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{-mmt}] [@b{-mno-mt}]
372 [@b{-mdebug}] [@b{-no-mdebug}]
373 [@b{-mpdr}] [@b{-mno-pdr}]
377 @emph{Target MMIX options:}
378 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
379 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
380 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
381 [@b{--linker-allocated-gregs}]
385 @emph{Target PDP11 options:}
386 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
387 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
388 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
392 @emph{Target picoJava options:}
397 @emph{Target PowerPC options:}
398 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
399 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
400 @b{-mbooke32}|@b{-mbooke64}]
401 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
402 [@b{-mregnames}|@b{-mno-regnames}]
403 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
404 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
405 [@b{-msolaris}|@b{-mno-solaris}]
409 @emph{Target SPARC options:}
410 @c The order here is important. See c-sparc.texi.
411 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
412 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
413 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
418 @emph{Target TIC54X options:}
419 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
420 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
423 @c Z8000 has no machine-dependent assembler options
427 @emph{Target Xtensa options:}
428 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
429 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
430 [@b{--[no-]transform}]
431 [@b{--rename-section} @var{oldname}=@var{newname}]
440 Turn on listings, in any of a variety of ways:
444 omit false conditionals
447 omit debugging directives
450 include high-level source
456 include macro expansions
459 omit forms processing
465 set the name of the listing file
468 You may combine these options; for example, use @samp{-aln} for assembly
469 listing without forms processing. The @samp{=file} option, if used, must be
470 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
473 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
476 Ignored. This option is accepted for script compatibility with calls to
479 @item --defsym @var{sym}=@var{value}
480 Define the symbol @var{sym} to be @var{value} before assembling the input file.
481 @var{value} must be an integer constant. As in C, a leading @samp{0x}
482 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
485 ``fast''---skip whitespace and comment preprocessing (assume source is
490 Generate debugging information for each assembler source line using whichever
491 debug format is preferred by the target. This currently means either STABS,
495 Generate stabs debugging information for each assembler line. This
496 may help debugging assembler code, if the debugger can handle it.
499 Generate stabs debugging information for each assembler line, with GNU
500 extensions that probably only gdb can handle, and that could make other
501 debuggers crash or refuse to read your program. This
502 may help debugging assembler code. Currently the only GNU extension is
503 the location of the current working directory at assembling time.
506 Generate DWARF2 debugging information for each assembler line. This
507 may help debugging assembler code, if the debugger can handle it. Note---this
508 option is only supported by some targets, not all of them.
511 Print a summary of the command line options and exit.
514 Print a summary of all target specific options and exit.
517 Add directory @var{dir} to the search list for @code{.include} directives.
520 Don't warn about signed overflow.
523 @ifclear DIFF-TBL-KLUGE
524 This option is accepted but has no effect on the @value{TARGET} family.
526 @ifset DIFF-TBL-KLUGE
527 Issue warnings when difference tables altered for long displacements.
532 Keep (in the symbol table) local symbols. On traditional a.out systems
533 these start with @samp{L}, but different systems have different local
536 @item --listing-lhs-width=@var{number}
537 Set the maximum width, in words, of the output data column for an assembler
538 listing to @var{number}.
540 @item --listing-lhs-width2=@var{number}
541 Set the maximum width, in words, of the output data column for continuation
542 lines in an assembler listing to @var{number}.
544 @item --listing-rhs-width=@var{number}
545 Set the maximum width of an input source line, as displayed in a listing, to
548 @item --listing-cont-lines=@var{number}
549 Set the maximum number of lines printed in a listing for a single line of input
552 @item -o @var{objfile}
553 Name the object-file output from @command{@value{AS}} @var{objfile}.
556 Fold the data section into the text section.
558 @kindex --hash-size=@var{number}
559 Set the default size of GAS's hash tables to a prime number close to
560 @var{number}. Increasing this value can reduce the length of time it takes the
561 assembler to perform its tasks, at the expense of increasing the assembler's
562 memory requirements. Similarly reducing this value can reduce the memory
563 requirements at the expense of speed.
565 @item --reduce-memory-overheads
566 This option reduces GAS's memory requirements, at the expense of making the
567 assembly processes slower. Currently this switch is a synonym for
568 @samp{--hash-size=4051}, but in the future it may have other effects as well.
571 Print the maximum space (in bytes) and total time (in seconds) used by
574 @item --strip-local-absolute
575 Remove local absolute symbols from the outgoing symbol table.
579 Print the @command{as} version.
582 Print the @command{as} version and exit.
586 Suppress warning messages.
588 @item --fatal-warnings
589 Treat warnings as errors.
592 Don't suppress warning messages or treat them as errors.
601 Generate an object file even after errors.
603 @item -- | @var{files} @dots{}
604 Standard input, or source files to assemble.
609 The following options are available when @value{AS} is configured for
614 This option selects the core processor variant.
616 Select either big-endian (-EB) or little-endian (-EL) output.
621 The following options are available when @value{AS} is configured for the ARM
625 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
626 Specify which ARM processor variant is the target.
627 @item -march=@var{architecture}[+@var{extension}@dots{}]
628 Specify which ARM architecture variant is used by the target.
629 @item -mfpu=@var{floating-point-format}
630 Select which Floating Point architecture is the target.
631 @item -mfloat-abi=@var{abi}
632 Select which floating point ABI is in use.
634 Enable Thumb only instruction decoding.
635 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
636 Select which procedure calling convention is in use.
638 Select either big-endian (-EB) or little-endian (-EL) output.
639 @item -mthumb-interwork
640 Specify that the code has been generated with interworking between Thumb and
643 Specify that PIC code has been generated.
648 See the info pages for documentation of the CRIS-specific options.
652 The following options are available when @value{AS} is configured for
655 @cindex D10V optimization
656 @cindex optimization, D10V
658 Optimize output by parallelizing instructions.
663 The following options are available when @value{AS} is configured for a D30V
666 @cindex D30V optimization
667 @cindex optimization, D30V
669 Optimize output by parallelizing instructions.
673 Warn when nops are generated.
675 @cindex D30V nops after 32-bit multiply
677 Warn when a nop after a 32-bit multiply instruction is generated.
682 The following options are available when @value{AS} is configured for the
683 Intel 80960 processor.
686 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
687 Specify which variant of the 960 architecture is the target.
690 Add code to collect statistics about branches taken.
693 Do not alter compare-and-branch instructions for long displacements;
700 The following options are available when @value{AS} is configured for the
706 Specifies that the extended IP2022 instructions are allowed.
709 Restores the default behaviour, which restricts the permitted instructions to
710 just the basic IP2022 ones.
716 The following options are available when @value{AS} is configured for the
717 Renesas M32C and M16C processors.
722 Assemble M32C instructions.
725 Assemble M16C instructions (the default).
731 The following options are available when @value{AS} is configured for the
732 Renesas M32R (formerly Mitsubishi M32R) series.
737 Specify which processor in the M32R family is the target. The default
738 is normally the M32R, but this option changes it to the M32RX.
740 @item --warn-explicit-parallel-conflicts or --Wp
741 Produce warning messages when questionable parallel constructs are
744 @item --no-warn-explicit-parallel-conflicts or --Wnp
745 Do not produce warning messages when questionable parallel constructs are
752 The following options are available when @value{AS} is configured for the
753 Motorola 68000 series.
758 Shorten references to undefined symbols, to one word instead of two.
760 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
761 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
762 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
763 Specify what processor in the 68000 family is the target. The default
764 is normally the 68020, but this can be changed at configuration time.
766 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
767 The target machine does (or does not) have a floating-point coprocessor.
768 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
769 the basic 68000 is not compatible with the 68881, a combination of the
770 two can be specified, since it's possible to do emulation of the
771 coprocessor instructions with the main processor.
773 @item -m68851 | -mno-68851
774 The target machine does (or does not) have a memory-management
775 unit coprocessor. The default is to assume an MMU for 68020 and up.
782 For details about the PDP-11 machine dependent features options,
783 see @ref{PDP-11-Options}.
786 @item -mpic | -mno-pic
787 Generate position-independent (or position-dependent) code. The
788 default is @option{-mpic}.
791 @itemx -mall-extensions
792 Enable all instruction set extensions. This is the default.
794 @item -mno-extensions
795 Disable all instruction set extensions.
797 @item -m@var{extension} | -mno-@var{extension}
798 Enable (or disable) a particular instruction set extension.
801 Enable the instruction set extensions supported by a particular CPU, and
802 disable all other extensions.
804 @item -m@var{machine}
805 Enable the instruction set extensions supported by a particular machine
806 model, and disable all other extensions.
812 The following options are available when @value{AS} is configured for
813 a picoJava processor.
817 @cindex PJ endianness
818 @cindex endianness, PJ
819 @cindex big endian output, PJ
821 Generate ``big endian'' format output.
823 @cindex little endian output, PJ
825 Generate ``little endian'' format output.
831 The following options are available when @value{AS} is configured for the
832 Motorola 68HC11 or 68HC12 series.
836 @item -m68hc11 | -m68hc12 | -m68hcs12
837 Specify what processor is the target. The default is
838 defined by the configuration option when building the assembler.
841 Specify to use the 16-bit integer ABI.
844 Specify to use the 32-bit integer ABI.
847 Specify to use the 32-bit double ABI.
850 Specify to use the 64-bit double ABI.
852 @item --force-long-branchs
853 Relative branches are turned into absolute ones. This concerns
854 conditional branches, unconditional branches and branches to a
857 @item -S | --short-branchs
858 Do not turn relative branchs into absolute ones
859 when the offset is out of range.
861 @item --strict-direct-mode
862 Do not turn the direct addressing mode into extended addressing mode
863 when the instruction does not support direct addressing mode.
865 @item --print-insn-syntax
866 Print the syntax of instruction in case of error.
868 @item --print-opcodes
869 print the list of instructions with syntax and then exit.
871 @item --generate-example
872 print an example of instruction for each possible instruction and then exit.
873 This option is only useful for testing @command{@value{AS}}.
879 The following options are available when @command{@value{AS}} is configured
880 for the SPARC architecture:
883 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
884 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
885 Explicitly select a variant of the SPARC architecture.
887 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
888 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
890 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
891 UltraSPARC extensions.
893 @item -xarch=v8plus | -xarch=v8plusa
894 For compatibility with the Solaris v9 assembler. These options are
895 equivalent to -Av8plus and -Av8plusa, respectively.
898 Warn when the assembler switches to another architecture.
903 The following options are available when @value{AS} is configured for the 'c54x
908 Enable extended addressing mode. All addresses and relocations will assume
909 extended addressing (usually 23 bits).
910 @item -mcpu=@var{CPU_VERSION}
911 Sets the CPU version being compiled for.
912 @item -merrors-to-file @var{FILENAME}
913 Redirect error output to a file, for broken systems which don't support such
914 behaviour in the shell.
919 The following options are available when @value{AS} is configured for
920 a @sc{mips} processor.
924 This option sets the largest size of an object that can be referenced
925 implicitly with the @code{gp} register. It is only accepted for targets that
926 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
928 @cindex MIPS endianness
929 @cindex endianness, MIPS
930 @cindex big endian output, MIPS
932 Generate ``big endian'' format output.
934 @cindex little endian output, MIPS
936 Generate ``little endian'' format output.
948 Generate code for a particular @sc{mips} Instruction Set Architecture level.
949 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
950 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
951 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
952 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
954 correspond to generic
955 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
956 and @samp{MIPS64 Release 2}
957 ISA processors, respectively.
959 @item -march=@var{CPU}
960 Generate code for a particular @sc{mips} cpu.
962 @item -mtune=@var{cpu}
963 Schedule and tune for a particular @sc{mips} cpu.
967 Cause nops to be inserted if the read of the destination register
968 of an mfhi or mflo instruction occurs in the following two instructions.
972 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
973 section instead of the standard ELF .stabs sections.
977 Control generation of @code{.pdr} sections.
981 The register sizes are normally inferred from the ISA and ABI, but these
982 flags force a certain group of registers to be treated as 32 bits wide at
983 all times. @samp{-mgp32} controls the size of general-purpose registers
984 and @samp{-mfp32} controls the size of floating-point registers.
988 Generate code for the MIPS 16 processor. This is equivalent to putting
989 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
990 turns off this option.
994 Generate code for the MIPS-3D Application Specific Extension.
995 This tells the assembler to accept MIPS-3D instructions.
996 @samp{-no-mips3d} turns off this option.
1000 Generate code for the MDMX Application Specific Extension.
1001 This tells the assembler to accept MDMX instructions.
1002 @samp{-no-mdmx} turns off this option.
1006 Generate code for the MT Application Specific Extension.
1007 This tells the assembler to accept MT instructions.
1008 @samp{-mno-mt} turns off this option.
1010 @item --construct-floats
1011 @itemx --no-construct-floats
1012 The @samp{--no-construct-floats} option disables the construction of
1013 double width floating point constants by loading the two halves of the
1014 value into the two single width floating point registers that make up
1015 the double width register. By default @samp{--construct-floats} is
1016 selected, allowing construction of these floating point constants.
1019 @item --emulation=@var{name}
1020 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1021 for some other target, in all respects, including output format (choosing
1022 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1023 debugging information or store symbol table information, and default
1024 endianness. The available configuration names are: @samp{mipsecoff},
1025 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1026 @samp{mipsbelf}. The first two do not alter the default endianness from that
1027 of the primary target for which the assembler was configured; the others change
1028 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1029 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1030 selection in any case.
1032 This option is currently supported only when the primary target
1033 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1034 Furthermore, the primary target or others specified with
1035 @samp{--enable-targets=@dots{}} at configuration time must include support for
1036 the other format, if both are to be available. For example, the Irix 5
1037 configuration includes support for both.
1039 Eventually, this option will support more configurations, with more
1040 fine-grained control over the assembler's behavior, and will be supported for
1044 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1051 Control how to deal with multiplication overflow and division by zero.
1052 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1053 (and only work for Instruction Set Architecture level 2 and higher);
1054 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1058 When this option is used, @command{@value{AS}} will issue a warning every
1059 time it generates a nop instruction from a macro.
1064 The following options are available when @value{AS} is configured for
1070 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1071 The command line option @samp{-nojsri2bsr} can be used to disable it.
1075 Enable or disable the silicon filter behaviour. By default this is disabled.
1076 The default can be overridden by the @samp{-sifilter} command line option.
1079 Alter jump instructions for long displacements.
1081 @item -mcpu=[210|340]
1082 Select the cpu type on the target hardware. This controls which instructions
1086 Assemble for a big endian target.
1089 Assemble for a little endian target.
1095 See the info pages for documentation of the MMIX-specific options.
1099 The following options are available when @value{AS} is configured for
1100 an Xtensa processor.
1103 @item --text-section-literals | --no-text-section-literals
1104 With @option{--text-@-section-@-literals}, literal pools are interspersed
1105 in the text section. The default is
1106 @option{--no-@-text-@-section-@-literals}, which places literals in a
1107 separate section in the output file. These options only affect literals
1108 referenced via PC-relative @code{L32R} instructions; literals for
1109 absolute mode @code{L32R} instructions are handled separately.
1111 @item --absolute-literals | --no-absolute-literals
1112 Indicate to the assembler whether @code{L32R} instructions use absolute
1113 or PC-relative addressing. The default is to assume absolute addressing
1114 if the Xtensa processor includes the absolute @code{L32R} addressing
1115 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1117 @item --target-align | --no-target-align
1118 Enable or disable automatic alignment to reduce branch penalties at the
1119 expense of some code density. The default is @option{--target-@-align}.
1121 @item --longcalls | --no-longcalls
1122 Enable or disable transformation of call instructions to allow calls
1123 across a greater range of addresses. The default is
1124 @option{--no-@-longcalls}.
1126 @item --transform | --no-transform
1127 Enable or disable all assembler transformations of Xtensa instructions.
1128 The default is @option{--transform};
1129 @option{--no-transform} should be used only in the rare cases when the
1130 instructions must be exactly as specified in the assembly source.
1137 * Manual:: Structure of this Manual
1138 * GNU Assembler:: The GNU Assembler
1139 * Object Formats:: Object File Formats
1140 * Command Line:: Command Line
1141 * Input Files:: Input Files
1142 * Object:: Output (Object) File
1143 * Errors:: Error and Warning Messages
1147 @section Structure of this Manual
1149 @cindex manual, structure and purpose
1150 This manual is intended to describe what you need to know to use
1151 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1152 notation for symbols, constants, and expressions; the directives that
1153 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1156 We also cover special features in the @value{TARGET}
1157 configuration of @command{@value{AS}}, including assembler directives.
1160 This manual also describes some of the machine-dependent features of
1161 various flavors of the assembler.
1164 @cindex machine instructions (not covered)
1165 On the other hand, this manual is @emph{not} intended as an introduction
1166 to programming in assembly language---let alone programming in general!
1167 In a similar vein, we make no attempt to introduce the machine
1168 architecture; we do @emph{not} describe the instruction set, standard
1169 mnemonics, registers or addressing modes that are standard to a
1170 particular architecture.
1172 You may want to consult the manufacturer's
1173 machine architecture manual for this information.
1177 For information on the H8/300 machine instruction set, see @cite{H8/300
1178 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1179 Programming Manual} (Renesas).
1182 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1183 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1184 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1185 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1188 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1192 @c I think this is premature---doc@cygnus.com, 17jan1991
1194 Throughout this manual, we assume that you are running @dfn{GNU},
1195 the portable operating system from the @dfn{Free Software
1196 Foundation, Inc.}. This restricts our attention to certain kinds of
1197 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1198 once this assumption is granted examples and definitions need less
1201 @command{@value{AS}} is part of a team of programs that turn a high-level
1202 human-readable series of instructions into a low-level
1203 computer-readable series of instructions. Different versions of
1204 @command{@value{AS}} are used for different kinds of computer.
1207 @c There used to be a section "Terminology" here, which defined
1208 @c "contents", "byte", "word", and "long". Defining "word" to any
1209 @c particular size is confusing when the .word directive may generate 16
1210 @c bits on one machine and 32 bits on another; in general, for the user
1211 @c version of this manual, none of these terms seem essential to define.
1212 @c They were used very little even in the former draft of the manual;
1213 @c this draft makes an effort to avoid them (except in names of
1217 @section The GNU Assembler
1219 @c man begin DESCRIPTION
1221 @sc{gnu} @command{as} is really a family of assemblers.
1223 This manual describes @command{@value{AS}}, a member of that family which is
1224 configured for the @value{TARGET} architectures.
1226 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1227 should find a fairly similar environment when you use it on another
1228 architecture. Each version has much in common with the others,
1229 including object file formats, most assembler directives (often called
1230 @dfn{pseudo-ops}) and assembler syntax.@refill
1232 @cindex purpose of @sc{gnu} assembler
1233 @command{@value{AS}} is primarily intended to assemble the output of the
1234 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1235 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1236 assemble correctly everything that other assemblers for the same
1237 machine would assemble.
1239 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1242 @c This remark should appear in generic version of manual; assumption
1243 @c here is that generic version sets M680x0.
1244 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1245 assembler for the same architecture; for example, we know of several
1246 incompatible versions of 680x0 assembly language syntax.
1251 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1252 program in one pass of the source file. This has a subtle impact on the
1253 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1255 @node Object Formats
1256 @section Object File Formats
1258 @cindex object file format
1259 The @sc{gnu} assembler can be configured to produce several alternative
1260 object file formats. For the most part, this does not affect how you
1261 write assembly language programs; but directives for debugging symbols
1262 are typically different in different file formats. @xref{Symbol
1263 Attributes,,Symbol Attributes}.
1266 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1267 @value{OBJ-NAME} format object files.
1269 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1271 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1272 @code{b.out} or COFF format object files.
1275 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1276 SOM or ELF format object files.
1281 @section Command Line
1283 @cindex command line conventions
1285 After the program name @command{@value{AS}}, the command line may contain
1286 options and file names. Options may appear in any order, and may be
1287 before, after, or between file names. The order of file names is
1290 @cindex standard input, as input file
1292 @file{--} (two hyphens) by itself names the standard input file
1293 explicitly, as one of the files for @command{@value{AS}} to assemble.
1295 @cindex options, command line
1296 Except for @samp{--} any command line argument that begins with a
1297 hyphen (@samp{-}) is an option. Each option changes the behavior of
1298 @command{@value{AS}}. No option changes the way another option works. An
1299 option is a @samp{-} followed by one or more letters; the case of
1300 the letter is important. All options are optional.
1302 Some options expect exactly one file name to follow them. The file
1303 name may either immediately follow the option's letter (compatible
1304 with older assemblers) or it may be the next command argument (@sc{gnu}
1305 standard). These two command lines are equivalent:
1308 @value{AS} -o my-object-file.o mumble.s
1309 @value{AS} -omy-object-file.o mumble.s
1313 @section Input Files
1316 @cindex source program
1317 @cindex files, input
1318 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1319 describe the program input to one run of @command{@value{AS}}. The program may
1320 be in one or more files; how the source is partitioned into files
1321 doesn't change the meaning of the source.
1323 @c I added "con" prefix to "catenation" just to prove I can overcome my
1324 @c APL training... doc@cygnus.com
1325 The source program is a concatenation of the text in all the files, in the
1328 @c man begin DESCRIPTION
1329 Each time you run @command{@value{AS}} it assembles exactly one source
1330 program. The source program is made up of one or more files.
1331 (The standard input is also a file.)
1333 You give @command{@value{AS}} a command line that has zero or more input file
1334 names. The input files are read (from left file name to right). A
1335 command line argument (in any position) that has no special meaning
1336 is taken to be an input file name.
1338 If you give @command{@value{AS}} no file names it attempts to read one input file
1339 from the @command{@value{AS}} standard input, which is normally your terminal. You
1340 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1343 Use @samp{--} if you need to explicitly name the standard input file
1344 in your command line.
1346 If the source is empty, @command{@value{AS}} produces a small, empty object
1351 @subheading Filenames and Line-numbers
1353 @cindex input file linenumbers
1354 @cindex line numbers, in input files
1355 There are two ways of locating a line in the input file (or files) and
1356 either may be used in reporting error messages. One way refers to a line
1357 number in a physical file; the other refers to a line number in a
1358 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1360 @dfn{Physical files} are those files named in the command line given
1361 to @command{@value{AS}}.
1363 @dfn{Logical files} are simply names declared explicitly by assembler
1364 directives; they bear no relation to physical files. Logical file names help
1365 error messages reflect the original source file, when @command{@value{AS}} source
1366 is itself synthesized from other files. @command{@value{AS}} understands the
1367 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1368 @ref{File,,@code{.file}}.
1371 @section Output (Object) File
1377 Every time you run @command{@value{AS}} it produces an output file, which is
1378 your assembly language program translated into numbers. This file
1379 is the object file. Its default name is
1387 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1389 You can give it another name by using the @option{-o} option. Conventionally,
1390 object file names end with @file{.o}. The default name is used for historical
1391 reasons: older assemblers were capable of assembling self-contained programs
1392 directly into a runnable program. (For some formats, this isn't currently
1393 possible, but it can be done for the @code{a.out} format.)
1397 The object file is meant for input to the linker @code{@value{LD}}. It contains
1398 assembled program code, information to help @code{@value{LD}} integrate
1399 the assembled program into a runnable file, and (optionally) symbolic
1400 information for the debugger.
1402 @c link above to some info file(s) like the description of a.out.
1403 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1406 @section Error and Warning Messages
1408 @c man begin DESCRIPTION
1410 @cindex error messages
1411 @cindex warning messages
1412 @cindex messages from assembler
1413 @command{@value{AS}} may write warnings and error messages to the standard error
1414 file (usually your terminal). This should not happen when a compiler
1415 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1416 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1417 grave problem that stops the assembly.
1421 @cindex format of warning messages
1422 Warning messages have the format
1425 file_name:@b{NNN}:Warning Message Text
1429 @cindex line numbers, in warnings/errors
1430 (where @b{NNN} is a line number). If a logical file name has been given
1431 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1432 the current input file is used. If a logical line number was given
1434 (@pxref{Line,,@code{.line}})
1436 then it is used to calculate the number printed,
1437 otherwise the actual line in the current source file is printed. The
1438 message text is intended to be self explanatory (in the grand Unix
1441 @cindex format of error messages
1442 Error messages have the format
1444 file_name:@b{NNN}:FATAL:Error Message Text
1446 The file name and line number are derived as for warning
1447 messages. The actual message text may be rather less explanatory
1448 because many of them aren't supposed to happen.
1451 @chapter Command-Line Options
1453 @cindex options, all versions of assembler
1454 This chapter describes command-line options available in @emph{all}
1455 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1457 to the @value{TARGET} target.
1460 to particular machine architectures.
1463 @c man begin DESCRIPTION
1465 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1466 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1467 The assembler arguments must be separated from each other (and the @samp{-Wa})
1468 by commas. For example:
1471 gcc -c -g -O -Wa,-alh,-L file.c
1475 This passes two options to the assembler: @samp{-alh} (emit a listing to
1476 standard output with high-level and assembly source) and @samp{-L} (retain
1477 local symbols in the symbol table).
1479 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1480 command-line options are automatically passed to the assembler by the compiler.
1481 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1482 precisely what options it passes to each compilation pass, including the
1488 * a:: -a[cdhlns] enable listings
1489 * alternate:: --alternate enable alternate macro syntax
1490 * D:: -D for compatibility
1491 * f:: -f to work faster
1492 * I:: -I for .include search path
1493 @ifclear DIFF-TBL-KLUGE
1494 * K:: -K for compatibility
1496 @ifset DIFF-TBL-KLUGE
1497 * K:: -K for difference tables
1500 * L:: -L to retain local labels
1501 * listing:: --listing-XXX to configure listing output
1502 * M:: -M or --mri to assemble in MRI compatibility mode
1503 * MD:: --MD for dependency tracking
1504 * o:: -o to name the object file
1505 * R:: -R to join data and text sections
1506 * statistics:: --statistics to see statistics about assembly
1507 * traditional-format:: --traditional-format for compatible output
1508 * v:: -v to announce version
1509 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1510 * Z:: -Z to make object file even after errors
1514 @section Enable Listings: @option{-a[cdhlns]}
1523 @cindex listings, enabling
1524 @cindex assembly listings, enabling
1526 These options enable listing output from the assembler. By itself,
1527 @samp{-a} requests high-level, assembly, and symbols listing.
1528 You can use other letters to select specific options for the list:
1529 @samp{-ah} requests a high-level language listing,
1530 @samp{-al} requests an output-program assembly listing, and
1531 @samp{-as} requests a symbol table listing.
1532 High-level listings require that a compiler debugging option like
1533 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1536 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1537 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1538 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1539 omitted from the listing.
1541 Use the @samp{-ad} option to omit debugging directives from the
1544 Once you have specified one of these options, you can further control
1545 listing output and its appearance using the directives @code{.list},
1546 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1548 The @samp{-an} option turns off all forms processing.
1549 If you do not request listing output with one of the @samp{-a} options, the
1550 listing-control directives have no effect.
1552 The letters after @samp{-a} may be combined into one option,
1553 @emph{e.g.}, @samp{-aln}.
1555 Note if the assembler source is coming from the standard input (eg because it
1556 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1557 is being used) then the listing will not contain any comments or preprocessor
1558 directives. This is because the listing code buffers input source lines from
1559 stdin only after they have been preprocessed by the assembler. This reduces
1560 memory usage and makes the code more efficient.
1563 @section @option{--alternate}
1566 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1569 @section @option{-D}
1572 This option has no effect whatsoever, but it is accepted to make it more
1573 likely that scripts written for other assemblers also work with
1574 @command{@value{AS}}.
1577 @section Work Faster: @option{-f}
1580 @cindex trusted compiler
1581 @cindex faster processing (@option{-f})
1582 @samp{-f} should only be used when assembling programs written by a
1583 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1584 and comment preprocessing on
1585 the input file(s) before assembling them. @xref{Preprocessing,
1589 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1590 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1595 @section @code{.include} Search Path: @option{-I} @var{path}
1597 @kindex -I @var{path}
1598 @cindex paths for @code{.include}
1599 @cindex search path for @code{.include}
1600 @cindex @code{include} directive search path
1601 Use this option to add a @var{path} to the list of directories
1602 @command{@value{AS}} searches for files specified in @code{.include}
1603 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1604 many times as necessary to include a variety of paths. The current
1605 working directory is always searched first; after that, @command{@value{AS}}
1606 searches any @samp{-I} directories in the same order as they were
1607 specified (left to right) on the command line.
1610 @section Difference Tables: @option{-K}
1613 @ifclear DIFF-TBL-KLUGE
1614 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1615 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1616 where it can be used to warn when the assembler alters the machine code
1617 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1618 family does not have the addressing limitations that sometimes lead to this
1619 alteration on other platforms.
1622 @ifset DIFF-TBL-KLUGE
1623 @cindex difference tables, warning
1624 @cindex warning for altered difference tables
1625 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1626 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1627 You can use the @samp{-K} option if you want a warning issued when this
1632 @section Include Local Labels: @option{-L}
1635 @cindex local labels, retaining in output
1636 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1637 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1638 debugging, because they are intended for the use of programs (like
1639 compilers) that compose assembler programs, not for your notice.
1640 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1641 normally debug with them.
1643 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1644 in the object file. Usually if you do this you also tell the linker
1645 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1647 By default, a local label is any label beginning with @samp{L}, but each
1648 target is allowed to redefine the local label prefix.
1650 On the HPPA local labels begin with @samp{L$}.
1654 @section Configuring listing output: @option{--listing}
1656 The listing feature of the assembler can be enabled via the command line switch
1657 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1658 hex dump of the corresponding locations in the output object file, and displays
1659 them as a listing file. The format of this listing can be controlled by pseudo
1660 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1661 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1664 @item --listing-lhs-width=@samp{number}
1665 @kindex --listing-lhs-width
1666 @cindex Width of first line disassembly output
1667 Sets the maximum width, in words, of the first line of the hex byte dump. This
1668 dump appears on the left hand side of the listing output.
1670 @item --listing-lhs-width2=@samp{number}
1671 @kindex --listing-lhs-width2
1672 @cindex Width of continuation lines of disassembly output
1673 Sets the maximum width, in words, of any further lines of the hex byte dump for
1674 a given input source line. If this value is not specified, it defaults to being
1675 the same as the value specified for @samp{--listing-lhs-width}. If neither
1676 switch is used the default is to one.
1678 @item --listing-rhs-width=@samp{number}
1679 @kindex --listing-rhs-width
1680 @cindex Width of source line output
1681 Sets the maximum width, in characters, of the source line that is displayed
1682 alongside the hex dump. The default value for this parameter is 100. The
1683 source line is displayed on the right hand side of the listing output.
1685 @item --listing-cont-lines=@samp{number}
1686 @kindex --listing-cont-lines
1687 @cindex Maximum number of continuation lines
1688 Sets the maximum number of continuation lines of hex dump that will be
1689 displayed for a given single line of source input. The default value is 4.
1693 @section Assemble in MRI Compatibility Mode: @option{-M}
1696 @cindex MRI compatibility mode
1697 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1698 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1699 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1700 configured target) assembler from Microtec Research. The exact nature of the
1701 MRI syntax will not be documented here; see the MRI manuals for more
1702 information. Note in particular that the handling of macros and macro
1703 arguments is somewhat different. The purpose of this option is to permit
1704 assembling existing MRI assembler code using @command{@value{AS}}.
1706 The MRI compatibility is not complete. Certain operations of the MRI assembler
1707 depend upon its object file format, and can not be supported using other object
1708 file formats. Supporting these would require enhancing each object file format
1709 individually. These are:
1712 @item global symbols in common section
1714 The m68k MRI assembler supports common sections which are merged by the linker.
1715 Other object file formats do not support this. @command{@value{AS}} handles
1716 common sections by treating them as a single common symbol. It permits local
1717 symbols to be defined within a common section, but it can not support global
1718 symbols, since it has no way to describe them.
1720 @item complex relocations
1722 The MRI assemblers support relocations against a negated section address, and
1723 relocations which combine the start addresses of two or more sections. These
1724 are not support by other object file formats.
1726 @item @code{END} pseudo-op specifying start address
1728 The MRI @code{END} pseudo-op permits the specification of a start address.
1729 This is not supported by other object file formats. The start address may
1730 instead be specified using the @option{-e} option to the linker, or in a linker
1733 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1735 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1736 name to the output file. This is not supported by other object file formats.
1738 @item @code{ORG} pseudo-op
1740 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1741 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1742 which changes the location within the current section. Absolute sections are
1743 not supported by other object file formats. The address of a section may be
1744 assigned within a linker script.
1747 There are some other features of the MRI assembler which are not supported by
1748 @command{@value{AS}}, typically either because they are difficult or because they
1749 seem of little consequence. Some of these may be supported in future releases.
1753 @item EBCDIC strings
1755 EBCDIC strings are not supported.
1757 @item packed binary coded decimal
1759 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1760 and @code{DCB.P} pseudo-ops are not supported.
1762 @item @code{FEQU} pseudo-op
1764 The m68k @code{FEQU} pseudo-op is not supported.
1766 @item @code{NOOBJ} pseudo-op
1768 The m68k @code{NOOBJ} pseudo-op is not supported.
1770 @item @code{OPT} branch control options
1772 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1773 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1774 relaxes all branches, whether forward or backward, to an appropriate size, so
1775 these options serve no purpose.
1777 @item @code{OPT} list control options
1779 The following m68k @code{OPT} list control options are ignored: @code{C},
1780 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1781 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1783 @item other @code{OPT} options
1785 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1786 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1788 @item @code{OPT} @code{D} option is default
1790 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1791 @code{OPT NOD} may be used to turn it off.
1793 @item @code{XREF} pseudo-op.
1795 The m68k @code{XREF} pseudo-op is ignored.
1797 @item @code{.debug} pseudo-op
1799 The i960 @code{.debug} pseudo-op is not supported.
1801 @item @code{.extended} pseudo-op
1803 The i960 @code{.extended} pseudo-op is not supported.
1805 @item @code{.list} pseudo-op.
1807 The various options of the i960 @code{.list} pseudo-op are not supported.
1809 @item @code{.optimize} pseudo-op
1811 The i960 @code{.optimize} pseudo-op is not supported.
1813 @item @code{.output} pseudo-op
1815 The i960 @code{.output} pseudo-op is not supported.
1817 @item @code{.setreal} pseudo-op
1819 The i960 @code{.setreal} pseudo-op is not supported.
1824 @section Dependency Tracking: @option{--MD}
1827 @cindex dependency tracking
1830 @command{@value{AS}} can generate a dependency file for the file it creates. This
1831 file consists of a single rule suitable for @code{make} describing the
1832 dependencies of the main source file.
1834 The rule is written to the file named in its argument.
1836 This feature is used in the automatic updating of makefiles.
1839 @section Name the Object File: @option{-o}
1842 @cindex naming object file
1843 @cindex object file name
1844 There is always one object file output when you run @command{@value{AS}}. By
1845 default it has the name
1848 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1862 You use this option (which takes exactly one filename) to give the
1863 object file a different name.
1865 Whatever the object file is called, @command{@value{AS}} overwrites any
1866 existing file of the same name.
1869 @section Join Data and Text Sections: @option{-R}
1872 @cindex data and text sections, joining
1873 @cindex text and data sections, joining
1874 @cindex joining text and data sections
1875 @cindex merging text and data sections
1876 @option{-R} tells @command{@value{AS}} to write the object file as if all
1877 data-section data lives in the text section. This is only done at
1878 the very last moment: your binary data are the same, but data
1879 section parts are relocated differently. The data section part of
1880 your object file is zero bytes long because all its bytes are
1881 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1883 When you specify @option{-R} it would be possible to generate shorter
1884 address displacements (because we do not have to cross between text and
1885 data section). We refrain from doing this simply for compatibility with
1886 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1889 When @command{@value{AS}} is configured for COFF or ELF output,
1890 this option is only useful if you use sections named @samp{.text} and
1895 @option{-R} is not supported for any of the HPPA targets. Using
1896 @option{-R} generates a warning from @command{@value{AS}}.
1900 @section Display Assembly Statistics: @option{--statistics}
1902 @kindex --statistics
1903 @cindex statistics, about assembly
1904 @cindex time, total for assembly
1905 @cindex space used, maximum for assembly
1906 Use @samp{--statistics} to display two statistics about the resources used by
1907 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1908 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1911 @node traditional-format
1912 @section Compatible Output: @option{--traditional-format}
1914 @kindex --traditional-format
1915 For some targets, the output of @command{@value{AS}} is different in some ways
1916 from the output of some existing assembler. This switch requests
1917 @command{@value{AS}} to use the traditional format instead.
1919 For example, it disables the exception frame optimizations which
1920 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1923 @section Announce Version: @option{-v}
1927 @cindex assembler version
1928 @cindex version of assembler
1929 You can find out what version of as is running by including the
1930 option @samp{-v} (which you can also spell as @samp{-version}) on the
1934 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1936 @command{@value{AS}} should never give a warning or error message when
1937 assembling compiler output. But programs written by people often
1938 cause @command{@value{AS}} to give a warning that a particular assumption was
1939 made. All such warnings are directed to the standard error file.
1943 @cindex suppressing warnings
1944 @cindex warnings, suppressing
1945 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1946 This only affects the warning messages: it does not change any particular of
1947 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1950 @kindex --fatal-warnings
1951 @cindex errors, caused by warnings
1952 @cindex warnings, causing error
1953 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
1954 files that generate warnings to be in error.
1957 @cindex warnings, switching on
1958 You can switch these options off again by specifying @option{--warn}, which
1959 causes warnings to be output as usual.
1962 @section Generate Object File in Spite of Errors: @option{-Z}
1963 @cindex object file, after errors
1964 @cindex errors, continuing after
1965 After an error message, @command{@value{AS}} normally produces no output. If for
1966 some reason you are interested in object file output even after
1967 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
1968 option. If there are any errors, @command{@value{AS}} continues anyways, and
1969 writes an object file after a final warning message of the form @samp{@var{n}
1970 errors, @var{m} warnings, generating bad object file.}
1975 @cindex machine-independent syntax
1976 @cindex syntax, machine-independent
1977 This chapter describes the machine-independent syntax allowed in a
1978 source file. @command{@value{AS}} syntax is similar to what many other
1979 assemblers use; it is inspired by the BSD 4.2
1984 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
1988 * Preprocessing:: Preprocessing
1989 * Whitespace:: Whitespace
1990 * Comments:: Comments
1991 * Symbol Intro:: Symbols
1992 * Statements:: Statements
1993 * Constants:: Constants
1997 @section Preprocessing
1999 @cindex preprocessing
2000 The @command{@value{AS}} internal preprocessor:
2002 @cindex whitespace, removed by preprocessor
2004 adjusts and removes extra whitespace. It leaves one space or tab before
2005 the keywords on a line, and turns any other whitespace on the line into
2008 @cindex comments, removed by preprocessor
2010 removes all comments, replacing them with a single space, or an
2011 appropriate number of newlines.
2013 @cindex constants, converted by preprocessor
2015 converts character constants into the appropriate numeric values.
2018 It does not do macro processing, include file handling, or
2019 anything else you may get from your C compiler's preprocessor. You can
2020 do include file processing with the @code{.include} directive
2021 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2022 to get other ``CPP'' style preprocessing by giving the input file a
2023 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
2024 Output, gcc.info, Using GNU CC}.
2026 Excess whitespace, comments, and character constants
2027 cannot be used in the portions of the input text that are not
2030 @cindex turning preprocessing on and off
2031 @cindex preprocessing, turning on and off
2034 If the first line of an input file is @code{#NO_APP} or if you use the
2035 @samp{-f} option, whitespace and comments are not removed from the input file.
2036 Within an input file, you can ask for whitespace and comment removal in
2037 specific portions of the by putting a line that says @code{#APP} before the
2038 text that may contain whitespace or comments, and putting a line that says
2039 @code{#NO_APP} after this text. This feature is mainly intend to support
2040 @code{asm} statements in compilers whose output is otherwise free of comments
2047 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2048 Whitespace is used to separate symbols, and to make programs neater for
2049 people to read. Unless within character constants
2050 (@pxref{Characters,,Character Constants}), any whitespace means the same
2051 as exactly one space.
2057 There are two ways of rendering comments to @command{@value{AS}}. In both
2058 cases the comment is equivalent to one space.
2060 Anything from @samp{/*} through the next @samp{*/} is a comment.
2061 This means you may not nest these comments.
2065 The only way to include a newline ('\n') in a comment
2066 is to use this sort of comment.
2069 /* This sort of comment does not nest. */
2072 @cindex line comment character
2073 Anything from the @dfn{line comment} character to the next newline
2074 is considered a comment and is ignored. The line comment character is
2076 @samp{;} on the ARC;
2079 @samp{@@} on the ARM;
2082 @samp{;} for the H8/300 family;
2085 @samp{;} for the HPPA;
2088 @samp{#} on the i386 and x86-64;
2091 @samp{#} on the i960;
2094 @samp{;} for the PDP-11;
2097 @samp{;} for picoJava;
2100 @samp{#} for Motorola PowerPC;
2103 @samp{!} for the Renesas / SuperH SH;
2106 @samp{!} on the SPARC;
2109 @samp{#} on the ip2k;
2112 @samp{#} on the m32c;
2115 @samp{#} on the m32r;
2118 @samp{|} on the 680x0;
2121 @samp{#} on the 68HC11 and 68HC12;
2124 @samp{#} on the Vax;
2127 @samp{!} for the Z8000;
2130 @samp{#} on the V850;
2133 @samp{#} for Xtensa systems;
2135 see @ref{Machine Dependencies}. @refill
2136 @c FIXME What about i860?
2139 On some machines there are two different line comment characters. One
2140 character only begins a comment if it is the first non-whitespace character on
2141 a line, while the other always begins a comment.
2145 The V850 assembler also supports a double dash as starting a comment that
2146 extends to the end of the line.
2152 @cindex lines starting with @code{#}
2153 @cindex logical line numbers
2154 To be compatible with past assemblers, lines that begin with @samp{#} have a
2155 special interpretation. Following the @samp{#} should be an absolute
2156 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2157 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2158 new logical file name. The rest of the line, if any, should be whitespace.
2160 If the first non-whitespace characters on the line are not numeric,
2161 the line is ignored. (Just like a comment.)
2164 # This is an ordinary comment.
2165 # 42-6 "new_file_name" # New logical file name
2166 # This is logical line # 36.
2168 This feature is deprecated, and may disappear from future versions
2169 of @command{@value{AS}}.
2174 @cindex characters used in symbols
2175 @ifclear SPECIAL-SYMS
2176 A @dfn{symbol} is one or more characters chosen from the set of all
2177 letters (both upper and lower case), digits and the three characters
2183 A @dfn{symbol} is one or more characters chosen from the set of all
2184 letters (both upper and lower case), digits and the three characters
2185 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2191 On most machines, you can also use @code{$} in symbol names; exceptions
2192 are noted in @ref{Machine Dependencies}.
2194 No symbol may begin with a digit. Case is significant.
2195 There is no length limit: all characters are significant. Symbols are
2196 delimited by characters not in that set, or by the beginning of a file
2197 (since the source program must end with a newline, the end of a file is
2198 not a possible symbol delimiter). @xref{Symbols}.
2199 @cindex length of symbols
2204 @cindex statements, structure of
2205 @cindex line separator character
2206 @cindex statement separator character
2208 @ifclear abnormal-separator
2209 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2210 semicolon (@samp{;}). The newline or semicolon is considered part of
2211 the preceding statement. Newlines and semicolons within character
2212 constants are an exception: they do not end statements.
2214 @ifset abnormal-separator
2216 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2217 point (@samp{!}). The newline or exclamation point is considered part of the
2218 preceding statement. Newlines and exclamation points within character
2219 constants are an exception: they do not end statements.
2222 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2223 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2224 (@samp{;}). The newline or separator character is considered part of
2225 the preceding statement. Newlines and separators within character
2226 constants are an exception: they do not end statements.
2231 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2232 separator character. (The line separator is usually @samp{;}, unless
2233 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2234 newline or separator character is considered part of the preceding
2235 statement. Newlines and separators within character constants are an
2236 exception: they do not end statements.
2239 @cindex newline, required at file end
2240 @cindex EOF, newline must precede
2241 It is an error to end any statement with end-of-file: the last
2242 character of any input file should be a newline.@refill
2244 An empty statement is allowed, and may include whitespace. It is ignored.
2246 @cindex instructions and directives
2247 @cindex directives and instructions
2248 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2249 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2251 A statement begins with zero or more labels, optionally followed by a
2252 key symbol which determines what kind of statement it is. The key
2253 symbol determines the syntax of the rest of the statement. If the
2254 symbol begins with a dot @samp{.} then the statement is an assembler
2255 directive: typically valid for any computer. If the symbol begins with
2256 a letter the statement is an assembly language @dfn{instruction}: it
2257 assembles into a machine language instruction.
2259 Different versions of @command{@value{AS}} for different computers
2260 recognize different instructions. In fact, the same symbol may
2261 represent a different instruction in a different computer's assembly
2265 @cindex @code{:} (label)
2266 @cindex label (@code{:})
2267 A label is a symbol immediately followed by a colon (@code{:}).
2268 Whitespace before a label or after a colon is permitted, but you may not
2269 have whitespace between a label's symbol and its colon. @xref{Labels}.
2272 For HPPA targets, labels need not be immediately followed by a colon, but
2273 the definition of a label must begin in column zero. This also implies that
2274 only one label may be defined on each line.
2278 label: .directive followed by something
2279 another_label: # This is an empty statement.
2280 instruction operand_1, operand_2, @dots{}
2287 A constant is a number, written so that its value is known by
2288 inspection, without knowing any context. Like this:
2291 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2292 .ascii "Ring the bell\7" # A string constant.
2293 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2294 .float 0f-314159265358979323846264338327\
2295 95028841971.693993751E-40 # - pi, a flonum.
2300 * Characters:: Character Constants
2301 * Numbers:: Number Constants
2305 @subsection Character Constants
2307 @cindex character constants
2308 @cindex constants, character
2309 There are two kinds of character constants. A @dfn{character} stands
2310 for one character in one byte and its value may be used in
2311 numeric expressions. String constants (properly called string
2312 @emph{literals}) are potentially many bytes and their values may not be
2313 used in arithmetic expressions.
2317 * Chars:: Characters
2321 @subsubsection Strings
2323 @cindex string constants
2324 @cindex constants, string
2325 A @dfn{string} is written between double-quotes. It may contain
2326 double-quotes or null characters. The way to get special characters
2327 into a string is to @dfn{escape} these characters: precede them with
2328 a backslash @samp{\} character. For example @samp{\\} represents
2329 one backslash: the first @code{\} is an escape which tells
2330 @command{@value{AS}} to interpret the second character literally as a backslash
2331 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2332 escape character). The complete list of escapes follows.
2334 @cindex escape codes, character
2335 @cindex character escape codes
2338 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2340 @cindex @code{\b} (backspace character)
2341 @cindex backspace (@code{\b})
2343 Mnemonic for backspace; for ASCII this is octal code 010.
2346 @c Mnemonic for EOText; for ASCII this is octal code 004.
2348 @cindex @code{\f} (formfeed character)
2349 @cindex formfeed (@code{\f})
2351 Mnemonic for FormFeed; for ASCII this is octal code 014.
2353 @cindex @code{\n} (newline character)
2354 @cindex newline (@code{\n})
2356 Mnemonic for newline; for ASCII this is octal code 012.
2359 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2361 @cindex @code{\r} (carriage return character)
2362 @cindex carriage return (@code{\r})
2364 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2367 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2368 @c other assemblers.
2370 @cindex @code{\t} (tab)
2371 @cindex tab (@code{\t})
2373 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2376 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2377 @c @item \x @var{digit} @var{digit} @var{digit}
2378 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2380 @cindex @code{\@var{ddd}} (octal character code)
2381 @cindex octal character code (@code{\@var{ddd}})
2382 @item \ @var{digit} @var{digit} @var{digit}
2383 An octal character code. The numeric code is 3 octal digits.
2384 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2385 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2387 @cindex @code{\@var{xd...}} (hex character code)
2388 @cindex hex character code (@code{\@var{xd...}})
2389 @item \@code{x} @var{hex-digits...}
2390 A hex character code. All trailing hex digits are combined. Either upper or
2391 lower case @code{x} works.
2393 @cindex @code{\\} (@samp{\} character)
2394 @cindex backslash (@code{\\})
2396 Represents one @samp{\} character.
2399 @c Represents one @samp{'} (accent acute) character.
2400 @c This is needed in single character literals
2401 @c (@xref{Characters,,Character Constants}.) to represent
2404 @cindex @code{\"} (doublequote character)
2405 @cindex doublequote (@code{\"})
2407 Represents one @samp{"} character. Needed in strings to represent
2408 this character, because an unescaped @samp{"} would end the string.
2410 @item \ @var{anything-else}
2411 Any other character when escaped by @kbd{\} gives a warning, but
2412 assembles as if the @samp{\} was not present. The idea is that if
2413 you used an escape sequence you clearly didn't want the literal
2414 interpretation of the following character. However @command{@value{AS}} has no
2415 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2416 code and warns you of the fact.
2419 Which characters are escapable, and what those escapes represent,
2420 varies widely among assemblers. The current set is what we think
2421 the BSD 4.2 assembler recognizes, and is a subset of what most C
2422 compilers recognize. If you are in doubt, do not use an escape
2426 @subsubsection Characters
2428 @cindex single character constant
2429 @cindex character, single
2430 @cindex constant, single character
2431 A single character may be written as a single quote immediately
2432 followed by that character. The same escapes apply to characters as
2433 to strings. So if you want to write the character backslash, you
2434 must write @kbd{'\\} where the first @code{\} escapes the second
2435 @code{\}. As you can see, the quote is an acute accent, not a
2436 grave accent. A newline
2438 @ifclear abnormal-separator
2439 (or semicolon @samp{;})
2441 @ifset abnormal-separator
2443 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2448 immediately following an acute accent is taken as a literal character
2449 and does not count as the end of a statement. The value of a character
2450 constant in a numeric expression is the machine's byte-wide code for
2451 that character. @command{@value{AS}} assumes your character code is ASCII:
2452 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2455 @subsection Number Constants
2457 @cindex constants, number
2458 @cindex number constants
2459 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2460 are stored in the target machine. @emph{Integers} are numbers that
2461 would fit into an @code{int} in the C language. @emph{Bignums} are
2462 integers, but they are stored in more than 32 bits. @emph{Flonums}
2463 are floating point numbers, described below.
2466 * Integers:: Integers
2471 * Bit Fields:: Bit Fields
2477 @subsubsection Integers
2479 @cindex constants, integer
2481 @cindex binary integers
2482 @cindex integers, binary
2483 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2484 the binary digits @samp{01}.
2486 @cindex octal integers
2487 @cindex integers, octal
2488 An octal integer is @samp{0} followed by zero or more of the octal
2489 digits (@samp{01234567}).
2491 @cindex decimal integers
2492 @cindex integers, decimal
2493 A decimal integer starts with a non-zero digit followed by zero or
2494 more digits (@samp{0123456789}).
2496 @cindex hexadecimal integers
2497 @cindex integers, hexadecimal
2498 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2499 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2501 Integers have the usual values. To denote a negative integer, use
2502 the prefix operator @samp{-} discussed under expressions
2503 (@pxref{Prefix Ops,,Prefix Operators}).
2506 @subsubsection Bignums
2509 @cindex constants, bignum
2510 A @dfn{bignum} has the same syntax and semantics as an integer
2511 except that the number (or its negative) takes more than 32 bits to
2512 represent in binary. The distinction is made because in some places
2513 integers are permitted while bignums are not.
2516 @subsubsection Flonums
2518 @cindex floating point numbers
2519 @cindex constants, floating point
2521 @cindex precision, floating point
2522 A @dfn{flonum} represents a floating point number. The translation is
2523 indirect: a decimal floating point number from the text is converted by
2524 @command{@value{AS}} to a generic binary floating point number of more than
2525 sufficient precision. This generic floating point number is converted
2526 to a particular computer's floating point format (or formats) by a
2527 portion of @command{@value{AS}} specialized to that computer.
2529 A flonum is written by writing (in order)
2534 (@samp{0} is optional on the HPPA.)
2538 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2540 @kbd{e} is recommended. Case is not important.
2542 @c FIXME: verify if flonum syntax really this vague for most cases
2543 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2544 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2547 On the H8/300, Renesas / SuperH SH,
2548 and AMD 29K architectures, the letter must be
2549 one of the letters @samp{DFPRSX} (in upper or lower case).
2551 On the ARC, the letter must be one of the letters @samp{DFRS}
2552 (in upper or lower case).
2554 On the Intel 960 architecture, the letter must be
2555 one of the letters @samp{DFT} (in upper or lower case).
2557 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2561 One of the letters @samp{DFRS} (in upper or lower case).
2564 One of the letters @samp{DFPRSX} (in upper or lower case).
2567 The letter @samp{E} (upper case only).
2570 One of the letters @samp{DFT} (in upper or lower case).
2575 An optional sign: either @samp{+} or @samp{-}.
2578 An optional @dfn{integer part}: zero or more decimal digits.
2581 An optional @dfn{fractional part}: @samp{.} followed by zero
2582 or more decimal digits.
2585 An optional exponent, consisting of:
2589 An @samp{E} or @samp{e}.
2590 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2591 @c principle this can perfectly well be different on different targets.
2593 Optional sign: either @samp{+} or @samp{-}.
2595 One or more decimal digits.
2600 At least one of the integer part or the fractional part must be
2601 present. The floating point number has the usual base-10 value.
2603 @command{@value{AS}} does all processing using integers. Flonums are computed
2604 independently of any floating point hardware in the computer running
2605 @command{@value{AS}}.
2609 @c Bit fields are written as a general facility but are also controlled
2610 @c by a conditional-compilation flag---which is as of now (21mar91)
2611 @c turned on only by the i960 config of GAS.
2613 @subsubsection Bit Fields
2616 @cindex constants, bit field
2617 You can also define numeric constants as @dfn{bit fields}.
2618 specify two numbers separated by a colon---
2620 @var{mask}:@var{value}
2623 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2626 The resulting number is then packed
2628 @c this conditional paren in case bit fields turned on elsewhere than 960
2629 (in host-dependent byte order)
2631 into a field whose width depends on which assembler directive has the
2632 bit-field as its argument. Overflow (a result from the bitwise and
2633 requiring more binary digits to represent) is not an error; instead,
2634 more constants are generated, of the specified width, beginning with the
2635 least significant digits.@refill
2637 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2638 @code{.short}, and @code{.word} accept bit-field arguments.
2643 @chapter Sections and Relocation
2648 * Secs Background:: Background
2649 * Ld Sections:: Linker Sections
2650 * As Sections:: Assembler Internal Sections
2651 * Sub-Sections:: Sub-Sections
2655 @node Secs Background
2658 Roughly, a section is a range of addresses, with no gaps; all data
2659 ``in'' those addresses is treated the same for some particular purpose.
2660 For example there may be a ``read only'' section.
2662 @cindex linker, and assembler
2663 @cindex assembler, and linker
2664 The linker @code{@value{LD}} reads many object files (partial programs) and
2665 combines their contents to form a runnable program. When @command{@value{AS}}
2666 emits an object file, the partial program is assumed to start at address 0.
2667 @code{@value{LD}} assigns the final addresses for the partial program, so that
2668 different partial programs do not overlap. This is actually an
2669 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2672 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2673 addresses. These blocks slide to their run-time addresses as rigid
2674 units; their length does not change and neither does the order of bytes
2675 within them. Such a rigid unit is called a @emph{section}. Assigning
2676 run-time addresses to sections is called @dfn{relocation}. It includes
2677 the task of adjusting mentions of object-file addresses so they refer to
2678 the proper run-time addresses.
2680 For the H8/300, and for the Renesas / SuperH SH,
2681 @command{@value{AS}} pads sections if needed to
2682 ensure they end on a word (sixteen bit) boundary.
2685 @cindex standard assembler sections
2686 An object file written by @command{@value{AS}} has at least three sections, any
2687 of which may be empty. These are named @dfn{text}, @dfn{data} and
2692 When it generates COFF or ELF output,
2694 @command{@value{AS}} can also generate whatever other named sections you specify
2695 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2696 If you do not use any directives that place output in the @samp{.text}
2697 or @samp{.data} sections, these sections still exist, but are empty.
2702 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2704 @command{@value{AS}} can also generate whatever other named sections you
2705 specify using the @samp{.space} and @samp{.subspace} directives. See
2706 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2707 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2708 assembler directives.
2711 Additionally, @command{@value{AS}} uses different names for the standard
2712 text, data, and bss sections when generating SOM output. Program text
2713 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2714 BSS into @samp{$BSS$}.
2718 Within the object file, the text section starts at address @code{0}, the
2719 data section follows, and the bss section follows the data section.
2722 When generating either SOM or ELF output files on the HPPA, the text
2723 section starts at address @code{0}, the data section at address
2724 @code{0x4000000}, and the bss section follows the data section.
2727 To let @code{@value{LD}} know which data changes when the sections are
2728 relocated, and how to change that data, @command{@value{AS}} also writes to the
2729 object file details of the relocation needed. To perform relocation
2730 @code{@value{LD}} must know, each time an address in the object
2734 Where in the object file is the beginning of this reference to
2737 How long (in bytes) is this reference?
2739 Which section does the address refer to? What is the numeric value of
2741 (@var{address}) @minus{} (@var{start-address of section})?
2744 Is the reference to an address ``Program-Counter relative''?
2747 @cindex addresses, format of
2748 @cindex section-relative addressing
2749 In fact, every address @command{@value{AS}} ever uses is expressed as
2751 (@var{section}) + (@var{offset into section})
2754 Further, most expressions @command{@value{AS}} computes have this section-relative
2757 (For some object formats, such as SOM for the HPPA, some expressions are
2758 symbol-relative instead.)
2761 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2762 @var{N} into section @var{secname}.''
2764 Apart from text, data and bss sections you need to know about the
2765 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2766 addresses in the absolute section remain unchanged. For example, address
2767 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2768 @code{@value{LD}}. Although the linker never arranges two partial programs'
2769 data sections with overlapping addresses after linking, @emph{by definition}
2770 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2771 part of a program is always the same address when the program is running as
2772 address @code{@{absolute@ 239@}} in any other part of the program.
2774 The idea of sections is extended to the @dfn{undefined} section. Any
2775 address whose section is unknown at assembly time is by definition
2776 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2777 Since numbers are always defined, the only way to generate an undefined
2778 address is to mention an undefined symbol. A reference to a named
2779 common block would be such a symbol: its value is unknown at assembly
2780 time so it has section @emph{undefined}.
2782 By analogy the word @emph{section} is used to describe groups of sections in
2783 the linked program. @code{@value{LD}} puts all partial programs' text
2784 sections in contiguous addresses in the linked program. It is
2785 customary to refer to the @emph{text section} of a program, meaning all
2786 the addresses of all partial programs' text sections. Likewise for
2787 data and bss sections.
2789 Some sections are manipulated by @code{@value{LD}}; others are invented for
2790 use of @command{@value{AS}} and have no meaning except during assembly.
2793 @section Linker Sections
2794 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2799 @cindex named sections
2800 @cindex sections, named
2801 @item named sections
2804 @cindex text section
2805 @cindex data section
2809 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2810 separate but equal sections. Anything you can say of one section is
2813 When the program is running, however, it is
2814 customary for the text section to be unalterable. The
2815 text section is often shared among processes: it contains
2816 instructions, constants and the like. The data section of a running
2817 program is usually alterable: for example, C variables would be stored
2818 in the data section.
2823 This section contains zeroed bytes when your program begins running. It
2824 is used to hold uninitialized variables or common storage. The length of
2825 each partial program's bss section is important, but because it starts
2826 out containing zeroed bytes there is no need to store explicit zero
2827 bytes in the object file. The bss section was invented to eliminate
2828 those explicit zeros from object files.
2830 @cindex absolute section
2831 @item absolute section
2832 Address 0 of this section is always ``relocated'' to runtime address 0.
2833 This is useful if you want to refer to an address that @code{@value{LD}} must
2834 not change when relocating. In this sense we speak of absolute
2835 addresses being ``unrelocatable'': they do not change during relocation.
2837 @cindex undefined section
2838 @item undefined section
2839 This ``section'' is a catch-all for address references to objects not in
2840 the preceding sections.
2841 @c FIXME: ref to some other doc on obj-file formats could go here.
2844 @cindex relocation example
2845 An idealized example of three relocatable sections follows.
2847 The example uses the traditional section names @samp{.text} and @samp{.data}.
2849 Memory addresses are on the horizontal axis.
2853 @c END TEXI2ROFF-KILL
2856 partial program # 1: |ttttt|dddd|00|
2863 partial program # 2: |TTT|DDD|000|
2866 +--+---+-----+--+----+---+-----+~~
2867 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2868 +--+---+-----+--+----+---+-----+~~
2870 addresses: 0 @dots{}
2877 \line{\it Partial program \#1: \hfil}
2878 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2879 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2881 \line{\it Partial program \#2: \hfil}
2882 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2883 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2885 \line{\it linked program: \hfil}
2886 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2887 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2888 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2889 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2891 \line{\it addresses: \hfil}
2895 @c END TEXI2ROFF-KILL
2898 @section Assembler Internal Sections
2900 @cindex internal assembler sections
2901 @cindex sections in messages, internal
2902 These sections are meant only for the internal use of @command{@value{AS}}. They
2903 have no meaning at run-time. You do not really need to know about these
2904 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2905 warning messages, so it might be helpful to have an idea of their
2906 meanings to @command{@value{AS}}. These sections are used to permit the
2907 value of every expression in your assembly language program to be a
2908 section-relative address.
2911 @cindex assembler internal logic error
2912 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2913 An internal assembler logic error has been found. This means there is a
2914 bug in the assembler.
2916 @cindex expr (internal section)
2918 The assembler stores complex expression internally as combinations of
2919 symbols. When it needs to represent an expression as a symbol, it puts
2920 it in the expr section.
2922 @c FIXME item transfer[t] vector preload
2923 @c FIXME item transfer[t] vector postload
2924 @c FIXME item register
2928 @section Sub-Sections
2930 @cindex numbered subsections
2931 @cindex grouping data
2937 fall into two sections: text and data.
2939 You may have separate groups of
2941 data in named sections
2945 data in named sections
2951 that you want to end up near to each other in the object file, even though they
2952 are not contiguous in the assembler source. @command{@value{AS}} allows you to
2953 use @dfn{subsections} for this purpose. Within each section, there can be
2954 numbered subsections with values from 0 to 8192. Objects assembled into the
2955 same subsection go into the object file together with other objects in the same
2956 subsection. For example, a compiler might want to store constants in the text
2957 section, but might not want to have them interspersed with the program being
2958 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2959 section of code being output, and a @samp{.text 1} before each group of
2960 constants being output.
2962 Subsections are optional. If you do not use subsections, everything
2963 goes in subsection number zero.
2966 Each subsection is zero-padded up to a multiple of four bytes.
2967 (Subsections may be padded a different amount on different flavors
2968 of @command{@value{AS}}.)
2972 On the H8/300 platform, each subsection is zero-padded to a word
2973 boundary (two bytes).
2974 The same is true on the Renesas SH.
2977 @c FIXME section padding (alignment)?
2978 @c Rich Pixley says padding here depends on target obj code format; that
2979 @c doesn't seem particularly useful to say without further elaboration,
2980 @c so for now I say nothing about it. If this is a generic BFD issue,
2981 @c these paragraphs might need to vanish from this manual, and be
2982 @c discussed in BFD chapter of binutils (or some such).
2986 Subsections appear in your object file in numeric order, lowest numbered
2987 to highest. (All this to be compatible with other people's assemblers.)
2988 The object file contains no representation of subsections; @code{@value{LD}} and
2989 other programs that manipulate object files see no trace of them.
2990 They just see all your text subsections as a text section, and all your
2991 data subsections as a data section.
2993 To specify which subsection you want subsequent statements assembled
2994 into, use a numeric argument to specify it, in a @samp{.text
2995 @var{expression}} or a @samp{.data @var{expression}} statement.
2998 When generating COFF output, you
3003 can also use an extra subsection
3004 argument with arbitrary named sections: @samp{.section @var{name},
3009 When generating ELF output, you
3014 can also use the @code{.subsection} directive (@pxref{SubSection})
3015 to specify a subsection: @samp{.subsection @var{expression}}.
3017 @var{Expression} should be an absolute expression.
3018 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
3019 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3020 begins in @code{text 0}. For instance:
3022 .text 0 # The default subsection is text 0 anyway.
3023 .ascii "This lives in the first text subsection. *"
3025 .ascii "But this lives in the second text subsection."
3027 .ascii "This lives in the data section,"
3028 .ascii "in the first data subsection."
3030 .ascii "This lives in the first text section,"
3031 .ascii "immediately following the asterisk (*)."
3034 Each section has a @dfn{location counter} incremented by one for every byte
3035 assembled into that section. Because subsections are merely a convenience
3036 restricted to @command{@value{AS}} there is no concept of a subsection location
3037 counter. There is no way to directly manipulate a location counter---but the
3038 @code{.align} directive changes it, and any label definition captures its
3039 current value. The location counter of the section where statements are being
3040 assembled is said to be the @dfn{active} location counter.
3043 @section bss Section
3046 @cindex common variable storage
3047 The bss section is used for local common variable storage.
3048 You may allocate address space in the bss section, but you may
3049 not dictate data to load into it before your program executes. When
3050 your program starts running, all the contents of the bss
3051 section are zeroed bytes.
3053 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3054 @ref{Lcomm,,@code{.lcomm}}.
3056 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3057 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
3060 When assembling for a target which supports multiple sections, such as ELF or
3061 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3062 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3063 section. Typically the section will only contain symbol definitions and
3064 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3071 Symbols are a central concept: the programmer uses symbols to name
3072 things, the linker uses symbols to link, and the debugger uses symbols
3076 @cindex debuggers, and symbol order
3077 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3078 the same order they were declared. This may break some debuggers.
3083 * Setting Symbols:: Giving Symbols Other Values
3084 * Symbol Names:: Symbol Names
3085 * Dot:: The Special Dot Symbol
3086 * Symbol Attributes:: Symbol Attributes
3093 A @dfn{label} is written as a symbol immediately followed by a colon
3094 @samp{:}. The symbol then represents the current value of the
3095 active location counter, and is, for example, a suitable instruction
3096 operand. You are warned if you use the same symbol to represent two
3097 different locations: the first definition overrides any other
3101 On the HPPA, the usual form for a label need not be immediately followed by a
3102 colon, but instead must start in column zero. Only one label may be defined on
3103 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3104 provides a special directive @code{.label} for defining labels more flexibly.
3107 @node Setting Symbols
3108 @section Giving Symbols Other Values
3110 @cindex assigning values to symbols
3111 @cindex symbol values, assigning
3112 A symbol can be given an arbitrary value by writing a symbol, followed
3113 by an equals sign @samp{=}, followed by an expression
3114 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3115 directive. @xref{Set,,@code{.set}}.
3118 @section Symbol Names
3120 @cindex symbol names
3121 @cindex names, symbol
3122 @ifclear SPECIAL-SYMS
3123 Symbol names begin with a letter or with one of @samp{._}. On most
3124 machines, you can also use @code{$} in symbol names; exceptions are
3125 noted in @ref{Machine Dependencies}. That character may be followed by any
3126 string of digits, letters, dollar signs (unless otherwise noted in
3127 @ref{Machine Dependencies}), and underscores.
3131 Symbol names begin with a letter or with one of @samp{._}. On the
3132 Renesas SH you can also use @code{$} in symbol names. That
3133 character may be followed by any string of digits, letters, dollar signs (save
3134 on the H8/300), and underscores.
3138 Case of letters is significant: @code{foo} is a different symbol name
3141 Each symbol has exactly one name. Each name in an assembly language program
3142 refers to exactly one symbol. You may use that symbol name any number of times
3145 @subheading Local Symbol Names
3147 @cindex local symbol names
3148 @cindex symbol names, local
3149 @cindex temporary symbol names
3150 @cindex symbol names, temporary
3151 Local symbols help compilers and programmers use names temporarily.
3152 They create symbols which are guaranteed to be unique over the entire scope of
3153 the input source code and which can be referred to by a simple notation.
3154 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3155 represents any positive integer). To refer to the most recent previous
3156 definition of that symbol write @samp{@b{N}b}, using the same number as when
3157 you defined the label. To refer to the next definition of a local label, write
3158 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3161 There is no restriction on how you can use these labels, and you can reuse them
3162 too. So that it is possible to repeatedly define the same local label (using
3163 the same number @samp{@b{N}}), although you can only refer to the most recently
3164 defined local label of that number (for a backwards reference) or the next
3165 definition of a specific local label for a forward reference. It is also worth
3166 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3167 implemented in a slightly more efficient manner than the others.
3178 Which is the equivalent of:
3181 label_1: branch label_3
3182 label_2: branch label_1
3183 label_3: branch label_4
3184 label_4: branch label_3
3187 Local symbol names are only a notational device. They are immediately
3188 transformed into more conventional symbol names before the assembler uses them.
3189 The symbol names stored in the symbol table, appearing in error messages and
3190 optionally emitted to the object file. The names are constructed using these
3195 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3196 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3197 used for symbols you are never intended to see. If you use the
3198 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3199 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3200 you may use them in debugging.
3203 This is the number that was used in the local label definition. So if the
3204 label is written @samp{55:} then the number is @samp{55}.
3207 This unusual character is included so you do not accidentally invent a symbol
3208 of the same name. The character has ASCII value of @samp{\002} (control-B).
3210 @item @emph{ordinal number}
3211 This is a serial number to keep the labels distinct. The first definition of
3212 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3213 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3214 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3217 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3218 @code{3:} is named @code{L3@kbd{C-B}44}.
3220 @subheading Dollar Local Labels
3221 @cindex dollar local symbols
3223 @code{@value{AS}} also supports an even more local form of local labels called
3224 dollar labels. These labels go out of scope (ie they become undefined) as soon
3225 as a non-local label is defined. Thus they remain valid for only a small
3226 region of the input source code. Normal local labels, by contrast, remain in
3227 scope for the entire file, or until they are redefined by another occurrence of
3228 the same local label.
3230 Dollar labels are defined in exactly the same way as ordinary local labels,
3231 except that instead of being terminated by a colon, they are terminated by a
3232 dollar sign. eg @samp{@b{55$}}.
3234 They can also be distinguished from ordinary local labels by their transformed
3235 name which uses ASCII character @samp{\001} (control-A) as the magic character
3236 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3237 is named @samp{L6@kbd{C-A}5}.
3240 @section The Special Dot Symbol
3242 @cindex dot (symbol)
3243 @cindex @code{.} (symbol)
3244 @cindex current address
3245 @cindex location counter
3246 The special symbol @samp{.} refers to the current address that
3247 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3248 .long .} defines @code{melvin} to contain its own address.
3249 Assigning a value to @code{.} is treated the same as a @code{.org}
3250 directive. Thus, the expression @samp{.=.+4} is the same as saying
3251 @ifclear no-space-dir
3255 @node Symbol Attributes
3256 @section Symbol Attributes
3258 @cindex symbol attributes
3259 @cindex attributes, symbol
3260 Every symbol has, as well as its name, the attributes ``Value'' and
3261 ``Type''. Depending on output format, symbols can also have auxiliary
3264 The detailed definitions are in @file{a.out.h}.
3267 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3268 all these attributes, and probably won't warn you. This makes the
3269 symbol an externally defined symbol, which is generally what you
3273 * Symbol Value:: Value
3274 * Symbol Type:: Type
3277 * a.out Symbols:: Symbol Attributes: @code{a.out}
3281 * a.out Symbols:: Symbol Attributes: @code{a.out}
3284 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3289 * COFF Symbols:: Symbol Attributes for COFF
3292 * SOM Symbols:: Symbol Attributes for SOM
3299 @cindex value of a symbol
3300 @cindex symbol value
3301 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3302 location in the text, data, bss or absolute sections the value is the
3303 number of addresses from the start of that section to the label.
3304 Naturally for text, data and bss sections the value of a symbol changes
3305 as @code{@value{LD}} changes section base addresses during linking. Absolute
3306 symbols' values do not change during linking: that is why they are
3309 The value of an undefined symbol is treated in a special way. If it is
3310 0 then the symbol is not defined in this assembler source file, and
3311 @code{@value{LD}} tries to determine its value from other files linked into the
3312 same program. You make this kind of symbol simply by mentioning a symbol
3313 name without defining it. A non-zero value represents a @code{.comm}
3314 common declaration. The value is how much common storage to reserve, in
3315 bytes (addresses). The symbol refers to the first address of the
3321 @cindex type of a symbol
3323 The type attribute of a symbol contains relocation (section)
3324 information, any flag settings indicating that a symbol is external, and
3325 (optionally), other information for linkers and debuggers. The exact
3326 format depends on the object-code output format in use.
3331 @c The following avoids a "widow" subsection title. @group would be
3332 @c better if it were available outside examples.
3335 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3337 @cindex @code{b.out} symbol attributes
3338 @cindex symbol attributes, @code{b.out}
3339 These symbol attributes appear only when @command{@value{AS}} is configured for
3340 one of the Berkeley-descended object output formats---@code{a.out} or
3346 @subsection Symbol Attributes: @code{a.out}
3348 @cindex @code{a.out} symbol attributes
3349 @cindex symbol attributes, @code{a.out}
3355 @subsection Symbol Attributes: @code{a.out}
3357 @cindex @code{a.out} symbol attributes
3358 @cindex symbol attributes, @code{a.out}
3362 * Symbol Desc:: Descriptor
3363 * Symbol Other:: Other
3367 @subsubsection Descriptor
3369 @cindex descriptor, of @code{a.out} symbol
3370 This is an arbitrary 16-bit value. You may establish a symbol's
3371 descriptor value by using a @code{.desc} statement
3372 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3373 @command{@value{AS}}.
3376 @subsubsection Other
3378 @cindex other attribute, of @code{a.out} symbol
3379 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3384 @subsection Symbol Attributes for COFF
3386 @cindex COFF symbol attributes
3387 @cindex symbol attributes, COFF
3389 The COFF format supports a multitude of auxiliary symbol attributes;
3390 like the primary symbol attributes, they are set between @code{.def} and
3391 @code{.endef} directives.
3393 @subsubsection Primary Attributes
3395 @cindex primary attributes, COFF symbols
3396 The symbol name is set with @code{.def}; the value and type,
3397 respectively, with @code{.val} and @code{.type}.
3399 @subsubsection Auxiliary Attributes
3401 @cindex auxiliary attributes, COFF symbols
3402 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3403 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3404 table information for COFF.
3409 @subsection Symbol Attributes for SOM
3411 @cindex SOM symbol attributes
3412 @cindex symbol attributes, SOM
3414 The SOM format for the HPPA supports a multitude of symbol attributes set with
3415 the @code{.EXPORT} and @code{.IMPORT} directives.
3417 The attributes are described in @cite{HP9000 Series 800 Assembly
3418 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3419 @code{EXPORT} assembler directive documentation.
3423 @chapter Expressions
3427 @cindex numeric values
3428 An @dfn{expression} specifies an address or numeric value.
3429 Whitespace may precede and/or follow an expression.
3431 The result of an expression must be an absolute number, or else an offset into
3432 a particular section. If an expression is not absolute, and there is not
3433 enough information when @command{@value{AS}} sees the expression to know its
3434 section, a second pass over the source program might be necessary to interpret
3435 the expression---but the second pass is currently not implemented.
3436 @command{@value{AS}} aborts with an error message in this situation.
3439 * Empty Exprs:: Empty Expressions
3440 * Integer Exprs:: Integer Expressions
3444 @section Empty Expressions
3446 @cindex empty expressions
3447 @cindex expressions, empty
3448 An empty expression has no value: it is just whitespace or null.
3449 Wherever an absolute expression is required, you may omit the
3450 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3451 is compatible with other assemblers.
3454 @section Integer Expressions
3456 @cindex integer expressions
3457 @cindex expressions, integer
3458 An @dfn{integer expression} is one or more @emph{arguments} delimited
3459 by @emph{operators}.
3462 * Arguments:: Arguments
3463 * Operators:: Operators
3464 * Prefix Ops:: Prefix Operators
3465 * Infix Ops:: Infix Operators
3469 @subsection Arguments
3471 @cindex expression arguments
3472 @cindex arguments in expressions
3473 @cindex operands in expressions
3474 @cindex arithmetic operands
3475 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3476 contexts arguments are sometimes called ``arithmetic operands''. In
3477 this manual, to avoid confusing them with the ``instruction operands'' of
3478 the machine language, we use the term ``argument'' to refer to parts of
3479 expressions only, reserving the word ``operand'' to refer only to machine
3480 instruction operands.
3482 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3483 @var{section} is one of text, data, bss, absolute,
3484 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3487 Numbers are usually integers.
3489 A number can be a flonum or bignum. In this case, you are warned
3490 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3491 these 32 bits are an integer. You may write integer-manipulating
3492 instructions that act on exotic constants, compatible with other
3495 @cindex subexpressions
3496 Subexpressions are a left parenthesis @samp{(} followed by an integer
3497 expression, followed by a right parenthesis @samp{)}; or a prefix
3498 operator followed by an argument.
3501 @subsection Operators
3503 @cindex operators, in expressions
3504 @cindex arithmetic functions
3505 @cindex functions, in expressions
3506 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3507 operators are followed by an argument. Infix operators appear
3508 between their arguments. Operators may be preceded and/or followed by
3512 @subsection Prefix Operator
3514 @cindex prefix operators
3515 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3516 one argument, which must be absolute.
3518 @c the tex/end tex stuff surrounding this small table is meant to make
3519 @c it align, on the printed page, with the similar table in the next
3520 @c section (which is inside an enumerate).
3522 \global\advance\leftskip by \itemindent
3527 @dfn{Negation}. Two's complement negation.
3529 @dfn{Complementation}. Bitwise not.
3533 \global\advance\leftskip by -\itemindent
3537 @subsection Infix Operators
3539 @cindex infix operators
3540 @cindex operators, permitted arguments
3541 @dfn{Infix operators} take two arguments, one on either side. Operators
3542 have precedence, but operations with equal precedence are performed left
3543 to right. Apart from @code{+} or @option{-}, both arguments must be
3544 absolute, and the result is absolute.
3547 @cindex operator precedence
3548 @cindex precedence of operators
3555 @dfn{Multiplication}.
3558 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3565 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3569 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3573 Intermediate precedence
3578 @dfn{Bitwise Inclusive Or}.
3584 @dfn{Bitwise Exclusive Or}.
3587 @dfn{Bitwise Or Not}.
3594 @cindex addition, permitted arguments
3595 @cindex plus, permitted arguments
3596 @cindex arguments for addition
3598 @dfn{Addition}. If either argument is absolute, the result has the section of
3599 the other argument. You may not add together arguments from different
3602 @cindex subtraction, permitted arguments
3603 @cindex minus, permitted arguments
3604 @cindex arguments for subtraction
3606 @dfn{Subtraction}. If the right argument is absolute, the
3607 result has the section of the left argument.
3608 If both arguments are in the same section, the result is absolute.
3609 You may not subtract arguments from different sections.
3610 @c FIXME is there still something useful to say about undefined - undefined ?
3612 @cindex comparison expressions
3613 @cindex expressions, comparison
3617 @dfn{Is Not Equal To}
3621 @dfn{Is Greater Than}
3623 @dfn{Is Greater Than Or Equal To}
3625 @dfn{Is Less Than Or Equal To}
3627 The comparison operators can be used as infix operators. A true results has a
3628 value of -1 whereas a false result has a value of 0. Note, these operators
3629 perform signed comparisons.
3632 @item Lowest Precedence
3641 These two logical operations can be used to combine the results of sub
3642 expressions. Note, unlike the comparison operators a true result returns a
3643 value of 1 but a false results does still return 0. Also note that the logical
3644 or operator has a slightly lower precedence than logical and.
3649 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3650 address; you can only have a defined section in one of the two arguments.
3653 @chapter Assembler Directives
3655 @cindex directives, machine independent
3656 @cindex pseudo-ops, machine independent
3657 @cindex machine independent directives
3658 All assembler directives have names that begin with a period (@samp{.}).
3659 The rest of the name is letters, usually in lower case.
3661 This chapter discusses directives that are available regardless of the
3662 target machine configuration for the @sc{gnu} assembler.
3664 Some machine configurations provide additional directives.
3665 @xref{Machine Dependencies}.
3668 @ifset machine-directives
3669 @xref{Machine Dependencies} for additional directives.
3674 * Abort:: @code{.abort}
3676 * ABORT:: @code{.ABORT}
3679 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3680 * Altmacro:: @code{.altmacro}
3681 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3682 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3683 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3684 * Byte:: @code{.byte @var{expressions}}
3685 * Comm:: @code{.comm @var{symbol} , @var{length} }
3687 * CFI directives:: @code{.cfi_startproc}, @code{.cfi_endproc}, etc.
3689 * Data:: @code{.data @var{subsection}}
3691 * Def:: @code{.def @var{name}}
3694 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3700 * Double:: @code{.double @var{flonums}}
3701 * Eject:: @code{.eject}
3702 * Else:: @code{.else}
3703 * Elseif:: @code{.elseif}
3706 * Endef:: @code{.endef}
3709 * Endfunc:: @code{.endfunc}
3710 * Endif:: @code{.endif}
3711 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3712 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3714 * Error:: @code{.error @var{string}}
3715 * Exitm:: @code{.exitm}
3716 * Extern:: @code{.extern}
3717 * Fail:: @code{.fail}
3718 @ifclear no-file-dir
3719 * File:: @code{.file @var{string}}
3722 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3723 * Float:: @code{.float @var{flonums}}
3724 * Func:: @code{.func}
3725 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3727 * Hidden:: @code{.hidden @var{names}}
3730 * hword:: @code{.hword @var{expressions}}
3731 * Ident:: @code{.ident}
3732 * If:: @code{.if @var{absolute expression}}
3733 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3734 * Include:: @code{.include "@var{file}"}
3735 * Int:: @code{.int @var{expressions}}
3737 * Internal:: @code{.internal @var{names}}
3740 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3741 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3742 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3743 * Lflags:: @code{.lflags}
3744 @ifclear no-line-dir
3745 * Line:: @code{.line @var{line-number}}
3748 * Linkonce:: @code{.linkonce [@var{type}]}
3749 * List:: @code{.list}
3750 * Ln:: @code{.ln @var{line-number}}
3752 * LNS directives:: @code{.file}, @code{.loc}, etc.
3754 * Long:: @code{.long @var{expressions}}
3756 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3759 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3760 * MRI:: @code{.mri @var{val}}
3761 * Noaltmacro:: @code{.noaltmacro}
3762 * Nolist:: @code{.nolist}
3763 * Octa:: @code{.octa @var{bignums}}
3764 * Org:: @code{.org @var{new-lc} , @var{fill}}
3765 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3767 * PopSection:: @code{.popsection}
3768 * Previous:: @code{.previous}
3771 * Print:: @code{.print @var{string}}
3773 * Protected:: @code{.protected @var{names}}
3776 * Psize:: @code{.psize @var{lines}, @var{columns}}
3777 * Purgem:: @code{.purgem @var{name}}
3779 * PushSection:: @code{.pushsection @var{name}}
3782 * Quad:: @code{.quad @var{bignums}}
3783 * Rept:: @code{.rept @var{count}}
3784 * Sbttl:: @code{.sbttl "@var{subheading}"}
3786 * Scl:: @code{.scl @var{class}}
3789 * Section:: @code{.section @var{name}}
3792 * Set:: @code{.set @var{symbol}, @var{expression}}
3793 * Short:: @code{.short @var{expressions}}
3794 * Single:: @code{.single @var{flonums}}
3796 * Size:: @code{.size [@var{name} , @var{expression}]}
3799 * Skip:: @code{.skip @var{size} , @var{fill}}
3800 * Sleb128:: @code{.sleb128 @var{expressions}}
3801 * Space:: @code{.space @var{size} , @var{fill}}
3803 * Stab:: @code{.stabd, .stabn, .stabs}
3806 * String:: @code{.string "@var{str}"}
3807 * Struct:: @code{.struct @var{expression}}
3809 * SubSection:: @code{.subsection}
3810 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3814 * Tag:: @code{.tag @var{structname}}
3817 * Text:: @code{.text @var{subsection}}
3818 * Title:: @code{.title "@var{heading}"}
3820 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3823 * Uleb128:: @code{.uleb128 @var{expressions}}
3825 * Val:: @code{.val @var{addr}}
3829 * Version:: @code{.version "@var{string}"}
3830 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3831 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3834 * Warning:: @code{.warning @var{string}}
3835 * Weak:: @code{.weak @var{names}}
3836 * Word:: @code{.word @var{expressions}}
3837 * Deprecated:: Deprecated Directives
3841 @section @code{.abort}
3843 @cindex @code{abort} directive
3844 @cindex stopping the assembly
3845 This directive stops the assembly immediately. It is for
3846 compatibility with other assemblers. The original idea was that the
3847 assembly language source would be piped into the assembler. If the sender
3848 of the source quit, it could use this directive tells @command{@value{AS}} to
3849 quit also. One day @code{.abort} will not be supported.
3853 @section @code{.ABORT}
3855 @cindex @code{ABORT} directive
3856 When producing COFF output, @command{@value{AS}} accepts this directive as a
3857 synonym for @samp{.abort}.
3860 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3866 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3868 @cindex padding the location counter
3869 @cindex @code{align} directive
3870 Pad the location counter (in the current subsection) to a particular storage
3871 boundary. The first expression (which must be absolute) is the alignment
3872 required, as described below.
3874 The second expression (also absolute) gives the fill value to be stored in the
3875 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3876 padding bytes are normally zero. However, on some systems, if the section is
3877 marked as containing code and the fill value is omitted, the space is filled
3878 with no-op instructions.
3880 The third expression is also absolute, and is also optional. If it is present,
3881 it is the maximum number of bytes that should be skipped by this alignment
3882 directive. If doing the alignment would require skipping more bytes than the
3883 specified maximum, then the alignment is not done at all. You can omit the
3884 fill value (the second argument) entirely by simply using two commas after the
3885 required alignment; this can be useful if you want the alignment to be filled
3886 with no-op instructions when appropriate.
3888 The way the required alignment is specified varies from system to system.
3889 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
3890 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
3891 alignment request in bytes. For example @samp{.align 8} advances
3892 the location counter until it is a multiple of 8. If the location counter
3893 is already a multiple of 8, no change is needed. For the tic54x, the
3894 first expression is the alignment request in words.
3896 For other systems, including the i386 using a.out format, and the arm and
3897 strongarm, it is the
3898 number of low-order zero bits the location counter must have after
3899 advancement. For example @samp{.align 3} advances the location
3900 counter until it a multiple of 8. If the location counter is already a
3901 multiple of 8, no change is needed.
3903 This inconsistency is due to the different behaviors of the various
3904 native assemblers for these systems which GAS must emulate.
3905 GAS also provides @code{.balign} and @code{.p2align} directives,
3906 described later, which have a consistent behavior across all
3907 architectures (but are specific to GAS).
3910 @section @code{.ascii "@var{string}"}@dots{}
3912 @cindex @code{ascii} directive
3913 @cindex string literals
3914 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3915 separated by commas. It assembles each string (with no automatic
3916 trailing zero byte) into consecutive addresses.
3919 @section @code{.asciz "@var{string}"}@dots{}
3921 @cindex @code{asciz} directive
3922 @cindex zero-terminated strings
3923 @cindex null-terminated strings
3924 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3925 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3928 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3930 @cindex padding the location counter given number of bytes
3931 @cindex @code{balign} directive
3932 Pad the location counter (in the current subsection) to a particular
3933 storage boundary. The first expression (which must be absolute) is the
3934 alignment request in bytes. For example @samp{.balign 8} advances
3935 the location counter until it is a multiple of 8. If the location counter
3936 is already a multiple of 8, no change is needed.
3938 The second expression (also absolute) gives the fill value to be stored in the
3939 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3940 padding bytes are normally zero. However, on some systems, if the section is
3941 marked as containing code and the fill value is omitted, the space is filled
3942 with no-op instructions.
3944 The third expression is also absolute, and is also optional. If it is present,
3945 it is the maximum number of bytes that should be skipped by this alignment
3946 directive. If doing the alignment would require skipping more bytes than the
3947 specified maximum, then the alignment is not done at all. You can omit the
3948 fill value (the second argument) entirely by simply using two commas after the
3949 required alignment; this can be useful if you want the alignment to be filled
3950 with no-op instructions when appropriate.
3952 @cindex @code{balignw} directive
3953 @cindex @code{balignl} directive
3954 The @code{.balignw} and @code{.balignl} directives are variants of the
3955 @code{.balign} directive. The @code{.balignw} directive treats the fill
3956 pattern as a two byte word value. The @code{.balignl} directives treats the
3957 fill pattern as a four byte longword value. For example, @code{.balignw
3958 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3959 filled in with the value 0x368d (the exact placement of the bytes depends upon
3960 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3964 @section @code{.byte @var{expressions}}
3966 @cindex @code{byte} directive
3967 @cindex integers, one byte
3968 @code{.byte} expects zero or more expressions, separated by commas.
3969 Each expression is assembled into the next byte.
3972 @section @code{.comm @var{symbol} , @var{length} }
3974 @cindex @code{comm} directive
3975 @cindex symbol, common
3976 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3977 common symbol in one object file may be merged with a defined or common symbol
3978 of the same name in another object file. If @code{@value{LD}} does not see a
3979 definition for the symbol--just one or more common symbols--then it will
3980 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3981 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3982 the same name, and they do not all have the same size, it will allocate space
3983 using the largest size.
3986 When using ELF, the @code{.comm} directive takes an optional third argument.
3987 This is the desired alignment of the symbol, specified as a byte boundary (for
3988 example, an alignment of 16 means that the least significant 4 bits of the
3989 address should be zero). The alignment must be an absolute expression, and it
3990 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3991 for the common symbol, it will use the alignment when placing the symbol. If
3992 no alignment is specified, @command{@value{AS}} will set the alignment to the
3993 largest power of two less than or equal to the size of the symbol, up to a
3998 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3999 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4002 @node CFI directives
4003 @section @code{.cfi_startproc}
4004 @cindex @code{cfi_startproc} directive
4005 @code{.cfi_startproc} is used at the beginning of each function that
4006 should have an entry in @code{.eh_frame}. It initializes some internal
4007 data structures and emits architecture dependent initial CFI instructions.
4008 Don't forget to close the function by
4009 @code{.cfi_endproc}.
4011 @section @code{.cfi_endproc}
4012 @cindex @code{cfi_endproc} directive
4013 @code{.cfi_endproc} is used at the end of a function where it closes its
4014 unwind entry previously opened by
4015 @code{.cfi_startproc}. and emits it to @code{.eh_frame}.
4017 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4018 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4019 address from @var{register} and add @var{offset} to it}.
4021 @section @code{.cfi_def_cfa_register @var{register}}
4022 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4023 now on @var{register} will be used instead of the old one. Offset
4026 @section @code{.cfi_def_cfa_offset @var{offset}}
4027 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4028 remains the same, but @var{offset} is new. Note that it is the
4029 absolute offset that will be added to a defined register to compute
4032 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4033 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4034 value that is added/substracted from the previous offset.
4036 @section @code{.cfi_offset @var{register}, @var{offset}}
4037 Previous value of @var{register} is saved at offset @var{offset} from
4040 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4041 Previous value of @var{register} is saved at offset @var{offset} from
4042 the current CFA register. This is transformed to @code{.cfi_offset}
4043 using the known displacement of the CFA register from the CFA.
4044 This is often easier to use, because the number will match the
4045 code it's annotating.
4047 @section @code{.cfi_window_save}
4048 SPARC register window has been saved.
4050 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4051 Allows the user to add arbitrary bytes to the unwind info. One
4052 might use this to add OS-specific CFI opcodes, or generic CFI
4053 opcodes that GAS does not yet support.
4055 @node LNS directives
4056 @section @code{.file @var{fileno} @var{filename}}
4057 @cindex @code{file} directive
4058 When emitting dwarf2 line number information @code{.file} assigns filenames
4059 to the @code{.debug_line} file name table. The @var{fileno} operand should
4060 be a unique positive integer to use as the index of the entry in the table.
4061 The @var{filename} operand is a C string literal.
4063 The detail of filename indicies is exposed to the user because the filename
4064 table is shared with the @code{.debug_info} section of the dwarf2 debugging
4065 information, and thus the user must know the exact indicies that table
4068 @section @code{.loc @var{fileno} @var{lineno} [@var{column}]}
4069 @cindex @code{loc} directive
4070 The @code{.loc} directive will add row to the @code{.debug_line} line
4071 number matrix corresponding to the immediately following assembly
4072 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
4073 arguments will be applied to the @code{.debug_line} state machine before
4076 @section @code{.loc basic_block}
4077 This directive will set the @code{basic_block} register in the
4078 @code{.debug_line} state machine to @code{true}.
4080 @section @code{.loc prologue_end}
4081 This directive will set the @code{prologue_end} register in the
4082 @code{.debug_line} state machine to @code{true}.
4084 @section @code{.loc epilogue_begin}
4085 This directive will set the @code{epilogue_begin} register in the
4086 @code{.debug_line} state machine to @code{true}.
4088 @section @code{.loc is_stmt @var{value}}
4089 This directive will set the @code{epilogue_begin} register in the
4090 @code{.debug_line} state machine to @code{value}, which must be
4093 @section @code{.loc isa @var{value}}
4094 This directive will set the @code{isa} register in the @code{.debug_line}
4095 state machine to @var{value}, which must be an unsigned integer.
4098 @section @code{.data @var{subsection}}
4100 @cindex @code{data} directive
4101 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4102 end of the data subsection numbered @var{subsection} (which is an
4103 absolute expression). If @var{subsection} is omitted, it defaults
4108 @section @code{.def @var{name}}
4110 @cindex @code{def} directive
4111 @cindex COFF symbols, debugging
4112 @cindex debugging COFF symbols
4113 Begin defining debugging information for a symbol @var{name}; the
4114 definition extends until the @code{.endef} directive is encountered.
4117 This directive is only observed when @command{@value{AS}} is configured for COFF
4118 format output; when producing @code{b.out}, @samp{.def} is recognized,
4125 @section @code{.desc @var{symbol}, @var{abs-expression}}
4127 @cindex @code{desc} directive
4128 @cindex COFF symbol descriptor
4129 @cindex symbol descriptor, COFF
4130 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4131 to the low 16 bits of an absolute expression.
4134 The @samp{.desc} directive is not available when @command{@value{AS}} is
4135 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4136 object format. For the sake of compatibility, @command{@value{AS}} accepts
4137 it, but produces no output, when configured for COFF.
4143 @section @code{.dim}
4145 @cindex @code{dim} directive
4146 @cindex COFF auxiliary symbol information
4147 @cindex auxiliary symbol information, COFF
4148 This directive is generated by compilers to include auxiliary debugging
4149 information in the symbol table. It is only permitted inside
4150 @code{.def}/@code{.endef} pairs.
4153 @samp{.dim} is only meaningful when generating COFF format output; when
4154 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4160 @section @code{.double @var{flonums}}
4162 @cindex @code{double} directive
4163 @cindex floating point numbers (double)
4164 @code{.double} expects zero or more flonums, separated by commas. It
4165 assembles floating point numbers.
4167 The exact kind of floating point numbers emitted depends on how
4168 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4172 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4173 in @sc{ieee} format.
4178 @section @code{.eject}
4180 @cindex @code{eject} directive
4181 @cindex new page, in listings
4182 @cindex page, in listings
4183 @cindex listing control: new page
4184 Force a page break at this point, when generating assembly listings.
4187 @section @code{.else}
4189 @cindex @code{else} directive
4190 @code{.else} is part of the @command{@value{AS}} support for conditional
4191 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
4192 of code to be assembled if the condition for the preceding @code{.if}
4196 @section @code{.elseif}
4198 @cindex @code{elseif} directive
4199 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4200 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
4201 @code{.if} block that would otherwise fill the entire @code{.else} section.
4204 @section @code{.end}
4206 @cindex @code{end} directive
4207 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4208 process anything in the file past the @code{.end} directive.
4212 @section @code{.endef}
4214 @cindex @code{endef} directive
4215 This directive flags the end of a symbol definition begun with
4219 @samp{.endef} is only meaningful when generating COFF format output; if
4220 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4221 directive but ignores it.
4226 @section @code{.endfunc}
4227 @cindex @code{endfunc} directive
4228 @code{.endfunc} marks the end of a function specified with @code{.func}.
4231 @section @code{.endif}
4233 @cindex @code{endif} directive
4234 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4235 it marks the end of a block of code that is only assembled
4236 conditionally. @xref{If,,@code{.if}}.
4239 @section @code{.equ @var{symbol}, @var{expression}}
4241 @cindex @code{equ} directive
4242 @cindex assigning values to symbols
4243 @cindex symbols, assigning values to
4244 This directive sets the value of @var{symbol} to @var{expression}.
4245 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4248 The syntax for @code{equ} on the HPPA is
4249 @samp{@var{symbol} .equ @var{expression}}.
4253 @section @code{.equiv @var{symbol}, @var{expression}}
4254 @cindex @code{equiv} directive
4255 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4256 the assembler will signal an error if @var{symbol} is already defined. Note a
4257 symbol which has been referenced but not actually defined is considered to be
4260 Except for the contents of the error message, this is roughly equivalent to
4269 @section @code{.err}
4270 @cindex @code{err} directive
4271 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4272 message and, unless the @option{-Z} option was used, it will not generate an
4273 object file. This can be used to signal error an conditionally compiled code.
4276 @section @code{.error "@var{string}"}
4277 @cindex error directive
4279 Similarly to @code{.err}, this directive emits an error, but you can specify a
4280 string that will be emitted as the error message. If you don't specify the
4281 message, it defaults to @code{".error directive invoked in source file"}.
4282 @xref{Errors, ,Error and Warning Messages}.
4285 .error "This code has not been assembled and tested."
4289 @section @code{.exitm}
4290 Exit early from the current macro definition. @xref{Macro}.
4293 @section @code{.extern}
4295 @cindex @code{extern} directive
4296 @code{.extern} is accepted in the source program---for compatibility
4297 with other assemblers---but it is ignored. @command{@value{AS}} treats
4298 all undefined symbols as external.
4301 @section @code{.fail @var{expression}}
4303 @cindex @code{fail} directive
4304 Generates an error or a warning. If the value of the @var{expression} is 500
4305 or more, @command{@value{AS}} will print a warning message. If the value is less
4306 than 500, @command{@value{AS}} will print an error message. The message will
4307 include the value of @var{expression}. This can occasionally be useful inside
4308 complex nested macros or conditional assembly.
4310 @ifclear no-file-dir
4312 @section @code{.file @var{string}}
4314 @cindex @code{file} directive
4315 @cindex logical file name
4316 @cindex file name, logical
4317 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4318 file. @var{string} is the new file name. In general, the filename is
4319 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4320 to specify an empty file name, you must give the quotes--@code{""}. This
4321 statement may go away in future: it is only recognized to be compatible with
4322 old @command{@value{AS}} programs.
4326 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4328 @cindex @code{fill} directive
4329 @cindex writing patterns in memory
4330 @cindex patterns, writing in memory
4331 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4332 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4333 may be zero or more. @var{Size} may be zero or more, but if it is
4334 more than 8, then it is deemed to have the value 8, compatible with
4335 other people's assemblers. The contents of each @var{repeat} bytes
4336 is taken from an 8-byte number. The highest order 4 bytes are
4337 zero. The lowest order 4 bytes are @var{value} rendered in the
4338 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4339 Each @var{size} bytes in a repetition is taken from the lowest order
4340 @var{size} bytes of this number. Again, this bizarre behavior is
4341 compatible with other people's assemblers.
4343 @var{size} and @var{value} are optional.
4344 If the second comma and @var{value} are absent, @var{value} is
4345 assumed zero. If the first comma and following tokens are absent,
4346 @var{size} is assumed to be 1.
4349 @section @code{.float @var{flonums}}
4351 @cindex floating point numbers (single)
4352 @cindex @code{float} directive
4353 This directive assembles zero or more flonums, separated by commas. It
4354 has the same effect as @code{.single}.
4356 The exact kind of floating point numbers emitted depends on how
4357 @command{@value{AS}} is configured.
4358 @xref{Machine Dependencies}.
4362 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4363 in @sc{ieee} format.
4368 @section @code{.func @var{name}[,@var{label}]}
4369 @cindex @code{func} directive
4370 @code{.func} emits debugging information to denote function @var{name}, and
4371 is ignored unless the file is assembled with debugging enabled.
4372 Only @samp{--gstabs[+]} is currently supported.
4373 @var{label} is the entry point of the function and if omitted @var{name}
4374 prepended with the @samp{leading char} is used.
4375 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4376 All functions are currently defined to have @code{void} return type.
4377 The function must be terminated with @code{.endfunc}.
4380 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4382 @cindex @code{global} directive
4383 @cindex symbol, making visible to linker
4384 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4385 @var{symbol} in your partial program, its value is made available to
4386 other partial programs that are linked with it. Otherwise,
4387 @var{symbol} takes its attributes from a symbol of the same name
4388 from another file linked into the same program.
4390 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4391 compatibility with other assemblers.
4394 On the HPPA, @code{.global} is not always enough to make it accessible to other
4395 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4396 @xref{HPPA Directives,, HPPA Assembler Directives}.
4401 @section @code{.hidden @var{names}}
4403 @cindex @code{hidden} directive
4405 This is one of the ELF visibility directives. The other two are
4406 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4407 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4409 This directive overrides the named symbols default visibility (which is set by
4410 their binding: local, global or weak). The directive sets the visibility to
4411 @code{hidden} which means that the symbols are not visible to other components.
4412 Such symbols are always considered to be @code{protected} as well.
4416 @section @code{.hword @var{expressions}}
4418 @cindex @code{hword} directive
4419 @cindex integers, 16-bit
4420 @cindex numbers, 16-bit
4421 @cindex sixteen bit integers
4422 This expects zero or more @var{expressions}, and emits
4423 a 16 bit number for each.
4426 This directive is a synonym for @samp{.short}; depending on the target
4427 architecture, it may also be a synonym for @samp{.word}.
4431 This directive is a synonym for @samp{.short}.
4434 This directive is a synonym for both @samp{.short} and @samp{.word}.
4439 @section @code{.ident}
4441 @cindex @code{ident} directive
4442 This directive is used by some assemblers to place tags in object files.
4443 @command{@value{AS}} simply accepts the directive for source-file
4444 compatibility with such assemblers, but does not actually emit anything
4448 @section @code{.if @var{absolute expression}}
4450 @cindex conditional assembly
4451 @cindex @code{if} directive
4452 @code{.if} marks the beginning of a section of code which is only
4453 considered part of the source program being assembled if the argument
4454 (which must be an @var{absolute expression}) is non-zero. The end of
4455 the conditional section of code must be marked by @code{.endif}
4456 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4457 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4458 If you have several conditions to check, @code{.elseif} may be used to avoid
4459 nesting blocks if/else within each subsequent @code{.else} block.
4461 The following variants of @code{.if} are also supported:
4463 @cindex @code{ifdef} directive
4464 @item .ifdef @var{symbol}
4465 Assembles the following section of code if the specified @var{symbol}
4466 has been defined. Note a symbol which has been referenced but not yet defined
4467 is considered to be undefined.
4469 @cindex @code{ifb} directive
4470 @item .ifb @var{text}
4471 Assembles the following section of code if the operand is blank (empty).
4473 @cindex @code{ifc} directive
4474 @item .ifc @var{string1},@var{string2}
4475 Assembles the following section of code if the two strings are the same. The
4476 strings may be optionally quoted with single quotes. If they are not quoted,
4477 the first string stops at the first comma, and the second string stops at the
4478 end of the line. Strings which contain whitespace should be quoted. The
4479 string comparison is case sensitive.
4481 @cindex @code{ifeq} directive
4482 @item .ifeq @var{absolute expression}
4483 Assembles the following section of code if the argument is zero.
4485 @cindex @code{ifeqs} directive
4486 @item .ifeqs @var{string1},@var{string2}
4487 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4489 @cindex @code{ifge} directive
4490 @item .ifge @var{absolute expression}
4491 Assembles the following section of code if the argument is greater than or
4494 @cindex @code{ifgt} directive
4495 @item .ifgt @var{absolute expression}
4496 Assembles the following section of code if the argument is greater than zero.
4498 @cindex @code{ifle} directive
4499 @item .ifle @var{absolute expression}
4500 Assembles the following section of code if the argument is less than or equal
4503 @cindex @code{iflt} directive
4504 @item .iflt @var{absolute expression}
4505 Assembles the following section of code if the argument is less than zero.
4507 @cindex @code{ifnb} directive
4508 @item .ifnb @var{text}
4509 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4510 following section of code if the operand is non-blank (non-empty).
4512 @cindex @code{ifnc} directive
4513 @item .ifnc @var{string1},@var{string2}.
4514 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4515 following section of code if the two strings are not the same.
4517 @cindex @code{ifndef} directive
4518 @cindex @code{ifnotdef} directive
4519 @item .ifndef @var{symbol}
4520 @itemx .ifnotdef @var{symbol}
4521 Assembles the following section of code if the specified @var{symbol}
4522 has not been defined. Both spelling variants are equivalent. Note a symbol
4523 which has been referenced but not yet defined is considered to be undefined.
4525 @cindex @code{ifne} directive
4526 @item .ifne @var{absolute expression}
4527 Assembles the following section of code if the argument is not equal to zero
4528 (in other words, this is equivalent to @code{.if}).
4530 @cindex @code{ifnes} directive
4531 @item .ifnes @var{string1},@var{string2}
4532 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4533 following section of code if the two strings are not the same.
4537 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4539 @cindex @code{incbin} directive
4540 @cindex binary files, including
4541 The @code{incbin} directive includes @var{file} verbatim at the current
4542 location. You can control the search paths used with the @samp{-I} command-line
4543 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4546 The @var{skip} argument skips a number of bytes from the start of the
4547 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4548 read. Note that the data is not aligned in any way, so it is the user's
4549 responsibility to make sure that proper alignment is provided both before and
4550 after the @code{incbin} directive.
4553 @section @code{.include "@var{file}"}
4555 @cindex @code{include} directive
4556 @cindex supporting files, including
4557 @cindex files, including
4558 This directive provides a way to include supporting files at specified
4559 points in your source program. The code from @var{file} is assembled as
4560 if it followed the point of the @code{.include}; when the end of the
4561 included file is reached, assembly of the original file continues. You
4562 can control the search paths used with the @samp{-I} command-line option
4563 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4567 @section @code{.int @var{expressions}}
4569 @cindex @code{int} directive
4570 @cindex integers, 32-bit
4571 Expect zero or more @var{expressions}, of any section, separated by commas.
4572 For each expression, emit a number that, at run time, is the value of that
4573 expression. The byte order and bit size of the number depends on what kind
4574 of target the assembly is for.
4578 On most forms of the H8/300, @code{.int} emits 16-bit
4579 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4586 @section @code{.internal @var{names}}
4588 @cindex @code{internal} directive
4590 This is one of the ELF visibility directives. The other two are
4591 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4592 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4594 This directive overrides the named symbols default visibility (which is set by
4595 their binding: local, global or weak). The directive sets the visibility to
4596 @code{internal} which means that the symbols are considered to be @code{hidden}
4597 (i.e., not visible to other components), and that some extra, processor specific
4598 processing must also be performed upon the symbols as well.
4602 @section @code{.irp @var{symbol},@var{values}}@dots{}
4604 @cindex @code{irp} directive
4605 Evaluate a sequence of statements assigning different values to @var{symbol}.
4606 The sequence of statements starts at the @code{.irp} directive, and is
4607 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4608 set to @var{value}, and the sequence of statements is assembled. If no
4609 @var{value} is listed, the sequence of statements is assembled once, with
4610 @var{symbol} set to the null string. To refer to @var{symbol} within the
4611 sequence of statements, use @var{\symbol}.
4613 For example, assembling
4621 is equivalent to assembling
4629 For some caveats with the spelling of @var{symbol}, see also the discussion
4633 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4635 @cindex @code{irpc} directive
4636 Evaluate a sequence of statements assigning different values to @var{symbol}.
4637 The sequence of statements starts at the @code{.irpc} directive, and is
4638 terminated by an @code{.endr} directive. For each character in @var{value},
4639 @var{symbol} is set to the character, and the sequence of statements is
4640 assembled. If no @var{value} is listed, the sequence of statements is
4641 assembled once, with @var{symbol} set to the null string. To refer to
4642 @var{symbol} within the sequence of statements, use @var{\symbol}.
4644 For example, assembling
4652 is equivalent to assembling
4660 For some caveats with the spelling of @var{symbol}, see also the discussion
4664 @section @code{.lcomm @var{symbol} , @var{length}}
4666 @cindex @code{lcomm} directive
4667 @cindex local common symbols
4668 @cindex symbols, local common
4669 Reserve @var{length} (an absolute expression) bytes for a local common
4670 denoted by @var{symbol}. The section and value of @var{symbol} are
4671 those of the new local common. The addresses are allocated in the bss
4672 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4673 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4674 not visible to @code{@value{LD}}.
4677 Some targets permit a third argument to be used with @code{.lcomm}. This
4678 argument specifies the desired alignment of the symbol in the bss section.
4682 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4683 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4687 @section @code{.lflags}
4689 @cindex @code{lflags} directive (ignored)
4690 @command{@value{AS}} accepts this directive, for compatibility with other
4691 assemblers, but ignores it.
4693 @ifclear no-line-dir
4695 @section @code{.line @var{line-number}}
4697 @cindex @code{line} directive
4701 @section @code{.ln @var{line-number}}
4703 @cindex @code{ln} directive
4705 @cindex logical line number
4707 Change the logical line number. @var{line-number} must be an absolute
4708 expression. The next line has that logical line number. Therefore any other
4709 statements on the current line (after a statement separator character) are
4710 reported as on logical line number @var{line-number} @minus{} 1. One day
4711 @command{@value{AS}} will no longer support this directive: it is recognized only
4712 for compatibility with existing assembler programs.
4716 @ifclear no-line-dir
4717 Even though this is a directive associated with the @code{a.out} or
4718 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4719 when producing COFF output, and treats @samp{.line} as though it
4720 were the COFF @samp{.ln} @emph{if} it is found outside a
4721 @code{.def}/@code{.endef} pair.
4723 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4724 used by compilers to generate auxiliary symbol information for
4729 @section @code{.linkonce [@var{type}]}
4731 @cindex @code{linkonce} directive
4732 @cindex common sections
4733 Mark the current section so that the linker only includes a single copy of it.
4734 This may be used to include the same section in several different object files,
4735 but ensure that the linker will only include it once in the final output file.
4736 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4737 Duplicate sections are detected based on the section name, so it should be
4740 This directive is only supported by a few object file formats; as of this
4741 writing, the only object file format which supports it is the Portable
4742 Executable format used on Windows NT.
4744 The @var{type} argument is optional. If specified, it must be one of the
4745 following strings. For example:
4749 Not all types may be supported on all object file formats.
4753 Silently discard duplicate sections. This is the default.
4756 Warn if there are duplicate sections, but still keep only one copy.
4759 Warn if any of the duplicates have different sizes.
4762 Warn if any of the duplicates do not have exactly the same contents.
4766 @section @code{.ln @var{line-number}}
4768 @cindex @code{ln} directive
4769 @ifclear no-line-dir
4770 @samp{.ln} is a synonym for @samp{.line}.
4773 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4774 must be an absolute expression. The next line has that logical
4775 line number, so any other statements on the current line (after a
4776 statement separator character @code{;}) are reported as on logical
4777 line number @var{line-number} @minus{} 1.
4780 This directive is accepted, but ignored, when @command{@value{AS}} is
4781 configured for @code{b.out}; its effect is only associated with COFF
4787 @section @code{.mri @var{val}}
4789 @cindex @code{mri} directive
4790 @cindex MRI mode, temporarily
4791 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4792 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4793 affects code assembled until the next @code{.mri} directive, or until the end
4794 of the file. @xref{M, MRI mode, MRI mode}.
4797 @section @code{.list}
4799 @cindex @code{list} directive
4800 @cindex listing control, turning on
4801 Control (in conjunction with the @code{.nolist} directive) whether or
4802 not assembly listings are generated. These two directives maintain an
4803 internal counter (which is zero initially). @code{.list} increments the
4804 counter, and @code{.nolist} decrements it. Assembly listings are
4805 generated whenever the counter is greater than zero.
4807 By default, listings are disabled. When you enable them (with the
4808 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4809 the initial value of the listing counter is one.
4812 @section @code{.long @var{expressions}}
4814 @cindex @code{long} directive
4815 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4818 @c no one seems to know what this is for or whether this description is
4819 @c what it really ought to do
4821 @section @code{.lsym @var{symbol}, @var{expression}}
4823 @cindex @code{lsym} directive
4824 @cindex symbol, not referenced in assembly
4825 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4826 the hash table, ensuring it cannot be referenced by name during the
4827 rest of the assembly. This sets the attributes of the symbol to be
4828 the same as the expression value:
4830 @var{other} = @var{descriptor} = 0
4831 @var{type} = @r{(section of @var{expression})}
4832 @var{value} = @var{expression}
4835 The new symbol is not flagged as external.
4839 @section @code{.macro}
4842 The commands @code{.macro} and @code{.endm} allow you to define macros that
4843 generate assembly output. For example, this definition specifies a macro
4844 @code{sum} that puts a sequence of numbers into memory:
4847 .macro sum from=0, to=5
4856 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4868 @item .macro @var{macname}
4869 @itemx .macro @var{macname} @var{macargs} @dots{}
4870 @cindex @code{macro} directive
4871 Begin the definition of a macro called @var{macname}. If your macro
4872 definition requires arguments, specify their names after the macro name,
4873 separated by commas or spaces. You can qualify the macro argument to
4874 indicate whether all invocations must specify a non-blank value (through
4875 @samp{:@code{req}}), or whether it takes all of the remaining arguments
4876 (through @samp{:@code{vararg}}). You can supply a default value for any
4877 macro argument by following the name with @samp{=@var{deflt}}. You
4878 cannot define two macros with the same @var{macname} unless it has been
4879 subject to the @code{.purgem} directive (@xref{Purgem}.) between the two
4880 definitions. For example, these are all valid @code{.macro} statements:
4884 Begin the definition of a macro called @code{comm}, which takes no
4887 @item .macro plus1 p, p1
4888 @itemx .macro plus1 p p1
4889 Either statement begins the definition of a macro called @code{plus1},
4890 which takes two arguments; within the macro definition, write
4891 @samp{\p} or @samp{\p1} to evaluate the arguments.
4893 @item .macro reserve_str p1=0 p2
4894 Begin the definition of a macro called @code{reserve_str}, with two
4895 arguments. The first argument has a default value, but not the second.
4896 After the definition is complete, you can call the macro either as
4897 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4898 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4899 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4900 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4903 @item .macro m p1:req, p2=0, p3:vararg
4904 Begin the definition of a macro called @code{m}, with at least three
4905 arguments. The first argument must always have a value specified, but
4906 not the second, which instead has a default value. The third formal
4907 will get assigned all remaining arguments specified at invocation time.
4909 When you call a macro, you can specify the argument values either by
4910 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4911 @samp{sum to=17, from=9}.
4913 Note that since each of the @var{macargs} can be an identifier exactly
4914 as any other one permitted by the target architecture, there may be
4915 occasional problems if the target hand-crafts special meanings to certain
4916 characters when they occur in a special position. For example, if colon
4917 (@code{:}) is generally permitted to be part of a symbol name, but the
4918 architecture specific code special-cases it when occuring as the final
4919 character of a symbol (to denote a label), then the macro parameter
4920 replacement code will have no way of knowing that and consider the whole
4921 construct (including the colon) an identifier, and check only this
4922 identifier for being the subject to parameter substitution. In this
4923 example, besides the potential of just separating identifier and colon
4924 by white space, using alternate macro syntax (@xref{Altmacro}.) and
4925 ampersand (@code{&}) as the character to separate literal text from macro
4926 parameters (or macro parameters from one another) would provide a way to
4927 achieve the same effect:
4936 This applies identically to the identifiers used in @code{.irp} (@xref{Irp}.)
4937 and @code{.irpc} (@xref{Irpc}.).
4940 @cindex @code{endm} directive
4941 Mark the end of a macro definition.
4944 @cindex @code{exitm} directive
4945 Exit early from the current macro definition.
4947 @cindex number of macros executed
4948 @cindex macros, count executed
4950 @command{@value{AS}} maintains a counter of how many macros it has
4951 executed in this pseudo-variable; you can copy that number to your
4952 output with @samp{\@@}, but @emph{only within a macro definition}.
4954 @item LOCAL @var{name} [ , @dots{} ]
4955 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4956 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
4957 @xref{Altmacro,,@code{.altmacro}}.
4961 @section @code{.altmacro}
4962 Enable alternate macro mode, enabling:
4965 @item LOCAL @var{name} [ , @dots{} ]
4966 One additional directive, @code{LOCAL}, is available. It is used to
4967 generate a string replacement for each of the @var{name} arguments, and
4968 replace any instances of @var{name} in each macro expansion. The
4969 replacement string is unique in the assembly, and different for each
4970 separate macro expansion. @code{LOCAL} allows you to write macros that
4971 define symbols, without fear of conflict between separate macro expansions.
4973 @item String delimiters
4974 You can write strings delimited in these other ways besides
4975 @code{"@var{string}"}:
4978 @item '@var{string}'
4979 You can delimit strings with single-quote charaters.
4981 @item <@var{string}>
4982 You can delimit strings with matching angle brackets.
4985 @item single-character string escape
4986 To include any single character literally in a string (even if the
4987 character would otherwise have some special meaning), you can prefix the
4988 character with @samp{!} (an exclamation mark). For example, you can
4989 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4991 @item Expression results as strings
4992 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4993 and use the result as a string.
4997 @section @code{.noaltmacro}
4998 Disable alternate macro mode. @ref{Altmacro}
5001 @section @code{.nolist}
5003 @cindex @code{nolist} directive
5004 @cindex listing control, turning off
5005 Control (in conjunction with the @code{.list} directive) whether or
5006 not assembly listings are generated. These two directives maintain an
5007 internal counter (which is zero initially). @code{.list} increments the
5008 counter, and @code{.nolist} decrements it. Assembly listings are
5009 generated whenever the counter is greater than zero.
5012 @section @code{.octa @var{bignums}}
5014 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5015 @cindex @code{octa} directive
5016 @cindex integer, 16-byte
5017 @cindex sixteen byte integer
5018 This directive expects zero or more bignums, separated by commas. For each
5019 bignum, it emits a 16-byte integer.
5021 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5022 hence @emph{octa}-word for 16 bytes.
5025 @section @code{.org @var{new-lc} , @var{fill}}
5027 @cindex @code{org} directive
5028 @cindex location counter, advancing
5029 @cindex advancing location counter
5030 @cindex current address, advancing
5031 Advance the location counter of the current section to
5032 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5033 expression with the same section as the current subsection. That is,
5034 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5035 wrong section, the @code{.org} directive is ignored. To be compatible
5036 with former assemblers, if the section of @var{new-lc} is absolute,
5037 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5038 is the same as the current subsection.
5040 @code{.org} may only increase the location counter, or leave it
5041 unchanged; you cannot use @code{.org} to move the location counter
5044 @c double negative used below "not undefined" because this is a specific
5045 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5046 @c section. doc@cygnus.com 18feb91
5047 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5048 may not be undefined. If you really detest this restriction we eagerly await
5049 a chance to share your improved assembler.
5051 Beware that the origin is relative to the start of the section, not
5052 to the start of the subsection. This is compatible with other
5053 people's assemblers.
5055 When the location counter (of the current subsection) is advanced, the
5056 intervening bytes are filled with @var{fill} which should be an
5057 absolute expression. If the comma and @var{fill} are omitted,
5058 @var{fill} defaults to zero.
5061 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5063 @cindex padding the location counter given a power of two
5064 @cindex @code{p2align} directive
5065 Pad the location counter (in the current subsection) to a particular
5066 storage boundary. The first expression (which must be absolute) is the
5067 number of low-order zero bits the location counter must have after
5068 advancement. For example @samp{.p2align 3} advances the location
5069 counter until it a multiple of 8. If the location counter is already a
5070 multiple of 8, no change is needed.
5072 The second expression (also absolute) gives the fill value to be stored in the
5073 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5074 padding bytes are normally zero. However, on some systems, if the section is
5075 marked as containing code and the fill value is omitted, the space is filled
5076 with no-op instructions.
5078 The third expression is also absolute, and is also optional. If it is present,
5079 it is the maximum number of bytes that should be skipped by this alignment
5080 directive. If doing the alignment would require skipping more bytes than the
5081 specified maximum, then the alignment is not done at all. You can omit the
5082 fill value (the second argument) entirely by simply using two commas after the
5083 required alignment; this can be useful if you want the alignment to be filled
5084 with no-op instructions when appropriate.
5086 @cindex @code{p2alignw} directive
5087 @cindex @code{p2alignl} directive
5088 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5089 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5090 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5091 fill pattern as a four byte longword value. For example, @code{.p2alignw
5092 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5093 filled in with the value 0x368d (the exact placement of the bytes depends upon
5094 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5099 @section @code{.previous}
5101 @cindex @code{previous} directive
5102 @cindex Section Stack
5103 This is one of the ELF section stack manipulation directives. The others are
5104 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5105 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5106 (@pxref{PopSection}).
5108 This directive swaps the current section (and subsection) with most recently
5109 referenced section (and subsection) prior to this one. Multiple
5110 @code{.previous} directives in a row will flip between two sections (and their
5113 In terms of the section stack, this directive swaps the current section with
5114 the top section on the section stack.
5119 @section @code{.popsection}
5121 @cindex @code{popsection} directive
5122 @cindex Section Stack
5123 This is one of the ELF section stack manipulation directives. The others are
5124 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5125 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5128 This directive replaces the current section (and subsection) with the top
5129 section (and subsection) on the section stack. This section is popped off the
5134 @section @code{.print @var{string}}
5136 @cindex @code{print} directive
5137 @command{@value{AS}} will print @var{string} on the standard output during
5138 assembly. You must put @var{string} in double quotes.
5142 @section @code{.protected @var{names}}
5144 @cindex @code{protected} directive
5146 This is one of the ELF visibility directives. The other two are
5147 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5149 This directive overrides the named symbols default visibility (which is set by
5150 their binding: local, global or weak). The directive sets the visibility to
5151 @code{protected} which means that any references to the symbols from within the
5152 components that defines them must be resolved to the definition in that
5153 component, even if a definition in another component would normally preempt
5158 @section @code{.psize @var{lines} , @var{columns}}
5160 @cindex @code{psize} directive
5161 @cindex listing control: paper size
5162 @cindex paper size, for listings
5163 Use this directive to declare the number of lines---and, optionally, the
5164 number of columns---to use for each page, when generating listings.
5166 If you do not use @code{.psize}, listings use a default line-count
5167 of 60. You may omit the comma and @var{columns} specification; the
5168 default width is 200 columns.
5170 @command{@value{AS}} generates formfeeds whenever the specified number of
5171 lines is exceeded (or whenever you explicitly request one, using
5174 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5175 those explicitly specified with @code{.eject}.
5178 @section @code{.purgem @var{name}}
5180 @cindex @code{purgem} directive
5181 Undefine the macro @var{name}, so that later uses of the string will not be
5182 expanded. @xref{Macro}.
5186 @section @code{.pushsection @var{name} , @var{subsection}}
5188 @cindex @code{pushsection} directive
5189 @cindex Section Stack
5190 This is one of the ELF section stack manipulation directives. The others are
5191 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5192 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5195 This directive pushes the current section (and subsection) onto the
5196 top of the section stack, and then replaces the current section and
5197 subsection with @code{name} and @code{subsection}.
5201 @section @code{.quad @var{bignums}}
5203 @cindex @code{quad} directive
5204 @code{.quad} expects zero or more bignums, separated by commas. For
5205 each bignum, it emits
5207 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5208 warning message; and just takes the lowest order 8 bytes of the bignum.
5209 @cindex eight-byte integer
5210 @cindex integer, 8-byte
5212 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5213 hence @emph{quad}-word for 8 bytes.
5216 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5217 warning message; and just takes the lowest order 16 bytes of the bignum.
5218 @cindex sixteen-byte integer
5219 @cindex integer, 16-byte
5223 @section @code{.rept @var{count}}
5225 @cindex @code{rept} directive
5226 Repeat the sequence of lines between the @code{.rept} directive and the next
5227 @code{.endr} directive @var{count} times.
5229 For example, assembling
5237 is equivalent to assembling
5246 @section @code{.sbttl "@var{subheading}"}
5248 @cindex @code{sbttl} directive
5249 @cindex subtitles for listings
5250 @cindex listing control: subtitle
5251 Use @var{subheading} as the title (third line, immediately after the
5252 title line) when generating assembly listings.
5254 This directive affects subsequent pages, as well as the current page if
5255 it appears within ten lines of the top of a page.
5259 @section @code{.scl @var{class}}
5261 @cindex @code{scl} directive
5262 @cindex symbol storage class (COFF)
5263 @cindex COFF symbol storage class
5264 Set the storage-class value for a symbol. This directive may only be
5265 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5266 whether a symbol is static or external, or it may record further
5267 symbolic debugging information.
5270 The @samp{.scl} directive is primarily associated with COFF output; when
5271 configured to generate @code{b.out} output format, @command{@value{AS}}
5272 accepts this directive but ignores it.
5278 @section @code{.section @var{name}}
5280 @cindex named section
5281 Use the @code{.section} directive to assemble the following code into a section
5284 This directive is only supported for targets that actually support arbitrarily
5285 named sections; on @code{a.out} targets, for example, it is not accepted, even
5286 with a standard @code{a.out} section name.
5290 @c only print the extra heading if both COFF and ELF are set
5291 @subheading COFF Version
5294 @cindex @code{section} directive (COFF version)
5295 For COFF targets, the @code{.section} directive is used in one of the following
5299 .section @var{name}[, "@var{flags}"]
5300 .section @var{name}[, @var{subsegment}]
5303 If the optional argument is quoted, it is taken as flags to use for the
5304 section. Each flag is a single character. The following flags are recognized:
5307 bss section (uninitialized data)
5309 section is not loaded
5319 shared section (meaningful for PE targets)
5321 ignored. (For compatibility with the ELF version)
5324 If no flags are specified, the default flags depend upon the section name. If
5325 the section name is not recognized, the default will be for the section to be
5326 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5327 from the section, rather than adding them, so if they are used on their own it
5328 will be as if no flags had been specified at all.
5330 If the optional argument to the @code{.section} directive is not quoted, it is
5331 taken as a subsegment number (@pxref{Sub-Sections}).
5336 @c only print the extra heading if both COFF and ELF are set
5337 @subheading ELF Version
5340 @cindex Section Stack
5341 This is one of the ELF section stack manipulation directives. The others are
5342 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5343 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5344 @code{.previous} (@pxref{Previous}).
5346 @cindex @code{section} directive (ELF version)
5347 For ELF targets, the @code{.section} directive is used like this:
5350 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]
5353 The optional @var{flags} argument is a quoted string which may contain any
5354 combination of the following characters:
5357 section is allocatable
5361 section is executable
5363 section is mergeable
5365 section contains zero terminated strings
5367 section is a member of a section group
5369 section is used for thread-local-storage
5372 The optional @var{type} argument may contain one of the following constants:
5375 section contains data
5377 section does not contain data (i.e., section only occupies space)
5379 section contains data which is used by things other than the program
5381 section contains an array of pointers to init functions
5383 section contains an array of pointers to finish functions
5384 @item @@preinit_array
5385 section contains an array of pointers to pre-init functions
5388 Many targets only support the first three section types.
5390 Note on targets where the @code{@@} character is the start of a comment (eg
5391 ARM) then another character is used instead. For example the ARM port uses the
5394 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5395 be specified as well as an extra argument - @var{entsize} - like this:
5398 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5401 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5402 constants, each @var{entsize} octets long. Sections with both @code{M} and
5403 @code{S} must contain zero terminated strings where each character is
5404 @var{entsize} bytes long. The linker may remove duplicates within sections with
5405 the same name, same entity size and same flags. @var{entsize} must be an
5406 absolute expression.
5408 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5409 be present along with an additional field like this:
5412 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5415 The @var{GroupName} field specifies the name of the section group to which this
5416 particular section belongs. The optional linkage field can contain:
5419 indicates that only one copy of this section should be retained
5424 Note - if both the @var{M} and @var{G} flags are present then the fields for
5425 the Merge flag should come first, like this:
5428 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5431 If no flags are specified, the default flags depend upon the section name. If
5432 the section name is not recognized, the default will be for the section to have
5433 none of the above flags: it will not be allocated in memory, nor writable, nor
5434 executable. The section will contain data.
5436 For ELF targets, the assembler supports another type of @code{.section}
5437 directive for compatibility with the Solaris assembler:
5440 .section "@var{name}"[, @var{flags}...]
5443 Note that the section name is quoted. There may be a sequence of comma
5447 section is allocatable
5451 section is executable
5453 section is used for thread local storage
5456 This directive replaces the current section and subsection. See the
5457 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5458 some examples of how this directive and the other section stack directives
5464 @section @code{.set @var{symbol}, @var{expression}}
5466 @cindex @code{set} directive
5467 @cindex symbol value, setting
5468 Set the value of @var{symbol} to @var{expression}. This
5469 changes @var{symbol}'s value and type to conform to
5470 @var{expression}. If @var{symbol} was flagged as external, it remains
5471 flagged (@pxref{Symbol Attributes}).
5473 You may @code{.set} a symbol many times in the same assembly.
5475 If you @code{.set} a global symbol, the value stored in the object
5476 file is the last value stored into it.
5479 The syntax for @code{set} on the HPPA is
5480 @samp{@var{symbol} .set @var{expression}}.
5484 @section @code{.short @var{expressions}}
5486 @cindex @code{short} directive
5488 @code{.short} is normally the same as @samp{.word}.
5489 @xref{Word,,@code{.word}}.
5491 In some configurations, however, @code{.short} and @code{.word} generate
5492 numbers of different lengths; @pxref{Machine Dependencies}.
5496 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5499 This expects zero or more @var{expressions}, and emits
5500 a 16 bit number for each.
5505 @section @code{.single @var{flonums}}
5507 @cindex @code{single} directive
5508 @cindex floating point numbers (single)
5509 This directive assembles zero or more flonums, separated by commas. It
5510 has the same effect as @code{.float}.
5512 The exact kind of floating point numbers emitted depends on how
5513 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5517 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5518 numbers in @sc{ieee} format.
5524 @section @code{.size}
5526 This directive is used to set the size associated with a symbol.
5530 @c only print the extra heading if both COFF and ELF are set
5531 @subheading COFF Version
5534 @cindex @code{size} directive (COFF version)
5535 For COFF targets, the @code{.size} directive is only permitted inside
5536 @code{.def}/@code{.endef} pairs. It is used like this:
5539 .size @var{expression}
5543 @samp{.size} is only meaningful when generating COFF format output; when
5544 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5551 @c only print the extra heading if both COFF and ELF are set
5552 @subheading ELF Version
5555 @cindex @code{size} directive (ELF version)
5556 For ELF targets, the @code{.size} directive is used like this:
5559 .size @var{name} , @var{expression}
5562 This directive sets the size associated with a symbol @var{name}.
5563 The size in bytes is computed from @var{expression} which can make use of label
5564 arithmetic. This directive is typically used to set the size of function
5570 @section @code{.sleb128 @var{expressions}}
5572 @cindex @code{sleb128} directive
5573 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5574 compact, variable length representation of numbers used by the DWARF
5575 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5577 @ifclear no-space-dir
5579 @section @code{.skip @var{size} , @var{fill}}
5581 @cindex @code{skip} directive
5582 @cindex filling memory
5583 This directive emits @var{size} bytes, each of value @var{fill}. Both
5584 @var{size} and @var{fill} are absolute expressions. If the comma and
5585 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5589 @section @code{.space @var{size} , @var{fill}}
5591 @cindex @code{space} directive
5592 @cindex filling memory
5593 This directive emits @var{size} bytes, each of value @var{fill}. Both
5594 @var{size} and @var{fill} are absolute expressions. If the comma
5595 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5600 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5601 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5602 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5603 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5611 @section @code{.stabd, .stabn, .stabs}
5613 @cindex symbolic debuggers, information for
5614 @cindex @code{stab@var{x}} directives
5615 There are three directives that begin @samp{.stab}.
5616 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5617 The symbols are not entered in the @command{@value{AS}} hash table: they
5618 cannot be referenced elsewhere in the source file.
5619 Up to five fields are required:
5623 This is the symbol's name. It may contain any character except
5624 @samp{\000}, so is more general than ordinary symbol names. Some
5625 debuggers used to code arbitrarily complex structures into symbol names
5629 An absolute expression. The symbol's type is set to the low 8 bits of
5630 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5631 and debuggers choke on silly bit patterns.
5634 An absolute expression. The symbol's ``other'' attribute is set to the
5635 low 8 bits of this expression.
5638 An absolute expression. The symbol's descriptor is set to the low 16
5639 bits of this expression.
5642 An absolute expression which becomes the symbol's value.
5645 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5646 or @code{.stabs} statement, the symbol has probably already been created;
5647 you get a half-formed symbol in your object file. This is
5648 compatible with earlier assemblers!
5651 @cindex @code{stabd} directive
5652 @item .stabd @var{type} , @var{other} , @var{desc}
5654 The ``name'' of the symbol generated is not even an empty string.
5655 It is a null pointer, for compatibility. Older assemblers used a
5656 null pointer so they didn't waste space in object files with empty
5659 The symbol's value is set to the location counter,
5660 relocatably. When your program is linked, the value of this symbol
5661 is the address of the location counter when the @code{.stabd} was
5664 @cindex @code{stabn} directive
5665 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5666 The name of the symbol is set to the empty string @code{""}.
5668 @cindex @code{stabs} directive
5669 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5670 All five fields are specified.
5676 @section @code{.string} "@var{str}"
5678 @cindex string, copying to object file
5679 @cindex @code{string} directive
5681 Copy the characters in @var{str} to the object file. You may specify more than
5682 one string to copy, separated by commas. Unless otherwise specified for a
5683 particular machine, the assembler marks the end of each string with a 0 byte.
5684 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5687 @section @code{.struct @var{expression}}
5689 @cindex @code{struct} directive
5690 Switch to the absolute section, and set the section offset to @var{expression},
5691 which must be an absolute expression. You might use this as follows:
5700 This would define the symbol @code{field1} to have the value 0, the symbol
5701 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5702 value 8. Assembly would be left in the absolute section, and you would need to
5703 use a @code{.section} directive of some sort to change to some other section
5704 before further assembly.
5708 @section @code{.subsection @var{name}}
5710 @cindex @code{subsection} directive
5711 @cindex Section Stack
5712 This is one of the ELF section stack manipulation directives. The others are
5713 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5714 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5717 This directive replaces the current subsection with @code{name}. The current
5718 section is not changed. The replaced subsection is put onto the section stack
5719 in place of the then current top of stack subsection.
5724 @section @code{.symver}
5725 @cindex @code{symver} directive
5726 @cindex symbol versioning
5727 @cindex versions of symbols
5728 Use the @code{.symver} directive to bind symbols to specific version nodes
5729 within a source file. This is only supported on ELF platforms, and is
5730 typically used when assembling files to be linked into a shared library.
5731 There are cases where it may make sense to use this in objects to be bound
5732 into an application itself so as to override a versioned symbol from a
5735 For ELF targets, the @code{.symver} directive can be used like this:
5737 .symver @var{name}, @var{name2@@nodename}
5739 If the symbol @var{name} is defined within the file
5740 being assembled, the @code{.symver} directive effectively creates a symbol
5741 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5742 just don't try and create a regular alias is that the @var{@@} character isn't
5743 permitted in symbol names. The @var{name2} part of the name is the actual name
5744 of the symbol by which it will be externally referenced. The name @var{name}
5745 itself is merely a name of convenience that is used so that it is possible to
5746 have definitions for multiple versions of a function within a single source
5747 file, and so that the compiler can unambiguously know which version of a
5748 function is being mentioned. The @var{nodename} portion of the alias should be
5749 the name of a node specified in the version script supplied to the linker when
5750 building a shared library. If you are attempting to override a versioned
5751 symbol from a shared library, then @var{nodename} should correspond to the
5752 nodename of the symbol you are trying to override.
5754 If the symbol @var{name} is not defined within the file being assembled, all
5755 references to @var{name} will be changed to @var{name2@@nodename}. If no
5756 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5759 Another usage of the @code{.symver} directive is:
5761 .symver @var{name}, @var{name2@@@@nodename}
5763 In this case, the symbol @var{name} must exist and be defined within
5764 the file being assembled. It is similar to @var{name2@@nodename}. The
5765 difference is @var{name2@@@@nodename} will also be used to resolve
5766 references to @var{name2} by the linker.
5768 The third usage of the @code{.symver} directive is:
5770 .symver @var{name}, @var{name2@@@@@@nodename}
5772 When @var{name} is not defined within the
5773 file being assembled, it is treated as @var{name2@@nodename}. When
5774 @var{name} is defined within the file being assembled, the symbol
5775 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5780 @section @code{.tag @var{structname}}
5782 @cindex COFF structure debugging
5783 @cindex structure debugging, COFF
5784 @cindex @code{tag} directive
5785 This directive is generated by compilers to include auxiliary debugging
5786 information in the symbol table. It is only permitted inside
5787 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5788 definitions in the symbol table with instances of those structures.
5791 @samp{.tag} is only used when generating COFF format output; when
5792 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5798 @section @code{.text @var{subsection}}
5800 @cindex @code{text} directive
5801 Tells @command{@value{AS}} to assemble the following statements onto the end of
5802 the text subsection numbered @var{subsection}, which is an absolute
5803 expression. If @var{subsection} is omitted, subsection number zero
5807 @section @code{.title "@var{heading}"}
5809 @cindex @code{title} directive
5810 @cindex listing control: title line
5811 Use @var{heading} as the title (second line, immediately after the
5812 source file name and pagenumber) when generating assembly listings.
5814 This directive affects subsequent pages, as well as the current page if
5815 it appears within ten lines of the top of a page.
5819 @section @code{.type}
5821 This directive is used to set the type of a symbol.
5825 @c only print the extra heading if both COFF and ELF are set
5826 @subheading COFF Version
5829 @cindex COFF symbol type
5830 @cindex symbol type, COFF
5831 @cindex @code{type} directive (COFF version)
5832 For COFF targets, this directive is permitted only within
5833 @code{.def}/@code{.endef} pairs. It is used like this:
5839 This records the integer @var{int} as the type attribute of a symbol table
5843 @samp{.type} is associated only with COFF format output; when
5844 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5845 directive but ignores it.
5851 @c only print the extra heading if both COFF and ELF are set
5852 @subheading ELF Version
5855 @cindex ELF symbol type
5856 @cindex symbol type, ELF
5857 @cindex @code{type} directive (ELF version)
5858 For ELF targets, the @code{.type} directive is used like this:
5861 .type @var{name} , @var{type description}
5864 This sets the type of symbol @var{name} to be either a
5865 function symbol or an object symbol. There are five different syntaxes
5866 supported for the @var{type description} field, in order to provide
5867 compatibility with various other assemblers. The syntaxes supported are:
5870 .type <name>,#function
5871 .type <name>,#object
5873 .type <name>,@@function
5874 .type <name>,@@object
5876 .type <name>,%function
5877 .type <name>,%object
5879 .type <name>,"function"
5880 .type <name>,"object"
5882 .type <name> STT_FUNCTION
5883 .type <name> STT_OBJECT
5889 @section @code{.uleb128 @var{expressions}}
5891 @cindex @code{uleb128} directive
5892 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5893 compact, variable length representation of numbers used by the DWARF
5894 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5898 @section @code{.val @var{addr}}
5900 @cindex @code{val} directive
5901 @cindex COFF value attribute
5902 @cindex value attribute, COFF
5903 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5904 records the address @var{addr} as the value attribute of a symbol table
5908 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5909 configured for @code{b.out}, it accepts this directive but ignores it.
5915 @section @code{.version "@var{string}"}
5917 @cindex @code{version} directive
5918 This directive creates a @code{.note} section and places into it an ELF
5919 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5924 @section @code{.vtable_entry @var{table}, @var{offset}}
5926 @cindex @code{vtable_entry} directive
5927 This directive finds or creates a symbol @code{table} and creates a
5928 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5931 @section @code{.vtable_inherit @var{child}, @var{parent}}
5933 @cindex @code{vtable_inherit} directive
5934 This directive finds the symbol @code{child} and finds or creates the symbol
5935 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5936 parent whose addend is the value of the child symbol. As a special case the
5937 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5941 @section @code{.warning "@var{string}"}
5942 @cindex warning directive
5943 Similar to the directive @code{.error}
5944 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
5947 @section @code{.weak @var{names}}
5949 @cindex @code{weak} directive
5950 This directive sets the weak attribute on the comma separated list of symbol
5951 @code{names}. If the symbols do not already exist, they will be created.
5953 On COFF targets other than PE, weak symbols are a GNU extension. This
5954 directive sets the weak attribute on the comma separated list of symbol
5955 @code{names}. If the symbols do not already exist, they will be created.
5957 On the PE target, weak symbols are supported natively as weak aliases.
5958 When a weak symbol is created that is not an alias, GAS creates an
5959 alternate symbol to hold the default value.
5962 @section @code{.word @var{expressions}}
5964 @cindex @code{word} directive
5965 This directive expects zero or more @var{expressions}, of any section,
5966 separated by commas.
5969 For each expression, @command{@value{AS}} emits a 32-bit number.
5972 For each expression, @command{@value{AS}} emits a 16-bit number.
5977 The size of the number emitted, and its byte order,
5978 depend on what target computer the assembly is for.
5981 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5982 @c happen---32-bit addressability, period; no long/short jumps.
5983 @ifset DIFF-TBL-KLUGE
5984 @cindex difference tables altered
5985 @cindex altered difference tables
5987 @emph{Warning: Special Treatment to support Compilers}
5991 Machines with a 32-bit address space, but that do less than 32-bit
5992 addressing, require the following special treatment. If the machine of
5993 interest to you does 32-bit addressing (or doesn't require it;
5994 @pxref{Machine Dependencies}), you can ignore this issue.
5997 In order to assemble compiler output into something that works,
5998 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
5999 Directives of the form @samp{.word sym1-sym2} are often emitted by
6000 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6001 directive of the form @samp{.word sym1-sym2}, and the difference between
6002 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6003 creates a @dfn{secondary jump table}, immediately before the next label.
6004 This secondary jump table is preceded by a short-jump to the
6005 first byte after the secondary table. This short-jump prevents the flow
6006 of control from accidentally falling into the new table. Inside the
6007 table is a long-jump to @code{sym2}. The original @samp{.word}
6008 contains @code{sym1} minus the address of the long-jump to
6011 If there were several occurrences of @samp{.word sym1-sym2} before the
6012 secondary jump table, all of them are adjusted. If there was a
6013 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6014 long-jump to @code{sym4} is included in the secondary jump table,
6015 and the @code{.word} directives are adjusted to contain @code{sym3}
6016 minus the address of the long-jump to @code{sym4}; and so on, for as many
6017 entries in the original jump table as necessary.
6020 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6021 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6022 assembly language programmers.
6025 @c end DIFF-TBL-KLUGE
6028 @section Deprecated Directives
6030 @cindex deprecated directives
6031 @cindex obsolescent directives
6032 One day these directives won't work.
6033 They are included for compatibility with older assemblers.
6040 @node Machine Dependencies
6041 @chapter Machine Dependent Features
6043 @cindex machine dependencies
6044 The machine instruction sets are (almost by definition) different on
6045 each machine where @command{@value{AS}} runs. Floating point representations
6046 vary as well, and @command{@value{AS}} often supports a few additional
6047 directives or command-line options for compatibility with other
6048 assemblers on a particular platform. Finally, some versions of
6049 @command{@value{AS}} support special pseudo-instructions for branch
6052 This chapter discusses most of these differences, though it does not
6053 include details on any machine's instruction set. For details on that
6054 subject, see the hardware manufacturer's manual.
6058 * Alpha-Dependent:: Alpha Dependent Features
6061 * ARC-Dependent:: ARC Dependent Features
6064 * ARM-Dependent:: ARM Dependent Features
6067 * CRIS-Dependent:: CRIS Dependent Features
6070 * D10V-Dependent:: D10V Dependent Features
6073 * D30V-Dependent:: D30V Dependent Features
6076 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6079 * HPPA-Dependent:: HPPA Dependent Features
6082 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6085 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6088 * i860-Dependent:: Intel 80860 Dependent Features
6091 * i960-Dependent:: Intel 80960 Dependent Features
6094 * IA-64-Dependent:: Intel IA-64 Dependent Features
6097 * IP2K-Dependent:: IP2K Dependent Features
6100 * M32C-Dependent:: M32C Dependent Features
6103 * M32R-Dependent:: M32R Dependent Features
6106 * M68K-Dependent:: M680x0 Dependent Features
6109 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6112 * MIPS-Dependent:: MIPS Dependent Features
6115 * MMIX-Dependent:: MMIX Dependent Features
6118 * MSP430-Dependent:: MSP430 Dependent Features
6121 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6122 * SH64-Dependent:: SuperH SH64 Dependent Features
6125 * PDP-11-Dependent:: PDP-11 Dependent Features
6128 * PJ-Dependent:: picoJava Dependent Features
6131 * PPC-Dependent:: PowerPC Dependent Features
6134 * Sparc-Dependent:: SPARC Dependent Features
6137 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6140 * V850-Dependent:: V850 Dependent Features
6143 * Xtensa-Dependent:: Xtensa Dependent Features
6146 * Z8000-Dependent:: Z8000 Dependent Features
6149 * Vax-Dependent:: VAX Dependent Features
6156 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6157 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6158 @c peculiarity: to preserve cross-references, there must be a node called
6159 @c "Machine Dependencies". Hence the conditional nodenames in each
6160 @c major node below. Node defaulting in makeinfo requires adjacency of
6161 @c node and sectioning commands; hence the repetition of @chapter BLAH
6162 @c in both conditional blocks.
6165 @include c-alpha.texi
6177 @include c-cris.texi
6182 @node Machine Dependencies
6183 @chapter Machine Dependent Features
6185 The machine instruction sets are different on each Renesas chip family,
6186 and there are also some syntax differences among the families. This
6187 chapter describes the specific @command{@value{AS}} features for each
6191 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6192 * SH-Dependent:: Renesas SH Dependent Features
6199 @include c-d10v.texi
6203 @include c-d30v.texi
6207 @include c-h8300.texi
6211 @include c-hppa.texi
6215 @include c-i370.texi
6219 @include c-i386.texi
6223 @include c-i860.texi
6227 @include c-i960.texi
6231 @include c-ia64.texi
6235 @include c-ip2k.texi
6239 @include c-m32c.texi
6243 @include c-m32r.texi
6247 @include c-m68k.texi
6251 @include c-m68hc11.texi
6255 @include c-mips.texi
6259 @include c-mmix.texi
6263 @include c-msp430.texi
6267 @include c-ns32k.texi
6271 @include c-pdp11.texi
6284 @include c-sh64.texi
6288 @include c-sparc.texi
6292 @include c-tic54x.texi
6304 @include c-v850.texi
6308 @include c-xtensa.texi
6312 @c reverse effect of @down at top of generic Machine-Dep chapter
6316 @node Reporting Bugs
6317 @chapter Reporting Bugs
6318 @cindex bugs in assembler
6319 @cindex reporting bugs in assembler
6321 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6323 Reporting a bug may help you by bringing a solution to your problem, or it may
6324 not. But in any case the principal function of a bug report is to help the
6325 entire community by making the next version of @command{@value{AS}} work better.
6326 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6328 In order for a bug report to serve its purpose, you must include the
6329 information that enables us to fix the bug.
6332 * Bug Criteria:: Have you found a bug?
6333 * Bug Reporting:: How to report bugs
6337 @section Have You Found a Bug?
6338 @cindex bug criteria
6340 If you are not sure whether you have found a bug, here are some guidelines:
6343 @cindex fatal signal
6344 @cindex assembler crash
6345 @cindex crash of assembler
6347 If the assembler gets a fatal signal, for any input whatever, that is a
6348 @command{@value{AS}} bug. Reliable assemblers never crash.
6350 @cindex error on valid input
6352 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6354 @cindex invalid input
6356 If @command{@value{AS}} does not produce an error message for invalid input, that
6357 is a bug. However, you should note that your idea of ``invalid input'' might
6358 be our idea of ``an extension'' or ``support for traditional practice''.
6361 If you are an experienced user of assemblers, your suggestions for improvement
6362 of @command{@value{AS}} are welcome in any case.
6366 @section How to Report Bugs
6368 @cindex assembler bugs, reporting
6370 A number of companies and individuals offer support for @sc{gnu} products. If
6371 you obtained @command{@value{AS}} from a support organization, we recommend you
6372 contact that organization first.
6374 You can find contact information for many support companies and
6375 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6378 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6379 to @samp{bug-binutils@@gnu.org}.
6381 The fundamental principle of reporting bugs usefully is this:
6382 @strong{report all the facts}. If you are not sure whether to state a
6383 fact or leave it out, state it!
6385 Often people omit facts because they think they know what causes the problem
6386 and assume that some details do not matter. Thus, you might assume that the
6387 name of a symbol you use in an example does not matter. Well, probably it does
6388 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6389 happens to fetch from the location where that name is stored in memory;
6390 perhaps, if the name were different, the contents of that location would fool
6391 the assembler into doing the right thing despite the bug. Play it safe and
6392 give a specific, complete example. That is the easiest thing for you to do,
6393 and the most helpful.
6395 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6396 it is new to us. Therefore, always write your bug reports on the assumption
6397 that the bug has not been reported previously.
6399 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6400 bell?'' This cannot help us fix a bug, so it is basically useless. We
6401 respond by asking for enough details to enable us to investigate.
6402 You might as well expedite matters by sending them to begin with.
6404 To enable us to fix the bug, you should include all these things:
6408 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6409 it with the @samp{--version} argument.
6411 Without this, we will not know whether there is any point in looking for
6412 the bug in the current version of @command{@value{AS}}.
6415 Any patches you may have applied to the @command{@value{AS}} source.
6418 The type of machine you are using, and the operating system name and
6422 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6426 The command arguments you gave the assembler to assemble your example and
6427 observe the bug. To guarantee you will not omit something important, list them
6428 all. A copy of the Makefile (or the output from make) is sufficient.
6430 If we were to try to guess the arguments, we would probably guess wrong
6431 and then we might not encounter the bug.
6434 A complete input file that will reproduce the bug. If the bug is observed when
6435 the assembler is invoked via a compiler, send the assembler source, not the
6436 high level language source. Most compilers will produce the assembler source
6437 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6438 the options @samp{-v --save-temps}; this will save the assembler source in a
6439 file with an extension of @file{.s}, and also show you exactly how
6440 @command{@value{AS}} is being run.
6443 A description of what behavior you observe that you believe is
6444 incorrect. For example, ``It gets a fatal signal.''
6446 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6447 will certainly notice it. But if the bug is incorrect output, we might not
6448 notice unless it is glaringly wrong. You might as well not give us a chance to
6451 Even if the problem you experience is a fatal signal, you should still say so
6452 explicitly. Suppose something strange is going on, such as, your copy of
6453 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6454 library on your system. (This has happened!) Your copy might crash and ours
6455 would not. If you told us to expect a crash, then when ours fails to crash, we
6456 would know that the bug was not happening for us. If you had not told us to
6457 expect a crash, then we would not be able to draw any conclusion from our
6461 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6462 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6463 option. Always send diffs from the old file to the new file. If you even
6464 discuss something in the @command{@value{AS}} source, refer to it by context, not
6467 The line numbers in our development sources will not match those in your
6468 sources. Your line numbers would convey no useful information to us.
6471 Here are some things that are not necessary:
6475 A description of the envelope of the bug.
6477 Often people who encounter a bug spend a lot of time investigating
6478 which changes to the input file will make the bug go away and which
6479 changes will not affect it.
6481 This is often time consuming and not very useful, because the way we
6482 will find the bug is by running a single example under the debugger
6483 with breakpoints, not by pure deduction from a series of examples.
6484 We recommend that you save your time for something else.
6486 Of course, if you can find a simpler example to report @emph{instead}
6487 of the original one, that is a convenience for us. Errors in the
6488 output will be easier to spot, running under the debugger will take
6489 less time, and so on.
6491 However, simplification is not vital; if you do not want to do this,
6492 report the bug anyway and send us the entire test case you used.
6495 A patch for the bug.
6497 A patch for the bug does help us if it is a good one. But do not omit
6498 the necessary information, such as the test case, on the assumption that
6499 a patch is all we need. We might see problems with your patch and decide
6500 to fix the problem another way, or we might not understand it at all.
6502 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6503 construct an example that will make the program follow a certain path through
6504 the code. If you do not send us the example, we will not be able to construct
6505 one, so we will not be able to verify that the bug is fixed.
6507 And if we cannot understand what bug you are trying to fix, or why your
6508 patch should be an improvement, we will not install it. A test case will
6509 help us to understand.
6512 A guess about what the bug is or what it depends on.
6514 Such guesses are usually wrong. Even we cannot guess right about such
6515 things without first using the debugger to find the facts.
6518 @node Acknowledgements
6519 @chapter Acknowledgements
6521 If you have contributed to GAS and your name isn't listed here,
6522 it is not meant as a slight. We just don't know about it. Send mail to the
6523 maintainer, and we'll correct the situation. Currently
6525 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6527 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6530 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6531 information and the 68k series machines, most of the preprocessing pass, and
6532 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6534 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6535 many bug fixes, including merging support for several processors, breaking GAS
6536 up to handle multiple object file format back ends (including heavy rewrite,
6537 testing, an integration of the coff and b.out back ends), adding configuration
6538 including heavy testing and verification of cross assemblers and file splits
6539 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6540 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6541 port (including considerable amounts of reverse engineering), a SPARC opcode
6542 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6543 assertions and made them work, much other reorganization, cleanup, and lint.
6545 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6546 in format-specific I/O modules.
6548 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6549 has done much work with it since.
6551 The Intel 80386 machine description was written by Eliot Dresselhaus.
6553 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6555 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6556 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6558 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6559 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6560 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6561 support a.out format.
6563 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
6564 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
6565 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6566 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6569 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6570 simplified the configuration of which versions accept which directives. He
6571 updated the 68k machine description so that Motorola's opcodes always produced
6572 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6573 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6574 cross-compilation support, and one bug in relaxation that took a week and
6575 required the proverbial one-bit fix.
6577 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6578 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6579 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6580 PowerPC assembler, and made a few other minor patches.
6582 Steve Chamberlain made GAS able to generate listings.
6584 Hewlett-Packard contributed support for the HP9000/300.
6586 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6587 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6588 formats). This work was supported by both the Center for Software Science at
6589 the University of Utah and Cygnus Support.
6591 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6592 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6593 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6594 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6595 and some initial 64-bit support).
6597 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6599 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6600 support for openVMS/Alpha.
6602 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6605 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6606 Inc. added support for Xtensa processors.
6608 Several engineers at Cygnus Support have also provided many small bug fixes and
6609 configuration enhancements.
6611 Many others have contributed large or small bugfixes and enhancements. If
6612 you have contributed significant work and are not mentioned on this list, and
6613 want to be, let us know. Some of the history has been lost; we are not
6614 intentionally leaving anyone out.
projects / platform / upstream / binutils.git / blob