1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
3 @c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
4 @c Free Software Foundation, Inc.
5 @c UPDATE!! On future updates--
6 @c (1) check for new machine-dep cmdline options in
7 @c md_parse_option definitions in config/tc-*.c
8 @c (2) for platform-specific directives, examine md_pseudo_op
10 @c (3) for object-format specific directives, examine obj_pseudo_op
12 @c (4) portable directives in potable[] in read.c
16 @macro gcctabopt{body}
19 @c defaults, config file may override:
24 @include asconfig.texi
29 @c common OR combinations of conditions
55 @set abnormal-separator
59 @settitle Using @value{AS}
62 @settitle Using @value{AS} (@value{TARGET})
64 @setchapternewpage odd
69 @c WARE! Some of the machine-dependent sections contain tables of machine
70 @c instructions. Except in multi-column format, these tables look silly.
71 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
72 @c the multi-col format is faked within @example sections.
74 @c Again unfortunately, the natural size that fits on a page, for these tables,
75 @c is different depending on whether or not smallbook is turned on.
76 @c This matters, because of order: text flow switches columns at each page
79 @c The format faked in this source works reasonably well for smallbook,
80 @c not well for the default large-page format. This manual expects that if you
81 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
82 @c tables in question. You can turn on one without the other at your
83 @c discretion, of course.
86 @c the insn tables look just as silly in info files regardless of smallbook,
87 @c might as well show 'em anyways.
91 @dircategory Software development
93 * As: (as). The GNU assembler.
94 * Gas: (as). The GNU assembler.
102 This file documents the GNU Assembler "@value{AS}".
104 @c man begin COPYRIGHT
105 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
106 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation,
109 Permission is granted to copy, distribute and/or modify this document
110 under the terms of the GNU Free Documentation License, Version 1.3
111 or any later version published by the Free Software Foundation;
112 with no Invariant Sections, with no Front-Cover Texts, and with no
113 Back-Cover Texts. A copy of the license is included in the
114 section entitled ``GNU Free Documentation License''.
120 @title Using @value{AS}
121 @subtitle The @sc{gnu} Assembler
123 @subtitle for the @value{TARGET} family
125 @ifset VERSION_PACKAGE
127 @subtitle @value{VERSION_PACKAGE}
130 @subtitle Version @value{VERSION}
133 The Free Software Foundation Inc.@: thanks The Nice Computer
134 Company of Australia for loaning Dean Elsner to write the
135 first (Vax) version of @command{as} for Project @sc{gnu}.
136 The proprietors, management and staff of TNCCA thank FSF for
137 distracting the boss while they got some work
140 @author Dean Elsner, Jay Fenlason & friends
144 \hfill {\it Using {\tt @value{AS}}}\par
145 \hfill Edited by Cygnus Support\par
147 %"boxit" macro for figures:
148 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
149 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
150 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
151 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
152 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
155 @vskip 0pt plus 1filll
156 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
157 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation,
160 Permission is granted to copy, distribute and/or modify this document
161 under the terms of the GNU Free Documentation License, Version 1.3
162 or any later version published by the Free Software Foundation;
163 with no Invariant Sections, with no Front-Cover Texts, and with no
164 Back-Cover Texts. A copy of the license is included in the
165 section entitled ``GNU Free Documentation License''.
172 @top Using @value{AS}
174 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
175 @ifset VERSION_PACKAGE
176 @value{VERSION_PACKAGE}
178 version @value{VERSION}.
180 This version of the file describes @command{@value{AS}} configured to generate
181 code for @value{TARGET} architectures.
184 This document is distributed under the terms of the GNU Free
185 Documentation License. A copy of the license is included in the
186 section entitled ``GNU Free Documentation License''.
189 * Overview:: Overview
190 * Invoking:: Command-Line Options
192 * Sections:: Sections and Relocation
194 * Expressions:: Expressions
195 * Pseudo Ops:: Assembler Directives
197 * Object Attributes:: Object Attributes
199 * Machine Dependencies:: Machine Dependent Features
200 * Reporting Bugs:: Reporting Bugs
201 * Acknowledgements:: Who Did What
202 * GNU Free Documentation License:: GNU Free Documentation License
203 * AS Index:: AS Index
210 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
212 This version of the manual describes @command{@value{AS}} configured to generate
213 code for @value{TARGET} architectures.
217 @cindex invocation summary
218 @cindex option summary
219 @cindex summary of options
220 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
221 see @ref{Invoking,,Command-Line Options}.
223 @c man title AS the portable GNU assembler.
227 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
231 @c We don't use deffn and friends for the following because they seem
232 @c to be limited to one line for the header.
234 @c man begin SYNOPSIS
235 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
236 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
237 [@b{--debug-prefix-map} @var{old}=@var{new}]
238 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
239 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
240 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
241 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
242 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
243 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
244 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
245 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
246 [@b{--size-check=[error|warning]}]
247 [@b{--target-help}] [@var{target-options}]
248 [@b{--}|@var{files} @dots{}]
250 @c Target dependent options are listed below. Keep the list sorted.
251 @c Add an empty line for separation.
254 @emph{Target Alpha options:}
256 [@b{-mdebug} | @b{-no-mdebug}]
257 [@b{-replace} | @b{-noreplace}]
258 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
259 [@b{-F}] [@b{-32addr}]
263 @emph{Target ARC options:}
269 @emph{Target ARM options:}
270 @c Don't document the deprecated options
271 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
272 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
273 [@b{-mfpu}=@var{floating-point-format}]
274 [@b{-mfloat-abi}=@var{abi}]
275 [@b{-meabi}=@var{ver}]
278 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
279 @b{-mapcs-reentrant}]
280 [@b{-mthumb-interwork}] [@b{-k}]
284 @emph{Target Blackfin options:}
285 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
292 @emph{Target CRIS options:}
293 [@b{--underscore} | @b{--no-underscore}]
295 [@b{--emulation=criself} | @b{--emulation=crisaout}]
296 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
297 @c Deprecated -- deliberately not documented.
302 @emph{Target D10V options:}
307 @emph{Target D30V options:}
308 [@b{-O}|@b{-n}|@b{-N}]
312 @emph{Target H8/300 options:}
316 @c HPPA has no machine-dependent assembler options (yet).
320 @emph{Target i386 options:}
321 [@b{--32}|@b{--64}] [@b{-n}]
322 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
326 @emph{Target i960 options:}
327 @c see md_parse_option in tc-i960.c
328 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
330 [@b{-b}] [@b{-no-relax}]
334 @emph{Target IA-64 options:}
335 [@b{-mconstant-gp}|@b{-mauto-pic}]
336 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
338 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
339 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
340 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
341 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
345 @emph{Target IP2K options:}
346 [@b{-mip2022}|@b{-mip2022ext}]
350 @emph{Target M32C options:}
351 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
355 @emph{Target M32R options:}
356 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
361 @emph{Target M680X0 options:}
362 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
366 @emph{Target M68HC11 options:}
367 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
368 [@b{-mshort}|@b{-mlong}]
369 [@b{-mshort-double}|@b{-mlong-double}]
370 [@b{--force-long-branches}] [@b{--short-branches}]
371 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
372 [@b{--print-opcodes}] [@b{--generate-example}]
376 @emph{Target MCORE options:}
377 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
378 [@b{-mcpu=[210|340]}]
381 @emph{Target MICROBLAZE options:}
382 @c MicroBlaze has no machine-dependent assembler options.
386 @emph{Target MIPS options:}
387 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
388 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
389 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
390 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
391 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
392 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
393 [@b{-mips64}] [@b{-mips64r2}]
394 [@b{-construct-floats}] [@b{-no-construct-floats}]
395 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
396 [@b{-mips16}] [@b{-no-mips16}]
397 [@b{-msmartmips}] [@b{-mno-smartmips}]
398 [@b{-mips3d}] [@b{-no-mips3d}]
399 [@b{-mdmx}] [@b{-no-mdmx}]
400 [@b{-mdsp}] [@b{-mno-dsp}]
401 [@b{-mdspr2}] [@b{-mno-dspr2}]
402 [@b{-mmt}] [@b{-mno-mt}]
403 [@b{-mfix7000}] [@b{-mno-fix7000}]
404 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
405 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
406 [@b{-mdebug}] [@b{-no-mdebug}]
407 [@b{-mpdr}] [@b{-mno-pdr}]
411 @emph{Target MMIX options:}
412 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
413 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
414 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
415 [@b{--linker-allocated-gregs}]
419 @emph{Target PDP11 options:}
420 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
421 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
422 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
426 @emph{Target picoJava options:}
431 @emph{Target PowerPC options:}
433 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
434 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
435 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-mppc64bridge}|@b{-mbooke}|
436 @b{-mpower4}|@b{-mpr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
437 @b{-mpower7}|@b{-mpw7}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
438 [@b{-many}] [@b{-maltivec}|@b{-mvsx}]
439 [@b{-mregnames}|@b{-mno-regnames}]
440 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
441 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
442 [@b{-msolaris}|@b{-mno-solaris}]
443 [@b{-nops=@var{count}}]
447 @emph{Target RX options:}
448 [@b{-mlittle-endian}|@b{-mbig-endian}]
449 [@b{-m32bit-ints}|@b{-m16bit-ints}]
450 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
454 @emph{Target s390 options:}
455 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
456 [@b{-mregnames}|@b{-mno-regnames}]
457 [@b{-mwarn-areg-zero}]
461 @emph{Target SCORE options:}
462 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
463 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
464 [@b{-march=score7}][@b{-march=score3}]
465 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
469 @emph{Target SPARC options:}
470 @c The order here is important. See c-sparc.texi.
471 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
472 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
473 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
478 @emph{Target TIC54X options:}
479 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
480 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
485 @emph{Target TIC6X options:}
486 [@b{-march=@var{arch}}] [@b{-matomic}|@b{-mno-atomic}]
487 [@b{-mbig-endian}|@b{-mlittle-endian}] [@b{-mdsbt}|@b{-mno-dsbt}]
488 [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}] [@b{-mpic}|@b{-mno-pic}]
493 @emph{Target Z80 options:}
494 [@b{-z80}] [@b{-r800}]
495 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
496 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
497 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
498 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
499 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
500 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
504 @c Z8000 has no machine-dependent assembler options
508 @emph{Target Xtensa options:}
509 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
510 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
511 [@b{--[no-]transform}]
512 [@b{--rename-section} @var{oldname}=@var{newname}]
520 @include at-file.texi
523 Turn on listings, in any of a variety of ways:
527 omit false conditionals
530 omit debugging directives
533 include general information, like @value{AS} version and options passed
536 include high-level source
542 include macro expansions
545 omit forms processing
551 set the name of the listing file
554 You may combine these options; for example, use @samp{-aln} for assembly
555 listing without forms processing. The @samp{=file} option, if used, must be
556 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
559 Begin in alternate macro mode.
561 @xref{Altmacro,,@code{.altmacro}}.
564 @item --compress-debug-sections
565 Compress DWARF debug sections using zlib. The debug sections are renamed
566 to begin with @samp{.zdebug}, and the resulting object file may not be
567 compatible with older linkers and object file utilities.
569 @item --nocompress-debug-sections
570 Do not compress DWARF debug sections. This is the default.
573 Ignored. This option is accepted for script compatibility with calls to
576 @item --debug-prefix-map @var{old}=@var{new}
577 When assembling files in directory @file{@var{old}}, record debugging
578 information describing them as in @file{@var{new}} instead.
580 @item --defsym @var{sym}=@var{value}
581 Define the symbol @var{sym} to be @var{value} before assembling the input file.
582 @var{value} must be an integer constant. As in C, a leading @samp{0x}
583 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
584 value. The value of the symbol can be overridden inside a source file via the
585 use of a @code{.set} pseudo-op.
588 ``fast''---skip whitespace and comment preprocessing (assume source is
593 Generate debugging information for each assembler source line using whichever
594 debug format is preferred by the target. This currently means either STABS,
598 Generate stabs debugging information for each assembler line. This
599 may help debugging assembler code, if the debugger can handle it.
602 Generate stabs debugging information for each assembler line, with GNU
603 extensions that probably only gdb can handle, and that could make other
604 debuggers crash or refuse to read your program. This
605 may help debugging assembler code. Currently the only GNU extension is
606 the location of the current working directory at assembling time.
609 Generate DWARF2 debugging information for each assembler line. This
610 may help debugging assembler code, if the debugger can handle it. Note---this
611 option is only supported by some targets, not all of them.
613 @item --size-check=error
614 @itemx --size-check=warning
615 Issue an error or warning for invalid ELF .size directive.
618 Print a summary of the command line options and exit.
621 Print a summary of all target specific options and exit.
624 Add directory @var{dir} to the search list for @code{.include} directives.
627 Don't warn about signed overflow.
630 @ifclear DIFF-TBL-KLUGE
631 This option is accepted but has no effect on the @value{TARGET} family.
633 @ifset DIFF-TBL-KLUGE
634 Issue warnings when difference tables altered for long displacements.
639 Keep (in the symbol table) local symbols. These symbols start with
640 system-specific local label prefixes, typically @samp{.L} for ELF systems
641 or @samp{L} for traditional a.out systems.
646 @item --listing-lhs-width=@var{number}
647 Set the maximum width, in words, of the output data column for an assembler
648 listing to @var{number}.
650 @item --listing-lhs-width2=@var{number}
651 Set the maximum width, in words, of the output data column for continuation
652 lines in an assembler listing to @var{number}.
654 @item --listing-rhs-width=@var{number}
655 Set the maximum width of an input source line, as displayed in a listing, to
658 @item --listing-cont-lines=@var{number}
659 Set the maximum number of lines printed in a listing for a single line of input
662 @item -o @var{objfile}
663 Name the object-file output from @command{@value{AS}} @var{objfile}.
666 Fold the data section into the text section.
668 @kindex --hash-size=@var{number}
669 Set the default size of GAS's hash tables to a prime number close to
670 @var{number}. Increasing this value can reduce the length of time it takes the
671 assembler to perform its tasks, at the expense of increasing the assembler's
672 memory requirements. Similarly reducing this value can reduce the memory
673 requirements at the expense of speed.
675 @item --reduce-memory-overheads
676 This option reduces GAS's memory requirements, at the expense of making the
677 assembly processes slower. Currently this switch is a synonym for
678 @samp{--hash-size=4051}, but in the future it may have other effects as well.
681 Print the maximum space (in bytes) and total time (in seconds) used by
684 @item --strip-local-absolute
685 Remove local absolute symbols from the outgoing symbol table.
689 Print the @command{as} version.
692 Print the @command{as} version and exit.
696 Suppress warning messages.
698 @item --fatal-warnings
699 Treat warnings as errors.
702 Don't suppress warning messages or treat them as errors.
711 Generate an object file even after errors.
713 @item -- | @var{files} @dots{}
714 Standard input, or source files to assemble.
719 The following options are available when @value{AS} is configured for
724 This option selects the core processor variant.
726 Select either big-endian (-EB) or little-endian (-EL) output.
731 The following options are available when @value{AS} is configured for the ARM
735 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
736 Specify which ARM processor variant is the target.
737 @item -march=@var{architecture}[+@var{extension}@dots{}]
738 Specify which ARM architecture variant is used by the target.
739 @item -mfpu=@var{floating-point-format}
740 Select which Floating Point architecture is the target.
741 @item -mfloat-abi=@var{abi}
742 Select which floating point ABI is in use.
744 Enable Thumb only instruction decoding.
745 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
746 Select which procedure calling convention is in use.
748 Select either big-endian (-EB) or little-endian (-EL) output.
749 @item -mthumb-interwork
750 Specify that the code has been generated with interworking between Thumb and
753 Specify that PIC code has been generated.
758 The following options are available when @value{AS} is configured for
759 the Blackfin processor family.
762 @item -mcpu=@var{processor}@r{[}-@var{sirevision}@r{]}
763 This option specifies the target processor. The optional @var{sirevision}
764 is not used in assembler.
766 Assemble for the FDPIC ABI.
774 See the info pages for documentation of the CRIS-specific options.
778 The following options are available when @value{AS} is configured for
781 @cindex D10V optimization
782 @cindex optimization, D10V
784 Optimize output by parallelizing instructions.
789 The following options are available when @value{AS} is configured for a D30V
792 @cindex D30V optimization
793 @cindex optimization, D30V
795 Optimize output by parallelizing instructions.
799 Warn when nops are generated.
801 @cindex D30V nops after 32-bit multiply
803 Warn when a nop after a 32-bit multiply instruction is generated.
808 The following options are available when @value{AS} is configured for the
809 Intel 80960 processor.
812 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
813 Specify which variant of the 960 architecture is the target.
816 Add code to collect statistics about branches taken.
819 Do not alter compare-and-branch instructions for long displacements;
826 The following options are available when @value{AS} is configured for the
832 Specifies that the extended IP2022 instructions are allowed.
835 Restores the default behaviour, which restricts the permitted instructions to
836 just the basic IP2022 ones.
842 The following options are available when @value{AS} is configured for the
843 Renesas M32C and M16C processors.
848 Assemble M32C instructions.
851 Assemble M16C instructions (the default).
854 Enable support for link-time relaxations.
857 Support H'00 style hex constants in addition to 0x00 style.
863 The following options are available when @value{AS} is configured for the
864 Renesas M32R (formerly Mitsubishi M32R) series.
869 Specify which processor in the M32R family is the target. The default
870 is normally the M32R, but this option changes it to the M32RX.
872 @item --warn-explicit-parallel-conflicts or --Wp
873 Produce warning messages when questionable parallel constructs are
876 @item --no-warn-explicit-parallel-conflicts or --Wnp
877 Do not produce warning messages when questionable parallel constructs are
884 The following options are available when @value{AS} is configured for the
885 Motorola 68000 series.
890 Shorten references to undefined symbols, to one word instead of two.
892 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
893 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
894 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
895 Specify what processor in the 68000 family is the target. The default
896 is normally the 68020, but this can be changed at configuration time.
898 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
899 The target machine does (or does not) have a floating-point coprocessor.
900 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
901 the basic 68000 is not compatible with the 68881, a combination of the
902 two can be specified, since it's possible to do emulation of the
903 coprocessor instructions with the main processor.
905 @item -m68851 | -mno-68851
906 The target machine does (or does not) have a memory-management
907 unit coprocessor. The default is to assume an MMU for 68020 and up.
914 For details about the PDP-11 machine dependent features options,
915 see @ref{PDP-11-Options}.
918 @item -mpic | -mno-pic
919 Generate position-independent (or position-dependent) code. The
920 default is @option{-mpic}.
923 @itemx -mall-extensions
924 Enable all instruction set extensions. This is the default.
926 @item -mno-extensions
927 Disable all instruction set extensions.
929 @item -m@var{extension} | -mno-@var{extension}
930 Enable (or disable) a particular instruction set extension.
933 Enable the instruction set extensions supported by a particular CPU, and
934 disable all other extensions.
936 @item -m@var{machine}
937 Enable the instruction set extensions supported by a particular machine
938 model, and disable all other extensions.
944 The following options are available when @value{AS} is configured for
945 a picoJava processor.
949 @cindex PJ endianness
950 @cindex endianness, PJ
951 @cindex big endian output, PJ
953 Generate ``big endian'' format output.
955 @cindex little endian output, PJ
957 Generate ``little endian'' format output.
963 The following options are available when @value{AS} is configured for the
964 Motorola 68HC11 or 68HC12 series.
968 @item -m68hc11 | -m68hc12 | -m68hcs12
969 Specify what processor is the target. The default is
970 defined by the configuration option when building the assembler.
973 Specify to use the 16-bit integer ABI.
976 Specify to use the 32-bit integer ABI.
979 Specify to use the 32-bit double ABI.
982 Specify to use the 64-bit double ABI.
984 @item --force-long-branches
985 Relative branches are turned into absolute ones. This concerns
986 conditional branches, unconditional branches and branches to a
989 @item -S | --short-branches
990 Do not turn relative branches into absolute ones
991 when the offset is out of range.
993 @item --strict-direct-mode
994 Do not turn the direct addressing mode into extended addressing mode
995 when the instruction does not support direct addressing mode.
997 @item --print-insn-syntax
998 Print the syntax of instruction in case of error.
1000 @item --print-opcodes
1001 print the list of instructions with syntax and then exit.
1003 @item --generate-example
1004 print an example of instruction for each possible instruction and then exit.
1005 This option is only useful for testing @command{@value{AS}}.
1011 The following options are available when @command{@value{AS}} is configured
1012 for the SPARC architecture:
1015 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1016 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1017 Explicitly select a variant of the SPARC architecture.
1019 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1020 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1022 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1023 UltraSPARC extensions.
1025 @item -xarch=v8plus | -xarch=v8plusa
1026 For compatibility with the Solaris v9 assembler. These options are
1027 equivalent to -Av8plus and -Av8plusa, respectively.
1030 Warn when the assembler switches to another architecture.
1035 The following options are available when @value{AS} is configured for the 'c54x
1040 Enable extended addressing mode. All addresses and relocations will assume
1041 extended addressing (usually 23 bits).
1042 @item -mcpu=@var{CPU_VERSION}
1043 Sets the CPU version being compiled for.
1044 @item -merrors-to-file @var{FILENAME}
1045 Redirect error output to a file, for broken systems which don't support such
1046 behaviour in the shell.
1051 The following options are available when @value{AS} is configured for
1052 a @sc{mips} processor.
1056 This option sets the largest size of an object that can be referenced
1057 implicitly with the @code{gp} register. It is only accepted for targets that
1058 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1060 @cindex MIPS endianness
1061 @cindex endianness, MIPS
1062 @cindex big endian output, MIPS
1064 Generate ``big endian'' format output.
1066 @cindex little endian output, MIPS
1068 Generate ``little endian'' format output.
1080 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1081 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1082 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1083 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1084 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1086 correspond to generic
1087 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1088 and @samp{MIPS64 Release 2}
1089 ISA processors, respectively.
1091 @item -march=@var{CPU}
1092 Generate code for a particular @sc{mips} cpu.
1094 @item -mtune=@var{cpu}
1095 Schedule and tune for a particular @sc{mips} cpu.
1099 Cause nops to be inserted if the read of the destination register
1100 of an mfhi or mflo instruction occurs in the following two instructions.
1104 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1105 section instead of the standard ELF .stabs sections.
1109 Control generation of @code{.pdr} sections.
1113 The register sizes are normally inferred from the ISA and ABI, but these
1114 flags force a certain group of registers to be treated as 32 bits wide at
1115 all times. @samp{-mgp32} controls the size of general-purpose registers
1116 and @samp{-mfp32} controls the size of floating-point registers.
1120 Generate code for the MIPS 16 processor. This is equivalent to putting
1121 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1122 turns off this option.
1125 @itemx -mno-smartmips
1126 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1127 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1128 @samp{-mno-smartmips} turns off this option.
1132 Generate code for the MIPS-3D Application Specific Extension.
1133 This tells the assembler to accept MIPS-3D instructions.
1134 @samp{-no-mips3d} turns off this option.
1138 Generate code for the MDMX Application Specific Extension.
1139 This tells the assembler to accept MDMX instructions.
1140 @samp{-no-mdmx} turns off this option.
1144 Generate code for the DSP Release 1 Application Specific Extension.
1145 This tells the assembler to accept DSP Release 1 instructions.
1146 @samp{-mno-dsp} turns off this option.
1150 Generate code for the DSP Release 2 Application Specific Extension.
1151 This option implies -mdsp.
1152 This tells the assembler to accept DSP Release 2 instructions.
1153 @samp{-mno-dspr2} turns off this option.
1157 Generate code for the MT Application Specific Extension.
1158 This tells the assembler to accept MT instructions.
1159 @samp{-mno-mt} turns off this option.
1161 @item --construct-floats
1162 @itemx --no-construct-floats
1163 The @samp{--no-construct-floats} option disables the construction of
1164 double width floating point constants by loading the two halves of the
1165 value into the two single width floating point registers that make up
1166 the double width register. By default @samp{--construct-floats} is
1167 selected, allowing construction of these floating point constants.
1170 @item --emulation=@var{name}
1171 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1172 for some other target, in all respects, including output format (choosing
1173 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1174 debugging information or store symbol table information, and default
1175 endianness. The available configuration names are: @samp{mipsecoff},
1176 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1177 @samp{mipsbelf}. The first two do not alter the default endianness from that
1178 of the primary target for which the assembler was configured; the others change
1179 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1180 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1181 selection in any case.
1183 This option is currently supported only when the primary target
1184 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1185 Furthermore, the primary target or others specified with
1186 @samp{--enable-targets=@dots{}} at configuration time must include support for
1187 the other format, if both are to be available. For example, the Irix 5
1188 configuration includes support for both.
1190 Eventually, this option will support more configurations, with more
1191 fine-grained control over the assembler's behavior, and will be supported for
1195 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1202 Control how to deal with multiplication overflow and division by zero.
1203 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1204 (and only work for Instruction Set Architecture level 2 and higher);
1205 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1209 When this option is used, @command{@value{AS}} will issue a warning every
1210 time it generates a nop instruction from a macro.
1215 The following options are available when @value{AS} is configured for
1221 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1222 The command line option @samp{-nojsri2bsr} can be used to disable it.
1226 Enable or disable the silicon filter behaviour. By default this is disabled.
1227 The default can be overridden by the @samp{-sifilter} command line option.
1230 Alter jump instructions for long displacements.
1232 @item -mcpu=[210|340]
1233 Select the cpu type on the target hardware. This controls which instructions
1237 Assemble for a big endian target.
1240 Assemble for a little endian target.
1246 See the info pages for documentation of the MMIX-specific options.
1250 See the info pages for documentation of the RX-specific options.
1254 The following options are available when @value{AS} is configured for the s390
1260 Select the word size, either 31/32 bits or 64 bits.
1263 Select the architecture mode, either the Enterprise System
1264 Architecture (esa) or the z/Architecture mode (zarch).
1265 @item -march=@var{processor}
1266 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1267 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1269 @itemx -mno-regnames
1270 Allow or disallow symbolic names for registers.
1271 @item -mwarn-areg-zero
1272 Warn whenever the operand for a base or index register has been specified
1273 but evaluates to zero.
1278 The following options are available when @value{AS} is configured for a
1279 TMS320C6000 processor.
1282 @item -march=@var{arch}
1283 Enable (only) instructions from architecture @var{arch}. By default,
1284 all instructions are permitted.
1286 The following values of @var{arch} are accepted: @code{c62x},
1287 @code{c64x}, @code{c64x+}, @code{c67x}, @code{c67x+}, @code{c674x}.
1291 Enable or disable the optional C64x+ atomic operation instructions.
1292 By default, they are enabled if no @option{-march} option is given, or
1293 if an architecture is specified with @option{-march} that implies
1294 these instructions are present (currently, there are no such
1295 architectures); they are disabled if an architecture is specified with
1296 @option{-march} on which the instructions are optional or not
1297 present. This option overrides such a default from the architecture,
1298 independent of the order in which the @option{-march} or
1299 @option{-matomic} or @option{-mno-atomic} options are passed.
1303 The @option{-mdsbt} option causes the assembler to generate the
1304 @code{Tag_ABI_DSBT} attribute with a value of 1, indicating that the
1305 code is using DSBT addressing. The @option{-mno-dsbt} option, the
1306 default, causes the tag to have a value of 0, indicating that the code
1307 does not use DSBT addressing. The linker will emit a warning if
1308 objects of different type (DSBT and non-DSBT) are linked together.
1313 The @option{-mpid=} option causes the assembler to generate the
1314 @code{Tag_ABI_PID} attribute with a value indicating the form of data
1315 addressing used by the code. @option{-mpid=no}, the default,
1316 indicates position-dependent data addressing, @option{-mpid=near}
1317 indicates position-independent addressing with GOT accesses using near
1318 DP addressing, and @option{-mpid=far} indicates position-independent
1319 addressing with GOT accesses using far DP addressing. The linker will
1320 emit a warning if objects built with different settings of this option
1321 are linked together.
1325 The @option{-mpic} option causes the assembler to generate the
1326 @code{Tag_ABI_PIC} attribute with a value of 1, indicating that the
1327 code is using position-independent code addressing, The
1328 @code{-mno-pic} option, the default, causes the tag to have a value of
1329 0, indicating position-dependent code addressing. The linker will
1330 emit a warning if objects of different type (position-dependent and
1331 position-independent) are linked together.
1334 @itemx -mlittle-endian
1335 Generate code for the specified endianness. The default is
1342 The following options are available when @value{AS} is configured for
1343 an Xtensa processor.
1346 @item --text-section-literals | --no-text-section-literals
1347 With @option{--text-@-section-@-literals}, literal pools are interspersed
1348 in the text section. The default is
1349 @option{--no-@-text-@-section-@-literals}, which places literals in a
1350 separate section in the output file. These options only affect literals
1351 referenced via PC-relative @code{L32R} instructions; literals for
1352 absolute mode @code{L32R} instructions are handled separately.
1354 @item --absolute-literals | --no-absolute-literals
1355 Indicate to the assembler whether @code{L32R} instructions use absolute
1356 or PC-relative addressing. The default is to assume absolute addressing
1357 if the Xtensa processor includes the absolute @code{L32R} addressing
1358 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1360 @item --target-align | --no-target-align
1361 Enable or disable automatic alignment to reduce branch penalties at the
1362 expense of some code density. The default is @option{--target-@-align}.
1364 @item --longcalls | --no-longcalls
1365 Enable or disable transformation of call instructions to allow calls
1366 across a greater range of addresses. The default is
1367 @option{--no-@-longcalls}.
1369 @item --transform | --no-transform
1370 Enable or disable all assembler transformations of Xtensa instructions.
1371 The default is @option{--transform};
1372 @option{--no-transform} should be used only in the rare cases when the
1373 instructions must be exactly as specified in the assembly source.
1375 @item --rename-section @var{oldname}=@var{newname}
1376 When generating output sections, rename the @var{oldname} section to
1382 The following options are available when @value{AS} is configured for
1383 a Z80 family processor.
1386 Assemble for Z80 processor.
1388 Assemble for R800 processor.
1389 @item -ignore-undocumented-instructions
1391 Assemble undocumented Z80 instructions that also work on R800 without warning.
1392 @item -ignore-unportable-instructions
1394 Assemble all undocumented Z80 instructions without warning.
1395 @item -warn-undocumented-instructions
1397 Issue a warning for undocumented Z80 instructions that also work on R800.
1398 @item -warn-unportable-instructions
1400 Issue a warning for undocumented Z80 instructions that do not work on R800.
1401 @item -forbid-undocumented-instructions
1403 Treat all undocumented instructions as errors.
1404 @item -forbid-unportable-instructions
1406 Treat undocumented Z80 instructions that do not work on R800 as errors.
1413 * Manual:: Structure of this Manual
1414 * GNU Assembler:: The GNU Assembler
1415 * Object Formats:: Object File Formats
1416 * Command Line:: Command Line
1417 * Input Files:: Input Files
1418 * Object:: Output (Object) File
1419 * Errors:: Error and Warning Messages
1423 @section Structure of this Manual
1425 @cindex manual, structure and purpose
1426 This manual is intended to describe what you need to know to use
1427 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1428 notation for symbols, constants, and expressions; the directives that
1429 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1432 We also cover special features in the @value{TARGET}
1433 configuration of @command{@value{AS}}, including assembler directives.
1436 This manual also describes some of the machine-dependent features of
1437 various flavors of the assembler.
1440 @cindex machine instructions (not covered)
1441 On the other hand, this manual is @emph{not} intended as an introduction
1442 to programming in assembly language---let alone programming in general!
1443 In a similar vein, we make no attempt to introduce the machine
1444 architecture; we do @emph{not} describe the instruction set, standard
1445 mnemonics, registers or addressing modes that are standard to a
1446 particular architecture.
1448 You may want to consult the manufacturer's
1449 machine architecture manual for this information.
1453 For information on the H8/300 machine instruction set, see @cite{H8/300
1454 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1455 Programming Manual} (Renesas).
1458 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1459 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1460 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1461 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1464 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1468 @c I think this is premature---doc@cygnus.com, 17jan1991
1470 Throughout this manual, we assume that you are running @dfn{GNU},
1471 the portable operating system from the @dfn{Free Software
1472 Foundation, Inc.}. This restricts our attention to certain kinds of
1473 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1474 once this assumption is granted examples and definitions need less
1477 @command{@value{AS}} is part of a team of programs that turn a high-level
1478 human-readable series of instructions into a low-level
1479 computer-readable series of instructions. Different versions of
1480 @command{@value{AS}} are used for different kinds of computer.
1483 @c There used to be a section "Terminology" here, which defined
1484 @c "contents", "byte", "word", and "long". Defining "word" to any
1485 @c particular size is confusing when the .word directive may generate 16
1486 @c bits on one machine and 32 bits on another; in general, for the user
1487 @c version of this manual, none of these terms seem essential to define.
1488 @c They were used very little even in the former draft of the manual;
1489 @c this draft makes an effort to avoid them (except in names of
1493 @section The GNU Assembler
1495 @c man begin DESCRIPTION
1497 @sc{gnu} @command{as} is really a family of assemblers.
1499 This manual describes @command{@value{AS}}, a member of that family which is
1500 configured for the @value{TARGET} architectures.
1502 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1503 should find a fairly similar environment when you use it on another
1504 architecture. Each version has much in common with the others,
1505 including object file formats, most assembler directives (often called
1506 @dfn{pseudo-ops}) and assembler syntax.@refill
1508 @cindex purpose of @sc{gnu} assembler
1509 @command{@value{AS}} is primarily intended to assemble the output of the
1510 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1511 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1512 assemble correctly everything that other assemblers for the same
1513 machine would assemble.
1515 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1518 @c This remark should appear in generic version of manual; assumption
1519 @c here is that generic version sets M680x0.
1520 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1521 assembler for the same architecture; for example, we know of several
1522 incompatible versions of 680x0 assembly language syntax.
1527 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1528 program in one pass of the source file. This has a subtle impact on the
1529 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1531 @node Object Formats
1532 @section Object File Formats
1534 @cindex object file format
1535 The @sc{gnu} assembler can be configured to produce several alternative
1536 object file formats. For the most part, this does not affect how you
1537 write assembly language programs; but directives for debugging symbols
1538 are typically different in different file formats. @xref{Symbol
1539 Attributes,,Symbol Attributes}.
1542 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1543 @value{OBJ-NAME} format object files.
1545 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1547 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1548 @code{b.out} or COFF format object files.
1551 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1552 SOM or ELF format object files.
1557 @section Command Line
1559 @cindex command line conventions
1561 After the program name @command{@value{AS}}, the command line may contain
1562 options and file names. Options may appear in any order, and may be
1563 before, after, or between file names. The order of file names is
1566 @cindex standard input, as input file
1568 @file{--} (two hyphens) by itself names the standard input file
1569 explicitly, as one of the files for @command{@value{AS}} to assemble.
1571 @cindex options, command line
1572 Except for @samp{--} any command line argument that begins with a
1573 hyphen (@samp{-}) is an option. Each option changes the behavior of
1574 @command{@value{AS}}. No option changes the way another option works. An
1575 option is a @samp{-} followed by one or more letters; the case of
1576 the letter is important. All options are optional.
1578 Some options expect exactly one file name to follow them. The file
1579 name may either immediately follow the option's letter (compatible
1580 with older assemblers) or it may be the next command argument (@sc{gnu}
1581 standard). These two command lines are equivalent:
1584 @value{AS} -o my-object-file.o mumble.s
1585 @value{AS} -omy-object-file.o mumble.s
1589 @section Input Files
1592 @cindex source program
1593 @cindex files, input
1594 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1595 describe the program input to one run of @command{@value{AS}}. The program may
1596 be in one or more files; how the source is partitioned into files
1597 doesn't change the meaning of the source.
1599 @c I added "con" prefix to "catenation" just to prove I can overcome my
1600 @c APL training... doc@cygnus.com
1601 The source program is a concatenation of the text in all the files, in the
1604 @c man begin DESCRIPTION
1605 Each time you run @command{@value{AS}} it assembles exactly one source
1606 program. The source program is made up of one or more files.
1607 (The standard input is also a file.)
1609 You give @command{@value{AS}} a command line that has zero or more input file
1610 names. The input files are read (from left file name to right). A
1611 command line argument (in any position) that has no special meaning
1612 is taken to be an input file name.
1614 If you give @command{@value{AS}} no file names it attempts to read one input file
1615 from the @command{@value{AS}} standard input, which is normally your terminal. You
1616 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1619 Use @samp{--} if you need to explicitly name the standard input file
1620 in your command line.
1622 If the source is empty, @command{@value{AS}} produces a small, empty object
1627 @subheading Filenames and Line-numbers
1629 @cindex input file linenumbers
1630 @cindex line numbers, in input files
1631 There are two ways of locating a line in the input file (or files) and
1632 either may be used in reporting error messages. One way refers to a line
1633 number in a physical file; the other refers to a line number in a
1634 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1636 @dfn{Physical files} are those files named in the command line given
1637 to @command{@value{AS}}.
1639 @dfn{Logical files} are simply names declared explicitly by assembler
1640 directives; they bear no relation to physical files. Logical file names help
1641 error messages reflect the original source file, when @command{@value{AS}} source
1642 is itself synthesized from other files. @command{@value{AS}} understands the
1643 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1644 @ref{File,,@code{.file}}.
1647 @section Output (Object) File
1653 Every time you run @command{@value{AS}} it produces an output file, which is
1654 your assembly language program translated into numbers. This file
1655 is the object file. Its default name is
1663 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1665 You can give it another name by using the @option{-o} option. Conventionally,
1666 object file names end with @file{.o}. The default name is used for historical
1667 reasons: older assemblers were capable of assembling self-contained programs
1668 directly into a runnable program. (For some formats, this isn't currently
1669 possible, but it can be done for the @code{a.out} format.)
1673 The object file is meant for input to the linker @code{@value{LD}}. It contains
1674 assembled program code, information to help @code{@value{LD}} integrate
1675 the assembled program into a runnable file, and (optionally) symbolic
1676 information for the debugger.
1678 @c link above to some info file(s) like the description of a.out.
1679 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1682 @section Error and Warning Messages
1684 @c man begin DESCRIPTION
1686 @cindex error messages
1687 @cindex warning messages
1688 @cindex messages from assembler
1689 @command{@value{AS}} may write warnings and error messages to the standard error
1690 file (usually your terminal). This should not happen when a compiler
1691 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1692 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1693 grave problem that stops the assembly.
1697 @cindex format of warning messages
1698 Warning messages have the format
1701 file_name:@b{NNN}:Warning Message Text
1705 @cindex line numbers, in warnings/errors
1706 (where @b{NNN} is a line number). If a logical file name has been given
1707 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1708 the current input file is used. If a logical line number was given
1710 (@pxref{Line,,@code{.line}})
1712 then it is used to calculate the number printed,
1713 otherwise the actual line in the current source file is printed. The
1714 message text is intended to be self explanatory (in the grand Unix
1717 @cindex format of error messages
1718 Error messages have the format
1720 file_name:@b{NNN}:FATAL:Error Message Text
1722 The file name and line number are derived as for warning
1723 messages. The actual message text may be rather less explanatory
1724 because many of them aren't supposed to happen.
1727 @chapter Command-Line Options
1729 @cindex options, all versions of assembler
1730 This chapter describes command-line options available in @emph{all}
1731 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1732 for options specific
1734 to the @value{TARGET} target.
1737 to particular machine architectures.
1740 @c man begin DESCRIPTION
1742 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1743 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1744 The assembler arguments must be separated from each other (and the @samp{-Wa})
1745 by commas. For example:
1748 gcc -c -g -O -Wa,-alh,-L file.c
1752 This passes two options to the assembler: @samp{-alh} (emit a listing to
1753 standard output with high-level and assembly source) and @samp{-L} (retain
1754 local symbols in the symbol table).
1756 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1757 command-line options are automatically passed to the assembler by the compiler.
1758 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1759 precisely what options it passes to each compilation pass, including the
1765 * a:: -a[cdghlns] enable listings
1766 * alternate:: --alternate enable alternate macro syntax
1767 * D:: -D for compatibility
1768 * f:: -f to work faster
1769 * I:: -I for .include search path
1770 @ifclear DIFF-TBL-KLUGE
1771 * K:: -K for compatibility
1773 @ifset DIFF-TBL-KLUGE
1774 * K:: -K for difference tables
1777 * L:: -L to retain local symbols
1778 * listing:: --listing-XXX to configure listing output
1779 * M:: -M or --mri to assemble in MRI compatibility mode
1780 * MD:: --MD for dependency tracking
1781 * o:: -o to name the object file
1782 * R:: -R to join data and text sections
1783 * statistics:: --statistics to see statistics about assembly
1784 * traditional-format:: --traditional-format for compatible output
1785 * v:: -v to announce version
1786 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1787 * Z:: -Z to make object file even after errors
1791 @section Enable Listings: @option{-a[cdghlns]}
1801 @cindex listings, enabling
1802 @cindex assembly listings, enabling
1804 These options enable listing output from the assembler. By itself,
1805 @samp{-a} requests high-level, assembly, and symbols listing.
1806 You can use other letters to select specific options for the list:
1807 @samp{-ah} requests a high-level language listing,
1808 @samp{-al} requests an output-program assembly listing, and
1809 @samp{-as} requests a symbol table listing.
1810 High-level listings require that a compiler debugging option like
1811 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1814 Use the @samp{-ag} option to print a first section with general assembly
1815 information, like @value{AS} version, switches passed, or time stamp.
1817 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1818 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1819 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1820 omitted from the listing.
1822 Use the @samp{-ad} option to omit debugging directives from the
1825 Once you have specified one of these options, you can further control
1826 listing output and its appearance using the directives @code{.list},
1827 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1829 The @samp{-an} option turns off all forms processing.
1830 If you do not request listing output with one of the @samp{-a} options, the
1831 listing-control directives have no effect.
1833 The letters after @samp{-a} may be combined into one option,
1834 @emph{e.g.}, @samp{-aln}.
1836 Note if the assembler source is coming from the standard input (e.g.,
1838 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1839 is being used) then the listing will not contain any comments or preprocessor
1840 directives. This is because the listing code buffers input source lines from
1841 stdin only after they have been preprocessed by the assembler. This reduces
1842 memory usage and makes the code more efficient.
1845 @section @option{--alternate}
1848 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1851 @section @option{-D}
1854 This option has no effect whatsoever, but it is accepted to make it more
1855 likely that scripts written for other assemblers also work with
1856 @command{@value{AS}}.
1859 @section Work Faster: @option{-f}
1862 @cindex trusted compiler
1863 @cindex faster processing (@option{-f})
1864 @samp{-f} should only be used when assembling programs written by a
1865 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1866 and comment preprocessing on
1867 the input file(s) before assembling them. @xref{Preprocessing,
1871 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1872 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1877 @section @code{.include} Search Path: @option{-I} @var{path}
1879 @kindex -I @var{path}
1880 @cindex paths for @code{.include}
1881 @cindex search path for @code{.include}
1882 @cindex @code{include} directive search path
1883 Use this option to add a @var{path} to the list of directories
1884 @command{@value{AS}} searches for files specified in @code{.include}
1885 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1886 many times as necessary to include a variety of paths. The current
1887 working directory is always searched first; after that, @command{@value{AS}}
1888 searches any @samp{-I} directories in the same order as they were
1889 specified (left to right) on the command line.
1892 @section Difference Tables: @option{-K}
1895 @ifclear DIFF-TBL-KLUGE
1896 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1897 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1898 where it can be used to warn when the assembler alters the machine code
1899 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1900 family does not have the addressing limitations that sometimes lead to this
1901 alteration on other platforms.
1904 @ifset DIFF-TBL-KLUGE
1905 @cindex difference tables, warning
1906 @cindex warning for altered difference tables
1907 @command{@value{AS}} sometimes alters the code emitted for directives of the
1908 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1909 You can use the @samp{-K} option if you want a warning issued when this
1914 @section Include Local Symbols: @option{-L}
1917 @cindex local symbols, retaining in output
1918 Symbols beginning with system-specific local label prefixes, typically
1919 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1920 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1921 such symbols when debugging, because they are intended for the use of
1922 programs (like compilers) that compose assembler programs, not for your
1923 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1924 such symbols, so you do not normally debug with them.
1926 This option tells @command{@value{AS}} to retain those local symbols
1927 in the object file. Usually if you do this you also tell the linker
1928 @code{@value{LD}} to preserve those symbols.
1931 @section Configuring listing output: @option{--listing}
1933 The listing feature of the assembler can be enabled via the command line switch
1934 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1935 hex dump of the corresponding locations in the output object file, and displays
1936 them as a listing file. The format of this listing can be controlled by
1937 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1938 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1939 @code{.psize} (@pxref{Psize}), and
1940 @code{.eject} (@pxref{Eject}) and also by the following switches:
1943 @item --listing-lhs-width=@samp{number}
1944 @kindex --listing-lhs-width
1945 @cindex Width of first line disassembly output
1946 Sets the maximum width, in words, of the first line of the hex byte dump. This
1947 dump appears on the left hand side of the listing output.
1949 @item --listing-lhs-width2=@samp{number}
1950 @kindex --listing-lhs-width2
1951 @cindex Width of continuation lines of disassembly output
1952 Sets the maximum width, in words, of any further lines of the hex byte dump for
1953 a given input source line. If this value is not specified, it defaults to being
1954 the same as the value specified for @samp{--listing-lhs-width}. If neither
1955 switch is used the default is to one.
1957 @item --listing-rhs-width=@samp{number}
1958 @kindex --listing-rhs-width
1959 @cindex Width of source line output
1960 Sets the maximum width, in characters, of the source line that is displayed
1961 alongside the hex dump. The default value for this parameter is 100. The
1962 source line is displayed on the right hand side of the listing output.
1964 @item --listing-cont-lines=@samp{number}
1965 @kindex --listing-cont-lines
1966 @cindex Maximum number of continuation lines
1967 Sets the maximum number of continuation lines of hex dump that will be
1968 displayed for a given single line of source input. The default value is 4.
1972 @section Assemble in MRI Compatibility Mode: @option{-M}
1975 @cindex MRI compatibility mode
1976 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1977 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1978 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1979 configured target) assembler from Microtec Research. The exact nature of the
1980 MRI syntax will not be documented here; see the MRI manuals for more
1981 information. Note in particular that the handling of macros and macro
1982 arguments is somewhat different. The purpose of this option is to permit
1983 assembling existing MRI assembler code using @command{@value{AS}}.
1985 The MRI compatibility is not complete. Certain operations of the MRI assembler
1986 depend upon its object file format, and can not be supported using other object
1987 file formats. Supporting these would require enhancing each object file format
1988 individually. These are:
1991 @item global symbols in common section
1993 The m68k MRI assembler supports common sections which are merged by the linker.
1994 Other object file formats do not support this. @command{@value{AS}} handles
1995 common sections by treating them as a single common symbol. It permits local
1996 symbols to be defined within a common section, but it can not support global
1997 symbols, since it has no way to describe them.
1999 @item complex relocations
2001 The MRI assemblers support relocations against a negated section address, and
2002 relocations which combine the start addresses of two or more sections. These
2003 are not support by other object file formats.
2005 @item @code{END} pseudo-op specifying start address
2007 The MRI @code{END} pseudo-op permits the specification of a start address.
2008 This is not supported by other object file formats. The start address may
2009 instead be specified using the @option{-e} option to the linker, or in a linker
2012 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2014 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2015 name to the output file. This is not supported by other object file formats.
2017 @item @code{ORG} pseudo-op
2019 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2020 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2021 which changes the location within the current section. Absolute sections are
2022 not supported by other object file formats. The address of a section may be
2023 assigned within a linker script.
2026 There are some other features of the MRI assembler which are not supported by
2027 @command{@value{AS}}, typically either because they are difficult or because they
2028 seem of little consequence. Some of these may be supported in future releases.
2032 @item EBCDIC strings
2034 EBCDIC strings are not supported.
2036 @item packed binary coded decimal
2038 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2039 and @code{DCB.P} pseudo-ops are not supported.
2041 @item @code{FEQU} pseudo-op
2043 The m68k @code{FEQU} pseudo-op is not supported.
2045 @item @code{NOOBJ} pseudo-op
2047 The m68k @code{NOOBJ} pseudo-op is not supported.
2049 @item @code{OPT} branch control options
2051 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2052 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2053 relaxes all branches, whether forward or backward, to an appropriate size, so
2054 these options serve no purpose.
2056 @item @code{OPT} list control options
2058 The following m68k @code{OPT} list control options are ignored: @code{C},
2059 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2060 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2062 @item other @code{OPT} options
2064 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2065 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2067 @item @code{OPT} @code{D} option is default
2069 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2070 @code{OPT NOD} may be used to turn it off.
2072 @item @code{XREF} pseudo-op.
2074 The m68k @code{XREF} pseudo-op is ignored.
2076 @item @code{.debug} pseudo-op
2078 The i960 @code{.debug} pseudo-op is not supported.
2080 @item @code{.extended} pseudo-op
2082 The i960 @code{.extended} pseudo-op is not supported.
2084 @item @code{.list} pseudo-op.
2086 The various options of the i960 @code{.list} pseudo-op are not supported.
2088 @item @code{.optimize} pseudo-op
2090 The i960 @code{.optimize} pseudo-op is not supported.
2092 @item @code{.output} pseudo-op
2094 The i960 @code{.output} pseudo-op is not supported.
2096 @item @code{.setreal} pseudo-op
2098 The i960 @code{.setreal} pseudo-op is not supported.
2103 @section Dependency Tracking: @option{--MD}
2106 @cindex dependency tracking
2109 @command{@value{AS}} can generate a dependency file for the file it creates. This
2110 file consists of a single rule suitable for @code{make} describing the
2111 dependencies of the main source file.
2113 The rule is written to the file named in its argument.
2115 This feature is used in the automatic updating of makefiles.
2118 @section Name the Object File: @option{-o}
2121 @cindex naming object file
2122 @cindex object file name
2123 There is always one object file output when you run @command{@value{AS}}. By
2124 default it has the name
2127 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2141 You use this option (which takes exactly one filename) to give the
2142 object file a different name.
2144 Whatever the object file is called, @command{@value{AS}} overwrites any
2145 existing file of the same name.
2148 @section Join Data and Text Sections: @option{-R}
2151 @cindex data and text sections, joining
2152 @cindex text and data sections, joining
2153 @cindex joining text and data sections
2154 @cindex merging text and data sections
2155 @option{-R} tells @command{@value{AS}} to write the object file as if all
2156 data-section data lives in the text section. This is only done at
2157 the very last moment: your binary data are the same, but data
2158 section parts are relocated differently. The data section part of
2159 your object file is zero bytes long because all its bytes are
2160 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2162 When you specify @option{-R} it would be possible to generate shorter
2163 address displacements (because we do not have to cross between text and
2164 data section). We refrain from doing this simply for compatibility with
2165 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2168 When @command{@value{AS}} is configured for COFF or ELF output,
2169 this option is only useful if you use sections named @samp{.text} and
2174 @option{-R} is not supported for any of the HPPA targets. Using
2175 @option{-R} generates a warning from @command{@value{AS}}.
2179 @section Display Assembly Statistics: @option{--statistics}
2181 @kindex --statistics
2182 @cindex statistics, about assembly
2183 @cindex time, total for assembly
2184 @cindex space used, maximum for assembly
2185 Use @samp{--statistics} to display two statistics about the resources used by
2186 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2187 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2190 @node traditional-format
2191 @section Compatible Output: @option{--traditional-format}
2193 @kindex --traditional-format
2194 For some targets, the output of @command{@value{AS}} is different in some ways
2195 from the output of some existing assembler. This switch requests
2196 @command{@value{AS}} to use the traditional format instead.
2198 For example, it disables the exception frame optimizations which
2199 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2202 @section Announce Version: @option{-v}
2206 @cindex assembler version
2207 @cindex version of assembler
2208 You can find out what version of as is running by including the
2209 option @samp{-v} (which you can also spell as @samp{-version}) on the
2213 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2215 @command{@value{AS}} should never give a warning or error message when
2216 assembling compiler output. But programs written by people often
2217 cause @command{@value{AS}} to give a warning that a particular assumption was
2218 made. All such warnings are directed to the standard error file.
2222 @cindex suppressing warnings
2223 @cindex warnings, suppressing
2224 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2225 This only affects the warning messages: it does not change any particular of
2226 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2229 @kindex --fatal-warnings
2230 @cindex errors, caused by warnings
2231 @cindex warnings, causing error
2232 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2233 files that generate warnings to be in error.
2236 @cindex warnings, switching on
2237 You can switch these options off again by specifying @option{--warn}, which
2238 causes warnings to be output as usual.
2241 @section Generate Object File in Spite of Errors: @option{-Z}
2242 @cindex object file, after errors
2243 @cindex errors, continuing after
2244 After an error message, @command{@value{AS}} normally produces no output. If for
2245 some reason you are interested in object file output even after
2246 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2247 option. If there are any errors, @command{@value{AS}} continues anyways, and
2248 writes an object file after a final warning message of the form @samp{@var{n}
2249 errors, @var{m} warnings, generating bad object file.}
2254 @cindex machine-independent syntax
2255 @cindex syntax, machine-independent
2256 This chapter describes the machine-independent syntax allowed in a
2257 source file. @command{@value{AS}} syntax is similar to what many other
2258 assemblers use; it is inspired by the BSD 4.2
2263 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2267 * Preprocessing:: Preprocessing
2268 * Whitespace:: Whitespace
2269 * Comments:: Comments
2270 * Symbol Intro:: Symbols
2271 * Statements:: Statements
2272 * Constants:: Constants
2276 @section Preprocessing
2278 @cindex preprocessing
2279 The @command{@value{AS}} internal preprocessor:
2281 @cindex whitespace, removed by preprocessor
2283 adjusts and removes extra whitespace. It leaves one space or tab before
2284 the keywords on a line, and turns any other whitespace on the line into
2287 @cindex comments, removed by preprocessor
2289 removes all comments, replacing them with a single space, or an
2290 appropriate number of newlines.
2292 @cindex constants, converted by preprocessor
2294 converts character constants into the appropriate numeric values.
2297 It does not do macro processing, include file handling, or
2298 anything else you may get from your C compiler's preprocessor. You can
2299 do include file processing with the @code{.include} directive
2300 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2301 to get other ``CPP'' style preprocessing by giving the input file a
2302 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2303 Output, gcc.info, Using GNU CC}.
2305 Excess whitespace, comments, and character constants
2306 cannot be used in the portions of the input text that are not
2309 @cindex turning preprocessing on and off
2310 @cindex preprocessing, turning on and off
2313 If the first line of an input file is @code{#NO_APP} or if you use the
2314 @samp{-f} option, whitespace and comments are not removed from the input file.
2315 Within an input file, you can ask for whitespace and comment removal in
2316 specific portions of the by putting a line that says @code{#APP} before the
2317 text that may contain whitespace or comments, and putting a line that says
2318 @code{#NO_APP} after this text. This feature is mainly intend to support
2319 @code{asm} statements in compilers whose output is otherwise free of comments
2326 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2327 Whitespace is used to separate symbols, and to make programs neater for
2328 people to read. Unless within character constants
2329 (@pxref{Characters,,Character Constants}), any whitespace means the same
2330 as exactly one space.
2336 There are two ways of rendering comments to @command{@value{AS}}. In both
2337 cases the comment is equivalent to one space.
2339 Anything from @samp{/*} through the next @samp{*/} is a comment.
2340 This means you may not nest these comments.
2344 The only way to include a newline ('\n') in a comment
2345 is to use this sort of comment.
2348 /* This sort of comment does not nest. */
2351 @cindex line comment character
2352 Anything from the @dfn{line comment} character to the next newline
2353 is considered a comment and is ignored. The line comment character is
2355 @samp{;} on the ARC;
2358 @samp{@@} on the ARM;
2361 @samp{;} for the H8/300 family;
2364 @samp{;} for the HPPA;
2367 @samp{#} on the i386 and x86-64;
2370 @samp{#} on the i960;
2373 @samp{;} for the PDP-11;
2376 @samp{;} for picoJava;
2379 @samp{#} for Motorola PowerPC;
2382 @samp{#} for IBM S/390;
2385 @samp{#} for the Sunplus SCORE;
2388 @samp{!} for the Renesas / SuperH SH;
2391 @samp{!} on the SPARC;
2394 @samp{#} on the ip2k;
2397 @samp{#} on the m32c;
2400 @samp{#} on the m32r;
2403 @samp{|} on the 680x0;
2406 @samp{#} on the 68HC11 and 68HC12;
2412 @samp{;} on the TMS320C6X;
2415 @samp{#} on the Vax;
2418 @samp{;} for the Z80;
2421 @samp{!} for the Z8000;
2424 @samp{#} on the V850;
2427 @samp{#} for Xtensa systems;
2429 see @ref{Machine Dependencies}. @refill
2430 @c FIXME What about i860?
2433 On some machines there are two different line comment characters. One
2434 character only begins a comment if it is the first non-whitespace character on
2435 a line, while the other always begins a comment.
2439 The V850 assembler also supports a double dash as starting a comment that
2440 extends to the end of the line.
2446 @cindex lines starting with @code{#}
2447 @cindex logical line numbers
2448 To be compatible with past assemblers, lines that begin with @samp{#} have a
2449 special interpretation. Following the @samp{#} should be an absolute
2450 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2451 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2452 new logical file name. The rest of the line, if any, should be whitespace.
2454 If the first non-whitespace characters on the line are not numeric,
2455 the line is ignored. (Just like a comment.)
2458 # This is an ordinary comment.
2459 # 42-6 "new_file_name" # New logical file name
2460 # This is logical line # 36.
2462 This feature is deprecated, and may disappear from future versions
2463 of @command{@value{AS}}.
2468 @cindex characters used in symbols
2469 @ifclear SPECIAL-SYMS
2470 A @dfn{symbol} is one or more characters chosen from the set of all
2471 letters (both upper and lower case), digits and the three characters
2477 A @dfn{symbol} is one or more characters chosen from the set of all
2478 letters (both upper and lower case), digits and the three characters
2479 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2485 On most machines, you can also use @code{$} in symbol names; exceptions
2486 are noted in @ref{Machine Dependencies}.
2488 No symbol may begin with a digit. Case is significant.
2489 There is no length limit: all characters are significant. Symbols are
2490 delimited by characters not in that set, or by the beginning of a file
2491 (since the source program must end with a newline, the end of a file is
2492 not a possible symbol delimiter). @xref{Symbols}.
2493 @cindex length of symbols
2498 @cindex statements, structure of
2499 @cindex line separator character
2500 @cindex statement separator character
2502 @ifclear abnormal-separator
2503 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2504 semicolon (@samp{;}). The newline or semicolon is considered part of
2505 the preceding statement. Newlines and semicolons within character
2506 constants are an exception: they do not end statements.
2508 @ifset abnormal-separator
2510 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2511 point (@samp{!}). The newline or exclamation point is considered part of the
2512 preceding statement. Newlines and exclamation points within character
2513 constants are an exception: they do not end statements.
2516 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2517 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2518 (@samp{;}). The newline or separator character is considered part of
2519 the preceding statement. Newlines and separators within character
2520 constants are an exception: they do not end statements.
2525 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2526 separator character. (The line separator is usually @samp{;}, unless this
2527 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2528 newline or separator character is considered part of the preceding
2529 statement. Newlines and separators within character constants are an
2530 exception: they do not end statements.
2533 @cindex newline, required at file end
2534 @cindex EOF, newline must precede
2535 It is an error to end any statement with end-of-file: the last
2536 character of any input file should be a newline.@refill
2538 An empty statement is allowed, and may include whitespace. It is ignored.
2540 @cindex instructions and directives
2541 @cindex directives and instructions
2542 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2543 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2545 A statement begins with zero or more labels, optionally followed by a
2546 key symbol which determines what kind of statement it is. The key
2547 symbol determines the syntax of the rest of the statement. If the
2548 symbol begins with a dot @samp{.} then the statement is an assembler
2549 directive: typically valid for any computer. If the symbol begins with
2550 a letter the statement is an assembly language @dfn{instruction}: it
2551 assembles into a machine language instruction.
2553 Different versions of @command{@value{AS}} for different computers
2554 recognize different instructions. In fact, the same symbol may
2555 represent a different instruction in a different computer's assembly
2559 @cindex @code{:} (label)
2560 @cindex label (@code{:})
2561 A label is a symbol immediately followed by a colon (@code{:}).
2562 Whitespace before a label or after a colon is permitted, but you may not
2563 have whitespace between a label's symbol and its colon. @xref{Labels}.
2566 For HPPA targets, labels need not be immediately followed by a colon, but
2567 the definition of a label must begin in column zero. This also implies that
2568 only one label may be defined on each line.
2572 label: .directive followed by something
2573 another_label: # This is an empty statement.
2574 instruction operand_1, operand_2, @dots{}
2581 A constant is a number, written so that its value is known by
2582 inspection, without knowing any context. Like this:
2585 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2586 .ascii "Ring the bell\7" # A string constant.
2587 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2588 .float 0f-314159265358979323846264338327\
2589 95028841971.693993751E-40 # - pi, a flonum.
2594 * Characters:: Character Constants
2595 * Numbers:: Number Constants
2599 @subsection Character Constants
2601 @cindex character constants
2602 @cindex constants, character
2603 There are two kinds of character constants. A @dfn{character} stands
2604 for one character in one byte and its value may be used in
2605 numeric expressions. String constants (properly called string
2606 @emph{literals}) are potentially many bytes and their values may not be
2607 used in arithmetic expressions.
2611 * Chars:: Characters
2615 @subsubsection Strings
2617 @cindex string constants
2618 @cindex constants, string
2619 A @dfn{string} is written between double-quotes. It may contain
2620 double-quotes or null characters. The way to get special characters
2621 into a string is to @dfn{escape} these characters: precede them with
2622 a backslash @samp{\} character. For example @samp{\\} represents
2623 one backslash: the first @code{\} is an escape which tells
2624 @command{@value{AS}} to interpret the second character literally as a backslash
2625 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2626 escape character). The complete list of escapes follows.
2628 @cindex escape codes, character
2629 @cindex character escape codes
2632 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2634 @cindex @code{\b} (backspace character)
2635 @cindex backspace (@code{\b})
2637 Mnemonic for backspace; for ASCII this is octal code 010.
2640 @c Mnemonic for EOText; for ASCII this is octal code 004.
2642 @cindex @code{\f} (formfeed character)
2643 @cindex formfeed (@code{\f})
2645 Mnemonic for FormFeed; for ASCII this is octal code 014.
2647 @cindex @code{\n} (newline character)
2648 @cindex newline (@code{\n})
2650 Mnemonic for newline; for ASCII this is octal code 012.
2653 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2655 @cindex @code{\r} (carriage return character)
2656 @cindex carriage return (@code{\r})
2658 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2661 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2662 @c other assemblers.
2664 @cindex @code{\t} (tab)
2665 @cindex tab (@code{\t})
2667 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2670 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2671 @c @item \x @var{digit} @var{digit} @var{digit}
2672 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2674 @cindex @code{\@var{ddd}} (octal character code)
2675 @cindex octal character code (@code{\@var{ddd}})
2676 @item \ @var{digit} @var{digit} @var{digit}
2677 An octal character code. The numeric code is 3 octal digits.
2678 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2679 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2681 @cindex @code{\@var{xd...}} (hex character code)
2682 @cindex hex character code (@code{\@var{xd...}})
2683 @item \@code{x} @var{hex-digits...}
2684 A hex character code. All trailing hex digits are combined. Either upper or
2685 lower case @code{x} works.
2687 @cindex @code{\\} (@samp{\} character)
2688 @cindex backslash (@code{\\})
2690 Represents one @samp{\} character.
2693 @c Represents one @samp{'} (accent acute) character.
2694 @c This is needed in single character literals
2695 @c (@xref{Characters,,Character Constants}.) to represent
2698 @cindex @code{\"} (doublequote character)
2699 @cindex doublequote (@code{\"})
2701 Represents one @samp{"} character. Needed in strings to represent
2702 this character, because an unescaped @samp{"} would end the string.
2704 @item \ @var{anything-else}
2705 Any other character when escaped by @kbd{\} gives a warning, but
2706 assembles as if the @samp{\} was not present. The idea is that if
2707 you used an escape sequence you clearly didn't want the literal
2708 interpretation of the following character. However @command{@value{AS}} has no
2709 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2710 code and warns you of the fact.
2713 Which characters are escapable, and what those escapes represent,
2714 varies widely among assemblers. The current set is what we think
2715 the BSD 4.2 assembler recognizes, and is a subset of what most C
2716 compilers recognize. If you are in doubt, do not use an escape
2720 @subsubsection Characters
2722 @cindex single character constant
2723 @cindex character, single
2724 @cindex constant, single character
2725 A single character may be written as a single quote immediately
2726 followed by that character. The same escapes apply to characters as
2727 to strings. So if you want to write the character backslash, you
2728 must write @kbd{'\\} where the first @code{\} escapes the second
2729 @code{\}. As you can see, the quote is an acute accent, not a
2730 grave accent. A newline
2732 @ifclear abnormal-separator
2733 (or semicolon @samp{;})
2735 @ifset abnormal-separator
2737 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2742 immediately following an acute accent is taken as a literal character
2743 and does not count as the end of a statement. The value of a character
2744 constant in a numeric expression is the machine's byte-wide code for
2745 that character. @command{@value{AS}} assumes your character code is ASCII:
2746 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2749 @subsection Number Constants
2751 @cindex constants, number
2752 @cindex number constants
2753 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2754 are stored in the target machine. @emph{Integers} are numbers that
2755 would fit into an @code{int} in the C language. @emph{Bignums} are
2756 integers, but they are stored in more than 32 bits. @emph{Flonums}
2757 are floating point numbers, described below.
2760 * Integers:: Integers
2765 * Bit Fields:: Bit Fields
2771 @subsubsection Integers
2773 @cindex constants, integer
2775 @cindex binary integers
2776 @cindex integers, binary
2777 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2778 the binary digits @samp{01}.
2780 @cindex octal integers
2781 @cindex integers, octal
2782 An octal integer is @samp{0} followed by zero or more of the octal
2783 digits (@samp{01234567}).
2785 @cindex decimal integers
2786 @cindex integers, decimal
2787 A decimal integer starts with a non-zero digit followed by zero or
2788 more digits (@samp{0123456789}).
2790 @cindex hexadecimal integers
2791 @cindex integers, hexadecimal
2792 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2793 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2795 Integers have the usual values. To denote a negative integer, use
2796 the prefix operator @samp{-} discussed under expressions
2797 (@pxref{Prefix Ops,,Prefix Operators}).
2800 @subsubsection Bignums
2803 @cindex constants, bignum
2804 A @dfn{bignum} has the same syntax and semantics as an integer
2805 except that the number (or its negative) takes more than 32 bits to
2806 represent in binary. The distinction is made because in some places
2807 integers are permitted while bignums are not.
2810 @subsubsection Flonums
2812 @cindex floating point numbers
2813 @cindex constants, floating point
2815 @cindex precision, floating point
2816 A @dfn{flonum} represents a floating point number. The translation is
2817 indirect: a decimal floating point number from the text is converted by
2818 @command{@value{AS}} to a generic binary floating point number of more than
2819 sufficient precision. This generic floating point number is converted
2820 to a particular computer's floating point format (or formats) by a
2821 portion of @command{@value{AS}} specialized to that computer.
2823 A flonum is written by writing (in order)
2828 (@samp{0} is optional on the HPPA.)
2832 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2834 @kbd{e} is recommended. Case is not important.
2836 @c FIXME: verify if flonum syntax really this vague for most cases
2837 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2838 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2841 On the H8/300, Renesas / SuperH SH,
2842 and AMD 29K architectures, the letter must be
2843 one of the letters @samp{DFPRSX} (in upper or lower case).
2845 On the ARC, the letter must be one of the letters @samp{DFRS}
2846 (in upper or lower case).
2848 On the Intel 960 architecture, the letter must be
2849 one of the letters @samp{DFT} (in upper or lower case).
2851 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2855 One of the letters @samp{DFRS} (in upper or lower case).
2858 One of the letters @samp{DFPRSX} (in upper or lower case).
2861 The letter @samp{E} (upper case only).
2864 One of the letters @samp{DFT} (in upper or lower case).
2869 An optional sign: either @samp{+} or @samp{-}.
2872 An optional @dfn{integer part}: zero or more decimal digits.
2875 An optional @dfn{fractional part}: @samp{.} followed by zero
2876 or more decimal digits.
2879 An optional exponent, consisting of:
2883 An @samp{E} or @samp{e}.
2884 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2885 @c principle this can perfectly well be different on different targets.
2887 Optional sign: either @samp{+} or @samp{-}.
2889 One or more decimal digits.
2894 At least one of the integer part or the fractional part must be
2895 present. The floating point number has the usual base-10 value.
2897 @command{@value{AS}} does all processing using integers. Flonums are computed
2898 independently of any floating point hardware in the computer running
2899 @command{@value{AS}}.
2903 @c Bit fields are written as a general facility but are also controlled
2904 @c by a conditional-compilation flag---which is as of now (21mar91)
2905 @c turned on only by the i960 config of GAS.
2907 @subsubsection Bit Fields
2910 @cindex constants, bit field
2911 You can also define numeric constants as @dfn{bit fields}.
2912 Specify two numbers separated by a colon---
2914 @var{mask}:@var{value}
2917 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2920 The resulting number is then packed
2922 @c this conditional paren in case bit fields turned on elsewhere than 960
2923 (in host-dependent byte order)
2925 into a field whose width depends on which assembler directive has the
2926 bit-field as its argument. Overflow (a result from the bitwise and
2927 requiring more binary digits to represent) is not an error; instead,
2928 more constants are generated, of the specified width, beginning with the
2929 least significant digits.@refill
2931 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2932 @code{.short}, and @code{.word} accept bit-field arguments.
2937 @chapter Sections and Relocation
2942 * Secs Background:: Background
2943 * Ld Sections:: Linker Sections
2944 * As Sections:: Assembler Internal Sections
2945 * Sub-Sections:: Sub-Sections
2949 @node Secs Background
2952 Roughly, a section is a range of addresses, with no gaps; all data
2953 ``in'' those addresses is treated the same for some particular purpose.
2954 For example there may be a ``read only'' section.
2956 @cindex linker, and assembler
2957 @cindex assembler, and linker
2958 The linker @code{@value{LD}} reads many object files (partial programs) and
2959 combines their contents to form a runnable program. When @command{@value{AS}}
2960 emits an object file, the partial program is assumed to start at address 0.
2961 @code{@value{LD}} assigns the final addresses for the partial program, so that
2962 different partial programs do not overlap. This is actually an
2963 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2966 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2967 addresses. These blocks slide to their run-time addresses as rigid
2968 units; their length does not change and neither does the order of bytes
2969 within them. Such a rigid unit is called a @emph{section}. Assigning
2970 run-time addresses to sections is called @dfn{relocation}. It includes
2971 the task of adjusting mentions of object-file addresses so they refer to
2972 the proper run-time addresses.
2974 For the H8/300, and for the Renesas / SuperH SH,
2975 @command{@value{AS}} pads sections if needed to
2976 ensure they end on a word (sixteen bit) boundary.
2979 @cindex standard assembler sections
2980 An object file written by @command{@value{AS}} has at least three sections, any
2981 of which may be empty. These are named @dfn{text}, @dfn{data} and
2986 When it generates COFF or ELF output,
2988 @command{@value{AS}} can also generate whatever other named sections you specify
2989 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2990 If you do not use any directives that place output in the @samp{.text}
2991 or @samp{.data} sections, these sections still exist, but are empty.
2996 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2998 @command{@value{AS}} can also generate whatever other named sections you
2999 specify using the @samp{.space} and @samp{.subspace} directives. See
3000 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3001 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3002 assembler directives.
3005 Additionally, @command{@value{AS}} uses different names for the standard
3006 text, data, and bss sections when generating SOM output. Program text
3007 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3008 BSS into @samp{$BSS$}.
3012 Within the object file, the text section starts at address @code{0}, the
3013 data section follows, and the bss section follows the data section.
3016 When generating either SOM or ELF output files on the HPPA, the text
3017 section starts at address @code{0}, the data section at address
3018 @code{0x4000000}, and the bss section follows the data section.
3021 To let @code{@value{LD}} know which data changes when the sections are
3022 relocated, and how to change that data, @command{@value{AS}} also writes to the
3023 object file details of the relocation needed. To perform relocation
3024 @code{@value{LD}} must know, each time an address in the object
3028 Where in the object file is the beginning of this reference to
3031 How long (in bytes) is this reference?
3033 Which section does the address refer to? What is the numeric value of
3035 (@var{address}) @minus{} (@var{start-address of section})?
3038 Is the reference to an address ``Program-Counter relative''?
3041 @cindex addresses, format of
3042 @cindex section-relative addressing
3043 In fact, every address @command{@value{AS}} ever uses is expressed as
3045 (@var{section}) + (@var{offset into section})
3048 Further, most expressions @command{@value{AS}} computes have this section-relative
3051 (For some object formats, such as SOM for the HPPA, some expressions are
3052 symbol-relative instead.)
3055 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3056 @var{N} into section @var{secname}.''
3058 Apart from text, data and bss sections you need to know about the
3059 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3060 addresses in the absolute section remain unchanged. For example, address
3061 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3062 @code{@value{LD}}. Although the linker never arranges two partial programs'
3063 data sections with overlapping addresses after linking, @emph{by definition}
3064 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3065 part of a program is always the same address when the program is running as
3066 address @code{@{absolute@ 239@}} in any other part of the program.
3068 The idea of sections is extended to the @dfn{undefined} section. Any
3069 address whose section is unknown at assembly time is by definition
3070 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3071 Since numbers are always defined, the only way to generate an undefined
3072 address is to mention an undefined symbol. A reference to a named
3073 common block would be such a symbol: its value is unknown at assembly
3074 time so it has section @emph{undefined}.
3076 By analogy the word @emph{section} is used to describe groups of sections in
3077 the linked program. @code{@value{LD}} puts all partial programs' text
3078 sections in contiguous addresses in the linked program. It is
3079 customary to refer to the @emph{text section} of a program, meaning all
3080 the addresses of all partial programs' text sections. Likewise for
3081 data and bss sections.
3083 Some sections are manipulated by @code{@value{LD}}; others are invented for
3084 use of @command{@value{AS}} and have no meaning except during assembly.
3087 @section Linker Sections
3088 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3093 @cindex named sections
3094 @cindex sections, named
3095 @item named sections
3098 @cindex text section
3099 @cindex data section
3103 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3104 separate but equal sections. Anything you can say of one section is
3107 When the program is running, however, it is
3108 customary for the text section to be unalterable. The
3109 text section is often shared among processes: it contains
3110 instructions, constants and the like. The data section of a running
3111 program is usually alterable: for example, C variables would be stored
3112 in the data section.
3117 This section contains zeroed bytes when your program begins running. It
3118 is used to hold uninitialized variables or common storage. The length of
3119 each partial program's bss section is important, but because it starts
3120 out containing zeroed bytes there is no need to store explicit zero
3121 bytes in the object file. The bss section was invented to eliminate
3122 those explicit zeros from object files.
3124 @cindex absolute section
3125 @item absolute section
3126 Address 0 of this section is always ``relocated'' to runtime address 0.
3127 This is useful if you want to refer to an address that @code{@value{LD}} must
3128 not change when relocating. In this sense we speak of absolute
3129 addresses being ``unrelocatable'': they do not change during relocation.
3131 @cindex undefined section
3132 @item undefined section
3133 This ``section'' is a catch-all for address references to objects not in
3134 the preceding sections.
3135 @c FIXME: ref to some other doc on obj-file formats could go here.
3138 @cindex relocation example
3139 An idealized example of three relocatable sections follows.
3141 The example uses the traditional section names @samp{.text} and @samp{.data}.
3143 Memory addresses are on the horizontal axis.
3147 @c END TEXI2ROFF-KILL
3150 partial program # 1: |ttttt|dddd|00|
3157 partial program # 2: |TTT|DDD|000|
3160 +--+---+-----+--+----+---+-----+~~
3161 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3162 +--+---+-----+--+----+---+-----+~~
3164 addresses: 0 @dots{}
3171 \line{\it Partial program \#1: \hfil}
3172 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3173 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3175 \line{\it Partial program \#2: \hfil}
3176 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3177 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3179 \line{\it linked program: \hfil}
3180 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3181 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3182 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3183 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3185 \line{\it addresses: \hfil}
3189 @c END TEXI2ROFF-KILL
3192 @section Assembler Internal Sections
3194 @cindex internal assembler sections
3195 @cindex sections in messages, internal
3196 These sections are meant only for the internal use of @command{@value{AS}}. They
3197 have no meaning at run-time. You do not really need to know about these
3198 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3199 warning messages, so it might be helpful to have an idea of their
3200 meanings to @command{@value{AS}}. These sections are used to permit the
3201 value of every expression in your assembly language program to be a
3202 section-relative address.
3205 @cindex assembler internal logic error
3206 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3207 An internal assembler logic error has been found. This means there is a
3208 bug in the assembler.
3210 @cindex expr (internal section)
3212 The assembler stores complex expression internally as combinations of
3213 symbols. When it needs to represent an expression as a symbol, it puts
3214 it in the expr section.
3216 @c FIXME item transfer[t] vector preload
3217 @c FIXME item transfer[t] vector postload
3218 @c FIXME item register
3222 @section Sub-Sections
3224 @cindex numbered subsections
3225 @cindex grouping data
3231 fall into two sections: text and data.
3233 You may have separate groups of
3235 data in named sections
3239 data in named sections
3245 that you want to end up near to each other in the object file, even though they
3246 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3247 use @dfn{subsections} for this purpose. Within each section, there can be
3248 numbered subsections with values from 0 to 8192. Objects assembled into the
3249 same subsection go into the object file together with other objects in the same
3250 subsection. For example, a compiler might want to store constants in the text
3251 section, but might not want to have them interspersed with the program being
3252 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3253 section of code being output, and a @samp{.text 1} before each group of
3254 constants being output.
3256 Subsections are optional. If you do not use subsections, everything
3257 goes in subsection number zero.
3260 Each subsection is zero-padded up to a multiple of four bytes.
3261 (Subsections may be padded a different amount on different flavors
3262 of @command{@value{AS}}.)
3266 On the H8/300 platform, each subsection is zero-padded to a word
3267 boundary (two bytes).
3268 The same is true on the Renesas SH.
3271 @c FIXME section padding (alignment)?
3272 @c Rich Pixley says padding here depends on target obj code format; that
3273 @c doesn't seem particularly useful to say without further elaboration,
3274 @c so for now I say nothing about it. If this is a generic BFD issue,
3275 @c these paragraphs might need to vanish from this manual, and be
3276 @c discussed in BFD chapter of binutils (or some such).
3280 Subsections appear in your object file in numeric order, lowest numbered
3281 to highest. (All this to be compatible with other people's assemblers.)
3282 The object file contains no representation of subsections; @code{@value{LD}} and
3283 other programs that manipulate object files see no trace of them.
3284 They just see all your text subsections as a text section, and all your
3285 data subsections as a data section.
3287 To specify which subsection you want subsequent statements assembled
3288 into, use a numeric argument to specify it, in a @samp{.text
3289 @var{expression}} or a @samp{.data @var{expression}} statement.
3292 When generating COFF output, you
3297 can also use an extra subsection
3298 argument with arbitrary named sections: @samp{.section @var{name},
3303 When generating ELF output, you
3308 can also use the @code{.subsection} directive (@pxref{SubSection})
3309 to specify a subsection: @samp{.subsection @var{expression}}.
3311 @var{Expression} should be an absolute expression
3312 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3313 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3314 begins in @code{text 0}. For instance:
3316 .text 0 # The default subsection is text 0 anyway.
3317 .ascii "This lives in the first text subsection. *"
3319 .ascii "But this lives in the second text subsection."
3321 .ascii "This lives in the data section,"
3322 .ascii "in the first data subsection."
3324 .ascii "This lives in the first text section,"
3325 .ascii "immediately following the asterisk (*)."
3328 Each section has a @dfn{location counter} incremented by one for every byte
3329 assembled into that section. Because subsections are merely a convenience
3330 restricted to @command{@value{AS}} there is no concept of a subsection location
3331 counter. There is no way to directly manipulate a location counter---but the
3332 @code{.align} directive changes it, and any label definition captures its
3333 current value. The location counter of the section where statements are being
3334 assembled is said to be the @dfn{active} location counter.
3337 @section bss Section
3340 @cindex common variable storage
3341 The bss section is used for local common variable storage.
3342 You may allocate address space in the bss section, but you may
3343 not dictate data to load into it before your program executes. When
3344 your program starts running, all the contents of the bss
3345 section are zeroed bytes.
3347 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3348 @ref{Lcomm,,@code{.lcomm}}.
3350 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3351 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3354 When assembling for a target which supports multiple sections, such as ELF or
3355 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3356 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3357 section. Typically the section will only contain symbol definitions and
3358 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3365 Symbols are a central concept: the programmer uses symbols to name
3366 things, the linker uses symbols to link, and the debugger uses symbols
3370 @cindex debuggers, and symbol order
3371 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3372 the same order they were declared. This may break some debuggers.
3377 * Setting Symbols:: Giving Symbols Other Values
3378 * Symbol Names:: Symbol Names
3379 * Dot:: The Special Dot Symbol
3380 * Symbol Attributes:: Symbol Attributes
3387 A @dfn{label} is written as a symbol immediately followed by a colon
3388 @samp{:}. The symbol then represents the current value of the
3389 active location counter, and is, for example, a suitable instruction
3390 operand. You are warned if you use the same symbol to represent two
3391 different locations: the first definition overrides any other
3395 On the HPPA, the usual form for a label need not be immediately followed by a
3396 colon, but instead must start in column zero. Only one label may be defined on
3397 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3398 provides a special directive @code{.label} for defining labels more flexibly.
3401 @node Setting Symbols
3402 @section Giving Symbols Other Values
3404 @cindex assigning values to symbols
3405 @cindex symbol values, assigning
3406 A symbol can be given an arbitrary value by writing a symbol, followed
3407 by an equals sign @samp{=}, followed by an expression
3408 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3409 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3410 equals sign @samp{=}@samp{=} here represents an equivalent of the
3411 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3414 Blackfin does not support symbol assignment with @samp{=}.
3418 @section Symbol Names
3420 @cindex symbol names
3421 @cindex names, symbol
3422 @ifclear SPECIAL-SYMS
3423 Symbol names begin with a letter or with one of @samp{._}. On most
3424 machines, you can also use @code{$} in symbol names; exceptions are
3425 noted in @ref{Machine Dependencies}. That character may be followed by any
3426 string of digits, letters, dollar signs (unless otherwise noted for a
3427 particular target machine), and underscores.
3431 Symbol names begin with a letter or with one of @samp{._}. On the
3432 Renesas SH you can also use @code{$} in symbol names. That
3433 character may be followed by any string of digits, letters, dollar signs (save
3434 on the H8/300), and underscores.
3438 Case of letters is significant: @code{foo} is a different symbol name
3441 Each symbol has exactly one name. Each name in an assembly language program
3442 refers to exactly one symbol. You may use that symbol name any number of times
3445 @subheading Local Symbol Names
3447 @cindex local symbol names
3448 @cindex symbol names, local
3449 A local symbol is any symbol beginning with certain local label prefixes.
3450 By default, the local label prefix is @samp{.L} for ELF systems or
3451 @samp{L} for traditional a.out systems, but each target may have its own
3452 set of local label prefixes.
3454 On the HPPA local symbols begin with @samp{L$}.
3457 Local symbols are defined and used within the assembler, but they are
3458 normally not saved in object files. Thus, they are not visible when debugging.
3459 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3460 @option{-L}}) to retain the local symbols in the object files.
3462 @subheading Local Labels
3464 @cindex local labels
3465 @cindex temporary symbol names
3466 @cindex symbol names, temporary
3467 Local labels help compilers and programmers use names temporarily.
3468 They create symbols which are guaranteed to be unique over the entire scope of
3469 the input source code and which can be referred to by a simple notation.
3470 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3471 represents any positive integer). To refer to the most recent previous
3472 definition of that label write @samp{@b{N}b}, using the same number as when
3473 you defined the label. To refer to the next definition of a local label, write
3474 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3477 There is no restriction on how you can use these labels, and you can reuse them
3478 too. So that it is possible to repeatedly define the same local label (using
3479 the same number @samp{@b{N}}), although you can only refer to the most recently
3480 defined local label of that number (for a backwards reference) or the next
3481 definition of a specific local label for a forward reference. It is also worth
3482 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3483 implemented in a slightly more efficient manner than the others.
3494 Which is the equivalent of:
3497 label_1: branch label_3
3498 label_2: branch label_1
3499 label_3: branch label_4
3500 label_4: branch label_3
3503 Local label names are only a notational device. They are immediately
3504 transformed into more conventional symbol names before the assembler uses them.
3505 The symbol names are stored in the symbol table, appear in error messages, and
3506 are optionally emitted to the object file. The names are constructed using
3510 @item @emph{local label prefix}
3511 All local symbols begin with the system-specific local label prefix.
3512 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3513 that start with the local label prefix. These labels are
3514 used for symbols you are never intended to see. If you use the
3515 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3516 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3517 you may use them in debugging.
3520 This is the number that was used in the local label definition. So if the
3521 label is written @samp{55:} then the number is @samp{55}.
3524 This unusual character is included so you do not accidentally invent a symbol
3525 of the same name. The character has ASCII value of @samp{\002} (control-B).
3527 @item @emph{ordinal number}
3528 This is a serial number to keep the labels distinct. The first definition of
3529 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3530 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3531 the number @samp{1} and its 15th definition gets @samp{15} as well.
3534 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3535 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3537 @subheading Dollar Local Labels
3538 @cindex dollar local symbols
3540 @code{@value{AS}} also supports an even more local form of local labels called
3541 dollar labels. These labels go out of scope (i.e., they become undefined) as
3542 soon as a non-local label is defined. Thus they remain valid for only a small
3543 region of the input source code. Normal local labels, by contrast, remain in
3544 scope for the entire file, or until they are redefined by another occurrence of
3545 the same local label.
3547 Dollar labels are defined in exactly the same way as ordinary local labels,
3548 except that they have a dollar sign suffix to their numeric value, e.g.,
3551 They can also be distinguished from ordinary local labels by their transformed
3552 names which use ASCII character @samp{\001} (control-A) as the magic character
3553 to distinguish them from ordinary labels. For example, the fifth definition of
3554 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3557 @section The Special Dot Symbol
3559 @cindex dot (symbol)
3560 @cindex @code{.} (symbol)
3561 @cindex current address
3562 @cindex location counter
3563 The special symbol @samp{.} refers to the current address that
3564 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3565 .long .} defines @code{melvin} to contain its own address.
3566 Assigning a value to @code{.} is treated the same as a @code{.org}
3568 @ifclear no-space-dir
3569 Thus, the expression @samp{.=.+4} is the same as saying
3573 @node Symbol Attributes
3574 @section Symbol Attributes
3576 @cindex symbol attributes
3577 @cindex attributes, symbol
3578 Every symbol has, as well as its name, the attributes ``Value'' and
3579 ``Type''. Depending on output format, symbols can also have auxiliary
3582 The detailed definitions are in @file{a.out.h}.
3585 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3586 all these attributes, and probably won't warn you. This makes the
3587 symbol an externally defined symbol, which is generally what you
3591 * Symbol Value:: Value
3592 * Symbol Type:: Type
3595 * a.out Symbols:: Symbol Attributes: @code{a.out}
3599 * a.out Symbols:: Symbol Attributes: @code{a.out}
3602 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3607 * COFF Symbols:: Symbol Attributes for COFF
3610 * SOM Symbols:: Symbol Attributes for SOM
3617 @cindex value of a symbol
3618 @cindex symbol value
3619 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3620 location in the text, data, bss or absolute sections the value is the
3621 number of addresses from the start of that section to the label.
3622 Naturally for text, data and bss sections the value of a symbol changes
3623 as @code{@value{LD}} changes section base addresses during linking. Absolute
3624 symbols' values do not change during linking: that is why they are
3627 The value of an undefined symbol is treated in a special way. If it is
3628 0 then the symbol is not defined in this assembler source file, and
3629 @code{@value{LD}} tries to determine its value from other files linked into the
3630 same program. You make this kind of symbol simply by mentioning a symbol
3631 name without defining it. A non-zero value represents a @code{.comm}
3632 common declaration. The value is how much common storage to reserve, in
3633 bytes (addresses). The symbol refers to the first address of the
3639 @cindex type of a symbol
3641 The type attribute of a symbol contains relocation (section)
3642 information, any flag settings indicating that a symbol is external, and
3643 (optionally), other information for linkers and debuggers. The exact
3644 format depends on the object-code output format in use.
3649 @c The following avoids a "widow" subsection title. @group would be
3650 @c better if it were available outside examples.
3653 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3655 @cindex @code{b.out} symbol attributes
3656 @cindex symbol attributes, @code{b.out}
3657 These symbol attributes appear only when @command{@value{AS}} is configured for
3658 one of the Berkeley-descended object output formats---@code{a.out} or
3664 @subsection Symbol Attributes: @code{a.out}
3666 @cindex @code{a.out} symbol attributes
3667 @cindex symbol attributes, @code{a.out}
3673 @subsection Symbol Attributes: @code{a.out}
3675 @cindex @code{a.out} symbol attributes
3676 @cindex symbol attributes, @code{a.out}
3680 * Symbol Desc:: Descriptor
3681 * Symbol Other:: Other
3685 @subsubsection Descriptor
3687 @cindex descriptor, of @code{a.out} symbol
3688 This is an arbitrary 16-bit value. You may establish a symbol's
3689 descriptor value by using a @code{.desc} statement
3690 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3691 @command{@value{AS}}.
3694 @subsubsection Other
3696 @cindex other attribute, of @code{a.out} symbol
3697 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3702 @subsection Symbol Attributes for COFF
3704 @cindex COFF symbol attributes
3705 @cindex symbol attributes, COFF
3707 The COFF format supports a multitude of auxiliary symbol attributes;
3708 like the primary symbol attributes, they are set between @code{.def} and
3709 @code{.endef} directives.
3711 @subsubsection Primary Attributes
3713 @cindex primary attributes, COFF symbols
3714 The symbol name is set with @code{.def}; the value and type,
3715 respectively, with @code{.val} and @code{.type}.
3717 @subsubsection Auxiliary Attributes
3719 @cindex auxiliary attributes, COFF symbols
3720 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3721 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3722 table information for COFF.
3727 @subsection Symbol Attributes for SOM
3729 @cindex SOM symbol attributes
3730 @cindex symbol attributes, SOM
3732 The SOM format for the HPPA supports a multitude of symbol attributes set with
3733 the @code{.EXPORT} and @code{.IMPORT} directives.
3735 The attributes are described in @cite{HP9000 Series 800 Assembly
3736 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3737 @code{EXPORT} assembler directive documentation.
3741 @chapter Expressions
3745 @cindex numeric values
3746 An @dfn{expression} specifies an address or numeric value.
3747 Whitespace may precede and/or follow an expression.
3749 The result of an expression must be an absolute number, or else an offset into
3750 a particular section. If an expression is not absolute, and there is not
3751 enough information when @command{@value{AS}} sees the expression to know its
3752 section, a second pass over the source program might be necessary to interpret
3753 the expression---but the second pass is currently not implemented.
3754 @command{@value{AS}} aborts with an error message in this situation.
3757 * Empty Exprs:: Empty Expressions
3758 * Integer Exprs:: Integer Expressions
3762 @section Empty Expressions
3764 @cindex empty expressions
3765 @cindex expressions, empty
3766 An empty expression has no value: it is just whitespace or null.
3767 Wherever an absolute expression is required, you may omit the
3768 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3769 is compatible with other assemblers.
3772 @section Integer Expressions
3774 @cindex integer expressions
3775 @cindex expressions, integer
3776 An @dfn{integer expression} is one or more @emph{arguments} delimited
3777 by @emph{operators}.
3780 * Arguments:: Arguments
3781 * Operators:: Operators
3782 * Prefix Ops:: Prefix Operators
3783 * Infix Ops:: Infix Operators
3787 @subsection Arguments
3789 @cindex expression arguments
3790 @cindex arguments in expressions
3791 @cindex operands in expressions
3792 @cindex arithmetic operands
3793 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3794 contexts arguments are sometimes called ``arithmetic operands''. In
3795 this manual, to avoid confusing them with the ``instruction operands'' of
3796 the machine language, we use the term ``argument'' to refer to parts of
3797 expressions only, reserving the word ``operand'' to refer only to machine
3798 instruction operands.
3800 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3801 @var{section} is one of text, data, bss, absolute,
3802 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3805 Numbers are usually integers.
3807 A number can be a flonum or bignum. In this case, you are warned
3808 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3809 these 32 bits are an integer. You may write integer-manipulating
3810 instructions that act on exotic constants, compatible with other
3813 @cindex subexpressions
3814 Subexpressions are a left parenthesis @samp{(} followed by an integer
3815 expression, followed by a right parenthesis @samp{)}; or a prefix
3816 operator followed by an argument.
3819 @subsection Operators
3821 @cindex operators, in expressions
3822 @cindex arithmetic functions
3823 @cindex functions, in expressions
3824 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3825 operators are followed by an argument. Infix operators appear
3826 between their arguments. Operators may be preceded and/or followed by
3830 @subsection Prefix Operator
3832 @cindex prefix operators
3833 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3834 one argument, which must be absolute.
3836 @c the tex/end tex stuff surrounding this small table is meant to make
3837 @c it align, on the printed page, with the similar table in the next
3838 @c section (which is inside an enumerate).
3840 \global\advance\leftskip by \itemindent
3845 @dfn{Negation}. Two's complement negation.
3847 @dfn{Complementation}. Bitwise not.
3851 \global\advance\leftskip by -\itemindent
3855 @subsection Infix Operators
3857 @cindex infix operators
3858 @cindex operators, permitted arguments
3859 @dfn{Infix operators} take two arguments, one on either side. Operators
3860 have precedence, but operations with equal precedence are performed left
3861 to right. Apart from @code{+} or @option{-}, both arguments must be
3862 absolute, and the result is absolute.
3865 @cindex operator precedence
3866 @cindex precedence of operators
3873 @dfn{Multiplication}.
3876 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3882 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3885 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3889 Intermediate precedence
3894 @dfn{Bitwise Inclusive Or}.
3900 @dfn{Bitwise Exclusive Or}.
3903 @dfn{Bitwise Or Not}.
3910 @cindex addition, permitted arguments
3911 @cindex plus, permitted arguments
3912 @cindex arguments for addition
3914 @dfn{Addition}. If either argument is absolute, the result has the section of
3915 the other argument. You may not add together arguments from different
3918 @cindex subtraction, permitted arguments
3919 @cindex minus, permitted arguments
3920 @cindex arguments for subtraction
3922 @dfn{Subtraction}. If the right argument is absolute, the
3923 result has the section of the left argument.
3924 If both arguments are in the same section, the result is absolute.
3925 You may not subtract arguments from different sections.
3926 @c FIXME is there still something useful to say about undefined - undefined ?
3928 @cindex comparison expressions
3929 @cindex expressions, comparison
3934 @dfn{Is Not Equal To}
3938 @dfn{Is Greater Than}
3940 @dfn{Is Greater Than Or Equal To}
3942 @dfn{Is Less Than Or Equal To}
3944 The comparison operators can be used as infix operators. A true results has a
3945 value of -1 whereas a false result has a value of 0. Note, these operators
3946 perform signed comparisons.
3949 @item Lowest Precedence
3958 These two logical operations can be used to combine the results of sub
3959 expressions. Note, unlike the comparison operators a true result returns a
3960 value of 1 but a false results does still return 0. Also note that the logical
3961 or operator has a slightly lower precedence than logical and.
3966 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3967 address; you can only have a defined section in one of the two arguments.
3970 @chapter Assembler Directives
3972 @cindex directives, machine independent
3973 @cindex pseudo-ops, machine independent
3974 @cindex machine independent directives
3975 All assembler directives have names that begin with a period (@samp{.}).
3976 The rest of the name is letters, usually in lower case.
3978 This chapter discusses directives that are available regardless of the
3979 target machine configuration for the @sc{gnu} assembler.
3981 Some machine configurations provide additional directives.
3982 @xref{Machine Dependencies}.
3985 @ifset machine-directives
3986 @xref{Machine Dependencies}, for additional directives.
3991 * Abort:: @code{.abort}
3993 * ABORT (COFF):: @code{.ABORT}
3996 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3997 * Altmacro:: @code{.altmacro}
3998 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3999 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4000 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4001 * Byte:: @code{.byte @var{expressions}}
4002 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4003 * Comm:: @code{.comm @var{symbol} , @var{length} }
4004 * Data:: @code{.data @var{subsection}}
4006 * Def:: @code{.def @var{name}}
4009 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4015 * Double:: @code{.double @var{flonums}}
4016 * Eject:: @code{.eject}
4017 * Else:: @code{.else}
4018 * Elseif:: @code{.elseif}
4021 * Endef:: @code{.endef}
4024 * Endfunc:: @code{.endfunc}
4025 * Endif:: @code{.endif}
4026 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4027 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4028 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4030 * Error:: @code{.error @var{string}}
4031 * Exitm:: @code{.exitm}
4032 * Extern:: @code{.extern}
4033 * Fail:: @code{.fail}
4034 * File:: @code{.file}
4035 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4036 * Float:: @code{.float @var{flonums}}
4037 * Func:: @code{.func}
4038 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4040 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4041 * Hidden:: @code{.hidden @var{names}}
4044 * hword:: @code{.hword @var{expressions}}
4045 * Ident:: @code{.ident}
4046 * If:: @code{.if @var{absolute expression}}
4047 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4048 * Include:: @code{.include "@var{file}"}
4049 * Int:: @code{.int @var{expressions}}
4051 * Internal:: @code{.internal @var{names}}
4054 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4055 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4056 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4057 * Lflags:: @code{.lflags}
4058 @ifclear no-line-dir
4059 * Line:: @code{.line @var{line-number}}
4062 * Linkonce:: @code{.linkonce [@var{type}]}
4063 * List:: @code{.list}
4064 * Ln:: @code{.ln @var{line-number}}
4065 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4066 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4068 * Local:: @code{.local @var{names}}
4071 * Long:: @code{.long @var{expressions}}
4073 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4076 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4077 * MRI:: @code{.mri @var{val}}
4078 * Noaltmacro:: @code{.noaltmacro}
4079 * Nolist:: @code{.nolist}
4080 * Octa:: @code{.octa @var{bignums}}
4081 * Org:: @code{.org @var{new-lc}, @var{fill}}
4082 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4084 * PopSection:: @code{.popsection}
4085 * Previous:: @code{.previous}
4088 * Print:: @code{.print @var{string}}
4090 * Protected:: @code{.protected @var{names}}
4093 * Psize:: @code{.psize @var{lines}, @var{columns}}
4094 * Purgem:: @code{.purgem @var{name}}
4096 * PushSection:: @code{.pushsection @var{name}}
4099 * Quad:: @code{.quad @var{bignums}}
4100 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4101 * Rept:: @code{.rept @var{count}}
4102 * Sbttl:: @code{.sbttl "@var{subheading}"}
4104 * Scl:: @code{.scl @var{class}}
4107 * Section:: @code{.section @var{name}[, @var{flags}]}
4110 * Set:: @code{.set @var{symbol}, @var{expression}}
4111 * Short:: @code{.short @var{expressions}}
4112 * Single:: @code{.single @var{flonums}}
4114 * Size:: @code{.size [@var{name} , @var{expression}]}
4116 @ifclear no-space-dir
4117 * Skip:: @code{.skip @var{size} , @var{fill}}
4120 * Sleb128:: @code{.sleb128 @var{expressions}}
4121 @ifclear no-space-dir
4122 * Space:: @code{.space @var{size} , @var{fill}}
4125 * Stab:: @code{.stabd, .stabn, .stabs}
4128 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4129 * Struct:: @code{.struct @var{expression}}
4131 * SubSection:: @code{.subsection}
4132 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4136 * Tag:: @code{.tag @var{structname}}
4139 * Text:: @code{.text @var{subsection}}
4140 * Title:: @code{.title "@var{heading}"}
4142 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4145 * Uleb128:: @code{.uleb128 @var{expressions}}
4147 * Val:: @code{.val @var{addr}}
4151 * Version:: @code{.version "@var{string}"}
4152 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4153 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4156 * Warning:: @code{.warning @var{string}}
4157 * Weak:: @code{.weak @var{names}}
4158 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4159 * Word:: @code{.word @var{expressions}}
4160 * Deprecated:: Deprecated Directives
4164 @section @code{.abort}
4166 @cindex @code{abort} directive
4167 @cindex stopping the assembly
4168 This directive stops the assembly immediately. It is for
4169 compatibility with other assemblers. The original idea was that the
4170 assembly language source would be piped into the assembler. If the sender
4171 of the source quit, it could use this directive tells @command{@value{AS}} to
4172 quit also. One day @code{.abort} will not be supported.
4176 @section @code{.ABORT} (COFF)
4178 @cindex @code{ABORT} directive
4179 When producing COFF output, @command{@value{AS}} accepts this directive as a
4180 synonym for @samp{.abort}.
4183 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4189 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4191 @cindex padding the location counter
4192 @cindex @code{align} directive
4193 Pad the location counter (in the current subsection) to a particular storage
4194 boundary. The first expression (which must be absolute) is the alignment
4195 required, as described below.
4197 The second expression (also absolute) gives the fill value to be stored in the
4198 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4199 padding bytes are normally zero. However, on some systems, if the section is
4200 marked as containing code and the fill value is omitted, the space is filled
4201 with no-op instructions.
4203 The third expression is also absolute, and is also optional. If it is present,
4204 it is the maximum number of bytes that should be skipped by this alignment
4205 directive. If doing the alignment would require skipping more bytes than the
4206 specified maximum, then the alignment is not done at all. You can omit the
4207 fill value (the second argument) entirely by simply using two commas after the
4208 required alignment; this can be useful if you want the alignment to be filled
4209 with no-op instructions when appropriate.
4211 The way the required alignment is specified varies from system to system.
4212 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4213 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4214 alignment request in bytes. For example @samp{.align 8} advances
4215 the location counter until it is a multiple of 8. If the location counter
4216 is already a multiple of 8, no change is needed. For the tic54x, the
4217 first expression is the alignment request in words.
4219 For other systems, including ppc, i386 using a.out format, arm and
4220 strongarm, it is the
4221 number of low-order zero bits the location counter must have after
4222 advancement. For example @samp{.align 3} advances the location
4223 counter until it a multiple of 8. If the location counter is already a
4224 multiple of 8, no change is needed.
4226 This inconsistency is due to the different behaviors of the various
4227 native assemblers for these systems which GAS must emulate.
4228 GAS also provides @code{.balign} and @code{.p2align} directives,
4229 described later, which have a consistent behavior across all
4230 architectures (but are specific to GAS).
4233 @section @code{.altmacro}
4234 Enable alternate macro mode, enabling:
4237 @item LOCAL @var{name} [ , @dots{} ]
4238 One additional directive, @code{LOCAL}, is available. It is used to
4239 generate a string replacement for each of the @var{name} arguments, and
4240 replace any instances of @var{name} in each macro expansion. The
4241 replacement string is unique in the assembly, and different for each
4242 separate macro expansion. @code{LOCAL} allows you to write macros that
4243 define symbols, without fear of conflict between separate macro expansions.
4245 @item String delimiters
4246 You can write strings delimited in these other ways besides
4247 @code{"@var{string}"}:
4250 @item '@var{string}'
4251 You can delimit strings with single-quote characters.
4253 @item <@var{string}>
4254 You can delimit strings with matching angle brackets.
4257 @item single-character string escape
4258 To include any single character literally in a string (even if the
4259 character would otherwise have some special meaning), you can prefix the
4260 character with @samp{!} (an exclamation mark). For example, you can
4261 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4263 @item Expression results as strings
4264 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4265 and use the result as a string.
4269 @section @code{.ascii "@var{string}"}@dots{}
4271 @cindex @code{ascii} directive
4272 @cindex string literals
4273 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4274 separated by commas. It assembles each string (with no automatic
4275 trailing zero byte) into consecutive addresses.
4278 @section @code{.asciz "@var{string}"}@dots{}
4280 @cindex @code{asciz} directive
4281 @cindex zero-terminated strings
4282 @cindex null-terminated strings
4283 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4284 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4287 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4289 @cindex padding the location counter given number of bytes
4290 @cindex @code{balign} directive
4291 Pad the location counter (in the current subsection) to a particular
4292 storage boundary. The first expression (which must be absolute) is the
4293 alignment request in bytes. For example @samp{.balign 8} advances
4294 the location counter until it is a multiple of 8. If the location counter
4295 is already a multiple of 8, no change is needed.
4297 The second expression (also absolute) gives the fill value to be stored in the
4298 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4299 padding bytes are normally zero. However, on some systems, if the section is
4300 marked as containing code and the fill value is omitted, the space is filled
4301 with no-op instructions.
4303 The third expression is also absolute, and is also optional. If it is present,
4304 it is the maximum number of bytes that should be skipped by this alignment
4305 directive. If doing the alignment would require skipping more bytes than the
4306 specified maximum, then the alignment is not done at all. You can omit the
4307 fill value (the second argument) entirely by simply using two commas after the
4308 required alignment; this can be useful if you want the alignment to be filled
4309 with no-op instructions when appropriate.
4311 @cindex @code{balignw} directive
4312 @cindex @code{balignl} directive
4313 The @code{.balignw} and @code{.balignl} directives are variants of the
4314 @code{.balign} directive. The @code{.balignw} directive treats the fill
4315 pattern as a two byte word value. The @code{.balignl} directives treats the
4316 fill pattern as a four byte longword value. For example, @code{.balignw
4317 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4318 filled in with the value 0x368d (the exact placement of the bytes depends upon
4319 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4323 @section @code{.byte @var{expressions}}
4325 @cindex @code{byte} directive
4326 @cindex integers, one byte
4327 @code{.byte} expects zero or more expressions, separated by commas.
4328 Each expression is assembled into the next byte.
4330 @node CFI directives
4331 @section @code{.cfi_sections @var{section_list}}
4332 @cindex @code{cfi_sections} directive
4333 @code{.cfi_sections} may be used to specify whether CFI directives
4334 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4335 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4336 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4337 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4338 directive is not used is @code{.cfi_sections .eh_frame}.
4340 @section @code{.cfi_startproc [simple]}
4341 @cindex @code{cfi_startproc} directive
4342 @code{.cfi_startproc} is used at the beginning of each function that
4343 should have an entry in @code{.eh_frame}. It initializes some internal
4344 data structures. Don't forget to close the function by
4345 @code{.cfi_endproc}.
4347 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4348 it also emits some architecture dependent initial CFI instructions.
4350 @section @code{.cfi_endproc}
4351 @cindex @code{cfi_endproc} directive
4352 @code{.cfi_endproc} is used at the end of a function where it closes its
4353 unwind entry previously opened by
4354 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4356 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4357 @code{.cfi_personality} defines personality routine and its encoding.
4358 @var{encoding} must be a constant determining how the personality
4359 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4360 argument is not present, otherwise second argument should be
4361 a constant or a symbol name. When using indirect encodings,
4362 the symbol provided should be the location where personality
4363 can be loaded from, not the personality routine itself.
4364 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4365 no personality routine.
4367 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4368 @code{.cfi_lsda} defines LSDA and its encoding.
4369 @var{encoding} must be a constant determining how the LSDA
4370 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4371 argument is not present, otherwise second argument should be a constant
4372 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4375 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4376 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4377 address from @var{register} and add @var{offset} to it}.
4379 @section @code{.cfi_def_cfa_register @var{register}}
4380 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4381 now on @var{register} will be used instead of the old one. Offset
4384 @section @code{.cfi_def_cfa_offset @var{offset}}
4385 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4386 remains the same, but @var{offset} is new. Note that it is the
4387 absolute offset that will be added to a defined register to compute
4390 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4391 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4392 value that is added/substracted from the previous offset.
4394 @section @code{.cfi_offset @var{register}, @var{offset}}
4395 Previous value of @var{register} is saved at offset @var{offset} from
4398 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4399 Previous value of @var{register} is saved at offset @var{offset} from
4400 the current CFA register. This is transformed to @code{.cfi_offset}
4401 using the known displacement of the CFA register from the CFA.
4402 This is often easier to use, because the number will match the
4403 code it's annotating.
4405 @section @code{.cfi_register @var{register1}, @var{register2}}
4406 Previous value of @var{register1} is saved in register @var{register2}.
4408 @section @code{.cfi_restore @var{register}}
4409 @code{.cfi_restore} says that the rule for @var{register} is now the
4410 same as it was at the beginning of the function, after all initial
4411 instruction added by @code{.cfi_startproc} were executed.
4413 @section @code{.cfi_undefined @var{register}}
4414 From now on the previous value of @var{register} can't be restored anymore.
4416 @section @code{.cfi_same_value @var{register}}
4417 Current value of @var{register} is the same like in the previous frame,
4418 i.e. no restoration needed.
4420 @section @code{.cfi_remember_state},
4421 First save all current rules for all registers by @code{.cfi_remember_state},
4422 then totally screw them up by subsequent @code{.cfi_*} directives and when
4423 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4424 the previous saved state.
4426 @section @code{.cfi_return_column @var{register}}
4427 Change return column @var{register}, i.e. the return address is either
4428 directly in @var{register} or can be accessed by rules for @var{register}.
4430 @section @code{.cfi_signal_frame}
4431 Mark current function as signal trampoline.
4433 @section @code{.cfi_window_save}
4434 SPARC register window has been saved.
4436 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4437 Allows the user to add arbitrary bytes to the unwind info. One
4438 might use this to add OS-specific CFI opcodes, or generic CFI
4439 opcodes that GAS does not yet support.
4441 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4442 The current value of @var{register} is @var{label}. The value of @var{label}
4443 will be encoded in the output file according to @var{encoding}; see the
4444 description of @code{.cfi_personality} for details on this encoding.
4446 The usefulness of equating a register to a fixed label is probably
4447 limited to the return address register. Here, it can be useful to
4448 mark a code segment that has only one return address which is reached
4449 by a direct branch and no copy of the return address exists in memory
4450 or another register.
4453 @section @code{.comm @var{symbol} , @var{length} }
4455 @cindex @code{comm} directive
4456 @cindex symbol, common
4457 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4458 common symbol in one object file may be merged with a defined or common symbol
4459 of the same name in another object file. If @code{@value{LD}} does not see a
4460 definition for the symbol--just one or more common symbols--then it will
4461 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4462 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4463 the same name, and they do not all have the same size, it will allocate space
4464 using the largest size.
4467 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4468 an optional third argument. This is the desired alignment of the symbol,
4469 specified for ELF as a byte boundary (for example, an alignment of 16 means
4470 that the least significant 4 bits of the address should be zero), and for PE
4471 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4472 boundary). The alignment must be an absolute expression, and it must be a
4473 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4474 common symbol, it will use the alignment when placing the symbol. If no
4475 alignment is specified, @command{@value{AS}} will set the alignment to the
4476 largest power of two less than or equal to the size of the symbol, up to a
4477 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4478 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4479 @samp{--section-alignment} option; image file sections in PE are aligned to
4480 multiples of 4096, which is far too large an alignment for ordinary variables.
4481 It is rather the default alignment for (non-debug) sections within object
4482 (@samp{*.o}) files, which are less strictly aligned.}.
4486 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4487 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4491 @section @code{.data @var{subsection}}
4493 @cindex @code{data} directive
4494 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4495 end of the data subsection numbered @var{subsection} (which is an
4496 absolute expression). If @var{subsection} is omitted, it defaults
4501 @section @code{.def @var{name}}
4503 @cindex @code{def} directive
4504 @cindex COFF symbols, debugging
4505 @cindex debugging COFF symbols
4506 Begin defining debugging information for a symbol @var{name}; the
4507 definition extends until the @code{.endef} directive is encountered.
4510 This directive is only observed when @command{@value{AS}} is configured for COFF
4511 format output; when producing @code{b.out}, @samp{.def} is recognized,
4518 @section @code{.desc @var{symbol}, @var{abs-expression}}
4520 @cindex @code{desc} directive
4521 @cindex COFF symbol descriptor
4522 @cindex symbol descriptor, COFF
4523 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4524 to the low 16 bits of an absolute expression.
4527 The @samp{.desc} directive is not available when @command{@value{AS}} is
4528 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4529 object format. For the sake of compatibility, @command{@value{AS}} accepts
4530 it, but produces no output, when configured for COFF.
4536 @section @code{.dim}
4538 @cindex @code{dim} directive
4539 @cindex COFF auxiliary symbol information
4540 @cindex auxiliary symbol information, COFF
4541 This directive is generated by compilers to include auxiliary debugging
4542 information in the symbol table. It is only permitted inside
4543 @code{.def}/@code{.endef} pairs.
4546 @samp{.dim} is only meaningful when generating COFF format output; when
4547 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4553 @section @code{.double @var{flonums}}
4555 @cindex @code{double} directive
4556 @cindex floating point numbers (double)
4557 @code{.double} expects zero or more flonums, separated by commas. It
4558 assembles floating point numbers.
4560 The exact kind of floating point numbers emitted depends on how
4561 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4565 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4566 in @sc{ieee} format.
4571 @section @code{.eject}
4573 @cindex @code{eject} directive
4574 @cindex new page, in listings
4575 @cindex page, in listings
4576 @cindex listing control: new page
4577 Force a page break at this point, when generating assembly listings.
4580 @section @code{.else}
4582 @cindex @code{else} directive
4583 @code{.else} is part of the @command{@value{AS}} support for conditional
4584 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4585 of code to be assembled if the condition for the preceding @code{.if}
4589 @section @code{.elseif}
4591 @cindex @code{elseif} directive
4592 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4593 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4594 @code{.if} block that would otherwise fill the entire @code{.else} section.
4597 @section @code{.end}
4599 @cindex @code{end} directive
4600 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4601 process anything in the file past the @code{.end} directive.
4605 @section @code{.endef}
4607 @cindex @code{endef} directive
4608 This directive flags the end of a symbol definition begun with
4612 @samp{.endef} is only meaningful when generating COFF format output; if
4613 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4614 directive but ignores it.
4619 @section @code{.endfunc}
4620 @cindex @code{endfunc} directive
4621 @code{.endfunc} marks the end of a function specified with @code{.func}.
4624 @section @code{.endif}
4626 @cindex @code{endif} directive
4627 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4628 it marks the end of a block of code that is only assembled
4629 conditionally. @xref{If,,@code{.if}}.
4632 @section @code{.equ @var{symbol}, @var{expression}}
4634 @cindex @code{equ} directive
4635 @cindex assigning values to symbols
4636 @cindex symbols, assigning values to
4637 This directive sets the value of @var{symbol} to @var{expression}.
4638 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4641 The syntax for @code{equ} on the HPPA is
4642 @samp{@var{symbol} .equ @var{expression}}.
4646 The syntax for @code{equ} on the Z80 is
4647 @samp{@var{symbol} equ @var{expression}}.
4648 On the Z80 it is an eror if @var{symbol} is already defined,
4649 but the symbol is not protected from later redefinition.
4650 Compare @ref{Equiv}.
4654 @section @code{.equiv @var{symbol}, @var{expression}}
4655 @cindex @code{equiv} directive
4656 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4657 the assembler will signal an error if @var{symbol} is already defined. Note a
4658 symbol which has been referenced but not actually defined is considered to be
4661 Except for the contents of the error message, this is roughly equivalent to
4668 plus it protects the symbol from later redefinition.
4671 @section @code{.eqv @var{symbol}, @var{expression}}
4672 @cindex @code{eqv} directive
4673 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4674 evaluate the expression or any part of it immediately. Instead each time
4675 the resulting symbol is used in an expression, a snapshot of its current
4679 @section @code{.err}
4680 @cindex @code{err} directive
4681 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4682 message and, unless the @option{-Z} option was used, it will not generate an
4683 object file. This can be used to signal an error in conditionally compiled code.
4686 @section @code{.error "@var{string}"}
4687 @cindex error directive
4689 Similarly to @code{.err}, this directive emits an error, but you can specify a
4690 string that will be emitted as the error message. If you don't specify the
4691 message, it defaults to @code{".error directive invoked in source file"}.
4692 @xref{Errors, ,Error and Warning Messages}.
4695 .error "This code has not been assembled and tested."
4699 @section @code{.exitm}
4700 Exit early from the current macro definition. @xref{Macro}.
4703 @section @code{.extern}
4705 @cindex @code{extern} directive
4706 @code{.extern} is accepted in the source program---for compatibility
4707 with other assemblers---but it is ignored. @command{@value{AS}} treats
4708 all undefined symbols as external.
4711 @section @code{.fail @var{expression}}
4713 @cindex @code{fail} directive
4714 Generates an error or a warning. If the value of the @var{expression} is 500
4715 or more, @command{@value{AS}} will print a warning message. If the value is less
4716 than 500, @command{@value{AS}} will print an error message. The message will
4717 include the value of @var{expression}. This can occasionally be useful inside
4718 complex nested macros or conditional assembly.
4721 @section @code{.file}
4722 @cindex @code{file} directive
4724 @ifclear no-file-dir
4725 There are two different versions of the @code{.file} directive. Targets
4726 that support DWARF2 line number information use the DWARF2 version of
4727 @code{.file}. Other targets use the default version.
4729 @subheading Default Version
4731 @cindex logical file name
4732 @cindex file name, logical
4733 This version of the @code{.file} directive tells @command{@value{AS}} that we
4734 are about to start a new logical file. The syntax is:
4740 @var{string} is the new file name. In general, the filename is
4741 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4742 to specify an empty file name, you must give the quotes--@code{""}. This
4743 statement may go away in future: it is only recognized to be compatible with
4744 old @command{@value{AS}} programs.
4746 @subheading DWARF2 Version
4749 When emitting DWARF2 line number information, @code{.file} assigns filenames
4750 to the @code{.debug_line} file name table. The syntax is:
4753 .file @var{fileno} @var{filename}
4756 The @var{fileno} operand should be a unique positive integer to use as the
4757 index of the entry in the table. The @var{filename} operand is a C string
4760 The detail of filename indices is exposed to the user because the filename
4761 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4762 information, and thus the user must know the exact indices that table
4766 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4768 @cindex @code{fill} directive
4769 @cindex writing patterns in memory
4770 @cindex patterns, writing in memory
4771 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4772 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4773 may be zero or more. @var{Size} may be zero or more, but if it is
4774 more than 8, then it is deemed to have the value 8, compatible with
4775 other people's assemblers. The contents of each @var{repeat} bytes
4776 is taken from an 8-byte number. The highest order 4 bytes are
4777 zero. The lowest order 4 bytes are @var{value} rendered in the
4778 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4779 Each @var{size} bytes in a repetition is taken from the lowest order
4780 @var{size} bytes of this number. Again, this bizarre behavior is
4781 compatible with other people's assemblers.
4783 @var{size} and @var{value} are optional.
4784 If the second comma and @var{value} are absent, @var{value} is
4785 assumed zero. If the first comma and following tokens are absent,
4786 @var{size} is assumed to be 1.
4789 @section @code{.float @var{flonums}}
4791 @cindex floating point numbers (single)
4792 @cindex @code{float} directive
4793 This directive assembles zero or more flonums, separated by commas. It
4794 has the same effect as @code{.single}.
4796 The exact kind of floating point numbers emitted depends on how
4797 @command{@value{AS}} is configured.
4798 @xref{Machine Dependencies}.
4802 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4803 in @sc{ieee} format.
4808 @section @code{.func @var{name}[,@var{label}]}
4809 @cindex @code{func} directive
4810 @code{.func} emits debugging information to denote function @var{name}, and
4811 is ignored unless the file is assembled with debugging enabled.
4812 Only @samp{--gstabs[+]} is currently supported.
4813 @var{label} is the entry point of the function and if omitted @var{name}
4814 prepended with the @samp{leading char} is used.
4815 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4816 All functions are currently defined to have @code{void} return type.
4817 The function must be terminated with @code{.endfunc}.
4820 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4822 @cindex @code{global} directive
4823 @cindex symbol, making visible to linker
4824 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4825 @var{symbol} in your partial program, its value is made available to
4826 other partial programs that are linked with it. Otherwise,
4827 @var{symbol} takes its attributes from a symbol of the same name
4828 from another file linked into the same program.
4830 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4831 compatibility with other assemblers.
4834 On the HPPA, @code{.global} is not always enough to make it accessible to other
4835 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4836 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4841 @section @code{.gnu_attribute @var{tag},@var{value}}
4842 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4845 @section @code{.hidden @var{names}}
4847 @cindex @code{hidden} directive
4849 This is one of the ELF visibility directives. The other two are
4850 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4851 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4853 This directive overrides the named symbols default visibility (which is set by
4854 their binding: local, global or weak). The directive sets the visibility to
4855 @code{hidden} which means that the symbols are not visible to other components.
4856 Such symbols are always considered to be @code{protected} as well.
4860 @section @code{.hword @var{expressions}}
4862 @cindex @code{hword} directive
4863 @cindex integers, 16-bit
4864 @cindex numbers, 16-bit
4865 @cindex sixteen bit integers
4866 This expects zero or more @var{expressions}, and emits
4867 a 16 bit number for each.
4870 This directive is a synonym for @samp{.short}; depending on the target
4871 architecture, it may also be a synonym for @samp{.word}.
4875 This directive is a synonym for @samp{.short}.
4878 This directive is a synonym for both @samp{.short} and @samp{.word}.
4883 @section @code{.ident}
4885 @cindex @code{ident} directive
4887 This directive is used by some assemblers to place tags in object files. The
4888 behavior of this directive varies depending on the target. When using the
4889 a.out object file format, @command{@value{AS}} simply accepts the directive for
4890 source-file compatibility with existing assemblers, but does not emit anything
4891 for it. When using COFF, comments are emitted to the @code{.comment} or
4892 @code{.rdata} section, depending on the target. When using ELF, comments are
4893 emitted to the @code{.comment} section.
4896 @section @code{.if @var{absolute expression}}
4898 @cindex conditional assembly
4899 @cindex @code{if} directive
4900 @code{.if} marks the beginning of a section of code which is only
4901 considered part of the source program being assembled if the argument
4902 (which must be an @var{absolute expression}) is non-zero. The end of
4903 the conditional section of code must be marked by @code{.endif}
4904 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4905 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4906 If you have several conditions to check, @code{.elseif} may be used to avoid
4907 nesting blocks if/else within each subsequent @code{.else} block.
4909 The following variants of @code{.if} are also supported:
4911 @cindex @code{ifdef} directive
4912 @item .ifdef @var{symbol}
4913 Assembles the following section of code if the specified @var{symbol}
4914 has been defined. Note a symbol which has been referenced but not yet defined
4915 is considered to be undefined.
4917 @cindex @code{ifb} directive
4918 @item .ifb @var{text}
4919 Assembles the following section of code if the operand is blank (empty).
4921 @cindex @code{ifc} directive
4922 @item .ifc @var{string1},@var{string2}
4923 Assembles the following section of code if the two strings are the same. The
4924 strings may be optionally quoted with single quotes. If they are not quoted,
4925 the first string stops at the first comma, and the second string stops at the
4926 end of the line. Strings which contain whitespace should be quoted. The
4927 string comparison is case sensitive.
4929 @cindex @code{ifeq} directive
4930 @item .ifeq @var{absolute expression}
4931 Assembles the following section of code if the argument is zero.
4933 @cindex @code{ifeqs} directive
4934 @item .ifeqs @var{string1},@var{string2}
4935 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4937 @cindex @code{ifge} directive
4938 @item .ifge @var{absolute expression}
4939 Assembles the following section of code if the argument is greater than or
4942 @cindex @code{ifgt} directive
4943 @item .ifgt @var{absolute expression}
4944 Assembles the following section of code if the argument is greater than zero.
4946 @cindex @code{ifle} directive
4947 @item .ifle @var{absolute expression}
4948 Assembles the following section of code if the argument is less than or equal
4951 @cindex @code{iflt} directive
4952 @item .iflt @var{absolute expression}
4953 Assembles the following section of code if the argument is less than zero.
4955 @cindex @code{ifnb} directive
4956 @item .ifnb @var{text}
4957 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4958 following section of code if the operand is non-blank (non-empty).
4960 @cindex @code{ifnc} directive
4961 @item .ifnc @var{string1},@var{string2}.
4962 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4963 following section of code if the two strings are not the same.
4965 @cindex @code{ifndef} directive
4966 @cindex @code{ifnotdef} directive
4967 @item .ifndef @var{symbol}
4968 @itemx .ifnotdef @var{symbol}
4969 Assembles the following section of code if the specified @var{symbol}
4970 has not been defined. Both spelling variants are equivalent. Note a symbol
4971 which has been referenced but not yet defined is considered to be undefined.
4973 @cindex @code{ifne} directive
4974 @item .ifne @var{absolute expression}
4975 Assembles the following section of code if the argument is not equal to zero
4976 (in other words, this is equivalent to @code{.if}).
4978 @cindex @code{ifnes} directive
4979 @item .ifnes @var{string1},@var{string2}
4980 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4981 following section of code if the two strings are not the same.
4985 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4987 @cindex @code{incbin} directive
4988 @cindex binary files, including
4989 The @code{incbin} directive includes @var{file} verbatim at the current
4990 location. You can control the search paths used with the @samp{-I} command-line
4991 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4994 The @var{skip} argument skips a number of bytes from the start of the
4995 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4996 read. Note that the data is not aligned in any way, so it is the user's
4997 responsibility to make sure that proper alignment is provided both before and
4998 after the @code{incbin} directive.
5001 @section @code{.include "@var{file}"}
5003 @cindex @code{include} directive
5004 @cindex supporting files, including
5005 @cindex files, including
5006 This directive provides a way to include supporting files at specified
5007 points in your source program. The code from @var{file} is assembled as
5008 if it followed the point of the @code{.include}; when the end of the
5009 included file is reached, assembly of the original file continues. You
5010 can control the search paths used with the @samp{-I} command-line option
5011 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5015 @section @code{.int @var{expressions}}
5017 @cindex @code{int} directive
5018 @cindex integers, 32-bit
5019 Expect zero or more @var{expressions}, of any section, separated by commas.
5020 For each expression, emit a number that, at run time, is the value of that
5021 expression. The byte order and bit size of the number depends on what kind
5022 of target the assembly is for.
5026 On most forms of the H8/300, @code{.int} emits 16-bit
5027 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5034 @section @code{.internal @var{names}}
5036 @cindex @code{internal} directive
5038 This is one of the ELF visibility directives. The other two are
5039 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5040 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5042 This directive overrides the named symbols default visibility (which is set by
5043 their binding: local, global or weak). The directive sets the visibility to
5044 @code{internal} which means that the symbols are considered to be @code{hidden}
5045 (i.e., not visible to other components), and that some extra, processor specific
5046 processing must also be performed upon the symbols as well.
5050 @section @code{.irp @var{symbol},@var{values}}@dots{}
5052 @cindex @code{irp} directive
5053 Evaluate a sequence of statements assigning different values to @var{symbol}.
5054 The sequence of statements starts at the @code{.irp} directive, and is
5055 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5056 set to @var{value}, and the sequence of statements is assembled. If no
5057 @var{value} is listed, the sequence of statements is assembled once, with
5058 @var{symbol} set to the null string. To refer to @var{symbol} within the
5059 sequence of statements, use @var{\symbol}.
5061 For example, assembling
5069 is equivalent to assembling
5077 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5080 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5082 @cindex @code{irpc} directive
5083 Evaluate a sequence of statements assigning different values to @var{symbol}.
5084 The sequence of statements starts at the @code{.irpc} directive, and is
5085 terminated by an @code{.endr} directive. For each character in @var{value},
5086 @var{symbol} is set to the character, and the sequence of statements is
5087 assembled. If no @var{value} is listed, the sequence of statements is
5088 assembled once, with @var{symbol} set to the null string. To refer to
5089 @var{symbol} within the sequence of statements, use @var{\symbol}.
5091 For example, assembling
5099 is equivalent to assembling
5107 For some caveats with the spelling of @var{symbol}, see also the discussion
5111 @section @code{.lcomm @var{symbol} , @var{length}}
5113 @cindex @code{lcomm} directive
5114 @cindex local common symbols
5115 @cindex symbols, local common
5116 Reserve @var{length} (an absolute expression) bytes for a local common
5117 denoted by @var{symbol}. The section and value of @var{symbol} are
5118 those of the new local common. The addresses are allocated in the bss
5119 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5120 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5121 not visible to @code{@value{LD}}.
5124 Some targets permit a third argument to be used with @code{.lcomm}. This
5125 argument specifies the desired alignment of the symbol in the bss section.
5129 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5130 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5134 @section @code{.lflags}
5136 @cindex @code{lflags} directive (ignored)
5137 @command{@value{AS}} accepts this directive, for compatibility with other
5138 assemblers, but ignores it.
5140 @ifclear no-line-dir
5142 @section @code{.line @var{line-number}}
5144 @cindex @code{line} directive
5145 @cindex logical line number
5147 Change the logical line number. @var{line-number} must be an absolute
5148 expression. The next line has that logical line number. Therefore any other
5149 statements on the current line (after a statement separator character) are
5150 reported as on logical line number @var{line-number} @minus{} 1. One day
5151 @command{@value{AS}} will no longer support this directive: it is recognized only
5152 for compatibility with existing assembler programs.
5155 Even though this is a directive associated with the @code{a.out} or
5156 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5157 when producing COFF output, and treats @samp{.line} as though it
5158 were the COFF @samp{.ln} @emph{if} it is found outside a
5159 @code{.def}/@code{.endef} pair.
5161 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5162 used by compilers to generate auxiliary symbol information for
5167 @section @code{.linkonce [@var{type}]}
5169 @cindex @code{linkonce} directive
5170 @cindex common sections
5171 Mark the current section so that the linker only includes a single copy of it.
5172 This may be used to include the same section in several different object files,
5173 but ensure that the linker will only include it once in the final output file.
5174 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5175 Duplicate sections are detected based on the section name, so it should be
5178 This directive is only supported by a few object file formats; as of this
5179 writing, the only object file format which supports it is the Portable
5180 Executable format used on Windows NT.
5182 The @var{type} argument is optional. If specified, it must be one of the
5183 following strings. For example:
5187 Not all types may be supported on all object file formats.
5191 Silently discard duplicate sections. This is the default.
5194 Warn if there are duplicate sections, but still keep only one copy.
5197 Warn if any of the duplicates have different sizes.
5200 Warn if any of the duplicates do not have exactly the same contents.
5204 @section @code{.list}
5206 @cindex @code{list} directive
5207 @cindex listing control, turning on
5208 Control (in conjunction with the @code{.nolist} directive) whether or
5209 not assembly listings are generated. These two directives maintain an
5210 internal counter (which is zero initially). @code{.list} increments the
5211 counter, and @code{.nolist} decrements it. Assembly listings are
5212 generated whenever the counter is greater than zero.
5214 By default, listings are disabled. When you enable them (with the
5215 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5216 the initial value of the listing counter is one.
5219 @section @code{.ln @var{line-number}}
5221 @cindex @code{ln} directive
5222 @ifclear no-line-dir
5223 @samp{.ln} is a synonym for @samp{.line}.
5226 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5227 must be an absolute expression. The next line has that logical
5228 line number, so any other statements on the current line (after a
5229 statement separator character @code{;}) are reported as on logical
5230 line number @var{line-number} @minus{} 1.
5233 This directive is accepted, but ignored, when @command{@value{AS}} is
5234 configured for @code{b.out}; its effect is only associated with COFF
5240 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5241 @cindex @code{loc} directive
5242 When emitting DWARF2 line number information,
5243 the @code{.loc} directive will add a row to the @code{.debug_line} line
5244 number matrix corresponding to the immediately following assembly
5245 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5246 arguments will be applied to the @code{.debug_line} state machine before
5249 The @var{options} are a sequence of the following tokens in any order:
5253 This option will set the @code{basic_block} register in the
5254 @code{.debug_line} state machine to @code{true}.
5257 This option will set the @code{prologue_end} register in the
5258 @code{.debug_line} state machine to @code{true}.
5260 @item epilogue_begin
5261 This option will set the @code{epilogue_begin} register in the
5262 @code{.debug_line} state machine to @code{true}.
5264 @item is_stmt @var{value}
5265 This option will set the @code{is_stmt} register in the
5266 @code{.debug_line} state machine to @code{value}, which must be
5269 @item isa @var{value}
5270 This directive will set the @code{isa} register in the @code{.debug_line}
5271 state machine to @var{value}, which must be an unsigned integer.
5273 @item discriminator @var{value}
5274 This directive will set the @code{discriminator} register in the @code{.debug_line}
5275 state machine to @var{value}, which must be an unsigned integer.
5279 @node Loc_mark_labels
5280 @section @code{.loc_mark_labels @var{enable}}
5281 @cindex @code{loc_mark_labels} directive
5282 When emitting DWARF2 line number information,
5283 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5284 to the @code{.debug_line} line number matrix with the @code{basic_block}
5285 register in the state machine set whenever a code label is seen.
5286 The @var{enable} argument should be either 1 or 0, to enable or disable
5287 this function respectively.
5291 @section @code{.local @var{names}}
5293 @cindex @code{local} directive
5294 This directive, which is available for ELF targets, marks each symbol in
5295 the comma-separated list of @code{names} as a local symbol so that it
5296 will not be externally visible. If the symbols do not already exist,
5297 they will be created.
5299 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5300 accept an alignment argument, which is the case for most ELF targets,
5301 the @code{.local} directive can be used in combination with @code{.comm}
5302 (@pxref{Comm}) to define aligned local common data.
5306 @section @code{.long @var{expressions}}
5308 @cindex @code{long} directive
5309 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5312 @c no one seems to know what this is for or whether this description is
5313 @c what it really ought to do
5315 @section @code{.lsym @var{symbol}, @var{expression}}
5317 @cindex @code{lsym} directive
5318 @cindex symbol, not referenced in assembly
5319 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5320 the hash table, ensuring it cannot be referenced by name during the
5321 rest of the assembly. This sets the attributes of the symbol to be
5322 the same as the expression value:
5324 @var{other} = @var{descriptor} = 0
5325 @var{type} = @r{(section of @var{expression})}
5326 @var{value} = @var{expression}
5329 The new symbol is not flagged as external.
5333 @section @code{.macro}
5336 The commands @code{.macro} and @code{.endm} allow you to define macros that
5337 generate assembly output. For example, this definition specifies a macro
5338 @code{sum} that puts a sequence of numbers into memory:
5341 .macro sum from=0, to=5
5350 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5362 @item .macro @var{macname}
5363 @itemx .macro @var{macname} @var{macargs} @dots{}
5364 @cindex @code{macro} directive
5365 Begin the definition of a macro called @var{macname}. If your macro
5366 definition requires arguments, specify their names after the macro name,
5367 separated by commas or spaces. You can qualify the macro argument to
5368 indicate whether all invocations must specify a non-blank value (through
5369 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5370 (through @samp{:@code{vararg}}). You can supply a default value for any
5371 macro argument by following the name with @samp{=@var{deflt}}. You
5372 cannot define two macros with the same @var{macname} unless it has been
5373 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5374 definitions. For example, these are all valid @code{.macro} statements:
5378 Begin the definition of a macro called @code{comm}, which takes no
5381 @item .macro plus1 p, p1
5382 @itemx .macro plus1 p p1
5383 Either statement begins the definition of a macro called @code{plus1},
5384 which takes two arguments; within the macro definition, write
5385 @samp{\p} or @samp{\p1} to evaluate the arguments.
5387 @item .macro reserve_str p1=0 p2
5388 Begin the definition of a macro called @code{reserve_str}, with two
5389 arguments. The first argument has a default value, but not the second.
5390 After the definition is complete, you can call the macro either as
5391 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5392 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5393 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5394 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5396 @item .macro m p1:req, p2=0, p3:vararg
5397 Begin the definition of a macro called @code{m}, with at least three
5398 arguments. The first argument must always have a value specified, but
5399 not the second, which instead has a default value. The third formal
5400 will get assigned all remaining arguments specified at invocation time.
5402 When you call a macro, you can specify the argument values either by
5403 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5404 @samp{sum to=17, from=9}.
5408 Note that since each of the @var{macargs} can be an identifier exactly
5409 as any other one permitted by the target architecture, there may be
5410 occasional problems if the target hand-crafts special meanings to certain
5411 characters when they occur in a special position. For example, if the colon
5412 (@code{:}) is generally permitted to be part of a symbol name, but the
5413 architecture specific code special-cases it when occurring as the final
5414 character of a symbol (to denote a label), then the macro parameter
5415 replacement code will have no way of knowing that and consider the whole
5416 construct (including the colon) an identifier, and check only this
5417 identifier for being the subject to parameter substitution. So for example
5418 this macro definition:
5426 might not work as expected. Invoking @samp{label foo} might not create a label
5427 called @samp{foo} but instead just insert the text @samp{\l:} into the
5428 assembler source, probably generating an error about an unrecognised
5431 Similarly problems might occur with the period character (@samp{.})
5432 which is often allowed inside opcode names (and hence identifier names). So
5433 for example constructing a macro to build an opcode from a base name and a
5434 length specifier like this:
5437 .macro opcode base length
5442 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5443 instruction but instead generate some kind of error as the assembler tries to
5444 interpret the text @samp{\base.\length}.
5446 There are several possible ways around this problem:
5449 @item Insert white space
5450 If it is possible to use white space characters then this is the simplest
5459 @item Use @samp{\()}
5460 The string @samp{\()} can be used to separate the end of a macro argument from
5461 the following text. eg:
5464 .macro opcode base length
5469 @item Use the alternate macro syntax mode
5470 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5471 used as a separator. eg:
5481 Note: this problem of correctly identifying string parameters to pseudo ops
5482 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5483 and @code{.irpc} (@pxref{Irpc}) as well.
5486 @cindex @code{endm} directive
5487 Mark the end of a macro definition.
5490 @cindex @code{exitm} directive
5491 Exit early from the current macro definition.
5493 @cindex number of macros executed
5494 @cindex macros, count executed
5496 @command{@value{AS}} maintains a counter of how many macros it has
5497 executed in this pseudo-variable; you can copy that number to your
5498 output with @samp{\@@}, but @emph{only within a macro definition}.
5500 @item LOCAL @var{name} [ , @dots{} ]
5501 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5502 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5503 @xref{Altmacro,,@code{.altmacro}}.
5507 @section @code{.mri @var{val}}
5509 @cindex @code{mri} directive
5510 @cindex MRI mode, temporarily
5511 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5512 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5513 affects code assembled until the next @code{.mri} directive, or until the end
5514 of the file. @xref{M, MRI mode, MRI mode}.
5517 @section @code{.noaltmacro}
5518 Disable alternate macro mode. @xref{Altmacro}.
5521 @section @code{.nolist}
5523 @cindex @code{nolist} directive
5524 @cindex listing control, turning off
5525 Control (in conjunction with the @code{.list} directive) whether or
5526 not assembly listings are generated. These two directives maintain an
5527 internal counter (which is zero initially). @code{.list} increments the
5528 counter, and @code{.nolist} decrements it. Assembly listings are
5529 generated whenever the counter is greater than zero.
5532 @section @code{.octa @var{bignums}}
5534 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5535 @cindex @code{octa} directive
5536 @cindex integer, 16-byte
5537 @cindex sixteen byte integer
5538 This directive expects zero or more bignums, separated by commas. For each
5539 bignum, it emits a 16-byte integer.
5541 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5542 hence @emph{octa}-word for 16 bytes.
5545 @section @code{.org @var{new-lc} , @var{fill}}
5547 @cindex @code{org} directive
5548 @cindex location counter, advancing
5549 @cindex advancing location counter
5550 @cindex current address, advancing
5551 Advance the location counter of the current section to
5552 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5553 expression with the same section as the current subsection. That is,
5554 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5555 wrong section, the @code{.org} directive is ignored. To be compatible
5556 with former assemblers, if the section of @var{new-lc} is absolute,
5557 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5558 is the same as the current subsection.
5560 @code{.org} may only increase the location counter, or leave it
5561 unchanged; you cannot use @code{.org} to move the location counter
5564 @c double negative used below "not undefined" because this is a specific
5565 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5566 @c section. doc@cygnus.com 18feb91
5567 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5568 may not be undefined. If you really detest this restriction we eagerly await
5569 a chance to share your improved assembler.
5571 Beware that the origin is relative to the start of the section, not
5572 to the start of the subsection. This is compatible with other
5573 people's assemblers.
5575 When the location counter (of the current subsection) is advanced, the
5576 intervening bytes are filled with @var{fill} which should be an
5577 absolute expression. If the comma and @var{fill} are omitted,
5578 @var{fill} defaults to zero.
5581 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5583 @cindex padding the location counter given a power of two
5584 @cindex @code{p2align} directive
5585 Pad the location counter (in the current subsection) to a particular
5586 storage boundary. The first expression (which must be absolute) is the
5587 number of low-order zero bits the location counter must have after
5588 advancement. For example @samp{.p2align 3} advances the location
5589 counter until it a multiple of 8. If the location counter is already a
5590 multiple of 8, no change is needed.
5592 The second expression (also absolute) gives the fill value to be stored in the
5593 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5594 padding bytes are normally zero. However, on some systems, if the section is
5595 marked as containing code and the fill value is omitted, the space is filled
5596 with no-op instructions.
5598 The third expression is also absolute, and is also optional. If it is present,
5599 it is the maximum number of bytes that should be skipped by this alignment
5600 directive. If doing the alignment would require skipping more bytes than the
5601 specified maximum, then the alignment is not done at all. You can omit the
5602 fill value (the second argument) entirely by simply using two commas after the
5603 required alignment; this can be useful if you want the alignment to be filled
5604 with no-op instructions when appropriate.
5606 @cindex @code{p2alignw} directive
5607 @cindex @code{p2alignl} directive
5608 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5609 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5610 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5611 fill pattern as a four byte longword value. For example, @code{.p2alignw
5612 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5613 filled in with the value 0x368d (the exact placement of the bytes depends upon
5614 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5619 @section @code{.popsection}
5621 @cindex @code{popsection} directive
5622 @cindex Section Stack
5623 This is one of the ELF section stack manipulation directives. The others are
5624 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5625 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5628 This directive replaces the current section (and subsection) with the top
5629 section (and subsection) on the section stack. This section is popped off the
5635 @section @code{.previous}
5637 @cindex @code{previous} directive
5638 @cindex Section Stack
5639 This is one of the ELF section stack manipulation directives. The others are
5640 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5641 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5642 (@pxref{PopSection}).
5644 This directive swaps the current section (and subsection) with most recently
5645 referenced section/subsection pair prior to this one. Multiple
5646 @code{.previous} directives in a row will flip between two sections (and their
5647 subsections). For example:
5659 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5665 # Now in section A subsection 1
5669 # Now in section B subsection 0
5672 # Now in section B subsection 1
5675 # Now in section B subsection 0
5679 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5680 section B and 0x9abc into subsection 1 of section B.
5682 In terms of the section stack, this directive swaps the current section with
5683 the top section on the section stack.
5687 @section @code{.print @var{string}}
5689 @cindex @code{print} directive
5690 @command{@value{AS}} will print @var{string} on the standard output during
5691 assembly. You must put @var{string} in double quotes.
5695 @section @code{.protected @var{names}}
5697 @cindex @code{protected} directive
5699 This is one of the ELF visibility directives. The other two are
5700 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5702 This directive overrides the named symbols default visibility (which is set by
5703 their binding: local, global or weak). The directive sets the visibility to
5704 @code{protected} which means that any references to the symbols from within the
5705 components that defines them must be resolved to the definition in that
5706 component, even if a definition in another component would normally preempt
5711 @section @code{.psize @var{lines} , @var{columns}}
5713 @cindex @code{psize} directive
5714 @cindex listing control: paper size
5715 @cindex paper size, for listings
5716 Use this directive to declare the number of lines---and, optionally, the
5717 number of columns---to use for each page, when generating listings.
5719 If you do not use @code{.psize}, listings use a default line-count
5720 of 60. You may omit the comma and @var{columns} specification; the
5721 default width is 200 columns.
5723 @command{@value{AS}} generates formfeeds whenever the specified number of
5724 lines is exceeded (or whenever you explicitly request one, using
5727 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5728 those explicitly specified with @code{.eject}.
5731 @section @code{.purgem @var{name}}
5733 @cindex @code{purgem} directive
5734 Undefine the macro @var{name}, so that later uses of the string will not be
5735 expanded. @xref{Macro}.
5739 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5741 @cindex @code{pushsection} directive
5742 @cindex Section Stack
5743 This is one of the ELF section stack manipulation directives. The others are
5744 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5745 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5748 This directive pushes the current section (and subsection) onto the
5749 top of the section stack, and then replaces the current section and
5750 subsection with @code{name} and @code{subsection}. The optional
5751 @code{flags}, @code{type} and @code{arguments} are treated the same
5752 as in the @code{.section} (@pxref{Section}) directive.
5756 @section @code{.quad @var{bignums}}
5758 @cindex @code{quad} directive
5759 @code{.quad} expects zero or more bignums, separated by commas. For
5760 each bignum, it emits
5762 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5763 warning message; and just takes the lowest order 8 bytes of the bignum.
5764 @cindex eight-byte integer
5765 @cindex integer, 8-byte
5767 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5768 hence @emph{quad}-word for 8 bytes.
5771 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5772 warning message; and just takes the lowest order 16 bytes of the bignum.
5773 @cindex sixteen-byte integer
5774 @cindex integer, 16-byte
5778 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5780 @cindex @code{reloc} directive
5781 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5782 @var{expression}. If @var{offset} is a number, the relocation is generated in
5783 the current section. If @var{offset} is an expression that resolves to a
5784 symbol plus offset, the relocation is generated in the given symbol's section.
5785 @var{expression}, if present, must resolve to a symbol plus addend or to an
5786 absolute value, but note that not all targets support an addend. e.g. ELF REL
5787 targets such as i386 store an addend in the section contents rather than in the
5788 relocation. This low level interface does not support addends stored in the
5792 @section @code{.rept @var{count}}
5794 @cindex @code{rept} directive
5795 Repeat the sequence of lines between the @code{.rept} directive and the next
5796 @code{.endr} directive @var{count} times.
5798 For example, assembling
5806 is equivalent to assembling
5815 @section @code{.sbttl "@var{subheading}"}
5817 @cindex @code{sbttl} directive
5818 @cindex subtitles for listings
5819 @cindex listing control: subtitle
5820 Use @var{subheading} as the title (third line, immediately after the
5821 title line) when generating assembly listings.
5823 This directive affects subsequent pages, as well as the current page if
5824 it appears within ten lines of the top of a page.
5828 @section @code{.scl @var{class}}
5830 @cindex @code{scl} directive
5831 @cindex symbol storage class (COFF)
5832 @cindex COFF symbol storage class
5833 Set the storage-class value for a symbol. This directive may only be
5834 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5835 whether a symbol is static or external, or it may record further
5836 symbolic debugging information.
5839 The @samp{.scl} directive is primarily associated with COFF output; when
5840 configured to generate @code{b.out} output format, @command{@value{AS}}
5841 accepts this directive but ignores it.
5847 @section @code{.section @var{name}}
5849 @cindex named section
5850 Use the @code{.section} directive to assemble the following code into a section
5853 This directive is only supported for targets that actually support arbitrarily
5854 named sections; on @code{a.out} targets, for example, it is not accepted, even
5855 with a standard @code{a.out} section name.
5859 @c only print the extra heading if both COFF and ELF are set
5860 @subheading COFF Version
5863 @cindex @code{section} directive (COFF version)
5864 For COFF targets, the @code{.section} directive is used in one of the following
5868 .section @var{name}[, "@var{flags}"]
5869 .section @var{name}[, @var{subsection}]
5872 If the optional argument is quoted, it is taken as flags to use for the
5873 section. Each flag is a single character. The following flags are recognized:
5876 bss section (uninitialized data)
5878 section is not loaded
5888 shared section (meaningful for PE targets)
5890 ignored. (For compatibility with the ELF version)
5892 section is not readable (meaningful for PE targets)
5894 single-digit power-of-two section alignment (GNU extension)
5897 If no flags are specified, the default flags depend upon the section name. If
5898 the section name is not recognized, the default will be for the section to be
5899 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5900 from the section, rather than adding them, so if they are used on their own it
5901 will be as if no flags had been specified at all.
5903 If the optional argument to the @code{.section} directive is not quoted, it is
5904 taken as a subsection number (@pxref{Sub-Sections}).
5909 @c only print the extra heading if both COFF and ELF are set
5910 @subheading ELF Version
5913 @cindex Section Stack
5914 This is one of the ELF section stack manipulation directives. The others are
5915 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5916 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5917 @code{.previous} (@pxref{Previous}).
5919 @cindex @code{section} directive (ELF version)
5920 For ELF targets, the @code{.section} directive is used like this:
5923 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5926 The optional @var{flags} argument is a quoted string which may contain any
5927 combination of the following characters:
5930 section is allocatable
5932 section is excluded from executable and shared library.
5936 section is executable
5938 section is mergeable
5940 section contains zero terminated strings
5942 section is a member of a section group
5944 section is used for thread-local-storage
5946 section is a member of the previously-current section's group, if any
5949 The optional @var{type} argument may contain one of the following constants:
5952 section contains data
5954 section does not contain data (i.e., section only occupies space)
5956 section contains data which is used by things other than the program
5958 section contains an array of pointers to init functions
5960 section contains an array of pointers to finish functions
5961 @item @@preinit_array
5962 section contains an array of pointers to pre-init functions
5965 Many targets only support the first three section types.
5967 Note on targets where the @code{@@} character is the start of a comment (eg
5968 ARM) then another character is used instead. For example the ARM port uses the
5971 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5972 be specified as well as an extra argument---@var{entsize}---like this:
5975 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5978 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5979 constants, each @var{entsize} octets long. Sections with both @code{M} and
5980 @code{S} must contain zero terminated strings where each character is
5981 @var{entsize} bytes long. The linker may remove duplicates within sections with
5982 the same name, same entity size and same flags. @var{entsize} must be an
5983 absolute expression. For sections with both @code{M} and @code{S}, a string
5984 which is a suffix of a larger string is considered a duplicate. Thus
5985 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5986 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5988 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5989 be present along with an additional field like this:
5992 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5995 The @var{GroupName} field specifies the name of the section group to which this
5996 particular section belongs. The optional linkage field can contain:
5999 indicates that only one copy of this section should be retained
6004 Note: if both the @var{M} and @var{G} flags are present then the fields for
6005 the Merge flag should come first, like this:
6008 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6011 If @var{flags} contains the @code{?} symbol then it may not also contain the
6012 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6013 present. Instead, @code{?} says to consider the section that's current before
6014 this directive. If that section used @code{G}, then the new section will use
6015 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6016 If not, then the @code{?} symbol has no effect.
6018 If no flags are specified, the default flags depend upon the section name. If
6019 the section name is not recognized, the default will be for the section to have
6020 none of the above flags: it will not be allocated in memory, nor writable, nor
6021 executable. The section will contain data.
6023 For ELF targets, the assembler supports another type of @code{.section}
6024 directive for compatibility with the Solaris assembler:
6027 .section "@var{name}"[, @var{flags}...]
6030 Note that the section name is quoted. There may be a sequence of comma
6034 section is allocatable
6038 section is executable
6040 section is excluded from executable and shared library.
6042 section is used for thread local storage
6045 This directive replaces the current section and subsection. See the
6046 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6047 some examples of how this directive and the other section stack directives
6053 @section @code{.set @var{symbol}, @var{expression}}
6055 @cindex @code{set} directive
6056 @cindex symbol value, setting
6057 Set the value of @var{symbol} to @var{expression}. This
6058 changes @var{symbol}'s value and type to conform to
6059 @var{expression}. If @var{symbol} was flagged as external, it remains
6060 flagged (@pxref{Symbol Attributes}).
6062 You may @code{.set} a symbol many times in the same assembly.
6064 If you @code{.set} a global symbol, the value stored in the object
6065 file is the last value stored into it.
6068 On Z80 @code{set} is a real instruction, use
6069 @samp{@var{symbol} defl @var{expression}} instead.
6073 @section @code{.short @var{expressions}}
6075 @cindex @code{short} directive
6077 @code{.short} is normally the same as @samp{.word}.
6078 @xref{Word,,@code{.word}}.
6080 In some configurations, however, @code{.short} and @code{.word} generate
6081 numbers of different lengths. @xref{Machine Dependencies}.
6085 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6088 This expects zero or more @var{expressions}, and emits
6089 a 16 bit number for each.
6094 @section @code{.single @var{flonums}}
6096 @cindex @code{single} directive
6097 @cindex floating point numbers (single)
6098 This directive assembles zero or more flonums, separated by commas. It
6099 has the same effect as @code{.float}.
6101 The exact kind of floating point numbers emitted depends on how
6102 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6106 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6107 numbers in @sc{ieee} format.
6113 @section @code{.size}
6115 This directive is used to set the size associated with a symbol.
6119 @c only print the extra heading if both COFF and ELF are set
6120 @subheading COFF Version
6123 @cindex @code{size} directive (COFF version)
6124 For COFF targets, the @code{.size} directive is only permitted inside
6125 @code{.def}/@code{.endef} pairs. It is used like this:
6128 .size @var{expression}
6132 @samp{.size} is only meaningful when generating COFF format output; when
6133 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6140 @c only print the extra heading if both COFF and ELF are set
6141 @subheading ELF Version
6144 @cindex @code{size} directive (ELF version)
6145 For ELF targets, the @code{.size} directive is used like this:
6148 .size @var{name} , @var{expression}
6151 This directive sets the size associated with a symbol @var{name}.
6152 The size in bytes is computed from @var{expression} which can make use of label
6153 arithmetic. This directive is typically used to set the size of function
6158 @ifclear no-space-dir
6160 @section @code{.skip @var{size} , @var{fill}}
6162 @cindex @code{skip} directive
6163 @cindex filling memory
6164 This directive emits @var{size} bytes, each of value @var{fill}. Both
6165 @var{size} and @var{fill} are absolute expressions. If the comma and
6166 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6171 @section @code{.sleb128 @var{expressions}}
6173 @cindex @code{sleb128} directive
6174 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6175 compact, variable length representation of numbers used by the DWARF
6176 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6178 @ifclear no-space-dir
6180 @section @code{.space @var{size} , @var{fill}}
6182 @cindex @code{space} directive
6183 @cindex filling memory
6184 This directive emits @var{size} bytes, each of value @var{fill}. Both
6185 @var{size} and @var{fill} are absolute expressions. If the comma
6186 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6191 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6192 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6193 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6194 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6202 @section @code{.stabd, .stabn, .stabs}
6204 @cindex symbolic debuggers, information for
6205 @cindex @code{stab@var{x}} directives
6206 There are three directives that begin @samp{.stab}.
6207 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6208 The symbols are not entered in the @command{@value{AS}} hash table: they
6209 cannot be referenced elsewhere in the source file.
6210 Up to five fields are required:
6214 This is the symbol's name. It may contain any character except
6215 @samp{\000}, so is more general than ordinary symbol names. Some
6216 debuggers used to code arbitrarily complex structures into symbol names
6220 An absolute expression. The symbol's type is set to the low 8 bits of
6221 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6222 and debuggers choke on silly bit patterns.
6225 An absolute expression. The symbol's ``other'' attribute is set to the
6226 low 8 bits of this expression.
6229 An absolute expression. The symbol's descriptor is set to the low 16
6230 bits of this expression.
6233 An absolute expression which becomes the symbol's value.
6236 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6237 or @code{.stabs} statement, the symbol has probably already been created;
6238 you get a half-formed symbol in your object file. This is
6239 compatible with earlier assemblers!
6242 @cindex @code{stabd} directive
6243 @item .stabd @var{type} , @var{other} , @var{desc}
6245 The ``name'' of the symbol generated is not even an empty string.
6246 It is a null pointer, for compatibility. Older assemblers used a
6247 null pointer so they didn't waste space in object files with empty
6250 The symbol's value is set to the location counter,
6251 relocatably. When your program is linked, the value of this symbol
6252 is the address of the location counter when the @code{.stabd} was
6255 @cindex @code{stabn} directive
6256 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6257 The name of the symbol is set to the empty string @code{""}.
6259 @cindex @code{stabs} directive
6260 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6261 All five fields are specified.
6267 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6268 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6270 @cindex string, copying to object file
6271 @cindex string8, copying to object file
6272 @cindex string16, copying to object file
6273 @cindex string32, copying to object file
6274 @cindex string64, copying to object file
6275 @cindex @code{string} directive
6276 @cindex @code{string8} directive
6277 @cindex @code{string16} directive
6278 @cindex @code{string32} directive
6279 @cindex @code{string64} directive
6281 Copy the characters in @var{str} to the object file. You may specify more than
6282 one string to copy, separated by commas. Unless otherwise specified for a
6283 particular machine, the assembler marks the end of each string with a 0 byte.
6284 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6286 The variants @code{string16}, @code{string32} and @code{string64} differ from
6287 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6288 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6289 are stored in target endianness byte order.
6295 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6296 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6301 @section @code{.struct @var{expression}}
6303 @cindex @code{struct} directive
6304 Switch to the absolute section, and set the section offset to @var{expression},
6305 which must be an absolute expression. You might use this as follows:
6314 This would define the symbol @code{field1} to have the value 0, the symbol
6315 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6316 value 8. Assembly would be left in the absolute section, and you would need to
6317 use a @code{.section} directive of some sort to change to some other section
6318 before further assembly.
6322 @section @code{.subsection @var{name}}
6324 @cindex @code{subsection} directive
6325 @cindex Section Stack
6326 This is one of the ELF section stack manipulation directives. The others are
6327 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6328 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6331 This directive replaces the current subsection with @code{name}. The current
6332 section is not changed. The replaced subsection is put onto the section stack
6333 in place of the then current top of stack subsection.
6338 @section @code{.symver}
6339 @cindex @code{symver} directive
6340 @cindex symbol versioning
6341 @cindex versions of symbols
6342 Use the @code{.symver} directive to bind symbols to specific version nodes
6343 within a source file. This is only supported on ELF platforms, and is
6344 typically used when assembling files to be linked into a shared library.
6345 There are cases where it may make sense to use this in objects to be bound
6346 into an application itself so as to override a versioned symbol from a
6349 For ELF targets, the @code{.symver} directive can be used like this:
6351 .symver @var{name}, @var{name2@@nodename}
6353 If the symbol @var{name} is defined within the file
6354 being assembled, the @code{.symver} directive effectively creates a symbol
6355 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6356 just don't try and create a regular alias is that the @var{@@} character isn't
6357 permitted in symbol names. The @var{name2} part of the name is the actual name
6358 of the symbol by which it will be externally referenced. The name @var{name}
6359 itself is merely a name of convenience that is used so that it is possible to
6360 have definitions for multiple versions of a function within a single source
6361 file, and so that the compiler can unambiguously know which version of a
6362 function is being mentioned. The @var{nodename} portion of the alias should be
6363 the name of a node specified in the version script supplied to the linker when
6364 building a shared library. If you are attempting to override a versioned
6365 symbol from a shared library, then @var{nodename} should correspond to the
6366 nodename of the symbol you are trying to override.
6368 If the symbol @var{name} is not defined within the file being assembled, all
6369 references to @var{name} will be changed to @var{name2@@nodename}. If no
6370 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6373 Another usage of the @code{.symver} directive is:
6375 .symver @var{name}, @var{name2@@@@nodename}
6377 In this case, the symbol @var{name} must exist and be defined within
6378 the file being assembled. It is similar to @var{name2@@nodename}. The
6379 difference is @var{name2@@@@nodename} will also be used to resolve
6380 references to @var{name2} by the linker.
6382 The third usage of the @code{.symver} directive is:
6384 .symver @var{name}, @var{name2@@@@@@nodename}
6386 When @var{name} is not defined within the
6387 file being assembled, it is treated as @var{name2@@nodename}. When
6388 @var{name} is defined within the file being assembled, the symbol
6389 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6394 @section @code{.tag @var{structname}}
6396 @cindex COFF structure debugging
6397 @cindex structure debugging, COFF
6398 @cindex @code{tag} directive
6399 This directive is generated by compilers to include auxiliary debugging
6400 information in the symbol table. It is only permitted inside
6401 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6402 definitions in the symbol table with instances of those structures.
6405 @samp{.tag} is only used when generating COFF format output; when
6406 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6412 @section @code{.text @var{subsection}}
6414 @cindex @code{text} directive
6415 Tells @command{@value{AS}} to assemble the following statements onto the end of
6416 the text subsection numbered @var{subsection}, which is an absolute
6417 expression. If @var{subsection} is omitted, subsection number zero
6421 @section @code{.title "@var{heading}"}
6423 @cindex @code{title} directive
6424 @cindex listing control: title line
6425 Use @var{heading} as the title (second line, immediately after the
6426 source file name and pagenumber) when generating assembly listings.
6428 This directive affects subsequent pages, as well as the current page if
6429 it appears within ten lines of the top of a page.
6433 @section @code{.type}
6435 This directive is used to set the type of a symbol.
6439 @c only print the extra heading if both COFF and ELF are set
6440 @subheading COFF Version
6443 @cindex COFF symbol type
6444 @cindex symbol type, COFF
6445 @cindex @code{type} directive (COFF version)
6446 For COFF targets, this directive is permitted only within
6447 @code{.def}/@code{.endef} pairs. It is used like this:
6453 This records the integer @var{int} as the type attribute of a symbol table
6457 @samp{.type} is associated only with COFF format output; when
6458 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6459 directive but ignores it.
6465 @c only print the extra heading if both COFF and ELF are set
6466 @subheading ELF Version
6469 @cindex ELF symbol type
6470 @cindex symbol type, ELF
6471 @cindex @code{type} directive (ELF version)
6472 For ELF targets, the @code{.type} directive is used like this:
6475 .type @var{name} , @var{type description}
6478 This sets the type of symbol @var{name} to be either a
6479 function symbol or an object symbol. There are five different syntaxes
6480 supported for the @var{type description} field, in order to provide
6481 compatibility with various other assemblers.
6483 Because some of the characters used in these syntaxes (such as @samp{@@} and
6484 @samp{#}) are comment characters for some architectures, some of the syntaxes
6485 below do not work on all architectures. The first variant will be accepted by
6486 the GNU assembler on all architectures so that variant should be used for
6487 maximum portability, if you do not need to assemble your code with other
6490 The syntaxes supported are:
6493 .type <name> STT_<TYPE_IN_UPPER_CASE>
6494 .type <name>,#<type>
6495 .type <name>,@@<type>
6496 .type <name>,%<type>
6497 .type <name>,"<type>"
6500 The types supported are:
6505 Mark the symbol as being a function name.
6508 @itemx gnu_indirect_function
6509 Mark the symbol as an indirect function when evaluated during reloc
6510 processing. (This is only supported on Linux targeted assemblers).
6514 Mark the symbol as being a data object.
6518 Mark the symbol as being a thead-local data object.
6522 Mark the symbol as being a common data object.
6526 Does not mark the symbol in any way. It is supported just for completeness.
6528 @item gnu_unique_object
6529 Marks the symbol as being a globally unique data object. The dynamic linker
6530 will make sure that in the entire process there is just one symbol with this
6531 name and type in use. (This is only supported on Linux targeted assemblers).
6535 Note: Some targets support extra types in addition to those listed above.
6541 @section @code{.uleb128 @var{expressions}}
6543 @cindex @code{uleb128} directive
6544 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6545 compact, variable length representation of numbers used by the DWARF
6546 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6550 @section @code{.val @var{addr}}
6552 @cindex @code{val} directive
6553 @cindex COFF value attribute
6554 @cindex value attribute, COFF
6555 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6556 records the address @var{addr} as the value attribute of a symbol table
6560 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6561 configured for @code{b.out}, it accepts this directive but ignores it.
6567 @section @code{.version "@var{string}"}
6569 @cindex @code{version} directive
6570 This directive creates a @code{.note} section and places into it an ELF
6571 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6576 @section @code{.vtable_entry @var{table}, @var{offset}}
6578 @cindex @code{vtable_entry} directive
6579 This directive finds or creates a symbol @code{table} and creates a
6580 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6583 @section @code{.vtable_inherit @var{child}, @var{parent}}
6585 @cindex @code{vtable_inherit} directive
6586 This directive finds the symbol @code{child} and finds or creates the symbol
6587 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6588 parent whose addend is the value of the child symbol. As a special case the
6589 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6593 @section @code{.warning "@var{string}"}
6594 @cindex warning directive
6595 Similar to the directive @code{.error}
6596 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6599 @section @code{.weak @var{names}}
6601 @cindex @code{weak} directive
6602 This directive sets the weak attribute on the comma separated list of symbol
6603 @code{names}. If the symbols do not already exist, they will be created.
6605 On COFF targets other than PE, weak symbols are a GNU extension. This
6606 directive sets the weak attribute on the comma separated list of symbol
6607 @code{names}. If the symbols do not already exist, they will be created.
6609 On the PE target, weak symbols are supported natively as weak aliases.
6610 When a weak symbol is created that is not an alias, GAS creates an
6611 alternate symbol to hold the default value.
6614 @section @code{.weakref @var{alias}, @var{target}}
6616 @cindex @code{weakref} directive
6617 This directive creates an alias to the target symbol that enables the symbol to
6618 be referenced with weak-symbol semantics, but without actually making it weak.
6619 If direct references or definitions of the symbol are present, then the symbol
6620 will not be weak, but if all references to it are through weak references, the
6621 symbol will be marked as weak in the symbol table.
6623 The effect is equivalent to moving all references to the alias to a separate
6624 assembly source file, renaming the alias to the symbol in it, declaring the
6625 symbol as weak there, and running a reloadable link to merge the object files
6626 resulting from the assembly of the new source file and the old source file that
6627 had the references to the alias removed.
6629 The alias itself never makes to the symbol table, and is entirely handled
6630 within the assembler.
6633 @section @code{.word @var{expressions}}
6635 @cindex @code{word} directive
6636 This directive expects zero or more @var{expressions}, of any section,
6637 separated by commas.
6640 For each expression, @command{@value{AS}} emits a 32-bit number.
6643 For each expression, @command{@value{AS}} emits a 16-bit number.
6648 The size of the number emitted, and its byte order,
6649 depend on what target computer the assembly is for.
6652 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6653 @c happen---32-bit addressability, period; no long/short jumps.
6654 @ifset DIFF-TBL-KLUGE
6655 @cindex difference tables altered
6656 @cindex altered difference tables
6658 @emph{Warning: Special Treatment to support Compilers}
6662 Machines with a 32-bit address space, but that do less than 32-bit
6663 addressing, require the following special treatment. If the machine of
6664 interest to you does 32-bit addressing (or doesn't require it;
6665 @pxref{Machine Dependencies}), you can ignore this issue.
6668 In order to assemble compiler output into something that works,
6669 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6670 Directives of the form @samp{.word sym1-sym2} are often emitted by
6671 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6672 directive of the form @samp{.word sym1-sym2}, and the difference between
6673 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6674 creates a @dfn{secondary jump table}, immediately before the next label.
6675 This secondary jump table is preceded by a short-jump to the
6676 first byte after the secondary table. This short-jump prevents the flow
6677 of control from accidentally falling into the new table. Inside the
6678 table is a long-jump to @code{sym2}. The original @samp{.word}
6679 contains @code{sym1} minus the address of the long-jump to
6682 If there were several occurrences of @samp{.word sym1-sym2} before the
6683 secondary jump table, all of them are adjusted. If there was a
6684 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6685 long-jump to @code{sym4} is included in the secondary jump table,
6686 and the @code{.word} directives are adjusted to contain @code{sym3}
6687 minus the address of the long-jump to @code{sym4}; and so on, for as many
6688 entries in the original jump table as necessary.
6691 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6692 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6693 assembly language programmers.
6696 @c end DIFF-TBL-KLUGE
6699 @section Deprecated Directives
6701 @cindex deprecated directives
6702 @cindex obsolescent directives
6703 One day these directives won't work.
6704 They are included for compatibility with older assemblers.
6711 @node Object Attributes
6712 @chapter Object Attributes
6713 @cindex object attributes
6715 @command{@value{AS}} assembles source files written for a specific architecture
6716 into object files for that architecture. But not all object files are alike.
6717 Many architectures support incompatible variations. For instance, floating
6718 point arguments might be passed in floating point registers if the object file
6719 requires hardware floating point support---or floating point arguments might be
6720 passed in integer registers if the object file supports processors with no
6721 hardware floating point unit. Or, if two objects are built for different
6722 generations of the same architecture, the combination may require the
6723 newer generation at run-time.
6725 This information is useful during and after linking. At link time,
6726 @command{@value{LD}} can warn about incompatible object files. After link
6727 time, tools like @command{gdb} can use it to process the linked file
6730 Compatibility information is recorded as a series of object attributes. Each
6731 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6732 string, and indicates who sets the meaning of the tag. The tag is an integer,
6733 and indicates what property the attribute describes. The value may be a string
6734 or an integer, and indicates how the property affects this object. Missing
6735 attributes are the same as attributes with a zero value or empty string value.
6737 Object attributes were developed as part of the ABI for the ARM Architecture.
6738 The file format is documented in @cite{ELF for the ARM Architecture}.
6741 * GNU Object Attributes:: @sc{gnu} Object Attributes
6742 * Defining New Object Attributes:: Defining New Object Attributes
6745 @node GNU Object Attributes
6746 @section @sc{gnu} Object Attributes
6748 The @code{.gnu_attribute} directive records an object attribute
6749 with vendor @samp{gnu}.
6751 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6752 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6753 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6754 2} is set for architecture-independent attributes and clear for
6755 architecture-dependent ones.
6757 @subsection Common @sc{gnu} attributes
6759 These attributes are valid on all architectures.
6762 @item Tag_compatibility (32)
6763 The compatibility attribute takes an integer flag value and a vendor name. If
6764 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6765 then the file is only compatible with the named toolchain. If it is greater
6766 than 1, the file can only be processed by other toolchains under some private
6767 arrangement indicated by the flag value and the vendor name.
6770 @subsection MIPS Attributes
6773 @item Tag_GNU_MIPS_ABI_FP (4)
6774 The floating-point ABI used by this object file. The value will be:
6778 0 for files not affected by the floating-point ABI.
6780 1 for files using the hardware floating-point with a standard double-precision
6783 2 for files using the hardware floating-point ABI with a single-precision FPU.
6785 3 for files using the software floating-point ABI.
6787 4 for files using the hardware floating-point ABI with 64-bit wide
6788 double-precision floating-point registers and 32-bit wide general
6793 @subsection PowerPC Attributes
6796 @item Tag_GNU_Power_ABI_FP (4)
6797 The floating-point ABI used by this object file. The value will be:
6801 0 for files not affected by the floating-point ABI.
6803 1 for files using double-precision hardware floating-point ABI.
6805 2 for files using the software floating-point ABI.
6807 3 for files using single-precision hardware floating-point ABI.
6810 @item Tag_GNU_Power_ABI_Vector (8)
6811 The vector ABI used by this object file. The value will be:
6815 0 for files not affected by the vector ABI.
6817 1 for files using general purpose registers to pass vectors.
6819 2 for files using AltiVec registers to pass vectors.
6821 3 for files using SPE registers to pass vectors.
6825 @node Defining New Object Attributes
6826 @section Defining New Object Attributes
6828 If you want to define a new @sc{gnu} object attribute, here are the places you
6829 will need to modify. New attributes should be discussed on the @samp{binutils}
6834 This manual, which is the official register of attributes.
6836 The header for your architecture @file{include/elf}, to define the tag.
6838 The @file{bfd} support file for your architecture, to merge the attribute
6839 and issue any appropriate link warnings.
6841 Test cases in @file{ld/testsuite} for merging and link warnings.
6843 @file{binutils/readelf.c} to display your attribute.
6845 GCC, if you want the compiler to mark the attribute automatically.
6851 @node Machine Dependencies
6852 @chapter Machine Dependent Features
6854 @cindex machine dependencies
6855 The machine instruction sets are (almost by definition) different on
6856 each machine where @command{@value{AS}} runs. Floating point representations
6857 vary as well, and @command{@value{AS}} often supports a few additional
6858 directives or command-line options for compatibility with other
6859 assemblers on a particular platform. Finally, some versions of
6860 @command{@value{AS}} support special pseudo-instructions for branch
6863 This chapter discusses most of these differences, though it does not
6864 include details on any machine's instruction set. For details on that
6865 subject, see the hardware manufacturer's manual.
6869 * Alpha-Dependent:: Alpha Dependent Features
6872 * ARC-Dependent:: ARC Dependent Features
6875 * ARM-Dependent:: ARM Dependent Features
6878 * AVR-Dependent:: AVR Dependent Features
6881 * Blackfin-Dependent:: Blackfin Dependent Features
6884 * CR16-Dependent:: CR16 Dependent Features
6887 * CRIS-Dependent:: CRIS Dependent Features
6890 * D10V-Dependent:: D10V Dependent Features
6893 * D30V-Dependent:: D30V Dependent Features
6896 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6899 * HPPA-Dependent:: HPPA Dependent Features
6902 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6905 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6908 * i860-Dependent:: Intel 80860 Dependent Features
6911 * i960-Dependent:: Intel 80960 Dependent Features
6914 * IA-64-Dependent:: Intel IA-64 Dependent Features
6917 * IP2K-Dependent:: IP2K Dependent Features
6920 * LM32-Dependent:: LM32 Dependent Features
6923 * M32C-Dependent:: M32C Dependent Features
6926 * M32R-Dependent:: M32R Dependent Features
6929 * M68K-Dependent:: M680x0 Dependent Features
6932 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6935 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6938 * MIPS-Dependent:: MIPS Dependent Features
6941 * MMIX-Dependent:: MMIX Dependent Features
6944 * MSP430-Dependent:: MSP430 Dependent Features
6947 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6948 * SH64-Dependent:: SuperH SH64 Dependent Features
6951 * PDP-11-Dependent:: PDP-11 Dependent Features
6954 * PJ-Dependent:: picoJava Dependent Features
6957 * PPC-Dependent:: PowerPC Dependent Features
6960 * RX-Dependent:: RX Dependent Features
6963 * S/390-Dependent:: IBM S/390 Dependent Features
6966 * SCORE-Dependent:: SCORE Dependent Features
6969 * Sparc-Dependent:: SPARC Dependent Features
6972 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6975 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
6978 * V850-Dependent:: V850 Dependent Features
6981 * Xtensa-Dependent:: Xtensa Dependent Features
6984 * Z80-Dependent:: Z80 Dependent Features
6987 * Z8000-Dependent:: Z8000 Dependent Features
6990 * Vax-Dependent:: VAX Dependent Features
6997 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6998 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6999 @c peculiarity: to preserve cross-references, there must be a node called
7000 @c "Machine Dependencies". Hence the conditional nodenames in each
7001 @c major node below. Node defaulting in makeinfo requires adjacency of
7002 @c node and sectioning commands; hence the repetition of @chapter BLAH
7003 @c in both conditional blocks.
7006 @include c-alpha.texi
7022 @include c-bfin.texi
7026 @include c-cr16.texi
7030 @include c-cris.texi
7035 @node Machine Dependencies
7036 @chapter Machine Dependent Features
7038 The machine instruction sets are different on each Renesas chip family,
7039 and there are also some syntax differences among the families. This
7040 chapter describes the specific @command{@value{AS}} features for each
7044 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7045 * SH-Dependent:: Renesas SH Dependent Features
7052 @include c-d10v.texi
7056 @include c-d30v.texi
7060 @include c-h8300.texi
7064 @include c-hppa.texi
7068 @include c-i370.texi
7072 @include c-i386.texi
7076 @include c-i860.texi
7080 @include c-i960.texi
7084 @include c-ia64.texi
7088 @include c-ip2k.texi
7092 @include c-lm32.texi
7096 @include c-m32c.texi
7100 @include c-m32r.texi
7104 @include c-m68k.texi
7108 @include c-m68hc11.texi
7112 @include c-microblaze.texi
7116 @include c-mips.texi
7120 @include c-mmix.texi
7124 @include c-msp430.texi
7128 @include c-ns32k.texi
7132 @include c-pdp11.texi
7148 @include c-s390.texi
7152 @include c-score.texi
7157 @include c-sh64.texi
7161 @include c-sparc.texi
7165 @include c-tic54x.texi
7169 @include c-tic6x.texi
7185 @include c-v850.texi
7189 @include c-xtensa.texi
7193 @c reverse effect of @down at top of generic Machine-Dep chapter
7197 @node Reporting Bugs
7198 @chapter Reporting Bugs
7199 @cindex bugs in assembler
7200 @cindex reporting bugs in assembler
7202 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7204 Reporting a bug may help you by bringing a solution to your problem, or it may
7205 not. But in any case the principal function of a bug report is to help the
7206 entire community by making the next version of @command{@value{AS}} work better.
7207 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7209 In order for a bug report to serve its purpose, you must include the
7210 information that enables us to fix the bug.
7213 * Bug Criteria:: Have you found a bug?
7214 * Bug Reporting:: How to report bugs
7218 @section Have You Found a Bug?
7219 @cindex bug criteria
7221 If you are not sure whether you have found a bug, here are some guidelines:
7224 @cindex fatal signal
7225 @cindex assembler crash
7226 @cindex crash of assembler
7228 If the assembler gets a fatal signal, for any input whatever, that is a
7229 @command{@value{AS}} bug. Reliable assemblers never crash.
7231 @cindex error on valid input
7233 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7235 @cindex invalid input
7237 If @command{@value{AS}} does not produce an error message for invalid input, that
7238 is a bug. However, you should note that your idea of ``invalid input'' might
7239 be our idea of ``an extension'' or ``support for traditional practice''.
7242 If you are an experienced user of assemblers, your suggestions for improvement
7243 of @command{@value{AS}} are welcome in any case.
7247 @section How to Report Bugs
7249 @cindex assembler bugs, reporting
7251 A number of companies and individuals offer support for @sc{gnu} products. If
7252 you obtained @command{@value{AS}} from a support organization, we recommend you
7253 contact that organization first.
7255 You can find contact information for many support companies and
7256 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7260 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7264 The fundamental principle of reporting bugs usefully is this:
7265 @strong{report all the facts}. If you are not sure whether to state a
7266 fact or leave it out, state it!
7268 Often people omit facts because they think they know what causes the problem
7269 and assume that some details do not matter. Thus, you might assume that the
7270 name of a symbol you use in an example does not matter. Well, probably it does
7271 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7272 happens to fetch from the location where that name is stored in memory;
7273 perhaps, if the name were different, the contents of that location would fool
7274 the assembler into doing the right thing despite the bug. Play it safe and
7275 give a specific, complete example. That is the easiest thing for you to do,
7276 and the most helpful.
7278 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7279 it is new to us. Therefore, always write your bug reports on the assumption
7280 that the bug has not been reported previously.
7282 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7283 bell?'' This cannot help us fix a bug, so it is basically useless. We
7284 respond by asking for enough details to enable us to investigate.
7285 You might as well expedite matters by sending them to begin with.
7287 To enable us to fix the bug, you should include all these things:
7291 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7292 it with the @samp{--version} argument.
7294 Without this, we will not know whether there is any point in looking for
7295 the bug in the current version of @command{@value{AS}}.
7298 Any patches you may have applied to the @command{@value{AS}} source.
7301 The type of machine you are using, and the operating system name and
7305 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7309 The command arguments you gave the assembler to assemble your example and
7310 observe the bug. To guarantee you will not omit something important, list them
7311 all. A copy of the Makefile (or the output from make) is sufficient.
7313 If we were to try to guess the arguments, we would probably guess wrong
7314 and then we might not encounter the bug.
7317 A complete input file that will reproduce the bug. If the bug is observed when
7318 the assembler is invoked via a compiler, send the assembler source, not the
7319 high level language source. Most compilers will produce the assembler source
7320 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7321 the options @samp{-v --save-temps}; this will save the assembler source in a
7322 file with an extension of @file{.s}, and also show you exactly how
7323 @command{@value{AS}} is being run.
7326 A description of what behavior you observe that you believe is
7327 incorrect. For example, ``It gets a fatal signal.''
7329 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7330 will certainly notice it. But if the bug is incorrect output, we might not
7331 notice unless it is glaringly wrong. You might as well not give us a chance to
7334 Even if the problem you experience is a fatal signal, you should still say so
7335 explicitly. Suppose something strange is going on, such as, your copy of
7336 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7337 library on your system. (This has happened!) Your copy might crash and ours
7338 would not. If you told us to expect a crash, then when ours fails to crash, we
7339 would know that the bug was not happening for us. If you had not told us to
7340 expect a crash, then we would not be able to draw any conclusion from our
7344 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7345 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7346 option. Always send diffs from the old file to the new file. If you even
7347 discuss something in the @command{@value{AS}} source, refer to it by context, not
7350 The line numbers in our development sources will not match those in your
7351 sources. Your line numbers would convey no useful information to us.
7354 Here are some things that are not necessary:
7358 A description of the envelope of the bug.
7360 Often people who encounter a bug spend a lot of time investigating
7361 which changes to the input file will make the bug go away and which
7362 changes will not affect it.
7364 This is often time consuming and not very useful, because the way we
7365 will find the bug is by running a single example under the debugger
7366 with breakpoints, not by pure deduction from a series of examples.
7367 We recommend that you save your time for something else.
7369 Of course, if you can find a simpler example to report @emph{instead}
7370 of the original one, that is a convenience for us. Errors in the
7371 output will be easier to spot, running under the debugger will take
7372 less time, and so on.
7374 However, simplification is not vital; if you do not want to do this,
7375 report the bug anyway and send us the entire test case you used.
7378 A patch for the bug.
7380 A patch for the bug does help us if it is a good one. But do not omit
7381 the necessary information, such as the test case, on the assumption that
7382 a patch is all we need. We might see problems with your patch and decide
7383 to fix the problem another way, or we might not understand it at all.
7385 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7386 construct an example that will make the program follow a certain path through
7387 the code. If you do not send us the example, we will not be able to construct
7388 one, so we will not be able to verify that the bug is fixed.
7390 And if we cannot understand what bug you are trying to fix, or why your
7391 patch should be an improvement, we will not install it. A test case will
7392 help us to understand.
7395 A guess about what the bug is or what it depends on.
7397 Such guesses are usually wrong. Even we cannot guess right about such
7398 things without first using the debugger to find the facts.
7401 @node Acknowledgements
7402 @chapter Acknowledgements
7404 If you have contributed to GAS and your name isn't listed here,
7405 it is not meant as a slight. We just don't know about it. Send mail to the
7406 maintainer, and we'll correct the situation. Currently
7408 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7410 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7413 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7414 information and the 68k series machines, most of the preprocessing pass, and
7415 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7417 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7418 many bug fixes, including merging support for several processors, breaking GAS
7419 up to handle multiple object file format back ends (including heavy rewrite,
7420 testing, an integration of the coff and b.out back ends), adding configuration
7421 including heavy testing and verification of cross assemblers and file splits
7422 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7423 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7424 port (including considerable amounts of reverse engineering), a SPARC opcode
7425 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7426 assertions and made them work, much other reorganization, cleanup, and lint.
7428 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7429 in format-specific I/O modules.
7431 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7432 has done much work with it since.
7434 The Intel 80386 machine description was written by Eliot Dresselhaus.
7436 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7438 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7439 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7441 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7442 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7443 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7444 support a.out format.
7446 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7447 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7448 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7449 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7452 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7453 simplified the configuration of which versions accept which directives. He
7454 updated the 68k machine description so that Motorola's opcodes always produced
7455 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7456 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7457 cross-compilation support, and one bug in relaxation that took a week and
7458 required the proverbial one-bit fix.
7460 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7461 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7462 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7463 PowerPC assembler, and made a few other minor patches.
7465 Steve Chamberlain made GAS able to generate listings.
7467 Hewlett-Packard contributed support for the HP9000/300.
7469 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7470 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7471 formats). This work was supported by both the Center for Software Science at
7472 the University of Utah and Cygnus Support.
7474 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7475 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7476 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7477 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7478 and some initial 64-bit support).
7480 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7482 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7483 support for openVMS/Alpha.
7485 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7488 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7489 Inc.@: added support for Xtensa processors.
7491 Several engineers at Cygnus Support have also provided many small bug fixes and
7492 configuration enhancements.
7494 Jon Beniston added support for the Lattice Mico32 architecture.
7496 Many others have contributed large or small bugfixes and enhancements. If
7497 you have contributed significant work and are not mentioned on this list, and
7498 want to be, let us know. Some of the history has been lost; we are not
7499 intentionally leaving anyone out.
7501 @node GNU Free Documentation License
7502 @appendix GNU Free Documentation License
7506 @unnumbered AS Index
projects / dragonfly.git / blob