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
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
52 @set abnormal-separator
56 @settitle Using @value{AS}
59 @settitle Using @value{AS} (@value{TARGET})
61 @setchapternewpage odd
66 @c WARE! Some of the machine-dependent sections contain tables of machine
67 @c instructions. Except in multi-column format, these tables look silly.
68 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
69 @c the multi-col format is faked within @example sections.
71 @c Again unfortunately, the natural size that fits on a page, for these tables,
72 @c is different depending on whether or not smallbook is turned on.
73 @c This matters, because of order: text flow switches columns at each page
76 @c The format faked in this source works reasonably well for smallbook,
77 @c not well for the default large-page format. This manual expects that if you
78 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
79 @c tables in question. You can turn on one without the other at your
80 @c discretion, of course.
83 @c the insn tables look just as silly in info files regardless of smallbook,
84 @c might as well show 'em anyways.
90 * As: (as). The GNU assembler.
91 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.1
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
115 Permission is granted to process this file through Tex and print the
116 results, provided the printed document carries copying permission
117 notice identical to this one except for the removal of this paragraph
118 (this paragraph not being relevant to the printed manual).
124 @title Using @value{AS}
125 @subtitle The @sc{gnu} Assembler
127 @subtitle for the @value{TARGET} family
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, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
158 Permission is granted to copy, distribute and/or modify this document
159 under the terms of the GNU Free Documentation License, Version 1.1
160 or any later version published by the Free Software Foundation;
161 with no Invariant Sections, with no Front-Cover Texts, and with no
162 Back-Cover Texts. A copy of the license is included in the
163 section entitled ``GNU Free Documentation License''.
169 @top Using @value{AS}
171 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}} version
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
190 * Machine Dependencies:: Machine Dependent Features
191 * Reporting Bugs:: Reporting Bugs
192 * Acknowledgements:: Who Did What
193 * GNU Free Documentation License:: GNU Free Documentation License
201 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
203 This version of the manual describes @command{@value{AS}} configured to generate
204 code for @value{TARGET} architectures.
208 @cindex invocation summary
209 @cindex option summary
210 @cindex summary of options
211 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
212 @pxref{Invoking,,Command-Line Options}.
214 @c man title AS the portable GNU assembler.
218 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
222 @c We don't use deffn and friends for the following because they seem
223 @c to be limited to one line for the header.
225 @c man begin SYNOPSIS
226 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
227 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
228 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
229 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
230 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
231 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
232 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
233 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
234 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{--target-help}]
235 [@var{target-options}] [@b{--}|@var{files} @dots{}]
237 @c Target dependent options are listed below. Keep the list sorted.
238 @c Add an empty line for separation.
241 @emph{Target Alpha options:}
243 [@b{-mdebug} | @b{-no-mdebug}]
244 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
245 [@b{-F}] [@b{-32addr}]
249 @emph{Target ARC options:}
255 @emph{Target ARM options:}
256 @c Don't document the deprecated options
257 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
258 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
259 [@b{-mfpu}=@var{floating-point-format}]
260 [@b{-mfloat-abi}=@var{abi}]
261 [@b{-meabi}=@var{ver}]
264 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
265 @b{-mapcs-reentrant}]
266 [@b{-mthumb-interwork}] [@b{-k}]
270 @emph{Target CRIS options:}
271 [@b{--underscore} | @b{--no-underscore}]
273 [@b{--emulation=criself} | @b{--emulation=crisaout}]
274 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
275 @c Deprecated -- deliberately not documented.
280 @emph{Target D10V options:}
285 @emph{Target D30V options:}
286 [@b{-O}|@b{-n}|@b{-N}]
289 @c Renesas family chips have no machine-dependent assembler options
292 @c HPPA has no machine-dependent assembler options (yet).
296 @emph{Target i386 options:}
297 [@b{--32}|@b{--64}] [@b{-n}]
301 @emph{Target i960 options:}
302 @c see md_parse_option in tc-i960.c
303 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
305 [@b{-b}] [@b{-no-relax}]
309 @emph{Target IA-64 options:}
310 [@b{-mconstant-gp}|@b{-mauto-pic}]
311 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
313 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
314 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
315 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
316 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
320 @emph{Target IP2K options:}
321 [@b{-mip2022}|@b{-mip2022ext}]
325 @emph{Target M32C options:}
326 [@b{-m32c}|@b{-m16c}]
330 @emph{Target M32R options:}
331 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
336 @emph{Target M680X0 options:}
337 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
341 @emph{Target M68HC11 options:}
342 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
343 [@b{-mshort}|@b{-mlong}]
344 [@b{-mshort-double}|@b{-mlong-double}]
345 [@b{--force-long-branchs}] [@b{--short-branchs}]
346 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
347 [@b{--print-opcodes}] [@b{--generate-example}]
351 @emph{Target MCORE options:}
352 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
353 [@b{-mcpu=[210|340]}]
357 @emph{Target MIPS options:}
358 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
359 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
360 [@b{-non_shared}] [@b{-xgot}]
361 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
362 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
363 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
364 [@b{-mips64}] [@b{-mips64r2}]
365 [@b{-construct-floats}] [@b{-no-construct-floats}]
366 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
367 [@b{-mfix7000}] [@b{-mno-fix7000}]
368 [@b{-mips16}] [@b{-no-mips16}]
369 [@b{-mips3d}] [@b{-no-mips3d}]
370 [@b{-mdmx}] [@b{-no-mdmx}]
371 [@b{-mdsp}] [@b{-mno-dsp}]
372 [@b{-mmt}] [@b{-mno-mt}]
373 [@b{-mdebug}] [@b{-no-mdebug}]
374 [@b{-mpdr}] [@b{-mno-pdr}]
378 @emph{Target MMIX options:}
379 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
380 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
381 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
382 [@b{--linker-allocated-gregs}]
386 @emph{Target PDP11 options:}
387 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
388 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
389 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
393 @emph{Target picoJava options:}
398 @emph{Target PowerPC options:}
399 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
400 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
401 @b{-mbooke32}|@b{-mbooke64}]
402 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
403 [@b{-mregnames}|@b{-mno-regnames}]
404 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
405 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
406 [@b{-msolaris}|@b{-mno-solaris}]
410 @emph{Target SPARC options:}
411 @c The order here is important. See c-sparc.texi.
412 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
413 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
414 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
419 @emph{Target TIC54X options:}
420 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
421 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
426 @emph{Target Z80 options:}
427 [@b{-z80}] [@b{-r800}]
428 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
429 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
430 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
431 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
432 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
433 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
437 @c Z8000 has no machine-dependent assembler options
441 @emph{Target Xtensa options:}
442 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
443 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
444 [@b{--[no-]transform}]
445 [@b{--rename-section} @var{oldname}=@var{newname}]
454 Turn on listings, in any of a variety of ways:
458 omit false conditionals
461 omit debugging directives
464 include high-level source
470 include macro expansions
473 omit forms processing
479 set the name of the listing file
482 You may combine these options; for example, use @samp{-aln} for assembly
483 listing without forms processing. The @samp{=file} option, if used, must be
484 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
487 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
490 Ignored. This option is accepted for script compatibility with calls to
493 @item --defsym @var{sym}=@var{value}
494 Define the symbol @var{sym} to be @var{value} before assembling the input file.
495 @var{value} must be an integer constant. As in C, a leading @samp{0x}
496 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
499 ``fast''---skip whitespace and comment preprocessing (assume source is
504 Generate debugging information for each assembler source line using whichever
505 debug format is preferred by the target. This currently means either STABS,
509 Generate stabs debugging information for each assembler line. This
510 may help debugging assembler code, if the debugger can handle it.
513 Generate stabs debugging information for each assembler line, with GNU
514 extensions that probably only gdb can handle, and that could make other
515 debuggers crash or refuse to read your program. This
516 may help debugging assembler code. Currently the only GNU extension is
517 the location of the current working directory at assembling time.
520 Generate DWARF2 debugging information for each assembler line. This
521 may help debugging assembler code, if the debugger can handle it. Note---this
522 option is only supported by some targets, not all of them.
525 Print a summary of the command line options and exit.
528 Print a summary of all target specific options and exit.
531 Add directory @var{dir} to the search list for @code{.include} directives.
534 Don't warn about signed overflow.
537 @ifclear DIFF-TBL-KLUGE
538 This option is accepted but has no effect on the @value{TARGET} family.
540 @ifset DIFF-TBL-KLUGE
541 Issue warnings when difference tables altered for long displacements.
546 Keep (in the symbol table) local symbols. On traditional a.out systems
547 these start with @samp{L}, but different systems have different local
550 @item --listing-lhs-width=@var{number}
551 Set the maximum width, in words, of the output data column for an assembler
552 listing to @var{number}.
554 @item --listing-lhs-width2=@var{number}
555 Set the maximum width, in words, of the output data column for continuation
556 lines in an assembler listing to @var{number}.
558 @item --listing-rhs-width=@var{number}
559 Set the maximum width of an input source line, as displayed in a listing, to
562 @item --listing-cont-lines=@var{number}
563 Set the maximum number of lines printed in a listing for a single line of input
566 @item -o @var{objfile}
567 Name the object-file output from @command{@value{AS}} @var{objfile}.
570 Fold the data section into the text section.
572 @kindex --hash-size=@var{number}
573 Set the default size of GAS's hash tables to a prime number close to
574 @var{number}. Increasing this value can reduce the length of time it takes the
575 assembler to perform its tasks, at the expense of increasing the assembler's
576 memory requirements. Similarly reducing this value can reduce the memory
577 requirements at the expense of speed.
579 @item --reduce-memory-overheads
580 This option reduces GAS's memory requirements, at the expense of making the
581 assembly processes slower. Currently this switch is a synonym for
582 @samp{--hash-size=4051}, but in the future it may have other effects as well.
585 Print the maximum space (in bytes) and total time (in seconds) used by
588 @item --strip-local-absolute
589 Remove local absolute symbols from the outgoing symbol table.
593 Print the @command{as} version.
596 Print the @command{as} version and exit.
600 Suppress warning messages.
602 @item --fatal-warnings
603 Treat warnings as errors.
606 Don't suppress warning messages or treat them as errors.
615 Generate an object file even after errors.
617 @item -- | @var{files} @dots{}
618 Standard input, or source files to assemble.
623 The following options are available when @value{AS} is configured for
628 This option selects the core processor variant.
630 Select either big-endian (-EB) or little-endian (-EL) output.
635 The following options are available when @value{AS} is configured for the ARM
639 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
640 Specify which ARM processor variant is the target.
641 @item -march=@var{architecture}[+@var{extension}@dots{}]
642 Specify which ARM architecture variant is used by the target.
643 @item -mfpu=@var{floating-point-format}
644 Select which Floating Point architecture is the target.
645 @item -mfloat-abi=@var{abi}
646 Select which floating point ABI is in use.
648 Enable Thumb only instruction decoding.
649 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
650 Select which procedure calling convention is in use.
652 Select either big-endian (-EB) or little-endian (-EL) output.
653 @item -mthumb-interwork
654 Specify that the code has been generated with interworking between Thumb and
657 Specify that PIC code has been generated.
662 See the info pages for documentation of the CRIS-specific options.
666 The following options are available when @value{AS} is configured for
669 @cindex D10V optimization
670 @cindex optimization, D10V
672 Optimize output by parallelizing instructions.
677 The following options are available when @value{AS} is configured for a D30V
680 @cindex D30V optimization
681 @cindex optimization, D30V
683 Optimize output by parallelizing instructions.
687 Warn when nops are generated.
689 @cindex D30V nops after 32-bit multiply
691 Warn when a nop after a 32-bit multiply instruction is generated.
696 The following options are available when @value{AS} is configured for the
697 Intel 80960 processor.
700 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
701 Specify which variant of the 960 architecture is the target.
704 Add code to collect statistics about branches taken.
707 Do not alter compare-and-branch instructions for long displacements;
714 The following options are available when @value{AS} is configured for the
720 Specifies that the extended IP2022 instructions are allowed.
723 Restores the default behaviour, which restricts the permitted instructions to
724 just the basic IP2022 ones.
730 The following options are available when @value{AS} is configured for the
731 Renesas M32C and M16C processors.
736 Assemble M32C instructions.
739 Assemble M16C instructions (the default).
745 The following options are available when @value{AS} is configured for the
746 Renesas M32R (formerly Mitsubishi M32R) series.
751 Specify which processor in the M32R family is the target. The default
752 is normally the M32R, but this option changes it to the M32RX.
754 @item --warn-explicit-parallel-conflicts or --Wp
755 Produce warning messages when questionable parallel constructs are
758 @item --no-warn-explicit-parallel-conflicts or --Wnp
759 Do not produce warning messages when questionable parallel constructs are
766 The following options are available when @value{AS} is configured for the
767 Motorola 68000 series.
772 Shorten references to undefined symbols, to one word instead of two.
774 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
775 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
776 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
777 Specify what processor in the 68000 family is the target. The default
778 is normally the 68020, but this can be changed at configuration time.
780 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
781 The target machine does (or does not) have a floating-point coprocessor.
782 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
783 the basic 68000 is not compatible with the 68881, a combination of the
784 two can be specified, since it's possible to do emulation of the
785 coprocessor instructions with the main processor.
787 @item -m68851 | -mno-68851
788 The target machine does (or does not) have a memory-management
789 unit coprocessor. The default is to assume an MMU for 68020 and up.
796 For details about the PDP-11 machine dependent features options,
797 see @ref{PDP-11-Options}.
800 @item -mpic | -mno-pic
801 Generate position-independent (or position-dependent) code. The
802 default is @option{-mpic}.
805 @itemx -mall-extensions
806 Enable all instruction set extensions. This is the default.
808 @item -mno-extensions
809 Disable all instruction set extensions.
811 @item -m@var{extension} | -mno-@var{extension}
812 Enable (or disable) a particular instruction set extension.
815 Enable the instruction set extensions supported by a particular CPU, and
816 disable all other extensions.
818 @item -m@var{machine}
819 Enable the instruction set extensions supported by a particular machine
820 model, and disable all other extensions.
826 The following options are available when @value{AS} is configured for
827 a picoJava processor.
831 @cindex PJ endianness
832 @cindex endianness, PJ
833 @cindex big endian output, PJ
835 Generate ``big endian'' format output.
837 @cindex little endian output, PJ
839 Generate ``little endian'' format output.
845 The following options are available when @value{AS} is configured for the
846 Motorola 68HC11 or 68HC12 series.
850 @item -m68hc11 | -m68hc12 | -m68hcs12
851 Specify what processor is the target. The default is
852 defined by the configuration option when building the assembler.
855 Specify to use the 16-bit integer ABI.
858 Specify to use the 32-bit integer ABI.
861 Specify to use the 32-bit double ABI.
864 Specify to use the 64-bit double ABI.
866 @item --force-long-branchs
867 Relative branches are turned into absolute ones. This concerns
868 conditional branches, unconditional branches and branches to a
871 @item -S | --short-branchs
872 Do not turn relative branchs into absolute ones
873 when the offset is out of range.
875 @item --strict-direct-mode
876 Do not turn the direct addressing mode into extended addressing mode
877 when the instruction does not support direct addressing mode.
879 @item --print-insn-syntax
880 Print the syntax of instruction in case of error.
882 @item --print-opcodes
883 print the list of instructions with syntax and then exit.
885 @item --generate-example
886 print an example of instruction for each possible instruction and then exit.
887 This option is only useful for testing @command{@value{AS}}.
893 The following options are available when @command{@value{AS}} is configured
894 for the SPARC architecture:
897 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
898 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
899 Explicitly select a variant of the SPARC architecture.
901 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
902 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
904 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
905 UltraSPARC extensions.
907 @item -xarch=v8plus | -xarch=v8plusa
908 For compatibility with the Solaris v9 assembler. These options are
909 equivalent to -Av8plus and -Av8plusa, respectively.
912 Warn when the assembler switches to another architecture.
917 The following options are available when @value{AS} is configured for the 'c54x
922 Enable extended addressing mode. All addresses and relocations will assume
923 extended addressing (usually 23 bits).
924 @item -mcpu=@var{CPU_VERSION}
925 Sets the CPU version being compiled for.
926 @item -merrors-to-file @var{FILENAME}
927 Redirect error output to a file, for broken systems which don't support such
928 behaviour in the shell.
933 The following options are available when @value{AS} is configured for
934 a @sc{mips} processor.
938 This option sets the largest size of an object that can be referenced
939 implicitly with the @code{gp} register. It is only accepted for targets that
940 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
942 @cindex MIPS endianness
943 @cindex endianness, MIPS
944 @cindex big endian output, MIPS
946 Generate ``big endian'' format output.
948 @cindex little endian output, MIPS
950 Generate ``little endian'' format output.
962 Generate code for a particular @sc{mips} Instruction Set Architecture level.
963 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
964 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
965 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
966 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
968 correspond to generic
969 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
970 and @samp{MIPS64 Release 2}
971 ISA processors, respectively.
973 @item -march=@var{CPU}
974 Generate code for a particular @sc{mips} cpu.
976 @item -mtune=@var{cpu}
977 Schedule and tune for a particular @sc{mips} cpu.
981 Cause nops to be inserted if the read of the destination register
982 of an mfhi or mflo instruction occurs in the following two instructions.
986 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
987 section instead of the standard ELF .stabs sections.
991 Control generation of @code{.pdr} sections.
995 The register sizes are normally inferred from the ISA and ABI, but these
996 flags force a certain group of registers to be treated as 32 bits wide at
997 all times. @samp{-mgp32} controls the size of general-purpose registers
998 and @samp{-mfp32} controls the size of floating-point registers.
1002 Generate code for the MIPS 16 processor. This is equivalent to putting
1003 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1004 turns off this option.
1008 Generate code for the MIPS-3D Application Specific Extension.
1009 This tells the assembler to accept MIPS-3D instructions.
1010 @samp{-no-mips3d} turns off this option.
1014 Generate code for the MDMX Application Specific Extension.
1015 This tells the assembler to accept MDMX instructions.
1016 @samp{-no-mdmx} turns off this option.
1020 Generate code for the DSP Application Specific Extension.
1021 This tells the assembler to accept DSP instructions.
1022 @samp{-mno-dsp} turns off this option.
1026 Generate code for the MT Application Specific Extension.
1027 This tells the assembler to accept MT instructions.
1028 @samp{-mno-mt} turns off this option.
1030 @item --construct-floats
1031 @itemx --no-construct-floats
1032 The @samp{--no-construct-floats} option disables the construction of
1033 double width floating point constants by loading the two halves of the
1034 value into the two single width floating point registers that make up
1035 the double width register. By default @samp{--construct-floats} is
1036 selected, allowing construction of these floating point constants.
1039 @item --emulation=@var{name}
1040 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1041 for some other target, in all respects, including output format (choosing
1042 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1043 debugging information or store symbol table information, and default
1044 endianness. The available configuration names are: @samp{mipsecoff},
1045 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1046 @samp{mipsbelf}. The first two do not alter the default endianness from that
1047 of the primary target for which the assembler was configured; the others change
1048 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1049 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1050 selection in any case.
1052 This option is currently supported only when the primary target
1053 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1054 Furthermore, the primary target or others specified with
1055 @samp{--enable-targets=@dots{}} at configuration time must include support for
1056 the other format, if both are to be available. For example, the Irix 5
1057 configuration includes support for both.
1059 Eventually, this option will support more configurations, with more
1060 fine-grained control over the assembler's behavior, and will be supported for
1064 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1071 Control how to deal with multiplication overflow and division by zero.
1072 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1073 (and only work for Instruction Set Architecture level 2 and higher);
1074 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1078 When this option is used, @command{@value{AS}} will issue a warning every
1079 time it generates a nop instruction from a macro.
1084 The following options are available when @value{AS} is configured for
1090 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1091 The command line option @samp{-nojsri2bsr} can be used to disable it.
1095 Enable or disable the silicon filter behaviour. By default this is disabled.
1096 The default can be overridden by the @samp{-sifilter} command line option.
1099 Alter jump instructions for long displacements.
1101 @item -mcpu=[210|340]
1102 Select the cpu type on the target hardware. This controls which instructions
1106 Assemble for a big endian target.
1109 Assemble for a little endian target.
1115 See the info pages for documentation of the MMIX-specific options.
1119 The following options are available when @value{AS} is configured for
1120 an Xtensa processor.
1123 @item --text-section-literals | --no-text-section-literals
1124 With @option{--text-@-section-@-literals}, literal pools are interspersed
1125 in the text section. The default is
1126 @option{--no-@-text-@-section-@-literals}, which places literals in a
1127 separate section in the output file. These options only affect literals
1128 referenced via PC-relative @code{L32R} instructions; literals for
1129 absolute mode @code{L32R} instructions are handled separately.
1131 @item --absolute-literals | --no-absolute-literals
1132 Indicate to the assembler whether @code{L32R} instructions use absolute
1133 or PC-relative addressing. The default is to assume absolute addressing
1134 if the Xtensa processor includes the absolute @code{L32R} addressing
1135 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1137 @item --target-align | --no-target-align
1138 Enable or disable automatic alignment to reduce branch penalties at the
1139 expense of some code density. The default is @option{--target-@-align}.
1141 @item --longcalls | --no-longcalls
1142 Enable or disable transformation of call instructions to allow calls
1143 across a greater range of addresses. The default is
1144 @option{--no-@-longcalls}.
1146 @item --transform | --no-transform
1147 Enable or disable all assembler transformations of Xtensa instructions.
1148 The default is @option{--transform};
1149 @option{--no-transform} should be used only in the rare cases when the
1150 instructions must be exactly as specified in the assembly source.
1155 The following options are available when @value{AS} is configured for
1156 a Z80 family processor.
1159 Assemble for Z80 processor.
1161 Assemble for R800 processor.
1162 @item -ignore-undocumented-instructions
1164 Assemble undocumented Z80 instructions that also work on R800 without warning.
1165 @item -ignore-unportable-instructions
1167 Assemble all undocumented Z80 instructions without warning.
1168 @item -warn-undocumented-instructions
1170 Issue a warning for undocumented Z80 instructions that also work on R800.
1171 @item -warn-unportable-instructions
1173 Issue a warning for undocumented Z80 instructions that do notwork on R800.
1174 @item -forbid-undocumented-instructions
1176 Treat all undocumented instructions as errors.
1177 @item -forbid-unportable-instructions
1179 Treat undocumented Z80 intructions that do notwork on R800 as errors.
1186 * Manual:: Structure of this Manual
1187 * GNU Assembler:: The GNU Assembler
1188 * Object Formats:: Object File Formats
1189 * Command Line:: Command Line
1190 * Input Files:: Input Files
1191 * Object:: Output (Object) File
1192 * Errors:: Error and Warning Messages
1196 @section Structure of this Manual
1198 @cindex manual, structure and purpose
1199 This manual is intended to describe what you need to know to use
1200 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1201 notation for symbols, constants, and expressions; the directives that
1202 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1205 We also cover special features in the @value{TARGET}
1206 configuration of @command{@value{AS}}, including assembler directives.
1209 This manual also describes some of the machine-dependent features of
1210 various flavors of the assembler.
1213 @cindex machine instructions (not covered)
1214 On the other hand, this manual is @emph{not} intended as an introduction
1215 to programming in assembly language---let alone programming in general!
1216 In a similar vein, we make no attempt to introduce the machine
1217 architecture; we do @emph{not} describe the instruction set, standard
1218 mnemonics, registers or addressing modes that are standard to a
1219 particular architecture.
1221 You may want to consult the manufacturer's
1222 machine architecture manual for this information.
1226 For information on the H8/300 machine instruction set, see @cite{H8/300
1227 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1228 Programming Manual} (Renesas).
1231 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1232 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1233 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1234 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1237 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1241 @c I think this is premature---doc@cygnus.com, 17jan1991
1243 Throughout this manual, we assume that you are running @dfn{GNU},
1244 the portable operating system from the @dfn{Free Software
1245 Foundation, Inc.}. This restricts our attention to certain kinds of
1246 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1247 once this assumption is granted examples and definitions need less
1250 @command{@value{AS}} is part of a team of programs that turn a high-level
1251 human-readable series of instructions into a low-level
1252 computer-readable series of instructions. Different versions of
1253 @command{@value{AS}} are used for different kinds of computer.
1256 @c There used to be a section "Terminology" here, which defined
1257 @c "contents", "byte", "word", and "long". Defining "word" to any
1258 @c particular size is confusing when the .word directive may generate 16
1259 @c bits on one machine and 32 bits on another; in general, for the user
1260 @c version of this manual, none of these terms seem essential to define.
1261 @c They were used very little even in the former draft of the manual;
1262 @c this draft makes an effort to avoid them (except in names of
1266 @section The GNU Assembler
1268 @c man begin DESCRIPTION
1270 @sc{gnu} @command{as} is really a family of assemblers.
1272 This manual describes @command{@value{AS}}, a member of that family which is
1273 configured for the @value{TARGET} architectures.
1275 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1276 should find a fairly similar environment when you use it on another
1277 architecture. Each version has much in common with the others,
1278 including object file formats, most assembler directives (often called
1279 @dfn{pseudo-ops}) and assembler syntax.@refill
1281 @cindex purpose of @sc{gnu} assembler
1282 @command{@value{AS}} is primarily intended to assemble the output of the
1283 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1284 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1285 assemble correctly everything that other assemblers for the same
1286 machine would assemble.
1288 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1291 @c This remark should appear in generic version of manual; assumption
1292 @c here is that generic version sets M680x0.
1293 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1294 assembler for the same architecture; for example, we know of several
1295 incompatible versions of 680x0 assembly language syntax.
1300 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1301 program in one pass of the source file. This has a subtle impact on the
1302 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1304 @node Object Formats
1305 @section Object File Formats
1307 @cindex object file format
1308 The @sc{gnu} assembler can be configured to produce several alternative
1309 object file formats. For the most part, this does not affect how you
1310 write assembly language programs; but directives for debugging symbols
1311 are typically different in different file formats. @xref{Symbol
1312 Attributes,,Symbol Attributes}.
1315 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1316 @value{OBJ-NAME} format object files.
1318 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1320 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1321 @code{b.out} or COFF format object files.
1324 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1325 SOM or ELF format object files.
1330 @section Command Line
1332 @cindex command line conventions
1334 After the program name @command{@value{AS}}, the command line may contain
1335 options and file names. Options may appear in any order, and may be
1336 before, after, or between file names. The order of file names is
1339 @cindex standard input, as input file
1341 @file{--} (two hyphens) by itself names the standard input file
1342 explicitly, as one of the files for @command{@value{AS}} to assemble.
1344 @cindex options, command line
1345 Except for @samp{--} any command line argument that begins with a
1346 hyphen (@samp{-}) is an option. Each option changes the behavior of
1347 @command{@value{AS}}. No option changes the way another option works. An
1348 option is a @samp{-} followed by one or more letters; the case of
1349 the letter is important. All options are optional.
1351 Some options expect exactly one file name to follow them. The file
1352 name may either immediately follow the option's letter (compatible
1353 with older assemblers) or it may be the next command argument (@sc{gnu}
1354 standard). These two command lines are equivalent:
1357 @value{AS} -o my-object-file.o mumble.s
1358 @value{AS} -omy-object-file.o mumble.s
1362 @section Input Files
1365 @cindex source program
1366 @cindex files, input
1367 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1368 describe the program input to one run of @command{@value{AS}}. The program may
1369 be in one or more files; how the source is partitioned into files
1370 doesn't change the meaning of the source.
1372 @c I added "con" prefix to "catenation" just to prove I can overcome my
1373 @c APL training... doc@cygnus.com
1374 The source program is a concatenation of the text in all the files, in the
1377 @c man begin DESCRIPTION
1378 Each time you run @command{@value{AS}} it assembles exactly one source
1379 program. The source program is made up of one or more files.
1380 (The standard input is also a file.)
1382 You give @command{@value{AS}} a command line that has zero or more input file
1383 names. The input files are read (from left file name to right). A
1384 command line argument (in any position) that has no special meaning
1385 is taken to be an input file name.
1387 If you give @command{@value{AS}} no file names it attempts to read one input file
1388 from the @command{@value{AS}} standard input, which is normally your terminal. You
1389 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1392 Use @samp{--} if you need to explicitly name the standard input file
1393 in your command line.
1395 If the source is empty, @command{@value{AS}} produces a small, empty object
1400 @subheading Filenames and Line-numbers
1402 @cindex input file linenumbers
1403 @cindex line numbers, in input files
1404 There are two ways of locating a line in the input file (or files) and
1405 either may be used in reporting error messages. One way refers to a line
1406 number in a physical file; the other refers to a line number in a
1407 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1409 @dfn{Physical files} are those files named in the command line given
1410 to @command{@value{AS}}.
1412 @dfn{Logical files} are simply names declared explicitly by assembler
1413 directives; they bear no relation to physical files. Logical file names help
1414 error messages reflect the original source file, when @command{@value{AS}} source
1415 is itself synthesized from other files. @command{@value{AS}} understands the
1416 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1417 @ref{File,,@code{.file}}.
1420 @section Output (Object) File
1426 Every time you run @command{@value{AS}} it produces an output file, which is
1427 your assembly language program translated into numbers. This file
1428 is the object file. Its default name is
1436 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1438 You can give it another name by using the @option{-o} option. Conventionally,
1439 object file names end with @file{.o}. The default name is used for historical
1440 reasons: older assemblers were capable of assembling self-contained programs
1441 directly into a runnable program. (For some formats, this isn't currently
1442 possible, but it can be done for the @code{a.out} format.)
1446 The object file is meant for input to the linker @code{@value{LD}}. It contains
1447 assembled program code, information to help @code{@value{LD}} integrate
1448 the assembled program into a runnable file, and (optionally) symbolic
1449 information for the debugger.
1451 @c link above to some info file(s) like the description of a.out.
1452 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1455 @section Error and Warning Messages
1457 @c man begin DESCRIPTION
1459 @cindex error messages
1460 @cindex warning messages
1461 @cindex messages from assembler
1462 @command{@value{AS}} may write warnings and error messages to the standard error
1463 file (usually your terminal). This should not happen when a compiler
1464 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1465 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1466 grave problem that stops the assembly.
1470 @cindex format of warning messages
1471 Warning messages have the format
1474 file_name:@b{NNN}:Warning Message Text
1478 @cindex line numbers, in warnings/errors
1479 (where @b{NNN} is a line number). If a logical file name has been given
1480 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1481 the current input file is used. If a logical line number was given
1483 (@pxref{Line,,@code{.line}})
1485 then it is used to calculate the number printed,
1486 otherwise the actual line in the current source file is printed. The
1487 message text is intended to be self explanatory (in the grand Unix
1490 @cindex format of error messages
1491 Error messages have the format
1493 file_name:@b{NNN}:FATAL:Error Message Text
1495 The file name and line number are derived as for warning
1496 messages. The actual message text may be rather less explanatory
1497 because many of them aren't supposed to happen.
1500 @chapter Command-Line Options
1502 @cindex options, all versions of assembler
1503 This chapter describes command-line options available in @emph{all}
1504 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1506 to the @value{TARGET} target.
1509 to particular machine architectures.
1512 @c man begin DESCRIPTION
1514 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1515 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1516 The assembler arguments must be separated from each other (and the @samp{-Wa})
1517 by commas. For example:
1520 gcc -c -g -O -Wa,-alh,-L file.c
1524 This passes two options to the assembler: @samp{-alh} (emit a listing to
1525 standard output with high-level and assembly source) and @samp{-L} (retain
1526 local symbols in the symbol table).
1528 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1529 command-line options are automatically passed to the assembler by the compiler.
1530 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1531 precisely what options it passes to each compilation pass, including the
1537 * a:: -a[cdhlns] enable listings
1538 * alternate:: --alternate enable alternate macro syntax
1539 * D:: -D for compatibility
1540 * f:: -f to work faster
1541 * I:: -I for .include search path
1542 @ifclear DIFF-TBL-KLUGE
1543 * K:: -K for compatibility
1545 @ifset DIFF-TBL-KLUGE
1546 * K:: -K for difference tables
1549 * L:: -L to retain local labels
1550 * listing:: --listing-XXX to configure listing output
1551 * M:: -M or --mri to assemble in MRI compatibility mode
1552 * MD:: --MD for dependency tracking
1553 * o:: -o to name the object file
1554 * R:: -R to join data and text sections
1555 * statistics:: --statistics to see statistics about assembly
1556 * traditional-format:: --traditional-format for compatible output
1557 * v:: -v to announce version
1558 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1559 * Z:: -Z to make object file even after errors
1563 @section Enable Listings: @option{-a[cdhlns]}
1572 @cindex listings, enabling
1573 @cindex assembly listings, enabling
1575 These options enable listing output from the assembler. By itself,
1576 @samp{-a} requests high-level, assembly, and symbols listing.
1577 You can use other letters to select specific options for the list:
1578 @samp{-ah} requests a high-level language listing,
1579 @samp{-al} requests an output-program assembly listing, and
1580 @samp{-as} requests a symbol table listing.
1581 High-level listings require that a compiler debugging option like
1582 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1585 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1586 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1587 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1588 omitted from the listing.
1590 Use the @samp{-ad} option to omit debugging directives from the
1593 Once you have specified one of these options, you can further control
1594 listing output and its appearance using the directives @code{.list},
1595 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1597 The @samp{-an} option turns off all forms processing.
1598 If you do not request listing output with one of the @samp{-a} options, the
1599 listing-control directives have no effect.
1601 The letters after @samp{-a} may be combined into one option,
1602 @emph{e.g.}, @samp{-aln}.
1604 Note if the assembler source is coming from the standard input (eg because it
1605 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1606 is being used) then the listing will not contain any comments or preprocessor
1607 directives. This is because the listing code buffers input source lines from
1608 stdin only after they have been preprocessed by the assembler. This reduces
1609 memory usage and makes the code more efficient.
1612 @section @option{--alternate}
1615 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1618 @section @option{-D}
1621 This option has no effect whatsoever, but it is accepted to make it more
1622 likely that scripts written for other assemblers also work with
1623 @command{@value{AS}}.
1626 @section Work Faster: @option{-f}
1629 @cindex trusted compiler
1630 @cindex faster processing (@option{-f})
1631 @samp{-f} should only be used when assembling programs written by a
1632 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1633 and comment preprocessing on
1634 the input file(s) before assembling them. @xref{Preprocessing,
1638 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1639 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1644 @section @code{.include} Search Path: @option{-I} @var{path}
1646 @kindex -I @var{path}
1647 @cindex paths for @code{.include}
1648 @cindex search path for @code{.include}
1649 @cindex @code{include} directive search path
1650 Use this option to add a @var{path} to the list of directories
1651 @command{@value{AS}} searches for files specified in @code{.include}
1652 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1653 many times as necessary to include a variety of paths. The current
1654 working directory is always searched first; after that, @command{@value{AS}}
1655 searches any @samp{-I} directories in the same order as they were
1656 specified (left to right) on the command line.
1659 @section Difference Tables: @option{-K}
1662 @ifclear DIFF-TBL-KLUGE
1663 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1664 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1665 where it can be used to warn when the assembler alters the machine code
1666 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1667 family does not have the addressing limitations that sometimes lead to this
1668 alteration on other platforms.
1671 @ifset DIFF-TBL-KLUGE
1672 @cindex difference tables, warning
1673 @cindex warning for altered difference tables
1674 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1675 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1676 You can use the @samp{-K} option if you want a warning issued when this
1681 @section Include Local Labels: @option{-L}
1684 @cindex local labels, retaining in output
1685 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1686 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1687 debugging, because they are intended for the use of programs (like
1688 compilers) that compose assembler programs, not for your notice.
1689 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1690 normally debug with them.
1692 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1693 in the object file. Usually if you do this you also tell the linker
1694 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1696 By default, a local label is any label beginning with @samp{L}, but each
1697 target is allowed to redefine the local label prefix.
1699 On the HPPA local labels begin with @samp{L$}.
1703 @section Configuring listing output: @option{--listing}
1705 The listing feature of the assembler can be enabled via the command line switch
1706 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1707 hex dump of the corresponding locations in the output object file, and displays
1708 them as a listing file. The format of this listing can be controlled by pseudo
1709 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1710 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1713 @item --listing-lhs-width=@samp{number}
1714 @kindex --listing-lhs-width
1715 @cindex Width of first line disassembly output
1716 Sets the maximum width, in words, of the first line of the hex byte dump. This
1717 dump appears on the left hand side of the listing output.
1719 @item --listing-lhs-width2=@samp{number}
1720 @kindex --listing-lhs-width2
1721 @cindex Width of continuation lines of disassembly output
1722 Sets the maximum width, in words, of any further lines of the hex byte dump for
1723 a given input source line. If this value is not specified, it defaults to being
1724 the same as the value specified for @samp{--listing-lhs-width}. If neither
1725 switch is used the default is to one.
1727 @item --listing-rhs-width=@samp{number}
1728 @kindex --listing-rhs-width
1729 @cindex Width of source line output
1730 Sets the maximum width, in characters, of the source line that is displayed
1731 alongside the hex dump. The default value for this parameter is 100. The
1732 source line is displayed on the right hand side of the listing output.
1734 @item --listing-cont-lines=@samp{number}
1735 @kindex --listing-cont-lines
1736 @cindex Maximum number of continuation lines
1737 Sets the maximum number of continuation lines of hex dump that will be
1738 displayed for a given single line of source input. The default value is 4.
1742 @section Assemble in MRI Compatibility Mode: @option{-M}
1745 @cindex MRI compatibility mode
1746 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1747 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1748 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1749 configured target) assembler from Microtec Research. The exact nature of the
1750 MRI syntax will not be documented here; see the MRI manuals for more
1751 information. Note in particular that the handling of macros and macro
1752 arguments is somewhat different. The purpose of this option is to permit
1753 assembling existing MRI assembler code using @command{@value{AS}}.
1755 The MRI compatibility is not complete. Certain operations of the MRI assembler
1756 depend upon its object file format, and can not be supported using other object
1757 file formats. Supporting these would require enhancing each object file format
1758 individually. These are:
1761 @item global symbols in common section
1763 The m68k MRI assembler supports common sections which are merged by the linker.
1764 Other object file formats do not support this. @command{@value{AS}} handles
1765 common sections by treating them as a single common symbol. It permits local
1766 symbols to be defined within a common section, but it can not support global
1767 symbols, since it has no way to describe them.
1769 @item complex relocations
1771 The MRI assemblers support relocations against a negated section address, and
1772 relocations which combine the start addresses of two or more sections. These
1773 are not support by other object file formats.
1775 @item @code{END} pseudo-op specifying start address
1777 The MRI @code{END} pseudo-op permits the specification of a start address.
1778 This is not supported by other object file formats. The start address may
1779 instead be specified using the @option{-e} option to the linker, or in a linker
1782 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1784 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1785 name to the output file. This is not supported by other object file formats.
1787 @item @code{ORG} pseudo-op
1789 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1790 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1791 which changes the location within the current section. Absolute sections are
1792 not supported by other object file formats. The address of a section may be
1793 assigned within a linker script.
1796 There are some other features of the MRI assembler which are not supported by
1797 @command{@value{AS}}, typically either because they are difficult or because they
1798 seem of little consequence. Some of these may be supported in future releases.
1802 @item EBCDIC strings
1804 EBCDIC strings are not supported.
1806 @item packed binary coded decimal
1808 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1809 and @code{DCB.P} pseudo-ops are not supported.
1811 @item @code{FEQU} pseudo-op
1813 The m68k @code{FEQU} pseudo-op is not supported.
1815 @item @code{NOOBJ} pseudo-op
1817 The m68k @code{NOOBJ} pseudo-op is not supported.
1819 @item @code{OPT} branch control options
1821 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1822 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1823 relaxes all branches, whether forward or backward, to an appropriate size, so
1824 these options serve no purpose.
1826 @item @code{OPT} list control options
1828 The following m68k @code{OPT} list control options are ignored: @code{C},
1829 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1830 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1832 @item other @code{OPT} options
1834 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1835 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1837 @item @code{OPT} @code{D} option is default
1839 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1840 @code{OPT NOD} may be used to turn it off.
1842 @item @code{XREF} pseudo-op.
1844 The m68k @code{XREF} pseudo-op is ignored.
1846 @item @code{.debug} pseudo-op
1848 The i960 @code{.debug} pseudo-op is not supported.
1850 @item @code{.extended} pseudo-op
1852 The i960 @code{.extended} pseudo-op is not supported.
1854 @item @code{.list} pseudo-op.
1856 The various options of the i960 @code{.list} pseudo-op are not supported.
1858 @item @code{.optimize} pseudo-op
1860 The i960 @code{.optimize} pseudo-op is not supported.
1862 @item @code{.output} pseudo-op
1864 The i960 @code{.output} pseudo-op is not supported.
1866 @item @code{.setreal} pseudo-op
1868 The i960 @code{.setreal} pseudo-op is not supported.
1873 @section Dependency Tracking: @option{--MD}
1876 @cindex dependency tracking
1879 @command{@value{AS}} can generate a dependency file for the file it creates. This
1880 file consists of a single rule suitable for @code{make} describing the
1881 dependencies of the main source file.
1883 The rule is written to the file named in its argument.
1885 This feature is used in the automatic updating of makefiles.
1888 @section Name the Object File: @option{-o}
1891 @cindex naming object file
1892 @cindex object file name
1893 There is always one object file output when you run @command{@value{AS}}. By
1894 default it has the name
1897 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1911 You use this option (which takes exactly one filename) to give the
1912 object file a different name.
1914 Whatever the object file is called, @command{@value{AS}} overwrites any
1915 existing file of the same name.
1918 @section Join Data and Text Sections: @option{-R}
1921 @cindex data and text sections, joining
1922 @cindex text and data sections, joining
1923 @cindex joining text and data sections
1924 @cindex merging text and data sections
1925 @option{-R} tells @command{@value{AS}} to write the object file as if all
1926 data-section data lives in the text section. This is only done at
1927 the very last moment: your binary data are the same, but data
1928 section parts are relocated differently. The data section part of
1929 your object file is zero bytes long because all its bytes are
1930 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1932 When you specify @option{-R} it would be possible to generate shorter
1933 address displacements (because we do not have to cross between text and
1934 data section). We refrain from doing this simply for compatibility with
1935 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1938 When @command{@value{AS}} is configured for COFF or ELF output,
1939 this option is only useful if you use sections named @samp{.text} and
1944 @option{-R} is not supported for any of the HPPA targets. Using
1945 @option{-R} generates a warning from @command{@value{AS}}.
1949 @section Display Assembly Statistics: @option{--statistics}
1951 @kindex --statistics
1952 @cindex statistics, about assembly
1953 @cindex time, total for assembly
1954 @cindex space used, maximum for assembly
1955 Use @samp{--statistics} to display two statistics about the resources used by
1956 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1957 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1960 @node traditional-format
1961 @section Compatible Output: @option{--traditional-format}
1963 @kindex --traditional-format
1964 For some targets, the output of @command{@value{AS}} is different in some ways
1965 from the output of some existing assembler. This switch requests
1966 @command{@value{AS}} to use the traditional format instead.
1968 For example, it disables the exception frame optimizations which
1969 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1972 @section Announce Version: @option{-v}
1976 @cindex assembler version
1977 @cindex version of assembler
1978 You can find out what version of as is running by including the
1979 option @samp{-v} (which you can also spell as @samp{-version}) on the
1983 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1985 @command{@value{AS}} should never give a warning or error message when
1986 assembling compiler output. But programs written by people often
1987 cause @command{@value{AS}} to give a warning that a particular assumption was
1988 made. All such warnings are directed to the standard error file.
1992 @cindex suppressing warnings
1993 @cindex warnings, suppressing
1994 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1995 This only affects the warning messages: it does not change any particular of
1996 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1999 @kindex --fatal-warnings
2000 @cindex errors, caused by warnings
2001 @cindex warnings, causing error
2002 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2003 files that generate warnings to be in error.
2006 @cindex warnings, switching on
2007 You can switch these options off again by specifying @option{--warn}, which
2008 causes warnings to be output as usual.
2011 @section Generate Object File in Spite of Errors: @option{-Z}
2012 @cindex object file, after errors
2013 @cindex errors, continuing after
2014 After an error message, @command{@value{AS}} normally produces no output. If for
2015 some reason you are interested in object file output even after
2016 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2017 option. If there are any errors, @command{@value{AS}} continues anyways, and
2018 writes an object file after a final warning message of the form @samp{@var{n}
2019 errors, @var{m} warnings, generating bad object file.}
2024 @cindex machine-independent syntax
2025 @cindex syntax, machine-independent
2026 This chapter describes the machine-independent syntax allowed in a
2027 source file. @command{@value{AS}} syntax is similar to what many other
2028 assemblers use; it is inspired by the BSD 4.2
2033 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2037 * Preprocessing:: Preprocessing
2038 * Whitespace:: Whitespace
2039 * Comments:: Comments
2040 * Symbol Intro:: Symbols
2041 * Statements:: Statements
2042 * Constants:: Constants
2046 @section Preprocessing
2048 @cindex preprocessing
2049 The @command{@value{AS}} internal preprocessor:
2051 @cindex whitespace, removed by preprocessor
2053 adjusts and removes extra whitespace. It leaves one space or tab before
2054 the keywords on a line, and turns any other whitespace on the line into
2057 @cindex comments, removed by preprocessor
2059 removes all comments, replacing them with a single space, or an
2060 appropriate number of newlines.
2062 @cindex constants, converted by preprocessor
2064 converts character constants into the appropriate numeric values.
2067 It does not do macro processing, include file handling, or
2068 anything else you may get from your C compiler's preprocessor. You can
2069 do include file processing with the @code{.include} directive
2070 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2071 to get other ``CPP'' style preprocessing by giving the input file a
2072 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
2073 Output, gcc.info, Using GNU CC}.
2075 Excess whitespace, comments, and character constants
2076 cannot be used in the portions of the input text that are not
2079 @cindex turning preprocessing on and off
2080 @cindex preprocessing, turning on and off
2083 If the first line of an input file is @code{#NO_APP} or if you use the
2084 @samp{-f} option, whitespace and comments are not removed from the input file.
2085 Within an input file, you can ask for whitespace and comment removal in
2086 specific portions of the by putting a line that says @code{#APP} before the
2087 text that may contain whitespace or comments, and putting a line that says
2088 @code{#NO_APP} after this text. This feature is mainly intend to support
2089 @code{asm} statements in compilers whose output is otherwise free of comments
2096 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2097 Whitespace is used to separate symbols, and to make programs neater for
2098 people to read. Unless within character constants
2099 (@pxref{Characters,,Character Constants}), any whitespace means the same
2100 as exactly one space.
2106 There are two ways of rendering comments to @command{@value{AS}}. In both
2107 cases the comment is equivalent to one space.
2109 Anything from @samp{/*} through the next @samp{*/} is a comment.
2110 This means you may not nest these comments.
2114 The only way to include a newline ('\n') in a comment
2115 is to use this sort of comment.
2118 /* This sort of comment does not nest. */
2121 @cindex line comment character
2122 Anything from the @dfn{line comment} character to the next newline
2123 is considered a comment and is ignored. The line comment character is
2125 @samp{;} on the ARC;
2128 @samp{@@} on the ARM;
2131 @samp{;} for the H8/300 family;
2134 @samp{;} for the HPPA;
2137 @samp{#} on the i386 and x86-64;
2140 @samp{#} on the i960;
2143 @samp{;} for the PDP-11;
2146 @samp{;} for picoJava;
2149 @samp{#} for Motorola PowerPC;
2152 @samp{!} for the Renesas / SuperH SH;
2155 @samp{!} on the SPARC;
2158 @samp{#} on the ip2k;
2161 @samp{#} on the m32c;
2164 @samp{#} on the m32r;
2167 @samp{|} on the 680x0;
2170 @samp{#} on the 68HC11 and 68HC12;
2173 @samp{#} on the Vax;
2176 @samp{;} for the Z80;
2179 @samp{!} for the Z8000;
2182 @samp{#} on the V850;
2185 @samp{#} for Xtensa systems;
2187 see @ref{Machine Dependencies}. @refill
2188 @c FIXME What about i860?
2191 On some machines there are two different line comment characters. One
2192 character only begins a comment if it is the first non-whitespace character on
2193 a line, while the other always begins a comment.
2197 The V850 assembler also supports a double dash as starting a comment that
2198 extends to the end of the line.
2204 @cindex lines starting with @code{#}
2205 @cindex logical line numbers
2206 To be compatible with past assemblers, lines that begin with @samp{#} have a
2207 special interpretation. Following the @samp{#} should be an absolute
2208 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2209 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2210 new logical file name. The rest of the line, if any, should be whitespace.
2212 If the first non-whitespace characters on the line are not numeric,
2213 the line is ignored. (Just like a comment.)
2216 # This is an ordinary comment.
2217 # 42-6 "new_file_name" # New logical file name
2218 # This is logical line # 36.
2220 This feature is deprecated, and may disappear from future versions
2221 of @command{@value{AS}}.
2226 @cindex characters used in symbols
2227 @ifclear SPECIAL-SYMS
2228 A @dfn{symbol} is one or more characters chosen from the set of all
2229 letters (both upper and lower case), digits and the three characters
2235 A @dfn{symbol} is one or more characters chosen from the set of all
2236 letters (both upper and lower case), digits and the three characters
2237 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2243 On most machines, you can also use @code{$} in symbol names; exceptions
2244 are noted in @ref{Machine Dependencies}.
2246 No symbol may begin with a digit. Case is significant.
2247 There is no length limit: all characters are significant. Symbols are
2248 delimited by characters not in that set, or by the beginning of a file
2249 (since the source program must end with a newline, the end of a file is
2250 not a possible symbol delimiter). @xref{Symbols}.
2251 @cindex length of symbols
2256 @cindex statements, structure of
2257 @cindex line separator character
2258 @cindex statement separator character
2260 @ifclear abnormal-separator
2261 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2262 semicolon (@samp{;}). The newline or semicolon is considered part of
2263 the preceding statement. Newlines and semicolons within character
2264 constants are an exception: they do not end statements.
2266 @ifset abnormal-separator
2268 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2269 point (@samp{!}). The newline or exclamation point is considered part of the
2270 preceding statement. Newlines and exclamation points within character
2271 constants are an exception: they do not end statements.
2274 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2275 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2276 (@samp{;}). The newline or separator character is considered part of
2277 the preceding statement. Newlines and separators within character
2278 constants are an exception: they do not end statements.
2283 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2284 separator character. (The line separator is usually @samp{;}, unless
2285 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2286 newline or separator character is considered part of the preceding
2287 statement. Newlines and separators within character constants are an
2288 exception: they do not end statements.
2291 @cindex newline, required at file end
2292 @cindex EOF, newline must precede
2293 It is an error to end any statement with end-of-file: the last
2294 character of any input file should be a newline.@refill
2296 An empty statement is allowed, and may include whitespace. It is ignored.
2298 @cindex instructions and directives
2299 @cindex directives and instructions
2300 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2301 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2303 A statement begins with zero or more labels, optionally followed by a
2304 key symbol which determines what kind of statement it is. The key
2305 symbol determines the syntax of the rest of the statement. If the
2306 symbol begins with a dot @samp{.} then the statement is an assembler
2307 directive: typically valid for any computer. If the symbol begins with
2308 a letter the statement is an assembly language @dfn{instruction}: it
2309 assembles into a machine language instruction.
2311 Different versions of @command{@value{AS}} for different computers
2312 recognize different instructions. In fact, the same symbol may
2313 represent a different instruction in a different computer's assembly
2317 @cindex @code{:} (label)
2318 @cindex label (@code{:})
2319 A label is a symbol immediately followed by a colon (@code{:}).
2320 Whitespace before a label or after a colon is permitted, but you may not
2321 have whitespace between a label's symbol and its colon. @xref{Labels}.
2324 For HPPA targets, labels need not be immediately followed by a colon, but
2325 the definition of a label must begin in column zero. This also implies that
2326 only one label may be defined on each line.
2330 label: .directive followed by something
2331 another_label: # This is an empty statement.
2332 instruction operand_1, operand_2, @dots{}
2339 A constant is a number, written so that its value is known by
2340 inspection, without knowing any context. Like this:
2343 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2344 .ascii "Ring the bell\7" # A string constant.
2345 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2346 .float 0f-314159265358979323846264338327\
2347 95028841971.693993751E-40 # - pi, a flonum.
2352 * Characters:: Character Constants
2353 * Numbers:: Number Constants
2357 @subsection Character Constants
2359 @cindex character constants
2360 @cindex constants, character
2361 There are two kinds of character constants. A @dfn{character} stands
2362 for one character in one byte and its value may be used in
2363 numeric expressions. String constants (properly called string
2364 @emph{literals}) are potentially many bytes and their values may not be
2365 used in arithmetic expressions.
2369 * Chars:: Characters
2373 @subsubsection Strings
2375 @cindex string constants
2376 @cindex constants, string
2377 A @dfn{string} is written between double-quotes. It may contain
2378 double-quotes or null characters. The way to get special characters
2379 into a string is to @dfn{escape} these characters: precede them with
2380 a backslash @samp{\} character. For example @samp{\\} represents
2381 one backslash: the first @code{\} is an escape which tells
2382 @command{@value{AS}} to interpret the second character literally as a backslash
2383 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2384 escape character). The complete list of escapes follows.
2386 @cindex escape codes, character
2387 @cindex character escape codes
2390 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2392 @cindex @code{\b} (backspace character)
2393 @cindex backspace (@code{\b})
2395 Mnemonic for backspace; for ASCII this is octal code 010.
2398 @c Mnemonic for EOText; for ASCII this is octal code 004.
2400 @cindex @code{\f} (formfeed character)
2401 @cindex formfeed (@code{\f})
2403 Mnemonic for FormFeed; for ASCII this is octal code 014.
2405 @cindex @code{\n} (newline character)
2406 @cindex newline (@code{\n})
2408 Mnemonic for newline; for ASCII this is octal code 012.
2411 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2413 @cindex @code{\r} (carriage return character)
2414 @cindex carriage return (@code{\r})
2416 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2419 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2420 @c other assemblers.
2422 @cindex @code{\t} (tab)
2423 @cindex tab (@code{\t})
2425 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2428 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2429 @c @item \x @var{digit} @var{digit} @var{digit}
2430 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2432 @cindex @code{\@var{ddd}} (octal character code)
2433 @cindex octal character code (@code{\@var{ddd}})
2434 @item \ @var{digit} @var{digit} @var{digit}
2435 An octal character code. The numeric code is 3 octal digits.
2436 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2437 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2439 @cindex @code{\@var{xd...}} (hex character code)
2440 @cindex hex character code (@code{\@var{xd...}})
2441 @item \@code{x} @var{hex-digits...}
2442 A hex character code. All trailing hex digits are combined. Either upper or
2443 lower case @code{x} works.
2445 @cindex @code{\\} (@samp{\} character)
2446 @cindex backslash (@code{\\})
2448 Represents one @samp{\} character.
2451 @c Represents one @samp{'} (accent acute) character.
2452 @c This is needed in single character literals
2453 @c (@xref{Characters,,Character Constants}.) to represent
2456 @cindex @code{\"} (doublequote character)
2457 @cindex doublequote (@code{\"})
2459 Represents one @samp{"} character. Needed in strings to represent
2460 this character, because an unescaped @samp{"} would end the string.
2462 @item \ @var{anything-else}
2463 Any other character when escaped by @kbd{\} gives a warning, but
2464 assembles as if the @samp{\} was not present. The idea is that if
2465 you used an escape sequence you clearly didn't want the literal
2466 interpretation of the following character. However @command{@value{AS}} has no
2467 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2468 code and warns you of the fact.
2471 Which characters are escapable, and what those escapes represent,
2472 varies widely among assemblers. The current set is what we think
2473 the BSD 4.2 assembler recognizes, and is a subset of what most C
2474 compilers recognize. If you are in doubt, do not use an escape
2478 @subsubsection Characters
2480 @cindex single character constant
2481 @cindex character, single
2482 @cindex constant, single character
2483 A single character may be written as a single quote immediately
2484 followed by that character. The same escapes apply to characters as
2485 to strings. So if you want to write the character backslash, you
2486 must write @kbd{'\\} where the first @code{\} escapes the second
2487 @code{\}. As you can see, the quote is an acute accent, not a
2488 grave accent. A newline
2490 @ifclear abnormal-separator
2491 (or semicolon @samp{;})
2493 @ifset abnormal-separator
2495 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2500 immediately following an acute accent is taken as a literal character
2501 and does not count as the end of a statement. The value of a character
2502 constant in a numeric expression is the machine's byte-wide code for
2503 that character. @command{@value{AS}} assumes your character code is ASCII:
2504 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2507 @subsection Number Constants
2509 @cindex constants, number
2510 @cindex number constants
2511 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2512 are stored in the target machine. @emph{Integers} are numbers that
2513 would fit into an @code{int} in the C language. @emph{Bignums} are
2514 integers, but they are stored in more than 32 bits. @emph{Flonums}
2515 are floating point numbers, described below.
2518 * Integers:: Integers
2523 * Bit Fields:: Bit Fields
2529 @subsubsection Integers
2531 @cindex constants, integer
2533 @cindex binary integers
2534 @cindex integers, binary
2535 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2536 the binary digits @samp{01}.
2538 @cindex octal integers
2539 @cindex integers, octal
2540 An octal integer is @samp{0} followed by zero or more of the octal
2541 digits (@samp{01234567}).
2543 @cindex decimal integers
2544 @cindex integers, decimal
2545 A decimal integer starts with a non-zero digit followed by zero or
2546 more digits (@samp{0123456789}).
2548 @cindex hexadecimal integers
2549 @cindex integers, hexadecimal
2550 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2551 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2553 Integers have the usual values. To denote a negative integer, use
2554 the prefix operator @samp{-} discussed under expressions
2555 (@pxref{Prefix Ops,,Prefix Operators}).
2558 @subsubsection Bignums
2561 @cindex constants, bignum
2562 A @dfn{bignum} has the same syntax and semantics as an integer
2563 except that the number (or its negative) takes more than 32 bits to
2564 represent in binary. The distinction is made because in some places
2565 integers are permitted while bignums are not.
2568 @subsubsection Flonums
2570 @cindex floating point numbers
2571 @cindex constants, floating point
2573 @cindex precision, floating point
2574 A @dfn{flonum} represents a floating point number. The translation is
2575 indirect: a decimal floating point number from the text is converted by
2576 @command{@value{AS}} to a generic binary floating point number of more than
2577 sufficient precision. This generic floating point number is converted
2578 to a particular computer's floating point format (or formats) by a
2579 portion of @command{@value{AS}} specialized to that computer.
2581 A flonum is written by writing (in order)
2586 (@samp{0} is optional on the HPPA.)
2590 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2592 @kbd{e} is recommended. Case is not important.
2594 @c FIXME: verify if flonum syntax really this vague for most cases
2595 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2596 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2599 On the H8/300, Renesas / SuperH SH,
2600 and AMD 29K architectures, the letter must be
2601 one of the letters @samp{DFPRSX} (in upper or lower case).
2603 On the ARC, the letter must be one of the letters @samp{DFRS}
2604 (in upper or lower case).
2606 On the Intel 960 architecture, the letter must be
2607 one of the letters @samp{DFT} (in upper or lower case).
2609 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2613 One of the letters @samp{DFRS} (in upper or lower case).
2616 One of the letters @samp{DFPRSX} (in upper or lower case).
2619 The letter @samp{E} (upper case only).
2622 One of the letters @samp{DFT} (in upper or lower case).
2627 An optional sign: either @samp{+} or @samp{-}.
2630 An optional @dfn{integer part}: zero or more decimal digits.
2633 An optional @dfn{fractional part}: @samp{.} followed by zero
2634 or more decimal digits.
2637 An optional exponent, consisting of:
2641 An @samp{E} or @samp{e}.
2642 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2643 @c principle this can perfectly well be different on different targets.
2645 Optional sign: either @samp{+} or @samp{-}.
2647 One or more decimal digits.
2652 At least one of the integer part or the fractional part must be
2653 present. The floating point number has the usual base-10 value.
2655 @command{@value{AS}} does all processing using integers. Flonums are computed
2656 independently of any floating point hardware in the computer running
2657 @command{@value{AS}}.
2661 @c Bit fields are written as a general facility but are also controlled
2662 @c by a conditional-compilation flag---which is as of now (21mar91)
2663 @c turned on only by the i960 config of GAS.
2665 @subsubsection Bit Fields
2668 @cindex constants, bit field
2669 You can also define numeric constants as @dfn{bit fields}.
2670 specify two numbers separated by a colon---
2672 @var{mask}:@var{value}
2675 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2678 The resulting number is then packed
2680 @c this conditional paren in case bit fields turned on elsewhere than 960
2681 (in host-dependent byte order)
2683 into a field whose width depends on which assembler directive has the
2684 bit-field as its argument. Overflow (a result from the bitwise and
2685 requiring more binary digits to represent) is not an error; instead,
2686 more constants are generated, of the specified width, beginning with the
2687 least significant digits.@refill
2689 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2690 @code{.short}, and @code{.word} accept bit-field arguments.
2695 @chapter Sections and Relocation
2700 * Secs Background:: Background
2701 * Ld Sections:: Linker Sections
2702 * As Sections:: Assembler Internal Sections
2703 * Sub-Sections:: Sub-Sections
2707 @node Secs Background
2710 Roughly, a section is a range of addresses, with no gaps; all data
2711 ``in'' those addresses is treated the same for some particular purpose.
2712 For example there may be a ``read only'' section.
2714 @cindex linker, and assembler
2715 @cindex assembler, and linker
2716 The linker @code{@value{LD}} reads many object files (partial programs) and
2717 combines their contents to form a runnable program. When @command{@value{AS}}
2718 emits an object file, the partial program is assumed to start at address 0.
2719 @code{@value{LD}} assigns the final addresses for the partial program, so that
2720 different partial programs do not overlap. This is actually an
2721 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2724 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2725 addresses. These blocks slide to their run-time addresses as rigid
2726 units; their length does not change and neither does the order of bytes
2727 within them. Such a rigid unit is called a @emph{section}. Assigning
2728 run-time addresses to sections is called @dfn{relocation}. It includes
2729 the task of adjusting mentions of object-file addresses so they refer to
2730 the proper run-time addresses.
2732 For the H8/300, and for the Renesas / SuperH SH,
2733 @command{@value{AS}} pads sections if needed to
2734 ensure they end on a word (sixteen bit) boundary.
2737 @cindex standard assembler sections
2738 An object file written by @command{@value{AS}} has at least three sections, any
2739 of which may be empty. These are named @dfn{text}, @dfn{data} and
2744 When it generates COFF or ELF output,
2746 @command{@value{AS}} can also generate whatever other named sections you specify
2747 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2748 If you do not use any directives that place output in the @samp{.text}
2749 or @samp{.data} sections, these sections still exist, but are empty.
2754 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2756 @command{@value{AS}} can also generate whatever other named sections you
2757 specify using the @samp{.space} and @samp{.subspace} directives. See
2758 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2759 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2760 assembler directives.
2763 Additionally, @command{@value{AS}} uses different names for the standard
2764 text, data, and bss sections when generating SOM output. Program text
2765 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2766 BSS into @samp{$BSS$}.
2770 Within the object file, the text section starts at address @code{0}, the
2771 data section follows, and the bss section follows the data section.
2774 When generating either SOM or ELF output files on the HPPA, the text
2775 section starts at address @code{0}, the data section at address
2776 @code{0x4000000}, and the bss section follows the data section.
2779 To let @code{@value{LD}} know which data changes when the sections are
2780 relocated, and how to change that data, @command{@value{AS}} also writes to the
2781 object file details of the relocation needed. To perform relocation
2782 @code{@value{LD}} must know, each time an address in the object
2786 Where in the object file is the beginning of this reference to
2789 How long (in bytes) is this reference?
2791 Which section does the address refer to? What is the numeric value of
2793 (@var{address}) @minus{} (@var{start-address of section})?
2796 Is the reference to an address ``Program-Counter relative''?
2799 @cindex addresses, format of
2800 @cindex section-relative addressing
2801 In fact, every address @command{@value{AS}} ever uses is expressed as
2803 (@var{section}) + (@var{offset into section})
2806 Further, most expressions @command{@value{AS}} computes have this section-relative
2809 (For some object formats, such as SOM for the HPPA, some expressions are
2810 symbol-relative instead.)
2813 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2814 @var{N} into section @var{secname}.''
2816 Apart from text, data and bss sections you need to know about the
2817 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2818 addresses in the absolute section remain unchanged. For example, address
2819 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2820 @code{@value{LD}}. Although the linker never arranges two partial programs'
2821 data sections with overlapping addresses after linking, @emph{by definition}
2822 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2823 part of a program is always the same address when the program is running as
2824 address @code{@{absolute@ 239@}} in any other part of the program.
2826 The idea of sections is extended to the @dfn{undefined} section. Any
2827 address whose section is unknown at assembly time is by definition
2828 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2829 Since numbers are always defined, the only way to generate an undefined
2830 address is to mention an undefined symbol. A reference to a named
2831 common block would be such a symbol: its value is unknown at assembly
2832 time so it has section @emph{undefined}.
2834 By analogy the word @emph{section} is used to describe groups of sections in
2835 the linked program. @code{@value{LD}} puts all partial programs' text
2836 sections in contiguous addresses in the linked program. It is
2837 customary to refer to the @emph{text section} of a program, meaning all
2838 the addresses of all partial programs' text sections. Likewise for
2839 data and bss sections.
2841 Some sections are manipulated by @code{@value{LD}}; others are invented for
2842 use of @command{@value{AS}} and have no meaning except during assembly.
2845 @section Linker Sections
2846 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2851 @cindex named sections
2852 @cindex sections, named
2853 @item named sections
2856 @cindex text section
2857 @cindex data section
2861 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2862 separate but equal sections. Anything you can say of one section is
2865 When the program is running, however, it is
2866 customary for the text section to be unalterable. The
2867 text section is often shared among processes: it contains
2868 instructions, constants and the like. The data section of a running
2869 program is usually alterable: for example, C variables would be stored
2870 in the data section.
2875 This section contains zeroed bytes when your program begins running. It
2876 is used to hold uninitialized variables or common storage. The length of
2877 each partial program's bss section is important, but because it starts
2878 out containing zeroed bytes there is no need to store explicit zero
2879 bytes in the object file. The bss section was invented to eliminate
2880 those explicit zeros from object files.
2882 @cindex absolute section
2883 @item absolute section
2884 Address 0 of this section is always ``relocated'' to runtime address 0.
2885 This is useful if you want to refer to an address that @code{@value{LD}} must
2886 not change when relocating. In this sense we speak of absolute
2887 addresses being ``unrelocatable'': they do not change during relocation.
2889 @cindex undefined section
2890 @item undefined section
2891 This ``section'' is a catch-all for address references to objects not in
2892 the preceding sections.
2893 @c FIXME: ref to some other doc on obj-file formats could go here.
2896 @cindex relocation example
2897 An idealized example of three relocatable sections follows.
2899 The example uses the traditional section names @samp{.text} and @samp{.data}.
2901 Memory addresses are on the horizontal axis.
2905 @c END TEXI2ROFF-KILL
2908 partial program # 1: |ttttt|dddd|00|
2915 partial program # 2: |TTT|DDD|000|
2918 +--+---+-----+--+----+---+-----+~~
2919 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2920 +--+---+-----+--+----+---+-----+~~
2922 addresses: 0 @dots{}
2929 \line{\it Partial program \#1: \hfil}
2930 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2931 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2933 \line{\it Partial program \#2: \hfil}
2934 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2935 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2937 \line{\it linked program: \hfil}
2938 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2939 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2940 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2941 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2943 \line{\it addresses: \hfil}
2947 @c END TEXI2ROFF-KILL
2950 @section Assembler Internal Sections
2952 @cindex internal assembler sections
2953 @cindex sections in messages, internal
2954 These sections are meant only for the internal use of @command{@value{AS}}. They
2955 have no meaning at run-time. You do not really need to know about these
2956 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2957 warning messages, so it might be helpful to have an idea of their
2958 meanings to @command{@value{AS}}. These sections are used to permit the
2959 value of every expression in your assembly language program to be a
2960 section-relative address.
2963 @cindex assembler internal logic error
2964 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2965 An internal assembler logic error has been found. This means there is a
2966 bug in the assembler.
2968 @cindex expr (internal section)
2970 The assembler stores complex expression internally as combinations of
2971 symbols. When it needs to represent an expression as a symbol, it puts
2972 it in the expr section.
2974 @c FIXME item transfer[t] vector preload
2975 @c FIXME item transfer[t] vector postload
2976 @c FIXME item register
2980 @section Sub-Sections
2982 @cindex numbered subsections
2983 @cindex grouping data
2989 fall into two sections: text and data.
2991 You may have separate groups of
2993 data in named sections
2997 data in named sections
3003 that you want to end up near to each other in the object file, even though they
3004 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3005 use @dfn{subsections} for this purpose. Within each section, there can be
3006 numbered subsections with values from 0 to 8192. Objects assembled into the
3007 same subsection go into the object file together with other objects in the same
3008 subsection. For example, a compiler might want to store constants in the text
3009 section, but might not want to have them interspersed with the program being
3010 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3011 section of code being output, and a @samp{.text 1} before each group of
3012 constants being output.
3014 Subsections are optional. If you do not use subsections, everything
3015 goes in subsection number zero.
3018 Each subsection is zero-padded up to a multiple of four bytes.
3019 (Subsections may be padded a different amount on different flavors
3020 of @command{@value{AS}}.)
3024 On the H8/300 platform, each subsection is zero-padded to a word
3025 boundary (two bytes).
3026 The same is true on the Renesas SH.
3029 @c FIXME section padding (alignment)?
3030 @c Rich Pixley says padding here depends on target obj code format; that
3031 @c doesn't seem particularly useful to say without further elaboration,
3032 @c so for now I say nothing about it. If this is a generic BFD issue,
3033 @c these paragraphs might need to vanish from this manual, and be
3034 @c discussed in BFD chapter of binutils (or some such).
3038 Subsections appear in your object file in numeric order, lowest numbered
3039 to highest. (All this to be compatible with other people's assemblers.)
3040 The object file contains no representation of subsections; @code{@value{LD}} and
3041 other programs that manipulate object files see no trace of them.
3042 They just see all your text subsections as a text section, and all your
3043 data subsections as a data section.
3045 To specify which subsection you want subsequent statements assembled
3046 into, use a numeric argument to specify it, in a @samp{.text
3047 @var{expression}} or a @samp{.data @var{expression}} statement.
3050 When generating COFF output, you
3055 can also use an extra subsection
3056 argument with arbitrary named sections: @samp{.section @var{name},
3061 When generating ELF output, you
3066 can also use the @code{.subsection} directive (@pxref{SubSection})
3067 to specify a subsection: @samp{.subsection @var{expression}}.
3069 @var{Expression} should be an absolute expression.
3070 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
3071 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3072 begins in @code{text 0}. For instance:
3074 .text 0 # The default subsection is text 0 anyway.
3075 .ascii "This lives in the first text subsection. *"
3077 .ascii "But this lives in the second text subsection."
3079 .ascii "This lives in the data section,"
3080 .ascii "in the first data subsection."
3082 .ascii "This lives in the first text section,"
3083 .ascii "immediately following the asterisk (*)."
3086 Each section has a @dfn{location counter} incremented by one for every byte
3087 assembled into that section. Because subsections are merely a convenience
3088 restricted to @command{@value{AS}} there is no concept of a subsection location
3089 counter. There is no way to directly manipulate a location counter---but the
3090 @code{.align} directive changes it, and any label definition captures its
3091 current value. The location counter of the section where statements are being
3092 assembled is said to be the @dfn{active} location counter.
3095 @section bss Section
3098 @cindex common variable storage
3099 The bss section is used for local common variable storage.
3100 You may allocate address space in the bss section, but you may
3101 not dictate data to load into it before your program executes. When
3102 your program starts running, all the contents of the bss
3103 section are zeroed bytes.
3105 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3106 @ref{Lcomm,,@code{.lcomm}}.
3108 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3109 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
3112 When assembling for a target which supports multiple sections, such as ELF or
3113 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3114 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3115 section. Typically the section will only contain symbol definitions and
3116 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3123 Symbols are a central concept: the programmer uses symbols to name
3124 things, the linker uses symbols to link, and the debugger uses symbols
3128 @cindex debuggers, and symbol order
3129 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3130 the same order they were declared. This may break some debuggers.
3135 * Setting Symbols:: Giving Symbols Other Values
3136 * Symbol Names:: Symbol Names
3137 * Dot:: The Special Dot Symbol
3138 * Symbol Attributes:: Symbol Attributes
3145 A @dfn{label} is written as a symbol immediately followed by a colon
3146 @samp{:}. The symbol then represents the current value of the
3147 active location counter, and is, for example, a suitable instruction
3148 operand. You are warned if you use the same symbol to represent two
3149 different locations: the first definition overrides any other
3153 On the HPPA, the usual form for a label need not be immediately followed by a
3154 colon, but instead must start in column zero. Only one label may be defined on
3155 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3156 provides a special directive @code{.label} for defining labels more flexibly.
3159 @node Setting Symbols
3160 @section Giving Symbols Other Values
3162 @cindex assigning values to symbols
3163 @cindex symbol values, assigning
3164 A symbol can be given an arbitrary value by writing a symbol, followed
3165 by an equals sign @samp{=}, followed by an expression
3166 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3167 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3168 equals sign @samp{=}@samp{=} here represents an equivalent of the
3169 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3172 @section Symbol Names
3174 @cindex symbol names
3175 @cindex names, symbol
3176 @ifclear SPECIAL-SYMS
3177 Symbol names begin with a letter or with one of @samp{._}. On most
3178 machines, you can also use @code{$} in symbol names; exceptions are
3179 noted in @ref{Machine Dependencies}. That character may be followed by any
3180 string of digits, letters, dollar signs (unless otherwise noted in
3181 @ref{Machine Dependencies}), and underscores.
3185 Symbol names begin with a letter or with one of @samp{._}. On the
3186 Renesas SH you can also use @code{$} in symbol names. That
3187 character may be followed by any string of digits, letters, dollar signs (save
3188 on the H8/300), and underscores.
3192 Case of letters is significant: @code{foo} is a different symbol name
3195 Each symbol has exactly one name. Each name in an assembly language program
3196 refers to exactly one symbol. You may use that symbol name any number of times
3199 @subheading Local Symbol Names
3201 @cindex local symbol names
3202 @cindex symbol names, local
3203 @cindex temporary symbol names
3204 @cindex symbol names, temporary
3205 Local symbols help compilers and programmers use names temporarily.
3206 They create symbols which are guaranteed to be unique over the entire scope of
3207 the input source code and which can be referred to by a simple notation.
3208 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3209 represents any positive integer). To refer to the most recent previous
3210 definition of that symbol write @samp{@b{N}b}, using the same number as when
3211 you defined the label. To refer to the next definition of a local label, write
3212 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3215 There is no restriction on how you can use these labels, and you can reuse them
3216 too. So that it is possible to repeatedly define the same local label (using
3217 the same number @samp{@b{N}}), although you can only refer to the most recently
3218 defined local label of that number (for a backwards reference) or the next
3219 definition of a specific local label for a forward reference. It is also worth
3220 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3221 implemented in a slightly more efficient manner than the others.
3232 Which is the equivalent of:
3235 label_1: branch label_3
3236 label_2: branch label_1
3237 label_3: branch label_4
3238 label_4: branch label_3
3241 Local symbol names are only a notational device. They are immediately
3242 transformed into more conventional symbol names before the assembler uses them.
3243 The symbol names stored in the symbol table, appearing in error messages and
3244 optionally emitted to the object file. The names are constructed using these
3249 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3250 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3251 used for symbols you are never intended to see. If you use the
3252 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3253 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3254 you may use them in debugging.
3257 This is the number that was used in the local label definition. So if the
3258 label is written @samp{55:} then the number is @samp{55}.
3261 This unusual character is included so you do not accidentally invent a symbol
3262 of the same name. The character has ASCII value of @samp{\002} (control-B).
3264 @item @emph{ordinal number}
3265 This is a serial number to keep the labels distinct. The first definition of
3266 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3267 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3268 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3271 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3272 @code{3:} is named @code{L3@kbd{C-B}44}.
3274 @subheading Dollar Local Labels
3275 @cindex dollar local symbols
3277 @code{@value{AS}} also supports an even more local form of local labels called
3278 dollar labels. These labels go out of scope (ie they become undefined) as soon
3279 as a non-local label is defined. Thus they remain valid for only a small
3280 region of the input source code. Normal local labels, by contrast, remain in
3281 scope for the entire file, or until they are redefined by another occurrence of
3282 the same local label.
3284 Dollar labels are defined in exactly the same way as ordinary local labels,
3285 except that instead of being terminated by a colon, they are terminated by a
3286 dollar sign. eg @samp{@b{55$}}.
3288 They can also be distinguished from ordinary local labels by their transformed
3289 name which uses ASCII character @samp{\001} (control-A) as the magic character
3290 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3291 is named @samp{L6@kbd{C-A}5}.
3294 @section The Special Dot Symbol
3296 @cindex dot (symbol)
3297 @cindex @code{.} (symbol)
3298 @cindex current address
3299 @cindex location counter
3300 The special symbol @samp{.} refers to the current address that
3301 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3302 .long .} defines @code{melvin} to contain its own address.
3303 Assigning a value to @code{.} is treated the same as a @code{.org}
3304 directive. Thus, the expression @samp{.=.+4} is the same as saying
3305 @ifclear no-space-dir
3309 @node Symbol Attributes
3310 @section Symbol Attributes
3312 @cindex symbol attributes
3313 @cindex attributes, symbol
3314 Every symbol has, as well as its name, the attributes ``Value'' and
3315 ``Type''. Depending on output format, symbols can also have auxiliary
3318 The detailed definitions are in @file{a.out.h}.
3321 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3322 all these attributes, and probably won't warn you. This makes the
3323 symbol an externally defined symbol, which is generally what you
3327 * Symbol Value:: Value
3328 * Symbol Type:: Type
3331 * a.out Symbols:: Symbol Attributes: @code{a.out}
3335 * a.out Symbols:: Symbol Attributes: @code{a.out}
3338 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3343 * COFF Symbols:: Symbol Attributes for COFF
3346 * SOM Symbols:: Symbol Attributes for SOM
3353 @cindex value of a symbol
3354 @cindex symbol value
3355 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3356 location in the text, data, bss or absolute sections the value is the
3357 number of addresses from the start of that section to the label.
3358 Naturally for text, data and bss sections the value of a symbol changes
3359 as @code{@value{LD}} changes section base addresses during linking. Absolute
3360 symbols' values do not change during linking: that is why they are
3363 The value of an undefined symbol is treated in a special way. If it is
3364 0 then the symbol is not defined in this assembler source file, and
3365 @code{@value{LD}} tries to determine its value from other files linked into the
3366 same program. You make this kind of symbol simply by mentioning a symbol
3367 name without defining it. A non-zero value represents a @code{.comm}
3368 common declaration. The value is how much common storage to reserve, in
3369 bytes (addresses). The symbol refers to the first address of the
3375 @cindex type of a symbol
3377 The type attribute of a symbol contains relocation (section)
3378 information, any flag settings indicating that a symbol is external, and
3379 (optionally), other information for linkers and debuggers. The exact
3380 format depends on the object-code output format in use.
3385 @c The following avoids a "widow" subsection title. @group would be
3386 @c better if it were available outside examples.
3389 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3391 @cindex @code{b.out} symbol attributes
3392 @cindex symbol attributes, @code{b.out}
3393 These symbol attributes appear only when @command{@value{AS}} is configured for
3394 one of the Berkeley-descended object output formats---@code{a.out} or
3400 @subsection Symbol Attributes: @code{a.out}
3402 @cindex @code{a.out} symbol attributes
3403 @cindex symbol attributes, @code{a.out}
3409 @subsection Symbol Attributes: @code{a.out}
3411 @cindex @code{a.out} symbol attributes
3412 @cindex symbol attributes, @code{a.out}
3416 * Symbol Desc:: Descriptor
3417 * Symbol Other:: Other
3421 @subsubsection Descriptor
3423 @cindex descriptor, of @code{a.out} symbol
3424 This is an arbitrary 16-bit value. You may establish a symbol's
3425 descriptor value by using a @code{.desc} statement
3426 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3427 @command{@value{AS}}.
3430 @subsubsection Other
3432 @cindex other attribute, of @code{a.out} symbol
3433 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3438 @subsection Symbol Attributes for COFF
3440 @cindex COFF symbol attributes
3441 @cindex symbol attributes, COFF
3443 The COFF format supports a multitude of auxiliary symbol attributes;
3444 like the primary symbol attributes, they are set between @code{.def} and
3445 @code{.endef} directives.
3447 @subsubsection Primary Attributes
3449 @cindex primary attributes, COFF symbols
3450 The symbol name is set with @code{.def}; the value and type,
3451 respectively, with @code{.val} and @code{.type}.
3453 @subsubsection Auxiliary Attributes
3455 @cindex auxiliary attributes, COFF symbols
3456 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3457 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3458 table information for COFF.
3463 @subsection Symbol Attributes for SOM
3465 @cindex SOM symbol attributes
3466 @cindex symbol attributes, SOM
3468 The SOM format for the HPPA supports a multitude of symbol attributes set with
3469 the @code{.EXPORT} and @code{.IMPORT} directives.
3471 The attributes are described in @cite{HP9000 Series 800 Assembly
3472 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3473 @code{EXPORT} assembler directive documentation.
3477 @chapter Expressions
3481 @cindex numeric values
3482 An @dfn{expression} specifies an address or numeric value.
3483 Whitespace may precede and/or follow an expression.
3485 The result of an expression must be an absolute number, or else an offset into
3486 a particular section. If an expression is not absolute, and there is not
3487 enough information when @command{@value{AS}} sees the expression to know its
3488 section, a second pass over the source program might be necessary to interpret
3489 the expression---but the second pass is currently not implemented.
3490 @command{@value{AS}} aborts with an error message in this situation.
3493 * Empty Exprs:: Empty Expressions
3494 * Integer Exprs:: Integer Expressions
3498 @section Empty Expressions
3500 @cindex empty expressions
3501 @cindex expressions, empty
3502 An empty expression has no value: it is just whitespace or null.
3503 Wherever an absolute expression is required, you may omit the
3504 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3505 is compatible with other assemblers.
3508 @section Integer Expressions
3510 @cindex integer expressions
3511 @cindex expressions, integer
3512 An @dfn{integer expression} is one or more @emph{arguments} delimited
3513 by @emph{operators}.
3516 * Arguments:: Arguments
3517 * Operators:: Operators
3518 * Prefix Ops:: Prefix Operators
3519 * Infix Ops:: Infix Operators
3523 @subsection Arguments
3525 @cindex expression arguments
3526 @cindex arguments in expressions
3527 @cindex operands in expressions
3528 @cindex arithmetic operands
3529 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3530 contexts arguments are sometimes called ``arithmetic operands''. In
3531 this manual, to avoid confusing them with the ``instruction operands'' of
3532 the machine language, we use the term ``argument'' to refer to parts of
3533 expressions only, reserving the word ``operand'' to refer only to machine
3534 instruction operands.
3536 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3537 @var{section} is one of text, data, bss, absolute,
3538 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3541 Numbers are usually integers.
3543 A number can be a flonum or bignum. In this case, you are warned
3544 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3545 these 32 bits are an integer. You may write integer-manipulating
3546 instructions that act on exotic constants, compatible with other
3549 @cindex subexpressions
3550 Subexpressions are a left parenthesis @samp{(} followed by an integer
3551 expression, followed by a right parenthesis @samp{)}; or a prefix
3552 operator followed by an argument.
3555 @subsection Operators
3557 @cindex operators, in expressions
3558 @cindex arithmetic functions
3559 @cindex functions, in expressions
3560 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3561 operators are followed by an argument. Infix operators appear
3562 between their arguments. Operators may be preceded and/or followed by
3566 @subsection Prefix Operator
3568 @cindex prefix operators
3569 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3570 one argument, which must be absolute.
3572 @c the tex/end tex stuff surrounding this small table is meant to make
3573 @c it align, on the printed page, with the similar table in the next
3574 @c section (which is inside an enumerate).
3576 \global\advance\leftskip by \itemindent
3581 @dfn{Negation}. Two's complement negation.
3583 @dfn{Complementation}. Bitwise not.
3587 \global\advance\leftskip by -\itemindent
3591 @subsection Infix Operators
3593 @cindex infix operators
3594 @cindex operators, permitted arguments
3595 @dfn{Infix operators} take two arguments, one on either side. Operators
3596 have precedence, but operations with equal precedence are performed left
3597 to right. Apart from @code{+} or @option{-}, both arguments must be
3598 absolute, and the result is absolute.
3601 @cindex operator precedence
3602 @cindex precedence of operators
3609 @dfn{Multiplication}.
3612 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3618 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3621 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3625 Intermediate precedence
3630 @dfn{Bitwise Inclusive Or}.
3636 @dfn{Bitwise Exclusive Or}.
3639 @dfn{Bitwise Or Not}.
3646 @cindex addition, permitted arguments
3647 @cindex plus, permitted arguments
3648 @cindex arguments for addition
3650 @dfn{Addition}. If either argument is absolute, the result has the section of
3651 the other argument. You may not add together arguments from different
3654 @cindex subtraction, permitted arguments
3655 @cindex minus, permitted arguments
3656 @cindex arguments for subtraction
3658 @dfn{Subtraction}. If the right argument is absolute, the
3659 result has the section of the left argument.
3660 If both arguments are in the same section, the result is absolute.
3661 You may not subtract arguments from different sections.
3662 @c FIXME is there still something useful to say about undefined - undefined ?
3664 @cindex comparison expressions
3665 @cindex expressions, comparison
3670 @dfn{Is Not Equal To}
3674 @dfn{Is Greater Than}
3676 @dfn{Is Greater Than Or Equal To}
3678 @dfn{Is Less Than Or Equal To}
3680 The comparison operators can be used as infix operators. A true results has a
3681 value of -1 whereas a false result has a value of 0. Note, these operators
3682 perform signed comparisons.
3685 @item Lowest Precedence
3694 These two logical operations can be used to combine the results of sub
3695 expressions. Note, unlike the comparison operators a true result returns a
3696 value of 1 but a false results does still return 0. Also note that the logical
3697 or operator has a slightly lower precedence than logical and.
3702 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3703 address; you can only have a defined section in one of the two arguments.
3706 @chapter Assembler Directives
3708 @cindex directives, machine independent
3709 @cindex pseudo-ops, machine independent
3710 @cindex machine independent directives
3711 All assembler directives have names that begin with a period (@samp{.}).
3712 The rest of the name is letters, usually in lower case.
3714 This chapter discusses directives that are available regardless of the
3715 target machine configuration for the @sc{gnu} assembler.
3717 Some machine configurations provide additional directives.
3718 @xref{Machine Dependencies}.
3721 @ifset machine-directives
3722 @xref{Machine Dependencies} for additional directives.
3727 * Abort:: @code{.abort}
3729 * ABORT:: @code{.ABORT}
3732 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3733 * Altmacro:: @code{.altmacro}
3734 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3735 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3736 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3737 * Byte:: @code{.byte @var{expressions}}
3738 * Comm:: @code{.comm @var{symbol} , @var{length} }
3740 * CFI directives:: @code{.cfi_startproc}, @code{.cfi_endproc}, etc.
3742 * Data:: @code{.data @var{subsection}}
3744 * Def:: @code{.def @var{name}}
3747 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3753 * Double:: @code{.double @var{flonums}}
3754 * Eject:: @code{.eject}
3755 * Else:: @code{.else}
3756 * Elseif:: @code{.elseif}
3759 * Endef:: @code{.endef}
3762 * Endfunc:: @code{.endfunc}
3763 * Endif:: @code{.endif}
3764 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3765 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3766 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3768 * Error:: @code{.error @var{string}}
3769 * Exitm:: @code{.exitm}
3770 * Extern:: @code{.extern}
3771 * Fail:: @code{.fail}
3772 @ifclear no-file-dir
3773 * File:: @code{.file @var{string}}
3776 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3777 * Float:: @code{.float @var{flonums}}
3778 * Func:: @code{.func}
3779 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3781 * Hidden:: @code{.hidden @var{names}}
3784 * hword:: @code{.hword @var{expressions}}
3785 * Ident:: @code{.ident}
3786 * If:: @code{.if @var{absolute expression}}
3787 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3788 * Include:: @code{.include "@var{file}"}
3789 * Int:: @code{.int @var{expressions}}
3791 * Internal:: @code{.internal @var{names}}
3794 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3795 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3796 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3797 * Lflags:: @code{.lflags}
3798 @ifclear no-line-dir
3799 * Line:: @code{.line @var{line-number}}
3802 * Linkonce:: @code{.linkonce [@var{type}]}
3803 * List:: @code{.list}
3804 * Ln:: @code{.ln @var{line-number}}
3806 * LNS directives:: @code{.file}, @code{.loc}, etc.
3808 * Long:: @code{.long @var{expressions}}
3810 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3813 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3814 * MRI:: @code{.mri @var{val}}
3815 * Noaltmacro:: @code{.noaltmacro}
3816 * Nolist:: @code{.nolist}
3817 * Octa:: @code{.octa @var{bignums}}
3818 * Org:: @code{.org @var{new-lc} , @var{fill}}
3819 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3821 * PopSection:: @code{.popsection}
3822 * Previous:: @code{.previous}
3825 * Print:: @code{.print @var{string}}
3827 * Protected:: @code{.protected @var{names}}
3830 * Psize:: @code{.psize @var{lines}, @var{columns}}
3831 * Purgem:: @code{.purgem @var{name}}
3833 * PushSection:: @code{.pushsection @var{name}}
3836 * Quad:: @code{.quad @var{bignums}}
3837 * Rept:: @code{.rept @var{count}}
3838 * Sbttl:: @code{.sbttl "@var{subheading}"}
3840 * Scl:: @code{.scl @var{class}}
3843 * Section:: @code{.section @var{name}}
3846 * Set:: @code{.set @var{symbol}, @var{expression}}
3847 * Short:: @code{.short @var{expressions}}
3848 * Single:: @code{.single @var{flonums}}
3850 * Size:: @code{.size [@var{name} , @var{expression}]}
3853 * Skip:: @code{.skip @var{size} , @var{fill}}
3854 * Sleb128:: @code{.sleb128 @var{expressions}}
3855 * Space:: @code{.space @var{size} , @var{fill}}
3857 * Stab:: @code{.stabd, .stabn, .stabs}
3860 * String:: @code{.string "@var{str}"}
3861 * Struct:: @code{.struct @var{expression}}
3863 * SubSection:: @code{.subsection}
3864 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3868 * Tag:: @code{.tag @var{structname}}
3871 * Text:: @code{.text @var{subsection}}
3872 * Title:: @code{.title "@var{heading}"}
3874 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3877 * Uleb128:: @code{.uleb128 @var{expressions}}
3879 * Val:: @code{.val @var{addr}}
3883 * Version:: @code{.version "@var{string}"}
3884 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3885 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3888 * Warning:: @code{.warning @var{string}}
3889 * Weak:: @code{.weak @var{names}}
3890 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
3891 * Word:: @code{.word @var{expressions}}
3892 * Deprecated:: Deprecated Directives
3896 @section @code{.abort}
3898 @cindex @code{abort} directive
3899 @cindex stopping the assembly
3900 This directive stops the assembly immediately. It is for
3901 compatibility with other assemblers. The original idea was that the
3902 assembly language source would be piped into the assembler. If the sender
3903 of the source quit, it could use this directive tells @command{@value{AS}} to
3904 quit also. One day @code{.abort} will not be supported.
3908 @section @code{.ABORT}
3910 @cindex @code{ABORT} directive
3911 When producing COFF output, @command{@value{AS}} accepts this directive as a
3912 synonym for @samp{.abort}.
3915 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3921 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3923 @cindex padding the location counter
3924 @cindex @code{align} directive
3925 Pad the location counter (in the current subsection) to a particular storage
3926 boundary. The first expression (which must be absolute) is the alignment
3927 required, as described below.
3929 The second expression (also absolute) gives the fill value to be stored in the
3930 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3931 padding bytes are normally zero. However, on some systems, if the section is
3932 marked as containing code and the fill value is omitted, the space is filled
3933 with no-op instructions.
3935 The third expression is also absolute, and is also optional. If it is present,
3936 it is the maximum number of bytes that should be skipped by this alignment
3937 directive. If doing the alignment would require skipping more bytes than the
3938 specified maximum, then the alignment is not done at all. You can omit the
3939 fill value (the second argument) entirely by simply using two commas after the
3940 required alignment; this can be useful if you want the alignment to be filled
3941 with no-op instructions when appropriate.
3943 The way the required alignment is specified varies from system to system.
3944 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
3945 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
3946 alignment request in bytes. For example @samp{.align 8} advances
3947 the location counter until it is a multiple of 8. If the location counter
3948 is already a multiple of 8, no change is needed. For the tic54x, the
3949 first expression is the alignment request in words.
3951 For other systems, including the i386 using a.out format, and the arm and
3952 strongarm, it is the
3953 number of low-order zero bits the location counter must have after
3954 advancement. For example @samp{.align 3} advances the location
3955 counter until it a multiple of 8. If the location counter is already a
3956 multiple of 8, no change is needed.
3958 This inconsistency is due to the different behaviors of the various
3959 native assemblers for these systems which GAS must emulate.
3960 GAS also provides @code{.balign} and @code{.p2align} directives,
3961 described later, which have a consistent behavior across all
3962 architectures (but are specific to GAS).
3965 @section @code{.ascii "@var{string}"}@dots{}
3967 @cindex @code{ascii} directive
3968 @cindex string literals
3969 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3970 separated by commas. It assembles each string (with no automatic
3971 trailing zero byte) into consecutive addresses.
3974 @section @code{.asciz "@var{string}"}@dots{}
3976 @cindex @code{asciz} directive
3977 @cindex zero-terminated strings
3978 @cindex null-terminated strings
3979 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3980 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3983 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3985 @cindex padding the location counter given number of bytes
3986 @cindex @code{balign} directive
3987 Pad the location counter (in the current subsection) to a particular
3988 storage boundary. The first expression (which must be absolute) is the
3989 alignment request in bytes. For example @samp{.balign 8} advances
3990 the location counter until it is a multiple of 8. If the location counter
3991 is already a multiple of 8, no change is needed.
3993 The second expression (also absolute) gives the fill value to be stored in the
3994 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3995 padding bytes are normally zero. However, on some systems, if the section is
3996 marked as containing code and the fill value is omitted, the space is filled
3997 with no-op instructions.
3999 The third expression is also absolute, and is also optional. If it is present,
4000 it is the maximum number of bytes that should be skipped by this alignment
4001 directive. If doing the alignment would require skipping more bytes than the
4002 specified maximum, then the alignment is not done at all. You can omit the
4003 fill value (the second argument) entirely by simply using two commas after the
4004 required alignment; this can be useful if you want the alignment to be filled
4005 with no-op instructions when appropriate.
4007 @cindex @code{balignw} directive
4008 @cindex @code{balignl} directive
4009 The @code{.balignw} and @code{.balignl} directives are variants of the
4010 @code{.balign} directive. The @code{.balignw} directive treats the fill
4011 pattern as a two byte word value. The @code{.balignl} directives treats the
4012 fill pattern as a four byte longword value. For example, @code{.balignw
4013 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4014 filled in with the value 0x368d (the exact placement of the bytes depends upon
4015 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4019 @section @code{.byte @var{expressions}}
4021 @cindex @code{byte} directive
4022 @cindex integers, one byte
4023 @code{.byte} expects zero or more expressions, separated by commas.
4024 Each expression is assembled into the next byte.
4027 @section @code{.comm @var{symbol} , @var{length} }
4029 @cindex @code{comm} directive
4030 @cindex symbol, common
4031 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4032 common symbol in one object file may be merged with a defined or common symbol
4033 of the same name in another object file. If @code{@value{LD}} does not see a
4034 definition for the symbol--just one or more common symbols--then it will
4035 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4036 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4037 the same name, and they do not all have the same size, it will allocate space
4038 using the largest size.
4041 When using ELF, the @code{.comm} directive takes an optional third argument.
4042 This is the desired alignment of the symbol, specified as a byte boundary (for
4043 example, an alignment of 16 means that the least significant 4 bits of the
4044 address should be zero). The alignment must be an absolute expression, and it
4045 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
4046 for the common symbol, it will use the alignment when placing the symbol. If
4047 no alignment is specified, @command{@value{AS}} will set the alignment to the
4048 largest power of two less than or equal to the size of the symbol, up to a
4053 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4054 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4057 @node CFI directives
4058 @section @code{.cfi_startproc}
4059 @cindex @code{cfi_startproc} directive
4060 @code{.cfi_startproc} is used at the beginning of each function that
4061 should have an entry in @code{.eh_frame}. It initializes some internal
4062 data structures and emits architecture dependent initial CFI instructions.
4063 Don't forget to close the function by
4064 @code{.cfi_endproc}.
4066 @section @code{.cfi_endproc}
4067 @cindex @code{cfi_endproc} directive
4068 @code{.cfi_endproc} is used at the end of a function where it closes its
4069 unwind entry previously opened by
4070 @code{.cfi_startproc}. and emits it to @code{.eh_frame}.
4072 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4073 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4074 address from @var{register} and add @var{offset} to it}.
4076 @section @code{.cfi_def_cfa_register @var{register}}
4077 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4078 now on @var{register} will be used instead of the old one. Offset
4081 @section @code{.cfi_def_cfa_offset @var{offset}}
4082 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4083 remains the same, but @var{offset} is new. Note that it is the
4084 absolute offset that will be added to a defined register to compute
4087 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4088 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4089 value that is added/substracted from the previous offset.
4091 @section @code{.cfi_offset @var{register}, @var{offset}}
4092 Previous value of @var{register} is saved at offset @var{offset} from
4095 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4096 Previous value of @var{register} is saved at offset @var{offset} from
4097 the current CFA register. This is transformed to @code{.cfi_offset}
4098 using the known displacement of the CFA register from the CFA.
4099 This is often easier to use, because the number will match the
4100 code it's annotating.
4102 @section @code{.cfi_window_save}
4103 SPARC register window has been saved.
4105 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4106 Allows the user to add arbitrary bytes to the unwind info. One
4107 might use this to add OS-specific CFI opcodes, or generic CFI
4108 opcodes that GAS does not yet support.
4110 @node LNS directives
4111 @section @code{.file @var{fileno} @var{filename}}
4112 @cindex @code{file} directive
4113 When emitting dwarf2 line number information @code{.file} assigns filenames
4114 to the @code{.debug_line} file name table. The @var{fileno} operand should
4115 be a unique positive integer to use as the index of the entry in the table.
4116 The @var{filename} operand is a C string literal.
4118 The detail of filename indicies is exposed to the user because the filename
4119 table is shared with the @code{.debug_info} section of the dwarf2 debugging
4120 information, and thus the user must know the exact indicies that table
4123 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
4124 @cindex @code{loc} directive
4125 The @code{.loc} directive will add row to the @code{.debug_line} line
4126 number matrix corresponding to the immediately following assembly
4127 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
4128 arguments will be applied to the @code{.debug_line} state machine before
4131 The @var{options} are a sequence of the following tokens in any order:
4135 This option will set the @code{basic_block} register in the
4136 @code{.debug_line} state machine to @code{true}.
4139 This option will set the @code{prologue_end} register in the
4140 @code{.debug_line} state machine to @code{true}.
4142 @item epilogue_begin
4143 This option will set the @code{epilogue_begin} register in the
4144 @code{.debug_line} state machine to @code{true}.
4146 @item is_stmt @var{value}
4147 This option will set the @code{is_stmt} register in the
4148 @code{.debug_line} state machine to @code{value}, which must be
4151 @item isa @var{value}
4152 This directive will set the @code{isa} register in the @code{.debug_line}
4153 state machine to @var{value}, which must be an unsigned integer.
4157 @section @code{.loc_mark_blocks @var{enable}}
4158 @cindex @code{loc_mark_blocks} directive
4159 The @code{.loc_mark_blocks} directive makes the assembler emit an entry
4160 to the @code{.debug_line} line number matrix with the @code{basic_block}
4161 register in the state machine set whenever a code label is seen.
4162 The @var{enable} argument should be either 1 or 0, to enable or disable
4163 this function respectively.
4166 @section @code{.data @var{subsection}}
4168 @cindex @code{data} directive
4169 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4170 end of the data subsection numbered @var{subsection} (which is an
4171 absolute expression). If @var{subsection} is omitted, it defaults
4176 @section @code{.def @var{name}}
4178 @cindex @code{def} directive
4179 @cindex COFF symbols, debugging
4180 @cindex debugging COFF symbols
4181 Begin defining debugging information for a symbol @var{name}; the
4182 definition extends until the @code{.endef} directive is encountered.
4185 This directive is only observed when @command{@value{AS}} is configured for COFF
4186 format output; when producing @code{b.out}, @samp{.def} is recognized,
4193 @section @code{.desc @var{symbol}, @var{abs-expression}}
4195 @cindex @code{desc} directive
4196 @cindex COFF symbol descriptor
4197 @cindex symbol descriptor, COFF
4198 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4199 to the low 16 bits of an absolute expression.
4202 The @samp{.desc} directive is not available when @command{@value{AS}} is
4203 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4204 object format. For the sake of compatibility, @command{@value{AS}} accepts
4205 it, but produces no output, when configured for COFF.
4211 @section @code{.dim}
4213 @cindex @code{dim} directive
4214 @cindex COFF auxiliary symbol information
4215 @cindex auxiliary symbol information, COFF
4216 This directive is generated by compilers to include auxiliary debugging
4217 information in the symbol table. It is only permitted inside
4218 @code{.def}/@code{.endef} pairs.
4221 @samp{.dim} is only meaningful when generating COFF format output; when
4222 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4228 @section @code{.double @var{flonums}}
4230 @cindex @code{double} directive
4231 @cindex floating point numbers (double)
4232 @code{.double} expects zero or more flonums, separated by commas. It
4233 assembles floating point numbers.
4235 The exact kind of floating point numbers emitted depends on how
4236 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4240 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4241 in @sc{ieee} format.
4246 @section @code{.eject}
4248 @cindex @code{eject} directive
4249 @cindex new page, in listings
4250 @cindex page, in listings
4251 @cindex listing control: new page
4252 Force a page break at this point, when generating assembly listings.
4255 @section @code{.else}
4257 @cindex @code{else} directive
4258 @code{.else} is part of the @command{@value{AS}} support for conditional
4259 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
4260 of code to be assembled if the condition for the preceding @code{.if}
4264 @section @code{.elseif}
4266 @cindex @code{elseif} directive
4267 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4268 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
4269 @code{.if} block that would otherwise fill the entire @code{.else} section.
4272 @section @code{.end}
4274 @cindex @code{end} directive
4275 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4276 process anything in the file past the @code{.end} directive.
4280 @section @code{.endef}
4282 @cindex @code{endef} directive
4283 This directive flags the end of a symbol definition begun with
4287 @samp{.endef} is only meaningful when generating COFF format output; if
4288 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4289 directive but ignores it.
4294 @section @code{.endfunc}
4295 @cindex @code{endfunc} directive
4296 @code{.endfunc} marks the end of a function specified with @code{.func}.
4299 @section @code{.endif}
4301 @cindex @code{endif} directive
4302 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4303 it marks the end of a block of code that is only assembled
4304 conditionally. @xref{If,,@code{.if}}.
4307 @section @code{.equ @var{symbol}, @var{expression}}
4309 @cindex @code{equ} directive
4310 @cindex assigning values to symbols
4311 @cindex symbols, assigning values to
4312 This directive sets the value of @var{symbol} to @var{expression}.
4313 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4316 The syntax for @code{equ} on the HPPA is
4317 @samp{@var{symbol} .equ @var{expression}}.
4321 The syntax for @code{equ} on the Z80 is
4322 @samp{@var{symbol} equ @var{expression}}.
4323 On the Z80 it is an eror if @var{symbol} is already defined,
4324 compare @xref{Equiv}.
4328 @section @code{.equiv @var{symbol}, @var{expression}}
4329 @cindex @code{equiv} directive
4330 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4331 the assembler will signal an error if @var{symbol} is already defined. Note a
4332 symbol which has been referenced but not actually defined is considered to be
4335 Except for the contents of the error message, this is roughly equivalent to
4342 plus it protects the symbol from later redefinition.
4345 @section @code{.eqv @var{symbol}, @var{expression}}
4346 @cindex @code{eqv} directive
4347 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4348 evaluate the expression or any part of it immediately. Instead each time
4349 the resulting symbol is used in an expression, a snapshot of its current
4353 @section @code{.err}
4354 @cindex @code{err} directive
4355 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4356 message and, unless the @option{-Z} option was used, it will not generate an
4357 object file. This can be used to signal error an conditionally compiled code.
4360 @section @code{.error "@var{string}"}
4361 @cindex error directive
4363 Similarly to @code{.err}, this directive emits an error, but you can specify a
4364 string that will be emitted as the error message. If you don't specify the
4365 message, it defaults to @code{".error directive invoked in source file"}.
4366 @xref{Errors, ,Error and Warning Messages}.
4369 .error "This code has not been assembled and tested."
4373 @section @code{.exitm}
4374 Exit early from the current macro definition. @xref{Macro}.
4377 @section @code{.extern}
4379 @cindex @code{extern} directive
4380 @code{.extern} is accepted in the source program---for compatibility
4381 with other assemblers---but it is ignored. @command{@value{AS}} treats
4382 all undefined symbols as external.
4385 @section @code{.fail @var{expression}}
4387 @cindex @code{fail} directive
4388 Generates an error or a warning. If the value of the @var{expression} is 500
4389 or more, @command{@value{AS}} will print a warning message. If the value is less
4390 than 500, @command{@value{AS}} will print an error message. The message will
4391 include the value of @var{expression}. This can occasionally be useful inside
4392 complex nested macros or conditional assembly.
4394 @ifclear no-file-dir
4396 @section @code{.file @var{string}}
4398 @cindex @code{file} directive
4399 @cindex logical file name
4400 @cindex file name, logical
4401 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4402 file. @var{string} is the new file name. In general, the filename is
4403 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4404 to specify an empty file name, you must give the quotes--@code{""}. This
4405 statement may go away in future: it is only recognized to be compatible with
4406 old @command{@value{AS}} programs.
4410 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4412 @cindex @code{fill} directive
4413 @cindex writing patterns in memory
4414 @cindex patterns, writing in memory
4415 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4416 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4417 may be zero or more. @var{Size} may be zero or more, but if it is
4418 more than 8, then it is deemed to have the value 8, compatible with
4419 other people's assemblers. The contents of each @var{repeat} bytes
4420 is taken from an 8-byte number. The highest order 4 bytes are
4421 zero. The lowest order 4 bytes are @var{value} rendered in the
4422 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4423 Each @var{size} bytes in a repetition is taken from the lowest order
4424 @var{size} bytes of this number. Again, this bizarre behavior is
4425 compatible with other people's assemblers.
4427 @var{size} and @var{value} are optional.
4428 If the second comma and @var{value} are absent, @var{value} is
4429 assumed zero. If the first comma and following tokens are absent,
4430 @var{size} is assumed to be 1.
4433 @section @code{.float @var{flonums}}
4435 @cindex floating point numbers (single)
4436 @cindex @code{float} directive
4437 This directive assembles zero or more flonums, separated by commas. It
4438 has the same effect as @code{.single}.
4440 The exact kind of floating point numbers emitted depends on how
4441 @command{@value{AS}} is configured.
4442 @xref{Machine Dependencies}.
4446 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4447 in @sc{ieee} format.
4452 @section @code{.func @var{name}[,@var{label}]}
4453 @cindex @code{func} directive
4454 @code{.func} emits debugging information to denote function @var{name}, and
4455 is ignored unless the file is assembled with debugging enabled.
4456 Only @samp{--gstabs[+]} is currently supported.
4457 @var{label} is the entry point of the function and if omitted @var{name}
4458 prepended with the @samp{leading char} is used.
4459 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4460 All functions are currently defined to have @code{void} return type.
4461 The function must be terminated with @code{.endfunc}.
4464 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4466 @cindex @code{global} directive
4467 @cindex symbol, making visible to linker
4468 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4469 @var{symbol} in your partial program, its value is made available to
4470 other partial programs that are linked with it. Otherwise,
4471 @var{symbol} takes its attributes from a symbol of the same name
4472 from another file linked into the same program.
4474 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4475 compatibility with other assemblers.
4478 On the HPPA, @code{.global} is not always enough to make it accessible to other
4479 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4480 @xref{HPPA Directives,, HPPA Assembler Directives}.
4485 @section @code{.hidden @var{names}}
4487 @cindex @code{hidden} directive
4489 This is one of the ELF visibility directives. The other two are
4490 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4491 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4493 This directive overrides the named symbols default visibility (which is set by
4494 their binding: local, global or weak). The directive sets the visibility to
4495 @code{hidden} which means that the symbols are not visible to other components.
4496 Such symbols are always considered to be @code{protected} as well.
4500 @section @code{.hword @var{expressions}}
4502 @cindex @code{hword} directive
4503 @cindex integers, 16-bit
4504 @cindex numbers, 16-bit
4505 @cindex sixteen bit integers
4506 This expects zero or more @var{expressions}, and emits
4507 a 16 bit number for each.
4510 This directive is a synonym for @samp{.short}; depending on the target
4511 architecture, it may also be a synonym for @samp{.word}.
4515 This directive is a synonym for @samp{.short}.
4518 This directive is a synonym for both @samp{.short} and @samp{.word}.
4523 @section @code{.ident}
4525 @cindex @code{ident} directive
4526 This directive is used by some assemblers to place tags in object files.
4527 @command{@value{AS}} simply accepts the directive for source-file
4528 compatibility with such assemblers, but does not actually emit anything
4532 @section @code{.if @var{absolute expression}}
4534 @cindex conditional assembly
4535 @cindex @code{if} directive
4536 @code{.if} marks the beginning of a section of code which is only
4537 considered part of the source program being assembled if the argument
4538 (which must be an @var{absolute expression}) is non-zero. The end of
4539 the conditional section of code must be marked by @code{.endif}
4540 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4541 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4542 If you have several conditions to check, @code{.elseif} may be used to avoid
4543 nesting blocks if/else within each subsequent @code{.else} block.
4545 The following variants of @code{.if} are also supported:
4547 @cindex @code{ifdef} directive
4548 @item .ifdef @var{symbol}
4549 Assembles the following section of code if the specified @var{symbol}
4550 has been defined. Note a symbol which has been referenced but not yet defined
4551 is considered to be undefined.
4553 @cindex @code{ifb} directive
4554 @item .ifb @var{text}
4555 Assembles the following section of code if the operand is blank (empty).
4557 @cindex @code{ifc} directive
4558 @item .ifc @var{string1},@var{string2}
4559 Assembles the following section of code if the two strings are the same. The
4560 strings may be optionally quoted with single quotes. If they are not quoted,
4561 the first string stops at the first comma, and the second string stops at the
4562 end of the line. Strings which contain whitespace should be quoted. The
4563 string comparison is case sensitive.
4565 @cindex @code{ifeq} directive
4566 @item .ifeq @var{absolute expression}
4567 Assembles the following section of code if the argument is zero.
4569 @cindex @code{ifeqs} directive
4570 @item .ifeqs @var{string1},@var{string2}
4571 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4573 @cindex @code{ifge} directive
4574 @item .ifge @var{absolute expression}
4575 Assembles the following section of code if the argument is greater than or
4578 @cindex @code{ifgt} directive
4579 @item .ifgt @var{absolute expression}
4580 Assembles the following section of code if the argument is greater than zero.
4582 @cindex @code{ifle} directive
4583 @item .ifle @var{absolute expression}
4584 Assembles the following section of code if the argument is less than or equal
4587 @cindex @code{iflt} directive
4588 @item .iflt @var{absolute expression}
4589 Assembles the following section of code if the argument is less than zero.
4591 @cindex @code{ifnb} directive
4592 @item .ifnb @var{text}
4593 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4594 following section of code if the operand is non-blank (non-empty).
4596 @cindex @code{ifnc} directive
4597 @item .ifnc @var{string1},@var{string2}.
4598 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4599 following section of code if the two strings are not the same.
4601 @cindex @code{ifndef} directive
4602 @cindex @code{ifnotdef} directive
4603 @item .ifndef @var{symbol}
4604 @itemx .ifnotdef @var{symbol}
4605 Assembles the following section of code if the specified @var{symbol}
4606 has not been defined. Both spelling variants are equivalent. Note a symbol
4607 which has been referenced but not yet defined is considered to be undefined.
4609 @cindex @code{ifne} directive
4610 @item .ifne @var{absolute expression}
4611 Assembles the following section of code if the argument is not equal to zero
4612 (in other words, this is equivalent to @code{.if}).
4614 @cindex @code{ifnes} directive
4615 @item .ifnes @var{string1},@var{string2}
4616 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4617 following section of code if the two strings are not the same.
4621 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4623 @cindex @code{incbin} directive
4624 @cindex binary files, including
4625 The @code{incbin} directive includes @var{file} verbatim at the current
4626 location. You can control the search paths used with the @samp{-I} command-line
4627 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4630 The @var{skip} argument skips a number of bytes from the start of the
4631 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4632 read. Note that the data is not aligned in any way, so it is the user's
4633 responsibility to make sure that proper alignment is provided both before and
4634 after the @code{incbin} directive.
4637 @section @code{.include "@var{file}"}
4639 @cindex @code{include} directive
4640 @cindex supporting files, including
4641 @cindex files, including
4642 This directive provides a way to include supporting files at specified
4643 points in your source program. The code from @var{file} is assembled as
4644 if it followed the point of the @code{.include}; when the end of the
4645 included file is reached, assembly of the original file continues. You
4646 can control the search paths used with the @samp{-I} command-line option
4647 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4651 @section @code{.int @var{expressions}}
4653 @cindex @code{int} directive
4654 @cindex integers, 32-bit
4655 Expect zero or more @var{expressions}, of any section, separated by commas.
4656 For each expression, emit a number that, at run time, is the value of that
4657 expression. The byte order and bit size of the number depends on what kind
4658 of target the assembly is for.
4662 On most forms of the H8/300, @code{.int} emits 16-bit
4663 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4670 @section @code{.internal @var{names}}
4672 @cindex @code{internal} directive
4674 This is one of the ELF visibility directives. The other two are
4675 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4676 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4678 This directive overrides the named symbols default visibility (which is set by
4679 their binding: local, global or weak). The directive sets the visibility to
4680 @code{internal} which means that the symbols are considered to be @code{hidden}
4681 (i.e., not visible to other components), and that some extra, processor specific
4682 processing must also be performed upon the symbols as well.
4686 @section @code{.irp @var{symbol},@var{values}}@dots{}
4688 @cindex @code{irp} directive
4689 Evaluate a sequence of statements assigning different values to @var{symbol}.
4690 The sequence of statements starts at the @code{.irp} directive, and is
4691 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4692 set to @var{value}, and the sequence of statements is assembled. If no
4693 @var{value} is listed, the sequence of statements is assembled once, with
4694 @var{symbol} set to the null string. To refer to @var{symbol} within the
4695 sequence of statements, use @var{\symbol}.
4697 For example, assembling
4705 is equivalent to assembling
4713 For some caveats with the spelling of @var{symbol}, see also the discussion
4717 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4719 @cindex @code{irpc} directive
4720 Evaluate a sequence of statements assigning different values to @var{symbol}.
4721 The sequence of statements starts at the @code{.irpc} directive, and is
4722 terminated by an @code{.endr} directive. For each character in @var{value},
4723 @var{symbol} is set to the character, and the sequence of statements is
4724 assembled. If no @var{value} is listed, the sequence of statements is
4725 assembled once, with @var{symbol} set to the null string. To refer to
4726 @var{symbol} within the sequence of statements, use @var{\symbol}.
4728 For example, assembling
4736 is equivalent to assembling
4744 For some caveats with the spelling of @var{symbol}, see also the discussion
4748 @section @code{.lcomm @var{symbol} , @var{length}}
4750 @cindex @code{lcomm} directive
4751 @cindex local common symbols
4752 @cindex symbols, local common
4753 Reserve @var{length} (an absolute expression) bytes for a local common
4754 denoted by @var{symbol}. The section and value of @var{symbol} are
4755 those of the new local common. The addresses are allocated in the bss
4756 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4757 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4758 not visible to @code{@value{LD}}.
4761 Some targets permit a third argument to be used with @code{.lcomm}. This
4762 argument specifies the desired alignment of the symbol in the bss section.
4766 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4767 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4771 @section @code{.lflags}
4773 @cindex @code{lflags} directive (ignored)
4774 @command{@value{AS}} accepts this directive, for compatibility with other
4775 assemblers, but ignores it.
4777 @ifclear no-line-dir
4779 @section @code{.line @var{line-number}}
4781 @cindex @code{line} directive
4785 @section @code{.ln @var{line-number}}
4787 @cindex @code{ln} directive
4789 @cindex logical line number
4791 Change the logical line number. @var{line-number} must be an absolute
4792 expression. The next line has that logical line number. Therefore any other
4793 statements on the current line (after a statement separator character) are
4794 reported as on logical line number @var{line-number} @minus{} 1. One day
4795 @command{@value{AS}} will no longer support this directive: it is recognized only
4796 for compatibility with existing assembler programs.
4800 @ifclear no-line-dir
4801 Even though this is a directive associated with the @code{a.out} or
4802 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4803 when producing COFF output, and treats @samp{.line} as though it
4804 were the COFF @samp{.ln} @emph{if} it is found outside a
4805 @code{.def}/@code{.endef} pair.
4807 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4808 used by compilers to generate auxiliary symbol information for
4813 @section @code{.linkonce [@var{type}]}
4815 @cindex @code{linkonce} directive
4816 @cindex common sections
4817 Mark the current section so that the linker only includes a single copy of it.
4818 This may be used to include the same section in several different object files,
4819 but ensure that the linker will only include it once in the final output file.
4820 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4821 Duplicate sections are detected based on the section name, so it should be
4824 This directive is only supported by a few object file formats; as of this
4825 writing, the only object file format which supports it is the Portable
4826 Executable format used on Windows NT.
4828 The @var{type} argument is optional. If specified, it must be one of the
4829 following strings. For example:
4833 Not all types may be supported on all object file formats.
4837 Silently discard duplicate sections. This is the default.
4840 Warn if there are duplicate sections, but still keep only one copy.
4843 Warn if any of the duplicates have different sizes.
4846 Warn if any of the duplicates do not have exactly the same contents.
4850 @section @code{.ln @var{line-number}}
4852 @cindex @code{ln} directive
4853 @ifclear no-line-dir
4854 @samp{.ln} is a synonym for @samp{.line}.
4857 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4858 must be an absolute expression. The next line has that logical
4859 line number, so any other statements on the current line (after a
4860 statement separator character @code{;}) are reported as on logical
4861 line number @var{line-number} @minus{} 1.
4864 This directive is accepted, but ignored, when @command{@value{AS}} is
4865 configured for @code{b.out}; its effect is only associated with COFF
4871 @section @code{.mri @var{val}}
4873 @cindex @code{mri} directive
4874 @cindex MRI mode, temporarily
4875 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4876 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4877 affects code assembled until the next @code{.mri} directive, or until the end
4878 of the file. @xref{M, MRI mode, MRI mode}.
4881 @section @code{.list}
4883 @cindex @code{list} directive
4884 @cindex listing control, turning on
4885 Control (in conjunction with the @code{.nolist} directive) whether or
4886 not assembly listings are generated. These two directives maintain an
4887 internal counter (which is zero initially). @code{.list} increments the
4888 counter, and @code{.nolist} decrements it. Assembly listings are
4889 generated whenever the counter is greater than zero.
4891 By default, listings are disabled. When you enable them (with the
4892 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4893 the initial value of the listing counter is one.
4896 @section @code{.long @var{expressions}}
4898 @cindex @code{long} directive
4899 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4902 @c no one seems to know what this is for or whether this description is
4903 @c what it really ought to do
4905 @section @code{.lsym @var{symbol}, @var{expression}}
4907 @cindex @code{lsym} directive
4908 @cindex symbol, not referenced in assembly
4909 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4910 the hash table, ensuring it cannot be referenced by name during the
4911 rest of the assembly. This sets the attributes of the symbol to be
4912 the same as the expression value:
4914 @var{other} = @var{descriptor} = 0
4915 @var{type} = @r{(section of @var{expression})}
4916 @var{value} = @var{expression}
4919 The new symbol is not flagged as external.
4923 @section @code{.macro}
4926 The commands @code{.macro} and @code{.endm} allow you to define macros that
4927 generate assembly output. For example, this definition specifies a macro
4928 @code{sum} that puts a sequence of numbers into memory:
4931 .macro sum from=0, to=5
4940 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4952 @item .macro @var{macname}
4953 @itemx .macro @var{macname} @var{macargs} @dots{}
4954 @cindex @code{macro} directive
4955 Begin the definition of a macro called @var{macname}. If your macro
4956 definition requires arguments, specify their names after the macro name,
4957 separated by commas or spaces. You can qualify the macro argument to
4958 indicate whether all invocations must specify a non-blank value (through
4959 @samp{:@code{req}}), or whether it takes all of the remaining arguments
4960 (through @samp{:@code{vararg}}). You can supply a default value for any
4961 macro argument by following the name with @samp{=@var{deflt}}. You
4962 cannot define two macros with the same @var{macname} unless it has been
4963 subject to the @code{.purgem} directive (@xref{Purgem}.) between the two
4964 definitions. For example, these are all valid @code{.macro} statements:
4968 Begin the definition of a macro called @code{comm}, which takes no
4971 @item .macro plus1 p, p1
4972 @itemx .macro plus1 p p1
4973 Either statement begins the definition of a macro called @code{plus1},
4974 which takes two arguments; within the macro definition, write
4975 @samp{\p} or @samp{\p1} to evaluate the arguments.
4977 @item .macro reserve_str p1=0 p2
4978 Begin the definition of a macro called @code{reserve_str}, with two
4979 arguments. The first argument has a default value, but not the second.
4980 After the definition is complete, you can call the macro either as
4981 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4982 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4983 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4984 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4987 @item .macro m p1:req, p2=0, p3:vararg
4988 Begin the definition of a macro called @code{m}, with at least three
4989 arguments. The first argument must always have a value specified, but
4990 not the second, which instead has a default value. The third formal
4991 will get assigned all remaining arguments specified at invocation time.
4993 When you call a macro, you can specify the argument values either by
4994 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4995 @samp{sum to=17, from=9}.
4997 Note that since each of the @var{macargs} can be an identifier exactly
4998 as any other one permitted by the target architecture, there may be
4999 occasional problems if the target hand-crafts special meanings to certain
5000 characters when they occur in a special position. For example, if colon
5001 (@code{:}) is generally permitted to be part of a symbol name, but the
5002 architecture specific code special-cases it when occuring as the final
5003 character of a symbol (to denote a label), then the macro parameter
5004 replacement code will have no way of knowing that and consider the whole
5005 construct (including the colon) an identifier, and check only this
5006 identifier for being the subject to parameter substitution. In this
5007 example, besides the potential of just separating identifier and colon
5008 by white space, using alternate macro syntax (@xref{Altmacro}.) and
5009 ampersand (@code{&}) as the character to separate literal text from macro
5010 parameters (or macro parameters from one another) would provide a way to
5011 achieve the same effect:
5020 This applies identically to the identifiers used in @code{.irp} (@xref{Irp}.)
5021 and @code{.irpc} (@xref{Irpc}.).
5024 @cindex @code{endm} directive
5025 Mark the end of a macro definition.
5028 @cindex @code{exitm} directive
5029 Exit early from the current macro definition.
5031 @cindex number of macros executed
5032 @cindex macros, count executed
5034 @command{@value{AS}} maintains a counter of how many macros it has
5035 executed in this pseudo-variable; you can copy that number to your
5036 output with @samp{\@@}, but @emph{only within a macro definition}.
5038 @item LOCAL @var{name} [ , @dots{} ]
5039 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5040 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5041 @xref{Altmacro,,@code{.altmacro}}.
5045 @section @code{.altmacro}
5046 Enable alternate macro mode, enabling:
5049 @item LOCAL @var{name} [ , @dots{} ]
5050 One additional directive, @code{LOCAL}, is available. It is used to
5051 generate a string replacement for each of the @var{name} arguments, and
5052 replace any instances of @var{name} in each macro expansion. The
5053 replacement string is unique in the assembly, and different for each
5054 separate macro expansion. @code{LOCAL} allows you to write macros that
5055 define symbols, without fear of conflict between separate macro expansions.
5057 @item String delimiters
5058 You can write strings delimited in these other ways besides
5059 @code{"@var{string}"}:
5062 @item '@var{string}'
5063 You can delimit strings with single-quote charaters.
5065 @item <@var{string}>
5066 You can delimit strings with matching angle brackets.
5069 @item single-character string escape
5070 To include any single character literally in a string (even if the
5071 character would otherwise have some special meaning), you can prefix the
5072 character with @samp{!} (an exclamation mark). For example, you can
5073 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
5075 @item Expression results as strings
5076 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
5077 and use the result as a string.
5081 @section @code{.noaltmacro}
5082 Disable alternate macro mode. @ref{Altmacro}
5085 @section @code{.nolist}
5087 @cindex @code{nolist} directive
5088 @cindex listing control, turning off
5089 Control (in conjunction with the @code{.list} directive) whether or
5090 not assembly listings are generated. These two directives maintain an
5091 internal counter (which is zero initially). @code{.list} increments the
5092 counter, and @code{.nolist} decrements it. Assembly listings are
5093 generated whenever the counter is greater than zero.
5096 @section @code{.octa @var{bignums}}
5098 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5099 @cindex @code{octa} directive
5100 @cindex integer, 16-byte
5101 @cindex sixteen byte integer
5102 This directive expects zero or more bignums, separated by commas. For each
5103 bignum, it emits a 16-byte integer.
5105 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5106 hence @emph{octa}-word for 16 bytes.
5109 @section @code{.org @var{new-lc} , @var{fill}}
5111 @cindex @code{org} directive
5112 @cindex location counter, advancing
5113 @cindex advancing location counter
5114 @cindex current address, advancing
5115 Advance the location counter of the current section to
5116 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5117 expression with the same section as the current subsection. That is,
5118 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5119 wrong section, the @code{.org} directive is ignored. To be compatible
5120 with former assemblers, if the section of @var{new-lc} is absolute,
5121 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5122 is the same as the current subsection.
5124 @code{.org} may only increase the location counter, or leave it
5125 unchanged; you cannot use @code{.org} to move the location counter
5128 @c double negative used below "not undefined" because this is a specific
5129 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5130 @c section. doc@cygnus.com 18feb91
5131 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5132 may not be undefined. If you really detest this restriction we eagerly await
5133 a chance to share your improved assembler.
5135 Beware that the origin is relative to the start of the section, not
5136 to the start of the subsection. This is compatible with other
5137 people's assemblers.
5139 When the location counter (of the current subsection) is advanced, the
5140 intervening bytes are filled with @var{fill} which should be an
5141 absolute expression. If the comma and @var{fill} are omitted,
5142 @var{fill} defaults to zero.
5145 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5147 @cindex padding the location counter given a power of two
5148 @cindex @code{p2align} directive
5149 Pad the location counter (in the current subsection) to a particular
5150 storage boundary. The first expression (which must be absolute) is the
5151 number of low-order zero bits the location counter must have after
5152 advancement. For example @samp{.p2align 3} advances the location
5153 counter until it a multiple of 8. If the location counter is already a
5154 multiple of 8, no change is needed.
5156 The second expression (also absolute) gives the fill value to be stored in the
5157 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5158 padding bytes are normally zero. However, on some systems, if the section is
5159 marked as containing code and the fill value is omitted, the space is filled
5160 with no-op instructions.
5162 The third expression is also absolute, and is also optional. If it is present,
5163 it is the maximum number of bytes that should be skipped by this alignment
5164 directive. If doing the alignment would require skipping more bytes than the
5165 specified maximum, then the alignment is not done at all. You can omit the
5166 fill value (the second argument) entirely by simply using two commas after the
5167 required alignment; this can be useful if you want the alignment to be filled
5168 with no-op instructions when appropriate.
5170 @cindex @code{p2alignw} directive
5171 @cindex @code{p2alignl} directive
5172 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5173 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5174 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5175 fill pattern as a four byte longword value. For example, @code{.p2alignw
5176 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5177 filled in with the value 0x368d (the exact placement of the bytes depends upon
5178 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5183 @section @code{.previous}
5185 @cindex @code{previous} directive
5186 @cindex Section Stack
5187 This is one of the ELF section stack manipulation directives. The others are
5188 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5189 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5190 (@pxref{PopSection}).
5192 This directive swaps the current section (and subsection) with most recently
5193 referenced section (and subsection) prior to this one. Multiple
5194 @code{.previous} directives in a row will flip between two sections (and their
5197 In terms of the section stack, this directive swaps the current section with
5198 the top section on the section stack.
5203 @section @code{.popsection}
5205 @cindex @code{popsection} directive
5206 @cindex Section Stack
5207 This is one of the ELF section stack manipulation directives. The others are
5208 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5209 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5212 This directive replaces the current section (and subsection) with the top
5213 section (and subsection) on the section stack. This section is popped off the
5218 @section @code{.print @var{string}}
5220 @cindex @code{print} directive
5221 @command{@value{AS}} will print @var{string} on the standard output during
5222 assembly. You must put @var{string} in double quotes.
5226 @section @code{.protected @var{names}}
5228 @cindex @code{protected} directive
5230 This is one of the ELF visibility directives. The other two are
5231 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5233 This directive overrides the named symbols default visibility (which is set by
5234 their binding: local, global or weak). The directive sets the visibility to
5235 @code{protected} which means that any references to the symbols from within the
5236 components that defines them must be resolved to the definition in that
5237 component, even if a definition in another component would normally preempt
5242 @section @code{.psize @var{lines} , @var{columns}}
5244 @cindex @code{psize} directive
5245 @cindex listing control: paper size
5246 @cindex paper size, for listings
5247 Use this directive to declare the number of lines---and, optionally, the
5248 number of columns---to use for each page, when generating listings.
5250 If you do not use @code{.psize}, listings use a default line-count
5251 of 60. You may omit the comma and @var{columns} specification; the
5252 default width is 200 columns.
5254 @command{@value{AS}} generates formfeeds whenever the specified number of
5255 lines is exceeded (or whenever you explicitly request one, using
5258 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5259 those explicitly specified with @code{.eject}.
5262 @section @code{.purgem @var{name}}
5264 @cindex @code{purgem} directive
5265 Undefine the macro @var{name}, so that later uses of the string will not be
5266 expanded. @xref{Macro}.
5270 @section @code{.pushsection @var{name} , @var{subsection}}
5272 @cindex @code{pushsection} directive
5273 @cindex Section Stack
5274 This is one of the ELF section stack manipulation directives. The others are
5275 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5276 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5279 This directive pushes the current section (and subsection) onto the
5280 top of the section stack, and then replaces the current section and
5281 subsection with @code{name} and @code{subsection}.
5285 @section @code{.quad @var{bignums}}
5287 @cindex @code{quad} directive
5288 @code{.quad} expects zero or more bignums, separated by commas. For
5289 each bignum, it emits
5291 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5292 warning message; and just takes the lowest order 8 bytes of the bignum.
5293 @cindex eight-byte integer
5294 @cindex integer, 8-byte
5296 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5297 hence @emph{quad}-word for 8 bytes.
5300 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5301 warning message; and just takes the lowest order 16 bytes of the bignum.
5302 @cindex sixteen-byte integer
5303 @cindex integer, 16-byte
5307 @section @code{.rept @var{count}}
5309 @cindex @code{rept} directive
5310 Repeat the sequence of lines between the @code{.rept} directive and the next
5311 @code{.endr} directive @var{count} times.
5313 For example, assembling
5321 is equivalent to assembling
5330 @section @code{.sbttl "@var{subheading}"}
5332 @cindex @code{sbttl} directive
5333 @cindex subtitles for listings
5334 @cindex listing control: subtitle
5335 Use @var{subheading} as the title (third line, immediately after the
5336 title line) when generating assembly listings.
5338 This directive affects subsequent pages, as well as the current page if
5339 it appears within ten lines of the top of a page.
5343 @section @code{.scl @var{class}}
5345 @cindex @code{scl} directive
5346 @cindex symbol storage class (COFF)
5347 @cindex COFF symbol storage class
5348 Set the storage-class value for a symbol. This directive may only be
5349 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5350 whether a symbol is static or external, or it may record further
5351 symbolic debugging information.
5354 The @samp{.scl} directive is primarily associated with COFF output; when
5355 configured to generate @code{b.out} output format, @command{@value{AS}}
5356 accepts this directive but ignores it.
5362 @section @code{.section @var{name}}
5364 @cindex named section
5365 Use the @code{.section} directive to assemble the following code into a section
5368 This directive is only supported for targets that actually support arbitrarily
5369 named sections; on @code{a.out} targets, for example, it is not accepted, even
5370 with a standard @code{a.out} section name.
5374 @c only print the extra heading if both COFF and ELF are set
5375 @subheading COFF Version
5378 @cindex @code{section} directive (COFF version)
5379 For COFF targets, the @code{.section} directive is used in one of the following
5383 .section @var{name}[, "@var{flags}"]
5384 .section @var{name}[, @var{subsegment}]
5387 If the optional argument is quoted, it is taken as flags to use for the
5388 section. Each flag is a single character. The following flags are recognized:
5391 bss section (uninitialized data)
5393 section is not loaded
5403 shared section (meaningful for PE targets)
5405 ignored. (For compatibility with the ELF version)
5408 If no flags are specified, the default flags depend upon the section name. If
5409 the section name is not recognized, the default will be for the section to be
5410 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5411 from the section, rather than adding them, so if they are used on their own it
5412 will be as if no flags had been specified at all.
5414 If the optional argument to the @code{.section} directive is not quoted, it is
5415 taken as a subsegment number (@pxref{Sub-Sections}).
5420 @c only print the extra heading if both COFF and ELF are set
5421 @subheading ELF Version
5424 @cindex Section Stack
5425 This is one of the ELF section stack manipulation directives. The others are
5426 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5427 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5428 @code{.previous} (@pxref{Previous}).
5430 @cindex @code{section} directive (ELF version)
5431 For ELF targets, the @code{.section} directive is used like this:
5434 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5437 The optional @var{flags} argument is a quoted string which may contain any
5438 combination of the following characters:
5441 section is allocatable
5445 section is executable
5447 section is mergeable
5449 section contains zero terminated strings
5451 section is a member of a section group
5453 section is used for thread-local-storage
5456 The optional @var{type} argument may contain one of the following constants:
5459 section contains data
5461 section does not contain data (i.e., section only occupies space)
5463 section contains data which is used by things other than the program
5465 section contains an array of pointers to init functions
5467 section contains an array of pointers to finish functions
5468 @item @@preinit_array
5469 section contains an array of pointers to pre-init functions
5472 Many targets only support the first three section types.
5474 Note on targets where the @code{@@} character is the start of a comment (eg
5475 ARM) then another character is used instead. For example the ARM port uses the
5478 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5479 be specified as well as an extra argument - @var{entsize} - like this:
5482 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5485 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5486 constants, each @var{entsize} octets long. Sections with both @code{M} and
5487 @code{S} must contain zero terminated strings where each character is
5488 @var{entsize} bytes long. The linker may remove duplicates within sections with
5489 the same name, same entity size and same flags. @var{entsize} must be an
5490 absolute expression.
5492 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5493 be present along with an additional field like this:
5496 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5499 The @var{GroupName} field specifies the name of the section group to which this
5500 particular section belongs. The optional linkage field can contain:
5503 indicates that only one copy of this section should be retained
5508 Note - if both the @var{M} and @var{G} flags are present then the fields for
5509 the Merge flag should come first, like this:
5512 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5515 If no flags are specified, the default flags depend upon the section name. If
5516 the section name is not recognized, the default will be for the section to have
5517 none of the above flags: it will not be allocated in memory, nor writable, nor
5518 executable. The section will contain data.
5520 For ELF targets, the assembler supports another type of @code{.section}
5521 directive for compatibility with the Solaris assembler:
5524 .section "@var{name}"[, @var{flags}...]
5527 Note that the section name is quoted. There may be a sequence of comma
5531 section is allocatable
5535 section is executable
5537 section is used for thread local storage
5540 This directive replaces the current section and subsection. See the
5541 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5542 some examples of how this directive and the other section stack directives
5548 @section @code{.set @var{symbol}, @var{expression}}
5550 @cindex @code{set} directive
5551 @cindex symbol value, setting
5552 Set the value of @var{symbol} to @var{expression}. This
5553 changes @var{symbol}'s value and type to conform to
5554 @var{expression}. If @var{symbol} was flagged as external, it remains
5555 flagged (@pxref{Symbol Attributes}).
5557 You may @code{.set} a symbol many times in the same assembly.
5559 If you @code{.set} a global symbol, the value stored in the object
5560 file is the last value stored into it.
5563 The syntax for @code{set} on the HPPA is
5564 @samp{@var{symbol} .set @var{expression}}.
5568 On Z80 @code{set} is a real instruction, use
5569 @samp{@var{symbol} defl @var{expression}} instead.
5573 @section @code{.short @var{expressions}}
5575 @cindex @code{short} directive
5577 @code{.short} is normally the same as @samp{.word}.
5578 @xref{Word,,@code{.word}}.
5580 In some configurations, however, @code{.short} and @code{.word} generate
5581 numbers of different lengths; @pxref{Machine Dependencies}.
5585 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5588 This expects zero or more @var{expressions}, and emits
5589 a 16 bit number for each.
5594 @section @code{.single @var{flonums}}
5596 @cindex @code{single} directive
5597 @cindex floating point numbers (single)
5598 This directive assembles zero or more flonums, separated by commas. It
5599 has the same effect as @code{.float}.
5601 The exact kind of floating point numbers emitted depends on how
5602 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5606 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5607 numbers in @sc{ieee} format.
5613 @section @code{.size}
5615 This directive is used to set the size associated with a symbol.
5619 @c only print the extra heading if both COFF and ELF are set
5620 @subheading COFF Version
5623 @cindex @code{size} directive (COFF version)
5624 For COFF targets, the @code{.size} directive is only permitted inside
5625 @code{.def}/@code{.endef} pairs. It is used like this:
5628 .size @var{expression}
5632 @samp{.size} is only meaningful when generating COFF format output; when
5633 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5640 @c only print the extra heading if both COFF and ELF are set
5641 @subheading ELF Version
5644 @cindex @code{size} directive (ELF version)
5645 For ELF targets, the @code{.size} directive is used like this:
5648 .size @var{name} , @var{expression}
5651 This directive sets the size associated with a symbol @var{name}.
5652 The size in bytes is computed from @var{expression} which can make use of label
5653 arithmetic. This directive is typically used to set the size of function
5659 @section @code{.sleb128 @var{expressions}}
5661 @cindex @code{sleb128} directive
5662 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5663 compact, variable length representation of numbers used by the DWARF
5664 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5666 @ifclear no-space-dir
5668 @section @code{.skip @var{size} , @var{fill}}
5670 @cindex @code{skip} directive
5671 @cindex filling memory
5672 This directive emits @var{size} bytes, each of value @var{fill}. Both
5673 @var{size} and @var{fill} are absolute expressions. If the comma and
5674 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5678 @section @code{.space @var{size} , @var{fill}}
5680 @cindex @code{space} directive
5681 @cindex filling memory
5682 This directive emits @var{size} bytes, each of value @var{fill}. Both
5683 @var{size} and @var{fill} are absolute expressions. If the comma
5684 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5689 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5690 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5691 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5692 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5700 @section @code{.stabd, .stabn, .stabs}
5702 @cindex symbolic debuggers, information for
5703 @cindex @code{stab@var{x}} directives
5704 There are three directives that begin @samp{.stab}.
5705 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5706 The symbols are not entered in the @command{@value{AS}} hash table: they
5707 cannot be referenced elsewhere in the source file.
5708 Up to five fields are required:
5712 This is the symbol's name. It may contain any character except
5713 @samp{\000}, so is more general than ordinary symbol names. Some
5714 debuggers used to code arbitrarily complex structures into symbol names
5718 An absolute expression. The symbol's type is set to the low 8 bits of
5719 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5720 and debuggers choke on silly bit patterns.
5723 An absolute expression. The symbol's ``other'' attribute is set to the
5724 low 8 bits of this expression.
5727 An absolute expression. The symbol's descriptor is set to the low 16
5728 bits of this expression.
5731 An absolute expression which becomes the symbol's value.
5734 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5735 or @code{.stabs} statement, the symbol has probably already been created;
5736 you get a half-formed symbol in your object file. This is
5737 compatible with earlier assemblers!
5740 @cindex @code{stabd} directive
5741 @item .stabd @var{type} , @var{other} , @var{desc}
5743 The ``name'' of the symbol generated is not even an empty string.
5744 It is a null pointer, for compatibility. Older assemblers used a
5745 null pointer so they didn't waste space in object files with empty
5748 The symbol's value is set to the location counter,
5749 relocatably. When your program is linked, the value of this symbol
5750 is the address of the location counter when the @code{.stabd} was
5753 @cindex @code{stabn} directive
5754 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5755 The name of the symbol is set to the empty string @code{""}.
5757 @cindex @code{stabs} directive
5758 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5759 All five fields are specified.
5765 @section @code{.string} "@var{str}"
5767 @cindex string, copying to object file
5768 @cindex @code{string} directive
5770 Copy the characters in @var{str} to the object file. You may specify more than
5771 one string to copy, separated by commas. Unless otherwise specified for a
5772 particular machine, the assembler marks the end of each string with a 0 byte.
5773 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5776 @section @code{.struct @var{expression}}
5778 @cindex @code{struct} directive
5779 Switch to the absolute section, and set the section offset to @var{expression},
5780 which must be an absolute expression. You might use this as follows:
5789 This would define the symbol @code{field1} to have the value 0, the symbol
5790 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5791 value 8. Assembly would be left in the absolute section, and you would need to
5792 use a @code{.section} directive of some sort to change to some other section
5793 before further assembly.
5797 @section @code{.subsection @var{name}}
5799 @cindex @code{subsection} directive
5800 @cindex Section Stack
5801 This is one of the ELF section stack manipulation directives. The others are
5802 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5803 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5806 This directive replaces the current subsection with @code{name}. The current
5807 section is not changed. The replaced subsection is put onto the section stack
5808 in place of the then current top of stack subsection.
5813 @section @code{.symver}
5814 @cindex @code{symver} directive
5815 @cindex symbol versioning
5816 @cindex versions of symbols
5817 Use the @code{.symver} directive to bind symbols to specific version nodes
5818 within a source file. This is only supported on ELF platforms, and is
5819 typically used when assembling files to be linked into a shared library.
5820 There are cases where it may make sense to use this in objects to be bound
5821 into an application itself so as to override a versioned symbol from a
5824 For ELF targets, the @code{.symver} directive can be used like this:
5826 .symver @var{name}, @var{name2@@nodename}
5828 If the symbol @var{name} is defined within the file
5829 being assembled, the @code{.symver} directive effectively creates a symbol
5830 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5831 just don't try and create a regular alias is that the @var{@@} character isn't
5832 permitted in symbol names. The @var{name2} part of the name is the actual name
5833 of the symbol by which it will be externally referenced. The name @var{name}
5834 itself is merely a name of convenience that is used so that it is possible to
5835 have definitions for multiple versions of a function within a single source
5836 file, and so that the compiler can unambiguously know which version of a
5837 function is being mentioned. The @var{nodename} portion of the alias should be
5838 the name of a node specified in the version script supplied to the linker when
5839 building a shared library. If you are attempting to override a versioned
5840 symbol from a shared library, then @var{nodename} should correspond to the
5841 nodename of the symbol you are trying to override.
5843 If the symbol @var{name} is not defined within the file being assembled, all
5844 references to @var{name} will be changed to @var{name2@@nodename}. If no
5845 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5848 Another usage of the @code{.symver} directive is:
5850 .symver @var{name}, @var{name2@@@@nodename}
5852 In this case, the symbol @var{name} must exist and be defined within
5853 the file being assembled. It is similar to @var{name2@@nodename}. The
5854 difference is @var{name2@@@@nodename} will also be used to resolve
5855 references to @var{name2} by the linker.
5857 The third usage of the @code{.symver} directive is:
5859 .symver @var{name}, @var{name2@@@@@@nodename}
5861 When @var{name} is not defined within the
5862 file being assembled, it is treated as @var{name2@@nodename}. When
5863 @var{name} is defined within the file being assembled, the symbol
5864 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5869 @section @code{.tag @var{structname}}
5871 @cindex COFF structure debugging
5872 @cindex structure debugging, COFF
5873 @cindex @code{tag} directive
5874 This directive is generated by compilers to include auxiliary debugging
5875 information in the symbol table. It is only permitted inside
5876 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5877 definitions in the symbol table with instances of those structures.
5880 @samp{.tag} is only used when generating COFF format output; when
5881 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5887 @section @code{.text @var{subsection}}
5889 @cindex @code{text} directive
5890 Tells @command{@value{AS}} to assemble the following statements onto the end of
5891 the text subsection numbered @var{subsection}, which is an absolute
5892 expression. If @var{subsection} is omitted, subsection number zero
5896 @section @code{.title "@var{heading}"}
5898 @cindex @code{title} directive
5899 @cindex listing control: title line
5900 Use @var{heading} as the title (second line, immediately after the
5901 source file name and pagenumber) when generating assembly listings.
5903 This directive affects subsequent pages, as well as the current page if
5904 it appears within ten lines of the top of a page.
5908 @section @code{.type}
5910 This directive is used to set the type of a symbol.
5914 @c only print the extra heading if both COFF and ELF are set
5915 @subheading COFF Version
5918 @cindex COFF symbol type
5919 @cindex symbol type, COFF
5920 @cindex @code{type} directive (COFF version)
5921 For COFF targets, this directive is permitted only within
5922 @code{.def}/@code{.endef} pairs. It is used like this:
5928 This records the integer @var{int} as the type attribute of a symbol table
5932 @samp{.type} is associated only with COFF format output; when
5933 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5934 directive but ignores it.
5940 @c only print the extra heading if both COFF and ELF are set
5941 @subheading ELF Version
5944 @cindex ELF symbol type
5945 @cindex symbol type, ELF
5946 @cindex @code{type} directive (ELF version)
5947 For ELF targets, the @code{.type} directive is used like this:
5950 .type @var{name} , @var{type description}
5953 This sets the type of symbol @var{name} to be either a
5954 function symbol or an object symbol. There are five different syntaxes
5955 supported for the @var{type description} field, in order to provide
5956 compatibility with various other assemblers. The syntaxes supported are:
5959 .type <name>,#function
5960 .type <name>,#object
5962 .type <name>,@@function
5963 .type <name>,@@object
5965 .type <name>,%function
5966 .type <name>,%object
5968 .type <name>,"function"
5969 .type <name>,"object"
5971 .type <name> STT_FUNCTION
5972 .type <name> STT_OBJECT
5978 @section @code{.uleb128 @var{expressions}}
5980 @cindex @code{uleb128} directive
5981 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5982 compact, variable length representation of numbers used by the DWARF
5983 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5987 @section @code{.val @var{addr}}
5989 @cindex @code{val} directive
5990 @cindex COFF value attribute
5991 @cindex value attribute, COFF
5992 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5993 records the address @var{addr} as the value attribute of a symbol table
5997 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5998 configured for @code{b.out}, it accepts this directive but ignores it.
6004 @section @code{.version "@var{string}"}
6006 @cindex @code{version} directive
6007 This directive creates a @code{.note} section and places into it an ELF
6008 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6013 @section @code{.vtable_entry @var{table}, @var{offset}}
6015 @cindex @code{vtable_entry} directive
6016 This directive finds or creates a symbol @code{table} and creates a
6017 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6020 @section @code{.vtable_inherit @var{child}, @var{parent}}
6022 @cindex @code{vtable_inherit} directive
6023 This directive finds the symbol @code{child} and finds or creates the symbol
6024 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6025 parent whose addend is the value of the child symbol. As a special case the
6026 parent name of @code{0} is treated as refering the @code{*ABS*} section.
6030 @section @code{.warning "@var{string}"}
6031 @cindex warning directive
6032 Similar to the directive @code{.error}
6033 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6036 @section @code{.weak @var{names}}
6038 @cindex @code{weak} directive
6039 This directive sets the weak attribute on the comma separated list of symbol
6040 @code{names}. If the symbols do not already exist, they will be created.
6042 On COFF targets other than PE, weak symbols are a GNU extension. This
6043 directive sets the weak attribute on the comma separated list of symbol
6044 @code{names}. If the symbols do not already exist, they will be created.
6046 On the PE target, weak symbols are supported natively as weak aliases.
6047 When a weak symbol is created that is not an alias, GAS creates an
6048 alternate symbol to hold the default value.
6051 @section @code{.weakref @var{alias}, @var{target}}
6053 @cindex @code{weakref} directive
6054 This directive creates an alias to the target symbol that enables the symbol to
6055 be referenced with weak-symbol semantics, but without actually making it weak.
6056 If direct references or definitions of the symbol are present, then the symbol
6057 will not be weak, but if all references to it are through weak references, the
6058 symbol will be marked as weak in the symbol table.
6060 The effect is equivalent to moving all references to the alias to a separate
6061 assembly source file, renaming the alias to the symbol in it, declaring the
6062 symbol as weak there, and running a reloadable link to merge the object files
6063 resulting from the assembly of the new source file and the old source file that
6064 had the references to the alias removed.
6066 The alias itself never makes to the symbol table, and is entirely handled
6067 within the assembler.
6070 @section @code{.word @var{expressions}}
6072 @cindex @code{word} directive
6073 This directive expects zero or more @var{expressions}, of any section,
6074 separated by commas.
6077 For each expression, @command{@value{AS}} emits a 32-bit number.
6080 For each expression, @command{@value{AS}} emits a 16-bit number.
6085 The size of the number emitted, and its byte order,
6086 depend on what target computer the assembly is for.
6089 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6090 @c happen---32-bit addressability, period; no long/short jumps.
6091 @ifset DIFF-TBL-KLUGE
6092 @cindex difference tables altered
6093 @cindex altered difference tables
6095 @emph{Warning: Special Treatment to support Compilers}
6099 Machines with a 32-bit address space, but that do less than 32-bit
6100 addressing, require the following special treatment. If the machine of
6101 interest to you does 32-bit addressing (or doesn't require it;
6102 @pxref{Machine Dependencies}), you can ignore this issue.
6105 In order to assemble compiler output into something that works,
6106 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6107 Directives of the form @samp{.word sym1-sym2} are often emitted by
6108 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6109 directive of the form @samp{.word sym1-sym2}, and the difference between
6110 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6111 creates a @dfn{secondary jump table}, immediately before the next label.
6112 This secondary jump table is preceded by a short-jump to the
6113 first byte after the secondary table. This short-jump prevents the flow
6114 of control from accidentally falling into the new table. Inside the
6115 table is a long-jump to @code{sym2}. The original @samp{.word}
6116 contains @code{sym1} minus the address of the long-jump to
6119 If there were several occurrences of @samp{.word sym1-sym2} before the
6120 secondary jump table, all of them are adjusted. If there was a
6121 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6122 long-jump to @code{sym4} is included in the secondary jump table,
6123 and the @code{.word} directives are adjusted to contain @code{sym3}
6124 minus the address of the long-jump to @code{sym4}; and so on, for as many
6125 entries in the original jump table as necessary.
6128 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6129 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6130 assembly language programmers.
6133 @c end DIFF-TBL-KLUGE
6136 @section Deprecated Directives
6138 @cindex deprecated directives
6139 @cindex obsolescent directives
6140 One day these directives won't work.
6141 They are included for compatibility with older assemblers.
6148 @node Machine Dependencies
6149 @chapter Machine Dependent Features
6151 @cindex machine dependencies
6152 The machine instruction sets are (almost by definition) different on
6153 each machine where @command{@value{AS}} runs. Floating point representations
6154 vary as well, and @command{@value{AS}} often supports a few additional
6155 directives or command-line options for compatibility with other
6156 assemblers on a particular platform. Finally, some versions of
6157 @command{@value{AS}} support special pseudo-instructions for branch
6160 This chapter discusses most of these differences, though it does not
6161 include details on any machine's instruction set. For details on that
6162 subject, see the hardware manufacturer's manual.
6166 * Alpha-Dependent:: Alpha Dependent Features
6169 * ARC-Dependent:: ARC Dependent Features
6172 * ARM-Dependent:: ARM Dependent Features
6175 * BFIN-Dependent:: BFIN Dependent Features
6178 * CRIS-Dependent:: CRIS Dependent Features
6181 * D10V-Dependent:: D10V Dependent Features
6184 * D30V-Dependent:: D30V Dependent Features
6187 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6190 * HPPA-Dependent:: HPPA Dependent Features
6193 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6196 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6199 * i860-Dependent:: Intel 80860 Dependent Features
6202 * i960-Dependent:: Intel 80960 Dependent Features
6205 * IA-64-Dependent:: Intel IA-64 Dependent Features
6208 * IP2K-Dependent:: IP2K Dependent Features
6211 * M32C-Dependent:: M32C Dependent Features
6214 * M32R-Dependent:: M32R Dependent Features
6217 * M68K-Dependent:: M680x0 Dependent Features
6220 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6223 * MIPS-Dependent:: MIPS Dependent Features
6226 * MMIX-Dependent:: MMIX Dependent Features
6229 * MSP430-Dependent:: MSP430 Dependent Features
6232 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6233 * SH64-Dependent:: SuperH SH64 Dependent Features
6236 * PDP-11-Dependent:: PDP-11 Dependent Features
6239 * PJ-Dependent:: picoJava Dependent Features
6242 * PPC-Dependent:: PowerPC Dependent Features
6245 * Sparc-Dependent:: SPARC Dependent Features
6248 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6251 * V850-Dependent:: V850 Dependent Features
6254 * Xtensa-Dependent:: Xtensa Dependent Features
6257 * Z80-Dependent:: Z80 Dependent Features
6260 * Z8000-Dependent:: Z8000 Dependent Features
6263 * Vax-Dependent:: VAX Dependent Features
6270 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6271 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6272 @c peculiarity: to preserve cross-references, there must be a node called
6273 @c "Machine Dependencies". Hence the conditional nodenames in each
6274 @c major node below. Node defaulting in makeinfo requires adjacency of
6275 @c node and sectioning commands; hence the repetition of @chapter BLAH
6276 @c in both conditional blocks.
6279 @include c-alpha.texi
6291 @include c-bfin.texi
6295 @include c-cris.texi
6300 @node Machine Dependencies
6301 @chapter Machine Dependent Features
6303 The machine instruction sets are different on each Renesas chip family,
6304 and there are also some syntax differences among the families. This
6305 chapter describes the specific @command{@value{AS}} features for each
6309 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6310 * SH-Dependent:: Renesas SH Dependent Features
6317 @include c-d10v.texi
6321 @include c-d30v.texi
6325 @include c-h8300.texi
6329 @include c-hppa.texi
6333 @include c-i370.texi
6337 @include c-i386.texi
6341 @include c-i860.texi
6345 @include c-i960.texi
6349 @include c-ia64.texi
6353 @include c-ip2k.texi
6357 @include c-m32c.texi
6361 @include c-m32r.texi
6365 @include c-m68k.texi
6369 @include c-m68hc11.texi
6373 @include c-mips.texi
6377 @include c-mmix.texi
6381 @include c-msp430.texi
6385 @include c-ns32k.texi
6389 @include c-pdp11.texi
6402 @include c-sh64.texi
6406 @include c-sparc.texi
6410 @include c-tic54x.texi
6426 @include c-v850.texi
6430 @include c-xtensa.texi
6434 @c reverse effect of @down at top of generic Machine-Dep chapter
6438 @node Reporting Bugs
6439 @chapter Reporting Bugs
6440 @cindex bugs in assembler
6441 @cindex reporting bugs in assembler
6443 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6445 Reporting a bug may help you by bringing a solution to your problem, or it may
6446 not. But in any case the principal function of a bug report is to help the
6447 entire community by making the next version of @command{@value{AS}} work better.
6448 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6450 In order for a bug report to serve its purpose, you must include the
6451 information that enables us to fix the bug.
6454 * Bug Criteria:: Have you found a bug?
6455 * Bug Reporting:: How to report bugs
6459 @section Have You Found a Bug?
6460 @cindex bug criteria
6462 If you are not sure whether you have found a bug, here are some guidelines:
6465 @cindex fatal signal
6466 @cindex assembler crash
6467 @cindex crash of assembler
6469 If the assembler gets a fatal signal, for any input whatever, that is a
6470 @command{@value{AS}} bug. Reliable assemblers never crash.
6472 @cindex error on valid input
6474 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6476 @cindex invalid input
6478 If @command{@value{AS}} does not produce an error message for invalid input, that
6479 is a bug. However, you should note that your idea of ``invalid input'' might
6480 be our idea of ``an extension'' or ``support for traditional practice''.
6483 If you are an experienced user of assemblers, your suggestions for improvement
6484 of @command{@value{AS}} are welcome in any case.
6488 @section How to Report Bugs
6490 @cindex assembler bugs, reporting
6492 A number of companies and individuals offer support for @sc{gnu} products. If
6493 you obtained @command{@value{AS}} from a support organization, we recommend you
6494 contact that organization first.
6496 You can find contact information for many support companies and
6497 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6500 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6501 to @samp{bug-binutils@@gnu.org}.
6503 The fundamental principle of reporting bugs usefully is this:
6504 @strong{report all the facts}. If you are not sure whether to state a
6505 fact or leave it out, state it!
6507 Often people omit facts because they think they know what causes the problem
6508 and assume that some details do not matter. Thus, you might assume that the
6509 name of a symbol you use in an example does not matter. Well, probably it does
6510 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6511 happens to fetch from the location where that name is stored in memory;
6512 perhaps, if the name were different, the contents of that location would fool
6513 the assembler into doing the right thing despite the bug. Play it safe and
6514 give a specific, complete example. That is the easiest thing for you to do,
6515 and the most helpful.
6517 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6518 it is new to us. Therefore, always write your bug reports on the assumption
6519 that the bug has not been reported previously.
6521 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6522 bell?'' This cannot help us fix a bug, so it is basically useless. We
6523 respond by asking for enough details to enable us to investigate.
6524 You might as well expedite matters by sending them to begin with.
6526 To enable us to fix the bug, you should include all these things:
6530 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6531 it with the @samp{--version} argument.
6533 Without this, we will not know whether there is any point in looking for
6534 the bug in the current version of @command{@value{AS}}.
6537 Any patches you may have applied to the @command{@value{AS}} source.
6540 The type of machine you are using, and the operating system name and
6544 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6548 The command arguments you gave the assembler to assemble your example and
6549 observe the bug. To guarantee you will not omit something important, list them
6550 all. A copy of the Makefile (or the output from make) is sufficient.
6552 If we were to try to guess the arguments, we would probably guess wrong
6553 and then we might not encounter the bug.
6556 A complete input file that will reproduce the bug. If the bug is observed when
6557 the assembler is invoked via a compiler, send the assembler source, not the
6558 high level language source. Most compilers will produce the assembler source
6559 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6560 the options @samp{-v --save-temps}; this will save the assembler source in a
6561 file with an extension of @file{.s}, and also show you exactly how
6562 @command{@value{AS}} is being run.
6565 A description of what behavior you observe that you believe is
6566 incorrect. For example, ``It gets a fatal signal.''
6568 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6569 will certainly notice it. But if the bug is incorrect output, we might not
6570 notice unless it is glaringly wrong. You might as well not give us a chance to
6573 Even if the problem you experience is a fatal signal, you should still say so
6574 explicitly. Suppose something strange is going on, such as, your copy of
6575 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6576 library on your system. (This has happened!) Your copy might crash and ours
6577 would not. If you told us to expect a crash, then when ours fails to crash, we
6578 would know that the bug was not happening for us. If you had not told us to
6579 expect a crash, then we would not be able to draw any conclusion from our
6583 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6584 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6585 option. Always send diffs from the old file to the new file. If you even
6586 discuss something in the @command{@value{AS}} source, refer to it by context, not
6589 The line numbers in our development sources will not match those in your
6590 sources. Your line numbers would convey no useful information to us.
6593 Here are some things that are not necessary:
6597 A description of the envelope of the bug.
6599 Often people who encounter a bug spend a lot of time investigating
6600 which changes to the input file will make the bug go away and which
6601 changes will not affect it.
6603 This is often time consuming and not very useful, because the way we
6604 will find the bug is by running a single example under the debugger
6605 with breakpoints, not by pure deduction from a series of examples.
6606 We recommend that you save your time for something else.
6608 Of course, if you can find a simpler example to report @emph{instead}
6609 of the original one, that is a convenience for us. Errors in the
6610 output will be easier to spot, running under the debugger will take
6611 less time, and so on.
6613 However, simplification is not vital; if you do not want to do this,
6614 report the bug anyway and send us the entire test case you used.
6617 A patch for the bug.
6619 A patch for the bug does help us if it is a good one. But do not omit
6620 the necessary information, such as the test case, on the assumption that
6621 a patch is all we need. We might see problems with your patch and decide
6622 to fix the problem another way, or we might not understand it at all.
6624 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6625 construct an example that will make the program follow a certain path through
6626 the code. If you do not send us the example, we will not be able to construct
6627 one, so we will not be able to verify that the bug is fixed.
6629 And if we cannot understand what bug you are trying to fix, or why your
6630 patch should be an improvement, we will not install it. A test case will
6631 help us to understand.
6634 A guess about what the bug is or what it depends on.
6636 Such guesses are usually wrong. Even we cannot guess right about such
6637 things without first using the debugger to find the facts.
6640 @node Acknowledgements
6641 @chapter Acknowledgements
6643 If you have contributed to GAS and your name isn't listed here,
6644 it is not meant as a slight. We just don't know about it. Send mail to the
6645 maintainer, and we'll correct the situation. Currently
6647 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6649 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6652 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6653 information and the 68k series machines, most of the preprocessing pass, and
6654 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6656 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6657 many bug fixes, including merging support for several processors, breaking GAS
6658 up to handle multiple object file format back ends (including heavy rewrite,
6659 testing, an integration of the coff and b.out back ends), adding configuration
6660 including heavy testing and verification of cross assemblers and file splits
6661 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6662 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6663 port (including considerable amounts of reverse engineering), a SPARC opcode
6664 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6665 assertions and made them work, much other reorganization, cleanup, and lint.
6667 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6668 in format-specific I/O modules.
6670 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6671 has done much work with it since.
6673 The Intel 80386 machine description was written by Eliot Dresselhaus.
6675 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6677 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6678 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6680 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6681 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6682 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6683 support a.out format.
6685 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
6686 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
6687 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6688 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6691 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6692 simplified the configuration of which versions accept which directives. He
6693 updated the 68k machine description so that Motorola's opcodes always produced
6694 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6695 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6696 cross-compilation support, and one bug in relaxation that took a week and
6697 required the proverbial one-bit fix.
6699 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6700 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6701 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6702 PowerPC assembler, and made a few other minor patches.
6704 Steve Chamberlain made GAS able to generate listings.
6706 Hewlett-Packard contributed support for the HP9000/300.
6708 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6709 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6710 formats). This work was supported by both the Center for Software Science at
6711 the University of Utah and Cygnus Support.
6713 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6714 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6715 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6716 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6717 and some initial 64-bit support).
6719 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6721 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6722 support for openVMS/Alpha.
6724 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6727 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6728 Inc. added support for Xtensa processors.
6730 Several engineers at Cygnus Support have also provided many small bug fixes and
6731 configuration enhancements.
6733 Many others have contributed large or small bugfixes and enhancements. If
6734 you have contributed significant work and are not mentioned on this list, and
6735 want to be, let us know. Some of the history has been lost; we are not
6736 intentionally leaving anyone out.
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