1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2017 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{} 1991-2017 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{} 1991-2017 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{-mignore-branch-isa}] [@b{-mno-ignore-branch-isa}]
420 [@b{-mnan=@var{encoding}}]
421 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
422 [@b{-mips16}] [@b{-no-mips16}]
423 [@b{-mmicromips}] [@b{-mno-micromips}]
424 [@b{-msmartmips}] [@b{-mno-smartmips}]
425 [@b{-mips3d}] [@b{-no-mips3d}]
426 [@b{-mdmx}] [@b{-no-mdmx}]
427 [@b{-mdsp}] [@b{-mno-dsp}]
428 [@b{-mdspr2}] [@b{-mno-dspr2}]
429 [@b{-mdspr3}] [@b{-mno-dspr3}]
430 [@b{-mmsa}] [@b{-mno-msa}]
431 [@b{-mxpa}] [@b{-mno-xpa}]
432 [@b{-mmt}] [@b{-mno-mt}]
433 [@b{-mmcu}] [@b{-mno-mcu}]
434 [@b{-minsn32}] [@b{-mno-insn32}]
435 [@b{-mfix7000}] [@b{-mno-fix7000}]
436 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
437 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
438 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
439 [@b{-mdebug}] [@b{-no-mdebug}]
440 [@b{-mpdr}] [@b{-mno-pdr}]
444 @emph{Target MMIX options:}
445 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
446 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
447 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
448 [@b{--linker-allocated-gregs}]
452 @emph{Target Nios II options:}
453 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
458 @emph{Target NDS32 options:}
459 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
460 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
461 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
462 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
463 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
464 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
465 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
470 @emph{Target PDP11 options:}
471 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
472 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
473 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
477 @emph{Target picoJava options:}
482 @emph{Target PowerPC options:}
484 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
485 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
486 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
487 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
488 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
489 @b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
490 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
491 [@b{-mregnames}|@b{-mno-regnames}]
492 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
493 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
494 [@b{-msolaris}|@b{-mno-solaris}]
495 [@b{-nops=@var{count}}]
499 @emph{Target PRU options:}
502 [@b{-mno-warn-regname-label}]
506 @emph{Target RL78 options:}
508 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
512 @emph{Target RX options:}
513 [@b{-mlittle-endian}|@b{-mbig-endian}]
514 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
515 [@b{-muse-conventional-section-names}]
516 [@b{-msmall-data-limit}]
519 [@b{-mint-register=@var{number}}]
520 [@b{-mgcc-abi}|@b{-mrx-abi}]
524 @emph{Target RISC-V options:}
525 [@b{-march}=@var{ISA}]
526 [@b{-mabi}=@var{ABI}]
530 @emph{Target s390 options:}
531 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
532 [@b{-mregnames}|@b{-mno-regnames}]
533 [@b{-mwarn-areg-zero}]
537 @emph{Target SCORE options:}
538 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
539 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
540 [@b{-march=score7}][@b{-march=score3}]
541 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
545 @emph{Target SPARC options:}
546 @c The order here is important. See c-sparc.texi.
547 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
548 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
549 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
550 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
551 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
552 @b{-Asparcvisr}|@b{-Asparc5}]
553 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
554 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
555 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
556 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
557 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
558 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
561 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
565 @emph{Target TIC54X options:}
566 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
567 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
571 @emph{Target TIC6X options:}
572 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
573 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
574 [@b{-mpic}|@b{-mno-pic}]
578 @emph{Target TILE-Gx options:}
579 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
582 @c TILEPro has no machine-dependent assembler options
586 @emph{Target Visium options:}
587 [@b{-mtune=@var{arch}}]
591 @emph{Target Xtensa options:}
592 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
593 [@b{--[no-]absolute-literals}]
594 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
595 [@b{--[no-]transform}]
596 [@b{--rename-section} @var{oldname}=@var{newname}]
597 [@b{--[no-]trampolines}]
601 @emph{Target Z80 options:}
602 [@b{-z80}] [@b{-r800}]
603 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
604 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
605 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
606 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
607 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
608 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
612 @c Z8000 has no machine-dependent assembler options
621 @include at-file.texi
624 Turn on listings, in any of a variety of ways:
628 omit false conditionals
631 omit debugging directives
634 include general information, like @value{AS} version and options passed
637 include high-level source
643 include macro expansions
646 omit forms processing
652 set the name of the listing file
655 You may combine these options; for example, use @samp{-aln} for assembly
656 listing without forms processing. The @samp{=file} option, if used, must be
657 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
660 Begin in alternate macro mode.
662 @xref{Altmacro,,@code{.altmacro}}.
665 @item --compress-debug-sections
666 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
667 ELF ABI. The resulting object file may not be compatible with older
668 linkers and object file utilities. Note if compression would make a
669 given section @emph{larger} then it is not compressed.
672 @cindex @samp{--compress-debug-sections=} option
673 @item --compress-debug-sections=none
674 @itemx --compress-debug-sections=zlib
675 @itemx --compress-debug-sections=zlib-gnu
676 @itemx --compress-debug-sections=zlib-gabi
677 These options control how DWARF debug sections are compressed.
678 @option{--compress-debug-sections=none} is equivalent to
679 @option{--nocompress-debug-sections}.
680 @option{--compress-debug-sections=zlib} and
681 @option{--compress-debug-sections=zlib-gabi} are equivalent to
682 @option{--compress-debug-sections}.
683 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
684 sections using zlib. The debug sections are renamed to begin with
685 @samp{.zdebug}. Note if compression would make a given section
686 @emph{larger} then it is not compressed nor renamed.
690 @item --nocompress-debug-sections
691 Do not compress DWARF debug sections. This is usually the default for all
692 targets except the x86/x86_64, but a configure time option can be used to
696 Ignored. This option is accepted for script compatibility with calls to
699 @item --debug-prefix-map @var{old}=@var{new}
700 When assembling files in directory @file{@var{old}}, record debugging
701 information describing them as in @file{@var{new}} instead.
703 @item --defsym @var{sym}=@var{value}
704 Define the symbol @var{sym} to be @var{value} before assembling the input file.
705 @var{value} must be an integer constant. As in C, a leading @samp{0x}
706 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
707 value. The value of the symbol can be overridden inside a source file via the
708 use of a @code{.set} pseudo-op.
711 ``fast''---skip whitespace and comment preprocessing (assume source is
716 Generate debugging information for each assembler source line using whichever
717 debug format is preferred by the target. This currently means either STABS,
721 Generate stabs debugging information for each assembler line. This
722 may help debugging assembler code, if the debugger can handle it.
725 Generate stabs debugging information for each assembler line, with GNU
726 extensions that probably only gdb can handle, and that could make other
727 debuggers crash or refuse to read your program. This
728 may help debugging assembler code. Currently the only GNU extension is
729 the location of the current working directory at assembling time.
732 Generate DWARF2 debugging information for each assembler line. This
733 may help debugging assembler code, if the debugger can handle it. Note---this
734 option is only supported by some targets, not all of them.
736 @item --gdwarf-sections
737 Instead of creating a .debug_line section, create a series of
738 .debug_line.@var{foo} sections where @var{foo} is the name of the
739 corresponding code section. For example a code section called @var{.text.func}
740 will have its dwarf line number information placed into a section called
741 @var{.debug_line.text.func}. If the code section is just called @var{.text}
742 then debug line section will still be called just @var{.debug_line} without any
746 @item --size-check=error
747 @itemx --size-check=warning
748 Issue an error or warning for invalid ELF .size directive.
750 @item --elf-stt-common=no
751 @itemx --elf-stt-common=yes
752 These options control whether the ELF assembler should generate common
753 symbols with the @code{STT_COMMON} type. The default can be controlled
754 by a configure option @option{--enable-elf-stt-common}.
758 Print a summary of the command line options and exit.
761 Print a summary of all target specific options and exit.
764 Add directory @var{dir} to the search list for @code{.include} directives.
767 Don't warn about signed overflow.
770 @ifclear DIFF-TBL-KLUGE
771 This option is accepted but has no effect on the @value{TARGET} family.
773 @ifset DIFF-TBL-KLUGE
774 Issue warnings when difference tables altered for long displacements.
779 Keep (in the symbol table) local symbols. These symbols start with
780 system-specific local label prefixes, typically @samp{.L} for ELF systems
781 or @samp{L} for traditional a.out systems.
786 @item --listing-lhs-width=@var{number}
787 Set the maximum width, in words, of the output data column for an assembler
788 listing to @var{number}.
790 @item --listing-lhs-width2=@var{number}
791 Set the maximum width, in words, of the output data column for continuation
792 lines in an assembler listing to @var{number}.
794 @item --listing-rhs-width=@var{number}
795 Set the maximum width of an input source line, as displayed in a listing, to
798 @item --listing-cont-lines=@var{number}
799 Set the maximum number of lines printed in a listing for a single line of input
802 @item --no-pad-sections
803 Stop the assembler for padding the ends of output sections to the alignment
804 of that section. The default is to pad the sections, but this can waste space
805 which might be needed on targets which have tight memory constraints.
807 @item -o @var{objfile}
808 Name the object-file output from @command{@value{AS}} @var{objfile}.
811 Fold the data section into the text section.
813 @item --hash-size=@var{number}
814 Set the default size of GAS's hash tables to a prime number close to
815 @var{number}. Increasing this value can reduce the length of time it takes the
816 assembler to perform its tasks, at the expense of increasing the assembler's
817 memory requirements. Similarly reducing this value can reduce the memory
818 requirements at the expense of speed.
820 @item --reduce-memory-overheads
821 This option reduces GAS's memory requirements, at the expense of making the
822 assembly processes slower. Currently this switch is a synonym for
823 @samp{--hash-size=4051}, but in the future it may have other effects as well.
826 @item --sectname-subst
827 Honor substitution sequences in section names.
829 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
834 Print the maximum space (in bytes) and total time (in seconds) used by
837 @item --strip-local-absolute
838 Remove local absolute symbols from the outgoing symbol table.
842 Print the @command{as} version.
845 Print the @command{as} version and exit.
849 Suppress warning messages.
851 @item --fatal-warnings
852 Treat warnings as errors.
855 Don't suppress warning messages or treat them as errors.
864 Generate an object file even after errors.
866 @item -- | @var{files} @dots{}
867 Standard input, or source files to assemble.
875 @xref{AArch64 Options}, for the options available when @value{AS} is configured
876 for the 64-bit mode of the ARM Architecture (AArch64).
881 The following options are available when @value{AS} is configured for the
882 64-bit mode of the ARM Architecture (AArch64).
885 @include c-aarch64.texi
886 @c ended inside the included file
894 @xref{Alpha Options}, for the options available when @value{AS} is configured
895 for an Alpha processor.
900 The following options are available when @value{AS} is configured for an Alpha
904 @include c-alpha.texi
905 @c ended inside the included file
912 The following options are available when @value{AS} is configured for an ARC
916 @item -mcpu=@var{cpu}
917 This option selects the core processor variant.
919 Select either big-endian (-EB) or little-endian (-EL) output.
921 Enable Code Density extenssion instructions.
926 The following options are available when @value{AS} is configured for the ARM
930 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
931 Specify which ARM processor variant is the target.
932 @item -march=@var{architecture}[+@var{extension}@dots{}]
933 Specify which ARM architecture variant is used by the target.
934 @item -mfpu=@var{floating-point-format}
935 Select which Floating Point architecture is the target.
936 @item -mfloat-abi=@var{abi}
937 Select which floating point ABI is in use.
939 Enable Thumb only instruction decoding.
940 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
941 Select which procedure calling convention is in use.
943 Select either big-endian (-EB) or little-endian (-EL) output.
944 @item -mthumb-interwork
945 Specify that the code has been generated with interworking between Thumb and
948 Turns on CodeComposer Studio assembly syntax compatibility mode.
950 Specify that PIC code has been generated.
958 @xref{Blackfin Options}, for the options available when @value{AS} is
959 configured for the Blackfin processor family.
964 The following options are available when @value{AS} is configured for
965 the Blackfin processor family.
969 @c ended inside the included file
976 See the info pages for documentation of the CRIS-specific options.
980 The following options are available when @value{AS} is configured for
983 @cindex D10V optimization
984 @cindex optimization, D10V
986 Optimize output by parallelizing instructions.
991 The following options are available when @value{AS} is configured for a D30V
994 @cindex D30V optimization
995 @cindex optimization, D30V
997 Optimize output by parallelizing instructions.
1001 Warn when nops are generated.
1003 @cindex D30V nops after 32-bit multiply
1005 Warn when a nop after a 32-bit multiply instruction is generated.
1011 The following options are available when @value{AS} is configured for the
1012 Adapteva EPIPHANY series.
1015 @xref{Epiphany Options}, for the options available when @value{AS} is
1016 configured for an Epiphany processor.
1020 @c man begin OPTIONS
1021 The following options are available when @value{AS} is configured for
1022 an Epiphany processor.
1024 @c man begin INCLUDE
1025 @include c-epiphany.texi
1026 @c ended inside the included file
1034 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1035 for an H8/300 processor.
1039 @c man begin OPTIONS
1040 The following options are available when @value{AS} is configured for an H8/300
1043 @c man begin INCLUDE
1044 @include c-h8300.texi
1045 @c ended inside the included file
1053 @xref{i386-Options}, for the options available when @value{AS} is
1054 configured for an i386 processor.
1058 @c man begin OPTIONS
1059 The following options are available when @value{AS} is configured for
1062 @c man begin INCLUDE
1063 @include c-i386.texi
1064 @c ended inside the included file
1069 @c man begin OPTIONS
1071 The following options are available when @value{AS} is configured for the
1072 Intel 80960 processor.
1075 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1076 Specify which variant of the 960 architecture is the target.
1079 Add code to collect statistics about branches taken.
1082 Do not alter compare-and-branch instructions for long displacements;
1089 The following options are available when @value{AS} is configured for the
1095 Specifies that the extended IP2022 instructions are allowed.
1098 Restores the default behaviour, which restricts the permitted instructions to
1099 just the basic IP2022 ones.
1105 The following options are available when @value{AS} is configured for the
1106 Renesas M32C and M16C processors.
1111 Assemble M32C instructions.
1114 Assemble M16C instructions (the default).
1117 Enable support for link-time relaxations.
1120 Support H'00 style hex constants in addition to 0x00 style.
1126 The following options are available when @value{AS} is configured for the
1127 Renesas M32R (formerly Mitsubishi M32R) series.
1132 Specify which processor in the M32R family is the target. The default
1133 is normally the M32R, but this option changes it to the M32RX.
1135 @item --warn-explicit-parallel-conflicts or --Wp
1136 Produce warning messages when questionable parallel constructs are
1139 @item --no-warn-explicit-parallel-conflicts or --Wnp
1140 Do not produce warning messages when questionable parallel constructs are
1147 The following options are available when @value{AS} is configured for the
1148 Motorola 68000 series.
1153 Shorten references to undefined symbols, to one word instead of two.
1155 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1156 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1157 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1158 Specify what processor in the 68000 family is the target. The default
1159 is normally the 68020, but this can be changed at configuration time.
1161 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1162 The target machine does (or does not) have a floating-point coprocessor.
1163 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1164 the basic 68000 is not compatible with the 68881, a combination of the
1165 two can be specified, since it's possible to do emulation of the
1166 coprocessor instructions with the main processor.
1168 @item -m68851 | -mno-68851
1169 The target machine does (or does not) have a memory-management
1170 unit coprocessor. The default is to assume an MMU for 68020 and up.
1178 @xref{Nios II Options}, for the options available when @value{AS} is configured
1179 for an Altera Nios II processor.
1183 @c man begin OPTIONS
1184 The following options are available when @value{AS} is configured for an
1185 Altera Nios II processor.
1187 @c man begin INCLUDE
1188 @include c-nios2.texi
1189 @c ended inside the included file
1195 For details about the PDP-11 machine dependent features options,
1196 see @ref{PDP-11-Options}.
1199 @item -mpic | -mno-pic
1200 Generate position-independent (or position-dependent) code. The
1201 default is @option{-mpic}.
1204 @itemx -mall-extensions
1205 Enable all instruction set extensions. This is the default.
1207 @item -mno-extensions
1208 Disable all instruction set extensions.
1210 @item -m@var{extension} | -mno-@var{extension}
1211 Enable (or disable) a particular instruction set extension.
1214 Enable the instruction set extensions supported by a particular CPU, and
1215 disable all other extensions.
1217 @item -m@var{machine}
1218 Enable the instruction set extensions supported by a particular machine
1219 model, and disable all other extensions.
1225 The following options are available when @value{AS} is configured for
1226 a picoJava processor.
1230 @cindex PJ endianness
1231 @cindex endianness, PJ
1232 @cindex big endian output, PJ
1234 Generate ``big endian'' format output.
1236 @cindex little endian output, PJ
1238 Generate ``little endian'' format output.
1246 @xref{PRU Options}, for the options available when @value{AS} is configured
1247 for a PRU processor.
1251 @c man begin OPTIONS
1252 The following options are available when @value{AS} is configured for a
1255 @c man begin INCLUDE
1257 @c ended inside the included file
1262 The following options are available when @value{AS} is configured for the
1263 Motorola 68HC11 or 68HC12 series.
1267 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1268 Specify what processor is the target. The default is
1269 defined by the configuration option when building the assembler.
1271 @item --xgate-ramoffset
1272 Instruct the linker to offset RAM addresses from S12X address space into
1273 XGATE address space.
1276 Specify to use the 16-bit integer ABI.
1279 Specify to use the 32-bit integer ABI.
1281 @item -mshort-double
1282 Specify to use the 32-bit double ABI.
1285 Specify to use the 64-bit double ABI.
1287 @item --force-long-branches
1288 Relative branches are turned into absolute ones. This concerns
1289 conditional branches, unconditional branches and branches to a
1292 @item -S | --short-branches
1293 Do not turn relative branches into absolute ones
1294 when the offset is out of range.
1296 @item --strict-direct-mode
1297 Do not turn the direct addressing mode into extended addressing mode
1298 when the instruction does not support direct addressing mode.
1300 @item --print-insn-syntax
1301 Print the syntax of instruction in case of error.
1303 @item --print-opcodes
1304 Print the list of instructions with syntax and then exit.
1306 @item --generate-example
1307 Print an example of instruction for each possible instruction and then exit.
1308 This option is only useful for testing @command{@value{AS}}.
1314 The following options are available when @command{@value{AS}} is configured
1315 for the SPARC architecture:
1318 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1319 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1320 Explicitly select a variant of the SPARC architecture.
1322 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1323 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1325 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1326 UltraSPARC extensions.
1328 @item -xarch=v8plus | -xarch=v8plusa
1329 For compatibility with the Solaris v9 assembler. These options are
1330 equivalent to -Av8plus and -Av8plusa, respectively.
1333 Warn when the assembler switches to another architecture.
1338 The following options are available when @value{AS} is configured for the 'c54x
1343 Enable extended addressing mode. All addresses and relocations will assume
1344 extended addressing (usually 23 bits).
1345 @item -mcpu=@var{CPU_VERSION}
1346 Sets the CPU version being compiled for.
1347 @item -merrors-to-file @var{FILENAME}
1348 Redirect error output to a file, for broken systems which don't support such
1349 behaviour in the shell.
1354 The following options are available when @value{AS} is configured for
1359 This option sets the largest size of an object that can be referenced
1360 implicitly with the @code{gp} register. It is only accepted for targets that
1361 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1363 @cindex MIPS endianness
1364 @cindex endianness, MIPS
1365 @cindex big endian output, MIPS
1367 Generate ``big endian'' format output.
1369 @cindex little endian output, MIPS
1371 Generate ``little endian'' format output.
1389 Generate code for a particular MIPS Instruction Set Architecture level.
1390 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1391 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1392 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1393 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1394 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1395 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1396 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1397 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1398 MIPS64 Release 6 ISA processors, respectively.
1400 @item -march=@var{cpu}
1401 Generate code for a particular MIPS CPU.
1403 @item -mtune=@var{cpu}
1404 Schedule and tune for a particular MIPS CPU.
1408 Cause nops to be inserted if the read of the destination register
1409 of an mfhi or mflo instruction occurs in the following two instructions.
1412 @itemx -mno-fix-rm7000
1413 Cause nops to be inserted if a dmult or dmultu instruction is
1414 followed by a load instruction.
1418 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1419 section instead of the standard ELF .stabs sections.
1423 Control generation of @code{.pdr} sections.
1427 The register sizes are normally inferred from the ISA and ABI, but these
1428 flags force a certain group of registers to be treated as 32 bits wide at
1429 all times. @samp{-mgp32} controls the size of general-purpose registers
1430 and @samp{-mfp32} controls the size of floating-point registers.
1434 The register sizes are normally inferred from the ISA and ABI, but these
1435 flags force a certain group of registers to be treated as 64 bits wide at
1436 all times. @samp{-mgp64} controls the size of general-purpose registers
1437 and @samp{-mfp64} controls the size of floating-point registers.
1440 The register sizes are normally inferred from the ISA and ABI, but using
1441 this flag in combination with @samp{-mabi=32} enables an ABI variant
1442 which will operate correctly with floating-point registers which are
1446 @itemx -mno-odd-spreg
1447 Enable use of floating-point operations on odd-numbered single-precision
1448 registers when supported by the ISA. @samp{-mfpxx} implies
1449 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1453 Generate code for the MIPS 16 processor. This is equivalent to putting
1454 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1455 turns off this option.
1458 @itemx -mno-micromips
1459 Generate code for the microMIPS processor. This is equivalent to putting
1460 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1461 turns off this option. This is equivalent to putting @code{.set nomicromips}
1462 at the start of the assembly file.
1465 @itemx -mno-smartmips
1466 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1467 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1468 @samp{-mno-smartmips} turns off this option.
1472 Generate code for the MIPS-3D Application Specific Extension.
1473 This tells the assembler to accept MIPS-3D instructions.
1474 @samp{-no-mips3d} turns off this option.
1478 Generate code for the MDMX Application Specific Extension.
1479 This tells the assembler to accept MDMX instructions.
1480 @samp{-no-mdmx} turns off this option.
1484 Generate code for the DSP Release 1 Application Specific Extension.
1485 This tells the assembler to accept DSP Release 1 instructions.
1486 @samp{-mno-dsp} turns off this option.
1490 Generate code for the DSP Release 2 Application Specific Extension.
1491 This option implies @samp{-mdsp}.
1492 This tells the assembler to accept DSP Release 2 instructions.
1493 @samp{-mno-dspr2} turns off this option.
1497 Generate code for the DSP Release 3 Application Specific Extension.
1498 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1499 This tells the assembler to accept DSP Release 3 instructions.
1500 @samp{-mno-dspr3} turns off this option.
1504 Generate code for the MIPS SIMD Architecture Extension.
1505 This tells the assembler to accept MSA instructions.
1506 @samp{-mno-msa} turns off this option.
1510 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1511 This tells the assembler to accept XPA instructions.
1512 @samp{-mno-xpa} turns off this option.
1516 Generate code for the MT Application Specific Extension.
1517 This tells the assembler to accept MT instructions.
1518 @samp{-mno-mt} turns off this option.
1522 Generate code for the MCU Application Specific Extension.
1523 This tells the assembler to accept MCU instructions.
1524 @samp{-mno-mcu} turns off this option.
1528 Only use 32-bit instruction encodings when generating code for the
1529 microMIPS processor. This option inhibits the use of any 16-bit
1530 instructions. This is equivalent to putting @code{.set insn32} at
1531 the start of the assembly file. @samp{-mno-insn32} turns off this
1532 option. This is equivalent to putting @code{.set noinsn32} at the
1533 start of the assembly file. By default @samp{-mno-insn32} is
1534 selected, allowing all instructions to be used.
1536 @item --construct-floats
1537 @itemx --no-construct-floats
1538 The @samp{--no-construct-floats} option disables the construction of
1539 double width floating point constants by loading the two halves of the
1540 value into the two single width floating point registers that make up
1541 the double width register. By default @samp{--construct-floats} is
1542 selected, allowing construction of these floating point constants.
1544 @item --relax-branch
1545 @itemx --no-relax-branch
1546 The @samp{--relax-branch} option enables the relaxation of out-of-range
1547 branches. By default @samp{--no-relax-branch} is selected, causing any
1548 out-of-range branches to produce an error.
1550 @item -mignore-branch-isa
1551 @itemx -mno-ignore-branch-isa
1552 Ignore branch checks for invalid transitions between ISA modes. The
1553 semantics of branches does not provide for an ISA mode switch, so in
1554 most cases the ISA mode a branch has been encoded for has to be the
1555 same as the ISA mode of the branch's target label. Therefore GAS has
1556 checks implemented that verify in branch assembly that the two ISA
1557 modes match. @samp{-mignore-branch-isa} disables these checks. By
1558 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1559 branch requiring a transition between ISA modes to produce an error.
1561 @item -mnan=@var{encoding}
1562 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1563 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1566 @item --emulation=@var{name}
1567 This option was formerly used to switch between ELF and ECOFF output
1568 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1569 removed in GAS 2.24, so the option now serves little purpose.
1570 It is retained for backwards compatibility.
1572 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1573 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1574 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1575 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1576 preferred options instead.
1579 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1586 Control how to deal with multiplication overflow and division by zero.
1587 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1588 (and only work for Instruction Set Architecture level 2 and higher);
1589 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1593 When this option is used, @command{@value{AS}} will issue a warning every
1594 time it generates a nop instruction from a macro.
1599 The following options are available when @value{AS} is configured for
1605 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1606 The command line option @samp{-nojsri2bsr} can be used to disable it.
1610 Enable or disable the silicon filter behaviour. By default this is disabled.
1611 The default can be overridden by the @samp{-sifilter} command line option.
1614 Alter jump instructions for long displacements.
1616 @item -mcpu=[210|340]
1617 Select the cpu type on the target hardware. This controls which instructions
1621 Assemble for a big endian target.
1624 Assemble for a little endian target.
1633 @xref{Meta Options}, for the options available when @value{AS} is configured
1634 for a Meta processor.
1638 @c man begin OPTIONS
1639 The following options are available when @value{AS} is configured for a
1642 @c man begin INCLUDE
1643 @include c-metag.texi
1644 @c ended inside the included file
1649 @c man begin OPTIONS
1651 See the info pages for documentation of the MMIX-specific options.
1657 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1658 for a NDS32 processor.
1660 @c ended inside the included file
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-nds32.texi
1670 @c ended inside the included file
1677 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1678 for a PowerPC processor.
1682 @c man begin OPTIONS
1683 The following options are available when @value{AS} is configured for a
1686 @c man begin INCLUDE
1688 @c ended inside the included file
1696 @xref{RISC-V-Opts}, for the options available when @value{AS} is configured
1697 for a RISC-V processor.
1701 @c man begin OPTIONS
1702 The following options are available when @value{AS} is configured for a
1705 @c man begin INCLUDE
1706 @include c-riscv.texi
1707 @c ended inside the included file
1712 @c man begin OPTIONS
1714 See the info pages for documentation of the RX-specific options.
1718 The following options are available when @value{AS} is configured for the s390
1724 Select the word size, either 31/32 bits or 64 bits.
1727 Select the architecture mode, either the Enterprise System
1728 Architecture (esa) or the z/Architecture mode (zarch).
1729 @item -march=@var{processor}
1730 Specify which s390 processor variant is the target, @samp{g5} (or
1731 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1732 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1733 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1734 or @samp{z13} (or @samp{arch11}).
1736 @itemx -mno-regnames
1737 Allow or disallow symbolic names for registers.
1738 @item -mwarn-areg-zero
1739 Warn whenever the operand for a base or index register has been specified
1740 but evaluates to zero.
1748 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1749 for a TMS320C6000 processor.
1753 @c man begin OPTIONS
1754 The following options are available when @value{AS} is configured for a
1755 TMS320C6000 processor.
1757 @c man begin INCLUDE
1758 @include c-tic6x.texi
1759 @c ended inside the included file
1767 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1768 for a TILE-Gx processor.
1772 @c man begin OPTIONS
1773 The following options are available when @value{AS} is configured for a TILE-Gx
1776 @c man begin INCLUDE
1777 @include c-tilegx.texi
1778 @c ended inside the included file
1786 @xref{Visium Options}, for the options available when @value{AS} is configured
1787 for a Visium processor.
1791 @c man begin OPTIONS
1792 The following option is available when @value{AS} is configured for a Visium
1795 @c man begin INCLUDE
1796 @include c-visium.texi
1797 @c ended inside the included file
1805 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1806 for an Xtensa processor.
1810 @c man begin OPTIONS
1811 The following options are available when @value{AS} is configured for an
1814 @c man begin INCLUDE
1815 @include c-xtensa.texi
1816 @c ended inside the included file
1821 @c man begin OPTIONS
1824 The following options are available when @value{AS} is configured for
1825 a Z80 family processor.
1828 Assemble for Z80 processor.
1830 Assemble for R800 processor.
1831 @item -ignore-undocumented-instructions
1833 Assemble undocumented Z80 instructions that also work on R800 without warning.
1834 @item -ignore-unportable-instructions
1836 Assemble all undocumented Z80 instructions without warning.
1837 @item -warn-undocumented-instructions
1839 Issue a warning for undocumented Z80 instructions that also work on R800.
1840 @item -warn-unportable-instructions
1842 Issue a warning for undocumented Z80 instructions that do not work on R800.
1843 @item -forbid-undocumented-instructions
1845 Treat all undocumented instructions as errors.
1846 @item -forbid-unportable-instructions
1848 Treat undocumented Z80 instructions that do not work on R800 as errors.
1855 * Manual:: Structure of this Manual
1856 * GNU Assembler:: The GNU Assembler
1857 * Object Formats:: Object File Formats
1858 * Command Line:: Command Line
1859 * Input Files:: Input Files
1860 * Object:: Output (Object) File
1861 * Errors:: Error and Warning Messages
1865 @section Structure of this Manual
1867 @cindex manual, structure and purpose
1868 This manual is intended to describe what you need to know to use
1869 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1870 notation for symbols, constants, and expressions; the directives that
1871 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1874 We also cover special features in the @value{TARGET}
1875 configuration of @command{@value{AS}}, including assembler directives.
1878 This manual also describes some of the machine-dependent features of
1879 various flavors of the assembler.
1882 @cindex machine instructions (not covered)
1883 On the other hand, this manual is @emph{not} intended as an introduction
1884 to programming in assembly language---let alone programming in general!
1885 In a similar vein, we make no attempt to introduce the machine
1886 architecture; we do @emph{not} describe the instruction set, standard
1887 mnemonics, registers or addressing modes that are standard to a
1888 particular architecture.
1890 You may want to consult the manufacturer's
1891 machine architecture manual for this information.
1895 For information on the H8/300 machine instruction set, see @cite{H8/300
1896 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1897 Programming Manual} (Renesas).
1900 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1901 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1902 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1903 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1906 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1910 @c I think this is premature---doc@cygnus.com, 17jan1991
1912 Throughout this manual, we assume that you are running @dfn{GNU},
1913 the portable operating system from the @dfn{Free Software
1914 Foundation, Inc.}. This restricts our attention to certain kinds of
1915 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1916 once this assumption is granted examples and definitions need less
1919 @command{@value{AS}} is part of a team of programs that turn a high-level
1920 human-readable series of instructions into a low-level
1921 computer-readable series of instructions. Different versions of
1922 @command{@value{AS}} are used for different kinds of computer.
1925 @c There used to be a section "Terminology" here, which defined
1926 @c "contents", "byte", "word", and "long". Defining "word" to any
1927 @c particular size is confusing when the .word directive may generate 16
1928 @c bits on one machine and 32 bits on another; in general, for the user
1929 @c version of this manual, none of these terms seem essential to define.
1930 @c They were used very little even in the former draft of the manual;
1931 @c this draft makes an effort to avoid them (except in names of
1935 @section The GNU Assembler
1937 @c man begin DESCRIPTION
1939 @sc{gnu} @command{as} is really a family of assemblers.
1941 This manual describes @command{@value{AS}}, a member of that family which is
1942 configured for the @value{TARGET} architectures.
1944 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1945 should find a fairly similar environment when you use it on another
1946 architecture. Each version has much in common with the others,
1947 including object file formats, most assembler directives (often called
1948 @dfn{pseudo-ops}) and assembler syntax.@refill
1950 @cindex purpose of @sc{gnu} assembler
1951 @command{@value{AS}} is primarily intended to assemble the output of the
1952 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1953 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1954 assemble correctly everything that other assemblers for the same
1955 machine would assemble.
1957 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1960 @c This remark should appear in generic version of manual; assumption
1961 @c here is that generic version sets M680x0.
1962 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1963 assembler for the same architecture; for example, we know of several
1964 incompatible versions of 680x0 assembly language syntax.
1969 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1970 program in one pass of the source file. This has a subtle impact on the
1971 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1973 @node Object Formats
1974 @section Object File Formats
1976 @cindex object file format
1977 The @sc{gnu} assembler can be configured to produce several alternative
1978 object file formats. For the most part, this does not affect how you
1979 write assembly language programs; but directives for debugging symbols
1980 are typically different in different file formats. @xref{Symbol
1981 Attributes,,Symbol Attributes}.
1984 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1985 @value{OBJ-NAME} format object files.
1987 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1989 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1990 @code{b.out} or COFF format object files.
1993 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1994 SOM or ELF format object files.
1999 @section Command Line
2001 @cindex command line conventions
2003 After the program name @command{@value{AS}}, the command line may contain
2004 options and file names. Options may appear in any order, and may be
2005 before, after, or between file names. The order of file names is
2008 @cindex standard input, as input file
2010 @file{--} (two hyphens) by itself names the standard input file
2011 explicitly, as one of the files for @command{@value{AS}} to assemble.
2013 @cindex options, command line
2014 Except for @samp{--} any command line argument that begins with a
2015 hyphen (@samp{-}) is an option. Each option changes the behavior of
2016 @command{@value{AS}}. No option changes the way another option works. An
2017 option is a @samp{-} followed by one or more letters; the case of
2018 the letter is important. All options are optional.
2020 Some options expect exactly one file name to follow them. The file
2021 name may either immediately follow the option's letter (compatible
2022 with older assemblers) or it may be the next command argument (@sc{gnu}
2023 standard). These two command lines are equivalent:
2026 @value{AS} -o my-object-file.o mumble.s
2027 @value{AS} -omy-object-file.o mumble.s
2031 @section Input Files
2034 @cindex source program
2035 @cindex files, input
2036 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2037 describe the program input to one run of @command{@value{AS}}. The program may
2038 be in one or more files; how the source is partitioned into files
2039 doesn't change the meaning of the source.
2041 @c I added "con" prefix to "catenation" just to prove I can overcome my
2042 @c APL training... doc@cygnus.com
2043 The source program is a concatenation of the text in all the files, in the
2046 @c man begin DESCRIPTION
2047 Each time you run @command{@value{AS}} it assembles exactly one source
2048 program. The source program is made up of one or more files.
2049 (The standard input is also a file.)
2051 You give @command{@value{AS}} a command line that has zero or more input file
2052 names. The input files are read (from left file name to right). A
2053 command line argument (in any position) that has no special meaning
2054 is taken to be an input file name.
2056 If you give @command{@value{AS}} no file names it attempts to read one input file
2057 from the @command{@value{AS}} standard input, which is normally your terminal. You
2058 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2061 Use @samp{--} if you need to explicitly name the standard input file
2062 in your command line.
2064 If the source is empty, @command{@value{AS}} produces a small, empty object
2069 @subheading Filenames and Line-numbers
2071 @cindex input file linenumbers
2072 @cindex line numbers, in input files
2073 There are two ways of locating a line in the input file (or files) and
2074 either may be used in reporting error messages. One way refers to a line
2075 number in a physical file; the other refers to a line number in a
2076 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2078 @dfn{Physical files} are those files named in the command line given
2079 to @command{@value{AS}}.
2081 @dfn{Logical files} are simply names declared explicitly by assembler
2082 directives; they bear no relation to physical files. Logical file names help
2083 error messages reflect the original source file, when @command{@value{AS}} source
2084 is itself synthesized from other files. @command{@value{AS}} understands the
2085 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2086 @ref{File,,@code{.file}}.
2089 @section Output (Object) File
2095 Every time you run @command{@value{AS}} it produces an output file, which is
2096 your assembly language program translated into numbers. This file
2097 is the object file. Its default name is
2105 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2107 You can give it another name by using the @option{-o} option. Conventionally,
2108 object file names end with @file{.o}. The default name is used for historical
2109 reasons: older assemblers were capable of assembling self-contained programs
2110 directly into a runnable program. (For some formats, this isn't currently
2111 possible, but it can be done for the @code{a.out} format.)
2115 The object file is meant for input to the linker @code{@value{LD}}. It contains
2116 assembled program code, information to help @code{@value{LD}} integrate
2117 the assembled program into a runnable file, and (optionally) symbolic
2118 information for the debugger.
2120 @c link above to some info file(s) like the description of a.out.
2121 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2124 @section Error and Warning Messages
2126 @c man begin DESCRIPTION
2128 @cindex error messages
2129 @cindex warning messages
2130 @cindex messages from assembler
2131 @command{@value{AS}} may write warnings and error messages to the standard error
2132 file (usually your terminal). This should not happen when a compiler
2133 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2134 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2135 grave problem that stops the assembly.
2139 @cindex format of warning messages
2140 Warning messages have the format
2143 file_name:@b{NNN}:Warning Message Text
2147 @cindex file names and line numbers, in warnings/errors
2148 (where @b{NNN} is a line number). If both a logical file name
2149 (@pxref{File,,@code{.file}}) and a logical line number
2151 (@pxref{Line,,@code{.line}})
2153 have been given then they will be used, otherwise the file name and line number
2154 in the current assembler source file will be used. The message text is
2155 intended to be self explanatory (in the grand Unix tradition).
2157 Note the file name must be set via the logical version of the @code{.file}
2158 directive, not the DWARF2 version of the @code{.file} directive. For example:
2162 error_assembler_source
2168 produces this output:
2172 asm.s:2: Error: no such instruction: `error_assembler_source'
2173 foo.c:31: Error: no such instruction: `error_c_source'
2176 @cindex format of error messages
2177 Error messages have the format
2180 file_name:@b{NNN}:FATAL:Error Message Text
2183 The file name and line number are derived as for warning
2184 messages. The actual message text may be rather less explanatory
2185 because many of them aren't supposed to happen.
2188 @chapter Command-Line Options
2190 @cindex options, all versions of assembler
2191 This chapter describes command-line options available in @emph{all}
2192 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2193 for options specific
2195 to the @value{TARGET} target.
2198 to particular machine architectures.
2201 @c man begin DESCRIPTION
2203 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2204 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2205 The assembler arguments must be separated from each other (and the @samp{-Wa})
2206 by commas. For example:
2209 gcc -c -g -O -Wa,-alh,-L file.c
2213 This passes two options to the assembler: @samp{-alh} (emit a listing to
2214 standard output with high-level and assembly source) and @samp{-L} (retain
2215 local symbols in the symbol table).
2217 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2218 command-line options are automatically passed to the assembler by the compiler.
2219 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2220 precisely what options it passes to each compilation pass, including the
2226 * a:: -a[cdghlns] enable listings
2227 * alternate:: --alternate enable alternate macro syntax
2228 * D:: -D for compatibility
2229 * f:: -f to work faster
2230 * I:: -I for .include search path
2231 @ifclear DIFF-TBL-KLUGE
2232 * K:: -K for compatibility
2234 @ifset DIFF-TBL-KLUGE
2235 * K:: -K for difference tables
2238 * L:: -L to retain local symbols
2239 * listing:: --listing-XXX to configure listing output
2240 * M:: -M or --mri to assemble in MRI compatibility mode
2241 * MD:: --MD for dependency tracking
2242 * no-pad-sections:: --no-pad-sections to stop section padding
2243 * o:: -o to name the object file
2244 * R:: -R to join data and text sections
2245 * statistics:: --statistics to see statistics about assembly
2246 * traditional-format:: --traditional-format for compatible output
2247 * v:: -v to announce version
2248 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2249 * Z:: -Z to make object file even after errors
2253 @section Enable Listings: @option{-a[cdghlns]}
2263 @cindex listings, enabling
2264 @cindex assembly listings, enabling
2266 These options enable listing output from the assembler. By itself,
2267 @samp{-a} requests high-level, assembly, and symbols listing.
2268 You can use other letters to select specific options for the list:
2269 @samp{-ah} requests a high-level language listing,
2270 @samp{-al} requests an output-program assembly listing, and
2271 @samp{-as} requests a symbol table listing.
2272 High-level listings require that a compiler debugging option like
2273 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2276 Use the @samp{-ag} option to print a first section with general assembly
2277 information, like @value{AS} version, switches passed, or time stamp.
2279 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2280 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2281 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2282 omitted from the listing.
2284 Use the @samp{-ad} option to omit debugging directives from the
2287 Once you have specified one of these options, you can further control
2288 listing output and its appearance using the directives @code{.list},
2289 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2291 The @samp{-an} option turns off all forms processing.
2292 If you do not request listing output with one of the @samp{-a} options, the
2293 listing-control directives have no effect.
2295 The letters after @samp{-a} may be combined into one option,
2296 @emph{e.g.}, @samp{-aln}.
2298 Note if the assembler source is coming from the standard input (e.g.,
2300 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2301 is being used) then the listing will not contain any comments or preprocessor
2302 directives. This is because the listing code buffers input source lines from
2303 stdin only after they have been preprocessed by the assembler. This reduces
2304 memory usage and makes the code more efficient.
2307 @section @option{--alternate}
2310 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2313 @section @option{-D}
2316 This option has no effect whatsoever, but it is accepted to make it more
2317 likely that scripts written for other assemblers also work with
2318 @command{@value{AS}}.
2321 @section Work Faster: @option{-f}
2324 @cindex trusted compiler
2325 @cindex faster processing (@option{-f})
2326 @samp{-f} should only be used when assembling programs written by a
2327 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2328 and comment preprocessing on
2329 the input file(s) before assembling them. @xref{Preprocessing,
2333 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2334 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2339 @section @code{.include} Search Path: @option{-I} @var{path}
2341 @kindex -I @var{path}
2342 @cindex paths for @code{.include}
2343 @cindex search path for @code{.include}
2344 @cindex @code{include} directive search path
2345 Use this option to add a @var{path} to the list of directories
2346 @command{@value{AS}} searches for files specified in @code{.include}
2347 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2348 many times as necessary to include a variety of paths. The current
2349 working directory is always searched first; after that, @command{@value{AS}}
2350 searches any @samp{-I} directories in the same order as they were
2351 specified (left to right) on the command line.
2354 @section Difference Tables: @option{-K}
2357 @ifclear DIFF-TBL-KLUGE
2358 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2359 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2360 where it can be used to warn when the assembler alters the machine code
2361 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2362 family does not have the addressing limitations that sometimes lead to this
2363 alteration on other platforms.
2366 @ifset DIFF-TBL-KLUGE
2367 @cindex difference tables, warning
2368 @cindex warning for altered difference tables
2369 @command{@value{AS}} sometimes alters the code emitted for directives of the
2370 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2371 You can use the @samp{-K} option if you want a warning issued when this
2376 @section Include Local Symbols: @option{-L}
2379 @cindex local symbols, retaining in output
2380 Symbols beginning with system-specific local label prefixes, typically
2381 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2382 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2383 such symbols when debugging, because they are intended for the use of
2384 programs (like compilers) that compose assembler programs, not for your
2385 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2386 such symbols, so you do not normally debug with them.
2388 This option tells @command{@value{AS}} to retain those local symbols
2389 in the object file. Usually if you do this you also tell the linker
2390 @code{@value{LD}} to preserve those symbols.
2393 @section Configuring listing output: @option{--listing}
2395 The listing feature of the assembler can be enabled via the command line switch
2396 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2397 hex dump of the corresponding locations in the output object file, and displays
2398 them as a listing file. The format of this listing can be controlled by
2399 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2400 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2401 @code{.psize} (@pxref{Psize}), and
2402 @code{.eject} (@pxref{Eject}) and also by the following switches:
2405 @item --listing-lhs-width=@samp{number}
2406 @kindex --listing-lhs-width
2407 @cindex Width of first line disassembly output
2408 Sets the maximum width, in words, of the first line of the hex byte dump. This
2409 dump appears on the left hand side of the listing output.
2411 @item --listing-lhs-width2=@samp{number}
2412 @kindex --listing-lhs-width2
2413 @cindex Width of continuation lines of disassembly output
2414 Sets the maximum width, in words, of any further lines of the hex byte dump for
2415 a given input source line. If this value is not specified, it defaults to being
2416 the same as the value specified for @samp{--listing-lhs-width}. If neither
2417 switch is used the default is to one.
2419 @item --listing-rhs-width=@samp{number}
2420 @kindex --listing-rhs-width
2421 @cindex Width of source line output
2422 Sets the maximum width, in characters, of the source line that is displayed
2423 alongside the hex dump. The default value for this parameter is 100. The
2424 source line is displayed on the right hand side of the listing output.
2426 @item --listing-cont-lines=@samp{number}
2427 @kindex --listing-cont-lines
2428 @cindex Maximum number of continuation lines
2429 Sets the maximum number of continuation lines of hex dump that will be
2430 displayed for a given single line of source input. The default value is 4.
2434 @section Assemble in MRI Compatibility Mode: @option{-M}
2437 @cindex MRI compatibility mode
2438 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2439 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2440 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2441 configured target) assembler from Microtec Research. The exact nature of the
2442 MRI syntax will not be documented here; see the MRI manuals for more
2443 information. Note in particular that the handling of macros and macro
2444 arguments is somewhat different. The purpose of this option is to permit
2445 assembling existing MRI assembler code using @command{@value{AS}}.
2447 The MRI compatibility is not complete. Certain operations of the MRI assembler
2448 depend upon its object file format, and can not be supported using other object
2449 file formats. Supporting these would require enhancing each object file format
2450 individually. These are:
2453 @item global symbols in common section
2455 The m68k MRI assembler supports common sections which are merged by the linker.
2456 Other object file formats do not support this. @command{@value{AS}} handles
2457 common sections by treating them as a single common symbol. It permits local
2458 symbols to be defined within a common section, but it can not support global
2459 symbols, since it has no way to describe them.
2461 @item complex relocations
2463 The MRI assemblers support relocations against a negated section address, and
2464 relocations which combine the start addresses of two or more sections. These
2465 are not support by other object file formats.
2467 @item @code{END} pseudo-op specifying start address
2469 The MRI @code{END} pseudo-op permits the specification of a start address.
2470 This is not supported by other object file formats. The start address may
2471 instead be specified using the @option{-e} option to the linker, or in a linker
2474 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2476 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2477 name to the output file. This is not supported by other object file formats.
2479 @item @code{ORG} pseudo-op
2481 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2482 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2483 which changes the location within the current section. Absolute sections are
2484 not supported by other object file formats. The address of a section may be
2485 assigned within a linker script.
2488 There are some other features of the MRI assembler which are not supported by
2489 @command{@value{AS}}, typically either because they are difficult or because they
2490 seem of little consequence. Some of these may be supported in future releases.
2494 @item EBCDIC strings
2496 EBCDIC strings are not supported.
2498 @item packed binary coded decimal
2500 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2501 and @code{DCB.P} pseudo-ops are not supported.
2503 @item @code{FEQU} pseudo-op
2505 The m68k @code{FEQU} pseudo-op is not supported.
2507 @item @code{NOOBJ} pseudo-op
2509 The m68k @code{NOOBJ} pseudo-op is not supported.
2511 @item @code{OPT} branch control options
2513 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2514 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2515 relaxes all branches, whether forward or backward, to an appropriate size, so
2516 these options serve no purpose.
2518 @item @code{OPT} list control options
2520 The following m68k @code{OPT} list control options are ignored: @code{C},
2521 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2522 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2524 @item other @code{OPT} options
2526 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2527 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2529 @item @code{OPT} @code{D} option is default
2531 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2532 @code{OPT NOD} may be used to turn it off.
2534 @item @code{XREF} pseudo-op.
2536 The m68k @code{XREF} pseudo-op is ignored.
2538 @item @code{.debug} pseudo-op
2540 The i960 @code{.debug} pseudo-op is not supported.
2542 @item @code{.extended} pseudo-op
2544 The i960 @code{.extended} pseudo-op is not supported.
2546 @item @code{.list} pseudo-op.
2548 The various options of the i960 @code{.list} pseudo-op are not supported.
2550 @item @code{.optimize} pseudo-op
2552 The i960 @code{.optimize} pseudo-op is not supported.
2554 @item @code{.output} pseudo-op
2556 The i960 @code{.output} pseudo-op is not supported.
2558 @item @code{.setreal} pseudo-op
2560 The i960 @code{.setreal} pseudo-op is not supported.
2565 @section Dependency Tracking: @option{--MD}
2568 @cindex dependency tracking
2571 @command{@value{AS}} can generate a dependency file for the file it creates. This
2572 file consists of a single rule suitable for @code{make} describing the
2573 dependencies of the main source file.
2575 The rule is written to the file named in its argument.
2577 This feature is used in the automatic updating of makefiles.
2579 @node no-pad-sections
2580 @section Output Section Padding
2581 @kindex --no-pad-sections
2582 @cindex output section padding
2583 Normally the assembler will pad the end of each output section up to its
2584 alignment boundary. But this can waste space, which can be significant on
2585 memory constrained targets. So the @option{--no-pad-sections} option will
2586 disable this behaviour.
2589 @section Name the Object File: @option{-o}
2592 @cindex naming object file
2593 @cindex object file name
2594 There is always one object file output when you run @command{@value{AS}}. By
2595 default it has the name
2598 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2612 You use this option (which takes exactly one filename) to give the
2613 object file a different name.
2615 Whatever the object file is called, @command{@value{AS}} overwrites any
2616 existing file of the same name.
2619 @section Join Data and Text Sections: @option{-R}
2622 @cindex data and text sections, joining
2623 @cindex text and data sections, joining
2624 @cindex joining text and data sections
2625 @cindex merging text and data sections
2626 @option{-R} tells @command{@value{AS}} to write the object file as if all
2627 data-section data lives in the text section. This is only done at
2628 the very last moment: your binary data are the same, but data
2629 section parts are relocated differently. The data section part of
2630 your object file is zero bytes long because all its bytes are
2631 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2633 When you specify @option{-R} it would be possible to generate shorter
2634 address displacements (because we do not have to cross between text and
2635 data section). We refrain from doing this simply for compatibility with
2636 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2639 When @command{@value{AS}} is configured for COFF or ELF output,
2640 this option is only useful if you use sections named @samp{.text} and
2645 @option{-R} is not supported for any of the HPPA targets. Using
2646 @option{-R} generates a warning from @command{@value{AS}}.
2650 @section Display Assembly Statistics: @option{--statistics}
2652 @kindex --statistics
2653 @cindex statistics, about assembly
2654 @cindex time, total for assembly
2655 @cindex space used, maximum for assembly
2656 Use @samp{--statistics} to display two statistics about the resources used by
2657 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2658 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2661 @node traditional-format
2662 @section Compatible Output: @option{--traditional-format}
2664 @kindex --traditional-format
2665 For some targets, the output of @command{@value{AS}} is different in some ways
2666 from the output of some existing assembler. This switch requests
2667 @command{@value{AS}} to use the traditional format instead.
2669 For example, it disables the exception frame optimizations which
2670 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2673 @section Announce Version: @option{-v}
2677 @cindex assembler version
2678 @cindex version of assembler
2679 You can find out what version of as is running by including the
2680 option @samp{-v} (which you can also spell as @samp{-version}) on the
2684 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2686 @command{@value{AS}} should never give a warning or error message when
2687 assembling compiler output. But programs written by people often
2688 cause @command{@value{AS}} to give a warning that a particular assumption was
2689 made. All such warnings are directed to the standard error file.
2693 @cindex suppressing warnings
2694 @cindex warnings, suppressing
2695 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2696 This only affects the warning messages: it does not change any particular of
2697 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2700 @kindex --fatal-warnings
2701 @cindex errors, caused by warnings
2702 @cindex warnings, causing error
2703 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2704 files that generate warnings to be in error.
2707 @cindex warnings, switching on
2708 You can switch these options off again by specifying @option{--warn}, which
2709 causes warnings to be output as usual.
2712 @section Generate Object File in Spite of Errors: @option{-Z}
2713 @cindex object file, after errors
2714 @cindex errors, continuing after
2715 After an error message, @command{@value{AS}} normally produces no output. If for
2716 some reason you are interested in object file output even after
2717 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2718 option. If there are any errors, @command{@value{AS}} continues anyways, and
2719 writes an object file after a final warning message of the form @samp{@var{n}
2720 errors, @var{m} warnings, generating bad object file.}
2725 @cindex machine-independent syntax
2726 @cindex syntax, machine-independent
2727 This chapter describes the machine-independent syntax allowed in a
2728 source file. @command{@value{AS}} syntax is similar to what many other
2729 assemblers use; it is inspired by the BSD 4.2
2734 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2738 * Preprocessing:: Preprocessing
2739 * Whitespace:: Whitespace
2740 * Comments:: Comments
2741 * Symbol Intro:: Symbols
2742 * Statements:: Statements
2743 * Constants:: Constants
2747 @section Preprocessing
2749 @cindex preprocessing
2750 The @command{@value{AS}} internal preprocessor:
2752 @cindex whitespace, removed by preprocessor
2754 adjusts and removes extra whitespace. It leaves one space or tab before
2755 the keywords on a line, and turns any other whitespace on the line into
2758 @cindex comments, removed by preprocessor
2760 removes all comments, replacing them with a single space, or an
2761 appropriate number of newlines.
2763 @cindex constants, converted by preprocessor
2765 converts character constants into the appropriate numeric values.
2768 It does not do macro processing, include file handling, or
2769 anything else you may get from your C compiler's preprocessor. You can
2770 do include file processing with the @code{.include} directive
2771 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2772 to get other ``CPP'' style preprocessing by giving the input file a
2773 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2774 Output, gcc info, Using GNU CC}.
2776 Excess whitespace, comments, and character constants
2777 cannot be used in the portions of the input text that are not
2780 @cindex turning preprocessing on and off
2781 @cindex preprocessing, turning on and off
2784 If the first line of an input file is @code{#NO_APP} or if you use the
2785 @samp{-f} option, whitespace and comments are not removed from the input file.
2786 Within an input file, you can ask for whitespace and comment removal in
2787 specific portions of the by putting a line that says @code{#APP} before the
2788 text that may contain whitespace or comments, and putting a line that says
2789 @code{#NO_APP} after this text. This feature is mainly intend to support
2790 @code{asm} statements in compilers whose output is otherwise free of comments
2797 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2798 Whitespace is used to separate symbols, and to make programs neater for
2799 people to read. Unless within character constants
2800 (@pxref{Characters,,Character Constants}), any whitespace means the same
2801 as exactly one space.
2807 There are two ways of rendering comments to @command{@value{AS}}. In both
2808 cases the comment is equivalent to one space.
2810 Anything from @samp{/*} through the next @samp{*/} is a comment.
2811 This means you may not nest these comments.
2815 The only way to include a newline ('\n') in a comment
2816 is to use this sort of comment.
2819 /* This sort of comment does not nest. */
2822 @cindex line comment character
2823 Anything from a @dfn{line comment} character up to the next newline is
2824 considered a comment and is ignored. The line comment character is target
2825 specific, and some targets multiple comment characters. Some targets also have
2826 line comment characters that only work if they are the first character on a
2827 line. Some targets use a sequence of two characters to introduce a line
2828 comment. Some targets can also change their line comment characters depending
2829 upon command line options that have been used. For more details see the
2830 @emph{Syntax} section in the documentation for individual targets.
2832 If the line comment character is the hash sign (@samp{#}) then it still has the
2833 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2834 to specify logical line numbers:
2837 @cindex lines starting with @code{#}
2838 @cindex logical line numbers
2839 To be compatible with past assemblers, lines that begin with @samp{#} have a
2840 special interpretation. Following the @samp{#} should be an absolute
2841 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2842 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2843 new logical file name. The rest of the line, if any, should be whitespace.
2845 If the first non-whitespace characters on the line are not numeric,
2846 the line is ignored. (Just like a comment.)
2849 # This is an ordinary comment.
2850 # 42-6 "new_file_name" # New logical file name
2851 # This is logical line # 36.
2853 This feature is deprecated, and may disappear from future versions
2854 of @command{@value{AS}}.
2859 @cindex characters used in symbols
2860 @ifclear SPECIAL-SYMS
2861 A @dfn{symbol} is one or more characters chosen from the set of all
2862 letters (both upper and lower case), digits and the three characters
2868 A @dfn{symbol} is one or more characters chosen from the set of all
2869 letters (both upper and lower case), digits and the three characters
2870 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2876 On most machines, you can also use @code{$} in symbol names; exceptions
2877 are noted in @ref{Machine Dependencies}.
2879 No symbol may begin with a digit. Case is significant.
2880 There is no length limit; all characters are significant. Multibyte characters
2881 are supported. Symbols are delimited by characters not in that set, or by the
2882 beginning of a file (since the source program must end with a newline, the end
2883 of a file is not a possible symbol delimiter). @xref{Symbols}.
2885 Symbol names may also be enclosed in double quote @code{"} characters. In such
2886 cases any characters are allowed, except for the NUL character. If a double
2887 quote character is to be included in the symbol name it must be preceeded by a
2888 backslash @code{\} character.
2889 @cindex length of symbols
2894 @cindex statements, structure of
2895 @cindex line separator character
2896 @cindex statement separator character
2898 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2899 @dfn{line separator character}. The line separator character is target
2900 specific and described in the @emph{Syntax} section of each
2901 target's documentation. Not all targets support a line separator character.
2902 The newline or line separator character is considered to be part of the
2903 preceding statement. Newlines and separators within character constants are an
2904 exception: they do not end statements.
2906 @cindex newline, required at file end
2907 @cindex EOF, newline must precede
2908 It is an error to end any statement with end-of-file: the last
2909 character of any input file should be a newline.@refill
2911 An empty statement is allowed, and may include whitespace. It is ignored.
2913 @cindex instructions and directives
2914 @cindex directives and instructions
2915 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2916 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2918 A statement begins with zero or more labels, optionally followed by a
2919 key symbol which determines what kind of statement it is. The key
2920 symbol determines the syntax of the rest of the statement. If the
2921 symbol begins with a dot @samp{.} then the statement is an assembler
2922 directive: typically valid for any computer. If the symbol begins with
2923 a letter the statement is an assembly language @dfn{instruction}: it
2924 assembles into a machine language instruction.
2926 Different versions of @command{@value{AS}} for different computers
2927 recognize different instructions. In fact, the same symbol may
2928 represent a different instruction in a different computer's assembly
2932 @cindex @code{:} (label)
2933 @cindex label (@code{:})
2934 A label is a symbol immediately followed by a colon (@code{:}).
2935 Whitespace before a label or after a colon is permitted, but you may not
2936 have whitespace between a label's symbol and its colon. @xref{Labels}.
2939 For HPPA targets, labels need not be immediately followed by a colon, but
2940 the definition of a label must begin in column zero. This also implies that
2941 only one label may be defined on each line.
2945 label: .directive followed by something
2946 another_label: # This is an empty statement.
2947 instruction operand_1, operand_2, @dots{}
2954 A constant is a number, written so that its value is known by
2955 inspection, without knowing any context. Like this:
2958 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2959 .ascii "Ring the bell\7" # A string constant.
2960 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2961 .float 0f-314159265358979323846264338327\
2962 95028841971.693993751E-40 # - pi, a flonum.
2967 * Characters:: Character Constants
2968 * Numbers:: Number Constants
2972 @subsection Character Constants
2974 @cindex character constants
2975 @cindex constants, character
2976 There are two kinds of character constants. A @dfn{character} stands
2977 for one character in one byte and its value may be used in
2978 numeric expressions. String constants (properly called string
2979 @emph{literals}) are potentially many bytes and their values may not be
2980 used in arithmetic expressions.
2984 * Chars:: Characters
2988 @subsubsection Strings
2990 @cindex string constants
2991 @cindex constants, string
2992 A @dfn{string} is written between double-quotes. It may contain
2993 double-quotes or null characters. The way to get special characters
2994 into a string is to @dfn{escape} these characters: precede them with
2995 a backslash @samp{\} character. For example @samp{\\} represents
2996 one backslash: the first @code{\} is an escape which tells
2997 @command{@value{AS}} to interpret the second character literally as a backslash
2998 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2999 escape character). The complete list of escapes follows.
3001 @cindex escape codes, character
3002 @cindex character escape codes
3003 @c NOTE: Cindex entries must not start with a backlash character.
3004 @c NOTE: This confuses the pdf2texi script when it is creating the
3005 @c NOTE: index based upon the first character and so it generates:
3006 @c NOTE: \initial {\\}
3007 @c NOTE: which then results in the error message:
3008 @c NOTE: Argument of \\ has an extra }.
3009 @c NOTE: So in the index entries below a space character has been
3010 @c NOTE: prepended to avoid this problem.
3013 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3015 @cindex @code{ \b} (backspace character)
3016 @cindex backspace (@code{\b})
3018 Mnemonic for backspace; for ASCII this is octal code 010.
3021 @c Mnemonic for EOText; for ASCII this is octal code 004.
3023 @cindex @code{ \f} (formfeed character)
3024 @cindex formfeed (@code{\f})
3026 Mnemonic for FormFeed; for ASCII this is octal code 014.
3028 @cindex @code{ \n} (newline character)
3029 @cindex newline (@code{\n})
3031 Mnemonic for newline; for ASCII this is octal code 012.
3034 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3036 @cindex @code{ \r} (carriage return character)
3037 @cindex carriage return (@code{backslash-r})
3039 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3042 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3043 @c other assemblers.
3045 @cindex @code{ \t} (tab)
3046 @cindex tab (@code{\t})
3048 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3051 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3052 @c @item \x @var{digit} @var{digit} @var{digit}
3053 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3055 @cindex @code{ \@var{ddd}} (octal character code)
3056 @cindex octal character code (@code{\@var{ddd}})
3057 @item \ @var{digit} @var{digit} @var{digit}
3058 An octal character code. The numeric code is 3 octal digits.
3059 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3060 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3062 @cindex @code{ \@var{xd...}} (hex character code)
3063 @cindex hex character code (@code{\@var{xd...}})
3064 @item \@code{x} @var{hex-digits...}
3065 A hex character code. All trailing hex digits are combined. Either upper or
3066 lower case @code{x} works.
3068 @cindex @code{ \\} (@samp{\} character)
3069 @cindex backslash (@code{\\})
3071 Represents one @samp{\} character.
3074 @c Represents one @samp{'} (accent acute) character.
3075 @c This is needed in single character literals
3076 @c (@xref{Characters,,Character Constants}.) to represent
3079 @cindex @code{ \"} (doublequote character)
3080 @cindex doublequote (@code{\"})
3082 Represents one @samp{"} character. Needed in strings to represent
3083 this character, because an unescaped @samp{"} would end the string.
3085 @item \ @var{anything-else}
3086 Any other character when escaped by @kbd{\} gives a warning, but
3087 assembles as if the @samp{\} was not present. The idea is that if
3088 you used an escape sequence you clearly didn't want the literal
3089 interpretation of the following character. However @command{@value{AS}} has no
3090 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3091 code and warns you of the fact.
3094 Which characters are escapable, and what those escapes represent,
3095 varies widely among assemblers. The current set is what we think
3096 the BSD 4.2 assembler recognizes, and is a subset of what most C
3097 compilers recognize. If you are in doubt, do not use an escape
3101 @subsubsection Characters
3103 @cindex single character constant
3104 @cindex character, single
3105 @cindex constant, single character
3106 A single character may be written as a single quote immediately followed by
3107 that character. Some backslash escapes apply to characters, @code{\b},
3108 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3109 as for strings, plus @code{\'} for a single quote. So if you want to write the
3110 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3111 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3114 @ifclear abnormal-separator
3115 (or semicolon @samp{;})
3117 @ifset abnormal-separator
3119 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3124 immediately following an acute accent is taken as a literal character
3125 and does not count as the end of a statement. The value of a character
3126 constant in a numeric expression is the machine's byte-wide code for
3127 that character. @command{@value{AS}} assumes your character code is ASCII:
3128 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3131 @subsection Number Constants
3133 @cindex constants, number
3134 @cindex number constants
3135 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3136 are stored in the target machine. @emph{Integers} are numbers that
3137 would fit into an @code{int} in the C language. @emph{Bignums} are
3138 integers, but they are stored in more than 32 bits. @emph{Flonums}
3139 are floating point numbers, described below.
3142 * Integers:: Integers
3147 * Bit Fields:: Bit Fields
3153 @subsubsection Integers
3155 @cindex constants, integer
3157 @cindex binary integers
3158 @cindex integers, binary
3159 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3160 the binary digits @samp{01}.
3162 @cindex octal integers
3163 @cindex integers, octal
3164 An octal integer is @samp{0} followed by zero or more of the octal
3165 digits (@samp{01234567}).
3167 @cindex decimal integers
3168 @cindex integers, decimal
3169 A decimal integer starts with a non-zero digit followed by zero or
3170 more digits (@samp{0123456789}).
3172 @cindex hexadecimal integers
3173 @cindex integers, hexadecimal
3174 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3175 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3177 Integers have the usual values. To denote a negative integer, use
3178 the prefix operator @samp{-} discussed under expressions
3179 (@pxref{Prefix Ops,,Prefix Operators}).
3182 @subsubsection Bignums
3185 @cindex constants, bignum
3186 A @dfn{bignum} has the same syntax and semantics as an integer
3187 except that the number (or its negative) takes more than 32 bits to
3188 represent in binary. The distinction is made because in some places
3189 integers are permitted while bignums are not.
3192 @subsubsection Flonums
3194 @cindex floating point numbers
3195 @cindex constants, floating point
3197 @cindex precision, floating point
3198 A @dfn{flonum} represents a floating point number. The translation is
3199 indirect: a decimal floating point number from the text is converted by
3200 @command{@value{AS}} to a generic binary floating point number of more than
3201 sufficient precision. This generic floating point number is converted
3202 to a particular computer's floating point format (or formats) by a
3203 portion of @command{@value{AS}} specialized to that computer.
3205 A flonum is written by writing (in order)
3210 (@samp{0} is optional on the HPPA.)
3214 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3216 @kbd{e} is recommended. Case is not important.
3218 @c FIXME: verify if flonum syntax really this vague for most cases
3219 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3220 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3223 On the H8/300, Renesas / SuperH SH,
3224 and AMD 29K architectures, the letter must be
3225 one of the letters @samp{DFPRSX} (in upper or lower case).
3227 On the ARC, the letter must be one of the letters @samp{DFRS}
3228 (in upper or lower case).
3230 On the Intel 960 architecture, the letter must be
3231 one of the letters @samp{DFT} (in upper or lower case).
3233 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3237 One of the letters @samp{DFRS} (in upper or lower case).
3240 One of the letters @samp{DFPRSX} (in upper or lower case).
3243 The letter @samp{E} (upper case only).
3246 One of the letters @samp{DFT} (in upper or lower case).
3251 An optional sign: either @samp{+} or @samp{-}.
3254 An optional @dfn{integer part}: zero or more decimal digits.
3257 An optional @dfn{fractional part}: @samp{.} followed by zero
3258 or more decimal digits.
3261 An optional exponent, consisting of:
3265 An @samp{E} or @samp{e}.
3266 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3267 @c principle this can perfectly well be different on different targets.
3269 Optional sign: either @samp{+} or @samp{-}.
3271 One or more decimal digits.
3276 At least one of the integer part or the fractional part must be
3277 present. The floating point number has the usual base-10 value.
3279 @command{@value{AS}} does all processing using integers. Flonums are computed
3280 independently of any floating point hardware in the computer running
3281 @command{@value{AS}}.
3285 @c Bit fields are written as a general facility but are also controlled
3286 @c by a conditional-compilation flag---which is as of now (21mar91)
3287 @c turned on only by the i960 config of GAS.
3289 @subsubsection Bit Fields
3292 @cindex constants, bit field
3293 You can also define numeric constants as @dfn{bit fields}.
3294 Specify two numbers separated by a colon---
3296 @var{mask}:@var{value}
3299 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3302 The resulting number is then packed
3304 @c this conditional paren in case bit fields turned on elsewhere than 960
3305 (in host-dependent byte order)
3307 into a field whose width depends on which assembler directive has the
3308 bit-field as its argument. Overflow (a result from the bitwise and
3309 requiring more binary digits to represent) is not an error; instead,
3310 more constants are generated, of the specified width, beginning with the
3311 least significant digits.@refill
3313 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3314 @code{.short}, and @code{.word} accept bit-field arguments.
3319 @chapter Sections and Relocation
3324 * Secs Background:: Background
3325 * Ld Sections:: Linker Sections
3326 * As Sections:: Assembler Internal Sections
3327 * Sub-Sections:: Sub-Sections
3331 @node Secs Background
3334 Roughly, a section is a range of addresses, with no gaps; all data
3335 ``in'' those addresses is treated the same for some particular purpose.
3336 For example there may be a ``read only'' section.
3338 @cindex linker, and assembler
3339 @cindex assembler, and linker
3340 The linker @code{@value{LD}} reads many object files (partial programs) and
3341 combines their contents to form a runnable program. When @command{@value{AS}}
3342 emits an object file, the partial program is assumed to start at address 0.
3343 @code{@value{LD}} assigns the final addresses for the partial program, so that
3344 different partial programs do not overlap. This is actually an
3345 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3348 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3349 addresses. These blocks slide to their run-time addresses as rigid
3350 units; their length does not change and neither does the order of bytes
3351 within them. Such a rigid unit is called a @emph{section}. Assigning
3352 run-time addresses to sections is called @dfn{relocation}. It includes
3353 the task of adjusting mentions of object-file addresses so they refer to
3354 the proper run-time addresses.
3356 For the H8/300, and for the Renesas / SuperH SH,
3357 @command{@value{AS}} pads sections if needed to
3358 ensure they end on a word (sixteen bit) boundary.
3361 @cindex standard assembler sections
3362 An object file written by @command{@value{AS}} has at least three sections, any
3363 of which may be empty. These are named @dfn{text}, @dfn{data} and
3368 When it generates COFF or ELF output,
3370 @command{@value{AS}} can also generate whatever other named sections you specify
3371 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3372 If you do not use any directives that place output in the @samp{.text}
3373 or @samp{.data} sections, these sections still exist, but are empty.
3378 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3380 @command{@value{AS}} can also generate whatever other named sections you
3381 specify using the @samp{.space} and @samp{.subspace} directives. See
3382 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3383 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3384 assembler directives.
3387 Additionally, @command{@value{AS}} uses different names for the standard
3388 text, data, and bss sections when generating SOM output. Program text
3389 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3390 BSS into @samp{$BSS$}.
3394 Within the object file, the text section starts at address @code{0}, the
3395 data section follows, and the bss section follows the data section.
3398 When generating either SOM or ELF output files on the HPPA, the text
3399 section starts at address @code{0}, the data section at address
3400 @code{0x4000000}, and the bss section follows the data section.
3403 To let @code{@value{LD}} know which data changes when the sections are
3404 relocated, and how to change that data, @command{@value{AS}} also writes to the
3405 object file details of the relocation needed. To perform relocation
3406 @code{@value{LD}} must know, each time an address in the object
3410 Where in the object file is the beginning of this reference to
3413 How long (in bytes) is this reference?
3415 Which section does the address refer to? What is the numeric value of
3417 (@var{address}) @minus{} (@var{start-address of section})?
3420 Is the reference to an address ``Program-Counter relative''?
3423 @cindex addresses, format of
3424 @cindex section-relative addressing
3425 In fact, every address @command{@value{AS}} ever uses is expressed as
3427 (@var{section}) + (@var{offset into section})
3430 Further, most expressions @command{@value{AS}} computes have this section-relative
3433 (For some object formats, such as SOM for the HPPA, some expressions are
3434 symbol-relative instead.)
3437 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3438 @var{N} into section @var{secname}.''
3440 Apart from text, data and bss sections you need to know about the
3441 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3442 addresses in the absolute section remain unchanged. For example, address
3443 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3444 @code{@value{LD}}. Although the linker never arranges two partial programs'
3445 data sections with overlapping addresses after linking, @emph{by definition}
3446 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3447 part of a program is always the same address when the program is running as
3448 address @code{@{absolute@ 239@}} in any other part of the program.
3450 The idea of sections is extended to the @dfn{undefined} section. Any
3451 address whose section is unknown at assembly time is by definition
3452 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3453 Since numbers are always defined, the only way to generate an undefined
3454 address is to mention an undefined symbol. A reference to a named
3455 common block would be such a symbol: its value is unknown at assembly
3456 time so it has section @emph{undefined}.
3458 By analogy the word @emph{section} is used to describe groups of sections in
3459 the linked program. @code{@value{LD}} puts all partial programs' text
3460 sections in contiguous addresses in the linked program. It is
3461 customary to refer to the @emph{text section} of a program, meaning all
3462 the addresses of all partial programs' text sections. Likewise for
3463 data and bss sections.
3465 Some sections are manipulated by @code{@value{LD}}; others are invented for
3466 use of @command{@value{AS}} and have no meaning except during assembly.
3469 @section Linker Sections
3470 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3475 @cindex named sections
3476 @cindex sections, named
3477 @item named sections
3480 @cindex text section
3481 @cindex data section
3485 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3486 separate but equal sections. Anything you can say of one section is
3489 When the program is running, however, it is
3490 customary for the text section to be unalterable. The
3491 text section is often shared among processes: it contains
3492 instructions, constants and the like. The data section of a running
3493 program is usually alterable: for example, C variables would be stored
3494 in the data section.
3499 This section contains zeroed bytes when your program begins running. It
3500 is used to hold uninitialized variables or common storage. The length of
3501 each partial program's bss section is important, but because it starts
3502 out containing zeroed bytes there is no need to store explicit zero
3503 bytes in the object file. The bss section was invented to eliminate
3504 those explicit zeros from object files.
3506 @cindex absolute section
3507 @item absolute section
3508 Address 0 of this section is always ``relocated'' to runtime address 0.
3509 This is useful if you want to refer to an address that @code{@value{LD}} must
3510 not change when relocating. In this sense we speak of absolute
3511 addresses being ``unrelocatable'': they do not change during relocation.
3513 @cindex undefined section
3514 @item undefined section
3515 This ``section'' is a catch-all for address references to objects not in
3516 the preceding sections.
3517 @c FIXME: ref to some other doc on obj-file formats could go here.
3520 @cindex relocation example
3521 An idealized example of three relocatable sections follows.
3523 The example uses the traditional section names @samp{.text} and @samp{.data}.
3525 Memory addresses are on the horizontal axis.
3529 @c END TEXI2ROFF-KILL
3532 partial program # 1: |ttttt|dddd|00|
3539 partial program # 2: |TTT|DDD|000|
3542 +--+---+-----+--+----+---+-----+~~
3543 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3544 +--+---+-----+--+----+---+-----+~~
3546 addresses: 0 @dots{}
3553 \line{\it Partial program \#1: \hfil}
3554 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3555 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3557 \line{\it Partial program \#2: \hfil}
3558 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3559 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3561 \line{\it linked program: \hfil}
3562 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3563 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3564 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3565 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3567 \line{\it addresses: \hfil}
3571 @c END TEXI2ROFF-KILL
3574 @section Assembler Internal Sections
3576 @cindex internal assembler sections
3577 @cindex sections in messages, internal
3578 These sections are meant only for the internal use of @command{@value{AS}}. They
3579 have no meaning at run-time. You do not really need to know about these
3580 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3581 warning messages, so it might be helpful to have an idea of their
3582 meanings to @command{@value{AS}}. These sections are used to permit the
3583 value of every expression in your assembly language program to be a
3584 section-relative address.
3587 @cindex assembler internal logic error
3588 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3589 An internal assembler logic error has been found. This means there is a
3590 bug in the assembler.
3592 @cindex expr (internal section)
3594 The assembler stores complex expression internally as combinations of
3595 symbols. When it needs to represent an expression as a symbol, it puts
3596 it in the expr section.
3598 @c FIXME item transfer[t] vector preload
3599 @c FIXME item transfer[t] vector postload
3600 @c FIXME item register
3604 @section Sub-Sections
3606 @cindex numbered subsections
3607 @cindex grouping data
3613 fall into two sections: text and data.
3615 You may have separate groups of
3617 data in named sections
3621 data in named sections
3627 that you want to end up near to each other in the object file, even though they
3628 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3629 use @dfn{subsections} for this purpose. Within each section, there can be
3630 numbered subsections with values from 0 to 8192. Objects assembled into the
3631 same subsection go into the object file together with other objects in the same
3632 subsection. For example, a compiler might want to store constants in the text
3633 section, but might not want to have them interspersed with the program being
3634 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3635 section of code being output, and a @samp{.text 1} before each group of
3636 constants being output.
3638 Subsections are optional. If you do not use subsections, everything
3639 goes in subsection number zero.
3642 Each subsection is zero-padded up to a multiple of four bytes.
3643 (Subsections may be padded a different amount on different flavors
3644 of @command{@value{AS}}.)
3648 On the H8/300 platform, each subsection is zero-padded to a word
3649 boundary (two bytes).
3650 The same is true on the Renesas SH.
3653 @c FIXME section padding (alignment)?
3654 @c Rich Pixley says padding here depends on target obj code format; that
3655 @c doesn't seem particularly useful to say without further elaboration,
3656 @c so for now I say nothing about it. If this is a generic BFD issue,
3657 @c these paragraphs might need to vanish from this manual, and be
3658 @c discussed in BFD chapter of binutils (or some such).
3662 Subsections appear in your object file in numeric order, lowest numbered
3663 to highest. (All this to be compatible with other people's assemblers.)
3664 The object file contains no representation of subsections; @code{@value{LD}} and
3665 other programs that manipulate object files see no trace of them.
3666 They just see all your text subsections as a text section, and all your
3667 data subsections as a data section.
3669 To specify which subsection you want subsequent statements assembled
3670 into, use a numeric argument to specify it, in a @samp{.text
3671 @var{expression}} or a @samp{.data @var{expression}} statement.
3674 When generating COFF output, you
3679 can also use an extra subsection
3680 argument with arbitrary named sections: @samp{.section @var{name},
3685 When generating ELF output, you
3690 can also use the @code{.subsection} directive (@pxref{SubSection})
3691 to specify a subsection: @samp{.subsection @var{expression}}.
3693 @var{Expression} should be an absolute expression
3694 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3695 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3696 begins in @code{text 0}. For instance:
3698 .text 0 # The default subsection is text 0 anyway.
3699 .ascii "This lives in the first text subsection. *"
3701 .ascii "But this lives in the second text subsection."
3703 .ascii "This lives in the data section,"
3704 .ascii "in the first data subsection."
3706 .ascii "This lives in the first text section,"
3707 .ascii "immediately following the asterisk (*)."
3710 Each section has a @dfn{location counter} incremented by one for every byte
3711 assembled into that section. Because subsections are merely a convenience
3712 restricted to @command{@value{AS}} there is no concept of a subsection location
3713 counter. There is no way to directly manipulate a location counter---but the
3714 @code{.align} directive changes it, and any label definition captures its
3715 current value. The location counter of the section where statements are being
3716 assembled is said to be the @dfn{active} location counter.
3719 @section bss Section
3722 @cindex common variable storage
3723 The bss section is used for local common variable storage.
3724 You may allocate address space in the bss section, but you may
3725 not dictate data to load into it before your program executes. When
3726 your program starts running, all the contents of the bss
3727 section are zeroed bytes.
3729 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3730 @ref{Lcomm,,@code{.lcomm}}.
3732 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3733 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3736 When assembling for a target which supports multiple sections, such as ELF or
3737 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3738 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3739 section. Typically the section will only contain symbol definitions and
3740 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3747 Symbols are a central concept: the programmer uses symbols to name
3748 things, the linker uses symbols to link, and the debugger uses symbols
3752 @cindex debuggers, and symbol order
3753 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3754 the same order they were declared. This may break some debuggers.
3759 * Setting Symbols:: Giving Symbols Other Values
3760 * Symbol Names:: Symbol Names
3761 * Dot:: The Special Dot Symbol
3762 * Symbol Attributes:: Symbol Attributes
3769 A @dfn{label} is written as a symbol immediately followed by a colon
3770 @samp{:}. The symbol then represents the current value of the
3771 active location counter, and is, for example, a suitable instruction
3772 operand. You are warned if you use the same symbol to represent two
3773 different locations: the first definition overrides any other
3777 On the HPPA, the usual form for a label need not be immediately followed by a
3778 colon, but instead must start in column zero. Only one label may be defined on
3779 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3780 provides a special directive @code{.label} for defining labels more flexibly.
3783 @node Setting Symbols
3784 @section Giving Symbols Other Values
3786 @cindex assigning values to symbols
3787 @cindex symbol values, assigning
3788 A symbol can be given an arbitrary value by writing a symbol, followed
3789 by an equals sign @samp{=}, followed by an expression
3790 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3791 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3792 equals sign @samp{=}@samp{=} here represents an equivalent of the
3793 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3796 Blackfin does not support symbol assignment with @samp{=}.
3800 @section Symbol Names
3802 @cindex symbol names
3803 @cindex names, symbol
3804 @ifclear SPECIAL-SYMS
3805 Symbol names begin with a letter or with one of @samp{._}. On most
3806 machines, you can also use @code{$} in symbol names; exceptions are
3807 noted in @ref{Machine Dependencies}. That character may be followed by any
3808 string of digits, letters, dollar signs (unless otherwise noted for a
3809 particular target machine), and underscores.
3813 Symbol names begin with a letter or with one of @samp{._}. On the
3814 Renesas SH you can also use @code{$} in symbol names. That
3815 character may be followed by any string of digits, letters, dollar signs (save
3816 on the H8/300), and underscores.
3820 Case of letters is significant: @code{foo} is a different symbol name
3823 Symbol names do not start with a digit. An exception to this rule is made for
3824 Local Labels. See below.
3826 Multibyte characters are supported. To generate a symbol name containing
3827 multibyte characters enclose it within double quotes and use escape codes. cf
3828 @xref{Strings}. Generating a multibyte symbol name from a label is not
3829 currently supported.
3831 Each symbol has exactly one name. Each name in an assembly language program
3832 refers to exactly one symbol. You may use that symbol name any number of times
3835 @subheading Local Symbol Names
3837 @cindex local symbol names
3838 @cindex symbol names, local
3839 A local symbol is any symbol beginning with certain local label prefixes.
3840 By default, the local label prefix is @samp{.L} for ELF systems or
3841 @samp{L} for traditional a.out systems, but each target may have its own
3842 set of local label prefixes.
3844 On the HPPA local symbols begin with @samp{L$}.
3847 Local symbols are defined and used within the assembler, but they are
3848 normally not saved in object files. Thus, they are not visible when debugging.
3849 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3850 to retain the local symbols in the object files.
3852 @subheading Local Labels
3854 @cindex local labels
3855 @cindex temporary symbol names
3856 @cindex symbol names, temporary
3857 Local labels are different from local symbols. Local labels help compilers and
3858 programmers use names temporarily. They create symbols which are guaranteed to
3859 be unique over the entire scope of the input source code and which can be
3860 referred to by a simple notation. To define a local label, write a label of
3861 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3862 To refer to the most recent previous definition of that label write
3863 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3864 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3865 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3867 There is no restriction on how you can use these labels, and you can reuse them
3868 too. So that it is possible to repeatedly define the same local label (using
3869 the same number @samp{@b{N}}), although you can only refer to the most recently
3870 defined local label of that number (for a backwards reference) or the next
3871 definition of a specific local label for a forward reference. It is also worth
3872 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3873 implemented in a slightly more efficient manner than the others.
3884 Which is the equivalent of:
3887 label_1: branch label_3
3888 label_2: branch label_1
3889 label_3: branch label_4
3890 label_4: branch label_3
3893 Local label names are only a notational device. They are immediately
3894 transformed into more conventional symbol names before the assembler uses them.
3895 The symbol names are stored in the symbol table, appear in error messages, and
3896 are optionally emitted to the object file. The names are constructed using
3900 @item @emph{local label prefix}
3901 All local symbols begin with the system-specific local label prefix.
3902 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3903 that start with the local label prefix. These labels are
3904 used for symbols you are never intended to see. If you use the
3905 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3906 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3907 you may use them in debugging.
3910 This is the number that was used in the local label definition. So if the
3911 label is written @samp{55:} then the number is @samp{55}.
3914 This unusual character is included so you do not accidentally invent a symbol
3915 of the same name. The character has ASCII value of @samp{\002} (control-B).
3917 @item @emph{ordinal number}
3918 This is a serial number to keep the labels distinct. The first definition of
3919 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3920 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3921 the number @samp{1} and its 15th definition gets @samp{15} as well.
3924 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3925 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3927 @subheading Dollar Local Labels
3928 @cindex dollar local symbols
3930 On some targets @code{@value{AS}} also supports an even more local form of
3931 local labels called dollar labels. These labels go out of scope (i.e., they
3932 become undefined) as soon as a non-local label is defined. Thus they remain
3933 valid for only a small region of the input source code. Normal local labels,
3934 by contrast, remain in scope for the entire file, or until they are redefined
3935 by another occurrence of the same local label.
3937 Dollar labels are defined in exactly the same way as ordinary local labels,
3938 except that they have a dollar sign suffix to their numeric value, e.g.,
3941 They can also be distinguished from ordinary local labels by their transformed
3942 names which use ASCII character @samp{\001} (control-A) as the magic character
3943 to distinguish them from ordinary labels. For example, the fifth definition of
3944 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3947 @section The Special Dot Symbol
3949 @cindex dot (symbol)
3950 @cindex @code{.} (symbol)
3951 @cindex current address
3952 @cindex location counter
3953 The special symbol @samp{.} refers to the current address that
3954 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3955 .long .} defines @code{melvin} to contain its own address.
3956 Assigning a value to @code{.} is treated the same as a @code{.org}
3958 @ifclear no-space-dir
3959 Thus, the expression @samp{.=.+4} is the same as saying
3963 @node Symbol Attributes
3964 @section Symbol Attributes
3966 @cindex symbol attributes
3967 @cindex attributes, symbol
3968 Every symbol has, as well as its name, the attributes ``Value'' and
3969 ``Type''. Depending on output format, symbols can also have auxiliary
3972 The detailed definitions are in @file{a.out.h}.
3975 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3976 all these attributes, and probably won't warn you. This makes the
3977 symbol an externally defined symbol, which is generally what you
3981 * Symbol Value:: Value
3982 * Symbol Type:: Type
3985 * a.out Symbols:: Symbol Attributes: @code{a.out}
3989 * a.out Symbols:: Symbol Attributes: @code{a.out}
3992 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3997 * COFF Symbols:: Symbol Attributes for COFF
4000 * SOM Symbols:: Symbol Attributes for SOM
4007 @cindex value of a symbol
4008 @cindex symbol value
4009 The value of a symbol is (usually) 32 bits. For a symbol which labels a
4010 location in the text, data, bss or absolute sections the value is the
4011 number of addresses from the start of that section to the label.
4012 Naturally for text, data and bss sections the value of a symbol changes
4013 as @code{@value{LD}} changes section base addresses during linking. Absolute
4014 symbols' values do not change during linking: that is why they are
4017 The value of an undefined symbol is treated in a special way. If it is
4018 0 then the symbol is not defined in this assembler source file, and
4019 @code{@value{LD}} tries to determine its value from other files linked into the
4020 same program. You make this kind of symbol simply by mentioning a symbol
4021 name without defining it. A non-zero value represents a @code{.comm}
4022 common declaration. The value is how much common storage to reserve, in
4023 bytes (addresses). The symbol refers to the first address of the
4029 @cindex type of a symbol
4031 The type attribute of a symbol contains relocation (section)
4032 information, any flag settings indicating that a symbol is external, and
4033 (optionally), other information for linkers and debuggers. The exact
4034 format depends on the object-code output format in use.
4039 @c The following avoids a "widow" subsection title. @group would be
4040 @c better if it were available outside examples.
4043 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
4045 @cindex @code{b.out} symbol attributes
4046 @cindex symbol attributes, @code{b.out}
4047 These symbol attributes appear only when @command{@value{AS}} is configured for
4048 one of the Berkeley-descended object output formats---@code{a.out} or
4054 @subsection Symbol Attributes: @code{a.out}
4056 @cindex @code{a.out} symbol attributes
4057 @cindex symbol attributes, @code{a.out}
4063 @subsection Symbol Attributes: @code{a.out}
4065 @cindex @code{a.out} symbol attributes
4066 @cindex symbol attributes, @code{a.out}
4070 * Symbol Desc:: Descriptor
4071 * Symbol Other:: Other
4075 @subsubsection Descriptor
4077 @cindex descriptor, of @code{a.out} symbol
4078 This is an arbitrary 16-bit value. You may establish a symbol's
4079 descriptor value by using a @code{.desc} statement
4080 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4081 @command{@value{AS}}.
4084 @subsubsection Other
4086 @cindex other attribute, of @code{a.out} symbol
4087 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4092 @subsection Symbol Attributes for COFF
4094 @cindex COFF symbol attributes
4095 @cindex symbol attributes, COFF
4097 The COFF format supports a multitude of auxiliary symbol attributes;
4098 like the primary symbol attributes, they are set between @code{.def} and
4099 @code{.endef} directives.
4101 @subsubsection Primary Attributes
4103 @cindex primary attributes, COFF symbols
4104 The symbol name is set with @code{.def}; the value and type,
4105 respectively, with @code{.val} and @code{.type}.
4107 @subsubsection Auxiliary Attributes
4109 @cindex auxiliary attributes, COFF symbols
4110 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4111 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4112 table information for COFF.
4117 @subsection Symbol Attributes for SOM
4119 @cindex SOM symbol attributes
4120 @cindex symbol attributes, SOM
4122 The SOM format for the HPPA supports a multitude of symbol attributes set with
4123 the @code{.EXPORT} and @code{.IMPORT} directives.
4125 The attributes are described in @cite{HP9000 Series 800 Assembly
4126 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4127 @code{EXPORT} assembler directive documentation.
4131 @chapter Expressions
4135 @cindex numeric values
4136 An @dfn{expression} specifies an address or numeric value.
4137 Whitespace may precede and/or follow an expression.
4139 The result of an expression must be an absolute number, or else an offset into
4140 a particular section. If an expression is not absolute, and there is not
4141 enough information when @command{@value{AS}} sees the expression to know its
4142 section, a second pass over the source program might be necessary to interpret
4143 the expression---but the second pass is currently not implemented.
4144 @command{@value{AS}} aborts with an error message in this situation.
4147 * Empty Exprs:: Empty Expressions
4148 * Integer Exprs:: Integer Expressions
4152 @section Empty Expressions
4154 @cindex empty expressions
4155 @cindex expressions, empty
4156 An empty expression has no value: it is just whitespace or null.
4157 Wherever an absolute expression is required, you may omit the
4158 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4159 is compatible with other assemblers.
4162 @section Integer Expressions
4164 @cindex integer expressions
4165 @cindex expressions, integer
4166 An @dfn{integer expression} is one or more @emph{arguments} delimited
4167 by @emph{operators}.
4170 * Arguments:: Arguments
4171 * Operators:: Operators
4172 * Prefix Ops:: Prefix Operators
4173 * Infix Ops:: Infix Operators
4177 @subsection Arguments
4179 @cindex expression arguments
4180 @cindex arguments in expressions
4181 @cindex operands in expressions
4182 @cindex arithmetic operands
4183 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4184 contexts arguments are sometimes called ``arithmetic operands''. In
4185 this manual, to avoid confusing them with the ``instruction operands'' of
4186 the machine language, we use the term ``argument'' to refer to parts of
4187 expressions only, reserving the word ``operand'' to refer only to machine
4188 instruction operands.
4190 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4191 @var{section} is one of text, data, bss, absolute,
4192 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4195 Numbers are usually integers.
4197 A number can be a flonum or bignum. In this case, you are warned
4198 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4199 these 32 bits are an integer. You may write integer-manipulating
4200 instructions that act on exotic constants, compatible with other
4203 @cindex subexpressions
4204 Subexpressions are a left parenthesis @samp{(} followed by an integer
4205 expression, followed by a right parenthesis @samp{)}; or a prefix
4206 operator followed by an argument.
4209 @subsection Operators
4211 @cindex operators, in expressions
4212 @cindex arithmetic functions
4213 @cindex functions, in expressions
4214 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4215 operators are followed by an argument. Infix operators appear
4216 between their arguments. Operators may be preceded and/or followed by
4220 @subsection Prefix Operator
4222 @cindex prefix operators
4223 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4224 one argument, which must be absolute.
4226 @c the tex/end tex stuff surrounding this small table is meant to make
4227 @c it align, on the printed page, with the similar table in the next
4228 @c section (which is inside an enumerate).
4230 \global\advance\leftskip by \itemindent
4235 @dfn{Negation}. Two's complement negation.
4237 @dfn{Complementation}. Bitwise not.
4241 \global\advance\leftskip by -\itemindent
4245 @subsection Infix Operators
4247 @cindex infix operators
4248 @cindex operators, permitted arguments
4249 @dfn{Infix operators} take two arguments, one on either side. Operators
4250 have precedence, but operations with equal precedence are performed left
4251 to right. Apart from @code{+} or @option{-}, both arguments must be
4252 absolute, and the result is absolute.
4255 @cindex operator precedence
4256 @cindex precedence of operators
4263 @dfn{Multiplication}.
4266 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4272 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4275 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4279 Intermediate precedence
4284 @dfn{Bitwise Inclusive Or}.
4290 @dfn{Bitwise Exclusive Or}.
4293 @dfn{Bitwise Or Not}.
4300 @cindex addition, permitted arguments
4301 @cindex plus, permitted arguments
4302 @cindex arguments for addition
4304 @dfn{Addition}. If either argument is absolute, the result has the section of
4305 the other argument. You may not add together arguments from different
4308 @cindex subtraction, permitted arguments
4309 @cindex minus, permitted arguments
4310 @cindex arguments for subtraction
4312 @dfn{Subtraction}. If the right argument is absolute, the
4313 result has the section of the left argument.
4314 If both arguments are in the same section, the result is absolute.
4315 You may not subtract arguments from different sections.
4316 @c FIXME is there still something useful to say about undefined - undefined ?
4318 @cindex comparison expressions
4319 @cindex expressions, comparison
4324 @dfn{Is Not Equal To}
4328 @dfn{Is Greater Than}
4330 @dfn{Is Greater Than Or Equal To}
4332 @dfn{Is Less Than Or Equal To}
4334 The comparison operators can be used as infix operators. A true results has a
4335 value of -1 whereas a false result has a value of 0. Note, these operators
4336 perform signed comparisons.
4339 @item Lowest Precedence
4348 These two logical operations can be used to combine the results of sub
4349 expressions. Note, unlike the comparison operators a true result returns a
4350 value of 1 but a false results does still return 0. Also note that the logical
4351 or operator has a slightly lower precedence than logical and.
4356 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4357 address; you can only have a defined section in one of the two arguments.
4360 @chapter Assembler Directives
4362 @cindex directives, machine independent
4363 @cindex pseudo-ops, machine independent
4364 @cindex machine independent directives
4365 All assembler directives have names that begin with a period (@samp{.}).
4366 The names are case insensitive for most targets, and usually written
4369 This chapter discusses directives that are available regardless of the
4370 target machine configuration for the @sc{gnu} assembler.
4372 Some machine configurations provide additional directives.
4373 @xref{Machine Dependencies}.
4376 @ifset machine-directives
4377 @xref{Machine Dependencies}, for additional directives.
4382 * Abort:: @code{.abort}
4384 * ABORT (COFF):: @code{.ABORT}
4387 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4388 * Altmacro:: @code{.altmacro}
4389 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4390 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4391 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4392 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4393 * Byte:: @code{.byte @var{expressions}}
4394 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4395 * Comm:: @code{.comm @var{symbol} , @var{length} }
4396 * Data:: @code{.data @var{subsection}}
4398 * Def:: @code{.def @var{name}}
4401 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4407 * Double:: @code{.double @var{flonums}}
4408 * Eject:: @code{.eject}
4409 * Else:: @code{.else}
4410 * Elseif:: @code{.elseif}
4413 * Endef:: @code{.endef}
4416 * Endfunc:: @code{.endfunc}
4417 * Endif:: @code{.endif}
4418 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4419 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4420 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4422 * Error:: @code{.error @var{string}}
4423 * Exitm:: @code{.exitm}
4424 * Extern:: @code{.extern}
4425 * Fail:: @code{.fail}
4426 * File:: @code{.file}
4427 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4428 * Float:: @code{.float @var{flonums}}
4429 * Func:: @code{.func}
4430 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4432 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4433 * Hidden:: @code{.hidden @var{names}}
4436 * hword:: @code{.hword @var{expressions}}
4437 * Ident:: @code{.ident}
4438 * If:: @code{.if @var{absolute expression}}
4439 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4440 * Include:: @code{.include "@var{file}"}
4441 * Int:: @code{.int @var{expressions}}
4443 * Internal:: @code{.internal @var{names}}
4446 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4447 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4448 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4449 * Lflags:: @code{.lflags}
4450 @ifclear no-line-dir
4451 * Line:: @code{.line @var{line-number}}
4454 * Linkonce:: @code{.linkonce [@var{type}]}
4455 * List:: @code{.list}
4456 * Ln:: @code{.ln @var{line-number}}
4457 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4458 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4460 * Local:: @code{.local @var{names}}
4463 * Long:: @code{.long @var{expressions}}
4465 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4468 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4469 * MRI:: @code{.mri @var{val}}
4470 * Noaltmacro:: @code{.noaltmacro}
4471 * Nolist:: @code{.nolist}
4472 * Octa:: @code{.octa @var{bignums}}
4473 * Offset:: @code{.offset @var{loc}}
4474 * Org:: @code{.org @var{new-lc}, @var{fill}}
4475 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4477 * PopSection:: @code{.popsection}
4478 * Previous:: @code{.previous}
4481 * Print:: @code{.print @var{string}}
4483 * Protected:: @code{.protected @var{names}}
4486 * Psize:: @code{.psize @var{lines}, @var{columns}}
4487 * Purgem:: @code{.purgem @var{name}}
4489 * PushSection:: @code{.pushsection @var{name}}
4492 * Quad:: @code{.quad @var{bignums}}
4493 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4494 * Rept:: @code{.rept @var{count}}
4495 * Sbttl:: @code{.sbttl "@var{subheading}"}
4497 * Scl:: @code{.scl @var{class}}
4500 * Section:: @code{.section @var{name}[, @var{flags}]}
4503 * Set:: @code{.set @var{symbol}, @var{expression}}
4504 * Short:: @code{.short @var{expressions}}
4505 * Single:: @code{.single @var{flonums}}
4507 * Size:: @code{.size [@var{name} , @var{expression}]}
4509 @ifclear no-space-dir
4510 * Skip:: @code{.skip @var{size} , @var{fill}}
4513 * Sleb128:: @code{.sleb128 @var{expressions}}
4514 @ifclear no-space-dir
4515 * Space:: @code{.space @var{size} , @var{fill}}
4518 * Stab:: @code{.stabd, .stabn, .stabs}
4521 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4522 * Struct:: @code{.struct @var{expression}}
4524 * SubSection:: @code{.subsection}
4525 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4529 * Tag:: @code{.tag @var{structname}}
4532 * Text:: @code{.text @var{subsection}}
4533 * Title:: @code{.title "@var{heading}"}
4535 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4538 * Uleb128:: @code{.uleb128 @var{expressions}}
4540 * Val:: @code{.val @var{addr}}
4544 * Version:: @code{.version "@var{string}"}
4545 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4546 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4549 * Warning:: @code{.warning @var{string}}
4550 * Weak:: @code{.weak @var{names}}
4551 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4552 * Word:: @code{.word @var{expressions}}
4553 @ifclear no-space-dir
4554 * Zero:: @code{.zero @var{size}}
4556 * Deprecated:: Deprecated Directives
4560 @section @code{.abort}
4562 @cindex @code{abort} directive
4563 @cindex stopping the assembly
4564 This directive stops the assembly immediately. It is for
4565 compatibility with other assemblers. The original idea was that the
4566 assembly language source would be piped into the assembler. If the sender
4567 of the source quit, it could use this directive tells @command{@value{AS}} to
4568 quit also. One day @code{.abort} will not be supported.
4572 @section @code{.ABORT} (COFF)
4574 @cindex @code{ABORT} directive
4575 When producing COFF output, @command{@value{AS}} accepts this directive as a
4576 synonym for @samp{.abort}.
4579 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4585 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4587 @cindex padding the location counter
4588 @cindex @code{align} directive
4589 Pad the location counter (in the current subsection) to a particular storage
4590 boundary. The first expression (which must be absolute) is the alignment
4591 required, as described below.
4593 The second expression (also absolute) gives the fill value to be stored in the
4594 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4595 padding bytes are normally zero. However, on some systems, if the section is
4596 marked as containing code and the fill value is omitted, the space is filled
4597 with no-op instructions.
4599 The third expression is also absolute, and is also optional. If it is present,
4600 it is the maximum number of bytes that should be skipped by this alignment
4601 directive. If doing the alignment would require skipping more bytes than the
4602 specified maximum, then the alignment is not done at all. You can omit the
4603 fill value (the second argument) entirely by simply using two commas after the
4604 required alignment; this can be useful if you want the alignment to be filled
4605 with no-op instructions when appropriate.
4607 The way the required alignment is specified varies from system to system.
4608 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4609 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4610 alignment request in bytes. For example @samp{.align 8} advances
4611 the location counter until it is a multiple of 8. If the location counter
4612 is already a multiple of 8, no change is needed. For the tic54x, the
4613 first expression is the alignment request in words.
4615 For other systems, including ppc, i386 using a.out format, arm and
4616 strongarm, it is the
4617 number of low-order zero bits the location counter must have after
4618 advancement. For example @samp{.align 3} advances the location
4619 counter until it a multiple of 8. If the location counter is already a
4620 multiple of 8, no change is needed.
4622 This inconsistency is due to the different behaviors of the various
4623 native assemblers for these systems which GAS must emulate.
4624 GAS also provides @code{.balign} and @code{.p2align} directives,
4625 described later, which have a consistent behavior across all
4626 architectures (but are specific to GAS).
4629 @section @code{.altmacro}
4630 Enable alternate macro mode, enabling:
4633 @item LOCAL @var{name} [ , @dots{} ]
4634 One additional directive, @code{LOCAL}, is available. It is used to
4635 generate a string replacement for each of the @var{name} arguments, and
4636 replace any instances of @var{name} in each macro expansion. The
4637 replacement string is unique in the assembly, and different for each
4638 separate macro expansion. @code{LOCAL} allows you to write macros that
4639 define symbols, without fear of conflict between separate macro expansions.
4641 @item String delimiters
4642 You can write strings delimited in these other ways besides
4643 @code{"@var{string}"}:
4646 @item '@var{string}'
4647 You can delimit strings with single-quote characters.
4649 @item <@var{string}>
4650 You can delimit strings with matching angle brackets.
4653 @item single-character string escape
4654 To include any single character literally in a string (even if the
4655 character would otherwise have some special meaning), you can prefix the
4656 character with @samp{!} (an exclamation mark). For example, you can
4657 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4659 @item Expression results as strings
4660 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4661 and use the result as a string.
4665 @section @code{.ascii "@var{string}"}@dots{}
4667 @cindex @code{ascii} directive
4668 @cindex string literals
4669 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4670 separated by commas. It assembles each string (with no automatic
4671 trailing zero byte) into consecutive addresses.
4674 @section @code{.asciz "@var{string}"}@dots{}
4676 @cindex @code{asciz} directive
4677 @cindex zero-terminated strings
4678 @cindex null-terminated strings
4679 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4680 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4683 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4685 @cindex padding the location counter given number of bytes
4686 @cindex @code{balign} directive
4687 Pad the location counter (in the current subsection) to a particular
4688 storage boundary. The first expression (which must be absolute) is the
4689 alignment request in bytes. For example @samp{.balign 8} advances
4690 the location counter until it is a multiple of 8. If the location counter
4691 is already a multiple of 8, no change is needed.
4693 The second expression (also absolute) gives the fill value to be stored in the
4694 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4695 padding bytes are normally zero. However, on some systems, if the section is
4696 marked as containing code and the fill value is omitted, the space is filled
4697 with no-op instructions.
4699 The third expression is also absolute, and is also optional. If it is present,
4700 it is the maximum number of bytes that should be skipped by this alignment
4701 directive. If doing the alignment would require skipping more bytes than the
4702 specified maximum, then the alignment is not done at all. You can omit the
4703 fill value (the second argument) entirely by simply using two commas after the
4704 required alignment; this can be useful if you want the alignment to be filled
4705 with no-op instructions when appropriate.
4707 @cindex @code{balignw} directive
4708 @cindex @code{balignl} directive
4709 The @code{.balignw} and @code{.balignl} directives are variants of the
4710 @code{.balign} directive. The @code{.balignw} directive treats the fill
4711 pattern as a two byte word value. The @code{.balignl} directives treats the
4712 fill pattern as a four byte longword value. For example, @code{.balignw
4713 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4714 filled in with the value 0x368d (the exact placement of the bytes depends upon
4715 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4718 @node Bundle directives
4719 @section Bundle directives
4720 @subsection @code{.bundle_align_mode @var{abs-expr}}
4721 @cindex @code{bundle_align_mode} directive
4723 @cindex instruction bundle
4724 @cindex aligned instruction bundle
4725 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4726 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4727 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4728 disabled (which is the default state). If the argument it not zero, it
4729 gives the size of an instruction bundle as a power of two (as for the
4730 @code{.p2align} directive, @pxref{P2align}).
4732 For some targets, it's an ABI requirement that no instruction may span a
4733 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4734 instructions that starts on an aligned boundary. For example, if
4735 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4736 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4737 effect, no single instruction may span a boundary between bundles. If an
4738 instruction would start too close to the end of a bundle for the length of
4739 that particular instruction to fit within the bundle, then the space at the
4740 end of that bundle is filled with no-op instructions so the instruction
4741 starts in the next bundle. As a corollary, it's an error if any single
4742 instruction's encoding is longer than the bundle size.
4744 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4745 @cindex @code{bundle_lock} directive
4746 @cindex @code{bundle_unlock} directive
4747 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4748 allow explicit control over instruction bundle padding. These directives
4749 are only valid when @code{.bundle_align_mode} has been used to enable
4750 aligned instruction bundle mode. It's an error if they appear when
4751 @code{.bundle_align_mode} has not been used at all, or when the last
4752 directive was @w{@code{.bundle_align_mode 0}}.
4754 @cindex bundle-locked
4755 For some targets, it's an ABI requirement that certain instructions may
4756 appear only as part of specified permissible sequences of multiple
4757 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4758 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4759 instruction sequence. For purposes of aligned instruction bundle mode, a
4760 sequence starting with @code{.bundle_lock} and ending with
4761 @code{.bundle_unlock} is treated as a single instruction. That is, the
4762 entire sequence must fit into a single bundle and may not span a bundle
4763 boundary. If necessary, no-op instructions will be inserted before the
4764 first instruction of the sequence so that the whole sequence starts on an
4765 aligned bundle boundary. It's an error if the sequence is longer than the
4768 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4769 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4770 nested. That is, a second @code{.bundle_lock} directive before the next
4771 @code{.bundle_unlock} directive has no effect except that it must be
4772 matched by another closing @code{.bundle_unlock} so that there is the
4773 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4776 @section @code{.byte @var{expressions}}
4778 @cindex @code{byte} directive
4779 @cindex integers, one byte
4780 @code{.byte} expects zero or more expressions, separated by commas.
4781 Each expression is assembled into the next byte.
4783 @node CFI directives
4784 @section CFI directives
4785 @subsection @code{.cfi_sections @var{section_list}}
4786 @cindex @code{cfi_sections} directive
4787 @code{.cfi_sections} may be used to specify whether CFI directives
4788 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4789 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4790 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4791 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4792 directive is not used is @code{.cfi_sections .eh_frame}.
4794 On targets that support compact unwinding tables these can be generated
4795 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4797 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4798 which is used by the @value{TIC6X} target.
4800 The @code{.cfi_sections} directive can be repeated, with the same or different
4801 arguments, provided that CFI generation has not yet started. Once CFI
4802 generation has started however the section list is fixed and any attempts to
4803 redefine it will result in an error.
4805 @subsection @code{.cfi_startproc [simple]}
4806 @cindex @code{cfi_startproc} directive
4807 @code{.cfi_startproc} is used at the beginning of each function that
4808 should have an entry in @code{.eh_frame}. It initializes some internal
4809 data structures. Don't forget to close the function by
4810 @code{.cfi_endproc}.
4812 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4813 it also emits some architecture dependent initial CFI instructions.
4815 @subsection @code{.cfi_endproc}
4816 @cindex @code{cfi_endproc} directive
4817 @code{.cfi_endproc} is used at the end of a function where it closes its
4818 unwind entry previously opened by
4819 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4821 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4822 @cindex @code{cfi_personality} directive
4823 @code{.cfi_personality} defines personality routine and its encoding.
4824 @var{encoding} must be a constant determining how the personality
4825 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4826 argument is not present, otherwise second argument should be
4827 a constant or a symbol name. When using indirect encodings,
4828 the symbol provided should be the location where personality
4829 can be loaded from, not the personality routine itself.
4830 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4831 no personality routine.
4833 @subsection @code{.cfi_personality_id @var{id}}
4834 @cindex @code{cfi_personality_id} directive
4835 @code{cfi_personality_id} defines a personality routine by its index as
4836 defined in a compact unwinding format.
4837 Only valid when generating compact EH frames (i.e.
4838 with @code{.cfi_sections eh_frame_entry}.
4840 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4841 @cindex @code{cfi_fde_data} directive
4842 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4843 used for the current function. These are emitted inline in the
4844 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4845 in the @code{.gnu.extab} section otherwise.
4846 Only valid when generating compact EH frames (i.e.
4847 with @code{.cfi_sections eh_frame_entry}.
4849 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4850 @code{.cfi_lsda} defines LSDA and its encoding.
4851 @var{encoding} must be a constant determining how the LSDA
4852 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4853 argument is not present, otherwise the second argument should be a constant
4854 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4855 meaning that no LSDA is present.
4857 @subsection @code{.cfi_inline_lsda} [@var{align}]
4858 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4859 switches to the corresponding @code{.gnu.extab} section.
4860 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4861 Only valid when generating compact EH frames (i.e.
4862 with @code{.cfi_sections eh_frame_entry}.
4864 The table header and unwinding opcodes will be generated at this point,
4865 so that they are immediately followed by the LSDA data. The symbol
4866 referenced by the @code{.cfi_lsda} directive should still be defined
4867 in case a fallback FDE based encoding is used. The LSDA data is terminated
4868 by a section directive.
4870 The optional @var{align} argument specifies the alignment required.
4871 The alignment is specified as a power of two, as with the
4872 @code{.p2align} directive.
4874 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4875 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4876 address from @var{register} and add @var{offset} to it}.
4878 @subsection @code{.cfi_def_cfa_register @var{register}}
4879 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4880 now on @var{register} will be used instead of the old one. Offset
4883 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4884 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4885 remains the same, but @var{offset} is new. Note that it is the
4886 absolute offset that will be added to a defined register to compute
4889 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4890 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4891 value that is added/subtracted from the previous offset.
4893 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4894 Previous value of @var{register} is saved at offset @var{offset} from
4897 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4898 Previous value of @var{register} is CFA + @var{offset}.
4900 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4901 Previous value of @var{register} is saved at offset @var{offset} from
4902 the current CFA register. This is transformed to @code{.cfi_offset}
4903 using the known displacement of the CFA register from the CFA.
4904 This is often easier to use, because the number will match the
4905 code it's annotating.
4907 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4908 Previous value of @var{register1} is saved in register @var{register2}.
4910 @subsection @code{.cfi_restore @var{register}}
4911 @code{.cfi_restore} says that the rule for @var{register} is now the
4912 same as it was at the beginning of the function, after all initial
4913 instruction added by @code{.cfi_startproc} were executed.
4915 @subsection @code{.cfi_undefined @var{register}}
4916 From now on the previous value of @var{register} can't be restored anymore.
4918 @subsection @code{.cfi_same_value @var{register}}
4919 Current value of @var{register} is the same like in the previous frame,
4920 i.e. no restoration needed.
4922 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4923 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4924 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4925 places them in the current row. This is useful for situations where you have
4926 multiple @code{.cfi_*} directives that need to be undone due to the control
4927 flow of the program. For example, we could have something like this (assuming
4928 the CFA is the value of @code{rbp}):
4938 .cfi_def_cfa %rsp, 8
4941 /* Do something else */
4944 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4945 to the instructions before @code{label}. This means we'd have to add multiple
4946 @code{.cfi} directives after @code{label} to recreate the original save
4947 locations of the registers, as well as setting the CFA back to the value of
4948 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4960 .cfi_def_cfa %rsp, 8
4964 /* Do something else */
4967 That way, the rules for the instructions after @code{label} will be the same
4968 as before the first @code{.cfi_restore} without having to use multiple
4969 @code{.cfi} directives.
4971 @subsection @code{.cfi_return_column @var{register}}
4972 Change return column @var{register}, i.e. the return address is either
4973 directly in @var{register} or can be accessed by rules for @var{register}.
4975 @subsection @code{.cfi_signal_frame}
4976 Mark current function as signal trampoline.
4978 @subsection @code{.cfi_window_save}
4979 SPARC register window has been saved.
4981 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4982 Allows the user to add arbitrary bytes to the unwind info. One
4983 might use this to add OS-specific CFI opcodes, or generic CFI
4984 opcodes that GAS does not yet support.
4986 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4987 The current value of @var{register} is @var{label}. The value of @var{label}
4988 will be encoded in the output file according to @var{encoding}; see the
4989 description of @code{.cfi_personality} for details on this encoding.
4991 The usefulness of equating a register to a fixed label is probably
4992 limited to the return address register. Here, it can be useful to
4993 mark a code segment that has only one return address which is reached
4994 by a direct branch and no copy of the return address exists in memory
4995 or another register.
4998 @section @code{.comm @var{symbol} , @var{length} }
5000 @cindex @code{comm} directive
5001 @cindex symbol, common
5002 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
5003 common symbol in one object file may be merged with a defined or common symbol
5004 of the same name in another object file. If @code{@value{LD}} does not see a
5005 definition for the symbol--just one or more common symbols--then it will
5006 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
5007 absolute expression. If @code{@value{LD}} sees multiple common symbols with
5008 the same name, and they do not all have the same size, it will allocate space
5009 using the largest size.
5012 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
5013 an optional third argument. This is the desired alignment of the symbol,
5014 specified for ELF as a byte boundary (for example, an alignment of 16 means
5015 that the least significant 4 bits of the address should be zero), and for PE
5016 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
5017 boundary). The alignment must be an absolute expression, and it must be a
5018 power of two. If @code{@value{LD}} allocates uninitialized memory for the
5019 common symbol, it will use the alignment when placing the symbol. If no
5020 alignment is specified, @command{@value{AS}} will set the alignment to the
5021 largest power of two less than or equal to the size of the symbol, up to a
5022 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
5023 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5024 @samp{--section-alignment} option; image file sections in PE are aligned to
5025 multiples of 4096, which is far too large an alignment for ordinary variables.
5026 It is rather the default alignment for (non-debug) sections within object
5027 (@samp{*.o}) files, which are less strictly aligned.}.
5031 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5032 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5036 @section @code{.data @var{subsection}}
5038 @cindex @code{data} directive
5039 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5040 end of the data subsection numbered @var{subsection} (which is an
5041 absolute expression). If @var{subsection} is omitted, it defaults
5046 @section @code{.def @var{name}}
5048 @cindex @code{def} directive
5049 @cindex COFF symbols, debugging
5050 @cindex debugging COFF symbols
5051 Begin defining debugging information for a symbol @var{name}; the
5052 definition extends until the @code{.endef} directive is encountered.
5055 This directive is only observed when @command{@value{AS}} is configured for COFF
5056 format output; when producing @code{b.out}, @samp{.def} is recognized,
5063 @section @code{.desc @var{symbol}, @var{abs-expression}}
5065 @cindex @code{desc} directive
5066 @cindex COFF symbol descriptor
5067 @cindex symbol descriptor, COFF
5068 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5069 to the low 16 bits of an absolute expression.
5072 The @samp{.desc} directive is not available when @command{@value{AS}} is
5073 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5074 object format. For the sake of compatibility, @command{@value{AS}} accepts
5075 it, but produces no output, when configured for COFF.
5081 @section @code{.dim}
5083 @cindex @code{dim} directive
5084 @cindex COFF auxiliary symbol information
5085 @cindex auxiliary symbol information, COFF
5086 This directive is generated by compilers to include auxiliary debugging
5087 information in the symbol table. It is only permitted inside
5088 @code{.def}/@code{.endef} pairs.
5091 @samp{.dim} is only meaningful when generating COFF format output; when
5092 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5098 @section @code{.double @var{flonums}}
5100 @cindex @code{double} directive
5101 @cindex floating point numbers (double)
5102 @code{.double} expects zero or more flonums, separated by commas. It
5103 assembles floating point numbers.
5105 The exact kind of floating point numbers emitted depends on how
5106 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5110 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5111 in @sc{ieee} format.
5116 @section @code{.eject}
5118 @cindex @code{eject} directive
5119 @cindex new page, in listings
5120 @cindex page, in listings
5121 @cindex listing control: new page
5122 Force a page break at this point, when generating assembly listings.
5125 @section @code{.else}
5127 @cindex @code{else} directive
5128 @code{.else} is part of the @command{@value{AS}} support for conditional
5129 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5130 of code to be assembled if the condition for the preceding @code{.if}
5134 @section @code{.elseif}
5136 @cindex @code{elseif} directive
5137 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5138 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5139 @code{.if} block that would otherwise fill the entire @code{.else} section.
5142 @section @code{.end}
5144 @cindex @code{end} directive
5145 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5146 process anything in the file past the @code{.end} directive.
5150 @section @code{.endef}
5152 @cindex @code{endef} directive
5153 This directive flags the end of a symbol definition begun with
5157 @samp{.endef} is only meaningful when generating COFF format output; if
5158 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5159 directive but ignores it.
5164 @section @code{.endfunc}
5165 @cindex @code{endfunc} directive
5166 @code{.endfunc} marks the end of a function specified with @code{.func}.
5169 @section @code{.endif}
5171 @cindex @code{endif} directive
5172 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5173 it marks the end of a block of code that is only assembled
5174 conditionally. @xref{If,,@code{.if}}.
5177 @section @code{.equ @var{symbol}, @var{expression}}
5179 @cindex @code{equ} directive
5180 @cindex assigning values to symbols
5181 @cindex symbols, assigning values to
5182 This directive sets the value of @var{symbol} to @var{expression}.
5183 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5186 The syntax for @code{equ} on the HPPA is
5187 @samp{@var{symbol} .equ @var{expression}}.
5191 The syntax for @code{equ} on the Z80 is
5192 @samp{@var{symbol} equ @var{expression}}.
5193 On the Z80 it is an error if @var{symbol} is already defined,
5194 but the symbol is not protected from later redefinition.
5195 Compare @ref{Equiv}.
5199 @section @code{.equiv @var{symbol}, @var{expression}}
5200 @cindex @code{equiv} directive
5201 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5202 the assembler will signal an error if @var{symbol} is already defined. Note a
5203 symbol which has been referenced but not actually defined is considered to be
5206 Except for the contents of the error message, this is roughly equivalent to
5213 plus it protects the symbol from later redefinition.
5216 @section @code{.eqv @var{symbol}, @var{expression}}
5217 @cindex @code{eqv} directive
5218 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5219 evaluate the expression or any part of it immediately. Instead each time
5220 the resulting symbol is used in an expression, a snapshot of its current
5224 @section @code{.err}
5225 @cindex @code{err} directive
5226 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5227 message and, unless the @option{-Z} option was used, it will not generate an
5228 object file. This can be used to signal an error in conditionally compiled code.
5231 @section @code{.error "@var{string}"}
5232 @cindex error directive
5234 Similarly to @code{.err}, this directive emits an error, but you can specify a
5235 string that will be emitted as the error message. If you don't specify the
5236 message, it defaults to @code{".error directive invoked in source file"}.
5237 @xref{Errors, ,Error and Warning Messages}.
5240 .error "This code has not been assembled and tested."
5244 @section @code{.exitm}
5245 Exit early from the current macro definition. @xref{Macro}.
5248 @section @code{.extern}
5250 @cindex @code{extern} directive
5251 @code{.extern} is accepted in the source program---for compatibility
5252 with other assemblers---but it is ignored. @command{@value{AS}} treats
5253 all undefined symbols as external.
5256 @section @code{.fail @var{expression}}
5258 @cindex @code{fail} directive
5259 Generates an error or a warning. If the value of the @var{expression} is 500
5260 or more, @command{@value{AS}} will print a warning message. If the value is less
5261 than 500, @command{@value{AS}} will print an error message. The message will
5262 include the value of @var{expression}. This can occasionally be useful inside
5263 complex nested macros or conditional assembly.
5266 @section @code{.file}
5267 @cindex @code{file} directive
5269 @ifclear no-file-dir
5270 There are two different versions of the @code{.file} directive. Targets
5271 that support DWARF2 line number information use the DWARF2 version of
5272 @code{.file}. Other targets use the default version.
5274 @subheading Default Version
5276 @cindex logical file name
5277 @cindex file name, logical
5278 This version of the @code{.file} directive tells @command{@value{AS}} that we
5279 are about to start a new logical file. The syntax is:
5285 @var{string} is the new file name. In general, the filename is
5286 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5287 to specify an empty file name, you must give the quotes--@code{""}. This
5288 statement may go away in future: it is only recognized to be compatible with
5289 old @command{@value{AS}} programs.
5291 @subheading DWARF2 Version
5294 When emitting DWARF2 line number information, @code{.file} assigns filenames
5295 to the @code{.debug_line} file name table. The syntax is:
5298 .file @var{fileno} @var{filename}
5301 The @var{fileno} operand should be a unique positive integer to use as the
5302 index of the entry in the table. The @var{filename} operand is a C string
5305 The detail of filename indices is exposed to the user because the filename
5306 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5307 information, and thus the user must know the exact indices that table
5311 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5313 @cindex @code{fill} directive
5314 @cindex writing patterns in memory
5315 @cindex patterns, writing in memory
5316 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5317 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5318 may be zero or more. @var{Size} may be zero or more, but if it is
5319 more than 8, then it is deemed to have the value 8, compatible with
5320 other people's assemblers. The contents of each @var{repeat} bytes
5321 is taken from an 8-byte number. The highest order 4 bytes are
5322 zero. The lowest order 4 bytes are @var{value} rendered in the
5323 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5324 Each @var{size} bytes in a repetition is taken from the lowest order
5325 @var{size} bytes of this number. Again, this bizarre behavior is
5326 compatible with other people's assemblers.
5328 @var{size} and @var{value} are optional.
5329 If the second comma and @var{value} are absent, @var{value} is
5330 assumed zero. If the first comma and following tokens are absent,
5331 @var{size} is assumed to be 1.
5334 @section @code{.float @var{flonums}}
5336 @cindex floating point numbers (single)
5337 @cindex @code{float} directive
5338 This directive assembles zero or more flonums, separated by commas. It
5339 has the same effect as @code{.single}.
5341 The exact kind of floating point numbers emitted depends on how
5342 @command{@value{AS}} is configured.
5343 @xref{Machine Dependencies}.
5347 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5348 in @sc{ieee} format.
5353 @section @code{.func @var{name}[,@var{label}]}
5354 @cindex @code{func} directive
5355 @code{.func} emits debugging information to denote function @var{name}, and
5356 is ignored unless the file is assembled with debugging enabled.
5357 Only @samp{--gstabs[+]} is currently supported.
5358 @var{label} is the entry point of the function and if omitted @var{name}
5359 prepended with the @samp{leading char} is used.
5360 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5361 All functions are currently defined to have @code{void} return type.
5362 The function must be terminated with @code{.endfunc}.
5365 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5367 @cindex @code{global} directive
5368 @cindex symbol, making visible to linker
5369 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5370 @var{symbol} in your partial program, its value is made available to
5371 other partial programs that are linked with it. Otherwise,
5372 @var{symbol} takes its attributes from a symbol of the same name
5373 from another file linked into the same program.
5375 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5376 compatibility with other assemblers.
5379 On the HPPA, @code{.global} is not always enough to make it accessible to other
5380 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5381 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5386 @section @code{.gnu_attribute @var{tag},@var{value}}
5387 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5390 @section @code{.hidden @var{names}}
5392 @cindex @code{hidden} directive
5394 This is one of the ELF visibility directives. The other two are
5395 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5396 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5398 This directive overrides the named symbols default visibility (which is set by
5399 their binding: local, global or weak). The directive sets the visibility to
5400 @code{hidden} which means that the symbols are not visible to other components.
5401 Such symbols are always considered to be @code{protected} as well.
5405 @section @code{.hword @var{expressions}}
5407 @cindex @code{hword} directive
5408 @cindex integers, 16-bit
5409 @cindex numbers, 16-bit
5410 @cindex sixteen bit integers
5411 This expects zero or more @var{expressions}, and emits
5412 a 16 bit number for each.
5415 This directive is a synonym for @samp{.short}; depending on the target
5416 architecture, it may also be a synonym for @samp{.word}.
5420 This directive is a synonym for @samp{.short}.
5423 This directive is a synonym for both @samp{.short} and @samp{.word}.
5428 @section @code{.ident}
5430 @cindex @code{ident} directive
5432 This directive is used by some assemblers to place tags in object files. The
5433 behavior of this directive varies depending on the target. When using the
5434 a.out object file format, @command{@value{AS}} simply accepts the directive for
5435 source-file compatibility with existing assemblers, but does not emit anything
5436 for it. When using COFF, comments are emitted to the @code{.comment} or
5437 @code{.rdata} section, depending on the target. When using ELF, comments are
5438 emitted to the @code{.comment} section.
5441 @section @code{.if @var{absolute expression}}
5443 @cindex conditional assembly
5444 @cindex @code{if} directive
5445 @code{.if} marks the beginning of a section of code which is only
5446 considered part of the source program being assembled if the argument
5447 (which must be an @var{absolute expression}) is non-zero. The end of
5448 the conditional section of code must be marked by @code{.endif}
5449 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5450 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5451 If you have several conditions to check, @code{.elseif} may be used to avoid
5452 nesting blocks if/else within each subsequent @code{.else} block.
5454 The following variants of @code{.if} are also supported:
5456 @cindex @code{ifdef} directive
5457 @item .ifdef @var{symbol}
5458 Assembles the following section of code if the specified @var{symbol}
5459 has been defined. Note a symbol which has been referenced but not yet defined
5460 is considered to be undefined.
5462 @cindex @code{ifb} directive
5463 @item .ifb @var{text}
5464 Assembles the following section of code if the operand is blank (empty).
5466 @cindex @code{ifc} directive
5467 @item .ifc @var{string1},@var{string2}
5468 Assembles the following section of code if the two strings are the same. The
5469 strings may be optionally quoted with single quotes. If they are not quoted,
5470 the first string stops at the first comma, and the second string stops at the
5471 end of the line. Strings which contain whitespace should be quoted. The
5472 string comparison is case sensitive.
5474 @cindex @code{ifeq} directive
5475 @item .ifeq @var{absolute expression}
5476 Assembles the following section of code if the argument is zero.
5478 @cindex @code{ifeqs} directive
5479 @item .ifeqs @var{string1},@var{string2}
5480 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5482 @cindex @code{ifge} directive
5483 @item .ifge @var{absolute expression}
5484 Assembles the following section of code if the argument is greater than or
5487 @cindex @code{ifgt} directive
5488 @item .ifgt @var{absolute expression}
5489 Assembles the following section of code if the argument is greater than zero.
5491 @cindex @code{ifle} directive
5492 @item .ifle @var{absolute expression}
5493 Assembles the following section of code if the argument is less than or equal
5496 @cindex @code{iflt} directive
5497 @item .iflt @var{absolute expression}
5498 Assembles the following section of code if the argument is less than zero.
5500 @cindex @code{ifnb} directive
5501 @item .ifnb @var{text}
5502 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5503 following section of code if the operand is non-blank (non-empty).
5505 @cindex @code{ifnc} directive
5506 @item .ifnc @var{string1},@var{string2}.
5507 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5508 following section of code if the two strings are not the same.
5510 @cindex @code{ifndef} directive
5511 @cindex @code{ifnotdef} directive
5512 @item .ifndef @var{symbol}
5513 @itemx .ifnotdef @var{symbol}
5514 Assembles the following section of code if the specified @var{symbol}
5515 has not been defined. Both spelling variants are equivalent. Note a symbol
5516 which has been referenced but not yet defined is considered to be undefined.
5518 @cindex @code{ifne} directive
5519 @item .ifne @var{absolute expression}
5520 Assembles the following section of code if the argument is not equal to zero
5521 (in other words, this is equivalent to @code{.if}).
5523 @cindex @code{ifnes} directive
5524 @item .ifnes @var{string1},@var{string2}
5525 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5526 following section of code if the two strings are not the same.
5530 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5532 @cindex @code{incbin} directive
5533 @cindex binary files, including
5534 The @code{incbin} directive includes @var{file} verbatim at the current
5535 location. You can control the search paths used with the @samp{-I} command-line
5536 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5539 The @var{skip} argument skips a number of bytes from the start of the
5540 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5541 read. Note that the data is not aligned in any way, so it is the user's
5542 responsibility to make sure that proper alignment is provided both before and
5543 after the @code{incbin} directive.
5546 @section @code{.include "@var{file}"}
5548 @cindex @code{include} directive
5549 @cindex supporting files, including
5550 @cindex files, including
5551 This directive provides a way to include supporting files at specified
5552 points in your source program. The code from @var{file} is assembled as
5553 if it followed the point of the @code{.include}; when the end of the
5554 included file is reached, assembly of the original file continues. You
5555 can control the search paths used with the @samp{-I} command-line option
5556 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5560 @section @code{.int @var{expressions}}
5562 @cindex @code{int} directive
5563 @cindex integers, 32-bit
5564 Expect zero or more @var{expressions}, of any section, separated by commas.
5565 For each expression, emit a number that, at run time, is the value of that
5566 expression. The byte order and bit size of the number depends on what kind
5567 of target the assembly is for.
5571 On most forms of the H8/300, @code{.int} emits 16-bit
5572 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5579 @section @code{.internal @var{names}}
5581 @cindex @code{internal} directive
5583 This is one of the ELF visibility directives. The other two are
5584 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5585 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5587 This directive overrides the named symbols default visibility (which is set by
5588 their binding: local, global or weak). The directive sets the visibility to
5589 @code{internal} which means that the symbols are considered to be @code{hidden}
5590 (i.e., not visible to other components), and that some extra, processor specific
5591 processing must also be performed upon the symbols as well.
5595 @section @code{.irp @var{symbol},@var{values}}@dots{}
5597 @cindex @code{irp} directive
5598 Evaluate a sequence of statements assigning different values to @var{symbol}.
5599 The sequence of statements starts at the @code{.irp} directive, and is
5600 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5601 set to @var{value}, and the sequence of statements is assembled. If no
5602 @var{value} is listed, the sequence of statements is assembled once, with
5603 @var{symbol} set to the null string. To refer to @var{symbol} within the
5604 sequence of statements, use @var{\symbol}.
5606 For example, assembling
5614 is equivalent to assembling
5622 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5625 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5627 @cindex @code{irpc} directive
5628 Evaluate a sequence of statements assigning different values to @var{symbol}.
5629 The sequence of statements starts at the @code{.irpc} directive, and is
5630 terminated by an @code{.endr} directive. For each character in @var{value},
5631 @var{symbol} is set to the character, and the sequence of statements is
5632 assembled. If no @var{value} is listed, the sequence of statements is
5633 assembled once, with @var{symbol} set to the null string. To refer to
5634 @var{symbol} within the sequence of statements, use @var{\symbol}.
5636 For example, assembling
5644 is equivalent to assembling
5652 For some caveats with the spelling of @var{symbol}, see also the discussion
5656 @section @code{.lcomm @var{symbol} , @var{length}}
5658 @cindex @code{lcomm} directive
5659 @cindex local common symbols
5660 @cindex symbols, local common
5661 Reserve @var{length} (an absolute expression) bytes for a local common
5662 denoted by @var{symbol}. The section and value of @var{symbol} are
5663 those of the new local common. The addresses are allocated in the bss
5664 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5665 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5666 not visible to @code{@value{LD}}.
5669 Some targets permit a third argument to be used with @code{.lcomm}. This
5670 argument specifies the desired alignment of the symbol in the bss section.
5674 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5675 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5679 @section @code{.lflags}
5681 @cindex @code{lflags} directive (ignored)
5682 @command{@value{AS}} accepts this directive, for compatibility with other
5683 assemblers, but ignores it.
5685 @ifclear no-line-dir
5687 @section @code{.line @var{line-number}}
5689 @cindex @code{line} directive
5690 @cindex logical line number
5692 Change the logical line number. @var{line-number} must be an absolute
5693 expression. The next line has that logical line number. Therefore any other
5694 statements on the current line (after a statement separator character) are
5695 reported as on logical line number @var{line-number} @minus{} 1. One day
5696 @command{@value{AS}} will no longer support this directive: it is recognized only
5697 for compatibility with existing assembler programs.
5700 Even though this is a directive associated with the @code{a.out} or
5701 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5702 when producing COFF output, and treats @samp{.line} as though it
5703 were the COFF @samp{.ln} @emph{if} it is found outside a
5704 @code{.def}/@code{.endef} pair.
5706 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5707 used by compilers to generate auxiliary symbol information for
5712 @section @code{.linkonce [@var{type}]}
5714 @cindex @code{linkonce} directive
5715 @cindex common sections
5716 Mark the current section so that the linker only includes a single copy of it.
5717 This may be used to include the same section in several different object files,
5718 but ensure that the linker will only include it once in the final output file.
5719 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5720 Duplicate sections are detected based on the section name, so it should be
5723 This directive is only supported by a few object file formats; as of this
5724 writing, the only object file format which supports it is the Portable
5725 Executable format used on Windows NT.
5727 The @var{type} argument is optional. If specified, it must be one of the
5728 following strings. For example:
5732 Not all types may be supported on all object file formats.
5736 Silently discard duplicate sections. This is the default.
5739 Warn if there are duplicate sections, but still keep only one copy.
5742 Warn if any of the duplicates have different sizes.
5745 Warn if any of the duplicates do not have exactly the same contents.
5749 @section @code{.list}
5751 @cindex @code{list} directive
5752 @cindex listing control, turning on
5753 Control (in conjunction with the @code{.nolist} directive) whether or
5754 not assembly listings are generated. These two directives maintain an
5755 internal counter (which is zero initially). @code{.list} increments the
5756 counter, and @code{.nolist} decrements it. Assembly listings are
5757 generated whenever the counter is greater than zero.
5759 By default, listings are disabled. When you enable them (with the
5760 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5761 the initial value of the listing counter is one.
5764 @section @code{.ln @var{line-number}}
5766 @cindex @code{ln} directive
5767 @ifclear no-line-dir
5768 @samp{.ln} is a synonym for @samp{.line}.
5771 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5772 must be an absolute expression. The next line has that logical
5773 line number, so any other statements on the current line (after a
5774 statement separator character @code{;}) are reported as on logical
5775 line number @var{line-number} @minus{} 1.
5778 This directive is accepted, but ignored, when @command{@value{AS}} is
5779 configured for @code{b.out}; its effect is only associated with COFF
5785 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5786 @cindex @code{loc} directive
5787 When emitting DWARF2 line number information,
5788 the @code{.loc} directive will add a row to the @code{.debug_line} line
5789 number matrix corresponding to the immediately following assembly
5790 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5791 arguments will be applied to the @code{.debug_line} state machine before
5794 The @var{options} are a sequence of the following tokens in any order:
5798 This option will set the @code{basic_block} register in the
5799 @code{.debug_line} state machine to @code{true}.
5802 This option will set the @code{prologue_end} register in the
5803 @code{.debug_line} state machine to @code{true}.
5805 @item epilogue_begin
5806 This option will set the @code{epilogue_begin} register in the
5807 @code{.debug_line} state machine to @code{true}.
5809 @item is_stmt @var{value}
5810 This option will set the @code{is_stmt} register in the
5811 @code{.debug_line} state machine to @code{value}, which must be
5814 @item isa @var{value}
5815 This directive will set the @code{isa} register in the @code{.debug_line}
5816 state machine to @var{value}, which must be an unsigned integer.
5818 @item discriminator @var{value}
5819 This directive will set the @code{discriminator} register in the @code{.debug_line}
5820 state machine to @var{value}, which must be an unsigned integer.
5824 @node Loc_mark_labels
5825 @section @code{.loc_mark_labels @var{enable}}
5826 @cindex @code{loc_mark_labels} directive
5827 When emitting DWARF2 line number information,
5828 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5829 to the @code{.debug_line} line number matrix with the @code{basic_block}
5830 register in the state machine set whenever a code label is seen.
5831 The @var{enable} argument should be either 1 or 0, to enable or disable
5832 this function respectively.
5836 @section @code{.local @var{names}}
5838 @cindex @code{local} directive
5839 This directive, which is available for ELF targets, marks each symbol in
5840 the comma-separated list of @code{names} as a local symbol so that it
5841 will not be externally visible. If the symbols do not already exist,
5842 they will be created.
5844 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5845 accept an alignment argument, which is the case for most ELF targets,
5846 the @code{.local} directive can be used in combination with @code{.comm}
5847 (@pxref{Comm}) to define aligned local common data.
5851 @section @code{.long @var{expressions}}
5853 @cindex @code{long} directive
5854 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5857 @c no one seems to know what this is for or whether this description is
5858 @c what it really ought to do
5860 @section @code{.lsym @var{symbol}, @var{expression}}
5862 @cindex @code{lsym} directive
5863 @cindex symbol, not referenced in assembly
5864 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5865 the hash table, ensuring it cannot be referenced by name during the
5866 rest of the assembly. This sets the attributes of the symbol to be
5867 the same as the expression value:
5869 @var{other} = @var{descriptor} = 0
5870 @var{type} = @r{(section of @var{expression})}
5871 @var{value} = @var{expression}
5874 The new symbol is not flagged as external.
5878 @section @code{.macro}
5881 The commands @code{.macro} and @code{.endm} allow you to define macros that
5882 generate assembly output. For example, this definition specifies a macro
5883 @code{sum} that puts a sequence of numbers into memory:
5886 .macro sum from=0, to=5
5895 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5907 @item .macro @var{macname}
5908 @itemx .macro @var{macname} @var{macargs} @dots{}
5909 @cindex @code{macro} directive
5910 Begin the definition of a macro called @var{macname}. If your macro
5911 definition requires arguments, specify their names after the macro name,
5912 separated by commas or spaces. You can qualify the macro argument to
5913 indicate whether all invocations must specify a non-blank value (through
5914 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5915 (through @samp{:@code{vararg}}). You can supply a default value for any
5916 macro argument by following the name with @samp{=@var{deflt}}. You
5917 cannot define two macros with the same @var{macname} unless it has been
5918 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5919 definitions. For example, these are all valid @code{.macro} statements:
5923 Begin the definition of a macro called @code{comm}, which takes no
5926 @item .macro plus1 p, p1
5927 @itemx .macro plus1 p p1
5928 Either statement begins the definition of a macro called @code{plus1},
5929 which takes two arguments; within the macro definition, write
5930 @samp{\p} or @samp{\p1} to evaluate the arguments.
5932 @item .macro reserve_str p1=0 p2
5933 Begin the definition of a macro called @code{reserve_str}, with two
5934 arguments. The first argument has a default value, but not the second.
5935 After the definition is complete, you can call the macro either as
5936 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5937 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5938 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5939 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5941 @item .macro m p1:req, p2=0, p3:vararg
5942 Begin the definition of a macro called @code{m}, with at least three
5943 arguments. The first argument must always have a value specified, but
5944 not the second, which instead has a default value. The third formal
5945 will get assigned all remaining arguments specified at invocation time.
5947 When you call a macro, you can specify the argument values either by
5948 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5949 @samp{sum to=17, from=9}.
5953 Note that since each of the @var{macargs} can be an identifier exactly
5954 as any other one permitted by the target architecture, there may be
5955 occasional problems if the target hand-crafts special meanings to certain
5956 characters when they occur in a special position. For example, if the colon
5957 (@code{:}) is generally permitted to be part of a symbol name, but the
5958 architecture specific code special-cases it when occurring as the final
5959 character of a symbol (to denote a label), then the macro parameter
5960 replacement code will have no way of knowing that and consider the whole
5961 construct (including the colon) an identifier, and check only this
5962 identifier for being the subject to parameter substitution. So for example
5963 this macro definition:
5971 might not work as expected. Invoking @samp{label foo} might not create a label
5972 called @samp{foo} but instead just insert the text @samp{\l:} into the
5973 assembler source, probably generating an error about an unrecognised
5976 Similarly problems might occur with the period character (@samp{.})
5977 which is often allowed inside opcode names (and hence identifier names). So
5978 for example constructing a macro to build an opcode from a base name and a
5979 length specifier like this:
5982 .macro opcode base length
5987 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5988 instruction but instead generate some kind of error as the assembler tries to
5989 interpret the text @samp{\base.\length}.
5991 There are several possible ways around this problem:
5994 @item Insert white space
5995 If it is possible to use white space characters then this is the simplest
6004 @item Use @samp{\()}
6005 The string @samp{\()} can be used to separate the end of a macro argument from
6006 the following text. eg:
6009 .macro opcode base length
6014 @item Use the alternate macro syntax mode
6015 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6016 used as a separator. eg:
6026 Note: this problem of correctly identifying string parameters to pseudo ops
6027 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6028 and @code{.irpc} (@pxref{Irpc}) as well.
6031 @cindex @code{endm} directive
6032 Mark the end of a macro definition.
6035 @cindex @code{exitm} directive
6036 Exit early from the current macro definition.
6038 @cindex number of macros executed
6039 @cindex macros, count executed
6041 @command{@value{AS}} maintains a counter of how many macros it has
6042 executed in this pseudo-variable; you can copy that number to your
6043 output with @samp{\@@}, but @emph{only within a macro definition}.
6045 @item LOCAL @var{name} [ , @dots{} ]
6046 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6047 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6048 @xref{Altmacro,,@code{.altmacro}}.
6052 @section @code{.mri @var{val}}
6054 @cindex @code{mri} directive
6055 @cindex MRI mode, temporarily
6056 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6057 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6058 affects code assembled until the next @code{.mri} directive, or until the end
6059 of the file. @xref{M, MRI mode, MRI mode}.
6062 @section @code{.noaltmacro}
6063 Disable alternate macro mode. @xref{Altmacro}.
6066 @section @code{.nolist}
6068 @cindex @code{nolist} directive
6069 @cindex listing control, turning off
6070 Control (in conjunction with the @code{.list} directive) whether or
6071 not assembly listings are generated. These two directives maintain an
6072 internal counter (which is zero initially). @code{.list} increments the
6073 counter, and @code{.nolist} decrements it. Assembly listings are
6074 generated whenever the counter is greater than zero.
6077 @section @code{.octa @var{bignums}}
6079 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
6080 @cindex @code{octa} directive
6081 @cindex integer, 16-byte
6082 @cindex sixteen byte integer
6083 This directive expects zero or more bignums, separated by commas. For each
6084 bignum, it emits a 16-byte integer.
6086 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6087 hence @emph{octa}-word for 16 bytes.
6090 @section @code{.offset @var{loc}}
6092 @cindex @code{offset} directive
6093 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6094 be an absolute expression. This directive may be useful for defining
6095 symbols with absolute values. Do not confuse it with the @code{.org}
6099 @section @code{.org @var{new-lc} , @var{fill}}
6101 @cindex @code{org} directive
6102 @cindex location counter, advancing
6103 @cindex advancing location counter
6104 @cindex current address, advancing
6105 Advance the location counter of the current section to
6106 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6107 expression with the same section as the current subsection. That is,
6108 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6109 wrong section, the @code{.org} directive is ignored. To be compatible
6110 with former assemblers, if the section of @var{new-lc} is absolute,
6111 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6112 is the same as the current subsection.
6114 @code{.org} may only increase the location counter, or leave it
6115 unchanged; you cannot use @code{.org} to move the location counter
6118 @c double negative used below "not undefined" because this is a specific
6119 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6120 @c section. doc@cygnus.com 18feb91
6121 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6122 may not be undefined. If you really detest this restriction we eagerly await
6123 a chance to share your improved assembler.
6125 Beware that the origin is relative to the start of the section, not
6126 to the start of the subsection. This is compatible with other
6127 people's assemblers.
6129 When the location counter (of the current subsection) is advanced, the
6130 intervening bytes are filled with @var{fill} which should be an
6131 absolute expression. If the comma and @var{fill} are omitted,
6132 @var{fill} defaults to zero.
6135 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6137 @cindex padding the location counter given a power of two
6138 @cindex @code{p2align} directive
6139 Pad the location counter (in the current subsection) to a particular
6140 storage boundary. The first expression (which must be absolute) is the
6141 number of low-order zero bits the location counter must have after
6142 advancement. For example @samp{.p2align 3} advances the location
6143 counter until it a multiple of 8. If the location counter is already a
6144 multiple of 8, no change is needed.
6146 The second expression (also absolute) gives the fill value to be stored in the
6147 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6148 padding bytes are normally zero. However, on some systems, if the section is
6149 marked as containing code and the fill value is omitted, the space is filled
6150 with no-op instructions.
6152 The third expression is also absolute, and is also optional. If it is present,
6153 it is the maximum number of bytes that should be skipped by this alignment
6154 directive. If doing the alignment would require skipping more bytes than the
6155 specified maximum, then the alignment is not done at all. You can omit the
6156 fill value (the second argument) entirely by simply using two commas after the
6157 required alignment; this can be useful if you want the alignment to be filled
6158 with no-op instructions when appropriate.
6160 @cindex @code{p2alignw} directive
6161 @cindex @code{p2alignl} directive
6162 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6163 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6164 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6165 fill pattern as a four byte longword value. For example, @code{.p2alignw
6166 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6167 filled in with the value 0x368d (the exact placement of the bytes depends upon
6168 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6173 @section @code{.popsection}
6175 @cindex @code{popsection} directive
6176 @cindex Section Stack
6177 This is one of the ELF section stack manipulation directives. The others are
6178 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6179 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6182 This directive replaces the current section (and subsection) with the top
6183 section (and subsection) on the section stack. This section is popped off the
6189 @section @code{.previous}
6191 @cindex @code{previous} directive
6192 @cindex Section Stack
6193 This is one of the ELF section stack manipulation directives. The others are
6194 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6195 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6196 (@pxref{PopSection}).
6198 This directive swaps the current section (and subsection) with most recently
6199 referenced section/subsection pair prior to this one. Multiple
6200 @code{.previous} directives in a row will flip between two sections (and their
6201 subsections). For example:
6213 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6219 # Now in section A subsection 1
6223 # Now in section B subsection 0
6226 # Now in section B subsection 1
6229 # Now in section B subsection 0
6233 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6234 section B and 0x9abc into subsection 1 of section B.
6236 In terms of the section stack, this directive swaps the current section with
6237 the top section on the section stack.
6241 @section @code{.print @var{string}}
6243 @cindex @code{print} directive
6244 @command{@value{AS}} will print @var{string} on the standard output during
6245 assembly. You must put @var{string} in double quotes.
6249 @section @code{.protected @var{names}}
6251 @cindex @code{protected} directive
6253 This is one of the ELF visibility directives. The other two are
6254 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6256 This directive overrides the named symbols default visibility (which is set by
6257 their binding: local, global or weak). The directive sets the visibility to
6258 @code{protected} which means that any references to the symbols from within the
6259 components that defines them must be resolved to the definition in that
6260 component, even if a definition in another component would normally preempt
6265 @section @code{.psize @var{lines} , @var{columns}}
6267 @cindex @code{psize} directive
6268 @cindex listing control: paper size
6269 @cindex paper size, for listings
6270 Use this directive to declare the number of lines---and, optionally, the
6271 number of columns---to use for each page, when generating listings.
6273 If you do not use @code{.psize}, listings use a default line-count
6274 of 60. You may omit the comma and @var{columns} specification; the
6275 default width is 200 columns.
6277 @command{@value{AS}} generates formfeeds whenever the specified number of
6278 lines is exceeded (or whenever you explicitly request one, using
6281 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6282 those explicitly specified with @code{.eject}.
6285 @section @code{.purgem @var{name}}
6287 @cindex @code{purgem} directive
6288 Undefine the macro @var{name}, so that later uses of the string will not be
6289 expanded. @xref{Macro}.
6293 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6295 @cindex @code{pushsection} directive
6296 @cindex Section Stack
6297 This is one of the ELF section stack manipulation directives. The others are
6298 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6299 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6302 This directive pushes the current section (and subsection) onto the
6303 top of the section stack, and then replaces the current section and
6304 subsection with @code{name} and @code{subsection}. The optional
6305 @code{flags}, @code{type} and @code{arguments} are treated the same
6306 as in the @code{.section} (@pxref{Section}) directive.
6310 @section @code{.quad @var{bignums}}
6312 @cindex @code{quad} directive
6313 @code{.quad} expects zero or more bignums, separated by commas. For
6314 each bignum, it emits
6316 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6317 warning message; and just takes the lowest order 8 bytes of the bignum.
6318 @cindex eight-byte integer
6319 @cindex integer, 8-byte
6321 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6322 hence @emph{quad}-word for 8 bytes.
6325 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6326 warning message; and just takes the lowest order 16 bytes of the bignum.
6327 @cindex sixteen-byte integer
6328 @cindex integer, 16-byte
6332 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6334 @cindex @code{reloc} directive
6335 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6336 @var{expression}. If @var{offset} is a number, the relocation is generated in
6337 the current section. If @var{offset} is an expression that resolves to a
6338 symbol plus offset, the relocation is generated in the given symbol's section.
6339 @var{expression}, if present, must resolve to a symbol plus addend or to an
6340 absolute value, but note that not all targets support an addend. e.g. ELF REL
6341 targets such as i386 store an addend in the section contents rather than in the
6342 relocation. This low level interface does not support addends stored in the
6346 @section @code{.rept @var{count}}
6348 @cindex @code{rept} directive
6349 Repeat the sequence of lines between the @code{.rept} directive and the next
6350 @code{.endr} directive @var{count} times.
6352 For example, assembling
6360 is equivalent to assembling
6369 @section @code{.sbttl "@var{subheading}"}
6371 @cindex @code{sbttl} directive
6372 @cindex subtitles for listings
6373 @cindex listing control: subtitle
6374 Use @var{subheading} as the title (third line, immediately after the
6375 title line) when generating assembly listings.
6377 This directive affects subsequent pages, as well as the current page if
6378 it appears within ten lines of the top of a page.
6382 @section @code{.scl @var{class}}
6384 @cindex @code{scl} directive
6385 @cindex symbol storage class (COFF)
6386 @cindex COFF symbol storage class
6387 Set the storage-class value for a symbol. This directive may only be
6388 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6389 whether a symbol is static or external, or it may record further
6390 symbolic debugging information.
6393 The @samp{.scl} directive is primarily associated with COFF output; when
6394 configured to generate @code{b.out} output format, @command{@value{AS}}
6395 accepts this directive but ignores it.
6401 @section @code{.section @var{name}}
6403 @cindex named section
6404 Use the @code{.section} directive to assemble the following code into a section
6407 This directive is only supported for targets that actually support arbitrarily
6408 named sections; on @code{a.out} targets, for example, it is not accepted, even
6409 with a standard @code{a.out} section name.
6413 @c only print the extra heading if both COFF and ELF are set
6414 @subheading COFF Version
6417 @cindex @code{section} directive (COFF version)
6418 For COFF targets, the @code{.section} directive is used in one of the following
6422 .section @var{name}[, "@var{flags}"]
6423 .section @var{name}[, @var{subsection}]
6426 If the optional argument is quoted, it is taken as flags to use for the
6427 section. Each flag is a single character. The following flags are recognized:
6431 bss section (uninitialized data)
6433 section is not loaded
6439 exclude section from linking
6445 shared section (meaningful for PE targets)
6447 ignored. (For compatibility with the ELF version)
6449 section is not readable (meaningful for PE targets)
6451 single-digit power-of-two section alignment (GNU extension)
6454 If no flags are specified, the default flags depend upon the section name. If
6455 the section name is not recognized, the default will be for the section to be
6456 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6457 from the section, rather than adding them, so if they are used on their own it
6458 will be as if no flags had been specified at all.
6460 If the optional argument to the @code{.section} directive is not quoted, it is
6461 taken as a subsection number (@pxref{Sub-Sections}).
6466 @c only print the extra heading if both COFF and ELF are set
6467 @subheading ELF Version
6470 @cindex Section Stack
6471 This is one of the ELF section stack manipulation directives. The others are
6472 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6473 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6474 @code{.previous} (@pxref{Previous}).
6476 @cindex @code{section} directive (ELF version)
6477 For ELF targets, the @code{.section} directive is used like this:
6480 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6483 @anchor{Section Name Substitutions}
6484 @kindex --sectname-subst
6485 @cindex section name substitution
6486 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6487 argument may contain a substitution sequence. Only @code{%S} is supported
6488 at the moment, and substitutes the current section name. For example:
6491 .macro exception_code
6492 .section %S.exception
6493 [exception code here]
6508 The two @code{exception_code} invocations above would create the
6509 @code{.text.exception} and @code{.init.exception} sections respectively.
6510 This is useful e.g. to discriminate between ancillary sections that are
6511 tied to setup code to be discarded after use from ancillary sections that
6512 need to stay resident without having to define multiple @code{exception_code}
6513 macros just for that purpose.
6515 The optional @var{flags} argument is a quoted string which may contain any
6516 combination of the following characters:
6520 section is allocatable
6522 section is excluded from executable and shared library.
6526 section is executable
6528 section is mergeable
6530 section contains zero terminated strings
6532 section is a member of a section group
6534 section is used for thread-local-storage
6536 section is a member of the previously-current section's group, if any
6537 @item @code{<number>}
6538 a numeric value indicating the bits to be set in the ELF section header's flags
6539 field. Note - if one or more of the alphabetic characters described above is
6540 also included in the flags field, their bit values will be ORed into the
6542 @item @code{<target specific>}
6543 some targets extend this list with their own flag characters
6546 Note - once a section's flags have been set they cannot be changed. There are
6547 a few exceptions to this rule however. Processor and application specific
6548 flags can be added to an already defined section. The @code{.interp},
6549 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6550 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6551 section may have the executable (@code{x}) flag added.
6553 The optional @var{type} argument may contain one of the following constants:
6557 section contains data
6559 section does not contain data (i.e., section only occupies space)
6561 section contains data which is used by things other than the program
6563 section contains an array of pointers to init functions
6565 section contains an array of pointers to finish functions
6566 @item @@preinit_array
6567 section contains an array of pointers to pre-init functions
6568 @item @@@code{<number>}
6569 a numeric value to be set as the ELF section header's type field.
6570 @item @@@code{<target specific>}
6571 some targets extend this list with their own types
6574 Many targets only support the first three section types. The type may be
6575 enclosed in double quotes if necessary.
6577 Note on targets where the @code{@@} character is the start of a comment (eg
6578 ARM) then another character is used instead. For example the ARM port uses the
6581 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6582 special and have fixed types. Any attempt to declare them with a different
6583 type will generate an error from the assembler.
6585 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6586 be specified as well as an extra argument---@var{entsize}---like this:
6589 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6592 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6593 constants, each @var{entsize} octets long. Sections with both @code{M} and
6594 @code{S} must contain zero terminated strings where each character is
6595 @var{entsize} bytes long. The linker may remove duplicates within sections with
6596 the same name, same entity size and same flags. @var{entsize} must be an
6597 absolute expression. For sections with both @code{M} and @code{S}, a string
6598 which is a suffix of a larger string is considered a duplicate. Thus
6599 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6600 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6602 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6603 be present along with an additional field like this:
6606 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6609 The @var{GroupName} field specifies the name of the section group to which this
6610 particular section belongs. The optional linkage field can contain:
6614 indicates that only one copy of this section should be retained
6619 Note: if both the @var{M} and @var{G} flags are present then the fields for
6620 the Merge flag should come first, like this:
6623 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6626 If @var{flags} contains the @code{?} symbol then it may not also contain the
6627 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6628 present. Instead, @code{?} says to consider the section that's current before
6629 this directive. If that section used @code{G}, then the new section will use
6630 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6631 If not, then the @code{?} symbol has no effect.
6633 If no flags are specified, the default flags depend upon the section name. If
6634 the section name is not recognized, the default will be for the section to have
6635 none of the above flags: it will not be allocated in memory, nor writable, nor
6636 executable. The section will contain data.
6638 For ELF targets, the assembler supports another type of @code{.section}
6639 directive for compatibility with the Solaris assembler:
6642 .section "@var{name}"[, @var{flags}...]
6645 Note that the section name is quoted. There may be a sequence of comma
6650 section is allocatable
6654 section is executable
6656 section is excluded from executable and shared library.
6658 section is used for thread local storage
6661 This directive replaces the current section and subsection. See the
6662 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6663 some examples of how this directive and the other section stack directives
6669 @section @code{.set @var{symbol}, @var{expression}}
6671 @cindex @code{set} directive
6672 @cindex symbol value, setting
6673 Set the value of @var{symbol} to @var{expression}. This
6674 changes @var{symbol}'s value and type to conform to
6675 @var{expression}. If @var{symbol} was flagged as external, it remains
6676 flagged (@pxref{Symbol Attributes}).
6678 You may @code{.set} a symbol many times in the same assembly provided that the
6679 values given to the symbol are constants. Values that are based on expressions
6680 involving other symbols are allowed, but some targets may restrict this to only
6681 being done once per assembly. This is because those targets do not set the
6682 addresses of symbols at assembly time, but rather delay the assignment until a
6683 final link is performed. This allows the linker a chance to change the code in
6684 the files, changing the location of, and the relative distance between, various
6687 If you @code{.set} a global symbol, the value stored in the object
6688 file is the last value stored into it.
6691 On Z80 @code{set} is a real instruction, use
6692 @samp{@var{symbol} defl @var{expression}} instead.
6696 @section @code{.short @var{expressions}}
6698 @cindex @code{short} directive
6700 @code{.short} is normally the same as @samp{.word}.
6701 @xref{Word,,@code{.word}}.
6703 In some configurations, however, @code{.short} and @code{.word} generate
6704 numbers of different lengths. @xref{Machine Dependencies}.
6708 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6711 This expects zero or more @var{expressions}, and emits
6712 a 16 bit number for each.
6717 @section @code{.single @var{flonums}}
6719 @cindex @code{single} directive
6720 @cindex floating point numbers (single)
6721 This directive assembles zero or more flonums, separated by commas. It
6722 has the same effect as @code{.float}.
6724 The exact kind of floating point numbers emitted depends on how
6725 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6729 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6730 numbers in @sc{ieee} format.
6736 @section @code{.size}
6738 This directive is used to set the size associated with a symbol.
6742 @c only print the extra heading if both COFF and ELF are set
6743 @subheading COFF Version
6746 @cindex @code{size} directive (COFF version)
6747 For COFF targets, the @code{.size} directive is only permitted inside
6748 @code{.def}/@code{.endef} pairs. It is used like this:
6751 .size @var{expression}
6755 @samp{.size} is only meaningful when generating COFF format output; when
6756 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6763 @c only print the extra heading if both COFF and ELF are set
6764 @subheading ELF Version
6767 @cindex @code{size} directive (ELF version)
6768 For ELF targets, the @code{.size} directive is used like this:
6771 .size @var{name} , @var{expression}
6774 This directive sets the size associated with a symbol @var{name}.
6775 The size in bytes is computed from @var{expression} which can make use of label
6776 arithmetic. This directive is typically used to set the size of function
6781 @ifclear no-space-dir
6783 @section @code{.skip @var{size} , @var{fill}}
6785 @cindex @code{skip} directive
6786 @cindex filling memory
6787 This directive emits @var{size} bytes, each of value @var{fill}. Both
6788 @var{size} and @var{fill} are absolute expressions. If the comma and
6789 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6794 @section @code{.sleb128 @var{expressions}}
6796 @cindex @code{sleb128} directive
6797 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6798 compact, variable length representation of numbers used by the DWARF
6799 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6801 @ifclear no-space-dir
6803 @section @code{.space @var{size} , @var{fill}}
6805 @cindex @code{space} directive
6806 @cindex filling memory
6807 This directive emits @var{size} bytes, each of value @var{fill}. Both
6808 @var{size} and @var{fill} are absolute expressions. If the comma
6809 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6814 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6815 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6816 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6817 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6825 @section @code{.stabd, .stabn, .stabs}
6827 @cindex symbolic debuggers, information for
6828 @cindex @code{stab@var{x}} directives
6829 There are three directives that begin @samp{.stab}.
6830 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6831 The symbols are not entered in the @command{@value{AS}} hash table: they
6832 cannot be referenced elsewhere in the source file.
6833 Up to five fields are required:
6837 This is the symbol's name. It may contain any character except
6838 @samp{\000}, so is more general than ordinary symbol names. Some
6839 debuggers used to code arbitrarily complex structures into symbol names
6843 An absolute expression. The symbol's type is set to the low 8 bits of
6844 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6845 and debuggers choke on silly bit patterns.
6848 An absolute expression. The symbol's ``other'' attribute is set to the
6849 low 8 bits of this expression.
6852 An absolute expression. The symbol's descriptor is set to the low 16
6853 bits of this expression.
6856 An absolute expression which becomes the symbol's value.
6859 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6860 or @code{.stabs} statement, the symbol has probably already been created;
6861 you get a half-formed symbol in your object file. This is
6862 compatible with earlier assemblers!
6865 @cindex @code{stabd} directive
6866 @item .stabd @var{type} , @var{other} , @var{desc}
6868 The ``name'' of the symbol generated is not even an empty string.
6869 It is a null pointer, for compatibility. Older assemblers used a
6870 null pointer so they didn't waste space in object files with empty
6873 The symbol's value is set to the location counter,
6874 relocatably. When your program is linked, the value of this symbol
6875 is the address of the location counter when the @code{.stabd} was
6878 @cindex @code{stabn} directive
6879 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6880 The name of the symbol is set to the empty string @code{""}.
6882 @cindex @code{stabs} directive
6883 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6884 All five fields are specified.
6890 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6891 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6893 @cindex string, copying to object file
6894 @cindex string8, copying to object file
6895 @cindex string16, copying to object file
6896 @cindex string32, copying to object file
6897 @cindex string64, copying to object file
6898 @cindex @code{string} directive
6899 @cindex @code{string8} directive
6900 @cindex @code{string16} directive
6901 @cindex @code{string32} directive
6902 @cindex @code{string64} directive
6904 Copy the characters in @var{str} to the object file. You may specify more than
6905 one string to copy, separated by commas. Unless otherwise specified for a
6906 particular machine, the assembler marks the end of each string with a 0 byte.
6907 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6909 The variants @code{string16}, @code{string32} and @code{string64} differ from
6910 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6911 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6912 are stored in target endianness byte order.
6918 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6919 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6924 @section @code{.struct @var{expression}}
6926 @cindex @code{struct} directive
6927 Switch to the absolute section, and set the section offset to @var{expression},
6928 which must be an absolute expression. You might use this as follows:
6937 This would define the symbol @code{field1} to have the value 0, the symbol
6938 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6939 value 8. Assembly would be left in the absolute section, and you would need to
6940 use a @code{.section} directive of some sort to change to some other section
6941 before further assembly.
6945 @section @code{.subsection @var{name}}
6947 @cindex @code{subsection} directive
6948 @cindex Section Stack
6949 This is one of the ELF section stack manipulation directives. The others are
6950 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6951 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6954 This directive replaces the current subsection with @code{name}. The current
6955 section is not changed. The replaced subsection is put onto the section stack
6956 in place of the then current top of stack subsection.
6961 @section @code{.symver}
6962 @cindex @code{symver} directive
6963 @cindex symbol versioning
6964 @cindex versions of symbols
6965 Use the @code{.symver} directive to bind symbols to specific version nodes
6966 within a source file. This is only supported on ELF platforms, and is
6967 typically used when assembling files to be linked into a shared library.
6968 There are cases where it may make sense to use this in objects to be bound
6969 into an application itself so as to override a versioned symbol from a
6972 For ELF targets, the @code{.symver} directive can be used like this:
6974 .symver @var{name}, @var{name2@@nodename}
6976 If the symbol @var{name} is defined within the file
6977 being assembled, the @code{.symver} directive effectively creates a symbol
6978 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6979 just don't try and create a regular alias is that the @var{@@} character isn't
6980 permitted in symbol names. The @var{name2} part of the name is the actual name
6981 of the symbol by which it will be externally referenced. The name @var{name}
6982 itself is merely a name of convenience that is used so that it is possible to
6983 have definitions for multiple versions of a function within a single source
6984 file, and so that the compiler can unambiguously know which version of a
6985 function is being mentioned. The @var{nodename} portion of the alias should be
6986 the name of a node specified in the version script supplied to the linker when
6987 building a shared library. If you are attempting to override a versioned
6988 symbol from a shared library, then @var{nodename} should correspond to the
6989 nodename of the symbol you are trying to override.
6991 If the symbol @var{name} is not defined within the file being assembled, all
6992 references to @var{name} will be changed to @var{name2@@nodename}. If no
6993 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6996 Another usage of the @code{.symver} directive is:
6998 .symver @var{name}, @var{name2@@@@nodename}
7000 In this case, the symbol @var{name} must exist and be defined within
7001 the file being assembled. It is similar to @var{name2@@nodename}. The
7002 difference is @var{name2@@@@nodename} will also be used to resolve
7003 references to @var{name2} by the linker.
7005 The third usage of the @code{.symver} directive is:
7007 .symver @var{name}, @var{name2@@@@@@nodename}
7009 When @var{name} is not defined within the
7010 file being assembled, it is treated as @var{name2@@nodename}. When
7011 @var{name} is defined within the file being assembled, the symbol
7012 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7017 @section @code{.tag @var{structname}}
7019 @cindex COFF structure debugging
7020 @cindex structure debugging, COFF
7021 @cindex @code{tag} directive
7022 This directive is generated by compilers to include auxiliary debugging
7023 information in the symbol table. It is only permitted inside
7024 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7025 definitions in the symbol table with instances of those structures.
7028 @samp{.tag} is only used when generating COFF format output; when
7029 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
7035 @section @code{.text @var{subsection}}
7037 @cindex @code{text} directive
7038 Tells @command{@value{AS}} to assemble the following statements onto the end of
7039 the text subsection numbered @var{subsection}, which is an absolute
7040 expression. If @var{subsection} is omitted, subsection number zero
7044 @section @code{.title "@var{heading}"}
7046 @cindex @code{title} directive
7047 @cindex listing control: title line
7048 Use @var{heading} as the title (second line, immediately after the
7049 source file name and pagenumber) when generating assembly listings.
7051 This directive affects subsequent pages, as well as the current page if
7052 it appears within ten lines of the top of a page.
7056 @section @code{.type}
7058 This directive is used to set the type of a symbol.
7062 @c only print the extra heading if both COFF and ELF are set
7063 @subheading COFF Version
7066 @cindex COFF symbol type
7067 @cindex symbol type, COFF
7068 @cindex @code{type} directive (COFF version)
7069 For COFF targets, this directive is permitted only within
7070 @code{.def}/@code{.endef} pairs. It is used like this:
7076 This records the integer @var{int} as the type attribute of a symbol table
7080 @samp{.type} is associated only with COFF format output; when
7081 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
7082 directive but ignores it.
7088 @c only print the extra heading if both COFF and ELF are set
7089 @subheading ELF Version
7092 @cindex ELF symbol type
7093 @cindex symbol type, ELF
7094 @cindex @code{type} directive (ELF version)
7095 For ELF targets, the @code{.type} directive is used like this:
7098 .type @var{name} , @var{type description}
7101 This sets the type of symbol @var{name} to be either a
7102 function symbol or an object symbol. There are five different syntaxes
7103 supported for the @var{type description} field, in order to provide
7104 compatibility with various other assemblers.
7106 Because some of the characters used in these syntaxes (such as @samp{@@} and
7107 @samp{#}) are comment characters for some architectures, some of the syntaxes
7108 below do not work on all architectures. The first variant will be accepted by
7109 the GNU assembler on all architectures so that variant should be used for
7110 maximum portability, if you do not need to assemble your code with other
7113 The syntaxes supported are:
7116 .type <name> STT_<TYPE_IN_UPPER_CASE>
7117 .type <name>,#<type>
7118 .type <name>,@@<type>
7119 .type <name>,%<type>
7120 .type <name>,"<type>"
7123 The types supported are:
7128 Mark the symbol as being a function name.
7131 @itemx gnu_indirect_function
7132 Mark the symbol as an indirect function when evaluated during reloc
7133 processing. (This is only supported on assemblers targeting GNU systems).
7137 Mark the symbol as being a data object.
7141 Mark the symbol as being a thread-local data object.
7145 Mark the symbol as being a common data object.
7149 Does not mark the symbol in any way. It is supported just for completeness.
7151 @item gnu_unique_object
7152 Marks the symbol as being a globally unique data object. The dynamic linker
7153 will make sure that in the entire process there is just one symbol with this
7154 name and type in use. (This is only supported on assemblers targeting GNU
7159 Note: Some targets support extra types in addition to those listed above.
7165 @section @code{.uleb128 @var{expressions}}
7167 @cindex @code{uleb128} directive
7168 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7169 compact, variable length representation of numbers used by the DWARF
7170 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7174 @section @code{.val @var{addr}}
7176 @cindex @code{val} directive
7177 @cindex COFF value attribute
7178 @cindex value attribute, COFF
7179 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7180 records the address @var{addr} as the value attribute of a symbol table
7184 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7185 configured for @code{b.out}, it accepts this directive but ignores it.
7191 @section @code{.version "@var{string}"}
7193 @cindex @code{version} directive
7194 This directive creates a @code{.note} section and places into it an ELF
7195 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7200 @section @code{.vtable_entry @var{table}, @var{offset}}
7202 @cindex @code{vtable_entry} directive
7203 This directive finds or creates a symbol @code{table} and creates a
7204 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7207 @section @code{.vtable_inherit @var{child}, @var{parent}}
7209 @cindex @code{vtable_inherit} directive
7210 This directive finds the symbol @code{child} and finds or creates the symbol
7211 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7212 parent whose addend is the value of the child symbol. As a special case the
7213 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7217 @section @code{.warning "@var{string}"}
7218 @cindex warning directive
7219 Similar to the directive @code{.error}
7220 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7223 @section @code{.weak @var{names}}
7225 @cindex @code{weak} directive
7226 This directive sets the weak attribute on the comma separated list of symbol
7227 @code{names}. If the symbols do not already exist, they will be created.
7229 On COFF targets other than PE, weak symbols are a GNU extension. This
7230 directive sets the weak attribute on the comma separated list of symbol
7231 @code{names}. If the symbols do not already exist, they will be created.
7233 On the PE target, weak symbols are supported natively as weak aliases.
7234 When a weak symbol is created that is not an alias, GAS creates an
7235 alternate symbol to hold the default value.
7238 @section @code{.weakref @var{alias}, @var{target}}
7240 @cindex @code{weakref} directive
7241 This directive creates an alias to the target symbol that enables the symbol to
7242 be referenced with weak-symbol semantics, but without actually making it weak.
7243 If direct references or definitions of the symbol are present, then the symbol
7244 will not be weak, but if all references to it are through weak references, the
7245 symbol will be marked as weak in the symbol table.
7247 The effect is equivalent to moving all references to the alias to a separate
7248 assembly source file, renaming the alias to the symbol in it, declaring the
7249 symbol as weak there, and running a reloadable link to merge the object files
7250 resulting from the assembly of the new source file and the old source file that
7251 had the references to the alias removed.
7253 The alias itself never makes to the symbol table, and is entirely handled
7254 within the assembler.
7257 @section @code{.word @var{expressions}}
7259 @cindex @code{word} directive
7260 This directive expects zero or more @var{expressions}, of any section,
7261 separated by commas.
7264 For each expression, @command{@value{AS}} emits a 32-bit number.
7267 For each expression, @command{@value{AS}} emits a 16-bit number.
7272 The size of the number emitted, and its byte order,
7273 depend on what target computer the assembly is for.
7276 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7277 @c happen---32-bit addressability, period; no long/short jumps.
7278 @ifset DIFF-TBL-KLUGE
7279 @cindex difference tables altered
7280 @cindex altered difference tables
7282 @emph{Warning: Special Treatment to support Compilers}
7286 Machines with a 32-bit address space, but that do less than 32-bit
7287 addressing, require the following special treatment. If the machine of
7288 interest to you does 32-bit addressing (or doesn't require it;
7289 @pxref{Machine Dependencies}), you can ignore this issue.
7292 In order to assemble compiler output into something that works,
7293 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7294 Directives of the form @samp{.word sym1-sym2} are often emitted by
7295 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7296 directive of the form @samp{.word sym1-sym2}, and the difference between
7297 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7298 creates a @dfn{secondary jump table}, immediately before the next label.
7299 This secondary jump table is preceded by a short-jump to the
7300 first byte after the secondary table. This short-jump prevents the flow
7301 of control from accidentally falling into the new table. Inside the
7302 table is a long-jump to @code{sym2}. The original @samp{.word}
7303 contains @code{sym1} minus the address of the long-jump to
7306 If there were several occurrences of @samp{.word sym1-sym2} before the
7307 secondary jump table, all of them are adjusted. If there was a
7308 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7309 long-jump to @code{sym4} is included in the secondary jump table,
7310 and the @code{.word} directives are adjusted to contain @code{sym3}
7311 minus the address of the long-jump to @code{sym4}; and so on, for as many
7312 entries in the original jump table as necessary.
7315 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7316 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7317 assembly language programmers.
7320 @c end DIFF-TBL-KLUGE
7322 @ifclear no-space-dir
7324 @section @code{.zero @var{size}}
7326 @cindex @code{zero} directive
7327 @cindex filling memory with zero bytes
7328 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7329 expression. This directive is actually an alias for the @samp{.skip} directive
7330 so in can take an optional second argument of the value to store in the bytes
7331 instead of zero. Using @samp{.zero} in this way would be confusing however.
7335 @section Deprecated Directives
7337 @cindex deprecated directives
7338 @cindex obsolescent directives
7339 One day these directives won't work.
7340 They are included for compatibility with older assemblers.
7347 @node Object Attributes
7348 @chapter Object Attributes
7349 @cindex object attributes
7351 @command{@value{AS}} assembles source files written for a specific architecture
7352 into object files for that architecture. But not all object files are alike.
7353 Many architectures support incompatible variations. For instance, floating
7354 point arguments might be passed in floating point registers if the object file
7355 requires hardware floating point support---or floating point arguments might be
7356 passed in integer registers if the object file supports processors with no
7357 hardware floating point unit. Or, if two objects are built for different
7358 generations of the same architecture, the combination may require the
7359 newer generation at run-time.
7361 This information is useful during and after linking. At link time,
7362 @command{@value{LD}} can warn about incompatible object files. After link
7363 time, tools like @command{gdb} can use it to process the linked file
7366 Compatibility information is recorded as a series of object attributes. Each
7367 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7368 string, and indicates who sets the meaning of the tag. The tag is an integer,
7369 and indicates what property the attribute describes. The value may be a string
7370 or an integer, and indicates how the property affects this object. Missing
7371 attributes are the same as attributes with a zero value or empty string value.
7373 Object attributes were developed as part of the ABI for the ARM Architecture.
7374 The file format is documented in @cite{ELF for the ARM Architecture}.
7377 * GNU Object Attributes:: @sc{gnu} Object Attributes
7378 * Defining New Object Attributes:: Defining New Object Attributes
7381 @node GNU Object Attributes
7382 @section @sc{gnu} Object Attributes
7384 The @code{.gnu_attribute} directive records an object attribute
7385 with vendor @samp{gnu}.
7387 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7388 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7389 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7390 2} is set for architecture-independent attributes and clear for
7391 architecture-dependent ones.
7393 @subsection Common @sc{gnu} attributes
7395 These attributes are valid on all architectures.
7398 @item Tag_compatibility (32)
7399 The compatibility attribute takes an integer flag value and a vendor name. If
7400 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7401 then the file is only compatible with the named toolchain. If it is greater
7402 than 1, the file can only be processed by other toolchains under some private
7403 arrangement indicated by the flag value and the vendor name.
7406 @subsection MIPS Attributes
7409 @item Tag_GNU_MIPS_ABI_FP (4)
7410 The floating-point ABI used by this object file. The value will be:
7414 0 for files not affected by the floating-point ABI.
7416 1 for files using the hardware floating-point ABI with a standard
7417 double-precision FPU.
7419 2 for files using the hardware floating-point ABI with a single-precision FPU.
7421 3 for files using the software floating-point ABI.
7423 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7424 floating-point registers, 32-bit general-purpose registers and increased the
7425 number of callee-saved floating-point registers.
7427 5 for files using the hardware floating-point ABI with a double-precision FPU
7428 with either 32-bit or 64-bit floating-point registers and 32-bit
7429 general-purpose registers.
7431 6 for files using the hardware floating-point ABI with 64-bit floating-point
7432 registers and 32-bit general-purpose registers.
7434 7 for files using the hardware floating-point ABI with 64-bit floating-point
7435 registers, 32-bit general-purpose registers and a rule that forbids the
7436 direct use of odd-numbered single-precision floating-point registers.
7440 @subsection PowerPC Attributes
7443 @item Tag_GNU_Power_ABI_FP (4)
7444 The floating-point ABI used by this object file. The value will be:
7448 0 for files not affected by the floating-point ABI.
7450 1 for files using double-precision hardware floating-point ABI.
7452 2 for files using the software floating-point ABI.
7454 3 for files using single-precision hardware floating-point ABI.
7457 @item Tag_GNU_Power_ABI_Vector (8)
7458 The vector ABI used by this object file. The value will be:
7462 0 for files not affected by the vector ABI.
7464 1 for files using general purpose registers to pass vectors.
7466 2 for files using AltiVec registers to pass vectors.
7468 3 for files using SPE registers to pass vectors.
7472 @subsection IBM z Systems Attributes
7475 @item Tag_GNU_S390_ABI_Vector (8)
7476 The vector ABI used by this object file. The value will be:
7480 0 for files not affected by the vector ABI.
7482 1 for files using software vector ABI.
7484 2 for files using hardware vector ABI.
7488 @node Defining New Object Attributes
7489 @section Defining New Object Attributes
7491 If you want to define a new @sc{gnu} object attribute, here are the places you
7492 will need to modify. New attributes should be discussed on the @samp{binutils}
7497 This manual, which is the official register of attributes.
7499 The header for your architecture @file{include/elf}, to define the tag.
7501 The @file{bfd} support file for your architecture, to merge the attribute
7502 and issue any appropriate link warnings.
7504 Test cases in @file{ld/testsuite} for merging and link warnings.
7506 @file{binutils/readelf.c} to display your attribute.
7508 GCC, if you want the compiler to mark the attribute automatically.
7514 @node Machine Dependencies
7515 @chapter Machine Dependent Features
7517 @cindex machine dependencies
7518 The machine instruction sets are (almost by definition) different on
7519 each machine where @command{@value{AS}} runs. Floating point representations
7520 vary as well, and @command{@value{AS}} often supports a few additional
7521 directives or command-line options for compatibility with other
7522 assemblers on a particular platform. Finally, some versions of
7523 @command{@value{AS}} support special pseudo-instructions for branch
7526 This chapter discusses most of these differences, though it does not
7527 include details on any machine's instruction set. For details on that
7528 subject, see the hardware manufacturer's manual.
7532 * AArch64-Dependent:: AArch64 Dependent Features
7535 * Alpha-Dependent:: Alpha Dependent Features
7538 * ARC-Dependent:: ARC Dependent Features
7541 * ARM-Dependent:: ARM Dependent Features
7544 * AVR-Dependent:: AVR Dependent Features
7547 * Blackfin-Dependent:: Blackfin Dependent Features
7550 * CR16-Dependent:: CR16 Dependent Features
7553 * CRIS-Dependent:: CRIS Dependent Features
7556 * D10V-Dependent:: D10V Dependent Features
7559 * D30V-Dependent:: D30V Dependent Features
7562 * Epiphany-Dependent:: EPIPHANY Dependent Features
7565 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7568 * HPPA-Dependent:: HPPA Dependent Features
7571 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7574 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7577 * i860-Dependent:: Intel 80860 Dependent Features
7580 * i960-Dependent:: Intel 80960 Dependent Features
7583 * IA-64-Dependent:: Intel IA-64 Dependent Features
7586 * IP2K-Dependent:: IP2K Dependent Features
7589 * LM32-Dependent:: LM32 Dependent Features
7592 * M32C-Dependent:: M32C Dependent Features
7595 * M32R-Dependent:: M32R Dependent Features
7598 * M68K-Dependent:: M680x0 Dependent Features
7601 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7604 * Meta-Dependent :: Meta Dependent Features
7607 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7610 * MIPS-Dependent:: MIPS Dependent Features
7613 * MMIX-Dependent:: MMIX Dependent Features
7616 * MSP430-Dependent:: MSP430 Dependent Features
7619 * NDS32-Dependent:: Andes NDS32 Dependent Features
7622 * NiosII-Dependent:: Altera Nios II Dependent Features
7625 * NS32K-Dependent:: NS32K Dependent Features
7628 * PDP-11-Dependent:: PDP-11 Dependent Features
7631 * PJ-Dependent:: picoJava Dependent Features
7634 * PPC-Dependent:: PowerPC Dependent Features
7637 * PRU-Dependent:: PRU Dependent Features
7640 * RL78-Dependent:: RL78 Dependent Features
7643 * RISC-V-Dependent:: RISC-V Dependent Features
7646 * RX-Dependent:: RX Dependent Features
7649 * S/390-Dependent:: IBM S/390 Dependent Features
7652 * SCORE-Dependent:: SCORE Dependent Features
7655 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7656 * SH64-Dependent:: SuperH SH64 Dependent Features
7659 * Sparc-Dependent:: SPARC Dependent Features
7662 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7665 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7668 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7671 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7674 * V850-Dependent:: V850 Dependent Features
7677 * Vax-Dependent:: VAX Dependent Features
7680 * Visium-Dependent:: Visium Dependent Features
7683 * XGATE-Dependent:: XGATE Features
7686 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7689 * Xtensa-Dependent:: Xtensa Dependent Features
7692 * Z80-Dependent:: Z80 Dependent Features
7695 * Z8000-Dependent:: Z8000 Dependent Features
7702 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7703 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7704 @c peculiarity: to preserve cross-references, there must be a node called
7705 @c "Machine Dependencies". Hence the conditional nodenames in each
7706 @c major node below. Node defaulting in makeinfo requires adjacency of
7707 @c node and sectioning commands; hence the repetition of @chapter BLAH
7708 @c in both conditional blocks.
7711 @include c-aarch64.texi
7715 @include c-alpha.texi
7731 @include c-bfin.texi
7735 @include c-cr16.texi
7739 @include c-cris.texi
7744 @node Machine Dependencies
7745 @chapter Machine Dependent Features
7747 The machine instruction sets are different on each Renesas chip family,
7748 and there are also some syntax differences among the families. This
7749 chapter describes the specific @command{@value{AS}} features for each
7753 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7754 * SH-Dependent:: Renesas SH Dependent Features
7761 @include c-d10v.texi
7765 @include c-d30v.texi
7769 @include c-epiphany.texi
7773 @include c-h8300.texi
7777 @include c-hppa.texi
7781 @include c-i370.texi
7785 @include c-i386.texi
7789 @include c-i860.texi
7793 @include c-i960.texi
7797 @include c-ia64.texi
7801 @include c-ip2k.texi
7805 @include c-lm32.texi
7809 @include c-m32c.texi
7813 @include c-m32r.texi
7817 @include c-m68k.texi
7821 @include c-m68hc11.texi
7825 @include c-metag.texi
7829 @include c-microblaze.texi
7833 @include c-mips.texi
7837 @include c-mmix.texi
7841 @include c-msp430.texi
7845 @include c-nds32.texi
7849 @include c-nios2.texi
7853 @include c-ns32k.texi
7857 @include c-pdp11.texi
7873 @include c-rl78.texi
7877 @include c-riscv.texi
7885 @include c-s390.texi
7889 @include c-score.texi
7894 @include c-sh64.texi
7898 @include c-sparc.texi
7902 @include c-tic54x.texi
7906 @include c-tic6x.texi
7910 @include c-tilegx.texi
7914 @include c-tilepro.texi
7918 @include c-v850.texi
7926 @include c-visium.texi
7930 @include c-xgate.texi
7934 @include c-xstormy16.texi
7938 @include c-xtensa.texi
7950 @c reverse effect of @down at top of generic Machine-Dep chapter
7954 @node Reporting Bugs
7955 @chapter Reporting Bugs
7956 @cindex bugs in assembler
7957 @cindex reporting bugs in assembler
7959 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7961 Reporting a bug may help you by bringing a solution to your problem, or it may
7962 not. But in any case the principal function of a bug report is to help the
7963 entire community by making the next version of @command{@value{AS}} work better.
7964 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7966 In order for a bug report to serve its purpose, you must include the
7967 information that enables us to fix the bug.
7970 * Bug Criteria:: Have you found a bug?
7971 * Bug Reporting:: How to report bugs
7975 @section Have You Found a Bug?
7976 @cindex bug criteria
7978 If you are not sure whether you have found a bug, here are some guidelines:
7981 @cindex fatal signal
7982 @cindex assembler crash
7983 @cindex crash of assembler
7985 If the assembler gets a fatal signal, for any input whatever, that is a
7986 @command{@value{AS}} bug. Reliable assemblers never crash.
7988 @cindex error on valid input
7990 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7992 @cindex invalid input
7994 If @command{@value{AS}} does not produce an error message for invalid input, that
7995 is a bug. However, you should note that your idea of ``invalid input'' might
7996 be our idea of ``an extension'' or ``support for traditional practice''.
7999 If you are an experienced user of assemblers, your suggestions for improvement
8000 of @command{@value{AS}} are welcome in any case.
8004 @section How to Report Bugs
8006 @cindex assembler bugs, reporting
8008 A number of companies and individuals offer support for @sc{gnu} products. If
8009 you obtained @command{@value{AS}} from a support organization, we recommend you
8010 contact that organization first.
8012 You can find contact information for many support companies and
8013 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8017 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8021 The fundamental principle of reporting bugs usefully is this:
8022 @strong{report all the facts}. If you are not sure whether to state a
8023 fact or leave it out, state it!
8025 Often people omit facts because they think they know what causes the problem
8026 and assume that some details do not matter. Thus, you might assume that the
8027 name of a symbol you use in an example does not matter. Well, probably it does
8028 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8029 happens to fetch from the location where that name is stored in memory;
8030 perhaps, if the name were different, the contents of that location would fool
8031 the assembler into doing the right thing despite the bug. Play it safe and
8032 give a specific, complete example. That is the easiest thing for you to do,
8033 and the most helpful.
8035 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8036 it is new to us. Therefore, always write your bug reports on the assumption
8037 that the bug has not been reported previously.
8039 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8040 bell?'' This cannot help us fix a bug, so it is basically useless. We
8041 respond by asking for enough details to enable us to investigate.
8042 You might as well expedite matters by sending them to begin with.
8044 To enable us to fix the bug, you should include all these things:
8048 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8049 it with the @samp{--version} argument.
8051 Without this, we will not know whether there is any point in looking for
8052 the bug in the current version of @command{@value{AS}}.
8055 Any patches you may have applied to the @command{@value{AS}} source.
8058 The type of machine you are using, and the operating system name and
8062 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8066 The command arguments you gave the assembler to assemble your example and
8067 observe the bug. To guarantee you will not omit something important, list them
8068 all. A copy of the Makefile (or the output from make) is sufficient.
8070 If we were to try to guess the arguments, we would probably guess wrong
8071 and then we might not encounter the bug.
8074 A complete input file that will reproduce the bug. If the bug is observed when
8075 the assembler is invoked via a compiler, send the assembler source, not the
8076 high level language source. Most compilers will produce the assembler source
8077 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8078 the options @samp{-v --save-temps}; this will save the assembler source in a
8079 file with an extension of @file{.s}, and also show you exactly how
8080 @command{@value{AS}} is being run.
8083 A description of what behavior you observe that you believe is
8084 incorrect. For example, ``It gets a fatal signal.''
8086 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8087 will certainly notice it. But if the bug is incorrect output, we might not
8088 notice unless it is glaringly wrong. You might as well not give us a chance to
8091 Even if the problem you experience is a fatal signal, you should still say so
8092 explicitly. Suppose something strange is going on, such as, your copy of
8093 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8094 library on your system. (This has happened!) Your copy might crash and ours
8095 would not. If you told us to expect a crash, then when ours fails to crash, we
8096 would know that the bug was not happening for us. If you had not told us to
8097 expect a crash, then we would not be able to draw any conclusion from our
8101 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8102 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8103 option. Always send diffs from the old file to the new file. If you even
8104 discuss something in the @command{@value{AS}} source, refer to it by context, not
8107 The line numbers in our development sources will not match those in your
8108 sources. Your line numbers would convey no useful information to us.
8111 Here are some things that are not necessary:
8115 A description of the envelope of the bug.
8117 Often people who encounter a bug spend a lot of time investigating
8118 which changes to the input file will make the bug go away and which
8119 changes will not affect it.
8121 This is often time consuming and not very useful, because the way we
8122 will find the bug is by running a single example under the debugger
8123 with breakpoints, not by pure deduction from a series of examples.
8124 We recommend that you save your time for something else.
8126 Of course, if you can find a simpler example to report @emph{instead}
8127 of the original one, that is a convenience for us. Errors in the
8128 output will be easier to spot, running under the debugger will take
8129 less time, and so on.
8131 However, simplification is not vital; if you do not want to do this,
8132 report the bug anyway and send us the entire test case you used.
8135 A patch for the bug.
8137 A patch for the bug does help us if it is a good one. But do not omit
8138 the necessary information, such as the test case, on the assumption that
8139 a patch is all we need. We might see problems with your patch and decide
8140 to fix the problem another way, or we might not understand it at all.
8142 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8143 construct an example that will make the program follow a certain path through
8144 the code. If you do not send us the example, we will not be able to construct
8145 one, so we will not be able to verify that the bug is fixed.
8147 And if we cannot understand what bug you are trying to fix, or why your
8148 patch should be an improvement, we will not install it. A test case will
8149 help us to understand.
8152 A guess about what the bug is or what it depends on.
8154 Such guesses are usually wrong. Even we cannot guess right about such
8155 things without first using the debugger to find the facts.
8158 @node Acknowledgements
8159 @chapter Acknowledgements
8161 If you have contributed to GAS and your name isn't listed here,
8162 it is not meant as a slight. We just don't know about it. Send mail to the
8163 maintainer, and we'll correct the situation. Currently
8165 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8167 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8170 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8171 information and the 68k series machines, most of the preprocessing pass, and
8172 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8174 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8175 many bug fixes, including merging support for several processors, breaking GAS
8176 up to handle multiple object file format back ends (including heavy rewrite,
8177 testing, an integration of the coff and b.out back ends), adding configuration
8178 including heavy testing and verification of cross assemblers and file splits
8179 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8180 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8181 port (including considerable amounts of reverse engineering), a SPARC opcode
8182 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8183 assertions and made them work, much other reorganization, cleanup, and lint.
8185 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8186 in format-specific I/O modules.
8188 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8189 has done much work with it since.
8191 The Intel 80386 machine description was written by Eliot Dresselhaus.
8193 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8195 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8196 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8198 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8199 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8200 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8201 support a.out format.
8203 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8204 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8205 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8206 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8209 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8210 simplified the configuration of which versions accept which directives. He
8211 updated the 68k machine description so that Motorola's opcodes always produced
8212 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8213 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8214 cross-compilation support, and one bug in relaxation that took a week and
8215 required the proverbial one-bit fix.
8217 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8218 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8219 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8220 PowerPC assembler, and made a few other minor patches.
8222 Steve Chamberlain made GAS able to generate listings.
8224 Hewlett-Packard contributed support for the HP9000/300.
8226 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8227 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8228 formats). This work was supported by both the Center for Software Science at
8229 the University of Utah and Cygnus Support.
8231 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8232 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8233 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8234 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8235 and some initial 64-bit support).
8237 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8239 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8240 support for openVMS/Alpha.
8242 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8245 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8246 Inc.@: added support for Xtensa processors.
8248 Several engineers at Cygnus Support have also provided many small bug fixes and
8249 configuration enhancements.
8251 Jon Beniston added support for the Lattice Mico32 architecture.
8253 Many others have contributed large or small bugfixes and enhancements. If
8254 you have contributed significant work and are not mentioned on this list, and
8255 want to be, let us know. Some of the history has been lost; we are not
8256 intentionally leaving anyone out.
8258 @node GNU Free Documentation License
8259 @appendix GNU Free Documentation License
8263 @unnumbered AS Index