1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2016 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2016 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2016 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@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}]
238 [@b{--no-pad-sections}]
239 [@b{-o} @var{objfile}] [@b{-R}]
240 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
242 [@b{-v}] [@b{-version}] [@b{--version}]
243 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
244 [@b{-Z}] [@b{@@@var{FILE}}]
245 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
246 [@b{--elf-stt-common=[no|yes]}]
247 [@b{--target-help}] [@var{target-options}]
248 [@b{--}|@var{files} @dots{}]
251 @c Target dependent options are listed below. Keep the list sorted.
252 @c Add an empty line for separation.
256 @emph{Target AArch64 options:}
258 [@b{-mabi}=@var{ABI}]
262 @emph{Target Alpha options:}
264 [@b{-mdebug} | @b{-no-mdebug}]
265 [@b{-replace} | @b{-noreplace}]
266 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
267 [@b{-F}] [@b{-32addr}]
271 @emph{Target ARC options:}
272 [@b{-mcpu=@var{cpu}}]
273 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
280 @emph{Target ARM options:}
281 @c Don't document the deprecated options
282 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
283 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
284 [@b{-mfpu}=@var{floating-point-format}]
285 [@b{-mfloat-abi}=@var{abi}]
286 [@b{-meabi}=@var{ver}]
289 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
290 @b{-mapcs-reentrant}]
291 [@b{-mthumb-interwork}] [@b{-k}]
295 @emph{Target Blackfin options:}
296 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
303 @emph{Target CRIS options:}
304 [@b{--underscore} | @b{--no-underscore}]
306 [@b{--emulation=criself} | @b{--emulation=crisaout}]
307 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
308 @c Deprecated -- deliberately not documented.
313 @emph{Target D10V options:}
318 @emph{Target D30V options:}
319 [@b{-O}|@b{-n}|@b{-N}]
323 @emph{Target EPIPHANY options:}
324 [@b{-mepiphany}|@b{-mepiphany16}]
328 @emph{Target H8/300 options:}
332 @c HPPA has no machine-dependent assembler options (yet).
336 @emph{Target i386 options:}
337 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
338 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
342 @emph{Target i960 options:}
343 @c see md_parse_option in tc-i960.c
344 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
346 [@b{-b}] [@b{-no-relax}]
350 @emph{Target IA-64 options:}
351 [@b{-mconstant-gp}|@b{-mauto-pic}]
352 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
354 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
355 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
356 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
357 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
361 @emph{Target IP2K options:}
362 [@b{-mip2022}|@b{-mip2022ext}]
366 @emph{Target M32C options:}
367 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
371 @emph{Target M32R options:}
372 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
377 @emph{Target M680X0 options:}
378 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
382 @emph{Target M68HC11 options:}
383 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
384 [@b{-mshort}|@b{-mlong}]
385 [@b{-mshort-double}|@b{-mlong-double}]
386 [@b{--force-long-branches}] [@b{--short-branches}]
387 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
388 [@b{--print-opcodes}] [@b{--generate-example}]
392 @emph{Target MCORE options:}
393 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
394 [@b{-mcpu=[210|340]}]
398 @emph{Target Meta options:}
399 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
402 @emph{Target MICROBLAZE options:}
403 @c MicroBlaze has no machine-dependent assembler options.
407 @emph{Target MIPS options:}
408 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
409 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
410 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
411 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
412 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
413 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
414 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
415 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
416 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
417 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
418 [@b{-construct-floats}] [@b{-no-construct-floats}]
419 [@b{-mnan=@var{encoding}}]
420 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
421 [@b{-mips16}] [@b{-no-mips16}]
422 [@b{-mmicromips}] [@b{-mno-micromips}]
423 [@b{-msmartmips}] [@b{-mno-smartmips}]
424 [@b{-mips3d}] [@b{-no-mips3d}]
425 [@b{-mdmx}] [@b{-no-mdmx}]
426 [@b{-mdsp}] [@b{-mno-dsp}]
427 [@b{-mdspr2}] [@b{-mno-dspr2}]
428 [@b{-mdspr3}] [@b{-mno-dspr3}]
429 [@b{-mmsa}] [@b{-mno-msa}]
430 [@b{-mxpa}] [@b{-mno-xpa}]
431 [@b{-mmt}] [@b{-mno-mt}]
432 [@b{-mmcu}] [@b{-mno-mcu}]
433 [@b{-minsn32}] [@b{-mno-insn32}]
434 [@b{-mfix7000}] [@b{-mno-fix7000}]
435 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
436 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
437 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
438 [@b{-mdebug}] [@b{-no-mdebug}]
439 [@b{-mpdr}] [@b{-mno-pdr}]
443 @emph{Target MMIX options:}
444 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
445 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
446 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
447 [@b{--linker-allocated-gregs}]
451 @emph{Target Nios II options:}
452 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
457 @emph{Target NDS32 options:}
458 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
459 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
460 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
461 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
462 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
463 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
464 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
469 @emph{Target PDP11 options:}
470 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
471 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
472 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
476 @emph{Target picoJava options:}
481 @emph{Target PowerPC options:}
483 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
484 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
485 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
486 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
487 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
488 @b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
489 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
490 [@b{-mregnames}|@b{-mno-regnames}]
491 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
492 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
493 [@b{-msolaris}|@b{-mno-solaris}]
494 [@b{-nops=@var{count}}]
498 @emph{Target RL78 options:}
500 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
504 @emph{Target RX options:}
505 [@b{-mlittle-endian}|@b{-mbig-endian}]
506 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
507 [@b{-muse-conventional-section-names}]
508 [@b{-msmall-data-limit}]
511 [@b{-mint-register=@var{number}}]
512 [@b{-mgcc-abi}|@b{-mrx-abi}]
516 @emph{Target s390 options:}
517 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
518 [@b{-mregnames}|@b{-mno-regnames}]
519 [@b{-mwarn-areg-zero}]
523 @emph{Target SCORE options:}
524 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
525 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
526 [@b{-march=score7}][@b{-march=score3}]
527 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
531 @emph{Target SPARC options:}
532 @c The order here is important. See c-sparc.texi.
533 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
534 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
535 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
536 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
537 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
538 @b{-Asparcvisr}|@b{-Asparc5}]
539 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
540 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
541 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
542 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
543 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
544 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
547 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
551 @emph{Target TIC54X options:}
552 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
553 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
557 @emph{Target TIC6X options:}
558 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
559 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
560 [@b{-mpic}|@b{-mno-pic}]
564 @emph{Target TILE-Gx options:}
565 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
568 @c TILEPro has no machine-dependent assembler options
572 @emph{Target Visium options:}
573 [@b{-mtune=@var{arch}}]
577 @emph{Target Xtensa options:}
578 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
579 [@b{--[no-]absolute-literals}]
580 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
581 [@b{--[no-]transform}]
582 [@b{--rename-section} @var{oldname}=@var{newname}]
583 [@b{--[no-]trampolines}]
587 @emph{Target Z80 options:}
588 [@b{-z80}] [@b{-r800}]
589 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
590 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
591 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
592 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
593 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
594 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
598 @c Z8000 has no machine-dependent assembler options
607 @include at-file.texi
610 Turn on listings, in any of a variety of ways:
614 omit false conditionals
617 omit debugging directives
620 include general information, like @value{AS} version and options passed
623 include high-level source
629 include macro expansions
632 omit forms processing
638 set the name of the listing file
641 You may combine these options; for example, use @samp{-aln} for assembly
642 listing without forms processing. The @samp{=file} option, if used, must be
643 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
646 Begin in alternate macro mode.
648 @xref{Altmacro,,@code{.altmacro}}.
651 @item --compress-debug-sections
652 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
653 ELF ABI. The resulting object file may not be compatible with older
654 linkers and object file utilities. Note if compression would make a
655 given section @emph{larger} then it is not compressed.
658 @cindex @samp{--compress-debug-sections=} option
659 @item --compress-debug-sections=none
660 @itemx --compress-debug-sections=zlib
661 @itemx --compress-debug-sections=zlib-gnu
662 @itemx --compress-debug-sections=zlib-gabi
663 These options control how DWARF debug sections are compressed.
664 @option{--compress-debug-sections=none} is equivalent to
665 @option{--nocompress-debug-sections}.
666 @option{--compress-debug-sections=zlib} and
667 @option{--compress-debug-sections=zlib-gabi} are equivalent to
668 @option{--compress-debug-sections}.
669 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
670 sections using zlib. The debug sections are renamed to begin with
671 @samp{.zdebug}. Note if compression would make a given section
672 @emph{larger} then it is not compressed nor renamed.
676 @item --nocompress-debug-sections
677 Do not compress DWARF debug sections. This is usually the default for all
678 targets except the x86/x86_64, but a configure time option can be used to
682 Ignored. This option is accepted for script compatibility with calls to
685 @item --debug-prefix-map @var{old}=@var{new}
686 When assembling files in directory @file{@var{old}}, record debugging
687 information describing them as in @file{@var{new}} instead.
689 @item --defsym @var{sym}=@var{value}
690 Define the symbol @var{sym} to be @var{value} before assembling the input file.
691 @var{value} must be an integer constant. As in C, a leading @samp{0x}
692 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
693 value. The value of the symbol can be overridden inside a source file via the
694 use of a @code{.set} pseudo-op.
697 ``fast''---skip whitespace and comment preprocessing (assume source is
702 Generate debugging information for each assembler source line using whichever
703 debug format is preferred by the target. This currently means either STABS,
707 Generate stabs debugging information for each assembler line. This
708 may help debugging assembler code, if the debugger can handle it.
711 Generate stabs debugging information for each assembler line, with GNU
712 extensions that probably only gdb can handle, and that could make other
713 debuggers crash or refuse to read your program. This
714 may help debugging assembler code. Currently the only GNU extension is
715 the location of the current working directory at assembling time.
718 Generate DWARF2 debugging information for each assembler line. This
719 may help debugging assembler code, if the debugger can handle it. Note---this
720 option is only supported by some targets, not all of them.
722 @item --gdwarf-sections
723 Instead of creating a .debug_line section, create a series of
724 .debug_line.@var{foo} sections where @var{foo} is the name of the
725 corresponding code section. For example a code section called @var{.text.func}
726 will have its dwarf line number information placed into a section called
727 @var{.debug_line.text.func}. If the code section is just called @var{.text}
728 then debug line section will still be called just @var{.debug_line} without any
732 @item --size-check=error
733 @itemx --size-check=warning
734 Issue an error or warning for invalid ELF .size directive.
736 @item --elf-stt-common=no
737 @itemx --elf-stt-common=yes
738 These options control whether the ELF assembler should generate common
739 symbols with the @code{STT_COMMON} type. The default can be controlled
740 by a configure option @option{--enable-elf-stt-common}.
744 Print a summary of the command line options and exit.
747 Print a summary of all target specific options and exit.
750 Add directory @var{dir} to the search list for @code{.include} directives.
753 Don't warn about signed overflow.
756 @ifclear DIFF-TBL-KLUGE
757 This option is accepted but has no effect on the @value{TARGET} family.
759 @ifset DIFF-TBL-KLUGE
760 Issue warnings when difference tables altered for long displacements.
765 Keep (in the symbol table) local symbols. These symbols start with
766 system-specific local label prefixes, typically @samp{.L} for ELF systems
767 or @samp{L} for traditional a.out systems.
772 @item --listing-lhs-width=@var{number}
773 Set the maximum width, in words, of the output data column for an assembler
774 listing to @var{number}.
776 @item --listing-lhs-width2=@var{number}
777 Set the maximum width, in words, of the output data column for continuation
778 lines in an assembler listing to @var{number}.
780 @item --listing-rhs-width=@var{number}
781 Set the maximum width of an input source line, as displayed in a listing, to
784 @item --listing-cont-lines=@var{number}
785 Set the maximum number of lines printed in a listing for a single line of input
788 @item --no-pad-sections
789 Stop the assembler for padding the ends of output sections to the alignment
790 of that section. The default is to pad the sections, but this can waste space
791 which might be needed on targets which have tight memory constraints.
793 @item -o @var{objfile}
794 Name the object-file output from @command{@value{AS}} @var{objfile}.
797 Fold the data section into the text section.
799 @item --hash-size=@var{number}
800 Set the default size of GAS's hash tables to a prime number close to
801 @var{number}. Increasing this value can reduce the length of time it takes the
802 assembler to perform its tasks, at the expense of increasing the assembler's
803 memory requirements. Similarly reducing this value can reduce the memory
804 requirements at the expense of speed.
806 @item --reduce-memory-overheads
807 This option reduces GAS's memory requirements, at the expense of making the
808 assembly processes slower. Currently this switch is a synonym for
809 @samp{--hash-size=4051}, but in the future it may have other effects as well.
812 @item --sectname-subst
813 Honor substitution sequences in section names.
815 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
820 Print the maximum space (in bytes) and total time (in seconds) used by
823 @item --strip-local-absolute
824 Remove local absolute symbols from the outgoing symbol table.
828 Print the @command{as} version.
831 Print the @command{as} version and exit.
835 Suppress warning messages.
837 @item --fatal-warnings
838 Treat warnings as errors.
841 Don't suppress warning messages or treat them as errors.
850 Generate an object file even after errors.
852 @item -- | @var{files} @dots{}
853 Standard input, or source files to assemble.
861 @xref{AArch64 Options}, for the options available when @value{AS} is configured
862 for the 64-bit mode of the ARM Architecture (AArch64).
867 The following options are available when @value{AS} is configured for the
868 64-bit mode of the ARM Architecture (AArch64).
871 @include c-aarch64.texi
872 @c ended inside the included file
880 @xref{Alpha Options}, for the options available when @value{AS} is configured
881 for an Alpha processor.
886 The following options are available when @value{AS} is configured for an Alpha
890 @include c-alpha.texi
891 @c ended inside the included file
898 The following options are available when @value{AS} is configured for an ARC
902 @item -mcpu=@var{cpu}
903 This option selects the core processor variant.
905 Select either big-endian (-EB) or little-endian (-EL) output.
907 Enable Code Density extenssion instructions.
912 The following options are available when @value{AS} is configured for the ARM
916 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
917 Specify which ARM processor variant is the target.
918 @item -march=@var{architecture}[+@var{extension}@dots{}]
919 Specify which ARM architecture variant is used by the target.
920 @item -mfpu=@var{floating-point-format}
921 Select which Floating Point architecture is the target.
922 @item -mfloat-abi=@var{abi}
923 Select which floating point ABI is in use.
925 Enable Thumb only instruction decoding.
926 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
927 Select which procedure calling convention is in use.
929 Select either big-endian (-EB) or little-endian (-EL) output.
930 @item -mthumb-interwork
931 Specify that the code has been generated with interworking between Thumb and
934 Turns on CodeComposer Studio assembly syntax compatibility mode.
936 Specify that PIC code has been generated.
944 @xref{Blackfin Options}, for the options available when @value{AS} is
945 configured for the Blackfin processor family.
950 The following options are available when @value{AS} is configured for
951 the Blackfin processor family.
955 @c ended inside the included file
962 See the info pages for documentation of the CRIS-specific options.
966 The following options are available when @value{AS} is configured for
969 @cindex D10V optimization
970 @cindex optimization, D10V
972 Optimize output by parallelizing instructions.
977 The following options are available when @value{AS} is configured for a D30V
980 @cindex D30V optimization
981 @cindex optimization, D30V
983 Optimize output by parallelizing instructions.
987 Warn when nops are generated.
989 @cindex D30V nops after 32-bit multiply
991 Warn when a nop after a 32-bit multiply instruction is generated.
997 The following options are available when @value{AS} is configured for the
998 Adapteva EPIPHANY series.
1001 @xref{Epiphany Options}, for the options available when @value{AS} is
1002 configured for an Epiphany processor.
1006 @c man begin OPTIONS
1007 The following options are available when @value{AS} is configured for
1008 an Epiphany processor.
1010 @c man begin INCLUDE
1011 @include c-epiphany.texi
1012 @c ended inside the included file
1020 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1021 for an H8/300 processor.
1025 @c man begin OPTIONS
1026 The following options are available when @value{AS} is configured for an H8/300
1029 @c man begin INCLUDE
1030 @include c-h8300.texi
1031 @c ended inside the included file
1039 @xref{i386-Options}, for the options available when @value{AS} is
1040 configured for an i386 processor.
1044 @c man begin OPTIONS
1045 The following options are available when @value{AS} is configured for
1048 @c man begin INCLUDE
1049 @include c-i386.texi
1050 @c ended inside the included file
1055 @c man begin OPTIONS
1057 The following options are available when @value{AS} is configured for the
1058 Intel 80960 processor.
1061 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1062 Specify which variant of the 960 architecture is the target.
1065 Add code to collect statistics about branches taken.
1068 Do not alter compare-and-branch instructions for long displacements;
1075 The following options are available when @value{AS} is configured for the
1081 Specifies that the extended IP2022 instructions are allowed.
1084 Restores the default behaviour, which restricts the permitted instructions to
1085 just the basic IP2022 ones.
1091 The following options are available when @value{AS} is configured for the
1092 Renesas M32C and M16C processors.
1097 Assemble M32C instructions.
1100 Assemble M16C instructions (the default).
1103 Enable support for link-time relaxations.
1106 Support H'00 style hex constants in addition to 0x00 style.
1112 The following options are available when @value{AS} is configured for the
1113 Renesas M32R (formerly Mitsubishi M32R) series.
1118 Specify which processor in the M32R family is the target. The default
1119 is normally the M32R, but this option changes it to the M32RX.
1121 @item --warn-explicit-parallel-conflicts or --Wp
1122 Produce warning messages when questionable parallel constructs are
1125 @item --no-warn-explicit-parallel-conflicts or --Wnp
1126 Do not produce warning messages when questionable parallel constructs are
1133 The following options are available when @value{AS} is configured for the
1134 Motorola 68000 series.
1139 Shorten references to undefined symbols, to one word instead of two.
1141 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1142 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1143 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1144 Specify what processor in the 68000 family is the target. The default
1145 is normally the 68020, but this can be changed at configuration time.
1147 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1148 The target machine does (or does not) have a floating-point coprocessor.
1149 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1150 the basic 68000 is not compatible with the 68881, a combination of the
1151 two can be specified, since it's possible to do emulation of the
1152 coprocessor instructions with the main processor.
1154 @item -m68851 | -mno-68851
1155 The target machine does (or does not) have a memory-management
1156 unit coprocessor. The default is to assume an MMU for 68020 and up.
1164 @xref{Nios II Options}, for the options available when @value{AS} is configured
1165 for an Altera Nios II processor.
1169 @c man begin OPTIONS
1170 The following options are available when @value{AS} is configured for an
1171 Altera Nios II processor.
1173 @c man begin INCLUDE
1174 @include c-nios2.texi
1175 @c ended inside the included file
1181 For details about the PDP-11 machine dependent features options,
1182 see @ref{PDP-11-Options}.
1185 @item -mpic | -mno-pic
1186 Generate position-independent (or position-dependent) code. The
1187 default is @option{-mpic}.
1190 @itemx -mall-extensions
1191 Enable all instruction set extensions. This is the default.
1193 @item -mno-extensions
1194 Disable all instruction set extensions.
1196 @item -m@var{extension} | -mno-@var{extension}
1197 Enable (or disable) a particular instruction set extension.
1200 Enable the instruction set extensions supported by a particular CPU, and
1201 disable all other extensions.
1203 @item -m@var{machine}
1204 Enable the instruction set extensions supported by a particular machine
1205 model, and disable all other extensions.
1211 The following options are available when @value{AS} is configured for
1212 a picoJava processor.
1216 @cindex PJ endianness
1217 @cindex endianness, PJ
1218 @cindex big endian output, PJ
1220 Generate ``big endian'' format output.
1222 @cindex little endian output, PJ
1224 Generate ``little endian'' format output.
1230 The following options are available when @value{AS} is configured for the
1231 Motorola 68HC11 or 68HC12 series.
1235 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1236 Specify what processor is the target. The default is
1237 defined by the configuration option when building the assembler.
1239 @item --xgate-ramoffset
1240 Instruct the linker to offset RAM addresses from S12X address space into
1241 XGATE address space.
1244 Specify to use the 16-bit integer ABI.
1247 Specify to use the 32-bit integer ABI.
1249 @item -mshort-double
1250 Specify to use the 32-bit double ABI.
1253 Specify to use the 64-bit double ABI.
1255 @item --force-long-branches
1256 Relative branches are turned into absolute ones. This concerns
1257 conditional branches, unconditional branches and branches to a
1260 @item -S | --short-branches
1261 Do not turn relative branches into absolute ones
1262 when the offset is out of range.
1264 @item --strict-direct-mode
1265 Do not turn the direct addressing mode into extended addressing mode
1266 when the instruction does not support direct addressing mode.
1268 @item --print-insn-syntax
1269 Print the syntax of instruction in case of error.
1271 @item --print-opcodes
1272 Print the list of instructions with syntax and then exit.
1274 @item --generate-example
1275 Print an example of instruction for each possible instruction and then exit.
1276 This option is only useful for testing @command{@value{AS}}.
1282 The following options are available when @command{@value{AS}} is configured
1283 for the SPARC architecture:
1286 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1287 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1288 Explicitly select a variant of the SPARC architecture.
1290 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1291 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1293 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1294 UltraSPARC extensions.
1296 @item -xarch=v8plus | -xarch=v8plusa
1297 For compatibility with the Solaris v9 assembler. These options are
1298 equivalent to -Av8plus and -Av8plusa, respectively.
1301 Warn when the assembler switches to another architecture.
1306 The following options are available when @value{AS} is configured for the 'c54x
1311 Enable extended addressing mode. All addresses and relocations will assume
1312 extended addressing (usually 23 bits).
1313 @item -mcpu=@var{CPU_VERSION}
1314 Sets the CPU version being compiled for.
1315 @item -merrors-to-file @var{FILENAME}
1316 Redirect error output to a file, for broken systems which don't support such
1317 behaviour in the shell.
1322 The following options are available when @value{AS} is configured for
1327 This option sets the largest size of an object that can be referenced
1328 implicitly with the @code{gp} register. It is only accepted for targets that
1329 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1331 @cindex MIPS endianness
1332 @cindex endianness, MIPS
1333 @cindex big endian output, MIPS
1335 Generate ``big endian'' format output.
1337 @cindex little endian output, MIPS
1339 Generate ``little endian'' format output.
1357 Generate code for a particular MIPS Instruction Set Architecture level.
1358 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1359 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1360 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1361 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1362 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1363 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1364 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1365 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1366 MIPS64 Release 6 ISA processors, respectively.
1368 @item -march=@var{cpu}
1369 Generate code for a particular MIPS CPU.
1371 @item -mtune=@var{cpu}
1372 Schedule and tune for a particular MIPS CPU.
1376 Cause nops to be inserted if the read of the destination register
1377 of an mfhi or mflo instruction occurs in the following two instructions.
1380 @itemx -mno-fix-rm7000
1381 Cause nops to be inserted if a dmult or dmultu instruction is
1382 followed by a load instruction.
1386 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1387 section instead of the standard ELF .stabs sections.
1391 Control generation of @code{.pdr} sections.
1395 The register sizes are normally inferred from the ISA and ABI, but these
1396 flags force a certain group of registers to be treated as 32 bits wide at
1397 all times. @samp{-mgp32} controls the size of general-purpose registers
1398 and @samp{-mfp32} controls the size of floating-point registers.
1402 The register sizes are normally inferred from the ISA and ABI, but these
1403 flags force a certain group of registers to be treated as 64 bits wide at
1404 all times. @samp{-mgp64} controls the size of general-purpose registers
1405 and @samp{-mfp64} controls the size of floating-point registers.
1408 The register sizes are normally inferred from the ISA and ABI, but using
1409 this flag in combination with @samp{-mabi=32} enables an ABI variant
1410 which will operate correctly with floating-point registers which are
1414 @itemx -mno-odd-spreg
1415 Enable use of floating-point operations on odd-numbered single-precision
1416 registers when supported by the ISA. @samp{-mfpxx} implies
1417 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1421 Generate code for the MIPS 16 processor. This is equivalent to putting
1422 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1423 turns off this option.
1426 @itemx -mno-micromips
1427 Generate code for the microMIPS processor. This is equivalent to putting
1428 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1429 turns off this option. This is equivalent to putting @code{.set nomicromips}
1430 at the start of the assembly file.
1433 @itemx -mno-smartmips
1434 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1435 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1436 @samp{-mno-smartmips} turns off this option.
1440 Generate code for the MIPS-3D Application Specific Extension.
1441 This tells the assembler to accept MIPS-3D instructions.
1442 @samp{-no-mips3d} turns off this option.
1446 Generate code for the MDMX Application Specific Extension.
1447 This tells the assembler to accept MDMX instructions.
1448 @samp{-no-mdmx} turns off this option.
1452 Generate code for the DSP Release 1 Application Specific Extension.
1453 This tells the assembler to accept DSP Release 1 instructions.
1454 @samp{-mno-dsp} turns off this option.
1458 Generate code for the DSP Release 2 Application Specific Extension.
1459 This option implies @samp{-mdsp}.
1460 This tells the assembler to accept DSP Release 2 instructions.
1461 @samp{-mno-dspr2} turns off this option.
1465 Generate code for the DSP Release 3 Application Specific Extension.
1466 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1467 This tells the assembler to accept DSP Release 3 instructions.
1468 @samp{-mno-dspr3} turns off this option.
1472 Generate code for the MIPS SIMD Architecture Extension.
1473 This tells the assembler to accept MSA instructions.
1474 @samp{-mno-msa} turns off this option.
1478 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1479 This tells the assembler to accept XPA instructions.
1480 @samp{-mno-xpa} turns off this option.
1484 Generate code for the MT Application Specific Extension.
1485 This tells the assembler to accept MT instructions.
1486 @samp{-mno-mt} turns off this option.
1490 Generate code for the MCU Application Specific Extension.
1491 This tells the assembler to accept MCU instructions.
1492 @samp{-mno-mcu} turns off this option.
1496 Only use 32-bit instruction encodings when generating code for the
1497 microMIPS processor. This option inhibits the use of any 16-bit
1498 instructions. This is equivalent to putting @code{.set insn32} at
1499 the start of the assembly file. @samp{-mno-insn32} turns off this
1500 option. This is equivalent to putting @code{.set noinsn32} at the
1501 start of the assembly file. By default @samp{-mno-insn32} is
1502 selected, allowing all instructions to be used.
1504 @item --construct-floats
1505 @itemx --no-construct-floats
1506 The @samp{--no-construct-floats} option disables the construction of
1507 double width floating point constants by loading the two halves of the
1508 value into the two single width floating point registers that make up
1509 the double width register. By default @samp{--construct-floats} is
1510 selected, allowing construction of these floating point constants.
1512 @item --relax-branch
1513 @itemx --no-relax-branch
1514 The @samp{--relax-branch} option enables the relaxation of out-of-range
1515 branches. By default @samp{--no-relax-branch} is selected, causing any
1516 out-of-range branches to produce an error.
1518 @item -mnan=@var{encoding}
1519 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1520 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1523 @item --emulation=@var{name}
1524 This option was formerly used to switch between ELF and ECOFF output
1525 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1526 removed in GAS 2.24, so the option now serves little purpose.
1527 It is retained for backwards compatibility.
1529 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1530 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1531 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1532 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1533 preferred options instead.
1536 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1543 Control how to deal with multiplication overflow and division by zero.
1544 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1545 (and only work for Instruction Set Architecture level 2 and higher);
1546 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1550 When this option is used, @command{@value{AS}} will issue a warning every
1551 time it generates a nop instruction from a macro.
1556 The following options are available when @value{AS} is configured for
1562 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1563 The command line option @samp{-nojsri2bsr} can be used to disable it.
1567 Enable or disable the silicon filter behaviour. By default this is disabled.
1568 The default can be overridden by the @samp{-sifilter} command line option.
1571 Alter jump instructions for long displacements.
1573 @item -mcpu=[210|340]
1574 Select the cpu type on the target hardware. This controls which instructions
1578 Assemble for a big endian target.
1581 Assemble for a little endian target.
1590 @xref{Meta Options}, for the options available when @value{AS} is configured
1591 for a Meta processor.
1595 @c man begin OPTIONS
1596 The following options are available when @value{AS} is configured for a
1599 @c man begin INCLUDE
1600 @include c-metag.texi
1601 @c ended inside the included file
1606 @c man begin OPTIONS
1608 See the info pages for documentation of the MMIX-specific options.
1614 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1615 for a NDS32 processor.
1617 @c ended inside the included file
1621 @c man begin OPTIONS
1622 The following options are available when @value{AS} is configured for a
1625 @c man begin INCLUDE
1626 @include c-nds32.texi
1627 @c ended inside the included file
1634 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1635 for a PowerPC processor.
1639 @c man begin OPTIONS
1640 The following options are available when @value{AS} is configured for a
1643 @c man begin INCLUDE
1645 @c ended inside the included file
1653 @xref{RISC-V-Opts}, for the options available when @value{AS} is configured
1654 for a RISC-V processor.
1658 @c man begin OPTIONS
1659 The following options are available when @value{AS} is configured for a
1662 @c man begin INCLUDE
1663 @include c-riscv.texi
1664 @c ended inside the included file
1669 @c man begin OPTIONS
1671 See the info pages for documentation of the RX-specific options.
1675 The following options are available when @value{AS} is configured for the s390
1681 Select the word size, either 31/32 bits or 64 bits.
1684 Select the architecture mode, either the Enterprise System
1685 Architecture (esa) or the z/Architecture mode (zarch).
1686 @item -march=@var{processor}
1687 Specify which s390 processor variant is the target, @samp{g5} (or
1688 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1689 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1690 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1691 or @samp{z13} (or @samp{arch11}).
1693 @itemx -mno-regnames
1694 Allow or disallow symbolic names for registers.
1695 @item -mwarn-areg-zero
1696 Warn whenever the operand for a base or index register has been specified
1697 but evaluates to zero.
1705 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1706 for a TMS320C6000 processor.
1710 @c man begin OPTIONS
1711 The following options are available when @value{AS} is configured for a
1712 TMS320C6000 processor.
1714 @c man begin INCLUDE
1715 @include c-tic6x.texi
1716 @c ended inside the included file
1724 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1725 for a TILE-Gx processor.
1729 @c man begin OPTIONS
1730 The following options are available when @value{AS} is configured for a TILE-Gx
1733 @c man begin INCLUDE
1734 @include c-tilegx.texi
1735 @c ended inside the included file
1743 @xref{Visium Options}, for the options available when @value{AS} is configured
1744 for a Visium processor.
1748 @c man begin OPTIONS
1749 The following option is available when @value{AS} is configured for a Visium
1752 @c man begin INCLUDE
1753 @include c-visium.texi
1754 @c ended inside the included file
1762 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1763 for an Xtensa processor.
1767 @c man begin OPTIONS
1768 The following options are available when @value{AS} is configured for an
1771 @c man begin INCLUDE
1772 @include c-xtensa.texi
1773 @c ended inside the included file
1778 @c man begin OPTIONS
1781 The following options are available when @value{AS} is configured for
1782 a Z80 family processor.
1785 Assemble for Z80 processor.
1787 Assemble for R800 processor.
1788 @item -ignore-undocumented-instructions
1790 Assemble undocumented Z80 instructions that also work on R800 without warning.
1791 @item -ignore-unportable-instructions
1793 Assemble all undocumented Z80 instructions without warning.
1794 @item -warn-undocumented-instructions
1796 Issue a warning for undocumented Z80 instructions that also work on R800.
1797 @item -warn-unportable-instructions
1799 Issue a warning for undocumented Z80 instructions that do not work on R800.
1800 @item -forbid-undocumented-instructions
1802 Treat all undocumented instructions as errors.
1803 @item -forbid-unportable-instructions
1805 Treat undocumented Z80 instructions that do not work on R800 as errors.
1812 * Manual:: Structure of this Manual
1813 * GNU Assembler:: The GNU Assembler
1814 * Object Formats:: Object File Formats
1815 * Command Line:: Command Line
1816 * Input Files:: Input Files
1817 * Object:: Output (Object) File
1818 * Errors:: Error and Warning Messages
1822 @section Structure of this Manual
1824 @cindex manual, structure and purpose
1825 This manual is intended to describe what you need to know to use
1826 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1827 notation for symbols, constants, and expressions; the directives that
1828 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1831 We also cover special features in the @value{TARGET}
1832 configuration of @command{@value{AS}}, including assembler directives.
1835 This manual also describes some of the machine-dependent features of
1836 various flavors of the assembler.
1839 @cindex machine instructions (not covered)
1840 On the other hand, this manual is @emph{not} intended as an introduction
1841 to programming in assembly language---let alone programming in general!
1842 In a similar vein, we make no attempt to introduce the machine
1843 architecture; we do @emph{not} describe the instruction set, standard
1844 mnemonics, registers or addressing modes that are standard to a
1845 particular architecture.
1847 You may want to consult the manufacturer's
1848 machine architecture manual for this information.
1852 For information on the H8/300 machine instruction set, see @cite{H8/300
1853 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1854 Programming Manual} (Renesas).
1857 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1858 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1859 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1860 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1863 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1867 @c I think this is premature---doc@cygnus.com, 17jan1991
1869 Throughout this manual, we assume that you are running @dfn{GNU},
1870 the portable operating system from the @dfn{Free Software
1871 Foundation, Inc.}. This restricts our attention to certain kinds of
1872 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1873 once this assumption is granted examples and definitions need less
1876 @command{@value{AS}} is part of a team of programs that turn a high-level
1877 human-readable series of instructions into a low-level
1878 computer-readable series of instructions. Different versions of
1879 @command{@value{AS}} are used for different kinds of computer.
1882 @c There used to be a section "Terminology" here, which defined
1883 @c "contents", "byte", "word", and "long". Defining "word" to any
1884 @c particular size is confusing when the .word directive may generate 16
1885 @c bits on one machine and 32 bits on another; in general, for the user
1886 @c version of this manual, none of these terms seem essential to define.
1887 @c They were used very little even in the former draft of the manual;
1888 @c this draft makes an effort to avoid them (except in names of
1892 @section The GNU Assembler
1894 @c man begin DESCRIPTION
1896 @sc{gnu} @command{as} is really a family of assemblers.
1898 This manual describes @command{@value{AS}}, a member of that family which is
1899 configured for the @value{TARGET} architectures.
1901 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1902 should find a fairly similar environment when you use it on another
1903 architecture. Each version has much in common with the others,
1904 including object file formats, most assembler directives (often called
1905 @dfn{pseudo-ops}) and assembler syntax.@refill
1907 @cindex purpose of @sc{gnu} assembler
1908 @command{@value{AS}} is primarily intended to assemble the output of the
1909 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1910 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1911 assemble correctly everything that other assemblers for the same
1912 machine would assemble.
1914 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1917 @c This remark should appear in generic version of manual; assumption
1918 @c here is that generic version sets M680x0.
1919 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1920 assembler for the same architecture; for example, we know of several
1921 incompatible versions of 680x0 assembly language syntax.
1926 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1927 program in one pass of the source file. This has a subtle impact on the
1928 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1930 @node Object Formats
1931 @section Object File Formats
1933 @cindex object file format
1934 The @sc{gnu} assembler can be configured to produce several alternative
1935 object file formats. For the most part, this does not affect how you
1936 write assembly language programs; but directives for debugging symbols
1937 are typically different in different file formats. @xref{Symbol
1938 Attributes,,Symbol Attributes}.
1941 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1942 @value{OBJ-NAME} format object files.
1944 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1946 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1947 @code{b.out} or COFF format object files.
1950 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1951 SOM or ELF format object files.
1956 @section Command Line
1958 @cindex command line conventions
1960 After the program name @command{@value{AS}}, the command line may contain
1961 options and file names. Options may appear in any order, and may be
1962 before, after, or between file names. The order of file names is
1965 @cindex standard input, as input file
1967 @file{--} (two hyphens) by itself names the standard input file
1968 explicitly, as one of the files for @command{@value{AS}} to assemble.
1970 @cindex options, command line
1971 Except for @samp{--} any command line argument that begins with a
1972 hyphen (@samp{-}) is an option. Each option changes the behavior of
1973 @command{@value{AS}}. No option changes the way another option works. An
1974 option is a @samp{-} followed by one or more letters; the case of
1975 the letter is important. All options are optional.
1977 Some options expect exactly one file name to follow them. The file
1978 name may either immediately follow the option's letter (compatible
1979 with older assemblers) or it may be the next command argument (@sc{gnu}
1980 standard). These two command lines are equivalent:
1983 @value{AS} -o my-object-file.o mumble.s
1984 @value{AS} -omy-object-file.o mumble.s
1988 @section Input Files
1991 @cindex source program
1992 @cindex files, input
1993 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1994 describe the program input to one run of @command{@value{AS}}. The program may
1995 be in one or more files; how the source is partitioned into files
1996 doesn't change the meaning of the source.
1998 @c I added "con" prefix to "catenation" just to prove I can overcome my
1999 @c APL training... doc@cygnus.com
2000 The source program is a concatenation of the text in all the files, in the
2003 @c man begin DESCRIPTION
2004 Each time you run @command{@value{AS}} it assembles exactly one source
2005 program. The source program is made up of one or more files.
2006 (The standard input is also a file.)
2008 You give @command{@value{AS}} a command line that has zero or more input file
2009 names. The input files are read (from left file name to right). A
2010 command line argument (in any position) that has no special meaning
2011 is taken to be an input file name.
2013 If you give @command{@value{AS}} no file names it attempts to read one input file
2014 from the @command{@value{AS}} standard input, which is normally your terminal. You
2015 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2018 Use @samp{--} if you need to explicitly name the standard input file
2019 in your command line.
2021 If the source is empty, @command{@value{AS}} produces a small, empty object
2026 @subheading Filenames and Line-numbers
2028 @cindex input file linenumbers
2029 @cindex line numbers, in input files
2030 There are two ways of locating a line in the input file (or files) and
2031 either may be used in reporting error messages. One way refers to a line
2032 number in a physical file; the other refers to a line number in a
2033 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2035 @dfn{Physical files} are those files named in the command line given
2036 to @command{@value{AS}}.
2038 @dfn{Logical files} are simply names declared explicitly by assembler
2039 directives; they bear no relation to physical files. Logical file names help
2040 error messages reflect the original source file, when @command{@value{AS}} source
2041 is itself synthesized from other files. @command{@value{AS}} understands the
2042 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2043 @ref{File,,@code{.file}}.
2046 @section Output (Object) File
2052 Every time you run @command{@value{AS}} it produces an output file, which is
2053 your assembly language program translated into numbers. This file
2054 is the object file. Its default name is
2062 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2064 You can give it another name by using the @option{-o} option. Conventionally,
2065 object file names end with @file{.o}. The default name is used for historical
2066 reasons: older assemblers were capable of assembling self-contained programs
2067 directly into a runnable program. (For some formats, this isn't currently
2068 possible, but it can be done for the @code{a.out} format.)
2072 The object file is meant for input to the linker @code{@value{LD}}. It contains
2073 assembled program code, information to help @code{@value{LD}} integrate
2074 the assembled program into a runnable file, and (optionally) symbolic
2075 information for the debugger.
2077 @c link above to some info file(s) like the description of a.out.
2078 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2081 @section Error and Warning Messages
2083 @c man begin DESCRIPTION
2085 @cindex error messages
2086 @cindex warning messages
2087 @cindex messages from assembler
2088 @command{@value{AS}} may write warnings and error messages to the standard error
2089 file (usually your terminal). This should not happen when a compiler
2090 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2091 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2092 grave problem that stops the assembly.
2096 @cindex format of warning messages
2097 Warning messages have the format
2100 file_name:@b{NNN}:Warning Message Text
2104 @cindex file names and line numbers, in warnings/errors
2105 (where @b{NNN} is a line number). If both a logical file name
2106 (@pxref{File,,@code{.file}}) and a logical line number
2108 (@pxref{Line,,@code{.line}})
2110 have been given then they will be used, otherwise the file name and line number
2111 in the current assembler source file will be used. The message text is
2112 intended to be self explanatory (in the grand Unix tradition).
2114 Note the file name must be set via the logical version of the @code{.file}
2115 directive, not the DWARF2 version of the @code{.file} directive. For example:
2119 error_assembler_source
2125 produces this output:
2129 asm.s:2: Error: no such instruction: `error_assembler_source'
2130 foo.c:31: Error: no such instruction: `error_c_source'
2133 @cindex format of error messages
2134 Error messages have the format
2137 file_name:@b{NNN}:FATAL:Error Message Text
2140 The file name and line number are derived as for warning
2141 messages. The actual message text may be rather less explanatory
2142 because many of them aren't supposed to happen.
2145 @chapter Command-Line Options
2147 @cindex options, all versions of assembler
2148 This chapter describes command-line options available in @emph{all}
2149 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2150 for options specific
2152 to the @value{TARGET} target.
2155 to particular machine architectures.
2158 @c man begin DESCRIPTION
2160 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2161 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2162 The assembler arguments must be separated from each other (and the @samp{-Wa})
2163 by commas. For example:
2166 gcc -c -g -O -Wa,-alh,-L file.c
2170 This passes two options to the assembler: @samp{-alh} (emit a listing to
2171 standard output with high-level and assembly source) and @samp{-L} (retain
2172 local symbols in the symbol table).
2174 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2175 command-line options are automatically passed to the assembler by the compiler.
2176 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2177 precisely what options it passes to each compilation pass, including the
2183 * a:: -a[cdghlns] enable listings
2184 * alternate:: --alternate enable alternate macro syntax
2185 * D:: -D for compatibility
2186 * f:: -f to work faster
2187 * I:: -I for .include search path
2188 @ifclear DIFF-TBL-KLUGE
2189 * K:: -K for compatibility
2191 @ifset DIFF-TBL-KLUGE
2192 * K:: -K for difference tables
2195 * L:: -L to retain local symbols
2196 * listing:: --listing-XXX to configure listing output
2197 * M:: -M or --mri to assemble in MRI compatibility mode
2198 * MD:: --MD for dependency tracking
2199 * no-pad-sections:: --no-pad-sections to stop section padding
2200 * o:: -o to name the object file
2201 * R:: -R to join data and text sections
2202 * statistics:: --statistics to see statistics about assembly
2203 * traditional-format:: --traditional-format for compatible output
2204 * v:: -v to announce version
2205 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2206 * Z:: -Z to make object file even after errors
2210 @section Enable Listings: @option{-a[cdghlns]}
2220 @cindex listings, enabling
2221 @cindex assembly listings, enabling
2223 These options enable listing output from the assembler. By itself,
2224 @samp{-a} requests high-level, assembly, and symbols listing.
2225 You can use other letters to select specific options for the list:
2226 @samp{-ah} requests a high-level language listing,
2227 @samp{-al} requests an output-program assembly listing, and
2228 @samp{-as} requests a symbol table listing.
2229 High-level listings require that a compiler debugging option like
2230 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2233 Use the @samp{-ag} option to print a first section with general assembly
2234 information, like @value{AS} version, switches passed, or time stamp.
2236 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2237 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2238 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2239 omitted from the listing.
2241 Use the @samp{-ad} option to omit debugging directives from the
2244 Once you have specified one of these options, you can further control
2245 listing output and its appearance using the directives @code{.list},
2246 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2248 The @samp{-an} option turns off all forms processing.
2249 If you do not request listing output with one of the @samp{-a} options, the
2250 listing-control directives have no effect.
2252 The letters after @samp{-a} may be combined into one option,
2253 @emph{e.g.}, @samp{-aln}.
2255 Note if the assembler source is coming from the standard input (e.g.,
2257 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2258 is being used) then the listing will not contain any comments or preprocessor
2259 directives. This is because the listing code buffers input source lines from
2260 stdin only after they have been preprocessed by the assembler. This reduces
2261 memory usage and makes the code more efficient.
2264 @section @option{--alternate}
2267 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2270 @section @option{-D}
2273 This option has no effect whatsoever, but it is accepted to make it more
2274 likely that scripts written for other assemblers also work with
2275 @command{@value{AS}}.
2278 @section Work Faster: @option{-f}
2281 @cindex trusted compiler
2282 @cindex faster processing (@option{-f})
2283 @samp{-f} should only be used when assembling programs written by a
2284 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2285 and comment preprocessing on
2286 the input file(s) before assembling them. @xref{Preprocessing,
2290 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2291 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2296 @section @code{.include} Search Path: @option{-I} @var{path}
2298 @kindex -I @var{path}
2299 @cindex paths for @code{.include}
2300 @cindex search path for @code{.include}
2301 @cindex @code{include} directive search path
2302 Use this option to add a @var{path} to the list of directories
2303 @command{@value{AS}} searches for files specified in @code{.include}
2304 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2305 many times as necessary to include a variety of paths. The current
2306 working directory is always searched first; after that, @command{@value{AS}}
2307 searches any @samp{-I} directories in the same order as they were
2308 specified (left to right) on the command line.
2311 @section Difference Tables: @option{-K}
2314 @ifclear DIFF-TBL-KLUGE
2315 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2316 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2317 where it can be used to warn when the assembler alters the machine code
2318 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2319 family does not have the addressing limitations that sometimes lead to this
2320 alteration on other platforms.
2323 @ifset DIFF-TBL-KLUGE
2324 @cindex difference tables, warning
2325 @cindex warning for altered difference tables
2326 @command{@value{AS}} sometimes alters the code emitted for directives of the
2327 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2328 You can use the @samp{-K} option if you want a warning issued when this
2333 @section Include Local Symbols: @option{-L}
2336 @cindex local symbols, retaining in output
2337 Symbols beginning with system-specific local label prefixes, typically
2338 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2339 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2340 such symbols when debugging, because they are intended for the use of
2341 programs (like compilers) that compose assembler programs, not for your
2342 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2343 such symbols, so you do not normally debug with them.
2345 This option tells @command{@value{AS}} to retain those local symbols
2346 in the object file. Usually if you do this you also tell the linker
2347 @code{@value{LD}} to preserve those symbols.
2350 @section Configuring listing output: @option{--listing}
2352 The listing feature of the assembler can be enabled via the command line switch
2353 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2354 hex dump of the corresponding locations in the output object file, and displays
2355 them as a listing file. The format of this listing can be controlled by
2356 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2357 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2358 @code{.psize} (@pxref{Psize}), and
2359 @code{.eject} (@pxref{Eject}) and also by the following switches:
2362 @item --listing-lhs-width=@samp{number}
2363 @kindex --listing-lhs-width
2364 @cindex Width of first line disassembly output
2365 Sets the maximum width, in words, of the first line of the hex byte dump. This
2366 dump appears on the left hand side of the listing output.
2368 @item --listing-lhs-width2=@samp{number}
2369 @kindex --listing-lhs-width2
2370 @cindex Width of continuation lines of disassembly output
2371 Sets the maximum width, in words, of any further lines of the hex byte dump for
2372 a given input source line. If this value is not specified, it defaults to being
2373 the same as the value specified for @samp{--listing-lhs-width}. If neither
2374 switch is used the default is to one.
2376 @item --listing-rhs-width=@samp{number}
2377 @kindex --listing-rhs-width
2378 @cindex Width of source line output
2379 Sets the maximum width, in characters, of the source line that is displayed
2380 alongside the hex dump. The default value for this parameter is 100. The
2381 source line is displayed on the right hand side of the listing output.
2383 @item --listing-cont-lines=@samp{number}
2384 @kindex --listing-cont-lines
2385 @cindex Maximum number of continuation lines
2386 Sets the maximum number of continuation lines of hex dump that will be
2387 displayed for a given single line of source input. The default value is 4.
2391 @section Assemble in MRI Compatibility Mode: @option{-M}
2394 @cindex MRI compatibility mode
2395 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2396 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2397 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2398 configured target) assembler from Microtec Research. The exact nature of the
2399 MRI syntax will not be documented here; see the MRI manuals for more
2400 information. Note in particular that the handling of macros and macro
2401 arguments is somewhat different. The purpose of this option is to permit
2402 assembling existing MRI assembler code using @command{@value{AS}}.
2404 The MRI compatibility is not complete. Certain operations of the MRI assembler
2405 depend upon its object file format, and can not be supported using other object
2406 file formats. Supporting these would require enhancing each object file format
2407 individually. These are:
2410 @item global symbols in common section
2412 The m68k MRI assembler supports common sections which are merged by the linker.
2413 Other object file formats do not support this. @command{@value{AS}} handles
2414 common sections by treating them as a single common symbol. It permits local
2415 symbols to be defined within a common section, but it can not support global
2416 symbols, since it has no way to describe them.
2418 @item complex relocations
2420 The MRI assemblers support relocations against a negated section address, and
2421 relocations which combine the start addresses of two or more sections. These
2422 are not support by other object file formats.
2424 @item @code{END} pseudo-op specifying start address
2426 The MRI @code{END} pseudo-op permits the specification of a start address.
2427 This is not supported by other object file formats. The start address may
2428 instead be specified using the @option{-e} option to the linker, or in a linker
2431 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2433 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2434 name to the output file. This is not supported by other object file formats.
2436 @item @code{ORG} pseudo-op
2438 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2439 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2440 which changes the location within the current section. Absolute sections are
2441 not supported by other object file formats. The address of a section may be
2442 assigned within a linker script.
2445 There are some other features of the MRI assembler which are not supported by
2446 @command{@value{AS}}, typically either because they are difficult or because they
2447 seem of little consequence. Some of these may be supported in future releases.
2451 @item EBCDIC strings
2453 EBCDIC strings are not supported.
2455 @item packed binary coded decimal
2457 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2458 and @code{DCB.P} pseudo-ops are not supported.
2460 @item @code{FEQU} pseudo-op
2462 The m68k @code{FEQU} pseudo-op is not supported.
2464 @item @code{NOOBJ} pseudo-op
2466 The m68k @code{NOOBJ} pseudo-op is not supported.
2468 @item @code{OPT} branch control options
2470 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2471 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2472 relaxes all branches, whether forward or backward, to an appropriate size, so
2473 these options serve no purpose.
2475 @item @code{OPT} list control options
2477 The following m68k @code{OPT} list control options are ignored: @code{C},
2478 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2479 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2481 @item other @code{OPT} options
2483 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2484 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2486 @item @code{OPT} @code{D} option is default
2488 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2489 @code{OPT NOD} may be used to turn it off.
2491 @item @code{XREF} pseudo-op.
2493 The m68k @code{XREF} pseudo-op is ignored.
2495 @item @code{.debug} pseudo-op
2497 The i960 @code{.debug} pseudo-op is not supported.
2499 @item @code{.extended} pseudo-op
2501 The i960 @code{.extended} pseudo-op is not supported.
2503 @item @code{.list} pseudo-op.
2505 The various options of the i960 @code{.list} pseudo-op are not supported.
2507 @item @code{.optimize} pseudo-op
2509 The i960 @code{.optimize} pseudo-op is not supported.
2511 @item @code{.output} pseudo-op
2513 The i960 @code{.output} pseudo-op is not supported.
2515 @item @code{.setreal} pseudo-op
2517 The i960 @code{.setreal} pseudo-op is not supported.
2522 @section Dependency Tracking: @option{--MD}
2525 @cindex dependency tracking
2528 @command{@value{AS}} can generate a dependency file for the file it creates. This
2529 file consists of a single rule suitable for @code{make} describing the
2530 dependencies of the main source file.
2532 The rule is written to the file named in its argument.
2534 This feature is used in the automatic updating of makefiles.
2536 @node no-pad-sections
2537 @section Output Section Padding
2538 @kindex --no-pad-sections
2539 @cindex output section padding
2540 Normally the assembler will pad the end of each output section up to its
2541 alignment boundary. But this can waste space, which can be significant on
2542 memory constrained targets. So the @option{--no-pad-sections} option will
2543 disable this behaviour.
2546 @section Name the Object File: @option{-o}
2549 @cindex naming object file
2550 @cindex object file name
2551 There is always one object file output when you run @command{@value{AS}}. By
2552 default it has the name
2555 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2569 You use this option (which takes exactly one filename) to give the
2570 object file a different name.
2572 Whatever the object file is called, @command{@value{AS}} overwrites any
2573 existing file of the same name.
2576 @section Join Data and Text Sections: @option{-R}
2579 @cindex data and text sections, joining
2580 @cindex text and data sections, joining
2581 @cindex joining text and data sections
2582 @cindex merging text and data sections
2583 @option{-R} tells @command{@value{AS}} to write the object file as if all
2584 data-section data lives in the text section. This is only done at
2585 the very last moment: your binary data are the same, but data
2586 section parts are relocated differently. The data section part of
2587 your object file is zero bytes long because all its bytes are
2588 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2590 When you specify @option{-R} it would be possible to generate shorter
2591 address displacements (because we do not have to cross between text and
2592 data section). We refrain from doing this simply for compatibility with
2593 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2596 When @command{@value{AS}} is configured for COFF or ELF output,
2597 this option is only useful if you use sections named @samp{.text} and
2602 @option{-R} is not supported for any of the HPPA targets. Using
2603 @option{-R} generates a warning from @command{@value{AS}}.
2607 @section Display Assembly Statistics: @option{--statistics}
2609 @kindex --statistics
2610 @cindex statistics, about assembly
2611 @cindex time, total for assembly
2612 @cindex space used, maximum for assembly
2613 Use @samp{--statistics} to display two statistics about the resources used by
2614 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2615 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2618 @node traditional-format
2619 @section Compatible Output: @option{--traditional-format}
2621 @kindex --traditional-format
2622 For some targets, the output of @command{@value{AS}} is different in some ways
2623 from the output of some existing assembler. This switch requests
2624 @command{@value{AS}} to use the traditional format instead.
2626 For example, it disables the exception frame optimizations which
2627 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2630 @section Announce Version: @option{-v}
2634 @cindex assembler version
2635 @cindex version of assembler
2636 You can find out what version of as is running by including the
2637 option @samp{-v} (which you can also spell as @samp{-version}) on the
2641 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2643 @command{@value{AS}} should never give a warning or error message when
2644 assembling compiler output. But programs written by people often
2645 cause @command{@value{AS}} to give a warning that a particular assumption was
2646 made. All such warnings are directed to the standard error file.
2650 @cindex suppressing warnings
2651 @cindex warnings, suppressing
2652 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2653 This only affects the warning messages: it does not change any particular of
2654 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2657 @kindex --fatal-warnings
2658 @cindex errors, caused by warnings
2659 @cindex warnings, causing error
2660 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2661 files that generate warnings to be in error.
2664 @cindex warnings, switching on
2665 You can switch these options off again by specifying @option{--warn}, which
2666 causes warnings to be output as usual.
2669 @section Generate Object File in Spite of Errors: @option{-Z}
2670 @cindex object file, after errors
2671 @cindex errors, continuing after
2672 After an error message, @command{@value{AS}} normally produces no output. If for
2673 some reason you are interested in object file output even after
2674 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2675 option. If there are any errors, @command{@value{AS}} continues anyways, and
2676 writes an object file after a final warning message of the form @samp{@var{n}
2677 errors, @var{m} warnings, generating bad object file.}
2682 @cindex machine-independent syntax
2683 @cindex syntax, machine-independent
2684 This chapter describes the machine-independent syntax allowed in a
2685 source file. @command{@value{AS}} syntax is similar to what many other
2686 assemblers use; it is inspired by the BSD 4.2
2691 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2695 * Preprocessing:: Preprocessing
2696 * Whitespace:: Whitespace
2697 * Comments:: Comments
2698 * Symbol Intro:: Symbols
2699 * Statements:: Statements
2700 * Constants:: Constants
2704 @section Preprocessing
2706 @cindex preprocessing
2707 The @command{@value{AS}} internal preprocessor:
2709 @cindex whitespace, removed by preprocessor
2711 adjusts and removes extra whitespace. It leaves one space or tab before
2712 the keywords on a line, and turns any other whitespace on the line into
2715 @cindex comments, removed by preprocessor
2717 removes all comments, replacing them with a single space, or an
2718 appropriate number of newlines.
2720 @cindex constants, converted by preprocessor
2722 converts character constants into the appropriate numeric values.
2725 It does not do macro processing, include file handling, or
2726 anything else you may get from your C compiler's preprocessor. You can
2727 do include file processing with the @code{.include} directive
2728 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2729 to get other ``CPP'' style preprocessing by giving the input file a
2730 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2731 Output, gcc info, Using GNU CC}.
2733 Excess whitespace, comments, and character constants
2734 cannot be used in the portions of the input text that are not
2737 @cindex turning preprocessing on and off
2738 @cindex preprocessing, turning on and off
2741 If the first line of an input file is @code{#NO_APP} or if you use the
2742 @samp{-f} option, whitespace and comments are not removed from the input file.
2743 Within an input file, you can ask for whitespace and comment removal in
2744 specific portions of the by putting a line that says @code{#APP} before the
2745 text that may contain whitespace or comments, and putting a line that says
2746 @code{#NO_APP} after this text. This feature is mainly intend to support
2747 @code{asm} statements in compilers whose output is otherwise free of comments
2754 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2755 Whitespace is used to separate symbols, and to make programs neater for
2756 people to read. Unless within character constants
2757 (@pxref{Characters,,Character Constants}), any whitespace means the same
2758 as exactly one space.
2764 There are two ways of rendering comments to @command{@value{AS}}. In both
2765 cases the comment is equivalent to one space.
2767 Anything from @samp{/*} through the next @samp{*/} is a comment.
2768 This means you may not nest these comments.
2772 The only way to include a newline ('\n') in a comment
2773 is to use this sort of comment.
2776 /* This sort of comment does not nest. */
2779 @cindex line comment character
2780 Anything from a @dfn{line comment} character up to the next newline is
2781 considered a comment and is ignored. The line comment character is target
2782 specific, and some targets multiple comment characters. Some targets also have
2783 line comment characters that only work if they are the first character on a
2784 line. Some targets use a sequence of two characters to introduce a line
2785 comment. Some targets can also change their line comment characters depending
2786 upon command line options that have been used. For more details see the
2787 @emph{Syntax} section in the documentation for individual targets.
2789 If the line comment character is the hash sign (@samp{#}) then it still has the
2790 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2791 to specify logical line numbers:
2794 @cindex lines starting with @code{#}
2795 @cindex logical line numbers
2796 To be compatible with past assemblers, lines that begin with @samp{#} have a
2797 special interpretation. Following the @samp{#} should be an absolute
2798 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2799 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2800 new logical file name. The rest of the line, if any, should be whitespace.
2802 If the first non-whitespace characters on the line are not numeric,
2803 the line is ignored. (Just like a comment.)
2806 # This is an ordinary comment.
2807 # 42-6 "new_file_name" # New logical file name
2808 # This is logical line # 36.
2810 This feature is deprecated, and may disappear from future versions
2811 of @command{@value{AS}}.
2816 @cindex characters used in symbols
2817 @ifclear SPECIAL-SYMS
2818 A @dfn{symbol} is one or more characters chosen from the set of all
2819 letters (both upper and lower case), digits and the three characters
2825 A @dfn{symbol} is one or more characters chosen from the set of all
2826 letters (both upper and lower case), digits and the three characters
2827 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2833 On most machines, you can also use @code{$} in symbol names; exceptions
2834 are noted in @ref{Machine Dependencies}.
2836 No symbol may begin with a digit. Case is significant.
2837 There is no length limit; all characters are significant. Multibyte characters
2838 are supported. Symbols are delimited by characters not in that set, or by the
2839 beginning of a file (since the source program must end with a newline, the end
2840 of a file is not a possible symbol delimiter). @xref{Symbols}.
2842 Symbol names may also be enclosed in double quote @code{"} characters. In such
2843 cases any characters are allowed, except for the NUL character. If a double
2844 quote character is to be included in the symbol name it must be preceeded by a
2845 backslash @code{\} character.
2846 @cindex length of symbols
2851 @cindex statements, structure of
2852 @cindex line separator character
2853 @cindex statement separator character
2855 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2856 @dfn{line separator character}. The line separator character is target
2857 specific and described in the @emph{Syntax} section of each
2858 target's documentation. Not all targets support a line separator character.
2859 The newline or line separator character is considered to be part of the
2860 preceding statement. Newlines and separators within character constants are an
2861 exception: they do not end statements.
2863 @cindex newline, required at file end
2864 @cindex EOF, newline must precede
2865 It is an error to end any statement with end-of-file: the last
2866 character of any input file should be a newline.@refill
2868 An empty statement is allowed, and may include whitespace. It is ignored.
2870 @cindex instructions and directives
2871 @cindex directives and instructions
2872 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2873 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2875 A statement begins with zero or more labels, optionally followed by a
2876 key symbol which determines what kind of statement it is. The key
2877 symbol determines the syntax of the rest of the statement. If the
2878 symbol begins with a dot @samp{.} then the statement is an assembler
2879 directive: typically valid for any computer. If the symbol begins with
2880 a letter the statement is an assembly language @dfn{instruction}: it
2881 assembles into a machine language instruction.
2883 Different versions of @command{@value{AS}} for different computers
2884 recognize different instructions. In fact, the same symbol may
2885 represent a different instruction in a different computer's assembly
2889 @cindex @code{:} (label)
2890 @cindex label (@code{:})
2891 A label is a symbol immediately followed by a colon (@code{:}).
2892 Whitespace before a label or after a colon is permitted, but you may not
2893 have whitespace between a label's symbol and its colon. @xref{Labels}.
2896 For HPPA targets, labels need not be immediately followed by a colon, but
2897 the definition of a label must begin in column zero. This also implies that
2898 only one label may be defined on each line.
2902 label: .directive followed by something
2903 another_label: # This is an empty statement.
2904 instruction operand_1, operand_2, @dots{}
2911 A constant is a number, written so that its value is known by
2912 inspection, without knowing any context. Like this:
2915 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2916 .ascii "Ring the bell\7" # A string constant.
2917 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2918 .float 0f-314159265358979323846264338327\
2919 95028841971.693993751E-40 # - pi, a flonum.
2924 * Characters:: Character Constants
2925 * Numbers:: Number Constants
2929 @subsection Character Constants
2931 @cindex character constants
2932 @cindex constants, character
2933 There are two kinds of character constants. A @dfn{character} stands
2934 for one character in one byte and its value may be used in
2935 numeric expressions. String constants (properly called string
2936 @emph{literals}) are potentially many bytes and their values may not be
2937 used in arithmetic expressions.
2941 * Chars:: Characters
2945 @subsubsection Strings
2947 @cindex string constants
2948 @cindex constants, string
2949 A @dfn{string} is written between double-quotes. It may contain
2950 double-quotes or null characters. The way to get special characters
2951 into a string is to @dfn{escape} these characters: precede them with
2952 a backslash @samp{\} character. For example @samp{\\} represents
2953 one backslash: the first @code{\} is an escape which tells
2954 @command{@value{AS}} to interpret the second character literally as a backslash
2955 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2956 escape character). The complete list of escapes follows.
2958 @cindex escape codes, character
2959 @cindex character escape codes
2960 @c NOTE: Cindex entries must not start with a backlash character.
2961 @c NOTE: This confuses the pdf2texi script when it is creating the
2962 @c NOTE: index based upon the first character and so it generates:
2963 @c NOTE: \initial {\\}
2964 @c NOTE: which then results in the error message:
2965 @c NOTE: Argument of \\ has an extra }.
2966 @c NOTE: So in the index entries below a space character has been
2967 @c NOTE: prepended to avoid this problem.
2970 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2972 @cindex @code{ \b} (backspace character)
2973 @cindex backspace (@code{\b})
2975 Mnemonic for backspace; for ASCII this is octal code 010.
2978 @c Mnemonic for EOText; for ASCII this is octal code 004.
2980 @cindex @code{ \f} (formfeed character)
2981 @cindex formfeed (@code{\f})
2983 Mnemonic for FormFeed; for ASCII this is octal code 014.
2985 @cindex @code{ \n} (newline character)
2986 @cindex newline (@code{\n})
2988 Mnemonic for newline; for ASCII this is octal code 012.
2991 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2993 @cindex @code{ \r} (carriage return character)
2994 @cindex carriage return (@code{backslash-r})
2996 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2999 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3000 @c other assemblers.
3002 @cindex @code{ \t} (tab)
3003 @cindex tab (@code{\t})
3005 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3008 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3009 @c @item \x @var{digit} @var{digit} @var{digit}
3010 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3012 @cindex @code{ \@var{ddd}} (octal character code)
3013 @cindex octal character code (@code{\@var{ddd}})
3014 @item \ @var{digit} @var{digit} @var{digit}
3015 An octal character code. The numeric code is 3 octal digits.
3016 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3017 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3019 @cindex @code{ \@var{xd...}} (hex character code)
3020 @cindex hex character code (@code{\@var{xd...}})
3021 @item \@code{x} @var{hex-digits...}
3022 A hex character code. All trailing hex digits are combined. Either upper or
3023 lower case @code{x} works.
3025 @cindex @code{ \\} (@samp{\} character)
3026 @cindex backslash (@code{\\})
3028 Represents one @samp{\} character.
3031 @c Represents one @samp{'} (accent acute) character.
3032 @c This is needed in single character literals
3033 @c (@xref{Characters,,Character Constants}.) to represent
3036 @cindex @code{ \"} (doublequote character)
3037 @cindex doublequote (@code{\"})
3039 Represents one @samp{"} character. Needed in strings to represent
3040 this character, because an unescaped @samp{"} would end the string.
3042 @item \ @var{anything-else}
3043 Any other character when escaped by @kbd{\} gives a warning, but
3044 assembles as if the @samp{\} was not present. The idea is that if
3045 you used an escape sequence you clearly didn't want the literal
3046 interpretation of the following character. However @command{@value{AS}} has no
3047 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3048 code and warns you of the fact.
3051 Which characters are escapable, and what those escapes represent,
3052 varies widely among assemblers. The current set is what we think
3053 the BSD 4.2 assembler recognizes, and is a subset of what most C
3054 compilers recognize. If you are in doubt, do not use an escape
3058 @subsubsection Characters
3060 @cindex single character constant
3061 @cindex character, single
3062 @cindex constant, single character
3063 A single character may be written as a single quote immediately
3064 followed by that character. The same escapes apply to characters as
3065 to strings. So if you want to write the character backslash, you
3066 must write @kbd{'\\} where the first @code{\} escapes the second
3067 @code{\}. As you can see, the quote is an acute accent, not a
3068 grave accent. A newline
3070 @ifclear abnormal-separator
3071 (or semicolon @samp{;})
3073 @ifset abnormal-separator
3075 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3080 immediately following an acute accent is taken as a literal character
3081 and does not count as the end of a statement. The value of a character
3082 constant in a numeric expression is the machine's byte-wide code for
3083 that character. @command{@value{AS}} assumes your character code is ASCII:
3084 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3087 @subsection Number Constants
3089 @cindex constants, number
3090 @cindex number constants
3091 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3092 are stored in the target machine. @emph{Integers} are numbers that
3093 would fit into an @code{int} in the C language. @emph{Bignums} are
3094 integers, but they are stored in more than 32 bits. @emph{Flonums}
3095 are floating point numbers, described below.
3098 * Integers:: Integers
3103 * Bit Fields:: Bit Fields
3109 @subsubsection Integers
3111 @cindex constants, integer
3113 @cindex binary integers
3114 @cindex integers, binary
3115 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3116 the binary digits @samp{01}.
3118 @cindex octal integers
3119 @cindex integers, octal
3120 An octal integer is @samp{0} followed by zero or more of the octal
3121 digits (@samp{01234567}).
3123 @cindex decimal integers
3124 @cindex integers, decimal
3125 A decimal integer starts with a non-zero digit followed by zero or
3126 more digits (@samp{0123456789}).
3128 @cindex hexadecimal integers
3129 @cindex integers, hexadecimal
3130 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3131 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3133 Integers have the usual values. To denote a negative integer, use
3134 the prefix operator @samp{-} discussed under expressions
3135 (@pxref{Prefix Ops,,Prefix Operators}).
3138 @subsubsection Bignums
3141 @cindex constants, bignum
3142 A @dfn{bignum} has the same syntax and semantics as an integer
3143 except that the number (or its negative) takes more than 32 bits to
3144 represent in binary. The distinction is made because in some places
3145 integers are permitted while bignums are not.
3148 @subsubsection Flonums
3150 @cindex floating point numbers
3151 @cindex constants, floating point
3153 @cindex precision, floating point
3154 A @dfn{flonum} represents a floating point number. The translation is
3155 indirect: a decimal floating point number from the text is converted by
3156 @command{@value{AS}} to a generic binary floating point number of more than
3157 sufficient precision. This generic floating point number is converted
3158 to a particular computer's floating point format (or formats) by a
3159 portion of @command{@value{AS}} specialized to that computer.
3161 A flonum is written by writing (in order)
3166 (@samp{0} is optional on the HPPA.)
3170 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3172 @kbd{e} is recommended. Case is not important.
3174 @c FIXME: verify if flonum syntax really this vague for most cases
3175 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3176 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3179 On the H8/300, Renesas / SuperH SH,
3180 and AMD 29K architectures, the letter must be
3181 one of the letters @samp{DFPRSX} (in upper or lower case).
3183 On the ARC, the letter must be one of the letters @samp{DFRS}
3184 (in upper or lower case).
3186 On the Intel 960 architecture, the letter must be
3187 one of the letters @samp{DFT} (in upper or lower case).
3189 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3193 One of the letters @samp{DFRS} (in upper or lower case).
3196 One of the letters @samp{DFPRSX} (in upper or lower case).
3199 The letter @samp{E} (upper case only).
3202 One of the letters @samp{DFT} (in upper or lower case).
3207 An optional sign: either @samp{+} or @samp{-}.
3210 An optional @dfn{integer part}: zero or more decimal digits.
3213 An optional @dfn{fractional part}: @samp{.} followed by zero
3214 or more decimal digits.
3217 An optional exponent, consisting of:
3221 An @samp{E} or @samp{e}.
3222 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3223 @c principle this can perfectly well be different on different targets.
3225 Optional sign: either @samp{+} or @samp{-}.
3227 One or more decimal digits.
3232 At least one of the integer part or the fractional part must be
3233 present. The floating point number has the usual base-10 value.
3235 @command{@value{AS}} does all processing using integers. Flonums are computed
3236 independently of any floating point hardware in the computer running
3237 @command{@value{AS}}.
3241 @c Bit fields are written as a general facility but are also controlled
3242 @c by a conditional-compilation flag---which is as of now (21mar91)
3243 @c turned on only by the i960 config of GAS.
3245 @subsubsection Bit Fields
3248 @cindex constants, bit field
3249 You can also define numeric constants as @dfn{bit fields}.
3250 Specify two numbers separated by a colon---
3252 @var{mask}:@var{value}
3255 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3258 The resulting number is then packed
3260 @c this conditional paren in case bit fields turned on elsewhere than 960
3261 (in host-dependent byte order)
3263 into a field whose width depends on which assembler directive has the
3264 bit-field as its argument. Overflow (a result from the bitwise and
3265 requiring more binary digits to represent) is not an error; instead,
3266 more constants are generated, of the specified width, beginning with the
3267 least significant digits.@refill
3269 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3270 @code{.short}, and @code{.word} accept bit-field arguments.
3275 @chapter Sections and Relocation
3280 * Secs Background:: Background
3281 * Ld Sections:: Linker Sections
3282 * As Sections:: Assembler Internal Sections
3283 * Sub-Sections:: Sub-Sections
3287 @node Secs Background
3290 Roughly, a section is a range of addresses, with no gaps; all data
3291 ``in'' those addresses is treated the same for some particular purpose.
3292 For example there may be a ``read only'' section.
3294 @cindex linker, and assembler
3295 @cindex assembler, and linker
3296 The linker @code{@value{LD}} reads many object files (partial programs) and
3297 combines their contents to form a runnable program. When @command{@value{AS}}
3298 emits an object file, the partial program is assumed to start at address 0.
3299 @code{@value{LD}} assigns the final addresses for the partial program, so that
3300 different partial programs do not overlap. This is actually an
3301 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3304 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3305 addresses. These blocks slide to their run-time addresses as rigid
3306 units; their length does not change and neither does the order of bytes
3307 within them. Such a rigid unit is called a @emph{section}. Assigning
3308 run-time addresses to sections is called @dfn{relocation}. It includes
3309 the task of adjusting mentions of object-file addresses so they refer to
3310 the proper run-time addresses.
3312 For the H8/300, and for the Renesas / SuperH SH,
3313 @command{@value{AS}} pads sections if needed to
3314 ensure they end on a word (sixteen bit) boundary.
3317 @cindex standard assembler sections
3318 An object file written by @command{@value{AS}} has at least three sections, any
3319 of which may be empty. These are named @dfn{text}, @dfn{data} and
3324 When it generates COFF or ELF output,
3326 @command{@value{AS}} can also generate whatever other named sections you specify
3327 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3328 If you do not use any directives that place output in the @samp{.text}
3329 or @samp{.data} sections, these sections still exist, but are empty.
3334 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3336 @command{@value{AS}} can also generate whatever other named sections you
3337 specify using the @samp{.space} and @samp{.subspace} directives. See
3338 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3339 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3340 assembler directives.
3343 Additionally, @command{@value{AS}} uses different names for the standard
3344 text, data, and bss sections when generating SOM output. Program text
3345 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3346 BSS into @samp{$BSS$}.
3350 Within the object file, the text section starts at address @code{0}, the
3351 data section follows, and the bss section follows the data section.
3354 When generating either SOM or ELF output files on the HPPA, the text
3355 section starts at address @code{0}, the data section at address
3356 @code{0x4000000}, and the bss section follows the data section.
3359 To let @code{@value{LD}} know which data changes when the sections are
3360 relocated, and how to change that data, @command{@value{AS}} also writes to the
3361 object file details of the relocation needed. To perform relocation
3362 @code{@value{LD}} must know, each time an address in the object
3366 Where in the object file is the beginning of this reference to
3369 How long (in bytes) is this reference?
3371 Which section does the address refer to? What is the numeric value of
3373 (@var{address}) @minus{} (@var{start-address of section})?
3376 Is the reference to an address ``Program-Counter relative''?
3379 @cindex addresses, format of
3380 @cindex section-relative addressing
3381 In fact, every address @command{@value{AS}} ever uses is expressed as
3383 (@var{section}) + (@var{offset into section})
3386 Further, most expressions @command{@value{AS}} computes have this section-relative
3389 (For some object formats, such as SOM for the HPPA, some expressions are
3390 symbol-relative instead.)
3393 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3394 @var{N} into section @var{secname}.''
3396 Apart from text, data and bss sections you need to know about the
3397 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3398 addresses in the absolute section remain unchanged. For example, address
3399 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3400 @code{@value{LD}}. Although the linker never arranges two partial programs'
3401 data sections with overlapping addresses after linking, @emph{by definition}
3402 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3403 part of a program is always the same address when the program is running as
3404 address @code{@{absolute@ 239@}} in any other part of the program.
3406 The idea of sections is extended to the @dfn{undefined} section. Any
3407 address whose section is unknown at assembly time is by definition
3408 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3409 Since numbers are always defined, the only way to generate an undefined
3410 address is to mention an undefined symbol. A reference to a named
3411 common block would be such a symbol: its value is unknown at assembly
3412 time so it has section @emph{undefined}.
3414 By analogy the word @emph{section} is used to describe groups of sections in
3415 the linked program. @code{@value{LD}} puts all partial programs' text
3416 sections in contiguous addresses in the linked program. It is
3417 customary to refer to the @emph{text section} of a program, meaning all
3418 the addresses of all partial programs' text sections. Likewise for
3419 data and bss sections.
3421 Some sections are manipulated by @code{@value{LD}}; others are invented for
3422 use of @command{@value{AS}} and have no meaning except during assembly.
3425 @section Linker Sections
3426 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3431 @cindex named sections
3432 @cindex sections, named
3433 @item named sections
3436 @cindex text section
3437 @cindex data section
3441 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3442 separate but equal sections. Anything you can say of one section is
3445 When the program is running, however, it is
3446 customary for the text section to be unalterable. The
3447 text section is often shared among processes: it contains
3448 instructions, constants and the like. The data section of a running
3449 program is usually alterable: for example, C variables would be stored
3450 in the data section.
3455 This section contains zeroed bytes when your program begins running. It
3456 is used to hold uninitialized variables or common storage. The length of
3457 each partial program's bss section is important, but because it starts
3458 out containing zeroed bytes there is no need to store explicit zero
3459 bytes in the object file. The bss section was invented to eliminate
3460 those explicit zeros from object files.
3462 @cindex absolute section
3463 @item absolute section
3464 Address 0 of this section is always ``relocated'' to runtime address 0.
3465 This is useful if you want to refer to an address that @code{@value{LD}} must
3466 not change when relocating. In this sense we speak of absolute
3467 addresses being ``unrelocatable'': they do not change during relocation.
3469 @cindex undefined section
3470 @item undefined section
3471 This ``section'' is a catch-all for address references to objects not in
3472 the preceding sections.
3473 @c FIXME: ref to some other doc on obj-file formats could go here.
3476 @cindex relocation example
3477 An idealized example of three relocatable sections follows.
3479 The example uses the traditional section names @samp{.text} and @samp{.data}.
3481 Memory addresses are on the horizontal axis.
3485 @c END TEXI2ROFF-KILL
3488 partial program # 1: |ttttt|dddd|00|
3495 partial program # 2: |TTT|DDD|000|
3498 +--+---+-----+--+----+---+-----+~~
3499 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3500 +--+---+-----+--+----+---+-----+~~
3502 addresses: 0 @dots{}
3509 \line{\it Partial program \#1: \hfil}
3510 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3511 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3513 \line{\it Partial program \#2: \hfil}
3514 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3515 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3517 \line{\it linked program: \hfil}
3518 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3519 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3520 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3521 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3523 \line{\it addresses: \hfil}
3527 @c END TEXI2ROFF-KILL
3530 @section Assembler Internal Sections
3532 @cindex internal assembler sections
3533 @cindex sections in messages, internal
3534 These sections are meant only for the internal use of @command{@value{AS}}. They
3535 have no meaning at run-time. You do not really need to know about these
3536 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3537 warning messages, so it might be helpful to have an idea of their
3538 meanings to @command{@value{AS}}. These sections are used to permit the
3539 value of every expression in your assembly language program to be a
3540 section-relative address.
3543 @cindex assembler internal logic error
3544 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3545 An internal assembler logic error has been found. This means there is a
3546 bug in the assembler.
3548 @cindex expr (internal section)
3550 The assembler stores complex expression internally as combinations of
3551 symbols. When it needs to represent an expression as a symbol, it puts
3552 it in the expr section.
3554 @c FIXME item transfer[t] vector preload
3555 @c FIXME item transfer[t] vector postload
3556 @c FIXME item register
3560 @section Sub-Sections
3562 @cindex numbered subsections
3563 @cindex grouping data
3569 fall into two sections: text and data.
3571 You may have separate groups of
3573 data in named sections
3577 data in named sections
3583 that you want to end up near to each other in the object file, even though they
3584 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3585 use @dfn{subsections} for this purpose. Within each section, there can be
3586 numbered subsections with values from 0 to 8192. Objects assembled into the
3587 same subsection go into the object file together with other objects in the same
3588 subsection. For example, a compiler might want to store constants in the text
3589 section, but might not want to have them interspersed with the program being
3590 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3591 section of code being output, and a @samp{.text 1} before each group of
3592 constants being output.
3594 Subsections are optional. If you do not use subsections, everything
3595 goes in subsection number zero.
3598 Each subsection is zero-padded up to a multiple of four bytes.
3599 (Subsections may be padded a different amount on different flavors
3600 of @command{@value{AS}}.)
3604 On the H8/300 platform, each subsection is zero-padded to a word
3605 boundary (two bytes).
3606 The same is true on the Renesas SH.
3609 @c FIXME section padding (alignment)?
3610 @c Rich Pixley says padding here depends on target obj code format; that
3611 @c doesn't seem particularly useful to say without further elaboration,
3612 @c so for now I say nothing about it. If this is a generic BFD issue,
3613 @c these paragraphs might need to vanish from this manual, and be
3614 @c discussed in BFD chapter of binutils (or some such).
3618 Subsections appear in your object file in numeric order, lowest numbered
3619 to highest. (All this to be compatible with other people's assemblers.)
3620 The object file contains no representation of subsections; @code{@value{LD}} and
3621 other programs that manipulate object files see no trace of them.
3622 They just see all your text subsections as a text section, and all your
3623 data subsections as a data section.
3625 To specify which subsection you want subsequent statements assembled
3626 into, use a numeric argument to specify it, in a @samp{.text
3627 @var{expression}} or a @samp{.data @var{expression}} statement.
3630 When generating COFF output, you
3635 can also use an extra subsection
3636 argument with arbitrary named sections: @samp{.section @var{name},
3641 When generating ELF output, you
3646 can also use the @code{.subsection} directive (@pxref{SubSection})
3647 to specify a subsection: @samp{.subsection @var{expression}}.
3649 @var{Expression} should be an absolute expression
3650 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3651 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3652 begins in @code{text 0}. For instance:
3654 .text 0 # The default subsection is text 0 anyway.
3655 .ascii "This lives in the first text subsection. *"
3657 .ascii "But this lives in the second text subsection."
3659 .ascii "This lives in the data section,"
3660 .ascii "in the first data subsection."
3662 .ascii "This lives in the first text section,"
3663 .ascii "immediately following the asterisk (*)."
3666 Each section has a @dfn{location counter} incremented by one for every byte
3667 assembled into that section. Because subsections are merely a convenience
3668 restricted to @command{@value{AS}} there is no concept of a subsection location
3669 counter. There is no way to directly manipulate a location counter---but the
3670 @code{.align} directive changes it, and any label definition captures its
3671 current value. The location counter of the section where statements are being
3672 assembled is said to be the @dfn{active} location counter.
3675 @section bss Section
3678 @cindex common variable storage
3679 The bss section is used for local common variable storage.
3680 You may allocate address space in the bss section, but you may
3681 not dictate data to load into it before your program executes. When
3682 your program starts running, all the contents of the bss
3683 section are zeroed bytes.
3685 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3686 @ref{Lcomm,,@code{.lcomm}}.
3688 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3689 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3692 When assembling for a target which supports multiple sections, such as ELF or
3693 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3694 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3695 section. Typically the section will only contain symbol definitions and
3696 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3703 Symbols are a central concept: the programmer uses symbols to name
3704 things, the linker uses symbols to link, and the debugger uses symbols
3708 @cindex debuggers, and symbol order
3709 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3710 the same order they were declared. This may break some debuggers.
3715 * Setting Symbols:: Giving Symbols Other Values
3716 * Symbol Names:: Symbol Names
3717 * Dot:: The Special Dot Symbol
3718 * Symbol Attributes:: Symbol Attributes
3725 A @dfn{label} is written as a symbol immediately followed by a colon
3726 @samp{:}. The symbol then represents the current value of the
3727 active location counter, and is, for example, a suitable instruction
3728 operand. You are warned if you use the same symbol to represent two
3729 different locations: the first definition overrides any other
3733 On the HPPA, the usual form for a label need not be immediately followed by a
3734 colon, but instead must start in column zero. Only one label may be defined on
3735 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3736 provides a special directive @code{.label} for defining labels more flexibly.
3739 @node Setting Symbols
3740 @section Giving Symbols Other Values
3742 @cindex assigning values to symbols
3743 @cindex symbol values, assigning
3744 A symbol can be given an arbitrary value by writing a symbol, followed
3745 by an equals sign @samp{=}, followed by an expression
3746 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3747 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3748 equals sign @samp{=}@samp{=} here represents an equivalent of the
3749 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3752 Blackfin does not support symbol assignment with @samp{=}.
3756 @section Symbol Names
3758 @cindex symbol names
3759 @cindex names, symbol
3760 @ifclear SPECIAL-SYMS
3761 Symbol names begin with a letter or with one of @samp{._}. On most
3762 machines, you can also use @code{$} in symbol names; exceptions are
3763 noted in @ref{Machine Dependencies}. That character may be followed by any
3764 string of digits, letters, dollar signs (unless otherwise noted for a
3765 particular target machine), and underscores.
3769 Symbol names begin with a letter or with one of @samp{._}. On the
3770 Renesas SH you can also use @code{$} in symbol names. That
3771 character may be followed by any string of digits, letters, dollar signs (save
3772 on the H8/300), and underscores.
3776 Case of letters is significant: @code{foo} is a different symbol name
3779 Symbol names do not start with a digit. An exception to this rule is made for
3780 Local Labels. See below.
3782 Multibyte characters are supported. To generate a symbol name containing
3783 multibyte characters enclose it within double quotes and use escape codes. cf
3784 @xref{Strings}. Generating a multibyte symbol name from a label is not
3785 currently supported.
3787 Each symbol has exactly one name. Each name in an assembly language program
3788 refers to exactly one symbol. You may use that symbol name any number of times
3791 @subheading Local Symbol Names
3793 @cindex local symbol names
3794 @cindex symbol names, local
3795 A local symbol is any symbol beginning with certain local label prefixes.
3796 By default, the local label prefix is @samp{.L} for ELF systems or
3797 @samp{L} for traditional a.out systems, but each target may have its own
3798 set of local label prefixes.
3800 On the HPPA local symbols begin with @samp{L$}.
3803 Local symbols are defined and used within the assembler, but they are
3804 normally not saved in object files. Thus, they are not visible when debugging.
3805 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3806 to retain the local symbols in the object files.
3808 @subheading Local Labels
3810 @cindex local labels
3811 @cindex temporary symbol names
3812 @cindex symbol names, temporary
3813 Local labels are different from local symbols. Local labels help compilers and
3814 programmers use names temporarily. They create symbols which are guaranteed to
3815 be unique over the entire scope of the input source code and which can be
3816 referred to by a simple notation. To define a local label, write a label of
3817 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3818 To refer to the most recent previous definition of that label write
3819 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3820 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3821 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3823 There is no restriction on how you can use these labels, and you can reuse them
3824 too. So that it is possible to repeatedly define the same local label (using
3825 the same number @samp{@b{N}}), although you can only refer to the most recently
3826 defined local label of that number (for a backwards reference) or the next
3827 definition of a specific local label for a forward reference. It is also worth
3828 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3829 implemented in a slightly more efficient manner than the others.
3840 Which is the equivalent of:
3843 label_1: branch label_3
3844 label_2: branch label_1
3845 label_3: branch label_4
3846 label_4: branch label_3
3849 Local label names are only a notational device. They are immediately
3850 transformed into more conventional symbol names before the assembler uses them.
3851 The symbol names are stored in the symbol table, appear in error messages, and
3852 are optionally emitted to the object file. The names are constructed using
3856 @item @emph{local label prefix}
3857 All local symbols begin with the system-specific local label prefix.
3858 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3859 that start with the local label prefix. These labels are
3860 used for symbols you are never intended to see. If you use the
3861 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3862 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3863 you may use them in debugging.
3866 This is the number that was used in the local label definition. So if the
3867 label is written @samp{55:} then the number is @samp{55}.
3870 This unusual character is included so you do not accidentally invent a symbol
3871 of the same name. The character has ASCII value of @samp{\002} (control-B).
3873 @item @emph{ordinal number}
3874 This is a serial number to keep the labels distinct. The first definition of
3875 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3876 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3877 the number @samp{1} and its 15th definition gets @samp{15} as well.
3880 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3881 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3883 @subheading Dollar Local Labels
3884 @cindex dollar local symbols
3886 On some targets @code{@value{AS}} also supports an even more local form of
3887 local labels called dollar labels. These labels go out of scope (i.e., they
3888 become undefined) as soon as a non-local label is defined. Thus they remain
3889 valid for only a small region of the input source code. Normal local labels,
3890 by contrast, remain in scope for the entire file, or until they are redefined
3891 by another occurrence of the same local label.
3893 Dollar labels are defined in exactly the same way as ordinary local labels,
3894 except that they have a dollar sign suffix to their numeric value, e.g.,
3897 They can also be distinguished from ordinary local labels by their transformed
3898 names which use ASCII character @samp{\001} (control-A) as the magic character
3899 to distinguish them from ordinary labels. For example, the fifth definition of
3900 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3903 @section The Special Dot Symbol
3905 @cindex dot (symbol)
3906 @cindex @code{.} (symbol)
3907 @cindex current address
3908 @cindex location counter
3909 The special symbol @samp{.} refers to the current address that
3910 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3911 .long .} defines @code{melvin} to contain its own address.
3912 Assigning a value to @code{.} is treated the same as a @code{.org}
3914 @ifclear no-space-dir
3915 Thus, the expression @samp{.=.+4} is the same as saying
3919 @node Symbol Attributes
3920 @section Symbol Attributes
3922 @cindex symbol attributes
3923 @cindex attributes, symbol
3924 Every symbol has, as well as its name, the attributes ``Value'' and
3925 ``Type''. Depending on output format, symbols can also have auxiliary
3928 The detailed definitions are in @file{a.out.h}.
3931 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3932 all these attributes, and probably won't warn you. This makes the
3933 symbol an externally defined symbol, which is generally what you
3937 * Symbol Value:: Value
3938 * Symbol Type:: Type
3941 * a.out Symbols:: Symbol Attributes: @code{a.out}
3945 * a.out Symbols:: Symbol Attributes: @code{a.out}
3948 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3953 * COFF Symbols:: Symbol Attributes for COFF
3956 * SOM Symbols:: Symbol Attributes for SOM
3963 @cindex value of a symbol
3964 @cindex symbol value
3965 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3966 location in the text, data, bss or absolute sections the value is the
3967 number of addresses from the start of that section to the label.
3968 Naturally for text, data and bss sections the value of a symbol changes
3969 as @code{@value{LD}} changes section base addresses during linking. Absolute
3970 symbols' values do not change during linking: that is why they are
3973 The value of an undefined symbol is treated in a special way. If it is
3974 0 then the symbol is not defined in this assembler source file, and
3975 @code{@value{LD}} tries to determine its value from other files linked into the
3976 same program. You make this kind of symbol simply by mentioning a symbol
3977 name without defining it. A non-zero value represents a @code{.comm}
3978 common declaration. The value is how much common storage to reserve, in
3979 bytes (addresses). The symbol refers to the first address of the
3985 @cindex type of a symbol
3987 The type attribute of a symbol contains relocation (section)
3988 information, any flag settings indicating that a symbol is external, and
3989 (optionally), other information for linkers and debuggers. The exact
3990 format depends on the object-code output format in use.
3995 @c The following avoids a "widow" subsection title. @group would be
3996 @c better if it were available outside examples.
3999 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
4001 @cindex @code{b.out} symbol attributes
4002 @cindex symbol attributes, @code{b.out}
4003 These symbol attributes appear only when @command{@value{AS}} is configured for
4004 one of the Berkeley-descended object output formats---@code{a.out} or
4010 @subsection Symbol Attributes: @code{a.out}
4012 @cindex @code{a.out} symbol attributes
4013 @cindex symbol attributes, @code{a.out}
4019 @subsection Symbol Attributes: @code{a.out}
4021 @cindex @code{a.out} symbol attributes
4022 @cindex symbol attributes, @code{a.out}
4026 * Symbol Desc:: Descriptor
4027 * Symbol Other:: Other
4031 @subsubsection Descriptor
4033 @cindex descriptor, of @code{a.out} symbol
4034 This is an arbitrary 16-bit value. You may establish a symbol's
4035 descriptor value by using a @code{.desc} statement
4036 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4037 @command{@value{AS}}.
4040 @subsubsection Other
4042 @cindex other attribute, of @code{a.out} symbol
4043 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4048 @subsection Symbol Attributes for COFF
4050 @cindex COFF symbol attributes
4051 @cindex symbol attributes, COFF
4053 The COFF format supports a multitude of auxiliary symbol attributes;
4054 like the primary symbol attributes, they are set between @code{.def} and
4055 @code{.endef} directives.
4057 @subsubsection Primary Attributes
4059 @cindex primary attributes, COFF symbols
4060 The symbol name is set with @code{.def}; the value and type,
4061 respectively, with @code{.val} and @code{.type}.
4063 @subsubsection Auxiliary Attributes
4065 @cindex auxiliary attributes, COFF symbols
4066 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4067 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4068 table information for COFF.
4073 @subsection Symbol Attributes for SOM
4075 @cindex SOM symbol attributes
4076 @cindex symbol attributes, SOM
4078 The SOM format for the HPPA supports a multitude of symbol attributes set with
4079 the @code{.EXPORT} and @code{.IMPORT} directives.
4081 The attributes are described in @cite{HP9000 Series 800 Assembly
4082 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4083 @code{EXPORT} assembler directive documentation.
4087 @chapter Expressions
4091 @cindex numeric values
4092 An @dfn{expression} specifies an address or numeric value.
4093 Whitespace may precede and/or follow an expression.
4095 The result of an expression must be an absolute number, or else an offset into
4096 a particular section. If an expression is not absolute, and there is not
4097 enough information when @command{@value{AS}} sees the expression to know its
4098 section, a second pass over the source program might be necessary to interpret
4099 the expression---but the second pass is currently not implemented.
4100 @command{@value{AS}} aborts with an error message in this situation.
4103 * Empty Exprs:: Empty Expressions
4104 * Integer Exprs:: Integer Expressions
4108 @section Empty Expressions
4110 @cindex empty expressions
4111 @cindex expressions, empty
4112 An empty expression has no value: it is just whitespace or null.
4113 Wherever an absolute expression is required, you may omit the
4114 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4115 is compatible with other assemblers.
4118 @section Integer Expressions
4120 @cindex integer expressions
4121 @cindex expressions, integer
4122 An @dfn{integer expression} is one or more @emph{arguments} delimited
4123 by @emph{operators}.
4126 * Arguments:: Arguments
4127 * Operators:: Operators
4128 * Prefix Ops:: Prefix Operators
4129 * Infix Ops:: Infix Operators
4133 @subsection Arguments
4135 @cindex expression arguments
4136 @cindex arguments in expressions
4137 @cindex operands in expressions
4138 @cindex arithmetic operands
4139 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4140 contexts arguments are sometimes called ``arithmetic operands''. In
4141 this manual, to avoid confusing them with the ``instruction operands'' of
4142 the machine language, we use the term ``argument'' to refer to parts of
4143 expressions only, reserving the word ``operand'' to refer only to machine
4144 instruction operands.
4146 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4147 @var{section} is one of text, data, bss, absolute,
4148 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4151 Numbers are usually integers.
4153 A number can be a flonum or bignum. In this case, you are warned
4154 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4155 these 32 bits are an integer. You may write integer-manipulating
4156 instructions that act on exotic constants, compatible with other
4159 @cindex subexpressions
4160 Subexpressions are a left parenthesis @samp{(} followed by an integer
4161 expression, followed by a right parenthesis @samp{)}; or a prefix
4162 operator followed by an argument.
4165 @subsection Operators
4167 @cindex operators, in expressions
4168 @cindex arithmetic functions
4169 @cindex functions, in expressions
4170 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4171 operators are followed by an argument. Infix operators appear
4172 between their arguments. Operators may be preceded and/or followed by
4176 @subsection Prefix Operator
4178 @cindex prefix operators
4179 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4180 one argument, which must be absolute.
4182 @c the tex/end tex stuff surrounding this small table is meant to make
4183 @c it align, on the printed page, with the similar table in the next
4184 @c section (which is inside an enumerate).
4186 \global\advance\leftskip by \itemindent
4191 @dfn{Negation}. Two's complement negation.
4193 @dfn{Complementation}. Bitwise not.
4197 \global\advance\leftskip by -\itemindent
4201 @subsection Infix Operators
4203 @cindex infix operators
4204 @cindex operators, permitted arguments
4205 @dfn{Infix operators} take two arguments, one on either side. Operators
4206 have precedence, but operations with equal precedence are performed left
4207 to right. Apart from @code{+} or @option{-}, both arguments must be
4208 absolute, and the result is absolute.
4211 @cindex operator precedence
4212 @cindex precedence of operators
4219 @dfn{Multiplication}.
4222 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4228 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4231 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4235 Intermediate precedence
4240 @dfn{Bitwise Inclusive Or}.
4246 @dfn{Bitwise Exclusive Or}.
4249 @dfn{Bitwise Or Not}.
4256 @cindex addition, permitted arguments
4257 @cindex plus, permitted arguments
4258 @cindex arguments for addition
4260 @dfn{Addition}. If either argument is absolute, the result has the section of
4261 the other argument. You may not add together arguments from different
4264 @cindex subtraction, permitted arguments
4265 @cindex minus, permitted arguments
4266 @cindex arguments for subtraction
4268 @dfn{Subtraction}. If the right argument is absolute, the
4269 result has the section of the left argument.
4270 If both arguments are in the same section, the result is absolute.
4271 You may not subtract arguments from different sections.
4272 @c FIXME is there still something useful to say about undefined - undefined ?
4274 @cindex comparison expressions
4275 @cindex expressions, comparison
4280 @dfn{Is Not Equal To}
4284 @dfn{Is Greater Than}
4286 @dfn{Is Greater Than Or Equal To}
4288 @dfn{Is Less Than Or Equal To}
4290 The comparison operators can be used as infix operators. A true results has a
4291 value of -1 whereas a false result has a value of 0. Note, these operators
4292 perform signed comparisons.
4295 @item Lowest Precedence
4304 These two logical operations can be used to combine the results of sub
4305 expressions. Note, unlike the comparison operators a true result returns a
4306 value of 1 but a false results does still return 0. Also note that the logical
4307 or operator has a slightly lower precedence than logical and.
4312 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4313 address; you can only have a defined section in one of the two arguments.
4316 @chapter Assembler Directives
4318 @cindex directives, machine independent
4319 @cindex pseudo-ops, machine independent
4320 @cindex machine independent directives
4321 All assembler directives have names that begin with a period (@samp{.}).
4322 The names are case insensitive for most targets, and usually written
4325 This chapter discusses directives that are available regardless of the
4326 target machine configuration for the @sc{gnu} assembler.
4328 Some machine configurations provide additional directives.
4329 @xref{Machine Dependencies}.
4332 @ifset machine-directives
4333 @xref{Machine Dependencies}, for additional directives.
4338 * Abort:: @code{.abort}
4340 * ABORT (COFF):: @code{.ABORT}
4343 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4344 * Altmacro:: @code{.altmacro}
4345 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4346 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4347 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4348 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4349 * Byte:: @code{.byte @var{expressions}}
4350 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4351 * Comm:: @code{.comm @var{symbol} , @var{length} }
4352 * Data:: @code{.data @var{subsection}}
4354 * Def:: @code{.def @var{name}}
4357 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4363 * Double:: @code{.double @var{flonums}}
4364 * Eject:: @code{.eject}
4365 * Else:: @code{.else}
4366 * Elseif:: @code{.elseif}
4369 * Endef:: @code{.endef}
4372 * Endfunc:: @code{.endfunc}
4373 * Endif:: @code{.endif}
4374 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4375 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4376 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4378 * Error:: @code{.error @var{string}}
4379 * Exitm:: @code{.exitm}
4380 * Extern:: @code{.extern}
4381 * Fail:: @code{.fail}
4382 * File:: @code{.file}
4383 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4384 * Float:: @code{.float @var{flonums}}
4385 * Func:: @code{.func}
4386 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4388 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4389 * Hidden:: @code{.hidden @var{names}}
4392 * hword:: @code{.hword @var{expressions}}
4393 * Ident:: @code{.ident}
4394 * If:: @code{.if @var{absolute expression}}
4395 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4396 * Include:: @code{.include "@var{file}"}
4397 * Int:: @code{.int @var{expressions}}
4399 * Internal:: @code{.internal @var{names}}
4402 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4403 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4404 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4405 * Lflags:: @code{.lflags}
4406 @ifclear no-line-dir
4407 * Line:: @code{.line @var{line-number}}
4410 * Linkonce:: @code{.linkonce [@var{type}]}
4411 * List:: @code{.list}
4412 * Ln:: @code{.ln @var{line-number}}
4413 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4414 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4416 * Local:: @code{.local @var{names}}
4419 * Long:: @code{.long @var{expressions}}
4421 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4424 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4425 * MRI:: @code{.mri @var{val}}
4426 * Noaltmacro:: @code{.noaltmacro}
4427 * Nolist:: @code{.nolist}
4428 * Octa:: @code{.octa @var{bignums}}
4429 * Offset:: @code{.offset @var{loc}}
4430 * Org:: @code{.org @var{new-lc}, @var{fill}}
4431 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4433 * PopSection:: @code{.popsection}
4434 * Previous:: @code{.previous}
4437 * Print:: @code{.print @var{string}}
4439 * Protected:: @code{.protected @var{names}}
4442 * Psize:: @code{.psize @var{lines}, @var{columns}}
4443 * Purgem:: @code{.purgem @var{name}}
4445 * PushSection:: @code{.pushsection @var{name}}
4448 * Quad:: @code{.quad @var{bignums}}
4449 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4450 * Rept:: @code{.rept @var{count}}
4451 * Sbttl:: @code{.sbttl "@var{subheading}"}
4453 * Scl:: @code{.scl @var{class}}
4456 * Section:: @code{.section @var{name}[, @var{flags}]}
4459 * Set:: @code{.set @var{symbol}, @var{expression}}
4460 * Short:: @code{.short @var{expressions}}
4461 * Single:: @code{.single @var{flonums}}
4463 * Size:: @code{.size [@var{name} , @var{expression}]}
4465 @ifclear no-space-dir
4466 * Skip:: @code{.skip @var{size} , @var{fill}}
4469 * Sleb128:: @code{.sleb128 @var{expressions}}
4470 @ifclear no-space-dir
4471 * Space:: @code{.space @var{size} , @var{fill}}
4474 * Stab:: @code{.stabd, .stabn, .stabs}
4477 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4478 * Struct:: @code{.struct @var{expression}}
4480 * SubSection:: @code{.subsection}
4481 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4485 * Tag:: @code{.tag @var{structname}}
4488 * Text:: @code{.text @var{subsection}}
4489 * Title:: @code{.title "@var{heading}"}
4491 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4494 * Uleb128:: @code{.uleb128 @var{expressions}}
4496 * Val:: @code{.val @var{addr}}
4500 * Version:: @code{.version "@var{string}"}
4501 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4502 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4505 * Warning:: @code{.warning @var{string}}
4506 * Weak:: @code{.weak @var{names}}
4507 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4508 * Word:: @code{.word @var{expressions}}
4509 @ifclear no-space-dir
4510 * Zero:: @code{.zero @var{size}}
4512 * Deprecated:: Deprecated Directives
4516 @section @code{.abort}
4518 @cindex @code{abort} directive
4519 @cindex stopping the assembly
4520 This directive stops the assembly immediately. It is for
4521 compatibility with other assemblers. The original idea was that the
4522 assembly language source would be piped into the assembler. If the sender
4523 of the source quit, it could use this directive tells @command{@value{AS}} to
4524 quit also. One day @code{.abort} will not be supported.
4528 @section @code{.ABORT} (COFF)
4530 @cindex @code{ABORT} directive
4531 When producing COFF output, @command{@value{AS}} accepts this directive as a
4532 synonym for @samp{.abort}.
4535 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4541 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4543 @cindex padding the location counter
4544 @cindex @code{align} directive
4545 Pad the location counter (in the current subsection) to a particular storage
4546 boundary. The first expression (which must be absolute) is the alignment
4547 required, as described below.
4549 The second expression (also absolute) gives the fill value to be stored in the
4550 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4551 padding bytes are normally zero. However, on some systems, if the section is
4552 marked as containing code and the fill value is omitted, the space is filled
4553 with no-op instructions.
4555 The third expression is also absolute, and is also optional. If it is present,
4556 it is the maximum number of bytes that should be skipped by this alignment
4557 directive. If doing the alignment would require skipping more bytes than the
4558 specified maximum, then the alignment is not done at all. You can omit the
4559 fill value (the second argument) entirely by simply using two commas after the
4560 required alignment; this can be useful if you want the alignment to be filled
4561 with no-op instructions when appropriate.
4563 The way the required alignment is specified varies from system to system.
4564 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4565 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4566 alignment request in bytes. For example @samp{.align 8} advances
4567 the location counter until it is a multiple of 8. If the location counter
4568 is already a multiple of 8, no change is needed. For the tic54x, the
4569 first expression is the alignment request in words.
4571 For other systems, including ppc, i386 using a.out format, arm and
4572 strongarm, it is the
4573 number of low-order zero bits the location counter must have after
4574 advancement. For example @samp{.align 3} advances the location
4575 counter until it a multiple of 8. If the location counter is already a
4576 multiple of 8, no change is needed.
4578 This inconsistency is due to the different behaviors of the various
4579 native assemblers for these systems which GAS must emulate.
4580 GAS also provides @code{.balign} and @code{.p2align} directives,
4581 described later, which have a consistent behavior across all
4582 architectures (but are specific to GAS).
4585 @section @code{.altmacro}
4586 Enable alternate macro mode, enabling:
4589 @item LOCAL @var{name} [ , @dots{} ]
4590 One additional directive, @code{LOCAL}, is available. It is used to
4591 generate a string replacement for each of the @var{name} arguments, and
4592 replace any instances of @var{name} in each macro expansion. The
4593 replacement string is unique in the assembly, and different for each
4594 separate macro expansion. @code{LOCAL} allows you to write macros that
4595 define symbols, without fear of conflict between separate macro expansions.
4597 @item String delimiters
4598 You can write strings delimited in these other ways besides
4599 @code{"@var{string}"}:
4602 @item '@var{string}'
4603 You can delimit strings with single-quote characters.
4605 @item <@var{string}>
4606 You can delimit strings with matching angle brackets.
4609 @item single-character string escape
4610 To include any single character literally in a string (even if the
4611 character would otherwise have some special meaning), you can prefix the
4612 character with @samp{!} (an exclamation mark). For example, you can
4613 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4615 @item Expression results as strings
4616 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4617 and use the result as a string.
4621 @section @code{.ascii "@var{string}"}@dots{}
4623 @cindex @code{ascii} directive
4624 @cindex string literals
4625 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4626 separated by commas. It assembles each string (with no automatic
4627 trailing zero byte) into consecutive addresses.
4630 @section @code{.asciz "@var{string}"}@dots{}
4632 @cindex @code{asciz} directive
4633 @cindex zero-terminated strings
4634 @cindex null-terminated strings
4635 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4636 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4639 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4641 @cindex padding the location counter given number of bytes
4642 @cindex @code{balign} directive
4643 Pad the location counter (in the current subsection) to a particular
4644 storage boundary. The first expression (which must be absolute) is the
4645 alignment request in bytes. For example @samp{.balign 8} advances
4646 the location counter until it is a multiple of 8. If the location counter
4647 is already a multiple of 8, no change is needed.
4649 The second expression (also absolute) gives the fill value to be stored in the
4650 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4651 padding bytes are normally zero. However, on some systems, if the section is
4652 marked as containing code and the fill value is omitted, the space is filled
4653 with no-op instructions.
4655 The third expression is also absolute, and is also optional. If it is present,
4656 it is the maximum number of bytes that should be skipped by this alignment
4657 directive. If doing the alignment would require skipping more bytes than the
4658 specified maximum, then the alignment is not done at all. You can omit the
4659 fill value (the second argument) entirely by simply using two commas after the
4660 required alignment; this can be useful if you want the alignment to be filled
4661 with no-op instructions when appropriate.
4663 @cindex @code{balignw} directive
4664 @cindex @code{balignl} directive
4665 The @code{.balignw} and @code{.balignl} directives are variants of the
4666 @code{.balign} directive. The @code{.balignw} directive treats the fill
4667 pattern as a two byte word value. The @code{.balignl} directives treats the
4668 fill pattern as a four byte longword value. For example, @code{.balignw
4669 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4670 filled in with the value 0x368d (the exact placement of the bytes depends upon
4671 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4674 @node Bundle directives
4675 @section Bundle directives
4676 @subsection @code{.bundle_align_mode @var{abs-expr}}
4677 @cindex @code{bundle_align_mode} directive
4679 @cindex instruction bundle
4680 @cindex aligned instruction bundle
4681 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4682 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4683 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4684 disabled (which is the default state). If the argument it not zero, it
4685 gives the size of an instruction bundle as a power of two (as for the
4686 @code{.p2align} directive, @pxref{P2align}).
4688 For some targets, it's an ABI requirement that no instruction may span a
4689 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4690 instructions that starts on an aligned boundary. For example, if
4691 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4692 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4693 effect, no single instruction may span a boundary between bundles. If an
4694 instruction would start too close to the end of a bundle for the length of
4695 that particular instruction to fit within the bundle, then the space at the
4696 end of that bundle is filled with no-op instructions so the instruction
4697 starts in the next bundle. As a corollary, it's an error if any single
4698 instruction's encoding is longer than the bundle size.
4700 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4701 @cindex @code{bundle_lock} directive
4702 @cindex @code{bundle_unlock} directive
4703 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4704 allow explicit control over instruction bundle padding. These directives
4705 are only valid when @code{.bundle_align_mode} has been used to enable
4706 aligned instruction bundle mode. It's an error if they appear when
4707 @code{.bundle_align_mode} has not been used at all, or when the last
4708 directive was @w{@code{.bundle_align_mode 0}}.
4710 @cindex bundle-locked
4711 For some targets, it's an ABI requirement that certain instructions may
4712 appear only as part of specified permissible sequences of multiple
4713 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4714 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4715 instruction sequence. For purposes of aligned instruction bundle mode, a
4716 sequence starting with @code{.bundle_lock} and ending with
4717 @code{.bundle_unlock} is treated as a single instruction. That is, the
4718 entire sequence must fit into a single bundle and may not span a bundle
4719 boundary. If necessary, no-op instructions will be inserted before the
4720 first instruction of the sequence so that the whole sequence starts on an
4721 aligned bundle boundary. It's an error if the sequence is longer than the
4724 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4725 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4726 nested. That is, a second @code{.bundle_lock} directive before the next
4727 @code{.bundle_unlock} directive has no effect except that it must be
4728 matched by another closing @code{.bundle_unlock} so that there is the
4729 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4732 @section @code{.byte @var{expressions}}
4734 @cindex @code{byte} directive
4735 @cindex integers, one byte
4736 @code{.byte} expects zero or more expressions, separated by commas.
4737 Each expression is assembled into the next byte.
4739 @node CFI directives
4740 @section CFI directives
4741 @subsection @code{.cfi_sections @var{section_list}}
4742 @cindex @code{cfi_sections} directive
4743 @code{.cfi_sections} may be used to specify whether CFI directives
4744 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4745 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4746 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4747 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4748 directive is not used is @code{.cfi_sections .eh_frame}.
4750 On targets that support compact unwinding tables these can be generated
4751 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4753 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4754 which is used by the @value{TIC6X} target.
4756 The @code{.cfi_sections} directive can be repeated, with the same or different
4757 arguments, provided that CFI generation has not yet started. Once CFI
4758 generation has started however the section list is fixed and any attempts to
4759 redefine it will result in an error.
4761 @subsection @code{.cfi_startproc [simple]}
4762 @cindex @code{cfi_startproc} directive
4763 @code{.cfi_startproc} is used at the beginning of each function that
4764 should have an entry in @code{.eh_frame}. It initializes some internal
4765 data structures. Don't forget to close the function by
4766 @code{.cfi_endproc}.
4768 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4769 it also emits some architecture dependent initial CFI instructions.
4771 @subsection @code{.cfi_endproc}
4772 @cindex @code{cfi_endproc} directive
4773 @code{.cfi_endproc} is used at the end of a function where it closes its
4774 unwind entry previously opened by
4775 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4777 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4778 @cindex @code{cfi_personality} directive
4779 @code{.cfi_personality} defines personality routine and its encoding.
4780 @var{encoding} must be a constant determining how the personality
4781 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4782 argument is not present, otherwise second argument should be
4783 a constant or a symbol name. When using indirect encodings,
4784 the symbol provided should be the location where personality
4785 can be loaded from, not the personality routine itself.
4786 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4787 no personality routine.
4789 @subsection @code{.cfi_personality_id @var{id}}
4790 @cindex @code{cfi_personality_id} directive
4791 @code{cfi_personality_id} defines a personality routine by its index as
4792 defined in a compact unwinding format.
4793 Only valid when generating compact EH frames (i.e.
4794 with @code{.cfi_sections eh_frame_entry}.
4796 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4797 @cindex @code{cfi_fde_data} directive
4798 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4799 used for the current function. These are emitted inline in the
4800 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4801 in the @code{.gnu.extab} section otherwise.
4802 Only valid when generating compact EH frames (i.e.
4803 with @code{.cfi_sections eh_frame_entry}.
4805 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4806 @code{.cfi_lsda} defines LSDA and its encoding.
4807 @var{encoding} must be a constant determining how the LSDA
4808 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4809 argument is not present, otherwise the second argument should be a constant
4810 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4811 meaning that no LSDA is present.
4813 @subsection @code{.cfi_inline_lsda} [@var{align}]
4814 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4815 switches to the corresponding @code{.gnu.extab} section.
4816 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4817 Only valid when generating compact EH frames (i.e.
4818 with @code{.cfi_sections eh_frame_entry}.
4820 The table header and unwinding opcodes will be generated at this point,
4821 so that they are immediately followed by the LSDA data. The symbol
4822 referenced by the @code{.cfi_lsda} directive should still be defined
4823 in case a fallback FDE based encoding is used. The LSDA data is terminated
4824 by a section directive.
4826 The optional @var{align} argument specifies the alignment required.
4827 The alignment is specified as a power of two, as with the
4828 @code{.p2align} directive.
4830 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4831 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4832 address from @var{register} and add @var{offset} to it}.
4834 @subsection @code{.cfi_def_cfa_register @var{register}}
4835 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4836 now on @var{register} will be used instead of the old one. Offset
4839 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4840 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4841 remains the same, but @var{offset} is new. Note that it is the
4842 absolute offset that will be added to a defined register to compute
4845 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4846 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4847 value that is added/substracted from the previous offset.
4849 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4850 Previous value of @var{register} is saved at offset @var{offset} from
4853 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4854 Previous value of @var{register} is CFA + @var{offset}.
4856 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4857 Previous value of @var{register} is saved at offset @var{offset} from
4858 the current CFA register. This is transformed to @code{.cfi_offset}
4859 using the known displacement of the CFA register from the CFA.
4860 This is often easier to use, because the number will match the
4861 code it's annotating.
4863 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4864 Previous value of @var{register1} is saved in register @var{register2}.
4866 @subsection @code{.cfi_restore @var{register}}
4867 @code{.cfi_restore} says that the rule for @var{register} is now the
4868 same as it was at the beginning of the function, after all initial
4869 instruction added by @code{.cfi_startproc} were executed.
4871 @subsection @code{.cfi_undefined @var{register}}
4872 From now on the previous value of @var{register} can't be restored anymore.
4874 @subsection @code{.cfi_same_value @var{register}}
4875 Current value of @var{register} is the same like in the previous frame,
4876 i.e. no restoration needed.
4878 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4879 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4880 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4881 places them in the current row. This is useful for situations where you have
4882 multiple @code{.cfi_*} directives that need to be undone due to the control
4883 flow of the program. For example, we could have something like this (assuming
4884 the CFA is the value of @code{rbp}):
4894 .cfi_def_cfa %rsp, 8
4897 /* Do something else */
4900 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4901 to the instructions before @code{label}. This means we'd have to add multiple
4902 @code{.cfi} directives after @code{label} to recreate the original save
4903 locations of the registers, as well as setting the CFA back to the value of
4904 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4916 .cfi_def_cfa %rsp, 8
4920 /* Do something else */
4923 That way, the rules for the instructions after @code{label} will be the same
4924 as before the first @code{.cfi_restore} without having to use multiple
4925 @code{.cfi} directives.
4927 @subsection @code{.cfi_return_column @var{register}}
4928 Change return column @var{register}, i.e. the return address is either
4929 directly in @var{register} or can be accessed by rules for @var{register}.
4931 @subsection @code{.cfi_signal_frame}
4932 Mark current function as signal trampoline.
4934 @subsection @code{.cfi_window_save}
4935 SPARC register window has been saved.
4937 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4938 Allows the user to add arbitrary bytes to the unwind info. One
4939 might use this to add OS-specific CFI opcodes, or generic CFI
4940 opcodes that GAS does not yet support.
4942 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4943 The current value of @var{register} is @var{label}. The value of @var{label}
4944 will be encoded in the output file according to @var{encoding}; see the
4945 description of @code{.cfi_personality} for details on this encoding.
4947 The usefulness of equating a register to a fixed label is probably
4948 limited to the return address register. Here, it can be useful to
4949 mark a code segment that has only one return address which is reached
4950 by a direct branch and no copy of the return address exists in memory
4951 or another register.
4954 @section @code{.comm @var{symbol} , @var{length} }
4956 @cindex @code{comm} directive
4957 @cindex symbol, common
4958 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4959 common symbol in one object file may be merged with a defined or common symbol
4960 of the same name in another object file. If @code{@value{LD}} does not see a
4961 definition for the symbol--just one or more common symbols--then it will
4962 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4963 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4964 the same name, and they do not all have the same size, it will allocate space
4965 using the largest size.
4968 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4969 an optional third argument. This is the desired alignment of the symbol,
4970 specified for ELF as a byte boundary (for example, an alignment of 16 means
4971 that the least significant 4 bits of the address should be zero), and for PE
4972 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4973 boundary). The alignment must be an absolute expression, and it must be a
4974 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4975 common symbol, it will use the alignment when placing the symbol. If no
4976 alignment is specified, @command{@value{AS}} will set the alignment to the
4977 largest power of two less than or equal to the size of the symbol, up to a
4978 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4979 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4980 @samp{--section-alignment} option; image file sections in PE are aligned to
4981 multiples of 4096, which is far too large an alignment for ordinary variables.
4982 It is rather the default alignment for (non-debug) sections within object
4983 (@samp{*.o}) files, which are less strictly aligned.}.
4987 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4988 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4992 @section @code{.data @var{subsection}}
4994 @cindex @code{data} directive
4995 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4996 end of the data subsection numbered @var{subsection} (which is an
4997 absolute expression). If @var{subsection} is omitted, it defaults
5002 @section @code{.def @var{name}}
5004 @cindex @code{def} directive
5005 @cindex COFF symbols, debugging
5006 @cindex debugging COFF symbols
5007 Begin defining debugging information for a symbol @var{name}; the
5008 definition extends until the @code{.endef} directive is encountered.
5011 This directive is only observed when @command{@value{AS}} is configured for COFF
5012 format output; when producing @code{b.out}, @samp{.def} is recognized,
5019 @section @code{.desc @var{symbol}, @var{abs-expression}}
5021 @cindex @code{desc} directive
5022 @cindex COFF symbol descriptor
5023 @cindex symbol descriptor, COFF
5024 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5025 to the low 16 bits of an absolute expression.
5028 The @samp{.desc} directive is not available when @command{@value{AS}} is
5029 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5030 object format. For the sake of compatibility, @command{@value{AS}} accepts
5031 it, but produces no output, when configured for COFF.
5037 @section @code{.dim}
5039 @cindex @code{dim} directive
5040 @cindex COFF auxiliary symbol information
5041 @cindex auxiliary symbol information, COFF
5042 This directive is generated by compilers to include auxiliary debugging
5043 information in the symbol table. It is only permitted inside
5044 @code{.def}/@code{.endef} pairs.
5047 @samp{.dim} is only meaningful when generating COFF format output; when
5048 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5054 @section @code{.double @var{flonums}}
5056 @cindex @code{double} directive
5057 @cindex floating point numbers (double)
5058 @code{.double} expects zero or more flonums, separated by commas. It
5059 assembles floating point numbers.
5061 The exact kind of floating point numbers emitted depends on how
5062 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5066 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5067 in @sc{ieee} format.
5072 @section @code{.eject}
5074 @cindex @code{eject} directive
5075 @cindex new page, in listings
5076 @cindex page, in listings
5077 @cindex listing control: new page
5078 Force a page break at this point, when generating assembly listings.
5081 @section @code{.else}
5083 @cindex @code{else} directive
5084 @code{.else} is part of the @command{@value{AS}} support for conditional
5085 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5086 of code to be assembled if the condition for the preceding @code{.if}
5090 @section @code{.elseif}
5092 @cindex @code{elseif} directive
5093 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5094 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5095 @code{.if} block that would otherwise fill the entire @code{.else} section.
5098 @section @code{.end}
5100 @cindex @code{end} directive
5101 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5102 process anything in the file past the @code{.end} directive.
5106 @section @code{.endef}
5108 @cindex @code{endef} directive
5109 This directive flags the end of a symbol definition begun with
5113 @samp{.endef} is only meaningful when generating COFF format output; if
5114 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5115 directive but ignores it.
5120 @section @code{.endfunc}
5121 @cindex @code{endfunc} directive
5122 @code{.endfunc} marks the end of a function specified with @code{.func}.
5125 @section @code{.endif}
5127 @cindex @code{endif} directive
5128 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5129 it marks the end of a block of code that is only assembled
5130 conditionally. @xref{If,,@code{.if}}.
5133 @section @code{.equ @var{symbol}, @var{expression}}
5135 @cindex @code{equ} directive
5136 @cindex assigning values to symbols
5137 @cindex symbols, assigning values to
5138 This directive sets the value of @var{symbol} to @var{expression}.
5139 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5142 The syntax for @code{equ} on the HPPA is
5143 @samp{@var{symbol} .equ @var{expression}}.
5147 The syntax for @code{equ} on the Z80 is
5148 @samp{@var{symbol} equ @var{expression}}.
5149 On the Z80 it is an eror if @var{symbol} is already defined,
5150 but the symbol is not protected from later redefinition.
5151 Compare @ref{Equiv}.
5155 @section @code{.equiv @var{symbol}, @var{expression}}
5156 @cindex @code{equiv} directive
5157 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5158 the assembler will signal an error if @var{symbol} is already defined. Note a
5159 symbol which has been referenced but not actually defined is considered to be
5162 Except for the contents of the error message, this is roughly equivalent to
5169 plus it protects the symbol from later redefinition.
5172 @section @code{.eqv @var{symbol}, @var{expression}}
5173 @cindex @code{eqv} directive
5174 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5175 evaluate the expression or any part of it immediately. Instead each time
5176 the resulting symbol is used in an expression, a snapshot of its current
5180 @section @code{.err}
5181 @cindex @code{err} directive
5182 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5183 message and, unless the @option{-Z} option was used, it will not generate an
5184 object file. This can be used to signal an error in conditionally compiled code.
5187 @section @code{.error "@var{string}"}
5188 @cindex error directive
5190 Similarly to @code{.err}, this directive emits an error, but you can specify a
5191 string that will be emitted as the error message. If you don't specify the
5192 message, it defaults to @code{".error directive invoked in source file"}.
5193 @xref{Errors, ,Error and Warning Messages}.
5196 .error "This code has not been assembled and tested."
5200 @section @code{.exitm}
5201 Exit early from the current macro definition. @xref{Macro}.
5204 @section @code{.extern}
5206 @cindex @code{extern} directive
5207 @code{.extern} is accepted in the source program---for compatibility
5208 with other assemblers---but it is ignored. @command{@value{AS}} treats
5209 all undefined symbols as external.
5212 @section @code{.fail @var{expression}}
5214 @cindex @code{fail} directive
5215 Generates an error or a warning. If the value of the @var{expression} is 500
5216 or more, @command{@value{AS}} will print a warning message. If the value is less
5217 than 500, @command{@value{AS}} will print an error message. The message will
5218 include the value of @var{expression}. This can occasionally be useful inside
5219 complex nested macros or conditional assembly.
5222 @section @code{.file}
5223 @cindex @code{file} directive
5225 @ifclear no-file-dir
5226 There are two different versions of the @code{.file} directive. Targets
5227 that support DWARF2 line number information use the DWARF2 version of
5228 @code{.file}. Other targets use the default version.
5230 @subheading Default Version
5232 @cindex logical file name
5233 @cindex file name, logical
5234 This version of the @code{.file} directive tells @command{@value{AS}} that we
5235 are about to start a new logical file. The syntax is:
5241 @var{string} is the new file name. In general, the filename is
5242 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5243 to specify an empty file name, you must give the quotes--@code{""}. This
5244 statement may go away in future: it is only recognized to be compatible with
5245 old @command{@value{AS}} programs.
5247 @subheading DWARF2 Version
5250 When emitting DWARF2 line number information, @code{.file} assigns filenames
5251 to the @code{.debug_line} file name table. The syntax is:
5254 .file @var{fileno} @var{filename}
5257 The @var{fileno} operand should be a unique positive integer to use as the
5258 index of the entry in the table. The @var{filename} operand is a C string
5261 The detail of filename indices is exposed to the user because the filename
5262 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5263 information, and thus the user must know the exact indices that table
5267 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5269 @cindex @code{fill} directive
5270 @cindex writing patterns in memory
5271 @cindex patterns, writing in memory
5272 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5273 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5274 may be zero or more. @var{Size} may be zero or more, but if it is
5275 more than 8, then it is deemed to have the value 8, compatible with
5276 other people's assemblers. The contents of each @var{repeat} bytes
5277 is taken from an 8-byte number. The highest order 4 bytes are
5278 zero. The lowest order 4 bytes are @var{value} rendered in the
5279 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5280 Each @var{size} bytes in a repetition is taken from the lowest order
5281 @var{size} bytes of this number. Again, this bizarre behavior is
5282 compatible with other people's assemblers.
5284 @var{size} and @var{value} are optional.
5285 If the second comma and @var{value} are absent, @var{value} is
5286 assumed zero. If the first comma and following tokens are absent,
5287 @var{size} is assumed to be 1.
5290 @section @code{.float @var{flonums}}
5292 @cindex floating point numbers (single)
5293 @cindex @code{float} directive
5294 This directive assembles zero or more flonums, separated by commas. It
5295 has the same effect as @code{.single}.
5297 The exact kind of floating point numbers emitted depends on how
5298 @command{@value{AS}} is configured.
5299 @xref{Machine Dependencies}.
5303 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5304 in @sc{ieee} format.
5309 @section @code{.func @var{name}[,@var{label}]}
5310 @cindex @code{func} directive
5311 @code{.func} emits debugging information to denote function @var{name}, and
5312 is ignored unless the file is assembled with debugging enabled.
5313 Only @samp{--gstabs[+]} is currently supported.
5314 @var{label} is the entry point of the function and if omitted @var{name}
5315 prepended with the @samp{leading char} is used.
5316 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5317 All functions are currently defined to have @code{void} return type.
5318 The function must be terminated with @code{.endfunc}.
5321 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5323 @cindex @code{global} directive
5324 @cindex symbol, making visible to linker
5325 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5326 @var{symbol} in your partial program, its value is made available to
5327 other partial programs that are linked with it. Otherwise,
5328 @var{symbol} takes its attributes from a symbol of the same name
5329 from another file linked into the same program.
5331 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5332 compatibility with other assemblers.
5335 On the HPPA, @code{.global} is not always enough to make it accessible to other
5336 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5337 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5342 @section @code{.gnu_attribute @var{tag},@var{value}}
5343 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5346 @section @code{.hidden @var{names}}
5348 @cindex @code{hidden} directive
5350 This is one of the ELF visibility directives. The other two are
5351 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5352 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5354 This directive overrides the named symbols default visibility (which is set by
5355 their binding: local, global or weak). The directive sets the visibility to
5356 @code{hidden} which means that the symbols are not visible to other components.
5357 Such symbols are always considered to be @code{protected} as well.
5361 @section @code{.hword @var{expressions}}
5363 @cindex @code{hword} directive
5364 @cindex integers, 16-bit
5365 @cindex numbers, 16-bit
5366 @cindex sixteen bit integers
5367 This expects zero or more @var{expressions}, and emits
5368 a 16 bit number for each.
5371 This directive is a synonym for @samp{.short}; depending on the target
5372 architecture, it may also be a synonym for @samp{.word}.
5376 This directive is a synonym for @samp{.short}.
5379 This directive is a synonym for both @samp{.short} and @samp{.word}.
5384 @section @code{.ident}
5386 @cindex @code{ident} directive
5388 This directive is used by some assemblers to place tags in object files. The
5389 behavior of this directive varies depending on the target. When using the
5390 a.out object file format, @command{@value{AS}} simply accepts the directive for
5391 source-file compatibility with existing assemblers, but does not emit anything
5392 for it. When using COFF, comments are emitted to the @code{.comment} or
5393 @code{.rdata} section, depending on the target. When using ELF, comments are
5394 emitted to the @code{.comment} section.
5397 @section @code{.if @var{absolute expression}}
5399 @cindex conditional assembly
5400 @cindex @code{if} directive
5401 @code{.if} marks the beginning of a section of code which is only
5402 considered part of the source program being assembled if the argument
5403 (which must be an @var{absolute expression}) is non-zero. The end of
5404 the conditional section of code must be marked by @code{.endif}
5405 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5406 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5407 If you have several conditions to check, @code{.elseif} may be used to avoid
5408 nesting blocks if/else within each subsequent @code{.else} block.
5410 The following variants of @code{.if} are also supported:
5412 @cindex @code{ifdef} directive
5413 @item .ifdef @var{symbol}
5414 Assembles the following section of code if the specified @var{symbol}
5415 has been defined. Note a symbol which has been referenced but not yet defined
5416 is considered to be undefined.
5418 @cindex @code{ifb} directive
5419 @item .ifb @var{text}
5420 Assembles the following section of code if the operand is blank (empty).
5422 @cindex @code{ifc} directive
5423 @item .ifc @var{string1},@var{string2}
5424 Assembles the following section of code if the two strings are the same. The
5425 strings may be optionally quoted with single quotes. If they are not quoted,
5426 the first string stops at the first comma, and the second string stops at the
5427 end of the line. Strings which contain whitespace should be quoted. The
5428 string comparison is case sensitive.
5430 @cindex @code{ifeq} directive
5431 @item .ifeq @var{absolute expression}
5432 Assembles the following section of code if the argument is zero.
5434 @cindex @code{ifeqs} directive
5435 @item .ifeqs @var{string1},@var{string2}
5436 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5438 @cindex @code{ifge} directive
5439 @item .ifge @var{absolute expression}
5440 Assembles the following section of code if the argument is greater than or
5443 @cindex @code{ifgt} directive
5444 @item .ifgt @var{absolute expression}
5445 Assembles the following section of code if the argument is greater than zero.
5447 @cindex @code{ifle} directive
5448 @item .ifle @var{absolute expression}
5449 Assembles the following section of code if the argument is less than or equal
5452 @cindex @code{iflt} directive
5453 @item .iflt @var{absolute expression}
5454 Assembles the following section of code if the argument is less than zero.
5456 @cindex @code{ifnb} directive
5457 @item .ifnb @var{text}
5458 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5459 following section of code if the operand is non-blank (non-empty).
5461 @cindex @code{ifnc} directive
5462 @item .ifnc @var{string1},@var{string2}.
5463 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5464 following section of code if the two strings are not the same.
5466 @cindex @code{ifndef} directive
5467 @cindex @code{ifnotdef} directive
5468 @item .ifndef @var{symbol}
5469 @itemx .ifnotdef @var{symbol}
5470 Assembles the following section of code if the specified @var{symbol}
5471 has not been defined. Both spelling variants are equivalent. Note a symbol
5472 which has been referenced but not yet defined is considered to be undefined.
5474 @cindex @code{ifne} directive
5475 @item .ifne @var{absolute expression}
5476 Assembles the following section of code if the argument is not equal to zero
5477 (in other words, this is equivalent to @code{.if}).
5479 @cindex @code{ifnes} directive
5480 @item .ifnes @var{string1},@var{string2}
5481 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5482 following section of code if the two strings are not the same.
5486 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5488 @cindex @code{incbin} directive
5489 @cindex binary files, including
5490 The @code{incbin} directive includes @var{file} verbatim at the current
5491 location. You can control the search paths used with the @samp{-I} command-line
5492 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5495 The @var{skip} argument skips a number of bytes from the start of the
5496 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5497 read. Note that the data is not aligned in any way, so it is the user's
5498 responsibility to make sure that proper alignment is provided both before and
5499 after the @code{incbin} directive.
5502 @section @code{.include "@var{file}"}
5504 @cindex @code{include} directive
5505 @cindex supporting files, including
5506 @cindex files, including
5507 This directive provides a way to include supporting files at specified
5508 points in your source program. The code from @var{file} is assembled as
5509 if it followed the point of the @code{.include}; when the end of the
5510 included file is reached, assembly of the original file continues. You
5511 can control the search paths used with the @samp{-I} command-line option
5512 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5516 @section @code{.int @var{expressions}}
5518 @cindex @code{int} directive
5519 @cindex integers, 32-bit
5520 Expect zero or more @var{expressions}, of any section, separated by commas.
5521 For each expression, emit a number that, at run time, is the value of that
5522 expression. The byte order and bit size of the number depends on what kind
5523 of target the assembly is for.
5527 On most forms of the H8/300, @code{.int} emits 16-bit
5528 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5535 @section @code{.internal @var{names}}
5537 @cindex @code{internal} directive
5539 This is one of the ELF visibility directives. The other two are
5540 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5541 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5543 This directive overrides the named symbols default visibility (which is set by
5544 their binding: local, global or weak). The directive sets the visibility to
5545 @code{internal} which means that the symbols are considered to be @code{hidden}
5546 (i.e., not visible to other components), and that some extra, processor specific
5547 processing must also be performed upon the symbols as well.
5551 @section @code{.irp @var{symbol},@var{values}}@dots{}
5553 @cindex @code{irp} directive
5554 Evaluate a sequence of statements assigning different values to @var{symbol}.
5555 The sequence of statements starts at the @code{.irp} directive, and is
5556 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5557 set to @var{value}, and the sequence of statements is assembled. If no
5558 @var{value} is listed, the sequence of statements is assembled once, with
5559 @var{symbol} set to the null string. To refer to @var{symbol} within the
5560 sequence of statements, use @var{\symbol}.
5562 For example, assembling
5570 is equivalent to assembling
5578 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5581 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5583 @cindex @code{irpc} directive
5584 Evaluate a sequence of statements assigning different values to @var{symbol}.
5585 The sequence of statements starts at the @code{.irpc} directive, and is
5586 terminated by an @code{.endr} directive. For each character in @var{value},
5587 @var{symbol} is set to the character, and the sequence of statements is
5588 assembled. If no @var{value} is listed, the sequence of statements is
5589 assembled once, with @var{symbol} set to the null string. To refer to
5590 @var{symbol} within the sequence of statements, use @var{\symbol}.
5592 For example, assembling
5600 is equivalent to assembling
5608 For some caveats with the spelling of @var{symbol}, see also the discussion
5612 @section @code{.lcomm @var{symbol} , @var{length}}
5614 @cindex @code{lcomm} directive
5615 @cindex local common symbols
5616 @cindex symbols, local common
5617 Reserve @var{length} (an absolute expression) bytes for a local common
5618 denoted by @var{symbol}. The section and value of @var{symbol} are
5619 those of the new local common. The addresses are allocated in the bss
5620 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5621 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5622 not visible to @code{@value{LD}}.
5625 Some targets permit a third argument to be used with @code{.lcomm}. This
5626 argument specifies the desired alignment of the symbol in the bss section.
5630 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5631 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5635 @section @code{.lflags}
5637 @cindex @code{lflags} directive (ignored)
5638 @command{@value{AS}} accepts this directive, for compatibility with other
5639 assemblers, but ignores it.
5641 @ifclear no-line-dir
5643 @section @code{.line @var{line-number}}
5645 @cindex @code{line} directive
5646 @cindex logical line number
5648 Change the logical line number. @var{line-number} must be an absolute
5649 expression. The next line has that logical line number. Therefore any other
5650 statements on the current line (after a statement separator character) are
5651 reported as on logical line number @var{line-number} @minus{} 1. One day
5652 @command{@value{AS}} will no longer support this directive: it is recognized only
5653 for compatibility with existing assembler programs.
5656 Even though this is a directive associated with the @code{a.out} or
5657 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5658 when producing COFF output, and treats @samp{.line} as though it
5659 were the COFF @samp{.ln} @emph{if} it is found outside a
5660 @code{.def}/@code{.endef} pair.
5662 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5663 used by compilers to generate auxiliary symbol information for
5668 @section @code{.linkonce [@var{type}]}
5670 @cindex @code{linkonce} directive
5671 @cindex common sections
5672 Mark the current section so that the linker only includes a single copy of it.
5673 This may be used to include the same section in several different object files,
5674 but ensure that the linker will only include it once in the final output file.
5675 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5676 Duplicate sections are detected based on the section name, so it should be
5679 This directive is only supported by a few object file formats; as of this
5680 writing, the only object file format which supports it is the Portable
5681 Executable format used on Windows NT.
5683 The @var{type} argument is optional. If specified, it must be one of the
5684 following strings. For example:
5688 Not all types may be supported on all object file formats.
5692 Silently discard duplicate sections. This is the default.
5695 Warn if there are duplicate sections, but still keep only one copy.
5698 Warn if any of the duplicates have different sizes.
5701 Warn if any of the duplicates do not have exactly the same contents.
5705 @section @code{.list}
5707 @cindex @code{list} directive
5708 @cindex listing control, turning on
5709 Control (in conjunction with the @code{.nolist} directive) whether or
5710 not assembly listings are generated. These two directives maintain an
5711 internal counter (which is zero initially). @code{.list} increments the
5712 counter, and @code{.nolist} decrements it. Assembly listings are
5713 generated whenever the counter is greater than zero.
5715 By default, listings are disabled. When you enable them (with the
5716 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5717 the initial value of the listing counter is one.
5720 @section @code{.ln @var{line-number}}
5722 @cindex @code{ln} directive
5723 @ifclear no-line-dir
5724 @samp{.ln} is a synonym for @samp{.line}.
5727 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5728 must be an absolute expression. The next line has that logical
5729 line number, so any other statements on the current line (after a
5730 statement separator character @code{;}) are reported as on logical
5731 line number @var{line-number} @minus{} 1.
5734 This directive is accepted, but ignored, when @command{@value{AS}} is
5735 configured for @code{b.out}; its effect is only associated with COFF
5741 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5742 @cindex @code{loc} directive
5743 When emitting DWARF2 line number information,
5744 the @code{.loc} directive will add a row to the @code{.debug_line} line
5745 number matrix corresponding to the immediately following assembly
5746 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5747 arguments will be applied to the @code{.debug_line} state machine before
5750 The @var{options} are a sequence of the following tokens in any order:
5754 This option will set the @code{basic_block} register in the
5755 @code{.debug_line} state machine to @code{true}.
5758 This option will set the @code{prologue_end} register in the
5759 @code{.debug_line} state machine to @code{true}.
5761 @item epilogue_begin
5762 This option will set the @code{epilogue_begin} register in the
5763 @code{.debug_line} state machine to @code{true}.
5765 @item is_stmt @var{value}
5766 This option will set the @code{is_stmt} register in the
5767 @code{.debug_line} state machine to @code{value}, which must be
5770 @item isa @var{value}
5771 This directive will set the @code{isa} register in the @code{.debug_line}
5772 state machine to @var{value}, which must be an unsigned integer.
5774 @item discriminator @var{value}
5775 This directive will set the @code{discriminator} register in the @code{.debug_line}
5776 state machine to @var{value}, which must be an unsigned integer.
5780 @node Loc_mark_labels
5781 @section @code{.loc_mark_labels @var{enable}}
5782 @cindex @code{loc_mark_labels} directive
5783 When emitting DWARF2 line number information,
5784 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5785 to the @code{.debug_line} line number matrix with the @code{basic_block}
5786 register in the state machine set whenever a code label is seen.
5787 The @var{enable} argument should be either 1 or 0, to enable or disable
5788 this function respectively.
5792 @section @code{.local @var{names}}
5794 @cindex @code{local} directive
5795 This directive, which is available for ELF targets, marks each symbol in
5796 the comma-separated list of @code{names} as a local symbol so that it
5797 will not be externally visible. If the symbols do not already exist,
5798 they will be created.
5800 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5801 accept an alignment argument, which is the case for most ELF targets,
5802 the @code{.local} directive can be used in combination with @code{.comm}
5803 (@pxref{Comm}) to define aligned local common data.
5807 @section @code{.long @var{expressions}}
5809 @cindex @code{long} directive
5810 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5813 @c no one seems to know what this is for or whether this description is
5814 @c what it really ought to do
5816 @section @code{.lsym @var{symbol}, @var{expression}}
5818 @cindex @code{lsym} directive
5819 @cindex symbol, not referenced in assembly
5820 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5821 the hash table, ensuring it cannot be referenced by name during the
5822 rest of the assembly. This sets the attributes of the symbol to be
5823 the same as the expression value:
5825 @var{other} = @var{descriptor} = 0
5826 @var{type} = @r{(section of @var{expression})}
5827 @var{value} = @var{expression}
5830 The new symbol is not flagged as external.
5834 @section @code{.macro}
5837 The commands @code{.macro} and @code{.endm} allow you to define macros that
5838 generate assembly output. For example, this definition specifies a macro
5839 @code{sum} that puts a sequence of numbers into memory:
5842 .macro sum from=0, to=5
5851 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5863 @item .macro @var{macname}
5864 @itemx .macro @var{macname} @var{macargs} @dots{}
5865 @cindex @code{macro} directive
5866 Begin the definition of a macro called @var{macname}. If your macro
5867 definition requires arguments, specify their names after the macro name,
5868 separated by commas or spaces. You can qualify the macro argument to
5869 indicate whether all invocations must specify a non-blank value (through
5870 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5871 (through @samp{:@code{vararg}}). You can supply a default value for any
5872 macro argument by following the name with @samp{=@var{deflt}}. You
5873 cannot define two macros with the same @var{macname} unless it has been
5874 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5875 definitions. For example, these are all valid @code{.macro} statements:
5879 Begin the definition of a macro called @code{comm}, which takes no
5882 @item .macro plus1 p, p1
5883 @itemx .macro plus1 p p1
5884 Either statement begins the definition of a macro called @code{plus1},
5885 which takes two arguments; within the macro definition, write
5886 @samp{\p} or @samp{\p1} to evaluate the arguments.
5888 @item .macro reserve_str p1=0 p2
5889 Begin the definition of a macro called @code{reserve_str}, with two
5890 arguments. The first argument has a default value, but not the second.
5891 After the definition is complete, you can call the macro either as
5892 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5893 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5894 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5895 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5897 @item .macro m p1:req, p2=0, p3:vararg
5898 Begin the definition of a macro called @code{m}, with at least three
5899 arguments. The first argument must always have a value specified, but
5900 not the second, which instead has a default value. The third formal
5901 will get assigned all remaining arguments specified at invocation time.
5903 When you call a macro, you can specify the argument values either by
5904 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5905 @samp{sum to=17, from=9}.
5909 Note that since each of the @var{macargs} can be an identifier exactly
5910 as any other one permitted by the target architecture, there may be
5911 occasional problems if the target hand-crafts special meanings to certain
5912 characters when they occur in a special position. For example, if the colon
5913 (@code{:}) is generally permitted to be part of a symbol name, but the
5914 architecture specific code special-cases it when occurring as the final
5915 character of a symbol (to denote a label), then the macro parameter
5916 replacement code will have no way of knowing that and consider the whole
5917 construct (including the colon) an identifier, and check only this
5918 identifier for being the subject to parameter substitution. So for example
5919 this macro definition:
5927 might not work as expected. Invoking @samp{label foo} might not create a label
5928 called @samp{foo} but instead just insert the text @samp{\l:} into the
5929 assembler source, probably generating an error about an unrecognised
5932 Similarly problems might occur with the period character (@samp{.})
5933 which is often allowed inside opcode names (and hence identifier names). So
5934 for example constructing a macro to build an opcode from a base name and a
5935 length specifier like this:
5938 .macro opcode base length
5943 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5944 instruction but instead generate some kind of error as the assembler tries to
5945 interpret the text @samp{\base.\length}.
5947 There are several possible ways around this problem:
5950 @item Insert white space
5951 If it is possible to use white space characters then this is the simplest
5960 @item Use @samp{\()}
5961 The string @samp{\()} can be used to separate the end of a macro argument from
5962 the following text. eg:
5965 .macro opcode base length
5970 @item Use the alternate macro syntax mode
5971 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5972 used as a separator. eg:
5982 Note: this problem of correctly identifying string parameters to pseudo ops
5983 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5984 and @code{.irpc} (@pxref{Irpc}) as well.
5987 @cindex @code{endm} directive
5988 Mark the end of a macro definition.
5991 @cindex @code{exitm} directive
5992 Exit early from the current macro definition.
5994 @cindex number of macros executed
5995 @cindex macros, count executed
5997 @command{@value{AS}} maintains a counter of how many macros it has
5998 executed in this pseudo-variable; you can copy that number to your
5999 output with @samp{\@@}, but @emph{only within a macro definition}.
6001 @item LOCAL @var{name} [ , @dots{} ]
6002 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6003 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6004 @xref{Altmacro,,@code{.altmacro}}.
6008 @section @code{.mri @var{val}}
6010 @cindex @code{mri} directive
6011 @cindex MRI mode, temporarily
6012 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6013 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6014 affects code assembled until the next @code{.mri} directive, or until the end
6015 of the file. @xref{M, MRI mode, MRI mode}.
6018 @section @code{.noaltmacro}
6019 Disable alternate macro mode. @xref{Altmacro}.
6022 @section @code{.nolist}
6024 @cindex @code{nolist} directive
6025 @cindex listing control, turning off
6026 Control (in conjunction with the @code{.list} directive) whether or
6027 not assembly listings are generated. These two directives maintain an
6028 internal counter (which is zero initially). @code{.list} increments the
6029 counter, and @code{.nolist} decrements it. Assembly listings are
6030 generated whenever the counter is greater than zero.
6033 @section @code{.octa @var{bignums}}
6035 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
6036 @cindex @code{octa} directive
6037 @cindex integer, 16-byte
6038 @cindex sixteen byte integer
6039 This directive expects zero or more bignums, separated by commas. For each
6040 bignum, it emits a 16-byte integer.
6042 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6043 hence @emph{octa}-word for 16 bytes.
6046 @section @code{.offset @var{loc}}
6048 @cindex @code{offset} directive
6049 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6050 be an absolute expression. This directive may be useful for defining
6051 symbols with absolute values. Do not confuse it with the @code{.org}
6055 @section @code{.org @var{new-lc} , @var{fill}}
6057 @cindex @code{org} directive
6058 @cindex location counter, advancing
6059 @cindex advancing location counter
6060 @cindex current address, advancing
6061 Advance the location counter of the current section to
6062 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6063 expression with the same section as the current subsection. That is,
6064 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6065 wrong section, the @code{.org} directive is ignored. To be compatible
6066 with former assemblers, if the section of @var{new-lc} is absolute,
6067 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6068 is the same as the current subsection.
6070 @code{.org} may only increase the location counter, or leave it
6071 unchanged; you cannot use @code{.org} to move the location counter
6074 @c double negative used below "not undefined" because this is a specific
6075 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6076 @c section. doc@cygnus.com 18feb91
6077 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6078 may not be undefined. If you really detest this restriction we eagerly await
6079 a chance to share your improved assembler.
6081 Beware that the origin is relative to the start of the section, not
6082 to the start of the subsection. This is compatible with other
6083 people's assemblers.
6085 When the location counter (of the current subsection) is advanced, the
6086 intervening bytes are filled with @var{fill} which should be an
6087 absolute expression. If the comma and @var{fill} are omitted,
6088 @var{fill} defaults to zero.
6091 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6093 @cindex padding the location counter given a power of two
6094 @cindex @code{p2align} directive
6095 Pad the location counter (in the current subsection) to a particular
6096 storage boundary. The first expression (which must be absolute) is the
6097 number of low-order zero bits the location counter must have after
6098 advancement. For example @samp{.p2align 3} advances the location
6099 counter until it a multiple of 8. If the location counter is already a
6100 multiple of 8, no change is needed.
6102 The second expression (also absolute) gives the fill value to be stored in the
6103 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6104 padding bytes are normally zero. However, on some systems, if the section is
6105 marked as containing code and the fill value is omitted, the space is filled
6106 with no-op instructions.
6108 The third expression is also absolute, and is also optional. If it is present,
6109 it is the maximum number of bytes that should be skipped by this alignment
6110 directive. If doing the alignment would require skipping more bytes than the
6111 specified maximum, then the alignment is not done at all. You can omit the
6112 fill value (the second argument) entirely by simply using two commas after the
6113 required alignment; this can be useful if you want the alignment to be filled
6114 with no-op instructions when appropriate.
6116 @cindex @code{p2alignw} directive
6117 @cindex @code{p2alignl} directive
6118 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6119 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6120 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6121 fill pattern as a four byte longword value. For example, @code{.p2alignw
6122 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6123 filled in with the value 0x368d (the exact placement of the bytes depends upon
6124 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6129 @section @code{.popsection}
6131 @cindex @code{popsection} directive
6132 @cindex Section Stack
6133 This is one of the ELF section stack manipulation directives. The others are
6134 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6135 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6138 This directive replaces the current section (and subsection) with the top
6139 section (and subsection) on the section stack. This section is popped off the
6145 @section @code{.previous}
6147 @cindex @code{previous} directive
6148 @cindex Section Stack
6149 This is one of the ELF section stack manipulation directives. The others are
6150 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6151 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6152 (@pxref{PopSection}).
6154 This directive swaps the current section (and subsection) with most recently
6155 referenced section/subsection pair prior to this one. Multiple
6156 @code{.previous} directives in a row will flip between two sections (and their
6157 subsections). For example:
6169 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6175 # Now in section A subsection 1
6179 # Now in section B subsection 0
6182 # Now in section B subsection 1
6185 # Now in section B subsection 0
6189 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6190 section B and 0x9abc into subsection 1 of section B.
6192 In terms of the section stack, this directive swaps the current section with
6193 the top section on the section stack.
6197 @section @code{.print @var{string}}
6199 @cindex @code{print} directive
6200 @command{@value{AS}} will print @var{string} on the standard output during
6201 assembly. You must put @var{string} in double quotes.
6205 @section @code{.protected @var{names}}
6207 @cindex @code{protected} directive
6209 This is one of the ELF visibility directives. The other two are
6210 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6212 This directive overrides the named symbols default visibility (which is set by
6213 their binding: local, global or weak). The directive sets the visibility to
6214 @code{protected} which means that any references to the symbols from within the
6215 components that defines them must be resolved to the definition in that
6216 component, even if a definition in another component would normally preempt
6221 @section @code{.psize @var{lines} , @var{columns}}
6223 @cindex @code{psize} directive
6224 @cindex listing control: paper size
6225 @cindex paper size, for listings
6226 Use this directive to declare the number of lines---and, optionally, the
6227 number of columns---to use for each page, when generating listings.
6229 If you do not use @code{.psize}, listings use a default line-count
6230 of 60. You may omit the comma and @var{columns} specification; the
6231 default width is 200 columns.
6233 @command{@value{AS}} generates formfeeds whenever the specified number of
6234 lines is exceeded (or whenever you explicitly request one, using
6237 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6238 those explicitly specified with @code{.eject}.
6241 @section @code{.purgem @var{name}}
6243 @cindex @code{purgem} directive
6244 Undefine the macro @var{name}, so that later uses of the string will not be
6245 expanded. @xref{Macro}.
6249 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6251 @cindex @code{pushsection} directive
6252 @cindex Section Stack
6253 This is one of the ELF section stack manipulation directives. The others are
6254 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6255 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6258 This directive pushes the current section (and subsection) onto the
6259 top of the section stack, and then replaces the current section and
6260 subsection with @code{name} and @code{subsection}. The optional
6261 @code{flags}, @code{type} and @code{arguments} are treated the same
6262 as in the @code{.section} (@pxref{Section}) directive.
6266 @section @code{.quad @var{bignums}}
6268 @cindex @code{quad} directive
6269 @code{.quad} expects zero or more bignums, separated by commas. For
6270 each bignum, it emits
6272 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6273 warning message; and just takes the lowest order 8 bytes of the bignum.
6274 @cindex eight-byte integer
6275 @cindex integer, 8-byte
6277 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6278 hence @emph{quad}-word for 8 bytes.
6281 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6282 warning message; and just takes the lowest order 16 bytes of the bignum.
6283 @cindex sixteen-byte integer
6284 @cindex integer, 16-byte
6288 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6290 @cindex @code{reloc} directive
6291 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6292 @var{expression}. If @var{offset} is a number, the relocation is generated in
6293 the current section. If @var{offset} is an expression that resolves to a
6294 symbol plus offset, the relocation is generated in the given symbol's section.
6295 @var{expression}, if present, must resolve to a symbol plus addend or to an
6296 absolute value, but note that not all targets support an addend. e.g. ELF REL
6297 targets such as i386 store an addend in the section contents rather than in the
6298 relocation. This low level interface does not support addends stored in the
6302 @section @code{.rept @var{count}}
6304 @cindex @code{rept} directive
6305 Repeat the sequence of lines between the @code{.rept} directive and the next
6306 @code{.endr} directive @var{count} times.
6308 For example, assembling
6316 is equivalent to assembling
6325 @section @code{.sbttl "@var{subheading}"}
6327 @cindex @code{sbttl} directive
6328 @cindex subtitles for listings
6329 @cindex listing control: subtitle
6330 Use @var{subheading} as the title (third line, immediately after the
6331 title line) when generating assembly listings.
6333 This directive affects subsequent pages, as well as the current page if
6334 it appears within ten lines of the top of a page.
6338 @section @code{.scl @var{class}}
6340 @cindex @code{scl} directive
6341 @cindex symbol storage class (COFF)
6342 @cindex COFF symbol storage class
6343 Set the storage-class value for a symbol. This directive may only be
6344 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6345 whether a symbol is static or external, or it may record further
6346 symbolic debugging information.
6349 The @samp{.scl} directive is primarily associated with COFF output; when
6350 configured to generate @code{b.out} output format, @command{@value{AS}}
6351 accepts this directive but ignores it.
6357 @section @code{.section @var{name}}
6359 @cindex named section
6360 Use the @code{.section} directive to assemble the following code into a section
6363 This directive is only supported for targets that actually support arbitrarily
6364 named sections; on @code{a.out} targets, for example, it is not accepted, even
6365 with a standard @code{a.out} section name.
6369 @c only print the extra heading if both COFF and ELF are set
6370 @subheading COFF Version
6373 @cindex @code{section} directive (COFF version)
6374 For COFF targets, the @code{.section} directive is used in one of the following
6378 .section @var{name}[, "@var{flags}"]
6379 .section @var{name}[, @var{subsection}]
6382 If the optional argument is quoted, it is taken as flags to use for the
6383 section. Each flag is a single character. The following flags are recognized:
6387 bss section (uninitialized data)
6389 section is not loaded
6395 exclude section from linking
6401 shared section (meaningful for PE targets)
6403 ignored. (For compatibility with the ELF version)
6405 section is not readable (meaningful for PE targets)
6407 single-digit power-of-two section alignment (GNU extension)
6410 If no flags are specified, the default flags depend upon the section name. If
6411 the section name is not recognized, the default will be for the section to be
6412 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6413 from the section, rather than adding them, so if they are used on their own it
6414 will be as if no flags had been specified at all.
6416 If the optional argument to the @code{.section} directive is not quoted, it is
6417 taken as a subsection number (@pxref{Sub-Sections}).
6422 @c only print the extra heading if both COFF and ELF are set
6423 @subheading ELF Version
6426 @cindex Section Stack
6427 This is one of the ELF section stack manipulation directives. The others are
6428 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6429 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6430 @code{.previous} (@pxref{Previous}).
6432 @cindex @code{section} directive (ELF version)
6433 For ELF targets, the @code{.section} directive is used like this:
6436 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6439 @anchor{Section Name Substitutions}
6440 @kindex --sectname-subst
6441 @cindex section name substitution
6442 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6443 argument may contain a substitution sequence. Only @code{%S} is supported
6444 at the moment, and substitutes the current section name. For example:
6447 .macro exception_code
6448 .section %S.exception
6449 [exception code here]
6464 The two @code{exception_code} invocations above would create the
6465 @code{.text.exception} and @code{.init.exception} sections respectively.
6466 This is useful e.g. to discriminate between anciliary sections that are
6467 tied to setup code to be discarded after use from anciliary sections that
6468 need to stay resident without having to define multiple @code{exception_code}
6469 macros just for that purpose.
6471 The optional @var{flags} argument is a quoted string which may contain any
6472 combination of the following characters:
6476 section is allocatable
6478 section is excluded from executable and shared library.
6482 section is executable
6484 section is mergeable
6486 section contains zero terminated strings
6488 section is a member of a section group
6490 section is used for thread-local-storage
6492 section is a member of the previously-current section's group, if any
6493 @item @code{<number>}
6494 a numeric value indicating the bits to be set in the ELF section header's flags
6495 field. Note - if one or more of the alphabetic characters described above is
6496 also included in the flags field, their bit values will be ORed into the
6498 @item @code{<target specific>}
6499 some targets extend this list with their own flag characters
6502 Note - once a section's flags have been set they cannot be changed. There are
6503 a few exceptions to this rule however. Processor and application specific
6504 flags can be added to an already defined section. The @code{.interp},
6505 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6506 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6507 section may have the executable (@code{x}) flag added.
6509 The optional @var{type} argument may contain one of the following constants:
6513 section contains data
6515 section does not contain data (i.e., section only occupies space)
6517 section contains data which is used by things other than the program
6519 section contains an array of pointers to init functions
6521 section contains an array of pointers to finish functions
6522 @item @@preinit_array
6523 section contains an array of pointers to pre-init functions
6524 @item @@@code{<number>}
6525 a numeric value to be set as the ELF section header's type field.
6526 @item @@@code{<target specific>}
6527 some targets extend this list with their own types
6530 Many targets only support the first three section types. The type may be
6531 enclosed in double quotes if necessary.
6533 Note on targets where the @code{@@} character is the start of a comment (eg
6534 ARM) then another character is used instead. For example the ARM port uses the
6537 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6538 special and have fixed types. Any attempt to declare them with a different
6539 type will generate an error from the assembler.
6541 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6542 be specified as well as an extra argument---@var{entsize}---like this:
6545 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6548 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6549 constants, each @var{entsize} octets long. Sections with both @code{M} and
6550 @code{S} must contain zero terminated strings where each character is
6551 @var{entsize} bytes long. The linker may remove duplicates within sections with
6552 the same name, same entity size and same flags. @var{entsize} must be an
6553 absolute expression. For sections with both @code{M} and @code{S}, a string
6554 which is a suffix of a larger string is considered a duplicate. Thus
6555 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6556 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6558 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6559 be present along with an additional field like this:
6562 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6565 The @var{GroupName} field specifies the name of the section group to which this
6566 particular section belongs. The optional linkage field can contain:
6570 indicates that only one copy of this section should be retained
6575 Note: if both the @var{M} and @var{G} flags are present then the fields for
6576 the Merge flag should come first, like this:
6579 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6582 If @var{flags} contains the @code{?} symbol then it may not also contain the
6583 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6584 present. Instead, @code{?} says to consider the section that's current before
6585 this directive. If that section used @code{G}, then the new section will use
6586 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6587 If not, then the @code{?} symbol has no effect.
6589 If no flags are specified, the default flags depend upon the section name. If
6590 the section name is not recognized, the default will be for the section to have
6591 none of the above flags: it will not be allocated in memory, nor writable, nor
6592 executable. The section will contain data.
6594 For ELF targets, the assembler supports another type of @code{.section}
6595 directive for compatibility with the Solaris assembler:
6598 .section "@var{name}"[, @var{flags}...]
6601 Note that the section name is quoted. There may be a sequence of comma
6606 section is allocatable
6610 section is executable
6612 section is excluded from executable and shared library.
6614 section is used for thread local storage
6617 This directive replaces the current section and subsection. See the
6618 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6619 some examples of how this directive and the other section stack directives
6625 @section @code{.set @var{symbol}, @var{expression}}
6627 @cindex @code{set} directive
6628 @cindex symbol value, setting
6629 Set the value of @var{symbol} to @var{expression}. This
6630 changes @var{symbol}'s value and type to conform to
6631 @var{expression}. If @var{symbol} was flagged as external, it remains
6632 flagged (@pxref{Symbol Attributes}).
6634 You may @code{.set} a symbol many times in the same assembly provided that the
6635 values given to the symbol are constants. Values that are based on expressions
6636 involving other symbols are allowed, but some targets may restrict this to only
6637 being done once per assembly. This is because those targets do not set the
6638 addresses of symbols at assembly time, but rather delay the assignment until a
6639 final link is performed. This allows the linker a chance to change the code in
6640 the files, changing the location of, and the relative distance between, various
6643 If you @code{.set} a global symbol, the value stored in the object
6644 file is the last value stored into it.
6647 On Z80 @code{set} is a real instruction, use
6648 @samp{@var{symbol} defl @var{expression}} instead.
6652 @section @code{.short @var{expressions}}
6654 @cindex @code{short} directive
6656 @code{.short} is normally the same as @samp{.word}.
6657 @xref{Word,,@code{.word}}.
6659 In some configurations, however, @code{.short} and @code{.word} generate
6660 numbers of different lengths. @xref{Machine Dependencies}.
6664 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6667 This expects zero or more @var{expressions}, and emits
6668 a 16 bit number for each.
6673 @section @code{.single @var{flonums}}
6675 @cindex @code{single} directive
6676 @cindex floating point numbers (single)
6677 This directive assembles zero or more flonums, separated by commas. It
6678 has the same effect as @code{.float}.
6680 The exact kind of floating point numbers emitted depends on how
6681 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6685 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6686 numbers in @sc{ieee} format.
6692 @section @code{.size}
6694 This directive is used to set the size associated with a symbol.
6698 @c only print the extra heading if both COFF and ELF are set
6699 @subheading COFF Version
6702 @cindex @code{size} directive (COFF version)
6703 For COFF targets, the @code{.size} directive is only permitted inside
6704 @code{.def}/@code{.endef} pairs. It is used like this:
6707 .size @var{expression}
6711 @samp{.size} is only meaningful when generating COFF format output; when
6712 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6719 @c only print the extra heading if both COFF and ELF are set
6720 @subheading ELF Version
6723 @cindex @code{size} directive (ELF version)
6724 For ELF targets, the @code{.size} directive is used like this:
6727 .size @var{name} , @var{expression}
6730 This directive sets the size associated with a symbol @var{name}.
6731 The size in bytes is computed from @var{expression} which can make use of label
6732 arithmetic. This directive is typically used to set the size of function
6737 @ifclear no-space-dir
6739 @section @code{.skip @var{size} , @var{fill}}
6741 @cindex @code{skip} directive
6742 @cindex filling memory
6743 This directive emits @var{size} bytes, each of value @var{fill}. Both
6744 @var{size} and @var{fill} are absolute expressions. If the comma and
6745 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6750 @section @code{.sleb128 @var{expressions}}
6752 @cindex @code{sleb128} directive
6753 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6754 compact, variable length representation of numbers used by the DWARF
6755 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6757 @ifclear no-space-dir
6759 @section @code{.space @var{size} , @var{fill}}
6761 @cindex @code{space} directive
6762 @cindex filling memory
6763 This directive emits @var{size} bytes, each of value @var{fill}. Both
6764 @var{size} and @var{fill} are absolute expressions. If the comma
6765 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6770 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6771 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6772 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6773 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6781 @section @code{.stabd, .stabn, .stabs}
6783 @cindex symbolic debuggers, information for
6784 @cindex @code{stab@var{x}} directives
6785 There are three directives that begin @samp{.stab}.
6786 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6787 The symbols are not entered in the @command{@value{AS}} hash table: they
6788 cannot be referenced elsewhere in the source file.
6789 Up to five fields are required:
6793 This is the symbol's name. It may contain any character except
6794 @samp{\000}, so is more general than ordinary symbol names. Some
6795 debuggers used to code arbitrarily complex structures into symbol names
6799 An absolute expression. The symbol's type is set to the low 8 bits of
6800 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6801 and debuggers choke on silly bit patterns.
6804 An absolute expression. The symbol's ``other'' attribute is set to the
6805 low 8 bits of this expression.
6808 An absolute expression. The symbol's descriptor is set to the low 16
6809 bits of this expression.
6812 An absolute expression which becomes the symbol's value.
6815 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6816 or @code{.stabs} statement, the symbol has probably already been created;
6817 you get a half-formed symbol in your object file. This is
6818 compatible with earlier assemblers!
6821 @cindex @code{stabd} directive
6822 @item .stabd @var{type} , @var{other} , @var{desc}
6824 The ``name'' of the symbol generated is not even an empty string.
6825 It is a null pointer, for compatibility. Older assemblers used a
6826 null pointer so they didn't waste space in object files with empty
6829 The symbol's value is set to the location counter,
6830 relocatably. When your program is linked, the value of this symbol
6831 is the address of the location counter when the @code{.stabd} was
6834 @cindex @code{stabn} directive
6835 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6836 The name of the symbol is set to the empty string @code{""}.
6838 @cindex @code{stabs} directive
6839 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6840 All five fields are specified.
6846 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6847 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6849 @cindex string, copying to object file
6850 @cindex string8, copying to object file
6851 @cindex string16, copying to object file
6852 @cindex string32, copying to object file
6853 @cindex string64, copying to object file
6854 @cindex @code{string} directive
6855 @cindex @code{string8} directive
6856 @cindex @code{string16} directive
6857 @cindex @code{string32} directive
6858 @cindex @code{string64} directive
6860 Copy the characters in @var{str} to the object file. You may specify more than
6861 one string to copy, separated by commas. Unless otherwise specified for a
6862 particular machine, the assembler marks the end of each string with a 0 byte.
6863 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6865 The variants @code{string16}, @code{string32} and @code{string64} differ from
6866 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6867 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6868 are stored in target endianness byte order.
6874 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6875 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6880 @section @code{.struct @var{expression}}
6882 @cindex @code{struct} directive
6883 Switch to the absolute section, and set the section offset to @var{expression},
6884 which must be an absolute expression. You might use this as follows:
6893 This would define the symbol @code{field1} to have the value 0, the symbol
6894 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6895 value 8. Assembly would be left in the absolute section, and you would need to
6896 use a @code{.section} directive of some sort to change to some other section
6897 before further assembly.
6901 @section @code{.subsection @var{name}}
6903 @cindex @code{subsection} directive
6904 @cindex Section Stack
6905 This is one of the ELF section stack manipulation directives. The others are
6906 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6907 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6910 This directive replaces the current subsection with @code{name}. The current
6911 section is not changed. The replaced subsection is put onto the section stack
6912 in place of the then current top of stack subsection.
6917 @section @code{.symver}
6918 @cindex @code{symver} directive
6919 @cindex symbol versioning
6920 @cindex versions of symbols
6921 Use the @code{.symver} directive to bind symbols to specific version nodes
6922 within a source file. This is only supported on ELF platforms, and is
6923 typically used when assembling files to be linked into a shared library.
6924 There are cases where it may make sense to use this in objects to be bound
6925 into an application itself so as to override a versioned symbol from a
6928 For ELF targets, the @code{.symver} directive can be used like this:
6930 .symver @var{name}, @var{name2@@nodename}
6932 If the symbol @var{name} is defined within the file
6933 being assembled, the @code{.symver} directive effectively creates a symbol
6934 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6935 just don't try and create a regular alias is that the @var{@@} character isn't
6936 permitted in symbol names. The @var{name2} part of the name is the actual name
6937 of the symbol by which it will be externally referenced. The name @var{name}
6938 itself is merely a name of convenience that is used so that it is possible to
6939 have definitions for multiple versions of a function within a single source
6940 file, and so that the compiler can unambiguously know which version of a
6941 function is being mentioned. The @var{nodename} portion of the alias should be
6942 the name of a node specified in the version script supplied to the linker when
6943 building a shared library. If you are attempting to override a versioned
6944 symbol from a shared library, then @var{nodename} should correspond to the
6945 nodename of the symbol you are trying to override.
6947 If the symbol @var{name} is not defined within the file being assembled, all
6948 references to @var{name} will be changed to @var{name2@@nodename}. If no
6949 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6952 Another usage of the @code{.symver} directive is:
6954 .symver @var{name}, @var{name2@@@@nodename}
6956 In this case, the symbol @var{name} must exist and be defined within
6957 the file being assembled. It is similar to @var{name2@@nodename}. The
6958 difference is @var{name2@@@@nodename} will also be used to resolve
6959 references to @var{name2} by the linker.
6961 The third usage of the @code{.symver} directive is:
6963 .symver @var{name}, @var{name2@@@@@@nodename}
6965 When @var{name} is not defined within the
6966 file being assembled, it is treated as @var{name2@@nodename}. When
6967 @var{name} is defined within the file being assembled, the symbol
6968 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6973 @section @code{.tag @var{structname}}
6975 @cindex COFF structure debugging
6976 @cindex structure debugging, COFF
6977 @cindex @code{tag} directive
6978 This directive is generated by compilers to include auxiliary debugging
6979 information in the symbol table. It is only permitted inside
6980 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6981 definitions in the symbol table with instances of those structures.
6984 @samp{.tag} is only used when generating COFF format output; when
6985 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6991 @section @code{.text @var{subsection}}
6993 @cindex @code{text} directive
6994 Tells @command{@value{AS}} to assemble the following statements onto the end of
6995 the text subsection numbered @var{subsection}, which is an absolute
6996 expression. If @var{subsection} is omitted, subsection number zero
7000 @section @code{.title "@var{heading}"}
7002 @cindex @code{title} directive
7003 @cindex listing control: title line
7004 Use @var{heading} as the title (second line, immediately after the
7005 source file name and pagenumber) when generating assembly listings.
7007 This directive affects subsequent pages, as well as the current page if
7008 it appears within ten lines of the top of a page.
7012 @section @code{.type}
7014 This directive is used to set the type of a symbol.
7018 @c only print the extra heading if both COFF and ELF are set
7019 @subheading COFF Version
7022 @cindex COFF symbol type
7023 @cindex symbol type, COFF
7024 @cindex @code{type} directive (COFF version)
7025 For COFF targets, this directive is permitted only within
7026 @code{.def}/@code{.endef} pairs. It is used like this:
7032 This records the integer @var{int} as the type attribute of a symbol table
7036 @samp{.type} is associated only with COFF format output; when
7037 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
7038 directive but ignores it.
7044 @c only print the extra heading if both COFF and ELF are set
7045 @subheading ELF Version
7048 @cindex ELF symbol type
7049 @cindex symbol type, ELF
7050 @cindex @code{type} directive (ELF version)
7051 For ELF targets, the @code{.type} directive is used like this:
7054 .type @var{name} , @var{type description}
7057 This sets the type of symbol @var{name} to be either a
7058 function symbol or an object symbol. There are five different syntaxes
7059 supported for the @var{type description} field, in order to provide
7060 compatibility with various other assemblers.
7062 Because some of the characters used in these syntaxes (such as @samp{@@} and
7063 @samp{#}) are comment characters for some architectures, some of the syntaxes
7064 below do not work on all architectures. The first variant will be accepted by
7065 the GNU assembler on all architectures so that variant should be used for
7066 maximum portability, if you do not need to assemble your code with other
7069 The syntaxes supported are:
7072 .type <name> STT_<TYPE_IN_UPPER_CASE>
7073 .type <name>,#<type>
7074 .type <name>,@@<type>
7075 .type <name>,%<type>
7076 .type <name>,"<type>"
7079 The types supported are:
7084 Mark the symbol as being a function name.
7087 @itemx gnu_indirect_function
7088 Mark the symbol as an indirect function when evaluated during reloc
7089 processing. (This is only supported on assemblers targeting GNU systems).
7093 Mark the symbol as being a data object.
7097 Mark the symbol as being a thead-local data object.
7101 Mark the symbol as being a common data object.
7105 Does not mark the symbol in any way. It is supported just for completeness.
7107 @item gnu_unique_object
7108 Marks the symbol as being a globally unique data object. The dynamic linker
7109 will make sure that in the entire process there is just one symbol with this
7110 name and type in use. (This is only supported on assemblers targeting GNU
7115 Note: Some targets support extra types in addition to those listed above.
7121 @section @code{.uleb128 @var{expressions}}
7123 @cindex @code{uleb128} directive
7124 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7125 compact, variable length representation of numbers used by the DWARF
7126 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7130 @section @code{.val @var{addr}}
7132 @cindex @code{val} directive
7133 @cindex COFF value attribute
7134 @cindex value attribute, COFF
7135 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7136 records the address @var{addr} as the value attribute of a symbol table
7140 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7141 configured for @code{b.out}, it accepts this directive but ignores it.
7147 @section @code{.version "@var{string}"}
7149 @cindex @code{version} directive
7150 This directive creates a @code{.note} section and places into it an ELF
7151 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7156 @section @code{.vtable_entry @var{table}, @var{offset}}
7158 @cindex @code{vtable_entry} directive
7159 This directive finds or creates a symbol @code{table} and creates a
7160 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7163 @section @code{.vtable_inherit @var{child}, @var{parent}}
7165 @cindex @code{vtable_inherit} directive
7166 This directive finds the symbol @code{child} and finds or creates the symbol
7167 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7168 parent whose addend is the value of the child symbol. As a special case the
7169 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7173 @section @code{.warning "@var{string}"}
7174 @cindex warning directive
7175 Similar to the directive @code{.error}
7176 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7179 @section @code{.weak @var{names}}
7181 @cindex @code{weak} directive
7182 This directive sets the weak attribute on the comma separated list of symbol
7183 @code{names}. If the symbols do not already exist, they will be created.
7185 On COFF targets other than PE, weak symbols are a GNU extension. This
7186 directive sets the weak attribute on the comma separated list of symbol
7187 @code{names}. If the symbols do not already exist, they will be created.
7189 On the PE target, weak symbols are supported natively as weak aliases.
7190 When a weak symbol is created that is not an alias, GAS creates an
7191 alternate symbol to hold the default value.
7194 @section @code{.weakref @var{alias}, @var{target}}
7196 @cindex @code{weakref} directive
7197 This directive creates an alias to the target symbol that enables the symbol to
7198 be referenced with weak-symbol semantics, but without actually making it weak.
7199 If direct references or definitions of the symbol are present, then the symbol
7200 will not be weak, but if all references to it are through weak references, the
7201 symbol will be marked as weak in the symbol table.
7203 The effect is equivalent to moving all references to the alias to a separate
7204 assembly source file, renaming the alias to the symbol in it, declaring the
7205 symbol as weak there, and running a reloadable link to merge the object files
7206 resulting from the assembly of the new source file and the old source file that
7207 had the references to the alias removed.
7209 The alias itself never makes to the symbol table, and is entirely handled
7210 within the assembler.
7213 @section @code{.word @var{expressions}}
7215 @cindex @code{word} directive
7216 This directive expects zero or more @var{expressions}, of any section,
7217 separated by commas.
7220 For each expression, @command{@value{AS}} emits a 32-bit number.
7223 For each expression, @command{@value{AS}} emits a 16-bit number.
7228 The size of the number emitted, and its byte order,
7229 depend on what target computer the assembly is for.
7232 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7233 @c happen---32-bit addressability, period; no long/short jumps.
7234 @ifset DIFF-TBL-KLUGE
7235 @cindex difference tables altered
7236 @cindex altered difference tables
7238 @emph{Warning: Special Treatment to support Compilers}
7242 Machines with a 32-bit address space, but that do less than 32-bit
7243 addressing, require the following special treatment. If the machine of
7244 interest to you does 32-bit addressing (or doesn't require it;
7245 @pxref{Machine Dependencies}), you can ignore this issue.
7248 In order to assemble compiler output into something that works,
7249 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7250 Directives of the form @samp{.word sym1-sym2} are often emitted by
7251 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7252 directive of the form @samp{.word sym1-sym2}, and the difference between
7253 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7254 creates a @dfn{secondary jump table}, immediately before the next label.
7255 This secondary jump table is preceded by a short-jump to the
7256 first byte after the secondary table. This short-jump prevents the flow
7257 of control from accidentally falling into the new table. Inside the
7258 table is a long-jump to @code{sym2}. The original @samp{.word}
7259 contains @code{sym1} minus the address of the long-jump to
7262 If there were several occurrences of @samp{.word sym1-sym2} before the
7263 secondary jump table, all of them are adjusted. If there was a
7264 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7265 long-jump to @code{sym4} is included in the secondary jump table,
7266 and the @code{.word} directives are adjusted to contain @code{sym3}
7267 minus the address of the long-jump to @code{sym4}; and so on, for as many
7268 entries in the original jump table as necessary.
7271 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7272 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7273 assembly language programmers.
7276 @c end DIFF-TBL-KLUGE
7278 @ifclear no-space-dir
7280 @section @code{.zero @var{size}}
7282 @cindex @code{zero} directive
7283 @cindex filling memory with zero bytes
7284 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7285 expression. This directive is actually an alias for the @samp{.skip} directive
7286 so in can take an optional second argument of the value to store in the bytes
7287 instead of zero. Using @samp{.zero} in this way would be confusing however.
7291 @section Deprecated Directives
7293 @cindex deprecated directives
7294 @cindex obsolescent directives
7295 One day these directives won't work.
7296 They are included for compatibility with older assemblers.
7303 @node Object Attributes
7304 @chapter Object Attributes
7305 @cindex object attributes
7307 @command{@value{AS}} assembles source files written for a specific architecture
7308 into object files for that architecture. But not all object files are alike.
7309 Many architectures support incompatible variations. For instance, floating
7310 point arguments might be passed in floating point registers if the object file
7311 requires hardware floating point support---or floating point arguments might be
7312 passed in integer registers if the object file supports processors with no
7313 hardware floating point unit. Or, if two objects are built for different
7314 generations of the same architecture, the combination may require the
7315 newer generation at run-time.
7317 This information is useful during and after linking. At link time,
7318 @command{@value{LD}} can warn about incompatible object files. After link
7319 time, tools like @command{gdb} can use it to process the linked file
7322 Compatibility information is recorded as a series of object attributes. Each
7323 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7324 string, and indicates who sets the meaning of the tag. The tag is an integer,
7325 and indicates what property the attribute describes. The value may be a string
7326 or an integer, and indicates how the property affects this object. Missing
7327 attributes are the same as attributes with a zero value or empty string value.
7329 Object attributes were developed as part of the ABI for the ARM Architecture.
7330 The file format is documented in @cite{ELF for the ARM Architecture}.
7333 * GNU Object Attributes:: @sc{gnu} Object Attributes
7334 * Defining New Object Attributes:: Defining New Object Attributes
7337 @node GNU Object Attributes
7338 @section @sc{gnu} Object Attributes
7340 The @code{.gnu_attribute} directive records an object attribute
7341 with vendor @samp{gnu}.
7343 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7344 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7345 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7346 2} is set for architecture-independent attributes and clear for
7347 architecture-dependent ones.
7349 @subsection Common @sc{gnu} attributes
7351 These attributes are valid on all architectures.
7354 @item Tag_compatibility (32)
7355 The compatibility attribute takes an integer flag value and a vendor name. If
7356 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7357 then the file is only compatible with the named toolchain. If it is greater
7358 than 1, the file can only be processed by other toolchains under some private
7359 arrangement indicated by the flag value and the vendor name.
7362 @subsection MIPS Attributes
7365 @item Tag_GNU_MIPS_ABI_FP (4)
7366 The floating-point ABI used by this object file. The value will be:
7370 0 for files not affected by the floating-point ABI.
7372 1 for files using the hardware floating-point ABI with a standard
7373 double-precision FPU.
7375 2 for files using the hardware floating-point ABI with a single-precision FPU.
7377 3 for files using the software floating-point ABI.
7379 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7380 floating-point registers, 32-bit general-purpose registers and increased the
7381 number of callee-saved floating-point registers.
7383 5 for files using the hardware floating-point ABI with a double-precision FPU
7384 with either 32-bit or 64-bit floating-point registers and 32-bit
7385 general-purpose registers.
7387 6 for files using the hardware floating-point ABI with 64-bit floating-point
7388 registers and 32-bit general-purpose registers.
7390 7 for files using the hardware floating-point ABI with 64-bit floating-point
7391 registers, 32-bit general-purpose registers and a rule that forbids the
7392 direct use of odd-numbered single-precision floating-point registers.
7396 @subsection PowerPC Attributes
7399 @item Tag_GNU_Power_ABI_FP (4)
7400 The floating-point ABI used by this object file. The value will be:
7404 0 for files not affected by the floating-point ABI.
7406 1 for files using double-precision hardware floating-point ABI.
7408 2 for files using the software floating-point ABI.
7410 3 for files using single-precision hardware floating-point ABI.
7413 @item Tag_GNU_Power_ABI_Vector (8)
7414 The vector ABI used by this object file. The value will be:
7418 0 for files not affected by the vector ABI.
7420 1 for files using general purpose registers to pass vectors.
7422 2 for files using AltiVec registers to pass vectors.
7424 3 for files using SPE registers to pass vectors.
7428 @subsection IBM z Systems Attributes
7431 @item Tag_GNU_S390_ABI_Vector (8)
7432 The vector ABI used by this object file. The value will be:
7436 0 for files not affected by the vector ABI.
7438 1 for files using software vector ABI.
7440 2 for files using hardware vector ABI.
7444 @node Defining New Object Attributes
7445 @section Defining New Object Attributes
7447 If you want to define a new @sc{gnu} object attribute, here are the places you
7448 will need to modify. New attributes should be discussed on the @samp{binutils}
7453 This manual, which is the official register of attributes.
7455 The header for your architecture @file{include/elf}, to define the tag.
7457 The @file{bfd} support file for your architecture, to merge the attribute
7458 and issue any appropriate link warnings.
7460 Test cases in @file{ld/testsuite} for merging and link warnings.
7462 @file{binutils/readelf.c} to display your attribute.
7464 GCC, if you want the compiler to mark the attribute automatically.
7470 @node Machine Dependencies
7471 @chapter Machine Dependent Features
7473 @cindex machine dependencies
7474 The machine instruction sets are (almost by definition) different on
7475 each machine where @command{@value{AS}} runs. Floating point representations
7476 vary as well, and @command{@value{AS}} often supports a few additional
7477 directives or command-line options for compatibility with other
7478 assemblers on a particular platform. Finally, some versions of
7479 @command{@value{AS}} support special pseudo-instructions for branch
7482 This chapter discusses most of these differences, though it does not
7483 include details on any machine's instruction set. For details on that
7484 subject, see the hardware manufacturer's manual.
7488 * AArch64-Dependent:: AArch64 Dependent Features
7491 * Alpha-Dependent:: Alpha Dependent Features
7494 * ARC-Dependent:: ARC Dependent Features
7497 * ARM-Dependent:: ARM Dependent Features
7500 * AVR-Dependent:: AVR Dependent Features
7503 * Blackfin-Dependent:: Blackfin Dependent Features
7506 * CR16-Dependent:: CR16 Dependent Features
7509 * CRIS-Dependent:: CRIS Dependent Features
7512 * D10V-Dependent:: D10V Dependent Features
7515 * D30V-Dependent:: D30V Dependent Features
7518 * Epiphany-Dependent:: EPIPHANY Dependent Features
7521 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7524 * HPPA-Dependent:: HPPA Dependent Features
7527 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7530 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7533 * i860-Dependent:: Intel 80860 Dependent Features
7536 * i960-Dependent:: Intel 80960 Dependent Features
7539 * IA-64-Dependent:: Intel IA-64 Dependent Features
7542 * IP2K-Dependent:: IP2K Dependent Features
7545 * LM32-Dependent:: LM32 Dependent Features
7548 * M32C-Dependent:: M32C Dependent Features
7551 * M32R-Dependent:: M32R Dependent Features
7554 * M68K-Dependent:: M680x0 Dependent Features
7557 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7560 * Meta-Dependent :: Meta Dependent Features
7563 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7566 * MIPS-Dependent:: MIPS Dependent Features
7569 * MMIX-Dependent:: MMIX Dependent Features
7572 * MSP430-Dependent:: MSP430 Dependent Features
7575 * NDS32-Dependent:: Andes NDS32 Dependent Features
7578 * NiosII-Dependent:: Altera Nios II Dependent Features
7581 * NS32K-Dependent:: NS32K Dependent Features
7584 * PDP-11-Dependent:: PDP-11 Dependent Features
7587 * PJ-Dependent:: picoJava Dependent Features
7590 * PPC-Dependent:: PowerPC Dependent Features
7593 * RL78-Dependent:: RL78 Dependent Features
7596 * RX-Dependent:: RX Dependent Features
7599 * S/390-Dependent:: IBM S/390 Dependent Features
7602 * SCORE-Dependent:: SCORE Dependent Features
7605 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7606 * SH64-Dependent:: SuperH SH64 Dependent Features
7609 * Sparc-Dependent:: SPARC Dependent Features
7612 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7615 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7618 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7621 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7624 * V850-Dependent:: V850 Dependent Features
7627 * Vax-Dependent:: VAX Dependent Features
7630 * Visium-Dependent:: Visium Dependent Features
7633 * XGATE-Dependent:: XGATE Features
7636 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7639 * Xtensa-Dependent:: Xtensa Dependent Features
7642 * Z80-Dependent:: Z80 Dependent Features
7645 * Z8000-Dependent:: Z8000 Dependent Features
7652 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7653 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7654 @c peculiarity: to preserve cross-references, there must be a node called
7655 @c "Machine Dependencies". Hence the conditional nodenames in each
7656 @c major node below. Node defaulting in makeinfo requires adjacency of
7657 @c node and sectioning commands; hence the repetition of @chapter BLAH
7658 @c in both conditional blocks.
7661 @include c-aarch64.texi
7665 @include c-alpha.texi
7681 @include c-bfin.texi
7685 @include c-cr16.texi
7689 @include c-cris.texi
7694 @node Machine Dependencies
7695 @chapter Machine Dependent Features
7697 The machine instruction sets are different on each Renesas chip family,
7698 and there are also some syntax differences among the families. This
7699 chapter describes the specific @command{@value{AS}} features for each
7703 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7704 * SH-Dependent:: Renesas SH Dependent Features
7711 @include c-d10v.texi
7715 @include c-d30v.texi
7719 @include c-epiphany.texi
7723 @include c-h8300.texi
7727 @include c-hppa.texi
7731 @include c-i370.texi
7735 @include c-i386.texi
7739 @include c-i860.texi
7743 @include c-i960.texi
7747 @include c-ia64.texi
7751 @include c-ip2k.texi
7755 @include c-lm32.texi
7759 @include c-m32c.texi
7763 @include c-m32r.texi
7767 @include c-m68k.texi
7771 @include c-m68hc11.texi
7775 @include c-metag.texi
7779 @include c-microblaze.texi
7783 @include c-mips.texi
7787 @include c-mmix.texi
7791 @include c-msp430.texi
7795 @include c-nds32.texi
7799 @include c-nios2.texi
7803 @include c-ns32k.texi
7807 @include c-pdp11.texi
7819 @include c-rl78.texi
7827 @include c-s390.texi
7831 @include c-score.texi
7836 @include c-sh64.texi
7840 @include c-sparc.texi
7844 @include c-tic54x.texi
7848 @include c-tic6x.texi
7852 @include c-tilegx.texi
7856 @include c-tilepro.texi
7860 @include c-v850.texi
7868 @include c-visium.texi
7872 @include c-xgate.texi
7876 @include c-xstormy16.texi
7880 @include c-xtensa.texi
7892 @c reverse effect of @down at top of generic Machine-Dep chapter
7896 @node Reporting Bugs
7897 @chapter Reporting Bugs
7898 @cindex bugs in assembler
7899 @cindex reporting bugs in assembler
7901 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7903 Reporting a bug may help you by bringing a solution to your problem, or it may
7904 not. But in any case the principal function of a bug report is to help the
7905 entire community by making the next version of @command{@value{AS}} work better.
7906 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7908 In order for a bug report to serve its purpose, you must include the
7909 information that enables us to fix the bug.
7912 * Bug Criteria:: Have you found a bug?
7913 * Bug Reporting:: How to report bugs
7917 @section Have You Found a Bug?
7918 @cindex bug criteria
7920 If you are not sure whether you have found a bug, here are some guidelines:
7923 @cindex fatal signal
7924 @cindex assembler crash
7925 @cindex crash of assembler
7927 If the assembler gets a fatal signal, for any input whatever, that is a
7928 @command{@value{AS}} bug. Reliable assemblers never crash.
7930 @cindex error on valid input
7932 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7934 @cindex invalid input
7936 If @command{@value{AS}} does not produce an error message for invalid input, that
7937 is a bug. However, you should note that your idea of ``invalid input'' might
7938 be our idea of ``an extension'' or ``support for traditional practice''.
7941 If you are an experienced user of assemblers, your suggestions for improvement
7942 of @command{@value{AS}} are welcome in any case.
7946 @section How to Report Bugs
7948 @cindex assembler bugs, reporting
7950 A number of companies and individuals offer support for @sc{gnu} products. If
7951 you obtained @command{@value{AS}} from a support organization, we recommend you
7952 contact that organization first.
7954 You can find contact information for many support companies and
7955 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7959 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7963 The fundamental principle of reporting bugs usefully is this:
7964 @strong{report all the facts}. If you are not sure whether to state a
7965 fact or leave it out, state it!
7967 Often people omit facts because they think they know what causes the problem
7968 and assume that some details do not matter. Thus, you might assume that the
7969 name of a symbol you use in an example does not matter. Well, probably it does
7970 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7971 happens to fetch from the location where that name is stored in memory;
7972 perhaps, if the name were different, the contents of that location would fool
7973 the assembler into doing the right thing despite the bug. Play it safe and
7974 give a specific, complete example. That is the easiest thing for you to do,
7975 and the most helpful.
7977 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7978 it is new to us. Therefore, always write your bug reports on the assumption
7979 that the bug has not been reported previously.
7981 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7982 bell?'' This cannot help us fix a bug, so it is basically useless. We
7983 respond by asking for enough details to enable us to investigate.
7984 You might as well expedite matters by sending them to begin with.
7986 To enable us to fix the bug, you should include all these things:
7990 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7991 it with the @samp{--version} argument.
7993 Without this, we will not know whether there is any point in looking for
7994 the bug in the current version of @command{@value{AS}}.
7997 Any patches you may have applied to the @command{@value{AS}} source.
8000 The type of machine you are using, and the operating system name and
8004 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8008 The command arguments you gave the assembler to assemble your example and
8009 observe the bug. To guarantee you will not omit something important, list them
8010 all. A copy of the Makefile (or the output from make) is sufficient.
8012 If we were to try to guess the arguments, we would probably guess wrong
8013 and then we might not encounter the bug.
8016 A complete input file that will reproduce the bug. If the bug is observed when
8017 the assembler is invoked via a compiler, send the assembler source, not the
8018 high level language source. Most compilers will produce the assembler source
8019 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8020 the options @samp{-v --save-temps}; this will save the assembler source in a
8021 file with an extension of @file{.s}, and also show you exactly how
8022 @command{@value{AS}} is being run.
8025 A description of what behavior you observe that you believe is
8026 incorrect. For example, ``It gets a fatal signal.''
8028 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8029 will certainly notice it. But if the bug is incorrect output, we might not
8030 notice unless it is glaringly wrong. You might as well not give us a chance to
8033 Even if the problem you experience is a fatal signal, you should still say so
8034 explicitly. Suppose something strange is going on, such as, your copy of
8035 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8036 library on your system. (This has happened!) Your copy might crash and ours
8037 would not. If you told us to expect a crash, then when ours fails to crash, we
8038 would know that the bug was not happening for us. If you had not told us to
8039 expect a crash, then we would not be able to draw any conclusion from our
8043 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8044 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8045 option. Always send diffs from the old file to the new file. If you even
8046 discuss something in the @command{@value{AS}} source, refer to it by context, not
8049 The line numbers in our development sources will not match those in your
8050 sources. Your line numbers would convey no useful information to us.
8053 Here are some things that are not necessary:
8057 A description of the envelope of the bug.
8059 Often people who encounter a bug spend a lot of time investigating
8060 which changes to the input file will make the bug go away and which
8061 changes will not affect it.
8063 This is often time consuming and not very useful, because the way we
8064 will find the bug is by running a single example under the debugger
8065 with breakpoints, not by pure deduction from a series of examples.
8066 We recommend that you save your time for something else.
8068 Of course, if you can find a simpler example to report @emph{instead}
8069 of the original one, that is a convenience for us. Errors in the
8070 output will be easier to spot, running under the debugger will take
8071 less time, and so on.
8073 However, simplification is not vital; if you do not want to do this,
8074 report the bug anyway and send us the entire test case you used.
8077 A patch for the bug.
8079 A patch for the bug does help us if it is a good one. But do not omit
8080 the necessary information, such as the test case, on the assumption that
8081 a patch is all we need. We might see problems with your patch and decide
8082 to fix the problem another way, or we might not understand it at all.
8084 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8085 construct an example that will make the program follow a certain path through
8086 the code. If you do not send us the example, we will not be able to construct
8087 one, so we will not be able to verify that the bug is fixed.
8089 And if we cannot understand what bug you are trying to fix, or why your
8090 patch should be an improvement, we will not install it. A test case will
8091 help us to understand.
8094 A guess about what the bug is or what it depends on.
8096 Such guesses are usually wrong. Even we cannot guess right about such
8097 things without first using the debugger to find the facts.
8100 @node Acknowledgements
8101 @chapter Acknowledgements
8103 If you have contributed to GAS and your name isn't listed here,
8104 it is not meant as a slight. We just don't know about it. Send mail to the
8105 maintainer, and we'll correct the situation. Currently
8107 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8109 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8112 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8113 information and the 68k series machines, most of the preprocessing pass, and
8114 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8116 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8117 many bug fixes, including merging support for several processors, breaking GAS
8118 up to handle multiple object file format back ends (including heavy rewrite,
8119 testing, an integration of the coff and b.out back ends), adding configuration
8120 including heavy testing and verification of cross assemblers and file splits
8121 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8122 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8123 port (including considerable amounts of reverse engineering), a SPARC opcode
8124 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8125 assertions and made them work, much other reorganization, cleanup, and lint.
8127 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8128 in format-specific I/O modules.
8130 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8131 has done much work with it since.
8133 The Intel 80386 machine description was written by Eliot Dresselhaus.
8135 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8137 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8138 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8140 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8141 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8142 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8143 support a.out format.
8145 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8146 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8147 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8148 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8151 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8152 simplified the configuration of which versions accept which directives. He
8153 updated the 68k machine description so that Motorola's opcodes always produced
8154 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8155 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8156 cross-compilation support, and one bug in relaxation that took a week and
8157 required the proverbial one-bit fix.
8159 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8160 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8161 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8162 PowerPC assembler, and made a few other minor patches.
8164 Steve Chamberlain made GAS able to generate listings.
8166 Hewlett-Packard contributed support for the HP9000/300.
8168 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8169 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8170 formats). This work was supported by both the Center for Software Science at
8171 the University of Utah and Cygnus Support.
8173 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8174 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8175 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8176 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8177 and some initial 64-bit support).
8179 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8181 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8182 support for openVMS/Alpha.
8184 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8187 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8188 Inc.@: added support for Xtensa processors.
8190 Several engineers at Cygnus Support have also provided many small bug fixes and
8191 configuration enhancements.
8193 Jon Beniston added support for the Lattice Mico32 architecture.
8195 Many others have contributed large or small bugfixes and enhancements. If
8196 you have contributed significant work and are not mentioned on this list, and
8197 want to be, let us know. Some of the history has been lost; we are not
8198 intentionally leaving anyone out.
8200 @node GNU Free Documentation License
8201 @appendix GNU Free Documentation License
8205 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob