1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
3 @c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
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 @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
104 2006, 2007, 2008, 2009 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 1.3
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''.
117 @title Using @value{AS}
118 @subtitle The @sc{gnu} Assembler
120 @subtitle for the @value{TARGET} family
122 @ifset VERSION_PACKAGE
124 @subtitle @value{VERSION_PACKAGE}
127 @subtitle Version @value{VERSION}
130 The Free Software Foundation Inc.@: thanks The Nice Computer
131 Company of Australia for loaning Dean Elsner to write the
132 first (Vax) version of @command{as} for Project @sc{gnu}.
133 The proprietors, management and staff of TNCCA thank FSF for
134 distracting the boss while they got some work
137 @author Dean Elsner, Jay Fenlason & friends
141 \hfill {\it Using {\tt @value{AS}}}\par
142 \hfill Edited by Cygnus Support\par
144 %"boxit" macro for figures:
145 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
146 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
147 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
148 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
149 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
152 @vskip 0pt plus 1filll
153 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
154 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
156 Permission is granted to copy, distribute and/or modify this document
157 under the terms of the GNU Free Documentation License, Version 1.3
158 or any later version published by the Free Software Foundation;
159 with no Invariant Sections, with no Front-Cover Texts, and with no
160 Back-Cover Texts. A copy of the license is included in the
161 section entitled ``GNU Free Documentation License''.
168 @top Using @value{AS}
170 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
171 @ifset VERSION_PACKAGE
172 @value{VERSION_PACKAGE}
174 version @value{VERSION}.
176 This version of the file describes @command{@value{AS}} configured to generate
177 code for @value{TARGET} architectures.
180 This document is distributed under the terms of the GNU Free
181 Documentation License. A copy of the license is included in the
182 section entitled ``GNU Free Documentation License''.
185 * Overview:: Overview
186 * Invoking:: Command-Line Options
188 * Sections:: Sections and Relocation
190 * Expressions:: Expressions
191 * Pseudo Ops:: Assembler Directives
193 * Object Attributes:: Object Attributes
195 * Machine Dependencies:: Machine Dependent Features
196 * Reporting Bugs:: Reporting Bugs
197 * Acknowledgements:: Who Did What
198 * GNU Free Documentation License:: GNU Free Documentation License
199 * AS Index:: AS Index
206 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
208 This version of the manual describes @command{@value{AS}} configured to generate
209 code for @value{TARGET} architectures.
213 @cindex invocation summary
214 @cindex option summary
215 @cindex summary of options
216 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
217 see @ref{Invoking,,Command-Line Options}.
219 @c man title AS the portable GNU assembler.
223 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
227 @c We don't use deffn and friends for the following because they seem
228 @c to be limited to one line for the header.
230 @c man begin SYNOPSIS
231 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
232 [@b{--debug-prefix-map} @var{old}=@var{new}]
233 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
234 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--target-help}] [@var{target-options}]
242 [@b{--}|@var{files} @dots{}]
244 @c Target dependent options are listed below. Keep the list sorted.
245 @c Add an empty line for separation.
248 @emph{Target Alpha options:}
250 [@b{-mdebug} | @b{-no-mdebug}]
251 [@b{-replace} | @b{-noreplace}]
252 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
253 [@b{-F}] [@b{-32addr}]
257 @emph{Target ARC options:}
263 @emph{Target ARM options:}
264 @c Don't document the deprecated options
265 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
266 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
267 [@b{-mfpu}=@var{floating-point-format}]
268 [@b{-mfloat-abi}=@var{abi}]
269 [@b{-meabi}=@var{ver}]
272 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
273 @b{-mapcs-reentrant}]
274 [@b{-mthumb-interwork}] [@b{-k}]
278 @emph{Target CRIS options:}
279 [@b{--underscore} | @b{--no-underscore}]
281 [@b{--emulation=criself} | @b{--emulation=crisaout}]
282 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
283 @c Deprecated -- deliberately not documented.
288 @emph{Target D10V options:}
293 @emph{Target D30V options:}
294 [@b{-O}|@b{-n}|@b{-N}]
298 @emph{Target H8/300 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}[+@var{EXTENSION}@dots{}]] [@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}] [-relax] [-h-tick-hex]
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]}]
367 @emph{Target MICROBLAZE options:}
368 @c MicroBlaze has no machine-dependent assembler options.
372 @emph{Target MIPS options:}
373 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
374 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
375 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
376 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
377 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
378 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
379 [@b{-mips64}] [@b{-mips64r2}]
380 [@b{-construct-floats}] [@b{-no-construct-floats}]
381 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
382 [@b{-mfix7000}] [@b{-mno-fix7000}]
383 [@b{-mips16}] [@b{-no-mips16}]
384 [@b{-msmartmips}] [@b{-mno-smartmips}]
385 [@b{-mips3d}] [@b{-no-mips3d}]
386 [@b{-mdmx}] [@b{-no-mdmx}]
387 [@b{-mdsp}] [@b{-mno-dsp}]
388 [@b{-mdspr2}] [@b{-mno-dspr2}]
389 [@b{-mmt}] [@b{-mno-mt}]
390 [@b{-mdebug}] [@b{-no-mdebug}]
391 [@b{-mpdr}] [@b{-mno-pdr}]
395 @emph{Target MMIX options:}
396 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
397 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
398 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
399 [@b{--linker-allocated-gregs}]
403 @emph{Target PDP11 options:}
404 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
405 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
406 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
410 @emph{Target picoJava options:}
415 @emph{Target PowerPC options:}
416 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
417 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}]
418 [@b{-mcom}|@b{-many}|@b{-maltivec}|@b{-mvsx}] [@b{-memb}]
419 [@b{-mregnames}|@b{-mno-regnames}]
420 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
421 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
422 [@b{-msolaris}|@b{-mno-solaris}]
426 @emph{Target RX options:}
427 [@b{-mlittle-endian}|@b{-mbig-endian}]
428 [@b{-m32bit-ints}|@b{-m16bit-ints}]
429 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
433 @emph{Target s390 options:}
434 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
435 [@b{-mregnames}|@b{-mno-regnames}]
436 [@b{-mwarn-areg-zero}]
440 @emph{Target SCORE options:}
441 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
442 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
443 [@b{-march=score7}][@b{-march=score3}]
444 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
448 @emph{Target SPARC options:}
449 @c The order here is important. See c-sparc.texi.
450 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
451 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
452 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
457 @emph{Target TIC54X options:}
458 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
459 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
464 @emph{Target Z80 options:}
465 [@b{-z80}] [@b{-r800}]
466 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
467 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
468 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
469 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
470 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
471 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
475 @c Z8000 has no machine-dependent assembler options
479 @emph{Target Xtensa options:}
480 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
481 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
482 [@b{--[no-]transform}]
483 [@b{--rename-section} @var{oldname}=@var{newname}]
491 @include at-file.texi
494 Turn on listings, in any of a variety of ways:
498 omit false conditionals
501 omit debugging directives
504 include general information, like @value{AS} version and options passed
507 include high-level source
513 include macro expansions
516 omit forms processing
522 set the name of the listing file
525 You may combine these options; for example, use @samp{-aln} for assembly
526 listing without forms processing. The @samp{=file} option, if used, must be
527 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
530 Begin in alternate macro mode.
532 @xref{Altmacro,,@code{.altmacro}}.
536 Ignored. This option is accepted for script compatibility with calls to
539 @item --debug-prefix-map @var{old}=@var{new}
540 When assembling files in directory @file{@var{old}}, record debugging
541 information describing them as in @file{@var{new}} instead.
543 @item --defsym @var{sym}=@var{value}
544 Define the symbol @var{sym} to be @var{value} before assembling the input file.
545 @var{value} must be an integer constant. As in C, a leading @samp{0x}
546 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
547 value. The value of the symbol can be overridden inside a source file via the
548 use of a @code{.set} pseudo-op.
551 ``fast''---skip whitespace and comment preprocessing (assume source is
556 Generate debugging information for each assembler source line using whichever
557 debug format is preferred by the target. This currently means either STABS,
561 Generate stabs debugging information for each assembler line. This
562 may help debugging assembler code, if the debugger can handle it.
565 Generate stabs debugging information for each assembler line, with GNU
566 extensions that probably only gdb can handle, and that could make other
567 debuggers crash or refuse to read your program. This
568 may help debugging assembler code. Currently the only GNU extension is
569 the location of the current working directory at assembling time.
572 Generate DWARF2 debugging information for each assembler line. This
573 may help debugging assembler code, if the debugger can handle it. Note---this
574 option is only supported by some targets, not all of them.
577 Print a summary of the command line options and exit.
580 Print a summary of all target specific options and exit.
583 Add directory @var{dir} to the search list for @code{.include} directives.
586 Don't warn about signed overflow.
589 @ifclear DIFF-TBL-KLUGE
590 This option is accepted but has no effect on the @value{TARGET} family.
592 @ifset DIFF-TBL-KLUGE
593 Issue warnings when difference tables altered for long displacements.
598 Keep (in the symbol table) local symbols. These symbols start with
599 system-specific local label prefixes, typically @samp{.L} for ELF systems
600 or @samp{L} for traditional a.out systems.
605 @item --listing-lhs-width=@var{number}
606 Set the maximum width, in words, of the output data column for an assembler
607 listing to @var{number}.
609 @item --listing-lhs-width2=@var{number}
610 Set the maximum width, in words, of the output data column for continuation
611 lines in an assembler listing to @var{number}.
613 @item --listing-rhs-width=@var{number}
614 Set the maximum width of an input source line, as displayed in a listing, to
617 @item --listing-cont-lines=@var{number}
618 Set the maximum number of lines printed in a listing for a single line of input
621 @item -o @var{objfile}
622 Name the object-file output from @command{@value{AS}} @var{objfile}.
625 Fold the data section into the text section.
627 @kindex --hash-size=@var{number}
628 Set the default size of GAS's hash tables to a prime number close to
629 @var{number}. Increasing this value can reduce the length of time it takes the
630 assembler to perform its tasks, at the expense of increasing the assembler's
631 memory requirements. Similarly reducing this value can reduce the memory
632 requirements at the expense of speed.
634 @item --reduce-memory-overheads
635 This option reduces GAS's memory requirements, at the expense of making the
636 assembly processes slower. Currently this switch is a synonym for
637 @samp{--hash-size=4051}, but in the future it may have other effects as well.
640 Print the maximum space (in bytes) and total time (in seconds) used by
643 @item --strip-local-absolute
644 Remove local absolute symbols from the outgoing symbol table.
648 Print the @command{as} version.
651 Print the @command{as} version and exit.
655 Suppress warning messages.
657 @item --fatal-warnings
658 Treat warnings as errors.
661 Don't suppress warning messages or treat them as errors.
670 Generate an object file even after errors.
672 @item -- | @var{files} @dots{}
673 Standard input, or source files to assemble.
678 The following options are available when @value{AS} is configured for
683 This option selects the core processor variant.
685 Select either big-endian (-EB) or little-endian (-EL) output.
690 The following options are available when @value{AS} is configured for the ARM
694 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
695 Specify which ARM processor variant is the target.
696 @item -march=@var{architecture}[+@var{extension}@dots{}]
697 Specify which ARM architecture variant is used by the target.
698 @item -mfpu=@var{floating-point-format}
699 Select which Floating Point architecture is the target.
700 @item -mfloat-abi=@var{abi}
701 Select which floating point ABI is in use.
703 Enable Thumb only instruction decoding.
704 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
705 Select which procedure calling convention is in use.
707 Select either big-endian (-EB) or little-endian (-EL) output.
708 @item -mthumb-interwork
709 Specify that the code has been generated with interworking between Thumb and
712 Specify that PIC code has been generated.
717 See the info pages for documentation of the CRIS-specific options.
721 The following options are available when @value{AS} is configured for
724 @cindex D10V optimization
725 @cindex optimization, D10V
727 Optimize output by parallelizing instructions.
732 The following options are available when @value{AS} is configured for a D30V
735 @cindex D30V optimization
736 @cindex optimization, D30V
738 Optimize output by parallelizing instructions.
742 Warn when nops are generated.
744 @cindex D30V nops after 32-bit multiply
746 Warn when a nop after a 32-bit multiply instruction is generated.
751 The following options are available when @value{AS} is configured for the
752 Intel 80960 processor.
755 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
756 Specify which variant of the 960 architecture is the target.
759 Add code to collect statistics about branches taken.
762 Do not alter compare-and-branch instructions for long displacements;
769 The following options are available when @value{AS} is configured for the
775 Specifies that the extended IP2022 instructions are allowed.
778 Restores the default behaviour, which restricts the permitted instructions to
779 just the basic IP2022 ones.
785 The following options are available when @value{AS} is configured for the
786 Renesas M32C and M16C processors.
791 Assemble M32C instructions.
794 Assemble M16C instructions (the default).
797 Enable support for link-time relaxations.
800 Support H'00 style hex constants in addition to 0x00 style.
806 The following options are available when @value{AS} is configured for the
807 Renesas M32R (formerly Mitsubishi M32R) series.
812 Specify which processor in the M32R family is the target. The default
813 is normally the M32R, but this option changes it to the M32RX.
815 @item --warn-explicit-parallel-conflicts or --Wp
816 Produce warning messages when questionable parallel constructs are
819 @item --no-warn-explicit-parallel-conflicts or --Wnp
820 Do not produce warning messages when questionable parallel constructs are
827 The following options are available when @value{AS} is configured for the
828 Motorola 68000 series.
833 Shorten references to undefined symbols, to one word instead of two.
835 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
836 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
837 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
838 Specify what processor in the 68000 family is the target. The default
839 is normally the 68020, but this can be changed at configuration time.
841 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
842 The target machine does (or does not) have a floating-point coprocessor.
843 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
844 the basic 68000 is not compatible with the 68881, a combination of the
845 two can be specified, since it's possible to do emulation of the
846 coprocessor instructions with the main processor.
848 @item -m68851 | -mno-68851
849 The target machine does (or does not) have a memory-management
850 unit coprocessor. The default is to assume an MMU for 68020 and up.
857 For details about the PDP-11 machine dependent features options,
858 see @ref{PDP-11-Options}.
861 @item -mpic | -mno-pic
862 Generate position-independent (or position-dependent) code. The
863 default is @option{-mpic}.
866 @itemx -mall-extensions
867 Enable all instruction set extensions. This is the default.
869 @item -mno-extensions
870 Disable all instruction set extensions.
872 @item -m@var{extension} | -mno-@var{extension}
873 Enable (or disable) a particular instruction set extension.
876 Enable the instruction set extensions supported by a particular CPU, and
877 disable all other extensions.
879 @item -m@var{machine}
880 Enable the instruction set extensions supported by a particular machine
881 model, and disable all other extensions.
887 The following options are available when @value{AS} is configured for
888 a picoJava processor.
892 @cindex PJ endianness
893 @cindex endianness, PJ
894 @cindex big endian output, PJ
896 Generate ``big endian'' format output.
898 @cindex little endian output, PJ
900 Generate ``little endian'' format output.
906 The following options are available when @value{AS} is configured for the
907 Motorola 68HC11 or 68HC12 series.
911 @item -m68hc11 | -m68hc12 | -m68hcs12
912 Specify what processor is the target. The default is
913 defined by the configuration option when building the assembler.
916 Specify to use the 16-bit integer ABI.
919 Specify to use the 32-bit integer ABI.
922 Specify to use the 32-bit double ABI.
925 Specify to use the 64-bit double ABI.
927 @item --force-long-branches
928 Relative branches are turned into absolute ones. This concerns
929 conditional branches, unconditional branches and branches to a
932 @item -S | --short-branches
933 Do not turn relative branches into absolute ones
934 when the offset is out of range.
936 @item --strict-direct-mode
937 Do not turn the direct addressing mode into extended addressing mode
938 when the instruction does not support direct addressing mode.
940 @item --print-insn-syntax
941 Print the syntax of instruction in case of error.
943 @item --print-opcodes
944 print the list of instructions with syntax and then exit.
946 @item --generate-example
947 print an example of instruction for each possible instruction and then exit.
948 This option is only useful for testing @command{@value{AS}}.
954 The following options are available when @command{@value{AS}} is configured
955 for the SPARC architecture:
958 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
959 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
960 Explicitly select a variant of the SPARC architecture.
962 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
963 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
965 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
966 UltraSPARC extensions.
968 @item -xarch=v8plus | -xarch=v8plusa
969 For compatibility with the Solaris v9 assembler. These options are
970 equivalent to -Av8plus and -Av8plusa, respectively.
973 Warn when the assembler switches to another architecture.
978 The following options are available when @value{AS} is configured for the 'c54x
983 Enable extended addressing mode. All addresses and relocations will assume
984 extended addressing (usually 23 bits).
985 @item -mcpu=@var{CPU_VERSION}
986 Sets the CPU version being compiled for.
987 @item -merrors-to-file @var{FILENAME}
988 Redirect error output to a file, for broken systems which don't support such
989 behaviour in the shell.
994 The following options are available when @value{AS} is configured for
995 a @sc{mips} processor.
999 This option sets the largest size of an object that can be referenced
1000 implicitly with the @code{gp} register. It is only accepted for targets that
1001 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1003 @cindex MIPS endianness
1004 @cindex endianness, MIPS
1005 @cindex big endian output, MIPS
1007 Generate ``big endian'' format output.
1009 @cindex little endian output, MIPS
1011 Generate ``little endian'' format output.
1023 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1024 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1025 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1026 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1027 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1029 correspond to generic
1030 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1031 and @samp{MIPS64 Release 2}
1032 ISA processors, respectively.
1034 @item -march=@var{CPU}
1035 Generate code for a particular @sc{mips} cpu.
1037 @item -mtune=@var{cpu}
1038 Schedule and tune for a particular @sc{mips} cpu.
1042 Cause nops to be inserted if the read of the destination register
1043 of an mfhi or mflo instruction occurs in the following two instructions.
1047 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1048 section instead of the standard ELF .stabs sections.
1052 Control generation of @code{.pdr} sections.
1056 The register sizes are normally inferred from the ISA and ABI, but these
1057 flags force a certain group of registers to be treated as 32 bits wide at
1058 all times. @samp{-mgp32} controls the size of general-purpose registers
1059 and @samp{-mfp32} controls the size of floating-point registers.
1063 Generate code for the MIPS 16 processor. This is equivalent to putting
1064 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1065 turns off this option.
1068 @itemx -mno-smartmips
1069 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1070 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1071 @samp{-mno-smartmips} turns off this option.
1075 Generate code for the MIPS-3D Application Specific Extension.
1076 This tells the assembler to accept MIPS-3D instructions.
1077 @samp{-no-mips3d} turns off this option.
1081 Generate code for the MDMX Application Specific Extension.
1082 This tells the assembler to accept MDMX instructions.
1083 @samp{-no-mdmx} turns off this option.
1087 Generate code for the DSP Release 1 Application Specific Extension.
1088 This tells the assembler to accept DSP Release 1 instructions.
1089 @samp{-mno-dsp} turns off this option.
1093 Generate code for the DSP Release 2 Application Specific Extension.
1094 This option implies -mdsp.
1095 This tells the assembler to accept DSP Release 2 instructions.
1096 @samp{-mno-dspr2} turns off this option.
1100 Generate code for the MT Application Specific Extension.
1101 This tells the assembler to accept MT instructions.
1102 @samp{-mno-mt} turns off this option.
1104 @item --construct-floats
1105 @itemx --no-construct-floats
1106 The @samp{--no-construct-floats} option disables the construction of
1107 double width floating point constants by loading the two halves of the
1108 value into the two single width floating point registers that make up
1109 the double width register. By default @samp{--construct-floats} is
1110 selected, allowing construction of these floating point constants.
1113 @item --emulation=@var{name}
1114 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1115 for some other target, in all respects, including output format (choosing
1116 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1117 debugging information or store symbol table information, and default
1118 endianness. The available configuration names are: @samp{mipsecoff},
1119 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1120 @samp{mipsbelf}. The first two do not alter the default endianness from that
1121 of the primary target for which the assembler was configured; the others change
1122 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1123 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1124 selection in any case.
1126 This option is currently supported only when the primary target
1127 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1128 Furthermore, the primary target or others specified with
1129 @samp{--enable-targets=@dots{}} at configuration time must include support for
1130 the other format, if both are to be available. For example, the Irix 5
1131 configuration includes support for both.
1133 Eventually, this option will support more configurations, with more
1134 fine-grained control over the assembler's behavior, and will be supported for
1138 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1145 Control how to deal with multiplication overflow and division by zero.
1146 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1147 (and only work for Instruction Set Architecture level 2 and higher);
1148 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1152 When this option is used, @command{@value{AS}} will issue a warning every
1153 time it generates a nop instruction from a macro.
1158 The following options are available when @value{AS} is configured for
1164 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1165 The command line option @samp{-nojsri2bsr} can be used to disable it.
1169 Enable or disable the silicon filter behaviour. By default this is disabled.
1170 The default can be overridden by the @samp{-sifilter} command line option.
1173 Alter jump instructions for long displacements.
1175 @item -mcpu=[210|340]
1176 Select the cpu type on the target hardware. This controls which instructions
1180 Assemble for a big endian target.
1183 Assemble for a little endian target.
1189 See the info pages for documentation of the MMIX-specific options.
1193 The following options are available when @value{AS} is configured for the s390
1199 Select the word size, either 31/32 bits or 64 bits.
1202 Select the architecture mode, either the Enterprise System
1203 Architecture (esa) or the z/Architecture mode (zarch).
1204 @item -march=@var{processor}
1205 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1206 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1208 @itemx -mno-regnames
1209 Allow or disallow symbolic names for registers.
1210 @item -mwarn-areg-zero
1211 Warn whenever the operand for a base or index register has been specified
1212 but evaluates to zero.
1217 The following options are available when @value{AS} is configured for
1218 an Xtensa processor.
1221 @item --text-section-literals | --no-text-section-literals
1222 With @option{--text-@-section-@-literals}, literal pools are interspersed
1223 in the text section. The default is
1224 @option{--no-@-text-@-section-@-literals}, which places literals in a
1225 separate section in the output file. These options only affect literals
1226 referenced via PC-relative @code{L32R} instructions; literals for
1227 absolute mode @code{L32R} instructions are handled separately.
1229 @item --absolute-literals | --no-absolute-literals
1230 Indicate to the assembler whether @code{L32R} instructions use absolute
1231 or PC-relative addressing. The default is to assume absolute addressing
1232 if the Xtensa processor includes the absolute @code{L32R} addressing
1233 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1235 @item --target-align | --no-target-align
1236 Enable or disable automatic alignment to reduce branch penalties at the
1237 expense of some code density. The default is @option{--target-@-align}.
1239 @item --longcalls | --no-longcalls
1240 Enable or disable transformation of call instructions to allow calls
1241 across a greater range of addresses. The default is
1242 @option{--no-@-longcalls}.
1244 @item --transform | --no-transform
1245 Enable or disable all assembler transformations of Xtensa instructions.
1246 The default is @option{--transform};
1247 @option{--no-transform} should be used only in the rare cases when the
1248 instructions must be exactly as specified in the assembly source.
1250 @item --rename-section @var{oldname}=@var{newname}
1251 When generating output sections, rename the @var{oldname} section to
1257 The following options are available when @value{AS} is configured for
1258 a Z80 family processor.
1261 Assemble for Z80 processor.
1263 Assemble for R800 processor.
1264 @item -ignore-undocumented-instructions
1266 Assemble undocumented Z80 instructions that also work on R800 without warning.
1267 @item -ignore-unportable-instructions
1269 Assemble all undocumented Z80 instructions without warning.
1270 @item -warn-undocumented-instructions
1272 Issue a warning for undocumented Z80 instructions that also work on R800.
1273 @item -warn-unportable-instructions
1275 Issue a warning for undocumented Z80 instructions that do not work on R800.
1276 @item -forbid-undocumented-instructions
1278 Treat all undocumented instructions as errors.
1279 @item -forbid-unportable-instructions
1281 Treat undocumented Z80 instructions that do not work on R800 as errors.
1288 * Manual:: Structure of this Manual
1289 * GNU Assembler:: The GNU Assembler
1290 * Object Formats:: Object File Formats
1291 * Command Line:: Command Line
1292 * Input Files:: Input Files
1293 * Object:: Output (Object) File
1294 * Errors:: Error and Warning Messages
1298 @section Structure of this Manual
1300 @cindex manual, structure and purpose
1301 This manual is intended to describe what you need to know to use
1302 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1303 notation for symbols, constants, and expressions; the directives that
1304 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1307 We also cover special features in the @value{TARGET}
1308 configuration of @command{@value{AS}}, including assembler directives.
1311 This manual also describes some of the machine-dependent features of
1312 various flavors of the assembler.
1315 @cindex machine instructions (not covered)
1316 On the other hand, this manual is @emph{not} intended as an introduction
1317 to programming in assembly language---let alone programming in general!
1318 In a similar vein, we make no attempt to introduce the machine
1319 architecture; we do @emph{not} describe the instruction set, standard
1320 mnemonics, registers or addressing modes that are standard to a
1321 particular architecture.
1323 You may want to consult the manufacturer's
1324 machine architecture manual for this information.
1328 For information on the H8/300 machine instruction set, see @cite{H8/300
1329 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1330 Programming Manual} (Renesas).
1333 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1334 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1335 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1336 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1339 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1343 @c I think this is premature---doc@cygnus.com, 17jan1991
1345 Throughout this manual, we assume that you are running @dfn{GNU},
1346 the portable operating system from the @dfn{Free Software
1347 Foundation, Inc.}. This restricts our attention to certain kinds of
1348 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1349 once this assumption is granted examples and definitions need less
1352 @command{@value{AS}} is part of a team of programs that turn a high-level
1353 human-readable series of instructions into a low-level
1354 computer-readable series of instructions. Different versions of
1355 @command{@value{AS}} are used for different kinds of computer.
1358 @c There used to be a section "Terminology" here, which defined
1359 @c "contents", "byte", "word", and "long". Defining "word" to any
1360 @c particular size is confusing when the .word directive may generate 16
1361 @c bits on one machine and 32 bits on another; in general, for the user
1362 @c version of this manual, none of these terms seem essential to define.
1363 @c They were used very little even in the former draft of the manual;
1364 @c this draft makes an effort to avoid them (except in names of
1368 @section The GNU Assembler
1370 @c man begin DESCRIPTION
1372 @sc{gnu} @command{as} is really a family of assemblers.
1374 This manual describes @command{@value{AS}}, a member of that family which is
1375 configured for the @value{TARGET} architectures.
1377 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1378 should find a fairly similar environment when you use it on another
1379 architecture. Each version has much in common with the others,
1380 including object file formats, most assembler directives (often called
1381 @dfn{pseudo-ops}) and assembler syntax.@refill
1383 @cindex purpose of @sc{gnu} assembler
1384 @command{@value{AS}} is primarily intended to assemble the output of the
1385 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1386 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1387 assemble correctly everything that other assemblers for the same
1388 machine would assemble.
1390 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1393 @c This remark should appear in generic version of manual; assumption
1394 @c here is that generic version sets M680x0.
1395 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1396 assembler for the same architecture; for example, we know of several
1397 incompatible versions of 680x0 assembly language syntax.
1402 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1403 program in one pass of the source file. This has a subtle impact on the
1404 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1406 @node Object Formats
1407 @section Object File Formats
1409 @cindex object file format
1410 The @sc{gnu} assembler can be configured to produce several alternative
1411 object file formats. For the most part, this does not affect how you
1412 write assembly language programs; but directives for debugging symbols
1413 are typically different in different file formats. @xref{Symbol
1414 Attributes,,Symbol Attributes}.
1417 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1418 @value{OBJ-NAME} format object files.
1420 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1422 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1423 @code{b.out} or COFF format object files.
1426 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1427 SOM or ELF format object files.
1432 @section Command Line
1434 @cindex command line conventions
1436 After the program name @command{@value{AS}}, the command line may contain
1437 options and file names. Options may appear in any order, and may be
1438 before, after, or between file names. The order of file names is
1441 @cindex standard input, as input file
1443 @file{--} (two hyphens) by itself names the standard input file
1444 explicitly, as one of the files for @command{@value{AS}} to assemble.
1446 @cindex options, command line
1447 Except for @samp{--} any command line argument that begins with a
1448 hyphen (@samp{-}) is an option. Each option changes the behavior of
1449 @command{@value{AS}}. No option changes the way another option works. An
1450 option is a @samp{-} followed by one or more letters; the case of
1451 the letter is important. All options are optional.
1453 Some options expect exactly one file name to follow them. The file
1454 name may either immediately follow the option's letter (compatible
1455 with older assemblers) or it may be the next command argument (@sc{gnu}
1456 standard). These two command lines are equivalent:
1459 @value{AS} -o my-object-file.o mumble.s
1460 @value{AS} -omy-object-file.o mumble.s
1464 @section Input Files
1467 @cindex source program
1468 @cindex files, input
1469 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1470 describe the program input to one run of @command{@value{AS}}. The program may
1471 be in one or more files; how the source is partitioned into files
1472 doesn't change the meaning of the source.
1474 @c I added "con" prefix to "catenation" just to prove I can overcome my
1475 @c APL training... doc@cygnus.com
1476 The source program is a concatenation of the text in all the files, in the
1479 @c man begin DESCRIPTION
1480 Each time you run @command{@value{AS}} it assembles exactly one source
1481 program. The source program is made up of one or more files.
1482 (The standard input is also a file.)
1484 You give @command{@value{AS}} a command line that has zero or more input file
1485 names. The input files are read (from left file name to right). A
1486 command line argument (in any position) that has no special meaning
1487 is taken to be an input file name.
1489 If you give @command{@value{AS}} no file names it attempts to read one input file
1490 from the @command{@value{AS}} standard input, which is normally your terminal. You
1491 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1494 Use @samp{--} if you need to explicitly name the standard input file
1495 in your command line.
1497 If the source is empty, @command{@value{AS}} produces a small, empty object
1502 @subheading Filenames and Line-numbers
1504 @cindex input file linenumbers
1505 @cindex line numbers, in input files
1506 There are two ways of locating a line in the input file (or files) and
1507 either may be used in reporting error messages. One way refers to a line
1508 number in a physical file; the other refers to a line number in a
1509 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1511 @dfn{Physical files} are those files named in the command line given
1512 to @command{@value{AS}}.
1514 @dfn{Logical files} are simply names declared explicitly by assembler
1515 directives; they bear no relation to physical files. Logical file names help
1516 error messages reflect the original source file, when @command{@value{AS}} source
1517 is itself synthesized from other files. @command{@value{AS}} understands the
1518 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1519 @ref{File,,@code{.file}}.
1522 @section Output (Object) File
1528 Every time you run @command{@value{AS}} it produces an output file, which is
1529 your assembly language program translated into numbers. This file
1530 is the object file. Its default name is
1538 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1540 You can give it another name by using the @option{-o} option. Conventionally,
1541 object file names end with @file{.o}. The default name is used for historical
1542 reasons: older assemblers were capable of assembling self-contained programs
1543 directly into a runnable program. (For some formats, this isn't currently
1544 possible, but it can be done for the @code{a.out} format.)
1548 The object file is meant for input to the linker @code{@value{LD}}. It contains
1549 assembled program code, information to help @code{@value{LD}} integrate
1550 the assembled program into a runnable file, and (optionally) symbolic
1551 information for the debugger.
1553 @c link above to some info file(s) like the description of a.out.
1554 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1557 @section Error and Warning Messages
1559 @c man begin DESCRIPTION
1561 @cindex error messages
1562 @cindex warning messages
1563 @cindex messages from assembler
1564 @command{@value{AS}} may write warnings and error messages to the standard error
1565 file (usually your terminal). This should not happen when a compiler
1566 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1567 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1568 grave problem that stops the assembly.
1572 @cindex format of warning messages
1573 Warning messages have the format
1576 file_name:@b{NNN}:Warning Message Text
1580 @cindex line numbers, in warnings/errors
1581 (where @b{NNN} is a line number). If a logical file name has been given
1582 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1583 the current input file is used. If a logical line number was given
1585 (@pxref{Line,,@code{.line}})
1587 then it is used to calculate the number printed,
1588 otherwise the actual line in the current source file is printed. The
1589 message text is intended to be self explanatory (in the grand Unix
1592 @cindex format of error messages
1593 Error messages have the format
1595 file_name:@b{NNN}:FATAL:Error Message Text
1597 The file name and line number are derived as for warning
1598 messages. The actual message text may be rather less explanatory
1599 because many of them aren't supposed to happen.
1602 @chapter Command-Line Options
1604 @cindex options, all versions of assembler
1605 This chapter describes command-line options available in @emph{all}
1606 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1607 for options specific
1609 to the @value{TARGET} target.
1612 to particular machine architectures.
1615 @c man begin DESCRIPTION
1617 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1618 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1619 The assembler arguments must be separated from each other (and the @samp{-Wa})
1620 by commas. For example:
1623 gcc -c -g -O -Wa,-alh,-L file.c
1627 This passes two options to the assembler: @samp{-alh} (emit a listing to
1628 standard output with high-level and assembly source) and @samp{-L} (retain
1629 local symbols in the symbol table).
1631 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1632 command-line options are automatically passed to the assembler by the compiler.
1633 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1634 precisely what options it passes to each compilation pass, including the
1640 * a:: -a[cdghlns] enable listings
1641 * alternate:: --alternate enable alternate macro syntax
1642 * D:: -D for compatibility
1643 * f:: -f to work faster
1644 * I:: -I for .include search path
1645 @ifclear DIFF-TBL-KLUGE
1646 * K:: -K for compatibility
1648 @ifset DIFF-TBL-KLUGE
1649 * K:: -K for difference tables
1652 * L:: -L to retain local symbols
1653 * listing:: --listing-XXX to configure listing output
1654 * M:: -M or --mri to assemble in MRI compatibility mode
1655 * MD:: --MD for dependency tracking
1656 * o:: -o to name the object file
1657 * R:: -R to join data and text sections
1658 * statistics:: --statistics to see statistics about assembly
1659 * traditional-format:: --traditional-format for compatible output
1660 * v:: -v to announce version
1661 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1662 * Z:: -Z to make object file even after errors
1666 @section Enable Listings: @option{-a[cdghlns]}
1676 @cindex listings, enabling
1677 @cindex assembly listings, enabling
1679 These options enable listing output from the assembler. By itself,
1680 @samp{-a} requests high-level, assembly, and symbols listing.
1681 You can use other letters to select specific options for the list:
1682 @samp{-ah} requests a high-level language listing,
1683 @samp{-al} requests an output-program assembly listing, and
1684 @samp{-as} requests a symbol table listing.
1685 High-level listings require that a compiler debugging option like
1686 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1689 Use the @samp{-ag} option to print a first section with general assembly
1690 information, like @value{AS} version, switches passed, or time stamp.
1692 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1693 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1694 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1695 omitted from the listing.
1697 Use the @samp{-ad} option to omit debugging directives from the
1700 Once you have specified one of these options, you can further control
1701 listing output and its appearance using the directives @code{.list},
1702 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1704 The @samp{-an} option turns off all forms processing.
1705 If you do not request listing output with one of the @samp{-a} options, the
1706 listing-control directives have no effect.
1708 The letters after @samp{-a} may be combined into one option,
1709 @emph{e.g.}, @samp{-aln}.
1711 Note if the assembler source is coming from the standard input (e.g.,
1713 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1714 is being used) then the listing will not contain any comments or preprocessor
1715 directives. This is because the listing code buffers input source lines from
1716 stdin only after they have been preprocessed by the assembler. This reduces
1717 memory usage and makes the code more efficient.
1720 @section @option{--alternate}
1723 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1726 @section @option{-D}
1729 This option has no effect whatsoever, but it is accepted to make it more
1730 likely that scripts written for other assemblers also work with
1731 @command{@value{AS}}.
1734 @section Work Faster: @option{-f}
1737 @cindex trusted compiler
1738 @cindex faster processing (@option{-f})
1739 @samp{-f} should only be used when assembling programs written by a
1740 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1741 and comment preprocessing on
1742 the input file(s) before assembling them. @xref{Preprocessing,
1746 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1747 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1752 @section @code{.include} Search Path: @option{-I} @var{path}
1754 @kindex -I @var{path}
1755 @cindex paths for @code{.include}
1756 @cindex search path for @code{.include}
1757 @cindex @code{include} directive search path
1758 Use this option to add a @var{path} to the list of directories
1759 @command{@value{AS}} searches for files specified in @code{.include}
1760 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1761 many times as necessary to include a variety of paths. The current
1762 working directory is always searched first; after that, @command{@value{AS}}
1763 searches any @samp{-I} directories in the same order as they were
1764 specified (left to right) on the command line.
1767 @section Difference Tables: @option{-K}
1770 @ifclear DIFF-TBL-KLUGE
1771 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1772 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1773 where it can be used to warn when the assembler alters the machine code
1774 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1775 family does not have the addressing limitations that sometimes lead to this
1776 alteration on other platforms.
1779 @ifset DIFF-TBL-KLUGE
1780 @cindex difference tables, warning
1781 @cindex warning for altered difference tables
1782 @command{@value{AS}} sometimes alters the code emitted for directives of the
1783 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1784 You can use the @samp{-K} option if you want a warning issued when this
1789 @section Include Local Symbols: @option{-L}
1792 @cindex local symbols, retaining in output
1793 Symbols beginning with system-specific local label prefixes, typically
1794 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1795 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1796 such symbols when debugging, because they are intended for the use of
1797 programs (like compilers) that compose assembler programs, not for your
1798 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1799 such symbols, so you do not normally debug with them.
1801 This option tells @command{@value{AS}} to retain those local symbols
1802 in the object file. Usually if you do this you also tell the linker
1803 @code{@value{LD}} to preserve those symbols.
1806 @section Configuring listing output: @option{--listing}
1808 The listing feature of the assembler can be enabled via the command line switch
1809 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1810 hex dump of the corresponding locations in the output object file, and displays
1811 them as a listing file. The format of this listing can be controlled by
1812 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1813 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1814 @code{.psize} (@pxref{Psize}), and
1815 @code{.eject} (@pxref{Eject}) and also by the following switches:
1818 @item --listing-lhs-width=@samp{number}
1819 @kindex --listing-lhs-width
1820 @cindex Width of first line disassembly output
1821 Sets the maximum width, in words, of the first line of the hex byte dump. This
1822 dump appears on the left hand side of the listing output.
1824 @item --listing-lhs-width2=@samp{number}
1825 @kindex --listing-lhs-width2
1826 @cindex Width of continuation lines of disassembly output
1827 Sets the maximum width, in words, of any further lines of the hex byte dump for
1828 a given input source line. If this value is not specified, it defaults to being
1829 the same as the value specified for @samp{--listing-lhs-width}. If neither
1830 switch is used the default is to one.
1832 @item --listing-rhs-width=@samp{number}
1833 @kindex --listing-rhs-width
1834 @cindex Width of source line output
1835 Sets the maximum width, in characters, of the source line that is displayed
1836 alongside the hex dump. The default value for this parameter is 100. The
1837 source line is displayed on the right hand side of the listing output.
1839 @item --listing-cont-lines=@samp{number}
1840 @kindex --listing-cont-lines
1841 @cindex Maximum number of continuation lines
1842 Sets the maximum number of continuation lines of hex dump that will be
1843 displayed for a given single line of source input. The default value is 4.
1847 @section Assemble in MRI Compatibility Mode: @option{-M}
1850 @cindex MRI compatibility mode
1851 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1852 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1853 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1854 configured target) assembler from Microtec Research. The exact nature of the
1855 MRI syntax will not be documented here; see the MRI manuals for more
1856 information. Note in particular that the handling of macros and macro
1857 arguments is somewhat different. The purpose of this option is to permit
1858 assembling existing MRI assembler code using @command{@value{AS}}.
1860 The MRI compatibility is not complete. Certain operations of the MRI assembler
1861 depend upon its object file format, and can not be supported using other object
1862 file formats. Supporting these would require enhancing each object file format
1863 individually. These are:
1866 @item global symbols in common section
1868 The m68k MRI assembler supports common sections which are merged by the linker.
1869 Other object file formats do not support this. @command{@value{AS}} handles
1870 common sections by treating them as a single common symbol. It permits local
1871 symbols to be defined within a common section, but it can not support global
1872 symbols, since it has no way to describe them.
1874 @item complex relocations
1876 The MRI assemblers support relocations against a negated section address, and
1877 relocations which combine the start addresses of two or more sections. These
1878 are not support by other object file formats.
1880 @item @code{END} pseudo-op specifying start address
1882 The MRI @code{END} pseudo-op permits the specification of a start address.
1883 This is not supported by other object file formats. The start address may
1884 instead be specified using the @option{-e} option to the linker, or in a linker
1887 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1889 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1890 name to the output file. This is not supported by other object file formats.
1892 @item @code{ORG} pseudo-op
1894 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1895 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1896 which changes the location within the current section. Absolute sections are
1897 not supported by other object file formats. The address of a section may be
1898 assigned within a linker script.
1901 There are some other features of the MRI assembler which are not supported by
1902 @command{@value{AS}}, typically either because they are difficult or because they
1903 seem of little consequence. Some of these may be supported in future releases.
1907 @item EBCDIC strings
1909 EBCDIC strings are not supported.
1911 @item packed binary coded decimal
1913 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1914 and @code{DCB.P} pseudo-ops are not supported.
1916 @item @code{FEQU} pseudo-op
1918 The m68k @code{FEQU} pseudo-op is not supported.
1920 @item @code{NOOBJ} pseudo-op
1922 The m68k @code{NOOBJ} pseudo-op is not supported.
1924 @item @code{OPT} branch control options
1926 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1927 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1928 relaxes all branches, whether forward or backward, to an appropriate size, so
1929 these options serve no purpose.
1931 @item @code{OPT} list control options
1933 The following m68k @code{OPT} list control options are ignored: @code{C},
1934 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1935 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1937 @item other @code{OPT} options
1939 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1940 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1942 @item @code{OPT} @code{D} option is default
1944 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1945 @code{OPT NOD} may be used to turn it off.
1947 @item @code{XREF} pseudo-op.
1949 The m68k @code{XREF} pseudo-op is ignored.
1951 @item @code{.debug} pseudo-op
1953 The i960 @code{.debug} pseudo-op is not supported.
1955 @item @code{.extended} pseudo-op
1957 The i960 @code{.extended} pseudo-op is not supported.
1959 @item @code{.list} pseudo-op.
1961 The various options of the i960 @code{.list} pseudo-op are not supported.
1963 @item @code{.optimize} pseudo-op
1965 The i960 @code{.optimize} pseudo-op is not supported.
1967 @item @code{.output} pseudo-op
1969 The i960 @code{.output} pseudo-op is not supported.
1971 @item @code{.setreal} pseudo-op
1973 The i960 @code{.setreal} pseudo-op is not supported.
1978 @section Dependency Tracking: @option{--MD}
1981 @cindex dependency tracking
1984 @command{@value{AS}} can generate a dependency file for the file it creates. This
1985 file consists of a single rule suitable for @code{make} describing the
1986 dependencies of the main source file.
1988 The rule is written to the file named in its argument.
1990 This feature is used in the automatic updating of makefiles.
1993 @section Name the Object File: @option{-o}
1996 @cindex naming object file
1997 @cindex object file name
1998 There is always one object file output when you run @command{@value{AS}}. By
1999 default it has the name
2002 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2016 You use this option (which takes exactly one filename) to give the
2017 object file a different name.
2019 Whatever the object file is called, @command{@value{AS}} overwrites any
2020 existing file of the same name.
2023 @section Join Data and Text Sections: @option{-R}
2026 @cindex data and text sections, joining
2027 @cindex text and data sections, joining
2028 @cindex joining text and data sections
2029 @cindex merging text and data sections
2030 @option{-R} tells @command{@value{AS}} to write the object file as if all
2031 data-section data lives in the text section. This is only done at
2032 the very last moment: your binary data are the same, but data
2033 section parts are relocated differently. The data section part of
2034 your object file is zero bytes long because all its bytes are
2035 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2037 When you specify @option{-R} it would be possible to generate shorter
2038 address displacements (because we do not have to cross between text and
2039 data section). We refrain from doing this simply for compatibility with
2040 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2043 When @command{@value{AS}} is configured for COFF or ELF output,
2044 this option is only useful if you use sections named @samp{.text} and
2049 @option{-R} is not supported for any of the HPPA targets. Using
2050 @option{-R} generates a warning from @command{@value{AS}}.
2054 @section Display Assembly Statistics: @option{--statistics}
2056 @kindex --statistics
2057 @cindex statistics, about assembly
2058 @cindex time, total for assembly
2059 @cindex space used, maximum for assembly
2060 Use @samp{--statistics} to display two statistics about the resources used by
2061 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2062 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2065 @node traditional-format
2066 @section Compatible Output: @option{--traditional-format}
2068 @kindex --traditional-format
2069 For some targets, the output of @command{@value{AS}} is different in some ways
2070 from the output of some existing assembler. This switch requests
2071 @command{@value{AS}} to use the traditional format instead.
2073 For example, it disables the exception frame optimizations which
2074 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2077 @section Announce Version: @option{-v}
2081 @cindex assembler version
2082 @cindex version of assembler
2083 You can find out what version of as is running by including the
2084 option @samp{-v} (which you can also spell as @samp{-version}) on the
2088 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2090 @command{@value{AS}} should never give a warning or error message when
2091 assembling compiler output. But programs written by people often
2092 cause @command{@value{AS}} to give a warning that a particular assumption was
2093 made. All such warnings are directed to the standard error file.
2097 @cindex suppressing warnings
2098 @cindex warnings, suppressing
2099 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2100 This only affects the warning messages: it does not change any particular of
2101 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2104 @kindex --fatal-warnings
2105 @cindex errors, caused by warnings
2106 @cindex warnings, causing error
2107 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2108 files that generate warnings to be in error.
2111 @cindex warnings, switching on
2112 You can switch these options off again by specifying @option{--warn}, which
2113 causes warnings to be output as usual.
2116 @section Generate Object File in Spite of Errors: @option{-Z}
2117 @cindex object file, after errors
2118 @cindex errors, continuing after
2119 After an error message, @command{@value{AS}} normally produces no output. If for
2120 some reason you are interested in object file output even after
2121 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2122 option. If there are any errors, @command{@value{AS}} continues anyways, and
2123 writes an object file after a final warning message of the form @samp{@var{n}
2124 errors, @var{m} warnings, generating bad object file.}
2129 @cindex machine-independent syntax
2130 @cindex syntax, machine-independent
2131 This chapter describes the machine-independent syntax allowed in a
2132 source file. @command{@value{AS}} syntax is similar to what many other
2133 assemblers use; it is inspired by the BSD 4.2
2138 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2142 * Preprocessing:: Preprocessing
2143 * Whitespace:: Whitespace
2144 * Comments:: Comments
2145 * Symbol Intro:: Symbols
2146 * Statements:: Statements
2147 * Constants:: Constants
2151 @section Preprocessing
2153 @cindex preprocessing
2154 The @command{@value{AS}} internal preprocessor:
2156 @cindex whitespace, removed by preprocessor
2158 adjusts and removes extra whitespace. It leaves one space or tab before
2159 the keywords on a line, and turns any other whitespace on the line into
2162 @cindex comments, removed by preprocessor
2164 removes all comments, replacing them with a single space, or an
2165 appropriate number of newlines.
2167 @cindex constants, converted by preprocessor
2169 converts character constants into the appropriate numeric values.
2172 It does not do macro processing, include file handling, or
2173 anything else you may get from your C compiler's preprocessor. You can
2174 do include file processing with the @code{.include} directive
2175 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2176 to get other ``CPP'' style preprocessing by giving the input file a
2177 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2178 Output, gcc.info, Using GNU CC}.
2180 Excess whitespace, comments, and character constants
2181 cannot be used in the portions of the input text that are not
2184 @cindex turning preprocessing on and off
2185 @cindex preprocessing, turning on and off
2188 If the first line of an input file is @code{#NO_APP} or if you use the
2189 @samp{-f} option, whitespace and comments are not removed from the input file.
2190 Within an input file, you can ask for whitespace and comment removal in
2191 specific portions of the by putting a line that says @code{#APP} before the
2192 text that may contain whitespace or comments, and putting a line that says
2193 @code{#NO_APP} after this text. This feature is mainly intend to support
2194 @code{asm} statements in compilers whose output is otherwise free of comments
2201 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2202 Whitespace is used to separate symbols, and to make programs neater for
2203 people to read. Unless within character constants
2204 (@pxref{Characters,,Character Constants}), any whitespace means the same
2205 as exactly one space.
2211 There are two ways of rendering comments to @command{@value{AS}}. In both
2212 cases the comment is equivalent to one space.
2214 Anything from @samp{/*} through the next @samp{*/} is a comment.
2215 This means you may not nest these comments.
2219 The only way to include a newline ('\n') in a comment
2220 is to use this sort of comment.
2223 /* This sort of comment does not nest. */
2226 @cindex line comment character
2227 Anything from the @dfn{line comment} character to the next newline
2228 is considered a comment and is ignored. The line comment character is
2230 @samp{;} on the ARC;
2233 @samp{@@} on the ARM;
2236 @samp{;} for the H8/300 family;
2239 @samp{;} for the HPPA;
2242 @samp{#} on the i386 and x86-64;
2245 @samp{#} on the i960;
2248 @samp{;} for the PDP-11;
2251 @samp{;} for picoJava;
2254 @samp{#} for Motorola PowerPC;
2257 @samp{#} for IBM S/390;
2260 @samp{#} for the Sunplus SCORE;
2263 @samp{!} for the Renesas / SuperH SH;
2266 @samp{!} on the SPARC;
2269 @samp{#} on the ip2k;
2272 @samp{#} on the m32c;
2275 @samp{#} on the m32r;
2278 @samp{|} on the 680x0;
2281 @samp{#} on the 68HC11 and 68HC12;
2284 @samp{#} on the Vax;
2287 @samp{;} for the Z80;
2290 @samp{!} for the Z8000;
2293 @samp{#} on the V850;
2296 @samp{#} for Xtensa systems;
2298 see @ref{Machine Dependencies}. @refill
2299 @c FIXME What about i860?
2302 On some machines there are two different line comment characters. One
2303 character only begins a comment if it is the first non-whitespace character on
2304 a line, while the other always begins a comment.
2308 The V850 assembler also supports a double dash as starting a comment that
2309 extends to the end of the line.
2315 @cindex lines starting with @code{#}
2316 @cindex logical line numbers
2317 To be compatible with past assemblers, lines that begin with @samp{#} have a
2318 special interpretation. Following the @samp{#} should be an absolute
2319 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2320 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2321 new logical file name. The rest of the line, if any, should be whitespace.
2323 If the first non-whitespace characters on the line are not numeric,
2324 the line is ignored. (Just like a comment.)
2327 # This is an ordinary comment.
2328 # 42-6 "new_file_name" # New logical file name
2329 # This is logical line # 36.
2331 This feature is deprecated, and may disappear from future versions
2332 of @command{@value{AS}}.
2337 @cindex characters used in symbols
2338 @ifclear SPECIAL-SYMS
2339 A @dfn{symbol} is one or more characters chosen from the set of all
2340 letters (both upper and lower case), digits and the three characters
2346 A @dfn{symbol} is one or more characters chosen from the set of all
2347 letters (both upper and lower case), digits and the three characters
2348 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2354 On most machines, you can also use @code{$} in symbol names; exceptions
2355 are noted in @ref{Machine Dependencies}.
2357 No symbol may begin with a digit. Case is significant.
2358 There is no length limit: all characters are significant. Symbols are
2359 delimited by characters not in that set, or by the beginning of a file
2360 (since the source program must end with a newline, the end of a file is
2361 not a possible symbol delimiter). @xref{Symbols}.
2362 @cindex length of symbols
2367 @cindex statements, structure of
2368 @cindex line separator character
2369 @cindex statement separator character
2371 @ifclear abnormal-separator
2372 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2373 semicolon (@samp{;}). The newline or semicolon is considered part of
2374 the preceding statement. Newlines and semicolons within character
2375 constants are an exception: they do not end statements.
2377 @ifset abnormal-separator
2379 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2380 point (@samp{!}). The newline or exclamation point is considered part of the
2381 preceding statement. Newlines and exclamation points within character
2382 constants are an exception: they do not end statements.
2385 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2386 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2387 (@samp{;}). The newline or separator character is considered part of
2388 the preceding statement. Newlines and separators within character
2389 constants are an exception: they do not end statements.
2394 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2395 separator character. (The line separator is usually @samp{;}, unless this
2396 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2397 newline or separator character is considered part of the preceding
2398 statement. Newlines and separators within character constants are an
2399 exception: they do not end statements.
2402 @cindex newline, required at file end
2403 @cindex EOF, newline must precede
2404 It is an error to end any statement with end-of-file: the last
2405 character of any input file should be a newline.@refill
2407 An empty statement is allowed, and may include whitespace. It is ignored.
2409 @cindex instructions and directives
2410 @cindex directives and instructions
2411 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2412 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2414 A statement begins with zero or more labels, optionally followed by a
2415 key symbol which determines what kind of statement it is. The key
2416 symbol determines the syntax of the rest of the statement. If the
2417 symbol begins with a dot @samp{.} then the statement is an assembler
2418 directive: typically valid for any computer. If the symbol begins with
2419 a letter the statement is an assembly language @dfn{instruction}: it
2420 assembles into a machine language instruction.
2422 Different versions of @command{@value{AS}} for different computers
2423 recognize different instructions. In fact, the same symbol may
2424 represent a different instruction in a different computer's assembly
2428 @cindex @code{:} (label)
2429 @cindex label (@code{:})
2430 A label is a symbol immediately followed by a colon (@code{:}).
2431 Whitespace before a label or after a colon is permitted, but you may not
2432 have whitespace between a label's symbol and its colon. @xref{Labels}.
2435 For HPPA targets, labels need not be immediately followed by a colon, but
2436 the definition of a label must begin in column zero. This also implies that
2437 only one label may be defined on each line.
2441 label: .directive followed by something
2442 another_label: # This is an empty statement.
2443 instruction operand_1, operand_2, @dots{}
2450 A constant is a number, written so that its value is known by
2451 inspection, without knowing any context. Like this:
2454 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2455 .ascii "Ring the bell\7" # A string constant.
2456 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2457 .float 0f-314159265358979323846264338327\
2458 95028841971.693993751E-40 # - pi, a flonum.
2463 * Characters:: Character Constants
2464 * Numbers:: Number Constants
2468 @subsection Character Constants
2470 @cindex character constants
2471 @cindex constants, character
2472 There are two kinds of character constants. A @dfn{character} stands
2473 for one character in one byte and its value may be used in
2474 numeric expressions. String constants (properly called string
2475 @emph{literals}) are potentially many bytes and their values may not be
2476 used in arithmetic expressions.
2480 * Chars:: Characters
2484 @subsubsection Strings
2486 @cindex string constants
2487 @cindex constants, string
2488 A @dfn{string} is written between double-quotes. It may contain
2489 double-quotes or null characters. The way to get special characters
2490 into a string is to @dfn{escape} these characters: precede them with
2491 a backslash @samp{\} character. For example @samp{\\} represents
2492 one backslash: the first @code{\} is an escape which tells
2493 @command{@value{AS}} to interpret the second character literally as a backslash
2494 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2495 escape character). The complete list of escapes follows.
2497 @cindex escape codes, character
2498 @cindex character escape codes
2501 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2503 @cindex @code{\b} (backspace character)
2504 @cindex backspace (@code{\b})
2506 Mnemonic for backspace; for ASCII this is octal code 010.
2509 @c Mnemonic for EOText; for ASCII this is octal code 004.
2511 @cindex @code{\f} (formfeed character)
2512 @cindex formfeed (@code{\f})
2514 Mnemonic for FormFeed; for ASCII this is octal code 014.
2516 @cindex @code{\n} (newline character)
2517 @cindex newline (@code{\n})
2519 Mnemonic for newline; for ASCII this is octal code 012.
2522 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2524 @cindex @code{\r} (carriage return character)
2525 @cindex carriage return (@code{\r})
2527 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2530 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2531 @c other assemblers.
2533 @cindex @code{\t} (tab)
2534 @cindex tab (@code{\t})
2536 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2539 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2540 @c @item \x @var{digit} @var{digit} @var{digit}
2541 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2543 @cindex @code{\@var{ddd}} (octal character code)
2544 @cindex octal character code (@code{\@var{ddd}})
2545 @item \ @var{digit} @var{digit} @var{digit}
2546 An octal character code. The numeric code is 3 octal digits.
2547 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2548 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2550 @cindex @code{\@var{xd...}} (hex character code)
2551 @cindex hex character code (@code{\@var{xd...}})
2552 @item \@code{x} @var{hex-digits...}
2553 A hex character code. All trailing hex digits are combined. Either upper or
2554 lower case @code{x} works.
2556 @cindex @code{\\} (@samp{\} character)
2557 @cindex backslash (@code{\\})
2559 Represents one @samp{\} character.
2562 @c Represents one @samp{'} (accent acute) character.
2563 @c This is needed in single character literals
2564 @c (@xref{Characters,,Character Constants}.) to represent
2567 @cindex @code{\"} (doublequote character)
2568 @cindex doublequote (@code{\"})
2570 Represents one @samp{"} character. Needed in strings to represent
2571 this character, because an unescaped @samp{"} would end the string.
2573 @item \ @var{anything-else}
2574 Any other character when escaped by @kbd{\} gives a warning, but
2575 assembles as if the @samp{\} was not present. The idea is that if
2576 you used an escape sequence you clearly didn't want the literal
2577 interpretation of the following character. However @command{@value{AS}} has no
2578 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2579 code and warns you of the fact.
2582 Which characters are escapable, and what those escapes represent,
2583 varies widely among assemblers. The current set is what we think
2584 the BSD 4.2 assembler recognizes, and is a subset of what most C
2585 compilers recognize. If you are in doubt, do not use an escape
2589 @subsubsection Characters
2591 @cindex single character constant
2592 @cindex character, single
2593 @cindex constant, single character
2594 A single character may be written as a single quote immediately
2595 followed by that character. The same escapes apply to characters as
2596 to strings. So if you want to write the character backslash, you
2597 must write @kbd{'\\} where the first @code{\} escapes the second
2598 @code{\}. As you can see, the quote is an acute accent, not a
2599 grave accent. A newline
2601 @ifclear abnormal-separator
2602 (or semicolon @samp{;})
2604 @ifset abnormal-separator
2606 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2611 immediately following an acute accent is taken as a literal character
2612 and does not count as the end of a statement. The value of a character
2613 constant in a numeric expression is the machine's byte-wide code for
2614 that character. @command{@value{AS}} assumes your character code is ASCII:
2615 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2618 @subsection Number Constants
2620 @cindex constants, number
2621 @cindex number constants
2622 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2623 are stored in the target machine. @emph{Integers} are numbers that
2624 would fit into an @code{int} in the C language. @emph{Bignums} are
2625 integers, but they are stored in more than 32 bits. @emph{Flonums}
2626 are floating point numbers, described below.
2629 * Integers:: Integers
2634 * Bit Fields:: Bit Fields
2640 @subsubsection Integers
2642 @cindex constants, integer
2644 @cindex binary integers
2645 @cindex integers, binary
2646 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2647 the binary digits @samp{01}.
2649 @cindex octal integers
2650 @cindex integers, octal
2651 An octal integer is @samp{0} followed by zero or more of the octal
2652 digits (@samp{01234567}).
2654 @cindex decimal integers
2655 @cindex integers, decimal
2656 A decimal integer starts with a non-zero digit followed by zero or
2657 more digits (@samp{0123456789}).
2659 @cindex hexadecimal integers
2660 @cindex integers, hexadecimal
2661 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2662 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2664 Integers have the usual values. To denote a negative integer, use
2665 the prefix operator @samp{-} discussed under expressions
2666 (@pxref{Prefix Ops,,Prefix Operators}).
2669 @subsubsection Bignums
2672 @cindex constants, bignum
2673 A @dfn{bignum} has the same syntax and semantics as an integer
2674 except that the number (or its negative) takes more than 32 bits to
2675 represent in binary. The distinction is made because in some places
2676 integers are permitted while bignums are not.
2679 @subsubsection Flonums
2681 @cindex floating point numbers
2682 @cindex constants, floating point
2684 @cindex precision, floating point
2685 A @dfn{flonum} represents a floating point number. The translation is
2686 indirect: a decimal floating point number from the text is converted by
2687 @command{@value{AS}} to a generic binary floating point number of more than
2688 sufficient precision. This generic floating point number is converted
2689 to a particular computer's floating point format (or formats) by a
2690 portion of @command{@value{AS}} specialized to that computer.
2692 A flonum is written by writing (in order)
2697 (@samp{0} is optional on the HPPA.)
2701 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2703 @kbd{e} is recommended. Case is not important.
2705 @c FIXME: verify if flonum syntax really this vague for most cases
2706 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2707 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2710 On the H8/300, Renesas / SuperH SH,
2711 and AMD 29K architectures, the letter must be
2712 one of the letters @samp{DFPRSX} (in upper or lower case).
2714 On the ARC, the letter must be one of the letters @samp{DFRS}
2715 (in upper or lower case).
2717 On the Intel 960 architecture, the letter must be
2718 one of the letters @samp{DFT} (in upper or lower case).
2720 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2724 One of the letters @samp{DFRS} (in upper or lower case).
2727 One of the letters @samp{DFPRSX} (in upper or lower case).
2730 The letter @samp{E} (upper case only).
2733 One of the letters @samp{DFT} (in upper or lower case).
2738 An optional sign: either @samp{+} or @samp{-}.
2741 An optional @dfn{integer part}: zero or more decimal digits.
2744 An optional @dfn{fractional part}: @samp{.} followed by zero
2745 or more decimal digits.
2748 An optional exponent, consisting of:
2752 An @samp{E} or @samp{e}.
2753 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2754 @c principle this can perfectly well be different on different targets.
2756 Optional sign: either @samp{+} or @samp{-}.
2758 One or more decimal digits.
2763 At least one of the integer part or the fractional part must be
2764 present. The floating point number has the usual base-10 value.
2766 @command{@value{AS}} does all processing using integers. Flonums are computed
2767 independently of any floating point hardware in the computer running
2768 @command{@value{AS}}.
2772 @c Bit fields are written as a general facility but are also controlled
2773 @c by a conditional-compilation flag---which is as of now (21mar91)
2774 @c turned on only by the i960 config of GAS.
2776 @subsubsection Bit Fields
2779 @cindex constants, bit field
2780 You can also define numeric constants as @dfn{bit fields}.
2781 Specify two numbers separated by a colon---
2783 @var{mask}:@var{value}
2786 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2789 The resulting number is then packed
2791 @c this conditional paren in case bit fields turned on elsewhere than 960
2792 (in host-dependent byte order)
2794 into a field whose width depends on which assembler directive has the
2795 bit-field as its argument. Overflow (a result from the bitwise and
2796 requiring more binary digits to represent) is not an error; instead,
2797 more constants are generated, of the specified width, beginning with the
2798 least significant digits.@refill
2800 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2801 @code{.short}, and @code{.word} accept bit-field arguments.
2806 @chapter Sections and Relocation
2811 * Secs Background:: Background
2812 * Ld Sections:: Linker Sections
2813 * As Sections:: Assembler Internal Sections
2814 * Sub-Sections:: Sub-Sections
2818 @node Secs Background
2821 Roughly, a section is a range of addresses, with no gaps; all data
2822 ``in'' those addresses is treated the same for some particular purpose.
2823 For example there may be a ``read only'' section.
2825 @cindex linker, and assembler
2826 @cindex assembler, and linker
2827 The linker @code{@value{LD}} reads many object files (partial programs) and
2828 combines their contents to form a runnable program. When @command{@value{AS}}
2829 emits an object file, the partial program is assumed to start at address 0.
2830 @code{@value{LD}} assigns the final addresses for the partial program, so that
2831 different partial programs do not overlap. This is actually an
2832 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2835 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2836 addresses. These blocks slide to their run-time addresses as rigid
2837 units; their length does not change and neither does the order of bytes
2838 within them. Such a rigid unit is called a @emph{section}. Assigning
2839 run-time addresses to sections is called @dfn{relocation}. It includes
2840 the task of adjusting mentions of object-file addresses so they refer to
2841 the proper run-time addresses.
2843 For the H8/300, and for the Renesas / SuperH SH,
2844 @command{@value{AS}} pads sections if needed to
2845 ensure they end on a word (sixteen bit) boundary.
2848 @cindex standard assembler sections
2849 An object file written by @command{@value{AS}} has at least three sections, any
2850 of which may be empty. These are named @dfn{text}, @dfn{data} and
2855 When it generates COFF or ELF output,
2857 @command{@value{AS}} can also generate whatever other named sections you specify
2858 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2859 If you do not use any directives that place output in the @samp{.text}
2860 or @samp{.data} sections, these sections still exist, but are empty.
2865 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2867 @command{@value{AS}} can also generate whatever other named sections you
2868 specify using the @samp{.space} and @samp{.subspace} directives. See
2869 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2870 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2871 assembler directives.
2874 Additionally, @command{@value{AS}} uses different names for the standard
2875 text, data, and bss sections when generating SOM output. Program text
2876 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2877 BSS into @samp{$BSS$}.
2881 Within the object file, the text section starts at address @code{0}, the
2882 data section follows, and the bss section follows the data section.
2885 When generating either SOM or ELF output files on the HPPA, the text
2886 section starts at address @code{0}, the data section at address
2887 @code{0x4000000}, and the bss section follows the data section.
2890 To let @code{@value{LD}} know which data changes when the sections are
2891 relocated, and how to change that data, @command{@value{AS}} also writes to the
2892 object file details of the relocation needed. To perform relocation
2893 @code{@value{LD}} must know, each time an address in the object
2897 Where in the object file is the beginning of this reference to
2900 How long (in bytes) is this reference?
2902 Which section does the address refer to? What is the numeric value of
2904 (@var{address}) @minus{} (@var{start-address of section})?
2907 Is the reference to an address ``Program-Counter relative''?
2910 @cindex addresses, format of
2911 @cindex section-relative addressing
2912 In fact, every address @command{@value{AS}} ever uses is expressed as
2914 (@var{section}) + (@var{offset into section})
2917 Further, most expressions @command{@value{AS}} computes have this section-relative
2920 (For some object formats, such as SOM for the HPPA, some expressions are
2921 symbol-relative instead.)
2924 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2925 @var{N} into section @var{secname}.''
2927 Apart from text, data and bss sections you need to know about the
2928 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2929 addresses in the absolute section remain unchanged. For example, address
2930 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2931 @code{@value{LD}}. Although the linker never arranges two partial programs'
2932 data sections with overlapping addresses after linking, @emph{by definition}
2933 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2934 part of a program is always the same address when the program is running as
2935 address @code{@{absolute@ 239@}} in any other part of the program.
2937 The idea of sections is extended to the @dfn{undefined} section. Any
2938 address whose section is unknown at assembly time is by definition
2939 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2940 Since numbers are always defined, the only way to generate an undefined
2941 address is to mention an undefined symbol. A reference to a named
2942 common block would be such a symbol: its value is unknown at assembly
2943 time so it has section @emph{undefined}.
2945 By analogy the word @emph{section} is used to describe groups of sections in
2946 the linked program. @code{@value{LD}} puts all partial programs' text
2947 sections in contiguous addresses in the linked program. It is
2948 customary to refer to the @emph{text section} of a program, meaning all
2949 the addresses of all partial programs' text sections. Likewise for
2950 data and bss sections.
2952 Some sections are manipulated by @code{@value{LD}}; others are invented for
2953 use of @command{@value{AS}} and have no meaning except during assembly.
2956 @section Linker Sections
2957 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2962 @cindex named sections
2963 @cindex sections, named
2964 @item named sections
2967 @cindex text section
2968 @cindex data section
2972 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2973 separate but equal sections. Anything you can say of one section is
2976 When the program is running, however, it is
2977 customary for the text section to be unalterable. The
2978 text section is often shared among processes: it contains
2979 instructions, constants and the like. The data section of a running
2980 program is usually alterable: for example, C variables would be stored
2981 in the data section.
2986 This section contains zeroed bytes when your program begins running. It
2987 is used to hold uninitialized variables or common storage. The length of
2988 each partial program's bss section is important, but because it starts
2989 out containing zeroed bytes there is no need to store explicit zero
2990 bytes in the object file. The bss section was invented to eliminate
2991 those explicit zeros from object files.
2993 @cindex absolute section
2994 @item absolute section
2995 Address 0 of this section is always ``relocated'' to runtime address 0.
2996 This is useful if you want to refer to an address that @code{@value{LD}} must
2997 not change when relocating. In this sense we speak of absolute
2998 addresses being ``unrelocatable'': they do not change during relocation.
3000 @cindex undefined section
3001 @item undefined section
3002 This ``section'' is a catch-all for address references to objects not in
3003 the preceding sections.
3004 @c FIXME: ref to some other doc on obj-file formats could go here.
3007 @cindex relocation example
3008 An idealized example of three relocatable sections follows.
3010 The example uses the traditional section names @samp{.text} and @samp{.data}.
3012 Memory addresses are on the horizontal axis.
3016 @c END TEXI2ROFF-KILL
3019 partial program # 1: |ttttt|dddd|00|
3026 partial program # 2: |TTT|DDD|000|
3029 +--+---+-----+--+----+---+-----+~~
3030 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3031 +--+---+-----+--+----+---+-----+~~
3033 addresses: 0 @dots{}
3040 \line{\it Partial program \#1: \hfil}
3041 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3042 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3044 \line{\it Partial program \#2: \hfil}
3045 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3046 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3048 \line{\it linked program: \hfil}
3049 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3050 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3051 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3052 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3054 \line{\it addresses: \hfil}
3058 @c END TEXI2ROFF-KILL
3061 @section Assembler Internal Sections
3063 @cindex internal assembler sections
3064 @cindex sections in messages, internal
3065 These sections are meant only for the internal use of @command{@value{AS}}. They
3066 have no meaning at run-time. You do not really need to know about these
3067 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3068 warning messages, so it might be helpful to have an idea of their
3069 meanings to @command{@value{AS}}. These sections are used to permit the
3070 value of every expression in your assembly language program to be a
3071 section-relative address.
3074 @cindex assembler internal logic error
3075 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3076 An internal assembler logic error has been found. This means there is a
3077 bug in the assembler.
3079 @cindex expr (internal section)
3081 The assembler stores complex expression internally as combinations of
3082 symbols. When it needs to represent an expression as a symbol, it puts
3083 it in the expr section.
3085 @c FIXME item transfer[t] vector preload
3086 @c FIXME item transfer[t] vector postload
3087 @c FIXME item register
3091 @section Sub-Sections
3093 @cindex numbered subsections
3094 @cindex grouping data
3100 fall into two sections: text and data.
3102 You may have separate groups of
3104 data in named sections
3108 data in named sections
3114 that you want to end up near to each other in the object file, even though they
3115 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3116 use @dfn{subsections} for this purpose. Within each section, there can be
3117 numbered subsections with values from 0 to 8192. Objects assembled into the
3118 same subsection go into the object file together with other objects in the same
3119 subsection. For example, a compiler might want to store constants in the text
3120 section, but might not want to have them interspersed with the program being
3121 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3122 section of code being output, and a @samp{.text 1} before each group of
3123 constants being output.
3125 Subsections are optional. If you do not use subsections, everything
3126 goes in subsection number zero.
3129 Each subsection is zero-padded up to a multiple of four bytes.
3130 (Subsections may be padded a different amount on different flavors
3131 of @command{@value{AS}}.)
3135 On the H8/300 platform, each subsection is zero-padded to a word
3136 boundary (two bytes).
3137 The same is true on the Renesas SH.
3140 @c FIXME section padding (alignment)?
3141 @c Rich Pixley says padding here depends on target obj code format; that
3142 @c doesn't seem particularly useful to say without further elaboration,
3143 @c so for now I say nothing about it. If this is a generic BFD issue,
3144 @c these paragraphs might need to vanish from this manual, and be
3145 @c discussed in BFD chapter of binutils (or some such).
3149 Subsections appear in your object file in numeric order, lowest numbered
3150 to highest. (All this to be compatible with other people's assemblers.)
3151 The object file contains no representation of subsections; @code{@value{LD}} and
3152 other programs that manipulate object files see no trace of them.
3153 They just see all your text subsections as a text section, and all your
3154 data subsections as a data section.
3156 To specify which subsection you want subsequent statements assembled
3157 into, use a numeric argument to specify it, in a @samp{.text
3158 @var{expression}} or a @samp{.data @var{expression}} statement.
3161 When generating COFF output, you
3166 can also use an extra subsection
3167 argument with arbitrary named sections: @samp{.section @var{name},
3172 When generating ELF output, you
3177 can also use the @code{.subsection} directive (@pxref{SubSection})
3178 to specify a subsection: @samp{.subsection @var{expression}}.
3180 @var{Expression} should be an absolute expression
3181 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3182 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3183 begins in @code{text 0}. For instance:
3185 .text 0 # The default subsection is text 0 anyway.
3186 .ascii "This lives in the first text subsection. *"
3188 .ascii "But this lives in the second text subsection."
3190 .ascii "This lives in the data section,"
3191 .ascii "in the first data subsection."
3193 .ascii "This lives in the first text section,"
3194 .ascii "immediately following the asterisk (*)."
3197 Each section has a @dfn{location counter} incremented by one for every byte
3198 assembled into that section. Because subsections are merely a convenience
3199 restricted to @command{@value{AS}} there is no concept of a subsection location
3200 counter. There is no way to directly manipulate a location counter---but the
3201 @code{.align} directive changes it, and any label definition captures its
3202 current value. The location counter of the section where statements are being
3203 assembled is said to be the @dfn{active} location counter.
3206 @section bss Section
3209 @cindex common variable storage
3210 The bss section is used for local common variable storage.
3211 You may allocate address space in the bss section, but you may
3212 not dictate data to load into it before your program executes. When
3213 your program starts running, all the contents of the bss
3214 section are zeroed bytes.
3216 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3217 @ref{Lcomm,,@code{.lcomm}}.
3219 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3220 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3223 When assembling for a target which supports multiple sections, such as ELF or
3224 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3225 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3226 section. Typically the section will only contain symbol definitions and
3227 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3234 Symbols are a central concept: the programmer uses symbols to name
3235 things, the linker uses symbols to link, and the debugger uses symbols
3239 @cindex debuggers, and symbol order
3240 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3241 the same order they were declared. This may break some debuggers.
3246 * Setting Symbols:: Giving Symbols Other Values
3247 * Symbol Names:: Symbol Names
3248 * Dot:: The Special Dot Symbol
3249 * Symbol Attributes:: Symbol Attributes
3256 A @dfn{label} is written as a symbol immediately followed by a colon
3257 @samp{:}. The symbol then represents the current value of the
3258 active location counter, and is, for example, a suitable instruction
3259 operand. You are warned if you use the same symbol to represent two
3260 different locations: the first definition overrides any other
3264 On the HPPA, the usual form for a label need not be immediately followed by a
3265 colon, but instead must start in column zero. Only one label may be defined on
3266 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3267 provides a special directive @code{.label} for defining labels more flexibly.
3270 @node Setting Symbols
3271 @section Giving Symbols Other Values
3273 @cindex assigning values to symbols
3274 @cindex symbol values, assigning
3275 A symbol can be given an arbitrary value by writing a symbol, followed
3276 by an equals sign @samp{=}, followed by an expression
3277 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3278 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3279 equals sign @samp{=}@samp{=} here represents an equivalent of the
3280 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3283 Blackfin does not support symbol assignment with @samp{=}.
3287 @section Symbol Names
3289 @cindex symbol names
3290 @cindex names, symbol
3291 @ifclear SPECIAL-SYMS
3292 Symbol names begin with a letter or with one of @samp{._}. On most
3293 machines, you can also use @code{$} in symbol names; exceptions are
3294 noted in @ref{Machine Dependencies}. That character may be followed by any
3295 string of digits, letters, dollar signs (unless otherwise noted for a
3296 particular target machine), and underscores.
3300 Symbol names begin with a letter or with one of @samp{._}. On the
3301 Renesas SH you can also use @code{$} in symbol names. That
3302 character may be followed by any string of digits, letters, dollar signs (save
3303 on the H8/300), and underscores.
3307 Case of letters is significant: @code{foo} is a different symbol name
3310 Each symbol has exactly one name. Each name in an assembly language program
3311 refers to exactly one symbol. You may use that symbol name any number of times
3314 @subheading Local Symbol Names
3316 @cindex local symbol names
3317 @cindex symbol names, local
3318 A local symbol is any symbol beginning with certain local label prefixes.
3319 By default, the local label prefix is @samp{.L} for ELF systems or
3320 @samp{L} for traditional a.out systems, but each target may have its own
3321 set of local label prefixes.
3323 On the HPPA local symbols begin with @samp{L$}.
3326 Local symbols are defined and used within the assembler, but they are
3327 normally not saved in object files. Thus, they are not visible when debugging.
3328 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3329 @option{-L}}) to retain the local symbols in the object files.
3331 @subheading Local Labels
3333 @cindex local labels
3334 @cindex temporary symbol names
3335 @cindex symbol names, temporary
3336 Local labels help compilers and programmers use names temporarily.
3337 They create symbols which are guaranteed to be unique over the entire scope of
3338 the input source code and which can be referred to by a simple notation.
3339 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3340 represents any positive integer). To refer to the most recent previous
3341 definition of that label write @samp{@b{N}b}, using the same number as when
3342 you defined the label. To refer to the next definition of a local label, write
3343 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3346 There is no restriction on how you can use these labels, and you can reuse them
3347 too. So that it is possible to repeatedly define the same local label (using
3348 the same number @samp{@b{N}}), although you can only refer to the most recently
3349 defined local label of that number (for a backwards reference) or the next
3350 definition of a specific local label for a forward reference. It is also worth
3351 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3352 implemented in a slightly more efficient manner than the others.
3363 Which is the equivalent of:
3366 label_1: branch label_3
3367 label_2: branch label_1
3368 label_3: branch label_4
3369 label_4: branch label_3
3372 Local label names are only a notational device. They are immediately
3373 transformed into more conventional symbol names before the assembler uses them.
3374 The symbol names are stored in the symbol table, appear in error messages, and
3375 are optionally emitted to the object file. The names are constructed using
3379 @item @emph{local label prefix}
3380 All local symbols begin with the system-specific local label prefix.
3381 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3382 that start with the local label prefix. These labels are
3383 used for symbols you are never intended to see. If you use the
3384 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3385 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3386 you may use them in debugging.
3389 This is the number that was used in the local label definition. So if the
3390 label is written @samp{55:} then the number is @samp{55}.
3393 This unusual character is included so you do not accidentally invent a symbol
3394 of the same name. The character has ASCII value of @samp{\002} (control-B).
3396 @item @emph{ordinal number}
3397 This is a serial number to keep the labels distinct. The first definition of
3398 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3399 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3400 the number @samp{1} and its 15th definition gets @samp{15} as well.
3403 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3404 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3406 @subheading Dollar Local Labels
3407 @cindex dollar local symbols
3409 @code{@value{AS}} also supports an even more local form of local labels called
3410 dollar labels. These labels go out of scope (i.e., they become undefined) as
3411 soon as a non-local label is defined. Thus they remain valid for only a small
3412 region of the input source code. Normal local labels, by contrast, remain in
3413 scope for the entire file, or until they are redefined by another occurrence of
3414 the same local label.
3416 Dollar labels are defined in exactly the same way as ordinary local labels,
3417 except that they have a dollar sign suffix to their numeric value, e.g.,
3420 They can also be distinguished from ordinary local labels by their transformed
3421 names which use ASCII character @samp{\001} (control-A) as the magic character
3422 to distinguish them from ordinary labels. For example, the fifth definition of
3423 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3426 @section The Special Dot Symbol
3428 @cindex dot (symbol)
3429 @cindex @code{.} (symbol)
3430 @cindex current address
3431 @cindex location counter
3432 The special symbol @samp{.} refers to the current address that
3433 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3434 .long .} defines @code{melvin} to contain its own address.
3435 Assigning a value to @code{.} is treated the same as a @code{.org}
3437 @ifclear no-space-dir
3438 Thus, the expression @samp{.=.+4} is the same as saying
3442 @node Symbol Attributes
3443 @section Symbol Attributes
3445 @cindex symbol attributes
3446 @cindex attributes, symbol
3447 Every symbol has, as well as its name, the attributes ``Value'' and
3448 ``Type''. Depending on output format, symbols can also have auxiliary
3451 The detailed definitions are in @file{a.out.h}.
3454 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3455 all these attributes, and probably won't warn you. This makes the
3456 symbol an externally defined symbol, which is generally what you
3460 * Symbol Value:: Value
3461 * Symbol Type:: Type
3464 * a.out Symbols:: Symbol Attributes: @code{a.out}
3468 * a.out Symbols:: Symbol Attributes: @code{a.out}
3471 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3476 * COFF Symbols:: Symbol Attributes for COFF
3479 * SOM Symbols:: Symbol Attributes for SOM
3486 @cindex value of a symbol
3487 @cindex symbol value
3488 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3489 location in the text, data, bss or absolute sections the value is the
3490 number of addresses from the start of that section to the label.
3491 Naturally for text, data and bss sections the value of a symbol changes
3492 as @code{@value{LD}} changes section base addresses during linking. Absolute
3493 symbols' values do not change during linking: that is why they are
3496 The value of an undefined symbol is treated in a special way. If it is
3497 0 then the symbol is not defined in this assembler source file, and
3498 @code{@value{LD}} tries to determine its value from other files linked into the
3499 same program. You make this kind of symbol simply by mentioning a symbol
3500 name without defining it. A non-zero value represents a @code{.comm}
3501 common declaration. The value is how much common storage to reserve, in
3502 bytes (addresses). The symbol refers to the first address of the
3508 @cindex type of a symbol
3510 The type attribute of a symbol contains relocation (section)
3511 information, any flag settings indicating that a symbol is external, and
3512 (optionally), other information for linkers and debuggers. The exact
3513 format depends on the object-code output format in use.
3518 @c The following avoids a "widow" subsection title. @group would be
3519 @c better if it were available outside examples.
3522 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3524 @cindex @code{b.out} symbol attributes
3525 @cindex symbol attributes, @code{b.out}
3526 These symbol attributes appear only when @command{@value{AS}} is configured for
3527 one of the Berkeley-descended object output formats---@code{a.out} or
3533 @subsection Symbol Attributes: @code{a.out}
3535 @cindex @code{a.out} symbol attributes
3536 @cindex symbol attributes, @code{a.out}
3542 @subsection Symbol Attributes: @code{a.out}
3544 @cindex @code{a.out} symbol attributes
3545 @cindex symbol attributes, @code{a.out}
3549 * Symbol Desc:: Descriptor
3550 * Symbol Other:: Other
3554 @subsubsection Descriptor
3556 @cindex descriptor, of @code{a.out} symbol
3557 This is an arbitrary 16-bit value. You may establish a symbol's
3558 descriptor value by using a @code{.desc} statement
3559 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3560 @command{@value{AS}}.
3563 @subsubsection Other
3565 @cindex other attribute, of @code{a.out} symbol
3566 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3571 @subsection Symbol Attributes for COFF
3573 @cindex COFF symbol attributes
3574 @cindex symbol attributes, COFF
3576 The COFF format supports a multitude of auxiliary symbol attributes;
3577 like the primary symbol attributes, they are set between @code{.def} and
3578 @code{.endef} directives.
3580 @subsubsection Primary Attributes
3582 @cindex primary attributes, COFF symbols
3583 The symbol name is set with @code{.def}; the value and type,
3584 respectively, with @code{.val} and @code{.type}.
3586 @subsubsection Auxiliary Attributes
3588 @cindex auxiliary attributes, COFF symbols
3589 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3590 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3591 table information for COFF.
3596 @subsection Symbol Attributes for SOM
3598 @cindex SOM symbol attributes
3599 @cindex symbol attributes, SOM
3601 The SOM format for the HPPA supports a multitude of symbol attributes set with
3602 the @code{.EXPORT} and @code{.IMPORT} directives.
3604 The attributes are described in @cite{HP9000 Series 800 Assembly
3605 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3606 @code{EXPORT} assembler directive documentation.
3610 @chapter Expressions
3614 @cindex numeric values
3615 An @dfn{expression} specifies an address or numeric value.
3616 Whitespace may precede and/or follow an expression.
3618 The result of an expression must be an absolute number, or else an offset into
3619 a particular section. If an expression is not absolute, and there is not
3620 enough information when @command{@value{AS}} sees the expression to know its
3621 section, a second pass over the source program might be necessary to interpret
3622 the expression---but the second pass is currently not implemented.
3623 @command{@value{AS}} aborts with an error message in this situation.
3626 * Empty Exprs:: Empty Expressions
3627 * Integer Exprs:: Integer Expressions
3631 @section Empty Expressions
3633 @cindex empty expressions
3634 @cindex expressions, empty
3635 An empty expression has no value: it is just whitespace or null.
3636 Wherever an absolute expression is required, you may omit the
3637 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3638 is compatible with other assemblers.
3641 @section Integer Expressions
3643 @cindex integer expressions
3644 @cindex expressions, integer
3645 An @dfn{integer expression} is one or more @emph{arguments} delimited
3646 by @emph{operators}.
3649 * Arguments:: Arguments
3650 * Operators:: Operators
3651 * Prefix Ops:: Prefix Operators
3652 * Infix Ops:: Infix Operators
3656 @subsection Arguments
3658 @cindex expression arguments
3659 @cindex arguments in expressions
3660 @cindex operands in expressions
3661 @cindex arithmetic operands
3662 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3663 contexts arguments are sometimes called ``arithmetic operands''. In
3664 this manual, to avoid confusing them with the ``instruction operands'' of
3665 the machine language, we use the term ``argument'' to refer to parts of
3666 expressions only, reserving the word ``operand'' to refer only to machine
3667 instruction operands.
3669 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3670 @var{section} is one of text, data, bss, absolute,
3671 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3674 Numbers are usually integers.
3676 A number can be a flonum or bignum. In this case, you are warned
3677 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3678 these 32 bits are an integer. You may write integer-manipulating
3679 instructions that act on exotic constants, compatible with other
3682 @cindex subexpressions
3683 Subexpressions are a left parenthesis @samp{(} followed by an integer
3684 expression, followed by a right parenthesis @samp{)}; or a prefix
3685 operator followed by an argument.
3688 @subsection Operators
3690 @cindex operators, in expressions
3691 @cindex arithmetic functions
3692 @cindex functions, in expressions
3693 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3694 operators are followed by an argument. Infix operators appear
3695 between their arguments. Operators may be preceded and/or followed by
3699 @subsection Prefix Operator
3701 @cindex prefix operators
3702 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3703 one argument, which must be absolute.
3705 @c the tex/end tex stuff surrounding this small table is meant to make
3706 @c it align, on the printed page, with the similar table in the next
3707 @c section (which is inside an enumerate).
3709 \global\advance\leftskip by \itemindent
3714 @dfn{Negation}. Two's complement negation.
3716 @dfn{Complementation}. Bitwise not.
3720 \global\advance\leftskip by -\itemindent
3724 @subsection Infix Operators
3726 @cindex infix operators
3727 @cindex operators, permitted arguments
3728 @dfn{Infix operators} take two arguments, one on either side. Operators
3729 have precedence, but operations with equal precedence are performed left
3730 to right. Apart from @code{+} or @option{-}, both arguments must be
3731 absolute, and the result is absolute.
3734 @cindex operator precedence
3735 @cindex precedence of operators
3742 @dfn{Multiplication}.
3745 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3751 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3754 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3758 Intermediate precedence
3763 @dfn{Bitwise Inclusive Or}.
3769 @dfn{Bitwise Exclusive Or}.
3772 @dfn{Bitwise Or Not}.
3779 @cindex addition, permitted arguments
3780 @cindex plus, permitted arguments
3781 @cindex arguments for addition
3783 @dfn{Addition}. If either argument is absolute, the result has the section of
3784 the other argument. You may not add together arguments from different
3787 @cindex subtraction, permitted arguments
3788 @cindex minus, permitted arguments
3789 @cindex arguments for subtraction
3791 @dfn{Subtraction}. If the right argument is absolute, the
3792 result has the section of the left argument.
3793 If both arguments are in the same section, the result is absolute.
3794 You may not subtract arguments from different sections.
3795 @c FIXME is there still something useful to say about undefined - undefined ?
3797 @cindex comparison expressions
3798 @cindex expressions, comparison
3803 @dfn{Is Not Equal To}
3807 @dfn{Is Greater Than}
3809 @dfn{Is Greater Than Or Equal To}
3811 @dfn{Is Less Than Or Equal To}
3813 The comparison operators can be used as infix operators. A true results has a
3814 value of -1 whereas a false result has a value of 0. Note, these operators
3815 perform signed comparisons.
3818 @item Lowest Precedence
3827 These two logical operations can be used to combine the results of sub
3828 expressions. Note, unlike the comparison operators a true result returns a
3829 value of 1 but a false results does still return 0. Also note that the logical
3830 or operator has a slightly lower precedence than logical and.
3835 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3836 address; you can only have a defined section in one of the two arguments.
3839 @chapter Assembler Directives
3841 @cindex directives, machine independent
3842 @cindex pseudo-ops, machine independent
3843 @cindex machine independent directives
3844 All assembler directives have names that begin with a period (@samp{.}).
3845 The rest of the name is letters, usually in lower case.
3847 This chapter discusses directives that are available regardless of the
3848 target machine configuration for the @sc{gnu} assembler.
3850 Some machine configurations provide additional directives.
3851 @xref{Machine Dependencies}.
3854 @ifset machine-directives
3855 @xref{Machine Dependencies}, for additional directives.
3860 * Abort:: @code{.abort}
3862 * ABORT (COFF):: @code{.ABORT}
3865 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3866 * Altmacro:: @code{.altmacro}
3867 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3868 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3869 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3870 * Byte:: @code{.byte @var{expressions}}
3871 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3872 * Comm:: @code{.comm @var{symbol} , @var{length} }
3873 * Data:: @code{.data @var{subsection}}
3875 * Def:: @code{.def @var{name}}
3878 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3884 * Double:: @code{.double @var{flonums}}
3885 * Eject:: @code{.eject}
3886 * Else:: @code{.else}
3887 * Elseif:: @code{.elseif}
3890 * Endef:: @code{.endef}
3893 * Endfunc:: @code{.endfunc}
3894 * Endif:: @code{.endif}
3895 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3896 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3897 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3899 * Error:: @code{.error @var{string}}
3900 * Exitm:: @code{.exitm}
3901 * Extern:: @code{.extern}
3902 * Fail:: @code{.fail}
3903 * File:: @code{.file}
3904 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3905 * Float:: @code{.float @var{flonums}}
3906 * Func:: @code{.func}
3907 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3909 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
3910 * Hidden:: @code{.hidden @var{names}}
3913 * hword:: @code{.hword @var{expressions}}
3914 * Ident:: @code{.ident}
3915 * If:: @code{.if @var{absolute expression}}
3916 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3917 * Include:: @code{.include "@var{file}"}
3918 * Int:: @code{.int @var{expressions}}
3920 * Internal:: @code{.internal @var{names}}
3923 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3924 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3925 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3926 * Lflags:: @code{.lflags}
3927 @ifclear no-line-dir
3928 * Line:: @code{.line @var{line-number}}
3931 * Linkonce:: @code{.linkonce [@var{type}]}
3932 * List:: @code{.list}
3933 * Ln:: @code{.ln @var{line-number}}
3934 * Loc:: @code{.loc @var{fileno} @var{lineno}}
3935 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
3937 * Local:: @code{.local @var{names}}
3940 * Long:: @code{.long @var{expressions}}
3942 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3945 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3946 * MRI:: @code{.mri @var{val}}
3947 * Noaltmacro:: @code{.noaltmacro}
3948 * Nolist:: @code{.nolist}
3949 * Octa:: @code{.octa @var{bignums}}
3950 * Org:: @code{.org @var{new-lc}, @var{fill}}
3951 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3953 * PopSection:: @code{.popsection}
3954 * Previous:: @code{.previous}
3957 * Print:: @code{.print @var{string}}
3959 * Protected:: @code{.protected @var{names}}
3962 * Psize:: @code{.psize @var{lines}, @var{columns}}
3963 * Purgem:: @code{.purgem @var{name}}
3965 * PushSection:: @code{.pushsection @var{name}}
3968 * Quad:: @code{.quad @var{bignums}}
3969 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
3970 * Rept:: @code{.rept @var{count}}
3971 * Sbttl:: @code{.sbttl "@var{subheading}"}
3973 * Scl:: @code{.scl @var{class}}
3976 * Section:: @code{.section @var{name}[, @var{flags}]}
3979 * Set:: @code{.set @var{symbol}, @var{expression}}
3980 * Short:: @code{.short @var{expressions}}
3981 * Single:: @code{.single @var{flonums}}
3983 * Size:: @code{.size [@var{name} , @var{expression}]}
3985 @ifclear no-space-dir
3986 * Skip:: @code{.skip @var{size} , @var{fill}}
3989 * Sleb128:: @code{.sleb128 @var{expressions}}
3990 @ifclear no-space-dir
3991 * Space:: @code{.space @var{size} , @var{fill}}
3994 * Stab:: @code{.stabd, .stabn, .stabs}
3997 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
3998 * Struct:: @code{.struct @var{expression}}
4000 * SubSection:: @code{.subsection}
4001 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4005 * Tag:: @code{.tag @var{structname}}
4008 * Text:: @code{.text @var{subsection}}
4009 * Title:: @code{.title "@var{heading}"}
4011 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4014 * Uleb128:: @code{.uleb128 @var{expressions}}
4016 * Val:: @code{.val @var{addr}}
4020 * Version:: @code{.version "@var{string}"}
4021 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4022 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4025 * Warning:: @code{.warning @var{string}}
4026 * Weak:: @code{.weak @var{names}}
4027 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4028 * Word:: @code{.word @var{expressions}}
4029 * Deprecated:: Deprecated Directives
4033 @section @code{.abort}
4035 @cindex @code{abort} directive
4036 @cindex stopping the assembly
4037 This directive stops the assembly immediately. It is for
4038 compatibility with other assemblers. The original idea was that the
4039 assembly language source would be piped into the assembler. If the sender
4040 of the source quit, it could use this directive tells @command{@value{AS}} to
4041 quit also. One day @code{.abort} will not be supported.
4045 @section @code{.ABORT} (COFF)
4047 @cindex @code{ABORT} directive
4048 When producing COFF output, @command{@value{AS}} accepts this directive as a
4049 synonym for @samp{.abort}.
4052 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4058 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4060 @cindex padding the location counter
4061 @cindex @code{align} directive
4062 Pad the location counter (in the current subsection) to a particular storage
4063 boundary. The first expression (which must be absolute) is the alignment
4064 required, as described below.
4066 The second expression (also absolute) gives the fill value to be stored in the
4067 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4068 padding bytes are normally zero. However, on some systems, if the section is
4069 marked as containing code and the fill value is omitted, the space is filled
4070 with no-op instructions.
4072 The third expression is also absolute, and is also optional. If it is present,
4073 it is the maximum number of bytes that should be skipped by this alignment
4074 directive. If doing the alignment would require skipping more bytes than the
4075 specified maximum, then the alignment is not done at all. You can omit the
4076 fill value (the second argument) entirely by simply using two commas after the
4077 required alignment; this can be useful if you want the alignment to be filled
4078 with no-op instructions when appropriate.
4080 The way the required alignment is specified varies from system to system.
4081 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4082 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4083 alignment request in bytes. For example @samp{.align 8} advances
4084 the location counter until it is a multiple of 8. If the location counter
4085 is already a multiple of 8, no change is needed. For the tic54x, the
4086 first expression is the alignment request in words.
4088 For other systems, including ppc, i386 using a.out format, arm and
4089 strongarm, it is the
4090 number of low-order zero bits the location counter must have after
4091 advancement. For example @samp{.align 3} advances the location
4092 counter until it a multiple of 8. If the location counter is already a
4093 multiple of 8, no change is needed.
4095 This inconsistency is due to the different behaviors of the various
4096 native assemblers for these systems which GAS must emulate.
4097 GAS also provides @code{.balign} and @code{.p2align} directives,
4098 described later, which have a consistent behavior across all
4099 architectures (but are specific to GAS).
4102 @section @code{.altmacro}
4103 Enable alternate macro mode, enabling:
4106 @item LOCAL @var{name} [ , @dots{} ]
4107 One additional directive, @code{LOCAL}, is available. It is used to
4108 generate a string replacement for each of the @var{name} arguments, and
4109 replace any instances of @var{name} in each macro expansion. The
4110 replacement string is unique in the assembly, and different for each
4111 separate macro expansion. @code{LOCAL} allows you to write macros that
4112 define symbols, without fear of conflict between separate macro expansions.
4114 @item String delimiters
4115 You can write strings delimited in these other ways besides
4116 @code{"@var{string}"}:
4119 @item '@var{string}'
4120 You can delimit strings with single-quote characters.
4122 @item <@var{string}>
4123 You can delimit strings with matching angle brackets.
4126 @item single-character string escape
4127 To include any single character literally in a string (even if the
4128 character would otherwise have some special meaning), you can prefix the
4129 character with @samp{!} (an exclamation mark). For example, you can
4130 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4132 @item Expression results as strings
4133 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4134 and use the result as a string.
4138 @section @code{.ascii "@var{string}"}@dots{}
4140 @cindex @code{ascii} directive
4141 @cindex string literals
4142 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4143 separated by commas. It assembles each string (with no automatic
4144 trailing zero byte) into consecutive addresses.
4147 @section @code{.asciz "@var{string}"}@dots{}
4149 @cindex @code{asciz} directive
4150 @cindex zero-terminated strings
4151 @cindex null-terminated strings
4152 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4153 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4156 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4158 @cindex padding the location counter given number of bytes
4159 @cindex @code{balign} directive
4160 Pad the location counter (in the current subsection) to a particular
4161 storage boundary. The first expression (which must be absolute) is the
4162 alignment request in bytes. For example @samp{.balign 8} advances
4163 the location counter until it is a multiple of 8. If the location counter
4164 is already a multiple of 8, no change is needed.
4166 The second expression (also absolute) gives the fill value to be stored in the
4167 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4168 padding bytes are normally zero. However, on some systems, if the section is
4169 marked as containing code and the fill value is omitted, the space is filled
4170 with no-op instructions.
4172 The third expression is also absolute, and is also optional. If it is present,
4173 it is the maximum number of bytes that should be skipped by this alignment
4174 directive. If doing the alignment would require skipping more bytes than the
4175 specified maximum, then the alignment is not done at all. You can omit the
4176 fill value (the second argument) entirely by simply using two commas after the
4177 required alignment; this can be useful if you want the alignment to be filled
4178 with no-op instructions when appropriate.
4180 @cindex @code{balignw} directive
4181 @cindex @code{balignl} directive
4182 The @code{.balignw} and @code{.balignl} directives are variants of the
4183 @code{.balign} directive. The @code{.balignw} directive treats the fill
4184 pattern as a two byte word value. The @code{.balignl} directives treats the
4185 fill pattern as a four byte longword value. For example, @code{.balignw
4186 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4187 filled in with the value 0x368d (the exact placement of the bytes depends upon
4188 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4192 @section @code{.byte @var{expressions}}
4194 @cindex @code{byte} directive
4195 @cindex integers, one byte
4196 @code{.byte} expects zero or more expressions, separated by commas.
4197 Each expression is assembled into the next byte.
4199 @node CFI directives
4200 @section @code{.cfi_sections @var{section_list}}
4201 @cindex @code{cfi_sections} directive
4202 @code{.cfi_sections} may be used to specify whether CFI directives
4203 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4204 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4205 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4206 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4207 directive is not used is @code{.cfi_sections .eh_frame}.
4209 @section @code{.cfi_startproc [simple]}
4210 @cindex @code{cfi_startproc} directive
4211 @code{.cfi_startproc} is used at the beginning of each function that
4212 should have an entry in @code{.eh_frame}. It initializes some internal
4213 data structures. Don't forget to close the function by
4214 @code{.cfi_endproc}.
4216 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4217 it also emits some architecture dependent initial CFI instructions.
4219 @section @code{.cfi_endproc}
4220 @cindex @code{cfi_endproc} directive
4221 @code{.cfi_endproc} is used at the end of a function where it closes its
4222 unwind entry previously opened by
4223 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4225 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4226 @code{.cfi_personality} defines personality routine and its encoding.
4227 @var{encoding} must be a constant determining how the personality
4228 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4229 argument is not present, otherwise second argument should be
4230 a constant or a symbol name. When using indirect encodings,
4231 the symbol provided should be the location where personality
4232 can be loaded from, not the personality routine itself.
4233 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4234 no personality routine.
4236 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4237 @code{.cfi_lsda} defines LSDA and its encoding.
4238 @var{encoding} must be a constant determining how the LSDA
4239 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4240 argument is not present, otherwise second argument should be a constant
4241 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4244 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4245 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4246 address from @var{register} and add @var{offset} to it}.
4248 @section @code{.cfi_def_cfa_register @var{register}}
4249 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4250 now on @var{register} will be used instead of the old one. Offset
4253 @section @code{.cfi_def_cfa_offset @var{offset}}
4254 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4255 remains the same, but @var{offset} is new. Note that it is the
4256 absolute offset that will be added to a defined register to compute
4259 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4260 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4261 value that is added/substracted from the previous offset.
4263 @section @code{.cfi_offset @var{register}, @var{offset}}
4264 Previous value of @var{register} is saved at offset @var{offset} from
4267 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4268 Previous value of @var{register} is saved at offset @var{offset} from
4269 the current CFA register. This is transformed to @code{.cfi_offset}
4270 using the known displacement of the CFA register from the CFA.
4271 This is often easier to use, because the number will match the
4272 code it's annotating.
4274 @section @code{.cfi_register @var{register1}, @var{register2}}
4275 Previous value of @var{register1} is saved in register @var{register2}.
4277 @section @code{.cfi_restore @var{register}}
4278 @code{.cfi_restore} says that the rule for @var{register} is now the
4279 same as it was at the beginning of the function, after all initial
4280 instruction added by @code{.cfi_startproc} were executed.
4282 @section @code{.cfi_undefined @var{register}}
4283 From now on the previous value of @var{register} can't be restored anymore.
4285 @section @code{.cfi_same_value @var{register}}
4286 Current value of @var{register} is the same like in the previous frame,
4287 i.e. no restoration needed.
4289 @section @code{.cfi_remember_state},
4290 First save all current rules for all registers by @code{.cfi_remember_state},
4291 then totally screw them up by subsequent @code{.cfi_*} directives and when
4292 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4293 the previous saved state.
4295 @section @code{.cfi_return_column @var{register}}
4296 Change return column @var{register}, i.e. the return address is either
4297 directly in @var{register} or can be accessed by rules for @var{register}.
4299 @section @code{.cfi_signal_frame}
4300 Mark current function as signal trampoline.
4302 @section @code{.cfi_window_save}
4303 SPARC register window has been saved.
4305 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4306 Allows the user to add arbitrary bytes to the unwind info. One
4307 might use this to add OS-specific CFI opcodes, or generic CFI
4308 opcodes that GAS does not yet support.
4310 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4311 The current value of @var{register} is @var{label}. The value of @var{label}
4312 will be encoded in the output file according to @var{encoding}; see the
4313 description of @code{.cfi_personality} for details on this encoding.
4315 The usefulness of equating a register to a fixed label is probably
4316 limited to the return address register. Here, it can be useful to
4317 mark a code segment that has only one return address which is reached
4318 by a direct branch and no copy of the return address exists in memory
4319 or another register.
4322 @section @code{.comm @var{symbol} , @var{length} }
4324 @cindex @code{comm} directive
4325 @cindex symbol, common
4326 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4327 common symbol in one object file may be merged with a defined or common symbol
4328 of the same name in another object file. If @code{@value{LD}} does not see a
4329 definition for the symbol--just one or more common symbols--then it will
4330 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4331 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4332 the same name, and they do not all have the same size, it will allocate space
4333 using the largest size.
4336 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4337 an optional third argument. This is the desired alignment of the symbol,
4338 specified for ELF as a byte boundary (for example, an alignment of 16 means
4339 that the least significant 4 bits of the address should be zero), and for PE
4340 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4341 boundary). The alignment must be an absolute expression, and it must be a
4342 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4343 common symbol, it will use the alignment when placing the symbol. If no
4344 alignment is specified, @command{@value{AS}} will set the alignment to the
4345 largest power of two less than or equal to the size of the symbol, up to a
4346 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4347 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4348 @samp{--section-alignment} option; image file sections in PE are aligned to
4349 multiples of 4096, which is far too large an alignment for ordinary variables.
4350 It is rather the default alignment for (non-debug) sections within object
4351 (@samp{*.o}) files, which are less strictly aligned.}.
4355 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4356 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4360 @section @code{.data @var{subsection}}
4362 @cindex @code{data} directive
4363 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4364 end of the data subsection numbered @var{subsection} (which is an
4365 absolute expression). If @var{subsection} is omitted, it defaults
4370 @section @code{.def @var{name}}
4372 @cindex @code{def} directive
4373 @cindex COFF symbols, debugging
4374 @cindex debugging COFF symbols
4375 Begin defining debugging information for a symbol @var{name}; the
4376 definition extends until the @code{.endef} directive is encountered.
4379 This directive is only observed when @command{@value{AS}} is configured for COFF
4380 format output; when producing @code{b.out}, @samp{.def} is recognized,
4387 @section @code{.desc @var{symbol}, @var{abs-expression}}
4389 @cindex @code{desc} directive
4390 @cindex COFF symbol descriptor
4391 @cindex symbol descriptor, COFF
4392 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4393 to the low 16 bits of an absolute expression.
4396 The @samp{.desc} directive is not available when @command{@value{AS}} is
4397 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4398 object format. For the sake of compatibility, @command{@value{AS}} accepts
4399 it, but produces no output, when configured for COFF.
4405 @section @code{.dim}
4407 @cindex @code{dim} directive
4408 @cindex COFF auxiliary symbol information
4409 @cindex auxiliary symbol information, COFF
4410 This directive is generated by compilers to include auxiliary debugging
4411 information in the symbol table. It is only permitted inside
4412 @code{.def}/@code{.endef} pairs.
4415 @samp{.dim} is only meaningful when generating COFF format output; when
4416 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4422 @section @code{.double @var{flonums}}
4424 @cindex @code{double} directive
4425 @cindex floating point numbers (double)
4426 @code{.double} expects zero or more flonums, separated by commas. It
4427 assembles floating point numbers.
4429 The exact kind of floating point numbers emitted depends on how
4430 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4434 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4435 in @sc{ieee} format.
4440 @section @code{.eject}
4442 @cindex @code{eject} directive
4443 @cindex new page, in listings
4444 @cindex page, in listings
4445 @cindex listing control: new page
4446 Force a page break at this point, when generating assembly listings.
4449 @section @code{.else}
4451 @cindex @code{else} directive
4452 @code{.else} is part of the @command{@value{AS}} support for conditional
4453 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4454 of code to be assembled if the condition for the preceding @code{.if}
4458 @section @code{.elseif}
4460 @cindex @code{elseif} directive
4461 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4462 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4463 @code{.if} block that would otherwise fill the entire @code{.else} section.
4466 @section @code{.end}
4468 @cindex @code{end} directive
4469 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4470 process anything in the file past the @code{.end} directive.
4474 @section @code{.endef}
4476 @cindex @code{endef} directive
4477 This directive flags the end of a symbol definition begun with
4481 @samp{.endef} is only meaningful when generating COFF format output; if
4482 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4483 directive but ignores it.
4488 @section @code{.endfunc}
4489 @cindex @code{endfunc} directive
4490 @code{.endfunc} marks the end of a function specified with @code{.func}.
4493 @section @code{.endif}
4495 @cindex @code{endif} directive
4496 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4497 it marks the end of a block of code that is only assembled
4498 conditionally. @xref{If,,@code{.if}}.
4501 @section @code{.equ @var{symbol}, @var{expression}}
4503 @cindex @code{equ} directive
4504 @cindex assigning values to symbols
4505 @cindex symbols, assigning values to
4506 This directive sets the value of @var{symbol} to @var{expression}.
4507 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4510 The syntax for @code{equ} on the HPPA is
4511 @samp{@var{symbol} .equ @var{expression}}.
4515 The syntax for @code{equ} on the Z80 is
4516 @samp{@var{symbol} equ @var{expression}}.
4517 On the Z80 it is an eror if @var{symbol} is already defined,
4518 but the symbol is not protected from later redefinition.
4519 Compare @ref{Equiv}.
4523 @section @code{.equiv @var{symbol}, @var{expression}}
4524 @cindex @code{equiv} directive
4525 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4526 the assembler will signal an error if @var{symbol} is already defined. Note a
4527 symbol which has been referenced but not actually defined is considered to be
4530 Except for the contents of the error message, this is roughly equivalent to
4537 plus it protects the symbol from later redefinition.
4540 @section @code{.eqv @var{symbol}, @var{expression}}
4541 @cindex @code{eqv} directive
4542 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4543 evaluate the expression or any part of it immediately. Instead each time
4544 the resulting symbol is used in an expression, a snapshot of its current
4548 @section @code{.err}
4549 @cindex @code{err} directive
4550 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4551 message and, unless the @option{-Z} option was used, it will not generate an
4552 object file. This can be used to signal an error in conditionally compiled code.
4555 @section @code{.error "@var{string}"}
4556 @cindex error directive
4558 Similarly to @code{.err}, this directive emits an error, but you can specify a
4559 string that will be emitted as the error message. If you don't specify the
4560 message, it defaults to @code{".error directive invoked in source file"}.
4561 @xref{Errors, ,Error and Warning Messages}.
4564 .error "This code has not been assembled and tested."
4568 @section @code{.exitm}
4569 Exit early from the current macro definition. @xref{Macro}.
4572 @section @code{.extern}
4574 @cindex @code{extern} directive
4575 @code{.extern} is accepted in the source program---for compatibility
4576 with other assemblers---but it is ignored. @command{@value{AS}} treats
4577 all undefined symbols as external.
4580 @section @code{.fail @var{expression}}
4582 @cindex @code{fail} directive
4583 Generates an error or a warning. If the value of the @var{expression} is 500
4584 or more, @command{@value{AS}} will print a warning message. If the value is less
4585 than 500, @command{@value{AS}} will print an error message. The message will
4586 include the value of @var{expression}. This can occasionally be useful inside
4587 complex nested macros or conditional assembly.
4590 @section @code{.file}
4591 @cindex @code{file} directive
4593 @ifclear no-file-dir
4594 There are two different versions of the @code{.file} directive. Targets
4595 that support DWARF2 line number information use the DWARF2 version of
4596 @code{.file}. Other targets use the default version.
4598 @subheading Default Version
4600 @cindex logical file name
4601 @cindex file name, logical
4602 This version of the @code{.file} directive tells @command{@value{AS}} that we
4603 are about to start a new logical file. The syntax is:
4609 @var{string} is the new file name. In general, the filename is
4610 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4611 to specify an empty file name, you must give the quotes--@code{""}. This
4612 statement may go away in future: it is only recognized to be compatible with
4613 old @command{@value{AS}} programs.
4615 @subheading DWARF2 Version
4618 When emitting DWARF2 line number information, @code{.file} assigns filenames
4619 to the @code{.debug_line} file name table. The syntax is:
4622 .file @var{fileno} @var{filename}
4625 The @var{fileno} operand should be a unique positive integer to use as the
4626 index of the entry in the table. The @var{filename} operand is a C string
4629 The detail of filename indices is exposed to the user because the filename
4630 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4631 information, and thus the user must know the exact indices that table
4635 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4637 @cindex @code{fill} directive
4638 @cindex writing patterns in memory
4639 @cindex patterns, writing in memory
4640 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4641 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4642 may be zero or more. @var{Size} may be zero or more, but if it is
4643 more than 8, then it is deemed to have the value 8, compatible with
4644 other people's assemblers. The contents of each @var{repeat} bytes
4645 is taken from an 8-byte number. The highest order 4 bytes are
4646 zero. The lowest order 4 bytes are @var{value} rendered in the
4647 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4648 Each @var{size} bytes in a repetition is taken from the lowest order
4649 @var{size} bytes of this number. Again, this bizarre behavior is
4650 compatible with other people's assemblers.
4652 @var{size} and @var{value} are optional.
4653 If the second comma and @var{value} are absent, @var{value} is
4654 assumed zero. If the first comma and following tokens are absent,
4655 @var{size} is assumed to be 1.
4658 @section @code{.float @var{flonums}}
4660 @cindex floating point numbers (single)
4661 @cindex @code{float} directive
4662 This directive assembles zero or more flonums, separated by commas. It
4663 has the same effect as @code{.single}.
4665 The exact kind of floating point numbers emitted depends on how
4666 @command{@value{AS}} is configured.
4667 @xref{Machine Dependencies}.
4671 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4672 in @sc{ieee} format.
4677 @section @code{.func @var{name}[,@var{label}]}
4678 @cindex @code{func} directive
4679 @code{.func} emits debugging information to denote function @var{name}, and
4680 is ignored unless the file is assembled with debugging enabled.
4681 Only @samp{--gstabs[+]} is currently supported.
4682 @var{label} is the entry point of the function and if omitted @var{name}
4683 prepended with the @samp{leading char} is used.
4684 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4685 All functions are currently defined to have @code{void} return type.
4686 The function must be terminated with @code{.endfunc}.
4689 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4691 @cindex @code{global} directive
4692 @cindex symbol, making visible to linker
4693 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4694 @var{symbol} in your partial program, its value is made available to
4695 other partial programs that are linked with it. Otherwise,
4696 @var{symbol} takes its attributes from a symbol of the same name
4697 from another file linked into the same program.
4699 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4700 compatibility with other assemblers.
4703 On the HPPA, @code{.global} is not always enough to make it accessible to other
4704 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4705 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4710 @section @code{.gnu_attribute @var{tag},@var{value}}
4711 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4714 @section @code{.hidden @var{names}}
4716 @cindex @code{hidden} directive
4718 This is one of the ELF visibility directives. The other two are
4719 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4720 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4722 This directive overrides the named symbols default visibility (which is set by
4723 their binding: local, global or weak). The directive sets the visibility to
4724 @code{hidden} which means that the symbols are not visible to other components.
4725 Such symbols are always considered to be @code{protected} as well.
4729 @section @code{.hword @var{expressions}}
4731 @cindex @code{hword} directive
4732 @cindex integers, 16-bit
4733 @cindex numbers, 16-bit
4734 @cindex sixteen bit integers
4735 This expects zero or more @var{expressions}, and emits
4736 a 16 bit number for each.
4739 This directive is a synonym for @samp{.short}; depending on the target
4740 architecture, it may also be a synonym for @samp{.word}.
4744 This directive is a synonym for @samp{.short}.
4747 This directive is a synonym for both @samp{.short} and @samp{.word}.
4752 @section @code{.ident}
4754 @cindex @code{ident} directive
4756 This directive is used by some assemblers to place tags in object files. The
4757 behavior of this directive varies depending on the target. When using the
4758 a.out object file format, @command{@value{AS}} simply accepts the directive for
4759 source-file compatibility with existing assemblers, but does not emit anything
4760 for it. When using COFF, comments are emitted to the @code{.comment} or
4761 @code{.rdata} section, depending on the target. When using ELF, comments are
4762 emitted to the @code{.comment} section.
4765 @section @code{.if @var{absolute expression}}
4767 @cindex conditional assembly
4768 @cindex @code{if} directive
4769 @code{.if} marks the beginning of a section of code which is only
4770 considered part of the source program being assembled if the argument
4771 (which must be an @var{absolute expression}) is non-zero. The end of
4772 the conditional section of code must be marked by @code{.endif}
4773 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4774 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4775 If you have several conditions to check, @code{.elseif} may be used to avoid
4776 nesting blocks if/else within each subsequent @code{.else} block.
4778 The following variants of @code{.if} are also supported:
4780 @cindex @code{ifdef} directive
4781 @item .ifdef @var{symbol}
4782 Assembles the following section of code if the specified @var{symbol}
4783 has been defined. Note a symbol which has been referenced but not yet defined
4784 is considered to be undefined.
4786 @cindex @code{ifb} directive
4787 @item .ifb @var{text}
4788 Assembles the following section of code if the operand is blank (empty).
4790 @cindex @code{ifc} directive
4791 @item .ifc @var{string1},@var{string2}
4792 Assembles the following section of code if the two strings are the same. The
4793 strings may be optionally quoted with single quotes. If they are not quoted,
4794 the first string stops at the first comma, and the second string stops at the
4795 end of the line. Strings which contain whitespace should be quoted. The
4796 string comparison is case sensitive.
4798 @cindex @code{ifeq} directive
4799 @item .ifeq @var{absolute expression}
4800 Assembles the following section of code if the argument is zero.
4802 @cindex @code{ifeqs} directive
4803 @item .ifeqs @var{string1},@var{string2}
4804 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4806 @cindex @code{ifge} directive
4807 @item .ifge @var{absolute expression}
4808 Assembles the following section of code if the argument is greater than or
4811 @cindex @code{ifgt} directive
4812 @item .ifgt @var{absolute expression}
4813 Assembles the following section of code if the argument is greater than zero.
4815 @cindex @code{ifle} directive
4816 @item .ifle @var{absolute expression}
4817 Assembles the following section of code if the argument is less than or equal
4820 @cindex @code{iflt} directive
4821 @item .iflt @var{absolute expression}
4822 Assembles the following section of code if the argument is less than zero.
4824 @cindex @code{ifnb} directive
4825 @item .ifnb @var{text}
4826 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4827 following section of code if the operand is non-blank (non-empty).
4829 @cindex @code{ifnc} directive
4830 @item .ifnc @var{string1},@var{string2}.
4831 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4832 following section of code if the two strings are not the same.
4834 @cindex @code{ifndef} directive
4835 @cindex @code{ifnotdef} directive
4836 @item .ifndef @var{symbol}
4837 @itemx .ifnotdef @var{symbol}
4838 Assembles the following section of code if the specified @var{symbol}
4839 has not been defined. Both spelling variants are equivalent. Note a symbol
4840 which has been referenced but not yet defined is considered to be undefined.
4842 @cindex @code{ifne} directive
4843 @item .ifne @var{absolute expression}
4844 Assembles the following section of code if the argument is not equal to zero
4845 (in other words, this is equivalent to @code{.if}).
4847 @cindex @code{ifnes} directive
4848 @item .ifnes @var{string1},@var{string2}
4849 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4850 following section of code if the two strings are not the same.
4854 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4856 @cindex @code{incbin} directive
4857 @cindex binary files, including
4858 The @code{incbin} directive includes @var{file} verbatim at the current
4859 location. You can control the search paths used with the @samp{-I} command-line
4860 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4863 The @var{skip} argument skips a number of bytes from the start of the
4864 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4865 read. Note that the data is not aligned in any way, so it is the user's
4866 responsibility to make sure that proper alignment is provided both before and
4867 after the @code{incbin} directive.
4870 @section @code{.include "@var{file}"}
4872 @cindex @code{include} directive
4873 @cindex supporting files, including
4874 @cindex files, including
4875 This directive provides a way to include supporting files at specified
4876 points in your source program. The code from @var{file} is assembled as
4877 if it followed the point of the @code{.include}; when the end of the
4878 included file is reached, assembly of the original file continues. You
4879 can control the search paths used with the @samp{-I} command-line option
4880 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4884 @section @code{.int @var{expressions}}
4886 @cindex @code{int} directive
4887 @cindex integers, 32-bit
4888 Expect zero or more @var{expressions}, of any section, separated by commas.
4889 For each expression, emit a number that, at run time, is the value of that
4890 expression. The byte order and bit size of the number depends on what kind
4891 of target the assembly is for.
4895 On most forms of the H8/300, @code{.int} emits 16-bit
4896 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4903 @section @code{.internal @var{names}}
4905 @cindex @code{internal} directive
4907 This is one of the ELF visibility directives. The other two are
4908 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4909 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4911 This directive overrides the named symbols default visibility (which is set by
4912 their binding: local, global or weak). The directive sets the visibility to
4913 @code{internal} which means that the symbols are considered to be @code{hidden}
4914 (i.e., not visible to other components), and that some extra, processor specific
4915 processing must also be performed upon the symbols as well.
4919 @section @code{.irp @var{symbol},@var{values}}@dots{}
4921 @cindex @code{irp} directive
4922 Evaluate a sequence of statements assigning different values to @var{symbol}.
4923 The sequence of statements starts at the @code{.irp} directive, and is
4924 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4925 set to @var{value}, and the sequence of statements is assembled. If no
4926 @var{value} is listed, the sequence of statements is assembled once, with
4927 @var{symbol} set to the null string. To refer to @var{symbol} within the
4928 sequence of statements, use @var{\symbol}.
4930 For example, assembling
4938 is equivalent to assembling
4946 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4949 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4951 @cindex @code{irpc} directive
4952 Evaluate a sequence of statements assigning different values to @var{symbol}.
4953 The sequence of statements starts at the @code{.irpc} directive, and is
4954 terminated by an @code{.endr} directive. For each character in @var{value},
4955 @var{symbol} is set to the character, and the sequence of statements is
4956 assembled. If no @var{value} is listed, the sequence of statements is
4957 assembled once, with @var{symbol} set to the null string. To refer to
4958 @var{symbol} within the sequence of statements, use @var{\symbol}.
4960 For example, assembling
4968 is equivalent to assembling
4976 For some caveats with the spelling of @var{symbol}, see also the discussion
4980 @section @code{.lcomm @var{symbol} , @var{length}}
4982 @cindex @code{lcomm} directive
4983 @cindex local common symbols
4984 @cindex symbols, local common
4985 Reserve @var{length} (an absolute expression) bytes for a local common
4986 denoted by @var{symbol}. The section and value of @var{symbol} are
4987 those of the new local common. The addresses are allocated in the bss
4988 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4989 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4990 not visible to @code{@value{LD}}.
4993 Some targets permit a third argument to be used with @code{.lcomm}. This
4994 argument specifies the desired alignment of the symbol in the bss section.
4998 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4999 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5003 @section @code{.lflags}
5005 @cindex @code{lflags} directive (ignored)
5006 @command{@value{AS}} accepts this directive, for compatibility with other
5007 assemblers, but ignores it.
5009 @ifclear no-line-dir
5011 @section @code{.line @var{line-number}}
5013 @cindex @code{line} directive
5014 @cindex logical line number
5016 Change the logical line number. @var{line-number} must be an absolute
5017 expression. The next line has that logical line number. Therefore any other
5018 statements on the current line (after a statement separator character) are
5019 reported as on logical line number @var{line-number} @minus{} 1. One day
5020 @command{@value{AS}} will no longer support this directive: it is recognized only
5021 for compatibility with existing assembler programs.
5024 Even though this is a directive associated with the @code{a.out} or
5025 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5026 when producing COFF output, and treats @samp{.line} as though it
5027 were the COFF @samp{.ln} @emph{if} it is found outside a
5028 @code{.def}/@code{.endef} pair.
5030 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5031 used by compilers to generate auxiliary symbol information for
5036 @section @code{.linkonce [@var{type}]}
5038 @cindex @code{linkonce} directive
5039 @cindex common sections
5040 Mark the current section so that the linker only includes a single copy of it.
5041 This may be used to include the same section in several different object files,
5042 but ensure that the linker will only include it once in the final output file.
5043 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5044 Duplicate sections are detected based on the section name, so it should be
5047 This directive is only supported by a few object file formats; as of this
5048 writing, the only object file format which supports it is the Portable
5049 Executable format used on Windows NT.
5051 The @var{type} argument is optional. If specified, it must be one of the
5052 following strings. For example:
5056 Not all types may be supported on all object file formats.
5060 Silently discard duplicate sections. This is the default.
5063 Warn if there are duplicate sections, but still keep only one copy.
5066 Warn if any of the duplicates have different sizes.
5069 Warn if any of the duplicates do not have exactly the same contents.
5073 @section @code{.list}
5075 @cindex @code{list} directive
5076 @cindex listing control, turning on
5077 Control (in conjunction with the @code{.nolist} directive) whether or
5078 not assembly listings are generated. These two directives maintain an
5079 internal counter (which is zero initially). @code{.list} increments the
5080 counter, and @code{.nolist} decrements it. Assembly listings are
5081 generated whenever the counter is greater than zero.
5083 By default, listings are disabled. When you enable them (with the
5084 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5085 the initial value of the listing counter is one.
5088 @section @code{.ln @var{line-number}}
5090 @cindex @code{ln} directive
5091 @ifclear no-line-dir
5092 @samp{.ln} is a synonym for @samp{.line}.
5095 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5096 must be an absolute expression. The next line has that logical
5097 line number, so any other statements on the current line (after a
5098 statement separator character @code{;}) are reported as on logical
5099 line number @var{line-number} @minus{} 1.
5102 This directive is accepted, but ignored, when @command{@value{AS}} is
5103 configured for @code{b.out}; its effect is only associated with COFF
5109 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5110 @cindex @code{loc} directive
5111 When emitting DWARF2 line number information,
5112 the @code{.loc} directive will add a row to the @code{.debug_line} line
5113 number matrix corresponding to the immediately following assembly
5114 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5115 arguments will be applied to the @code{.debug_line} state machine before
5118 The @var{options} are a sequence of the following tokens in any order:
5122 This option will set the @code{basic_block} register in the
5123 @code{.debug_line} state machine to @code{true}.
5126 This option will set the @code{prologue_end} register in the
5127 @code{.debug_line} state machine to @code{true}.
5129 @item epilogue_begin
5130 This option will set the @code{epilogue_begin} register in the
5131 @code{.debug_line} state machine to @code{true}.
5133 @item is_stmt @var{value}
5134 This option will set the @code{is_stmt} register in the
5135 @code{.debug_line} state machine to @code{value}, which must be
5138 @item isa @var{value}
5139 This directive will set the @code{isa} register in the @code{.debug_line}
5140 state machine to @var{value}, which must be an unsigned integer.
5142 @item discriminator @var{value}
5143 This directive will set the @code{discriminator} register in the @code{.debug_line}
5144 state machine to @var{value}, which must be an unsigned integer.
5148 @node Loc_mark_labels
5149 @section @code{.loc_mark_labels @var{enable}}
5150 @cindex @code{loc_mark_labels} directive
5151 When emitting DWARF2 line number information,
5152 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5153 to the @code{.debug_line} line number matrix with the @code{basic_block}
5154 register in the state machine set whenever a code label is seen.
5155 The @var{enable} argument should be either 1 or 0, to enable or disable
5156 this function respectively.
5160 @section @code{.local @var{names}}
5162 @cindex @code{local} directive
5163 This directive, which is available for ELF targets, marks each symbol in
5164 the comma-separated list of @code{names} as a local symbol so that it
5165 will not be externally visible. If the symbols do not already exist,
5166 they will be created.
5168 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5169 accept an alignment argument, which is the case for most ELF targets,
5170 the @code{.local} directive can be used in combination with @code{.comm}
5171 (@pxref{Comm}) to define aligned local common data.
5175 @section @code{.long @var{expressions}}
5177 @cindex @code{long} directive
5178 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5181 @c no one seems to know what this is for or whether this description is
5182 @c what it really ought to do
5184 @section @code{.lsym @var{symbol}, @var{expression}}
5186 @cindex @code{lsym} directive
5187 @cindex symbol, not referenced in assembly
5188 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5189 the hash table, ensuring it cannot be referenced by name during the
5190 rest of the assembly. This sets the attributes of the symbol to be
5191 the same as the expression value:
5193 @var{other} = @var{descriptor} = 0
5194 @var{type} = @r{(section of @var{expression})}
5195 @var{value} = @var{expression}
5198 The new symbol is not flagged as external.
5202 @section @code{.macro}
5205 The commands @code{.macro} and @code{.endm} allow you to define macros that
5206 generate assembly output. For example, this definition specifies a macro
5207 @code{sum} that puts a sequence of numbers into memory:
5210 .macro sum from=0, to=5
5219 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5231 @item .macro @var{macname}
5232 @itemx .macro @var{macname} @var{macargs} @dots{}
5233 @cindex @code{macro} directive
5234 Begin the definition of a macro called @var{macname}. If your macro
5235 definition requires arguments, specify their names after the macro name,
5236 separated by commas or spaces. You can qualify the macro argument to
5237 indicate whether all invocations must specify a non-blank value (through
5238 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5239 (through @samp{:@code{vararg}}). You can supply a default value for any
5240 macro argument by following the name with @samp{=@var{deflt}}. You
5241 cannot define two macros with the same @var{macname} unless it has been
5242 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5243 definitions. For example, these are all valid @code{.macro} statements:
5247 Begin the definition of a macro called @code{comm}, which takes no
5250 @item .macro plus1 p, p1
5251 @itemx .macro plus1 p p1
5252 Either statement begins the definition of a macro called @code{plus1},
5253 which takes two arguments; within the macro definition, write
5254 @samp{\p} or @samp{\p1} to evaluate the arguments.
5256 @item .macro reserve_str p1=0 p2
5257 Begin the definition of a macro called @code{reserve_str}, with two
5258 arguments. The first argument has a default value, but not the second.
5259 After the definition is complete, you can call the macro either as
5260 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5261 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5262 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5263 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5265 @item .macro m p1:req, p2=0, p3:vararg
5266 Begin the definition of a macro called @code{m}, with at least three
5267 arguments. The first argument must always have a value specified, but
5268 not the second, which instead has a default value. The third formal
5269 will get assigned all remaining arguments specified at invocation time.
5271 When you call a macro, you can specify the argument values either by
5272 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5273 @samp{sum to=17, from=9}.
5277 Note that since each of the @var{macargs} can be an identifier exactly
5278 as any other one permitted by the target architecture, there may be
5279 occasional problems if the target hand-crafts special meanings to certain
5280 characters when they occur in a special position. For example, if the colon
5281 (@code{:}) is generally permitted to be part of a symbol name, but the
5282 architecture specific code special-cases it when occurring as the final
5283 character of a symbol (to denote a label), then the macro parameter
5284 replacement code will have no way of knowing that and consider the whole
5285 construct (including the colon) an identifier, and check only this
5286 identifier for being the subject to parameter substitution. So for example
5287 this macro definition:
5295 might not work as expected. Invoking @samp{label foo} might not create a label
5296 called @samp{foo} but instead just insert the text @samp{\l:} into the
5297 assembler source, probably generating an error about an unrecognised
5300 Similarly problems might occur with the period character (@samp{.})
5301 which is often allowed inside opcode names (and hence identifier names). So
5302 for example constructing a macro to build an opcode from a base name and a
5303 length specifier like this:
5306 .macro opcode base length
5311 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5312 instruction but instead generate some kind of error as the assembler tries to
5313 interpret the text @samp{\base.\length}.
5315 There are several possible ways around this problem:
5318 @item Insert white space
5319 If it is possible to use white space characters then this is the simplest
5328 @item Use @samp{\()}
5329 The string @samp{\()} can be used to separate the end of a macro argument from
5330 the following text. eg:
5333 .macro opcode base length
5338 @item Use the alternate macro syntax mode
5339 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5340 used as a separator. eg:
5350 Note: this problem of correctly identifying string parameters to pseudo ops
5351 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5352 and @code{.irpc} (@pxref{Irpc}) as well.
5355 @cindex @code{endm} directive
5356 Mark the end of a macro definition.
5359 @cindex @code{exitm} directive
5360 Exit early from the current macro definition.
5362 @cindex number of macros executed
5363 @cindex macros, count executed
5365 @command{@value{AS}} maintains a counter of how many macros it has
5366 executed in this pseudo-variable; you can copy that number to your
5367 output with @samp{\@@}, but @emph{only within a macro definition}.
5369 @item LOCAL @var{name} [ , @dots{} ]
5370 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5371 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5372 @xref{Altmacro,,@code{.altmacro}}.
5376 @section @code{.mri @var{val}}
5378 @cindex @code{mri} directive
5379 @cindex MRI mode, temporarily
5380 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5381 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5382 affects code assembled until the next @code{.mri} directive, or until the end
5383 of the file. @xref{M, MRI mode, MRI mode}.
5386 @section @code{.noaltmacro}
5387 Disable alternate macro mode. @xref{Altmacro}.
5390 @section @code{.nolist}
5392 @cindex @code{nolist} directive
5393 @cindex listing control, turning off
5394 Control (in conjunction with the @code{.list} directive) whether or
5395 not assembly listings are generated. These two directives maintain an
5396 internal counter (which is zero initially). @code{.list} increments the
5397 counter, and @code{.nolist} decrements it. Assembly listings are
5398 generated whenever the counter is greater than zero.
5401 @section @code{.octa @var{bignums}}
5403 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5404 @cindex @code{octa} directive
5405 @cindex integer, 16-byte
5406 @cindex sixteen byte integer
5407 This directive expects zero or more bignums, separated by commas. For each
5408 bignum, it emits a 16-byte integer.
5410 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5411 hence @emph{octa}-word for 16 bytes.
5414 @section @code{.org @var{new-lc} , @var{fill}}
5416 @cindex @code{org} directive
5417 @cindex location counter, advancing
5418 @cindex advancing location counter
5419 @cindex current address, advancing
5420 Advance the location counter of the current section to
5421 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5422 expression with the same section as the current subsection. That is,
5423 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5424 wrong section, the @code{.org} directive is ignored. To be compatible
5425 with former assemblers, if the section of @var{new-lc} is absolute,
5426 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5427 is the same as the current subsection.
5429 @code{.org} may only increase the location counter, or leave it
5430 unchanged; you cannot use @code{.org} to move the location counter
5433 @c double negative used below "not undefined" because this is a specific
5434 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5435 @c section. doc@cygnus.com 18feb91
5436 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5437 may not be undefined. If you really detest this restriction we eagerly await
5438 a chance to share your improved assembler.
5440 Beware that the origin is relative to the start of the section, not
5441 to the start of the subsection. This is compatible with other
5442 people's assemblers.
5444 When the location counter (of the current subsection) is advanced, the
5445 intervening bytes are filled with @var{fill} which should be an
5446 absolute expression. If the comma and @var{fill} are omitted,
5447 @var{fill} defaults to zero.
5450 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5452 @cindex padding the location counter given a power of two
5453 @cindex @code{p2align} directive
5454 Pad the location counter (in the current subsection) to a particular
5455 storage boundary. The first expression (which must be absolute) is the
5456 number of low-order zero bits the location counter must have after
5457 advancement. For example @samp{.p2align 3} advances the location
5458 counter until it a multiple of 8. If the location counter is already a
5459 multiple of 8, no change is needed.
5461 The second expression (also absolute) gives the fill value to be stored in the
5462 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5463 padding bytes are normally zero. However, on some systems, if the section is
5464 marked as containing code and the fill value is omitted, the space is filled
5465 with no-op instructions.
5467 The third expression is also absolute, and is also optional. If it is present,
5468 it is the maximum number of bytes that should be skipped by this alignment
5469 directive. If doing the alignment would require skipping more bytes than the
5470 specified maximum, then the alignment is not done at all. You can omit the
5471 fill value (the second argument) entirely by simply using two commas after the
5472 required alignment; this can be useful if you want the alignment to be filled
5473 with no-op instructions when appropriate.
5475 @cindex @code{p2alignw} directive
5476 @cindex @code{p2alignl} directive
5477 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5478 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5479 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5480 fill pattern as a four byte longword value. For example, @code{.p2alignw
5481 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5482 filled in with the value 0x368d (the exact placement of the bytes depends upon
5483 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5488 @section @code{.popsection}
5490 @cindex @code{popsection} directive
5491 @cindex Section Stack
5492 This is one of the ELF section stack manipulation directives. The others are
5493 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5494 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5497 This directive replaces the current section (and subsection) with the top
5498 section (and subsection) on the section stack. This section is popped off the
5504 @section @code{.previous}
5506 @cindex @code{previous} directive
5507 @cindex Section Stack
5508 This is one of the ELF section stack manipulation directives. The others are
5509 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5510 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5511 (@pxref{PopSection}).
5513 This directive swaps the current section (and subsection) with most recently
5514 referenced section/subsection pair prior to this one. Multiple
5515 @code{.previous} directives in a row will flip between two sections (and their
5516 subsections). For example:
5528 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5534 # Now in section A subsection 1
5538 # Now in section B subsection 0
5541 # Now in section B subsection 1
5544 # Now in section B subsection 0
5548 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5549 section B and 0x9abc into subsection 1 of section B.
5551 In terms of the section stack, this directive swaps the current section with
5552 the top section on the section stack.
5556 @section @code{.print @var{string}}
5558 @cindex @code{print} directive
5559 @command{@value{AS}} will print @var{string} on the standard output during
5560 assembly. You must put @var{string} in double quotes.
5564 @section @code{.protected @var{names}}
5566 @cindex @code{protected} directive
5568 This is one of the ELF visibility directives. The other two are
5569 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5571 This directive overrides the named symbols default visibility (which is set by
5572 their binding: local, global or weak). The directive sets the visibility to
5573 @code{protected} which means that any references to the symbols from within the
5574 components that defines them must be resolved to the definition in that
5575 component, even if a definition in another component would normally preempt
5580 @section @code{.psize @var{lines} , @var{columns}}
5582 @cindex @code{psize} directive
5583 @cindex listing control: paper size
5584 @cindex paper size, for listings
5585 Use this directive to declare the number of lines---and, optionally, the
5586 number of columns---to use for each page, when generating listings.
5588 If you do not use @code{.psize}, listings use a default line-count
5589 of 60. You may omit the comma and @var{columns} specification; the
5590 default width is 200 columns.
5592 @command{@value{AS}} generates formfeeds whenever the specified number of
5593 lines is exceeded (or whenever you explicitly request one, using
5596 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5597 those explicitly specified with @code{.eject}.
5600 @section @code{.purgem @var{name}}
5602 @cindex @code{purgem} directive
5603 Undefine the macro @var{name}, so that later uses of the string will not be
5604 expanded. @xref{Macro}.
5608 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5610 @cindex @code{pushsection} directive
5611 @cindex Section Stack
5612 This is one of the ELF section stack manipulation directives. The others are
5613 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5614 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5617 This directive pushes the current section (and subsection) onto the
5618 top of the section stack, and then replaces the current section and
5619 subsection with @code{name} and @code{subsection}. The optional
5620 @code{flags}, @code{type} and @code{arguments} are treated the same
5621 as in the @code{.section} (@pxref{Section}) directive.
5625 @section @code{.quad @var{bignums}}
5627 @cindex @code{quad} directive
5628 @code{.quad} expects zero or more bignums, separated by commas. For
5629 each bignum, it emits
5631 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5632 warning message; and just takes the lowest order 8 bytes of the bignum.
5633 @cindex eight-byte integer
5634 @cindex integer, 8-byte
5636 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5637 hence @emph{quad}-word for 8 bytes.
5640 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5641 warning message; and just takes the lowest order 16 bytes of the bignum.
5642 @cindex sixteen-byte integer
5643 @cindex integer, 16-byte
5647 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5649 @cindex @code{reloc} directive
5650 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5651 @var{expression}. If @var{offset} is a number, the relocation is generated in
5652 the current section. If @var{offset} is an expression that resolves to a
5653 symbol plus offset, the relocation is generated in the given symbol's section.
5654 @var{expression}, if present, must resolve to a symbol plus addend or to an
5655 absolute value, but note that not all targets support an addend. e.g. ELF REL
5656 targets such as i386 store an addend in the section contents rather than in the
5657 relocation. This low level interface does not support addends stored in the
5661 @section @code{.rept @var{count}}
5663 @cindex @code{rept} directive
5664 Repeat the sequence of lines between the @code{.rept} directive and the next
5665 @code{.endr} directive @var{count} times.
5667 For example, assembling
5675 is equivalent to assembling
5684 @section @code{.sbttl "@var{subheading}"}
5686 @cindex @code{sbttl} directive
5687 @cindex subtitles for listings
5688 @cindex listing control: subtitle
5689 Use @var{subheading} as the title (third line, immediately after the
5690 title line) when generating assembly listings.
5692 This directive affects subsequent pages, as well as the current page if
5693 it appears within ten lines of the top of a page.
5697 @section @code{.scl @var{class}}
5699 @cindex @code{scl} directive
5700 @cindex symbol storage class (COFF)
5701 @cindex COFF symbol storage class
5702 Set the storage-class value for a symbol. This directive may only be
5703 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5704 whether a symbol is static or external, or it may record further
5705 symbolic debugging information.
5708 The @samp{.scl} directive is primarily associated with COFF output; when
5709 configured to generate @code{b.out} output format, @command{@value{AS}}
5710 accepts this directive but ignores it.
5716 @section @code{.section @var{name}}
5718 @cindex named section
5719 Use the @code{.section} directive to assemble the following code into a section
5722 This directive is only supported for targets that actually support arbitrarily
5723 named sections; on @code{a.out} targets, for example, it is not accepted, even
5724 with a standard @code{a.out} section name.
5728 @c only print the extra heading if both COFF and ELF are set
5729 @subheading COFF Version
5732 @cindex @code{section} directive (COFF version)
5733 For COFF targets, the @code{.section} directive is used in one of the following
5737 .section @var{name}[, "@var{flags}"]
5738 .section @var{name}[, @var{subsection}]
5741 If the optional argument is quoted, it is taken as flags to use for the
5742 section. Each flag is a single character. The following flags are recognized:
5745 bss section (uninitialized data)
5747 section is not loaded
5757 shared section (meaningful for PE targets)
5759 ignored. (For compatibility with the ELF version)
5761 section is not readable (meaningful for PE targets)
5764 If no flags are specified, the default flags depend upon the section name. If
5765 the section name is not recognized, the default will be for the section to be
5766 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5767 from the section, rather than adding them, so if they are used on their own it
5768 will be as if no flags had been specified at all.
5770 If the optional argument to the @code{.section} directive is not quoted, it is
5771 taken as a subsection number (@pxref{Sub-Sections}).
5776 @c only print the extra heading if both COFF and ELF are set
5777 @subheading ELF Version
5780 @cindex Section Stack
5781 This is one of the ELF section stack manipulation directives. The others are
5782 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5783 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5784 @code{.previous} (@pxref{Previous}).
5786 @cindex @code{section} directive (ELF version)
5787 For ELF targets, the @code{.section} directive is used like this:
5790 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5793 The optional @var{flags} argument is a quoted string which may contain any
5794 combination of the following characters:
5797 section is allocatable
5801 section is executable
5803 section is mergeable
5805 section contains zero terminated strings
5807 section is a member of a section group
5809 section is used for thread-local-storage
5812 The optional @var{type} argument may contain one of the following constants:
5815 section contains data
5817 section does not contain data (i.e., section only occupies space)
5819 section contains data which is used by things other than the program
5821 section contains an array of pointers to init functions
5823 section contains an array of pointers to finish functions
5824 @item @@preinit_array
5825 section contains an array of pointers to pre-init functions
5828 Many targets only support the first three section types.
5830 Note on targets where the @code{@@} character is the start of a comment (eg
5831 ARM) then another character is used instead. For example the ARM port uses the
5834 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5835 be specified as well as an extra argument---@var{entsize}---like this:
5838 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5841 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5842 constants, each @var{entsize} octets long. Sections with both @code{M} and
5843 @code{S} must contain zero terminated strings where each character is
5844 @var{entsize} bytes long. The linker may remove duplicates within sections with
5845 the same name, same entity size and same flags. @var{entsize} must be an
5846 absolute expression. For sections with both @code{M} and @code{S}, a string
5847 which is a suffix of a larger string is considered a duplicate. Thus
5848 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5849 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5851 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5852 be present along with an additional field like this:
5855 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5858 The @var{GroupName} field specifies the name of the section group to which this
5859 particular section belongs. The optional linkage field can contain:
5862 indicates that only one copy of this section should be retained
5867 Note: if both the @var{M} and @var{G} flags are present then the fields for
5868 the Merge flag should come first, like this:
5871 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5874 If no flags are specified, the default flags depend upon the section name. If
5875 the section name is not recognized, the default will be for the section to have
5876 none of the above flags: it will not be allocated in memory, nor writable, nor
5877 executable. The section will contain data.
5879 For ELF targets, the assembler supports another type of @code{.section}
5880 directive for compatibility with the Solaris assembler:
5883 .section "@var{name}"[, @var{flags}...]
5886 Note that the section name is quoted. There may be a sequence of comma
5890 section is allocatable
5894 section is executable
5896 section is used for thread local storage
5899 This directive replaces the current section and subsection. See the
5900 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5901 some examples of how this directive and the other section stack directives
5907 @section @code{.set @var{symbol}, @var{expression}}
5909 @cindex @code{set} directive
5910 @cindex symbol value, setting
5911 Set the value of @var{symbol} to @var{expression}. This
5912 changes @var{symbol}'s value and type to conform to
5913 @var{expression}. If @var{symbol} was flagged as external, it remains
5914 flagged (@pxref{Symbol Attributes}).
5916 You may @code{.set} a symbol many times in the same assembly.
5918 If you @code{.set} a global symbol, the value stored in the object
5919 file is the last value stored into it.
5922 The syntax for @code{set} on the HPPA is
5923 @samp{@var{symbol} .set @var{expression}}.
5927 On Z80 @code{set} is a real instruction, use
5928 @samp{@var{symbol} defl @var{expression}} instead.
5932 @section @code{.short @var{expressions}}
5934 @cindex @code{short} directive
5936 @code{.short} is normally the same as @samp{.word}.
5937 @xref{Word,,@code{.word}}.
5939 In some configurations, however, @code{.short} and @code{.word} generate
5940 numbers of different lengths. @xref{Machine Dependencies}.
5944 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5947 This expects zero or more @var{expressions}, and emits
5948 a 16 bit number for each.
5953 @section @code{.single @var{flonums}}
5955 @cindex @code{single} directive
5956 @cindex floating point numbers (single)
5957 This directive assembles zero or more flonums, separated by commas. It
5958 has the same effect as @code{.float}.
5960 The exact kind of floating point numbers emitted depends on how
5961 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5965 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5966 numbers in @sc{ieee} format.
5972 @section @code{.size}
5974 This directive is used to set the size associated with a symbol.
5978 @c only print the extra heading if both COFF and ELF are set
5979 @subheading COFF Version
5982 @cindex @code{size} directive (COFF version)
5983 For COFF targets, the @code{.size} directive is only permitted inside
5984 @code{.def}/@code{.endef} pairs. It is used like this:
5987 .size @var{expression}
5991 @samp{.size} is only meaningful when generating COFF format output; when
5992 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5999 @c only print the extra heading if both COFF and ELF are set
6000 @subheading ELF Version
6003 @cindex @code{size} directive (ELF version)
6004 For ELF targets, the @code{.size} directive is used like this:
6007 .size @var{name} , @var{expression}
6010 This directive sets the size associated with a symbol @var{name}.
6011 The size in bytes is computed from @var{expression} which can make use of label
6012 arithmetic. This directive is typically used to set the size of function
6017 @ifclear no-space-dir
6019 @section @code{.skip @var{size} , @var{fill}}
6021 @cindex @code{skip} directive
6022 @cindex filling memory
6023 This directive emits @var{size} bytes, each of value @var{fill}. Both
6024 @var{size} and @var{fill} are absolute expressions. If the comma and
6025 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6030 @section @code{.sleb128 @var{expressions}}
6032 @cindex @code{sleb128} directive
6033 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6034 compact, variable length representation of numbers used by the DWARF
6035 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6037 @ifclear no-space-dir
6039 @section @code{.space @var{size} , @var{fill}}
6041 @cindex @code{space} directive
6042 @cindex filling memory
6043 This directive emits @var{size} bytes, each of value @var{fill}. Both
6044 @var{size} and @var{fill} are absolute expressions. If the comma
6045 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6050 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6051 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6052 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6053 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6061 @section @code{.stabd, .stabn, .stabs}
6063 @cindex symbolic debuggers, information for
6064 @cindex @code{stab@var{x}} directives
6065 There are three directives that begin @samp{.stab}.
6066 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6067 The symbols are not entered in the @command{@value{AS}} hash table: they
6068 cannot be referenced elsewhere in the source file.
6069 Up to five fields are required:
6073 This is the symbol's name. It may contain any character except
6074 @samp{\000}, so is more general than ordinary symbol names. Some
6075 debuggers used to code arbitrarily complex structures into symbol names
6079 An absolute expression. The symbol's type is set to the low 8 bits of
6080 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6081 and debuggers choke on silly bit patterns.
6084 An absolute expression. The symbol's ``other'' attribute is set to the
6085 low 8 bits of this expression.
6088 An absolute expression. The symbol's descriptor is set to the low 16
6089 bits of this expression.
6092 An absolute expression which becomes the symbol's value.
6095 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6096 or @code{.stabs} statement, the symbol has probably already been created;
6097 you get a half-formed symbol in your object file. This is
6098 compatible with earlier assemblers!
6101 @cindex @code{stabd} directive
6102 @item .stabd @var{type} , @var{other} , @var{desc}
6104 The ``name'' of the symbol generated is not even an empty string.
6105 It is a null pointer, for compatibility. Older assemblers used a
6106 null pointer so they didn't waste space in object files with empty
6109 The symbol's value is set to the location counter,
6110 relocatably. When your program is linked, the value of this symbol
6111 is the address of the location counter when the @code{.stabd} was
6114 @cindex @code{stabn} directive
6115 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6116 The name of the symbol is set to the empty string @code{""}.
6118 @cindex @code{stabs} directive
6119 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6120 All five fields are specified.
6126 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6127 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6129 @cindex string, copying to object file
6130 @cindex string8, copying to object file
6131 @cindex string16, copying to object file
6132 @cindex string32, copying to object file
6133 @cindex string64, copying to object file
6134 @cindex @code{string} directive
6135 @cindex @code{string8} directive
6136 @cindex @code{string16} directive
6137 @cindex @code{string32} directive
6138 @cindex @code{string64} directive
6140 Copy the characters in @var{str} to the object file. You may specify more than
6141 one string to copy, separated by commas. Unless otherwise specified for a
6142 particular machine, the assembler marks the end of each string with a 0 byte.
6143 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6145 The variants @code{string16}, @code{string32} and @code{string64} differ from
6146 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6147 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6148 are stored in target endianness byte order.
6154 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6155 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6160 @section @code{.struct @var{expression}}
6162 @cindex @code{struct} directive
6163 Switch to the absolute section, and set the section offset to @var{expression},
6164 which must be an absolute expression. You might use this as follows:
6173 This would define the symbol @code{field1} to have the value 0, the symbol
6174 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6175 value 8. Assembly would be left in the absolute section, and you would need to
6176 use a @code{.section} directive of some sort to change to some other section
6177 before further assembly.
6181 @section @code{.subsection @var{name}}
6183 @cindex @code{subsection} directive
6184 @cindex Section Stack
6185 This is one of the ELF section stack manipulation directives. The others are
6186 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6187 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6190 This directive replaces the current subsection with @code{name}. The current
6191 section is not changed. The replaced subsection is put onto the section stack
6192 in place of the then current top of stack subsection.
6197 @section @code{.symver}
6198 @cindex @code{symver} directive
6199 @cindex symbol versioning
6200 @cindex versions of symbols
6201 Use the @code{.symver} directive to bind symbols to specific version nodes
6202 within a source file. This is only supported on ELF platforms, and is
6203 typically used when assembling files to be linked into a shared library.
6204 There are cases where it may make sense to use this in objects to be bound
6205 into an application itself so as to override a versioned symbol from a
6208 For ELF targets, the @code{.symver} directive can be used like this:
6210 .symver @var{name}, @var{name2@@nodename}
6212 If the symbol @var{name} is defined within the file
6213 being assembled, the @code{.symver} directive effectively creates a symbol
6214 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6215 just don't try and create a regular alias is that the @var{@@} character isn't
6216 permitted in symbol names. The @var{name2} part of the name is the actual name
6217 of the symbol by which it will be externally referenced. The name @var{name}
6218 itself is merely a name of convenience that is used so that it is possible to
6219 have definitions for multiple versions of a function within a single source
6220 file, and so that the compiler can unambiguously know which version of a
6221 function is being mentioned. The @var{nodename} portion of the alias should be
6222 the name of a node specified in the version script supplied to the linker when
6223 building a shared library. If you are attempting to override a versioned
6224 symbol from a shared library, then @var{nodename} should correspond to the
6225 nodename of the symbol you are trying to override.
6227 If the symbol @var{name} is not defined within the file being assembled, all
6228 references to @var{name} will be changed to @var{name2@@nodename}. If no
6229 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6232 Another usage of the @code{.symver} directive is:
6234 .symver @var{name}, @var{name2@@@@nodename}
6236 In this case, the symbol @var{name} must exist and be defined within
6237 the file being assembled. It is similar to @var{name2@@nodename}. The
6238 difference is @var{name2@@@@nodename} will also be used to resolve
6239 references to @var{name2} by the linker.
6241 The third usage of the @code{.symver} directive is:
6243 .symver @var{name}, @var{name2@@@@@@nodename}
6245 When @var{name} is not defined within the
6246 file being assembled, it is treated as @var{name2@@nodename}. When
6247 @var{name} is defined within the file being assembled, the symbol
6248 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6253 @section @code{.tag @var{structname}}
6255 @cindex COFF structure debugging
6256 @cindex structure debugging, COFF
6257 @cindex @code{tag} directive
6258 This directive is generated by compilers to include auxiliary debugging
6259 information in the symbol table. It is only permitted inside
6260 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6261 definitions in the symbol table with instances of those structures.
6264 @samp{.tag} is only used when generating COFF format output; when
6265 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6271 @section @code{.text @var{subsection}}
6273 @cindex @code{text} directive
6274 Tells @command{@value{AS}} to assemble the following statements onto the end of
6275 the text subsection numbered @var{subsection}, which is an absolute
6276 expression. If @var{subsection} is omitted, subsection number zero
6280 @section @code{.title "@var{heading}"}
6282 @cindex @code{title} directive
6283 @cindex listing control: title line
6284 Use @var{heading} as the title (second line, immediately after the
6285 source file name and pagenumber) when generating assembly listings.
6287 This directive affects subsequent pages, as well as the current page if
6288 it appears within ten lines of the top of a page.
6292 @section @code{.type}
6294 This directive is used to set the type of a symbol.
6298 @c only print the extra heading if both COFF and ELF are set
6299 @subheading COFF Version
6302 @cindex COFF symbol type
6303 @cindex symbol type, COFF
6304 @cindex @code{type} directive (COFF version)
6305 For COFF targets, this directive is permitted only within
6306 @code{.def}/@code{.endef} pairs. It is used like this:
6312 This records the integer @var{int} as the type attribute of a symbol table
6316 @samp{.type} is associated only with COFF format output; when
6317 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6318 directive but ignores it.
6324 @c only print the extra heading if both COFF and ELF are set
6325 @subheading ELF Version
6328 @cindex ELF symbol type
6329 @cindex symbol type, ELF
6330 @cindex @code{type} directive (ELF version)
6331 For ELF targets, the @code{.type} directive is used like this:
6334 .type @var{name} , @var{type description}
6337 This sets the type of symbol @var{name} to be either a
6338 function symbol or an object symbol. There are five different syntaxes
6339 supported for the @var{type description} field, in order to provide
6340 compatibility with various other assemblers.
6342 Because some of the characters used in these syntaxes (such as @samp{@@} and
6343 @samp{#}) are comment characters for some architectures, some of the syntaxes
6344 below do not work on all architectures. The first variant will be accepted by
6345 the GNU assembler on all architectures so that variant should be used for
6346 maximum portability, if you do not need to assemble your code with other
6349 The syntaxes supported are:
6352 .type <name> STT_<TYPE_IN_UPPER_CASE>
6353 .type <name>,#<type>
6354 .type <name>,@@<type>
6355 .type <name>,%<type>
6356 .type <name>,"<type>"
6359 The types supported are:
6364 Mark the symbol as being a function name.
6367 @itemx gnu_indirect_function
6368 Mark the symbol as an indirect function when evaluated during reloc
6369 processing. (This is only supported on Linux targeted assemblers).
6373 Mark the symbol as being a data object.
6377 Mark the symbol as being a thead-local data object.
6381 Mark the symbol as being a common data object.
6385 Does not mark the symbol in any way. It is supported just for completeness.
6387 @item gnu_unique_object
6388 Marks the symbol as being a globally unique data object. The dynamic linker
6389 will make sure that in the entire process there is just one symbol with this
6390 name and type in use. (This is only supported on Linux targeted assemblers).
6394 Note: Some targets support extra types in addition to those listed above.
6400 @section @code{.uleb128 @var{expressions}}
6402 @cindex @code{uleb128} directive
6403 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6404 compact, variable length representation of numbers used by the DWARF
6405 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6409 @section @code{.val @var{addr}}
6411 @cindex @code{val} directive
6412 @cindex COFF value attribute
6413 @cindex value attribute, COFF
6414 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6415 records the address @var{addr} as the value attribute of a symbol table
6419 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6420 configured for @code{b.out}, it accepts this directive but ignores it.
6426 @section @code{.version "@var{string}"}
6428 @cindex @code{version} directive
6429 This directive creates a @code{.note} section and places into it an ELF
6430 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6435 @section @code{.vtable_entry @var{table}, @var{offset}}
6437 @cindex @code{vtable_entry} directive
6438 This directive finds or creates a symbol @code{table} and creates a
6439 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6442 @section @code{.vtable_inherit @var{child}, @var{parent}}
6444 @cindex @code{vtable_inherit} directive
6445 This directive finds the symbol @code{child} and finds or creates the symbol
6446 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6447 parent whose addend is the value of the child symbol. As a special case the
6448 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6452 @section @code{.warning "@var{string}"}
6453 @cindex warning directive
6454 Similar to the directive @code{.error}
6455 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6458 @section @code{.weak @var{names}}
6460 @cindex @code{weak} directive
6461 This directive sets the weak attribute on the comma separated list of symbol
6462 @code{names}. If the symbols do not already exist, they will be created.
6464 On COFF targets other than PE, weak symbols are a GNU extension. This
6465 directive sets the weak attribute on the comma separated list of symbol
6466 @code{names}. If the symbols do not already exist, they will be created.
6468 On the PE target, weak symbols are supported natively as weak aliases.
6469 When a weak symbol is created that is not an alias, GAS creates an
6470 alternate symbol to hold the default value.
6473 @section @code{.weakref @var{alias}, @var{target}}
6475 @cindex @code{weakref} directive
6476 This directive creates an alias to the target symbol that enables the symbol to
6477 be referenced with weak-symbol semantics, but without actually making it weak.
6478 If direct references or definitions of the symbol are present, then the symbol
6479 will not be weak, but if all references to it are through weak references, the
6480 symbol will be marked as weak in the symbol table.
6482 The effect is equivalent to moving all references to the alias to a separate
6483 assembly source file, renaming the alias to the symbol in it, declaring the
6484 symbol as weak there, and running a reloadable link to merge the object files
6485 resulting from the assembly of the new source file and the old source file that
6486 had the references to the alias removed.
6488 The alias itself never makes to the symbol table, and is entirely handled
6489 within the assembler.
6492 @section @code{.word @var{expressions}}
6494 @cindex @code{word} directive
6495 This directive expects zero or more @var{expressions}, of any section,
6496 separated by commas.
6499 For each expression, @command{@value{AS}} emits a 32-bit number.
6502 For each expression, @command{@value{AS}} emits a 16-bit number.
6507 The size of the number emitted, and its byte order,
6508 depend on what target computer the assembly is for.
6511 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6512 @c happen---32-bit addressability, period; no long/short jumps.
6513 @ifset DIFF-TBL-KLUGE
6514 @cindex difference tables altered
6515 @cindex altered difference tables
6517 @emph{Warning: Special Treatment to support Compilers}
6521 Machines with a 32-bit address space, but that do less than 32-bit
6522 addressing, require the following special treatment. If the machine of
6523 interest to you does 32-bit addressing (or doesn't require it;
6524 @pxref{Machine Dependencies}), you can ignore this issue.
6527 In order to assemble compiler output into something that works,
6528 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6529 Directives of the form @samp{.word sym1-sym2} are often emitted by
6530 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6531 directive of the form @samp{.word sym1-sym2}, and the difference between
6532 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6533 creates a @dfn{secondary jump table}, immediately before the next label.
6534 This secondary jump table is preceded by a short-jump to the
6535 first byte after the secondary table. This short-jump prevents the flow
6536 of control from accidentally falling into the new table. Inside the
6537 table is a long-jump to @code{sym2}. The original @samp{.word}
6538 contains @code{sym1} minus the address of the long-jump to
6541 If there were several occurrences of @samp{.word sym1-sym2} before the
6542 secondary jump table, all of them are adjusted. If there was a
6543 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6544 long-jump to @code{sym4} is included in the secondary jump table,
6545 and the @code{.word} directives are adjusted to contain @code{sym3}
6546 minus the address of the long-jump to @code{sym4}; and so on, for as many
6547 entries in the original jump table as necessary.
6550 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6551 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6552 assembly language programmers.
6555 @c end DIFF-TBL-KLUGE
6558 @section Deprecated Directives
6560 @cindex deprecated directives
6561 @cindex obsolescent directives
6562 One day these directives won't work.
6563 They are included for compatibility with older assemblers.
6570 @node Object Attributes
6571 @chapter Object Attributes
6572 @cindex object attributes
6574 @command{@value{AS}} assembles source files written for a specific architecture
6575 into object files for that architecture. But not all object files are alike.
6576 Many architectures support incompatible variations. For instance, floating
6577 point arguments might be passed in floating point registers if the object file
6578 requires hardware floating point support---or floating point arguments might be
6579 passed in integer registers if the object file supports processors with no
6580 hardware floating point unit. Or, if two objects are built for different
6581 generations of the same architecture, the combination may require the
6582 newer generation at run-time.
6584 This information is useful during and after linking. At link time,
6585 @command{@value{LD}} can warn about incompatible object files. After link
6586 time, tools like @command{gdb} can use it to process the linked file
6589 Compatibility information is recorded as a series of object attributes. Each
6590 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6591 string, and indicates who sets the meaning of the tag. The tag is an integer,
6592 and indicates what property the attribute describes. The value may be a string
6593 or an integer, and indicates how the property affects this object. Missing
6594 attributes are the same as attributes with a zero value or empty string value.
6596 Object attributes were developed as part of the ABI for the ARM Architecture.
6597 The file format is documented in @cite{ELF for the ARM Architecture}.
6600 * GNU Object Attributes:: @sc{gnu} Object Attributes
6601 * Defining New Object Attributes:: Defining New Object Attributes
6604 @node GNU Object Attributes
6605 @section @sc{gnu} Object Attributes
6607 The @code{.gnu_attribute} directive records an object attribute
6608 with vendor @samp{gnu}.
6610 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6611 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6612 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6613 2} is set for architecture-independent attributes and clear for
6614 architecture-dependent ones.
6616 @subsection Common @sc{gnu} attributes
6618 These attributes are valid on all architectures.
6621 @item Tag_compatibility (32)
6622 The compatibility attribute takes an integer flag value and a vendor name. If
6623 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6624 then the file is only compatible with the named toolchain. If it is greater
6625 than 1, the file can only be processed by other toolchains under some private
6626 arrangement indicated by the flag value and the vendor name.
6629 @subsection MIPS Attributes
6632 @item Tag_GNU_MIPS_ABI_FP (4)
6633 The floating-point ABI used by this object file. The value will be:
6637 0 for files not affected by the floating-point ABI.
6639 1 for files using the hardware floating-point with a standard double-precision
6642 2 for files using the hardware floating-point ABI with a single-precision FPU.
6644 3 for files using the software floating-point ABI.
6646 4 for files using the hardware floating-point ABI with 64-bit wide
6647 double-precision floating-point registers and 32-bit wide general
6652 @subsection PowerPC Attributes
6655 @item Tag_GNU_Power_ABI_FP (4)
6656 The floating-point ABI used by this object file. The value will be:
6660 0 for files not affected by the floating-point ABI.
6662 1 for files using double-precision hardware floating-point ABI.
6664 2 for files using the software floating-point ABI.
6666 3 for files using single-precision hardware floating-point ABI.
6669 @item Tag_GNU_Power_ABI_Vector (8)
6670 The vector ABI used by this object file. The value will be:
6674 0 for files not affected by the vector ABI.
6676 1 for files using general purpose registers to pass vectors.
6678 2 for files using AltiVec registers to pass vectors.
6680 3 for files using SPE registers to pass vectors.
6684 @node Defining New Object Attributes
6685 @section Defining New Object Attributes
6687 If you want to define a new @sc{gnu} object attribute, here are the places you
6688 will need to modify. New attributes should be discussed on the @samp{binutils}
6693 This manual, which is the official register of attributes.
6695 The header for your architecture @file{include/elf}, to define the tag.
6697 The @file{bfd} support file for your architecture, to merge the attribute
6698 and issue any appropriate link warnings.
6700 Test cases in @file{ld/testsuite} for merging and link warnings.
6702 @file{binutils/readelf.c} to display your attribute.
6704 GCC, if you want the compiler to mark the attribute automatically.
6710 @node Machine Dependencies
6711 @chapter Machine Dependent Features
6713 @cindex machine dependencies
6714 The machine instruction sets are (almost by definition) different on
6715 each machine where @command{@value{AS}} runs. Floating point representations
6716 vary as well, and @command{@value{AS}} often supports a few additional
6717 directives or command-line options for compatibility with other
6718 assemblers on a particular platform. Finally, some versions of
6719 @command{@value{AS}} support special pseudo-instructions for branch
6722 This chapter discusses most of these differences, though it does not
6723 include details on any machine's instruction set. For details on that
6724 subject, see the hardware manufacturer's manual.
6728 * Alpha-Dependent:: Alpha Dependent Features
6731 * ARC-Dependent:: ARC Dependent Features
6734 * ARM-Dependent:: ARM Dependent Features
6737 * AVR-Dependent:: AVR Dependent Features
6740 * Blackfin-Dependent:: Blackfin Dependent Features
6743 * CR16-Dependent:: CR16 Dependent Features
6746 * CRIS-Dependent:: CRIS Dependent Features
6749 * D10V-Dependent:: D10V Dependent Features
6752 * D30V-Dependent:: D30V Dependent Features
6755 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6758 * HPPA-Dependent:: HPPA Dependent Features
6761 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6764 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6767 * i860-Dependent:: Intel 80860 Dependent Features
6770 * i960-Dependent:: Intel 80960 Dependent Features
6773 * IA-64-Dependent:: Intel IA-64 Dependent Features
6776 * IP2K-Dependent:: IP2K Dependent Features
6779 * LM32-Dependent:: LM32 Dependent Features
6782 * M32C-Dependent:: M32C Dependent Features
6785 * M32R-Dependent:: M32R Dependent Features
6788 * M68K-Dependent:: M680x0 Dependent Features
6791 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6794 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6797 * MIPS-Dependent:: MIPS Dependent Features
6800 * MMIX-Dependent:: MMIX Dependent Features
6803 * MSP430-Dependent:: MSP430 Dependent Features
6806 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6807 * SH64-Dependent:: SuperH SH64 Dependent Features
6810 * PDP-11-Dependent:: PDP-11 Dependent Features
6813 * PJ-Dependent:: picoJava Dependent Features
6816 * PPC-Dependent:: PowerPC Dependent Features
6819 * S/390-Dependent:: IBM S/390 Dependent Features
6822 * SCORE-Dependent:: SCORE Dependent Features
6825 * Sparc-Dependent:: SPARC Dependent Features
6828 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6831 * V850-Dependent:: V850 Dependent Features
6834 * Xtensa-Dependent:: Xtensa Dependent Features
6837 * Z80-Dependent:: Z80 Dependent Features
6840 * Z8000-Dependent:: Z8000 Dependent Features
6843 * Vax-Dependent:: VAX Dependent Features
6850 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6851 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6852 @c peculiarity: to preserve cross-references, there must be a node called
6853 @c "Machine Dependencies". Hence the conditional nodenames in each
6854 @c major node below. Node defaulting in makeinfo requires adjacency of
6855 @c node and sectioning commands; hence the repetition of @chapter BLAH
6856 @c in both conditional blocks.
6859 @include c-alpha.texi
6875 @include c-bfin.texi
6879 @include c-cr16.texi
6883 @include c-cris.texi
6888 @node Machine Dependencies
6889 @chapter Machine Dependent Features
6891 The machine instruction sets are different on each Renesas chip family,
6892 and there are also some syntax differences among the families. This
6893 chapter describes the specific @command{@value{AS}} features for each
6897 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6898 * SH-Dependent:: Renesas SH Dependent Features
6905 @include c-d10v.texi
6909 @include c-d30v.texi
6913 @include c-h8300.texi
6917 @include c-hppa.texi
6921 @include c-i370.texi
6925 @include c-i386.texi
6929 @include c-i860.texi
6933 @include c-i960.texi
6937 @include c-ia64.texi
6941 @include c-ip2k.texi
6945 @include c-lm32.texi
6949 @include c-m32c.texi
6953 @include c-m32r.texi
6957 @include c-m68k.texi
6961 @include c-m68hc11.texi
6965 @include c-microblaze.texi
6969 @include c-mips.texi
6973 @include c-mmix.texi
6977 @include c-msp430.texi
6981 @include c-ns32k.texi
6985 @include c-pdp11.texi
6997 @include c-s390.texi
7001 @include c-score.texi
7006 @include c-sh64.texi
7010 @include c-sparc.texi
7014 @include c-tic54x.texi
7030 @include c-v850.texi
7034 @include c-xtensa.texi
7038 @c reverse effect of @down at top of generic Machine-Dep chapter
7042 @node Reporting Bugs
7043 @chapter Reporting Bugs
7044 @cindex bugs in assembler
7045 @cindex reporting bugs in assembler
7047 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7049 Reporting a bug may help you by bringing a solution to your problem, or it may
7050 not. But in any case the principal function of a bug report is to help the
7051 entire community by making the next version of @command{@value{AS}} work better.
7052 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7054 In order for a bug report to serve its purpose, you must include the
7055 information that enables us to fix the bug.
7058 * Bug Criteria:: Have you found a bug?
7059 * Bug Reporting:: How to report bugs
7063 @section Have You Found a Bug?
7064 @cindex bug criteria
7066 If you are not sure whether you have found a bug, here are some guidelines:
7069 @cindex fatal signal
7070 @cindex assembler crash
7071 @cindex crash of assembler
7073 If the assembler gets a fatal signal, for any input whatever, that is a
7074 @command{@value{AS}} bug. Reliable assemblers never crash.
7076 @cindex error on valid input
7078 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7080 @cindex invalid input
7082 If @command{@value{AS}} does not produce an error message for invalid input, that
7083 is a bug. However, you should note that your idea of ``invalid input'' might
7084 be our idea of ``an extension'' or ``support for traditional practice''.
7087 If you are an experienced user of assemblers, your suggestions for improvement
7088 of @command{@value{AS}} are welcome in any case.
7092 @section How to Report Bugs
7094 @cindex assembler bugs, reporting
7096 A number of companies and individuals offer support for @sc{gnu} products. If
7097 you obtained @command{@value{AS}} from a support organization, we recommend you
7098 contact that organization first.
7100 You can find contact information for many support companies and
7101 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7105 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7109 The fundamental principle of reporting bugs usefully is this:
7110 @strong{report all the facts}. If you are not sure whether to state a
7111 fact or leave it out, state it!
7113 Often people omit facts because they think they know what causes the problem
7114 and assume that some details do not matter. Thus, you might assume that the
7115 name of a symbol you use in an example does not matter. Well, probably it does
7116 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7117 happens to fetch from the location where that name is stored in memory;
7118 perhaps, if the name were different, the contents of that location would fool
7119 the assembler into doing the right thing despite the bug. Play it safe and
7120 give a specific, complete example. That is the easiest thing for you to do,
7121 and the most helpful.
7123 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7124 it is new to us. Therefore, always write your bug reports on the assumption
7125 that the bug has not been reported previously.
7127 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7128 bell?'' This cannot help us fix a bug, so it is basically useless. We
7129 respond by asking for enough details to enable us to investigate.
7130 You might as well expedite matters by sending them to begin with.
7132 To enable us to fix the bug, you should include all these things:
7136 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7137 it with the @samp{--version} argument.
7139 Without this, we will not know whether there is any point in looking for
7140 the bug in the current version of @command{@value{AS}}.
7143 Any patches you may have applied to the @command{@value{AS}} source.
7146 The type of machine you are using, and the operating system name and
7150 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7154 The command arguments you gave the assembler to assemble your example and
7155 observe the bug. To guarantee you will not omit something important, list them
7156 all. A copy of the Makefile (or the output from make) is sufficient.
7158 If we were to try to guess the arguments, we would probably guess wrong
7159 and then we might not encounter the bug.
7162 A complete input file that will reproduce the bug. If the bug is observed when
7163 the assembler is invoked via a compiler, send the assembler source, not the
7164 high level language source. Most compilers will produce the assembler source
7165 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7166 the options @samp{-v --save-temps}; this will save the assembler source in a
7167 file with an extension of @file{.s}, and also show you exactly how
7168 @command{@value{AS}} is being run.
7171 A description of what behavior you observe that you believe is
7172 incorrect. For example, ``It gets a fatal signal.''
7174 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7175 will certainly notice it. But if the bug is incorrect output, we might not
7176 notice unless it is glaringly wrong. You might as well not give us a chance to
7179 Even if the problem you experience is a fatal signal, you should still say so
7180 explicitly. Suppose something strange is going on, such as, your copy of
7181 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7182 library on your system. (This has happened!) Your copy might crash and ours
7183 would not. If you told us to expect a crash, then when ours fails to crash, we
7184 would know that the bug was not happening for us. If you had not told us to
7185 expect a crash, then we would not be able to draw any conclusion from our
7189 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7190 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7191 option. Always send diffs from the old file to the new file. If you even
7192 discuss something in the @command{@value{AS}} source, refer to it by context, not
7195 The line numbers in our development sources will not match those in your
7196 sources. Your line numbers would convey no useful information to us.
7199 Here are some things that are not necessary:
7203 A description of the envelope of the bug.
7205 Often people who encounter a bug spend a lot of time investigating
7206 which changes to the input file will make the bug go away and which
7207 changes will not affect it.
7209 This is often time consuming and not very useful, because the way we
7210 will find the bug is by running a single example under the debugger
7211 with breakpoints, not by pure deduction from a series of examples.
7212 We recommend that you save your time for something else.
7214 Of course, if you can find a simpler example to report @emph{instead}
7215 of the original one, that is a convenience for us. Errors in the
7216 output will be easier to spot, running under the debugger will take
7217 less time, and so on.
7219 However, simplification is not vital; if you do not want to do this,
7220 report the bug anyway and send us the entire test case you used.
7223 A patch for the bug.
7225 A patch for the bug does help us if it is a good one. But do not omit
7226 the necessary information, such as the test case, on the assumption that
7227 a patch is all we need. We might see problems with your patch and decide
7228 to fix the problem another way, or we might not understand it at all.
7230 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7231 construct an example that will make the program follow a certain path through
7232 the code. If you do not send us the example, we will not be able to construct
7233 one, so we will not be able to verify that the bug is fixed.
7235 And if we cannot understand what bug you are trying to fix, or why your
7236 patch should be an improvement, we will not install it. A test case will
7237 help us to understand.
7240 A guess about what the bug is or what it depends on.
7242 Such guesses are usually wrong. Even we cannot guess right about such
7243 things without first using the debugger to find the facts.
7246 @node Acknowledgements
7247 @chapter Acknowledgements
7249 If you have contributed to GAS and your name isn't listed here,
7250 it is not meant as a slight. We just don't know about it. Send mail to the
7251 maintainer, and we'll correct the situation. Currently
7253 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7255 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7258 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7259 information and the 68k series machines, most of the preprocessing pass, and
7260 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7262 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7263 many bug fixes, including merging support for several processors, breaking GAS
7264 up to handle multiple object file format back ends (including heavy rewrite,
7265 testing, an integration of the coff and b.out back ends), adding configuration
7266 including heavy testing and verification of cross assemblers and file splits
7267 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7268 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7269 port (including considerable amounts of reverse engineering), a SPARC opcode
7270 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7271 assertions and made them work, much other reorganization, cleanup, and lint.
7273 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7274 in format-specific I/O modules.
7276 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7277 has done much work with it since.
7279 The Intel 80386 machine description was written by Eliot Dresselhaus.
7281 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7283 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7284 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7286 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7287 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7288 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7289 support a.out format.
7291 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7292 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7293 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7294 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7297 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7298 simplified the configuration of which versions accept which directives. He
7299 updated the 68k machine description so that Motorola's opcodes always produced
7300 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7301 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7302 cross-compilation support, and one bug in relaxation that took a week and
7303 required the proverbial one-bit fix.
7305 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7306 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7307 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7308 PowerPC assembler, and made a few other minor patches.
7310 Steve Chamberlain made GAS able to generate listings.
7312 Hewlett-Packard contributed support for the HP9000/300.
7314 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7315 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7316 formats). This work was supported by both the Center for Software Science at
7317 the University of Utah and Cygnus Support.
7319 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7320 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7321 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7322 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7323 and some initial 64-bit support).
7325 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7327 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7328 support for openVMS/Alpha.
7330 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7333 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7334 Inc.@: added support for Xtensa processors.
7336 Several engineers at Cygnus Support have also provided many small bug fixes and
7337 configuration enhancements.
7339 Jon Beniston added support for the Lattice Mico32 architecture.
7341 Many others have contributed large or small bugfixes and enhancements. If
7342 you have contributed significant work and are not mentioned on this list, and
7343 want to be, let us know. Some of the history has been lost; we are not
7344 intentionally leaving anyone out.
7346 @node GNU Free Documentation License
7347 @appendix GNU Free Documentation License
7351 @unnumbered AS Index
projects / binutils-gdb.git / blob