1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
3 @c 2001, 2002, 2003, 2004, 2005, 2006, 2007
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,
104 2006, 2007 Free Software Foundation, Inc.
106 Permission is granted to copy, distribute and/or modify this document
107 under the terms of the GNU Free Documentation License, Version 1.1
108 or any later version published by the Free Software Foundation;
109 with no Invariant Sections, with no Front-Cover Texts, and with no
110 Back-Cover Texts. A copy of the license is included in the
111 section entitled ``GNU Free Documentation License''.
116 Permission is granted to process this file through Tex and print the
117 results, provided the printed document carries copying permission
118 notice identical to this one except for the removal of this paragraph
119 (this paragraph not being relevant to the printed manual).
125 @title Using @value{AS}
126 @subtitle The @sc{gnu} Assembler
128 @subtitle for the @value{TARGET} family
130 @ifset VERSION_PACKAGE
132 @subtitle @value{VERSION_PACKAGE}
135 @subtitle Version @value{VERSION}
138 The Free Software Foundation Inc.@: thanks The Nice Computer
139 Company of Australia for loaning Dean Elsner to write the
140 first (Vax) version of @command{as} for Project @sc{gnu}.
141 The proprietors, management and staff of TNCCA thank FSF for
142 distracting the boss while they got some work
145 @author Dean Elsner, Jay Fenlason & friends
149 \hfill {\it Using {\tt @value{AS}}}\par
150 \hfill Edited by Cygnus Support\par
152 %"boxit" macro for figures:
153 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
154 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
155 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
156 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
157 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
160 @vskip 0pt plus 1filll
161 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
162 2006, 2007 Free Software Foundation, Inc.
164 Permission is granted to copy, distribute and/or modify this document
165 under the terms of the GNU Free Documentation License, Version 1.1
166 or any later version published by the Free Software Foundation;
167 with no Invariant Sections, with no Front-Cover Texts, and with no
168 Back-Cover Texts. A copy of the license is included in the
169 section entitled ``GNU Free Documentation License''.
175 @top Using @value{AS}
177 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
178 @ifset VERSION_PACKAGE
179 @value{VERSION_PACKAGE}
181 version @value{VERSION}.
183 This version of the file describes @command{@value{AS}} configured to generate
184 code for @value{TARGET} architectures.
187 This document is distributed under the terms of the GNU Free
188 Documentation License. A copy of the license is included in the
189 section entitled ``GNU Free Documentation License''.
192 * Overview:: Overview
193 * Invoking:: Command-Line Options
195 * Sections:: Sections and Relocation
197 * Expressions:: Expressions
198 * Pseudo Ops:: Assembler Directives
199 * Machine Dependencies:: Machine Dependent Features
200 * Reporting Bugs:: Reporting Bugs
201 * Acknowledgements:: Who Did What
202 * GNU Free Documentation License:: GNU Free Documentation License
203 * AS Index:: AS Index
210 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
212 This version of the manual describes @command{@value{AS}} configured to generate
213 code for @value{TARGET} architectures.
217 @cindex invocation summary
218 @cindex option summary
219 @cindex summary of options
220 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
221 see @ref{Invoking,,Command-Line Options}.
223 @c man title AS the portable GNU assembler.
227 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
231 @c We don't use deffn and friends for the following because they seem
232 @c to be limited to one line for the header.
234 @c man begin SYNOPSIS
235 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
236 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
237 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
238 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
239 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
240 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
241 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
242 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
243 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
244 [@b{--target-help}] [@var{target-options}]
245 [@b{--}|@var{files} @dots{}]
247 @c Target dependent options are listed below. Keep the list sorted.
248 @c Add an empty line for separation.
251 @emph{Target Alpha options:}
253 [@b{-mdebug} | @b{-no-mdebug}]
254 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
255 [@b{-F}] [@b{-32addr}]
259 @emph{Target ARC options:}
265 @emph{Target ARM options:}
266 @c Don't document the deprecated options
267 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
268 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
269 [@b{-mfpu}=@var{floating-point-format}]
270 [@b{-mfloat-abi}=@var{abi}]
271 [@b{-meabi}=@var{ver}]
274 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
275 @b{-mapcs-reentrant}]
276 [@b{-mthumb-interwork}] [@b{-k}]
280 @emph{Target CRIS options:}
281 [@b{--underscore} | @b{--no-underscore}]
283 [@b{--emulation=criself} | @b{--emulation=crisaout}]
284 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
285 @c Deprecated -- deliberately not documented.
290 @emph{Target D10V options:}
295 @emph{Target D30V options:}
296 [@b{-O}|@b{-n}|@b{-N}]
299 @c Renesas family chips have no machine-dependent assembler options
302 @c HPPA has no machine-dependent assembler options (yet).
306 @emph{Target i386 options:}
307 [@b{--32}|@b{--64}] [@b{-n}]
308 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}]
312 @emph{Target i960 options:}
313 @c see md_parse_option in tc-i960.c
314 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
316 [@b{-b}] [@b{-no-relax}]
320 @emph{Target IA-64 options:}
321 [@b{-mconstant-gp}|@b{-mauto-pic}]
322 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
324 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
325 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
326 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
327 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
331 @emph{Target IP2K options:}
332 [@b{-mip2022}|@b{-mip2022ext}]
336 @emph{Target M32C options:}
337 [@b{-m32c}|@b{-m16c}]
341 @emph{Target M32R options:}
342 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
347 @emph{Target M680X0 options:}
348 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
352 @emph{Target M68HC11 options:}
353 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
354 [@b{-mshort}|@b{-mlong}]
355 [@b{-mshort-double}|@b{-mlong-double}]
356 [@b{--force-long-branches}] [@b{--short-branches}]
357 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
358 [@b{--print-opcodes}] [@b{--generate-example}]
362 @emph{Target MCORE options:}
363 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
364 [@b{-mcpu=[210|340]}]
368 @emph{Target MIPS options:}
369 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
370 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
371 [@b{-non_shared}] [@b{-xgot}]
372 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
373 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
374 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
375 [@b{-mips64}] [@b{-mips64r2}]
376 [@b{-construct-floats}] [@b{-no-construct-floats}]
377 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
378 [@b{-mfix7000}] [@b{-mno-fix7000}]
379 [@b{-mips16}] [@b{-no-mips16}]
380 [@b{-msmartmips}] [@b{-mno-smartmips}]
381 [@b{-mips3d}] [@b{-no-mips3d}]
382 [@b{-mdmx}] [@b{-no-mdmx}]
383 [@b{-mdsp}] [@b{-mno-dsp}]
384 [@b{-mdspr2}] [@b{-mno-dspr2}]
385 [@b{-mmt}] [@b{-mno-mt}]
386 [@b{-mdebug}] [@b{-no-mdebug}]
387 [@b{-mpdr}] [@b{-mno-pdr}]
391 @emph{Target MMIX options:}
392 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
393 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
394 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
395 [@b{--linker-allocated-gregs}]
399 @emph{Target PDP11 options:}
400 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
401 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
402 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
406 @emph{Target picoJava options:}
411 @emph{Target PowerPC options:}
412 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
413 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
414 @b{-mbooke32}|@b{-mbooke64}]
415 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
416 [@b{-mregnames}|@b{-mno-regnames}]
417 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
418 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
419 [@b{-msolaris}|@b{-mno-solaris}]
423 @emph{Target SPARC options:}
424 @c The order here is important. See c-sparc.texi.
425 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
426 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
427 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
432 @emph{Target TIC54X options:}
433 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
434 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
439 @emph{Target Z80 options:}
440 [@b{-z80}] [@b{-r800}]
441 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
442 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
443 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
444 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
445 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
446 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
450 @c Z8000 has no machine-dependent assembler options
454 @emph{Target Xtensa options:}
455 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
456 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
457 [@b{--[no-]transform}]
458 [@b{--rename-section} @var{oldname}=@var{newname}]
466 @include at-file.texi
469 Turn on listings, in any of a variety of ways:
473 omit false conditionals
476 omit debugging directives
479 include high-level source
485 include macro expansions
488 omit forms processing
494 set the name of the listing file
497 You may combine these options; for example, use @samp{-aln} for assembly
498 listing without forms processing. The @samp{=file} option, if used, must be
499 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
502 Begin in alternate macro mode.
504 @xref{Altmacro,,@code{.altmacro}}.
508 Ignored. This option is accepted for script compatibility with calls to
511 @item --defsym @var{sym}=@var{value}
512 Define the symbol @var{sym} to be @var{value} before assembling the input file.
513 @var{value} must be an integer constant. As in C, a leading @samp{0x}
514 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
515 value. The value of the symbol can be overridden inside a source file via the
516 use of a @code{.set} pseudo-op.
519 ``fast''---skip whitespace and comment preprocessing (assume source is
524 Generate debugging information for each assembler source line using whichever
525 debug format is preferred by the target. This currently means either STABS,
529 Generate stabs debugging information for each assembler line. This
530 may help debugging assembler code, if the debugger can handle it.
533 Generate stabs debugging information for each assembler line, with GNU
534 extensions that probably only gdb can handle, and that could make other
535 debuggers crash or refuse to read your program. This
536 may help debugging assembler code. Currently the only GNU extension is
537 the location of the current working directory at assembling time.
540 Generate DWARF2 debugging information for each assembler line. This
541 may help debugging assembler code, if the debugger can handle it. Note---this
542 option is only supported by some targets, not all of them.
545 Print a summary of the command line options and exit.
548 Print a summary of all target specific options and exit.
551 Add directory @var{dir} to the search list for @code{.include} directives.
554 Don't warn about signed overflow.
557 @ifclear DIFF-TBL-KLUGE
558 This option is accepted but has no effect on the @value{TARGET} family.
560 @ifset DIFF-TBL-KLUGE
561 Issue warnings when difference tables altered for long displacements.
566 Keep (in the symbol table) local symbols. These symbols start with
567 system-specific local label prefixes, typically @samp{.L} for ELF systems
568 or @samp{L} for traditional a.out systems.
573 @item --listing-lhs-width=@var{number}
574 Set the maximum width, in words, of the output data column for an assembler
575 listing to @var{number}.
577 @item --listing-lhs-width2=@var{number}
578 Set the maximum width, in words, of the output data column for continuation
579 lines in an assembler listing to @var{number}.
581 @item --listing-rhs-width=@var{number}
582 Set the maximum width of an input source line, as displayed in a listing, to
585 @item --listing-cont-lines=@var{number}
586 Set the maximum number of lines printed in a listing for a single line of input
589 @item -o @var{objfile}
590 Name the object-file output from @command{@value{AS}} @var{objfile}.
593 Fold the data section into the text section.
595 @kindex --hash-size=@var{number}
596 Set the default size of GAS's hash tables to a prime number close to
597 @var{number}. Increasing this value can reduce the length of time it takes the
598 assembler to perform its tasks, at the expense of increasing the assembler's
599 memory requirements. Similarly reducing this value can reduce the memory
600 requirements at the expense of speed.
602 @item --reduce-memory-overheads
603 This option reduces GAS's memory requirements, at the expense of making the
604 assembly processes slower. Currently this switch is a synonym for
605 @samp{--hash-size=4051}, but in the future it may have other effects as well.
608 Print the maximum space (in bytes) and total time (in seconds) used by
611 @item --strip-local-absolute
612 Remove local absolute symbols from the outgoing symbol table.
616 Print the @command{as} version.
619 Print the @command{as} version and exit.
623 Suppress warning messages.
625 @item --fatal-warnings
626 Treat warnings as errors.
629 Don't suppress warning messages or treat them as errors.
638 Generate an object file even after errors.
640 @item -- | @var{files} @dots{}
641 Standard input, or source files to assemble.
646 The following options are available when @value{AS} is configured for
651 This option selects the core processor variant.
653 Select either big-endian (-EB) or little-endian (-EL) output.
658 The following options are available when @value{AS} is configured for the ARM
662 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
663 Specify which ARM processor variant is the target.
664 @item -march=@var{architecture}[+@var{extension}@dots{}]
665 Specify which ARM architecture variant is used by the target.
666 @item -mfpu=@var{floating-point-format}
667 Select which Floating Point architecture is the target.
668 @item -mfloat-abi=@var{abi}
669 Select which floating point ABI is in use.
671 Enable Thumb only instruction decoding.
672 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
673 Select which procedure calling convention is in use.
675 Select either big-endian (-EB) or little-endian (-EL) output.
676 @item -mthumb-interwork
677 Specify that the code has been generated with interworking between Thumb and
680 Specify that PIC code has been generated.
685 See the info pages for documentation of the CRIS-specific options.
689 The following options are available when @value{AS} is configured for
692 @cindex D10V optimization
693 @cindex optimization, D10V
695 Optimize output by parallelizing instructions.
700 The following options are available when @value{AS} is configured for a D30V
703 @cindex D30V optimization
704 @cindex optimization, D30V
706 Optimize output by parallelizing instructions.
710 Warn when nops are generated.
712 @cindex D30V nops after 32-bit multiply
714 Warn when a nop after a 32-bit multiply instruction is generated.
719 The following options are available when @value{AS} is configured for the
720 Intel 80960 processor.
723 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
724 Specify which variant of the 960 architecture is the target.
727 Add code to collect statistics about branches taken.
730 Do not alter compare-and-branch instructions for long displacements;
737 The following options are available when @value{AS} is configured for the
743 Specifies that the extended IP2022 instructions are allowed.
746 Restores the default behaviour, which restricts the permitted instructions to
747 just the basic IP2022 ones.
753 The following options are available when @value{AS} is configured for the
754 Renesas M32C and M16C processors.
759 Assemble M32C instructions.
762 Assemble M16C instructions (the default).
768 The following options are available when @value{AS} is configured for the
769 Renesas M32R (formerly Mitsubishi M32R) series.
774 Specify which processor in the M32R family is the target. The default
775 is normally the M32R, but this option changes it to the M32RX.
777 @item --warn-explicit-parallel-conflicts or --Wp
778 Produce warning messages when questionable parallel constructs are
781 @item --no-warn-explicit-parallel-conflicts or --Wnp
782 Do not produce warning messages when questionable parallel constructs are
789 The following options are available when @value{AS} is configured for the
790 Motorola 68000 series.
795 Shorten references to undefined symbols, to one word instead of two.
797 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
798 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
799 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
800 Specify what processor in the 68000 family is the target. The default
801 is normally the 68020, but this can be changed at configuration time.
803 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
804 The target machine does (or does not) have a floating-point coprocessor.
805 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
806 the basic 68000 is not compatible with the 68881, a combination of the
807 two can be specified, since it's possible to do emulation of the
808 coprocessor instructions with the main processor.
810 @item -m68851 | -mno-68851
811 The target machine does (or does not) have a memory-management
812 unit coprocessor. The default is to assume an MMU for 68020 and up.
819 For details about the PDP-11 machine dependent features options,
820 see @ref{PDP-11-Options}.
823 @item -mpic | -mno-pic
824 Generate position-independent (or position-dependent) code. The
825 default is @option{-mpic}.
828 @itemx -mall-extensions
829 Enable all instruction set extensions. This is the default.
831 @item -mno-extensions
832 Disable all instruction set extensions.
834 @item -m@var{extension} | -mno-@var{extension}
835 Enable (or disable) a particular instruction set extension.
838 Enable the instruction set extensions supported by a particular CPU, and
839 disable all other extensions.
841 @item -m@var{machine}
842 Enable the instruction set extensions supported by a particular machine
843 model, and disable all other extensions.
849 The following options are available when @value{AS} is configured for
850 a picoJava processor.
854 @cindex PJ endianness
855 @cindex endianness, PJ
856 @cindex big endian output, PJ
858 Generate ``big endian'' format output.
860 @cindex little endian output, PJ
862 Generate ``little endian'' format output.
868 The following options are available when @value{AS} is configured for the
869 Motorola 68HC11 or 68HC12 series.
873 @item -m68hc11 | -m68hc12 | -m68hcs12
874 Specify what processor is the target. The default is
875 defined by the configuration option when building the assembler.
878 Specify to use the 16-bit integer ABI.
881 Specify to use the 32-bit integer ABI.
884 Specify to use the 32-bit double ABI.
887 Specify to use the 64-bit double ABI.
889 @item --force-long-branches
890 Relative branches are turned into absolute ones. This concerns
891 conditional branches, unconditional branches and branches to a
894 @item -S | --short-branches
895 Do not turn relative branches into absolute ones
896 when the offset is out of range.
898 @item --strict-direct-mode
899 Do not turn the direct addressing mode into extended addressing mode
900 when the instruction does not support direct addressing mode.
902 @item --print-insn-syntax
903 Print the syntax of instruction in case of error.
905 @item --print-opcodes
906 print the list of instructions with syntax and then exit.
908 @item --generate-example
909 print an example of instruction for each possible instruction and then exit.
910 This option is only useful for testing @command{@value{AS}}.
916 The following options are available when @command{@value{AS}} is configured
917 for the SPARC architecture:
920 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
921 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
922 Explicitly select a variant of the SPARC architecture.
924 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
925 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
927 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
928 UltraSPARC extensions.
930 @item -xarch=v8plus | -xarch=v8plusa
931 For compatibility with the Solaris v9 assembler. These options are
932 equivalent to -Av8plus and -Av8plusa, respectively.
935 Warn when the assembler switches to another architecture.
940 The following options are available when @value{AS} is configured for the 'c54x
945 Enable extended addressing mode. All addresses and relocations will assume
946 extended addressing (usually 23 bits).
947 @item -mcpu=@var{CPU_VERSION}
948 Sets the CPU version being compiled for.
949 @item -merrors-to-file @var{FILENAME}
950 Redirect error output to a file, for broken systems which don't support such
951 behaviour in the shell.
956 The following options are available when @value{AS} is configured for
957 a @sc{mips} processor.
961 This option sets the largest size of an object that can be referenced
962 implicitly with the @code{gp} register. It is only accepted for targets that
963 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
965 @cindex MIPS endianness
966 @cindex endianness, MIPS
967 @cindex big endian output, MIPS
969 Generate ``big endian'' format output.
971 @cindex little endian output, MIPS
973 Generate ``little endian'' format output.
985 Generate code for a particular @sc{mips} Instruction Set Architecture level.
986 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
987 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
988 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
989 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
991 correspond to generic
992 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
993 and @samp{MIPS64 Release 2}
994 ISA processors, respectively.
996 @item -march=@var{CPU}
997 Generate code for a particular @sc{mips} cpu.
999 @item -mtune=@var{cpu}
1000 Schedule and tune for a particular @sc{mips} cpu.
1004 Cause nops to be inserted if the read of the destination register
1005 of an mfhi or mflo instruction occurs in the following two instructions.
1009 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1010 section instead of the standard ELF .stabs sections.
1014 Control generation of @code{.pdr} sections.
1018 The register sizes are normally inferred from the ISA and ABI, but these
1019 flags force a certain group of registers to be treated as 32 bits wide at
1020 all times. @samp{-mgp32} controls the size of general-purpose registers
1021 and @samp{-mfp32} controls the size of floating-point registers.
1025 Generate code for the MIPS 16 processor. This is equivalent to putting
1026 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1027 turns off this option.
1030 @itemx -mno-smartmips
1031 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1032 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1033 @samp{-mno-smartmips} turns off this option.
1037 Generate code for the MIPS-3D Application Specific Extension.
1038 This tells the assembler to accept MIPS-3D instructions.
1039 @samp{-no-mips3d} turns off this option.
1043 Generate code for the MDMX Application Specific Extension.
1044 This tells the assembler to accept MDMX instructions.
1045 @samp{-no-mdmx} turns off this option.
1049 Generate code for the DSP Release 1 Application Specific Extension.
1050 This tells the assembler to accept DSP Release 1 instructions.
1051 @samp{-mno-dsp} turns off this option.
1055 Generate code for the DSP Release 2 Application Specific Extension.
1056 This option implies -mdsp.
1057 This tells the assembler to accept DSP Release 2 instructions.
1058 @samp{-mno-dspr2} turns off this option.
1062 Generate code for the MT Application Specific Extension.
1063 This tells the assembler to accept MT instructions.
1064 @samp{-mno-mt} turns off this option.
1066 @item --construct-floats
1067 @itemx --no-construct-floats
1068 The @samp{--no-construct-floats} option disables the construction of
1069 double width floating point constants by loading the two halves of the
1070 value into the two single width floating point registers that make up
1071 the double width register. By default @samp{--construct-floats} is
1072 selected, allowing construction of these floating point constants.
1075 @item --emulation=@var{name}
1076 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1077 for some other target, in all respects, including output format (choosing
1078 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1079 debugging information or store symbol table information, and default
1080 endianness. The available configuration names are: @samp{mipsecoff},
1081 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1082 @samp{mipsbelf}. The first two do not alter the default endianness from that
1083 of the primary target for which the assembler was configured; the others change
1084 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1085 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1086 selection in any case.
1088 This option is currently supported only when the primary target
1089 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1090 Furthermore, the primary target or others specified with
1091 @samp{--enable-targets=@dots{}} at configuration time must include support for
1092 the other format, if both are to be available. For example, the Irix 5
1093 configuration includes support for both.
1095 Eventually, this option will support more configurations, with more
1096 fine-grained control over the assembler's behavior, and will be supported for
1100 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1107 Control how to deal with multiplication overflow and division by zero.
1108 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1109 (and only work for Instruction Set Architecture level 2 and higher);
1110 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1114 When this option is used, @command{@value{AS}} will issue a warning every
1115 time it generates a nop instruction from a macro.
1120 The following options are available when @value{AS} is configured for
1126 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1127 The command line option @samp{-nojsri2bsr} can be used to disable it.
1131 Enable or disable the silicon filter behaviour. By default this is disabled.
1132 The default can be overridden by the @samp{-sifilter} command line option.
1135 Alter jump instructions for long displacements.
1137 @item -mcpu=[210|340]
1138 Select the cpu type on the target hardware. This controls which instructions
1142 Assemble for a big endian target.
1145 Assemble for a little endian target.
1151 See the info pages for documentation of the MMIX-specific options.
1155 The following options are available when @value{AS} is configured for
1156 an Xtensa processor.
1159 @item --text-section-literals | --no-text-section-literals
1160 With @option{--text-@-section-@-literals}, literal pools are interspersed
1161 in the text section. The default is
1162 @option{--no-@-text-@-section-@-literals}, which places literals in a
1163 separate section in the output file. These options only affect literals
1164 referenced via PC-relative @code{L32R} instructions; literals for
1165 absolute mode @code{L32R} instructions are handled separately.
1167 @item --absolute-literals | --no-absolute-literals
1168 Indicate to the assembler whether @code{L32R} instructions use absolute
1169 or PC-relative addressing. The default is to assume absolute addressing
1170 if the Xtensa processor includes the absolute @code{L32R} addressing
1171 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1173 @item --target-align | --no-target-align
1174 Enable or disable automatic alignment to reduce branch penalties at the
1175 expense of some code density. The default is @option{--target-@-align}.
1177 @item --longcalls | --no-longcalls
1178 Enable or disable transformation of call instructions to allow calls
1179 across a greater range of addresses. The default is
1180 @option{--no-@-longcalls}.
1182 @item --transform | --no-transform
1183 Enable or disable all assembler transformations of Xtensa instructions.
1184 The default is @option{--transform};
1185 @option{--no-transform} should be used only in the rare cases when the
1186 instructions must be exactly as specified in the assembly source.
1191 The following options are available when @value{AS} is configured for
1192 a Z80 family processor.
1195 Assemble for Z80 processor.
1197 Assemble for R800 processor.
1198 @item -ignore-undocumented-instructions
1200 Assemble undocumented Z80 instructions that also work on R800 without warning.
1201 @item -ignore-unportable-instructions
1203 Assemble all undocumented Z80 instructions without warning.
1204 @item -warn-undocumented-instructions
1206 Issue a warning for undocumented Z80 instructions that also work on R800.
1207 @item -warn-unportable-instructions
1209 Issue a warning for undocumented Z80 instructions that do not work on R800.
1210 @item -forbid-undocumented-instructions
1212 Treat all undocumented instructions as errors.
1213 @item -forbid-unportable-instructions
1215 Treat undocumented Z80 instructions that do not work on R800 as errors.
1222 * Manual:: Structure of this Manual
1223 * GNU Assembler:: The GNU Assembler
1224 * Object Formats:: Object File Formats
1225 * Command Line:: Command Line
1226 * Input Files:: Input Files
1227 * Object:: Output (Object) File
1228 * Errors:: Error and Warning Messages
1232 @section Structure of this Manual
1234 @cindex manual, structure and purpose
1235 This manual is intended to describe what you need to know to use
1236 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1237 notation for symbols, constants, and expressions; the directives that
1238 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1241 We also cover special features in the @value{TARGET}
1242 configuration of @command{@value{AS}}, including assembler directives.
1245 This manual also describes some of the machine-dependent features of
1246 various flavors of the assembler.
1249 @cindex machine instructions (not covered)
1250 On the other hand, this manual is @emph{not} intended as an introduction
1251 to programming in assembly language---let alone programming in general!
1252 In a similar vein, we make no attempt to introduce the machine
1253 architecture; we do @emph{not} describe the instruction set, standard
1254 mnemonics, registers or addressing modes that are standard to a
1255 particular architecture.
1257 You may want to consult the manufacturer's
1258 machine architecture manual for this information.
1262 For information on the H8/300 machine instruction set, see @cite{H8/300
1263 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1264 Programming Manual} (Renesas).
1267 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1268 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1269 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1270 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1273 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1277 @c I think this is premature---doc@cygnus.com, 17jan1991
1279 Throughout this manual, we assume that you are running @dfn{GNU},
1280 the portable operating system from the @dfn{Free Software
1281 Foundation, Inc.}. This restricts our attention to certain kinds of
1282 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1283 once this assumption is granted examples and definitions need less
1286 @command{@value{AS}} is part of a team of programs that turn a high-level
1287 human-readable series of instructions into a low-level
1288 computer-readable series of instructions. Different versions of
1289 @command{@value{AS}} are used for different kinds of computer.
1292 @c There used to be a section "Terminology" here, which defined
1293 @c "contents", "byte", "word", and "long". Defining "word" to any
1294 @c particular size is confusing when the .word directive may generate 16
1295 @c bits on one machine and 32 bits on another; in general, for the user
1296 @c version of this manual, none of these terms seem essential to define.
1297 @c They were used very little even in the former draft of the manual;
1298 @c this draft makes an effort to avoid them (except in names of
1302 @section The GNU Assembler
1304 @c man begin DESCRIPTION
1306 @sc{gnu} @command{as} is really a family of assemblers.
1308 This manual describes @command{@value{AS}}, a member of that family which is
1309 configured for the @value{TARGET} architectures.
1311 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1312 should find a fairly similar environment when you use it on another
1313 architecture. Each version has much in common with the others,
1314 including object file formats, most assembler directives (often called
1315 @dfn{pseudo-ops}) and assembler syntax.@refill
1317 @cindex purpose of @sc{gnu} assembler
1318 @command{@value{AS}} is primarily intended to assemble the output of the
1319 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1320 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1321 assemble correctly everything that other assemblers for the same
1322 machine would assemble.
1324 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1327 @c This remark should appear in generic version of manual; assumption
1328 @c here is that generic version sets M680x0.
1329 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1330 assembler for the same architecture; for example, we know of several
1331 incompatible versions of 680x0 assembly language syntax.
1336 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1337 program in one pass of the source file. This has a subtle impact on the
1338 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1340 @node Object Formats
1341 @section Object File Formats
1343 @cindex object file format
1344 The @sc{gnu} assembler can be configured to produce several alternative
1345 object file formats. For the most part, this does not affect how you
1346 write assembly language programs; but directives for debugging symbols
1347 are typically different in different file formats. @xref{Symbol
1348 Attributes,,Symbol Attributes}.
1351 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1352 @value{OBJ-NAME} format object files.
1354 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1356 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1357 @code{b.out} or COFF format object files.
1360 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1361 SOM or ELF format object files.
1366 @section Command Line
1368 @cindex command line conventions
1370 After the program name @command{@value{AS}}, the command line may contain
1371 options and file names. Options may appear in any order, and may be
1372 before, after, or between file names. The order of file names is
1375 @cindex standard input, as input file
1377 @file{--} (two hyphens) by itself names the standard input file
1378 explicitly, as one of the files for @command{@value{AS}} to assemble.
1380 @cindex options, command line
1381 Except for @samp{--} any command line argument that begins with a
1382 hyphen (@samp{-}) is an option. Each option changes the behavior of
1383 @command{@value{AS}}. No option changes the way another option works. An
1384 option is a @samp{-} followed by one or more letters; the case of
1385 the letter is important. All options are optional.
1387 Some options expect exactly one file name to follow them. The file
1388 name may either immediately follow the option's letter (compatible
1389 with older assemblers) or it may be the next command argument (@sc{gnu}
1390 standard). These two command lines are equivalent:
1393 @value{AS} -o my-object-file.o mumble.s
1394 @value{AS} -omy-object-file.o mumble.s
1398 @section Input Files
1401 @cindex source program
1402 @cindex files, input
1403 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1404 describe the program input to one run of @command{@value{AS}}. The program may
1405 be in one or more files; how the source is partitioned into files
1406 doesn't change the meaning of the source.
1408 @c I added "con" prefix to "catenation" just to prove I can overcome my
1409 @c APL training... doc@cygnus.com
1410 The source program is a concatenation of the text in all the files, in the
1413 @c man begin DESCRIPTION
1414 Each time you run @command{@value{AS}} it assembles exactly one source
1415 program. The source program is made up of one or more files.
1416 (The standard input is also a file.)
1418 You give @command{@value{AS}} a command line that has zero or more input file
1419 names. The input files are read (from left file name to right). A
1420 command line argument (in any position) that has no special meaning
1421 is taken to be an input file name.
1423 If you give @command{@value{AS}} no file names it attempts to read one input file
1424 from the @command{@value{AS}} standard input, which is normally your terminal. You
1425 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1428 Use @samp{--} if you need to explicitly name the standard input file
1429 in your command line.
1431 If the source is empty, @command{@value{AS}} produces a small, empty object
1436 @subheading Filenames and Line-numbers
1438 @cindex input file linenumbers
1439 @cindex line numbers, in input files
1440 There are two ways of locating a line in the input file (or files) and
1441 either may be used in reporting error messages. One way refers to a line
1442 number in a physical file; the other refers to a line number in a
1443 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1445 @dfn{Physical files} are those files named in the command line given
1446 to @command{@value{AS}}.
1448 @dfn{Logical files} are simply names declared explicitly by assembler
1449 directives; they bear no relation to physical files. Logical file names help
1450 error messages reflect the original source file, when @command{@value{AS}} source
1451 is itself synthesized from other files. @command{@value{AS}} understands the
1452 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1453 @ref{File,,@code{.file}}.
1456 @section Output (Object) File
1462 Every time you run @command{@value{AS}} it produces an output file, which is
1463 your assembly language program translated into numbers. This file
1464 is the object file. Its default name is
1472 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1474 You can give it another name by using the @option{-o} option. Conventionally,
1475 object file names end with @file{.o}. The default name is used for historical
1476 reasons: older assemblers were capable of assembling self-contained programs
1477 directly into a runnable program. (For some formats, this isn't currently
1478 possible, but it can be done for the @code{a.out} format.)
1482 The object file is meant for input to the linker @code{@value{LD}}. It contains
1483 assembled program code, information to help @code{@value{LD}} integrate
1484 the assembled program into a runnable file, and (optionally) symbolic
1485 information for the debugger.
1487 @c link above to some info file(s) like the description of a.out.
1488 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1491 @section Error and Warning Messages
1493 @c man begin DESCRIPTION
1495 @cindex error messages
1496 @cindex warning messages
1497 @cindex messages from assembler
1498 @command{@value{AS}} may write warnings and error messages to the standard error
1499 file (usually your terminal). This should not happen when a compiler
1500 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1501 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1502 grave problem that stops the assembly.
1506 @cindex format of warning messages
1507 Warning messages have the format
1510 file_name:@b{NNN}:Warning Message Text
1514 @cindex line numbers, in warnings/errors
1515 (where @b{NNN} is a line number). If a logical file name has been given
1516 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1517 the current input file is used. If a logical line number was given
1519 (@pxref{Line,,@code{.line}})
1521 then it is used to calculate the number printed,
1522 otherwise the actual line in the current source file is printed. The
1523 message text is intended to be self explanatory (in the grand Unix
1526 @cindex format of error messages
1527 Error messages have the format
1529 file_name:@b{NNN}:FATAL:Error Message Text
1531 The file name and line number are derived as for warning
1532 messages. The actual message text may be rather less explanatory
1533 because many of them aren't supposed to happen.
1536 @chapter Command-Line Options
1538 @cindex options, all versions of assembler
1539 This chapter describes command-line options available in @emph{all}
1540 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1541 for options specific
1543 to the @value{TARGET} target.
1546 to particular machine architectures.
1549 @c man begin DESCRIPTION
1551 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1552 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1553 The assembler arguments must be separated from each other (and the @samp{-Wa})
1554 by commas. For example:
1557 gcc -c -g -O -Wa,-alh,-L file.c
1561 This passes two options to the assembler: @samp{-alh} (emit a listing to
1562 standard output with high-level and assembly source) and @samp{-L} (retain
1563 local symbols in the symbol table).
1565 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1566 command-line options are automatically passed to the assembler by the compiler.
1567 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1568 precisely what options it passes to each compilation pass, including the
1574 * a:: -a[cdhlns] enable listings
1575 * alternate:: --alternate enable alternate macro syntax
1576 * D:: -D for compatibility
1577 * f:: -f to work faster
1578 * I:: -I for .include search path
1579 @ifclear DIFF-TBL-KLUGE
1580 * K:: -K for compatibility
1582 @ifset DIFF-TBL-KLUGE
1583 * K:: -K for difference tables
1586 * L:: -L to retain local symbols
1587 * listing:: --listing-XXX to configure listing output
1588 * M:: -M or --mri to assemble in MRI compatibility mode
1589 * MD:: --MD for dependency tracking
1590 * o:: -o to name the object file
1591 * R:: -R to join data and text sections
1592 * statistics:: --statistics to see statistics about assembly
1593 * traditional-format:: --traditional-format for compatible output
1594 * v:: -v to announce version
1595 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1596 * Z:: -Z to make object file even after errors
1600 @section Enable Listings: @option{-a[cdhlns]}
1609 @cindex listings, enabling
1610 @cindex assembly listings, enabling
1612 These options enable listing output from the assembler. By itself,
1613 @samp{-a} requests high-level, assembly, and symbols listing.
1614 You can use other letters to select specific options for the list:
1615 @samp{-ah} requests a high-level language listing,
1616 @samp{-al} requests an output-program assembly listing, and
1617 @samp{-as} requests a symbol table listing.
1618 High-level listings require that a compiler debugging option like
1619 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1622 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1623 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1624 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1625 omitted from the listing.
1627 Use the @samp{-ad} option to omit debugging directives from the
1630 Once you have specified one of these options, you can further control
1631 listing output and its appearance using the directives @code{.list},
1632 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1634 The @samp{-an} option turns off all forms processing.
1635 If you do not request listing output with one of the @samp{-a} options, the
1636 listing-control directives have no effect.
1638 The letters after @samp{-a} may be combined into one option,
1639 @emph{e.g.}, @samp{-aln}.
1641 Note if the assembler source is coming from the standard input (e.g.,
1643 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1644 is being used) then the listing will not contain any comments or preprocessor
1645 directives. This is because the listing code buffers input source lines from
1646 stdin only after they have been preprocessed by the assembler. This reduces
1647 memory usage and makes the code more efficient.
1650 @section @option{--alternate}
1653 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1656 @section @option{-D}
1659 This option has no effect whatsoever, but it is accepted to make it more
1660 likely that scripts written for other assemblers also work with
1661 @command{@value{AS}}.
1664 @section Work Faster: @option{-f}
1667 @cindex trusted compiler
1668 @cindex faster processing (@option{-f})
1669 @samp{-f} should only be used when assembling programs written by a
1670 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1671 and comment preprocessing on
1672 the input file(s) before assembling them. @xref{Preprocessing,
1676 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1677 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1682 @section @code{.include} Search Path: @option{-I} @var{path}
1684 @kindex -I @var{path}
1685 @cindex paths for @code{.include}
1686 @cindex search path for @code{.include}
1687 @cindex @code{include} directive search path
1688 Use this option to add a @var{path} to the list of directories
1689 @command{@value{AS}} searches for files specified in @code{.include}
1690 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1691 many times as necessary to include a variety of paths. The current
1692 working directory is always searched first; after that, @command{@value{AS}}
1693 searches any @samp{-I} directories in the same order as they were
1694 specified (left to right) on the command line.
1697 @section Difference Tables: @option{-K}
1700 @ifclear DIFF-TBL-KLUGE
1701 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1702 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1703 where it can be used to warn when the assembler alters the machine code
1704 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1705 family does not have the addressing limitations that sometimes lead to this
1706 alteration on other platforms.
1709 @ifset DIFF-TBL-KLUGE
1710 @cindex difference tables, warning
1711 @cindex warning for altered difference tables
1712 @command{@value{AS}} sometimes alters the code emitted for directives of the
1713 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1714 You can use the @samp{-K} option if you want a warning issued when this
1719 @section Include Local Symbols: @option{-L}
1722 @cindex local symbols, retaining in output
1723 Symbols beginning with system-specific local label prefixes, typically
1724 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1725 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1726 such symbols when debugging, because they are intended for the use of
1727 programs (like compilers) that compose assembler programs, not for your
1728 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1729 such symbols, so you do not normally debug with them.
1731 This option tells @command{@value{AS}} to retain those local symbols
1732 in the object file. Usually if you do this you also tell the linker
1733 @code{@value{LD}} to preserve those symbols.
1736 @section Configuring listing output: @option{--listing}
1738 The listing feature of the assembler can be enabled via the command line switch
1739 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1740 hex dump of the corresponding locations in the output object file, and displays
1741 them as a listing file. The format of this listing can be controlled by
1742 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1743 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1744 @code{.psize} (@pxref{Psize}), and
1745 @code{.eject} (@pxref{Eject}) and also by the following switches:
1748 @item --listing-lhs-width=@samp{number}
1749 @kindex --listing-lhs-width
1750 @cindex Width of first line disassembly output
1751 Sets the maximum width, in words, of the first line of the hex byte dump. This
1752 dump appears on the left hand side of the listing output.
1754 @item --listing-lhs-width2=@samp{number}
1755 @kindex --listing-lhs-width2
1756 @cindex Width of continuation lines of disassembly output
1757 Sets the maximum width, in words, of any further lines of the hex byte dump for
1758 a given input source line. If this value is not specified, it defaults to being
1759 the same as the value specified for @samp{--listing-lhs-width}. If neither
1760 switch is used the default is to one.
1762 @item --listing-rhs-width=@samp{number}
1763 @kindex --listing-rhs-width
1764 @cindex Width of source line output
1765 Sets the maximum width, in characters, of the source line that is displayed
1766 alongside the hex dump. The default value for this parameter is 100. The
1767 source line is displayed on the right hand side of the listing output.
1769 @item --listing-cont-lines=@samp{number}
1770 @kindex --listing-cont-lines
1771 @cindex Maximum number of continuation lines
1772 Sets the maximum number of continuation lines of hex dump that will be
1773 displayed for a given single line of source input. The default value is 4.
1777 @section Assemble in MRI Compatibility Mode: @option{-M}
1780 @cindex MRI compatibility mode
1781 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1782 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1783 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1784 configured target) assembler from Microtec Research. The exact nature of the
1785 MRI syntax will not be documented here; see the MRI manuals for more
1786 information. Note in particular that the handling of macros and macro
1787 arguments is somewhat different. The purpose of this option is to permit
1788 assembling existing MRI assembler code using @command{@value{AS}}.
1790 The MRI compatibility is not complete. Certain operations of the MRI assembler
1791 depend upon its object file format, and can not be supported using other object
1792 file formats. Supporting these would require enhancing each object file format
1793 individually. These are:
1796 @item global symbols in common section
1798 The m68k MRI assembler supports common sections which are merged by the linker.
1799 Other object file formats do not support this. @command{@value{AS}} handles
1800 common sections by treating them as a single common symbol. It permits local
1801 symbols to be defined within a common section, but it can not support global
1802 symbols, since it has no way to describe them.
1804 @item complex relocations
1806 The MRI assemblers support relocations against a negated section address, and
1807 relocations which combine the start addresses of two or more sections. These
1808 are not support by other object file formats.
1810 @item @code{END} pseudo-op specifying start address
1812 The MRI @code{END} pseudo-op permits the specification of a start address.
1813 This is not supported by other object file formats. The start address may
1814 instead be specified using the @option{-e} option to the linker, or in a linker
1817 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1819 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1820 name to the output file. This is not supported by other object file formats.
1822 @item @code{ORG} pseudo-op
1824 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1825 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1826 which changes the location within the current section. Absolute sections are
1827 not supported by other object file formats. The address of a section may be
1828 assigned within a linker script.
1831 There are some other features of the MRI assembler which are not supported by
1832 @command{@value{AS}}, typically either because they are difficult or because they
1833 seem of little consequence. Some of these may be supported in future releases.
1837 @item EBCDIC strings
1839 EBCDIC strings are not supported.
1841 @item packed binary coded decimal
1843 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1844 and @code{DCB.P} pseudo-ops are not supported.
1846 @item @code{FEQU} pseudo-op
1848 The m68k @code{FEQU} pseudo-op is not supported.
1850 @item @code{NOOBJ} pseudo-op
1852 The m68k @code{NOOBJ} pseudo-op is not supported.
1854 @item @code{OPT} branch control options
1856 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1857 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1858 relaxes all branches, whether forward or backward, to an appropriate size, so
1859 these options serve no purpose.
1861 @item @code{OPT} list control options
1863 The following m68k @code{OPT} list control options are ignored: @code{C},
1864 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1865 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1867 @item other @code{OPT} options
1869 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1870 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1872 @item @code{OPT} @code{D} option is default
1874 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1875 @code{OPT NOD} may be used to turn it off.
1877 @item @code{XREF} pseudo-op.
1879 The m68k @code{XREF} pseudo-op is ignored.
1881 @item @code{.debug} pseudo-op
1883 The i960 @code{.debug} pseudo-op is not supported.
1885 @item @code{.extended} pseudo-op
1887 The i960 @code{.extended} pseudo-op is not supported.
1889 @item @code{.list} pseudo-op.
1891 The various options of the i960 @code{.list} pseudo-op are not supported.
1893 @item @code{.optimize} pseudo-op
1895 The i960 @code{.optimize} pseudo-op is not supported.
1897 @item @code{.output} pseudo-op
1899 The i960 @code{.output} pseudo-op is not supported.
1901 @item @code{.setreal} pseudo-op
1903 The i960 @code{.setreal} pseudo-op is not supported.
1908 @section Dependency Tracking: @option{--MD}
1911 @cindex dependency tracking
1914 @command{@value{AS}} can generate a dependency file for the file it creates. This
1915 file consists of a single rule suitable for @code{make} describing the
1916 dependencies of the main source file.
1918 The rule is written to the file named in its argument.
1920 This feature is used in the automatic updating of makefiles.
1923 @section Name the Object File: @option{-o}
1926 @cindex naming object file
1927 @cindex object file name
1928 There is always one object file output when you run @command{@value{AS}}. By
1929 default it has the name
1932 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1946 You use this option (which takes exactly one filename) to give the
1947 object file a different name.
1949 Whatever the object file is called, @command{@value{AS}} overwrites any
1950 existing file of the same name.
1953 @section Join Data and Text Sections: @option{-R}
1956 @cindex data and text sections, joining
1957 @cindex text and data sections, joining
1958 @cindex joining text and data sections
1959 @cindex merging text and data sections
1960 @option{-R} tells @command{@value{AS}} to write the object file as if all
1961 data-section data lives in the text section. This is only done at
1962 the very last moment: your binary data are the same, but data
1963 section parts are relocated differently. The data section part of
1964 your object file is zero bytes long because all its bytes are
1965 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1967 When you specify @option{-R} it would be possible to generate shorter
1968 address displacements (because we do not have to cross between text and
1969 data section). We refrain from doing this simply for compatibility with
1970 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1973 When @command{@value{AS}} is configured for COFF or ELF output,
1974 this option is only useful if you use sections named @samp{.text} and
1979 @option{-R} is not supported for any of the HPPA targets. Using
1980 @option{-R} generates a warning from @command{@value{AS}}.
1984 @section Display Assembly Statistics: @option{--statistics}
1986 @kindex --statistics
1987 @cindex statistics, about assembly
1988 @cindex time, total for assembly
1989 @cindex space used, maximum for assembly
1990 Use @samp{--statistics} to display two statistics about the resources used by
1991 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1992 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1995 @node traditional-format
1996 @section Compatible Output: @option{--traditional-format}
1998 @kindex --traditional-format
1999 For some targets, the output of @command{@value{AS}} is different in some ways
2000 from the output of some existing assembler. This switch requests
2001 @command{@value{AS}} to use the traditional format instead.
2003 For example, it disables the exception frame optimizations which
2004 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2007 @section Announce Version: @option{-v}
2011 @cindex assembler version
2012 @cindex version of assembler
2013 You can find out what version of as is running by including the
2014 option @samp{-v} (which you can also spell as @samp{-version}) on the
2018 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2020 @command{@value{AS}} should never give a warning or error message when
2021 assembling compiler output. But programs written by people often
2022 cause @command{@value{AS}} to give a warning that a particular assumption was
2023 made. All such warnings are directed to the standard error file.
2027 @cindex suppressing warnings
2028 @cindex warnings, suppressing
2029 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2030 This only affects the warning messages: it does not change any particular of
2031 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2034 @kindex --fatal-warnings
2035 @cindex errors, caused by warnings
2036 @cindex warnings, causing error
2037 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2038 files that generate warnings to be in error.
2041 @cindex warnings, switching on
2042 You can switch these options off again by specifying @option{--warn}, which
2043 causes warnings to be output as usual.
2046 @section Generate Object File in Spite of Errors: @option{-Z}
2047 @cindex object file, after errors
2048 @cindex errors, continuing after
2049 After an error message, @command{@value{AS}} normally produces no output. If for
2050 some reason you are interested in object file output even after
2051 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2052 option. If there are any errors, @command{@value{AS}} continues anyways, and
2053 writes an object file after a final warning message of the form @samp{@var{n}
2054 errors, @var{m} warnings, generating bad object file.}
2059 @cindex machine-independent syntax
2060 @cindex syntax, machine-independent
2061 This chapter describes the machine-independent syntax allowed in a
2062 source file. @command{@value{AS}} syntax is similar to what many other
2063 assemblers use; it is inspired by the BSD 4.2
2068 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2072 * Preprocessing:: Preprocessing
2073 * Whitespace:: Whitespace
2074 * Comments:: Comments
2075 * Symbol Intro:: Symbols
2076 * Statements:: Statements
2077 * Constants:: Constants
2081 @section Preprocessing
2083 @cindex preprocessing
2084 The @command{@value{AS}} internal preprocessor:
2086 @cindex whitespace, removed by preprocessor
2088 adjusts and removes extra whitespace. It leaves one space or tab before
2089 the keywords on a line, and turns any other whitespace on the line into
2092 @cindex comments, removed by preprocessor
2094 removes all comments, replacing them with a single space, or an
2095 appropriate number of newlines.
2097 @cindex constants, converted by preprocessor
2099 converts character constants into the appropriate numeric values.
2102 It does not do macro processing, include file handling, or
2103 anything else you may get from your C compiler's preprocessor. You can
2104 do include file processing with the @code{.include} directive
2105 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2106 to get other ``CPP'' style preprocessing by giving the input file a
2107 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2108 Output, gcc.info, Using GNU CC}.
2110 Excess whitespace, comments, and character constants
2111 cannot be used in the portions of the input text that are not
2114 @cindex turning preprocessing on and off
2115 @cindex preprocessing, turning on and off
2118 If the first line of an input file is @code{#NO_APP} or if you use the
2119 @samp{-f} option, whitespace and comments are not removed from the input file.
2120 Within an input file, you can ask for whitespace and comment removal in
2121 specific portions of the by putting a line that says @code{#APP} before the
2122 text that may contain whitespace or comments, and putting a line that says
2123 @code{#NO_APP} after this text. This feature is mainly intend to support
2124 @code{asm} statements in compilers whose output is otherwise free of comments
2131 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2132 Whitespace is used to separate symbols, and to make programs neater for
2133 people to read. Unless within character constants
2134 (@pxref{Characters,,Character Constants}), any whitespace means the same
2135 as exactly one space.
2141 There are two ways of rendering comments to @command{@value{AS}}. In both
2142 cases the comment is equivalent to one space.
2144 Anything from @samp{/*} through the next @samp{*/} is a comment.
2145 This means you may not nest these comments.
2149 The only way to include a newline ('\n') in a comment
2150 is to use this sort of comment.
2153 /* This sort of comment does not nest. */
2156 @cindex line comment character
2157 Anything from the @dfn{line comment} character to the next newline
2158 is considered a comment and is ignored. The line comment character is
2160 @samp{;} on the ARC;
2163 @samp{@@} on the ARM;
2166 @samp{;} for the H8/300 family;
2169 @samp{;} for the HPPA;
2172 @samp{#} on the i386 and x86-64;
2175 @samp{#} on the i960;
2178 @samp{;} for the PDP-11;
2181 @samp{;} for picoJava;
2184 @samp{#} for Motorola PowerPC;
2187 @samp{!} for the Renesas / SuperH SH;
2190 @samp{!} on the SPARC;
2193 @samp{#} on the ip2k;
2196 @samp{#} on the m32c;
2199 @samp{#} on the m32r;
2202 @samp{|} on the 680x0;
2205 @samp{#} on the 68HC11 and 68HC12;
2208 @samp{#} on the Vax;
2211 @samp{;} for the Z80;
2214 @samp{!} for the Z8000;
2217 @samp{#} on the V850;
2220 @samp{#} for Xtensa systems;
2222 see @ref{Machine Dependencies}. @refill
2223 @c FIXME What about i860?
2226 On some machines there are two different line comment characters. One
2227 character only begins a comment if it is the first non-whitespace character on
2228 a line, while the other always begins a comment.
2232 The V850 assembler also supports a double dash as starting a comment that
2233 extends to the end of the line.
2239 @cindex lines starting with @code{#}
2240 @cindex logical line numbers
2241 To be compatible with past assemblers, lines that begin with @samp{#} have a
2242 special interpretation. Following the @samp{#} should be an absolute
2243 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2244 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2245 new logical file name. The rest of the line, if any, should be whitespace.
2247 If the first non-whitespace characters on the line are not numeric,
2248 the line is ignored. (Just like a comment.)
2251 # This is an ordinary comment.
2252 # 42-6 "new_file_name" # New logical file name
2253 # This is logical line # 36.
2255 This feature is deprecated, and may disappear from future versions
2256 of @command{@value{AS}}.
2261 @cindex characters used in symbols
2262 @ifclear SPECIAL-SYMS
2263 A @dfn{symbol} is one or more characters chosen from the set of all
2264 letters (both upper and lower case), digits and the three characters
2270 A @dfn{symbol} is one or more characters chosen from the set of all
2271 letters (both upper and lower case), digits and the three characters
2272 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2278 On most machines, you can also use @code{$} in symbol names; exceptions
2279 are noted in @ref{Machine Dependencies}.
2281 No symbol may begin with a digit. Case is significant.
2282 There is no length limit: all characters are significant. Symbols are
2283 delimited by characters not in that set, or by the beginning of a file
2284 (since the source program must end with a newline, the end of a file is
2285 not a possible symbol delimiter). @xref{Symbols}.
2286 @cindex length of symbols
2291 @cindex statements, structure of
2292 @cindex line separator character
2293 @cindex statement separator character
2295 @ifclear abnormal-separator
2296 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2297 semicolon (@samp{;}). The newline or semicolon is considered part of
2298 the preceding statement. Newlines and semicolons within character
2299 constants are an exception: they do not end statements.
2301 @ifset abnormal-separator
2303 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2304 point (@samp{!}). The newline or exclamation point is considered part of the
2305 preceding statement. Newlines and exclamation points within character
2306 constants are an exception: they do not end statements.
2309 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2310 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2311 (@samp{;}). The newline or separator character is considered part of
2312 the preceding statement. Newlines and separators within character
2313 constants are an exception: they do not end statements.
2318 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2319 separator character. (The line separator is usually @samp{;}, unless this
2320 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2321 newline or separator character is considered part of the preceding
2322 statement. Newlines and separators within character constants are an
2323 exception: they do not end statements.
2326 @cindex newline, required at file end
2327 @cindex EOF, newline must precede
2328 It is an error to end any statement with end-of-file: the last
2329 character of any input file should be a newline.@refill
2331 An empty statement is allowed, and may include whitespace. It is ignored.
2333 @cindex instructions and directives
2334 @cindex directives and instructions
2335 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2336 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2338 A statement begins with zero or more labels, optionally followed by a
2339 key symbol which determines what kind of statement it is. The key
2340 symbol determines the syntax of the rest of the statement. If the
2341 symbol begins with a dot @samp{.} then the statement is an assembler
2342 directive: typically valid for any computer. If the symbol begins with
2343 a letter the statement is an assembly language @dfn{instruction}: it
2344 assembles into a machine language instruction.
2346 Different versions of @command{@value{AS}} for different computers
2347 recognize different instructions. In fact, the same symbol may
2348 represent a different instruction in a different computer's assembly
2352 @cindex @code{:} (label)
2353 @cindex label (@code{:})
2354 A label is a symbol immediately followed by a colon (@code{:}).
2355 Whitespace before a label or after a colon is permitted, but you may not
2356 have whitespace between a label's symbol and its colon. @xref{Labels}.
2359 For HPPA targets, labels need not be immediately followed by a colon, but
2360 the definition of a label must begin in column zero. This also implies that
2361 only one label may be defined on each line.
2365 label: .directive followed by something
2366 another_label: # This is an empty statement.
2367 instruction operand_1, operand_2, @dots{}
2374 A constant is a number, written so that its value is known by
2375 inspection, without knowing any context. Like this:
2378 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2379 .ascii "Ring the bell\7" # A string constant.
2380 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2381 .float 0f-314159265358979323846264338327\
2382 95028841971.693993751E-40 # - pi, a flonum.
2387 * Characters:: Character Constants
2388 * Numbers:: Number Constants
2392 @subsection Character Constants
2394 @cindex character constants
2395 @cindex constants, character
2396 There are two kinds of character constants. A @dfn{character} stands
2397 for one character in one byte and its value may be used in
2398 numeric expressions. String constants (properly called string
2399 @emph{literals}) are potentially many bytes and their values may not be
2400 used in arithmetic expressions.
2404 * Chars:: Characters
2408 @subsubsection Strings
2410 @cindex string constants
2411 @cindex constants, string
2412 A @dfn{string} is written between double-quotes. It may contain
2413 double-quotes or null characters. The way to get special characters
2414 into a string is to @dfn{escape} these characters: precede them with
2415 a backslash @samp{\} character. For example @samp{\\} represents
2416 one backslash: the first @code{\} is an escape which tells
2417 @command{@value{AS}} to interpret the second character literally as a backslash
2418 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2419 escape character). The complete list of escapes follows.
2421 @cindex escape codes, character
2422 @cindex character escape codes
2425 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2427 @cindex @code{\b} (backspace character)
2428 @cindex backspace (@code{\b})
2430 Mnemonic for backspace; for ASCII this is octal code 010.
2433 @c Mnemonic for EOText; for ASCII this is octal code 004.
2435 @cindex @code{\f} (formfeed character)
2436 @cindex formfeed (@code{\f})
2438 Mnemonic for FormFeed; for ASCII this is octal code 014.
2440 @cindex @code{\n} (newline character)
2441 @cindex newline (@code{\n})
2443 Mnemonic for newline; for ASCII this is octal code 012.
2446 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2448 @cindex @code{\r} (carriage return character)
2449 @cindex carriage return (@code{\r})
2451 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2454 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2455 @c other assemblers.
2457 @cindex @code{\t} (tab)
2458 @cindex tab (@code{\t})
2460 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2463 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2464 @c @item \x @var{digit} @var{digit} @var{digit}
2465 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2467 @cindex @code{\@var{ddd}} (octal character code)
2468 @cindex octal character code (@code{\@var{ddd}})
2469 @item \ @var{digit} @var{digit} @var{digit}
2470 An octal character code. The numeric code is 3 octal digits.
2471 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2472 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2474 @cindex @code{\@var{xd...}} (hex character code)
2475 @cindex hex character code (@code{\@var{xd...}})
2476 @item \@code{x} @var{hex-digits...}
2477 A hex character code. All trailing hex digits are combined. Either upper or
2478 lower case @code{x} works.
2480 @cindex @code{\\} (@samp{\} character)
2481 @cindex backslash (@code{\\})
2483 Represents one @samp{\} character.
2486 @c Represents one @samp{'} (accent acute) character.
2487 @c This is needed in single character literals
2488 @c (@xref{Characters,,Character Constants}.) to represent
2491 @cindex @code{\"} (doublequote character)
2492 @cindex doublequote (@code{\"})
2494 Represents one @samp{"} character. Needed in strings to represent
2495 this character, because an unescaped @samp{"} would end the string.
2497 @item \ @var{anything-else}
2498 Any other character when escaped by @kbd{\} gives a warning, but
2499 assembles as if the @samp{\} was not present. The idea is that if
2500 you used an escape sequence you clearly didn't want the literal
2501 interpretation of the following character. However @command{@value{AS}} has no
2502 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2503 code and warns you of the fact.
2506 Which characters are escapable, and what those escapes represent,
2507 varies widely among assemblers. The current set is what we think
2508 the BSD 4.2 assembler recognizes, and is a subset of what most C
2509 compilers recognize. If you are in doubt, do not use an escape
2513 @subsubsection Characters
2515 @cindex single character constant
2516 @cindex character, single
2517 @cindex constant, single character
2518 A single character may be written as a single quote immediately
2519 followed by that character. The same escapes apply to characters as
2520 to strings. So if you want to write the character backslash, you
2521 must write @kbd{'\\} where the first @code{\} escapes the second
2522 @code{\}. As you can see, the quote is an acute accent, not a
2523 grave accent. A newline
2525 @ifclear abnormal-separator
2526 (or semicolon @samp{;})
2528 @ifset abnormal-separator
2530 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2535 immediately following an acute accent is taken as a literal character
2536 and does not count as the end of a statement. The value of a character
2537 constant in a numeric expression is the machine's byte-wide code for
2538 that character. @command{@value{AS}} assumes your character code is ASCII:
2539 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2542 @subsection Number Constants
2544 @cindex constants, number
2545 @cindex number constants
2546 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2547 are stored in the target machine. @emph{Integers} are numbers that
2548 would fit into an @code{int} in the C language. @emph{Bignums} are
2549 integers, but they are stored in more than 32 bits. @emph{Flonums}
2550 are floating point numbers, described below.
2553 * Integers:: Integers
2558 * Bit Fields:: Bit Fields
2564 @subsubsection Integers
2566 @cindex constants, integer
2568 @cindex binary integers
2569 @cindex integers, binary
2570 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2571 the binary digits @samp{01}.
2573 @cindex octal integers
2574 @cindex integers, octal
2575 An octal integer is @samp{0} followed by zero or more of the octal
2576 digits (@samp{01234567}).
2578 @cindex decimal integers
2579 @cindex integers, decimal
2580 A decimal integer starts with a non-zero digit followed by zero or
2581 more digits (@samp{0123456789}).
2583 @cindex hexadecimal integers
2584 @cindex integers, hexadecimal
2585 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2586 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2588 Integers have the usual values. To denote a negative integer, use
2589 the prefix operator @samp{-} discussed under expressions
2590 (@pxref{Prefix Ops,,Prefix Operators}).
2593 @subsubsection Bignums
2596 @cindex constants, bignum
2597 A @dfn{bignum} has the same syntax and semantics as an integer
2598 except that the number (or its negative) takes more than 32 bits to
2599 represent in binary. The distinction is made because in some places
2600 integers are permitted while bignums are not.
2603 @subsubsection Flonums
2605 @cindex floating point numbers
2606 @cindex constants, floating point
2608 @cindex precision, floating point
2609 A @dfn{flonum} represents a floating point number. The translation is
2610 indirect: a decimal floating point number from the text is converted by
2611 @command{@value{AS}} to a generic binary floating point number of more than
2612 sufficient precision. This generic floating point number is converted
2613 to a particular computer's floating point format (or formats) by a
2614 portion of @command{@value{AS}} specialized to that computer.
2616 A flonum is written by writing (in order)
2621 (@samp{0} is optional on the HPPA.)
2625 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2627 @kbd{e} is recommended. Case is not important.
2629 @c FIXME: verify if flonum syntax really this vague for most cases
2630 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2631 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2634 On the H8/300, Renesas / SuperH SH,
2635 and AMD 29K architectures, the letter must be
2636 one of the letters @samp{DFPRSX} (in upper or lower case).
2638 On the ARC, the letter must be one of the letters @samp{DFRS}
2639 (in upper or lower case).
2641 On the Intel 960 architecture, the letter must be
2642 one of the letters @samp{DFT} (in upper or lower case).
2644 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2648 One of the letters @samp{DFRS} (in upper or lower case).
2651 One of the letters @samp{DFPRSX} (in upper or lower case).
2654 The letter @samp{E} (upper case only).
2657 One of the letters @samp{DFT} (in upper or lower case).
2662 An optional sign: either @samp{+} or @samp{-}.
2665 An optional @dfn{integer part}: zero or more decimal digits.
2668 An optional @dfn{fractional part}: @samp{.} followed by zero
2669 or more decimal digits.
2672 An optional exponent, consisting of:
2676 An @samp{E} or @samp{e}.
2677 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2678 @c principle this can perfectly well be different on different targets.
2680 Optional sign: either @samp{+} or @samp{-}.
2682 One or more decimal digits.
2687 At least one of the integer part or the fractional part must be
2688 present. The floating point number has the usual base-10 value.
2690 @command{@value{AS}} does all processing using integers. Flonums are computed
2691 independently of any floating point hardware in the computer running
2692 @command{@value{AS}}.
2696 @c Bit fields are written as a general facility but are also controlled
2697 @c by a conditional-compilation flag---which is as of now (21mar91)
2698 @c turned on only by the i960 config of GAS.
2700 @subsubsection Bit Fields
2703 @cindex constants, bit field
2704 You can also define numeric constants as @dfn{bit fields}.
2705 Specify two numbers separated by a colon---
2707 @var{mask}:@var{value}
2710 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2713 The resulting number is then packed
2715 @c this conditional paren in case bit fields turned on elsewhere than 960
2716 (in host-dependent byte order)
2718 into a field whose width depends on which assembler directive has the
2719 bit-field as its argument. Overflow (a result from the bitwise and
2720 requiring more binary digits to represent) is not an error; instead,
2721 more constants are generated, of the specified width, beginning with the
2722 least significant digits.@refill
2724 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2725 @code{.short}, and @code{.word} accept bit-field arguments.
2730 @chapter Sections and Relocation
2735 * Secs Background:: Background
2736 * Ld Sections:: Linker Sections
2737 * As Sections:: Assembler Internal Sections
2738 * Sub-Sections:: Sub-Sections
2742 @node Secs Background
2745 Roughly, a section is a range of addresses, with no gaps; all data
2746 ``in'' those addresses is treated the same for some particular purpose.
2747 For example there may be a ``read only'' section.
2749 @cindex linker, and assembler
2750 @cindex assembler, and linker
2751 The linker @code{@value{LD}} reads many object files (partial programs) and
2752 combines their contents to form a runnable program. When @command{@value{AS}}
2753 emits an object file, the partial program is assumed to start at address 0.
2754 @code{@value{LD}} assigns the final addresses for the partial program, so that
2755 different partial programs do not overlap. This is actually an
2756 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2759 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2760 addresses. These blocks slide to their run-time addresses as rigid
2761 units; their length does not change and neither does the order of bytes
2762 within them. Such a rigid unit is called a @emph{section}. Assigning
2763 run-time addresses to sections is called @dfn{relocation}. It includes
2764 the task of adjusting mentions of object-file addresses so they refer to
2765 the proper run-time addresses.
2767 For the H8/300, and for the Renesas / SuperH SH,
2768 @command{@value{AS}} pads sections if needed to
2769 ensure they end on a word (sixteen bit) boundary.
2772 @cindex standard assembler sections
2773 An object file written by @command{@value{AS}} has at least three sections, any
2774 of which may be empty. These are named @dfn{text}, @dfn{data} and
2779 When it generates COFF or ELF output,
2781 @command{@value{AS}} can also generate whatever other named sections you specify
2782 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2783 If you do not use any directives that place output in the @samp{.text}
2784 or @samp{.data} sections, these sections still exist, but are empty.
2789 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2791 @command{@value{AS}} can also generate whatever other named sections you
2792 specify using the @samp{.space} and @samp{.subspace} directives. See
2793 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2794 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2795 assembler directives.
2798 Additionally, @command{@value{AS}} uses different names for the standard
2799 text, data, and bss sections when generating SOM output. Program text
2800 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2801 BSS into @samp{$BSS$}.
2805 Within the object file, the text section starts at address @code{0}, the
2806 data section follows, and the bss section follows the data section.
2809 When generating either SOM or ELF output files on the HPPA, the text
2810 section starts at address @code{0}, the data section at address
2811 @code{0x4000000}, and the bss section follows the data section.
2814 To let @code{@value{LD}} know which data changes when the sections are
2815 relocated, and how to change that data, @command{@value{AS}} also writes to the
2816 object file details of the relocation needed. To perform relocation
2817 @code{@value{LD}} must know, each time an address in the object
2821 Where in the object file is the beginning of this reference to
2824 How long (in bytes) is this reference?
2826 Which section does the address refer to? What is the numeric value of
2828 (@var{address}) @minus{} (@var{start-address of section})?
2831 Is the reference to an address ``Program-Counter relative''?
2834 @cindex addresses, format of
2835 @cindex section-relative addressing
2836 In fact, every address @command{@value{AS}} ever uses is expressed as
2838 (@var{section}) + (@var{offset into section})
2841 Further, most expressions @command{@value{AS}} computes have this section-relative
2844 (For some object formats, such as SOM for the HPPA, some expressions are
2845 symbol-relative instead.)
2848 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2849 @var{N} into section @var{secname}.''
2851 Apart from text, data and bss sections you need to know about the
2852 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2853 addresses in the absolute section remain unchanged. For example, address
2854 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2855 @code{@value{LD}}. Although the linker never arranges two partial programs'
2856 data sections with overlapping addresses after linking, @emph{by definition}
2857 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2858 part of a program is always the same address when the program is running as
2859 address @code{@{absolute@ 239@}} in any other part of the program.
2861 The idea of sections is extended to the @dfn{undefined} section. Any
2862 address whose section is unknown at assembly time is by definition
2863 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2864 Since numbers are always defined, the only way to generate an undefined
2865 address is to mention an undefined symbol. A reference to a named
2866 common block would be such a symbol: its value is unknown at assembly
2867 time so it has section @emph{undefined}.
2869 By analogy the word @emph{section} is used to describe groups of sections in
2870 the linked program. @code{@value{LD}} puts all partial programs' text
2871 sections in contiguous addresses in the linked program. It is
2872 customary to refer to the @emph{text section} of a program, meaning all
2873 the addresses of all partial programs' text sections. Likewise for
2874 data and bss sections.
2876 Some sections are manipulated by @code{@value{LD}}; others are invented for
2877 use of @command{@value{AS}} and have no meaning except during assembly.
2880 @section Linker Sections
2881 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2886 @cindex named sections
2887 @cindex sections, named
2888 @item named sections
2891 @cindex text section
2892 @cindex data section
2896 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2897 separate but equal sections. Anything you can say of one section is
2900 When the program is running, however, it is
2901 customary for the text section to be unalterable. The
2902 text section is often shared among processes: it contains
2903 instructions, constants and the like. The data section of a running
2904 program is usually alterable: for example, C variables would be stored
2905 in the data section.
2910 This section contains zeroed bytes when your program begins running. It
2911 is used to hold uninitialized variables or common storage. The length of
2912 each partial program's bss section is important, but because it starts
2913 out containing zeroed bytes there is no need to store explicit zero
2914 bytes in the object file. The bss section was invented to eliminate
2915 those explicit zeros from object files.
2917 @cindex absolute section
2918 @item absolute section
2919 Address 0 of this section is always ``relocated'' to runtime address 0.
2920 This is useful if you want to refer to an address that @code{@value{LD}} must
2921 not change when relocating. In this sense we speak of absolute
2922 addresses being ``unrelocatable'': they do not change during relocation.
2924 @cindex undefined section
2925 @item undefined section
2926 This ``section'' is a catch-all for address references to objects not in
2927 the preceding sections.
2928 @c FIXME: ref to some other doc on obj-file formats could go here.
2931 @cindex relocation example
2932 An idealized example of three relocatable sections follows.
2934 The example uses the traditional section names @samp{.text} and @samp{.data}.
2936 Memory addresses are on the horizontal axis.
2940 @c END TEXI2ROFF-KILL
2943 partial program # 1: |ttttt|dddd|00|
2950 partial program # 2: |TTT|DDD|000|
2953 +--+---+-----+--+----+---+-----+~~
2954 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2955 +--+---+-----+--+----+---+-----+~~
2957 addresses: 0 @dots{}
2964 \line{\it Partial program \#1: \hfil}
2965 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2966 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2968 \line{\it Partial program \#2: \hfil}
2969 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2970 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2972 \line{\it linked program: \hfil}
2973 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2974 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2975 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2976 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2978 \line{\it addresses: \hfil}
2982 @c END TEXI2ROFF-KILL
2985 @section Assembler Internal Sections
2987 @cindex internal assembler sections
2988 @cindex sections in messages, internal
2989 These sections are meant only for the internal use of @command{@value{AS}}. They
2990 have no meaning at run-time. You do not really need to know about these
2991 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2992 warning messages, so it might be helpful to have an idea of their
2993 meanings to @command{@value{AS}}. These sections are used to permit the
2994 value of every expression in your assembly language program to be a
2995 section-relative address.
2998 @cindex assembler internal logic error
2999 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3000 An internal assembler logic error has been found. This means there is a
3001 bug in the assembler.
3003 @cindex expr (internal section)
3005 The assembler stores complex expression internally as combinations of
3006 symbols. When it needs to represent an expression as a symbol, it puts
3007 it in the expr section.
3009 @c FIXME item transfer[t] vector preload
3010 @c FIXME item transfer[t] vector postload
3011 @c FIXME item register
3015 @section Sub-Sections
3017 @cindex numbered subsections
3018 @cindex grouping data
3024 fall into two sections: text and data.
3026 You may have separate groups of
3028 data in named sections
3032 data in named sections
3038 that you want to end up near to each other in the object file, even though they
3039 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3040 use @dfn{subsections} for this purpose. Within each section, there can be
3041 numbered subsections with values from 0 to 8192. Objects assembled into the
3042 same subsection go into the object file together with other objects in the same
3043 subsection. For example, a compiler might want to store constants in the text
3044 section, but might not want to have them interspersed with the program being
3045 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3046 section of code being output, and a @samp{.text 1} before each group of
3047 constants being output.
3049 Subsections are optional. If you do not use subsections, everything
3050 goes in subsection number zero.
3053 Each subsection is zero-padded up to a multiple of four bytes.
3054 (Subsections may be padded a different amount on different flavors
3055 of @command{@value{AS}}.)
3059 On the H8/300 platform, each subsection is zero-padded to a word
3060 boundary (two bytes).
3061 The same is true on the Renesas SH.
3064 @c FIXME section padding (alignment)?
3065 @c Rich Pixley says padding here depends on target obj code format; that
3066 @c doesn't seem particularly useful to say without further elaboration,
3067 @c so for now I say nothing about it. If this is a generic BFD issue,
3068 @c these paragraphs might need to vanish from this manual, and be
3069 @c discussed in BFD chapter of binutils (or some such).
3073 Subsections appear in your object file in numeric order, lowest numbered
3074 to highest. (All this to be compatible with other people's assemblers.)
3075 The object file contains no representation of subsections; @code{@value{LD}} and
3076 other programs that manipulate object files see no trace of them.
3077 They just see all your text subsections as a text section, and all your
3078 data subsections as a data section.
3080 To specify which subsection you want subsequent statements assembled
3081 into, use a numeric argument to specify it, in a @samp{.text
3082 @var{expression}} or a @samp{.data @var{expression}} statement.
3085 When generating COFF output, you
3090 can also use an extra subsection
3091 argument with arbitrary named sections: @samp{.section @var{name},
3096 When generating ELF output, you
3101 can also use the @code{.subsection} directive (@pxref{SubSection})
3102 to specify a subsection: @samp{.subsection @var{expression}}.
3104 @var{Expression} should be an absolute expression
3105 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3106 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3107 begins in @code{text 0}. For instance:
3109 .text 0 # The default subsection is text 0 anyway.
3110 .ascii "This lives in the first text subsection. *"
3112 .ascii "But this lives in the second text subsection."
3114 .ascii "This lives in the data section,"
3115 .ascii "in the first data subsection."
3117 .ascii "This lives in the first text section,"
3118 .ascii "immediately following the asterisk (*)."
3121 Each section has a @dfn{location counter} incremented by one for every byte
3122 assembled into that section. Because subsections are merely a convenience
3123 restricted to @command{@value{AS}} there is no concept of a subsection location
3124 counter. There is no way to directly manipulate a location counter---but the
3125 @code{.align} directive changes it, and any label definition captures its
3126 current value. The location counter of the section where statements are being
3127 assembled is said to be the @dfn{active} location counter.
3130 @section bss Section
3133 @cindex common variable storage
3134 The bss section is used for local common variable storage.
3135 You may allocate address space in the bss section, but you may
3136 not dictate data to load into it before your program executes. When
3137 your program starts running, all the contents of the bss
3138 section are zeroed bytes.
3140 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3141 @ref{Lcomm,,@code{.lcomm}}.
3143 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3144 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3147 When assembling for a target which supports multiple sections, such as ELF or
3148 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3149 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3150 section. Typically the section will only contain symbol definitions and
3151 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3158 Symbols are a central concept: the programmer uses symbols to name
3159 things, the linker uses symbols to link, and the debugger uses symbols
3163 @cindex debuggers, and symbol order
3164 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3165 the same order they were declared. This may break some debuggers.
3170 * Setting Symbols:: Giving Symbols Other Values
3171 * Symbol Names:: Symbol Names
3172 * Dot:: The Special Dot Symbol
3173 * Symbol Attributes:: Symbol Attributes
3180 A @dfn{label} is written as a symbol immediately followed by a colon
3181 @samp{:}. The symbol then represents the current value of the
3182 active location counter, and is, for example, a suitable instruction
3183 operand. You are warned if you use the same symbol to represent two
3184 different locations: the first definition overrides any other
3188 On the HPPA, the usual form for a label need not be immediately followed by a
3189 colon, but instead must start in column zero. Only one label may be defined on
3190 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3191 provides a special directive @code{.label} for defining labels more flexibly.
3194 @node Setting Symbols
3195 @section Giving Symbols Other Values
3197 @cindex assigning values to symbols
3198 @cindex symbol values, assigning
3199 A symbol can be given an arbitrary value by writing a symbol, followed
3200 by an equals sign @samp{=}, followed by an expression
3201 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3202 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3203 equals sign @samp{=}@samp{=} here represents an equivalent of the
3204 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3207 @section Symbol Names
3209 @cindex symbol names
3210 @cindex names, symbol
3211 @ifclear SPECIAL-SYMS
3212 Symbol names begin with a letter or with one of @samp{._}. On most
3213 machines, you can also use @code{$} in symbol names; exceptions are
3214 noted in @ref{Machine Dependencies}. That character may be followed by any
3215 string of digits, letters, dollar signs (unless otherwise noted for a
3216 particular target machine), and underscores.
3220 Symbol names begin with a letter or with one of @samp{._}. On the
3221 Renesas SH you can also use @code{$} in symbol names. That
3222 character may be followed by any string of digits, letters, dollar signs (save
3223 on the H8/300), and underscores.
3227 Case of letters is significant: @code{foo} is a different symbol name
3230 Each symbol has exactly one name. Each name in an assembly language program
3231 refers to exactly one symbol. You may use that symbol name any number of times
3234 @subheading Local Symbol Names
3236 @cindex local symbol names
3237 @cindex symbol names, local
3238 A local symbol is any symbol beginning with certain local label prefixes.
3239 By default, the local label prefix is @samp{.L} for ELF systems or
3240 @samp{L} for traditional a.out systems, but each target may have its own
3241 set of local label prefixes.
3243 On the HPPA local symbols begin with @samp{L$}.
3246 Local symbols are defined and used within the assembler, but they are
3247 normally not saved in object files. Thus, they are not visible when debugging.
3248 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3249 @option{-L}}) to retain the local symbols in the object files.
3251 @subheading Local Labels
3253 @cindex local labels
3254 @cindex temporary symbol names
3255 @cindex symbol names, temporary
3256 Local labels help compilers and programmers use names temporarily.
3257 They create symbols which are guaranteed to be unique over the entire scope of
3258 the input source code and which can be referred to by a simple notation.
3259 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3260 represents any positive integer). To refer to the most recent previous
3261 definition of that label write @samp{@b{N}b}, using the same number as when
3262 you defined the label. To refer to the next definition of a local label, write
3263 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3266 There is no restriction on how you can use these labels, and you can reuse them
3267 too. So that it is possible to repeatedly define the same local label (using
3268 the same number @samp{@b{N}}), although you can only refer to the most recently
3269 defined local label of that number (for a backwards reference) or the next
3270 definition of a specific local label for a forward reference. It is also worth
3271 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3272 implemented in a slightly more efficient manner than the others.
3283 Which is the equivalent of:
3286 label_1: branch label_3
3287 label_2: branch label_1
3288 label_3: branch label_4
3289 label_4: branch label_3
3292 Local label names are only a notational device. They are immediately
3293 transformed into more conventional symbol names before the assembler uses them.
3294 The symbol names are stored in the symbol table, appear in error messages, and
3295 are optionally emitted to the object file. The names are constructed using
3299 @item @emph{local label prefix}
3300 All local symbols begin with the system-specific local label prefix.
3301 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3302 that start with the local label prefix. These labels are
3303 used for symbols you are never intended to see. If you use the
3304 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3305 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3306 you may use them in debugging.
3309 This is the number that was used in the local label definition. So if the
3310 label is written @samp{55:} then the number is @samp{55}.
3313 This unusual character is included so you do not accidentally invent a symbol
3314 of the same name. The character has ASCII value of @samp{\002} (control-B).
3316 @item @emph{ordinal number}
3317 This is a serial number to keep the labels distinct. The first definition of
3318 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3319 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3320 the number @samp{1} and its 15th definition gets @samp{15} as well.
3323 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3324 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3326 @subheading Dollar Local Labels
3327 @cindex dollar local symbols
3329 @code{@value{AS}} also supports an even more local form of local labels called
3330 dollar labels. These labels go out of scope (i.e., they become undefined) as
3331 soon as a non-local label is defined. Thus they remain valid for only a small
3332 region of the input source code. Normal local labels, by contrast, remain in
3333 scope for the entire file, or until they are redefined by another occurrence of
3334 the same local label.
3336 Dollar labels are defined in exactly the same way as ordinary local labels,
3337 except that instead of being terminated by a colon, they are terminated by a
3338 dollar sign, e.g., @samp{@b{55$}}.
3340 They can also be distinguished from ordinary local labels by their transformed
3341 names which use ASCII character @samp{\001} (control-A) as the magic character
3342 to distinguish them from ordinary labels. For example, the fifth definition of
3343 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3346 @section The Special Dot Symbol
3348 @cindex dot (symbol)
3349 @cindex @code{.} (symbol)
3350 @cindex current address
3351 @cindex location counter
3352 The special symbol @samp{.} refers to the current address that
3353 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3354 .long .} defines @code{melvin} to contain its own address.
3355 Assigning a value to @code{.} is treated the same as a @code{.org}
3356 directive. Thus, the expression @samp{.=.+4} is the same as saying
3357 @ifclear no-space-dir
3361 @node Symbol Attributes
3362 @section Symbol Attributes
3364 @cindex symbol attributes
3365 @cindex attributes, symbol
3366 Every symbol has, as well as its name, the attributes ``Value'' and
3367 ``Type''. Depending on output format, symbols can also have auxiliary
3370 The detailed definitions are in @file{a.out.h}.
3373 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3374 all these attributes, and probably won't warn you. This makes the
3375 symbol an externally defined symbol, which is generally what you
3379 * Symbol Value:: Value
3380 * Symbol Type:: Type
3383 * a.out Symbols:: Symbol Attributes: @code{a.out}
3387 * a.out Symbols:: Symbol Attributes: @code{a.out}
3390 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3395 * COFF Symbols:: Symbol Attributes for COFF
3398 * SOM Symbols:: Symbol Attributes for SOM
3405 @cindex value of a symbol
3406 @cindex symbol value
3407 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3408 location in the text, data, bss or absolute sections the value is the
3409 number of addresses from the start of that section to the label.
3410 Naturally for text, data and bss sections the value of a symbol changes
3411 as @code{@value{LD}} changes section base addresses during linking. Absolute
3412 symbols' values do not change during linking: that is why they are
3415 The value of an undefined symbol is treated in a special way. If it is
3416 0 then the symbol is not defined in this assembler source file, and
3417 @code{@value{LD}} tries to determine its value from other files linked into the
3418 same program. You make this kind of symbol simply by mentioning a symbol
3419 name without defining it. A non-zero value represents a @code{.comm}
3420 common declaration. The value is how much common storage to reserve, in
3421 bytes (addresses). The symbol refers to the first address of the
3427 @cindex type of a symbol
3429 The type attribute of a symbol contains relocation (section)
3430 information, any flag settings indicating that a symbol is external, and
3431 (optionally), other information for linkers and debuggers. The exact
3432 format depends on the object-code output format in use.
3437 @c The following avoids a "widow" subsection title. @group would be
3438 @c better if it were available outside examples.
3441 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3443 @cindex @code{b.out} symbol attributes
3444 @cindex symbol attributes, @code{b.out}
3445 These symbol attributes appear only when @command{@value{AS}} is configured for
3446 one of the Berkeley-descended object output formats---@code{a.out} or
3452 @subsection Symbol Attributes: @code{a.out}
3454 @cindex @code{a.out} symbol attributes
3455 @cindex symbol attributes, @code{a.out}
3461 @subsection Symbol Attributes: @code{a.out}
3463 @cindex @code{a.out} symbol attributes
3464 @cindex symbol attributes, @code{a.out}
3468 * Symbol Desc:: Descriptor
3469 * Symbol Other:: Other
3473 @subsubsection Descriptor
3475 @cindex descriptor, of @code{a.out} symbol
3476 This is an arbitrary 16-bit value. You may establish a symbol's
3477 descriptor value by using a @code{.desc} statement
3478 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3479 @command{@value{AS}}.
3482 @subsubsection Other
3484 @cindex other attribute, of @code{a.out} symbol
3485 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3490 @subsection Symbol Attributes for COFF
3492 @cindex COFF symbol attributes
3493 @cindex symbol attributes, COFF
3495 The COFF format supports a multitude of auxiliary symbol attributes;
3496 like the primary symbol attributes, they are set between @code{.def} and
3497 @code{.endef} directives.
3499 @subsubsection Primary Attributes
3501 @cindex primary attributes, COFF symbols
3502 The symbol name is set with @code{.def}; the value and type,
3503 respectively, with @code{.val} and @code{.type}.
3505 @subsubsection Auxiliary Attributes
3507 @cindex auxiliary attributes, COFF symbols
3508 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3509 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3510 table information for COFF.
3515 @subsection Symbol Attributes for SOM
3517 @cindex SOM symbol attributes
3518 @cindex symbol attributes, SOM
3520 The SOM format for the HPPA supports a multitude of symbol attributes set with
3521 the @code{.EXPORT} and @code{.IMPORT} directives.
3523 The attributes are described in @cite{HP9000 Series 800 Assembly
3524 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3525 @code{EXPORT} assembler directive documentation.
3529 @chapter Expressions
3533 @cindex numeric values
3534 An @dfn{expression} specifies an address or numeric value.
3535 Whitespace may precede and/or follow an expression.
3537 The result of an expression must be an absolute number, or else an offset into
3538 a particular section. If an expression is not absolute, and there is not
3539 enough information when @command{@value{AS}} sees the expression to know its
3540 section, a second pass over the source program might be necessary to interpret
3541 the expression---but the second pass is currently not implemented.
3542 @command{@value{AS}} aborts with an error message in this situation.
3545 * Empty Exprs:: Empty Expressions
3546 * Integer Exprs:: Integer Expressions
3550 @section Empty Expressions
3552 @cindex empty expressions
3553 @cindex expressions, empty
3554 An empty expression has no value: it is just whitespace or null.
3555 Wherever an absolute expression is required, you may omit the
3556 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3557 is compatible with other assemblers.
3560 @section Integer Expressions
3562 @cindex integer expressions
3563 @cindex expressions, integer
3564 An @dfn{integer expression} is one or more @emph{arguments} delimited
3565 by @emph{operators}.
3568 * Arguments:: Arguments
3569 * Operators:: Operators
3570 * Prefix Ops:: Prefix Operators
3571 * Infix Ops:: Infix Operators
3575 @subsection Arguments
3577 @cindex expression arguments
3578 @cindex arguments in expressions
3579 @cindex operands in expressions
3580 @cindex arithmetic operands
3581 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3582 contexts arguments are sometimes called ``arithmetic operands''. In
3583 this manual, to avoid confusing them with the ``instruction operands'' of
3584 the machine language, we use the term ``argument'' to refer to parts of
3585 expressions only, reserving the word ``operand'' to refer only to machine
3586 instruction operands.
3588 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3589 @var{section} is one of text, data, bss, absolute,
3590 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3593 Numbers are usually integers.
3595 A number can be a flonum or bignum. In this case, you are warned
3596 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3597 these 32 bits are an integer. You may write integer-manipulating
3598 instructions that act on exotic constants, compatible with other
3601 @cindex subexpressions
3602 Subexpressions are a left parenthesis @samp{(} followed by an integer
3603 expression, followed by a right parenthesis @samp{)}; or a prefix
3604 operator followed by an argument.
3607 @subsection Operators
3609 @cindex operators, in expressions
3610 @cindex arithmetic functions
3611 @cindex functions, in expressions
3612 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3613 operators are followed by an argument. Infix operators appear
3614 between their arguments. Operators may be preceded and/or followed by
3618 @subsection Prefix Operator
3620 @cindex prefix operators
3621 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3622 one argument, which must be absolute.
3624 @c the tex/end tex stuff surrounding this small table is meant to make
3625 @c it align, on the printed page, with the similar table in the next
3626 @c section (which is inside an enumerate).
3628 \global\advance\leftskip by \itemindent
3633 @dfn{Negation}. Two's complement negation.
3635 @dfn{Complementation}. Bitwise not.
3639 \global\advance\leftskip by -\itemindent
3643 @subsection Infix Operators
3645 @cindex infix operators
3646 @cindex operators, permitted arguments
3647 @dfn{Infix operators} take two arguments, one on either side. Operators
3648 have precedence, but operations with equal precedence are performed left
3649 to right. Apart from @code{+} or @option{-}, both arguments must be
3650 absolute, and the result is absolute.
3653 @cindex operator precedence
3654 @cindex precedence of operators
3661 @dfn{Multiplication}.
3664 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3670 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3673 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3677 Intermediate precedence
3682 @dfn{Bitwise Inclusive Or}.
3688 @dfn{Bitwise Exclusive Or}.
3691 @dfn{Bitwise Or Not}.
3698 @cindex addition, permitted arguments
3699 @cindex plus, permitted arguments
3700 @cindex arguments for addition
3702 @dfn{Addition}. If either argument is absolute, the result has the section of
3703 the other argument. You may not add together arguments from different
3706 @cindex subtraction, permitted arguments
3707 @cindex minus, permitted arguments
3708 @cindex arguments for subtraction
3710 @dfn{Subtraction}. If the right argument is absolute, the
3711 result has the section of the left argument.
3712 If both arguments are in the same section, the result is absolute.
3713 You may not subtract arguments from different sections.
3714 @c FIXME is there still something useful to say about undefined - undefined ?
3716 @cindex comparison expressions
3717 @cindex expressions, comparison
3722 @dfn{Is Not Equal To}
3726 @dfn{Is Greater Than}
3728 @dfn{Is Greater Than Or Equal To}
3730 @dfn{Is Less Than Or Equal To}
3732 The comparison operators can be used as infix operators. A true results has a
3733 value of -1 whereas a false result has a value of 0. Note, these operators
3734 perform signed comparisons.
3737 @item Lowest Precedence
3746 These two logical operations can be used to combine the results of sub
3747 expressions. Note, unlike the comparison operators a true result returns a
3748 value of 1 but a false results does still return 0. Also note that the logical
3749 or operator has a slightly lower precedence than logical and.
3754 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3755 address; you can only have a defined section in one of the two arguments.
3758 @chapter Assembler Directives
3760 @cindex directives, machine independent
3761 @cindex pseudo-ops, machine independent
3762 @cindex machine independent directives
3763 All assembler directives have names that begin with a period (@samp{.}).
3764 The rest of the name is letters, usually in lower case.
3766 This chapter discusses directives that are available regardless of the
3767 target machine configuration for the @sc{gnu} assembler.
3769 Some machine configurations provide additional directives.
3770 @xref{Machine Dependencies}.
3773 @ifset machine-directives
3774 @xref{Machine Dependencies}, for additional directives.
3779 * Abort:: @code{.abort}
3781 * ABORT (COFF):: @code{.ABORT}
3784 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3785 * Altmacro:: @code{.altmacro}
3786 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3787 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3788 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3789 * Byte:: @code{.byte @var{expressions}}
3790 * Comm:: @code{.comm @var{symbol} , @var{length} }
3792 * CFI directives:: @code{.cfi_startproc}, @code{.cfi_endproc}, etc.
3794 * Data:: @code{.data @var{subsection}}
3796 * Def:: @code{.def @var{name}}
3799 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3805 * Double:: @code{.double @var{flonums}}
3806 * Eject:: @code{.eject}
3807 * Else:: @code{.else}
3808 * Elseif:: @code{.elseif}
3811 * Endef:: @code{.endef}
3814 * Endfunc:: @code{.endfunc}
3815 * Endif:: @code{.endif}
3816 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3817 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3818 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3820 * Error:: @code{.error @var{string}}
3821 * Exitm:: @code{.exitm}
3822 * Extern:: @code{.extern}
3823 * Fail:: @code{.fail}
3824 @ifclear no-file-dir
3825 * File:: @code{.file @var{string}}
3828 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3829 * Float:: @code{.float @var{flonums}}
3830 * Func:: @code{.func}
3831 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3833 * Hidden:: @code{.hidden @var{names}}
3836 * hword:: @code{.hword @var{expressions}}
3837 * Ident:: @code{.ident}
3838 * If:: @code{.if @var{absolute expression}}
3839 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3840 * Include:: @code{.include "@var{file}"}
3841 * Int:: @code{.int @var{expressions}}
3843 * Internal:: @code{.internal @var{names}}
3846 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3847 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3848 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3849 * Lflags:: @code{.lflags}
3850 @ifclear no-line-dir
3851 * Line:: @code{.line @var{line-number}}
3854 * Linkonce:: @code{.linkonce [@var{type}]}
3855 * List:: @code{.list}
3856 * Ln:: @code{.ln @var{line-number}}
3858 * LNS directives:: @code{.file}, @code{.loc}, etc.
3860 * Long:: @code{.long @var{expressions}}
3862 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3865 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3866 * MRI:: @code{.mri @var{val}}
3867 * Noaltmacro:: @code{.noaltmacro}
3868 * Nolist:: @code{.nolist}
3869 * Octa:: @code{.octa @var{bignums}}
3870 * Org:: @code{.org @var{new-lc}, @var{fill}}
3871 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3873 * PopSection:: @code{.popsection}
3874 * Previous:: @code{.previous}
3877 * Print:: @code{.print @var{string}}
3879 * Protected:: @code{.protected @var{names}}
3882 * Psize:: @code{.psize @var{lines}, @var{columns}}
3883 * Purgem:: @code{.purgem @var{name}}
3885 * PushSection:: @code{.pushsection @var{name}}
3888 * Quad:: @code{.quad @var{bignums}}
3889 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
3890 * Rept:: @code{.rept @var{count}}
3891 * Sbttl:: @code{.sbttl "@var{subheading}"}
3893 * Scl:: @code{.scl @var{class}}
3896 * Section:: @code{.section @var{name}}
3899 * Set:: @code{.set @var{symbol}, @var{expression}}
3900 * Short:: @code{.short @var{expressions}}
3901 * Single:: @code{.single @var{flonums}}
3903 * Size:: @code{.size [@var{name} , @var{expression}]}
3906 * Skip:: @code{.skip @var{size} , @var{fill}}
3907 * Sleb128:: @code{.sleb128 @var{expressions}}
3908 * Space:: @code{.space @var{size} , @var{fill}}
3910 * Stab:: @code{.stabd, .stabn, .stabs}
3913 * String:: @code{.string "@var{str}"}
3914 * Struct:: @code{.struct @var{expression}}
3916 * SubSection:: @code{.subsection}
3917 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3921 * Tag:: @code{.tag @var{structname}}
3924 * Text:: @code{.text @var{subsection}}
3925 * Title:: @code{.title "@var{heading}"}
3927 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3930 * Uleb128:: @code{.uleb128 @var{expressions}}
3932 * Val:: @code{.val @var{addr}}
3936 * Version:: @code{.version "@var{string}"}
3937 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3938 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3941 * Warning:: @code{.warning @var{string}}
3942 * Weak:: @code{.weak @var{names}}
3943 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
3944 * Word:: @code{.word @var{expressions}}
3945 * Deprecated:: Deprecated Directives
3949 @section @code{.abort}
3951 @cindex @code{abort} directive
3952 @cindex stopping the assembly
3953 This directive stops the assembly immediately. It is for
3954 compatibility with other assemblers. The original idea was that the
3955 assembly language source would be piped into the assembler. If the sender
3956 of the source quit, it could use this directive tells @command{@value{AS}} to
3957 quit also. One day @code{.abort} will not be supported.
3961 @section @code{.ABORT} (COFF)
3963 @cindex @code{ABORT} directive
3964 When producing COFF output, @command{@value{AS}} accepts this directive as a
3965 synonym for @samp{.abort}.
3968 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3974 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3976 @cindex padding the location counter
3977 @cindex @code{align} directive
3978 Pad the location counter (in the current subsection) to a particular storage
3979 boundary. The first expression (which must be absolute) is the alignment
3980 required, as described below.
3982 The second expression (also absolute) gives the fill value to be stored in the
3983 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3984 padding bytes are normally zero. However, on some systems, if the section is
3985 marked as containing code and the fill value is omitted, the space is filled
3986 with no-op instructions.
3988 The third expression is also absolute, and is also optional. If it is present,
3989 it is the maximum number of bytes that should be skipped by this alignment
3990 directive. If doing the alignment would require skipping more bytes than the
3991 specified maximum, then the alignment is not done at all. You can omit the
3992 fill value (the second argument) entirely by simply using two commas after the
3993 required alignment; this can be useful if you want the alignment to be filled
3994 with no-op instructions when appropriate.
3996 The way the required alignment is specified varies from system to system.
3997 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
3998 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
3999 alignment request in bytes. For example @samp{.align 8} advances
4000 the location counter until it is a multiple of 8. If the location counter
4001 is already a multiple of 8, no change is needed. For the tic54x, the
4002 first expression is the alignment request in words.
4004 For other systems, including the i386 using a.out format, and the arm and
4005 strongarm, it is the
4006 number of low-order zero bits the location counter must have after
4007 advancement. For example @samp{.align 3} advances the location
4008 counter until it a multiple of 8. If the location counter is already a
4009 multiple of 8, no change is needed.
4011 This inconsistency is due to the different behaviors of the various
4012 native assemblers for these systems which GAS must emulate.
4013 GAS also provides @code{.balign} and @code{.p2align} directives,
4014 described later, which have a consistent behavior across all
4015 architectures (but are specific to GAS).
4018 @section @code{.ascii "@var{string}"}@dots{}
4020 @cindex @code{ascii} directive
4021 @cindex string literals
4022 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4023 separated by commas. It assembles each string (with no automatic
4024 trailing zero byte) into consecutive addresses.
4027 @section @code{.asciz "@var{string}"}@dots{}
4029 @cindex @code{asciz} directive
4030 @cindex zero-terminated strings
4031 @cindex null-terminated strings
4032 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4033 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4036 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4038 @cindex padding the location counter given number of bytes
4039 @cindex @code{balign} directive
4040 Pad the location counter (in the current subsection) to a particular
4041 storage boundary. The first expression (which must be absolute) is the
4042 alignment request in bytes. For example @samp{.balign 8} advances
4043 the location counter until it is a multiple of 8. If the location counter
4044 is already a multiple of 8, no change is needed.
4046 The second expression (also absolute) gives the fill value to be stored in the
4047 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4048 padding bytes are normally zero. However, on some systems, if the section is
4049 marked as containing code and the fill value is omitted, the space is filled
4050 with no-op instructions.
4052 The third expression is also absolute, and is also optional. If it is present,
4053 it is the maximum number of bytes that should be skipped by this alignment
4054 directive. If doing the alignment would require skipping more bytes than the
4055 specified maximum, then the alignment is not done at all. You can omit the
4056 fill value (the second argument) entirely by simply using two commas after the
4057 required alignment; this can be useful if you want the alignment to be filled
4058 with no-op instructions when appropriate.
4060 @cindex @code{balignw} directive
4061 @cindex @code{balignl} directive
4062 The @code{.balignw} and @code{.balignl} directives are variants of the
4063 @code{.balign} directive. The @code{.balignw} directive treats the fill
4064 pattern as a two byte word value. The @code{.balignl} directives treats the
4065 fill pattern as a four byte longword value. For example, @code{.balignw
4066 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4067 filled in with the value 0x368d (the exact placement of the bytes depends upon
4068 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4072 @section @code{.byte @var{expressions}}
4074 @cindex @code{byte} directive
4075 @cindex integers, one byte
4076 @code{.byte} expects zero or more expressions, separated by commas.
4077 Each expression is assembled into the next byte.
4080 @section @code{.comm @var{symbol} , @var{length} }
4082 @cindex @code{comm} directive
4083 @cindex symbol, common
4084 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4085 common symbol in one object file may be merged with a defined or common symbol
4086 of the same name in another object file. If @code{@value{LD}} does not see a
4087 definition for the symbol--just one or more common symbols--then it will
4088 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4089 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4090 the same name, and they do not all have the same size, it will allocate space
4091 using the largest size.
4094 When using ELF, the @code{.comm} directive takes an optional third argument.
4095 This is the desired alignment of the symbol, specified as a byte boundary (for
4096 example, an alignment of 16 means that the least significant 4 bits of the
4097 address should be zero). The alignment must be an absolute expression, and it
4098 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
4099 for the common symbol, it will use the alignment when placing the symbol. If
4100 no alignment is specified, @command{@value{AS}} will set the alignment to the
4101 largest power of two less than or equal to the size of the symbol, up to a
4106 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4107 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4110 @node CFI directives
4111 @section @code{.cfi_startproc}
4112 @cindex @code{cfi_startproc} directive
4113 @code{.cfi_startproc} is used at the beginning of each function that
4114 should have an entry in @code{.eh_frame}. It initializes some internal
4115 data structures and emits architecture dependent initial CFI instructions.
4116 Don't forget to close the function by
4117 @code{.cfi_endproc}.
4119 @section @code{.cfi_endproc}
4120 @cindex @code{cfi_endproc} directive
4121 @code{.cfi_endproc} is used at the end of a function where it closes its
4122 unwind entry previously opened by
4123 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4125 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4126 @code{.cfi_personality} defines personality routine and its encoding.
4127 @var{encoding} must be a constant determining how the personality
4128 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4129 argument is not present, otherwise second argument should be
4130 a constant or a symbol name. When using indirect encodings,
4131 the symbol provided should be the location where personality
4132 can be loaded from, not the personality routine itself.
4133 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4134 no personality routine.
4136 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4137 @code{.cfi_lsda} defines LSDA and its encoding.
4138 @var{encoding} must be a constant determining how the LSDA
4139 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4140 argument is not present, otherwise second argument should be a constant
4141 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4144 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4145 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4146 address from @var{register} and add @var{offset} to it}.
4148 @section @code{.cfi_def_cfa_register @var{register}}
4149 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4150 now on @var{register} will be used instead of the old one. Offset
4153 @section @code{.cfi_def_cfa_offset @var{offset}}
4154 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4155 remains the same, but @var{offset} is new. Note that it is the
4156 absolute offset that will be added to a defined register to compute
4159 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4160 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4161 value that is added/substracted from the previous offset.
4163 @section @code{.cfi_offset @var{register}, @var{offset}}
4164 Previous value of @var{register} is saved at offset @var{offset} from
4167 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4168 Previous value of @var{register} is saved at offset @var{offset} from
4169 the current CFA register. This is transformed to @code{.cfi_offset}
4170 using the known displacement of the CFA register from the CFA.
4171 This is often easier to use, because the number will match the
4172 code it's annotating.
4174 @section @code{.cfi_signal_frame}
4175 Mark current function as signal trampoline.
4177 @section @code{.cfi_window_save}
4178 SPARC register window has been saved.
4180 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4181 Allows the user to add arbitrary bytes to the unwind info. One
4182 might use this to add OS-specific CFI opcodes, or generic CFI
4183 opcodes that GAS does not yet support.
4185 @node LNS directives
4186 @section @code{.file @var{fileno} @var{filename}}
4187 @cindex @code{file} directive
4188 When emitting dwarf2 line number information @code{.file} assigns filenames
4189 to the @code{.debug_line} file name table. The @var{fileno} operand should
4190 be a unique positive integer to use as the index of the entry in the table.
4191 The @var{filename} operand is a C string literal.
4193 The detail of filename indices is exposed to the user because the filename
4194 table is shared with the @code{.debug_info} section of the dwarf2 debugging
4195 information, and thus the user must know the exact indices that table
4198 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
4199 @cindex @code{loc} directive
4200 The @code{.loc} directive will add row to the @code{.debug_line} line
4201 number matrix corresponding to the immediately following assembly
4202 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
4203 arguments will be applied to the @code{.debug_line} state machine before
4206 The @var{options} are a sequence of the following tokens in any order:
4210 This option will set the @code{basic_block} register in the
4211 @code{.debug_line} state machine to @code{true}.
4214 This option will set the @code{prologue_end} register in the
4215 @code{.debug_line} state machine to @code{true}.
4217 @item epilogue_begin
4218 This option will set the @code{epilogue_begin} register in the
4219 @code{.debug_line} state machine to @code{true}.
4221 @item is_stmt @var{value}
4222 This option will set the @code{is_stmt} register in the
4223 @code{.debug_line} state machine to @code{value}, which must be
4226 @item isa @var{value}
4227 This directive will set the @code{isa} register in the @code{.debug_line}
4228 state machine to @var{value}, which must be an unsigned integer.
4232 @section @code{.loc_mark_blocks @var{enable}}
4233 @cindex @code{loc_mark_blocks} directive
4234 The @code{.loc_mark_blocks} directive makes the assembler emit an entry
4235 to the @code{.debug_line} line number matrix with the @code{basic_block}
4236 register in the state machine set whenever a code label is seen.
4237 The @var{enable} argument should be either 1 or 0, to enable or disable
4238 this function respectively.
4241 @section @code{.data @var{subsection}}
4243 @cindex @code{data} directive
4244 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4245 end of the data subsection numbered @var{subsection} (which is an
4246 absolute expression). If @var{subsection} is omitted, it defaults
4251 @section @code{.def @var{name}}
4253 @cindex @code{def} directive
4254 @cindex COFF symbols, debugging
4255 @cindex debugging COFF symbols
4256 Begin defining debugging information for a symbol @var{name}; the
4257 definition extends until the @code{.endef} directive is encountered.
4260 This directive is only observed when @command{@value{AS}} is configured for COFF
4261 format output; when producing @code{b.out}, @samp{.def} is recognized,
4268 @section @code{.desc @var{symbol}, @var{abs-expression}}
4270 @cindex @code{desc} directive
4271 @cindex COFF symbol descriptor
4272 @cindex symbol descriptor, COFF
4273 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4274 to the low 16 bits of an absolute expression.
4277 The @samp{.desc} directive is not available when @command{@value{AS}} is
4278 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4279 object format. For the sake of compatibility, @command{@value{AS}} accepts
4280 it, but produces no output, when configured for COFF.
4286 @section @code{.dim}
4288 @cindex @code{dim} directive
4289 @cindex COFF auxiliary symbol information
4290 @cindex auxiliary symbol information, COFF
4291 This directive is generated by compilers to include auxiliary debugging
4292 information in the symbol table. It is only permitted inside
4293 @code{.def}/@code{.endef} pairs.
4296 @samp{.dim} is only meaningful when generating COFF format output; when
4297 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4303 @section @code{.double @var{flonums}}
4305 @cindex @code{double} directive
4306 @cindex floating point numbers (double)
4307 @code{.double} expects zero or more flonums, separated by commas. It
4308 assembles floating point numbers.
4310 The exact kind of floating point numbers emitted depends on how
4311 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4315 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4316 in @sc{ieee} format.
4321 @section @code{.eject}
4323 @cindex @code{eject} directive
4324 @cindex new page, in listings
4325 @cindex page, in listings
4326 @cindex listing control: new page
4327 Force a page break at this point, when generating assembly listings.
4330 @section @code{.else}
4332 @cindex @code{else} directive
4333 @code{.else} is part of the @command{@value{AS}} support for conditional
4334 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4335 of code to be assembled if the condition for the preceding @code{.if}
4339 @section @code{.elseif}
4341 @cindex @code{elseif} directive
4342 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4343 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4344 @code{.if} block that would otherwise fill the entire @code{.else} section.
4347 @section @code{.end}
4349 @cindex @code{end} directive
4350 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4351 process anything in the file past the @code{.end} directive.
4355 @section @code{.endef}
4357 @cindex @code{endef} directive
4358 This directive flags the end of a symbol definition begun with
4362 @samp{.endef} is only meaningful when generating COFF format output; if
4363 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4364 directive but ignores it.
4369 @section @code{.endfunc}
4370 @cindex @code{endfunc} directive
4371 @code{.endfunc} marks the end of a function specified with @code{.func}.
4374 @section @code{.endif}
4376 @cindex @code{endif} directive
4377 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4378 it marks the end of a block of code that is only assembled
4379 conditionally. @xref{If,,@code{.if}}.
4382 @section @code{.equ @var{symbol}, @var{expression}}
4384 @cindex @code{equ} directive
4385 @cindex assigning values to symbols
4386 @cindex symbols, assigning values to
4387 This directive sets the value of @var{symbol} to @var{expression}.
4388 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4391 The syntax for @code{equ} on the HPPA is
4392 @samp{@var{symbol} .equ @var{expression}}.
4396 The syntax for @code{equ} on the Z80 is
4397 @samp{@var{symbol} equ @var{expression}}.
4398 On the Z80 it is an eror if @var{symbol} is already defined,
4399 but the symbol is not protected from later redefinition.
4400 Compare @ref{Equiv}.
4404 @section @code{.equiv @var{symbol}, @var{expression}}
4405 @cindex @code{equiv} directive
4406 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4407 the assembler will signal an error if @var{symbol} is already defined. Note a
4408 symbol which has been referenced but not actually defined is considered to be
4411 Except for the contents of the error message, this is roughly equivalent to
4418 plus it protects the symbol from later redefinition.
4421 @section @code{.eqv @var{symbol}, @var{expression}}
4422 @cindex @code{eqv} directive
4423 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4424 evaluate the expression or any part of it immediately. Instead each time
4425 the resulting symbol is used in an expression, a snapshot of its current
4429 @section @code{.err}
4430 @cindex @code{err} directive
4431 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4432 message and, unless the @option{-Z} option was used, it will not generate an
4433 object file. This can be used to signal an error in conditionally compiled code.
4436 @section @code{.error "@var{string}"}
4437 @cindex error directive
4439 Similarly to @code{.err}, this directive emits an error, but you can specify a
4440 string that will be emitted as the error message. If you don't specify the
4441 message, it defaults to @code{".error directive invoked in source file"}.
4442 @xref{Errors, ,Error and Warning Messages}.
4445 .error "This code has not been assembled and tested."
4449 @section @code{.exitm}
4450 Exit early from the current macro definition. @xref{Macro}.
4453 @section @code{.extern}
4455 @cindex @code{extern} directive
4456 @code{.extern} is accepted in the source program---for compatibility
4457 with other assemblers---but it is ignored. @command{@value{AS}} treats
4458 all undefined symbols as external.
4461 @section @code{.fail @var{expression}}
4463 @cindex @code{fail} directive
4464 Generates an error or a warning. If the value of the @var{expression} is 500
4465 or more, @command{@value{AS}} will print a warning message. If the value is less
4466 than 500, @command{@value{AS}} will print an error message. The message will
4467 include the value of @var{expression}. This can occasionally be useful inside
4468 complex nested macros or conditional assembly.
4470 @ifclear no-file-dir
4472 @section @code{.file @var{string}}
4474 @cindex @code{file} directive
4475 @cindex logical file name
4476 @cindex file name, logical
4477 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4478 file. @var{string} is the new file name. In general, the filename is
4479 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4480 to specify an empty file name, you must give the quotes--@code{""}. This
4481 statement may go away in future: it is only recognized to be compatible with
4482 old @command{@value{AS}} programs.
4486 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4488 @cindex @code{fill} directive
4489 @cindex writing patterns in memory
4490 @cindex patterns, writing in memory
4491 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4492 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4493 may be zero or more. @var{Size} may be zero or more, but if it is
4494 more than 8, then it is deemed to have the value 8, compatible with
4495 other people's assemblers. The contents of each @var{repeat} bytes
4496 is taken from an 8-byte number. The highest order 4 bytes are
4497 zero. The lowest order 4 bytes are @var{value} rendered in the
4498 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4499 Each @var{size} bytes in a repetition is taken from the lowest order
4500 @var{size} bytes of this number. Again, this bizarre behavior is
4501 compatible with other people's assemblers.
4503 @var{size} and @var{value} are optional.
4504 If the second comma and @var{value} are absent, @var{value} is
4505 assumed zero. If the first comma and following tokens are absent,
4506 @var{size} is assumed to be 1.
4509 @section @code{.float @var{flonums}}
4511 @cindex floating point numbers (single)
4512 @cindex @code{float} directive
4513 This directive assembles zero or more flonums, separated by commas. It
4514 has the same effect as @code{.single}.
4516 The exact kind of floating point numbers emitted depends on how
4517 @command{@value{AS}} is configured.
4518 @xref{Machine Dependencies}.
4522 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4523 in @sc{ieee} format.
4528 @section @code{.func @var{name}[,@var{label}]}
4529 @cindex @code{func} directive
4530 @code{.func} emits debugging information to denote function @var{name}, and
4531 is ignored unless the file is assembled with debugging enabled.
4532 Only @samp{--gstabs[+]} is currently supported.
4533 @var{label} is the entry point of the function and if omitted @var{name}
4534 prepended with the @samp{leading char} is used.
4535 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4536 All functions are currently defined to have @code{void} return type.
4537 The function must be terminated with @code{.endfunc}.
4540 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4542 @cindex @code{global} directive
4543 @cindex symbol, making visible to linker
4544 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4545 @var{symbol} in your partial program, its value is made available to
4546 other partial programs that are linked with it. Otherwise,
4547 @var{symbol} takes its attributes from a symbol of the same name
4548 from another file linked into the same program.
4550 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4551 compatibility with other assemblers.
4554 On the HPPA, @code{.global} is not always enough to make it accessible to other
4555 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4556 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4561 @section @code{.hidden @var{names}}
4563 @cindex @code{hidden} directive
4565 This is one of the ELF visibility directives. The other two are
4566 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4567 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4569 This directive overrides the named symbols default visibility (which is set by
4570 their binding: local, global or weak). The directive sets the visibility to
4571 @code{hidden} which means that the symbols are not visible to other components.
4572 Such symbols are always considered to be @code{protected} as well.
4576 @section @code{.hword @var{expressions}}
4578 @cindex @code{hword} directive
4579 @cindex integers, 16-bit
4580 @cindex numbers, 16-bit
4581 @cindex sixteen bit integers
4582 This expects zero or more @var{expressions}, and emits
4583 a 16 bit number for each.
4586 This directive is a synonym for @samp{.short}; depending on the target
4587 architecture, it may also be a synonym for @samp{.word}.
4591 This directive is a synonym for @samp{.short}.
4594 This directive is a synonym for both @samp{.short} and @samp{.word}.
4599 @section @code{.ident}
4601 @cindex @code{ident} directive
4603 This directive is used by some assemblers to place tags in object files. The
4604 behavior of this directive varies depending on the target. When using the
4605 a.out object file format, @command{@value{AS}} simply accepts the directive for
4606 source-file compatibility with existing assemblers, but does not emit anything
4607 for it. When using COFF, comments are emitted to the @code{.comment} or
4608 @code{.rdata} section, depending on the target. When using ELF, comments are
4609 emitted to the @code{.comment} section.
4612 @section @code{.if @var{absolute expression}}
4614 @cindex conditional assembly
4615 @cindex @code{if} directive
4616 @code{.if} marks the beginning of a section of code which is only
4617 considered part of the source program being assembled if the argument
4618 (which must be an @var{absolute expression}) is non-zero. The end of
4619 the conditional section of code must be marked by @code{.endif}
4620 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4621 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4622 If you have several conditions to check, @code{.elseif} may be used to avoid
4623 nesting blocks if/else within each subsequent @code{.else} block.
4625 The following variants of @code{.if} are also supported:
4627 @cindex @code{ifdef} directive
4628 @item .ifdef @var{symbol}
4629 Assembles the following section of code if the specified @var{symbol}
4630 has been defined. Note a symbol which has been referenced but not yet defined
4631 is considered to be undefined.
4633 @cindex @code{ifb} directive
4634 @item .ifb @var{text}
4635 Assembles the following section of code if the operand is blank (empty).
4637 @cindex @code{ifc} directive
4638 @item .ifc @var{string1},@var{string2}
4639 Assembles the following section of code if the two strings are the same. The
4640 strings may be optionally quoted with single quotes. If they are not quoted,
4641 the first string stops at the first comma, and the second string stops at the
4642 end of the line. Strings which contain whitespace should be quoted. The
4643 string comparison is case sensitive.
4645 @cindex @code{ifeq} directive
4646 @item .ifeq @var{absolute expression}
4647 Assembles the following section of code if the argument is zero.
4649 @cindex @code{ifeqs} directive
4650 @item .ifeqs @var{string1},@var{string2}
4651 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4653 @cindex @code{ifge} directive
4654 @item .ifge @var{absolute expression}
4655 Assembles the following section of code if the argument is greater than or
4658 @cindex @code{ifgt} directive
4659 @item .ifgt @var{absolute expression}
4660 Assembles the following section of code if the argument is greater than zero.
4662 @cindex @code{ifle} directive
4663 @item .ifle @var{absolute expression}
4664 Assembles the following section of code if the argument is less than or equal
4667 @cindex @code{iflt} directive
4668 @item .iflt @var{absolute expression}
4669 Assembles the following section of code if the argument is less than zero.
4671 @cindex @code{ifnb} directive
4672 @item .ifnb @var{text}
4673 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4674 following section of code if the operand is non-blank (non-empty).
4676 @cindex @code{ifnc} directive
4677 @item .ifnc @var{string1},@var{string2}.
4678 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4679 following section of code if the two strings are not the same.
4681 @cindex @code{ifndef} directive
4682 @cindex @code{ifnotdef} directive
4683 @item .ifndef @var{symbol}
4684 @itemx .ifnotdef @var{symbol}
4685 Assembles the following section of code if the specified @var{symbol}
4686 has not been defined. Both spelling variants are equivalent. Note a symbol
4687 which has been referenced but not yet defined is considered to be undefined.
4689 @cindex @code{ifne} directive
4690 @item .ifne @var{absolute expression}
4691 Assembles the following section of code if the argument is not equal to zero
4692 (in other words, this is equivalent to @code{.if}).
4694 @cindex @code{ifnes} directive
4695 @item .ifnes @var{string1},@var{string2}
4696 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4697 following section of code if the two strings are not the same.
4701 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4703 @cindex @code{incbin} directive
4704 @cindex binary files, including
4705 The @code{incbin} directive includes @var{file} verbatim at the current
4706 location. You can control the search paths used with the @samp{-I} command-line
4707 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4710 The @var{skip} argument skips a number of bytes from the start of the
4711 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4712 read. Note that the data is not aligned in any way, so it is the user's
4713 responsibility to make sure that proper alignment is provided both before and
4714 after the @code{incbin} directive.
4717 @section @code{.include "@var{file}"}
4719 @cindex @code{include} directive
4720 @cindex supporting files, including
4721 @cindex files, including
4722 This directive provides a way to include supporting files at specified
4723 points in your source program. The code from @var{file} is assembled as
4724 if it followed the point of the @code{.include}; when the end of the
4725 included file is reached, assembly of the original file continues. You
4726 can control the search paths used with the @samp{-I} command-line option
4727 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4731 @section @code{.int @var{expressions}}
4733 @cindex @code{int} directive
4734 @cindex integers, 32-bit
4735 Expect zero or more @var{expressions}, of any section, separated by commas.
4736 For each expression, emit a number that, at run time, is the value of that
4737 expression. The byte order and bit size of the number depends on what kind
4738 of target the assembly is for.
4742 On most forms of the H8/300, @code{.int} emits 16-bit
4743 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4750 @section @code{.internal @var{names}}
4752 @cindex @code{internal} directive
4754 This is one of the ELF visibility directives. The other two are
4755 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4756 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4758 This directive overrides the named symbols default visibility (which is set by
4759 their binding: local, global or weak). The directive sets the visibility to
4760 @code{internal} which means that the symbols are considered to be @code{hidden}
4761 (i.e., not visible to other components), and that some extra, processor specific
4762 processing must also be performed upon the symbols as well.
4766 @section @code{.irp @var{symbol},@var{values}}@dots{}
4768 @cindex @code{irp} directive
4769 Evaluate a sequence of statements assigning different values to @var{symbol}.
4770 The sequence of statements starts at the @code{.irp} directive, and is
4771 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4772 set to @var{value}, and the sequence of statements is assembled. If no
4773 @var{value} is listed, the sequence of statements is assembled once, with
4774 @var{symbol} set to the null string. To refer to @var{symbol} within the
4775 sequence of statements, use @var{\symbol}.
4777 For example, assembling
4785 is equivalent to assembling
4793 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4796 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4798 @cindex @code{irpc} directive
4799 Evaluate a sequence of statements assigning different values to @var{symbol}.
4800 The sequence of statements starts at the @code{.irpc} directive, and is
4801 terminated by an @code{.endr} directive. For each character in @var{value},
4802 @var{symbol} is set to the character, and the sequence of statements is
4803 assembled. If no @var{value} is listed, the sequence of statements is
4804 assembled once, with @var{symbol} set to the null string. To refer to
4805 @var{symbol} within the sequence of statements, use @var{\symbol}.
4807 For example, assembling
4815 is equivalent to assembling
4823 For some caveats with the spelling of @var{symbol}, see also the discussion
4827 @section @code{.lcomm @var{symbol} , @var{length}}
4829 @cindex @code{lcomm} directive
4830 @cindex local common symbols
4831 @cindex symbols, local common
4832 Reserve @var{length} (an absolute expression) bytes for a local common
4833 denoted by @var{symbol}. The section and value of @var{symbol} are
4834 those of the new local common. The addresses are allocated in the bss
4835 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4836 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4837 not visible to @code{@value{LD}}.
4840 Some targets permit a third argument to be used with @code{.lcomm}. This
4841 argument specifies the desired alignment of the symbol in the bss section.
4845 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4846 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4850 @section @code{.lflags}
4852 @cindex @code{lflags} directive (ignored)
4853 @command{@value{AS}} accepts this directive, for compatibility with other
4854 assemblers, but ignores it.
4856 @ifclear no-line-dir
4858 @section @code{.line @var{line-number}}
4860 @cindex @code{line} directive
4864 @section @code{.ln @var{line-number}}
4866 @cindex @code{ln} directive
4868 @cindex logical line number
4870 Change the logical line number. @var{line-number} must be an absolute
4871 expression. The next line has that logical line number. Therefore any other
4872 statements on the current line (after a statement separator character) are
4873 reported as on logical line number @var{line-number} @minus{} 1. One day
4874 @command{@value{AS}} will no longer support this directive: it is recognized only
4875 for compatibility with existing assembler programs.
4879 @ifclear no-line-dir
4880 Even though this is a directive associated with the @code{a.out} or
4881 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4882 when producing COFF output, and treats @samp{.line} as though it
4883 were the COFF @samp{.ln} @emph{if} it is found outside a
4884 @code{.def}/@code{.endef} pair.
4886 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4887 used by compilers to generate auxiliary symbol information for
4892 @section @code{.linkonce [@var{type}]}
4894 @cindex @code{linkonce} directive
4895 @cindex common sections
4896 Mark the current section so that the linker only includes a single copy of it.
4897 This may be used to include the same section in several different object files,
4898 but ensure that the linker will only include it once in the final output file.
4899 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4900 Duplicate sections are detected based on the section name, so it should be
4903 This directive is only supported by a few object file formats; as of this
4904 writing, the only object file format which supports it is the Portable
4905 Executable format used on Windows NT.
4907 The @var{type} argument is optional. If specified, it must be one of the
4908 following strings. For example:
4912 Not all types may be supported on all object file formats.
4916 Silently discard duplicate sections. This is the default.
4919 Warn if there are duplicate sections, but still keep only one copy.
4922 Warn if any of the duplicates have different sizes.
4925 Warn if any of the duplicates do not have exactly the same contents.
4929 @section @code{.ln @var{line-number}}
4931 @cindex @code{ln} directive
4932 @ifclear no-line-dir
4933 @samp{.ln} is a synonym for @samp{.line}.
4936 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4937 must be an absolute expression. The next line has that logical
4938 line number, so any other statements on the current line (after a
4939 statement separator character @code{;}) are reported as on logical
4940 line number @var{line-number} @minus{} 1.
4943 This directive is accepted, but ignored, when @command{@value{AS}} is
4944 configured for @code{b.out}; its effect is only associated with COFF
4950 @section @code{.mri @var{val}}
4952 @cindex @code{mri} directive
4953 @cindex MRI mode, temporarily
4954 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4955 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4956 affects code assembled until the next @code{.mri} directive, or until the end
4957 of the file. @xref{M, MRI mode, MRI mode}.
4960 @section @code{.list}
4962 @cindex @code{list} directive
4963 @cindex listing control, turning on
4964 Control (in conjunction with the @code{.nolist} directive) whether or
4965 not assembly listings are generated. These two directives maintain an
4966 internal counter (which is zero initially). @code{.list} increments the
4967 counter, and @code{.nolist} decrements it. Assembly listings are
4968 generated whenever the counter is greater than zero.
4970 By default, listings are disabled. When you enable them (with the
4971 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4972 the initial value of the listing counter is one.
4975 @section @code{.long @var{expressions}}
4977 @cindex @code{long} directive
4978 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
4981 @c no one seems to know what this is for or whether this description is
4982 @c what it really ought to do
4984 @section @code{.lsym @var{symbol}, @var{expression}}
4986 @cindex @code{lsym} directive
4987 @cindex symbol, not referenced in assembly
4988 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4989 the hash table, ensuring it cannot be referenced by name during the
4990 rest of the assembly. This sets the attributes of the symbol to be
4991 the same as the expression value:
4993 @var{other} = @var{descriptor} = 0
4994 @var{type} = @r{(section of @var{expression})}
4995 @var{value} = @var{expression}
4998 The new symbol is not flagged as external.
5002 @section @code{.macro}
5005 The commands @code{.macro} and @code{.endm} allow you to define macros that
5006 generate assembly output. For example, this definition specifies a macro
5007 @code{sum} that puts a sequence of numbers into memory:
5010 .macro sum from=0, to=5
5019 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5031 @item .macro @var{macname}
5032 @itemx .macro @var{macname} @var{macargs} @dots{}
5033 @cindex @code{macro} directive
5034 Begin the definition of a macro called @var{macname}. If your macro
5035 definition requires arguments, specify their names after the macro name,
5036 separated by commas or spaces. You can qualify the macro argument to
5037 indicate whether all invocations must specify a non-blank value (through
5038 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5039 (through @samp{:@code{vararg}}). You can supply a default value for any
5040 macro argument by following the name with @samp{=@var{deflt}}. You
5041 cannot define two macros with the same @var{macname} unless it has been
5042 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5043 definitions. For example, these are all valid @code{.macro} statements:
5047 Begin the definition of a macro called @code{comm}, which takes no
5050 @item .macro plus1 p, p1
5051 @itemx .macro plus1 p p1
5052 Either statement begins the definition of a macro called @code{plus1},
5053 which takes two arguments; within the macro definition, write
5054 @samp{\p} or @samp{\p1} to evaluate the arguments.
5056 @item .macro reserve_str p1=0 p2
5057 Begin the definition of a macro called @code{reserve_str}, with two
5058 arguments. The first argument has a default value, but not the second.
5059 After the definition is complete, you can call the macro either as
5060 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5061 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5062 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5063 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5065 @item .macro m p1:req, p2=0, p3:vararg
5066 Begin the definition of a macro called @code{m}, with at least three
5067 arguments. The first argument must always have a value specified, but
5068 not the second, which instead has a default value. The third formal
5069 will get assigned all remaining arguments specified at invocation time.
5071 When you call a macro, you can specify the argument values either by
5072 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5073 @samp{sum to=17, from=9}.
5077 Note that since each of the @var{macargs} can be an identifier exactly
5078 as any other one permitted by the target architecture, there may be
5079 occasional problems if the target hand-crafts special meanings to certain
5080 characters when they occur in a special position. For example, if the colon
5081 (@code{:}) is generally permitted to be part of a symbol name, but the
5082 architecture specific code special-cases it when occurring as the final
5083 character of a symbol (to denote a label), then the macro parameter
5084 replacement code will have no way of knowing that and consider the whole
5085 construct (including the colon) an identifier, and check only this
5086 identifier for being the subject to parameter substitution. So for example
5087 this macro definition:
5095 might not work as expected. Invoking @samp{label foo} might not create a label
5096 called @samp{foo} but instead just insert the text @samp{\l:} into the
5097 assembler source, probably generating an error about an unrecognised
5100 Similarly problems might occur with the period character (@samp{.})
5101 which is often allowed inside opcode names (and hence identifier names). So
5102 for example constructing a macro to build an opcode from a base name and a
5103 length specifier like this:
5106 .macro opcode base length
5111 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5112 instruction but instead generate some kind of error as the assembler tries to
5113 interpret the text @samp{\base.\length}.
5115 There are several possible ways around this problem:
5118 @item Insert white space
5119 If it is possible to use white space characters then this is the simplest
5128 @item Use @samp{\()}
5129 The string @samp{\()} can be used to separate the end of a macro argument from
5130 the following text. eg:
5133 .macro opcode base length
5138 @item Use the alternate macro syntax mode
5139 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5140 used as a separator. eg:
5150 Note: this problem of correctly identifying string parameters to pseudo ops
5151 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5152 and @code{.irpc} (@pxref{Irpc}) as well.
5155 @cindex @code{endm} directive
5156 Mark the end of a macro definition.
5159 @cindex @code{exitm} directive
5160 Exit early from the current macro definition.
5162 @cindex number of macros executed
5163 @cindex macros, count executed
5165 @command{@value{AS}} maintains a counter of how many macros it has
5166 executed in this pseudo-variable; you can copy that number to your
5167 output with @samp{\@@}, but @emph{only within a macro definition}.
5169 @item LOCAL @var{name} [ , @dots{} ]
5170 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5171 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5172 @xref{Altmacro,,@code{.altmacro}}.
5176 @section @code{.altmacro}
5177 Enable alternate macro mode, enabling:
5180 @item LOCAL @var{name} [ , @dots{} ]
5181 One additional directive, @code{LOCAL}, is available. It is used to
5182 generate a string replacement for each of the @var{name} arguments, and
5183 replace any instances of @var{name} in each macro expansion. The
5184 replacement string is unique in the assembly, and different for each
5185 separate macro expansion. @code{LOCAL} allows you to write macros that
5186 define symbols, without fear of conflict between separate macro expansions.
5188 @item String delimiters
5189 You can write strings delimited in these other ways besides
5190 @code{"@var{string}"}:
5193 @item '@var{string}'
5194 You can delimit strings with single-quote characters.
5196 @item <@var{string}>
5197 You can delimit strings with matching angle brackets.
5200 @item single-character string escape
5201 To include any single character literally in a string (even if the
5202 character would otherwise have some special meaning), you can prefix the
5203 character with @samp{!} (an exclamation mark). For example, you can
5204 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
5206 @item Expression results as strings
5207 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
5208 and use the result as a string.
5212 @section @code{.noaltmacro}
5213 Disable alternate macro mode. @xref{Altmacro}.
5216 @section @code{.nolist}
5218 @cindex @code{nolist} directive
5219 @cindex listing control, turning off
5220 Control (in conjunction with the @code{.list} directive) whether or
5221 not assembly listings are generated. These two directives maintain an
5222 internal counter (which is zero initially). @code{.list} increments the
5223 counter, and @code{.nolist} decrements it. Assembly listings are
5224 generated whenever the counter is greater than zero.
5227 @section @code{.octa @var{bignums}}
5229 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5230 @cindex @code{octa} directive
5231 @cindex integer, 16-byte
5232 @cindex sixteen byte integer
5233 This directive expects zero or more bignums, separated by commas. For each
5234 bignum, it emits a 16-byte integer.
5236 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5237 hence @emph{octa}-word for 16 bytes.
5240 @section @code{.org @var{new-lc} , @var{fill}}
5242 @cindex @code{org} directive
5243 @cindex location counter, advancing
5244 @cindex advancing location counter
5245 @cindex current address, advancing
5246 Advance the location counter of the current section to
5247 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5248 expression with the same section as the current subsection. That is,
5249 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5250 wrong section, the @code{.org} directive is ignored. To be compatible
5251 with former assemblers, if the section of @var{new-lc} is absolute,
5252 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5253 is the same as the current subsection.
5255 @code{.org} may only increase the location counter, or leave it
5256 unchanged; you cannot use @code{.org} to move the location counter
5259 @c double negative used below "not undefined" because this is a specific
5260 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5261 @c section. doc@cygnus.com 18feb91
5262 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5263 may not be undefined. If you really detest this restriction we eagerly await
5264 a chance to share your improved assembler.
5266 Beware that the origin is relative to the start of the section, not
5267 to the start of the subsection. This is compatible with other
5268 people's assemblers.
5270 When the location counter (of the current subsection) is advanced, the
5271 intervening bytes are filled with @var{fill} which should be an
5272 absolute expression. If the comma and @var{fill} are omitted,
5273 @var{fill} defaults to zero.
5276 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5278 @cindex padding the location counter given a power of two
5279 @cindex @code{p2align} directive
5280 Pad the location counter (in the current subsection) to a particular
5281 storage boundary. The first expression (which must be absolute) is the
5282 number of low-order zero bits the location counter must have after
5283 advancement. For example @samp{.p2align 3} advances the location
5284 counter until it a multiple of 8. If the location counter is already a
5285 multiple of 8, no change is needed.
5287 The second expression (also absolute) gives the fill value to be stored in the
5288 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5289 padding bytes are normally zero. However, on some systems, if the section is
5290 marked as containing code and the fill value is omitted, the space is filled
5291 with no-op instructions.
5293 The third expression is also absolute, and is also optional. If it is present,
5294 it is the maximum number of bytes that should be skipped by this alignment
5295 directive. If doing the alignment would require skipping more bytes than the
5296 specified maximum, then the alignment is not done at all. You can omit the
5297 fill value (the second argument) entirely by simply using two commas after the
5298 required alignment; this can be useful if you want the alignment to be filled
5299 with no-op instructions when appropriate.
5301 @cindex @code{p2alignw} directive
5302 @cindex @code{p2alignl} directive
5303 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5304 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5305 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5306 fill pattern as a four byte longword value. For example, @code{.p2alignw
5307 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5308 filled in with the value 0x368d (the exact placement of the bytes depends upon
5309 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5314 @section @code{.previous}
5316 @cindex @code{previous} directive
5317 @cindex Section Stack
5318 This is one of the ELF section stack manipulation directives. The others are
5319 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5320 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5321 (@pxref{PopSection}).
5323 This directive swaps the current section (and subsection) with most recently
5324 referenced section (and subsection) prior to this one. Multiple
5325 @code{.previous} directives in a row will flip between two sections (and their
5328 In terms of the section stack, this directive swaps the current section with
5329 the top section on the section stack.
5334 @section @code{.popsection}
5336 @cindex @code{popsection} directive
5337 @cindex Section Stack
5338 This is one of the ELF section stack manipulation directives. The others are
5339 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5340 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5343 This directive replaces the current section (and subsection) with the top
5344 section (and subsection) on the section stack. This section is popped off the
5349 @section @code{.print @var{string}}
5351 @cindex @code{print} directive
5352 @command{@value{AS}} will print @var{string} on the standard output during
5353 assembly. You must put @var{string} in double quotes.
5357 @section @code{.protected @var{names}}
5359 @cindex @code{protected} directive
5361 This is one of the ELF visibility directives. The other two are
5362 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5364 This directive overrides the named symbols default visibility (which is set by
5365 their binding: local, global or weak). The directive sets the visibility to
5366 @code{protected} which means that any references to the symbols from within the
5367 components that defines them must be resolved to the definition in that
5368 component, even if a definition in another component would normally preempt
5373 @section @code{.psize @var{lines} , @var{columns}}
5375 @cindex @code{psize} directive
5376 @cindex listing control: paper size
5377 @cindex paper size, for listings
5378 Use this directive to declare the number of lines---and, optionally, the
5379 number of columns---to use for each page, when generating listings.
5381 If you do not use @code{.psize}, listings use a default line-count
5382 of 60. You may omit the comma and @var{columns} specification; the
5383 default width is 200 columns.
5385 @command{@value{AS}} generates formfeeds whenever the specified number of
5386 lines is exceeded (or whenever you explicitly request one, using
5389 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5390 those explicitly specified with @code{.eject}.
5393 @section @code{.purgem @var{name}}
5395 @cindex @code{purgem} directive
5396 Undefine the macro @var{name}, so that later uses of the string will not be
5397 expanded. @xref{Macro}.
5401 @section @code{.pushsection @var{name} , @var{subsection}}
5403 @cindex @code{pushsection} directive
5404 @cindex Section Stack
5405 This is one of the ELF section stack manipulation directives. The others are
5406 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5407 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5410 This directive pushes the current section (and subsection) onto the
5411 top of the section stack, and then replaces the current section and
5412 subsection with @code{name} and @code{subsection}.
5416 @section @code{.quad @var{bignums}}
5418 @cindex @code{quad} directive
5419 @code{.quad} expects zero or more bignums, separated by commas. For
5420 each bignum, it emits
5422 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5423 warning message; and just takes the lowest order 8 bytes of the bignum.
5424 @cindex eight-byte integer
5425 @cindex integer, 8-byte
5427 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5428 hence @emph{quad}-word for 8 bytes.
5431 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5432 warning message; and just takes the lowest order 16 bytes of the bignum.
5433 @cindex sixteen-byte integer
5434 @cindex integer, 16-byte
5438 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5440 @cindex @code{reloc} directive
5441 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5442 @var{expression}. If @var{offset} is a number, the relocation is generated in
5443 the current section. If @var{offset} is an expression that resolves to a
5444 symbol plus offset, the relocation is generated in the given symbol's section.
5445 @var{expression}, if present, must resolve to a symbol plus addend or to an
5446 absolute value, but note that not all targets support an addend. e.g. ELF REL
5447 targets such as i386 store an addend in the section contents rather than in the
5448 relocation. This low level interface does not support addends stored in the
5452 @section @code{.rept @var{count}}
5454 @cindex @code{rept} directive
5455 Repeat the sequence of lines between the @code{.rept} directive and the next
5456 @code{.endr} directive @var{count} times.
5458 For example, assembling
5466 is equivalent to assembling
5475 @section @code{.sbttl "@var{subheading}"}
5477 @cindex @code{sbttl} directive
5478 @cindex subtitles for listings
5479 @cindex listing control: subtitle
5480 Use @var{subheading} as the title (third line, immediately after the
5481 title line) when generating assembly listings.
5483 This directive affects subsequent pages, as well as the current page if
5484 it appears within ten lines of the top of a page.
5488 @section @code{.scl @var{class}}
5490 @cindex @code{scl} directive
5491 @cindex symbol storage class (COFF)
5492 @cindex COFF symbol storage class
5493 Set the storage-class value for a symbol. This directive may only be
5494 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5495 whether a symbol is static or external, or it may record further
5496 symbolic debugging information.
5499 The @samp{.scl} directive is primarily associated with COFF output; when
5500 configured to generate @code{b.out} output format, @command{@value{AS}}
5501 accepts this directive but ignores it.
5507 @section @code{.section @var{name}}
5509 @cindex named section
5510 Use the @code{.section} directive to assemble the following code into a section
5513 This directive is only supported for targets that actually support arbitrarily
5514 named sections; on @code{a.out} targets, for example, it is not accepted, even
5515 with a standard @code{a.out} section name.
5519 @c only print the extra heading if both COFF and ELF are set
5520 @subheading COFF Version
5523 @cindex @code{section} directive (COFF version)
5524 For COFF targets, the @code{.section} directive is used in one of the following
5528 .section @var{name}[, "@var{flags}"]
5529 .section @var{name}[, @var{subsegment}]
5532 If the optional argument is quoted, it is taken as flags to use for the
5533 section. Each flag is a single character. The following flags are recognized:
5536 bss section (uninitialized data)
5538 section is not loaded
5548 shared section (meaningful for PE targets)
5550 ignored. (For compatibility with the ELF version)
5553 If no flags are specified, the default flags depend upon the section name. If
5554 the section name is not recognized, the default will be for the section to be
5555 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5556 from the section, rather than adding them, so if they are used on their own it
5557 will be as if no flags had been specified at all.
5559 If the optional argument to the @code{.section} directive is not quoted, it is
5560 taken as a subsegment number (@pxref{Sub-Sections}).
5565 @c only print the extra heading if both COFF and ELF are set
5566 @subheading ELF Version
5569 @cindex Section Stack
5570 This is one of the ELF section stack manipulation directives. The others are
5571 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5572 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5573 @code{.previous} (@pxref{Previous}).
5575 @cindex @code{section} directive (ELF version)
5576 For ELF targets, the @code{.section} directive is used like this:
5579 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5582 The optional @var{flags} argument is a quoted string which may contain any
5583 combination of the following characters:
5586 section is allocatable
5590 section is executable
5592 section is mergeable
5594 section contains zero terminated strings
5596 section is a member of a section group
5598 section is used for thread-local-storage
5601 The optional @var{type} argument may contain one of the following constants:
5604 section contains data
5606 section does not contain data (i.e., section only occupies space)
5608 section contains data which is used by things other than the program
5610 section contains an array of pointers to init functions
5612 section contains an array of pointers to finish functions
5613 @item @@preinit_array
5614 section contains an array of pointers to pre-init functions
5617 Many targets only support the first three section types.
5619 Note on targets where the @code{@@} character is the start of a comment (eg
5620 ARM) then another character is used instead. For example the ARM port uses the
5623 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5624 be specified as well as an extra argument---@var{entsize}---like this:
5627 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5630 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5631 constants, each @var{entsize} octets long. Sections with both @code{M} and
5632 @code{S} must contain zero terminated strings where each character is
5633 @var{entsize} bytes long. The linker may remove duplicates within sections with
5634 the same name, same entity size and same flags. @var{entsize} must be an
5635 absolute expression.
5637 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5638 be present along with an additional field like this:
5641 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5644 The @var{GroupName} field specifies the name of the section group to which this
5645 particular section belongs. The optional linkage field can contain:
5648 indicates that only one copy of this section should be retained
5653 Note: if both the @var{M} and @var{G} flags are present then the fields for
5654 the Merge flag should come first, like this:
5657 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5660 If no flags are specified, the default flags depend upon the section name. If
5661 the section name is not recognized, the default will be for the section to have
5662 none of the above flags: it will not be allocated in memory, nor writable, nor
5663 executable. The section will contain data.
5665 For ELF targets, the assembler supports another type of @code{.section}
5666 directive for compatibility with the Solaris assembler:
5669 .section "@var{name}"[, @var{flags}...]
5672 Note that the section name is quoted. There may be a sequence of comma
5676 section is allocatable
5680 section is executable
5682 section is used for thread local storage
5685 This directive replaces the current section and subsection. See the
5686 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5687 some examples of how this directive and the other section stack directives
5693 @section @code{.set @var{symbol}, @var{expression}}
5695 @cindex @code{set} directive
5696 @cindex symbol value, setting
5697 Set the value of @var{symbol} to @var{expression}. This
5698 changes @var{symbol}'s value and type to conform to
5699 @var{expression}. If @var{symbol} was flagged as external, it remains
5700 flagged (@pxref{Symbol Attributes}).
5702 You may @code{.set} a symbol many times in the same assembly.
5704 If you @code{.set} a global symbol, the value stored in the object
5705 file is the last value stored into it.
5708 The syntax for @code{set} on the HPPA is
5709 @samp{@var{symbol} .set @var{expression}}.
5713 On Z80 @code{set} is a real instruction, use
5714 @samp{@var{symbol} defl @var{expression}} instead.
5718 @section @code{.short @var{expressions}}
5720 @cindex @code{short} directive
5722 @code{.short} is normally the same as @samp{.word}.
5723 @xref{Word,,@code{.word}}.
5725 In some configurations, however, @code{.short} and @code{.word} generate
5726 numbers of different lengths. @xref{Machine Dependencies}.
5730 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5733 This expects zero or more @var{expressions}, and emits
5734 a 16 bit number for each.
5739 @section @code{.single @var{flonums}}
5741 @cindex @code{single} directive
5742 @cindex floating point numbers (single)
5743 This directive assembles zero or more flonums, separated by commas. It
5744 has the same effect as @code{.float}.
5746 The exact kind of floating point numbers emitted depends on how
5747 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5751 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5752 numbers in @sc{ieee} format.
5758 @section @code{.size}
5760 This directive is used to set the size associated with a symbol.
5764 @c only print the extra heading if both COFF and ELF are set
5765 @subheading COFF Version
5768 @cindex @code{size} directive (COFF version)
5769 For COFF targets, the @code{.size} directive is only permitted inside
5770 @code{.def}/@code{.endef} pairs. It is used like this:
5773 .size @var{expression}
5777 @samp{.size} is only meaningful when generating COFF format output; when
5778 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5785 @c only print the extra heading if both COFF and ELF are set
5786 @subheading ELF Version
5789 @cindex @code{size} directive (ELF version)
5790 For ELF targets, the @code{.size} directive is used like this:
5793 .size @var{name} , @var{expression}
5796 This directive sets the size associated with a symbol @var{name}.
5797 The size in bytes is computed from @var{expression} which can make use of label
5798 arithmetic. This directive is typically used to set the size of function
5804 @section @code{.sleb128 @var{expressions}}
5806 @cindex @code{sleb128} directive
5807 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5808 compact, variable length representation of numbers used by the DWARF
5809 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
5811 @ifclear no-space-dir
5813 @section @code{.skip @var{size} , @var{fill}}
5815 @cindex @code{skip} directive
5816 @cindex filling memory
5817 This directive emits @var{size} bytes, each of value @var{fill}. Both
5818 @var{size} and @var{fill} are absolute expressions. If the comma and
5819 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5823 @section @code{.space @var{size} , @var{fill}}
5825 @cindex @code{space} directive
5826 @cindex filling memory
5827 This directive emits @var{size} bytes, each of value @var{fill}. Both
5828 @var{size} and @var{fill} are absolute expressions. If the comma
5829 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5834 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5835 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5836 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5837 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5845 @section @code{.stabd, .stabn, .stabs}
5847 @cindex symbolic debuggers, information for
5848 @cindex @code{stab@var{x}} directives
5849 There are three directives that begin @samp{.stab}.
5850 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5851 The symbols are not entered in the @command{@value{AS}} hash table: they
5852 cannot be referenced elsewhere in the source file.
5853 Up to five fields are required:
5857 This is the symbol's name. It may contain any character except
5858 @samp{\000}, so is more general than ordinary symbol names. Some
5859 debuggers used to code arbitrarily complex structures into symbol names
5863 An absolute expression. The symbol's type is set to the low 8 bits of
5864 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5865 and debuggers choke on silly bit patterns.
5868 An absolute expression. The symbol's ``other'' attribute is set to the
5869 low 8 bits of this expression.
5872 An absolute expression. The symbol's descriptor is set to the low 16
5873 bits of this expression.
5876 An absolute expression which becomes the symbol's value.
5879 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5880 or @code{.stabs} statement, the symbol has probably already been created;
5881 you get a half-formed symbol in your object file. This is
5882 compatible with earlier assemblers!
5885 @cindex @code{stabd} directive
5886 @item .stabd @var{type} , @var{other} , @var{desc}
5888 The ``name'' of the symbol generated is not even an empty string.
5889 It is a null pointer, for compatibility. Older assemblers used a
5890 null pointer so they didn't waste space in object files with empty
5893 The symbol's value is set to the location counter,
5894 relocatably. When your program is linked, the value of this symbol
5895 is the address of the location counter when the @code{.stabd} was
5898 @cindex @code{stabn} directive
5899 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5900 The name of the symbol is set to the empty string @code{""}.
5902 @cindex @code{stabs} directive
5903 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5904 All five fields are specified.
5910 @section @code{.string} "@var{str}"
5912 @cindex string, copying to object file
5913 @cindex @code{string} directive
5915 Copy the characters in @var{str} to the object file. You may specify more than
5916 one string to copy, separated by commas. Unless otherwise specified for a
5917 particular machine, the assembler marks the end of each string with a 0 byte.
5918 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5921 @section @code{.struct @var{expression}}
5923 @cindex @code{struct} directive
5924 Switch to the absolute section, and set the section offset to @var{expression},
5925 which must be an absolute expression. You might use this as follows:
5934 This would define the symbol @code{field1} to have the value 0, the symbol
5935 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5936 value 8. Assembly would be left in the absolute section, and you would need to
5937 use a @code{.section} directive of some sort to change to some other section
5938 before further assembly.
5942 @section @code{.subsection @var{name}}
5944 @cindex @code{subsection} directive
5945 @cindex Section Stack
5946 This is one of the ELF section stack manipulation directives. The others are
5947 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5948 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5951 This directive replaces the current subsection with @code{name}. The current
5952 section is not changed. The replaced subsection is put onto the section stack
5953 in place of the then current top of stack subsection.
5958 @section @code{.symver}
5959 @cindex @code{symver} directive
5960 @cindex symbol versioning
5961 @cindex versions of symbols
5962 Use the @code{.symver} directive to bind symbols to specific version nodes
5963 within a source file. This is only supported on ELF platforms, and is
5964 typically used when assembling files to be linked into a shared library.
5965 There are cases where it may make sense to use this in objects to be bound
5966 into an application itself so as to override a versioned symbol from a
5969 For ELF targets, the @code{.symver} directive can be used like this:
5971 .symver @var{name}, @var{name2@@nodename}
5973 If the symbol @var{name} is defined within the file
5974 being assembled, the @code{.symver} directive effectively creates a symbol
5975 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5976 just don't try and create a regular alias is that the @var{@@} character isn't
5977 permitted in symbol names. The @var{name2} part of the name is the actual name
5978 of the symbol by which it will be externally referenced. The name @var{name}
5979 itself is merely a name of convenience that is used so that it is possible to
5980 have definitions for multiple versions of a function within a single source
5981 file, and so that the compiler can unambiguously know which version of a
5982 function is being mentioned. The @var{nodename} portion of the alias should be
5983 the name of a node specified in the version script supplied to the linker when
5984 building a shared library. If you are attempting to override a versioned
5985 symbol from a shared library, then @var{nodename} should correspond to the
5986 nodename of the symbol you are trying to override.
5988 If the symbol @var{name} is not defined within the file being assembled, all
5989 references to @var{name} will be changed to @var{name2@@nodename}. If no
5990 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5993 Another usage of the @code{.symver} directive is:
5995 .symver @var{name}, @var{name2@@@@nodename}
5997 In this case, the symbol @var{name} must exist and be defined within
5998 the file being assembled. It is similar to @var{name2@@nodename}. The
5999 difference is @var{name2@@@@nodename} will also be used to resolve
6000 references to @var{name2} by the linker.
6002 The third usage of the @code{.symver} directive is:
6004 .symver @var{name}, @var{name2@@@@@@nodename}
6006 When @var{name} is not defined within the
6007 file being assembled, it is treated as @var{name2@@nodename}. When
6008 @var{name} is defined within the file being assembled, the symbol
6009 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6014 @section @code{.tag @var{structname}}
6016 @cindex COFF structure debugging
6017 @cindex structure debugging, COFF
6018 @cindex @code{tag} directive
6019 This directive is generated by compilers to include auxiliary debugging
6020 information in the symbol table. It is only permitted inside
6021 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6022 definitions in the symbol table with instances of those structures.
6025 @samp{.tag} is only used when generating COFF format output; when
6026 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6032 @section @code{.text @var{subsection}}
6034 @cindex @code{text} directive
6035 Tells @command{@value{AS}} to assemble the following statements onto the end of
6036 the text subsection numbered @var{subsection}, which is an absolute
6037 expression. If @var{subsection} is omitted, subsection number zero
6041 @section @code{.title "@var{heading}"}
6043 @cindex @code{title} directive
6044 @cindex listing control: title line
6045 Use @var{heading} as the title (second line, immediately after the
6046 source file name and pagenumber) when generating assembly listings.
6048 This directive affects subsequent pages, as well as the current page if
6049 it appears within ten lines of the top of a page.
6053 @section @code{.type}
6055 This directive is used to set the type of a symbol.
6059 @c only print the extra heading if both COFF and ELF are set
6060 @subheading COFF Version
6063 @cindex COFF symbol type
6064 @cindex symbol type, COFF
6065 @cindex @code{type} directive (COFF version)
6066 For COFF targets, this directive is permitted only within
6067 @code{.def}/@code{.endef} pairs. It is used like this:
6073 This records the integer @var{int} as the type attribute of a symbol table
6077 @samp{.type} is associated only with COFF format output; when
6078 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6079 directive but ignores it.
6085 @c only print the extra heading if both COFF and ELF are set
6086 @subheading ELF Version
6089 @cindex ELF symbol type
6090 @cindex symbol type, ELF
6091 @cindex @code{type} directive (ELF version)
6092 For ELF targets, the @code{.type} directive is used like this:
6095 .type @var{name} , @var{type description}
6098 This sets the type of symbol @var{name} to be either a
6099 function symbol or an object symbol. There are five different syntaxes
6100 supported for the @var{type description} field, in order to provide
6101 compatibility with various other assemblers.
6103 Because some of the characters used in these syntaxes (such as @samp{@@} and
6104 @samp{#}) are comment characters for some architectures, some of the syntaxes
6105 below do not work on all architectures. The first variant will be accepted by
6106 the GNU assembler on all architectures so that variant should be used for
6107 maximum portability, if you do not need to assemble your code with other
6110 The syntaxes supported are:
6113 .type <name> STT_FUNCTION
6114 .type <name> STT_OBJECT
6116 .type <name>,#function
6117 .type <name>,#object
6119 .type <name>,@@function
6120 .type <name>,@@object
6122 .type <name>,%function
6123 .type <name>,%object
6125 .type <name>,"function"
6126 .type <name>,"object"
6132 @section @code{.uleb128 @var{expressions}}
6134 @cindex @code{uleb128} directive
6135 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6136 compact, variable length representation of numbers used by the DWARF
6137 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6141 @section @code{.val @var{addr}}
6143 @cindex @code{val} directive
6144 @cindex COFF value attribute
6145 @cindex value attribute, COFF
6146 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6147 records the address @var{addr} as the value attribute of a symbol table
6151 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6152 configured for @code{b.out}, it accepts this directive but ignores it.
6158 @section @code{.version "@var{string}"}
6160 @cindex @code{version} directive
6161 This directive creates a @code{.note} section and places into it an ELF
6162 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6167 @section @code{.vtable_entry @var{table}, @var{offset}}
6169 @cindex @code{vtable_entry} directive
6170 This directive finds or creates a symbol @code{table} and creates a
6171 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6174 @section @code{.vtable_inherit @var{child}, @var{parent}}
6176 @cindex @code{vtable_inherit} directive
6177 This directive finds the symbol @code{child} and finds or creates the symbol
6178 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6179 parent whose addend is the value of the child symbol. As a special case the
6180 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6184 @section @code{.warning "@var{string}"}
6185 @cindex warning directive
6186 Similar to the directive @code{.error}
6187 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6190 @section @code{.weak @var{names}}
6192 @cindex @code{weak} directive
6193 This directive sets the weak attribute on the comma separated list of symbol
6194 @code{names}. If the symbols do not already exist, they will be created.
6196 On COFF targets other than PE, weak symbols are a GNU extension. This
6197 directive sets the weak attribute on the comma separated list of symbol
6198 @code{names}. If the symbols do not already exist, they will be created.
6200 On the PE target, weak symbols are supported natively as weak aliases.
6201 When a weak symbol is created that is not an alias, GAS creates an
6202 alternate symbol to hold the default value.
6205 @section @code{.weakref @var{alias}, @var{target}}
6207 @cindex @code{weakref} directive
6208 This directive creates an alias to the target symbol that enables the symbol to
6209 be referenced with weak-symbol semantics, but without actually making it weak.
6210 If direct references or definitions of the symbol are present, then the symbol
6211 will not be weak, but if all references to it are through weak references, the
6212 symbol will be marked as weak in the symbol table.
6214 The effect is equivalent to moving all references to the alias to a separate
6215 assembly source file, renaming the alias to the symbol in it, declaring the
6216 symbol as weak there, and running a reloadable link to merge the object files
6217 resulting from the assembly of the new source file and the old source file that
6218 had the references to the alias removed.
6220 The alias itself never makes to the symbol table, and is entirely handled
6221 within the assembler.
6224 @section @code{.word @var{expressions}}
6226 @cindex @code{word} directive
6227 This directive expects zero or more @var{expressions}, of any section,
6228 separated by commas.
6231 For each expression, @command{@value{AS}} emits a 32-bit number.
6234 For each expression, @command{@value{AS}} emits a 16-bit number.
6239 The size of the number emitted, and its byte order,
6240 depend on what target computer the assembly is for.
6243 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6244 @c happen---32-bit addressability, period; no long/short jumps.
6245 @ifset DIFF-TBL-KLUGE
6246 @cindex difference tables altered
6247 @cindex altered difference tables
6249 @emph{Warning: Special Treatment to support Compilers}
6253 Machines with a 32-bit address space, but that do less than 32-bit
6254 addressing, require the following special treatment. If the machine of
6255 interest to you does 32-bit addressing (or doesn't require it;
6256 @pxref{Machine Dependencies}), you can ignore this issue.
6259 In order to assemble compiler output into something that works,
6260 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6261 Directives of the form @samp{.word sym1-sym2} are often emitted by
6262 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6263 directive of the form @samp{.word sym1-sym2}, and the difference between
6264 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6265 creates a @dfn{secondary jump table}, immediately before the next label.
6266 This secondary jump table is preceded by a short-jump to the
6267 first byte after the secondary table. This short-jump prevents the flow
6268 of control from accidentally falling into the new table. Inside the
6269 table is a long-jump to @code{sym2}. The original @samp{.word}
6270 contains @code{sym1} minus the address of the long-jump to
6273 If there were several occurrences of @samp{.word sym1-sym2} before the
6274 secondary jump table, all of them are adjusted. If there was a
6275 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6276 long-jump to @code{sym4} is included in the secondary jump table,
6277 and the @code{.word} directives are adjusted to contain @code{sym3}
6278 minus the address of the long-jump to @code{sym4}; and so on, for as many
6279 entries in the original jump table as necessary.
6282 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6283 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6284 assembly language programmers.
6287 @c end DIFF-TBL-KLUGE
6290 @section Deprecated Directives
6292 @cindex deprecated directives
6293 @cindex obsolescent directives
6294 One day these directives won't work.
6295 They are included for compatibility with older assemblers.
6302 @node Machine Dependencies
6303 @chapter Machine Dependent Features
6305 @cindex machine dependencies
6306 The machine instruction sets are (almost by definition) different on
6307 each machine where @command{@value{AS}} runs. Floating point representations
6308 vary as well, and @command{@value{AS}} often supports a few additional
6309 directives or command-line options for compatibility with other
6310 assemblers on a particular platform. Finally, some versions of
6311 @command{@value{AS}} support special pseudo-instructions for branch
6314 This chapter discusses most of these differences, though it does not
6315 include details on any machine's instruction set. For details on that
6316 subject, see the hardware manufacturer's manual.
6320 * Alpha-Dependent:: Alpha Dependent Features
6323 * ARC-Dependent:: ARC Dependent Features
6326 * ARM-Dependent:: ARM Dependent Features
6329 * AVR-Dependent:: AVR Dependent Features
6332 * BFIN-Dependent:: BFIN Dependent Features
6335 * CRIS-Dependent:: CRIS Dependent Features
6338 * D10V-Dependent:: D10V Dependent Features
6341 * D30V-Dependent:: D30V Dependent Features
6344 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6347 * HPPA-Dependent:: HPPA Dependent Features
6350 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6353 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6356 * i860-Dependent:: Intel 80860 Dependent Features
6359 * i960-Dependent:: Intel 80960 Dependent Features
6362 * IA-64-Dependent:: Intel IA-64 Dependent Features
6365 * IP2K-Dependent:: IP2K Dependent Features
6368 * M32C-Dependent:: M32C Dependent Features
6371 * M32R-Dependent:: M32R Dependent Features
6374 * M68K-Dependent:: M680x0 Dependent Features
6377 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6380 * MIPS-Dependent:: MIPS Dependent Features
6383 * MMIX-Dependent:: MMIX Dependent Features
6386 * MSP430-Dependent:: MSP430 Dependent Features
6389 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6390 * SH64-Dependent:: SuperH SH64 Dependent Features
6393 * PDP-11-Dependent:: PDP-11 Dependent Features
6396 * PJ-Dependent:: picoJava Dependent Features
6399 * PPC-Dependent:: PowerPC Dependent Features
6402 * Sparc-Dependent:: SPARC Dependent Features
6405 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6408 * V850-Dependent:: V850 Dependent Features
6411 * Xtensa-Dependent:: Xtensa Dependent Features
6414 * Z80-Dependent:: Z80 Dependent Features
6417 * Z8000-Dependent:: Z8000 Dependent Features
6420 * Vax-Dependent:: VAX Dependent Features
6427 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6428 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6429 @c peculiarity: to preserve cross-references, there must be a node called
6430 @c "Machine Dependencies". Hence the conditional nodenames in each
6431 @c major node below. Node defaulting in makeinfo requires adjacency of
6432 @c node and sectioning commands; hence the repetition of @chapter BLAH
6433 @c in both conditional blocks.
6436 @include c-alpha.texi
6452 @include c-bfin.texi
6456 @include c-cris.texi
6461 @node Machine Dependencies
6462 @chapter Machine Dependent Features
6464 The machine instruction sets are different on each Renesas chip family,
6465 and there are also some syntax differences among the families. This
6466 chapter describes the specific @command{@value{AS}} features for each
6470 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6471 * SH-Dependent:: Renesas SH Dependent Features
6478 @include c-d10v.texi
6482 @include c-d30v.texi
6486 @include c-h8300.texi
6490 @include c-hppa.texi
6494 @include c-i370.texi
6498 @include c-i386.texi
6502 @include c-i860.texi
6506 @include c-i960.texi
6510 @include c-ia64.texi
6514 @include c-ip2k.texi
6518 @include c-m32c.texi
6522 @include c-m32r.texi
6526 @include c-m68k.texi
6530 @include c-m68hc11.texi
6534 @include c-mips.texi
6538 @include c-mmix.texi
6542 @include c-msp430.texi
6546 @include c-ns32k.texi
6550 @include c-pdp11.texi
6563 @include c-sh64.texi
6567 @include c-sparc.texi
6571 @include c-tic54x.texi
6587 @include c-v850.texi
6591 @include c-xtensa.texi
6595 @c reverse effect of @down at top of generic Machine-Dep chapter
6599 @node Reporting Bugs
6600 @chapter Reporting Bugs
6601 @cindex bugs in assembler
6602 @cindex reporting bugs in assembler
6604 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6606 Reporting a bug may help you by bringing a solution to your problem, or it may
6607 not. But in any case the principal function of a bug report is to help the
6608 entire community by making the next version of @command{@value{AS}} work better.
6609 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6611 In order for a bug report to serve its purpose, you must include the
6612 information that enables us to fix the bug.
6615 * Bug Criteria:: Have you found a bug?
6616 * Bug Reporting:: How to report bugs
6620 @section Have You Found a Bug?
6621 @cindex bug criteria
6623 If you are not sure whether you have found a bug, here are some guidelines:
6626 @cindex fatal signal
6627 @cindex assembler crash
6628 @cindex crash of assembler
6630 If the assembler gets a fatal signal, for any input whatever, that is a
6631 @command{@value{AS}} bug. Reliable assemblers never crash.
6633 @cindex error on valid input
6635 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6637 @cindex invalid input
6639 If @command{@value{AS}} does not produce an error message for invalid input, that
6640 is a bug. However, you should note that your idea of ``invalid input'' might
6641 be our idea of ``an extension'' or ``support for traditional practice''.
6644 If you are an experienced user of assemblers, your suggestions for improvement
6645 of @command{@value{AS}} are welcome in any case.
6649 @section How to Report Bugs
6651 @cindex assembler bugs, reporting
6653 A number of companies and individuals offer support for @sc{gnu} products. If
6654 you obtained @command{@value{AS}} from a support organization, we recommend you
6655 contact that organization first.
6657 You can find contact information for many support companies and
6658 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6662 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6666 The fundamental principle of reporting bugs usefully is this:
6667 @strong{report all the facts}. If you are not sure whether to state a
6668 fact or leave it out, state it!
6670 Often people omit facts because they think they know what causes the problem
6671 and assume that some details do not matter. Thus, you might assume that the
6672 name of a symbol you use in an example does not matter. Well, probably it does
6673 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6674 happens to fetch from the location where that name is stored in memory;
6675 perhaps, if the name were different, the contents of that location would fool
6676 the assembler into doing the right thing despite the bug. Play it safe and
6677 give a specific, complete example. That is the easiest thing for you to do,
6678 and the most helpful.
6680 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6681 it is new to us. Therefore, always write your bug reports on the assumption
6682 that the bug has not been reported previously.
6684 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6685 bell?'' This cannot help us fix a bug, so it is basically useless. We
6686 respond by asking for enough details to enable us to investigate.
6687 You might as well expedite matters by sending them to begin with.
6689 To enable us to fix the bug, you should include all these things:
6693 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6694 it with the @samp{--version} argument.
6696 Without this, we will not know whether there is any point in looking for
6697 the bug in the current version of @command{@value{AS}}.
6700 Any patches you may have applied to the @command{@value{AS}} source.
6703 The type of machine you are using, and the operating system name and
6707 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6711 The command arguments you gave the assembler to assemble your example and
6712 observe the bug. To guarantee you will not omit something important, list them
6713 all. A copy of the Makefile (or the output from make) is sufficient.
6715 If we were to try to guess the arguments, we would probably guess wrong
6716 and then we might not encounter the bug.
6719 A complete input file that will reproduce the bug. If the bug is observed when
6720 the assembler is invoked via a compiler, send the assembler source, not the
6721 high level language source. Most compilers will produce the assembler source
6722 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6723 the options @samp{-v --save-temps}; this will save the assembler source in a
6724 file with an extension of @file{.s}, and also show you exactly how
6725 @command{@value{AS}} is being run.
6728 A description of what behavior you observe that you believe is
6729 incorrect. For example, ``It gets a fatal signal.''
6731 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6732 will certainly notice it. But if the bug is incorrect output, we might not
6733 notice unless it is glaringly wrong. You might as well not give us a chance to
6736 Even if the problem you experience is a fatal signal, you should still say so
6737 explicitly. Suppose something strange is going on, such as, your copy of
6738 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
6739 library on your system. (This has happened!) Your copy might crash and ours
6740 would not. If you told us to expect a crash, then when ours fails to crash, we
6741 would know that the bug was not happening for us. If you had not told us to
6742 expect a crash, then we would not be able to draw any conclusion from our
6746 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6747 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6748 option. Always send diffs from the old file to the new file. If you even
6749 discuss something in the @command{@value{AS}} source, refer to it by context, not
6752 The line numbers in our development sources will not match those in your
6753 sources. Your line numbers would convey no useful information to us.
6756 Here are some things that are not necessary:
6760 A description of the envelope of the bug.
6762 Often people who encounter a bug spend a lot of time investigating
6763 which changes to the input file will make the bug go away and which
6764 changes will not affect it.
6766 This is often time consuming and not very useful, because the way we
6767 will find the bug is by running a single example under the debugger
6768 with breakpoints, not by pure deduction from a series of examples.
6769 We recommend that you save your time for something else.
6771 Of course, if you can find a simpler example to report @emph{instead}
6772 of the original one, that is a convenience for us. Errors in the
6773 output will be easier to spot, running under the debugger will take
6774 less time, and so on.
6776 However, simplification is not vital; if you do not want to do this,
6777 report the bug anyway and send us the entire test case you used.
6780 A patch for the bug.
6782 A patch for the bug does help us if it is a good one. But do not omit
6783 the necessary information, such as the test case, on the assumption that
6784 a patch is all we need. We might see problems with your patch and decide
6785 to fix the problem another way, or we might not understand it at all.
6787 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6788 construct an example that will make the program follow a certain path through
6789 the code. If you do not send us the example, we will not be able to construct
6790 one, so we will not be able to verify that the bug is fixed.
6792 And if we cannot understand what bug you are trying to fix, or why your
6793 patch should be an improvement, we will not install it. A test case will
6794 help us to understand.
6797 A guess about what the bug is or what it depends on.
6799 Such guesses are usually wrong. Even we cannot guess right about such
6800 things without first using the debugger to find the facts.
6803 @node Acknowledgements
6804 @chapter Acknowledgements
6806 If you have contributed to GAS and your name isn't listed here,
6807 it is not meant as a slight. We just don't know about it. Send mail to the
6808 maintainer, and we'll correct the situation. Currently
6810 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6812 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6815 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6816 information and the 68k series machines, most of the preprocessing pass, and
6817 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6819 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6820 many bug fixes, including merging support for several processors, breaking GAS
6821 up to handle multiple object file format back ends (including heavy rewrite,
6822 testing, an integration of the coff and b.out back ends), adding configuration
6823 including heavy testing and verification of cross assemblers and file splits
6824 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6825 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6826 port (including considerable amounts of reverse engineering), a SPARC opcode
6827 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6828 assertions and made them work, much other reorganization, cleanup, and lint.
6830 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6831 in format-specific I/O modules.
6833 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6834 has done much work with it since.
6836 The Intel 80386 machine description was written by Eliot Dresselhaus.
6838 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6840 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6841 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6843 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6844 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6845 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6846 support a.out format.
6848 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
6849 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
6850 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6851 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6854 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6855 simplified the configuration of which versions accept which directives. He
6856 updated the 68k machine description so that Motorola's opcodes always produced
6857 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6858 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6859 cross-compilation support, and one bug in relaxation that took a week and
6860 required the proverbial one-bit fix.
6862 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6863 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6864 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6865 PowerPC assembler, and made a few other minor patches.
6867 Steve Chamberlain made GAS able to generate listings.
6869 Hewlett-Packard contributed support for the HP9000/300.
6871 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6872 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6873 formats). This work was supported by both the Center for Software Science at
6874 the University of Utah and Cygnus Support.
6876 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6877 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6878 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6879 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6880 and some initial 64-bit support).
6882 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6884 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6885 support for openVMS/Alpha.
6887 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6890 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6891 Inc.@: added support for Xtensa processors.
6893 Several engineers at Cygnus Support have also provided many small bug fixes and
6894 configuration enhancements.
6896 Many others have contributed large or small bugfixes and enhancements. If
6897 you have contributed significant work and are not mentioned on this list, and
6898 want to be, let us know. Some of the history has been lost; we are not
6899 intentionally leaving anyone out.
6904 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob