @value{GDBN} needs to obtain a
40473 memory map from the target. This section describes the format of the
40476 The memory map is obtained using the @samp{qXfer:memory-map:read}
40477 (@pxref{qXfer memory map read}) packet and is an XML document that
40478 lists memory regions.
40480 @value{GDBN} must be linked with the Expat library to support XML
40481 memory maps. @xref{Expat}.
40483 The top-level structure of the document is shown below:
40486 <?xml version="1.0"?>
40487 <!DOCTYPE memory-map
40488 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40489 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40495 Each region can be either:
40500 A region of RAM starting at @var{addr} and extending for @var{length}
40504 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40509 A region of read-only memory:
40512 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40517 A region of flash memory, with erasure blocks @var{blocksize}
40521 <memory type="flash" start="@var{addr}" length="@var{length}">
40522 <property name="blocksize">@var{blocksize}</property>
40528 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40529 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40530 packets to write to addresses in such ranges.
40532 The formal DTD for memory map format is given below:
40535 <!-- ................................................... -->
40536 <!-- Memory Map XML DTD ................................ -->
40537 <!-- File: memory-map.dtd .............................. -->
40538 <!-- .................................... .............. -->
40539 <!-- memory-map.dtd -->
40540 <!-- memory-map: Root element with versioning -->
40541 <!ELEMENT memory-map (memory | property)>
40542 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40543 <!ELEMENT memory (property)>
40544 <!-- memory: Specifies a memory region,
40545 and its type, or device. -->
40546 <!ATTLIST memory type CDATA #REQUIRED
40547 start CDATA #REQUIRED
40548 length CDATA #REQUIRED
40549 device CDATA #IMPLIED>
40550 <!-- property: Generic attribute tag -->
40551 <!ELEMENT property (#PCDATA | property)*>
40552 <!ATTLIST property name CDATA #REQUIRED>
40555 @node Thread List Format
40556 @section Thread List Format
40557 @cindex thread list format
40559 To efficiently update the list of threads and their attributes,
40560 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40561 (@pxref{qXfer threads read}) and obtains the XML document with
40562 the following structure:
40565 <?xml version="1.0"?>
40567 <thread id="id" core="0">
40568 ... description ...
40573 Each @samp{thread} element must have the @samp{id} attribute that
40574 identifies the thread (@pxref{thread-id syntax}). The
40575 @samp{core} attribute, if present, specifies which processor core
40576 the thread was last executing on. The content of the of @samp{thread}
40577 element is interpreted as human-readable auxilliary information.
40579 @node Traceframe Info Format
40580 @section Traceframe Info Format
40581 @cindex traceframe info format
40583 To be able to know which objects in the inferior can be examined when
40584 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40585 memory ranges, registers and trace state variables that have been
40586 collected in a traceframe.
40588 This list is obtained using the @samp{qXfer:traceframe-info:read}
40589 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40591 @value{GDBN} must be linked with the Expat library to support XML
40592 traceframe info discovery. @xref{Expat}.
40594 The top-level structure of the document is shown below:
40597 <?xml version="1.0"?>
40598 <!DOCTYPE traceframe-info
40599 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40600 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40606 Each traceframe block can be either:
40611 A region of collected memory starting at @var{addr} and extending for
40612 @var{length} bytes from there:
40615 <memory start="@var{addr}" length="@var{length}"/>
40620 The formal DTD for the traceframe info format is given below:
40623 <!ELEMENT traceframe-info (memory)* >
40624 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40626 <!ELEMENT memory EMPTY>
40627 <!ATTLIST memory start CDATA #REQUIRED
40628 length CDATA #REQUIRED>
40631 @node Branch Trace Format
40632 @section Branch Trace Format
40633 @cindex branch trace format
40635 In order to display the branch trace of an inferior thread,
40636 @value{GDBN} needs to obtain the list of branches. This list is
40637 represented as list of sequential code blocks that are connected via
40638 branches. The code in each block has been executed sequentially.
40640 This list is obtained using the @samp{qXfer:btrace:read}
40641 (@pxref{qXfer btrace read}) packet and is an XML document.
40643 @value{GDBN} must be linked with the Expat library to support XML
40644 traceframe info discovery. @xref{Expat}.
40646 The top-level structure of the document is shown below:
40649 <?xml version="1.0"?>
40651 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40652 "http://sourceware.org/gdb/gdb-btrace.dtd">
40661 A block of sequentially executed instructions starting at @var{begin}
40662 and ending at @var{end}:
40665 <block begin="@var{begin}" end="@var{end}"/>
40670 The formal DTD for the branch trace format is given below:
40673 <!ELEMENT btrace (block)* >
40674 <!ATTLIST btrace version CDATA #FIXED "1.0">
40676 <!ELEMENT block EMPTY>
40677 <!ATTLIST block begin CDATA #REQUIRED
40678 end CDATA #REQUIRED>
40681 @include agentexpr.texi
40683 @node Target Descriptions
40684 @appendix Target Descriptions
40685 @cindex target descriptions
40687 One of the challenges of using @value{GDBN} to debug embedded systems
40688 is that there are so many minor variants of each processor
40689 architecture in use. It is common practice for vendors to start with
40690 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40691 and then make changes to adapt it to a particular market niche. Some
40692 architectures have hundreds of variants, available from dozens of
40693 vendors. This leads to a number of problems:
40697 With so many different customized processors, it is difficult for
40698 the @value{GDBN} maintainers to keep up with the changes.
40700 Since individual variants may have short lifetimes or limited
40701 audiences, it may not be worthwhile to carry information about every
40702 variant in the @value{GDBN} source tree.
40704 When @value{GDBN} does support the architecture of the embedded system
40705 at hand, the task of finding the correct architecture name to give the
40706 @command{set architecture} command can be error-prone.
40709 To address these problems, the @value{GDBN} remote protocol allows a
40710 target system to not only identify itself to @value{GDBN}, but to
40711 actually describe its own features. This lets @value{GDBN} support
40712 processor variants it has never seen before --- to the extent that the
40713 descriptions are accurate, and that @value{GDBN} understands them.
40715 @value{GDBN} must be linked with the Expat library to support XML
40716 target descriptions. @xref{Expat}.
40719 * Retrieving Descriptions:: How descriptions are fetched from a target.
40720 * Target Description Format:: The contents of a target description.
40721 * Predefined Target Types:: Standard types available for target
40723 * Standard Target Features:: Features @value{GDBN} knows about.
40726 @node Retrieving Descriptions
40727 @section Retrieving Descriptions
40729 Target descriptions can be read from the target automatically, or
40730 specified by the user manually. The default behavior is to read the
40731 description from the target. @value{GDBN} retrieves it via the remote
40732 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40733 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40734 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40735 XML document, of the form described in @ref{Target Description
40738 Alternatively, you can specify a file to read for the target description.
40739 If a file is set, the target will not be queried. The commands to
40740 specify a file are:
40743 @cindex set tdesc filename
40744 @item set tdesc filename @var{path}
40745 Read the target description from @var{path}.
40747 @cindex unset tdesc filename
40748 @item unset tdesc filename
40749 Do not read the XML target description from a file. @value{GDBN}
40750 will use the description supplied by the current target.
40752 @cindex show tdesc filename
40753 @item show tdesc filename
40754 Show the filename to read for a target description, if any.
40758 @node Target Description Format
40759 @section Target Description Format
40760 @cindex target descriptions, XML format
40762 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40763 document which complies with the Document Type Definition provided in
40764 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40765 means you can use generally available tools like @command{xmllint} to
40766 check that your feature descriptions are well-formed and valid.
40767 However, to help people unfamiliar with XML write descriptions for
40768 their targets, we also describe the grammar here.
40770 Target descriptions can identify the architecture of the remote target
40771 and (for some architectures) provide information about custom register
40772 sets. They can also identify the OS ABI of the remote target.
40773 @value{GDBN} can use this information to autoconfigure for your
40774 target, or to warn you if you connect to an unsupported target.
40776 Here is a simple target description:
40779 <target version="1.0">
40780 <architecture>i386:x86-64</architecture>
40785 This minimal description only says that the target uses
40786 the x86-64 architecture.
40788 A target description has the following overall form, with [ ] marking
40789 optional elements and @dots{} marking repeatable elements. The elements
40790 are explained further below.
40793 <?xml version="1.0"?>
40794 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40795 <target version="1.0">
40796 @r{[}@var{architecture}@r{]}
40797 @r{[}@var{osabi}@r{]}
40798 @r{[}@var{compatible}@r{]}
40799 @r{[}@var{feature}@dots{}@r{]}
40804 The description is generally insensitive to whitespace and line
40805 breaks, under the usual common-sense rules. The XML version
40806 declaration and document type declaration can generally be omitted
40807 (@value{GDBN} does not require them), but specifying them may be
40808 useful for XML validation tools. The @samp{version} attribute for
40809 @samp{<target>} may also be omitted, but we recommend
40810 including it; if future versions of @value{GDBN} use an incompatible
40811 revision of @file{gdb-target.dtd}, they will detect and report
40812 the version mismatch.
40814 @subsection Inclusion
40815 @cindex target descriptions, inclusion
40818 @cindex <xi:include>
40821 It can sometimes be valuable to split a target description up into
40822 several different annexes, either for organizational purposes, or to
40823 share files between different possible target descriptions. You can
40824 divide a description into multiple files by replacing any element of
40825 the target description with an inclusion directive of the form:
40828 <xi:include href="@var{document}"/>
40832 When @value{GDBN} encounters an element of this form, it will retrieve
40833 the named XML @var{document}, and replace the inclusion directive with
40834 the contents of that document. If the current description was read
40835 using @samp{qXfer}, then so will be the included document;
40836 @var{document} will be interpreted as the name of an annex. If the
40837 current description was read from a file, @value{GDBN} will look for
40838 @var{document} as a file in the same directory where it found the
40839 original description.
40841 @subsection Architecture
40842 @cindex <architecture>
40844 An @samp{<architecture>} element has this form:
40847 <architecture>@var{arch}</architecture>
40850 @var{arch} is one of the architectures from the set accepted by
40851 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40854 @cindex @code{<osabi>}
40856 This optional field was introduced in @value{GDBN} version 7.0.
40857 Previous versions of @value{GDBN} ignore it.
40859 An @samp{<osabi>} element has this form:
40862 <osabi>@var{abi-name}</osabi>
40865 @var{abi-name} is an OS ABI name from the same selection accepted by
40866 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40868 @subsection Compatible Architecture
40869 @cindex @code{<compatible>}
40871 This optional field was introduced in @value{GDBN} version 7.0.
40872 Previous versions of @value{GDBN} ignore it.
40874 A @samp{<compatible>} element has this form:
40877 <compatible>@var{arch}</compatible>
40880 @var{arch} is one of the architectures from the set accepted by
40881 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40883 A @samp{<compatible>} element is used to specify that the target
40884 is able to run binaries in some other than the main target architecture
40885 given by the @samp{<architecture>} element. For example, on the
40886 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40887 or @code{powerpc:common64}, but the system is able to run binaries
40888 in the @code{spu} architecture as well. The way to describe this
40889 capability with @samp{<compatible>} is as follows:
40892 <architecture>powerpc:common</architecture>
40893 <compatible>spu</compatible>
40896 @subsection Features
40899 Each @samp{<feature>} describes some logical portion of the target
40900 system. Features are currently used to describe available CPU
40901 registers and the types of their contents. A @samp{<feature>} element
40905 <feature name="@var{name}">
40906 @r{[}@var{type}@dots{}@r{]}
40912 Each feature's name should be unique within the description. The name
40913 of a feature does not matter unless @value{GDBN} has some special
40914 knowledge of the contents of that feature; if it does, the feature
40915 should have its standard name. @xref{Standard Target Features}.
40919 Any register's value is a collection of bits which @value{GDBN} must
40920 interpret. The default interpretation is a two's complement integer,
40921 but other types can be requested by name in the register description.
40922 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40923 Target Types}), and the description can define additional composite types.
40925 Each type element must have an @samp{id} attribute, which gives
40926 a unique (within the containing @samp{<feature>}) name to the type.
40927 Types must be defined before they are used.
40930 Some targets offer vector registers, which can be treated as arrays
40931 of scalar elements. These types are written as @samp{<vector>} elements,
40932 specifying the array element type, @var{type}, and the number of elements,
40936 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40940 If a register's value is usefully viewed in multiple ways, define it
40941 with a union type containing the useful representations. The
40942 @samp{<union>} element contains one or more @samp{<field>} elements,
40943 each of which has a @var{name} and a @var{type}:
40946 <union id="@var{id}">
40947 <field name="@var{name}" type="@var{type}"/>
40953 If a register's value is composed from several separate values, define
40954 it with a structure type. There are two forms of the @samp{<struct>}
40955 element; a @samp{<struct>} element must either contain only bitfields
40956 or contain no bitfields. If the structure contains only bitfields,
40957 its total size in bytes must be specified, each bitfield must have an
40958 explicit start and end, and bitfields are automatically assigned an
40959 integer type. The field's @var{start} should be less than or
40960 equal to its @var{end}, and zero represents the least significant bit.
40963 <struct id="@var{id}" size="@var{size}">
40964 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40969 If the structure contains no bitfields, then each field has an
40970 explicit type, and no implicit padding is added.
40973 <struct id="@var{id}">
40974 <field name="@var{name}" type="@var{type}"/>
40980 If a register's value is a series of single-bit flags, define it with
40981 a flags type. The @samp{<flags>} element has an explicit @var{size}
40982 and contains one or more @samp{<field>} elements. Each field has a
40983 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40987 <flags id="@var{id}" size="@var{size}">
40988 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40993 @subsection Registers
40996 Each register is represented as an element with this form:
40999 <reg name="@var{name}"
41000 bitsize="@var{size}"
41001 @r{[}regnum="@var{num}"@r{]}
41002 @r{[}save-restore="@var{save-restore}"@r{]}
41003 @r{[}type="@var{type}"@r{]}
41004 @r{[}group="@var{group}"@r{]}/>
41008 The components are as follows:
41013 The register's name; it must be unique within the target description.
41016 The register's size, in bits.
41019 The register's number. If omitted, a register's number is one greater
41020 than that of the previous register (either in the current feature or in
41021 a preceding feature); the first register in the target description
41022 defaults to zero. This register number is used to read or write
41023 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41024 packets, and registers appear in the @code{g} and @code{G} packets
41025 in order of increasing register number.
41028 Whether the register should be preserved across inferior function
41029 calls; this must be either @code{yes} or @code{no}. The default is
41030 @code{yes}, which is appropriate for most registers except for
41031 some system control registers; this is not related to the target's
41035 The type of the register. @var{type} may be a predefined type, a type
41036 defined in the current feature, or one of the special types @code{int}
41037 and @code{float}. @code{int} is an integer type of the correct size
41038 for @var{bitsize}, and @code{float} is a floating point type (in the
41039 architecture's normal floating point format) of the correct size for
41040 @var{bitsize}. The default is @code{int}.
41043 The register group to which this register belongs. @var{group} must
41044 be either @code{general}, @code{float}, or @code{vector}. If no
41045 @var{group} is specified, @value{GDBN} will not display the register
41046 in @code{info registers}.
41050 @node Predefined Target Types
41051 @section Predefined Target Types
41052 @cindex target descriptions, predefined types
41054 Type definitions in the self-description can build up composite types
41055 from basic building blocks, but can not define fundamental types. Instead,
41056 standard identifiers are provided by @value{GDBN} for the fundamental
41057 types. The currently supported types are:
41066 Signed integer types holding the specified number of bits.
41073 Unsigned integer types holding the specified number of bits.
41077 Pointers to unspecified code and data. The program counter and
41078 any dedicated return address register may be marked as code
41079 pointers; printing a code pointer converts it into a symbolic
41080 address. The stack pointer and any dedicated address registers
41081 may be marked as data pointers.
41084 Single precision IEEE floating point.
41087 Double precision IEEE floating point.
41090 The 12-byte extended precision format used by ARM FPA registers.
41093 The 10-byte extended precision format used by x87 registers.
41096 32bit @sc{eflags} register used by x86.
41099 32bit @sc{mxcsr} register used by x86.
41103 @node Standard Target Features
41104 @section Standard Target Features
41105 @cindex target descriptions, standard features
41107 A target description must contain either no registers or all the
41108 target's registers. If the description contains no registers, then
41109 @value{GDBN} will assume a default register layout, selected based on
41110 the architecture. If the description contains any registers, the
41111 default layout will not be used; the standard registers must be
41112 described in the target description, in such a way that @value{GDBN}
41113 can recognize them.
41115 This is accomplished by giving specific names to feature elements
41116 which contain standard registers. @value{GDBN} will look for features
41117 with those names and verify that they contain the expected registers;
41118 if any known feature is missing required registers, or if any required
41119 feature is missing, @value{GDBN} will reject the target
41120 description. You can add additional registers to any of the
41121 standard features --- @value{GDBN} will display them just as if
41122 they were added to an unrecognized feature.
41124 This section lists the known features and their expected contents.
41125 Sample XML documents for these features are included in the
41126 @value{GDBN} source tree, in the directory @file{gdb/features}.
41128 Names recognized by @value{GDBN} should include the name of the
41129 company or organization which selected the name, and the overall
41130 architecture to which the feature applies; so e.g.@: the feature
41131 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41133 The names of registers are not case sensitive for the purpose
41134 of recognizing standard features, but @value{GDBN} will only display
41135 registers using the capitalization used in the description.
41138 * AArch64 Features::
41143 * PowerPC Features::
41148 @node AArch64 Features
41149 @subsection AArch64 Features
41150 @cindex target descriptions, AArch64 features
41152 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41153 targets. It should contain registers @samp{x0} through @samp{x30},
41154 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41156 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41157 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41161 @subsection ARM Features
41162 @cindex target descriptions, ARM features
41164 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41166 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41167 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41169 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41170 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41171 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41174 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41175 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41177 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41178 it should contain at least registers @samp{wR0} through @samp{wR15} and
41179 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41180 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41182 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41183 should contain at least registers @samp{d0} through @samp{d15}. If
41184 they are present, @samp{d16} through @samp{d31} should also be included.
41185 @value{GDBN} will synthesize the single-precision registers from
41186 halves of the double-precision registers.
41188 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41189 need to contain registers; it instructs @value{GDBN} to display the
41190 VFP double-precision registers as vectors and to synthesize the
41191 quad-precision registers from pairs of double-precision registers.
41192 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41193 be present and include 32 double-precision registers.
41195 @node i386 Features
41196 @subsection i386 Features
41197 @cindex target descriptions, i386 features
41199 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41200 targets. It should describe the following registers:
41204 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41206 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41208 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41209 @samp{fs}, @samp{gs}
41211 @samp{st0} through @samp{st7}
41213 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41214 @samp{foseg}, @samp{fooff} and @samp{fop}
41217 The register sets may be different, depending on the target.
41219 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41220 describe registers:
41224 @samp{xmm0} through @samp{xmm7} for i386
41226 @samp{xmm0} through @samp{xmm15} for amd64
41231 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41232 @samp{org.gnu.gdb.i386.sse} feature. It should
41233 describe the upper 128 bits of @sc{ymm} registers:
41237 @samp{ymm0h} through @samp{ymm7h} for i386
41239 @samp{ymm0h} through @samp{ymm15h} for amd64
41242 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41243 describe a single register, @samp{orig_eax}.
41245 @node MIPS Features
41246 @subsection @acronym{MIPS} Features
41247 @cindex target descriptions, @acronym{MIPS} features
41249 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41250 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41251 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41254 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41255 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41256 registers. They may be 32-bit or 64-bit depending on the target.
41258 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41259 it may be optional in a future version of @value{GDBN}. It should
41260 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41261 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41263 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41264 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41265 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41266 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41268 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41269 contain a single register, @samp{restart}, which is used by the
41270 Linux kernel to control restartable syscalls.
41272 @node M68K Features
41273 @subsection M68K Features
41274 @cindex target descriptions, M68K features
41277 @item @samp{org.gnu.gdb.m68k.core}
41278 @itemx @samp{org.gnu.gdb.coldfire.core}
41279 @itemx @samp{org.gnu.gdb.fido.core}
41280 One of those features must be always present.
41281 The feature that is present determines which flavor of m68k is
41282 used. The feature that is present should contain registers
41283 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41284 @samp{sp}, @samp{ps} and @samp{pc}.
41286 @item @samp{org.gnu.gdb.coldfire.fp}
41287 This feature is optional. If present, it should contain registers
41288 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41292 @node PowerPC Features
41293 @subsection PowerPC Features
41294 @cindex target descriptions, PowerPC features
41296 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41297 targets. It should contain registers @samp{r0} through @samp{r31},
41298 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41299 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41301 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41302 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41304 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41305 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41308 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41309 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41310 will combine these registers with the floating point registers
41311 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41312 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41313 through @samp{vs63}, the set of vector registers for POWER7.
41315 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41316 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41317 @samp{spefscr}. SPE targets should provide 32-bit registers in
41318 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41319 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41320 these to present registers @samp{ev0} through @samp{ev31} to the
41323 @node TIC6x Features
41324 @subsection TMS320C6x Features
41325 @cindex target descriptions, TIC6x features
41326 @cindex target descriptions, TMS320C6x features
41327 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41328 targets. It should contain registers @samp{A0} through @samp{A15},
41329 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41331 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41332 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41333 through @samp{B31}.
41335 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41336 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41338 @node Operating System Information
41339 @appendix Operating System Information
41340 @cindex operating system information
41346 Users of @value{GDBN} often wish to obtain information about the state of
41347 the operating system running on the target---for example the list of
41348 processes, or the list of open files. This section describes the
41349 mechanism that makes it possible. This mechanism is similar to the
41350 target features mechanism (@pxref{Target Descriptions}), but focuses
41351 on a different aspect of target.
41353 Operating system information is retrived from the target via the
41354 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41355 read}). The object name in the request should be @samp{osdata}, and
41356 the @var{annex} identifies the data to be fetched.
41359 @appendixsection Process list
41360 @cindex operating system information, process list
41362 When requesting the process list, the @var{annex} field in the
41363 @samp{qXfer} request should be @samp{processes}. The returned data is
41364 an XML document. The formal syntax of this document is defined in
41365 @file{gdb/features/osdata.dtd}.
41367 An example document is:
41370 <?xml version="1.0"?>
41371 <!DOCTYPE target SYSTEM "osdata.dtd">
41372 <osdata type="processes">
41374 <column name="pid">1</column>
41375 <column name="user">root</column>
41376 <column name="command">/sbin/init</column>
41377 <column name="cores">1,2,3</column>
41382 Each item should include a column whose name is @samp{pid}. The value
41383 of that column should identify the process on the target. The
41384 @samp{user} and @samp{command} columns are optional, and will be
41385 displayed by @value{GDBN}. The @samp{cores} column, if present,
41386 should contain a comma-separated list of cores that this process
41387 is running on. Target may provide additional columns,
41388 which @value{GDBN} currently ignores.
41390 @node Trace File Format
41391 @appendix Trace File Format
41392 @cindex trace file format
41394 The trace file comes in three parts: a header, a textual description
41395 section, and a trace frame section with binary data.
41397 The header has the form @code{\x7fTRACE0\n}. The first byte is
41398 @code{0x7f} so as to indicate that the file contains binary data,
41399 while the @code{0} is a version number that may have different values
41402 The description section consists of multiple lines of @sc{ascii} text
41403 separated by newline characters (@code{0xa}). The lines may include a
41404 variety of optional descriptive or context-setting information, such
41405 as tracepoint definitions or register set size. @value{GDBN} will
41406 ignore any line that it does not recognize. An empty line marks the end
41409 @c FIXME add some specific types of data
41411 The trace frame section consists of a number of consecutive frames.
41412 Each frame begins with a two-byte tracepoint number, followed by a
41413 four-byte size giving the amount of data in the frame. The data in
41414 the frame consists of a number of blocks, each introduced by a
41415 character indicating its type (at least register, memory, and trace
41416 state variable). The data in this section is raw binary, not a
41417 hexadecimal or other encoding; its endianness matches the target's
41420 @c FIXME bi-arch may require endianness/arch info in description section
41423 @item R @var{bytes}
41424 Register block. The number and ordering of bytes matches that of a
41425 @code{g} packet in the remote protocol. Note that these are the
41426 actual bytes, in target order and @value{GDBN} register order, not a
41427 hexadecimal encoding.
41429 @item M @var{address} @var{length} @var{bytes}...
41430 Memory block. This is a contiguous block of memory, at the 8-byte
41431 address @var{address}, with a 2-byte length @var{length}, followed by
41432 @var{length} bytes.
41434 @item V @var{number} @var{value}
41435 Trace state variable block. This records the 8-byte signed value
41436 @var{value} of trace state variable numbered @var{number}.
41440 Future enhancements of the trace file format may include additional types
41443 @node Index Section Format
41444 @appendix @code{.gdb_index} section format
41445 @cindex .gdb_index section format
41446 @cindex index section format
41448 This section documents the index section that is created by @code{save
41449 gdb-index} (@pxref{Index Files}). The index section is
41450 DWARF-specific; some knowledge of DWARF is assumed in this
41453 The mapped index file format is designed to be directly
41454 @code{mmap}able on any architecture. In most cases, a datum is
41455 represented using a little-endian 32-bit integer value, called an
41456 @code{offset_type}. Big endian machines must byte-swap the values
41457 before using them. Exceptions to this rule are noted. The data is
41458 laid out such that alignment is always respected.
41460 A mapped index consists of several areas, laid out in order.
41464 The file header. This is a sequence of values, of @code{offset_type}
41465 unless otherwise noted:
41469 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41470 Version 4 uses a different hashing function from versions 5 and 6.
41471 Version 6 includes symbols for inlined functions, whereas versions 4
41472 and 5 do not. Version 7 adds attributes to the CU indices in the
41473 symbol table. Version 8 specifies that symbols from DWARF type units
41474 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41475 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41477 @value{GDBN} will only read version 4, 5, or 6 indices
41478 by specifying @code{set use-deprecated-index-sections on}.
41479 GDB has a workaround for potentially broken version 7 indices so it is
41480 currently not flagged as deprecated.
41483 The offset, from the start of the file, of the CU list.
41486 The offset, from the start of the file, of the types CU list. Note
41487 that this area can be empty, in which case this offset will be equal
41488 to the next offset.
41491 The offset, from the start of the file, of the address area.
41494 The offset, from the start of the file, of the symbol table.
41497 The offset, from the start of the file, of the constant pool.
41501 The CU list. This is a sequence of pairs of 64-bit little-endian
41502 values, sorted by the CU offset. The first element in each pair is
41503 the offset of a CU in the @code{.debug_info} section. The second
41504 element in each pair is the length of that CU. References to a CU
41505 elsewhere in the map are done using a CU index, which is just the
41506 0-based index into this table. Note that if there are type CUs, then
41507 conceptually CUs and type CUs form a single list for the purposes of
41511 The types CU list. This is a sequence of triplets of 64-bit
41512 little-endian values. In a triplet, the first value is the CU offset,
41513 the second value is the type offset in the CU, and the third value is
41514 the type signature. The types CU list is not sorted.
41517 The address area. The address area consists of a sequence of address
41518 entries. Each address entry has three elements:
41522 The low address. This is a 64-bit little-endian value.
41525 The high address. This is a 64-bit little-endian value. Like
41526 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41529 The CU index. This is an @code{offset_type} value.
41533 The symbol table. This is an open-addressed hash table. The size of
41534 the hash table is always a power of 2.
41536 Each slot in the hash table consists of a pair of @code{offset_type}
41537 values. The first value is the offset of the symbol's name in the
41538 constant pool. The second value is the offset of the CU vector in the
41541 If both values are 0, then this slot in the hash table is empty. This
41542 is ok because while 0 is a valid constant pool index, it cannot be a
41543 valid index for both a string and a CU vector.
41545 The hash value for a table entry is computed by applying an
41546 iterative hash function to the symbol's name. Starting with an
41547 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41548 the string is incorporated into the hash using the formula depending on the
41553 The formula is @code{r = r * 67 + c - 113}.
41555 @item Versions 5 to 7
41556 The formula is @code{r = r * 67 + tolower (c) - 113}.
41559 The terminating @samp{\0} is not incorporated into the hash.
41561 The step size used in the hash table is computed via
41562 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41563 value, and @samp{size} is the size of the hash table. The step size
41564 is used to find the next candidate slot when handling a hash
41567 The names of C@t{++} symbols in the hash table are canonicalized. We
41568 don't currently have a simple description of the canonicalization
41569 algorithm; if you intend to create new index sections, you must read
41573 The constant pool. This is simply a bunch of bytes. It is organized
41574 so that alignment is correct: CU vectors are stored first, followed by
41577 A CU vector in the constant pool is a sequence of @code{offset_type}
41578 values. The first value is the number of CU indices in the vector.
41579 Each subsequent value is the index and symbol attributes of a CU in
41580 the CU list. This element in the hash table is used to indicate which
41581 CUs define the symbol and how the symbol is used.
41582 See below for the format of each CU index+attributes entry.
41584 A string in the constant pool is zero-terminated.
41587 Attributes were added to CU index values in @code{.gdb_index} version 7.
41588 If a symbol has multiple uses within a CU then there is one
41589 CU index+attributes value for each use.
41591 The format of each CU index+attributes entry is as follows
41597 This is the index of the CU in the CU list.
41599 These bits are reserved for future purposes and must be zero.
41601 The kind of the symbol in the CU.
41605 This value is reserved and should not be used.
41606 By reserving zero the full @code{offset_type} value is backwards compatible
41607 with previous versions of the index.
41609 The symbol is a type.
41611 The symbol is a variable or an enum value.
41613 The symbol is a function.
41615 Any other kind of symbol.
41617 These values are reserved.
41621 This bit is zero if the value is global and one if it is static.
41623 The determination of whether a symbol is global or static is complicated.
41624 The authorative reference is the file @file{dwarf2read.c} in
41625 @value{GDBN} sources.
41629 This pseudo-code describes the computation of a symbol's kind and
41630 global/static attributes in the index.
41633 is_external = get_attribute (die, DW_AT_external);
41634 language = get_attribute (cu_die, DW_AT_language);
41637 case DW_TAG_typedef:
41638 case DW_TAG_base_type:
41639 case DW_TAG_subrange_type:
41643 case DW_TAG_enumerator:
41645 is_static = (language != CPLUS && language != JAVA);
41647 case DW_TAG_subprogram:
41649 is_static = ! (is_external || language == ADA);
41651 case DW_TAG_constant:
41653 is_static = ! is_external;
41655 case DW_TAG_variable:
41657 is_static = ! is_external;
41659 case DW_TAG_namespace:
41663 case DW_TAG_class_type:
41664 case DW_TAG_interface_type:
41665 case DW_TAG_structure_type:
41666 case DW_TAG_union_type:
41667 case DW_TAG_enumeration_type:
41669 is_static = (language != CPLUS && language != JAVA);
41678 @node GNU Free Documentation License
41679 @appendix GNU Free Documentation License
41682 @node Concept Index
41683 @unnumbered Concept Index
41687 @node Command and Variable Index
41688 @unnumbered Command, Variable, and Function Index
41693 % I think something like @@colophon should be in texinfo. In the
41695 \long\def\colophon{\hbox to0pt{}\vfill
41696 \centerline{The body of this manual is set in}
41697 \centerline{\fontname\tenrm,}
41698 \centerline{with headings in {\bf\fontname\tenbf}}
41699 \centerline{and examples in {\tt\fontname\tentt}.}
41700 \centerline{{\it\fontname\tenit\/},}
41701 \centerline{{\bf\fontname\tenbf}, and}
41702 \centerline{{\sl\fontname\tensl\/}}
41703 \centerline{are used for emphasis.}\vfill}
41705 % Blame: doc@@cygnus.com, 1991.