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 RISC-V options:}
517 [@b{-march}=@var{ISA}]
518 [@b{-mabi}=@var{ABI}]
522 @emph{Target s390 options:}
523 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
524 [@b{-mregnames}|@b{-mno-regnames}]
525 [@b{-mwarn-areg-zero}]
529 @emph{Target SCORE options:}
530 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
531 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
532 [@b{-march=score7}][@b{-march=score3}]
533 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
537 @emph{Target SPARC options:}
538 @c The order here is important. See c-sparc.texi.
539 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
540 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
541 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
542 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
543 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
544 @b{-Asparcvisr}|@b{-Asparc5}]
545 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
546 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
547 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
548 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
549 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
550 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
553 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
557 @emph{Target TIC54X options:}
558 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
559 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
563 @emph{Target TIC6X options:}
564 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
565 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
566 [@b{-mpic}|@b{-mno-pic}]
570 @emph{Target TILE-Gx options:}
571 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
574 @c TILEPro has no machine-dependent assembler options
578 @emph{Target Visium options:}
579 [@b{-mtune=@var{arch}}]
583 @emph{Target Xtensa options:}
584 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
585 [@b{--[no-]absolute-literals}]
586 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
587 [@b{--[no-]transform}]
588 [@b{--rename-section} @var{oldname}=@var{newname}]
589 [@b{--[no-]trampolines}]
593 @emph{Target Z80 options:}
594 [@b{-z80}] [@b{-r800}]
595 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
596 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
597 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
598 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
599 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
600 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
604 @c Z8000 has no machine-dependent assembler options
613 @include at-file.texi
616 Turn on listings, in any of a variety of ways:
620 omit false conditionals
623 omit debugging directives
626 include general information, like @value{AS} version and options passed
629 include high-level source
635 include macro expansions
638 omit forms processing
644 set the name of the listing file
647 You may combine these options; for example, use @samp{-aln} for assembly
648 listing without forms processing. The @samp{=file} option, if used, must be
649 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
652 Begin in alternate macro mode.
654 @xref{Altmacro,,@code{.altmacro}}.
657 @item --compress-debug-sections
658 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
659 ELF ABI. The resulting object file may not be compatible with older
660 linkers and object file utilities. Note if compression would make a
661 given section @emph{larger} then it is not compressed.
664 @cindex @samp{--compress-debug-sections=} option
665 @item --compress-debug-sections=none
666 @itemx --compress-debug-sections=zlib
667 @itemx --compress-debug-sections=zlib-gnu
668 @itemx --compress-debug-sections=zlib-gabi
669 These options control how DWARF debug sections are compressed.
670 @option{--compress-debug-sections=none} is equivalent to
671 @option{--nocompress-debug-sections}.
672 @option{--compress-debug-sections=zlib} and
673 @option{--compress-debug-sections=zlib-gabi} are equivalent to
674 @option{--compress-debug-sections}.
675 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
676 sections using zlib. The debug sections are renamed to begin with
677 @samp{.zdebug}. Note if compression would make a given section
678 @emph{larger} then it is not compressed nor renamed.
682 @item --nocompress-debug-sections
683 Do not compress DWARF debug sections. This is usually the default for all
684 targets except the x86/x86_64, but a configure time option can be used to
688 Ignored. This option is accepted for script compatibility with calls to
691 @item --debug-prefix-map @var{old}=@var{new}
692 When assembling files in directory @file{@var{old}}, record debugging
693 information describing them as in @file{@var{new}} instead.
695 @item --defsym @var{sym}=@var{value}
696 Define the symbol @var{sym} to be @var{value} before assembling the input file.
697 @var{value} must be an integer constant. As in C, a leading @samp{0x}
698 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
699 value. The value of the symbol can be overridden inside a source file via the
700 use of a @code{.set} pseudo-op.
703 ``fast''---skip whitespace and comment preprocessing (assume source is
708 Generate debugging information for each assembler source line using whichever
709 debug format is preferred by the target. This currently means either STABS,
713 Generate stabs debugging information for each assembler line. This
714 may help debugging assembler code, if the debugger can handle it.
717 Generate stabs debugging information for each assembler line, with GNU
718 extensions that probably only gdb can handle, and that could make other
719 debuggers crash or refuse to read your program. This
720 may help debugging assembler code. Currently the only GNU extension is
721 the location of the current working directory at assembling time.
724 Generate DWARF2 debugging information for each assembler line. This
725 may help debugging assembler code, if the debugger can handle it. Note---this
726 option is only supported by some targets, not all of them.
728 @item --gdwarf-sections
729 Instead of creating a .debug_line section, create a series of
730 .debug_line.@var{foo} sections where @var{foo} is the name of the
731 corresponding code section. For example a code section called @var{.text.func}
732 will have its dwarf line number information placed into a section called
733 @var{.debug_line.text.func}. If the code section is just called @var{.text}
734 then debug line section will still be called just @var{.debug_line} without any
738 @item --size-check=error
739 @itemx --size-check=warning
740 Issue an error or warning for invalid ELF .size directive.
742 @item --elf-stt-common=no
743 @itemx --elf-stt-common=yes
744 These options control whether the ELF assembler should generate common
745 symbols with the @code{STT_COMMON} type. The default can be controlled
746 by a configure option @option{--enable-elf-stt-common}.
750 Print a summary of the command line options and exit.
753 Print a summary of all target specific options and exit.
756 Add directory @var{dir} to the search list for @code{.include} directives.
759 Don't warn about signed overflow.
762 @ifclear DIFF-TBL-KLUGE
763 This option is accepted but has no effect on the @value{TARGET} family.
765 @ifset DIFF-TBL-KLUGE
766 Issue warnings when difference tables altered for long displacements.
771 Keep (in the symbol table) local symbols. These symbols start with
772 system-specific local label prefixes, typically @samp{.L} for ELF systems
773 or @samp{L} for traditional a.out systems.
778 @item --listing-lhs-width=@var{number}
779 Set the maximum width, in words, of the output data column for an assembler
780 listing to @var{number}.
782 @item --listing-lhs-width2=@var{number}
783 Set the maximum width, in words, of the output data column for continuation
784 lines in an assembler listing to @var{number}.
786 @item --listing-rhs-width=@var{number}
787 Set the maximum width of an input source line, as displayed in a listing, to
790 @item --listing-cont-lines=@var{number}
791 Set the maximum number of lines printed in a listing for a single line of input
794 @item --no-pad-sections
795 Stop the assembler for padding the ends of output sections to the alignment
796 of that section. The default is to pad the sections, but this can waste space
797 which might be needed on targets which have tight memory constraints.
799 @item -o @var{objfile}
800 Name the object-file output from @command{@value{AS}} @var{objfile}.
803 Fold the data section into the text section.
805 @item --hash-size=@var{number}
806 Set the default size of GAS's hash tables to a prime number close to
807 @var{number}. Increasing this value can reduce the length of time it takes the
808 assembler to perform its tasks, at the expense of increasing the assembler's
809 memory requirements. Similarly reducing this value can reduce the memory
810 requirements at the expense of speed.
812 @item --reduce-memory-overheads
813 This option reduces GAS's memory requirements, at the expense of making the
814 assembly processes slower. Currently this switch is a synonym for
815 @samp{--hash-size=4051}, but in the future it may have other effects as well.
818 @item --sectname-subst
819 Honor substitution sequences in section names.
821 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
826 Print the maximum space (in bytes) and total time (in seconds) used by
829 @item --strip-local-absolute
830 Remove local absolute symbols from the outgoing symbol table.
834 Print the @command{as} version.
837 Print the @command{as} version and exit.
841 Suppress warning messages.
843 @item --fatal-warnings
844 Treat warnings as errors.
847 Don't suppress warning messages or treat them as errors.
856 Generate an object file even after errors.
858 @item -- | @var{files} @dots{}
859 Standard input, or source files to assemble.
867 @xref{AArch64 Options}, for the options available when @value{AS} is configured
868 for the 64-bit mode of the ARM Architecture (AArch64).
873 The following options are available when @value{AS} is configured for the
874 64-bit mode of the ARM Architecture (AArch64).
877 @include c-aarch64.texi
878 @c ended inside the included file
886 @xref{Alpha Options}, for the options available when @value{AS} is configured
887 for an Alpha processor.
892 The following options are available when @value{AS} is configured for an Alpha
896 @include c-alpha.texi
897 @c ended inside the included file
904 The following options are available when @value{AS} is configured for an ARC
908 @item -mcpu=@var{cpu}
909 This option selects the core processor variant.
911 Select either big-endian (-EB) or little-endian (-EL) output.
913 Enable Code Density extenssion instructions.
918 The following options are available when @value{AS} is configured for the ARM
922 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
923 Specify which ARM processor variant is the target.
924 @item -march=@var{architecture}[+@var{extension}@dots{}]
925 Specify which ARM architecture variant is used by the target.
926 @item -mfpu=@var{floating-point-format}
927 Select which Floating Point architecture is the target.
928 @item -mfloat-abi=@var{abi}
929 Select which floating point ABI is in use.
931 Enable Thumb only instruction decoding.
932 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
933 Select which procedure calling convention is in use.
935 Select either big-endian (-EB) or little-endian (-EL) output.
936 @item -mthumb-interwork
937 Specify that the code has been generated with interworking between Thumb and
940 Turns on CodeComposer Studio assembly syntax compatibility mode.
942 Specify that PIC code has been generated.
950 @xref{Blackfin Options}, for the options available when @value{AS} is
951 configured for the Blackfin processor family.
956 The following options are available when @value{AS} is configured for
957 the Blackfin processor family.
961 @c ended inside the included file
968 See the info pages for documentation of the CRIS-specific options.
972 The following options are available when @value{AS} is configured for
975 @cindex D10V optimization
976 @cindex optimization, D10V
978 Optimize output by parallelizing instructions.
983 The following options are available when @value{AS} is configured for a D30V
986 @cindex D30V optimization
987 @cindex optimization, D30V
989 Optimize output by parallelizing instructions.
993 Warn when nops are generated.
995 @cindex D30V nops after 32-bit multiply
997 Warn when a nop after a 32-bit multiply instruction is generated.
1003 The following options are available when @value{AS} is configured for the
1004 Adapteva EPIPHANY series.
1007 @xref{Epiphany Options}, for the options available when @value{AS} is
1008 configured for an Epiphany processor.
1012 @c man begin OPTIONS
1013 The following options are available when @value{AS} is configured for
1014 an Epiphany processor.
1016 @c man begin INCLUDE
1017 @include c-epiphany.texi
1018 @c ended inside the included file
1026 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1027 for an H8/300 processor.
1031 @c man begin OPTIONS
1032 The following options are available when @value{AS} is configured for an H8/300
1035 @c man begin INCLUDE
1036 @include c-h8300.texi
1037 @c ended inside the included file
1045 @xref{i386-Options}, for the options available when @value{AS} is
1046 configured for an i386 processor.
1050 @c man begin OPTIONS
1051 The following options are available when @value{AS} is configured for
1054 @c man begin INCLUDE
1055 @include c-i386.texi
1056 @c ended inside the included file
1061 @c man begin OPTIONS
1063 The following options are available when @value{AS} is configured for the
1064 Intel 80960 processor.
1067 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1068 Specify which variant of the 960 architecture is the target.
1071 Add code to collect statistics about branches taken.
1074 Do not alter compare-and-branch instructions for long displacements;
1081 The following options are available when @value{AS} is configured for the
1087 Specifies that the extended IP2022 instructions are allowed.
1090 Restores the default behaviour, which restricts the permitted instructions to
1091 just the basic IP2022 ones.
1097 The following options are available when @value{AS} is configured for the
1098 Renesas M32C and M16C processors.
1103 Assemble M32C instructions.
1106 Assemble M16C instructions (the default).
1109 Enable support for link-time relaxations.
1112 Support H'00 style hex constants in addition to 0x00 style.
1118 The following options are available when @value{AS} is configured for the
1119 Renesas M32R (formerly Mitsubishi M32R) series.
1124 Specify which processor in the M32R family is the target. The default
1125 is normally the M32R, but this option changes it to the M32RX.
1127 @item --warn-explicit-parallel-conflicts or --Wp
1128 Produce warning messages when questionable parallel constructs are
1131 @item --no-warn-explicit-parallel-conflicts or --Wnp
1132 Do not produce warning messages when questionable parallel constructs are
1139 The following options are available when @value{AS} is configured for the
1140 Motorola 68000 series.
1145 Shorten references to undefined symbols, to one word instead of two.
1147 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1148 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1149 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1150 Specify what processor in the 68000 family is the target. The default
1151 is normally the 68020, but this can be changed at configuration time.
1153 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1154 The target machine does (or does not) have a floating-point coprocessor.
1155 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1156 the basic 68000 is not compatible with the 68881, a combination of the
1157 two can be specified, since it's possible to do emulation of the
1158 coprocessor instructions with the main processor.
1160 @item -m68851 | -mno-68851
1161 The target machine does (or does not) have a memory-management
1162 unit coprocessor. The default is to assume an MMU for 68020 and up.
1170 @xref{Nios II Options}, for the options available when @value{AS} is configured
1171 for an Altera Nios II processor.
1175 @c man begin OPTIONS
1176 The following options are available when @value{AS} is configured for an
1177 Altera Nios II processor.
1179 @c man begin INCLUDE
1180 @include c-nios2.texi
1181 @c ended inside the included file
1187 For details about the PDP-11 machine dependent features options,
1188 see @ref{PDP-11-Options}.
1191 @item -mpic | -mno-pic
1192 Generate position-independent (or position-dependent) code. The
1193 default is @option{-mpic}.
1196 @itemx -mall-extensions
1197 Enable all instruction set extensions. This is the default.
1199 @item -mno-extensions
1200 Disable all instruction set extensions.
1202 @item -m@var{extension} | -mno-@var{extension}
1203 Enable (or disable) a particular instruction set extension.
1206 Enable the instruction set extensions supported by a particular CPU, and
1207 disable all other extensions.
1209 @item -m@var{machine}
1210 Enable the instruction set extensions supported by a particular machine
1211 model, and disable all other extensions.
1217 The following options are available when @value{AS} is configured for
1218 a picoJava processor.
1222 @cindex PJ endianness
1223 @cindex endianness, PJ
1224 @cindex big endian output, PJ
1226 Generate ``big endian'' format output.
1228 @cindex little endian output, PJ
1230 Generate ``little endian'' format output.
1236 The following options are available when @value{AS} is configured for the
1237 Motorola 68HC11 or 68HC12 series.
1241 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1242 Specify what processor is the target. The default is
1243 defined by the configuration option when building the assembler.
1245 @item --xgate-ramoffset
1246 Instruct the linker to offset RAM addresses from S12X address space into
1247 XGATE address space.
1250 Specify to use the 16-bit integer ABI.
1253 Specify to use the 32-bit integer ABI.
1255 @item -mshort-double
1256 Specify to use the 32-bit double ABI.
1259 Specify to use the 64-bit double ABI.
1261 @item --force-long-branches
1262 Relative branches are turned into absolute ones. This concerns
1263 conditional branches, unconditional branches and branches to a
1266 @item -S | --short-branches
1267 Do not turn relative branches into absolute ones
1268 when the offset is out of range.
1270 @item --strict-direct-mode
1271 Do not turn the direct addressing mode into extended addressing mode
1272 when the instruction does not support direct addressing mode.
1274 @item --print-insn-syntax
1275 Print the syntax of instruction in case of error.
1277 @item --print-opcodes
1278 Print the list of instructions with syntax and then exit.
1280 @item --generate-example
1281 Print an example of instruction for each possible instruction and then exit.
1282 This option is only useful for testing @command{@value{AS}}.
1288 The following options are available when @command{@value{AS}} is configured
1289 for the SPARC architecture:
1292 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1293 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1294 Explicitly select a variant of the SPARC architecture.
1296 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1297 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1299 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1300 UltraSPARC extensions.
1302 @item -xarch=v8plus | -xarch=v8plusa
1303 For compatibility with the Solaris v9 assembler. These options are
1304 equivalent to -Av8plus and -Av8plusa, respectively.
1307 Warn when the assembler switches to another architecture.
1312 The following options are available when @value{AS} is configured for the 'c54x
1317 Enable extended addressing mode. All addresses and relocations will assume
1318 extended addressing (usually 23 bits).
1319 @item -mcpu=@var{CPU_VERSION}
1320 Sets the CPU version being compiled for.
1321 @item -merrors-to-file @var{FILENAME}
1322 Redirect error output to a file, for broken systems which don't support such
1323 behaviour in the shell.
1328 The following options are available when @value{AS} is configured for
1333 This option sets the largest size of an object that can be referenced
1334 implicitly with the @code{gp} register. It is only accepted for targets that
1335 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1337 @cindex MIPS endianness
1338 @cindex endianness, MIPS
1339 @cindex big endian output, MIPS
1341 Generate ``big endian'' format output.
1343 @cindex little endian output, MIPS
1345 Generate ``little endian'' format output.
1363 Generate code for a particular MIPS Instruction Set Architecture level.
1364 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1365 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1366 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1367 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1368 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1369 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1370 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1371 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1372 MIPS64 Release 6 ISA processors, respectively.
1374 @item -march=@var{cpu}
1375 Generate code for a particular MIPS CPU.
1377 @item -mtune=@var{cpu}
1378 Schedule and tune for a particular MIPS CPU.
1382 Cause nops to be inserted if the read of the destination register
1383 of an mfhi or mflo instruction occurs in the following two instructions.
1386 @itemx -mno-fix-rm7000
1387 Cause nops to be inserted if a dmult or dmultu instruction is
1388 followed by a load instruction.
1392 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1393 section instead of the standard ELF .stabs sections.
1397 Control generation of @code{.pdr} sections.
1401 The register sizes are normally inferred from the ISA and ABI, but these
1402 flags force a certain group of registers to be treated as 32 bits wide at
1403 all times. @samp{-mgp32} controls the size of general-purpose registers
1404 and @samp{-mfp32} controls the size of floating-point registers.
1408 The register sizes are normally inferred from the ISA and ABI, but these
1409 flags force a certain group of registers to be treated as 64 bits wide at
1410 all times. @samp{-mgp64} controls the size of general-purpose registers
1411 and @samp{-mfp64} controls the size of floating-point registers.
1414 The register sizes are normally inferred from the ISA and ABI, but using
1415 this flag in combination with @samp{-mabi=32} enables an ABI variant
1416 which will operate correctly with floating-point registers which are
1420 @itemx -mno-odd-spreg
1421 Enable use of floating-point operations on odd-numbered single-precision
1422 registers when supported by the ISA. @samp{-mfpxx} implies
1423 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1427 Generate code for the MIPS 16 processor. This is equivalent to putting
1428 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1429 turns off this option.
1432 @itemx -mno-micromips
1433 Generate code for the microMIPS processor. This is equivalent to putting
1434 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1435 turns off this option. This is equivalent to putting @code{.set nomicromips}
1436 at the start of the assembly file.
1439 @itemx -mno-smartmips
1440 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1441 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1442 @samp{-mno-smartmips} turns off this option.
1446 Generate code for the MIPS-3D Application Specific Extension.
1447 This tells the assembler to accept MIPS-3D instructions.
1448 @samp{-no-mips3d} turns off this option.
1452 Generate code for the MDMX Application Specific Extension.
1453 This tells the assembler to accept MDMX instructions.
1454 @samp{-no-mdmx} turns off this option.
1458 Generate code for the DSP Release 1 Application Specific Extension.
1459 This tells the assembler to accept DSP Release 1 instructions.
1460 @samp{-mno-dsp} turns off this option.
1464 Generate code for the DSP Release 2 Application Specific Extension.
1465 This option implies @samp{-mdsp}.
1466 This tells the assembler to accept DSP Release 2 instructions.
1467 @samp{-mno-dspr2} turns off this option.
1471 Generate code for the DSP Release 3 Application Specific Extension.
1472 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1473 This tells the assembler to accept DSP Release 3 instructions.
1474 @samp{-mno-dspr3} turns off this option.
1478 Generate code for the MIPS SIMD Architecture Extension.
1479 This tells the assembler to accept MSA instructions.
1480 @samp{-mno-msa} turns off this option.
1484 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1485 This tells the assembler to accept XPA instructions.
1486 @samp{-mno-xpa} turns off this option.
1490 Generate code for the MT Application Specific Extension.
1491 This tells the assembler to accept MT instructions.
1492 @samp{-mno-mt} turns off this option.
1496 Generate code for the MCU Application Specific Extension.
1497 This tells the assembler to accept MCU instructions.
1498 @samp{-mno-mcu} turns off this option.
1502 Only use 32-bit instruction encodings when generating code for the
1503 microMIPS processor. This option inhibits the use of any 16-bit
1504 instructions. This is equivalent to putting @code{.set insn32} at
1505 the start of the assembly file. @samp{-mno-insn32} turns off this
1506 option. This is equivalent to putting @code{.set noinsn32} at the
1507 start of the assembly file. By default @samp{-mno-insn32} is
1508 selected, allowing all instructions to be used.
1510 @item --construct-floats
1511 @itemx --no-construct-floats
1512 The @samp{--no-construct-floats} option disables the construction of
1513 double width floating point constants by loading the two halves of the
1514 value into the two single width floating point registers that make up
1515 the double width register. By default @samp{--construct-floats} is
1516 selected, allowing construction of these floating point constants.
1518 @item --relax-branch
1519 @itemx --no-relax-branch
1520 The @samp{--relax-branch} option enables the relaxation of out-of-range
1521 branches. By default @samp{--no-relax-branch} is selected, causing any
1522 out-of-range branches to produce an error.
1524 @item -mnan=@var{encoding}
1525 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1526 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1529 @item --emulation=@var{name}
1530 This option was formerly used to switch between ELF and ECOFF output
1531 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1532 removed in GAS 2.24, so the option now serves little purpose.
1533 It is retained for backwards compatibility.
1535 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1536 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1537 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1538 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1539 preferred options instead.
1542 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1549 Control how to deal with multiplication overflow and division by zero.
1550 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1551 (and only work for Instruction Set Architecture level 2 and higher);
1552 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1556 When this option is used, @command{@value{AS}} will issue a warning every
1557 time it generates a nop instruction from a macro.
1562 The following options are available when @value{AS} is configured for
1568 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1569 The command line option @samp{-nojsri2bsr} can be used to disable it.
1573 Enable or disable the silicon filter behaviour. By default this is disabled.
1574 The default can be overridden by the @samp{-sifilter} command line option.
1577 Alter jump instructions for long displacements.
1579 @item -mcpu=[210|340]
1580 Select the cpu type on the target hardware. This controls which instructions
1584 Assemble for a big endian target.
1587 Assemble for a little endian target.
1596 @xref{Meta Options}, for the options available when @value{AS} is configured
1597 for a Meta processor.
1601 @c man begin OPTIONS
1602 The following options are available when @value{AS} is configured for a
1605 @c man begin INCLUDE
1606 @include c-metag.texi
1607 @c ended inside the included file
1612 @c man begin OPTIONS
1614 See the info pages for documentation of the MMIX-specific options.
1620 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1621 for a NDS32 processor.
1623 @c ended inside the included file
1627 @c man begin OPTIONS
1628 The following options are available when @value{AS} is configured for a
1631 @c man begin INCLUDE
1632 @include c-nds32.texi
1633 @c ended inside the included file
1640 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1641 for a PowerPC processor.
1645 @c man begin OPTIONS
1646 The following options are available when @value{AS} is configured for a
1649 @c man begin INCLUDE
1651 @c ended inside the included file
1659 @xref{RISC-V-Opts}, for the options available when @value{AS} is configured
1660 for a RISC-V processor.
1664 @c man begin OPTIONS
1665 The following options are available when @value{AS} is configured for a
1668 @c man begin INCLUDE
1669 @include c-riscv.texi
1670 @c ended inside the included file
1675 @c man begin OPTIONS
1677 See the info pages for documentation of the RX-specific options.
1681 The following options are available when @value{AS} is configured for the s390
1687 Select the word size, either 31/32 bits or 64 bits.
1690 Select the architecture mode, either the Enterprise System
1691 Architecture (esa) or the z/Architecture mode (zarch).
1692 @item -march=@var{processor}
1693 Specify which s390 processor variant is the target, @samp{g5} (or
1694 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1695 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1696 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1697 or @samp{z13} (or @samp{arch11}).
1699 @itemx -mno-regnames
1700 Allow or disallow symbolic names for registers.
1701 @item -mwarn-areg-zero
1702 Warn whenever the operand for a base or index register has been specified
1703 but evaluates to zero.
1711 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1712 for a TMS320C6000 processor.
1716 @c man begin OPTIONS
1717 The following options are available when @value{AS} is configured for a
1718 TMS320C6000 processor.
1720 @c man begin INCLUDE
1721 @include c-tic6x.texi
1722 @c ended inside the included file
1730 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1731 for a TILE-Gx processor.
1735 @c man begin OPTIONS
1736 The following options are available when @value{AS} is configured for a TILE-Gx
1739 @c man begin INCLUDE
1740 @include c-tilegx.texi
1741 @c ended inside the included file
1749 @xref{Visium Options}, for the options available when @value{AS} is configured
1750 for a Visium processor.
1754 @c man begin OPTIONS
1755 The following option is available when @value{AS} is configured for a Visium
1758 @c man begin INCLUDE
1759 @include c-visium.texi
1760 @c ended inside the included file
1768 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1769 for an Xtensa processor.
1773 @c man begin OPTIONS
1774 The following options are available when @value{AS} is configured for an
1777 @c man begin INCLUDE
1778 @include c-xtensa.texi
1779 @c ended inside the included file
1784 @c man begin OPTIONS
1787 The following options are available when @value{AS} is configured for
1788 a Z80 family processor.
1791 Assemble for Z80 processor.
1793 Assemble for R800 processor.
1794 @item -ignore-undocumented-instructions
1796 Assemble undocumented Z80 instructions that also work on R800 without warning.
1797 @item -ignore-unportable-instructions
1799 Assemble all undocumented Z80 instructions without warning.
1800 @item -warn-undocumented-instructions
1802 Issue a warning for undocumented Z80 instructions that also work on R800.
1803 @item -warn-unportable-instructions
1805 Issue a warning for undocumented Z80 instructions that do not work on R800.
1806 @item -forbid-undocumented-instructions
1808 Treat all undocumented instructions as errors.
1809 @item -forbid-unportable-instructions
1811 Treat undocumented Z80 instructions that do not work on R800 as errors.
1818 * Manual:: Structure of this Manual
1819 * GNU Assembler:: The GNU Assembler
1820 * Object Formats:: Object File Formats
1821 * Command Line:: Command Line
1822 * Input Files:: Input Files
1823 * Object:: Output (Object) File
1824 * Errors:: Error and Warning Messages
1828 @section Structure of this Manual
1830 @cindex manual, structure and purpose
1831 This manual is intended to describe what you need to know to use
1832 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1833 notation for symbols, constants, and expressions; the directives that
1834 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1837 We also cover special features in the @value{TARGET}
1838 configuration of @command{@value{AS}}, including assembler directives.
1841 This manual also describes some of the machine-dependent features of
1842 various flavors of the assembler.
1845 @cindex machine instructions (not covered)
1846 On the other hand, this manual is @emph{not} intended as an introduction
1847 to programming in assembly language---let alone programming in general!
1848 In a similar vein, we make no attempt to introduce the machine
1849 architecture; we do @emph{not} describe the instruction set, standard
1850 mnemonics, registers or addressing modes that are standard to a
1851 particular architecture.
1853 You may want to consult the manufacturer's
1854 machine architecture manual for this information.
1858 For information on the H8/300 machine instruction set, see @cite{H8/300
1859 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1860 Programming Manual} (Renesas).
1863 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1864 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1865 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1866 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1869 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1873 @c I think this is premature---doc@cygnus.com, 17jan1991
1875 Throughout this manual, we assume that you are running @dfn{GNU},
1876 the portable operating system from the @dfn{Free Software
1877 Foundation, Inc.}. This restricts our attention to certain kinds of
1878 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1879 once this assumption is granted examples and definitions need less
1882 @command{@value{AS}} is part of a team of programs that turn a high-level
1883 human-readable series of instructions into a low-level
1884 computer-readable series of instructions. Different versions of
1885 @command{@value{AS}} are used for different kinds of computer.
1888 @c There used to be a section "Terminology" here, which defined
1889 @c "contents", "byte", "word", and "long". Defining "word" to any
1890 @c particular size is confusing when the .word directive may generate 16
1891 @c bits on one machine and 32 bits on another; in general, for the user
1892 @c version of this manual, none of these terms seem essential to define.
1893 @c They were used very little even in the former draft of the manual;
1894 @c this draft makes an effort to avoid them (except in names of
1898 @section The GNU Assembler
1900 @c man begin DESCRIPTION
1902 @sc{gnu} @command{as} is really a family of assemblers.
1904 This manual describes @command{@value{AS}}, a member of that family which is
1905 configured for the @value{TARGET} architectures.
1907 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1908 should find a fairly similar environment when you use it on another
1909 architecture. Each version has much in common with the others,
1910 including object file formats, most assembler directives (often called
1911 @dfn{pseudo-ops}) and assembler syntax.@refill
1913 @cindex purpose of @sc{gnu} assembler
1914 @command{@value{AS}} is primarily intended to assemble the output of the
1915 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1916 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1917 assemble correctly everything that other assemblers for the same
1918 machine would assemble.
1920 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1923 @c This remark should appear in generic version of manual; assumption
1924 @c here is that generic version sets M680x0.
1925 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1926 assembler for the same architecture; for example, we know of several
1927 incompatible versions of 680x0 assembly language syntax.
1932 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1933 program in one pass of the source file. This has a subtle impact on the
1934 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1936 @node Object Formats
1937 @section Object File Formats
1939 @cindex object file format
1940 The @sc{gnu} assembler can be configured to produce several alternative
1941 object file formats. For the most part, this does not affect how you
1942 write assembly language programs; but directives for debugging symbols
1943 are typically different in different file formats. @xref{Symbol
1944 Attributes,,Symbol Attributes}.
1947 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1948 @value{OBJ-NAME} format object files.
1950 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1952 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1953 @code{b.out} or COFF format object files.
1956 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1957 SOM or ELF format object files.
1962 @section Command Line
1964 @cindex command line conventions
1966 After the program name @command{@value{AS}}, the command line may contain
1967 options and file names. Options may appear in any order, and may be
1968 before, after, or between file names. The order of file names is
1971 @cindex standard input, as input file
1973 @file{--} (two hyphens) by itself names the standard input file
1974 explicitly, as one of the files for @command{@value{AS}} to assemble.
1976 @cindex options, command line
1977 Except for @samp{--} any command line argument that begins with a
1978 hyphen (@samp{-}) is an option. Each option changes the behavior of
1979 @command{@value{AS}}. No option changes the way another option works. An
1980 option is a @samp{-} followed by one or more letters; the case of
1981 the letter is important. All options are optional.
1983 Some options expect exactly one file name to follow them. The file
1984 name may either immediately follow the option's letter (compatible
1985 with older assemblers) or it may be the next command argument (@sc{gnu}
1986 standard). These two command lines are equivalent:
1989 @value{AS} -o my-object-file.o mumble.s
1990 @value{AS} -omy-object-file.o mumble.s
1994 @section Input Files
1997 @cindex source program
1998 @cindex files, input
1999 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2000 describe the program input to one run of @command{@value{AS}}. The program may
2001 be in one or more files; how the source is partitioned into files
2002 doesn't change the meaning of the source.
2004 @c I added "con" prefix to "catenation" just to prove I can overcome my
2005 @c APL training... doc@cygnus.com
2006 The source program is a concatenation of the text in all the files, in the
2009 @c man begin DESCRIPTION
2010 Each time you run @command{@value{AS}} it assembles exactly one source
2011 program. The source program is made up of one or more files.
2012 (The standard input is also a file.)
2014 You give @command{@value{AS}} a command line that has zero or more input file
2015 names. The input files are read (from left file name to right). A
2016 command line argument (in any position) that has no special meaning
2017 is taken to be an input file name.
2019 If you give @command{@value{AS}} no file names it attempts to read one input file
2020 from the @command{@value{AS}} standard input, which is normally your terminal. You
2021 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2024 Use @samp{--} if you need to explicitly name the standard input file
2025 in your command line.
2027 If the source is empty, @command{@value{AS}} produces a small, empty object
2032 @subheading Filenames and Line-numbers
2034 @cindex input file linenumbers
2035 @cindex line numbers, in input files
2036 There are two ways of locating a line in the input file (or files) and
2037 either may be used in reporting error messages. One way refers to a line
2038 number in a physical file; the other refers to a line number in a
2039 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2041 @dfn{Physical files} are those files named in the command line given
2042 to @command{@value{AS}}.
2044 @dfn{Logical files} are simply names declared explicitly by assembler
2045 directives; they bear no relation to physical files. Logical file names help
2046 error messages reflect the original source file, when @command{@value{AS}} source
2047 is itself synthesized from other files. @command{@value{AS}} understands the
2048 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2049 @ref{File,,@code{.file}}.
2052 @section Output (Object) File
2058 Every time you run @command{@value{AS}} it produces an output file, which is
2059 your assembly language program translated into numbers. This file
2060 is the object file. Its default name is
2068 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2070 You can give it another name by using the @option{-o} option. Conventionally,
2071 object file names end with @file{.o}. The default name is used for historical
2072 reasons: older assemblers were capable of assembling self-contained programs
2073 directly into a runnable program. (For some formats, this isn't currently
2074 possible, but it can be done for the @code{a.out} format.)
2078 The object file is meant for input to the linker @code{@value{LD}}. It contains
2079 assembled program code, information to help @code{@value{LD}} integrate
2080 the assembled program into a runnable file, and (optionally) symbolic
2081 information for the debugger.
2083 @c link above to some info file(s) like the description of a.out.
2084 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2087 @section Error and Warning Messages
2089 @c man begin DESCRIPTION
2091 @cindex error messages
2092 @cindex warning messages
2093 @cindex messages from assembler
2094 @command{@value{AS}} may write warnings and error messages to the standard error
2095 file (usually your terminal). This should not happen when a compiler
2096 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2097 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2098 grave problem that stops the assembly.
2102 @cindex format of warning messages
2103 Warning messages have the format
2106 file_name:@b{NNN}:Warning Message Text
2110 @cindex file names and line numbers, in warnings/errors
2111 (where @b{NNN} is a line number). If both a logical file name
2112 (@pxref{File,,@code{.file}}) and a logical line number
2114 (@pxref{Line,,@code{.line}})
2116 have been given then they will be used, otherwise the file name and line number
2117 in the current assembler source file will be used. The message text is
2118 intended to be self explanatory (in the grand Unix tradition).
2120 Note the file name must be set via the logical version of the @code{.file}
2121 directive, not the DWARF2 version of the @code{.file} directive. For example:
2125 error_assembler_source
2131 produces this output:
2135 asm.s:2: Error: no such instruction: `error_assembler_source'
2136 foo.c:31: Error: no such instruction: `error_c_source'
2139 @cindex format of error messages
2140 Error messages have the format
2143 file_name:@b{NNN}:FATAL:Error Message Text
2146 The file name and line number are derived as for warning
2147 messages. The actual message text may be rather less explanatory
2148 because many of them aren't supposed to happen.
2151 @chapter Command-Line Options
2153 @cindex options, all versions of assembler
2154 This chapter describes command-line options available in @emph{all}
2155 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2156 for options specific
2158 to the @value{TARGET} target.
2161 to particular machine architectures.
2164 @c man begin DESCRIPTION
2166 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2167 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2168 The assembler arguments must be separated from each other (and the @samp{-Wa})
2169 by commas. For example:
2172 gcc -c -g -O -Wa,-alh,-L file.c
2176 This passes two options to the assembler: @samp{-alh} (emit a listing to
2177 standard output with high-level and assembly source) and @samp{-L} (retain
2178 local symbols in the symbol table).
2180 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2181 command-line options are automatically passed to the assembler by the compiler.
2182 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2183 precisely what options it passes to each compilation pass, including the
2189 * a:: -a[cdghlns] enable listings
2190 * alternate:: --alternate enable alternate macro syntax
2191 * D:: -D for compatibility
2192 * f:: -f to work faster
2193 * I:: -I for .include search path
2194 @ifclear DIFF-TBL-KLUGE
2195 * K:: -K for compatibility
2197 @ifset DIFF-TBL-KLUGE
2198 * K:: -K for difference tables
2201 * L:: -L to retain local symbols
2202 * listing:: --listing-XXX to configure listing output
2203 * M:: -M or --mri to assemble in MRI compatibility mode
2204 * MD:: --MD for dependency tracking
2205 * no-pad-sections:: --no-pad-sections to stop section padding
2206 * o:: -o to name the object file
2207 * R:: -R to join data and text sections
2208 * statistics:: --statistics to see statistics about assembly
2209 * traditional-format:: --traditional-format for compatible output
2210 * v:: -v to announce version
2211 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2212 * Z:: -Z to make object file even after errors
2216 @section Enable Listings: @option{-a[cdghlns]}
2226 @cindex listings, enabling
2227 @cindex assembly listings, enabling
2229 These options enable listing output from the assembler. By itself,
2230 @samp{-a} requests high-level, assembly, and symbols listing.
2231 You can use other letters to select specific options for the list:
2232 @samp{-ah} requests a high-level language listing,
2233 @samp{-al} requests an output-program assembly listing, and
2234 @samp{-as} requests a symbol table listing.
2235 High-level listings require that a compiler debugging option like
2236 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2239 Use the @samp{-ag} option to print a first section with general assembly
2240 information, like @value{AS} version, switches passed, or time stamp.
2242 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2243 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2244 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2245 omitted from the listing.
2247 Use the @samp{-ad} option to omit debugging directives from the
2250 Once you have specified one of these options, you can further control
2251 listing output and its appearance using the directives @code{.list},
2252 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2254 The @samp{-an} option turns off all forms processing.
2255 If you do not request listing output with one of the @samp{-a} options, the
2256 listing-control directives have no effect.
2258 The letters after @samp{-a} may be combined into one option,
2259 @emph{e.g.}, @samp{-aln}.
2261 Note if the assembler source is coming from the standard input (e.g.,
2263 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2264 is being used) then the listing will not contain any comments or preprocessor
2265 directives. This is because the listing code buffers input source lines from
2266 stdin only after they have been preprocessed by the assembler. This reduces
2267 memory usage and makes the code more efficient.
2270 @section @option{--alternate}
2273 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2276 @section @option{-D}
2279 This option has no effect whatsoever, but it is accepted to make it more
2280 likely that scripts written for other assemblers also work with
2281 @command{@value{AS}}.
2284 @section Work Faster: @option{-f}
2287 @cindex trusted compiler
2288 @cindex faster processing (@option{-f})
2289 @samp{-f} should only be used when assembling programs written by a
2290 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2291 and comment preprocessing on
2292 the input file(s) before assembling them. @xref{Preprocessing,
2296 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2297 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2302 @section @code{.include} Search Path: @option{-I} @var{path}
2304 @kindex -I @var{path}
2305 @cindex paths for @code{.include}
2306 @cindex search path for @code{.include}
2307 @cindex @code{include} directive search path
2308 Use this option to add a @var{path} to the list of directories
2309 @command{@value{AS}} searches for files specified in @code{.include}
2310 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2311 many times as necessary to include a variety of paths. The current
2312 working directory is always searched first; after that, @command{@value{AS}}
2313 searches any @samp{-I} directories in the same order as they were
2314 specified (left to right) on the command line.
2317 @section Difference Tables: @option{-K}
2320 @ifclear DIFF-TBL-KLUGE
2321 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2322 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2323 where it can be used to warn when the assembler alters the machine code
2324 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2325 family does not have the addressing limitations that sometimes lead to this
2326 alteration on other platforms.
2329 @ifset DIFF-TBL-KLUGE
2330 @cindex difference tables, warning
2331 @cindex warning for altered difference tables
2332 @command{@value{AS}} sometimes alters the code emitted for directives of the
2333 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2334 You can use the @samp{-K} option if you want a warning issued when this
2339 @section Include Local Symbols: @option{-L}
2342 @cindex local symbols, retaining in output
2343 Symbols beginning with system-specific local label prefixes, typically
2344 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2345 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2346 such symbols when debugging, because they are intended for the use of
2347 programs (like compilers) that compose assembler programs, not for your
2348 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2349 such symbols, so you do not normally debug with them.
2351 This option tells @command{@value{AS}} to retain those local symbols
2352 in the object file. Usually if you do this you also tell the linker
2353 @code{@value{LD}} to preserve those symbols.
2356 @section Configuring listing output: @option{--listing}
2358 The listing feature of the assembler can be enabled via the command line switch
2359 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2360 hex dump of the corresponding locations in the output object file, and displays
2361 them as a listing file. The format of this listing can be controlled by
2362 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2363 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2364 @code{.psize} (@pxref{Psize}), and
2365 @code{.eject} (@pxref{Eject}) and also by the following switches:
2368 @item --listing-lhs-width=@samp{number}
2369 @kindex --listing-lhs-width
2370 @cindex Width of first line disassembly output
2371 Sets the maximum width, in words, of the first line of the hex byte dump. This
2372 dump appears on the left hand side of the listing output.
2374 @item --listing-lhs-width2=@samp{number}
2375 @kindex --listing-lhs-width2
2376 @cindex Width of continuation lines of disassembly output
2377 Sets the maximum width, in words, of any further lines of the hex byte dump for
2378 a given input source line. If this value is not specified, it defaults to being
2379 the same as the value specified for @samp{--listing-lhs-width}. If neither
2380 switch is used the default is to one.
2382 @item --listing-rhs-width=@samp{number}
2383 @kindex --listing-rhs-width
2384 @cindex Width of source line output
2385 Sets the maximum width, in characters, of the source line that is displayed
2386 alongside the hex dump. The default value for this parameter is 100. The
2387 source line is displayed on the right hand side of the listing output.
2389 @item --listing-cont-lines=@samp{number}
2390 @kindex --listing-cont-lines
2391 @cindex Maximum number of continuation lines
2392 Sets the maximum number of continuation lines of hex dump that will be
2393 displayed for a given single line of source input. The default value is 4.
2397 @section Assemble in MRI Compatibility Mode: @option{-M}
2400 @cindex MRI compatibility mode
2401 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2402 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2403 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2404 configured target) assembler from Microtec Research. The exact nature of the
2405 MRI syntax will not be documented here; see the MRI manuals for more
2406 information. Note in particular that the handling of macros and macro
2407 arguments is somewhat different. The purpose of this option is to permit
2408 assembling existing MRI assembler code using @command{@value{AS}}.
2410 The MRI compatibility is not complete. Certain operations of the MRI assembler
2411 depend upon its object file format, and can not be supported using other object
2412 file formats. Supporting these would require enhancing each object file format
2413 individually. These are:
2416 @item global symbols in common section
2418 The m68k MRI assembler supports common sections which are merged by the linker.
2419 Other object file formats do not support this. @command{@value{AS}} handles
2420 common sections by treating them as a single common symbol. It permits local
2421 symbols to be defined within a common section, but it can not support global
2422 symbols, since it has no way to describe them.
2424 @item complex relocations
2426 The MRI assemblers support relocations against a negated section address, and
2427 relocations which combine the start addresses of two or more sections. These
2428 are not support by other object file formats.
2430 @item @code{END} pseudo-op specifying start address
2432 The MRI @code{END} pseudo-op permits the specification of a start address.
2433 This is not supported by other object file formats. The start address may
2434 instead be specified using the @option{-e} option to the linker, or in a linker
2437 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2439 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2440 name to the output file. This is not supported by other object file formats.
2442 @item @code{ORG} pseudo-op
2444 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2445 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2446 which changes the location within the current section. Absolute sections are
2447 not supported by other object file formats. The address of a section may be
2448 assigned within a linker script.
2451 There are some other features of the MRI assembler which are not supported by
2452 @command{@value{AS}}, typically either because they are difficult or because they
2453 seem of little consequence. Some of these may be supported in future releases.
2457 @item EBCDIC strings
2459 EBCDIC strings are not supported.
2461 @item packed binary coded decimal
2463 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2464 and @code{DCB.P} pseudo-ops are not supported.
2466 @item @code{FEQU} pseudo-op
2468 The m68k @code{FEQU} pseudo-op is not supported.
2470 @item @code{NOOBJ} pseudo-op
2472 The m68k @code{NOOBJ} pseudo-op is not supported.
2474 @item @code{OPT} branch control options
2476 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2477 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2478 relaxes all branches, whether forward or backward, to an appropriate size, so
2479 these options serve no purpose.
2481 @item @code{OPT} list control options
2483 The following m68k @code{OPT} list control options are ignored: @code{C},
2484 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2485 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2487 @item other @code{OPT} options
2489 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2490 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2492 @item @code{OPT} @code{D} option is default
2494 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2495 @code{OPT NOD} may be used to turn it off.
2497 @item @code{XREF} pseudo-op.
2499 The m68k @code{XREF} pseudo-op is ignored.
2501 @item @code{.debug} pseudo-op
2503 The i960 @code{.debug} pseudo-op is not supported.
2505 @item @code{.extended} pseudo-op
2507 The i960 @code{.extended} pseudo-op is not supported.
2509 @item @code{.list} pseudo-op.
2511 The various options of the i960 @code{.list} pseudo-op are not supported.
2513 @item @code{.optimize} pseudo-op
2515 The i960 @code{.optimize} pseudo-op is not supported.
2517 @item @code{.output} pseudo-op
2519 The i960 @code{.output} pseudo-op is not supported.
2521 @item @code{.setreal} pseudo-op
2523 The i960 @code{.setreal} pseudo-op is not supported.
2528 @section Dependency Tracking: @option{--MD}
2531 @cindex dependency tracking
2534 @command{@value{AS}} can generate a dependency file for the file it creates. This
2535 file consists of a single rule suitable for @code{make} describing the
2536 dependencies of the main source file.
2538 The rule is written to the file named in its argument.
2540 This feature is used in the automatic updating of makefiles.
2542 @node no-pad-sections
2543 @section Output Section Padding
2544 @kindex --no-pad-sections
2545 @cindex output section padding
2546 Normally the assembler will pad the end of each output section up to its
2547 alignment boundary. But this can waste space, which can be significant on
2548 memory constrained targets. So the @option{--no-pad-sections} option will
2549 disable this behaviour.
2552 @section Name the Object File: @option{-o}
2555 @cindex naming object file
2556 @cindex object file name
2557 There is always one object file output when you run @command{@value{AS}}. By
2558 default it has the name
2561 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2575 You use this option (which takes exactly one filename) to give the
2576 object file a different name.
2578 Whatever the object file is called, @command{@value{AS}} overwrites any
2579 existing file of the same name.
2582 @section Join Data and Text Sections: @option{-R}
2585 @cindex data and text sections, joining
2586 @cindex text and data sections, joining
2587 @cindex joining text and data sections
2588 @cindex merging text and data sections
2589 @option{-R} tells @command{@value{AS}} to write the object file as if all
2590 data-section data lives in the text section. This is only done at
2591 the very last moment: your binary data are the same, but data
2592 section parts are relocated differently. The data section part of
2593 your object file is zero bytes long because all its bytes are
2594 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2596 When you specify @option{-R} it would be possible to generate shorter
2597 address displacements (because we do not have to cross between text and
2598 data section). We refrain from doing this simply for compatibility with
2599 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2602 When @command{@value{AS}} is configured for COFF or ELF output,
2603 this option is only useful if you use sections named @samp{.text} and
2608 @option{-R} is not supported for any of the HPPA targets. Using
2609 @option{-R} generates a warning from @command{@value{AS}}.
2613 @section Display Assembly Statistics: @option{--statistics}
2615 @kindex --statistics
2616 @cindex statistics, about assembly
2617 @cindex time, total for assembly
2618 @cindex space used, maximum for assembly
2619 Use @samp{--statistics} to display two statistics about the resources used by
2620 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2621 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2624 @node traditional-format
2625 @section Compatible Output: @option{--traditional-format}
2627 @kindex --traditional-format
2628 For some targets, the output of @command{@value{AS}} is different in some ways
2629 from the output of some existing assembler. This switch requests
2630 @command{@value{AS}} to use the traditional format instead.
2632 For example, it disables the exception frame optimizations which
2633 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2636 @section Announce Version: @option{-v}
2640 @cindex assembler version
2641 @cindex version of assembler
2642 You can find out what version of as is running by including the
2643 option @samp{-v} (which you can also spell as @samp{-version}) on the
2647 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2649 @command{@value{AS}} should never give a warning or error message when
2650 assembling compiler output. But programs written by people often
2651 cause @command{@value{AS}} to give a warning that a particular assumption was
2652 made. All such warnings are directed to the standard error file.
2656 @cindex suppressing warnings
2657 @cindex warnings, suppressing
2658 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2659 This only affects the warning messages: it does not change any particular of
2660 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2663 @kindex --fatal-warnings
2664 @cindex errors, caused by warnings
2665 @cindex warnings, causing error
2666 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2667 files that generate warnings to be in error.
2670 @cindex warnings, switching on
2671 You can switch these options off again by specifying @option{--warn}, which
2672 causes warnings to be output as usual.
2675 @section Generate Object File in Spite of Errors: @option{-Z}
2676 @cindex object file, after errors
2677 @cindex errors, continuing after
2678 After an error message, @command{@value{AS}} normally produces no output. If for
2679 some reason you are interested in object file output even after
2680 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2681 option. If there are any errors, @command{@value{AS}} continues anyways, and
2682 writes an object file after a final warning message of the form @samp{@var{n}
2683 errors, @var{m} warnings, generating bad object file.}
2688 @cindex machine-independent syntax
2689 @cindex syntax, machine-independent
2690 This chapter describes the machine-independent syntax allowed in a
2691 source file. @command{@value{AS}} syntax is similar to what many other
2692 assemblers use; it is inspired by the BSD 4.2
2697 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2701 * Preprocessing:: Preprocessing
2702 * Whitespace:: Whitespace
2703 * Comments:: Comments
2704 * Symbol Intro:: Symbols
2705 * Statements:: Statements
2706 * Constants:: Constants
2710 @section Preprocessing
2712 @cindex preprocessing
2713 The @command{@value{AS}} internal preprocessor:
2715 @cindex whitespace, removed by preprocessor
2717 adjusts and removes extra whitespace. It leaves one space or tab before
2718 the keywords on a line, and turns any other whitespace on the line into
2721 @cindex comments, removed by preprocessor
2723 removes all comments, replacing them with a single space, or an
2724 appropriate number of newlines.
2726 @cindex constants, converted by preprocessor
2728 converts character constants into the appropriate numeric values.
2731 It does not do macro processing, include file handling, or
2732 anything else you may get from your C compiler's preprocessor. You can
2733 do include file processing with the @code{.include} directive
2734 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2735 to get other ``CPP'' style preprocessing by giving the input file a
2736 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2737 Output, gcc info, Using GNU CC}.
2739 Excess whitespace, comments, and character constants
2740 cannot be used in the portions of the input text that are not
2743 @cindex turning preprocessing on and off
2744 @cindex preprocessing, turning on and off
2747 If the first line of an input file is @code{#NO_APP} or if you use the
2748 @samp{-f} option, whitespace and comments are not removed from the input file.
2749 Within an input file, you can ask for whitespace and comment removal in
2750 specific portions of the by putting a line that says @code{#APP} before the
2751 text that may contain whitespace or comments, and putting a line that says
2752 @code{#NO_APP} after this text. This feature is mainly intend to support
2753 @code{asm} statements in compilers whose output is otherwise free of comments
2760 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2761 Whitespace is used to separate symbols, and to make programs neater for
2762 people to read. Unless within character constants
2763 (@pxref{Characters,,Character Constants}), any whitespace means the same
2764 as exactly one space.
2770 There are two ways of rendering comments to @command{@value{AS}}. In both
2771 cases the comment is equivalent to one space.
2773 Anything from @samp{/*} through the next @samp{*/} is a comment.
2774 This means you may not nest these comments.
2778 The only way to include a newline ('\n') in a comment
2779 is to use this sort of comment.
2782 /* This sort of comment does not nest. */
2785 @cindex line comment character
2786 Anything from a @dfn{line comment} character up to the next newline is
2787 considered a comment and is ignored. The line comment character is target
2788 specific, and some targets multiple comment characters. Some targets also have
2789 line comment characters that only work if they are the first character on a
2790 line. Some targets use a sequence of two characters to introduce a line
2791 comment. Some targets can also change their line comment characters depending
2792 upon command line options that have been used. For more details see the
2793 @emph{Syntax} section in the documentation for individual targets.
2795 If the line comment character is the hash sign (@samp{#}) then it still has the
2796 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2797 to specify logical line numbers:
2800 @cindex lines starting with @code{#}
2801 @cindex logical line numbers
2802 To be compatible with past assemblers, lines that begin with @samp{#} have a
2803 special interpretation. Following the @samp{#} should be an absolute
2804 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2805 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2806 new logical file name. The rest of the line, if any, should be whitespace.
2808 If the first non-whitespace characters on the line are not numeric,
2809 the line is ignored. (Just like a comment.)
2812 # This is an ordinary comment.
2813 # 42-6 "new_file_name" # New logical file name
2814 # This is logical line # 36.
2816 This feature is deprecated, and may disappear from future versions
2817 of @command{@value{AS}}.
2822 @cindex characters used in symbols
2823 @ifclear SPECIAL-SYMS
2824 A @dfn{symbol} is one or more characters chosen from the set of all
2825 letters (both upper and lower case), digits and the three characters
2831 A @dfn{symbol} is one or more characters chosen from the set of all
2832 letters (both upper and lower case), digits and the three characters
2833 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2839 On most machines, you can also use @code{$} in symbol names; exceptions
2840 are noted in @ref{Machine Dependencies}.
2842 No symbol may begin with a digit. Case is significant.
2843 There is no length limit; all characters are significant. Multibyte characters
2844 are supported. Symbols are delimited by characters not in that set, or by the
2845 beginning of a file (since the source program must end with a newline, the end
2846 of a file is not a possible symbol delimiter). @xref{Symbols}.
2848 Symbol names may also be enclosed in double quote @code{"} characters. In such
2849 cases any characters are allowed, except for the NUL character. If a double
2850 quote character is to be included in the symbol name it must be preceeded by a
2851 backslash @code{\} character.
2852 @cindex length of symbols
2857 @cindex statements, structure of
2858 @cindex line separator character
2859 @cindex statement separator character
2861 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2862 @dfn{line separator character}. The line separator character is target
2863 specific and described in the @emph{Syntax} section of each
2864 target's documentation. Not all targets support a line separator character.
2865 The newline or line separator character is considered to be part of the
2866 preceding statement. Newlines and separators within character constants are an
2867 exception: they do not end statements.
2869 @cindex newline, required at file end
2870 @cindex EOF, newline must precede
2871 It is an error to end any statement with end-of-file: the last
2872 character of any input file should be a newline.@refill
2874 An empty statement is allowed, and may include whitespace. It is ignored.
2876 @cindex instructions and directives
2877 @cindex directives and instructions
2878 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2879 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2881 A statement begins with zero or more labels, optionally followed by a
2882 key symbol which determines what kind of statement it is. The key
2883 symbol determines the syntax of the rest of the statement. If the
2884 symbol begins with a dot @samp{.} then the statement is an assembler
2885 directive: typically valid for any computer. If the symbol begins with
2886 a letter the statement is an assembly language @dfn{instruction}: it
2887 assembles into a machine language instruction.
2889 Different versions of @command{@value{AS}} for different computers
2890 recognize different instructions. In fact, the same symbol may
2891 represent a different instruction in a different computer's assembly
2895 @cindex @code{:} (label)
2896 @cindex label (@code{:})
2897 A label is a symbol immediately followed by a colon (@code{:}).
2898 Whitespace before a label or after a colon is permitted, but you may not
2899 have whitespace between a label's symbol and its colon. @xref{Labels}.
2902 For HPPA targets, labels need not be immediately followed by a colon, but
2903 the definition of a label must begin in column zero. This also implies that
2904 only one label may be defined on each line.
2908 label: .directive followed by something
2909 another_label: # This is an empty statement.
2910 instruction operand_1, operand_2, @dots{}
2917 A constant is a number, written so that its value is known by
2918 inspection, without knowing any context. Like this:
2921 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2922 .ascii "Ring the bell\7" # A string constant.
2923 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2924 .float 0f-314159265358979323846264338327\
2925 95028841971.693993751E-40 # - pi, a flonum.
2930 * Characters:: Character Constants
2931 * Numbers:: Number Constants
2935 @subsection Character Constants
2937 @cindex character constants
2938 @cindex constants, character
2939 There are two kinds of character constants. A @dfn{character} stands
2940 for one character in one byte and its value may be used in
2941 numeric expressions. String constants (properly called string
2942 @emph{literals}) are potentially many bytes and their values may not be
2943 used in arithmetic expressions.
2947 * Chars:: Characters
2951 @subsubsection Strings
2953 @cindex string constants
2954 @cindex constants, string
2955 A @dfn{string} is written between double-quotes. It may contain
2956 double-quotes or null characters. The way to get special characters
2957 into a string is to @dfn{escape} these characters: precede them with
2958 a backslash @samp{\} character. For example @samp{\\} represents
2959 one backslash: the first @code{\} is an escape which tells
2960 @command{@value{AS}} to interpret the second character literally as a backslash
2961 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2962 escape character). The complete list of escapes follows.
2964 @cindex escape codes, character
2965 @cindex character escape codes
2966 @c NOTE: Cindex entries must not start with a backlash character.
2967 @c NOTE: This confuses the pdf2texi script when it is creating the
2968 @c NOTE: index based upon the first character and so it generates:
2969 @c NOTE: \initial {\\}
2970 @c NOTE: which then results in the error message:
2971 @c NOTE: Argument of \\ has an extra }.
2972 @c NOTE: So in the index entries below a space character has been
2973 @c NOTE: prepended to avoid this problem.
2976 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2978 @cindex @code{ \b} (backspace character)
2979 @cindex backspace (@code{\b})
2981 Mnemonic for backspace; for ASCII this is octal code 010.
2984 @c Mnemonic for EOText; for ASCII this is octal code 004.
2986 @cindex @code{ \f} (formfeed character)
2987 @cindex formfeed (@code{\f})
2989 Mnemonic for FormFeed; for ASCII this is octal code 014.
2991 @cindex @code{ \n} (newline character)
2992 @cindex newline (@code{\n})
2994 Mnemonic for newline; for ASCII this is octal code 012.
2997 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2999 @cindex @code{ \r} (carriage return character)
3000 @cindex carriage return (@code{backslash-r})
3002 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3005 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3006 @c other assemblers.
3008 @cindex @code{ \t} (tab)
3009 @cindex tab (@code{\t})
3011 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3014 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3015 @c @item \x @var{digit} @var{digit} @var{digit}
3016 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3018 @cindex @code{ \@var{ddd}} (octal character code)
3019 @cindex octal character code (@code{\@var{ddd}})
3020 @item \ @var{digit} @var{digit} @var{digit}
3021 An octal character code. The numeric code is 3 octal digits.
3022 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3023 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3025 @cindex @code{ \@var{xd...}} (hex character code)
3026 @cindex hex character code (@code{\@var{xd...}})
3027 @item \@code{x} @var{hex-digits...}
3028 A hex character code. All trailing hex digits are combined. Either upper or
3029 lower case @code{x} works.
3031 @cindex @code{ \\} (@samp{\} character)
3032 @cindex backslash (@code{\\})
3034 Represents one @samp{\} character.
3037 @c Represents one @samp{'} (accent acute) character.
3038 @c This is needed in single character literals
3039 @c (@xref{Characters,,Character Constants}.) to represent
3042 @cindex @code{ \"} (doublequote character)
3043 @cindex doublequote (@code{\"})
3045 Represents one @samp{"} character. Needed in strings to represent
3046 this character, because an unescaped @samp{"} would end the string.
3048 @item \ @var{anything-else}
3049 Any other character when escaped by @kbd{\} gives a warning, but
3050 assembles as if the @samp{\} was not present. The idea is that if
3051 you used an escape sequence you clearly didn't want the literal
3052 interpretation of the following character. However @command{@value{AS}} has no
3053 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3054 code and warns you of the fact.
3057 Which characters are escapable, and what those escapes represent,
3058 varies widely among assemblers. The current set is what we think
3059 the BSD 4.2 assembler recognizes, and is a subset of what most C
3060 compilers recognize. If you are in doubt, do not use an escape
3064 @subsubsection Characters
3066 @cindex single character constant
3067 @cindex character, single
3068 @cindex constant, single character
3069 A single character may be written as a single quote immediately
3070 followed by that character. The same escapes apply to characters as
3071 to strings. So if you want to write the character backslash, you
3072 must write @kbd{'\\} where the first @code{\} escapes the second
3073 @code{\}. As you can see, the quote is an acute accent, not a
3074 grave accent. A newline
3076 @ifclear abnormal-separator
3077 (or semicolon @samp{;})
3079 @ifset abnormal-separator
3081 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3086 immediately following an acute accent is taken as a literal character
3087 and does not count as the end of a statement. The value of a character
3088 constant in a numeric expression is the machine's byte-wide code for
3089 that character. @command{@value{AS}} assumes your character code is ASCII:
3090 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3093 @subsection Number Constants
3095 @cindex constants, number
3096 @cindex number constants
3097 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3098 are stored in the target machine. @emph{Integers} are numbers that
3099 would fit into an @code{int} in the C language. @emph{Bignums} are
3100 integers, but they are stored in more than 32 bits. @emph{Flonums}
3101 are floating point numbers, described below.
3104 * Integers:: Integers
3109 * Bit Fields:: Bit Fields
3115 @subsubsection Integers
3117 @cindex constants, integer
3119 @cindex binary integers
3120 @cindex integers, binary
3121 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3122 the binary digits @samp{01}.
3124 @cindex octal integers
3125 @cindex integers, octal
3126 An octal integer is @samp{0} followed by zero or more of the octal
3127 digits (@samp{01234567}).
3129 @cindex decimal integers
3130 @cindex integers, decimal
3131 A decimal integer starts with a non-zero digit followed by zero or
3132 more digits (@samp{0123456789}).
3134 @cindex hexadecimal integers
3135 @cindex integers, hexadecimal
3136 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3137 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3139 Integers have the usual values. To denote a negative integer, use
3140 the prefix operator @samp{-} discussed under expressions
3141 (@pxref{Prefix Ops,,Prefix Operators}).
3144 @subsubsection Bignums
3147 @cindex constants, bignum
3148 A @dfn{bignum} has the same syntax and semantics as an integer
3149 except that the number (or its negative) takes more than 32 bits to
3150 represent in binary. The distinction is made because in some places
3151 integers are permitted while bignums are not.
3154 @subsubsection Flonums
3156 @cindex floating point numbers
3157 @cindex constants, floating point
3159 @cindex precision, floating point
3160 A @dfn{flonum} represents a floating point number. The translation is
3161 indirect: a decimal floating point number from the text is converted by
3162 @command{@value{AS}} to a generic binary floating point number of more than
3163 sufficient precision. This generic floating point number is converted
3164 to a particular computer's floating point format (or formats) by a
3165 portion of @command{@value{AS}} specialized to that computer.
3167 A flonum is written by writing (in order)
3172 (@samp{0} is optional on the HPPA.)
3176 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3178 @kbd{e} is recommended. Case is not important.
3180 @c FIXME: verify if flonum syntax really this vague for most cases
3181 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3182 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3185 On the H8/300, Renesas / SuperH SH,
3186 and AMD 29K architectures, the letter must be
3187 one of the letters @samp{DFPRSX} (in upper or lower case).
3189 On the ARC, the letter must be one of the letters @samp{DFRS}
3190 (in upper or lower case).
3192 On the Intel 960 architecture, the letter must be
3193 one of the letters @samp{DFT} (in upper or lower case).
3195 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3199 One of the letters @samp{DFRS} (in upper or lower case).
3202 One of the letters @samp{DFPRSX} (in upper or lower case).
3205 The letter @samp{E} (upper case only).
3208 One of the letters @samp{DFT} (in upper or lower case).
3213 An optional sign: either @samp{+} or @samp{-}.
3216 An optional @dfn{integer part}: zero or more decimal digits.
3219 An optional @dfn{fractional part}: @samp{.} followed by zero
3220 or more decimal digits.
3223 An optional exponent, consisting of:
3227 An @samp{E} or @samp{e}.
3228 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3229 @c principle this can perfectly well be different on different targets.
3231 Optional sign: either @samp{+} or @samp{-}.
3233 One or more decimal digits.
3238 At least one of the integer part or the fractional part must be
3239 present. The floating point number has the usual base-10 value.
3241 @command{@value{AS}} does all processing using integers. Flonums are computed
3242 independently of any floating point hardware in the computer running
3243 @command{@value{AS}}.
3247 @c Bit fields are written as a general facility but are also controlled
3248 @c by a conditional-compilation flag---which is as of now (21mar91)
3249 @c turned on only by the i960 config of GAS.
3251 @subsubsection Bit Fields
3254 @cindex constants, bit field
3255 You can also define numeric constants as @dfn{bit fields}.
3256 Specify two numbers separated by a colon---
3258 @var{mask}:@var{value}
3261 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3264 The resulting number is then packed
3266 @c this conditional paren in case bit fields turned on elsewhere than 960
3267 (in host-dependent byte order)
3269 into a field whose width depends on which assembler directive has the
3270 bit-field as its argument. Overflow (a result from the bitwise and
3271 requiring more binary digits to represent) is not an error; instead,
3272 more constants are generated, of the specified width, beginning with the
3273 least significant digits.@refill
3275 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3276 @code{.short}, and @code{.word} accept bit-field arguments.
3281 @chapter Sections and Relocation
3286 * Secs Background:: Background
3287 * Ld Sections:: Linker Sections
3288 * As Sections:: Assembler Internal Sections
3289 * Sub-Sections:: Sub-Sections
3293 @node Secs Background
3296 Roughly, a section is a range of addresses, with no gaps; all data
3297 ``in'' those addresses is treated the same for some particular purpose.
3298 For example there may be a ``read only'' section.
3300 @cindex linker, and assembler
3301 @cindex assembler, and linker
3302 The linker @code{@value{LD}} reads many object files (partial programs) and
3303 combines their contents to form a runnable program. When @command{@value{AS}}
3304 emits an object file, the partial program is assumed to start at address 0.
3305 @code{@value{LD}} assigns the final addresses for the partial program, so that
3306 different partial programs do not overlap. This is actually an
3307 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3310 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3311 addresses. These blocks slide to their run-time addresses as rigid
3312 units; their length does not change and neither does the order of bytes
3313 within them. Such a rigid unit is called a @emph{section}. Assigning
3314 run-time addresses to sections is called @dfn{relocation}. It includes
3315 the task of adjusting mentions of object-file addresses so they refer to
3316 the proper run-time addresses.
3318 For the H8/300, and for the Renesas / SuperH SH,
3319 @command{@value{AS}} pads sections if needed to
3320 ensure they end on a word (sixteen bit) boundary.
3323 @cindex standard assembler sections
3324 An object file written by @command{@value{AS}} has at least three sections, any
3325 of which may be empty. These are named @dfn{text}, @dfn{data} and
3330 When it generates COFF or ELF output,
3332 @command{@value{AS}} can also generate whatever other named sections you specify
3333 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3334 If you do not use any directives that place output in the @samp{.text}
3335 or @samp{.data} sections, these sections still exist, but are empty.
3340 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3342 @command{@value{AS}} can also generate whatever other named sections you
3343 specify using the @samp{.space} and @samp{.subspace} directives. See
3344 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3345 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3346 assembler directives.
3349 Additionally, @command{@value{AS}} uses different names for the standard
3350 text, data, and bss sections when generating SOM output. Program text
3351 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3352 BSS into @samp{$BSS$}.
3356 Within the object file, the text section starts at address @code{0}, the
3357 data section follows, and the bss section follows the data section.
3360 When generating either SOM or ELF output files on the HPPA, the text
3361 section starts at address @code{0}, the data section at address
3362 @code{0x4000000}, and the bss section follows the data section.
3365 To let @code{@value{LD}} know which data changes when the sections are
3366 relocated, and how to change that data, @command{@value{AS}} also writes to the
3367 object file details of the relocation needed. To perform relocation
3368 @code{@value{LD}} must know, each time an address in the object
3372 Where in the object file is the beginning of this reference to
3375 How long (in bytes) is this reference?
3377 Which section does the address refer to? What is the numeric value of
3379 (@var{address}) @minus{} (@var{start-address of section})?
3382 Is the reference to an address ``Program-Counter relative''?
3385 @cindex addresses, format of
3386 @cindex section-relative addressing
3387 In fact, every address @command{@value{AS}} ever uses is expressed as
3389 (@var{section}) + (@var{offset into section})
3392 Further, most expressions @command{@value{AS}} computes have this section-relative
3395 (For some object formats, such as SOM for the HPPA, some expressions are
3396 symbol-relative instead.)
3399 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3400 @var{N} into section @var{secname}.''
3402 Apart from text, data and bss sections you need to know about the
3403 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3404 addresses in the absolute section remain unchanged. For example, address
3405 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3406 @code{@value{LD}}. Although the linker never arranges two partial programs'
3407 data sections with overlapping addresses after linking, @emph{by definition}
3408 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3409 part of a program is always the same address when the program is running as
3410 address @code{@{absolute@ 239@}} in any other part of the program.
3412 The idea of sections is extended to the @dfn{undefined} section. Any
3413 address whose section is unknown at assembly time is by definition
3414 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3415 Since numbers are always defined, the only way to generate an undefined
3416 address is to mention an undefined symbol. A reference to a named
3417 common block would be such a symbol: its value is unknown at assembly
3418 time so it has section @emph{undefined}.
3420 By analogy the word @emph{section} is used to describe groups of sections in
3421 the linked program. @code{@value{LD}} puts all partial programs' text
3422 sections in contiguous addresses in the linked program. It is
3423 customary to refer to the @emph{text section} of a program, meaning all
3424 the addresses of all partial programs' text sections. Likewise for
3425 data and bss sections.
3427 Some sections are manipulated by @code{@value{LD}}; others are invented for
3428 use of @command{@value{AS}} and have no meaning except during assembly.
3431 @section Linker Sections
3432 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3437 @cindex named sections
3438 @cindex sections, named
3439 @item named sections
3442 @cindex text section
3443 @cindex data section
3447 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3448 separate but equal sections. Anything you can say of one section is
3451 When the program is running, however, it is
3452 customary for the text section to be unalterable. The
3453 text section is often shared among processes: it contains
3454 instructions, constants and the like. The data section of a running
3455 program is usually alterable: for example, C variables would be stored
3456 in the data section.
3461 This section contains zeroed bytes when your program begins running. It
3462 is used to hold uninitialized variables or common storage. The length of
3463 each partial program's bss section is important, but because it starts
3464 out containing zeroed bytes there is no need to store explicit zero
3465 bytes in the object file. The bss section was invented to eliminate
3466 those explicit zeros from object files.
3468 @cindex absolute section
3469 @item absolute section
3470 Address 0 of this section is always ``relocated'' to runtime address 0.
3471 This is useful if you want to refer to an address that @code{@value{LD}} must
3472 not change when relocating. In this sense we speak of absolute
3473 addresses being ``unrelocatable'': they do not change during relocation.
3475 @cindex undefined section
3476 @item undefined section
3477 This ``section'' is a catch-all for address references to objects not in
3478 the preceding sections.
3479 @c FIXME: ref to some other doc on obj-file formats could go here.
3482 @cindex relocation example
3483 An idealized example of three relocatable sections follows.
3485 The example uses the traditional section names @samp{.text} and @samp{.data}.
3487 Memory addresses are on the horizontal axis.
3491 @c END TEXI2ROFF-KILL
3494 partial program # 1: |ttttt|dddd|00|
3501 partial program # 2: |TTT|DDD|000|
3504 +--+---+-----+--+----+---+-----+~~
3505 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3506 +--+---+-----+--+----+---+-----+~~
3508 addresses: 0 @dots{}
3515 \line{\it Partial program \#1: \hfil}
3516 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3517 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3519 \line{\it Partial program \#2: \hfil}
3520 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3521 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3523 \line{\it linked program: \hfil}
3524 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3525 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3526 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3527 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3529 \line{\it addresses: \hfil}
3533 @c END TEXI2ROFF-KILL
3536 @section Assembler Internal Sections
3538 @cindex internal assembler sections
3539 @cindex sections in messages, internal
3540 These sections are meant only for the internal use of @command{@value{AS}}. They
3541 have no meaning at run-time. You do not really need to know about these
3542 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3543 warning messages, so it might be helpful to have an idea of their
3544 meanings to @command{@value{AS}}. These sections are used to permit the
3545 value of every expression in your assembly language program to be a
3546 section-relative address.
3549 @cindex assembler internal logic error
3550 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3551 An internal assembler logic error has been found. This means there is a
3552 bug in the assembler.
3554 @cindex expr (internal section)
3556 The assembler stores complex expression internally as combinations of
3557 symbols. When it needs to represent an expression as a symbol, it puts
3558 it in the expr section.
3560 @c FIXME item transfer[t] vector preload
3561 @c FIXME item transfer[t] vector postload
3562 @c FIXME item register
3566 @section Sub-Sections
3568 @cindex numbered subsections
3569 @cindex grouping data
3575 fall into two sections: text and data.
3577 You may have separate groups of
3579 data in named sections
3583 data in named sections
3589 that you want to end up near to each other in the object file, even though they
3590 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3591 use @dfn{subsections} for this purpose. Within each section, there can be
3592 numbered subsections with values from 0 to 8192. Objects assembled into the
3593 same subsection go into the object file together with other objects in the same
3594 subsection. For example, a compiler might want to store constants in the text
3595 section, but might not want to have them interspersed with the program being
3596 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3597 section of code being output, and a @samp{.text 1} before each group of
3598 constants being output.
3600 Subsections are optional. If you do not use subsections, everything
3601 goes in subsection number zero.
3604 Each subsection is zero-padded up to a multiple of four bytes.
3605 (Subsections may be padded a different amount on different flavors
3606 of @command{@value{AS}}.)
3610 On the H8/300 platform, each subsection is zero-padded to a word
3611 boundary (two bytes).
3612 The same is true on the Renesas SH.
3615 @c FIXME section padding (alignment)?
3616 @c Rich Pixley says padding here depends on target obj code format; that
3617 @c doesn't seem particularly useful to say without further elaboration,
3618 @c so for now I say nothing about it. If this is a generic BFD issue,
3619 @c these paragraphs might need to vanish from this manual, and be
3620 @c discussed in BFD chapter of binutils (or some such).
3624 Subsections appear in your object file in numeric order, lowest numbered
3625 to highest. (All this to be compatible with other people's assemblers.)
3626 The object file contains no representation of subsections; @code{@value{LD}} and
3627 other programs that manipulate object files see no trace of them.
3628 They just see all your text subsections as a text section, and all your
3629 data subsections as a data section.
3631 To specify which subsection you want subsequent statements assembled
3632 into, use a numeric argument to specify it, in a @samp{.text
3633 @var{expression}} or a @samp{.data @var{expression}} statement.
3636 When generating COFF output, you
3641 can also use an extra subsection
3642 argument with arbitrary named sections: @samp{.section @var{name},
3647 When generating ELF output, you
3652 can also use the @code{.subsection} directive (@pxref{SubSection})
3653 to specify a subsection: @samp{.subsection @var{expression}}.
3655 @var{Expression} should be an absolute expression
3656 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3657 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3658 begins in @code{text 0}. For instance:
3660 .text 0 # The default subsection is text 0 anyway.
3661 .ascii "This lives in the first text subsection. *"
3663 .ascii "But this lives in the second text subsection."
3665 .ascii "This lives in the data section,"
3666 .ascii "in the first data subsection."
3668 .ascii "This lives in the first text section,"
3669 .ascii "immediately following the asterisk (*)."
3672 Each section has a @dfn{location counter} incremented by one for every byte
3673 assembled into that section. Because subsections are merely a convenience
3674 restricted to @command{@value{AS}} there is no concept of a subsection location
3675 counter. There is no way to directly manipulate a location counter---but the
3676 @code{.align} directive changes it, and any label definition captures its
3677 current value. The location counter of the section where statements are being
3678 assembled is said to be the @dfn{active} location counter.
3681 @section bss Section
3684 @cindex common variable storage
3685 The bss section is used for local common variable storage.
3686 You may allocate address space in the bss section, but you may
3687 not dictate data to load into it before your program executes. When
3688 your program starts running, all the contents of the bss
3689 section are zeroed bytes.
3691 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3692 @ref{Lcomm,,@code{.lcomm}}.
3694 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3695 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3698 When assembling for a target which supports multiple sections, such as ELF or
3699 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3700 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3701 section. Typically the section will only contain symbol definitions and
3702 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3709 Symbols are a central concept: the programmer uses symbols to name
3710 things, the linker uses symbols to link, and the debugger uses symbols
3714 @cindex debuggers, and symbol order
3715 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3716 the same order they were declared. This may break some debuggers.
3721 * Setting Symbols:: Giving Symbols Other Values
3722 * Symbol Names:: Symbol Names
3723 * Dot:: The Special Dot Symbol
3724 * Symbol Attributes:: Symbol Attributes
3731 A @dfn{label} is written as a symbol immediately followed by a colon
3732 @samp{:}. The symbol then represents the current value of the
3733 active location counter, and is, for example, a suitable instruction
3734 operand. You are warned if you use the same symbol to represent two
3735 different locations: the first definition overrides any other
3739 On the HPPA, the usual form for a label need not be immediately followed by a
3740 colon, but instead must start in column zero. Only one label may be defined on
3741 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3742 provides a special directive @code{.label} for defining labels more flexibly.
3745 @node Setting Symbols
3746 @section Giving Symbols Other Values
3748 @cindex assigning values to symbols
3749 @cindex symbol values, assigning
3750 A symbol can be given an arbitrary value by writing a symbol, followed
3751 by an equals sign @samp{=}, followed by an expression
3752 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3753 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3754 equals sign @samp{=}@samp{=} here represents an equivalent of the
3755 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3758 Blackfin does not support symbol assignment with @samp{=}.
3762 @section Symbol Names
3764 @cindex symbol names
3765 @cindex names, symbol
3766 @ifclear SPECIAL-SYMS
3767 Symbol names begin with a letter or with one of @samp{._}. On most
3768 machines, you can also use @code{$} in symbol names; exceptions are
3769 noted in @ref{Machine Dependencies}. That character may be followed by any
3770 string of digits, letters, dollar signs (unless otherwise noted for a
3771 particular target machine), and underscores.
3775 Symbol names begin with a letter or with one of @samp{._}. On the
3776 Renesas SH you can also use @code{$} in symbol names. That
3777 character may be followed by any string of digits, letters, dollar signs (save
3778 on the H8/300), and underscores.
3782 Case of letters is significant: @code{foo} is a different symbol name
3785 Symbol names do not start with a digit. An exception to this rule is made for
3786 Local Labels. See below.
3788 Multibyte characters are supported. To generate a symbol name containing
3789 multibyte characters enclose it within double quotes and use escape codes. cf
3790 @xref{Strings}. Generating a multibyte symbol name from a label is not
3791 currently supported.
3793 Each symbol has exactly one name. Each name in an assembly language program
3794 refers to exactly one symbol. You may use that symbol name any number of times
3797 @subheading Local Symbol Names
3799 @cindex local symbol names
3800 @cindex symbol names, local
3801 A local symbol is any symbol beginning with certain local label prefixes.
3802 By default, the local label prefix is @samp{.L} for ELF systems or
3803 @samp{L} for traditional a.out systems, but each target may have its own
3804 set of local label prefixes.
3806 On the HPPA local symbols begin with @samp{L$}.
3809 Local symbols are defined and used within the assembler, but they are
3810 normally not saved in object files. Thus, they are not visible when debugging.
3811 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3812 to retain the local symbols in the object files.
3814 @subheading Local Labels
3816 @cindex local labels
3817 @cindex temporary symbol names
3818 @cindex symbol names, temporary
3819 Local labels are different from local symbols. Local labels help compilers and
3820 programmers use names temporarily. They create symbols which are guaranteed to
3821 be unique over the entire scope of the input source code and which can be
3822 referred to by a simple notation. To define a local label, write a label of
3823 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3824 To refer to the most recent previous definition of that label write
3825 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3826 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3827 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3829 There is no restriction on how you can use these labels, and you can reuse them
3830 too. So that it is possible to repeatedly define the same local label (using
3831 the same number @samp{@b{N}}), although you can only refer to the most recently
3832 defined local label of that number (for a backwards reference) or the next
3833 definition of a specific local label for a forward reference. It is also worth
3834 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3835 implemented in a slightly more efficient manner than the others.
3846 Which is the equivalent of:
3849 label_1: branch label_3
3850 label_2: branch label_1
3851 label_3: branch label_4
3852 label_4: branch label_3
3855 Local label names are only a notational device. They are immediately
3856 transformed into more conventional symbol names before the assembler uses them.
3857 The symbol names are stored in the symbol table, appear in error messages, and
3858 are optionally emitted to the object file. The names are constructed using
3862 @item @emph{local label prefix}
3863 All local symbols begin with the system-specific local label prefix.
3864 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3865 that start with the local label prefix. These labels are
3866 used for symbols you are never intended to see. If you use the
3867 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3868 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3869 you may use them in debugging.
3872 This is the number that was used in the local label definition. So if the
3873 label is written @samp{55:} then the number is @samp{55}.
3876 This unusual character is included so you do not accidentally invent a symbol
3877 of the same name. The character has ASCII value of @samp{\002} (control-B).
3879 @item @emph{ordinal number}
3880 This is a serial number to keep the labels distinct. The first definition of
3881 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3882 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3883 the number @samp{1} and its 15th definition gets @samp{15} as well.
3886 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3887 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3889 @subheading Dollar Local Labels
3890 @cindex dollar local symbols
3892 On some targets @code{@value{AS}} also supports an even more local form of
3893 local labels called dollar labels. These labels go out of scope (i.e., they
3894 become undefined) as soon as a non-local label is defined. Thus they remain
3895 valid for only a small region of the input source code. Normal local labels,
3896 by contrast, remain in scope for the entire file, or until they are redefined
3897 by another occurrence of the same local label.
3899 Dollar labels are defined in exactly the same way as ordinary local labels,
3900 except that they have a dollar sign suffix to their numeric value, e.g.,
3903 They can also be distinguished from ordinary local labels by their transformed
3904 names which use ASCII character @samp{\001} (control-A) as the magic character
3905 to distinguish them from ordinary labels. For example, the fifth definition of
3906 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3909 @section The Special Dot Symbol
3911 @cindex dot (symbol)
3912 @cindex @code{.} (symbol)
3913 @cindex current address
3914 @cindex location counter
3915 The special symbol @samp{.} refers to the current address that
3916 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3917 .long .} defines @code{melvin} to contain its own address.
3918 Assigning a value to @code{.} is treated the same as a @code{.org}
3920 @ifclear no-space-dir
3921 Thus, the expression @samp{.=.+4} is the same as saying
3925 @node Symbol Attributes
3926 @section Symbol Attributes
3928 @cindex symbol attributes
3929 @cindex attributes, symbol
3930 Every symbol has, as well as its name, the attributes ``Value'' and
3931 ``Type''. Depending on output format, symbols can also have auxiliary
3934 The detailed definitions are in @file{a.out.h}.
3937 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3938 all these attributes, and probably won't warn you. This makes the
3939 symbol an externally defined symbol, which is generally what you
3943 * Symbol Value:: Value
3944 * Symbol Type:: Type
3947 * a.out Symbols:: Symbol Attributes: @code{a.out}
3951 * a.out Symbols:: Symbol Attributes: @code{a.out}
3954 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3959 * COFF Symbols:: Symbol Attributes for COFF
3962 * SOM Symbols:: Symbol Attributes for SOM
3969 @cindex value of a symbol
3970 @cindex symbol value
3971 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3972 location in the text, data, bss or absolute sections the value is the
3973 number of addresses from the start of that section to the label.
3974 Naturally for text, data and bss sections the value of a symbol changes
3975 as @code{@value{LD}} changes section base addresses during linking. Absolute
3976 symbols' values do not change during linking: that is why they are
3979 The value of an undefined symbol is treated in a special way. If it is
3980 0 then the symbol is not defined in this assembler source file, and
3981 @code{@value{LD}} tries to determine its value from other files linked into the
3982 same program. You make this kind of symbol simply by mentioning a symbol
3983 name without defining it. A non-zero value represents a @code{.comm}
3984 common declaration. The value is how much common storage to reserve, in
3985 bytes (addresses). The symbol refers to the first address of the
3991 @cindex type of a symbol
3993 The type attribute of a symbol contains relocation (section)
3994 information, any flag settings indicating that a symbol is external, and
3995 (optionally), other information for linkers and debuggers. The exact
3996 format depends on the object-code output format in use.
4001 @c The following avoids a "widow" subsection title. @group would be
4002 @c better if it were available outside examples.
4005 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
4007 @cindex @code{b.out} symbol attributes
4008 @cindex symbol attributes, @code{b.out}
4009 These symbol attributes appear only when @command{@value{AS}} is configured for
4010 one of the Berkeley-descended object output formats---@code{a.out} or
4016 @subsection Symbol Attributes: @code{a.out}
4018 @cindex @code{a.out} symbol attributes
4019 @cindex symbol attributes, @code{a.out}
4025 @subsection Symbol Attributes: @code{a.out}
4027 @cindex @code{a.out} symbol attributes
4028 @cindex symbol attributes, @code{a.out}
4032 * Symbol Desc:: Descriptor
4033 * Symbol Other:: Other
4037 @subsubsection Descriptor
4039 @cindex descriptor, of @code{a.out} symbol
4040 This is an arbitrary 16-bit value. You may establish a symbol's
4041 descriptor value by using a @code{.desc} statement
4042 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4043 @command{@value{AS}}.
4046 @subsubsection Other
4048 @cindex other attribute, of @code{a.out} symbol
4049 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4054 @subsection Symbol Attributes for COFF
4056 @cindex COFF symbol attributes
4057 @cindex symbol attributes, COFF
4059 The COFF format supports a multitude of auxiliary symbol attributes;
4060 like the primary symbol attributes, they are set between @code{.def} and
4061 @code{.endef} directives.
4063 @subsubsection Primary Attributes
4065 @cindex primary attributes, COFF symbols
4066 The symbol name is set with @code{.def}; the value and type,
4067 respectively, with @code{.val} and @code{.type}.
4069 @subsubsection Auxiliary Attributes
4071 @cindex auxiliary attributes, COFF symbols
4072 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4073 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4074 table information for COFF.
4079 @subsection Symbol Attributes for SOM
4081 @cindex SOM symbol attributes
4082 @cindex symbol attributes, SOM
4084 The SOM format for the HPPA supports a multitude of symbol attributes set with
4085 the @code{.EXPORT} and @code{.IMPORT} directives.
4087 The attributes are described in @cite{HP9000 Series 800 Assembly
4088 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4089 @code{EXPORT} assembler directive documentation.
4093 @chapter Expressions
4097 @cindex numeric values
4098 An @dfn{expression} specifies an address or numeric value.
4099 Whitespace may precede and/or follow an expression.
4101 The result of an expression must be an absolute number, or else an offset into
4102 a particular section. If an expression is not absolute, and there is not
4103 enough information when @command{@value{AS}} sees the expression to know its
4104 section, a second pass over the source program might be necessary to interpret
4105 the expression---but the second pass is currently not implemented.
4106 @command{@value{AS}} aborts with an error message in this situation.
4109 * Empty Exprs:: Empty Expressions
4110 * Integer Exprs:: Integer Expressions
4114 @section Empty Expressions
4116 @cindex empty expressions
4117 @cindex expressions, empty
4118 An empty expression has no value: it is just whitespace or null.
4119 Wherever an absolute expression is required, you may omit the
4120 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4121 is compatible with other assemblers.
4124 @section Integer Expressions
4126 @cindex integer expressions
4127 @cindex expressions, integer
4128 An @dfn{integer expression} is one or more @emph{arguments} delimited
4129 by @emph{operators}.
4132 * Arguments:: Arguments
4133 * Operators:: Operators
4134 * Prefix Ops:: Prefix Operators
4135 * Infix Ops:: Infix Operators
4139 @subsection Arguments
4141 @cindex expression arguments
4142 @cindex arguments in expressions
4143 @cindex operands in expressions
4144 @cindex arithmetic operands
4145 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4146 contexts arguments are sometimes called ``arithmetic operands''. In
4147 this manual, to avoid confusing them with the ``instruction operands'' of
4148 the machine language, we use the term ``argument'' to refer to parts of
4149 expressions only, reserving the word ``operand'' to refer only to machine
4150 instruction operands.
4152 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4153 @var{section} is one of text, data, bss, absolute,
4154 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4157 Numbers are usually integers.
4159 A number can be a flonum or bignum. In this case, you are warned
4160 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4161 these 32 bits are an integer. You may write integer-manipulating
4162 instructions that act on exotic constants, compatible with other
4165 @cindex subexpressions
4166 Subexpressions are a left parenthesis @samp{(} followed by an integer
4167 expression, followed by a right parenthesis @samp{)}; or a prefix
4168 operator followed by an argument.
4171 @subsection Operators
4173 @cindex operators, in expressions
4174 @cindex arithmetic functions
4175 @cindex functions, in expressions
4176 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4177 operators are followed by an argument. Infix operators appear
4178 between their arguments. Operators may be preceded and/or followed by
4182 @subsection Prefix Operator
4184 @cindex prefix operators
4185 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4186 one argument, which must be absolute.
4188 @c the tex/end tex stuff surrounding this small table is meant to make
4189 @c it align, on the printed page, with the similar table in the next
4190 @c section (which is inside an enumerate).
4192 \global\advance\leftskip by \itemindent
4197 @dfn{Negation}. Two's complement negation.
4199 @dfn{Complementation}. Bitwise not.
4203 \global\advance\leftskip by -\itemindent
4207 @subsection Infix Operators
4209 @cindex infix operators
4210 @cindex operators, permitted arguments
4211 @dfn{Infix operators} take two arguments, one on either side. Operators
4212 have precedence, but operations with equal precedence are performed left
4213 to right. Apart from @code{+} or @option{-}, both arguments must be
4214 absolute, and the result is absolute.
4217 @cindex operator precedence
4218 @cindex precedence of operators
4225 @dfn{Multiplication}.
4228 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4234 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4237 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4241 Intermediate precedence
4246 @dfn{Bitwise Inclusive Or}.
4252 @dfn{Bitwise Exclusive Or}.
4255 @dfn{Bitwise Or Not}.
4262 @cindex addition, permitted arguments
4263 @cindex plus, permitted arguments
4264 @cindex arguments for addition
4266 @dfn{Addition}. If either argument is absolute, the result has the section of
4267 the other argument. You may not add together arguments from different
4270 @cindex subtraction, permitted arguments
4271 @cindex minus, permitted arguments
4272 @cindex arguments for subtraction
4274 @dfn{Subtraction}. If the right argument is absolute, the
4275 result has the section of the left argument.
4276 If both arguments are in the same section, the result is absolute.
4277 You may not subtract arguments from different sections.
4278 @c FIXME is there still something useful to say about undefined - undefined ?
4280 @cindex comparison expressions
4281 @cindex expressions, comparison
4286 @dfn{Is Not Equal To}
4290 @dfn{Is Greater Than}
4292 @dfn{Is Greater Than Or Equal To}
4294 @dfn{Is Less Than Or Equal To}
4296 The comparison operators can be used as infix operators. A true results has a
4297 value of -1 whereas a false result has a value of 0. Note, these operators
4298 perform signed comparisons.
4301 @item Lowest Precedence
4310 These two logical operations can be used to combine the results of sub
4311 expressions. Note, unlike the comparison operators a true result returns a
4312 value of 1 but a false results does still return 0. Also note that the logical
4313 or operator has a slightly lower precedence than logical and.
4318 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4319 address; you can only have a defined section in one of the two arguments.
4322 @chapter Assembler Directives
4324 @cindex directives, machine independent
4325 @cindex pseudo-ops, machine independent
4326 @cindex machine independent directives
4327 All assembler directives have names that begin with a period (@samp{.}).
4328 The names are case insensitive for most targets, and usually written
4331 This chapter discusses directives that are available regardless of the
4332 target machine configuration for the @sc{gnu} assembler.
4334 Some machine configurations provide additional directives.
4335 @xref{Machine Dependencies}.
4338 @ifset machine-directives
4339 @xref{Machine Dependencies}, for additional directives.
4344 * Abort:: @code{.abort}
4346 * ABORT (COFF):: @code{.ABORT}
4349 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4350 * Altmacro:: @code{.altmacro}
4351 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4352 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4353 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4354 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4355 * Byte:: @code{.byte @var{expressions}}
4356 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4357 * Comm:: @code{.comm @var{symbol} , @var{length} }
4358 * Data:: @code{.data @var{subsection}}
4360 * Def:: @code{.def @var{name}}
4363 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4369 * Double:: @code{.double @var{flonums}}
4370 * Eject:: @code{.eject}
4371 * Else:: @code{.else}
4372 * Elseif:: @code{.elseif}
4375 * Endef:: @code{.endef}
4378 * Endfunc:: @code{.endfunc}
4379 * Endif:: @code{.endif}
4380 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4381 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4382 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4384 * Error:: @code{.error @var{string}}
4385 * Exitm:: @code{.exitm}
4386 * Extern:: @code{.extern}
4387 * Fail:: @code{.fail}
4388 * File:: @code{.file}
4389 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4390 * Float:: @code{.float @var{flonums}}
4391 * Func:: @code{.func}
4392 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4394 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4395 * Hidden:: @code{.hidden @var{names}}
4398 * hword:: @code{.hword @var{expressions}}
4399 * Ident:: @code{.ident}
4400 * If:: @code{.if @var{absolute expression}}
4401 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4402 * Include:: @code{.include "@var{file}"}
4403 * Int:: @code{.int @var{expressions}}
4405 * Internal:: @code{.internal @var{names}}
4408 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4409 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4410 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4411 * Lflags:: @code{.lflags}
4412 @ifclear no-line-dir
4413 * Line:: @code{.line @var{line-number}}
4416 * Linkonce:: @code{.linkonce [@var{type}]}
4417 * List:: @code{.list}
4418 * Ln:: @code{.ln @var{line-number}}
4419 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4420 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4422 * Local:: @code{.local @var{names}}
4425 * Long:: @code{.long @var{expressions}}
4427 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4430 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4431 * MRI:: @code{.mri @var{val}}
4432 * Noaltmacro:: @code{.noaltmacro}
4433 * Nolist:: @code{.nolist}
4434 * Octa:: @code{.octa @var{bignums}}
4435 * Offset:: @code{.offset @var{loc}}
4436 * Org:: @code{.org @var{new-lc}, @var{fill}}
4437 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4439 * PopSection:: @code{.popsection}
4440 * Previous:: @code{.previous}
4443 * Print:: @code{.print @var{string}}
4445 * Protected:: @code{.protected @var{names}}
4448 * Psize:: @code{.psize @var{lines}, @var{columns}}
4449 * Purgem:: @code{.purgem @var{name}}
4451 * PushSection:: @code{.pushsection @var{name}}
4454 * Quad:: @code{.quad @var{bignums}}
4455 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4456 * Rept:: @code{.rept @var{count}}
4457 * Sbttl:: @code{.sbttl "@var{subheading}"}
4459 * Scl:: @code{.scl @var{class}}
4462 * Section:: @code{.section @var{name}[, @var{flags}]}
4465 * Set:: @code{.set @var{symbol}, @var{expression}}
4466 * Short:: @code{.short @var{expressions}}
4467 * Single:: @code{.single @var{flonums}}
4469 * Size:: @code{.size [@var{name} , @var{expression}]}
4471 @ifclear no-space-dir
4472 * Skip:: @code{.skip @var{size} , @var{fill}}
4475 * Sleb128:: @code{.sleb128 @var{expressions}}
4476 @ifclear no-space-dir
4477 * Space:: @code{.space @var{size} , @var{fill}}
4480 * Stab:: @code{.stabd, .stabn, .stabs}
4483 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4484 * Struct:: @code{.struct @var{expression}}
4486 * SubSection:: @code{.subsection}
4487 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4491 * Tag:: @code{.tag @var{structname}}
4494 * Text:: @code{.text @var{subsection}}
4495 * Title:: @code{.title "@var{heading}"}
4497 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4500 * Uleb128:: @code{.uleb128 @var{expressions}}
4502 * Val:: @code{.val @var{addr}}
4506 * Version:: @code{.version "@var{string}"}
4507 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4508 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4511 * Warning:: @code{.warning @var{string}}
4512 * Weak:: @code{.weak @var{names}}
4513 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4514 * Word:: @code{.word @var{expressions}}
4515 @ifclear no-space-dir
4516 * Zero:: @code{.zero @var{size}}
4518 * Deprecated:: Deprecated Directives
4522 @section @code{.abort}
4524 @cindex @code{abort} directive
4525 @cindex stopping the assembly
4526 This directive stops the assembly immediately. It is for
4527 compatibility with other assemblers. The original idea was that the
4528 assembly language source would be piped into the assembler. If the sender
4529 of the source quit, it could use this directive tells @command{@value{AS}} to
4530 quit also. One day @code{.abort} will not be supported.
4534 @section @code{.ABORT} (COFF)
4536 @cindex @code{ABORT} directive
4537 When producing COFF output, @command{@value{AS}} accepts this directive as a
4538 synonym for @samp{.abort}.
4541 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4547 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4549 @cindex padding the location counter
4550 @cindex @code{align} directive
4551 Pad the location counter (in the current subsection) to a particular storage
4552 boundary. The first expression (which must be absolute) is the alignment
4553 required, as described below.
4555 The second expression (also absolute) gives the fill value to be stored in the
4556 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4557 padding bytes are normally zero. However, on some systems, if the section is
4558 marked as containing code and the fill value is omitted, the space is filled
4559 with no-op instructions.
4561 The third expression is also absolute, and is also optional. If it is present,
4562 it is the maximum number of bytes that should be skipped by this alignment
4563 directive. If doing the alignment would require skipping more bytes than the
4564 specified maximum, then the alignment is not done at all. You can omit the
4565 fill value (the second argument) entirely by simply using two commas after the
4566 required alignment; this can be useful if you want the alignment to be filled
4567 with no-op instructions when appropriate.
4569 The way the required alignment is specified varies from system to system.
4570 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4571 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4572 alignment request in bytes. For example @samp{.align 8} advances
4573 the location counter until it is a multiple of 8. If the location counter
4574 is already a multiple of 8, no change is needed. For the tic54x, the
4575 first expression is the alignment request in words.
4577 For other systems, including ppc, i386 using a.out format, arm and
4578 strongarm, it is the
4579 number of low-order zero bits the location counter must have after
4580 advancement. For example @samp{.align 3} advances the location
4581 counter until it a multiple of 8. If the location counter is already a
4582 multiple of 8, no change is needed.
4584 This inconsistency is due to the different behaviors of the various
4585 native assemblers for these systems which GAS must emulate.
4586 GAS also provides @code{.balign} and @code{.p2align} directives,
4587 described later, which have a consistent behavior across all
4588 architectures (but are specific to GAS).
4591 @section @code{.altmacro}
4592 Enable alternate macro mode, enabling:
4595 @item LOCAL @var{name} [ , @dots{} ]
4596 One additional directive, @code{LOCAL}, is available. It is used to
4597 generate a string replacement for each of the @var{name} arguments, and
4598 replace any instances of @var{name} in each macro expansion. The
4599 replacement string is unique in the assembly, and different for each
4600 separate macro expansion. @code{LOCAL} allows you to write macros that
4601 define symbols, without fear of conflict between separate macro expansions.
4603 @item String delimiters
4604 You can write strings delimited in these other ways besides
4605 @code{"@var{string}"}:
4608 @item '@var{string}'
4609 You can delimit strings with single-quote characters.
4611 @item <@var{string}>
4612 You can delimit strings with matching angle brackets.
4615 @item single-character string escape
4616 To include any single character literally in a string (even if the
4617 character would otherwise have some special meaning), you can prefix the
4618 character with @samp{!} (an exclamation mark). For example, you can
4619 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4621 @item Expression results as strings
4622 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4623 and use the result as a string.
4627 @section @code{.ascii "@var{string}"}@dots{}
4629 @cindex @code{ascii} directive
4630 @cindex string literals
4631 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4632 separated by commas. It assembles each string (with no automatic
4633 trailing zero byte) into consecutive addresses.
4636 @section @code{.asciz "@var{string}"}@dots{}
4638 @cindex @code{asciz} directive
4639 @cindex zero-terminated strings
4640 @cindex null-terminated strings
4641 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4642 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4645 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4647 @cindex padding the location counter given number of bytes
4648 @cindex @code{balign} directive
4649 Pad the location counter (in the current subsection) to a particular
4650 storage boundary. The first expression (which must be absolute) is the
4651 alignment request in bytes. For example @samp{.balign 8} advances
4652 the location counter until it is a multiple of 8. If the location counter
4653 is already a multiple of 8, no change is needed.
4655 The second expression (also absolute) gives the fill value to be stored in the
4656 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4657 padding bytes are normally zero. However, on some systems, if the section is
4658 marked as containing code and the fill value is omitted, the space is filled
4659 with no-op instructions.
4661 The third expression is also absolute, and is also optional. If it is present,
4662 it is the maximum number of bytes that should be skipped by this alignment
4663 directive. If doing the alignment would require skipping more bytes than the
4664 specified maximum, then the alignment is not done at all. You can omit the
4665 fill value (the second argument) entirely by simply using two commas after the
4666 required alignment; this can be useful if you want the alignment to be filled
4667 with no-op instructions when appropriate.
4669 @cindex @code{balignw} directive
4670 @cindex @code{balignl} directive
4671 The @code{.balignw} and @code{.balignl} directives are variants of the
4672 @code{.balign} directive. The @code{.balignw} directive treats the fill
4673 pattern as a two byte word value. The @code{.balignl} directives treats the
4674 fill pattern as a four byte longword value. For example, @code{.balignw
4675 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4676 filled in with the value 0x368d (the exact placement of the bytes depends upon
4677 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4680 @node Bundle directives
4681 @section Bundle directives
4682 @subsection @code{.bundle_align_mode @var{abs-expr}}
4683 @cindex @code{bundle_align_mode} directive
4685 @cindex instruction bundle
4686 @cindex aligned instruction bundle
4687 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4688 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4689 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4690 disabled (which is the default state). If the argument it not zero, it
4691 gives the size of an instruction bundle as a power of two (as for the
4692 @code{.p2align} directive, @pxref{P2align}).
4694 For some targets, it's an ABI requirement that no instruction may span a
4695 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4696 instructions that starts on an aligned boundary. For example, if
4697 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4698 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4699 effect, no single instruction may span a boundary between bundles. If an
4700 instruction would start too close to the end of a bundle for the length of
4701 that particular instruction to fit within the bundle, then the space at the
4702 end of that bundle is filled with no-op instructions so the instruction
4703 starts in the next bundle. As a corollary, it's an error if any single
4704 instruction's encoding is longer than the bundle size.
4706 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4707 @cindex @code{bundle_lock} directive
4708 @cindex @code{bundle_unlock} directive
4709 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4710 allow explicit control over instruction bundle padding. These directives
4711 are only valid when @code{.bundle_align_mode} has been used to enable
4712 aligned instruction bundle mode. It's an error if they appear when
4713 @code{.bundle_align_mode} has not been used at all, or when the last
4714 directive was @w{@code{.bundle_align_mode 0}}.
4716 @cindex bundle-locked
4717 For some targets, it's an ABI requirement that certain instructions may
4718 appear only as part of specified permissible sequences of multiple
4719 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4720 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4721 instruction sequence. For purposes of aligned instruction bundle mode, a
4722 sequence starting with @code{.bundle_lock} and ending with
4723 @code{.bundle_unlock} is treated as a single instruction. That is, the
4724 entire sequence must fit into a single bundle and may not span a bundle
4725 boundary. If necessary, no-op instructions will be inserted before the
4726 first instruction of the sequence so that the whole sequence starts on an
4727 aligned bundle boundary. It's an error if the sequence is longer than the
4730 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4731 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4732 nested. That is, a second @code{.bundle_lock} directive before the next
4733 @code{.bundle_unlock} directive has no effect except that it must be
4734 matched by another closing @code{.bundle_unlock} so that there is the
4735 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4738 @section @code{.byte @var{expressions}}
4740 @cindex @code{byte} directive
4741 @cindex integers, one byte
4742 @code{.byte} expects zero or more expressions, separated by commas.
4743 Each expression is assembled into the next byte.
4745 @node CFI directives
4746 @section CFI directives
4747 @subsection @code{.cfi_sections @var{section_list}}
4748 @cindex @code{cfi_sections} directive
4749 @code{.cfi_sections} may be used to specify whether CFI directives
4750 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4751 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4752 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4753 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4754 directive is not used is @code{.cfi_sections .eh_frame}.
4756 On targets that support compact unwinding tables these can be generated
4757 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4759 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4760 which is used by the @value{TIC6X} target.
4762 The @code{.cfi_sections} directive can be repeated, with the same or different
4763 arguments, provided that CFI generation has not yet started. Once CFI
4764 generation has started however the section list is fixed and any attempts to
4765 redefine it will result in an error.
4767 @subsection @code{.cfi_startproc [simple]}
4768 @cindex @code{cfi_startproc} directive
4769 @code{.cfi_startproc} is used at the beginning of each function that
4770 should have an entry in @code{.eh_frame}. It initializes some internal
4771 data structures. Don't forget to close the function by
4772 @code{.cfi_endproc}.
4774 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4775 it also emits some architecture dependent initial CFI instructions.
4777 @subsection @code{.cfi_endproc}
4778 @cindex @code{cfi_endproc} directive
4779 @code{.cfi_endproc} is used at the end of a function where it closes its
4780 unwind entry previously opened by
4781 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4783 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4784 @cindex @code{cfi_personality} directive
4785 @code{.cfi_personality} defines personality routine and its encoding.
4786 @var{encoding} must be a constant determining how the personality
4787 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4788 argument is not present, otherwise second argument should be
4789 a constant or a symbol name. When using indirect encodings,
4790 the symbol provided should be the location where personality
4791 can be loaded from, not the personality routine itself.
4792 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4793 no personality routine.
4795 @subsection @code{.cfi_personality_id @var{id}}
4796 @cindex @code{cfi_personality_id} directive
4797 @code{cfi_personality_id} defines a personality routine by its index as
4798 defined in a compact unwinding format.
4799 Only valid when generating compact EH frames (i.e.
4800 with @code{.cfi_sections eh_frame_entry}.
4802 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4803 @cindex @code{cfi_fde_data} directive
4804 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4805 used for the current function. These are emitted inline in the
4806 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4807 in the @code{.gnu.extab} section otherwise.
4808 Only valid when generating compact EH frames (i.e.
4809 with @code{.cfi_sections eh_frame_entry}.
4811 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4812 @code{.cfi_lsda} defines LSDA and its encoding.
4813 @var{encoding} must be a constant determining how the LSDA
4814 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4815 argument is not present, otherwise the second argument should be a constant
4816 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4817 meaning that no LSDA is present.
4819 @subsection @code{.cfi_inline_lsda} [@var{align}]
4820 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4821 switches to the corresponding @code{.gnu.extab} section.
4822 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4823 Only valid when generating compact EH frames (i.e.
4824 with @code{.cfi_sections eh_frame_entry}.
4826 The table header and unwinding opcodes will be generated at this point,
4827 so that they are immediately followed by the LSDA data. The symbol
4828 referenced by the @code{.cfi_lsda} directive should still be defined
4829 in case a fallback FDE based encoding is used. The LSDA data is terminated
4830 by a section directive.
4832 The optional @var{align} argument specifies the alignment required.
4833 The alignment is specified as a power of two, as with the
4834 @code{.p2align} directive.
4836 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4837 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4838 address from @var{register} and add @var{offset} to it}.
4840 @subsection @code{.cfi_def_cfa_register @var{register}}
4841 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4842 now on @var{register} will be used instead of the old one. Offset
4845 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4846 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4847 remains the same, but @var{offset} is new. Note that it is the
4848 absolute offset that will be added to a defined register to compute
4851 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4852 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4853 value that is added/substracted from the previous offset.
4855 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4856 Previous value of @var{register} is saved at offset @var{offset} from
4859 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4860 Previous value of @var{register} is CFA + @var{offset}.
4862 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4863 Previous value of @var{register} is saved at offset @var{offset} from
4864 the current CFA register. This is transformed to @code{.cfi_offset}
4865 using the known displacement of the CFA register from the CFA.
4866 This is often easier to use, because the number will match the
4867 code it's annotating.
4869 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4870 Previous value of @var{register1} is saved in register @var{register2}.
4872 @subsection @code{.cfi_restore @var{register}}
4873 @code{.cfi_restore} says that the rule for @var{register} is now the
4874 same as it was at the beginning of the function, after all initial
4875 instruction added by @code{.cfi_startproc} were executed.
4877 @subsection @code{.cfi_undefined @var{register}}
4878 From now on the previous value of @var{register} can't be restored anymore.
4880 @subsection @code{.cfi_same_value @var{register}}
4881 Current value of @var{register} is the same like in the previous frame,
4882 i.e. no restoration needed.
4884 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4885 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4886 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4887 places them in the current row. This is useful for situations where you have
4888 multiple @code{.cfi_*} directives that need to be undone due to the control
4889 flow of the program. For example, we could have something like this (assuming
4890 the CFA is the value of @code{rbp}):
4900 .cfi_def_cfa %rsp, 8
4903 /* Do something else */
4906 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4907 to the instructions before @code{label}. This means we'd have to add multiple
4908 @code{.cfi} directives after @code{label} to recreate the original save
4909 locations of the registers, as well as setting the CFA back to the value of
4910 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4922 .cfi_def_cfa %rsp, 8
4926 /* Do something else */
4929 That way, the rules for the instructions after @code{label} will be the same
4930 as before the first @code{.cfi_restore} without having to use multiple
4931 @code{.cfi} directives.
4933 @subsection @code{.cfi_return_column @var{register}}
4934 Change return column @var{register}, i.e. the return address is either
4935 directly in @var{register} or can be accessed by rules for @var{register}.
4937 @subsection @code{.cfi_signal_frame}
4938 Mark current function as signal trampoline.
4940 @subsection @code{.cfi_window_save}
4941 SPARC register window has been saved.
4943 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4944 Allows the user to add arbitrary bytes to the unwind info. One
4945 might use this to add OS-specific CFI opcodes, or generic CFI
4946 opcodes that GAS does not yet support.
4948 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4949 The current value of @var{register} is @var{label}. The value of @var{label}
4950 will be encoded in the output file according to @var{encoding}; see the
4951 description of @code{.cfi_personality} for details on this encoding.
4953 The usefulness of equating a register to a fixed label is probably
4954 limited to the return address register. Here, it can be useful to
4955 mark a code segment that has only one return address which is reached
4956 by a direct branch and no copy of the return address exists in memory
4957 or another register.
4960 @section @code{.comm @var{symbol} , @var{length} }
4962 @cindex @code{comm} directive
4963 @cindex symbol, common
4964 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4965 common symbol in one object file may be merged with a defined or common symbol
4966 of the same name in another object file. If @code{@value{LD}} does not see a
4967 definition for the symbol--just one or more common symbols--then it will
4968 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4969 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4970 the same name, and they do not all have the same size, it will allocate space
4971 using the largest size.
4974 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4975 an optional third argument. This is the desired alignment of the symbol,
4976 specified for ELF as a byte boundary (for example, an alignment of 16 means
4977 that the least significant 4 bits of the address should be zero), and for PE
4978 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4979 boundary). The alignment must be an absolute expression, and it must be a
4980 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4981 common symbol, it will use the alignment when placing the symbol. If no
4982 alignment is specified, @command{@value{AS}} will set the alignment to the
4983 largest power of two less than or equal to the size of the symbol, up to a
4984 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4985 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4986 @samp{--section-alignment} option; image file sections in PE are aligned to
4987 multiples of 4096, which is far too large an alignment for ordinary variables.
4988 It is rather the default alignment for (non-debug) sections within object
4989 (@samp{*.o}) files, which are less strictly aligned.}.
4993 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4994 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4998 @section @code{.data @var{subsection}}
5000 @cindex @code{data} directive
5001 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5002 end of the data subsection numbered @var{subsection} (which is an
5003 absolute expression). If @var{subsection} is omitted, it defaults
5008 @section @code{.def @var{name}}
5010 @cindex @code{def} directive
5011 @cindex COFF symbols, debugging
5012 @cindex debugging COFF symbols
5013 Begin defining debugging information for a symbol @var{name}; the
5014 definition extends until the @code{.endef} directive is encountered.
5017 This directive is only observed when @command{@value{AS}} is configured for COFF
5018 format output; when producing @code{b.out}, @samp{.def} is recognized,
5025 @section @code{.desc @var{symbol}, @var{abs-expression}}
5027 @cindex @code{desc} directive
5028 @cindex COFF symbol descriptor
5029 @cindex symbol descriptor, COFF
5030 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5031 to the low 16 bits of an absolute expression.
5034 The @samp{.desc} directive is not available when @command{@value{AS}} is
5035 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5036 object format. For the sake of compatibility, @command{@value{AS}} accepts
5037 it, but produces no output, when configured for COFF.
5043 @section @code{.dim}
5045 @cindex @code{dim} directive
5046 @cindex COFF auxiliary symbol information
5047 @cindex auxiliary symbol information, COFF
5048 This directive is generated by compilers to include auxiliary debugging
5049 information in the symbol table. It is only permitted inside
5050 @code{.def}/@code{.endef} pairs.
5053 @samp{.dim} is only meaningful when generating COFF format output; when
5054 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5060 @section @code{.double @var{flonums}}
5062 @cindex @code{double} directive
5063 @cindex floating point numbers (double)
5064 @code{.double} expects zero or more flonums, separated by commas. It
5065 assembles floating point numbers.
5067 The exact kind of floating point numbers emitted depends on how
5068 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5072 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5073 in @sc{ieee} format.
5078 @section @code{.eject}
5080 @cindex @code{eject} directive
5081 @cindex new page, in listings
5082 @cindex page, in listings
5083 @cindex listing control: new page
5084 Force a page break at this point, when generating assembly listings.
5087 @section @code{.else}
5089 @cindex @code{else} directive
5090 @code{.else} is part of the @command{@value{AS}} support for conditional
5091 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5092 of code to be assembled if the condition for the preceding @code{.if}
5096 @section @code{.elseif}
5098 @cindex @code{elseif} directive
5099 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5100 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5101 @code{.if} block that would otherwise fill the entire @code{.else} section.
5104 @section @code{.end}
5106 @cindex @code{end} directive
5107 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5108 process anything in the file past the @code{.end} directive.
5112 @section @code{.endef}
5114 @cindex @code{endef} directive
5115 This directive flags the end of a symbol definition begun with
5119 @samp{.endef} is only meaningful when generating COFF format output; if
5120 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5121 directive but ignores it.
5126 @section @code{.endfunc}
5127 @cindex @code{endfunc} directive
5128 @code{.endfunc} marks the end of a function specified with @code{.func}.
5131 @section @code{.endif}
5133 @cindex @code{endif} directive
5134 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5135 it marks the end of a block of code that is only assembled
5136 conditionally. @xref{If,,@code{.if}}.
5139 @section @code{.equ @var{symbol}, @var{expression}}
5141 @cindex @code{equ} directive
5142 @cindex assigning values to symbols
5143 @cindex symbols, assigning values to
5144 This directive sets the value of @var{symbol} to @var{expression}.
5145 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5148 The syntax for @code{equ} on the HPPA is
5149 @samp{@var{symbol} .equ @var{expression}}.
5153 The syntax for @code{equ} on the Z80 is
5154 @samp{@var{symbol} equ @var{expression}}.
5155 On the Z80 it is an eror if @var{symbol} is already defined,
5156 but the symbol is not protected from later redefinition.
5157 Compare @ref{Equiv}.
5161 @section @code{.equiv @var{symbol}, @var{expression}}
5162 @cindex @code{equiv} directive
5163 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5164 the assembler will signal an error if @var{symbol} is already defined. Note a
5165 symbol which has been referenced but not actually defined is considered to be
5168 Except for the contents of the error message, this is roughly equivalent to
5175 plus it protects the symbol from later redefinition.
5178 @section @code{.eqv @var{symbol}, @var{expression}}
5179 @cindex @code{eqv} directive
5180 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5181 evaluate the expression or any part of it immediately. Instead each time
5182 the resulting symbol is used in an expression, a snapshot of its current
5186 @section @code{.err}
5187 @cindex @code{err} directive
5188 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5189 message and, unless the @option{-Z} option was used, it will not generate an
5190 object file. This can be used to signal an error in conditionally compiled code.
5193 @section @code{.error "@var{string}"}
5194 @cindex error directive
5196 Similarly to @code{.err}, this directive emits an error, but you can specify a
5197 string that will be emitted as the error message. If you don't specify the
5198 message, it defaults to @code{".error directive invoked in source file"}.
5199 @xref{Errors, ,Error and Warning Messages}.
5202 .error "This code has not been assembled and tested."
5206 @section @code{.exitm}
5207 Exit early from the current macro definition. @xref{Macro}.
5210 @section @code{.extern}
5212 @cindex @code{extern} directive
5213 @code{.extern} is accepted in the source program---for compatibility
5214 with other assemblers---but it is ignored. @command{@value{AS}} treats
5215 all undefined symbols as external.
5218 @section @code{.fail @var{expression}}
5220 @cindex @code{fail} directive
5221 Generates an error or a warning. If the value of the @var{expression} is 500
5222 or more, @command{@value{AS}} will print a warning message. If the value is less
5223 than 500, @command{@value{AS}} will print an error message. The message will
5224 include the value of @var{expression}. This can occasionally be useful inside
5225 complex nested macros or conditional assembly.
5228 @section @code{.file}
5229 @cindex @code{file} directive
5231 @ifclear no-file-dir
5232 There are two different versions of the @code{.file} directive. Targets
5233 that support DWARF2 line number information use the DWARF2 version of
5234 @code{.file}. Other targets use the default version.
5236 @subheading Default Version
5238 @cindex logical file name
5239 @cindex file name, logical
5240 This version of the @code{.file} directive tells @command{@value{AS}} that we
5241 are about to start a new logical file. The syntax is:
5247 @var{string} is the new file name. In general, the filename is
5248 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5249 to specify an empty file name, you must give the quotes--@code{""}. This
5250 statement may go away in future: it is only recognized to be compatible with
5251 old @command{@value{AS}} programs.
5253 @subheading DWARF2 Version
5256 When emitting DWARF2 line number information, @code{.file} assigns filenames
5257 to the @code{.debug_line} file name table. The syntax is:
5260 .file @var{fileno} @var{filename}
5263 The @var{fileno} operand should be a unique positive integer to use as the
5264 index of the entry in the table. The @var{filename} operand is a C string
5267 The detail of filename indices is exposed to the user because the filename
5268 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5269 information, and thus the user must know the exact indices that table
5273 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5275 @cindex @code{fill} directive
5276 @cindex writing patterns in memory
5277 @cindex patterns, writing in memory
5278 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5279 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5280 may be zero or more. @var{Size} may be zero or more, but if it is
5281 more than 8, then it is deemed to have the value 8, compatible with
5282 other people's assemblers. The contents of each @var{repeat} bytes
5283 is taken from an 8-byte number. The highest order 4 bytes are
5284 zero. The lowest order 4 bytes are @var{value} rendered in the
5285 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5286 Each @var{size} bytes in a repetition is taken from the lowest order
5287 @var{size} bytes of this number. Again, this bizarre behavior is
5288 compatible with other people's assemblers.
5290 @var{size} and @var{value} are optional.
5291 If the second comma and @var{value} are absent, @var{value} is
5292 assumed zero. If the first comma and following tokens are absent,
5293 @var{size} is assumed to be 1.
5296 @section @code{.float @var{flonums}}
5298 @cindex floating point numbers (single)
5299 @cindex @code{float} directive
5300 This directive assembles zero or more flonums, separated by commas. It
5301 has the same effect as @code{.single}.
5303 The exact kind of floating point numbers emitted depends on how
5304 @command{@value{AS}} is configured.
5305 @xref{Machine Dependencies}.
5309 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5310 in @sc{ieee} format.
5315 @section @code{.func @var{name}[,@var{label}]}
5316 @cindex @code{func} directive
5317 @code{.func} emits debugging information to denote function @var{name}, and
5318 is ignored unless the file is assembled with debugging enabled.
5319 Only @samp{--gstabs[+]} is currently supported.
5320 @var{label} is the entry point of the function and if omitted @var{name}
5321 prepended with the @samp{leading char} is used.
5322 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5323 All functions are currently defined to have @code{void} return type.
5324 The function must be terminated with @code{.endfunc}.
5327 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5329 @cindex @code{global} directive
5330 @cindex symbol, making visible to linker
5331 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5332 @var{symbol} in your partial program, its value is made available to
5333 other partial programs that are linked with it. Otherwise,
5334 @var{symbol} takes its attributes from a symbol of the same name
5335 from another file linked into the same program.
5337 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5338 compatibility with other assemblers.
5341 On the HPPA, @code{.global} is not always enough to make it accessible to other
5342 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5343 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5348 @section @code{.gnu_attribute @var{tag},@var{value}}
5349 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5352 @section @code{.hidden @var{names}}
5354 @cindex @code{hidden} directive
5356 This is one of the ELF visibility directives. The other two are
5357 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5358 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5360 This directive overrides the named symbols default visibility (which is set by
5361 their binding: local, global or weak). The directive sets the visibility to
5362 @code{hidden} which means that the symbols are not visible to other components.
5363 Such symbols are always considered to be @code{protected} as well.
5367 @section @code{.hword @var{expressions}}
5369 @cindex @code{hword} directive
5370 @cindex integers, 16-bit
5371 @cindex numbers, 16-bit
5372 @cindex sixteen bit integers
5373 This expects zero or more @var{expressions}, and emits
5374 a 16 bit number for each.
5377 This directive is a synonym for @samp{.short}; depending on the target
5378 architecture, it may also be a synonym for @samp{.word}.
5382 This directive is a synonym for @samp{.short}.
5385 This directive is a synonym for both @samp{.short} and @samp{.word}.
5390 @section @code{.ident}
5392 @cindex @code{ident} directive
5394 This directive is used by some assemblers to place tags in object files. The
5395 behavior of this directive varies depending on the target. When using the
5396 a.out object file format, @command{@value{AS}} simply accepts the directive for
5397 source-file compatibility with existing assemblers, but does not emit anything
5398 for it. When using COFF, comments are emitted to the @code{.comment} or
5399 @code{.rdata} section, depending on the target. When using ELF, comments are
5400 emitted to the @code{.comment} section.
5403 @section @code{.if @var{absolute expression}}
5405 @cindex conditional assembly
5406 @cindex @code{if} directive
5407 @code{.if} marks the beginning of a section of code which is only
5408 considered part of the source program being assembled if the argument
5409 (which must be an @var{absolute expression}) is non-zero. The end of
5410 the conditional section of code must be marked by @code{.endif}
5411 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5412 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5413 If you have several conditions to check, @code{.elseif} may be used to avoid
5414 nesting blocks if/else within each subsequent @code{.else} block.
5416 The following variants of @code{.if} are also supported:
5418 @cindex @code{ifdef} directive
5419 @item .ifdef @var{symbol}
5420 Assembles the following section of code if the specified @var{symbol}
5421 has been defined. Note a symbol which has been referenced but not yet defined
5422 is considered to be undefined.
5424 @cindex @code{ifb} directive
5425 @item .ifb @var{text}
5426 Assembles the following section of code if the operand is blank (empty).
5428 @cindex @code{ifc} directive
5429 @item .ifc @var{string1},@var{string2}
5430 Assembles the following section of code if the two strings are the same. The
5431 strings may be optionally quoted with single quotes. If they are not quoted,
5432 the first string stops at the first comma, and the second string stops at the
5433 end of the line. Strings which contain whitespace should be quoted. The
5434 string comparison is case sensitive.
5436 @cindex @code{ifeq} directive
5437 @item .ifeq @var{absolute expression}
5438 Assembles the following section of code if the argument is zero.
5440 @cindex @code{ifeqs} directive
5441 @item .ifeqs @var{string1},@var{string2}
5442 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5444 @cindex @code{ifge} directive
5445 @item .ifge @var{absolute expression}
5446 Assembles the following section of code if the argument is greater than or
5449 @cindex @code{ifgt} directive
5450 @item .ifgt @var{absolute expression}
5451 Assembles the following section of code if the argument is greater than zero.
5453 @cindex @code{ifle} directive
5454 @item .ifle @var{absolute expression}
5455 Assembles the following section of code if the argument is less than or equal
5458 @cindex @code{iflt} directive
5459 @item .iflt @var{absolute expression}
5460 Assembles the following section of code if the argument is less than zero.
5462 @cindex @code{ifnb} directive
5463 @item .ifnb @var{text}
5464 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5465 following section of code if the operand is non-blank (non-empty).
5467 @cindex @code{ifnc} directive
5468 @item .ifnc @var{string1},@var{string2}.
5469 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5470 following section of code if the two strings are not the same.
5472 @cindex @code{ifndef} directive
5473 @cindex @code{ifnotdef} directive
5474 @item .ifndef @var{symbol}
5475 @itemx .ifnotdef @var{symbol}
5476 Assembles the following section of code if the specified @var{symbol}
5477 has not been defined. Both spelling variants are equivalent. Note a symbol
5478 which has been referenced but not yet defined is considered to be undefined.
5480 @cindex @code{ifne} directive
5481 @item .ifne @var{absolute expression}
5482 Assembles the following section of code if the argument is not equal to zero
5483 (in other words, this is equivalent to @code{.if}).
5485 @cindex @code{ifnes} directive
5486 @item .ifnes @var{string1},@var{string2}
5487 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5488 following section of code if the two strings are not the same.
5492 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5494 @cindex @code{incbin} directive
5495 @cindex binary files, including
5496 The @code{incbin} directive includes @var{file} verbatim at the current
5497 location. You can control the search paths used with the @samp{-I} command-line
5498 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5501 The @var{skip} argument skips a number of bytes from the start of the
5502 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5503 read. Note that the data is not aligned in any way, so it is the user's
5504 responsibility to make sure that proper alignment is provided both before and
5505 after the @code{incbin} directive.
5508 @section @code{.include "@var{file}"}
5510 @cindex @code{include} directive
5511 @cindex supporting files, including
5512 @cindex files, including
5513 This directive provides a way to include supporting files at specified
5514 points in your source program. The code from @var{file} is assembled as
5515 if it followed the point of the @code{.include}; when the end of the
5516 included file is reached, assembly of the original file continues. You
5517 can control the search paths used with the @samp{-I} command-line option
5518 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5522 @section @code{.int @var{expressions}}
5524 @cindex @code{int} directive
5525 @cindex integers, 32-bit
5526 Expect zero or more @var{expressions}, of any section, separated by commas.
5527 For each expression, emit a number that, at run time, is the value of that
5528 expression. The byte order and bit size of the number depends on what kind
5529 of target the assembly is for.
5533 On most forms of the H8/300, @code{.int} emits 16-bit
5534 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5541 @section @code{.internal @var{names}}
5543 @cindex @code{internal} directive
5545 This is one of the ELF visibility directives. The other two are
5546 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5547 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5549 This directive overrides the named symbols default visibility (which is set by
5550 their binding: local, global or weak). The directive sets the visibility to
5551 @code{internal} which means that the symbols are considered to be @code{hidden}
5552 (i.e., not visible to other components), and that some extra, processor specific
5553 processing must also be performed upon the symbols as well.
5557 @section @code{.irp @var{symbol},@var{values}}@dots{}
5559 @cindex @code{irp} directive
5560 Evaluate a sequence of statements assigning different values to @var{symbol}.
5561 The sequence of statements starts at the @code{.irp} directive, and is
5562 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5563 set to @var{value}, and the sequence of statements is assembled. If no
5564 @var{value} is listed, the sequence of statements is assembled once, with
5565 @var{symbol} set to the null string. To refer to @var{symbol} within the
5566 sequence of statements, use @var{\symbol}.
5568 For example, assembling
5576 is equivalent to assembling
5584 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5587 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5589 @cindex @code{irpc} directive
5590 Evaluate a sequence of statements assigning different values to @var{symbol}.
5591 The sequence of statements starts at the @code{.irpc} directive, and is
5592 terminated by an @code{.endr} directive. For each character in @var{value},
5593 @var{symbol} is set to the character, and the sequence of statements is
5594 assembled. If no @var{value} is listed, the sequence of statements is
5595 assembled once, with @var{symbol} set to the null string. To refer to
5596 @var{symbol} within the sequence of statements, use @var{\symbol}.
5598 For example, assembling
5606 is equivalent to assembling
5614 For some caveats with the spelling of @var{symbol}, see also the discussion
5618 @section @code{.lcomm @var{symbol} , @var{length}}
5620 @cindex @code{lcomm} directive
5621 @cindex local common symbols
5622 @cindex symbols, local common
5623 Reserve @var{length} (an absolute expression) bytes for a local common
5624 denoted by @var{symbol}. The section and value of @var{symbol} are
5625 those of the new local common. The addresses are allocated in the bss
5626 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5627 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5628 not visible to @code{@value{LD}}.
5631 Some targets permit a third argument to be used with @code{.lcomm}. This
5632 argument specifies the desired alignment of the symbol in the bss section.
5636 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5637 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5641 @section @code{.lflags}
5643 @cindex @code{lflags} directive (ignored)
5644 @command{@value{AS}} accepts this directive, for compatibility with other
5645 assemblers, but ignores it.
5647 @ifclear no-line-dir
5649 @section @code{.line @var{line-number}}
5651 @cindex @code{line} directive
5652 @cindex logical line number
5654 Change the logical line number. @var{line-number} must be an absolute
5655 expression. The next line has that logical line number. Therefore any other
5656 statements on the current line (after a statement separator character) are
5657 reported as on logical line number @var{line-number} @minus{} 1. One day
5658 @command{@value{AS}} will no longer support this directive: it is recognized only
5659 for compatibility with existing assembler programs.
5662 Even though this is a directive associated with the @code{a.out} or
5663 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5664 when producing COFF output, and treats @samp{.line} as though it
5665 were the COFF @samp{.ln} @emph{if} it is found outside a
5666 @code{.def}/@code{.endef} pair.
5668 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5669 used by compilers to generate auxiliary symbol information for
5674 @section @code{.linkonce [@var{type}]}
5676 @cindex @code{linkonce} directive
5677 @cindex common sections
5678 Mark the current section so that the linker only includes a single copy of it.
5679 This may be used to include the same section in several different object files,
5680 but ensure that the linker will only include it once in the final output file.
5681 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5682 Duplicate sections are detected based on the section name, so it should be
5685 This directive is only supported by a few object file formats; as of this
5686 writing, the only object file format which supports it is the Portable
5687 Executable format used on Windows NT.
5689 The @var{type} argument is optional. If specified, it must be one of the
5690 following strings. For example:
5694 Not all types may be supported on all object file formats.
5698 Silently discard duplicate sections. This is the default.
5701 Warn if there are duplicate sections, but still keep only one copy.
5704 Warn if any of the duplicates have different sizes.
5707 Warn if any of the duplicates do not have exactly the same contents.
5711 @section @code{.list}
5713 @cindex @code{list} directive
5714 @cindex listing control, turning on
5715 Control (in conjunction with the @code{.nolist} directive) whether or
5716 not assembly listings are generated. These two directives maintain an
5717 internal counter (which is zero initially). @code{.list} increments the
5718 counter, and @code{.nolist} decrements it. Assembly listings are
5719 generated whenever the counter is greater than zero.
5721 By default, listings are disabled. When you enable them (with the
5722 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5723 the initial value of the listing counter is one.
5726 @section @code{.ln @var{line-number}}
5728 @cindex @code{ln} directive
5729 @ifclear no-line-dir
5730 @samp{.ln} is a synonym for @samp{.line}.
5733 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5734 must be an absolute expression. The next line has that logical
5735 line number, so any other statements on the current line (after a
5736 statement separator character @code{;}) are reported as on logical
5737 line number @var{line-number} @minus{} 1.
5740 This directive is accepted, but ignored, when @command{@value{AS}} is
5741 configured for @code{b.out}; its effect is only associated with COFF
5747 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5748 @cindex @code{loc} directive
5749 When emitting DWARF2 line number information,
5750 the @code{.loc} directive will add a row to the @code{.debug_line} line
5751 number matrix corresponding to the immediately following assembly
5752 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5753 arguments will be applied to the @code{.debug_line} state machine before
5756 The @var{options} are a sequence of the following tokens in any order:
5760 This option will set the @code{basic_block} register in the
5761 @code{.debug_line} state machine to @code{true}.
5764 This option will set the @code{prologue_end} register in the
5765 @code{.debug_line} state machine to @code{true}.
5767 @item epilogue_begin
5768 This option will set the @code{epilogue_begin} register in the
5769 @code{.debug_line} state machine to @code{true}.
5771 @item is_stmt @var{value}
5772 This option will set the @code{is_stmt} register in the
5773 @code{.debug_line} state machine to @code{value}, which must be
5776 @item isa @var{value}
5777 This directive will set the @code{isa} register in the @code{.debug_line}
5778 state machine to @var{value}, which must be an unsigned integer.
5780 @item discriminator @var{value}
5781 This directive will set the @code{discriminator} register in the @code{.debug_line}
5782 state machine to @var{value}, which must be an unsigned integer.
5786 @node Loc_mark_labels
5787 @section @code{.loc_mark_labels @var{enable}}
5788 @cindex @code{loc_mark_labels} directive
5789 When emitting DWARF2 line number information,
5790 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5791 to the @code{.debug_line} line number matrix with the @code{basic_block}
5792 register in the state machine set whenever a code label is seen.
5793 The @var{enable} argument should be either 1 or 0, to enable or disable
5794 this function respectively.
5798 @section @code{.local @var{names}}
5800 @cindex @code{local} directive
5801 This directive, which is available for ELF targets, marks each symbol in
5802 the comma-separated list of @code{names} as a local symbol so that it
5803 will not be externally visible. If the symbols do not already exist,
5804 they will be created.
5806 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5807 accept an alignment argument, which is the case for most ELF targets,
5808 the @code{.local} directive can be used in combination with @code{.comm}
5809 (@pxref{Comm}) to define aligned local common data.
5813 @section @code{.long @var{expressions}}
5815 @cindex @code{long} directive
5816 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5819 @c no one seems to know what this is for or whether this description is
5820 @c what it really ought to do
5822 @section @code{.lsym @var{symbol}, @var{expression}}
5824 @cindex @code{lsym} directive
5825 @cindex symbol, not referenced in assembly
5826 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5827 the hash table, ensuring it cannot be referenced by name during the
5828 rest of the assembly. This sets the attributes of the symbol to be
5829 the same as the expression value:
5831 @var{other} = @var{descriptor} = 0
5832 @var{type} = @r{(section of @var{expression})}
5833 @var{value} = @var{expression}
5836 The new symbol is not flagged as external.
5840 @section @code{.macro}
5843 The commands @code{.macro} and @code{.endm} allow you to define macros that
5844 generate assembly output. For example, this definition specifies a macro
5845 @code{sum} that puts a sequence of numbers into memory:
5848 .macro sum from=0, to=5
5857 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5869 @item .macro @var{macname}
5870 @itemx .macro @var{macname} @var{macargs} @dots{}
5871 @cindex @code{macro} directive
5872 Begin the definition of a macro called @var{macname}. If your macro
5873 definition requires arguments, specify their names after the macro name,
5874 separated by commas or spaces. You can qualify the macro argument to
5875 indicate whether all invocations must specify a non-blank value (through
5876 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5877 (through @samp{:@code{vararg}}). You can supply a default value for any
5878 macro argument by following the name with @samp{=@var{deflt}}. You
5879 cannot define two macros with the same @var{macname} unless it has been
5880 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5881 definitions. For example, these are all valid @code{.macro} statements:
5885 Begin the definition of a macro called @code{comm}, which takes no
5888 @item .macro plus1 p, p1
5889 @itemx .macro plus1 p p1
5890 Either statement begins the definition of a macro called @code{plus1},
5891 which takes two arguments; within the macro definition, write
5892 @samp{\p} or @samp{\p1} to evaluate the arguments.
5894 @item .macro reserve_str p1=0 p2
5895 Begin the definition of a macro called @code{reserve_str}, with two
5896 arguments. The first argument has a default value, but not the second.
5897 After the definition is complete, you can call the macro either as
5898 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5899 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5900 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5901 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5903 @item .macro m p1:req, p2=0, p3:vararg
5904 Begin the definition of a macro called @code{m}, with at least three
5905 arguments. The first argument must always have a value specified, but
5906 not the second, which instead has a default value. The third formal
5907 will get assigned all remaining arguments specified at invocation time.
5909 When you call a macro, you can specify the argument values either by
5910 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5911 @samp{sum to=17, from=9}.
5915 Note that since each of the @var{macargs} can be an identifier exactly
5916 as any other one permitted by the target architecture, there may be
5917 occasional problems if the target hand-crafts special meanings to certain
5918 characters when they occur in a special position. For example, if the colon
5919 (@code{:}) is generally permitted to be part of a symbol name, but the
5920 architecture specific code special-cases it when occurring as the final
5921 character of a symbol (to denote a label), then the macro parameter
5922 replacement code will have no way of knowing that and consider the whole
5923 construct (including the colon) an identifier, and check only this
5924 identifier for being the subject to parameter substitution. So for example
5925 this macro definition:
5933 might not work as expected. Invoking @samp{label foo} might not create a label
5934 called @samp{foo} but instead just insert the text @samp{\l:} into the
5935 assembler source, probably generating an error about an unrecognised
5938 Similarly problems might occur with the period character (@samp{.})
5939 which is often allowed inside opcode names (and hence identifier names). So
5940 for example constructing a macro to build an opcode from a base name and a
5941 length specifier like this:
5944 .macro opcode base length
5949 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5950 instruction but instead generate some kind of error as the assembler tries to
5951 interpret the text @samp{\base.\length}.
5953 There are several possible ways around this problem:
5956 @item Insert white space
5957 If it is possible to use white space characters then this is the simplest
5966 @item Use @samp{\()}
5967 The string @samp{\()} can be used to separate the end of a macro argument from
5968 the following text. eg:
5971 .macro opcode base length
5976 @item Use the alternate macro syntax mode
5977 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5978 used as a separator. eg:
5988 Note: this problem of correctly identifying string parameters to pseudo ops
5989 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5990 and @code{.irpc} (@pxref{Irpc}) as well.
5993 @cindex @code{endm} directive
5994 Mark the end of a macro definition.
5997 @cindex @code{exitm} directive
5998 Exit early from the current macro definition.
6000 @cindex number of macros executed
6001 @cindex macros, count executed
6003 @command{@value{AS}} maintains a counter of how many macros it has
6004 executed in this pseudo-variable; you can copy that number to your
6005 output with @samp{\@@}, but @emph{only within a macro definition}.
6007 @item LOCAL @var{name} [ , @dots{} ]
6008 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6009 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6010 @xref{Altmacro,,@code{.altmacro}}.
6014 @section @code{.mri @var{val}}
6016 @cindex @code{mri} directive
6017 @cindex MRI mode, temporarily
6018 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6019 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6020 affects code assembled until the next @code{.mri} directive, or until the end
6021 of the file. @xref{M, MRI mode, MRI mode}.
6024 @section @code{.noaltmacro}
6025 Disable alternate macro mode. @xref{Altmacro}.
6028 @section @code{.nolist}
6030 @cindex @code{nolist} directive
6031 @cindex listing control, turning off
6032 Control (in conjunction with the @code{.list} directive) whether or
6033 not assembly listings are generated. These two directives maintain an
6034 internal counter (which is zero initially). @code{.list} increments the
6035 counter, and @code{.nolist} decrements it. Assembly listings are
6036 generated whenever the counter is greater than zero.
6039 @section @code{.octa @var{bignums}}
6041 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
6042 @cindex @code{octa} directive
6043 @cindex integer, 16-byte
6044 @cindex sixteen byte integer
6045 This directive expects zero or more bignums, separated by commas. For each
6046 bignum, it emits a 16-byte integer.
6048 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6049 hence @emph{octa}-word for 16 bytes.
6052 @section @code{.offset @var{loc}}
6054 @cindex @code{offset} directive
6055 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6056 be an absolute expression. This directive may be useful for defining
6057 symbols with absolute values. Do not confuse it with the @code{.org}
6061 @section @code{.org @var{new-lc} , @var{fill}}
6063 @cindex @code{org} directive
6064 @cindex location counter, advancing
6065 @cindex advancing location counter
6066 @cindex current address, advancing
6067 Advance the location counter of the current section to
6068 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6069 expression with the same section as the current subsection. That is,
6070 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6071 wrong section, the @code{.org} directive is ignored. To be compatible
6072 with former assemblers, if the section of @var{new-lc} is absolute,
6073 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6074 is the same as the current subsection.
6076 @code{.org} may only increase the location counter, or leave it
6077 unchanged; you cannot use @code{.org} to move the location counter
6080 @c double negative used below "not undefined" because this is a specific
6081 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6082 @c section. doc@cygnus.com 18feb91
6083 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6084 may not be undefined. If you really detest this restriction we eagerly await
6085 a chance to share your improved assembler.
6087 Beware that the origin is relative to the start of the section, not
6088 to the start of the subsection. This is compatible with other
6089 people's assemblers.
6091 When the location counter (of the current subsection) is advanced, the
6092 intervening bytes are filled with @var{fill} which should be an
6093 absolute expression. If the comma and @var{fill} are omitted,
6094 @var{fill} defaults to zero.
6097 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6099 @cindex padding the location counter given a power of two
6100 @cindex @code{p2align} directive
6101 Pad the location counter (in the current subsection) to a particular
6102 storage boundary. The first expression (which must be absolute) is the
6103 number of low-order zero bits the location counter must have after
6104 advancement. For example @samp{.p2align 3} advances the location
6105 counter until it a multiple of 8. If the location counter is already a
6106 multiple of 8, no change is needed.
6108 The second expression (also absolute) gives the fill value to be stored in the
6109 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6110 padding bytes are normally zero. However, on some systems, if the section is
6111 marked as containing code and the fill value is omitted, the space is filled
6112 with no-op instructions.
6114 The third expression is also absolute, and is also optional. If it is present,
6115 it is the maximum number of bytes that should be skipped by this alignment
6116 directive. If doing the alignment would require skipping more bytes than the
6117 specified maximum, then the alignment is not done at all. You can omit the
6118 fill value (the second argument) entirely by simply using two commas after the
6119 required alignment; this can be useful if you want the alignment to be filled
6120 with no-op instructions when appropriate.
6122 @cindex @code{p2alignw} directive
6123 @cindex @code{p2alignl} directive
6124 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6125 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6126 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6127 fill pattern as a four byte longword value. For example, @code{.p2alignw
6128 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6129 filled in with the value 0x368d (the exact placement of the bytes depends upon
6130 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6135 @section @code{.popsection}
6137 @cindex @code{popsection} directive
6138 @cindex Section Stack
6139 This is one of the ELF section stack manipulation directives. The others are
6140 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6141 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6144 This directive replaces the current section (and subsection) with the top
6145 section (and subsection) on the section stack. This section is popped off the
6151 @section @code{.previous}
6153 @cindex @code{previous} directive
6154 @cindex Section Stack
6155 This is one of the ELF section stack manipulation directives. The others are
6156 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6157 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6158 (@pxref{PopSection}).
6160 This directive swaps the current section (and subsection) with most recently
6161 referenced section/subsection pair prior to this one. Multiple
6162 @code{.previous} directives in a row will flip between two sections (and their
6163 subsections). For example:
6175 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6181 # Now in section A subsection 1
6185 # Now in section B subsection 0
6188 # Now in section B subsection 1
6191 # Now in section B subsection 0
6195 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6196 section B and 0x9abc into subsection 1 of section B.
6198 In terms of the section stack, this directive swaps the current section with
6199 the top section on the section stack.
6203 @section @code{.print @var{string}}
6205 @cindex @code{print} directive
6206 @command{@value{AS}} will print @var{string} on the standard output during
6207 assembly. You must put @var{string} in double quotes.
6211 @section @code{.protected @var{names}}
6213 @cindex @code{protected} directive
6215 This is one of the ELF visibility directives. The other two are
6216 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6218 This directive overrides the named symbols default visibility (which is set by
6219 their binding: local, global or weak). The directive sets the visibility to
6220 @code{protected} which means that any references to the symbols from within the
6221 components that defines them must be resolved to the definition in that
6222 component, even if a definition in another component would normally preempt
6227 @section @code{.psize @var{lines} , @var{columns}}
6229 @cindex @code{psize} directive
6230 @cindex listing control: paper size
6231 @cindex paper size, for listings
6232 Use this directive to declare the number of lines---and, optionally, the
6233 number of columns---to use for each page, when generating listings.
6235 If you do not use @code{.psize}, listings use a default line-count
6236 of 60. You may omit the comma and @var{columns} specification; the
6237 default width is 200 columns.
6239 @command{@value{AS}} generates formfeeds whenever the specified number of
6240 lines is exceeded (or whenever you explicitly request one, using
6243 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6244 those explicitly specified with @code{.eject}.
6247 @section @code{.purgem @var{name}}
6249 @cindex @code{purgem} directive
6250 Undefine the macro @var{name}, so that later uses of the string will not be
6251 expanded. @xref{Macro}.
6255 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6257 @cindex @code{pushsection} directive
6258 @cindex Section Stack
6259 This is one of the ELF section stack manipulation directives. The others are
6260 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6261 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6264 This directive pushes the current section (and subsection) onto the
6265 top of the section stack, and then replaces the current section and
6266 subsection with @code{name} and @code{subsection}. The optional
6267 @code{flags}, @code{type} and @code{arguments} are treated the same
6268 as in the @code{.section} (@pxref{Section}) directive.
6272 @section @code{.quad @var{bignums}}
6274 @cindex @code{quad} directive
6275 @code{.quad} expects zero or more bignums, separated by commas. For
6276 each bignum, it emits
6278 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6279 warning message; and just takes the lowest order 8 bytes of the bignum.
6280 @cindex eight-byte integer
6281 @cindex integer, 8-byte
6283 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6284 hence @emph{quad}-word for 8 bytes.
6287 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6288 warning message; and just takes the lowest order 16 bytes of the bignum.
6289 @cindex sixteen-byte integer
6290 @cindex integer, 16-byte
6294 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6296 @cindex @code{reloc} directive
6297 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6298 @var{expression}. If @var{offset} is a number, the relocation is generated in
6299 the current section. If @var{offset} is an expression that resolves to a
6300 symbol plus offset, the relocation is generated in the given symbol's section.
6301 @var{expression}, if present, must resolve to a symbol plus addend or to an
6302 absolute value, but note that not all targets support an addend. e.g. ELF REL
6303 targets such as i386 store an addend in the section contents rather than in the
6304 relocation. This low level interface does not support addends stored in the
6308 @section @code{.rept @var{count}}
6310 @cindex @code{rept} directive
6311 Repeat the sequence of lines between the @code{.rept} directive and the next
6312 @code{.endr} directive @var{count} times.
6314 For example, assembling
6322 is equivalent to assembling
6331 @section @code{.sbttl "@var{subheading}"}
6333 @cindex @code{sbttl} directive
6334 @cindex subtitles for listings
6335 @cindex listing control: subtitle
6336 Use @var{subheading} as the title (third line, immediately after the
6337 title line) when generating assembly listings.
6339 This directive affects subsequent pages, as well as the current page if
6340 it appears within ten lines of the top of a page.
6344 @section @code{.scl @var{class}}
6346 @cindex @code{scl} directive
6347 @cindex symbol storage class (COFF)
6348 @cindex COFF symbol storage class
6349 Set the storage-class value for a symbol. This directive may only be
6350 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6351 whether a symbol is static or external, or it may record further
6352 symbolic debugging information.
6355 The @samp{.scl} directive is primarily associated with COFF output; when
6356 configured to generate @code{b.out} output format, @command{@value{AS}}
6357 accepts this directive but ignores it.
6363 @section @code{.section @var{name}}
6365 @cindex named section
6366 Use the @code{.section} directive to assemble the following code into a section
6369 This directive is only supported for targets that actually support arbitrarily
6370 named sections; on @code{a.out} targets, for example, it is not accepted, even
6371 with a standard @code{a.out} section name.
6375 @c only print the extra heading if both COFF and ELF are set
6376 @subheading COFF Version
6379 @cindex @code{section} directive (COFF version)
6380 For COFF targets, the @code{.section} directive is used in one of the following
6384 .section @var{name}[, "@var{flags}"]
6385 .section @var{name}[, @var{subsection}]
6388 If the optional argument is quoted, it is taken as flags to use for the
6389 section. Each flag is a single character. The following flags are recognized:
6393 bss section (uninitialized data)
6395 section is not loaded
6401 exclude section from linking
6407 shared section (meaningful for PE targets)
6409 ignored. (For compatibility with the ELF version)
6411 section is not readable (meaningful for PE targets)
6413 single-digit power-of-two section alignment (GNU extension)
6416 If no flags are specified, the default flags depend upon the section name. If
6417 the section name is not recognized, the default will be for the section to be
6418 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6419 from the section, rather than adding them, so if they are used on their own it
6420 will be as if no flags had been specified at all.
6422 If the optional argument to the @code{.section} directive is not quoted, it is
6423 taken as a subsection number (@pxref{Sub-Sections}).
6428 @c only print the extra heading if both COFF and ELF are set
6429 @subheading ELF Version
6432 @cindex Section Stack
6433 This is one of the ELF section stack manipulation directives. The others are
6434 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6435 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6436 @code{.previous} (@pxref{Previous}).
6438 @cindex @code{section} directive (ELF version)
6439 For ELF targets, the @code{.section} directive is used like this:
6442 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6445 @anchor{Section Name Substitutions}
6446 @kindex --sectname-subst
6447 @cindex section name substitution
6448 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6449 argument may contain a substitution sequence. Only @code{%S} is supported
6450 at the moment, and substitutes the current section name. For example:
6453 .macro exception_code
6454 .section %S.exception
6455 [exception code here]
6470 The two @code{exception_code} invocations above would create the
6471 @code{.text.exception} and @code{.init.exception} sections respectively.
6472 This is useful e.g. to discriminate between anciliary sections that are
6473 tied to setup code to be discarded after use from anciliary sections that
6474 need to stay resident without having to define multiple @code{exception_code}
6475 macros just for that purpose.
6477 The optional @var{flags} argument is a quoted string which may contain any
6478 combination of the following characters:
6482 section is allocatable
6484 section is excluded from executable and shared library.
6488 section is executable
6490 section is mergeable
6492 section contains zero terminated strings
6494 section is a member of a section group
6496 section is used for thread-local-storage
6498 section is a member of the previously-current section's group, if any
6499 @item @code{<number>}
6500 a numeric value indicating the bits to be set in the ELF section header's flags
6501 field. Note - if one or more of the alphabetic characters described above is
6502 also included in the flags field, their bit values will be ORed into the
6504 @item @code{<target specific>}
6505 some targets extend this list with their own flag characters
6508 Note - once a section's flags have been set they cannot be changed. There are
6509 a few exceptions to this rule however. Processor and application specific
6510 flags can be added to an already defined section. The @code{.interp},
6511 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6512 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6513 section may have the executable (@code{x}) flag added.
6515 The optional @var{type} argument may contain one of the following constants:
6519 section contains data
6521 section does not contain data (i.e., section only occupies space)
6523 section contains data which is used by things other than the program
6525 section contains an array of pointers to init functions
6527 section contains an array of pointers to finish functions
6528 @item @@preinit_array
6529 section contains an array of pointers to pre-init functions
6530 @item @@@code{<number>}
6531 a numeric value to be set as the ELF section header's type field.
6532 @item @@@code{<target specific>}
6533 some targets extend this list with their own types
6536 Many targets only support the first three section types. The type may be
6537 enclosed in double quotes if necessary.
6539 Note on targets where the @code{@@} character is the start of a comment (eg
6540 ARM) then another character is used instead. For example the ARM port uses the
6543 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6544 special and have fixed types. Any attempt to declare them with a different
6545 type will generate an error from the assembler.
6547 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6548 be specified as well as an extra argument---@var{entsize}---like this:
6551 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6554 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6555 constants, each @var{entsize} octets long. Sections with both @code{M} and
6556 @code{S} must contain zero terminated strings where each character is
6557 @var{entsize} bytes long. The linker may remove duplicates within sections with
6558 the same name, same entity size and same flags. @var{entsize} must be an
6559 absolute expression. For sections with both @code{M} and @code{S}, a string
6560 which is a suffix of a larger string is considered a duplicate. Thus
6561 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6562 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6564 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6565 be present along with an additional field like this:
6568 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6571 The @var{GroupName} field specifies the name of the section group to which this
6572 particular section belongs. The optional linkage field can contain:
6576 indicates that only one copy of this section should be retained
6581 Note: if both the @var{M} and @var{G} flags are present then the fields for
6582 the Merge flag should come first, like this:
6585 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6588 If @var{flags} contains the @code{?} symbol then it may not also contain the
6589 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6590 present. Instead, @code{?} says to consider the section that's current before
6591 this directive. If that section used @code{G}, then the new section will use
6592 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6593 If not, then the @code{?} symbol has no effect.
6595 If no flags are specified, the default flags depend upon the section name. If
6596 the section name is not recognized, the default will be for the section to have
6597 none of the above flags: it will not be allocated in memory, nor writable, nor
6598 executable. The section will contain data.
6600 For ELF targets, the assembler supports another type of @code{.section}
6601 directive for compatibility with the Solaris assembler:
6604 .section "@var{name}"[, @var{flags}...]
6607 Note that the section name is quoted. There may be a sequence of comma
6612 section is allocatable
6616 section is executable
6618 section is excluded from executable and shared library.
6620 section is used for thread local storage
6623 This directive replaces the current section and subsection. See the
6624 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6625 some examples of how this directive and the other section stack directives
6631 @section @code{.set @var{symbol}, @var{expression}}
6633 @cindex @code{set} directive
6634 @cindex symbol value, setting
6635 Set the value of @var{symbol} to @var{expression}. This
6636 changes @var{symbol}'s value and type to conform to
6637 @var{expression}. If @var{symbol} was flagged as external, it remains
6638 flagged (@pxref{Symbol Attributes}).
6640 You may @code{.set} a symbol many times in the same assembly provided that the
6641 values given to the symbol are constants. Values that are based on expressions
6642 involving other symbols are allowed, but some targets may restrict this to only
6643 being done once per assembly. This is because those targets do not set the
6644 addresses of symbols at assembly time, but rather delay the assignment until a
6645 final link is performed. This allows the linker a chance to change the code in
6646 the files, changing the location of, and the relative distance between, various
6649 If you @code{.set} a global symbol, the value stored in the object
6650 file is the last value stored into it.
6653 On Z80 @code{set} is a real instruction, use
6654 @samp{@var{symbol} defl @var{expression}} instead.
6658 @section @code{.short @var{expressions}}
6660 @cindex @code{short} directive
6662 @code{.short} is normally the same as @samp{.word}.
6663 @xref{Word,,@code{.word}}.
6665 In some configurations, however, @code{.short} and @code{.word} generate
6666 numbers of different lengths. @xref{Machine Dependencies}.
6670 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6673 This expects zero or more @var{expressions}, and emits
6674 a 16 bit number for each.
6679 @section @code{.single @var{flonums}}
6681 @cindex @code{single} directive
6682 @cindex floating point numbers (single)
6683 This directive assembles zero or more flonums, separated by commas. It
6684 has the same effect as @code{.float}.
6686 The exact kind of floating point numbers emitted depends on how
6687 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6691 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6692 numbers in @sc{ieee} format.
6698 @section @code{.size}
6700 This directive is used to set the size associated with a symbol.
6704 @c only print the extra heading if both COFF and ELF are set
6705 @subheading COFF Version
6708 @cindex @code{size} directive (COFF version)
6709 For COFF targets, the @code{.size} directive is only permitted inside
6710 @code{.def}/@code{.endef} pairs. It is used like this:
6713 .size @var{expression}
6717 @samp{.size} is only meaningful when generating COFF format output; when
6718 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6725 @c only print the extra heading if both COFF and ELF are set
6726 @subheading ELF Version
6729 @cindex @code{size} directive (ELF version)
6730 For ELF targets, the @code{.size} directive is used like this:
6733 .size @var{name} , @var{expression}
6736 This directive sets the size associated with a symbol @var{name}.
6737 The size in bytes is computed from @var{expression} which can make use of label
6738 arithmetic. This directive is typically used to set the size of function
6743 @ifclear no-space-dir
6745 @section @code{.skip @var{size} , @var{fill}}
6747 @cindex @code{skip} directive
6748 @cindex filling memory
6749 This directive emits @var{size} bytes, each of value @var{fill}. Both
6750 @var{size} and @var{fill} are absolute expressions. If the comma and
6751 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6756 @section @code{.sleb128 @var{expressions}}
6758 @cindex @code{sleb128} directive
6759 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6760 compact, variable length representation of numbers used by the DWARF
6761 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6763 @ifclear no-space-dir
6765 @section @code{.space @var{size} , @var{fill}}
6767 @cindex @code{space} directive
6768 @cindex filling memory
6769 This directive emits @var{size} bytes, each of value @var{fill}. Both
6770 @var{size} and @var{fill} are absolute expressions. If the comma
6771 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6776 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6777 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6778 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6779 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6787 @section @code{.stabd, .stabn, .stabs}
6789 @cindex symbolic debuggers, information for
6790 @cindex @code{stab@var{x}} directives
6791 There are three directives that begin @samp{.stab}.
6792 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6793 The symbols are not entered in the @command{@value{AS}} hash table: they
6794 cannot be referenced elsewhere in the source file.
6795 Up to five fields are required:
6799 This is the symbol's name. It may contain any character except
6800 @samp{\000}, so is more general than ordinary symbol names. Some
6801 debuggers used to code arbitrarily complex structures into symbol names
6805 An absolute expression. The symbol's type is set to the low 8 bits of
6806 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6807 and debuggers choke on silly bit patterns.
6810 An absolute expression. The symbol's ``other'' attribute is set to the
6811 low 8 bits of this expression.
6814 An absolute expression. The symbol's descriptor is set to the low 16
6815 bits of this expression.
6818 An absolute expression which becomes the symbol's value.
6821 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6822 or @code{.stabs} statement, the symbol has probably already been created;
6823 you get a half-formed symbol in your object file. This is
6824 compatible with earlier assemblers!
6827 @cindex @code{stabd} directive
6828 @item .stabd @var{type} , @var{other} , @var{desc}
6830 The ``name'' of the symbol generated is not even an empty string.
6831 It is a null pointer, for compatibility. Older assemblers used a
6832 null pointer so they didn't waste space in object files with empty
6835 The symbol's value is set to the location counter,
6836 relocatably. When your program is linked, the value of this symbol
6837 is the address of the location counter when the @code{.stabd} was
6840 @cindex @code{stabn} directive
6841 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6842 The name of the symbol is set to the empty string @code{""}.
6844 @cindex @code{stabs} directive
6845 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6846 All five fields are specified.
6852 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6853 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6855 @cindex string, copying to object file
6856 @cindex string8, copying to object file
6857 @cindex string16, copying to object file
6858 @cindex string32, copying to object file
6859 @cindex string64, copying to object file
6860 @cindex @code{string} directive
6861 @cindex @code{string8} directive
6862 @cindex @code{string16} directive
6863 @cindex @code{string32} directive
6864 @cindex @code{string64} directive
6866 Copy the characters in @var{str} to the object file. You may specify more than
6867 one string to copy, separated by commas. Unless otherwise specified for a
6868 particular machine, the assembler marks the end of each string with a 0 byte.
6869 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6871 The variants @code{string16}, @code{string32} and @code{string64} differ from
6872 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6873 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6874 are stored in target endianness byte order.
6880 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6881 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6886 @section @code{.struct @var{expression}}
6888 @cindex @code{struct} directive
6889 Switch to the absolute section, and set the section offset to @var{expression},
6890 which must be an absolute expression. You might use this as follows:
6899 This would define the symbol @code{field1} to have the value 0, the symbol
6900 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6901 value 8. Assembly would be left in the absolute section, and you would need to
6902 use a @code{.section} directive of some sort to change to some other section
6903 before further assembly.
6907 @section @code{.subsection @var{name}}
6909 @cindex @code{subsection} directive
6910 @cindex Section Stack
6911 This is one of the ELF section stack manipulation directives. The others are
6912 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6913 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6916 This directive replaces the current subsection with @code{name}. The current
6917 section is not changed. The replaced subsection is put onto the section stack
6918 in place of the then current top of stack subsection.
6923 @section @code{.symver}
6924 @cindex @code{symver} directive
6925 @cindex symbol versioning
6926 @cindex versions of symbols
6927 Use the @code{.symver} directive to bind symbols to specific version nodes
6928 within a source file. This is only supported on ELF platforms, and is
6929 typically used when assembling files to be linked into a shared library.
6930 There are cases where it may make sense to use this in objects to be bound
6931 into an application itself so as to override a versioned symbol from a
6934 For ELF targets, the @code{.symver} directive can be used like this:
6936 .symver @var{name}, @var{name2@@nodename}
6938 If the symbol @var{name} is defined within the file
6939 being assembled, the @code{.symver} directive effectively creates a symbol
6940 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6941 just don't try and create a regular alias is that the @var{@@} character isn't
6942 permitted in symbol names. The @var{name2} part of the name is the actual name
6943 of the symbol by which it will be externally referenced. The name @var{name}
6944 itself is merely a name of convenience that is used so that it is possible to
6945 have definitions for multiple versions of a function within a single source
6946 file, and so that the compiler can unambiguously know which version of a
6947 function is being mentioned. The @var{nodename} portion of the alias should be
6948 the name of a node specified in the version script supplied to the linker when
6949 building a shared library. If you are attempting to override a versioned
6950 symbol from a shared library, then @var{nodename} should correspond to the
6951 nodename of the symbol you are trying to override.
6953 If the symbol @var{name} is not defined within the file being assembled, all
6954 references to @var{name} will be changed to @var{name2@@nodename}. If no
6955 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6958 Another usage of the @code{.symver} directive is:
6960 .symver @var{name}, @var{name2@@@@nodename}
6962 In this case, the symbol @var{name} must exist and be defined within
6963 the file being assembled. It is similar to @var{name2@@nodename}. The
6964 difference is @var{name2@@@@nodename} will also be used to resolve
6965 references to @var{name2} by the linker.
6967 The third usage of the @code{.symver} directive is:
6969 .symver @var{name}, @var{name2@@@@@@nodename}
6971 When @var{name} is not defined within the
6972 file being assembled, it is treated as @var{name2@@nodename}. When
6973 @var{name} is defined within the file being assembled, the symbol
6974 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6979 @section @code{.tag @var{structname}}
6981 @cindex COFF structure debugging
6982 @cindex structure debugging, COFF
6983 @cindex @code{tag} directive
6984 This directive is generated by compilers to include auxiliary debugging
6985 information in the symbol table. It is only permitted inside
6986 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6987 definitions in the symbol table with instances of those structures.
6990 @samp{.tag} is only used when generating COFF format output; when
6991 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6997 @section @code{.text @var{subsection}}
6999 @cindex @code{text} directive
7000 Tells @command{@value{AS}} to assemble the following statements onto the end of
7001 the text subsection numbered @var{subsection}, which is an absolute
7002 expression. If @var{subsection} is omitted, subsection number zero
7006 @section @code{.title "@var{heading}"}
7008 @cindex @code{title} directive
7009 @cindex listing control: title line
7010 Use @var{heading} as the title (second line, immediately after the
7011 source file name and pagenumber) when generating assembly listings.
7013 This directive affects subsequent pages, as well as the current page if
7014 it appears within ten lines of the top of a page.
7018 @section @code{.type}
7020 This directive is used to set the type of a symbol.
7024 @c only print the extra heading if both COFF and ELF are set
7025 @subheading COFF Version
7028 @cindex COFF symbol type
7029 @cindex symbol type, COFF
7030 @cindex @code{type} directive (COFF version)
7031 For COFF targets, this directive is permitted only within
7032 @code{.def}/@code{.endef} pairs. It is used like this:
7038 This records the integer @var{int} as the type attribute of a symbol table
7042 @samp{.type} is associated only with COFF format output; when
7043 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
7044 directive but ignores it.
7050 @c only print the extra heading if both COFF and ELF are set
7051 @subheading ELF Version
7054 @cindex ELF symbol type
7055 @cindex symbol type, ELF
7056 @cindex @code{type} directive (ELF version)
7057 For ELF targets, the @code{.type} directive is used like this:
7060 .type @var{name} , @var{type description}
7063 This sets the type of symbol @var{name} to be either a
7064 function symbol or an object symbol. There are five different syntaxes
7065 supported for the @var{type description} field, in order to provide
7066 compatibility with various other assemblers.
7068 Because some of the characters used in these syntaxes (such as @samp{@@} and
7069 @samp{#}) are comment characters for some architectures, some of the syntaxes
7070 below do not work on all architectures. The first variant will be accepted by
7071 the GNU assembler on all architectures so that variant should be used for
7072 maximum portability, if you do not need to assemble your code with other
7075 The syntaxes supported are:
7078 .type <name> STT_<TYPE_IN_UPPER_CASE>
7079 .type <name>,#<type>
7080 .type <name>,@@<type>
7081 .type <name>,%<type>
7082 .type <name>,"<type>"
7085 The types supported are:
7090 Mark the symbol as being a function name.
7093 @itemx gnu_indirect_function
7094 Mark the symbol as an indirect function when evaluated during reloc
7095 processing. (This is only supported on assemblers targeting GNU systems).
7099 Mark the symbol as being a data object.
7103 Mark the symbol as being a thead-local data object.
7107 Mark the symbol as being a common data object.
7111 Does not mark the symbol in any way. It is supported just for completeness.
7113 @item gnu_unique_object
7114 Marks the symbol as being a globally unique data object. The dynamic linker
7115 will make sure that in the entire process there is just one symbol with this
7116 name and type in use. (This is only supported on assemblers targeting GNU
7121 Note: Some targets support extra types in addition to those listed above.
7127 @section @code{.uleb128 @var{expressions}}
7129 @cindex @code{uleb128} directive
7130 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7131 compact, variable length representation of numbers used by the DWARF
7132 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7136 @section @code{.val @var{addr}}
7138 @cindex @code{val} directive
7139 @cindex COFF value attribute
7140 @cindex value attribute, COFF
7141 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7142 records the address @var{addr} as the value attribute of a symbol table
7146 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7147 configured for @code{b.out}, it accepts this directive but ignores it.
7153 @section @code{.version "@var{string}"}
7155 @cindex @code{version} directive
7156 This directive creates a @code{.note} section and places into it an ELF
7157 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7162 @section @code{.vtable_entry @var{table}, @var{offset}}
7164 @cindex @code{vtable_entry} directive
7165 This directive finds or creates a symbol @code{table} and creates a
7166 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7169 @section @code{.vtable_inherit @var{child}, @var{parent}}
7171 @cindex @code{vtable_inherit} directive
7172 This directive finds the symbol @code{child} and finds or creates the symbol
7173 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7174 parent whose addend is the value of the child symbol. As a special case the
7175 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7179 @section @code{.warning "@var{string}"}
7180 @cindex warning directive
7181 Similar to the directive @code{.error}
7182 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7185 @section @code{.weak @var{names}}
7187 @cindex @code{weak} directive
7188 This directive sets the weak attribute on the comma separated list of symbol
7189 @code{names}. If the symbols do not already exist, they will be created.
7191 On COFF targets other than PE, weak symbols are a GNU extension. This
7192 directive sets the weak attribute on the comma separated list of symbol
7193 @code{names}. If the symbols do not already exist, they will be created.
7195 On the PE target, weak symbols are supported natively as weak aliases.
7196 When a weak symbol is created that is not an alias, GAS creates an
7197 alternate symbol to hold the default value.
7200 @section @code{.weakref @var{alias}, @var{target}}
7202 @cindex @code{weakref} directive
7203 This directive creates an alias to the target symbol that enables the symbol to
7204 be referenced with weak-symbol semantics, but without actually making it weak.
7205 If direct references or definitions of the symbol are present, then the symbol
7206 will not be weak, but if all references to it are through weak references, the
7207 symbol will be marked as weak in the symbol table.
7209 The effect is equivalent to moving all references to the alias to a separate
7210 assembly source file, renaming the alias to the symbol in it, declaring the
7211 symbol as weak there, and running a reloadable link to merge the object files
7212 resulting from the assembly of the new source file and the old source file that
7213 had the references to the alias removed.
7215 The alias itself never makes to the symbol table, and is entirely handled
7216 within the assembler.
7219 @section @code{.word @var{expressions}}
7221 @cindex @code{word} directive
7222 This directive expects zero or more @var{expressions}, of any section,
7223 separated by commas.
7226 For each expression, @command{@value{AS}} emits a 32-bit number.
7229 For each expression, @command{@value{AS}} emits a 16-bit number.
7234 The size of the number emitted, and its byte order,
7235 depend on what target computer the assembly is for.
7238 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7239 @c happen---32-bit addressability, period; no long/short jumps.
7240 @ifset DIFF-TBL-KLUGE
7241 @cindex difference tables altered
7242 @cindex altered difference tables
7244 @emph{Warning: Special Treatment to support Compilers}
7248 Machines with a 32-bit address space, but that do less than 32-bit
7249 addressing, require the following special treatment. If the machine of
7250 interest to you does 32-bit addressing (or doesn't require it;
7251 @pxref{Machine Dependencies}), you can ignore this issue.
7254 In order to assemble compiler output into something that works,
7255 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7256 Directives of the form @samp{.word sym1-sym2} are often emitted by
7257 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7258 directive of the form @samp{.word sym1-sym2}, and the difference between
7259 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7260 creates a @dfn{secondary jump table}, immediately before the next label.
7261 This secondary jump table is preceded by a short-jump to the
7262 first byte after the secondary table. This short-jump prevents the flow
7263 of control from accidentally falling into the new table. Inside the
7264 table is a long-jump to @code{sym2}. The original @samp{.word}
7265 contains @code{sym1} minus the address of the long-jump to
7268 If there were several occurrences of @samp{.word sym1-sym2} before the
7269 secondary jump table, all of them are adjusted. If there was a
7270 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7271 long-jump to @code{sym4} is included in the secondary jump table,
7272 and the @code{.word} directives are adjusted to contain @code{sym3}
7273 minus the address of the long-jump to @code{sym4}; and so on, for as many
7274 entries in the original jump table as necessary.
7277 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7278 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7279 assembly language programmers.
7282 @c end DIFF-TBL-KLUGE
7284 @ifclear no-space-dir
7286 @section @code{.zero @var{size}}
7288 @cindex @code{zero} directive
7289 @cindex filling memory with zero bytes
7290 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7291 expression. This directive is actually an alias for the @samp{.skip} directive
7292 so in can take an optional second argument of the value to store in the bytes
7293 instead of zero. Using @samp{.zero} in this way would be confusing however.
7297 @section Deprecated Directives
7299 @cindex deprecated directives
7300 @cindex obsolescent directives
7301 One day these directives won't work.
7302 They are included for compatibility with older assemblers.
7309 @node Object Attributes
7310 @chapter Object Attributes
7311 @cindex object attributes
7313 @command{@value{AS}} assembles source files written for a specific architecture
7314 into object files for that architecture. But not all object files are alike.
7315 Many architectures support incompatible variations. For instance, floating
7316 point arguments might be passed in floating point registers if the object file
7317 requires hardware floating point support---or floating point arguments might be
7318 passed in integer registers if the object file supports processors with no
7319 hardware floating point unit. Or, if two objects are built for different
7320 generations of the same architecture, the combination may require the
7321 newer generation at run-time.
7323 This information is useful during and after linking. At link time,
7324 @command{@value{LD}} can warn about incompatible object files. After link
7325 time, tools like @command{gdb} can use it to process the linked file
7328 Compatibility information is recorded as a series of object attributes. Each
7329 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7330 string, and indicates who sets the meaning of the tag. The tag is an integer,
7331 and indicates what property the attribute describes. The value may be a string
7332 or an integer, and indicates how the property affects this object. Missing
7333 attributes are the same as attributes with a zero value or empty string value.
7335 Object attributes were developed as part of the ABI for the ARM Architecture.
7336 The file format is documented in @cite{ELF for the ARM Architecture}.
7339 * GNU Object Attributes:: @sc{gnu} Object Attributes
7340 * Defining New Object Attributes:: Defining New Object Attributes
7343 @node GNU Object Attributes
7344 @section @sc{gnu} Object Attributes
7346 The @code{.gnu_attribute} directive records an object attribute
7347 with vendor @samp{gnu}.
7349 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7350 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7351 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7352 2} is set for architecture-independent attributes and clear for
7353 architecture-dependent ones.
7355 @subsection Common @sc{gnu} attributes
7357 These attributes are valid on all architectures.
7360 @item Tag_compatibility (32)
7361 The compatibility attribute takes an integer flag value and a vendor name. If
7362 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7363 then the file is only compatible with the named toolchain. If it is greater
7364 than 1, the file can only be processed by other toolchains under some private
7365 arrangement indicated by the flag value and the vendor name.
7368 @subsection MIPS Attributes
7371 @item Tag_GNU_MIPS_ABI_FP (4)
7372 The floating-point ABI used by this object file. The value will be:
7376 0 for files not affected by the floating-point ABI.
7378 1 for files using the hardware floating-point ABI with a standard
7379 double-precision FPU.
7381 2 for files using the hardware floating-point ABI with a single-precision FPU.
7383 3 for files using the software floating-point ABI.
7385 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7386 floating-point registers, 32-bit general-purpose registers and increased the
7387 number of callee-saved floating-point registers.
7389 5 for files using the hardware floating-point ABI with a double-precision FPU
7390 with either 32-bit or 64-bit floating-point registers and 32-bit
7391 general-purpose registers.
7393 6 for files using the hardware floating-point ABI with 64-bit floating-point
7394 registers and 32-bit general-purpose registers.
7396 7 for files using the hardware floating-point ABI with 64-bit floating-point
7397 registers, 32-bit general-purpose registers and a rule that forbids the
7398 direct use of odd-numbered single-precision floating-point registers.
7402 @subsection PowerPC Attributes
7405 @item Tag_GNU_Power_ABI_FP (4)
7406 The floating-point ABI used by this object file. The value will be:
7410 0 for files not affected by the floating-point ABI.
7412 1 for files using double-precision hardware floating-point ABI.
7414 2 for files using the software floating-point ABI.
7416 3 for files using single-precision hardware floating-point ABI.
7419 @item Tag_GNU_Power_ABI_Vector (8)
7420 The vector ABI used by this object file. The value will be:
7424 0 for files not affected by the vector ABI.
7426 1 for files using general purpose registers to pass vectors.
7428 2 for files using AltiVec registers to pass vectors.
7430 3 for files using SPE registers to pass vectors.
7434 @subsection IBM z Systems Attributes
7437 @item Tag_GNU_S390_ABI_Vector (8)
7438 The vector ABI used by this object file. The value will be:
7442 0 for files not affected by the vector ABI.
7444 1 for files using software vector ABI.
7446 2 for files using hardware vector ABI.
7450 @node Defining New Object Attributes
7451 @section Defining New Object Attributes
7453 If you want to define a new @sc{gnu} object attribute, here are the places you
7454 will need to modify. New attributes should be discussed on the @samp{binutils}
7459 This manual, which is the official register of attributes.
7461 The header for your architecture @file{include/elf}, to define the tag.
7463 The @file{bfd} support file for your architecture, to merge the attribute
7464 and issue any appropriate link warnings.
7466 Test cases in @file{ld/testsuite} for merging and link warnings.
7468 @file{binutils/readelf.c} to display your attribute.
7470 GCC, if you want the compiler to mark the attribute automatically.
7476 @node Machine Dependencies
7477 @chapter Machine Dependent Features
7479 @cindex machine dependencies
7480 The machine instruction sets are (almost by definition) different on
7481 each machine where @command{@value{AS}} runs. Floating point representations
7482 vary as well, and @command{@value{AS}} often supports a few additional
7483 directives or command-line options for compatibility with other
7484 assemblers on a particular platform. Finally, some versions of
7485 @command{@value{AS}} support special pseudo-instructions for branch
7488 This chapter discusses most of these differences, though it does not
7489 include details on any machine's instruction set. For details on that
7490 subject, see the hardware manufacturer's manual.
7494 * AArch64-Dependent:: AArch64 Dependent Features
7497 * Alpha-Dependent:: Alpha Dependent Features
7500 * ARC-Dependent:: ARC Dependent Features
7503 * ARM-Dependent:: ARM Dependent Features
7506 * AVR-Dependent:: AVR Dependent Features
7509 * Blackfin-Dependent:: Blackfin Dependent Features
7512 * CR16-Dependent:: CR16 Dependent Features
7515 * CRIS-Dependent:: CRIS Dependent Features
7518 * D10V-Dependent:: D10V Dependent Features
7521 * D30V-Dependent:: D30V Dependent Features
7524 * Epiphany-Dependent:: EPIPHANY Dependent Features
7527 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7530 * HPPA-Dependent:: HPPA Dependent Features
7533 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7536 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7539 * i860-Dependent:: Intel 80860 Dependent Features
7542 * i960-Dependent:: Intel 80960 Dependent Features
7545 * IA-64-Dependent:: Intel IA-64 Dependent Features
7548 * IP2K-Dependent:: IP2K Dependent Features
7551 * LM32-Dependent:: LM32 Dependent Features
7554 * M32C-Dependent:: M32C Dependent Features
7557 * M32R-Dependent:: M32R Dependent Features
7560 * M68K-Dependent:: M680x0 Dependent Features
7563 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7566 * Meta-Dependent :: Meta Dependent Features
7569 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7572 * MIPS-Dependent:: MIPS Dependent Features
7575 * MMIX-Dependent:: MMIX Dependent Features
7578 * MSP430-Dependent:: MSP430 Dependent Features
7581 * NDS32-Dependent:: Andes NDS32 Dependent Features
7584 * NiosII-Dependent:: Altera Nios II Dependent Features
7587 * NS32K-Dependent:: NS32K Dependent Features
7590 * PDP-11-Dependent:: PDP-11 Dependent Features
7593 * PJ-Dependent:: picoJava Dependent Features
7596 * PPC-Dependent:: PowerPC Dependent Features
7599 * RL78-Dependent:: RL78 Dependent Features
7602 * RISC-V-Dependent:: RISC-V Dependent Features
7605 * RX-Dependent:: RX Dependent Features
7608 * S/390-Dependent:: IBM S/390 Dependent Features
7611 * SCORE-Dependent:: SCORE Dependent Features
7614 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7615 * SH64-Dependent:: SuperH SH64 Dependent Features
7618 * Sparc-Dependent:: SPARC Dependent Features
7621 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7624 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7627 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7630 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7633 * V850-Dependent:: V850 Dependent Features
7636 * Vax-Dependent:: VAX Dependent Features
7639 * Visium-Dependent:: Visium Dependent Features
7642 * XGATE-Dependent:: XGATE Features
7645 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7648 * Xtensa-Dependent:: Xtensa Dependent Features
7651 * Z80-Dependent:: Z80 Dependent Features
7654 * Z8000-Dependent:: Z8000 Dependent Features
7661 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7662 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7663 @c peculiarity: to preserve cross-references, there must be a node called
7664 @c "Machine Dependencies". Hence the conditional nodenames in each
7665 @c major node below. Node defaulting in makeinfo requires adjacency of
7666 @c node and sectioning commands; hence the repetition of @chapter BLAH
7667 @c in both conditional blocks.
7670 @include c-aarch64.texi
7674 @include c-alpha.texi
7690 @include c-bfin.texi
7694 @include c-cr16.texi
7698 @include c-cris.texi
7703 @node Machine Dependencies
7704 @chapter Machine Dependent Features
7706 The machine instruction sets are different on each Renesas chip family,
7707 and there are also some syntax differences among the families. This
7708 chapter describes the specific @command{@value{AS}} features for each
7712 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7713 * SH-Dependent:: Renesas SH Dependent Features
7720 @include c-d10v.texi
7724 @include c-d30v.texi
7728 @include c-epiphany.texi
7732 @include c-h8300.texi
7736 @include c-hppa.texi
7740 @include c-i370.texi
7744 @include c-i386.texi
7748 @include c-i860.texi
7752 @include c-i960.texi
7756 @include c-ia64.texi
7760 @include c-ip2k.texi
7764 @include c-lm32.texi
7768 @include c-m32c.texi
7772 @include c-m32r.texi
7776 @include c-m68k.texi
7780 @include c-m68hc11.texi
7784 @include c-metag.texi
7788 @include c-microblaze.texi
7792 @include c-mips.texi
7796 @include c-mmix.texi
7800 @include c-msp430.texi
7804 @include c-nds32.texi
7808 @include c-nios2.texi
7812 @include c-ns32k.texi
7816 @include c-pdp11.texi
7828 @include c-rl78.texi
7832 @include c-riscv.texi
7840 @include c-s390.texi
7844 @include c-score.texi
7849 @include c-sh64.texi
7853 @include c-sparc.texi
7857 @include c-tic54x.texi
7861 @include c-tic6x.texi
7865 @include c-tilegx.texi
7869 @include c-tilepro.texi
7873 @include c-v850.texi
7881 @include c-visium.texi
7885 @include c-xgate.texi
7889 @include c-xstormy16.texi
7893 @include c-xtensa.texi
7905 @c reverse effect of @down at top of generic Machine-Dep chapter
7909 @node Reporting Bugs
7910 @chapter Reporting Bugs
7911 @cindex bugs in assembler
7912 @cindex reporting bugs in assembler
7914 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7916 Reporting a bug may help you by bringing a solution to your problem, or it may
7917 not. But in any case the principal function of a bug report is to help the
7918 entire community by making the next version of @command{@value{AS}} work better.
7919 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7921 In order for a bug report to serve its purpose, you must include the
7922 information that enables us to fix the bug.
7925 * Bug Criteria:: Have you found a bug?
7926 * Bug Reporting:: How to report bugs
7930 @section Have You Found a Bug?
7931 @cindex bug criteria
7933 If you are not sure whether you have found a bug, here are some guidelines:
7936 @cindex fatal signal
7937 @cindex assembler crash
7938 @cindex crash of assembler
7940 If the assembler gets a fatal signal, for any input whatever, that is a
7941 @command{@value{AS}} bug. Reliable assemblers never crash.
7943 @cindex error on valid input
7945 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7947 @cindex invalid input
7949 If @command{@value{AS}} does not produce an error message for invalid input, that
7950 is a bug. However, you should note that your idea of ``invalid input'' might
7951 be our idea of ``an extension'' or ``support for traditional practice''.
7954 If you are an experienced user of assemblers, your suggestions for improvement
7955 of @command{@value{AS}} are welcome in any case.
7959 @section How to Report Bugs
7961 @cindex assembler bugs, reporting
7963 A number of companies and individuals offer support for @sc{gnu} products. If
7964 you obtained @command{@value{AS}} from a support organization, we recommend you
7965 contact that organization first.
7967 You can find contact information for many support companies and
7968 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7972 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7976 The fundamental principle of reporting bugs usefully is this:
7977 @strong{report all the facts}. If you are not sure whether to state a
7978 fact or leave it out, state it!
7980 Often people omit facts because they think they know what causes the problem
7981 and assume that some details do not matter. Thus, you might assume that the
7982 name of a symbol you use in an example does not matter. Well, probably it does
7983 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7984 happens to fetch from the location where that name is stored in memory;
7985 perhaps, if the name were different, the contents of that location would fool
7986 the assembler into doing the right thing despite the bug. Play it safe and
7987 give a specific, complete example. That is the easiest thing for you to do,
7988 and the most helpful.
7990 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7991 it is new to us. Therefore, always write your bug reports on the assumption
7992 that the bug has not been reported previously.
7994 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7995 bell?'' This cannot help us fix a bug, so it is basically useless. We
7996 respond by asking for enough details to enable us to investigate.
7997 You might as well expedite matters by sending them to begin with.
7999 To enable us to fix the bug, you should include all these things:
8003 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8004 it with the @samp{--version} argument.
8006 Without this, we will not know whether there is any point in looking for
8007 the bug in the current version of @command{@value{AS}}.
8010 Any patches you may have applied to the @command{@value{AS}} source.
8013 The type of machine you are using, and the operating system name and
8017 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8021 The command arguments you gave the assembler to assemble your example and
8022 observe the bug. To guarantee you will not omit something important, list them
8023 all. A copy of the Makefile (or the output from make) is sufficient.
8025 If we were to try to guess the arguments, we would probably guess wrong
8026 and then we might not encounter the bug.
8029 A complete input file that will reproduce the bug. If the bug is observed when
8030 the assembler is invoked via a compiler, send the assembler source, not the
8031 high level language source. Most compilers will produce the assembler source
8032 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8033 the options @samp{-v --save-temps}; this will save the assembler source in a
8034 file with an extension of @file{.s}, and also show you exactly how
8035 @command{@value{AS}} is being run.
8038 A description of what behavior you observe that you believe is
8039 incorrect. For example, ``It gets a fatal signal.''
8041 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8042 will certainly notice it. But if the bug is incorrect output, we might not
8043 notice unless it is glaringly wrong. You might as well not give us a chance to
8046 Even if the problem you experience is a fatal signal, you should still say so
8047 explicitly. Suppose something strange is going on, such as, your copy of
8048 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8049 library on your system. (This has happened!) Your copy might crash and ours
8050 would not. If you told us to expect a crash, then when ours fails to crash, we
8051 would know that the bug was not happening for us. If you had not told us to
8052 expect a crash, then we would not be able to draw any conclusion from our
8056 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8057 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8058 option. Always send diffs from the old file to the new file. If you even
8059 discuss something in the @command{@value{AS}} source, refer to it by context, not
8062 The line numbers in our development sources will not match those in your
8063 sources. Your line numbers would convey no useful information to us.
8066 Here are some things that are not necessary:
8070 A description of the envelope of the bug.
8072 Often people who encounter a bug spend a lot of time investigating
8073 which changes to the input file will make the bug go away and which
8074 changes will not affect it.
8076 This is often time consuming and not very useful, because the way we
8077 will find the bug is by running a single example under the debugger
8078 with breakpoints, not by pure deduction from a series of examples.
8079 We recommend that you save your time for something else.
8081 Of course, if you can find a simpler example to report @emph{instead}
8082 of the original one, that is a convenience for us. Errors in the
8083 output will be easier to spot, running under the debugger will take
8084 less time, and so on.
8086 However, simplification is not vital; if you do not want to do this,
8087 report the bug anyway and send us the entire test case you used.
8090 A patch for the bug.
8092 A patch for the bug does help us if it is a good one. But do not omit
8093 the necessary information, such as the test case, on the assumption that
8094 a patch is all we need. We might see problems with your patch and decide
8095 to fix the problem another way, or we might not understand it at all.
8097 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8098 construct an example that will make the program follow a certain path through
8099 the code. If you do not send us the example, we will not be able to construct
8100 one, so we will not be able to verify that the bug is fixed.
8102 And if we cannot understand what bug you are trying to fix, or why your
8103 patch should be an improvement, we will not install it. A test case will
8104 help us to understand.
8107 A guess about what the bug is or what it depends on.
8109 Such guesses are usually wrong. Even we cannot guess right about such
8110 things without first using the debugger to find the facts.
8113 @node Acknowledgements
8114 @chapter Acknowledgements
8116 If you have contributed to GAS and your name isn't listed here,
8117 it is not meant as a slight. We just don't know about it. Send mail to the
8118 maintainer, and we'll correct the situation. Currently
8120 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8122 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8125 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8126 information and the 68k series machines, most of the preprocessing pass, and
8127 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8129 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8130 many bug fixes, including merging support for several processors, breaking GAS
8131 up to handle multiple object file format back ends (including heavy rewrite,
8132 testing, an integration of the coff and b.out back ends), adding configuration
8133 including heavy testing and verification of cross assemblers and file splits
8134 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8135 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8136 port (including considerable amounts of reverse engineering), a SPARC opcode
8137 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8138 assertions and made them work, much other reorganization, cleanup, and lint.
8140 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8141 in format-specific I/O modules.
8143 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8144 has done much work with it since.
8146 The Intel 80386 machine description was written by Eliot Dresselhaus.
8148 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8150 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8151 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8153 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8154 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8155 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8156 support a.out format.
8158 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8159 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8160 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8161 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8164 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8165 simplified the configuration of which versions accept which directives. He
8166 updated the 68k machine description so that Motorola's opcodes always produced
8167 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8168 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8169 cross-compilation support, and one bug in relaxation that took a week and
8170 required the proverbial one-bit fix.
8172 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8173 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8174 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8175 PowerPC assembler, and made a few other minor patches.
8177 Steve Chamberlain made GAS able to generate listings.
8179 Hewlett-Packard contributed support for the HP9000/300.
8181 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8182 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8183 formats). This work was supported by both the Center for Software Science at
8184 the University of Utah and Cygnus Support.
8186 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8187 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8188 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8189 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8190 and some initial 64-bit support).
8192 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8194 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8195 support for openVMS/Alpha.
8197 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8200 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8201 Inc.@: added support for Xtensa processors.
8203 Several engineers at Cygnus Support have also provided many small bug fixes and
8204 configuration enhancements.
8206 Jon Beniston added support for the Lattice Mico32 architecture.
8208 Many others have contributed large or small bugfixes and enhancements. If
8209 you have contributed significant work and are not mentioned on this list, and
8210 want to be, let us know. Some of the history has been lost; we are not
8211 intentionally leaving anyone out.
8213 @node GNU Free Documentation License
8214 @appendix GNU Free Documentation License
8218 @unnumbered AS Index