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 @c man begin OPTIONS
1355 The following options are available when @value{AS} is configured for
1360 This option sets the largest size of an object that can be referenced
1361 implicitly with the @code{gp} register. It is only accepted for targets that
1362 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1364 @cindex MIPS endianness
1365 @cindex endianness, MIPS
1366 @cindex big endian output, MIPS
1368 Generate ``big endian'' format output.
1370 @cindex little endian output, MIPS
1372 Generate ``little endian'' format output.
1390 Generate code for a particular MIPS Instruction Set Architecture level.
1391 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1392 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1393 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1394 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1395 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1396 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1397 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1398 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1399 MIPS64 Release 6 ISA processors, respectively.
1401 @item -march=@var{cpu}
1402 Generate code for a particular MIPS CPU.
1404 @item -mtune=@var{cpu}
1405 Schedule and tune for a particular MIPS CPU.
1409 Cause nops to be inserted if the read of the destination register
1410 of an mfhi or mflo instruction occurs in the following two instructions.
1413 @itemx -mno-fix-rm7000
1414 Cause nops to be inserted if a dmult or dmultu instruction is
1415 followed by a load instruction.
1419 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1420 section instead of the standard ELF .stabs sections.
1424 Control generation of @code{.pdr} sections.
1428 The register sizes are normally inferred from the ISA and ABI, but these
1429 flags force a certain group of registers to be treated as 32 bits wide at
1430 all times. @samp{-mgp32} controls the size of general-purpose registers
1431 and @samp{-mfp32} controls the size of floating-point registers.
1435 The register sizes are normally inferred from the ISA and ABI, but these
1436 flags force a certain group of registers to be treated as 64 bits wide at
1437 all times. @samp{-mgp64} controls the size of general-purpose registers
1438 and @samp{-mfp64} controls the size of floating-point registers.
1441 The register sizes are normally inferred from the ISA and ABI, but using
1442 this flag in combination with @samp{-mabi=32} enables an ABI variant
1443 which will operate correctly with floating-point registers which are
1447 @itemx -mno-odd-spreg
1448 Enable use of floating-point operations on odd-numbered single-precision
1449 registers when supported by the ISA. @samp{-mfpxx} implies
1450 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1454 Generate code for the MIPS 16 processor. This is equivalent to putting
1455 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1456 turns off this option.
1459 @itemx -mno-micromips
1460 Generate code for the microMIPS processor. This is equivalent to putting
1461 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1462 turns off this option. This is equivalent to putting @code{.set nomicromips}
1463 at the start of the assembly file.
1466 @itemx -mno-smartmips
1467 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1468 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1469 @samp{-mno-smartmips} turns off this option.
1473 Generate code for the MIPS-3D Application Specific Extension.
1474 This tells the assembler to accept MIPS-3D instructions.
1475 @samp{-no-mips3d} turns off this option.
1479 Generate code for the MDMX Application Specific Extension.
1480 This tells the assembler to accept MDMX instructions.
1481 @samp{-no-mdmx} turns off this option.
1485 Generate code for the DSP Release 1 Application Specific Extension.
1486 This tells the assembler to accept DSP Release 1 instructions.
1487 @samp{-mno-dsp} turns off this option.
1491 Generate code for the DSP Release 2 Application Specific Extension.
1492 This option implies @samp{-mdsp}.
1493 This tells the assembler to accept DSP Release 2 instructions.
1494 @samp{-mno-dspr2} turns off this option.
1498 Generate code for the DSP Release 3 Application Specific Extension.
1499 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1500 This tells the assembler to accept DSP Release 3 instructions.
1501 @samp{-mno-dspr3} turns off this option.
1505 Generate code for the MIPS SIMD Architecture Extension.
1506 This tells the assembler to accept MSA instructions.
1507 @samp{-mno-msa} turns off this option.
1511 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1512 This tells the assembler to accept XPA instructions.
1513 @samp{-mno-xpa} turns off this option.
1517 Generate code for the MT Application Specific Extension.
1518 This tells the assembler to accept MT instructions.
1519 @samp{-mno-mt} turns off this option.
1523 Generate code for the MCU Application Specific Extension.
1524 This tells the assembler to accept MCU instructions.
1525 @samp{-mno-mcu} turns off this option.
1529 Only use 32-bit instruction encodings when generating code for the
1530 microMIPS processor. This option inhibits the use of any 16-bit
1531 instructions. This is equivalent to putting @code{.set insn32} at
1532 the start of the assembly file. @samp{-mno-insn32} turns off this
1533 option. This is equivalent to putting @code{.set noinsn32} at the
1534 start of the assembly file. By default @samp{-mno-insn32} is
1535 selected, allowing all instructions to be used.
1537 @item --construct-floats
1538 @itemx --no-construct-floats
1539 The @samp{--no-construct-floats} option disables the construction of
1540 double width floating point constants by loading the two halves of the
1541 value into the two single width floating point registers that make up
1542 the double width register. By default @samp{--construct-floats} is
1543 selected, allowing construction of these floating point constants.
1545 @item --relax-branch
1546 @itemx --no-relax-branch
1547 The @samp{--relax-branch} option enables the relaxation of out-of-range
1548 branches. By default @samp{--no-relax-branch} is selected, causing any
1549 out-of-range branches to produce an error.
1551 @item -mignore-branch-isa
1552 @itemx -mno-ignore-branch-isa
1553 Ignore branch checks for invalid transitions between ISA modes. The
1554 semantics of branches does not provide for an ISA mode switch, so in
1555 most cases the ISA mode a branch has been encoded for has to be the
1556 same as the ISA mode of the branch's target label. Therefore GAS has
1557 checks implemented that verify in branch assembly that the two ISA
1558 modes match. @samp{-mignore-branch-isa} disables these checks. By
1559 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1560 branch requiring a transition between ISA modes to produce an error.
1562 @item -mnan=@var{encoding}
1563 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1564 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1567 @item --emulation=@var{name}
1568 This option was formerly used to switch between ELF and ECOFF output
1569 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1570 removed in GAS 2.24, so the option now serves little purpose.
1571 It is retained for backwards compatibility.
1573 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1574 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1575 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1576 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1577 preferred options instead.
1580 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1587 Control how to deal with multiplication overflow and division by zero.
1588 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1589 (and only work for Instruction Set Architecture level 2 and higher);
1590 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1594 When this option is used, @command{@value{AS}} will issue a warning every
1595 time it generates a nop instruction from a macro.
1601 The following options are available when @value{AS} is configured for
1607 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1608 The command line option @samp{-nojsri2bsr} can be used to disable it.
1612 Enable or disable the silicon filter behaviour. By default this is disabled.
1613 The default can be overridden by the @samp{-sifilter} command line option.
1616 Alter jump instructions for long displacements.
1618 @item -mcpu=[210|340]
1619 Select the cpu type on the target hardware. This controls which instructions
1623 Assemble for a big endian target.
1626 Assemble for a little endian target.
1635 @xref{Meta Options}, for the options available when @value{AS} is configured
1636 for a Meta processor.
1640 @c man begin OPTIONS
1641 The following options are available when @value{AS} is configured for a
1644 @c man begin INCLUDE
1645 @include c-metag.texi
1646 @c ended inside the included file
1651 @c man begin OPTIONS
1653 See the info pages for documentation of the MMIX-specific options.
1659 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1660 for a NDS32 processor.
1662 @c ended inside the included file
1666 @c man begin OPTIONS
1667 The following options are available when @value{AS} is configured for a
1670 @c man begin INCLUDE
1671 @include c-nds32.texi
1672 @c ended inside the included file
1679 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1680 for a PowerPC processor.
1684 @c man begin OPTIONS
1685 The following options are available when @value{AS} is configured for a
1688 @c man begin INCLUDE
1690 @c ended inside the included file
1698 @xref{RISC-V-Opts}, for the options available when @value{AS} is configured
1699 for a RISC-V processor.
1703 @c man begin OPTIONS
1704 The following options are available when @value{AS} is configured for a
1707 @c man begin INCLUDE
1708 @include c-riscv.texi
1709 @c ended inside the included file
1714 @c man begin OPTIONS
1716 See the info pages for documentation of the RX-specific options.
1720 The following options are available when @value{AS} is configured for the s390
1726 Select the word size, either 31/32 bits or 64 bits.
1729 Select the architecture mode, either the Enterprise System
1730 Architecture (esa) or the z/Architecture mode (zarch).
1731 @item -march=@var{processor}
1732 Specify which s390 processor variant is the target, @samp{g5} (or
1733 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1734 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1735 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1736 @samp{z13} (or @samp{arch11}), or @samp{arch12}.
1738 @itemx -mno-regnames
1739 Allow or disallow symbolic names for registers.
1740 @item -mwarn-areg-zero
1741 Warn whenever the operand for a base or index register has been specified
1742 but evaluates to zero.
1750 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1751 for a TMS320C6000 processor.
1755 @c man begin OPTIONS
1756 The following options are available when @value{AS} is configured for a
1757 TMS320C6000 processor.
1759 @c man begin INCLUDE
1760 @include c-tic6x.texi
1761 @c ended inside the included file
1769 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1770 for a TILE-Gx processor.
1774 @c man begin OPTIONS
1775 The following options are available when @value{AS} is configured for a TILE-Gx
1778 @c man begin INCLUDE
1779 @include c-tilegx.texi
1780 @c ended inside the included file
1788 @xref{Visium Options}, for the options available when @value{AS} is configured
1789 for a Visium processor.
1793 @c man begin OPTIONS
1794 The following option is available when @value{AS} is configured for a Visium
1797 @c man begin INCLUDE
1798 @include c-visium.texi
1799 @c ended inside the included file
1807 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1808 for an Xtensa processor.
1812 @c man begin OPTIONS
1813 The following options are available when @value{AS} is configured for an
1816 @c man begin INCLUDE
1817 @include c-xtensa.texi
1818 @c ended inside the included file
1823 @c man begin OPTIONS
1826 The following options are available when @value{AS} is configured for
1827 a Z80 family processor.
1830 Assemble for Z80 processor.
1832 Assemble for R800 processor.
1833 @item -ignore-undocumented-instructions
1835 Assemble undocumented Z80 instructions that also work on R800 without warning.
1836 @item -ignore-unportable-instructions
1838 Assemble all undocumented Z80 instructions without warning.
1839 @item -warn-undocumented-instructions
1841 Issue a warning for undocumented Z80 instructions that also work on R800.
1842 @item -warn-unportable-instructions
1844 Issue a warning for undocumented Z80 instructions that do not work on R800.
1845 @item -forbid-undocumented-instructions
1847 Treat all undocumented instructions as errors.
1848 @item -forbid-unportable-instructions
1850 Treat undocumented Z80 instructions that do not work on R800 as errors.
1857 * Manual:: Structure of this Manual
1858 * GNU Assembler:: The GNU Assembler
1859 * Object Formats:: Object File Formats
1860 * Command Line:: Command Line
1861 * Input Files:: Input Files
1862 * Object:: Output (Object) File
1863 * Errors:: Error and Warning Messages
1867 @section Structure of this Manual
1869 @cindex manual, structure and purpose
1870 This manual is intended to describe what you need to know to use
1871 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1872 notation for symbols, constants, and expressions; the directives that
1873 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1876 We also cover special features in the @value{TARGET}
1877 configuration of @command{@value{AS}}, including assembler directives.
1880 This manual also describes some of the machine-dependent features of
1881 various flavors of the assembler.
1884 @cindex machine instructions (not covered)
1885 On the other hand, this manual is @emph{not} intended as an introduction
1886 to programming in assembly language---let alone programming in general!
1887 In a similar vein, we make no attempt to introduce the machine
1888 architecture; we do @emph{not} describe the instruction set, standard
1889 mnemonics, registers or addressing modes that are standard to a
1890 particular architecture.
1892 You may want to consult the manufacturer's
1893 machine architecture manual for this information.
1897 For information on the H8/300 machine instruction set, see @cite{H8/300
1898 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1899 Programming Manual} (Renesas).
1902 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1903 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1904 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1905 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1908 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1912 @c I think this is premature---doc@cygnus.com, 17jan1991
1914 Throughout this manual, we assume that you are running @dfn{GNU},
1915 the portable operating system from the @dfn{Free Software
1916 Foundation, Inc.}. This restricts our attention to certain kinds of
1917 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1918 once this assumption is granted examples and definitions need less
1921 @command{@value{AS}} is part of a team of programs that turn a high-level
1922 human-readable series of instructions into a low-level
1923 computer-readable series of instructions. Different versions of
1924 @command{@value{AS}} are used for different kinds of computer.
1927 @c There used to be a section "Terminology" here, which defined
1928 @c "contents", "byte", "word", and "long". Defining "word" to any
1929 @c particular size is confusing when the .word directive may generate 16
1930 @c bits on one machine and 32 bits on another; in general, for the user
1931 @c version of this manual, none of these terms seem essential to define.
1932 @c They were used very little even in the former draft of the manual;
1933 @c this draft makes an effort to avoid them (except in names of
1937 @section The GNU Assembler
1939 @c man begin DESCRIPTION
1941 @sc{gnu} @command{as} is really a family of assemblers.
1943 This manual describes @command{@value{AS}}, a member of that family which is
1944 configured for the @value{TARGET} architectures.
1946 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1947 should find a fairly similar environment when you use it on another
1948 architecture. Each version has much in common with the others,
1949 including object file formats, most assembler directives (often called
1950 @dfn{pseudo-ops}) and assembler syntax.@refill
1952 @cindex purpose of @sc{gnu} assembler
1953 @command{@value{AS}} is primarily intended to assemble the output of the
1954 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1955 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1956 assemble correctly everything that other assemblers for the same
1957 machine would assemble.
1959 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1962 @c This remark should appear in generic version of manual; assumption
1963 @c here is that generic version sets M680x0.
1964 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1965 assembler for the same architecture; for example, we know of several
1966 incompatible versions of 680x0 assembly language syntax.
1971 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1972 program in one pass of the source file. This has a subtle impact on the
1973 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1975 @node Object Formats
1976 @section Object File Formats
1978 @cindex object file format
1979 The @sc{gnu} assembler can be configured to produce several alternative
1980 object file formats. For the most part, this does not affect how you
1981 write assembly language programs; but directives for debugging symbols
1982 are typically different in different file formats. @xref{Symbol
1983 Attributes,,Symbol Attributes}.
1986 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1987 @value{OBJ-NAME} format object files.
1989 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1991 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1992 @code{b.out} or COFF format object files.
1995 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1996 SOM or ELF format object files.
2001 @section Command Line
2003 @cindex command line conventions
2005 After the program name @command{@value{AS}}, the command line may contain
2006 options and file names. Options may appear in any order, and may be
2007 before, after, or between file names. The order of file names is
2010 @cindex standard input, as input file
2012 @file{--} (two hyphens) by itself names the standard input file
2013 explicitly, as one of the files for @command{@value{AS}} to assemble.
2015 @cindex options, command line
2016 Except for @samp{--} any command line argument that begins with a
2017 hyphen (@samp{-}) is an option. Each option changes the behavior of
2018 @command{@value{AS}}. No option changes the way another option works. An
2019 option is a @samp{-} followed by one or more letters; the case of
2020 the letter is important. All options are optional.
2022 Some options expect exactly one file name to follow them. The file
2023 name may either immediately follow the option's letter (compatible
2024 with older assemblers) or it may be the next command argument (@sc{gnu}
2025 standard). These two command lines are equivalent:
2028 @value{AS} -o my-object-file.o mumble.s
2029 @value{AS} -omy-object-file.o mumble.s
2033 @section Input Files
2036 @cindex source program
2037 @cindex files, input
2038 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2039 describe the program input to one run of @command{@value{AS}}. The program may
2040 be in one or more files; how the source is partitioned into files
2041 doesn't change the meaning of the source.
2043 @c I added "con" prefix to "catenation" just to prove I can overcome my
2044 @c APL training... doc@cygnus.com
2045 The source program is a concatenation of the text in all the files, in the
2048 @c man begin DESCRIPTION
2049 Each time you run @command{@value{AS}} it assembles exactly one source
2050 program. The source program is made up of one or more files.
2051 (The standard input is also a file.)
2053 You give @command{@value{AS}} a command line that has zero or more input file
2054 names. The input files are read (from left file name to right). A
2055 command line argument (in any position) that has no special meaning
2056 is taken to be an input file name.
2058 If you give @command{@value{AS}} no file names it attempts to read one input file
2059 from the @command{@value{AS}} standard input, which is normally your terminal. You
2060 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2063 Use @samp{--} if you need to explicitly name the standard input file
2064 in your command line.
2066 If the source is empty, @command{@value{AS}} produces a small, empty object
2071 @subheading Filenames and Line-numbers
2073 @cindex input file linenumbers
2074 @cindex line numbers, in input files
2075 There are two ways of locating a line in the input file (or files) and
2076 either may be used in reporting error messages. One way refers to a line
2077 number in a physical file; the other refers to a line number in a
2078 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2080 @dfn{Physical files} are those files named in the command line given
2081 to @command{@value{AS}}.
2083 @dfn{Logical files} are simply names declared explicitly by assembler
2084 directives; they bear no relation to physical files. Logical file names help
2085 error messages reflect the original source file, when @command{@value{AS}} source
2086 is itself synthesized from other files. @command{@value{AS}} understands the
2087 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2088 @ref{File,,@code{.file}}.
2091 @section Output (Object) File
2097 Every time you run @command{@value{AS}} it produces an output file, which is
2098 your assembly language program translated into numbers. This file
2099 is the object file. Its default name is
2107 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2109 You can give it another name by using the @option{-o} option. Conventionally,
2110 object file names end with @file{.o}. The default name is used for historical
2111 reasons: older assemblers were capable of assembling self-contained programs
2112 directly into a runnable program. (For some formats, this isn't currently
2113 possible, but it can be done for the @code{a.out} format.)
2117 The object file is meant for input to the linker @code{@value{LD}}. It contains
2118 assembled program code, information to help @code{@value{LD}} integrate
2119 the assembled program into a runnable file, and (optionally) symbolic
2120 information for the debugger.
2122 @c link above to some info file(s) like the description of a.out.
2123 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2126 @section Error and Warning Messages
2128 @c man begin DESCRIPTION
2130 @cindex error messages
2131 @cindex warning messages
2132 @cindex messages from assembler
2133 @command{@value{AS}} may write warnings and error messages to the standard error
2134 file (usually your terminal). This should not happen when a compiler
2135 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2136 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2137 grave problem that stops the assembly.
2141 @cindex format of warning messages
2142 Warning messages have the format
2145 file_name:@b{NNN}:Warning Message Text
2149 @cindex file names and line numbers, in warnings/errors
2150 (where @b{NNN} is a line number). If both a logical file name
2151 (@pxref{File,,@code{.file}}) and a logical line number
2153 (@pxref{Line,,@code{.line}})
2155 have been given then they will be used, otherwise the file name and line number
2156 in the current assembler source file will be used. The message text is
2157 intended to be self explanatory (in the grand Unix tradition).
2159 Note the file name must be set via the logical version of the @code{.file}
2160 directive, not the DWARF2 version of the @code{.file} directive. For example:
2164 error_assembler_source
2170 produces this output:
2174 asm.s:2: Error: no such instruction: `error_assembler_source'
2175 foo.c:31: Error: no such instruction: `error_c_source'
2178 @cindex format of error messages
2179 Error messages have the format
2182 file_name:@b{NNN}:FATAL:Error Message Text
2185 The file name and line number are derived as for warning
2186 messages. The actual message text may be rather less explanatory
2187 because many of them aren't supposed to happen.
2190 @chapter Command-Line Options
2192 @cindex options, all versions of assembler
2193 This chapter describes command-line options available in @emph{all}
2194 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2195 for options specific
2197 to the @value{TARGET} target.
2200 to particular machine architectures.
2203 @c man begin DESCRIPTION
2205 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2206 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2207 The assembler arguments must be separated from each other (and the @samp{-Wa})
2208 by commas. For example:
2211 gcc -c -g -O -Wa,-alh,-L file.c
2215 This passes two options to the assembler: @samp{-alh} (emit a listing to
2216 standard output with high-level and assembly source) and @samp{-L} (retain
2217 local symbols in the symbol table).
2219 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2220 command-line options are automatically passed to the assembler by the compiler.
2221 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2222 precisely what options it passes to each compilation pass, including the
2228 * a:: -a[cdghlns] enable listings
2229 * alternate:: --alternate enable alternate macro syntax
2230 * D:: -D for compatibility
2231 * f:: -f to work faster
2232 * I:: -I for .include search path
2233 @ifclear DIFF-TBL-KLUGE
2234 * K:: -K for compatibility
2236 @ifset DIFF-TBL-KLUGE
2237 * K:: -K for difference tables
2240 * L:: -L to retain local symbols
2241 * listing:: --listing-XXX to configure listing output
2242 * M:: -M or --mri to assemble in MRI compatibility mode
2243 * MD:: --MD for dependency tracking
2244 * no-pad-sections:: --no-pad-sections to stop section padding
2245 * o:: -o to name the object file
2246 * R:: -R to join data and text sections
2247 * statistics:: --statistics to see statistics about assembly
2248 * traditional-format:: --traditional-format for compatible output
2249 * v:: -v to announce version
2250 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2251 * Z:: -Z to make object file even after errors
2255 @section Enable Listings: @option{-a[cdghlns]}
2265 @cindex listings, enabling
2266 @cindex assembly listings, enabling
2268 These options enable listing output from the assembler. By itself,
2269 @samp{-a} requests high-level, assembly, and symbols listing.
2270 You can use other letters to select specific options for the list:
2271 @samp{-ah} requests a high-level language listing,
2272 @samp{-al} requests an output-program assembly listing, and
2273 @samp{-as} requests a symbol table listing.
2274 High-level listings require that a compiler debugging option like
2275 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2278 Use the @samp{-ag} option to print a first section with general assembly
2279 information, like @value{AS} version, switches passed, or time stamp.
2281 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2282 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2283 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2284 omitted from the listing.
2286 Use the @samp{-ad} option to omit debugging directives from the
2289 Once you have specified one of these options, you can further control
2290 listing output and its appearance using the directives @code{.list},
2291 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2293 The @samp{-an} option turns off all forms processing.
2294 If you do not request listing output with one of the @samp{-a} options, the
2295 listing-control directives have no effect.
2297 The letters after @samp{-a} may be combined into one option,
2298 @emph{e.g.}, @samp{-aln}.
2300 Note if the assembler source is coming from the standard input (e.g.,
2302 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2303 is being used) then the listing will not contain any comments or preprocessor
2304 directives. This is because the listing code buffers input source lines from
2305 stdin only after they have been preprocessed by the assembler. This reduces
2306 memory usage and makes the code more efficient.
2309 @section @option{--alternate}
2312 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2315 @section @option{-D}
2318 This option has no effect whatsoever, but it is accepted to make it more
2319 likely that scripts written for other assemblers also work with
2320 @command{@value{AS}}.
2323 @section Work Faster: @option{-f}
2326 @cindex trusted compiler
2327 @cindex faster processing (@option{-f})
2328 @samp{-f} should only be used when assembling programs written by a
2329 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2330 and comment preprocessing on
2331 the input file(s) before assembling them. @xref{Preprocessing,
2335 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2336 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2341 @section @code{.include} Search Path: @option{-I} @var{path}
2343 @kindex -I @var{path}
2344 @cindex paths for @code{.include}
2345 @cindex search path for @code{.include}
2346 @cindex @code{include} directive search path
2347 Use this option to add a @var{path} to the list of directories
2348 @command{@value{AS}} searches for files specified in @code{.include}
2349 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2350 many times as necessary to include a variety of paths. The current
2351 working directory is always searched first; after that, @command{@value{AS}}
2352 searches any @samp{-I} directories in the same order as they were
2353 specified (left to right) on the command line.
2356 @section Difference Tables: @option{-K}
2359 @ifclear DIFF-TBL-KLUGE
2360 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2361 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2362 where it can be used to warn when the assembler alters the machine code
2363 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2364 family does not have the addressing limitations that sometimes lead to this
2365 alteration on other platforms.
2368 @ifset DIFF-TBL-KLUGE
2369 @cindex difference tables, warning
2370 @cindex warning for altered difference tables
2371 @command{@value{AS}} sometimes alters the code emitted for directives of the
2372 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2373 You can use the @samp{-K} option if you want a warning issued when this
2378 @section Include Local Symbols: @option{-L}
2381 @cindex local symbols, retaining in output
2382 Symbols beginning with system-specific local label prefixes, typically
2383 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2384 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2385 such symbols when debugging, because they are intended for the use of
2386 programs (like compilers) that compose assembler programs, not for your
2387 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2388 such symbols, so you do not normally debug with them.
2390 This option tells @command{@value{AS}} to retain those local symbols
2391 in the object file. Usually if you do this you also tell the linker
2392 @code{@value{LD}} to preserve those symbols.
2395 @section Configuring listing output: @option{--listing}
2397 The listing feature of the assembler can be enabled via the command line switch
2398 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2399 hex dump of the corresponding locations in the output object file, and displays
2400 them as a listing file. The format of this listing can be controlled by
2401 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2402 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2403 @code{.psize} (@pxref{Psize}), and
2404 @code{.eject} (@pxref{Eject}) and also by the following switches:
2407 @item --listing-lhs-width=@samp{number}
2408 @kindex --listing-lhs-width
2409 @cindex Width of first line disassembly output
2410 Sets the maximum width, in words, of the first line of the hex byte dump. This
2411 dump appears on the left hand side of the listing output.
2413 @item --listing-lhs-width2=@samp{number}
2414 @kindex --listing-lhs-width2
2415 @cindex Width of continuation lines of disassembly output
2416 Sets the maximum width, in words, of any further lines of the hex byte dump for
2417 a given input source line. If this value is not specified, it defaults to being
2418 the same as the value specified for @samp{--listing-lhs-width}. If neither
2419 switch is used the default is to one.
2421 @item --listing-rhs-width=@samp{number}
2422 @kindex --listing-rhs-width
2423 @cindex Width of source line output
2424 Sets the maximum width, in characters, of the source line that is displayed
2425 alongside the hex dump. The default value for this parameter is 100. The
2426 source line is displayed on the right hand side of the listing output.
2428 @item --listing-cont-lines=@samp{number}
2429 @kindex --listing-cont-lines
2430 @cindex Maximum number of continuation lines
2431 Sets the maximum number of continuation lines of hex dump that will be
2432 displayed for a given single line of source input. The default value is 4.
2436 @section Assemble in MRI Compatibility Mode: @option{-M}
2439 @cindex MRI compatibility mode
2440 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2441 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2442 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2443 configured target) assembler from Microtec Research. The exact nature of the
2444 MRI syntax will not be documented here; see the MRI manuals for more
2445 information. Note in particular that the handling of macros and macro
2446 arguments is somewhat different. The purpose of this option is to permit
2447 assembling existing MRI assembler code using @command{@value{AS}}.
2449 The MRI compatibility is not complete. Certain operations of the MRI assembler
2450 depend upon its object file format, and can not be supported using other object
2451 file formats. Supporting these would require enhancing each object file format
2452 individually. These are:
2455 @item global symbols in common section
2457 The m68k MRI assembler supports common sections which are merged by the linker.
2458 Other object file formats do not support this. @command{@value{AS}} handles
2459 common sections by treating them as a single common symbol. It permits local
2460 symbols to be defined within a common section, but it can not support global
2461 symbols, since it has no way to describe them.
2463 @item complex relocations
2465 The MRI assemblers support relocations against a negated section address, and
2466 relocations which combine the start addresses of two or more sections. These
2467 are not support by other object file formats.
2469 @item @code{END} pseudo-op specifying start address
2471 The MRI @code{END} pseudo-op permits the specification of a start address.
2472 This is not supported by other object file formats. The start address may
2473 instead be specified using the @option{-e} option to the linker, or in a linker
2476 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2478 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2479 name to the output file. This is not supported by other object file formats.
2481 @item @code{ORG} pseudo-op
2483 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2484 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2485 which changes the location within the current section. Absolute sections are
2486 not supported by other object file formats. The address of a section may be
2487 assigned within a linker script.
2490 There are some other features of the MRI assembler which are not supported by
2491 @command{@value{AS}}, typically either because they are difficult or because they
2492 seem of little consequence. Some of these may be supported in future releases.
2496 @item EBCDIC strings
2498 EBCDIC strings are not supported.
2500 @item packed binary coded decimal
2502 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2503 and @code{DCB.P} pseudo-ops are not supported.
2505 @item @code{FEQU} pseudo-op
2507 The m68k @code{FEQU} pseudo-op is not supported.
2509 @item @code{NOOBJ} pseudo-op
2511 The m68k @code{NOOBJ} pseudo-op is not supported.
2513 @item @code{OPT} branch control options
2515 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2516 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2517 relaxes all branches, whether forward or backward, to an appropriate size, so
2518 these options serve no purpose.
2520 @item @code{OPT} list control options
2522 The following m68k @code{OPT} list control options are ignored: @code{C},
2523 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2524 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2526 @item other @code{OPT} options
2528 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2529 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2531 @item @code{OPT} @code{D} option is default
2533 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2534 @code{OPT NOD} may be used to turn it off.
2536 @item @code{XREF} pseudo-op.
2538 The m68k @code{XREF} pseudo-op is ignored.
2540 @item @code{.debug} pseudo-op
2542 The i960 @code{.debug} pseudo-op is not supported.
2544 @item @code{.extended} pseudo-op
2546 The i960 @code{.extended} pseudo-op is not supported.
2548 @item @code{.list} pseudo-op.
2550 The various options of the i960 @code{.list} pseudo-op are not supported.
2552 @item @code{.optimize} pseudo-op
2554 The i960 @code{.optimize} pseudo-op is not supported.
2556 @item @code{.output} pseudo-op
2558 The i960 @code{.output} pseudo-op is not supported.
2560 @item @code{.setreal} pseudo-op
2562 The i960 @code{.setreal} pseudo-op is not supported.
2567 @section Dependency Tracking: @option{--MD}
2570 @cindex dependency tracking
2573 @command{@value{AS}} can generate a dependency file for the file it creates. This
2574 file consists of a single rule suitable for @code{make} describing the
2575 dependencies of the main source file.
2577 The rule is written to the file named in its argument.
2579 This feature is used in the automatic updating of makefiles.
2581 @node no-pad-sections
2582 @section Output Section Padding
2583 @kindex --no-pad-sections
2584 @cindex output section padding
2585 Normally the assembler will pad the end of each output section up to its
2586 alignment boundary. But this can waste space, which can be significant on
2587 memory constrained targets. So the @option{--no-pad-sections} option will
2588 disable this behaviour.
2591 @section Name the Object File: @option{-o}
2594 @cindex naming object file
2595 @cindex object file name
2596 There is always one object file output when you run @command{@value{AS}}. By
2597 default it has the name
2600 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2614 You use this option (which takes exactly one filename) to give the
2615 object file a different name.
2617 Whatever the object file is called, @command{@value{AS}} overwrites any
2618 existing file of the same name.
2621 @section Join Data and Text Sections: @option{-R}
2624 @cindex data and text sections, joining
2625 @cindex text and data sections, joining
2626 @cindex joining text and data sections
2627 @cindex merging text and data sections
2628 @option{-R} tells @command{@value{AS}} to write the object file as if all
2629 data-section data lives in the text section. This is only done at
2630 the very last moment: your binary data are the same, but data
2631 section parts are relocated differently. The data section part of
2632 your object file is zero bytes long because all its bytes are
2633 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2635 When you specify @option{-R} it would be possible to generate shorter
2636 address displacements (because we do not have to cross between text and
2637 data section). We refrain from doing this simply for compatibility with
2638 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2641 When @command{@value{AS}} is configured for COFF or ELF output,
2642 this option is only useful if you use sections named @samp{.text} and
2647 @option{-R} is not supported for any of the HPPA targets. Using
2648 @option{-R} generates a warning from @command{@value{AS}}.
2652 @section Display Assembly Statistics: @option{--statistics}
2654 @kindex --statistics
2655 @cindex statistics, about assembly
2656 @cindex time, total for assembly
2657 @cindex space used, maximum for assembly
2658 Use @samp{--statistics} to display two statistics about the resources used by
2659 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2660 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2663 @node traditional-format
2664 @section Compatible Output: @option{--traditional-format}
2666 @kindex --traditional-format
2667 For some targets, the output of @command{@value{AS}} is different in some ways
2668 from the output of some existing assembler. This switch requests
2669 @command{@value{AS}} to use the traditional format instead.
2671 For example, it disables the exception frame optimizations which
2672 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2675 @section Announce Version: @option{-v}
2679 @cindex assembler version
2680 @cindex version of assembler
2681 You can find out what version of as is running by including the
2682 option @samp{-v} (which you can also spell as @samp{-version}) on the
2686 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2688 @command{@value{AS}} should never give a warning or error message when
2689 assembling compiler output. But programs written by people often
2690 cause @command{@value{AS}} to give a warning that a particular assumption was
2691 made. All such warnings are directed to the standard error file.
2695 @cindex suppressing warnings
2696 @cindex warnings, suppressing
2697 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2698 This only affects the warning messages: it does not change any particular of
2699 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2702 @kindex --fatal-warnings
2703 @cindex errors, caused by warnings
2704 @cindex warnings, causing error
2705 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2706 files that generate warnings to be in error.
2709 @cindex warnings, switching on
2710 You can switch these options off again by specifying @option{--warn}, which
2711 causes warnings to be output as usual.
2714 @section Generate Object File in Spite of Errors: @option{-Z}
2715 @cindex object file, after errors
2716 @cindex errors, continuing after
2717 After an error message, @command{@value{AS}} normally produces no output. If for
2718 some reason you are interested in object file output even after
2719 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2720 option. If there are any errors, @command{@value{AS}} continues anyways, and
2721 writes an object file after a final warning message of the form @samp{@var{n}
2722 errors, @var{m} warnings, generating bad object file.}
2727 @cindex machine-independent syntax
2728 @cindex syntax, machine-independent
2729 This chapter describes the machine-independent syntax allowed in a
2730 source file. @command{@value{AS}} syntax is similar to what many other
2731 assemblers use; it is inspired by the BSD 4.2
2736 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2740 * Preprocessing:: Preprocessing
2741 * Whitespace:: Whitespace
2742 * Comments:: Comments
2743 * Symbol Intro:: Symbols
2744 * Statements:: Statements
2745 * Constants:: Constants
2749 @section Preprocessing
2751 @cindex preprocessing
2752 The @command{@value{AS}} internal preprocessor:
2754 @cindex whitespace, removed by preprocessor
2756 adjusts and removes extra whitespace. It leaves one space or tab before
2757 the keywords on a line, and turns any other whitespace on the line into
2760 @cindex comments, removed by preprocessor
2762 removes all comments, replacing them with a single space, or an
2763 appropriate number of newlines.
2765 @cindex constants, converted by preprocessor
2767 converts character constants into the appropriate numeric values.
2770 It does not do macro processing, include file handling, or
2771 anything else you may get from your C compiler's preprocessor. You can
2772 do include file processing with the @code{.include} directive
2773 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2774 to get other ``CPP'' style preprocessing by giving the input file a
2775 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2776 Output, gcc info, Using GNU CC}.
2778 Excess whitespace, comments, and character constants
2779 cannot be used in the portions of the input text that are not
2782 @cindex turning preprocessing on and off
2783 @cindex preprocessing, turning on and off
2786 If the first line of an input file is @code{#NO_APP} or if you use the
2787 @samp{-f} option, whitespace and comments are not removed from the input file.
2788 Within an input file, you can ask for whitespace and comment removal in
2789 specific portions of the by putting a line that says @code{#APP} before the
2790 text that may contain whitespace or comments, and putting a line that says
2791 @code{#NO_APP} after this text. This feature is mainly intend to support
2792 @code{asm} statements in compilers whose output is otherwise free of comments
2799 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2800 Whitespace is used to separate symbols, and to make programs neater for
2801 people to read. Unless within character constants
2802 (@pxref{Characters,,Character Constants}), any whitespace means the same
2803 as exactly one space.
2809 There are two ways of rendering comments to @command{@value{AS}}. In both
2810 cases the comment is equivalent to one space.
2812 Anything from @samp{/*} through the next @samp{*/} is a comment.
2813 This means you may not nest these comments.
2817 The only way to include a newline ('\n') in a comment
2818 is to use this sort of comment.
2821 /* This sort of comment does not nest. */
2824 @cindex line comment character
2825 Anything from a @dfn{line comment} character up to the next newline is
2826 considered a comment and is ignored. The line comment character is target
2827 specific, and some targets multiple comment characters. Some targets also have
2828 line comment characters that only work if they are the first character on a
2829 line. Some targets use a sequence of two characters to introduce a line
2830 comment. Some targets can also change their line comment characters depending
2831 upon command line options that have been used. For more details see the
2832 @emph{Syntax} section in the documentation for individual targets.
2834 If the line comment character is the hash sign (@samp{#}) then it still has the
2835 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2836 to specify logical line numbers:
2839 @cindex lines starting with @code{#}
2840 @cindex logical line numbers
2841 To be compatible with past assemblers, lines that begin with @samp{#} have a
2842 special interpretation. Following the @samp{#} should be an absolute
2843 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2844 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2845 new logical file name. The rest of the line, if any, should be whitespace.
2847 If the first non-whitespace characters on the line are not numeric,
2848 the line is ignored. (Just like a comment.)
2851 # This is an ordinary comment.
2852 # 42-6 "new_file_name" # New logical file name
2853 # This is logical line # 36.
2855 This feature is deprecated, and may disappear from future versions
2856 of @command{@value{AS}}.
2861 @cindex characters used in symbols
2862 @ifclear SPECIAL-SYMS
2863 A @dfn{symbol} is one or more characters chosen from the set of all
2864 letters (both upper and lower case), digits and the three characters
2870 A @dfn{symbol} is one or more characters chosen from the set of all
2871 letters (both upper and lower case), digits and the three characters
2872 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2878 On most machines, you can also use @code{$} in symbol names; exceptions
2879 are noted in @ref{Machine Dependencies}.
2881 No symbol may begin with a digit. Case is significant.
2882 There is no length limit; all characters are significant. Multibyte characters
2883 are supported. Symbols are delimited by characters not in that set, or by the
2884 beginning of a file (since the source program must end with a newline, the end
2885 of a file is not a possible symbol delimiter). @xref{Symbols}.
2887 Symbol names may also be enclosed in double quote @code{"} characters. In such
2888 cases any characters are allowed, except for the NUL character. If a double
2889 quote character is to be included in the symbol name it must be preceeded by a
2890 backslash @code{\} character.
2891 @cindex length of symbols
2896 @cindex statements, structure of
2897 @cindex line separator character
2898 @cindex statement separator character
2900 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2901 @dfn{line separator character}. The line separator character is target
2902 specific and described in the @emph{Syntax} section of each
2903 target's documentation. Not all targets support a line separator character.
2904 The newline or line separator character is considered to be part of the
2905 preceding statement. Newlines and separators within character constants are an
2906 exception: they do not end statements.
2908 @cindex newline, required at file end
2909 @cindex EOF, newline must precede
2910 It is an error to end any statement with end-of-file: the last
2911 character of any input file should be a newline.@refill
2913 An empty statement is allowed, and may include whitespace. It is ignored.
2915 @cindex instructions and directives
2916 @cindex directives and instructions
2917 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2918 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2920 A statement begins with zero or more labels, optionally followed by a
2921 key symbol which determines what kind of statement it is. The key
2922 symbol determines the syntax of the rest of the statement. If the
2923 symbol begins with a dot @samp{.} then the statement is an assembler
2924 directive: typically valid for any computer. If the symbol begins with
2925 a letter the statement is an assembly language @dfn{instruction}: it
2926 assembles into a machine language instruction.
2928 Different versions of @command{@value{AS}} for different computers
2929 recognize different instructions. In fact, the same symbol may
2930 represent a different instruction in a different computer's assembly
2934 @cindex @code{:} (label)
2935 @cindex label (@code{:})
2936 A label is a symbol immediately followed by a colon (@code{:}).
2937 Whitespace before a label or after a colon is permitted, but you may not
2938 have whitespace between a label's symbol and its colon. @xref{Labels}.
2941 For HPPA targets, labels need not be immediately followed by a colon, but
2942 the definition of a label must begin in column zero. This also implies that
2943 only one label may be defined on each line.
2947 label: .directive followed by something
2948 another_label: # This is an empty statement.
2949 instruction operand_1, operand_2, @dots{}
2956 A constant is a number, written so that its value is known by
2957 inspection, without knowing any context. Like this:
2960 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2961 .ascii "Ring the bell\7" # A string constant.
2962 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2963 .float 0f-314159265358979323846264338327\
2964 95028841971.693993751E-40 # - pi, a flonum.
2969 * Characters:: Character Constants
2970 * Numbers:: Number Constants
2974 @subsection Character Constants
2976 @cindex character constants
2977 @cindex constants, character
2978 There are two kinds of character constants. A @dfn{character} stands
2979 for one character in one byte and its value may be used in
2980 numeric expressions. String constants (properly called string
2981 @emph{literals}) are potentially many bytes and their values may not be
2982 used in arithmetic expressions.
2986 * Chars:: Characters
2990 @subsubsection Strings
2992 @cindex string constants
2993 @cindex constants, string
2994 A @dfn{string} is written between double-quotes. It may contain
2995 double-quotes or null characters. The way to get special characters
2996 into a string is to @dfn{escape} these characters: precede them with
2997 a backslash @samp{\} character. For example @samp{\\} represents
2998 one backslash: the first @code{\} is an escape which tells
2999 @command{@value{AS}} to interpret the second character literally as a backslash
3000 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3001 escape character). The complete list of escapes follows.
3003 @cindex escape codes, character
3004 @cindex character escape codes
3005 @c NOTE: Cindex entries must not start with a backlash character.
3006 @c NOTE: This confuses the pdf2texi script when it is creating the
3007 @c NOTE: index based upon the first character and so it generates:
3008 @c NOTE: \initial {\\}
3009 @c NOTE: which then results in the error message:
3010 @c NOTE: Argument of \\ has an extra }.
3011 @c NOTE: So in the index entries below a space character has been
3012 @c NOTE: prepended to avoid this problem.
3015 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3017 @cindex @code{ \b} (backspace character)
3018 @cindex backspace (@code{\b})
3020 Mnemonic for backspace; for ASCII this is octal code 010.
3023 @c Mnemonic for EOText; for ASCII this is octal code 004.
3025 @cindex @code{ \f} (formfeed character)
3026 @cindex formfeed (@code{\f})
3028 Mnemonic for FormFeed; for ASCII this is octal code 014.
3030 @cindex @code{ \n} (newline character)
3031 @cindex newline (@code{\n})
3033 Mnemonic for newline; for ASCII this is octal code 012.
3036 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3038 @cindex @code{ \r} (carriage return character)
3039 @cindex carriage return (@code{backslash-r})
3041 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3044 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3045 @c other assemblers.
3047 @cindex @code{ \t} (tab)
3048 @cindex tab (@code{\t})
3050 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3053 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3054 @c @item \x @var{digit} @var{digit} @var{digit}
3055 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3057 @cindex @code{ \@var{ddd}} (octal character code)
3058 @cindex octal character code (@code{\@var{ddd}})
3059 @item \ @var{digit} @var{digit} @var{digit}
3060 An octal character code. The numeric code is 3 octal digits.
3061 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3062 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3064 @cindex @code{ \@var{xd...}} (hex character code)
3065 @cindex hex character code (@code{\@var{xd...}})
3066 @item \@code{x} @var{hex-digits...}
3067 A hex character code. All trailing hex digits are combined. Either upper or
3068 lower case @code{x} works.
3070 @cindex @code{ \\} (@samp{\} character)
3071 @cindex backslash (@code{\\})
3073 Represents one @samp{\} character.
3076 @c Represents one @samp{'} (accent acute) character.
3077 @c This is needed in single character literals
3078 @c (@xref{Characters,,Character Constants}.) to represent
3081 @cindex @code{ \"} (doublequote character)
3082 @cindex doublequote (@code{\"})
3084 Represents one @samp{"} character. Needed in strings to represent
3085 this character, because an unescaped @samp{"} would end the string.
3087 @item \ @var{anything-else}
3088 Any other character when escaped by @kbd{\} gives a warning, but
3089 assembles as if the @samp{\} was not present. The idea is that if
3090 you used an escape sequence you clearly didn't want the literal
3091 interpretation of the following character. However @command{@value{AS}} has no
3092 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3093 code and warns you of the fact.
3096 Which characters are escapable, and what those escapes represent,
3097 varies widely among assemblers. The current set is what we think
3098 the BSD 4.2 assembler recognizes, and is a subset of what most C
3099 compilers recognize. If you are in doubt, do not use an escape
3103 @subsubsection Characters
3105 @cindex single character constant
3106 @cindex character, single
3107 @cindex constant, single character
3108 A single character may be written as a single quote immediately followed by
3109 that character. Some backslash escapes apply to characters, @code{\b},
3110 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3111 as for strings, plus @code{\'} for a single quote. So if you want to write the
3112 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3113 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3116 @ifclear abnormal-separator
3117 (or semicolon @samp{;})
3119 @ifset abnormal-separator
3121 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3126 immediately following an acute accent is taken as a literal character
3127 and does not count as the end of a statement. The value of a character
3128 constant in a numeric expression is the machine's byte-wide code for
3129 that character. @command{@value{AS}} assumes your character code is ASCII:
3130 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3133 @subsection Number Constants
3135 @cindex constants, number
3136 @cindex number constants
3137 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3138 are stored in the target machine. @emph{Integers} are numbers that
3139 would fit into an @code{int} in the C language. @emph{Bignums} are
3140 integers, but they are stored in more than 32 bits. @emph{Flonums}
3141 are floating point numbers, described below.
3144 * Integers:: Integers
3149 * Bit Fields:: Bit Fields
3155 @subsubsection Integers
3157 @cindex constants, integer
3159 @cindex binary integers
3160 @cindex integers, binary
3161 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3162 the binary digits @samp{01}.
3164 @cindex octal integers
3165 @cindex integers, octal
3166 An octal integer is @samp{0} followed by zero or more of the octal
3167 digits (@samp{01234567}).
3169 @cindex decimal integers
3170 @cindex integers, decimal
3171 A decimal integer starts with a non-zero digit followed by zero or
3172 more digits (@samp{0123456789}).
3174 @cindex hexadecimal integers
3175 @cindex integers, hexadecimal
3176 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3177 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3179 Integers have the usual values. To denote a negative integer, use
3180 the prefix operator @samp{-} discussed under expressions
3181 (@pxref{Prefix Ops,,Prefix Operators}).
3184 @subsubsection Bignums
3187 @cindex constants, bignum
3188 A @dfn{bignum} has the same syntax and semantics as an integer
3189 except that the number (or its negative) takes more than 32 bits to
3190 represent in binary. The distinction is made because in some places
3191 integers are permitted while bignums are not.
3194 @subsubsection Flonums
3196 @cindex floating point numbers
3197 @cindex constants, floating point
3199 @cindex precision, floating point
3200 A @dfn{flonum} represents a floating point number. The translation is
3201 indirect: a decimal floating point number from the text is converted by
3202 @command{@value{AS}} to a generic binary floating point number of more than
3203 sufficient precision. This generic floating point number is converted
3204 to a particular computer's floating point format (or formats) by a
3205 portion of @command{@value{AS}} specialized to that computer.
3207 A flonum is written by writing (in order)
3212 (@samp{0} is optional on the HPPA.)
3216 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3218 @kbd{e} is recommended. Case is not important.
3220 @c FIXME: verify if flonum syntax really this vague for most cases
3221 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3222 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3225 On the H8/300, Renesas / SuperH SH,
3226 and AMD 29K architectures, the letter must be
3227 one of the letters @samp{DFPRSX} (in upper or lower case).
3229 On the ARC, the letter must be one of the letters @samp{DFRS}
3230 (in upper or lower case).
3232 On the Intel 960 architecture, the letter must be
3233 one of the letters @samp{DFT} (in upper or lower case).
3235 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3239 One of the letters @samp{DFRS} (in upper or lower case).
3242 One of the letters @samp{DFPRSX} (in upper or lower case).
3245 The letter @samp{E} (upper case only).
3248 One of the letters @samp{DFT} (in upper or lower case).
3253 An optional sign: either @samp{+} or @samp{-}.
3256 An optional @dfn{integer part}: zero or more decimal digits.
3259 An optional @dfn{fractional part}: @samp{.} followed by zero
3260 or more decimal digits.
3263 An optional exponent, consisting of:
3267 An @samp{E} or @samp{e}.
3268 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3269 @c principle this can perfectly well be different on different targets.
3271 Optional sign: either @samp{+} or @samp{-}.
3273 One or more decimal digits.
3278 At least one of the integer part or the fractional part must be
3279 present. The floating point number has the usual base-10 value.
3281 @command{@value{AS}} does all processing using integers. Flonums are computed
3282 independently of any floating point hardware in the computer running
3283 @command{@value{AS}}.
3287 @c Bit fields are written as a general facility but are also controlled
3288 @c by a conditional-compilation flag---which is as of now (21mar91)
3289 @c turned on only by the i960 config of GAS.
3291 @subsubsection Bit Fields
3294 @cindex constants, bit field
3295 You can also define numeric constants as @dfn{bit fields}.
3296 Specify two numbers separated by a colon---
3298 @var{mask}:@var{value}
3301 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3304 The resulting number is then packed
3306 @c this conditional paren in case bit fields turned on elsewhere than 960
3307 (in host-dependent byte order)
3309 into a field whose width depends on which assembler directive has the
3310 bit-field as its argument. Overflow (a result from the bitwise and
3311 requiring more binary digits to represent) is not an error; instead,
3312 more constants are generated, of the specified width, beginning with the
3313 least significant digits.@refill
3315 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3316 @code{.short}, and @code{.word} accept bit-field arguments.
3321 @chapter Sections and Relocation
3326 * Secs Background:: Background
3327 * Ld Sections:: Linker Sections
3328 * As Sections:: Assembler Internal Sections
3329 * Sub-Sections:: Sub-Sections
3333 @node Secs Background
3336 Roughly, a section is a range of addresses, with no gaps; all data
3337 ``in'' those addresses is treated the same for some particular purpose.
3338 For example there may be a ``read only'' section.
3340 @cindex linker, and assembler
3341 @cindex assembler, and linker
3342 The linker @code{@value{LD}} reads many object files (partial programs) and
3343 combines their contents to form a runnable program. When @command{@value{AS}}
3344 emits an object file, the partial program is assumed to start at address 0.
3345 @code{@value{LD}} assigns the final addresses for the partial program, so that
3346 different partial programs do not overlap. This is actually an
3347 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3350 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3351 addresses. These blocks slide to their run-time addresses as rigid
3352 units; their length does not change and neither does the order of bytes
3353 within them. Such a rigid unit is called a @emph{section}. Assigning
3354 run-time addresses to sections is called @dfn{relocation}. It includes
3355 the task of adjusting mentions of object-file addresses so they refer to
3356 the proper run-time addresses.
3358 For the H8/300, and for the Renesas / SuperH SH,
3359 @command{@value{AS}} pads sections if needed to
3360 ensure they end on a word (sixteen bit) boundary.
3363 @cindex standard assembler sections
3364 An object file written by @command{@value{AS}} has at least three sections, any
3365 of which may be empty. These are named @dfn{text}, @dfn{data} and
3370 When it generates COFF or ELF output,
3372 @command{@value{AS}} can also generate whatever other named sections you specify
3373 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3374 If you do not use any directives that place output in the @samp{.text}
3375 or @samp{.data} sections, these sections still exist, but are empty.
3380 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3382 @command{@value{AS}} can also generate whatever other named sections you
3383 specify using the @samp{.space} and @samp{.subspace} directives. See
3384 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3385 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3386 assembler directives.
3389 Additionally, @command{@value{AS}} uses different names for the standard
3390 text, data, and bss sections when generating SOM output. Program text
3391 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3392 BSS into @samp{$BSS$}.
3396 Within the object file, the text section starts at address @code{0}, the
3397 data section follows, and the bss section follows the data section.
3400 When generating either SOM or ELF output files on the HPPA, the text
3401 section starts at address @code{0}, the data section at address
3402 @code{0x4000000}, and the bss section follows the data section.
3405 To let @code{@value{LD}} know which data changes when the sections are
3406 relocated, and how to change that data, @command{@value{AS}} also writes to the
3407 object file details of the relocation needed. To perform relocation
3408 @code{@value{LD}} must know, each time an address in the object
3412 Where in the object file is the beginning of this reference to
3415 How long (in bytes) is this reference?
3417 Which section does the address refer to? What is the numeric value of
3419 (@var{address}) @minus{} (@var{start-address of section})?
3422 Is the reference to an address ``Program-Counter relative''?
3425 @cindex addresses, format of
3426 @cindex section-relative addressing
3427 In fact, every address @command{@value{AS}} ever uses is expressed as
3429 (@var{section}) + (@var{offset into section})
3432 Further, most expressions @command{@value{AS}} computes have this section-relative
3435 (For some object formats, such as SOM for the HPPA, some expressions are
3436 symbol-relative instead.)
3439 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3440 @var{N} into section @var{secname}.''
3442 Apart from text, data and bss sections you need to know about the
3443 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3444 addresses in the absolute section remain unchanged. For example, address
3445 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3446 @code{@value{LD}}. Although the linker never arranges two partial programs'
3447 data sections with overlapping addresses after linking, @emph{by definition}
3448 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3449 part of a program is always the same address when the program is running as
3450 address @code{@{absolute@ 239@}} in any other part of the program.
3452 The idea of sections is extended to the @dfn{undefined} section. Any
3453 address whose section is unknown at assembly time is by definition
3454 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3455 Since numbers are always defined, the only way to generate an undefined
3456 address is to mention an undefined symbol. A reference to a named
3457 common block would be such a symbol: its value is unknown at assembly
3458 time so it has section @emph{undefined}.
3460 By analogy the word @emph{section} is used to describe groups of sections in
3461 the linked program. @code{@value{LD}} puts all partial programs' text
3462 sections in contiguous addresses in the linked program. It is
3463 customary to refer to the @emph{text section} of a program, meaning all
3464 the addresses of all partial programs' text sections. Likewise for
3465 data and bss sections.
3467 Some sections are manipulated by @code{@value{LD}}; others are invented for
3468 use of @command{@value{AS}} and have no meaning except during assembly.
3471 @section Linker Sections
3472 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3477 @cindex named sections
3478 @cindex sections, named
3479 @item named sections
3482 @cindex text section
3483 @cindex data section
3487 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3488 separate but equal sections. Anything you can say of one section is
3491 When the program is running, however, it is
3492 customary for the text section to be unalterable. The
3493 text section is often shared among processes: it contains
3494 instructions, constants and the like. The data section of a running
3495 program is usually alterable: for example, C variables would be stored
3496 in the data section.
3501 This section contains zeroed bytes when your program begins running. It
3502 is used to hold uninitialized variables or common storage. The length of
3503 each partial program's bss section is important, but because it starts
3504 out containing zeroed bytes there is no need to store explicit zero
3505 bytes in the object file. The bss section was invented to eliminate
3506 those explicit zeros from object files.
3508 @cindex absolute section
3509 @item absolute section
3510 Address 0 of this section is always ``relocated'' to runtime address 0.
3511 This is useful if you want to refer to an address that @code{@value{LD}} must
3512 not change when relocating. In this sense we speak of absolute
3513 addresses being ``unrelocatable'': they do not change during relocation.
3515 @cindex undefined section
3516 @item undefined section
3517 This ``section'' is a catch-all for address references to objects not in
3518 the preceding sections.
3519 @c FIXME: ref to some other doc on obj-file formats could go here.
3522 @cindex relocation example
3523 An idealized example of three relocatable sections follows.
3525 The example uses the traditional section names @samp{.text} and @samp{.data}.
3527 Memory addresses are on the horizontal axis.
3531 @c END TEXI2ROFF-KILL
3534 partial program # 1: |ttttt|dddd|00|
3541 partial program # 2: |TTT|DDD|000|
3544 +--+---+-----+--+----+---+-----+~~
3545 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3546 +--+---+-----+--+----+---+-----+~~
3548 addresses: 0 @dots{}
3555 \line{\it Partial program \#1: \hfil}
3556 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3557 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3559 \line{\it Partial program \#2: \hfil}
3560 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3561 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3563 \line{\it linked program: \hfil}
3564 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3565 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3566 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3567 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3569 \line{\it addresses: \hfil}
3573 @c END TEXI2ROFF-KILL
3576 @section Assembler Internal Sections
3578 @cindex internal assembler sections
3579 @cindex sections in messages, internal
3580 These sections are meant only for the internal use of @command{@value{AS}}. They
3581 have no meaning at run-time. You do not really need to know about these
3582 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3583 warning messages, so it might be helpful to have an idea of their
3584 meanings to @command{@value{AS}}. These sections are used to permit the
3585 value of every expression in your assembly language program to be a
3586 section-relative address.
3589 @cindex assembler internal logic error
3590 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3591 An internal assembler logic error has been found. This means there is a
3592 bug in the assembler.
3594 @cindex expr (internal section)
3596 The assembler stores complex expression internally as combinations of
3597 symbols. When it needs to represent an expression as a symbol, it puts
3598 it in the expr section.
3600 @c FIXME item transfer[t] vector preload
3601 @c FIXME item transfer[t] vector postload
3602 @c FIXME item register
3606 @section Sub-Sections
3608 @cindex numbered subsections
3609 @cindex grouping data
3615 fall into two sections: text and data.
3617 You may have separate groups of
3619 data in named sections
3623 data in named sections
3629 that you want to end up near to each other in the object file, even though they
3630 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3631 use @dfn{subsections} for this purpose. Within each section, there can be
3632 numbered subsections with values from 0 to 8192. Objects assembled into the
3633 same subsection go into the object file together with other objects in the same
3634 subsection. For example, a compiler might want to store constants in the text
3635 section, but might not want to have them interspersed with the program being
3636 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3637 section of code being output, and a @samp{.text 1} before each group of
3638 constants being output.
3640 Subsections are optional. If you do not use subsections, everything
3641 goes in subsection number zero.
3644 Each subsection is zero-padded up to a multiple of four bytes.
3645 (Subsections may be padded a different amount on different flavors
3646 of @command{@value{AS}}.)
3650 On the H8/300 platform, each subsection is zero-padded to a word
3651 boundary (two bytes).
3652 The same is true on the Renesas SH.
3655 @c FIXME section padding (alignment)?
3656 @c Rich Pixley says padding here depends on target obj code format; that
3657 @c doesn't seem particularly useful to say without further elaboration,
3658 @c so for now I say nothing about it. If this is a generic BFD issue,
3659 @c these paragraphs might need to vanish from this manual, and be
3660 @c discussed in BFD chapter of binutils (or some such).
3664 Subsections appear in your object file in numeric order, lowest numbered
3665 to highest. (All this to be compatible with other people's assemblers.)
3666 The object file contains no representation of subsections; @code{@value{LD}} and
3667 other programs that manipulate object files see no trace of them.
3668 They just see all your text subsections as a text section, and all your
3669 data subsections as a data section.
3671 To specify which subsection you want subsequent statements assembled
3672 into, use a numeric argument to specify it, in a @samp{.text
3673 @var{expression}} or a @samp{.data @var{expression}} statement.
3676 When generating COFF output, you
3681 can also use an extra subsection
3682 argument with arbitrary named sections: @samp{.section @var{name},
3687 When generating ELF output, you
3692 can also use the @code{.subsection} directive (@pxref{SubSection})
3693 to specify a subsection: @samp{.subsection @var{expression}}.
3695 @var{Expression} should be an absolute expression
3696 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3697 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3698 begins in @code{text 0}. For instance:
3700 .text 0 # The default subsection is text 0 anyway.
3701 .ascii "This lives in the first text subsection. *"
3703 .ascii "But this lives in the second text subsection."
3705 .ascii "This lives in the data section,"
3706 .ascii "in the first data subsection."
3708 .ascii "This lives in the first text section,"
3709 .ascii "immediately following the asterisk (*)."
3712 Each section has a @dfn{location counter} incremented by one for every byte
3713 assembled into that section. Because subsections are merely a convenience
3714 restricted to @command{@value{AS}} there is no concept of a subsection location
3715 counter. There is no way to directly manipulate a location counter---but the
3716 @code{.align} directive changes it, and any label definition captures its
3717 current value. The location counter of the section where statements are being
3718 assembled is said to be the @dfn{active} location counter.
3721 @section bss Section
3724 @cindex common variable storage
3725 The bss section is used for local common variable storage.
3726 You may allocate address space in the bss section, but you may
3727 not dictate data to load into it before your program executes. When
3728 your program starts running, all the contents of the bss
3729 section are zeroed bytes.
3731 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3732 @ref{Lcomm,,@code{.lcomm}}.
3734 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3735 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3738 When assembling for a target which supports multiple sections, such as ELF or
3739 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3740 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3741 section. Typically the section will only contain symbol definitions and
3742 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3749 Symbols are a central concept: the programmer uses symbols to name
3750 things, the linker uses symbols to link, and the debugger uses symbols
3754 @cindex debuggers, and symbol order
3755 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3756 the same order they were declared. This may break some debuggers.
3761 * Setting Symbols:: Giving Symbols Other Values
3762 * Symbol Names:: Symbol Names
3763 * Dot:: The Special Dot Symbol
3764 * Symbol Attributes:: Symbol Attributes
3771 A @dfn{label} is written as a symbol immediately followed by a colon
3772 @samp{:}. The symbol then represents the current value of the
3773 active location counter, and is, for example, a suitable instruction
3774 operand. You are warned if you use the same symbol to represent two
3775 different locations: the first definition overrides any other
3779 On the HPPA, the usual form for a label need not be immediately followed by a
3780 colon, but instead must start in column zero. Only one label may be defined on
3781 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3782 provides a special directive @code{.label} for defining labels more flexibly.
3785 @node Setting Symbols
3786 @section Giving Symbols Other Values
3788 @cindex assigning values to symbols
3789 @cindex symbol values, assigning
3790 A symbol can be given an arbitrary value by writing a symbol, followed
3791 by an equals sign @samp{=}, followed by an expression
3792 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3793 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3794 equals sign @samp{=}@samp{=} here represents an equivalent of the
3795 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3798 Blackfin does not support symbol assignment with @samp{=}.
3802 @section Symbol Names
3804 @cindex symbol names
3805 @cindex names, symbol
3806 @ifclear SPECIAL-SYMS
3807 Symbol names begin with a letter or with one of @samp{._}. On most
3808 machines, you can also use @code{$} in symbol names; exceptions are
3809 noted in @ref{Machine Dependencies}. That character may be followed by any
3810 string of digits, letters, dollar signs (unless otherwise noted for a
3811 particular target machine), and underscores.
3815 Symbol names begin with a letter or with one of @samp{._}. On the
3816 Renesas SH you can also use @code{$} in symbol names. That
3817 character may be followed by any string of digits, letters, dollar signs (save
3818 on the H8/300), and underscores.
3822 Case of letters is significant: @code{foo} is a different symbol name
3825 Symbol names do not start with a digit. An exception to this rule is made for
3826 Local Labels. See below.
3828 Multibyte characters are supported. To generate a symbol name containing
3829 multibyte characters enclose it within double quotes and use escape codes. cf
3830 @xref{Strings}. Generating a multibyte symbol name from a label is not
3831 currently supported.
3833 Each symbol has exactly one name. Each name in an assembly language program
3834 refers to exactly one symbol. You may use that symbol name any number of times
3837 @subheading Local Symbol Names
3839 @cindex local symbol names
3840 @cindex symbol names, local
3841 A local symbol is any symbol beginning with certain local label prefixes.
3842 By default, the local label prefix is @samp{.L} for ELF systems or
3843 @samp{L} for traditional a.out systems, but each target may have its own
3844 set of local label prefixes.
3846 On the HPPA local symbols begin with @samp{L$}.
3849 Local symbols are defined and used within the assembler, but they are
3850 normally not saved in object files. Thus, they are not visible when debugging.
3851 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3852 to retain the local symbols in the object files.
3854 @subheading Local Labels
3856 @cindex local labels
3857 @cindex temporary symbol names
3858 @cindex symbol names, temporary
3859 Local labels are different from local symbols. Local labels help compilers and
3860 programmers use names temporarily. They create symbols which are guaranteed to
3861 be unique over the entire scope of the input source code and which can be
3862 referred to by a simple notation. To define a local label, write a label of
3863 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3864 To refer to the most recent previous definition of that label write
3865 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3866 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3867 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3869 There is no restriction on how you can use these labels, and you can reuse them
3870 too. So that it is possible to repeatedly define the same local label (using
3871 the same number @samp{@b{N}}), although you can only refer to the most recently
3872 defined local label of that number (for a backwards reference) or the next
3873 definition of a specific local label for a forward reference. It is also worth
3874 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3875 implemented in a slightly more efficient manner than the others.
3886 Which is the equivalent of:
3889 label_1: branch label_3
3890 label_2: branch label_1
3891 label_3: branch label_4
3892 label_4: branch label_3
3895 Local label names are only a notational device. They are immediately
3896 transformed into more conventional symbol names before the assembler uses them.
3897 The symbol names are stored in the symbol table, appear in error messages, and
3898 are optionally emitted to the object file. The names are constructed using
3902 @item @emph{local label prefix}
3903 All local symbols begin with the system-specific local label prefix.
3904 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3905 that start with the local label prefix. These labels are
3906 used for symbols you are never intended to see. If you use the
3907 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3908 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3909 you may use them in debugging.
3912 This is the number that was used in the local label definition. So if the
3913 label is written @samp{55:} then the number is @samp{55}.
3916 This unusual character is included so you do not accidentally invent a symbol
3917 of the same name. The character has ASCII value of @samp{\002} (control-B).
3919 @item @emph{ordinal number}
3920 This is a serial number to keep the labels distinct. The first definition of
3921 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3922 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3923 the number @samp{1} and its 15th definition gets @samp{15} as well.
3926 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3927 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3929 @subheading Dollar Local Labels
3930 @cindex dollar local symbols
3932 On some targets @code{@value{AS}} also supports an even more local form of
3933 local labels called dollar labels. These labels go out of scope (i.e., they
3934 become undefined) as soon as a non-local label is defined. Thus they remain
3935 valid for only a small region of the input source code. Normal local labels,
3936 by contrast, remain in scope for the entire file, or until they are redefined
3937 by another occurrence of the same local label.
3939 Dollar labels are defined in exactly the same way as ordinary local labels,
3940 except that they have a dollar sign suffix to their numeric value, e.g.,
3943 They can also be distinguished from ordinary local labels by their transformed
3944 names which use ASCII character @samp{\001} (control-A) as the magic character
3945 to distinguish them from ordinary labels. For example, the fifth definition of
3946 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3949 @section The Special Dot Symbol
3951 @cindex dot (symbol)
3952 @cindex @code{.} (symbol)
3953 @cindex current address
3954 @cindex location counter
3955 The special symbol @samp{.} refers to the current address that
3956 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3957 .long .} defines @code{melvin} to contain its own address.
3958 Assigning a value to @code{.} is treated the same as a @code{.org}
3960 @ifclear no-space-dir
3961 Thus, the expression @samp{.=.+4} is the same as saying
3965 @node Symbol Attributes
3966 @section Symbol Attributes
3968 @cindex symbol attributes
3969 @cindex attributes, symbol
3970 Every symbol has, as well as its name, the attributes ``Value'' and
3971 ``Type''. Depending on output format, symbols can also have auxiliary
3974 The detailed definitions are in @file{a.out.h}.
3977 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3978 all these attributes, and probably won't warn you. This makes the
3979 symbol an externally defined symbol, which is generally what you
3983 * Symbol Value:: Value
3984 * Symbol Type:: Type
3987 * a.out Symbols:: Symbol Attributes: @code{a.out}
3991 * a.out Symbols:: Symbol Attributes: @code{a.out}
3994 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3999 * COFF Symbols:: Symbol Attributes for COFF
4002 * SOM Symbols:: Symbol Attributes for SOM
4009 @cindex value of a symbol
4010 @cindex symbol value
4011 The value of a symbol is (usually) 32 bits. For a symbol which labels a
4012 location in the text, data, bss or absolute sections the value is the
4013 number of addresses from the start of that section to the label.
4014 Naturally for text, data and bss sections the value of a symbol changes
4015 as @code{@value{LD}} changes section base addresses during linking. Absolute
4016 symbols' values do not change during linking: that is why they are
4019 The value of an undefined symbol is treated in a special way. If it is
4020 0 then the symbol is not defined in this assembler source file, and
4021 @code{@value{LD}} tries to determine its value from other files linked into the
4022 same program. You make this kind of symbol simply by mentioning a symbol
4023 name without defining it. A non-zero value represents a @code{.comm}
4024 common declaration. The value is how much common storage to reserve, in
4025 bytes (addresses). The symbol refers to the first address of the
4031 @cindex type of a symbol
4033 The type attribute of a symbol contains relocation (section)
4034 information, any flag settings indicating that a symbol is external, and
4035 (optionally), other information for linkers and debuggers. The exact
4036 format depends on the object-code output format in use.
4041 @c The following avoids a "widow" subsection title. @group would be
4042 @c better if it were available outside examples.
4045 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
4047 @cindex @code{b.out} symbol attributes
4048 @cindex symbol attributes, @code{b.out}
4049 These symbol attributes appear only when @command{@value{AS}} is configured for
4050 one of the Berkeley-descended object output formats---@code{a.out} or
4056 @subsection Symbol Attributes: @code{a.out}
4058 @cindex @code{a.out} symbol attributes
4059 @cindex symbol attributes, @code{a.out}
4065 @subsection Symbol Attributes: @code{a.out}
4067 @cindex @code{a.out} symbol attributes
4068 @cindex symbol attributes, @code{a.out}
4072 * Symbol Desc:: Descriptor
4073 * Symbol Other:: Other
4077 @subsubsection Descriptor
4079 @cindex descriptor, of @code{a.out} symbol
4080 This is an arbitrary 16-bit value. You may establish a symbol's
4081 descriptor value by using a @code{.desc} statement
4082 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4083 @command{@value{AS}}.
4086 @subsubsection Other
4088 @cindex other attribute, of @code{a.out} symbol
4089 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4094 @subsection Symbol Attributes for COFF
4096 @cindex COFF symbol attributes
4097 @cindex symbol attributes, COFF
4099 The COFF format supports a multitude of auxiliary symbol attributes;
4100 like the primary symbol attributes, they are set between @code{.def} and
4101 @code{.endef} directives.
4103 @subsubsection Primary Attributes
4105 @cindex primary attributes, COFF symbols
4106 The symbol name is set with @code{.def}; the value and type,
4107 respectively, with @code{.val} and @code{.type}.
4109 @subsubsection Auxiliary Attributes
4111 @cindex auxiliary attributes, COFF symbols
4112 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4113 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4114 table information for COFF.
4119 @subsection Symbol Attributes for SOM
4121 @cindex SOM symbol attributes
4122 @cindex symbol attributes, SOM
4124 The SOM format for the HPPA supports a multitude of symbol attributes set with
4125 the @code{.EXPORT} and @code{.IMPORT} directives.
4127 The attributes are described in @cite{HP9000 Series 800 Assembly
4128 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4129 @code{EXPORT} assembler directive documentation.
4133 @chapter Expressions
4137 @cindex numeric values
4138 An @dfn{expression} specifies an address or numeric value.
4139 Whitespace may precede and/or follow an expression.
4141 The result of an expression must be an absolute number, or else an offset into
4142 a particular section. If an expression is not absolute, and there is not
4143 enough information when @command{@value{AS}} sees the expression to know its
4144 section, a second pass over the source program might be necessary to interpret
4145 the expression---but the second pass is currently not implemented.
4146 @command{@value{AS}} aborts with an error message in this situation.
4149 * Empty Exprs:: Empty Expressions
4150 * Integer Exprs:: Integer Expressions
4154 @section Empty Expressions
4156 @cindex empty expressions
4157 @cindex expressions, empty
4158 An empty expression has no value: it is just whitespace or null.
4159 Wherever an absolute expression is required, you may omit the
4160 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4161 is compatible with other assemblers.
4164 @section Integer Expressions
4166 @cindex integer expressions
4167 @cindex expressions, integer
4168 An @dfn{integer expression} is one or more @emph{arguments} delimited
4169 by @emph{operators}.
4172 * Arguments:: Arguments
4173 * Operators:: Operators
4174 * Prefix Ops:: Prefix Operators
4175 * Infix Ops:: Infix Operators
4179 @subsection Arguments
4181 @cindex expression arguments
4182 @cindex arguments in expressions
4183 @cindex operands in expressions
4184 @cindex arithmetic operands
4185 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4186 contexts arguments are sometimes called ``arithmetic operands''. In
4187 this manual, to avoid confusing them with the ``instruction operands'' of
4188 the machine language, we use the term ``argument'' to refer to parts of
4189 expressions only, reserving the word ``operand'' to refer only to machine
4190 instruction operands.
4192 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4193 @var{section} is one of text, data, bss, absolute,
4194 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4197 Numbers are usually integers.
4199 A number can be a flonum or bignum. In this case, you are warned
4200 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4201 these 32 bits are an integer. You may write integer-manipulating
4202 instructions that act on exotic constants, compatible with other
4205 @cindex subexpressions
4206 Subexpressions are a left parenthesis @samp{(} followed by an integer
4207 expression, followed by a right parenthesis @samp{)}; or a prefix
4208 operator followed by an argument.
4211 @subsection Operators
4213 @cindex operators, in expressions
4214 @cindex arithmetic functions
4215 @cindex functions, in expressions
4216 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4217 operators are followed by an argument. Infix operators appear
4218 between their arguments. Operators may be preceded and/or followed by
4222 @subsection Prefix Operator
4224 @cindex prefix operators
4225 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4226 one argument, which must be absolute.
4228 @c the tex/end tex stuff surrounding this small table is meant to make
4229 @c it align, on the printed page, with the similar table in the next
4230 @c section (which is inside an enumerate).
4232 \global\advance\leftskip by \itemindent
4237 @dfn{Negation}. Two's complement negation.
4239 @dfn{Complementation}. Bitwise not.
4243 \global\advance\leftskip by -\itemindent
4247 @subsection Infix Operators
4249 @cindex infix operators
4250 @cindex operators, permitted arguments
4251 @dfn{Infix operators} take two arguments, one on either side. Operators
4252 have precedence, but operations with equal precedence are performed left
4253 to right. Apart from @code{+} or @option{-}, both arguments must be
4254 absolute, and the result is absolute.
4257 @cindex operator precedence
4258 @cindex precedence of operators
4265 @dfn{Multiplication}.
4268 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4274 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4277 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4281 Intermediate precedence
4286 @dfn{Bitwise Inclusive Or}.
4292 @dfn{Bitwise Exclusive Or}.
4295 @dfn{Bitwise Or Not}.
4302 @cindex addition, permitted arguments
4303 @cindex plus, permitted arguments
4304 @cindex arguments for addition
4306 @dfn{Addition}. If either argument is absolute, the result has the section of
4307 the other argument. You may not add together arguments from different
4310 @cindex subtraction, permitted arguments
4311 @cindex minus, permitted arguments
4312 @cindex arguments for subtraction
4314 @dfn{Subtraction}. If the right argument is absolute, the
4315 result has the section of the left argument.
4316 If both arguments are in the same section, the result is absolute.
4317 You may not subtract arguments from different sections.
4318 @c FIXME is there still something useful to say about undefined - undefined ?
4320 @cindex comparison expressions
4321 @cindex expressions, comparison
4326 @dfn{Is Not Equal To}
4330 @dfn{Is Greater Than}
4332 @dfn{Is Greater Than Or Equal To}
4334 @dfn{Is Less Than Or Equal To}
4336 The comparison operators can be used as infix operators. A true results has a
4337 value of -1 whereas a false result has a value of 0. Note, these operators
4338 perform signed comparisons.
4341 @item Lowest Precedence
4350 These two logical operations can be used to combine the results of sub
4351 expressions. Note, unlike the comparison operators a true result returns a
4352 value of 1 but a false results does still return 0. Also note that the logical
4353 or operator has a slightly lower precedence than logical and.
4358 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4359 address; you can only have a defined section in one of the two arguments.
4362 @chapter Assembler Directives
4364 @cindex directives, machine independent
4365 @cindex pseudo-ops, machine independent
4366 @cindex machine independent directives
4367 All assembler directives have names that begin with a period (@samp{.}).
4368 The names are case insensitive for most targets, and usually written
4371 This chapter discusses directives that are available regardless of the
4372 target machine configuration for the @sc{gnu} assembler.
4374 Some machine configurations provide additional directives.
4375 @xref{Machine Dependencies}.
4378 @ifset machine-directives
4379 @xref{Machine Dependencies}, for additional directives.
4384 * Abort:: @code{.abort}
4386 * ABORT (COFF):: @code{.ABORT}
4389 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4390 * Altmacro:: @code{.altmacro}
4391 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4392 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4393 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4394 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4395 * Byte:: @code{.byte @var{expressions}}
4396 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4397 * Comm:: @code{.comm @var{symbol} , @var{length} }
4398 * Data:: @code{.data @var{subsection}}
4400 * Def:: @code{.def @var{name}}
4403 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4409 * Double:: @code{.double @var{flonums}}
4410 * Eject:: @code{.eject}
4411 * Else:: @code{.else}
4412 * Elseif:: @code{.elseif}
4415 * Endef:: @code{.endef}
4418 * Endfunc:: @code{.endfunc}
4419 * Endif:: @code{.endif}
4420 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4421 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4422 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4424 * Error:: @code{.error @var{string}}
4425 * Exitm:: @code{.exitm}
4426 * Extern:: @code{.extern}
4427 * Fail:: @code{.fail}
4428 * File:: @code{.file}
4429 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4430 * Float:: @code{.float @var{flonums}}
4431 * Func:: @code{.func}
4432 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4434 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4435 * Hidden:: @code{.hidden @var{names}}
4438 * hword:: @code{.hword @var{expressions}}
4439 * Ident:: @code{.ident}
4440 * If:: @code{.if @var{absolute expression}}
4441 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4442 * Include:: @code{.include "@var{file}"}
4443 * Int:: @code{.int @var{expressions}}
4445 * Internal:: @code{.internal @var{names}}
4448 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4449 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4450 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4451 * Lflags:: @code{.lflags}
4452 @ifclear no-line-dir
4453 * Line:: @code{.line @var{line-number}}
4456 * Linkonce:: @code{.linkonce [@var{type}]}
4457 * List:: @code{.list}
4458 * Ln:: @code{.ln @var{line-number}}
4459 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4460 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4462 * Local:: @code{.local @var{names}}
4465 * Long:: @code{.long @var{expressions}}
4467 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4470 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4471 * MRI:: @code{.mri @var{val}}
4472 * Noaltmacro:: @code{.noaltmacro}
4473 * Nolist:: @code{.nolist}
4474 * Octa:: @code{.octa @var{bignums}}
4475 * Offset:: @code{.offset @var{loc}}
4476 * Org:: @code{.org @var{new-lc}, @var{fill}}
4477 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4479 * PopSection:: @code{.popsection}
4480 * Previous:: @code{.previous}
4483 * Print:: @code{.print @var{string}}
4485 * Protected:: @code{.protected @var{names}}
4488 * Psize:: @code{.psize @var{lines}, @var{columns}}
4489 * Purgem:: @code{.purgem @var{name}}
4491 * PushSection:: @code{.pushsection @var{name}}
4494 * Quad:: @code{.quad @var{bignums}}
4495 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4496 * Rept:: @code{.rept @var{count}}
4497 * Sbttl:: @code{.sbttl "@var{subheading}"}
4499 * Scl:: @code{.scl @var{class}}
4502 * Section:: @code{.section @var{name}[, @var{flags}]}
4505 * Set:: @code{.set @var{symbol}, @var{expression}}
4506 * Short:: @code{.short @var{expressions}}
4507 * Single:: @code{.single @var{flonums}}
4509 * Size:: @code{.size [@var{name} , @var{expression}]}
4511 @ifclear no-space-dir
4512 * Skip:: @code{.skip @var{size} , @var{fill}}
4515 * Sleb128:: @code{.sleb128 @var{expressions}}
4516 @ifclear no-space-dir
4517 * Space:: @code{.space @var{size} , @var{fill}}
4520 * Stab:: @code{.stabd, .stabn, .stabs}
4523 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4524 * Struct:: @code{.struct @var{expression}}
4526 * SubSection:: @code{.subsection}
4527 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4531 * Tag:: @code{.tag @var{structname}}
4534 * Text:: @code{.text @var{subsection}}
4535 * Title:: @code{.title "@var{heading}"}
4537 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4540 * Uleb128:: @code{.uleb128 @var{expressions}}
4542 * Val:: @code{.val @var{addr}}
4546 * Version:: @code{.version "@var{string}"}
4547 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4548 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4551 * Warning:: @code{.warning @var{string}}
4552 * Weak:: @code{.weak @var{names}}
4553 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4554 * Word:: @code{.word @var{expressions}}
4555 @ifclear no-space-dir
4556 * Zero:: @code{.zero @var{size}}
4558 * Deprecated:: Deprecated Directives
4562 @section @code{.abort}
4564 @cindex @code{abort} directive
4565 @cindex stopping the assembly
4566 This directive stops the assembly immediately. It is for
4567 compatibility with other assemblers. The original idea was that the
4568 assembly language source would be piped into the assembler. If the sender
4569 of the source quit, it could use this directive tells @command{@value{AS}} to
4570 quit also. One day @code{.abort} will not be supported.
4574 @section @code{.ABORT} (COFF)
4576 @cindex @code{ABORT} directive
4577 When producing COFF output, @command{@value{AS}} accepts this directive as a
4578 synonym for @samp{.abort}.
4581 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4587 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4589 @cindex padding the location counter
4590 @cindex @code{align} directive
4591 Pad the location counter (in the current subsection) to a particular storage
4592 boundary. The first expression (which must be absolute) is the alignment
4593 required, as described below.
4595 The second expression (also absolute) gives the fill value to be stored in the
4596 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4597 padding bytes are normally zero. However, on some systems, if the section is
4598 marked as containing code and the fill value is omitted, the space is filled
4599 with no-op instructions.
4601 The third expression is also absolute, and is also optional. If it is present,
4602 it is the maximum number of bytes that should be skipped by this alignment
4603 directive. If doing the alignment would require skipping more bytes than the
4604 specified maximum, then the alignment is not done at all. You can omit the
4605 fill value (the second argument) entirely by simply using two commas after the
4606 required alignment; this can be useful if you want the alignment to be filled
4607 with no-op instructions when appropriate.
4609 The way the required alignment is specified varies from system to system.
4610 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4611 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4612 alignment request in bytes. For example @samp{.align 8} advances
4613 the location counter until it is a multiple of 8. If the location counter
4614 is already a multiple of 8, no change is needed. For the tic54x, the
4615 first expression is the alignment request in words.
4617 For other systems, including ppc, i386 using a.out format, arm and
4618 strongarm, it is the
4619 number of low-order zero bits the location counter must have after
4620 advancement. For example @samp{.align 3} advances the location
4621 counter until it a multiple of 8. If the location counter is already a
4622 multiple of 8, no change is needed.
4624 This inconsistency is due to the different behaviors of the various
4625 native assemblers for these systems which GAS must emulate.
4626 GAS also provides @code{.balign} and @code{.p2align} directives,
4627 described later, which have a consistent behavior across all
4628 architectures (but are specific to GAS).
4631 @section @code{.altmacro}
4632 Enable alternate macro mode, enabling:
4635 @item LOCAL @var{name} [ , @dots{} ]
4636 One additional directive, @code{LOCAL}, is available. It is used to
4637 generate a string replacement for each of the @var{name} arguments, and
4638 replace any instances of @var{name} in each macro expansion. The
4639 replacement string is unique in the assembly, and different for each
4640 separate macro expansion. @code{LOCAL} allows you to write macros that
4641 define symbols, without fear of conflict between separate macro expansions.
4643 @item String delimiters
4644 You can write strings delimited in these other ways besides
4645 @code{"@var{string}"}:
4648 @item '@var{string}'
4649 You can delimit strings with single-quote characters.
4651 @item <@var{string}>
4652 You can delimit strings with matching angle brackets.
4655 @item single-character string escape
4656 To include any single character literally in a string (even if the
4657 character would otherwise have some special meaning), you can prefix the
4658 character with @samp{!} (an exclamation mark). For example, you can
4659 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4661 @item Expression results as strings
4662 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4663 and use the result as a string.
4667 @section @code{.ascii "@var{string}"}@dots{}
4669 @cindex @code{ascii} directive
4670 @cindex string literals
4671 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4672 separated by commas. It assembles each string (with no automatic
4673 trailing zero byte) into consecutive addresses.
4676 @section @code{.asciz "@var{string}"}@dots{}
4678 @cindex @code{asciz} directive
4679 @cindex zero-terminated strings
4680 @cindex null-terminated strings
4681 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4682 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4685 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4687 @cindex padding the location counter given number of bytes
4688 @cindex @code{balign} directive
4689 Pad the location counter (in the current subsection) to a particular
4690 storage boundary. The first expression (which must be absolute) is the
4691 alignment request in bytes. For example @samp{.balign 8} advances
4692 the location counter until it is a multiple of 8. If the location counter
4693 is already a multiple of 8, no change is needed.
4695 The second expression (also absolute) gives the fill value to be stored in the
4696 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4697 padding bytes are normally zero. However, on some systems, if the section is
4698 marked as containing code and the fill value is omitted, the space is filled
4699 with no-op instructions.
4701 The third expression is also absolute, and is also optional. If it is present,
4702 it is the maximum number of bytes that should be skipped by this alignment
4703 directive. If doing the alignment would require skipping more bytes than the
4704 specified maximum, then the alignment is not done at all. You can omit the
4705 fill value (the second argument) entirely by simply using two commas after the
4706 required alignment; this can be useful if you want the alignment to be filled
4707 with no-op instructions when appropriate.
4709 @cindex @code{balignw} directive
4710 @cindex @code{balignl} directive
4711 The @code{.balignw} and @code{.balignl} directives are variants of the
4712 @code{.balign} directive. The @code{.balignw} directive treats the fill
4713 pattern as a two byte word value. The @code{.balignl} directives treats the
4714 fill pattern as a four byte longword value. For example, @code{.balignw
4715 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4716 filled in with the value 0x368d (the exact placement of the bytes depends upon
4717 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4720 @node Bundle directives
4721 @section Bundle directives
4722 @subsection @code{.bundle_align_mode @var{abs-expr}}
4723 @cindex @code{bundle_align_mode} directive
4725 @cindex instruction bundle
4726 @cindex aligned instruction bundle
4727 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4728 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4729 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4730 disabled (which is the default state). If the argument it not zero, it
4731 gives the size of an instruction bundle as a power of two (as for the
4732 @code{.p2align} directive, @pxref{P2align}).
4734 For some targets, it's an ABI requirement that no instruction may span a
4735 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4736 instructions that starts on an aligned boundary. For example, if
4737 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4738 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4739 effect, no single instruction may span a boundary between bundles. If an
4740 instruction would start too close to the end of a bundle for the length of
4741 that particular instruction to fit within the bundle, then the space at the
4742 end of that bundle is filled with no-op instructions so the instruction
4743 starts in the next bundle. As a corollary, it's an error if any single
4744 instruction's encoding is longer than the bundle size.
4746 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4747 @cindex @code{bundle_lock} directive
4748 @cindex @code{bundle_unlock} directive
4749 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4750 allow explicit control over instruction bundle padding. These directives
4751 are only valid when @code{.bundle_align_mode} has been used to enable
4752 aligned instruction bundle mode. It's an error if they appear when
4753 @code{.bundle_align_mode} has not been used at all, or when the last
4754 directive was @w{@code{.bundle_align_mode 0}}.
4756 @cindex bundle-locked
4757 For some targets, it's an ABI requirement that certain instructions may
4758 appear only as part of specified permissible sequences of multiple
4759 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4760 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4761 instruction sequence. For purposes of aligned instruction bundle mode, a
4762 sequence starting with @code{.bundle_lock} and ending with
4763 @code{.bundle_unlock} is treated as a single instruction. That is, the
4764 entire sequence must fit into a single bundle and may not span a bundle
4765 boundary. If necessary, no-op instructions will be inserted before the
4766 first instruction of the sequence so that the whole sequence starts on an
4767 aligned bundle boundary. It's an error if the sequence is longer than the
4770 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4771 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4772 nested. That is, a second @code{.bundle_lock} directive before the next
4773 @code{.bundle_unlock} directive has no effect except that it must be
4774 matched by another closing @code{.bundle_unlock} so that there is the
4775 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4778 @section @code{.byte @var{expressions}}
4780 @cindex @code{byte} directive
4781 @cindex integers, one byte
4782 @code{.byte} expects zero or more expressions, separated by commas.
4783 Each expression is assembled into the next byte.
4785 @node CFI directives
4786 @section CFI directives
4787 @subsection @code{.cfi_sections @var{section_list}}
4788 @cindex @code{cfi_sections} directive
4789 @code{.cfi_sections} may be used to specify whether CFI directives
4790 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4791 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4792 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4793 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4794 directive is not used is @code{.cfi_sections .eh_frame}.
4796 On targets that support compact unwinding tables these can be generated
4797 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4799 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4800 which is used by the @value{TIC6X} target.
4802 The @code{.cfi_sections} directive can be repeated, with the same or different
4803 arguments, provided that CFI generation has not yet started. Once CFI
4804 generation has started however the section list is fixed and any attempts to
4805 redefine it will result in an error.
4807 @subsection @code{.cfi_startproc [simple]}
4808 @cindex @code{cfi_startproc} directive
4809 @code{.cfi_startproc} is used at the beginning of each function that
4810 should have an entry in @code{.eh_frame}. It initializes some internal
4811 data structures. Don't forget to close the function by
4812 @code{.cfi_endproc}.
4814 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4815 it also emits some architecture dependent initial CFI instructions.
4817 @subsection @code{.cfi_endproc}
4818 @cindex @code{cfi_endproc} directive
4819 @code{.cfi_endproc} is used at the end of a function where it closes its
4820 unwind entry previously opened by
4821 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4823 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4824 @cindex @code{cfi_personality} directive
4825 @code{.cfi_personality} defines personality routine and its encoding.
4826 @var{encoding} must be a constant determining how the personality
4827 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4828 argument is not present, otherwise second argument should be
4829 a constant or a symbol name. When using indirect encodings,
4830 the symbol provided should be the location where personality
4831 can be loaded from, not the personality routine itself.
4832 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4833 no personality routine.
4835 @subsection @code{.cfi_personality_id @var{id}}
4836 @cindex @code{cfi_personality_id} directive
4837 @code{cfi_personality_id} defines a personality routine by its index as
4838 defined in a compact unwinding format.
4839 Only valid when generating compact EH frames (i.e.
4840 with @code{.cfi_sections eh_frame_entry}.
4842 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4843 @cindex @code{cfi_fde_data} directive
4844 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4845 used for the current function. These are emitted inline in the
4846 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4847 in the @code{.gnu.extab} section otherwise.
4848 Only valid when generating compact EH frames (i.e.
4849 with @code{.cfi_sections eh_frame_entry}.
4851 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4852 @code{.cfi_lsda} defines LSDA and its encoding.
4853 @var{encoding} must be a constant determining how the LSDA
4854 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4855 argument is not present, otherwise the second argument should be a constant
4856 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4857 meaning that no LSDA is present.
4859 @subsection @code{.cfi_inline_lsda} [@var{align}]
4860 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4861 switches to the corresponding @code{.gnu.extab} section.
4862 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4863 Only valid when generating compact EH frames (i.e.
4864 with @code{.cfi_sections eh_frame_entry}.
4866 The table header and unwinding opcodes will be generated at this point,
4867 so that they are immediately followed by the LSDA data. The symbol
4868 referenced by the @code{.cfi_lsda} directive should still be defined
4869 in case a fallback FDE based encoding is used. The LSDA data is terminated
4870 by a section directive.
4872 The optional @var{align} argument specifies the alignment required.
4873 The alignment is specified as a power of two, as with the
4874 @code{.p2align} directive.
4876 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4877 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4878 address from @var{register} and add @var{offset} to it}.
4880 @subsection @code{.cfi_def_cfa_register @var{register}}
4881 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4882 now on @var{register} will be used instead of the old one. Offset
4885 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4886 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4887 remains the same, but @var{offset} is new. Note that it is the
4888 absolute offset that will be added to a defined register to compute
4891 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4892 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4893 value that is added/subtracted from the previous offset.
4895 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4896 Previous value of @var{register} is saved at offset @var{offset} from
4899 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4900 Previous value of @var{register} is CFA + @var{offset}.
4902 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4903 Previous value of @var{register} is saved at offset @var{offset} from
4904 the current CFA register. This is transformed to @code{.cfi_offset}
4905 using the known displacement of the CFA register from the CFA.
4906 This is often easier to use, because the number will match the
4907 code it's annotating.
4909 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4910 Previous value of @var{register1} is saved in register @var{register2}.
4912 @subsection @code{.cfi_restore @var{register}}
4913 @code{.cfi_restore} says that the rule for @var{register} is now the
4914 same as it was at the beginning of the function, after all initial
4915 instruction added by @code{.cfi_startproc} were executed.
4917 @subsection @code{.cfi_undefined @var{register}}
4918 From now on the previous value of @var{register} can't be restored anymore.
4920 @subsection @code{.cfi_same_value @var{register}}
4921 Current value of @var{register} is the same like in the previous frame,
4922 i.e. no restoration needed.
4924 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4925 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4926 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4927 places them in the current row. This is useful for situations where you have
4928 multiple @code{.cfi_*} directives that need to be undone due to the control
4929 flow of the program. For example, we could have something like this (assuming
4930 the CFA is the value of @code{rbp}):
4940 .cfi_def_cfa %rsp, 8
4943 /* Do something else */
4946 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4947 to the instructions before @code{label}. This means we'd have to add multiple
4948 @code{.cfi} directives after @code{label} to recreate the original save
4949 locations of the registers, as well as setting the CFA back to the value of
4950 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4962 .cfi_def_cfa %rsp, 8
4966 /* Do something else */
4969 That way, the rules for the instructions after @code{label} will be the same
4970 as before the first @code{.cfi_restore} without having to use multiple
4971 @code{.cfi} directives.
4973 @subsection @code{.cfi_return_column @var{register}}
4974 Change return column @var{register}, i.e. the return address is either
4975 directly in @var{register} or can be accessed by rules for @var{register}.
4977 @subsection @code{.cfi_signal_frame}
4978 Mark current function as signal trampoline.
4980 @subsection @code{.cfi_window_save}
4981 SPARC register window has been saved.
4983 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4984 Allows the user to add arbitrary bytes to the unwind info. One
4985 might use this to add OS-specific CFI opcodes, or generic CFI
4986 opcodes that GAS does not yet support.
4988 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4989 The current value of @var{register} is @var{label}. The value of @var{label}
4990 will be encoded in the output file according to @var{encoding}; see the
4991 description of @code{.cfi_personality} for details on this encoding.
4993 The usefulness of equating a register to a fixed label is probably
4994 limited to the return address register. Here, it can be useful to
4995 mark a code segment that has only one return address which is reached
4996 by a direct branch and no copy of the return address exists in memory
4997 or another register.
5000 @section @code{.comm @var{symbol} , @var{length} }
5002 @cindex @code{comm} directive
5003 @cindex symbol, common
5004 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
5005 common symbol in one object file may be merged with a defined or common symbol
5006 of the same name in another object file. If @code{@value{LD}} does not see a
5007 definition for the symbol--just one or more common symbols--then it will
5008 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
5009 absolute expression. If @code{@value{LD}} sees multiple common symbols with
5010 the same name, and they do not all have the same size, it will allocate space
5011 using the largest size.
5014 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
5015 an optional third argument. This is the desired alignment of the symbol,
5016 specified for ELF as a byte boundary (for example, an alignment of 16 means
5017 that the least significant 4 bits of the address should be zero), and for PE
5018 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
5019 boundary). The alignment must be an absolute expression, and it must be a
5020 power of two. If @code{@value{LD}} allocates uninitialized memory for the
5021 common symbol, it will use the alignment when placing the symbol. If no
5022 alignment is specified, @command{@value{AS}} will set the alignment to the
5023 largest power of two less than or equal to the size of the symbol, up to a
5024 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
5025 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5026 @samp{--section-alignment} option; image file sections in PE are aligned to
5027 multiples of 4096, which is far too large an alignment for ordinary variables.
5028 It is rather the default alignment for (non-debug) sections within object
5029 (@samp{*.o}) files, which are less strictly aligned.}.
5033 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5034 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5038 @section @code{.data @var{subsection}}
5040 @cindex @code{data} directive
5041 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5042 end of the data subsection numbered @var{subsection} (which is an
5043 absolute expression). If @var{subsection} is omitted, it defaults
5048 @section @code{.def @var{name}}
5050 @cindex @code{def} directive
5051 @cindex COFF symbols, debugging
5052 @cindex debugging COFF symbols
5053 Begin defining debugging information for a symbol @var{name}; the
5054 definition extends until the @code{.endef} directive is encountered.
5057 This directive is only observed when @command{@value{AS}} is configured for COFF
5058 format output; when producing @code{b.out}, @samp{.def} is recognized,
5065 @section @code{.desc @var{symbol}, @var{abs-expression}}
5067 @cindex @code{desc} directive
5068 @cindex COFF symbol descriptor
5069 @cindex symbol descriptor, COFF
5070 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5071 to the low 16 bits of an absolute expression.
5074 The @samp{.desc} directive is not available when @command{@value{AS}} is
5075 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5076 object format. For the sake of compatibility, @command{@value{AS}} accepts
5077 it, but produces no output, when configured for COFF.
5083 @section @code{.dim}
5085 @cindex @code{dim} directive
5086 @cindex COFF auxiliary symbol information
5087 @cindex auxiliary symbol information, COFF
5088 This directive is generated by compilers to include auxiliary debugging
5089 information in the symbol table. It is only permitted inside
5090 @code{.def}/@code{.endef} pairs.
5093 @samp{.dim} is only meaningful when generating COFF format output; when
5094 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5100 @section @code{.double @var{flonums}}
5102 @cindex @code{double} directive
5103 @cindex floating point numbers (double)
5104 @code{.double} expects zero or more flonums, separated by commas. It
5105 assembles floating point numbers.
5107 The exact kind of floating point numbers emitted depends on how
5108 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5112 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5113 in @sc{ieee} format.
5118 @section @code{.eject}
5120 @cindex @code{eject} directive
5121 @cindex new page, in listings
5122 @cindex page, in listings
5123 @cindex listing control: new page
5124 Force a page break at this point, when generating assembly listings.
5127 @section @code{.else}
5129 @cindex @code{else} directive
5130 @code{.else} is part of the @command{@value{AS}} support for conditional
5131 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5132 of code to be assembled if the condition for the preceding @code{.if}
5136 @section @code{.elseif}
5138 @cindex @code{elseif} directive
5139 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5140 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5141 @code{.if} block that would otherwise fill the entire @code{.else} section.
5144 @section @code{.end}
5146 @cindex @code{end} directive
5147 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5148 process anything in the file past the @code{.end} directive.
5152 @section @code{.endef}
5154 @cindex @code{endef} directive
5155 This directive flags the end of a symbol definition begun with
5159 @samp{.endef} is only meaningful when generating COFF format output; if
5160 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5161 directive but ignores it.
5166 @section @code{.endfunc}
5167 @cindex @code{endfunc} directive
5168 @code{.endfunc} marks the end of a function specified with @code{.func}.
5171 @section @code{.endif}
5173 @cindex @code{endif} directive
5174 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5175 it marks the end of a block of code that is only assembled
5176 conditionally. @xref{If,,@code{.if}}.
5179 @section @code{.equ @var{symbol}, @var{expression}}
5181 @cindex @code{equ} directive
5182 @cindex assigning values to symbols
5183 @cindex symbols, assigning values to
5184 This directive sets the value of @var{symbol} to @var{expression}.
5185 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5188 The syntax for @code{equ} on the HPPA is
5189 @samp{@var{symbol} .equ @var{expression}}.
5193 The syntax for @code{equ} on the Z80 is
5194 @samp{@var{symbol} equ @var{expression}}.
5195 On the Z80 it is an error if @var{symbol} is already defined,
5196 but the symbol is not protected from later redefinition.
5197 Compare @ref{Equiv}.
5201 @section @code{.equiv @var{symbol}, @var{expression}}
5202 @cindex @code{equiv} directive
5203 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5204 the assembler will signal an error if @var{symbol} is already defined. Note a
5205 symbol which has been referenced but not actually defined is considered to be
5208 Except for the contents of the error message, this is roughly equivalent to
5215 plus it protects the symbol from later redefinition.
5218 @section @code{.eqv @var{symbol}, @var{expression}}
5219 @cindex @code{eqv} directive
5220 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5221 evaluate the expression or any part of it immediately. Instead each time
5222 the resulting symbol is used in an expression, a snapshot of its current
5226 @section @code{.err}
5227 @cindex @code{err} directive
5228 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5229 message and, unless the @option{-Z} option was used, it will not generate an
5230 object file. This can be used to signal an error in conditionally compiled code.
5233 @section @code{.error "@var{string}"}
5234 @cindex error directive
5236 Similarly to @code{.err}, this directive emits an error, but you can specify a
5237 string that will be emitted as the error message. If you don't specify the
5238 message, it defaults to @code{".error directive invoked in source file"}.
5239 @xref{Errors, ,Error and Warning Messages}.
5242 .error "This code has not been assembled and tested."
5246 @section @code{.exitm}
5247 Exit early from the current macro definition. @xref{Macro}.
5250 @section @code{.extern}
5252 @cindex @code{extern} directive
5253 @code{.extern} is accepted in the source program---for compatibility
5254 with other assemblers---but it is ignored. @command{@value{AS}} treats
5255 all undefined symbols as external.
5258 @section @code{.fail @var{expression}}
5260 @cindex @code{fail} directive
5261 Generates an error or a warning. If the value of the @var{expression} is 500
5262 or more, @command{@value{AS}} will print a warning message. If the value is less
5263 than 500, @command{@value{AS}} will print an error message. The message will
5264 include the value of @var{expression}. This can occasionally be useful inside
5265 complex nested macros or conditional assembly.
5268 @section @code{.file}
5269 @cindex @code{file} directive
5271 @ifclear no-file-dir
5272 There are two different versions of the @code{.file} directive. Targets
5273 that support DWARF2 line number information use the DWARF2 version of
5274 @code{.file}. Other targets use the default version.
5276 @subheading Default Version
5278 @cindex logical file name
5279 @cindex file name, logical
5280 This version of the @code{.file} directive tells @command{@value{AS}} that we
5281 are about to start a new logical file. The syntax is:
5287 @var{string} is the new file name. In general, the filename is
5288 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5289 to specify an empty file name, you must give the quotes--@code{""}. This
5290 statement may go away in future: it is only recognized to be compatible with
5291 old @command{@value{AS}} programs.
5293 @subheading DWARF2 Version
5296 When emitting DWARF2 line number information, @code{.file} assigns filenames
5297 to the @code{.debug_line} file name table. The syntax is:
5300 .file @var{fileno} @var{filename}
5303 The @var{fileno} operand should be a unique positive integer to use as the
5304 index of the entry in the table. The @var{filename} operand is a C string
5307 The detail of filename indices is exposed to the user because the filename
5308 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5309 information, and thus the user must know the exact indices that table
5313 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5315 @cindex @code{fill} directive
5316 @cindex writing patterns in memory
5317 @cindex patterns, writing in memory
5318 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5319 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5320 may be zero or more. @var{Size} may be zero or more, but if it is
5321 more than 8, then it is deemed to have the value 8, compatible with
5322 other people's assemblers. The contents of each @var{repeat} bytes
5323 is taken from an 8-byte number. The highest order 4 bytes are
5324 zero. The lowest order 4 bytes are @var{value} rendered in the
5325 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5326 Each @var{size} bytes in a repetition is taken from the lowest order
5327 @var{size} bytes of this number. Again, this bizarre behavior is
5328 compatible with other people's assemblers.
5330 @var{size} and @var{value} are optional.
5331 If the second comma and @var{value} are absent, @var{value} is
5332 assumed zero. If the first comma and following tokens are absent,
5333 @var{size} is assumed to be 1.
5336 @section @code{.float @var{flonums}}
5338 @cindex floating point numbers (single)
5339 @cindex @code{float} directive
5340 This directive assembles zero or more flonums, separated by commas. It
5341 has the same effect as @code{.single}.
5343 The exact kind of floating point numbers emitted depends on how
5344 @command{@value{AS}} is configured.
5345 @xref{Machine Dependencies}.
5349 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5350 in @sc{ieee} format.
5355 @section @code{.func @var{name}[,@var{label}]}
5356 @cindex @code{func} directive
5357 @code{.func} emits debugging information to denote function @var{name}, and
5358 is ignored unless the file is assembled with debugging enabled.
5359 Only @samp{--gstabs[+]} is currently supported.
5360 @var{label} is the entry point of the function and if omitted @var{name}
5361 prepended with the @samp{leading char} is used.
5362 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5363 All functions are currently defined to have @code{void} return type.
5364 The function must be terminated with @code{.endfunc}.
5367 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5369 @cindex @code{global} directive
5370 @cindex symbol, making visible to linker
5371 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5372 @var{symbol} in your partial program, its value is made available to
5373 other partial programs that are linked with it. Otherwise,
5374 @var{symbol} takes its attributes from a symbol of the same name
5375 from another file linked into the same program.
5377 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5378 compatibility with other assemblers.
5381 On the HPPA, @code{.global} is not always enough to make it accessible to other
5382 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5383 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5388 @section @code{.gnu_attribute @var{tag},@var{value}}
5389 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5392 @section @code{.hidden @var{names}}
5394 @cindex @code{hidden} directive
5396 This is one of the ELF visibility directives. The other two are
5397 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5398 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5400 This directive overrides the named symbols default visibility (which is set by
5401 their binding: local, global or weak). The directive sets the visibility to
5402 @code{hidden} which means that the symbols are not visible to other components.
5403 Such symbols are always considered to be @code{protected} as well.
5407 @section @code{.hword @var{expressions}}
5409 @cindex @code{hword} directive
5410 @cindex integers, 16-bit
5411 @cindex numbers, 16-bit
5412 @cindex sixteen bit integers
5413 This expects zero or more @var{expressions}, and emits
5414 a 16 bit number for each.
5417 This directive is a synonym for @samp{.short}; depending on the target
5418 architecture, it may also be a synonym for @samp{.word}.
5422 This directive is a synonym for @samp{.short}.
5425 This directive is a synonym for both @samp{.short} and @samp{.word}.
5430 @section @code{.ident}
5432 @cindex @code{ident} directive
5434 This directive is used by some assemblers to place tags in object files. The
5435 behavior of this directive varies depending on the target. When using the
5436 a.out object file format, @command{@value{AS}} simply accepts the directive for
5437 source-file compatibility with existing assemblers, but does not emit anything
5438 for it. When using COFF, comments are emitted to the @code{.comment} or
5439 @code{.rdata} section, depending on the target. When using ELF, comments are
5440 emitted to the @code{.comment} section.
5443 @section @code{.if @var{absolute expression}}
5445 @cindex conditional assembly
5446 @cindex @code{if} directive
5447 @code{.if} marks the beginning of a section of code which is only
5448 considered part of the source program being assembled if the argument
5449 (which must be an @var{absolute expression}) is non-zero. The end of
5450 the conditional section of code must be marked by @code{.endif}
5451 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5452 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5453 If you have several conditions to check, @code{.elseif} may be used to avoid
5454 nesting blocks if/else within each subsequent @code{.else} block.
5456 The following variants of @code{.if} are also supported:
5458 @cindex @code{ifdef} directive
5459 @item .ifdef @var{symbol}
5460 Assembles the following section of code if the specified @var{symbol}
5461 has been defined. Note a symbol which has been referenced but not yet defined
5462 is considered to be undefined.
5464 @cindex @code{ifb} directive
5465 @item .ifb @var{text}
5466 Assembles the following section of code if the operand is blank (empty).
5468 @cindex @code{ifc} directive
5469 @item .ifc @var{string1},@var{string2}
5470 Assembles the following section of code if the two strings are the same. The
5471 strings may be optionally quoted with single quotes. If they are not quoted,
5472 the first string stops at the first comma, and the second string stops at the
5473 end of the line. Strings which contain whitespace should be quoted. The
5474 string comparison is case sensitive.
5476 @cindex @code{ifeq} directive
5477 @item .ifeq @var{absolute expression}
5478 Assembles the following section of code if the argument is zero.
5480 @cindex @code{ifeqs} directive
5481 @item .ifeqs @var{string1},@var{string2}
5482 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5484 @cindex @code{ifge} directive
5485 @item .ifge @var{absolute expression}
5486 Assembles the following section of code if the argument is greater than or
5489 @cindex @code{ifgt} directive
5490 @item .ifgt @var{absolute expression}
5491 Assembles the following section of code if the argument is greater than zero.
5493 @cindex @code{ifle} directive
5494 @item .ifle @var{absolute expression}
5495 Assembles the following section of code if the argument is less than or equal
5498 @cindex @code{iflt} directive
5499 @item .iflt @var{absolute expression}
5500 Assembles the following section of code if the argument is less than zero.
5502 @cindex @code{ifnb} directive
5503 @item .ifnb @var{text}
5504 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5505 following section of code if the operand is non-blank (non-empty).
5507 @cindex @code{ifnc} directive
5508 @item .ifnc @var{string1},@var{string2}.
5509 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5510 following section of code if the two strings are not the same.
5512 @cindex @code{ifndef} directive
5513 @cindex @code{ifnotdef} directive
5514 @item .ifndef @var{symbol}
5515 @itemx .ifnotdef @var{symbol}
5516 Assembles the following section of code if the specified @var{symbol}
5517 has not been defined. Both spelling variants are equivalent. Note a symbol
5518 which has been referenced but not yet defined is considered to be undefined.
5520 @cindex @code{ifne} directive
5521 @item .ifne @var{absolute expression}
5522 Assembles the following section of code if the argument is not equal to zero
5523 (in other words, this is equivalent to @code{.if}).
5525 @cindex @code{ifnes} directive
5526 @item .ifnes @var{string1},@var{string2}
5527 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5528 following section of code if the two strings are not the same.
5532 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5534 @cindex @code{incbin} directive
5535 @cindex binary files, including
5536 The @code{incbin} directive includes @var{file} verbatim at the current
5537 location. You can control the search paths used with the @samp{-I} command-line
5538 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5541 The @var{skip} argument skips a number of bytes from the start of the
5542 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5543 read. Note that the data is not aligned in any way, so it is the user's
5544 responsibility to make sure that proper alignment is provided both before and
5545 after the @code{incbin} directive.
5548 @section @code{.include "@var{file}"}
5550 @cindex @code{include} directive
5551 @cindex supporting files, including
5552 @cindex files, including
5553 This directive provides a way to include supporting files at specified
5554 points in your source program. The code from @var{file} is assembled as
5555 if it followed the point of the @code{.include}; when the end of the
5556 included file is reached, assembly of the original file continues. You
5557 can control the search paths used with the @samp{-I} command-line option
5558 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5562 @section @code{.int @var{expressions}}
5564 @cindex @code{int} directive
5565 @cindex integers, 32-bit
5566 Expect zero or more @var{expressions}, of any section, separated by commas.
5567 For each expression, emit a number that, at run time, is the value of that
5568 expression. The byte order and bit size of the number depends on what kind
5569 of target the assembly is for.
5573 On most forms of the H8/300, @code{.int} emits 16-bit
5574 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5581 @section @code{.internal @var{names}}
5583 @cindex @code{internal} directive
5585 This is one of the ELF visibility directives. The other two are
5586 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5587 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5589 This directive overrides the named symbols default visibility (which is set by
5590 their binding: local, global or weak). The directive sets the visibility to
5591 @code{internal} which means that the symbols are considered to be @code{hidden}
5592 (i.e., not visible to other components), and that some extra, processor specific
5593 processing must also be performed upon the symbols as well.
5597 @section @code{.irp @var{symbol},@var{values}}@dots{}
5599 @cindex @code{irp} directive
5600 Evaluate a sequence of statements assigning different values to @var{symbol}.
5601 The sequence of statements starts at the @code{.irp} directive, and is
5602 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5603 set to @var{value}, and the sequence of statements is assembled. If no
5604 @var{value} is listed, the sequence of statements is assembled once, with
5605 @var{symbol} set to the null string. To refer to @var{symbol} within the
5606 sequence of statements, use @var{\symbol}.
5608 For example, assembling
5616 is equivalent to assembling
5624 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5627 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5629 @cindex @code{irpc} directive
5630 Evaluate a sequence of statements assigning different values to @var{symbol}.
5631 The sequence of statements starts at the @code{.irpc} directive, and is
5632 terminated by an @code{.endr} directive. For each character in @var{value},
5633 @var{symbol} is set to the character, and the sequence of statements is
5634 assembled. If no @var{value} is listed, the sequence of statements is
5635 assembled once, with @var{symbol} set to the null string. To refer to
5636 @var{symbol} within the sequence of statements, use @var{\symbol}.
5638 For example, assembling
5646 is equivalent to assembling
5654 For some caveats with the spelling of @var{symbol}, see also the discussion
5658 @section @code{.lcomm @var{symbol} , @var{length}}
5660 @cindex @code{lcomm} directive
5661 @cindex local common symbols
5662 @cindex symbols, local common
5663 Reserve @var{length} (an absolute expression) bytes for a local common
5664 denoted by @var{symbol}. The section and value of @var{symbol} are
5665 those of the new local common. The addresses are allocated in the bss
5666 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5667 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5668 not visible to @code{@value{LD}}.
5671 Some targets permit a third argument to be used with @code{.lcomm}. This
5672 argument specifies the desired alignment of the symbol in the bss section.
5676 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5677 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5681 @section @code{.lflags}
5683 @cindex @code{lflags} directive (ignored)
5684 @command{@value{AS}} accepts this directive, for compatibility with other
5685 assemblers, but ignores it.
5687 @ifclear no-line-dir
5689 @section @code{.line @var{line-number}}
5691 @cindex @code{line} directive
5692 @cindex logical line number
5694 Change the logical line number. @var{line-number} must be an absolute
5695 expression. The next line has that logical line number. Therefore any other
5696 statements on the current line (after a statement separator character) are
5697 reported as on logical line number @var{line-number} @minus{} 1. One day
5698 @command{@value{AS}} will no longer support this directive: it is recognized only
5699 for compatibility with existing assembler programs.
5702 Even though this is a directive associated with the @code{a.out} or
5703 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5704 when producing COFF output, and treats @samp{.line} as though it
5705 were the COFF @samp{.ln} @emph{if} it is found outside a
5706 @code{.def}/@code{.endef} pair.
5708 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5709 used by compilers to generate auxiliary symbol information for
5714 @section @code{.linkonce [@var{type}]}
5716 @cindex @code{linkonce} directive
5717 @cindex common sections
5718 Mark the current section so that the linker only includes a single copy of it.
5719 This may be used to include the same section in several different object files,
5720 but ensure that the linker will only include it once in the final output file.
5721 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5722 Duplicate sections are detected based on the section name, so it should be
5725 This directive is only supported by a few object file formats; as of this
5726 writing, the only object file format which supports it is the Portable
5727 Executable format used on Windows NT.
5729 The @var{type} argument is optional. If specified, it must be one of the
5730 following strings. For example:
5734 Not all types may be supported on all object file formats.
5738 Silently discard duplicate sections. This is the default.
5741 Warn if there are duplicate sections, but still keep only one copy.
5744 Warn if any of the duplicates have different sizes.
5747 Warn if any of the duplicates do not have exactly the same contents.
5751 @section @code{.list}
5753 @cindex @code{list} directive
5754 @cindex listing control, turning on
5755 Control (in conjunction with the @code{.nolist} directive) whether or
5756 not assembly listings are generated. These two directives maintain an
5757 internal counter (which is zero initially). @code{.list} increments the
5758 counter, and @code{.nolist} decrements it. Assembly listings are
5759 generated whenever the counter is greater than zero.
5761 By default, listings are disabled. When you enable them (with the
5762 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5763 the initial value of the listing counter is one.
5766 @section @code{.ln @var{line-number}}
5768 @cindex @code{ln} directive
5769 @ifclear no-line-dir
5770 @samp{.ln} is a synonym for @samp{.line}.
5773 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5774 must be an absolute expression. The next line has that logical
5775 line number, so any other statements on the current line (after a
5776 statement separator character @code{;}) are reported as on logical
5777 line number @var{line-number} @minus{} 1.
5780 This directive is accepted, but ignored, when @command{@value{AS}} is
5781 configured for @code{b.out}; its effect is only associated with COFF
5787 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5788 @cindex @code{loc} directive
5789 When emitting DWARF2 line number information,
5790 the @code{.loc} directive will add a row to the @code{.debug_line} line
5791 number matrix corresponding to the immediately following assembly
5792 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5793 arguments will be applied to the @code{.debug_line} state machine before
5796 The @var{options} are a sequence of the following tokens in any order:
5800 This option will set the @code{basic_block} register in the
5801 @code{.debug_line} state machine to @code{true}.
5804 This option will set the @code{prologue_end} register in the
5805 @code{.debug_line} state machine to @code{true}.
5807 @item epilogue_begin
5808 This option will set the @code{epilogue_begin} register in the
5809 @code{.debug_line} state machine to @code{true}.
5811 @item is_stmt @var{value}
5812 This option will set the @code{is_stmt} register in the
5813 @code{.debug_line} state machine to @code{value}, which must be
5816 @item isa @var{value}
5817 This directive will set the @code{isa} register in the @code{.debug_line}
5818 state machine to @var{value}, which must be an unsigned integer.
5820 @item discriminator @var{value}
5821 This directive will set the @code{discriminator} register in the @code{.debug_line}
5822 state machine to @var{value}, which must be an unsigned integer.
5826 @node Loc_mark_labels
5827 @section @code{.loc_mark_labels @var{enable}}
5828 @cindex @code{loc_mark_labels} directive
5829 When emitting DWARF2 line number information,
5830 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5831 to the @code{.debug_line} line number matrix with the @code{basic_block}
5832 register in the state machine set whenever a code label is seen.
5833 The @var{enable} argument should be either 1 or 0, to enable or disable
5834 this function respectively.
5838 @section @code{.local @var{names}}
5840 @cindex @code{local} directive
5841 This directive, which is available for ELF targets, marks each symbol in
5842 the comma-separated list of @code{names} as a local symbol so that it
5843 will not be externally visible. If the symbols do not already exist,
5844 they will be created.
5846 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5847 accept an alignment argument, which is the case for most ELF targets,
5848 the @code{.local} directive can be used in combination with @code{.comm}
5849 (@pxref{Comm}) to define aligned local common data.
5853 @section @code{.long @var{expressions}}
5855 @cindex @code{long} directive
5856 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5859 @c no one seems to know what this is for or whether this description is
5860 @c what it really ought to do
5862 @section @code{.lsym @var{symbol}, @var{expression}}
5864 @cindex @code{lsym} directive
5865 @cindex symbol, not referenced in assembly
5866 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5867 the hash table, ensuring it cannot be referenced by name during the
5868 rest of the assembly. This sets the attributes of the symbol to be
5869 the same as the expression value:
5871 @var{other} = @var{descriptor} = 0
5872 @var{type} = @r{(section of @var{expression})}
5873 @var{value} = @var{expression}
5876 The new symbol is not flagged as external.
5880 @section @code{.macro}
5883 The commands @code{.macro} and @code{.endm} allow you to define macros that
5884 generate assembly output. For example, this definition specifies a macro
5885 @code{sum} that puts a sequence of numbers into memory:
5888 .macro sum from=0, to=5
5897 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5909 @item .macro @var{macname}
5910 @itemx .macro @var{macname} @var{macargs} @dots{}
5911 @cindex @code{macro} directive
5912 Begin the definition of a macro called @var{macname}. If your macro
5913 definition requires arguments, specify their names after the macro name,
5914 separated by commas or spaces. You can qualify the macro argument to
5915 indicate whether all invocations must specify a non-blank value (through
5916 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5917 (through @samp{:@code{vararg}}). You can supply a default value for any
5918 macro argument by following the name with @samp{=@var{deflt}}. You
5919 cannot define two macros with the same @var{macname} unless it has been
5920 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5921 definitions. For example, these are all valid @code{.macro} statements:
5925 Begin the definition of a macro called @code{comm}, which takes no
5928 @item .macro plus1 p, p1
5929 @itemx .macro plus1 p p1
5930 Either statement begins the definition of a macro called @code{plus1},
5931 which takes two arguments; within the macro definition, write
5932 @samp{\p} or @samp{\p1} to evaluate the arguments.
5934 @item .macro reserve_str p1=0 p2
5935 Begin the definition of a macro called @code{reserve_str}, with two
5936 arguments. The first argument has a default value, but not the second.
5937 After the definition is complete, you can call the macro either as
5938 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5939 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5940 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5941 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5943 @item .macro m p1:req, p2=0, p3:vararg
5944 Begin the definition of a macro called @code{m}, with at least three
5945 arguments. The first argument must always have a value specified, but
5946 not the second, which instead has a default value. The third formal
5947 will get assigned all remaining arguments specified at invocation time.
5949 When you call a macro, you can specify the argument values either by
5950 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5951 @samp{sum to=17, from=9}.
5955 Note that since each of the @var{macargs} can be an identifier exactly
5956 as any other one permitted by the target architecture, there may be
5957 occasional problems if the target hand-crafts special meanings to certain
5958 characters when they occur in a special position. For example, if the colon
5959 (@code{:}) is generally permitted to be part of a symbol name, but the
5960 architecture specific code special-cases it when occurring as the final
5961 character of a symbol (to denote a label), then the macro parameter
5962 replacement code will have no way of knowing that and consider the whole
5963 construct (including the colon) an identifier, and check only this
5964 identifier for being the subject to parameter substitution. So for example
5965 this macro definition:
5973 might not work as expected. Invoking @samp{label foo} might not create a label
5974 called @samp{foo} but instead just insert the text @samp{\l:} into the
5975 assembler source, probably generating an error about an unrecognised
5978 Similarly problems might occur with the period character (@samp{.})
5979 which is often allowed inside opcode names (and hence identifier names). So
5980 for example constructing a macro to build an opcode from a base name and a
5981 length specifier like this:
5984 .macro opcode base length
5989 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5990 instruction but instead generate some kind of error as the assembler tries to
5991 interpret the text @samp{\base.\length}.
5993 There are several possible ways around this problem:
5996 @item Insert white space
5997 If it is possible to use white space characters then this is the simplest
6006 @item Use @samp{\()}
6007 The string @samp{\()} can be used to separate the end of a macro argument from
6008 the following text. eg:
6011 .macro opcode base length
6016 @item Use the alternate macro syntax mode
6017 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6018 used as a separator. eg:
6028 Note: this problem of correctly identifying string parameters to pseudo ops
6029 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6030 and @code{.irpc} (@pxref{Irpc}) as well.
6033 @cindex @code{endm} directive
6034 Mark the end of a macro definition.
6037 @cindex @code{exitm} directive
6038 Exit early from the current macro definition.
6040 @cindex number of macros executed
6041 @cindex macros, count executed
6043 @command{@value{AS}} maintains a counter of how many macros it has
6044 executed in this pseudo-variable; you can copy that number to your
6045 output with @samp{\@@}, but @emph{only within a macro definition}.
6047 @item LOCAL @var{name} [ , @dots{} ]
6048 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6049 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6050 @xref{Altmacro,,@code{.altmacro}}.
6054 @section @code{.mri @var{val}}
6056 @cindex @code{mri} directive
6057 @cindex MRI mode, temporarily
6058 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6059 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6060 affects code assembled until the next @code{.mri} directive, or until the end
6061 of the file. @xref{M, MRI mode, MRI mode}.
6064 @section @code{.noaltmacro}
6065 Disable alternate macro mode. @xref{Altmacro}.
6068 @section @code{.nolist}
6070 @cindex @code{nolist} directive
6071 @cindex listing control, turning off
6072 Control (in conjunction with the @code{.list} directive) whether or
6073 not assembly listings are generated. These two directives maintain an
6074 internal counter (which is zero initially). @code{.list} increments the
6075 counter, and @code{.nolist} decrements it. Assembly listings are
6076 generated whenever the counter is greater than zero.
6079 @section @code{.octa @var{bignums}}
6081 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
6082 @cindex @code{octa} directive
6083 @cindex integer, 16-byte
6084 @cindex sixteen byte integer
6085 This directive expects zero or more bignums, separated by commas. For each
6086 bignum, it emits a 16-byte integer.
6088 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6089 hence @emph{octa}-word for 16 bytes.
6092 @section @code{.offset @var{loc}}
6094 @cindex @code{offset} directive
6095 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6096 be an absolute expression. This directive may be useful for defining
6097 symbols with absolute values. Do not confuse it with the @code{.org}
6101 @section @code{.org @var{new-lc} , @var{fill}}
6103 @cindex @code{org} directive
6104 @cindex location counter, advancing
6105 @cindex advancing location counter
6106 @cindex current address, advancing
6107 Advance the location counter of the current section to
6108 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6109 expression with the same section as the current subsection. That is,
6110 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6111 wrong section, the @code{.org} directive is ignored. To be compatible
6112 with former assemblers, if the section of @var{new-lc} is absolute,
6113 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6114 is the same as the current subsection.
6116 @code{.org} may only increase the location counter, or leave it
6117 unchanged; you cannot use @code{.org} to move the location counter
6120 @c double negative used below "not undefined" because this is a specific
6121 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6122 @c section. doc@cygnus.com 18feb91
6123 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6124 may not be undefined. If you really detest this restriction we eagerly await
6125 a chance to share your improved assembler.
6127 Beware that the origin is relative to the start of the section, not
6128 to the start of the subsection. This is compatible with other
6129 people's assemblers.
6131 When the location counter (of the current subsection) is advanced, the
6132 intervening bytes are filled with @var{fill} which should be an
6133 absolute expression. If the comma and @var{fill} are omitted,
6134 @var{fill} defaults to zero.
6137 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6139 @cindex padding the location counter given a power of two
6140 @cindex @code{p2align} directive
6141 Pad the location counter (in the current subsection) to a particular
6142 storage boundary. The first expression (which must be absolute) is the
6143 number of low-order zero bits the location counter must have after
6144 advancement. For example @samp{.p2align 3} advances the location
6145 counter until it a multiple of 8. If the location counter is already a
6146 multiple of 8, no change is needed.
6148 The second expression (also absolute) gives the fill value to be stored in the
6149 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6150 padding bytes are normally zero. However, on some systems, if the section is
6151 marked as containing code and the fill value is omitted, the space is filled
6152 with no-op instructions.
6154 The third expression is also absolute, and is also optional. If it is present,
6155 it is the maximum number of bytes that should be skipped by this alignment
6156 directive. If doing the alignment would require skipping more bytes than the
6157 specified maximum, then the alignment is not done at all. You can omit the
6158 fill value (the second argument) entirely by simply using two commas after the
6159 required alignment; this can be useful if you want the alignment to be filled
6160 with no-op instructions when appropriate.
6162 @cindex @code{p2alignw} directive
6163 @cindex @code{p2alignl} directive
6164 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6165 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6166 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6167 fill pattern as a four byte longword value. For example, @code{.p2alignw
6168 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6169 filled in with the value 0x368d (the exact placement of the bytes depends upon
6170 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6175 @section @code{.popsection}
6177 @cindex @code{popsection} directive
6178 @cindex Section Stack
6179 This is one of the ELF section stack manipulation directives. The others are
6180 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6181 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6184 This directive replaces the current section (and subsection) with the top
6185 section (and subsection) on the section stack. This section is popped off the
6191 @section @code{.previous}
6193 @cindex @code{previous} directive
6194 @cindex Section Stack
6195 This is one of the ELF section stack manipulation directives. The others are
6196 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6197 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6198 (@pxref{PopSection}).
6200 This directive swaps the current section (and subsection) with most recently
6201 referenced section/subsection pair prior to this one. Multiple
6202 @code{.previous} directives in a row will flip between two sections (and their
6203 subsections). For example:
6215 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6221 # Now in section A subsection 1
6225 # Now in section B subsection 0
6228 # Now in section B subsection 1
6231 # Now in section B subsection 0
6235 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6236 section B and 0x9abc into subsection 1 of section B.
6238 In terms of the section stack, this directive swaps the current section with
6239 the top section on the section stack.
6243 @section @code{.print @var{string}}
6245 @cindex @code{print} directive
6246 @command{@value{AS}} will print @var{string} on the standard output during
6247 assembly. You must put @var{string} in double quotes.
6251 @section @code{.protected @var{names}}
6253 @cindex @code{protected} directive
6255 This is one of the ELF visibility directives. The other two are
6256 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6258 This directive overrides the named symbols default visibility (which is set by
6259 their binding: local, global or weak). The directive sets the visibility to
6260 @code{protected} which means that any references to the symbols from within the
6261 components that defines them must be resolved to the definition in that
6262 component, even if a definition in another component would normally preempt
6267 @section @code{.psize @var{lines} , @var{columns}}
6269 @cindex @code{psize} directive
6270 @cindex listing control: paper size
6271 @cindex paper size, for listings
6272 Use this directive to declare the number of lines---and, optionally, the
6273 number of columns---to use for each page, when generating listings.
6275 If you do not use @code{.psize}, listings use a default line-count
6276 of 60. You may omit the comma and @var{columns} specification; the
6277 default width is 200 columns.
6279 @command{@value{AS}} generates formfeeds whenever the specified number of
6280 lines is exceeded (or whenever you explicitly request one, using
6283 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6284 those explicitly specified with @code{.eject}.
6287 @section @code{.purgem @var{name}}
6289 @cindex @code{purgem} directive
6290 Undefine the macro @var{name}, so that later uses of the string will not be
6291 expanded. @xref{Macro}.
6295 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6297 @cindex @code{pushsection} directive
6298 @cindex Section Stack
6299 This is one of the ELF section stack manipulation directives. The others are
6300 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6301 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6304 This directive pushes the current section (and subsection) onto the
6305 top of the section stack, and then replaces the current section and
6306 subsection with @code{name} and @code{subsection}. The optional
6307 @code{flags}, @code{type} and @code{arguments} are treated the same
6308 as in the @code{.section} (@pxref{Section}) directive.
6312 @section @code{.quad @var{bignums}}
6314 @cindex @code{quad} directive
6315 @code{.quad} expects zero or more bignums, separated by commas. For
6316 each bignum, it emits
6318 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6319 warning message; and just takes the lowest order 8 bytes of the bignum.
6320 @cindex eight-byte integer
6321 @cindex integer, 8-byte
6323 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6324 hence @emph{quad}-word for 8 bytes.
6327 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6328 warning message; and just takes the lowest order 16 bytes of the bignum.
6329 @cindex sixteen-byte integer
6330 @cindex integer, 16-byte
6334 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6336 @cindex @code{reloc} directive
6337 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6338 @var{expression}. If @var{offset} is a number, the relocation is generated in
6339 the current section. If @var{offset} is an expression that resolves to a
6340 symbol plus offset, the relocation is generated in the given symbol's section.
6341 @var{expression}, if present, must resolve to a symbol plus addend or to an
6342 absolute value, but note that not all targets support an addend. e.g. ELF REL
6343 targets such as i386 store an addend in the section contents rather than in the
6344 relocation. This low level interface does not support addends stored in the
6348 @section @code{.rept @var{count}}
6350 @cindex @code{rept} directive
6351 Repeat the sequence of lines between the @code{.rept} directive and the next
6352 @code{.endr} directive @var{count} times.
6354 For example, assembling
6362 is equivalent to assembling
6371 @section @code{.sbttl "@var{subheading}"}
6373 @cindex @code{sbttl} directive
6374 @cindex subtitles for listings
6375 @cindex listing control: subtitle
6376 Use @var{subheading} as the title (third line, immediately after the
6377 title line) when generating assembly listings.
6379 This directive affects subsequent pages, as well as the current page if
6380 it appears within ten lines of the top of a page.
6384 @section @code{.scl @var{class}}
6386 @cindex @code{scl} directive
6387 @cindex symbol storage class (COFF)
6388 @cindex COFF symbol storage class
6389 Set the storage-class value for a symbol. This directive may only be
6390 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6391 whether a symbol is static or external, or it may record further
6392 symbolic debugging information.
6395 The @samp{.scl} directive is primarily associated with COFF output; when
6396 configured to generate @code{b.out} output format, @command{@value{AS}}
6397 accepts this directive but ignores it.
6403 @section @code{.section @var{name}}
6405 @cindex named section
6406 Use the @code{.section} directive to assemble the following code into a section
6409 This directive is only supported for targets that actually support arbitrarily
6410 named sections; on @code{a.out} targets, for example, it is not accepted, even
6411 with a standard @code{a.out} section name.
6415 @c only print the extra heading if both COFF and ELF are set
6416 @subheading COFF Version
6419 @cindex @code{section} directive (COFF version)
6420 For COFF targets, the @code{.section} directive is used in one of the following
6424 .section @var{name}[, "@var{flags}"]
6425 .section @var{name}[, @var{subsection}]
6428 If the optional argument is quoted, it is taken as flags to use for the
6429 section. Each flag is a single character. The following flags are recognized:
6433 bss section (uninitialized data)
6435 section is not loaded
6441 exclude section from linking
6447 shared section (meaningful for PE targets)
6449 ignored. (For compatibility with the ELF version)
6451 section is not readable (meaningful for PE targets)
6453 single-digit power-of-two section alignment (GNU extension)
6456 If no flags are specified, the default flags depend upon the section name. If
6457 the section name is not recognized, the default will be for the section to be
6458 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6459 from the section, rather than adding them, so if they are used on their own it
6460 will be as if no flags had been specified at all.
6462 If the optional argument to the @code{.section} directive is not quoted, it is
6463 taken as a subsection number (@pxref{Sub-Sections}).
6468 @c only print the extra heading if both COFF and ELF are set
6469 @subheading ELF Version
6472 @cindex Section Stack
6473 This is one of the ELF section stack manipulation directives. The others are
6474 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6475 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6476 @code{.previous} (@pxref{Previous}).
6478 @cindex @code{section} directive (ELF version)
6479 For ELF targets, the @code{.section} directive is used like this:
6482 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6485 @anchor{Section Name Substitutions}
6486 @kindex --sectname-subst
6487 @cindex section name substitution
6488 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6489 argument may contain a substitution sequence. Only @code{%S} is supported
6490 at the moment, and substitutes the current section name. For example:
6493 .macro exception_code
6494 .section %S.exception
6495 [exception code here]
6510 The two @code{exception_code} invocations above would create the
6511 @code{.text.exception} and @code{.init.exception} sections respectively.
6512 This is useful e.g. to discriminate between ancillary sections that are
6513 tied to setup code to be discarded after use from ancillary sections that
6514 need to stay resident without having to define multiple @code{exception_code}
6515 macros just for that purpose.
6517 The optional @var{flags} argument is a quoted string which may contain any
6518 combination of the following characters:
6522 section is allocatable
6524 section is excluded from executable and shared library.
6528 section is executable
6530 section is mergeable
6532 section contains zero terminated strings
6534 section is a member of a section group
6536 section is used for thread-local-storage
6538 section is a member of the previously-current section's group, if any
6539 @item @code{<number>}
6540 a numeric value indicating the bits to be set in the ELF section header's flags
6541 field. Note - if one or more of the alphabetic characters described above is
6542 also included in the flags field, their bit values will be ORed into the
6544 @item @code{<target specific>}
6545 some targets extend this list with their own flag characters
6548 Note - once a section's flags have been set they cannot be changed. There are
6549 a few exceptions to this rule however. Processor and application specific
6550 flags can be added to an already defined section. The @code{.interp},
6551 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6552 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6553 section may have the executable (@code{x}) flag added.
6555 The optional @var{type} argument may contain one of the following constants:
6559 section contains data
6561 section does not contain data (i.e., section only occupies space)
6563 section contains data which is used by things other than the program
6565 section contains an array of pointers to init functions
6567 section contains an array of pointers to finish functions
6568 @item @@preinit_array
6569 section contains an array of pointers to pre-init functions
6570 @item @@@code{<number>}
6571 a numeric value to be set as the ELF section header's type field.
6572 @item @@@code{<target specific>}
6573 some targets extend this list with their own types
6576 Many targets only support the first three section types. The type may be
6577 enclosed in double quotes if necessary.
6579 Note on targets where the @code{@@} character is the start of a comment (eg
6580 ARM) then another character is used instead. For example the ARM port uses the
6583 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6584 special and have fixed types. Any attempt to declare them with a different
6585 type will generate an error from the assembler.
6587 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6588 be specified as well as an extra argument---@var{entsize}---like this:
6591 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6594 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6595 constants, each @var{entsize} octets long. Sections with both @code{M} and
6596 @code{S} must contain zero terminated strings where each character is
6597 @var{entsize} bytes long. The linker may remove duplicates within sections with
6598 the same name, same entity size and same flags. @var{entsize} must be an
6599 absolute expression. For sections with both @code{M} and @code{S}, a string
6600 which is a suffix of a larger string is considered a duplicate. Thus
6601 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6602 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6604 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6605 be present along with an additional field like this:
6608 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6611 The @var{GroupName} field specifies the name of the section group to which this
6612 particular section belongs. The optional linkage field can contain:
6616 indicates that only one copy of this section should be retained
6621 Note: if both the @var{M} and @var{G} flags are present then the fields for
6622 the Merge flag should come first, like this:
6625 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6628 If @var{flags} contains the @code{?} symbol then it may not also contain the
6629 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6630 present. Instead, @code{?} says to consider the section that's current before
6631 this directive. If that section used @code{G}, then the new section will use
6632 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6633 If not, then the @code{?} symbol has no effect.
6635 If no flags are specified, the default flags depend upon the section name. If
6636 the section name is not recognized, the default will be for the section to have
6637 none of the above flags: it will not be allocated in memory, nor writable, nor
6638 executable. The section will contain data.
6640 For ELF targets, the assembler supports another type of @code{.section}
6641 directive for compatibility with the Solaris assembler:
6644 .section "@var{name}"[, @var{flags}...]
6647 Note that the section name is quoted. There may be a sequence of comma
6652 section is allocatable
6656 section is executable
6658 section is excluded from executable and shared library.
6660 section is used for thread local storage
6663 This directive replaces the current section and subsection. See the
6664 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6665 some examples of how this directive and the other section stack directives
6671 @section @code{.set @var{symbol}, @var{expression}}
6673 @cindex @code{set} directive
6674 @cindex symbol value, setting
6675 Set the value of @var{symbol} to @var{expression}. This
6676 changes @var{symbol}'s value and type to conform to
6677 @var{expression}. If @var{symbol} was flagged as external, it remains
6678 flagged (@pxref{Symbol Attributes}).
6680 You may @code{.set} a symbol many times in the same assembly provided that the
6681 values given to the symbol are constants. Values that are based on expressions
6682 involving other symbols are allowed, but some targets may restrict this to only
6683 being done once per assembly. This is because those targets do not set the
6684 addresses of symbols at assembly time, but rather delay the assignment until a
6685 final link is performed. This allows the linker a chance to change the code in
6686 the files, changing the location of, and the relative distance between, various
6689 If you @code{.set} a global symbol, the value stored in the object
6690 file is the last value stored into it.
6693 On Z80 @code{set} is a real instruction, use
6694 @samp{@var{symbol} defl @var{expression}} instead.
6698 @section @code{.short @var{expressions}}
6700 @cindex @code{short} directive
6702 @code{.short} is normally the same as @samp{.word}.
6703 @xref{Word,,@code{.word}}.
6705 In some configurations, however, @code{.short} and @code{.word} generate
6706 numbers of different lengths. @xref{Machine Dependencies}.
6710 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6713 This expects zero or more @var{expressions}, and emits
6714 a 16 bit number for each.
6719 @section @code{.single @var{flonums}}
6721 @cindex @code{single} directive
6722 @cindex floating point numbers (single)
6723 This directive assembles zero or more flonums, separated by commas. It
6724 has the same effect as @code{.float}.
6726 The exact kind of floating point numbers emitted depends on how
6727 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6731 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6732 numbers in @sc{ieee} format.
6738 @section @code{.size}
6740 This directive is used to set the size associated with a symbol.
6744 @c only print the extra heading if both COFF and ELF are set
6745 @subheading COFF Version
6748 @cindex @code{size} directive (COFF version)
6749 For COFF targets, the @code{.size} directive is only permitted inside
6750 @code{.def}/@code{.endef} pairs. It is used like this:
6753 .size @var{expression}
6757 @samp{.size} is only meaningful when generating COFF format output; when
6758 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6765 @c only print the extra heading if both COFF and ELF are set
6766 @subheading ELF Version
6769 @cindex @code{size} directive (ELF version)
6770 For ELF targets, the @code{.size} directive is used like this:
6773 .size @var{name} , @var{expression}
6776 This directive sets the size associated with a symbol @var{name}.
6777 The size in bytes is computed from @var{expression} which can make use of label
6778 arithmetic. This directive is typically used to set the size of function
6783 @ifclear no-space-dir
6785 @section @code{.skip @var{size} , @var{fill}}
6787 @cindex @code{skip} directive
6788 @cindex filling memory
6789 This directive emits @var{size} bytes, each of value @var{fill}. Both
6790 @var{size} and @var{fill} are absolute expressions. If the comma and
6791 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6796 @section @code{.sleb128 @var{expressions}}
6798 @cindex @code{sleb128} directive
6799 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6800 compact, variable length representation of numbers used by the DWARF
6801 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6803 @ifclear no-space-dir
6805 @section @code{.space @var{size} , @var{fill}}
6807 @cindex @code{space} directive
6808 @cindex filling memory
6809 This directive emits @var{size} bytes, each of value @var{fill}. Both
6810 @var{size} and @var{fill} are absolute expressions. If the comma
6811 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6816 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6817 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6818 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6819 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6827 @section @code{.stabd, .stabn, .stabs}
6829 @cindex symbolic debuggers, information for
6830 @cindex @code{stab@var{x}} directives
6831 There are three directives that begin @samp{.stab}.
6832 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6833 The symbols are not entered in the @command{@value{AS}} hash table: they
6834 cannot be referenced elsewhere in the source file.
6835 Up to five fields are required:
6839 This is the symbol's name. It may contain any character except
6840 @samp{\000}, so is more general than ordinary symbol names. Some
6841 debuggers used to code arbitrarily complex structures into symbol names
6845 An absolute expression. The symbol's type is set to the low 8 bits of
6846 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6847 and debuggers choke on silly bit patterns.
6850 An absolute expression. The symbol's ``other'' attribute is set to the
6851 low 8 bits of this expression.
6854 An absolute expression. The symbol's descriptor is set to the low 16
6855 bits of this expression.
6858 An absolute expression which becomes the symbol's value.
6861 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6862 or @code{.stabs} statement, the symbol has probably already been created;
6863 you get a half-formed symbol in your object file. This is
6864 compatible with earlier assemblers!
6867 @cindex @code{stabd} directive
6868 @item .stabd @var{type} , @var{other} , @var{desc}
6870 The ``name'' of the symbol generated is not even an empty string.
6871 It is a null pointer, for compatibility. Older assemblers used a
6872 null pointer so they didn't waste space in object files with empty
6875 The symbol's value is set to the location counter,
6876 relocatably. When your program is linked, the value of this symbol
6877 is the address of the location counter when the @code{.stabd} was
6880 @cindex @code{stabn} directive
6881 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6882 The name of the symbol is set to the empty string @code{""}.
6884 @cindex @code{stabs} directive
6885 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6886 All five fields are specified.
6892 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6893 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6895 @cindex string, copying to object file
6896 @cindex string8, copying to object file
6897 @cindex string16, copying to object file
6898 @cindex string32, copying to object file
6899 @cindex string64, copying to object file
6900 @cindex @code{string} directive
6901 @cindex @code{string8} directive
6902 @cindex @code{string16} directive
6903 @cindex @code{string32} directive
6904 @cindex @code{string64} directive
6906 Copy the characters in @var{str} to the object file. You may specify more than
6907 one string to copy, separated by commas. Unless otherwise specified for a
6908 particular machine, the assembler marks the end of each string with a 0 byte.
6909 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6911 The variants @code{string16}, @code{string32} and @code{string64} differ from
6912 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6913 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6914 are stored in target endianness byte order.
6920 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6921 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6926 @section @code{.struct @var{expression}}
6928 @cindex @code{struct} directive
6929 Switch to the absolute section, and set the section offset to @var{expression},
6930 which must be an absolute expression. You might use this as follows:
6939 This would define the symbol @code{field1} to have the value 0, the symbol
6940 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6941 value 8. Assembly would be left in the absolute section, and you would need to
6942 use a @code{.section} directive of some sort to change to some other section
6943 before further assembly.
6947 @section @code{.subsection @var{name}}
6949 @cindex @code{subsection} directive
6950 @cindex Section Stack
6951 This is one of the ELF section stack manipulation directives. The others are
6952 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6953 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6956 This directive replaces the current subsection with @code{name}. The current
6957 section is not changed. The replaced subsection is put onto the section stack
6958 in place of the then current top of stack subsection.
6963 @section @code{.symver}
6964 @cindex @code{symver} directive
6965 @cindex symbol versioning
6966 @cindex versions of symbols
6967 Use the @code{.symver} directive to bind symbols to specific version nodes
6968 within a source file. This is only supported on ELF platforms, and is
6969 typically used when assembling files to be linked into a shared library.
6970 There are cases where it may make sense to use this in objects to be bound
6971 into an application itself so as to override a versioned symbol from a
6974 For ELF targets, the @code{.symver} directive can be used like this:
6976 .symver @var{name}, @var{name2@@nodename}
6978 If the symbol @var{name} is defined within the file
6979 being assembled, the @code{.symver} directive effectively creates a symbol
6980 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6981 just don't try and create a regular alias is that the @var{@@} character isn't
6982 permitted in symbol names. The @var{name2} part of the name is the actual name
6983 of the symbol by which it will be externally referenced. The name @var{name}
6984 itself is merely a name of convenience that is used so that it is possible to
6985 have definitions for multiple versions of a function within a single source
6986 file, and so that the compiler can unambiguously know which version of a
6987 function is being mentioned. The @var{nodename} portion of the alias should be
6988 the name of a node specified in the version script supplied to the linker when
6989 building a shared library. If you are attempting to override a versioned
6990 symbol from a shared library, then @var{nodename} should correspond to the
6991 nodename of the symbol you are trying to override.
6993 If the symbol @var{name} is not defined within the file being assembled, all
6994 references to @var{name} will be changed to @var{name2@@nodename}. If no
6995 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6998 Another usage of the @code{.symver} directive is:
7000 .symver @var{name}, @var{name2@@@@nodename}
7002 In this case, the symbol @var{name} must exist and be defined within
7003 the file being assembled. It is similar to @var{name2@@nodename}. The
7004 difference is @var{name2@@@@nodename} will also be used to resolve
7005 references to @var{name2} by the linker.
7007 The third usage of the @code{.symver} directive is:
7009 .symver @var{name}, @var{name2@@@@@@nodename}
7011 When @var{name} is not defined within the
7012 file being assembled, it is treated as @var{name2@@nodename}. When
7013 @var{name} is defined within the file being assembled, the symbol
7014 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7019 @section @code{.tag @var{structname}}
7021 @cindex COFF structure debugging
7022 @cindex structure debugging, COFF
7023 @cindex @code{tag} directive
7024 This directive is generated by compilers to include auxiliary debugging
7025 information in the symbol table. It is only permitted inside
7026 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7027 definitions in the symbol table with instances of those structures.
7030 @samp{.tag} is only used when generating COFF format output; when
7031 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
7037 @section @code{.text @var{subsection}}
7039 @cindex @code{text} directive
7040 Tells @command{@value{AS}} to assemble the following statements onto the end of
7041 the text subsection numbered @var{subsection}, which is an absolute
7042 expression. If @var{subsection} is omitted, subsection number zero
7046 @section @code{.title "@var{heading}"}
7048 @cindex @code{title} directive
7049 @cindex listing control: title line
7050 Use @var{heading} as the title (second line, immediately after the
7051 source file name and pagenumber) when generating assembly listings.
7053 This directive affects subsequent pages, as well as the current page if
7054 it appears within ten lines of the top of a page.
7058 @section @code{.type}
7060 This directive is used to set the type of a symbol.
7064 @c only print the extra heading if both COFF and ELF are set
7065 @subheading COFF Version
7068 @cindex COFF symbol type
7069 @cindex symbol type, COFF
7070 @cindex @code{type} directive (COFF version)
7071 For COFF targets, this directive is permitted only within
7072 @code{.def}/@code{.endef} pairs. It is used like this:
7078 This records the integer @var{int} as the type attribute of a symbol table
7082 @samp{.type} is associated only with COFF format output; when
7083 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
7084 directive but ignores it.
7090 @c only print the extra heading if both COFF and ELF are set
7091 @subheading ELF Version
7094 @cindex ELF symbol type
7095 @cindex symbol type, ELF
7096 @cindex @code{type} directive (ELF version)
7097 For ELF targets, the @code{.type} directive is used like this:
7100 .type @var{name} , @var{type description}
7103 This sets the type of symbol @var{name} to be either a
7104 function symbol or an object symbol. There are five different syntaxes
7105 supported for the @var{type description} field, in order to provide
7106 compatibility with various other assemblers.
7108 Because some of the characters used in these syntaxes (such as @samp{@@} and
7109 @samp{#}) are comment characters for some architectures, some of the syntaxes
7110 below do not work on all architectures. The first variant will be accepted by
7111 the GNU assembler on all architectures so that variant should be used for
7112 maximum portability, if you do not need to assemble your code with other
7115 The syntaxes supported are:
7118 .type <name> STT_<TYPE_IN_UPPER_CASE>
7119 .type <name>,#<type>
7120 .type <name>,@@<type>
7121 .type <name>,%<type>
7122 .type <name>,"<type>"
7125 The types supported are:
7130 Mark the symbol as being a function name.
7133 @itemx gnu_indirect_function
7134 Mark the symbol as an indirect function when evaluated during reloc
7135 processing. (This is only supported on assemblers targeting GNU systems).
7139 Mark the symbol as being a data object.
7143 Mark the symbol as being a thread-local data object.
7147 Mark the symbol as being a common data object.
7151 Does not mark the symbol in any way. It is supported just for completeness.
7153 @item gnu_unique_object
7154 Marks the symbol as being a globally unique data object. The dynamic linker
7155 will make sure that in the entire process there is just one symbol with this
7156 name and type in use. (This is only supported on assemblers targeting GNU
7161 Note: Some targets support extra types in addition to those listed above.
7167 @section @code{.uleb128 @var{expressions}}
7169 @cindex @code{uleb128} directive
7170 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7171 compact, variable length representation of numbers used by the DWARF
7172 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7176 @section @code{.val @var{addr}}
7178 @cindex @code{val} directive
7179 @cindex COFF value attribute
7180 @cindex value attribute, COFF
7181 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7182 records the address @var{addr} as the value attribute of a symbol table
7186 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7187 configured for @code{b.out}, it accepts this directive but ignores it.
7193 @section @code{.version "@var{string}"}
7195 @cindex @code{version} directive
7196 This directive creates a @code{.note} section and places into it an ELF
7197 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7202 @section @code{.vtable_entry @var{table}, @var{offset}}
7204 @cindex @code{vtable_entry} directive
7205 This directive finds or creates a symbol @code{table} and creates a
7206 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7209 @section @code{.vtable_inherit @var{child}, @var{parent}}
7211 @cindex @code{vtable_inherit} directive
7212 This directive finds the symbol @code{child} and finds or creates the symbol
7213 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7214 parent whose addend is the value of the child symbol. As a special case the
7215 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7219 @section @code{.warning "@var{string}"}
7220 @cindex warning directive
7221 Similar to the directive @code{.error}
7222 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7225 @section @code{.weak @var{names}}
7227 @cindex @code{weak} directive
7228 This directive sets the weak attribute on the comma separated list of symbol
7229 @code{names}. If the symbols do not already exist, they will be created.
7231 On COFF targets other than PE, weak symbols are a GNU extension. This
7232 directive sets the weak attribute on the comma separated list of symbol
7233 @code{names}. If the symbols do not already exist, they will be created.
7235 On the PE target, weak symbols are supported natively as weak aliases.
7236 When a weak symbol is created that is not an alias, GAS creates an
7237 alternate symbol to hold the default value.
7240 @section @code{.weakref @var{alias}, @var{target}}
7242 @cindex @code{weakref} directive
7243 This directive creates an alias to the target symbol that enables the symbol to
7244 be referenced with weak-symbol semantics, but without actually making it weak.
7245 If direct references or definitions of the symbol are present, then the symbol
7246 will not be weak, but if all references to it are through weak references, the
7247 symbol will be marked as weak in the symbol table.
7249 The effect is equivalent to moving all references to the alias to a separate
7250 assembly source file, renaming the alias to the symbol in it, declaring the
7251 symbol as weak there, and running a reloadable link to merge the object files
7252 resulting from the assembly of the new source file and the old source file that
7253 had the references to the alias removed.
7255 The alias itself never makes to the symbol table, and is entirely handled
7256 within the assembler.
7259 @section @code{.word @var{expressions}}
7261 @cindex @code{word} directive
7262 This directive expects zero or more @var{expressions}, of any section,
7263 separated by commas.
7266 For each expression, @command{@value{AS}} emits a 32-bit number.
7269 For each expression, @command{@value{AS}} emits a 16-bit number.
7274 The size of the number emitted, and its byte order,
7275 depend on what target computer the assembly is for.
7278 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7279 @c happen---32-bit addressability, period; no long/short jumps.
7280 @ifset DIFF-TBL-KLUGE
7281 @cindex difference tables altered
7282 @cindex altered difference tables
7284 @emph{Warning: Special Treatment to support Compilers}
7288 Machines with a 32-bit address space, but that do less than 32-bit
7289 addressing, require the following special treatment. If the machine of
7290 interest to you does 32-bit addressing (or doesn't require it;
7291 @pxref{Machine Dependencies}), you can ignore this issue.
7294 In order to assemble compiler output into something that works,
7295 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7296 Directives of the form @samp{.word sym1-sym2} are often emitted by
7297 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7298 directive of the form @samp{.word sym1-sym2}, and the difference between
7299 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7300 creates a @dfn{secondary jump table}, immediately before the next label.
7301 This secondary jump table is preceded by a short-jump to the
7302 first byte after the secondary table. This short-jump prevents the flow
7303 of control from accidentally falling into the new table. Inside the
7304 table is a long-jump to @code{sym2}. The original @samp{.word}
7305 contains @code{sym1} minus the address of the long-jump to
7308 If there were several occurrences of @samp{.word sym1-sym2} before the
7309 secondary jump table, all of them are adjusted. If there was a
7310 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7311 long-jump to @code{sym4} is included in the secondary jump table,
7312 and the @code{.word} directives are adjusted to contain @code{sym3}
7313 minus the address of the long-jump to @code{sym4}; and so on, for as many
7314 entries in the original jump table as necessary.
7317 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7318 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7319 assembly language programmers.
7322 @c end DIFF-TBL-KLUGE
7324 @ifclear no-space-dir
7326 @section @code{.zero @var{size}}
7328 @cindex @code{zero} directive
7329 @cindex filling memory with zero bytes
7330 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7331 expression. This directive is actually an alias for the @samp{.skip} directive
7332 so in can take an optional second argument of the value to store in the bytes
7333 instead of zero. Using @samp{.zero} in this way would be confusing however.
7337 @section Deprecated Directives
7339 @cindex deprecated directives
7340 @cindex obsolescent directives
7341 One day these directives won't work.
7342 They are included for compatibility with older assemblers.
7349 @node Object Attributes
7350 @chapter Object Attributes
7351 @cindex object attributes
7353 @command{@value{AS}} assembles source files written for a specific architecture
7354 into object files for that architecture. But not all object files are alike.
7355 Many architectures support incompatible variations. For instance, floating
7356 point arguments might be passed in floating point registers if the object file
7357 requires hardware floating point support---or floating point arguments might be
7358 passed in integer registers if the object file supports processors with no
7359 hardware floating point unit. Or, if two objects are built for different
7360 generations of the same architecture, the combination may require the
7361 newer generation at run-time.
7363 This information is useful during and after linking. At link time,
7364 @command{@value{LD}} can warn about incompatible object files. After link
7365 time, tools like @command{gdb} can use it to process the linked file
7368 Compatibility information is recorded as a series of object attributes. Each
7369 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7370 string, and indicates who sets the meaning of the tag. The tag is an integer,
7371 and indicates what property the attribute describes. The value may be a string
7372 or an integer, and indicates how the property affects this object. Missing
7373 attributes are the same as attributes with a zero value or empty string value.
7375 Object attributes were developed as part of the ABI for the ARM Architecture.
7376 The file format is documented in @cite{ELF for the ARM Architecture}.
7379 * GNU Object Attributes:: @sc{gnu} Object Attributes
7380 * Defining New Object Attributes:: Defining New Object Attributes
7383 @node GNU Object Attributes
7384 @section @sc{gnu} Object Attributes
7386 The @code{.gnu_attribute} directive records an object attribute
7387 with vendor @samp{gnu}.
7389 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7390 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7391 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7392 2} is set for architecture-independent attributes and clear for
7393 architecture-dependent ones.
7395 @subsection Common @sc{gnu} attributes
7397 These attributes are valid on all architectures.
7400 @item Tag_compatibility (32)
7401 The compatibility attribute takes an integer flag value and a vendor name. If
7402 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7403 then the file is only compatible with the named toolchain. If it is greater
7404 than 1, the file can only be processed by other toolchains under some private
7405 arrangement indicated by the flag value and the vendor name.
7408 @subsection MIPS Attributes
7411 @item Tag_GNU_MIPS_ABI_FP (4)
7412 The floating-point ABI used by this object file. The value will be:
7416 0 for files not affected by the floating-point ABI.
7418 1 for files using the hardware floating-point ABI with a standard
7419 double-precision FPU.
7421 2 for files using the hardware floating-point ABI with a single-precision FPU.
7423 3 for files using the software floating-point ABI.
7425 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7426 floating-point registers, 32-bit general-purpose registers and increased the
7427 number of callee-saved floating-point registers.
7429 5 for files using the hardware floating-point ABI with a double-precision FPU
7430 with either 32-bit or 64-bit floating-point registers and 32-bit
7431 general-purpose registers.
7433 6 for files using the hardware floating-point ABI with 64-bit floating-point
7434 registers and 32-bit general-purpose registers.
7436 7 for files using the hardware floating-point ABI with 64-bit floating-point
7437 registers, 32-bit general-purpose registers and a rule that forbids the
7438 direct use of odd-numbered single-precision floating-point registers.
7442 @subsection PowerPC Attributes
7445 @item Tag_GNU_Power_ABI_FP (4)
7446 The floating-point ABI used by this object file. The value will be:
7450 0 for files not affected by the floating-point ABI.
7452 1 for files using double-precision hardware floating-point ABI.
7454 2 for files using the software floating-point ABI.
7456 3 for files using single-precision hardware floating-point ABI.
7459 @item Tag_GNU_Power_ABI_Vector (8)
7460 The vector ABI used by this object file. The value will be:
7464 0 for files not affected by the vector ABI.
7466 1 for files using general purpose registers to pass vectors.
7468 2 for files using AltiVec registers to pass vectors.
7470 3 for files using SPE registers to pass vectors.
7474 @subsection IBM z Systems Attributes
7477 @item Tag_GNU_S390_ABI_Vector (8)
7478 The vector ABI used by this object file. The value will be:
7482 0 for files not affected by the vector ABI.
7484 1 for files using software vector ABI.
7486 2 for files using hardware vector ABI.
7490 @node Defining New Object Attributes
7491 @section Defining New Object Attributes
7493 If you want to define a new @sc{gnu} object attribute, here are the places you
7494 will need to modify. New attributes should be discussed on the @samp{binutils}
7499 This manual, which is the official register of attributes.
7501 The header for your architecture @file{include/elf}, to define the tag.
7503 The @file{bfd} support file for your architecture, to merge the attribute
7504 and issue any appropriate link warnings.
7506 Test cases in @file{ld/testsuite} for merging and link warnings.
7508 @file{binutils/readelf.c} to display your attribute.
7510 GCC, if you want the compiler to mark the attribute automatically.
7516 @node Machine Dependencies
7517 @chapter Machine Dependent Features
7519 @cindex machine dependencies
7520 The machine instruction sets are (almost by definition) different on
7521 each machine where @command{@value{AS}} runs. Floating point representations
7522 vary as well, and @command{@value{AS}} often supports a few additional
7523 directives or command-line options for compatibility with other
7524 assemblers on a particular platform. Finally, some versions of
7525 @command{@value{AS}} support special pseudo-instructions for branch
7528 This chapter discusses most of these differences, though it does not
7529 include details on any machine's instruction set. For details on that
7530 subject, see the hardware manufacturer's manual.
7534 * AArch64-Dependent:: AArch64 Dependent Features
7537 * Alpha-Dependent:: Alpha Dependent Features
7540 * ARC-Dependent:: ARC Dependent Features
7543 * ARM-Dependent:: ARM Dependent Features
7546 * AVR-Dependent:: AVR Dependent Features
7549 * Blackfin-Dependent:: Blackfin Dependent Features
7552 * CR16-Dependent:: CR16 Dependent Features
7555 * CRIS-Dependent:: CRIS Dependent Features
7558 * D10V-Dependent:: D10V Dependent Features
7561 * D30V-Dependent:: D30V Dependent Features
7564 * Epiphany-Dependent:: EPIPHANY Dependent Features
7567 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7570 * HPPA-Dependent:: HPPA Dependent Features
7573 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7576 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7579 * i860-Dependent:: Intel 80860 Dependent Features
7582 * i960-Dependent:: Intel 80960 Dependent Features
7585 * IA-64-Dependent:: Intel IA-64 Dependent Features
7588 * IP2K-Dependent:: IP2K Dependent Features
7591 * LM32-Dependent:: LM32 Dependent Features
7594 * M32C-Dependent:: M32C Dependent Features
7597 * M32R-Dependent:: M32R Dependent Features
7600 * M68K-Dependent:: M680x0 Dependent Features
7603 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7606 * Meta-Dependent :: Meta Dependent Features
7609 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7612 * MIPS-Dependent:: MIPS Dependent Features
7615 * MMIX-Dependent:: MMIX Dependent Features
7618 * MSP430-Dependent:: MSP430 Dependent Features
7621 * NDS32-Dependent:: Andes NDS32 Dependent Features
7624 * NiosII-Dependent:: Altera Nios II Dependent Features
7627 * NS32K-Dependent:: NS32K Dependent Features
7630 * PDP-11-Dependent:: PDP-11 Dependent Features
7633 * PJ-Dependent:: picoJava Dependent Features
7636 * PPC-Dependent:: PowerPC Dependent Features
7639 * PRU-Dependent:: PRU Dependent Features
7642 * RL78-Dependent:: RL78 Dependent Features
7645 * RISC-V-Dependent:: RISC-V Dependent Features
7648 * RX-Dependent:: RX Dependent Features
7651 * S/390-Dependent:: IBM S/390 Dependent Features
7654 * SCORE-Dependent:: SCORE Dependent Features
7657 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7658 * SH64-Dependent:: SuperH SH64 Dependent Features
7661 * Sparc-Dependent:: SPARC Dependent Features
7664 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7667 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7670 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7673 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7676 * V850-Dependent:: V850 Dependent Features
7679 * Vax-Dependent:: VAX Dependent Features
7682 * Visium-Dependent:: Visium Dependent Features
7685 * XGATE-Dependent:: XGATE Features
7688 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7691 * Xtensa-Dependent:: Xtensa Dependent Features
7694 * Z80-Dependent:: Z80 Dependent Features
7697 * Z8000-Dependent:: Z8000 Dependent Features
7704 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7705 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7706 @c peculiarity: to preserve cross-references, there must be a node called
7707 @c "Machine Dependencies". Hence the conditional nodenames in each
7708 @c major node below. Node defaulting in makeinfo requires adjacency of
7709 @c node and sectioning commands; hence the repetition of @chapter BLAH
7710 @c in both conditional blocks.
7713 @include c-aarch64.texi
7717 @include c-alpha.texi
7733 @include c-bfin.texi
7737 @include c-cr16.texi
7741 @include c-cris.texi
7746 @node Machine Dependencies
7747 @chapter Machine Dependent Features
7749 The machine instruction sets are different on each Renesas chip family,
7750 and there are also some syntax differences among the families. This
7751 chapter describes the specific @command{@value{AS}} features for each
7755 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7756 * SH-Dependent:: Renesas SH Dependent Features
7763 @include c-d10v.texi
7767 @include c-d30v.texi
7771 @include c-epiphany.texi
7775 @include c-h8300.texi
7779 @include c-hppa.texi
7783 @include c-i370.texi
7787 @include c-i386.texi
7791 @include c-i860.texi
7795 @include c-i960.texi
7799 @include c-ia64.texi
7803 @include c-ip2k.texi
7807 @include c-lm32.texi
7811 @include c-m32c.texi
7815 @include c-m32r.texi
7819 @include c-m68k.texi
7823 @include c-m68hc11.texi
7827 @include c-metag.texi
7831 @include c-microblaze.texi
7835 @include c-mips.texi
7839 @include c-mmix.texi
7843 @include c-msp430.texi
7847 @include c-nds32.texi
7851 @include c-nios2.texi
7855 @include c-ns32k.texi
7859 @include c-pdp11.texi
7875 @include c-rl78.texi
7879 @include c-riscv.texi
7887 @include c-s390.texi
7891 @include c-score.texi
7896 @include c-sh64.texi
7900 @include c-sparc.texi
7904 @include c-tic54x.texi
7908 @include c-tic6x.texi
7912 @include c-tilegx.texi
7916 @include c-tilepro.texi
7920 @include c-v850.texi
7928 @include c-visium.texi
7932 @include c-xgate.texi
7936 @include c-xstormy16.texi
7940 @include c-xtensa.texi
7952 @c reverse effect of @down at top of generic Machine-Dep chapter
7956 @node Reporting Bugs
7957 @chapter Reporting Bugs
7958 @cindex bugs in assembler
7959 @cindex reporting bugs in assembler
7961 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7963 Reporting a bug may help you by bringing a solution to your problem, or it may
7964 not. But in any case the principal function of a bug report is to help the
7965 entire community by making the next version of @command{@value{AS}} work better.
7966 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7968 In order for a bug report to serve its purpose, you must include the
7969 information that enables us to fix the bug.
7972 * Bug Criteria:: Have you found a bug?
7973 * Bug Reporting:: How to report bugs
7977 @section Have You Found a Bug?
7978 @cindex bug criteria
7980 If you are not sure whether you have found a bug, here are some guidelines:
7983 @cindex fatal signal
7984 @cindex assembler crash
7985 @cindex crash of assembler
7987 If the assembler gets a fatal signal, for any input whatever, that is a
7988 @command{@value{AS}} bug. Reliable assemblers never crash.
7990 @cindex error on valid input
7992 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7994 @cindex invalid input
7996 If @command{@value{AS}} does not produce an error message for invalid input, that
7997 is a bug. However, you should note that your idea of ``invalid input'' might
7998 be our idea of ``an extension'' or ``support for traditional practice''.
8001 If you are an experienced user of assemblers, your suggestions for improvement
8002 of @command{@value{AS}} are welcome in any case.
8006 @section How to Report Bugs
8008 @cindex assembler bugs, reporting
8010 A number of companies and individuals offer support for @sc{gnu} products. If
8011 you obtained @command{@value{AS}} from a support organization, we recommend you
8012 contact that organization first.
8014 You can find contact information for many support companies and
8015 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8019 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8023 The fundamental principle of reporting bugs usefully is this:
8024 @strong{report all the facts}. If you are not sure whether to state a
8025 fact or leave it out, state it!
8027 Often people omit facts because they think they know what causes the problem
8028 and assume that some details do not matter. Thus, you might assume that the
8029 name of a symbol you use in an example does not matter. Well, probably it does
8030 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8031 happens to fetch from the location where that name is stored in memory;
8032 perhaps, if the name were different, the contents of that location would fool
8033 the assembler into doing the right thing despite the bug. Play it safe and
8034 give a specific, complete example. That is the easiest thing for you to do,
8035 and the most helpful.
8037 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8038 it is new to us. Therefore, always write your bug reports on the assumption
8039 that the bug has not been reported previously.
8041 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8042 bell?'' This cannot help us fix a bug, so it is basically useless. We
8043 respond by asking for enough details to enable us to investigate.
8044 You might as well expedite matters by sending them to begin with.
8046 To enable us to fix the bug, you should include all these things:
8050 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8051 it with the @samp{--version} argument.
8053 Without this, we will not know whether there is any point in looking for
8054 the bug in the current version of @command{@value{AS}}.
8057 Any patches you may have applied to the @command{@value{AS}} source.
8060 The type of machine you are using, and the operating system name and
8064 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8068 The command arguments you gave the assembler to assemble your example and
8069 observe the bug. To guarantee you will not omit something important, list them
8070 all. A copy of the Makefile (or the output from make) is sufficient.
8072 If we were to try to guess the arguments, we would probably guess wrong
8073 and then we might not encounter the bug.
8076 A complete input file that will reproduce the bug. If the bug is observed when
8077 the assembler is invoked via a compiler, send the assembler source, not the
8078 high level language source. Most compilers will produce the assembler source
8079 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8080 the options @samp{-v --save-temps}; this will save the assembler source in a
8081 file with an extension of @file{.s}, and also show you exactly how
8082 @command{@value{AS}} is being run.
8085 A description of what behavior you observe that you believe is
8086 incorrect. For example, ``It gets a fatal signal.''
8088 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8089 will certainly notice it. But if the bug is incorrect output, we might not
8090 notice unless it is glaringly wrong. You might as well not give us a chance to
8093 Even if the problem you experience is a fatal signal, you should still say so
8094 explicitly. Suppose something strange is going on, such as, your copy of
8095 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8096 library on your system. (This has happened!) Your copy might crash and ours
8097 would not. If you told us to expect a crash, then when ours fails to crash, we
8098 would know that the bug was not happening for us. If you had not told us to
8099 expect a crash, then we would not be able to draw any conclusion from our
8103 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8104 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8105 option. Always send diffs from the old file to the new file. If you even
8106 discuss something in the @command{@value{AS}} source, refer to it by context, not
8109 The line numbers in our development sources will not match those in your
8110 sources. Your line numbers would convey no useful information to us.
8113 Here are some things that are not necessary:
8117 A description of the envelope of the bug.
8119 Often people who encounter a bug spend a lot of time investigating
8120 which changes to the input file will make the bug go away and which
8121 changes will not affect it.
8123 This is often time consuming and not very useful, because the way we
8124 will find the bug is by running a single example under the debugger
8125 with breakpoints, not by pure deduction from a series of examples.
8126 We recommend that you save your time for something else.
8128 Of course, if you can find a simpler example to report @emph{instead}
8129 of the original one, that is a convenience for us. Errors in the
8130 output will be easier to spot, running under the debugger will take
8131 less time, and so on.
8133 However, simplification is not vital; if you do not want to do this,
8134 report the bug anyway and send us the entire test case you used.
8137 A patch for the bug.
8139 A patch for the bug does help us if it is a good one. But do not omit
8140 the necessary information, such as the test case, on the assumption that
8141 a patch is all we need. We might see problems with your patch and decide
8142 to fix the problem another way, or we might not understand it at all.
8144 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8145 construct an example that will make the program follow a certain path through
8146 the code. If you do not send us the example, we will not be able to construct
8147 one, so we will not be able to verify that the bug is fixed.
8149 And if we cannot understand what bug you are trying to fix, or why your
8150 patch should be an improvement, we will not install it. A test case will
8151 help us to understand.
8154 A guess about what the bug is or what it depends on.
8156 Such guesses are usually wrong. Even we cannot guess right about such
8157 things without first using the debugger to find the facts.
8160 @node Acknowledgements
8161 @chapter Acknowledgements
8163 If you have contributed to GAS and your name isn't listed here,
8164 it is not meant as a slight. We just don't know about it. Send mail to the
8165 maintainer, and we'll correct the situation. Currently
8167 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8169 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8172 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8173 information and the 68k series machines, most of the preprocessing pass, and
8174 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8176 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8177 many bug fixes, including merging support for several processors, breaking GAS
8178 up to handle multiple object file format back ends (including heavy rewrite,
8179 testing, an integration of the coff and b.out back ends), adding configuration
8180 including heavy testing and verification of cross assemblers and file splits
8181 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8182 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8183 port (including considerable amounts of reverse engineering), a SPARC opcode
8184 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8185 assertions and made them work, much other reorganization, cleanup, and lint.
8187 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8188 in format-specific I/O modules.
8190 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8191 has done much work with it since.
8193 The Intel 80386 machine description was written by Eliot Dresselhaus.
8195 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8197 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8198 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8200 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8201 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8202 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8203 support a.out format.
8205 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8206 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8207 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8208 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8211 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8212 simplified the configuration of which versions accept which directives. He
8213 updated the 68k machine description so that Motorola's opcodes always produced
8214 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8215 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8216 cross-compilation support, and one bug in relaxation that took a week and
8217 required the proverbial one-bit fix.
8219 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8220 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8221 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8222 PowerPC assembler, and made a few other minor patches.
8224 Steve Chamberlain made GAS able to generate listings.
8226 Hewlett-Packard contributed support for the HP9000/300.
8228 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8229 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8230 formats). This work was supported by both the Center for Software Science at
8231 the University of Utah and Cygnus Support.
8233 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8234 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8235 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8236 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8237 and some initial 64-bit support).
8239 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8241 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8242 support for openVMS/Alpha.
8244 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8247 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8248 Inc.@: added support for Xtensa processors.
8250 Several engineers at Cygnus Support have also provided many small bug fixes and
8251 configuration enhancements.
8253 Jon Beniston added support for the Lattice Mico32 architecture.
8255 Many others have contributed large or small bugfixes and enhancements. If
8256 you have contributed significant work and are not mentioned on this list, and
8257 want to be, let us know. Some of the history has been lost; we are not
8258 intentionally leaving anyone out.
8260 @node GNU Free Documentation License
8261 @appendix GNU Free Documentation License
8265 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob