1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2018 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
50 @set abnormal-separator
54 @settitle Using @value{AS}
57 @settitle Using @value{AS} (@value{TARGET})
59 @setchapternewpage odd
64 @c WARE! Some of the machine-dependent sections contain tables of machine
65 @c instructions. Except in multi-column format, these tables look silly.
66 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
67 @c the multi-col format is faked within @example sections.
69 @c Again unfortunately, the natural size that fits on a page, for these tables,
70 @c is different depending on whether or not smallbook is turned on.
71 @c This matters, because of order: text flow switches columns at each page
74 @c The format faked in this source works reasonably well for smallbook,
75 @c not well for the default large-page format. This manual expects that if you
76 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
77 @c tables in question. You can turn on one without the other at your
78 @c discretion, of course.
81 @c the insn tables look just as silly in info files regardless of smallbook,
82 @c might as well show 'em anyways.
86 @dircategory Software development
88 * As: (as). The GNU assembler.
89 * Gas: (as). The GNU assembler.
97 This file documents the GNU Assembler "@value{AS}".
99 @c man begin COPYRIGHT
100 Copyright @copyright{} 1991-2018 Free Software Foundation, Inc.
102 Permission is granted to copy, distribute and/or modify this document
103 under the terms of the GNU Free Documentation License, Version 1.3
104 or any later version published by the Free Software Foundation;
105 with no Invariant Sections, with no Front-Cover Texts, and with no
106 Back-Cover Texts. A copy of the license is included in the
107 section entitled ``GNU Free Documentation License''.
113 @title Using @value{AS}
114 @subtitle The @sc{gnu} Assembler
116 @subtitle for the @value{TARGET} family
118 @ifset VERSION_PACKAGE
120 @subtitle @value{VERSION_PACKAGE}
123 @subtitle Version @value{VERSION}
126 The Free Software Foundation Inc.@: thanks The Nice Computer
127 Company of Australia for loaning Dean Elsner to write the
128 first (Vax) version of @command{as} for Project @sc{gnu}.
129 The proprietors, management and staff of TNCCA thank FSF for
130 distracting the boss while they got some work
133 @author Dean Elsner, Jay Fenlason & friends
137 \hfill {\it Using {\tt @value{AS}}}\par
138 \hfill Edited by Cygnus Support\par
140 %"boxit" macro for figures:
141 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
142 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
143 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
144 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
145 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
148 @vskip 0pt plus 1filll
149 Copyright @copyright{} 1991-2018 Free Software Foundation, Inc.
151 Permission is granted to copy, distribute and/or modify this document
152 under the terms of the GNU Free Documentation License, Version 1.3
153 or any later version published by the Free Software Foundation;
154 with no Invariant Sections, with no Front-Cover Texts, and with no
155 Back-Cover Texts. A copy of the license is included in the
156 section entitled ``GNU Free Documentation License''.
163 @top Using @value{AS}
165 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
166 @ifset VERSION_PACKAGE
167 @value{VERSION_PACKAGE}
169 version @value{VERSION}.
171 This version of the file describes @command{@value{AS}} configured to generate
172 code for @value{TARGET} architectures.
175 This document is distributed under the terms of the GNU Free
176 Documentation License. A copy of the license is included in the
177 section entitled ``GNU Free Documentation License''.
180 * Overview:: Overview
181 * Invoking:: Command-Line Options
183 * Sections:: Sections and Relocation
185 * Expressions:: Expressions
186 * Pseudo Ops:: Assembler Directives
188 * Object Attributes:: Object Attributes
190 * Machine Dependencies:: Machine Dependent Features
191 * Reporting Bugs:: Reporting Bugs
192 * Acknowledgements:: Who Did What
193 * GNU Free Documentation License:: GNU Free Documentation License
194 * AS Index:: AS Index
201 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
203 This version of the manual describes @command{@value{AS}} configured to generate
204 code for @value{TARGET} architectures.
208 @cindex invocation summary
209 @cindex option summary
210 @cindex summary of options
211 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
212 see @ref{Invoking,,Command-Line Options}.
214 @c man title AS the portable GNU assembler.
218 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
222 @c We don't use deffn and friends for the following because they seem
223 @c to be limited to one line for the header.
225 @c man begin SYNOPSIS
226 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
227 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
228 [@b{--debug-prefix-map} @var{old}=@var{new}]
229 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
230 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
231 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
232 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
233 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
234 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
235 [@b{--no-pad-sections}]
236 [@b{-o} @var{objfile}] [@b{-R}]
237 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
239 [@b{-v}] [@b{-version}] [@b{--version}]
240 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
241 [@b{-Z}] [@b{@@@var{FILE}}]
242 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
243 [@b{--elf-stt-common=[no|yes]}]
244 [@b{--generate-missing-build-notes=[no|yes]}]
245 [@b{--target-help}] [@var{target-options}]
246 [@b{--}|@var{files} @dots{}]
249 @c Target dependent options are listed below. Keep the list sorted.
250 @c Add an empty line for separation.
254 @emph{Target AArch64 options:}
256 [@b{-mabi}=@var{ABI}]
260 @emph{Target Alpha options:}
262 [@b{-mdebug} | @b{-no-mdebug}]
263 [@b{-replace} | @b{-noreplace}]
264 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
265 [@b{-F}] [@b{-32addr}]
269 @emph{Target ARC options:}
270 [@b{-mcpu=@var{cpu}}]
271 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
278 @emph{Target ARM options:}
279 @c Don't document the deprecated options
280 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
281 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
282 [@b{-mfpu}=@var{floating-point-format}]
283 [@b{-mfloat-abi}=@var{abi}]
284 [@b{-meabi}=@var{ver}]
287 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
288 @b{-mapcs-reentrant}]
289 [@b{-mthumb-interwork}] [@b{-k}]
293 @emph{Target Blackfin options:}
294 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
301 @emph{Target CRIS options:}
302 [@b{--underscore} | @b{--no-underscore}]
304 [@b{--emulation=criself} | @b{--emulation=crisaout}]
305 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
306 @c Deprecated -- deliberately not documented.
311 @emph{Target D10V options:}
316 @emph{Target D30V options:}
317 [@b{-O}|@b{-n}|@b{-N}]
321 @emph{Target EPIPHANY options:}
322 [@b{-mepiphany}|@b{-mepiphany16}]
326 @emph{Target H8/300 options:}
330 @c HPPA has no machine-dependent assembler options (yet).
334 @emph{Target i386 options:}
335 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
336 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
340 @emph{Target IA-64 options:}
341 [@b{-mconstant-gp}|@b{-mauto-pic}]
342 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
344 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
345 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
346 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
347 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
351 @emph{Target IP2K options:}
352 [@b{-mip2022}|@b{-mip2022ext}]
356 @emph{Target M32C options:}
357 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
361 @emph{Target M32R options:}
362 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
367 @emph{Target M680X0 options:}
368 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
372 @emph{Target M68HC11 options:}
373 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
374 [@b{-mshort}|@b{-mlong}]
375 [@b{-mshort-double}|@b{-mlong-double}]
376 [@b{--force-long-branches}] [@b{--short-branches}]
377 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
378 [@b{--print-opcodes}] [@b{--generate-example}]
382 @emph{Target MCORE options:}
383 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
384 [@b{-mcpu=[210|340]}]
388 @emph{Target Meta options:}
389 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
392 @emph{Target MICROBLAZE options:}
393 @c MicroBlaze has no machine-dependent assembler options.
397 @emph{Target MIPS options:}
398 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
399 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
400 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
401 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
402 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
403 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
404 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
405 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
406 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
407 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
408 [@b{-construct-floats}] [@b{-no-construct-floats}]
409 [@b{-mignore-branch-isa}] [@b{-mno-ignore-branch-isa}]
410 [@b{-mnan=@var{encoding}}]
411 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
412 [@b{-mips16}] [@b{-no-mips16}]
413 [@b{-mmips16e2}] [@b{-mno-mips16e2}]
414 [@b{-mmicromips}] [@b{-mno-micromips}]
415 [@b{-msmartmips}] [@b{-mno-smartmips}]
416 [@b{-mips3d}] [@b{-no-mips3d}]
417 [@b{-mdmx}] [@b{-no-mdmx}]
418 [@b{-mdsp}] [@b{-mno-dsp}]
419 [@b{-mdspr2}] [@b{-mno-dspr2}]
420 [@b{-mdspr3}] [@b{-mno-dspr3}]
421 [@b{-mmsa}] [@b{-mno-msa}]
422 [@b{-mxpa}] [@b{-mno-xpa}]
423 [@b{-mmt}] [@b{-mno-mt}]
424 [@b{-mmcu}] [@b{-mno-mcu}]
425 [@b{-mcrc}] [@b{-mno-crc}]
426 [@b{-mginv}] [@b{-mno-ginv}]
427 [@b{-minsn32}] [@b{-mno-insn32}]
428 [@b{-mfix7000}] [@b{-mno-fix7000}]
429 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
430 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
431 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
432 [@b{-mdebug}] [@b{-no-mdebug}]
433 [@b{-mpdr}] [@b{-mno-pdr}]
437 @emph{Target MMIX options:}
438 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
439 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
440 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
441 [@b{--linker-allocated-gregs}]
445 @emph{Target Nios II options:}
446 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
451 @emph{Target NDS32 options:}
452 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
453 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
454 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
455 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
456 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
457 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
458 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
463 @emph{Target PDP11 options:}
464 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
465 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
466 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
470 @emph{Target picoJava options:}
475 @emph{Target PowerPC options:}
477 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
478 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
479 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
480 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
481 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
482 @b{-mcell}|@b{-mspe}|@b{-mspe2}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
483 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
484 [@b{-mregnames}|@b{-mno-regnames}]
485 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
486 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
487 [@b{-msolaris}|@b{-mno-solaris}]
488 [@b{-nops=@var{count}}]
492 @emph{Target PRU options:}
495 [@b{-mno-warn-regname-label}]
499 @emph{Target RISC-V options:}
500 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
501 [@b{-march}=@var{ISA}]
502 [@b{-mabi}=@var{ABI}]
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 s390 options:}
525 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
526 [@b{-mregnames}|@b{-mno-regnames}]
527 [@b{-mwarn-areg-zero}]
531 @emph{Target SCORE options:}
532 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
533 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
534 [@b{-march=score7}][@b{-march=score3}]
535 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
539 @emph{Target SPARC options:}
540 @c The order here is important. See c-sparc.texi.
541 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
542 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
543 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
544 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
545 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
546 @b{-Asparcvisr}|@b{-Asparc5}]
547 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
548 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
549 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
550 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
551 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
552 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
555 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
559 @emph{Target TIC54X options:}
560 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
561 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
565 @emph{Target TIC6X options:}
566 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
567 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
568 [@b{-mpic}|@b{-mno-pic}]
572 @emph{Target TILE-Gx options:}
573 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
576 @c TILEPro has no machine-dependent assembler options
580 @emph{Target Visium options:}
581 [@b{-mtune=@var{arch}}]
585 @emph{Target Xtensa options:}
586 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
587 [@b{--[no-]absolute-literals}]
588 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
589 [@b{--[no-]transform}]
590 [@b{--rename-section} @var{oldname}=@var{newname}]
591 [@b{--[no-]trampolines}]
595 @emph{Target Z80 options:}
596 [@b{-z80}] [@b{-r800}]
597 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
598 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
599 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
600 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
601 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
602 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
606 @c Z8000 has no machine-dependent assembler options
615 @include at-file.texi
618 Turn on listings, in any of a variety of ways:
622 omit false conditionals
625 omit debugging directives
628 include general information, like @value{AS} version and options passed
631 include high-level source
637 include macro expansions
640 omit forms processing
646 set the name of the listing file
649 You may combine these options; for example, use @samp{-aln} for assembly
650 listing without forms processing. The @samp{=file} option, if used, must be
651 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
654 Begin in alternate macro mode.
656 @xref{Altmacro,,@code{.altmacro}}.
659 @item --compress-debug-sections
660 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
661 ELF ABI. The resulting object file may not be compatible with older
662 linkers and object file utilities. Note if compression would make a
663 given section @emph{larger} then it is not compressed.
666 @cindex @samp{--compress-debug-sections=} option
667 @item --compress-debug-sections=none
668 @itemx --compress-debug-sections=zlib
669 @itemx --compress-debug-sections=zlib-gnu
670 @itemx --compress-debug-sections=zlib-gabi
671 These options control how DWARF debug sections are compressed.
672 @option{--compress-debug-sections=none} is equivalent to
673 @option{--nocompress-debug-sections}.
674 @option{--compress-debug-sections=zlib} and
675 @option{--compress-debug-sections=zlib-gabi} are equivalent to
676 @option{--compress-debug-sections}.
677 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
678 sections using zlib. The debug sections are renamed to begin with
679 @samp{.zdebug}. Note if compression would make a given section
680 @emph{larger} then it is not compressed nor renamed.
684 @item --nocompress-debug-sections
685 Do not compress DWARF debug sections. This is usually the default for all
686 targets except the x86/x86_64, but a configure time option can be used to
690 Ignored. This option is accepted for script compatibility with calls to
693 @item --debug-prefix-map @var{old}=@var{new}
694 When assembling files in directory @file{@var{old}}, record debugging
695 information describing them as in @file{@var{new}} instead.
697 @item --defsym @var{sym}=@var{value}
698 Define the symbol @var{sym} to be @var{value} before assembling the input file.
699 @var{value} must be an integer constant. As in C, a leading @samp{0x}
700 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
701 value. The value of the symbol can be overridden inside a source file via the
702 use of a @code{.set} pseudo-op.
705 ``fast''---skip whitespace and comment preprocessing (assume source is
710 Generate debugging information for each assembler source line using whichever
711 debug format is preferred by the target. This currently means either STABS,
715 Generate stabs debugging information for each assembler line. This
716 may help debugging assembler code, if the debugger can handle it.
719 Generate stabs debugging information for each assembler line, with GNU
720 extensions that probably only gdb can handle, and that could make other
721 debuggers crash or refuse to read your program. This
722 may help debugging assembler code. Currently the only GNU extension is
723 the location of the current working directory at assembling time.
726 Generate DWARF2 debugging information for each assembler line. This
727 may help debugging assembler code, if the debugger can handle it. Note---this
728 option is only supported by some targets, not all of them.
730 @item --gdwarf-sections
731 Instead of creating a .debug_line section, create a series of
732 .debug_line.@var{foo} sections where @var{foo} is the name of the
733 corresponding code section. For example a code section called @var{.text.func}
734 will have its dwarf line number information placed into a section called
735 @var{.debug_line.text.func}. If the code section is just called @var{.text}
736 then debug line section will still be called just @var{.debug_line} without any
740 @item --size-check=error
741 @itemx --size-check=warning
742 Issue an error or warning for invalid ELF .size directive.
744 @item --elf-stt-common=no
745 @itemx --elf-stt-common=yes
746 These options control whether the ELF assembler should generate common
747 symbols with the @code{STT_COMMON} type. The default can be controlled
748 by a configure option @option{--enable-elf-stt-common}.
750 @item --generate-missing-build-notes=yes
751 @itemx --generate-missing-build-notes=no
752 These options control whether the ELF assembler should generate GNU Build
753 attribute notes if none are present in the input sources.
754 The default can be controlled by the @option{--enable-generate-build-notes}
760 Print a summary of the command line options and exit.
763 Print a summary of all target specific options and exit.
766 Add directory @var{dir} to the search list for @code{.include} directives.
769 Don't warn about signed overflow.
772 @ifclear DIFF-TBL-KLUGE
773 This option is accepted but has no effect on the @value{TARGET} family.
775 @ifset DIFF-TBL-KLUGE
776 Issue warnings when difference tables altered for long displacements.
781 Keep (in the symbol table) local symbols. These symbols start with
782 system-specific local label prefixes, typically @samp{.L} for ELF systems
783 or @samp{L} for traditional a.out systems.
788 @item --listing-lhs-width=@var{number}
789 Set the maximum width, in words, of the output data column for an assembler
790 listing to @var{number}.
792 @item --listing-lhs-width2=@var{number}
793 Set the maximum width, in words, of the output data column for continuation
794 lines in an assembler listing to @var{number}.
796 @item --listing-rhs-width=@var{number}
797 Set the maximum width of an input source line, as displayed in a listing, to
800 @item --listing-cont-lines=@var{number}
801 Set the maximum number of lines printed in a listing for a single line of input
804 @item --no-pad-sections
805 Stop the assembler for padding the ends of output sections to the alignment
806 of that section. The default is to pad the sections, but this can waste space
807 which might be needed on targets which have tight memory constraints.
809 @item -o @var{objfile}
810 Name the object-file output from @command{@value{AS}} @var{objfile}.
813 Fold the data section into the text section.
815 @item --hash-size=@var{number}
816 Set the default size of GAS's hash tables to a prime number close to
817 @var{number}. Increasing this value can reduce the length of time it takes the
818 assembler to perform its tasks, at the expense of increasing the assembler's
819 memory requirements. Similarly reducing this value can reduce the memory
820 requirements at the expense of speed.
822 @item --reduce-memory-overheads
823 This option reduces GAS's memory requirements, at the expense of making the
824 assembly processes slower. Currently this switch is a synonym for
825 @samp{--hash-size=4051}, but in the future it may have other effects as well.
828 @item --sectname-subst
829 Honor substitution sequences in section names.
831 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
836 Print the maximum space (in bytes) and total time (in seconds) used by
839 @item --strip-local-absolute
840 Remove local absolute symbols from the outgoing symbol table.
844 Print the @command{as} version.
847 Print the @command{as} version and exit.
851 Suppress warning messages.
853 @item --fatal-warnings
854 Treat warnings as errors.
857 Don't suppress warning messages or treat them as errors.
866 Generate an object file even after errors.
868 @item -- | @var{files} @dots{}
869 Standard input, or source files to assemble.
877 @xref{AArch64 Options}, for the options available when @value{AS} is configured
878 for the 64-bit mode of the ARM Architecture (AArch64).
883 The following options are available when @value{AS} is configured for the
884 64-bit mode of the ARM Architecture (AArch64).
887 @include c-aarch64.texi
888 @c ended inside the included file
896 @xref{Alpha Options}, for the options available when @value{AS} is configured
897 for an Alpha processor.
902 The following options are available when @value{AS} is configured for an Alpha
906 @include c-alpha.texi
907 @c ended inside the included file
914 The following options are available when @value{AS} is configured for an ARC
918 @item -mcpu=@var{cpu}
919 This option selects the core processor variant.
921 Select either big-endian (-EB) or little-endian (-EL) output.
923 Enable Code Density extenssion instructions.
928 The following options are available when @value{AS} is configured for the ARM
932 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
933 Specify which ARM processor variant is the target.
934 @item -march=@var{architecture}[+@var{extension}@dots{}]
935 Specify which ARM architecture variant is used by the target.
936 @item -mfpu=@var{floating-point-format}
937 Select which Floating Point architecture is the target.
938 @item -mfloat-abi=@var{abi}
939 Select which floating point ABI is in use.
941 Enable Thumb only instruction decoding.
942 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
943 Select which procedure calling convention is in use.
945 Select either big-endian (-EB) or little-endian (-EL) output.
946 @item -mthumb-interwork
947 Specify that the code has been generated with interworking between Thumb and
950 Turns on CodeComposer Studio assembly syntax compatibility mode.
952 Specify that PIC code has been generated.
960 @xref{Blackfin Options}, for the options available when @value{AS} is
961 configured for the Blackfin processor family.
966 The following options are available when @value{AS} is configured for
967 the Blackfin processor family.
971 @c ended inside the included file
978 See the info pages for documentation of the CRIS-specific options.
982 The following options are available when @value{AS} is configured for
985 @cindex D10V optimization
986 @cindex optimization, D10V
988 Optimize output by parallelizing instructions.
993 The following options are available when @value{AS} is configured for a D30V
996 @cindex D30V optimization
997 @cindex optimization, D30V
999 Optimize output by parallelizing instructions.
1003 Warn when nops are generated.
1005 @cindex D30V nops after 32-bit multiply
1007 Warn when a nop after a 32-bit multiply instruction is generated.
1013 The following options are available when @value{AS} is configured for the
1014 Adapteva EPIPHANY series.
1017 @xref{Epiphany Options}, for the options available when @value{AS} is
1018 configured for an Epiphany processor.
1022 @c man begin OPTIONS
1023 The following options are available when @value{AS} is configured for
1024 an Epiphany processor.
1026 @c man begin INCLUDE
1027 @include c-epiphany.texi
1028 @c ended inside the included file
1036 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1037 for an H8/300 processor.
1041 @c man begin OPTIONS
1042 The following options are available when @value{AS} is configured for an H8/300
1045 @c man begin INCLUDE
1046 @include c-h8300.texi
1047 @c ended inside the included file
1055 @xref{i386-Options}, for the options available when @value{AS} is
1056 configured for an i386 processor.
1060 @c man begin OPTIONS
1061 The following options are available when @value{AS} is configured for
1064 @c man begin INCLUDE
1065 @include c-i386.texi
1066 @c ended inside the included file
1071 @c man begin OPTIONS
1073 The following options are available when @value{AS} is configured for the
1079 Specifies that the extended IP2022 instructions are allowed.
1082 Restores the default behaviour, which restricts the permitted instructions to
1083 just the basic IP2022 ones.
1089 The following options are available when @value{AS} is configured for the
1090 Renesas M32C and M16C processors.
1095 Assemble M32C instructions.
1098 Assemble M16C instructions (the default).
1101 Enable support for link-time relaxations.
1104 Support H'00 style hex constants in addition to 0x00 style.
1110 The following options are available when @value{AS} is configured for the
1111 Renesas M32R (formerly Mitsubishi M32R) series.
1116 Specify which processor in the M32R family is the target. The default
1117 is normally the M32R, but this option changes it to the M32RX.
1119 @item --warn-explicit-parallel-conflicts or --Wp
1120 Produce warning messages when questionable parallel constructs are
1123 @item --no-warn-explicit-parallel-conflicts or --Wnp
1124 Do not produce warning messages when questionable parallel constructs are
1131 The following options are available when @value{AS} is configured for the
1132 Motorola 68000 series.
1137 Shorten references to undefined symbols, to one word instead of two.
1139 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1140 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1141 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1142 Specify what processor in the 68000 family is the target. The default
1143 is normally the 68020, but this can be changed at configuration time.
1145 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1146 The target machine does (or does not) have a floating-point coprocessor.
1147 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1148 the basic 68000 is not compatible with the 68881, a combination of the
1149 two can be specified, since it's possible to do emulation of the
1150 coprocessor instructions with the main processor.
1152 @item -m68851 | -mno-68851
1153 The target machine does (or does not) have a memory-management
1154 unit coprocessor. The default is to assume an MMU for 68020 and up.
1162 @xref{Nios II Options}, for the options available when @value{AS} is configured
1163 for an Altera Nios II processor.
1167 @c man begin OPTIONS
1168 The following options are available when @value{AS} is configured for an
1169 Altera Nios II processor.
1171 @c man begin INCLUDE
1172 @include c-nios2.texi
1173 @c ended inside the included file
1179 For details about the PDP-11 machine dependent features options,
1180 see @ref{PDP-11-Options}.
1183 @item -mpic | -mno-pic
1184 Generate position-independent (or position-dependent) code. The
1185 default is @option{-mpic}.
1188 @itemx -mall-extensions
1189 Enable all instruction set extensions. This is the default.
1191 @item -mno-extensions
1192 Disable all instruction set extensions.
1194 @item -m@var{extension} | -mno-@var{extension}
1195 Enable (or disable) a particular instruction set extension.
1198 Enable the instruction set extensions supported by a particular CPU, and
1199 disable all other extensions.
1201 @item -m@var{machine}
1202 Enable the instruction set extensions supported by a particular machine
1203 model, and disable all other extensions.
1209 The following options are available when @value{AS} is configured for
1210 a picoJava processor.
1214 @cindex PJ endianness
1215 @cindex endianness, PJ
1216 @cindex big endian output, PJ
1218 Generate ``big endian'' format output.
1220 @cindex little endian output, PJ
1222 Generate ``little endian'' format output.
1230 @xref{PRU Options}, for the options available when @value{AS} is configured
1231 for a PRU processor.
1235 @c man begin OPTIONS
1236 The following options are available when @value{AS} is configured for a
1239 @c man begin INCLUDE
1241 @c ended inside the included file
1246 The following options are available when @value{AS} is configured for the
1247 Motorola 68HC11 or 68HC12 series.
1251 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1252 Specify what processor is the target. The default is
1253 defined by the configuration option when building the assembler.
1255 @item --xgate-ramoffset
1256 Instruct the linker to offset RAM addresses from S12X address space into
1257 XGATE address space.
1260 Specify to use the 16-bit integer ABI.
1263 Specify to use the 32-bit integer ABI.
1265 @item -mshort-double
1266 Specify to use the 32-bit double ABI.
1269 Specify to use the 64-bit double ABI.
1271 @item --force-long-branches
1272 Relative branches are turned into absolute ones. This concerns
1273 conditional branches, unconditional branches and branches to a
1276 @item -S | --short-branches
1277 Do not turn relative branches into absolute ones
1278 when the offset is out of range.
1280 @item --strict-direct-mode
1281 Do not turn the direct addressing mode into extended addressing mode
1282 when the instruction does not support direct addressing mode.
1284 @item --print-insn-syntax
1285 Print the syntax of instruction in case of error.
1287 @item --print-opcodes
1288 Print the list of instructions with syntax and then exit.
1290 @item --generate-example
1291 Print an example of instruction for each possible instruction and then exit.
1292 This option is only useful for testing @command{@value{AS}}.
1298 The following options are available when @command{@value{AS}} is configured
1299 for the SPARC architecture:
1302 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1303 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1304 Explicitly select a variant of the SPARC architecture.
1306 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1307 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1309 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1310 UltraSPARC extensions.
1312 @item -xarch=v8plus | -xarch=v8plusa
1313 For compatibility with the Solaris v9 assembler. These options are
1314 equivalent to -Av8plus and -Av8plusa, respectively.
1317 Warn when the assembler switches to another architecture.
1322 The following options are available when @value{AS} is configured for the 'c54x
1327 Enable extended addressing mode. All addresses and relocations will assume
1328 extended addressing (usually 23 bits).
1329 @item -mcpu=@var{CPU_VERSION}
1330 Sets the CPU version being compiled for.
1331 @item -merrors-to-file @var{FILENAME}
1332 Redirect error output to a file, for broken systems which don't support such
1333 behaviour in the shell.
1338 @c man begin OPTIONS
1339 The following options are available when @value{AS} is configured for
1344 This option sets the largest size of an object that can be referenced
1345 implicitly with the @code{gp} register. It is only accepted for targets that
1346 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1348 @cindex MIPS endianness
1349 @cindex endianness, MIPS
1350 @cindex big endian output, MIPS
1352 Generate ``big endian'' format output.
1354 @cindex little endian output, MIPS
1356 Generate ``little endian'' format output.
1374 Generate code for a particular MIPS Instruction Set Architecture level.
1375 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1376 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1377 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1378 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1379 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1380 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1381 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1382 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1383 MIPS64 Release 6 ISA processors, respectively.
1385 @item -march=@var{cpu}
1386 Generate code for a particular MIPS CPU.
1388 @item -mtune=@var{cpu}
1389 Schedule and tune for a particular MIPS CPU.
1393 Cause nops to be inserted if the read of the destination register
1394 of an mfhi or mflo instruction occurs in the following two instructions.
1397 @itemx -mno-fix-rm7000
1398 Cause nops to be inserted if a dmult or dmultu instruction is
1399 followed by a load instruction.
1403 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1404 section instead of the standard ELF .stabs sections.
1408 Control generation of @code{.pdr} sections.
1412 The register sizes are normally inferred from the ISA and ABI, but these
1413 flags force a certain group of registers to be treated as 32 bits wide at
1414 all times. @samp{-mgp32} controls the size of general-purpose registers
1415 and @samp{-mfp32} controls the size of floating-point registers.
1419 The register sizes are normally inferred from the ISA and ABI, but these
1420 flags force a certain group of registers to be treated as 64 bits wide at
1421 all times. @samp{-mgp64} controls the size of general-purpose registers
1422 and @samp{-mfp64} controls the size of floating-point registers.
1425 The register sizes are normally inferred from the ISA and ABI, but using
1426 this flag in combination with @samp{-mabi=32} enables an ABI variant
1427 which will operate correctly with floating-point registers which are
1431 @itemx -mno-odd-spreg
1432 Enable use of floating-point operations on odd-numbered single-precision
1433 registers when supported by the ISA. @samp{-mfpxx} implies
1434 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1438 Generate code for the MIPS 16 processor. This is equivalent to putting
1439 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1440 turns off this option.
1443 @itemx -mno-mips16e2
1444 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1445 to putting @code{.module mips16e2} at the start of the assembly file.
1446 @samp{-mno-mips16e2} turns off this option.
1449 @itemx -mno-micromips
1450 Generate code for the microMIPS processor. This is equivalent to putting
1451 @code{.module micromips} at the start of the assembly file.
1452 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1453 @code{.module nomicromips} at the start of the assembly file.
1456 @itemx -mno-smartmips
1457 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1458 equivalent to putting @code{.module smartmips} at the start of the assembly
1459 file. @samp{-mno-smartmips} turns off this option.
1463 Generate code for the MIPS-3D Application Specific Extension.
1464 This tells the assembler to accept MIPS-3D instructions.
1465 @samp{-no-mips3d} turns off this option.
1469 Generate code for the MDMX Application Specific Extension.
1470 This tells the assembler to accept MDMX instructions.
1471 @samp{-no-mdmx} turns off this option.
1475 Generate code for the DSP Release 1 Application Specific Extension.
1476 This tells the assembler to accept DSP Release 1 instructions.
1477 @samp{-mno-dsp} turns off this option.
1481 Generate code for the DSP Release 2 Application Specific Extension.
1482 This option implies @samp{-mdsp}.
1483 This tells the assembler to accept DSP Release 2 instructions.
1484 @samp{-mno-dspr2} turns off this option.
1488 Generate code for the DSP Release 3 Application Specific Extension.
1489 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1490 This tells the assembler to accept DSP Release 3 instructions.
1491 @samp{-mno-dspr3} turns off this option.
1495 Generate code for the MIPS SIMD Architecture Extension.
1496 This tells the assembler to accept MSA instructions.
1497 @samp{-mno-msa} turns off this option.
1501 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1502 This tells the assembler to accept XPA instructions.
1503 @samp{-mno-xpa} turns off this option.
1507 Generate code for the MT Application Specific Extension.
1508 This tells the assembler to accept MT instructions.
1509 @samp{-mno-mt} turns off this option.
1513 Generate code for the MCU Application Specific Extension.
1514 This tells the assembler to accept MCU instructions.
1515 @samp{-mno-mcu} turns off this option.
1519 Generate code for the MIPS cyclic redundancy check (CRC) Application
1520 Specific Extension. This tells the assembler to accept CRC instructions.
1521 @samp{-mno-crc} turns off this option.
1525 Generate code for the Global INValidate (GINV) Application Specific
1526 Extension. This tells the assembler to accept GINV instructions.
1527 @samp{-mno-ginv} turns off this option.
1531 Only use 32-bit instruction encodings when generating code for the
1532 microMIPS processor. This option inhibits the use of any 16-bit
1533 instructions. This is equivalent to putting @code{.set insn32} at
1534 the start of the assembly file. @samp{-mno-insn32} turns off this
1535 option. This is equivalent to putting @code{.set noinsn32} at the
1536 start of the assembly file. By default @samp{-mno-insn32} is
1537 selected, allowing all instructions to be used.
1539 @item --construct-floats
1540 @itemx --no-construct-floats
1541 The @samp{--no-construct-floats} option disables the construction of
1542 double width floating point constants by loading the two halves of the
1543 value into the two single width floating point registers that make up
1544 the double width register. By default @samp{--construct-floats} is
1545 selected, allowing construction of these floating point constants.
1547 @item --relax-branch
1548 @itemx --no-relax-branch
1549 The @samp{--relax-branch} option enables the relaxation of out-of-range
1550 branches. By default @samp{--no-relax-branch} is selected, causing any
1551 out-of-range branches to produce an error.
1553 @item -mignore-branch-isa
1554 @itemx -mno-ignore-branch-isa
1555 Ignore branch checks for invalid transitions between ISA modes. The
1556 semantics of branches does not provide for an ISA mode switch, so in
1557 most cases the ISA mode a branch has been encoded for has to be the
1558 same as the ISA mode of the branch's target label. Therefore GAS has
1559 checks implemented that verify in branch assembly that the two ISA
1560 modes match. @samp{-mignore-branch-isa} disables these checks. By
1561 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1562 branch requiring a transition between ISA modes to produce an error.
1564 @item -mnan=@var{encoding}
1565 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1566 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1569 @item --emulation=@var{name}
1570 This option was formerly used to switch between ELF and ECOFF output
1571 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1572 removed in GAS 2.24, so the option now serves little purpose.
1573 It is retained for backwards compatibility.
1575 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1576 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1577 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1578 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1579 preferred options instead.
1582 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1589 Control how to deal with multiplication overflow and division by zero.
1590 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1591 (and only work for Instruction Set Architecture level 2 and higher);
1592 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1596 When this option is used, @command{@value{AS}} will issue a warning every
1597 time it generates a nop instruction from a macro.
1603 The following options are available when @value{AS} is configured for
1609 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1610 The command line option @samp{-nojsri2bsr} can be used to disable it.
1614 Enable or disable the silicon filter behaviour. By default this is disabled.
1615 The default can be overridden by the @samp{-sifilter} command line option.
1618 Alter jump instructions for long displacements.
1620 @item -mcpu=[210|340]
1621 Select the cpu type on the target hardware. This controls which instructions
1625 Assemble for a big endian target.
1628 Assemble for a little endian target.
1637 @xref{Meta Options}, for the options available when @value{AS} is configured
1638 for a Meta processor.
1642 @c man begin OPTIONS
1643 The following options are available when @value{AS} is configured for a
1646 @c man begin INCLUDE
1647 @include c-metag.texi
1648 @c ended inside the included file
1653 @c man begin OPTIONS
1655 See the info pages for documentation of the MMIX-specific options.
1661 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1662 for a NDS32 processor.
1664 @c ended inside the included file
1668 @c man begin OPTIONS
1669 The following options are available when @value{AS} is configured for a
1672 @c man begin INCLUDE
1673 @include c-nds32.texi
1674 @c ended inside the included file
1681 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1682 for a PowerPC processor.
1686 @c man begin OPTIONS
1687 The following options are available when @value{AS} is configured for a
1690 @c man begin INCLUDE
1692 @c ended inside the included file
1700 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1701 for a RISC-V processor.
1705 @c man begin OPTIONS
1706 The following options are available when @value{AS} is configured for a
1709 @c man begin INCLUDE
1710 @include c-riscv.texi
1711 @c ended inside the included file
1716 @c man begin OPTIONS
1718 See the info pages for documentation of the RX-specific options.
1722 The following options are available when @value{AS} is configured for the s390
1728 Select the word size, either 31/32 bits or 64 bits.
1731 Select the architecture mode, either the Enterprise System
1732 Architecture (esa) or the z/Architecture mode (zarch).
1733 @item -march=@var{processor}
1734 Specify which s390 processor variant is the target, @samp{g5} (or
1735 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1736 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1737 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1738 @samp{z13} (or @samp{arch11}), or @samp{z14} (or @samp{arch12}).
1740 @itemx -mno-regnames
1741 Allow or disallow symbolic names for registers.
1742 @item -mwarn-areg-zero
1743 Warn whenever the operand for a base or index register has been specified
1744 but evaluates to zero.
1752 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1753 for a TMS320C6000 processor.
1757 @c man begin OPTIONS
1758 The following options are available when @value{AS} is configured for a
1759 TMS320C6000 processor.
1761 @c man begin INCLUDE
1762 @include c-tic6x.texi
1763 @c ended inside the included file
1771 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1772 for a TILE-Gx processor.
1776 @c man begin OPTIONS
1777 The following options are available when @value{AS} is configured for a TILE-Gx
1780 @c man begin INCLUDE
1781 @include c-tilegx.texi
1782 @c ended inside the included file
1790 @xref{Visium Options}, for the options available when @value{AS} is configured
1791 for a Visium processor.
1795 @c man begin OPTIONS
1796 The following option is available when @value{AS} is configured for a Visium
1799 @c man begin INCLUDE
1800 @include c-visium.texi
1801 @c ended inside the included file
1809 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1810 for an Xtensa processor.
1814 @c man begin OPTIONS
1815 The following options are available when @value{AS} is configured for an
1818 @c man begin INCLUDE
1819 @include c-xtensa.texi
1820 @c ended inside the included file
1825 @c man begin OPTIONS
1828 The following options are available when @value{AS} is configured for
1829 a Z80 family processor.
1832 Assemble for Z80 processor.
1834 Assemble for R800 processor.
1835 @item -ignore-undocumented-instructions
1837 Assemble undocumented Z80 instructions that also work on R800 without warning.
1838 @item -ignore-unportable-instructions
1840 Assemble all undocumented Z80 instructions without warning.
1841 @item -warn-undocumented-instructions
1843 Issue a warning for undocumented Z80 instructions that also work on R800.
1844 @item -warn-unportable-instructions
1846 Issue a warning for undocumented Z80 instructions that do not work on R800.
1847 @item -forbid-undocumented-instructions
1849 Treat all undocumented instructions as errors.
1850 @item -forbid-unportable-instructions
1852 Treat undocumented Z80 instructions that do not work on R800 as errors.
1859 * Manual:: Structure of this Manual
1860 * GNU Assembler:: The GNU Assembler
1861 * Object Formats:: Object File Formats
1862 * Command Line:: Command Line
1863 * Input Files:: Input Files
1864 * Object:: Output (Object) File
1865 * Errors:: Error and Warning Messages
1869 @section Structure of this Manual
1871 @cindex manual, structure and purpose
1872 This manual is intended to describe what you need to know to use
1873 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1874 notation for symbols, constants, and expressions; the directives that
1875 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1878 We also cover special features in the @value{TARGET}
1879 configuration of @command{@value{AS}}, including assembler directives.
1882 This manual also describes some of the machine-dependent features of
1883 various flavors of the assembler.
1886 @cindex machine instructions (not covered)
1887 On the other hand, this manual is @emph{not} intended as an introduction
1888 to programming in assembly language---let alone programming in general!
1889 In a similar vein, we make no attempt to introduce the machine
1890 architecture; we do @emph{not} describe the instruction set, standard
1891 mnemonics, registers or addressing modes that are standard to a
1892 particular architecture.
1894 You may want to consult the manufacturer's
1895 machine architecture manual for this information.
1899 For information on the H8/300 machine instruction set, see @cite{H8/300
1900 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1901 Programming Manual} (Renesas).
1904 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1905 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1906 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1907 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1910 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1914 @c I think this is premature---doc@cygnus.com, 17jan1991
1916 Throughout this manual, we assume that you are running @dfn{GNU},
1917 the portable operating system from the @dfn{Free Software
1918 Foundation, Inc.}. This restricts our attention to certain kinds of
1919 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1920 once this assumption is granted examples and definitions need less
1923 @command{@value{AS}} is part of a team of programs that turn a high-level
1924 human-readable series of instructions into a low-level
1925 computer-readable series of instructions. Different versions of
1926 @command{@value{AS}} are used for different kinds of computer.
1929 @c There used to be a section "Terminology" here, which defined
1930 @c "contents", "byte", "word", and "long". Defining "word" to any
1931 @c particular size is confusing when the .word directive may generate 16
1932 @c bits on one machine and 32 bits on another; in general, for the user
1933 @c version of this manual, none of these terms seem essential to define.
1934 @c They were used very little even in the former draft of the manual;
1935 @c this draft makes an effort to avoid them (except in names of
1939 @section The GNU Assembler
1941 @c man begin DESCRIPTION
1943 @sc{gnu} @command{as} is really a family of assemblers.
1945 This manual describes @command{@value{AS}}, a member of that family which is
1946 configured for the @value{TARGET} architectures.
1948 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1949 should find a fairly similar environment when you use it on another
1950 architecture. Each version has much in common with the others,
1951 including object file formats, most assembler directives (often called
1952 @dfn{pseudo-ops}) and assembler syntax.@refill
1954 @cindex purpose of @sc{gnu} assembler
1955 @command{@value{AS}} is primarily intended to assemble the output of the
1956 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1957 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1958 assemble correctly everything that other assemblers for the same
1959 machine would assemble.
1961 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1964 @c This remark should appear in generic version of manual; assumption
1965 @c here is that generic version sets M680x0.
1966 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1967 assembler for the same architecture; for example, we know of several
1968 incompatible versions of 680x0 assembly language syntax.
1973 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1974 program in one pass of the source file. This has a subtle impact on the
1975 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1977 @node Object Formats
1978 @section Object File Formats
1980 @cindex object file format
1981 The @sc{gnu} assembler can be configured to produce several alternative
1982 object file formats. For the most part, this does not affect how you
1983 write assembly language programs; but directives for debugging symbols
1984 are typically different in different file formats. @xref{Symbol
1985 Attributes,,Symbol Attributes}.
1988 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1989 @value{OBJ-NAME} format object files.
1991 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1993 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1994 SOM or ELF format object files.
1999 @section Command Line
2001 @cindex command line conventions
2003 After the program name @command{@value{AS}}, the command line may contain
2004 options and file names. Options may appear in any order, and may be
2005 before, after, or between file names. The order of file names is
2008 @cindex standard input, as input file
2010 @file{--} (two hyphens) by itself names the standard input file
2011 explicitly, as one of the files for @command{@value{AS}} to assemble.
2013 @cindex options, command line
2014 Except for @samp{--} any command line argument that begins with a
2015 hyphen (@samp{-}) is an option. Each option changes the behavior of
2016 @command{@value{AS}}. No option changes the way another option works. An
2017 option is a @samp{-} followed by one or more letters; the case of
2018 the letter is important. All options are optional.
2020 Some options expect exactly one file name to follow them. The file
2021 name may either immediately follow the option's letter (compatible
2022 with older assemblers) or it may be the next command argument (@sc{gnu}
2023 standard). These two command lines are equivalent:
2026 @value{AS} -o my-object-file.o mumble.s
2027 @value{AS} -omy-object-file.o mumble.s
2031 @section Input Files
2034 @cindex source program
2035 @cindex files, input
2036 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2037 describe the program input to one run of @command{@value{AS}}. The program may
2038 be in one or more files; how the source is partitioned into files
2039 doesn't change the meaning of the source.
2041 @c I added "con" prefix to "catenation" just to prove I can overcome my
2042 @c APL training... doc@cygnus.com
2043 The source program is a concatenation of the text in all the files, in the
2046 @c man begin DESCRIPTION
2047 Each time you run @command{@value{AS}} it assembles exactly one source
2048 program. The source program is made up of one or more files.
2049 (The standard input is also a file.)
2051 You give @command{@value{AS}} a command line that has zero or more input file
2052 names. The input files are read (from left file name to right). A
2053 command line argument (in any position) that has no special meaning
2054 is taken to be an input file name.
2056 If you give @command{@value{AS}} no file names it attempts to read one input file
2057 from the @command{@value{AS}} standard input, which is normally your terminal. You
2058 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2061 Use @samp{--} if you need to explicitly name the standard input file
2062 in your command line.
2064 If the source is empty, @command{@value{AS}} produces a small, empty object
2069 @subheading Filenames and Line-numbers
2071 @cindex input file linenumbers
2072 @cindex line numbers, in input files
2073 There are two ways of locating a line in the input file (or files) and
2074 either may be used in reporting error messages. One way refers to a line
2075 number in a physical file; the other refers to a line number in a
2076 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2078 @dfn{Physical files} are those files named in the command line given
2079 to @command{@value{AS}}.
2081 @dfn{Logical files} are simply names declared explicitly by assembler
2082 directives; they bear no relation to physical files. Logical file names help
2083 error messages reflect the original source file, when @command{@value{AS}} source
2084 is itself synthesized from other files. @command{@value{AS}} understands the
2085 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2086 @ref{File,,@code{.file}}.
2089 @section Output (Object) File
2095 Every time you run @command{@value{AS}} it produces an output file, which is
2096 your assembly language program translated into numbers. This file
2097 is the object file. Its default name is @code{a.out}.
2098 You can give it another name by using the @option{-o} option. Conventionally,
2099 object file names end with @file{.o}. The default name is used for historical
2100 reasons: older assemblers were capable of assembling self-contained programs
2101 directly into a runnable program. (For some formats, this isn't currently
2102 possible, but it can be done for the @code{a.out} format.)
2106 The object file is meant for input to the linker @code{@value{LD}}. It contains
2107 assembled program code, information to help @code{@value{LD}} integrate
2108 the assembled program into a runnable file, and (optionally) symbolic
2109 information for the debugger.
2111 @c link above to some info file(s) like the description of a.out.
2112 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2115 @section Error and Warning Messages
2117 @c man begin DESCRIPTION
2119 @cindex error messages
2120 @cindex warning messages
2121 @cindex messages from assembler
2122 @command{@value{AS}} may write warnings and error messages to the standard error
2123 file (usually your terminal). This should not happen when a compiler
2124 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2125 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2126 grave problem that stops the assembly.
2130 @cindex format of warning messages
2131 Warning messages have the format
2134 file_name:@b{NNN}:Warning Message Text
2138 @cindex file names and line numbers, in warnings/errors
2139 (where @b{NNN} is a line number). If both a logical file name
2140 (@pxref{File,,@code{.file}}) and a logical line number
2142 (@pxref{Line,,@code{.line}})
2144 have been given then they will be used, otherwise the file name and line number
2145 in the current assembler source file will be used. The message text is
2146 intended to be self explanatory (in the grand Unix tradition).
2148 Note the file name must be set via the logical version of the @code{.file}
2149 directive, not the DWARF2 version of the @code{.file} directive. For example:
2153 error_assembler_source
2159 produces this output:
2163 asm.s:2: Error: no such instruction: `error_assembler_source'
2164 foo.c:31: Error: no such instruction: `error_c_source'
2167 @cindex format of error messages
2168 Error messages have the format
2171 file_name:@b{NNN}:FATAL:Error Message Text
2174 The file name and line number are derived as for warning
2175 messages. The actual message text may be rather less explanatory
2176 because many of them aren't supposed to happen.
2179 @chapter Command-Line Options
2181 @cindex options, all versions of assembler
2182 This chapter describes command-line options available in @emph{all}
2183 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2184 for options specific
2186 to the @value{TARGET} target.
2189 to particular machine architectures.
2192 @c man begin DESCRIPTION
2194 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2195 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2196 The assembler arguments must be separated from each other (and the @samp{-Wa})
2197 by commas. For example:
2200 gcc -c -g -O -Wa,-alh,-L file.c
2204 This passes two options to the assembler: @samp{-alh} (emit a listing to
2205 standard output with high-level and assembly source) and @samp{-L} (retain
2206 local symbols in the symbol table).
2208 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2209 command-line options are automatically passed to the assembler by the compiler.
2210 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2211 precisely what options it passes to each compilation pass, including the
2217 * a:: -a[cdghlns] enable listings
2218 * alternate:: --alternate enable alternate macro syntax
2219 * D:: -D for compatibility
2220 * f:: -f to work faster
2221 * I:: -I for .include search path
2222 @ifclear DIFF-TBL-KLUGE
2223 * K:: -K for compatibility
2225 @ifset DIFF-TBL-KLUGE
2226 * K:: -K for difference tables
2229 * L:: -L to retain local symbols
2230 * listing:: --listing-XXX to configure listing output
2231 * M:: -M or --mri to assemble in MRI compatibility mode
2232 * MD:: --MD for dependency tracking
2233 * no-pad-sections:: --no-pad-sections to stop section padding
2234 * o:: -o to name the object file
2235 * R:: -R to join data and text sections
2236 * statistics:: --statistics to see statistics about assembly
2237 * traditional-format:: --traditional-format for compatible output
2238 * v:: -v to announce version
2239 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2240 * Z:: -Z to make object file even after errors
2244 @section Enable Listings: @option{-a[cdghlns]}
2254 @cindex listings, enabling
2255 @cindex assembly listings, enabling
2257 These options enable listing output from the assembler. By itself,
2258 @samp{-a} requests high-level, assembly, and symbols listing.
2259 You can use other letters to select specific options for the list:
2260 @samp{-ah} requests a high-level language listing,
2261 @samp{-al} requests an output-program assembly listing, and
2262 @samp{-as} requests a symbol table listing.
2263 High-level listings require that a compiler debugging option like
2264 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2267 Use the @samp{-ag} option to print a first section with general assembly
2268 information, like @value{AS} version, switches passed, or time stamp.
2270 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2271 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2272 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2273 omitted from the listing.
2275 Use the @samp{-ad} option to omit debugging directives from the
2278 Once you have specified one of these options, you can further control
2279 listing output and its appearance using the directives @code{.list},
2280 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2282 The @samp{-an} option turns off all forms processing.
2283 If you do not request listing output with one of the @samp{-a} options, the
2284 listing-control directives have no effect.
2286 The letters after @samp{-a} may be combined into one option,
2287 @emph{e.g.}, @samp{-aln}.
2289 Note if the assembler source is coming from the standard input (e.g.,
2291 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2292 is being used) then the listing will not contain any comments or preprocessor
2293 directives. This is because the listing code buffers input source lines from
2294 stdin only after they have been preprocessed by the assembler. This reduces
2295 memory usage and makes the code more efficient.
2298 @section @option{--alternate}
2301 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2304 @section @option{-D}
2307 This option has no effect whatsoever, but it is accepted to make it more
2308 likely that scripts written for other assemblers also work with
2309 @command{@value{AS}}.
2312 @section Work Faster: @option{-f}
2315 @cindex trusted compiler
2316 @cindex faster processing (@option{-f})
2317 @samp{-f} should only be used when assembling programs written by a
2318 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2319 and comment preprocessing on
2320 the input file(s) before assembling them. @xref{Preprocessing,
2324 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2325 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2330 @section @code{.include} Search Path: @option{-I} @var{path}
2332 @kindex -I @var{path}
2333 @cindex paths for @code{.include}
2334 @cindex search path for @code{.include}
2335 @cindex @code{include} directive search path
2336 Use this option to add a @var{path} to the list of directories
2337 @command{@value{AS}} searches for files specified in @code{.include}
2338 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2339 many times as necessary to include a variety of paths. The current
2340 working directory is always searched first; after that, @command{@value{AS}}
2341 searches any @samp{-I} directories in the same order as they were
2342 specified (left to right) on the command line.
2345 @section Difference Tables: @option{-K}
2348 @ifclear DIFF-TBL-KLUGE
2349 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2350 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2351 where it can be used to warn when the assembler alters the machine code
2352 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2353 family does not have the addressing limitations that sometimes lead to this
2354 alteration on other platforms.
2357 @ifset DIFF-TBL-KLUGE
2358 @cindex difference tables, warning
2359 @cindex warning for altered difference tables
2360 @command{@value{AS}} sometimes alters the code emitted for directives of the
2361 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2362 You can use the @samp{-K} option if you want a warning issued when this
2367 @section Include Local Symbols: @option{-L}
2370 @cindex local symbols, retaining in output
2371 Symbols beginning with system-specific local label prefixes, typically
2372 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2373 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2374 such symbols when debugging, because they are intended for the use of
2375 programs (like compilers) that compose assembler programs, not for your
2376 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2377 such symbols, so you do not normally debug with them.
2379 This option tells @command{@value{AS}} to retain those local symbols
2380 in the object file. Usually if you do this you also tell the linker
2381 @code{@value{LD}} to preserve those symbols.
2384 @section Configuring listing output: @option{--listing}
2386 The listing feature of the assembler can be enabled via the command line switch
2387 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2388 hex dump of the corresponding locations in the output object file, and displays
2389 them as a listing file. The format of this listing can be controlled by
2390 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2391 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2392 @code{.psize} (@pxref{Psize}), and
2393 @code{.eject} (@pxref{Eject}) and also by the following switches:
2396 @item --listing-lhs-width=@samp{number}
2397 @kindex --listing-lhs-width
2398 @cindex Width of first line disassembly output
2399 Sets the maximum width, in words, of the first line of the hex byte dump. This
2400 dump appears on the left hand side of the listing output.
2402 @item --listing-lhs-width2=@samp{number}
2403 @kindex --listing-lhs-width2
2404 @cindex Width of continuation lines of disassembly output
2405 Sets the maximum width, in words, of any further lines of the hex byte dump for
2406 a given input source line. If this value is not specified, it defaults to being
2407 the same as the value specified for @samp{--listing-lhs-width}. If neither
2408 switch is used the default is to one.
2410 @item --listing-rhs-width=@samp{number}
2411 @kindex --listing-rhs-width
2412 @cindex Width of source line output
2413 Sets the maximum width, in characters, of the source line that is displayed
2414 alongside the hex dump. The default value for this parameter is 100. The
2415 source line is displayed on the right hand side of the listing output.
2417 @item --listing-cont-lines=@samp{number}
2418 @kindex --listing-cont-lines
2419 @cindex Maximum number of continuation lines
2420 Sets the maximum number of continuation lines of hex dump that will be
2421 displayed for a given single line of source input. The default value is 4.
2425 @section Assemble in MRI Compatibility Mode: @option{-M}
2428 @cindex MRI compatibility mode
2429 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2430 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2431 compatible with the @code{ASM68K} assembler from Microtec Research.
2432 The exact nature of the
2433 MRI syntax will not be documented here; see the MRI manuals for more
2434 information. Note in particular that the handling of macros and macro
2435 arguments is somewhat different. The purpose of this option is to permit
2436 assembling existing MRI assembler code using @command{@value{AS}}.
2438 The MRI compatibility is not complete. Certain operations of the MRI assembler
2439 depend upon its object file format, and can not be supported using other object
2440 file formats. Supporting these would require enhancing each object file format
2441 individually. These are:
2444 @item global symbols in common section
2446 The m68k MRI assembler supports common sections which are merged by the linker.
2447 Other object file formats do not support this. @command{@value{AS}} handles
2448 common sections by treating them as a single common symbol. It permits local
2449 symbols to be defined within a common section, but it can not support global
2450 symbols, since it has no way to describe them.
2452 @item complex relocations
2454 The MRI assemblers support relocations against a negated section address, and
2455 relocations which combine the start addresses of two or more sections. These
2456 are not support by other object file formats.
2458 @item @code{END} pseudo-op specifying start address
2460 The MRI @code{END} pseudo-op permits the specification of a start address.
2461 This is not supported by other object file formats. The start address may
2462 instead be specified using the @option{-e} option to the linker, or in a linker
2465 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2467 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2468 name to the output file. This is not supported by other object file formats.
2470 @item @code{ORG} pseudo-op
2472 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2473 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2474 which changes the location within the current section. Absolute sections are
2475 not supported by other object file formats. The address of a section may be
2476 assigned within a linker script.
2479 There are some other features of the MRI assembler which are not supported by
2480 @command{@value{AS}}, typically either because they are difficult or because they
2481 seem of little consequence. Some of these may be supported in future releases.
2485 @item EBCDIC strings
2487 EBCDIC strings are not supported.
2489 @item packed binary coded decimal
2491 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2492 and @code{DCB.P} pseudo-ops are not supported.
2494 @item @code{FEQU} pseudo-op
2496 The m68k @code{FEQU} pseudo-op is not supported.
2498 @item @code{NOOBJ} pseudo-op
2500 The m68k @code{NOOBJ} pseudo-op is not supported.
2502 @item @code{OPT} branch control options
2504 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2505 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2506 relaxes all branches, whether forward or backward, to an appropriate size, so
2507 these options serve no purpose.
2509 @item @code{OPT} list control options
2511 The following m68k @code{OPT} list control options are ignored: @code{C},
2512 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2513 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2515 @item other @code{OPT} options
2517 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2518 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2520 @item @code{OPT} @code{D} option is default
2522 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2523 @code{OPT NOD} may be used to turn it off.
2525 @item @code{XREF} pseudo-op.
2527 The m68k @code{XREF} pseudo-op is ignored.
2532 @section Dependency Tracking: @option{--MD}
2535 @cindex dependency tracking
2538 @command{@value{AS}} can generate a dependency file for the file it creates. This
2539 file consists of a single rule suitable for @code{make} describing the
2540 dependencies of the main source file.
2542 The rule is written to the file named in its argument.
2544 This feature is used in the automatic updating of makefiles.
2546 @node no-pad-sections
2547 @section Output Section Padding
2548 @kindex --no-pad-sections
2549 @cindex output section padding
2550 Normally the assembler will pad the end of each output section up to its
2551 alignment boundary. But this can waste space, which can be significant on
2552 memory constrained targets. So the @option{--no-pad-sections} option will
2553 disable this behaviour.
2556 @section Name the Object File: @option{-o}
2559 @cindex naming object file
2560 @cindex object file name
2561 There is always one object file output when you run @command{@value{AS}}. By
2562 default it has the name @file{a.out}.
2563 You use this option (which takes exactly one filename) to give the
2564 object file a different name.
2566 Whatever the object file is called, @command{@value{AS}} overwrites any
2567 existing file of the same name.
2570 @section Join Data and Text Sections: @option{-R}
2573 @cindex data and text sections, joining
2574 @cindex text and data sections, joining
2575 @cindex joining text and data sections
2576 @cindex merging text and data sections
2577 @option{-R} tells @command{@value{AS}} to write the object file as if all
2578 data-section data lives in the text section. This is only done at
2579 the very last moment: your binary data are the same, but data
2580 section parts are relocated differently. The data section part of
2581 your object file is zero bytes long because all its bytes are
2582 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2584 When you specify @option{-R} it would be possible to generate shorter
2585 address displacements (because we do not have to cross between text and
2586 data section). We refrain from doing this simply for compatibility with
2587 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2590 When @command{@value{AS}} is configured for COFF or ELF output,
2591 this option is only useful if you use sections named @samp{.text} and
2596 @option{-R} is not supported for any of the HPPA targets. Using
2597 @option{-R} generates a warning from @command{@value{AS}}.
2601 @section Display Assembly Statistics: @option{--statistics}
2603 @kindex --statistics
2604 @cindex statistics, about assembly
2605 @cindex time, total for assembly
2606 @cindex space used, maximum for assembly
2607 Use @samp{--statistics} to display two statistics about the resources used by
2608 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2609 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2612 @node traditional-format
2613 @section Compatible Output: @option{--traditional-format}
2615 @kindex --traditional-format
2616 For some targets, the output of @command{@value{AS}} is different in some ways
2617 from the output of some existing assembler. This switch requests
2618 @command{@value{AS}} to use the traditional format instead.
2620 For example, it disables the exception frame optimizations which
2621 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2624 @section Announce Version: @option{-v}
2628 @cindex assembler version
2629 @cindex version of assembler
2630 You can find out what version of as is running by including the
2631 option @samp{-v} (which you can also spell as @samp{-version}) on the
2635 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2637 @command{@value{AS}} should never give a warning or error message when
2638 assembling compiler output. But programs written by people often
2639 cause @command{@value{AS}} to give a warning that a particular assumption was
2640 made. All such warnings are directed to the standard error file.
2644 @cindex suppressing warnings
2645 @cindex warnings, suppressing
2646 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2647 This only affects the warning messages: it does not change any particular of
2648 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2651 @kindex --fatal-warnings
2652 @cindex errors, caused by warnings
2653 @cindex warnings, causing error
2654 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2655 files that generate warnings to be in error.
2658 @cindex warnings, switching on
2659 You can switch these options off again by specifying @option{--warn}, which
2660 causes warnings to be output as usual.
2663 @section Generate Object File in Spite of Errors: @option{-Z}
2664 @cindex object file, after errors
2665 @cindex errors, continuing after
2666 After an error message, @command{@value{AS}} normally produces no output. If for
2667 some reason you are interested in object file output even after
2668 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2669 option. If there are any errors, @command{@value{AS}} continues anyways, and
2670 writes an object file after a final warning message of the form @samp{@var{n}
2671 errors, @var{m} warnings, generating bad object file.}
2676 @cindex machine-independent syntax
2677 @cindex syntax, machine-independent
2678 This chapter describes the machine-independent syntax allowed in a
2679 source file. @command{@value{AS}} syntax is similar to what many other
2680 assemblers use; it is inspired by the BSD 4.2
2685 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2689 * Preprocessing:: Preprocessing
2690 * Whitespace:: Whitespace
2691 * Comments:: Comments
2692 * Symbol Intro:: Symbols
2693 * Statements:: Statements
2694 * Constants:: Constants
2698 @section Preprocessing
2700 @cindex preprocessing
2701 The @command{@value{AS}} internal preprocessor:
2703 @cindex whitespace, removed by preprocessor
2705 adjusts and removes extra whitespace. It leaves one space or tab before
2706 the keywords on a line, and turns any other whitespace on the line into
2709 @cindex comments, removed by preprocessor
2711 removes all comments, replacing them with a single space, or an
2712 appropriate number of newlines.
2714 @cindex constants, converted by preprocessor
2716 converts character constants into the appropriate numeric values.
2719 It does not do macro processing, include file handling, or
2720 anything else you may get from your C compiler's preprocessor. You can
2721 do include file processing with the @code{.include} directive
2722 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2723 to get other ``CPP'' style preprocessing by giving the input file a
2724 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2725 Output, gcc info, Using GNU CC}.
2727 Excess whitespace, comments, and character constants
2728 cannot be used in the portions of the input text that are not
2731 @cindex turning preprocessing on and off
2732 @cindex preprocessing, turning on and off
2735 If the first line of an input file is @code{#NO_APP} or if you use the
2736 @samp{-f} option, whitespace and comments are not removed from the input file.
2737 Within an input file, you can ask for whitespace and comment removal in
2738 specific portions of the by putting a line that says @code{#APP} before the
2739 text that may contain whitespace or comments, and putting a line that says
2740 @code{#NO_APP} after this text. This feature is mainly intend to support
2741 @code{asm} statements in compilers whose output is otherwise free of comments
2748 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2749 Whitespace is used to separate symbols, and to make programs neater for
2750 people to read. Unless within character constants
2751 (@pxref{Characters,,Character Constants}), any whitespace means the same
2752 as exactly one space.
2758 There are two ways of rendering comments to @command{@value{AS}}. In both
2759 cases the comment is equivalent to one space.
2761 Anything from @samp{/*} through the next @samp{*/} is a comment.
2762 This means you may not nest these comments.
2766 The only way to include a newline ('\n') in a comment
2767 is to use this sort of comment.
2770 /* This sort of comment does not nest. */
2773 @cindex line comment character
2774 Anything from a @dfn{line comment} character up to the next newline is
2775 considered a comment and is ignored. The line comment character is target
2776 specific, and some targets multiple comment characters. Some targets also have
2777 line comment characters that only work if they are the first character on a
2778 line. Some targets use a sequence of two characters to introduce a line
2779 comment. Some targets can also change their line comment characters depending
2780 upon command line options that have been used. For more details see the
2781 @emph{Syntax} section in the documentation for individual targets.
2783 If the line comment character is the hash sign (@samp{#}) then it still has the
2784 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2785 to specify logical line numbers:
2788 @cindex lines starting with @code{#}
2789 @cindex logical line numbers
2790 To be compatible with past assemblers, lines that begin with @samp{#} have a
2791 special interpretation. Following the @samp{#} should be an absolute
2792 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2793 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2794 new logical file name. The rest of the line, if any, should be whitespace.
2796 If the first non-whitespace characters on the line are not numeric,
2797 the line is ignored. (Just like a comment.)
2800 # This is an ordinary comment.
2801 # 42-6 "new_file_name" # New logical file name
2802 # This is logical line # 36.
2804 This feature is deprecated, and may disappear from future versions
2805 of @command{@value{AS}}.
2810 @cindex characters used in symbols
2811 @ifclear SPECIAL-SYMS
2812 A @dfn{symbol} is one or more characters chosen from the set of all
2813 letters (both upper and lower case), digits and the three characters
2819 A @dfn{symbol} is one or more characters chosen from the set of all
2820 letters (both upper and lower case), digits and the three characters
2821 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2827 On most machines, you can also use @code{$} in symbol names; exceptions
2828 are noted in @ref{Machine Dependencies}.
2830 No symbol may begin with a digit. Case is significant.
2831 There is no length limit; all characters are significant. Multibyte characters
2832 are supported. Symbols are delimited by characters not in that set, or by the
2833 beginning of a file (since the source program must end with a newline, the end
2834 of a file is not a possible symbol delimiter). @xref{Symbols}.
2836 Symbol names may also be enclosed in double quote @code{"} characters. In such
2837 cases any characters are allowed, except for the NUL character. If a double
2838 quote character is to be included in the symbol name it must be preceeded by a
2839 backslash @code{\} character.
2840 @cindex length of symbols
2845 @cindex statements, structure of
2846 @cindex line separator character
2847 @cindex statement separator character
2849 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2850 @dfn{line separator character}. The line separator character is target
2851 specific and described in the @emph{Syntax} section of each
2852 target's documentation. Not all targets support a line separator character.
2853 The newline or line separator character is considered to be part of the
2854 preceding statement. Newlines and separators within character constants are an
2855 exception: they do not end statements.
2857 @cindex newline, required at file end
2858 @cindex EOF, newline must precede
2859 It is an error to end any statement with end-of-file: the last
2860 character of any input file should be a newline.@refill
2862 An empty statement is allowed, and may include whitespace. It is ignored.
2864 @cindex instructions and directives
2865 @cindex directives and instructions
2866 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2867 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2869 A statement begins with zero or more labels, optionally followed by a
2870 key symbol which determines what kind of statement it is. The key
2871 symbol determines the syntax of the rest of the statement. If the
2872 symbol begins with a dot @samp{.} then the statement is an assembler
2873 directive: typically valid for any computer. If the symbol begins with
2874 a letter the statement is an assembly language @dfn{instruction}: it
2875 assembles into a machine language instruction.
2877 Different versions of @command{@value{AS}} for different computers
2878 recognize different instructions. In fact, the same symbol may
2879 represent a different instruction in a different computer's assembly
2883 @cindex @code{:} (label)
2884 @cindex label (@code{:})
2885 A label is a symbol immediately followed by a colon (@code{:}).
2886 Whitespace before a label or after a colon is permitted, but you may not
2887 have whitespace between a label's symbol and its colon. @xref{Labels}.
2890 For HPPA targets, labels need not be immediately followed by a colon, but
2891 the definition of a label must begin in column zero. This also implies that
2892 only one label may be defined on each line.
2896 label: .directive followed by something
2897 another_label: # This is an empty statement.
2898 instruction operand_1, operand_2, @dots{}
2905 A constant is a number, written so that its value is known by
2906 inspection, without knowing any context. Like this:
2909 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2910 .ascii "Ring the bell\7" # A string constant.
2911 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2912 .float 0f-314159265358979323846264338327\
2913 95028841971.693993751E-40 # - pi, a flonum.
2918 * Characters:: Character Constants
2919 * Numbers:: Number Constants
2923 @subsection Character Constants
2925 @cindex character constants
2926 @cindex constants, character
2927 There are two kinds of character constants. A @dfn{character} stands
2928 for one character in one byte and its value may be used in
2929 numeric expressions. String constants (properly called string
2930 @emph{literals}) are potentially many bytes and their values may not be
2931 used in arithmetic expressions.
2935 * Chars:: Characters
2939 @subsubsection Strings
2941 @cindex string constants
2942 @cindex constants, string
2943 A @dfn{string} is written between double-quotes. It may contain
2944 double-quotes or null characters. The way to get special characters
2945 into a string is to @dfn{escape} these characters: precede them with
2946 a backslash @samp{\} character. For example @samp{\\} represents
2947 one backslash: the first @code{\} is an escape which tells
2948 @command{@value{AS}} to interpret the second character literally as a backslash
2949 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2950 escape character). The complete list of escapes follows.
2952 @cindex escape codes, character
2953 @cindex character escape codes
2954 @c NOTE: Cindex entries must not start with a backlash character.
2955 @c NOTE: This confuses the pdf2texi script when it is creating the
2956 @c NOTE: index based upon the first character and so it generates:
2957 @c NOTE: \initial {\\}
2958 @c NOTE: which then results in the error message:
2959 @c NOTE: Argument of \\ has an extra }.
2960 @c NOTE: So in the index entries below a space character has been
2961 @c NOTE: prepended to avoid this problem.
2964 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2966 @cindex @code{ \b} (backspace character)
2967 @cindex backspace (@code{\b})
2969 Mnemonic for backspace; for ASCII this is octal code 010.
2972 @c Mnemonic for EOText; for ASCII this is octal code 004.
2974 @cindex @code{ \f} (formfeed character)
2975 @cindex formfeed (@code{\f})
2977 Mnemonic for FormFeed; for ASCII this is octal code 014.
2979 @cindex @code{ \n} (newline character)
2980 @cindex newline (@code{\n})
2982 Mnemonic for newline; for ASCII this is octal code 012.
2985 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2987 @cindex @code{ \r} (carriage return character)
2988 @cindex carriage return (@code{backslash-r})
2990 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2993 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2994 @c other assemblers.
2996 @cindex @code{ \t} (tab)
2997 @cindex tab (@code{\t})
2999 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3002 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3003 @c @item \x @var{digit} @var{digit} @var{digit}
3004 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3006 @cindex @code{ \@var{ddd}} (octal character code)
3007 @cindex octal character code (@code{\@var{ddd}})
3008 @item \ @var{digit} @var{digit} @var{digit}
3009 An octal character code. The numeric code is 3 octal digits.
3010 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3011 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3013 @cindex @code{ \@var{xd...}} (hex character code)
3014 @cindex hex character code (@code{\@var{xd...}})
3015 @item \@code{x} @var{hex-digits...}
3016 A hex character code. All trailing hex digits are combined. Either upper or
3017 lower case @code{x} works.
3019 @cindex @code{ \\} (@samp{\} character)
3020 @cindex backslash (@code{\\})
3022 Represents one @samp{\} character.
3025 @c Represents one @samp{'} (accent acute) character.
3026 @c This is needed in single character literals
3027 @c (@xref{Characters,,Character Constants}.) to represent
3030 @cindex @code{ \"} (doublequote character)
3031 @cindex doublequote (@code{\"})
3033 Represents one @samp{"} character. Needed in strings to represent
3034 this character, because an unescaped @samp{"} would end the string.
3036 @item \ @var{anything-else}
3037 Any other character when escaped by @kbd{\} gives a warning, but
3038 assembles as if the @samp{\} was not present. The idea is that if
3039 you used an escape sequence you clearly didn't want the literal
3040 interpretation of the following character. However @command{@value{AS}} has no
3041 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3042 code and warns you of the fact.
3045 Which characters are escapable, and what those escapes represent,
3046 varies widely among assemblers. The current set is what we think
3047 the BSD 4.2 assembler recognizes, and is a subset of what most C
3048 compilers recognize. If you are in doubt, do not use an escape
3052 @subsubsection Characters
3054 @cindex single character constant
3055 @cindex character, single
3056 @cindex constant, single character
3057 A single character may be written as a single quote immediately followed by
3058 that character. Some backslash escapes apply to characters, @code{\b},
3059 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3060 as for strings, plus @code{\'} for a single quote. So if you want to write the
3061 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3062 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3065 @ifclear abnormal-separator
3066 (or semicolon @samp{;})
3068 @ifset abnormal-separator
3070 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3075 immediately following an acute accent is taken as a literal character
3076 and does not count as the end of a statement. The value of a character
3077 constant in a numeric expression is the machine's byte-wide code for
3078 that character. @command{@value{AS}} assumes your character code is ASCII:
3079 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3082 @subsection Number Constants
3084 @cindex constants, number
3085 @cindex number constants
3086 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3087 are stored in the target machine. @emph{Integers} are numbers that
3088 would fit into an @code{int} in the C language. @emph{Bignums} are
3089 integers, but they are stored in more than 32 bits. @emph{Flonums}
3090 are floating point numbers, described below.
3093 * Integers:: Integers
3101 @subsubsection Integers
3103 @cindex constants, integer
3105 @cindex binary integers
3106 @cindex integers, binary
3107 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3108 the binary digits @samp{01}.
3110 @cindex octal integers
3111 @cindex integers, octal
3112 An octal integer is @samp{0} followed by zero or more of the octal
3113 digits (@samp{01234567}).
3115 @cindex decimal integers
3116 @cindex integers, decimal
3117 A decimal integer starts with a non-zero digit followed by zero or
3118 more digits (@samp{0123456789}).
3120 @cindex hexadecimal integers
3121 @cindex integers, hexadecimal
3122 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3123 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3125 Integers have the usual values. To denote a negative integer, use
3126 the prefix operator @samp{-} discussed under expressions
3127 (@pxref{Prefix Ops,,Prefix Operators}).
3130 @subsubsection Bignums
3133 @cindex constants, bignum
3134 A @dfn{bignum} has the same syntax and semantics as an integer
3135 except that the number (or its negative) takes more than 32 bits to
3136 represent in binary. The distinction is made because in some places
3137 integers are permitted while bignums are not.
3140 @subsubsection Flonums
3142 @cindex floating point numbers
3143 @cindex constants, floating point
3145 @cindex precision, floating point
3146 A @dfn{flonum} represents a floating point number. The translation is
3147 indirect: a decimal floating point number from the text is converted by
3148 @command{@value{AS}} to a generic binary floating point number of more than
3149 sufficient precision. This generic floating point number is converted
3150 to a particular computer's floating point format (or formats) by a
3151 portion of @command{@value{AS}} specialized to that computer.
3153 A flonum is written by writing (in order)
3158 (@samp{0} is optional on the HPPA.)
3162 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3164 @kbd{e} is recommended. Case is not important.
3166 @c FIXME: verify if flonum syntax really this vague for most cases
3167 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3168 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3171 On the H8/300 and Renesas / SuperH SH architectures, the letter must be
3172 one of the letters @samp{DFPRSX} (in upper or lower case).
3174 On the ARC, the letter must be one of the letters @samp{DFRS}
3175 (in upper or lower case).
3177 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3181 One of the letters @samp{DFRS} (in upper or lower case).
3184 One of the letters @samp{DFPRSX} (in upper or lower case).
3187 The letter @samp{E} (upper case only).
3192 An optional sign: either @samp{+} or @samp{-}.
3195 An optional @dfn{integer part}: zero or more decimal digits.
3198 An optional @dfn{fractional part}: @samp{.} followed by zero
3199 or more decimal digits.
3202 An optional exponent, consisting of:
3206 An @samp{E} or @samp{e}.
3207 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3208 @c principle this can perfectly well be different on different targets.
3210 Optional sign: either @samp{+} or @samp{-}.
3212 One or more decimal digits.
3217 At least one of the integer part or the fractional part must be
3218 present. The floating point number has the usual base-10 value.
3220 @command{@value{AS}} does all processing using integers. Flonums are computed
3221 independently of any floating point hardware in the computer running
3222 @command{@value{AS}}.
3225 @chapter Sections and Relocation
3230 * Secs Background:: Background
3231 * Ld Sections:: Linker Sections
3232 * As Sections:: Assembler Internal Sections
3233 * Sub-Sections:: Sub-Sections
3237 @node Secs Background
3240 Roughly, a section is a range of addresses, with no gaps; all data
3241 ``in'' those addresses is treated the same for some particular purpose.
3242 For example there may be a ``read only'' section.
3244 @cindex linker, and assembler
3245 @cindex assembler, and linker
3246 The linker @code{@value{LD}} reads many object files (partial programs) and
3247 combines their contents to form a runnable program. When @command{@value{AS}}
3248 emits an object file, the partial program is assumed to start at address 0.
3249 @code{@value{LD}} assigns the final addresses for the partial program, so that
3250 different partial programs do not overlap. This is actually an
3251 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3254 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3255 addresses. These blocks slide to their run-time addresses as rigid
3256 units; their length does not change and neither does the order of bytes
3257 within them. Such a rigid unit is called a @emph{section}. Assigning
3258 run-time addresses to sections is called @dfn{relocation}. It includes
3259 the task of adjusting mentions of object-file addresses so they refer to
3260 the proper run-time addresses.
3262 For the H8/300, and for the Renesas / SuperH SH,
3263 @command{@value{AS}} pads sections if needed to
3264 ensure they end on a word (sixteen bit) boundary.
3267 @cindex standard assembler sections
3268 An object file written by @command{@value{AS}} has at least three sections, any
3269 of which may be empty. These are named @dfn{text}, @dfn{data} and
3274 When it generates COFF or ELF output,
3276 @command{@value{AS}} can also generate whatever other named sections you specify
3277 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3278 If you do not use any directives that place output in the @samp{.text}
3279 or @samp{.data} sections, these sections still exist, but are empty.
3284 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3286 @command{@value{AS}} can also generate whatever other named sections you
3287 specify using the @samp{.space} and @samp{.subspace} directives. See
3288 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3289 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3290 assembler directives.
3293 Additionally, @command{@value{AS}} uses different names for the standard
3294 text, data, and bss sections when generating SOM output. Program text
3295 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3296 BSS into @samp{$BSS$}.
3300 Within the object file, the text section starts at address @code{0}, the
3301 data section follows, and the bss section follows the data section.
3304 When generating either SOM or ELF output files on the HPPA, the text
3305 section starts at address @code{0}, the data section at address
3306 @code{0x4000000}, and the bss section follows the data section.
3309 To let @code{@value{LD}} know which data changes when the sections are
3310 relocated, and how to change that data, @command{@value{AS}} also writes to the
3311 object file details of the relocation needed. To perform relocation
3312 @code{@value{LD}} must know, each time an address in the object
3316 Where in the object file is the beginning of this reference to
3319 How long (in bytes) is this reference?
3321 Which section does the address refer to? What is the numeric value of
3323 (@var{address}) @minus{} (@var{start-address of section})?
3326 Is the reference to an address ``Program-Counter relative''?
3329 @cindex addresses, format of
3330 @cindex section-relative addressing
3331 In fact, every address @command{@value{AS}} ever uses is expressed as
3333 (@var{section}) + (@var{offset into section})
3336 Further, most expressions @command{@value{AS}} computes have this section-relative
3339 (For some object formats, such as SOM for the HPPA, some expressions are
3340 symbol-relative instead.)
3343 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3344 @var{N} into section @var{secname}.''
3346 Apart from text, data and bss sections you need to know about the
3347 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3348 addresses in the absolute section remain unchanged. For example, address
3349 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3350 @code{@value{LD}}. Although the linker never arranges two partial programs'
3351 data sections with overlapping addresses after linking, @emph{by definition}
3352 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3353 part of a program is always the same address when the program is running as
3354 address @code{@{absolute@ 239@}} in any other part of the program.
3356 The idea of sections is extended to the @dfn{undefined} section. Any
3357 address whose section is unknown at assembly time is by definition
3358 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3359 Since numbers are always defined, the only way to generate an undefined
3360 address is to mention an undefined symbol. A reference to a named
3361 common block would be such a symbol: its value is unknown at assembly
3362 time so it has section @emph{undefined}.
3364 By analogy the word @emph{section} is used to describe groups of sections in
3365 the linked program. @code{@value{LD}} puts all partial programs' text
3366 sections in contiguous addresses in the linked program. It is
3367 customary to refer to the @emph{text section} of a program, meaning all
3368 the addresses of all partial programs' text sections. Likewise for
3369 data and bss sections.
3371 Some sections are manipulated by @code{@value{LD}}; others are invented for
3372 use of @command{@value{AS}} and have no meaning except during assembly.
3375 @section Linker Sections
3376 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3381 @cindex named sections
3382 @cindex sections, named
3383 @item named sections
3386 @cindex text section
3387 @cindex data section
3391 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3392 separate but equal sections. Anything you can say of one section is
3395 When the program is running, however, it is
3396 customary for the text section to be unalterable. The
3397 text section is often shared among processes: it contains
3398 instructions, constants and the like. The data section of a running
3399 program is usually alterable: for example, C variables would be stored
3400 in the data section.
3405 This section contains zeroed bytes when your program begins running. It
3406 is used to hold uninitialized variables or common storage. The length of
3407 each partial program's bss section is important, but because it starts
3408 out containing zeroed bytes there is no need to store explicit zero
3409 bytes in the object file. The bss section was invented to eliminate
3410 those explicit zeros from object files.
3412 @cindex absolute section
3413 @item absolute section
3414 Address 0 of this section is always ``relocated'' to runtime address 0.
3415 This is useful if you want to refer to an address that @code{@value{LD}} must
3416 not change when relocating. In this sense we speak of absolute
3417 addresses being ``unrelocatable'': they do not change during relocation.
3419 @cindex undefined section
3420 @item undefined section
3421 This ``section'' is a catch-all for address references to objects not in
3422 the preceding sections.
3423 @c FIXME: ref to some other doc on obj-file formats could go here.
3426 @cindex relocation example
3427 An idealized example of three relocatable sections follows.
3429 The example uses the traditional section names @samp{.text} and @samp{.data}.
3431 Memory addresses are on the horizontal axis.
3435 @c END TEXI2ROFF-KILL
3438 partial program # 1: |ttttt|dddd|00|
3445 partial program # 2: |TTT|DDD|000|
3448 +--+---+-----+--+----+---+-----+~~
3449 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3450 +--+---+-----+--+----+---+-----+~~
3452 addresses: 0 @dots{}
3459 \line{\it Partial program \#1: \hfil}
3460 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3461 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3463 \line{\it Partial program \#2: \hfil}
3464 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3465 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3467 \line{\it linked program: \hfil}
3468 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3469 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3470 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3471 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3473 \line{\it addresses: \hfil}
3477 @c END TEXI2ROFF-KILL
3480 @section Assembler Internal Sections
3482 @cindex internal assembler sections
3483 @cindex sections in messages, internal
3484 These sections are meant only for the internal use of @command{@value{AS}}. They
3485 have no meaning at run-time. You do not really need to know about these
3486 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3487 warning messages, so it might be helpful to have an idea of their
3488 meanings to @command{@value{AS}}. These sections are used to permit the
3489 value of every expression in your assembly language program to be a
3490 section-relative address.
3493 @cindex assembler internal logic error
3494 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3495 An internal assembler logic error has been found. This means there is a
3496 bug in the assembler.
3498 @cindex expr (internal section)
3500 The assembler stores complex expression internally as combinations of
3501 symbols. When it needs to represent an expression as a symbol, it puts
3502 it in the expr section.
3504 @c FIXME item transfer[t] vector preload
3505 @c FIXME item transfer[t] vector postload
3506 @c FIXME item register
3510 @section Sub-Sections
3512 @cindex numbered subsections
3513 @cindex grouping data
3519 fall into two sections: text and data.
3521 You may have separate groups of
3523 data in named sections
3527 data in named sections
3533 that you want to end up near to each other in the object file, even though they
3534 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3535 use @dfn{subsections} for this purpose. Within each section, there can be
3536 numbered subsections with values from 0 to 8192. Objects assembled into the
3537 same subsection go into the object file together with other objects in the same
3538 subsection. For example, a compiler might want to store constants in the text
3539 section, but might not want to have them interspersed with the program being
3540 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3541 section of code being output, and a @samp{.text 1} before each group of
3542 constants being output.
3544 Subsections are optional. If you do not use subsections, everything
3545 goes in subsection number zero.
3548 Each subsection is zero-padded up to a multiple of four bytes.
3549 (Subsections may be padded a different amount on different flavors
3550 of @command{@value{AS}}.)
3554 On the H8/300 platform, each subsection is zero-padded to a word
3555 boundary (two bytes).
3556 The same is true on the Renesas SH.
3560 Subsections appear in your object file in numeric order, lowest numbered
3561 to highest. (All this to be compatible with other people's assemblers.)
3562 The object file contains no representation of subsections; @code{@value{LD}} and
3563 other programs that manipulate object files see no trace of them.
3564 They just see all your text subsections as a text section, and all your
3565 data subsections as a data section.
3567 To specify which subsection you want subsequent statements assembled
3568 into, use a numeric argument to specify it, in a @samp{.text
3569 @var{expression}} or a @samp{.data @var{expression}} statement.
3572 When generating COFF output, you
3577 can also use an extra subsection
3578 argument with arbitrary named sections: @samp{.section @var{name},
3583 When generating ELF output, you
3588 can also use the @code{.subsection} directive (@pxref{SubSection})
3589 to specify a subsection: @samp{.subsection @var{expression}}.
3591 @var{Expression} should be an absolute expression
3592 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3593 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3594 begins in @code{text 0}. For instance:
3596 .text 0 # The default subsection is text 0 anyway.
3597 .ascii "This lives in the first text subsection. *"
3599 .ascii "But this lives in the second text subsection."
3601 .ascii "This lives in the data section,"
3602 .ascii "in the first data subsection."
3604 .ascii "This lives in the first text section,"
3605 .ascii "immediately following the asterisk (*)."
3608 Each section has a @dfn{location counter} incremented by one for every byte
3609 assembled into that section. Because subsections are merely a convenience
3610 restricted to @command{@value{AS}} there is no concept of a subsection location
3611 counter. There is no way to directly manipulate a location counter---but the
3612 @code{.align} directive changes it, and any label definition captures its
3613 current value. The location counter of the section where statements are being
3614 assembled is said to be the @dfn{active} location counter.
3617 @section bss Section
3620 @cindex common variable storage
3621 The bss section is used for local common variable storage.
3622 You may allocate address space in the bss section, but you may
3623 not dictate data to load into it before your program executes. When
3624 your program starts running, all the contents of the bss
3625 section are zeroed bytes.
3627 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3628 @ref{Lcomm,,@code{.lcomm}}.
3630 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3631 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3634 When assembling for a target which supports multiple sections, such as ELF or
3635 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3636 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3637 section. Typically the section will only contain symbol definitions and
3638 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3645 Symbols are a central concept: the programmer uses symbols to name
3646 things, the linker uses symbols to link, and the debugger uses symbols
3650 @cindex debuggers, and symbol order
3651 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3652 the same order they were declared. This may break some debuggers.
3657 * Setting Symbols:: Giving Symbols Other Values
3658 * Symbol Names:: Symbol Names
3659 * Dot:: The Special Dot Symbol
3660 * Symbol Attributes:: Symbol Attributes
3667 A @dfn{label} is written as a symbol immediately followed by a colon
3668 @samp{:}. The symbol then represents the current value of the
3669 active location counter, and is, for example, a suitable instruction
3670 operand. You are warned if you use the same symbol to represent two
3671 different locations: the first definition overrides any other
3675 On the HPPA, the usual form for a label need not be immediately followed by a
3676 colon, but instead must start in column zero. Only one label may be defined on
3677 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3678 provides a special directive @code{.label} for defining labels more flexibly.
3681 @node Setting Symbols
3682 @section Giving Symbols Other Values
3684 @cindex assigning values to symbols
3685 @cindex symbol values, assigning
3686 A symbol can be given an arbitrary value by writing a symbol, followed
3687 by an equals sign @samp{=}, followed by an expression
3688 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3689 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3690 equals sign @samp{=}@samp{=} here represents an equivalent of the
3691 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3694 Blackfin does not support symbol assignment with @samp{=}.
3698 @section Symbol Names
3700 @cindex symbol names
3701 @cindex names, symbol
3702 @ifclear SPECIAL-SYMS
3703 Symbol names begin with a letter or with one of @samp{._}. On most
3704 machines, you can also use @code{$} in symbol names; exceptions are
3705 noted in @ref{Machine Dependencies}. That character may be followed by any
3706 string of digits, letters, dollar signs (unless otherwise noted for a
3707 particular target machine), and underscores.
3711 Symbol names begin with a letter or with one of @samp{._}. On the
3712 Renesas SH you can also use @code{$} in symbol names. That
3713 character may be followed by any string of digits, letters, dollar signs (save
3714 on the H8/300), and underscores.
3718 Case of letters is significant: @code{foo} is a different symbol name
3721 Symbol names do not start with a digit. An exception to this rule is made for
3722 Local Labels. See below.
3724 Multibyte characters are supported. To generate a symbol name containing
3725 multibyte characters enclose it within double quotes and use escape codes. cf
3726 @xref{Strings}. Generating a multibyte symbol name from a label is not
3727 currently supported.
3729 Each symbol has exactly one name. Each name in an assembly language program
3730 refers to exactly one symbol. You may use that symbol name any number of times
3733 @subheading Local Symbol Names
3735 @cindex local symbol names
3736 @cindex symbol names, local
3737 A local symbol is any symbol beginning with certain local label prefixes.
3738 By default, the local label prefix is @samp{.L} for ELF systems or
3739 @samp{L} for traditional a.out systems, but each target may have its own
3740 set of local label prefixes.
3742 On the HPPA local symbols begin with @samp{L$}.
3745 Local symbols are defined and used within the assembler, but they are
3746 normally not saved in object files. Thus, they are not visible when debugging.
3747 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3748 to retain the local symbols in the object files.
3750 @subheading Local Labels
3752 @cindex local labels
3753 @cindex temporary symbol names
3754 @cindex symbol names, temporary
3755 Local labels are different from local symbols. Local labels help compilers and
3756 programmers use names temporarily. They create symbols which are guaranteed to
3757 be unique over the entire scope of the input source code and which can be
3758 referred to by a simple notation. To define a local label, write a label of
3759 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3760 To refer to the most recent previous definition of that label write
3761 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3762 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3763 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3765 There is no restriction on how you can use these labels, and you can reuse them
3766 too. So that it is possible to repeatedly define the same local label (using
3767 the same number @samp{@b{N}}), although you can only refer to the most recently
3768 defined local label of that number (for a backwards reference) or the next
3769 definition of a specific local label for a forward reference. It is also worth
3770 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3771 implemented in a slightly more efficient manner than the others.
3782 Which is the equivalent of:
3785 label_1: branch label_3
3786 label_2: branch label_1
3787 label_3: branch label_4
3788 label_4: branch label_3
3791 Local label names are only a notational device. They are immediately
3792 transformed into more conventional symbol names before the assembler uses them.
3793 The symbol names are stored in the symbol table, appear in error messages, and
3794 are optionally emitted to the object file. The names are constructed using
3798 @item @emph{local label prefix}
3799 All local symbols begin with the system-specific local label prefix.
3800 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3801 that start with the local label prefix. These labels are
3802 used for symbols you are never intended to see. If you use the
3803 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3804 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3805 you may use them in debugging.
3808 This is the number that was used in the local label definition. So if the
3809 label is written @samp{55:} then the number is @samp{55}.
3812 This unusual character is included so you do not accidentally invent a symbol
3813 of the same name. The character has ASCII value of @samp{\002} (control-B).
3815 @item @emph{ordinal number}
3816 This is a serial number to keep the labels distinct. The first definition of
3817 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3818 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3819 the number @samp{1} and its 15th definition gets @samp{15} as well.
3822 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3823 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3825 @subheading Dollar Local Labels
3826 @cindex dollar local symbols
3828 On some targets @code{@value{AS}} also supports an even more local form of
3829 local labels called dollar labels. These labels go out of scope (i.e., they
3830 become undefined) as soon as a non-local label is defined. Thus they remain
3831 valid for only a small region of the input source code. Normal local labels,
3832 by contrast, remain in scope for the entire file, or until they are redefined
3833 by another occurrence of the same local label.
3835 Dollar labels are defined in exactly the same way as ordinary local labels,
3836 except that they have a dollar sign suffix to their numeric value, e.g.,
3839 They can also be distinguished from ordinary local labels by their transformed
3840 names which use ASCII character @samp{\001} (control-A) as the magic character
3841 to distinguish them from ordinary labels. For example, the fifth definition of
3842 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3845 @section The Special Dot Symbol
3847 @cindex dot (symbol)
3848 @cindex @code{.} (symbol)
3849 @cindex current address
3850 @cindex location counter
3851 The special symbol @samp{.} refers to the current address that
3852 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3853 .long .} defines @code{melvin} to contain its own address.
3854 Assigning a value to @code{.} is treated the same as a @code{.org}
3856 @ifclear no-space-dir
3857 Thus, the expression @samp{.=.+4} is the same as saying
3861 @node Symbol Attributes
3862 @section Symbol Attributes
3864 @cindex symbol attributes
3865 @cindex attributes, symbol
3866 Every symbol has, as well as its name, the attributes ``Value'' and
3867 ``Type''. Depending on output format, symbols can also have auxiliary
3870 The detailed definitions are in @file{a.out.h}.
3873 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3874 all these attributes, and probably won't warn you. This makes the
3875 symbol an externally defined symbol, which is generally what you
3879 * Symbol Value:: Value
3880 * Symbol Type:: Type
3882 * a.out Symbols:: Symbol Attributes: @code{a.out}
3885 * COFF Symbols:: Symbol Attributes for COFF
3888 * SOM Symbols:: Symbol Attributes for SOM
3895 @cindex value of a symbol
3896 @cindex symbol value
3897 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3898 location in the text, data, bss or absolute sections the value is the
3899 number of addresses from the start of that section to the label.
3900 Naturally for text, data and bss sections the value of a symbol changes
3901 as @code{@value{LD}} changes section base addresses during linking. Absolute
3902 symbols' values do not change during linking: that is why they are
3905 The value of an undefined symbol is treated in a special way. If it is
3906 0 then the symbol is not defined in this assembler source file, and
3907 @code{@value{LD}} tries to determine its value from other files linked into the
3908 same program. You make this kind of symbol simply by mentioning a symbol
3909 name without defining it. A non-zero value represents a @code{.comm}
3910 common declaration. The value is how much common storage to reserve, in
3911 bytes (addresses). The symbol refers to the first address of the
3917 @cindex type of a symbol
3919 The type attribute of a symbol contains relocation (section)
3920 information, any flag settings indicating that a symbol is external, and
3921 (optionally), other information for linkers and debuggers. The exact
3922 format depends on the object-code output format in use.
3926 @subsection Symbol Attributes: @code{a.out}
3928 @cindex @code{a.out} symbol attributes
3929 @cindex symbol attributes, @code{a.out}
3932 * Symbol Desc:: Descriptor
3933 * Symbol Other:: Other
3937 @subsubsection Descriptor
3939 @cindex descriptor, of @code{a.out} symbol
3940 This is an arbitrary 16-bit value. You may establish a symbol's
3941 descriptor value by using a @code{.desc} statement
3942 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3943 @command{@value{AS}}.
3946 @subsubsection Other
3948 @cindex other attribute, of @code{a.out} symbol
3949 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3954 @subsection Symbol Attributes for COFF
3956 @cindex COFF symbol attributes
3957 @cindex symbol attributes, COFF
3959 The COFF format supports a multitude of auxiliary symbol attributes;
3960 like the primary symbol attributes, they are set between @code{.def} and
3961 @code{.endef} directives.
3963 @subsubsection Primary Attributes
3965 @cindex primary attributes, COFF symbols
3966 The symbol name is set with @code{.def}; the value and type,
3967 respectively, with @code{.val} and @code{.type}.
3969 @subsubsection Auxiliary Attributes
3971 @cindex auxiliary attributes, COFF symbols
3972 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3973 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3974 table information for COFF.
3979 @subsection Symbol Attributes for SOM
3981 @cindex SOM symbol attributes
3982 @cindex symbol attributes, SOM
3984 The SOM format for the HPPA supports a multitude of symbol attributes set with
3985 the @code{.EXPORT} and @code{.IMPORT} directives.
3987 The attributes are described in @cite{HP9000 Series 800 Assembly
3988 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3989 @code{EXPORT} assembler directive documentation.
3993 @chapter Expressions
3997 @cindex numeric values
3998 An @dfn{expression} specifies an address or numeric value.
3999 Whitespace may precede and/or follow an expression.
4001 The result of an expression must be an absolute number, or else an offset into
4002 a particular section. If an expression is not absolute, and there is not
4003 enough information when @command{@value{AS}} sees the expression to know its
4004 section, a second pass over the source program might be necessary to interpret
4005 the expression---but the second pass is currently not implemented.
4006 @command{@value{AS}} aborts with an error message in this situation.
4009 * Empty Exprs:: Empty Expressions
4010 * Integer Exprs:: Integer Expressions
4014 @section Empty Expressions
4016 @cindex empty expressions
4017 @cindex expressions, empty
4018 An empty expression has no value: it is just whitespace or null.
4019 Wherever an absolute expression is required, you may omit the
4020 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4021 is compatible with other assemblers.
4024 @section Integer Expressions
4026 @cindex integer expressions
4027 @cindex expressions, integer
4028 An @dfn{integer expression} is one or more @emph{arguments} delimited
4029 by @emph{operators}.
4032 * Arguments:: Arguments
4033 * Operators:: Operators
4034 * Prefix Ops:: Prefix Operators
4035 * Infix Ops:: Infix Operators
4039 @subsection Arguments
4041 @cindex expression arguments
4042 @cindex arguments in expressions
4043 @cindex operands in expressions
4044 @cindex arithmetic operands
4045 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4046 contexts arguments are sometimes called ``arithmetic operands''. In
4047 this manual, to avoid confusing them with the ``instruction operands'' of
4048 the machine language, we use the term ``argument'' to refer to parts of
4049 expressions only, reserving the word ``operand'' to refer only to machine
4050 instruction operands.
4052 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4053 @var{section} is one of text, data, bss, absolute,
4054 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4057 Numbers are usually integers.
4059 A number can be a flonum or bignum. In this case, you are warned
4060 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4061 these 32 bits are an integer. You may write integer-manipulating
4062 instructions that act on exotic constants, compatible with other
4065 @cindex subexpressions
4066 Subexpressions are a left parenthesis @samp{(} followed by an integer
4067 expression, followed by a right parenthesis @samp{)}; or a prefix
4068 operator followed by an argument.
4071 @subsection Operators
4073 @cindex operators, in expressions
4074 @cindex arithmetic functions
4075 @cindex functions, in expressions
4076 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4077 operators are followed by an argument. Infix operators appear
4078 between their arguments. Operators may be preceded and/or followed by
4082 @subsection Prefix Operator
4084 @cindex prefix operators
4085 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4086 one argument, which must be absolute.
4088 @c the tex/end tex stuff surrounding this small table is meant to make
4089 @c it align, on the printed page, with the similar table in the next
4090 @c section (which is inside an enumerate).
4092 \global\advance\leftskip by \itemindent
4097 @dfn{Negation}. Two's complement negation.
4099 @dfn{Complementation}. Bitwise not.
4103 \global\advance\leftskip by -\itemindent
4107 @subsection Infix Operators
4109 @cindex infix operators
4110 @cindex operators, permitted arguments
4111 @dfn{Infix operators} take two arguments, one on either side. Operators
4112 have precedence, but operations with equal precedence are performed left
4113 to right. Apart from @code{+} or @option{-}, both arguments must be
4114 absolute, and the result is absolute.
4117 @cindex operator precedence
4118 @cindex precedence of operators
4125 @dfn{Multiplication}.
4128 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4134 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4137 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4141 Intermediate precedence
4146 @dfn{Bitwise Inclusive Or}.
4152 @dfn{Bitwise Exclusive Or}.
4155 @dfn{Bitwise Or Not}.
4162 @cindex addition, permitted arguments
4163 @cindex plus, permitted arguments
4164 @cindex arguments for addition
4166 @dfn{Addition}. If either argument is absolute, the result has the section of
4167 the other argument. You may not add together arguments from different
4170 @cindex subtraction, permitted arguments
4171 @cindex minus, permitted arguments
4172 @cindex arguments for subtraction
4174 @dfn{Subtraction}. If the right argument is absolute, the
4175 result has the section of the left argument.
4176 If both arguments are in the same section, the result is absolute.
4177 You may not subtract arguments from different sections.
4178 @c FIXME is there still something useful to say about undefined - undefined ?
4180 @cindex comparison expressions
4181 @cindex expressions, comparison
4186 @dfn{Is Not Equal To}
4190 @dfn{Is Greater Than}
4192 @dfn{Is Greater Than Or Equal To}
4194 @dfn{Is Less Than Or Equal To}
4196 The comparison operators can be used as infix operators. A true results has a
4197 value of -1 whereas a false result has a value of 0. Note, these operators
4198 perform signed comparisons.
4201 @item Lowest Precedence
4210 These two logical operations can be used to combine the results of sub
4211 expressions. Note, unlike the comparison operators a true result returns a
4212 value of 1 but a false results does still return 0. Also note that the logical
4213 or operator has a slightly lower precedence than logical and.
4218 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4219 address; you can only have a defined section in one of the two arguments.
4222 @chapter Assembler Directives
4224 @cindex directives, machine independent
4225 @cindex pseudo-ops, machine independent
4226 @cindex machine independent directives
4227 All assembler directives have names that begin with a period (@samp{.}).
4228 The names are case insensitive for most targets, and usually written
4231 This chapter discusses directives that are available regardless of the
4232 target machine configuration for the @sc{gnu} assembler.
4234 Some machine configurations provide additional directives.
4235 @xref{Machine Dependencies}.
4238 @ifset machine-directives
4239 @xref{Machine Dependencies}, for additional directives.
4244 * Abort:: @code{.abort}
4246 * ABORT (COFF):: @code{.ABORT}
4249 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4250 * Altmacro:: @code{.altmacro}
4251 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4252 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4253 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4254 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4255 * Byte:: @code{.byte @var{expressions}}
4256 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4257 * Comm:: @code{.comm @var{symbol} , @var{length} }
4258 * Data:: @code{.data @var{subsection}}
4259 * Dc:: @code{.dc[@var{size}] @var{expressions}}
4260 * Dcb:: @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4261 * Ds:: @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4263 * Def:: @code{.def @var{name}}
4266 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4272 * Double:: @code{.double @var{flonums}}
4273 * Eject:: @code{.eject}
4274 * Else:: @code{.else}
4275 * Elseif:: @code{.elseif}
4278 * Endef:: @code{.endef}
4281 * Endfunc:: @code{.endfunc}
4282 * Endif:: @code{.endif}
4283 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4284 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4285 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4287 * Error:: @code{.error @var{string}}
4288 * Exitm:: @code{.exitm}
4289 * Extern:: @code{.extern}
4290 * Fail:: @code{.fail}
4291 * File:: @code{.file}
4292 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4293 * Float:: @code{.float @var{flonums}}
4294 * Func:: @code{.func}
4295 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4297 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4298 * Hidden:: @code{.hidden @var{names}}
4301 * hword:: @code{.hword @var{expressions}}
4302 * Ident:: @code{.ident}
4303 * If:: @code{.if @var{absolute expression}}
4304 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4305 * Include:: @code{.include "@var{file}"}
4306 * Int:: @code{.int @var{expressions}}
4308 * Internal:: @code{.internal @var{names}}
4311 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4312 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4313 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4314 * Lflags:: @code{.lflags}
4315 @ifclear no-line-dir
4316 * Line:: @code{.line @var{line-number}}
4319 * Linkonce:: @code{.linkonce [@var{type}]}
4320 * List:: @code{.list}
4321 * Ln:: @code{.ln @var{line-number}}
4322 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4323 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4325 * Local:: @code{.local @var{names}}
4328 * Long:: @code{.long @var{expressions}}
4330 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4333 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4334 * MRI:: @code{.mri @var{val}}
4335 * Noaltmacro:: @code{.noaltmacro}
4336 * Nolist:: @code{.nolist}
4337 * Nops:: @code{.nops @var{size}[, @var{control}]}
4338 * Octa:: @code{.octa @var{bignums}}
4339 * Offset:: @code{.offset @var{loc}}
4340 * Org:: @code{.org @var{new-lc}, @var{fill}}
4341 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4343 * PopSection:: @code{.popsection}
4344 * Previous:: @code{.previous}
4347 * Print:: @code{.print @var{string}}
4349 * Protected:: @code{.protected @var{names}}
4352 * Psize:: @code{.psize @var{lines}, @var{columns}}
4353 * Purgem:: @code{.purgem @var{name}}
4355 * PushSection:: @code{.pushsection @var{name}}
4358 * Quad:: @code{.quad @var{bignums}}
4359 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4360 * Rept:: @code{.rept @var{count}}
4361 * Sbttl:: @code{.sbttl "@var{subheading}"}
4363 * Scl:: @code{.scl @var{class}}
4366 * Section:: @code{.section @var{name}[, @var{flags}]}
4369 * Set:: @code{.set @var{symbol}, @var{expression}}
4370 * Short:: @code{.short @var{expressions}}
4371 * Single:: @code{.single @var{flonums}}
4373 * Size:: @code{.size [@var{name} , @var{expression}]}
4375 @ifclear no-space-dir
4376 * Skip:: @code{.skip @var{size} [,@var{fill}]}
4379 * Sleb128:: @code{.sleb128 @var{expressions}}
4380 @ifclear no-space-dir
4381 * Space:: @code{.space @var{size} [,@var{fill}]}
4384 * Stab:: @code{.stabd, .stabn, .stabs}
4387 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4388 * Struct:: @code{.struct @var{expression}}
4390 * SubSection:: @code{.subsection}
4391 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4395 * Tag:: @code{.tag @var{structname}}
4398 * Text:: @code{.text @var{subsection}}
4399 * Title:: @code{.title "@var{heading}"}
4401 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4404 * Uleb128:: @code{.uleb128 @var{expressions}}
4406 * Val:: @code{.val @var{addr}}
4410 * Version:: @code{.version "@var{string}"}
4411 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4412 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4415 * Warning:: @code{.warning @var{string}}
4416 * Weak:: @code{.weak @var{names}}
4417 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4418 * Word:: @code{.word @var{expressions}}
4419 @ifclear no-space-dir
4420 * Zero:: @code{.zero @var{size}}
4423 * 2byte:: @code{.2byte @var{expressions}}
4424 * 4byte:: @code{.4byte @var{expressions}}
4425 * 8byte:: @code{.8byte @var{bignums}}
4427 * Deprecated:: Deprecated Directives
4431 @section @code{.abort}
4433 @cindex @code{abort} directive
4434 @cindex stopping the assembly
4435 This directive stops the assembly immediately. It is for
4436 compatibility with other assemblers. The original idea was that the
4437 assembly language source would be piped into the assembler. If the sender
4438 of the source quit, it could use this directive tells @command{@value{AS}} to
4439 quit also. One day @code{.abort} will not be supported.
4443 @section @code{.ABORT} (COFF)
4445 @cindex @code{ABORT} directive
4446 When producing COFF output, @command{@value{AS}} accepts this directive as a
4447 synonym for @samp{.abort}.
4452 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4454 @cindex padding the location counter
4455 @cindex @code{align} directive
4456 Pad the location counter (in the current subsection) to a particular storage
4457 boundary. The first expression (which must be absolute) is the alignment
4458 required, as described below.
4460 The second expression (also absolute) gives the fill value to be stored in the
4461 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4462 padding bytes are normally zero. However, on most systems, if the section is
4463 marked as containing code and the fill value is omitted, the space is filled
4464 with no-op instructions.
4466 The third expression is also absolute, and is also optional. If it is present,
4467 it is the maximum number of bytes that should be skipped by this alignment
4468 directive. If doing the alignment would require skipping more bytes than the
4469 specified maximum, then the alignment is not done at all. You can omit the
4470 fill value (the second argument) entirely by simply using two commas after the
4471 required alignment; this can be useful if you want the alignment to be filled
4472 with no-op instructions when appropriate.
4474 The way the required alignment is specified varies from system to system.
4475 For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
4476 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4477 alignment request in bytes. For example @samp{.align 8} advances
4478 the location counter until it is a multiple of 8. If the location counter
4479 is already a multiple of 8, no change is needed. For the tic54x, the
4480 first expression is the alignment request in words.
4482 For other systems, including ppc, i386 using a.out format, arm and
4483 strongarm, it is the
4484 number of low-order zero bits the location counter must have after
4485 advancement. For example @samp{.align 3} advances the location
4486 counter until it a multiple of 8. If the location counter is already a
4487 multiple of 8, no change is needed.
4489 This inconsistency is due to the different behaviors of the various
4490 native assemblers for these systems which GAS must emulate.
4491 GAS also provides @code{.balign} and @code{.p2align} directives,
4492 described later, which have a consistent behavior across all
4493 architectures (but are specific to GAS).
4496 @section @code{.altmacro}
4497 Enable alternate macro mode, enabling:
4500 @item LOCAL @var{name} [ , @dots{} ]
4501 One additional directive, @code{LOCAL}, is available. It is used to
4502 generate a string replacement for each of the @var{name} arguments, and
4503 replace any instances of @var{name} in each macro expansion. The
4504 replacement string is unique in the assembly, and different for each
4505 separate macro expansion. @code{LOCAL} allows you to write macros that
4506 define symbols, without fear of conflict between separate macro expansions.
4508 @item String delimiters
4509 You can write strings delimited in these other ways besides
4510 @code{"@var{string}"}:
4513 @item '@var{string}'
4514 You can delimit strings with single-quote characters.
4516 @item <@var{string}>
4517 You can delimit strings with matching angle brackets.
4520 @item single-character string escape
4521 To include any single character literally in a string (even if the
4522 character would otherwise have some special meaning), you can prefix the
4523 character with @samp{!} (an exclamation mark). For example, you can
4524 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4526 @item Expression results as strings
4527 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4528 and use the result as a string.
4532 @section @code{.ascii "@var{string}"}@dots{}
4534 @cindex @code{ascii} directive
4535 @cindex string literals
4536 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4537 separated by commas. It assembles each string (with no automatic
4538 trailing zero byte) into consecutive addresses.
4541 @section @code{.asciz "@var{string}"}@dots{}
4543 @cindex @code{asciz} directive
4544 @cindex zero-terminated strings
4545 @cindex null-terminated strings
4546 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4547 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4550 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4552 @cindex padding the location counter given number of bytes
4553 @cindex @code{balign} directive
4554 Pad the location counter (in the current subsection) to a particular
4555 storage boundary. The first expression (which must be absolute) is the
4556 alignment request in bytes. For example @samp{.balign 8} advances
4557 the location counter until it is a multiple of 8. If the location counter
4558 is already a multiple of 8, no change is needed.
4560 The second expression (also absolute) gives the fill value to be stored in the
4561 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4562 padding bytes are normally zero. However, on most systems, if the section is
4563 marked as containing code and the fill value is omitted, the space is filled
4564 with no-op instructions.
4566 The third expression is also absolute, and is also optional. If it is present,
4567 it is the maximum number of bytes that should be skipped by this alignment
4568 directive. If doing the alignment would require skipping more bytes than the
4569 specified maximum, then the alignment is not done at all. You can omit the
4570 fill value (the second argument) entirely by simply using two commas after the
4571 required alignment; this can be useful if you want the alignment to be filled
4572 with no-op instructions when appropriate.
4574 @cindex @code{balignw} directive
4575 @cindex @code{balignl} directive
4576 The @code{.balignw} and @code{.balignl} directives are variants of the
4577 @code{.balign} directive. The @code{.balignw} directive treats the fill
4578 pattern as a two byte word value. The @code{.balignl} directives treats the
4579 fill pattern as a four byte longword value. For example, @code{.balignw
4580 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4581 filled in with the value 0x368d (the exact placement of the bytes depends upon
4582 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4585 @node Bundle directives
4586 @section Bundle directives
4587 @subsection @code{.bundle_align_mode @var{abs-expr}}
4588 @cindex @code{bundle_align_mode} directive
4590 @cindex instruction bundle
4591 @cindex aligned instruction bundle
4592 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4593 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4594 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4595 disabled (which is the default state). If the argument it not zero, it
4596 gives the size of an instruction bundle as a power of two (as for the
4597 @code{.p2align} directive, @pxref{P2align}).
4599 For some targets, it's an ABI requirement that no instruction may span a
4600 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4601 instructions that starts on an aligned boundary. For example, if
4602 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4603 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4604 effect, no single instruction may span a boundary between bundles. If an
4605 instruction would start too close to the end of a bundle for the length of
4606 that particular instruction to fit within the bundle, then the space at the
4607 end of that bundle is filled with no-op instructions so the instruction
4608 starts in the next bundle. As a corollary, it's an error if any single
4609 instruction's encoding is longer than the bundle size.
4611 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4612 @cindex @code{bundle_lock} directive
4613 @cindex @code{bundle_unlock} directive
4614 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4615 allow explicit control over instruction bundle padding. These directives
4616 are only valid when @code{.bundle_align_mode} has been used to enable
4617 aligned instruction bundle mode. It's an error if they appear when
4618 @code{.bundle_align_mode} has not been used at all, or when the last
4619 directive was @w{@code{.bundle_align_mode 0}}.
4621 @cindex bundle-locked
4622 For some targets, it's an ABI requirement that certain instructions may
4623 appear only as part of specified permissible sequences of multiple
4624 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4625 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4626 instruction sequence. For purposes of aligned instruction bundle mode, a
4627 sequence starting with @code{.bundle_lock} and ending with
4628 @code{.bundle_unlock} is treated as a single instruction. That is, the
4629 entire sequence must fit into a single bundle and may not span a bundle
4630 boundary. If necessary, no-op instructions will be inserted before the
4631 first instruction of the sequence so that the whole sequence starts on an
4632 aligned bundle boundary. It's an error if the sequence is longer than the
4635 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4636 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4637 nested. That is, a second @code{.bundle_lock} directive before the next
4638 @code{.bundle_unlock} directive has no effect except that it must be
4639 matched by another closing @code{.bundle_unlock} so that there is the
4640 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4643 @section @code{.byte @var{expressions}}
4645 @cindex @code{byte} directive
4646 @cindex integers, one byte
4647 @code{.byte} expects zero or more expressions, separated by commas.
4648 Each expression is assembled into the next byte.
4650 @node CFI directives
4651 @section CFI directives
4652 @subsection @code{.cfi_sections @var{section_list}}
4653 @cindex @code{cfi_sections} directive
4654 @code{.cfi_sections} may be used to specify whether CFI directives
4655 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4656 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4657 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4658 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4659 directive is not used is @code{.cfi_sections .eh_frame}.
4661 On targets that support compact unwinding tables these can be generated
4662 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4664 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4665 which is used by the @value{TIC6X} target.
4667 The @code{.cfi_sections} directive can be repeated, with the same or different
4668 arguments, provided that CFI generation has not yet started. Once CFI
4669 generation has started however the section list is fixed and any attempts to
4670 redefine it will result in an error.
4672 @subsection @code{.cfi_startproc [simple]}
4673 @cindex @code{cfi_startproc} directive
4674 @code{.cfi_startproc} is used at the beginning of each function that
4675 should have an entry in @code{.eh_frame}. It initializes some internal
4676 data structures. Don't forget to close the function by
4677 @code{.cfi_endproc}.
4679 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4680 it also emits some architecture dependent initial CFI instructions.
4682 @subsection @code{.cfi_endproc}
4683 @cindex @code{cfi_endproc} directive
4684 @code{.cfi_endproc} is used at the end of a function where it closes its
4685 unwind entry previously opened by
4686 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4688 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4689 @cindex @code{cfi_personality} directive
4690 @code{.cfi_personality} defines personality routine and its encoding.
4691 @var{encoding} must be a constant determining how the personality
4692 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4693 argument is not present, otherwise second argument should be
4694 a constant or a symbol name. When using indirect encodings,
4695 the symbol provided should be the location where personality
4696 can be loaded from, not the personality routine itself.
4697 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4698 no personality routine.
4700 @subsection @code{.cfi_personality_id @var{id}}
4701 @cindex @code{cfi_personality_id} directive
4702 @code{cfi_personality_id} defines a personality routine by its index as
4703 defined in a compact unwinding format.
4704 Only valid when generating compact EH frames (i.e.
4705 with @code{.cfi_sections eh_frame_entry}.
4707 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4708 @cindex @code{cfi_fde_data} directive
4709 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4710 used for the current function. These are emitted inline in the
4711 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4712 in the @code{.gnu.extab} section otherwise.
4713 Only valid when generating compact EH frames (i.e.
4714 with @code{.cfi_sections eh_frame_entry}.
4716 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4717 @code{.cfi_lsda} defines LSDA and its encoding.
4718 @var{encoding} must be a constant determining how the LSDA
4719 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4720 argument is not present, otherwise the second argument should be a constant
4721 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4722 meaning that no LSDA is present.
4724 @subsection @code{.cfi_inline_lsda} [@var{align}]
4725 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4726 switches to the corresponding @code{.gnu.extab} section.
4727 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4728 Only valid when generating compact EH frames (i.e.
4729 with @code{.cfi_sections eh_frame_entry}.
4731 The table header and unwinding opcodes will be generated at this point,
4732 so that they are immediately followed by the LSDA data. The symbol
4733 referenced by the @code{.cfi_lsda} directive should still be defined
4734 in case a fallback FDE based encoding is used. The LSDA data is terminated
4735 by a section directive.
4737 The optional @var{align} argument specifies the alignment required.
4738 The alignment is specified as a power of two, as with the
4739 @code{.p2align} directive.
4741 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4742 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4743 address from @var{register} and add @var{offset} to it}.
4745 @subsection @code{.cfi_def_cfa_register @var{register}}
4746 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4747 now on @var{register} will be used instead of the old one. Offset
4750 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4751 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4752 remains the same, but @var{offset} is new. Note that it is the
4753 absolute offset that will be added to a defined register to compute
4756 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4757 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4758 value that is added/subtracted from the previous offset.
4760 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4761 Previous value of @var{register} is saved at offset @var{offset} from
4764 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4765 Previous value of @var{register} is CFA + @var{offset}.
4767 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4768 Previous value of @var{register} is saved at offset @var{offset} from
4769 the current CFA register. This is transformed to @code{.cfi_offset}
4770 using the known displacement of the CFA register from the CFA.
4771 This is often easier to use, because the number will match the
4772 code it's annotating.
4774 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4775 Previous value of @var{register1} is saved in register @var{register2}.
4777 @subsection @code{.cfi_restore @var{register}}
4778 @code{.cfi_restore} says that the rule for @var{register} is now the
4779 same as it was at the beginning of the function, after all initial
4780 instruction added by @code{.cfi_startproc} were executed.
4782 @subsection @code{.cfi_undefined @var{register}}
4783 From now on the previous value of @var{register} can't be restored anymore.
4785 @subsection @code{.cfi_same_value @var{register}}
4786 Current value of @var{register} is the same like in the previous frame,
4787 i.e. no restoration needed.
4789 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4790 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4791 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4792 places them in the current row. This is useful for situations where you have
4793 multiple @code{.cfi_*} directives that need to be undone due to the control
4794 flow of the program. For example, we could have something like this (assuming
4795 the CFA is the value of @code{rbp}):
4805 .cfi_def_cfa %rsp, 8
4808 /* Do something else */
4811 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4812 to the instructions before @code{label}. This means we'd have to add multiple
4813 @code{.cfi} directives after @code{label} to recreate the original save
4814 locations of the registers, as well as setting the CFA back to the value of
4815 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4827 .cfi_def_cfa %rsp, 8
4831 /* Do something else */
4834 That way, the rules for the instructions after @code{label} will be the same
4835 as before the first @code{.cfi_restore} without having to use multiple
4836 @code{.cfi} directives.
4838 @subsection @code{.cfi_return_column @var{register}}
4839 Change return column @var{register}, i.e. the return address is either
4840 directly in @var{register} or can be accessed by rules for @var{register}.
4842 @subsection @code{.cfi_signal_frame}
4843 Mark current function as signal trampoline.
4845 @subsection @code{.cfi_window_save}
4846 SPARC register window has been saved.
4848 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4849 Allows the user to add arbitrary bytes to the unwind info. One
4850 might use this to add OS-specific CFI opcodes, or generic CFI
4851 opcodes that GAS does not yet support.
4853 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4854 The current value of @var{register} is @var{label}. The value of @var{label}
4855 will be encoded in the output file according to @var{encoding}; see the
4856 description of @code{.cfi_personality} for details on this encoding.
4858 The usefulness of equating a register to a fixed label is probably
4859 limited to the return address register. Here, it can be useful to
4860 mark a code segment that has only one return address which is reached
4861 by a direct branch and no copy of the return address exists in memory
4862 or another register.
4865 @section @code{.comm @var{symbol} , @var{length} }
4867 @cindex @code{comm} directive
4868 @cindex symbol, common
4869 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4870 common symbol in one object file may be merged with a defined or common symbol
4871 of the same name in another object file. If @code{@value{LD}} does not see a
4872 definition for the symbol--just one or more common symbols--then it will
4873 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4874 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4875 the same name, and they do not all have the same size, it will allocate space
4876 using the largest size.
4879 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4880 an optional third argument. This is the desired alignment of the symbol,
4881 specified for ELF as a byte boundary (for example, an alignment of 16 means
4882 that the least significant 4 bits of the address should be zero), and for PE
4883 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4884 boundary). The alignment must be an absolute expression, and it must be a
4885 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4886 common symbol, it will use the alignment when placing the symbol. If no
4887 alignment is specified, @command{@value{AS}} will set the alignment to the
4888 largest power of two less than or equal to the size of the symbol, up to a
4889 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4890 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4891 @samp{--section-alignment} option; image file sections in PE are aligned to
4892 multiples of 4096, which is far too large an alignment for ordinary variables.
4893 It is rather the default alignment for (non-debug) sections within object
4894 (@samp{*.o}) files, which are less strictly aligned.}.
4898 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4899 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4903 @section @code{.data @var{subsection}}
4904 @cindex @code{data} directive
4906 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4907 end of the data subsection numbered @var{subsection} (which is an
4908 absolute expression). If @var{subsection} is omitted, it defaults
4912 @section @code{.dc[@var{size}] @var{expressions}}
4913 @cindex @code{dc} directive
4915 The @code{.dc} directive expects zero or more @var{expressions} separated by
4916 commas. These expressions are evaluated and their values inserted into the
4917 current section. The size of the emitted value depends upon the suffix to the
4918 @code{.dc} directive:
4922 Emits N-bit values, where N is the size of an address on the target system.
4926 Emits double precision floating-point values.
4928 Emits 32-bit values.
4930 Emits single precision floating-point values.
4932 Emits 16-bit values.
4933 Note - this is true even on targets where the @code{.word} directive would emit
4936 Emits long double precision floating-point values.
4939 If no suffix is used then @samp{.w} is assumed.
4941 The byte ordering is target dependent, as is the size and format of floating
4945 @section @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4946 @cindex @code{dcb} directive
4947 This directive emits @var{number} copies of @var{fill}, each of @var{size}
4948 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
4949 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
4950 @var{size} suffix, if present, must be one of:
4954 Emits single byte values.
4956 Emits double-precision floating point values.
4958 Emits 4-byte values.
4960 Emits single-precision floating point values.
4962 Emits 2-byte values.
4964 Emits long double-precision floating point values.
4967 If the @var{size} suffix is omitted then @samp{.w} is assumed.
4969 The byte ordering is target dependent, as is the size and format of floating
4973 @section @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4974 @cindex @code{ds} directive
4975 This directive emits @var{number} copies of @var{fill}, each of @var{size}
4976 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
4977 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
4978 @var{size} suffix, if present, must be one of:
4982 Emits single byte values.
4984 Emits 8-byte values.
4986 Emits 4-byte values.
4988 Emits 12-byte values.
4990 Emits 4-byte values.
4992 Emits 2-byte values.
4994 Emits 12-byte values.
4997 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}
4998 suffixes do not indicate that floating-point values are to be inserted.
5000 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5002 The byte ordering is target dependent.
5007 @section @code{.def @var{name}}
5009 @cindex @code{def} directive
5010 @cindex COFF symbols, debugging
5011 @cindex debugging COFF symbols
5012 Begin defining debugging information for a symbol @var{name}; the
5013 definition extends until the @code{.endef} directive is encountered.
5018 @section @code{.desc @var{symbol}, @var{abs-expression}}
5020 @cindex @code{desc} directive
5021 @cindex COFF symbol descriptor
5022 @cindex symbol descriptor, COFF
5023 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5024 to the low 16 bits of an absolute expression.
5027 The @samp{.desc} directive is not available when @command{@value{AS}} is
5028 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5029 object format. For the sake of compatibility, @command{@value{AS}} accepts
5030 it, but produces no output, when configured for COFF.
5036 @section @code{.dim}
5038 @cindex @code{dim} directive
5039 @cindex COFF auxiliary symbol information
5040 @cindex auxiliary symbol information, COFF
5041 This directive is generated by compilers to include auxiliary debugging
5042 information in the symbol table. It is only permitted inside
5043 @code{.def}/@code{.endef} pairs.
5047 @section @code{.double @var{flonums}}
5049 @cindex @code{double} directive
5050 @cindex floating point numbers (double)
5051 @code{.double} expects zero or more flonums, separated by commas. It
5052 assembles floating point numbers.
5054 The exact kind of floating point numbers emitted depends on how
5055 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5059 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5060 in @sc{ieee} format.
5065 @section @code{.eject}
5067 @cindex @code{eject} directive
5068 @cindex new page, in listings
5069 @cindex page, in listings
5070 @cindex listing control: new page
5071 Force a page break at this point, when generating assembly listings.
5074 @section @code{.else}
5076 @cindex @code{else} directive
5077 @code{.else} is part of the @command{@value{AS}} support for conditional
5078 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5079 of code to be assembled if the condition for the preceding @code{.if}
5083 @section @code{.elseif}
5085 @cindex @code{elseif} directive
5086 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5087 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5088 @code{.if} block that would otherwise fill the entire @code{.else} section.
5091 @section @code{.end}
5093 @cindex @code{end} directive
5094 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5095 process anything in the file past the @code{.end} directive.
5099 @section @code{.endef}
5101 @cindex @code{endef} directive
5102 This directive flags the end of a symbol definition begun with
5107 @section @code{.endfunc}
5108 @cindex @code{endfunc} directive
5109 @code{.endfunc} marks the end of a function specified with @code{.func}.
5112 @section @code{.endif}
5114 @cindex @code{endif} directive
5115 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5116 it marks the end of a block of code that is only assembled
5117 conditionally. @xref{If,,@code{.if}}.
5120 @section @code{.equ @var{symbol}, @var{expression}}
5122 @cindex @code{equ} directive
5123 @cindex assigning values to symbols
5124 @cindex symbols, assigning values to
5125 This directive sets the value of @var{symbol} to @var{expression}.
5126 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5129 The syntax for @code{equ} on the HPPA is
5130 @samp{@var{symbol} .equ @var{expression}}.
5134 The syntax for @code{equ} on the Z80 is
5135 @samp{@var{symbol} equ @var{expression}}.
5136 On the Z80 it is an error if @var{symbol} is already defined,
5137 but the symbol is not protected from later redefinition.
5138 Compare @ref{Equiv}.
5142 @section @code{.equiv @var{symbol}, @var{expression}}
5143 @cindex @code{equiv} directive
5144 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5145 the assembler will signal an error if @var{symbol} is already defined. Note a
5146 symbol which has been referenced but not actually defined is considered to be
5149 Except for the contents of the error message, this is roughly equivalent to
5156 plus it protects the symbol from later redefinition.
5159 @section @code{.eqv @var{symbol}, @var{expression}}
5160 @cindex @code{eqv} directive
5161 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5162 evaluate the expression or any part of it immediately. Instead each time
5163 the resulting symbol is used in an expression, a snapshot of its current
5167 @section @code{.err}
5168 @cindex @code{err} directive
5169 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5170 message and, unless the @option{-Z} option was used, it will not generate an
5171 object file. This can be used to signal an error in conditionally compiled code.
5174 @section @code{.error "@var{string}"}
5175 @cindex error directive
5177 Similarly to @code{.err}, this directive emits an error, but you can specify a
5178 string that will be emitted as the error message. If you don't specify the
5179 message, it defaults to @code{".error directive invoked in source file"}.
5180 @xref{Errors, ,Error and Warning Messages}.
5183 .error "This code has not been assembled and tested."
5187 @section @code{.exitm}
5188 Exit early from the current macro definition. @xref{Macro}.
5191 @section @code{.extern}
5193 @cindex @code{extern} directive
5194 @code{.extern} is accepted in the source program---for compatibility
5195 with other assemblers---but it is ignored. @command{@value{AS}} treats
5196 all undefined symbols as external.
5199 @section @code{.fail @var{expression}}
5201 @cindex @code{fail} directive
5202 Generates an error or a warning. If the value of the @var{expression} is 500
5203 or more, @command{@value{AS}} will print a warning message. If the value is less
5204 than 500, @command{@value{AS}} will print an error message. The message will
5205 include the value of @var{expression}. This can occasionally be useful inside
5206 complex nested macros or conditional assembly.
5209 @section @code{.file}
5210 @cindex @code{file} directive
5212 @ifclear no-file-dir
5213 There are two different versions of the @code{.file} directive. Targets
5214 that support DWARF2 line number information use the DWARF2 version of
5215 @code{.file}. Other targets use the default version.
5217 @subheading Default Version
5219 @cindex logical file name
5220 @cindex file name, logical
5221 This version of the @code{.file} directive tells @command{@value{AS}} that we
5222 are about to start a new logical file. The syntax is:
5228 @var{string} is the new file name. In general, the filename is
5229 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5230 to specify an empty file name, you must give the quotes--@code{""}. This
5231 statement may go away in future: it is only recognized to be compatible with
5232 old @command{@value{AS}} programs.
5234 @subheading DWARF2 Version
5237 When emitting DWARF2 line number information, @code{.file} assigns filenames
5238 to the @code{.debug_line} file name table. The syntax is:
5241 .file @var{fileno} @var{filename}
5244 The @var{fileno} operand should be a unique positive integer to use as the
5245 index of the entry in the table. The @var{filename} operand is a C string
5248 The detail of filename indices is exposed to the user because the filename
5249 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5250 information, and thus the user must know the exact indices that table
5254 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5256 @cindex @code{fill} directive
5257 @cindex writing patterns in memory
5258 @cindex patterns, writing in memory
5259 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5260 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5261 may be zero or more. @var{Size} may be zero or more, but if it is
5262 more than 8, then it is deemed to have the value 8, compatible with
5263 other people's assemblers. The contents of each @var{repeat} bytes
5264 is taken from an 8-byte number. The highest order 4 bytes are
5265 zero. The lowest order 4 bytes are @var{value} rendered in the
5266 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5267 Each @var{size} bytes in a repetition is taken from the lowest order
5268 @var{size} bytes of this number. Again, this bizarre behavior is
5269 compatible with other people's assemblers.
5271 @var{size} and @var{value} are optional.
5272 If the second comma and @var{value} are absent, @var{value} is
5273 assumed zero. If the first comma and following tokens are absent,
5274 @var{size} is assumed to be 1.
5277 @section @code{.float @var{flonums}}
5279 @cindex floating point numbers (single)
5280 @cindex @code{float} directive
5281 This directive assembles zero or more flonums, separated by commas. It
5282 has the same effect as @code{.single}.
5284 The exact kind of floating point numbers emitted depends on how
5285 @command{@value{AS}} is configured.
5286 @xref{Machine Dependencies}.
5290 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5291 in @sc{ieee} format.
5296 @section @code{.func @var{name}[,@var{label}]}
5297 @cindex @code{func} directive
5298 @code{.func} emits debugging information to denote function @var{name}, and
5299 is ignored unless the file is assembled with debugging enabled.
5300 Only @samp{--gstabs[+]} is currently supported.
5301 @var{label} is the entry point of the function and if omitted @var{name}
5302 prepended with the @samp{leading char} is used.
5303 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5304 All functions are currently defined to have @code{void} return type.
5305 The function must be terminated with @code{.endfunc}.
5308 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5310 @cindex @code{global} directive
5311 @cindex symbol, making visible to linker
5312 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5313 @var{symbol} in your partial program, its value is made available to
5314 other partial programs that are linked with it. Otherwise,
5315 @var{symbol} takes its attributes from a symbol of the same name
5316 from another file linked into the same program.
5318 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5319 compatibility with other assemblers.
5322 On the HPPA, @code{.global} is not always enough to make it accessible to other
5323 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5324 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5329 @section @code{.gnu_attribute @var{tag},@var{value}}
5330 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5333 @section @code{.hidden @var{names}}
5335 @cindex @code{hidden} directive
5337 This is one of the ELF visibility directives. The other two are
5338 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5339 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5341 This directive overrides the named symbols default visibility (which is set by
5342 their binding: local, global or weak). The directive sets the visibility to
5343 @code{hidden} which means that the symbols are not visible to other components.
5344 Such symbols are always considered to be @code{protected} as well.
5348 @section @code{.hword @var{expressions}}
5350 @cindex @code{hword} directive
5351 @cindex integers, 16-bit
5352 @cindex numbers, 16-bit
5353 @cindex sixteen bit integers
5354 This expects zero or more @var{expressions}, and emits
5355 a 16 bit number for each.
5358 This directive is a synonym for @samp{.short}; depending on the target
5359 architecture, it may also be a synonym for @samp{.word}.
5363 This directive is a synonym for @samp{.short}.
5366 This directive is a synonym for both @samp{.short} and @samp{.word}.
5371 @section @code{.ident}
5373 @cindex @code{ident} directive
5375 This directive is used by some assemblers to place tags in object files. The
5376 behavior of this directive varies depending on the target. When using the
5377 a.out object file format, @command{@value{AS}} simply accepts the directive for
5378 source-file compatibility with existing assemblers, but does not emit anything
5379 for it. When using COFF, comments are emitted to the @code{.comment} or
5380 @code{.rdata} section, depending on the target. When using ELF, comments are
5381 emitted to the @code{.comment} section.
5384 @section @code{.if @var{absolute expression}}
5386 @cindex conditional assembly
5387 @cindex @code{if} directive
5388 @code{.if} marks the beginning of a section of code which is only
5389 considered part of the source program being assembled if the argument
5390 (which must be an @var{absolute expression}) is non-zero. The end of
5391 the conditional section of code must be marked by @code{.endif}
5392 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5393 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5394 If you have several conditions to check, @code{.elseif} may be used to avoid
5395 nesting blocks if/else within each subsequent @code{.else} block.
5397 The following variants of @code{.if} are also supported:
5399 @cindex @code{ifdef} directive
5400 @item .ifdef @var{symbol}
5401 Assembles the following section of code if the specified @var{symbol}
5402 has been defined. Note a symbol which has been referenced but not yet defined
5403 is considered to be undefined.
5405 @cindex @code{ifb} directive
5406 @item .ifb @var{text}
5407 Assembles the following section of code if the operand is blank (empty).
5409 @cindex @code{ifc} directive
5410 @item .ifc @var{string1},@var{string2}
5411 Assembles the following section of code if the two strings are the same. The
5412 strings may be optionally quoted with single quotes. If they are not quoted,
5413 the first string stops at the first comma, and the second string stops at the
5414 end of the line. Strings which contain whitespace should be quoted. The
5415 string comparison is case sensitive.
5417 @cindex @code{ifeq} directive
5418 @item .ifeq @var{absolute expression}
5419 Assembles the following section of code if the argument is zero.
5421 @cindex @code{ifeqs} directive
5422 @item .ifeqs @var{string1},@var{string2}
5423 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5425 @cindex @code{ifge} directive
5426 @item .ifge @var{absolute expression}
5427 Assembles the following section of code if the argument is greater than or
5430 @cindex @code{ifgt} directive
5431 @item .ifgt @var{absolute expression}
5432 Assembles the following section of code if the argument is greater than zero.
5434 @cindex @code{ifle} directive
5435 @item .ifle @var{absolute expression}
5436 Assembles the following section of code if the argument is less than or equal
5439 @cindex @code{iflt} directive
5440 @item .iflt @var{absolute expression}
5441 Assembles the following section of code if the argument is less than zero.
5443 @cindex @code{ifnb} directive
5444 @item .ifnb @var{text}
5445 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5446 following section of code if the operand is non-blank (non-empty).
5448 @cindex @code{ifnc} directive
5449 @item .ifnc @var{string1},@var{string2}.
5450 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5451 following section of code if the two strings are not the same.
5453 @cindex @code{ifndef} directive
5454 @cindex @code{ifnotdef} directive
5455 @item .ifndef @var{symbol}
5456 @itemx .ifnotdef @var{symbol}
5457 Assembles the following section of code if the specified @var{symbol}
5458 has not been defined. Both spelling variants are equivalent. Note a symbol
5459 which has been referenced but not yet defined is considered to be undefined.
5461 @cindex @code{ifne} directive
5462 @item .ifne @var{absolute expression}
5463 Assembles the following section of code if the argument is not equal to zero
5464 (in other words, this is equivalent to @code{.if}).
5466 @cindex @code{ifnes} directive
5467 @item .ifnes @var{string1},@var{string2}
5468 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5469 following section of code if the two strings are not the same.
5473 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5475 @cindex @code{incbin} directive
5476 @cindex binary files, including
5477 The @code{incbin} directive includes @var{file} verbatim at the current
5478 location. You can control the search paths used with the @samp{-I} command-line
5479 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5482 The @var{skip} argument skips a number of bytes from the start of the
5483 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5484 read. Note that the data is not aligned in any way, so it is the user's
5485 responsibility to make sure that proper alignment is provided both before and
5486 after the @code{incbin} directive.
5489 @section @code{.include "@var{file}"}
5491 @cindex @code{include} directive
5492 @cindex supporting files, including
5493 @cindex files, including
5494 This directive provides a way to include supporting files at specified
5495 points in your source program. The code from @var{file} is assembled as
5496 if it followed the point of the @code{.include}; when the end of the
5497 included file is reached, assembly of the original file continues. You
5498 can control the search paths used with the @samp{-I} command-line option
5499 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5503 @section @code{.int @var{expressions}}
5505 @cindex @code{int} directive
5506 @cindex integers, 32-bit
5507 Expect zero or more @var{expressions}, of any section, separated by commas.
5508 For each expression, emit a number that, at run time, is the value of that
5509 expression. The byte order and bit size of the number depends on what kind
5510 of target the assembly is for.
5514 On most forms of the H8/300, @code{.int} emits 16-bit
5515 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5522 @section @code{.internal @var{names}}
5524 @cindex @code{internal} directive
5526 This is one of the ELF visibility directives. The other two are
5527 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5528 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5530 This directive overrides the named symbols default visibility (which is set by
5531 their binding: local, global or weak). The directive sets the visibility to
5532 @code{internal} which means that the symbols are considered to be @code{hidden}
5533 (i.e., not visible to other components), and that some extra, processor specific
5534 processing must also be performed upon the symbols as well.
5538 @section @code{.irp @var{symbol},@var{values}}@dots{}
5540 @cindex @code{irp} directive
5541 Evaluate a sequence of statements assigning different values to @var{symbol}.
5542 The sequence of statements starts at the @code{.irp} directive, and is
5543 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5544 set to @var{value}, and the sequence of statements is assembled. If no
5545 @var{value} is listed, the sequence of statements is assembled once, with
5546 @var{symbol} set to the null string. To refer to @var{symbol} within the
5547 sequence of statements, use @var{\symbol}.
5549 For example, assembling
5557 is equivalent to assembling
5565 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5568 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5570 @cindex @code{irpc} directive
5571 Evaluate a sequence of statements assigning different values to @var{symbol}.
5572 The sequence of statements starts at the @code{.irpc} directive, and is
5573 terminated by an @code{.endr} directive. For each character in @var{value},
5574 @var{symbol} is set to the character, and the sequence of statements is
5575 assembled. If no @var{value} is listed, the sequence of statements is
5576 assembled once, with @var{symbol} set to the null string. To refer to
5577 @var{symbol} within the sequence of statements, use @var{\symbol}.
5579 For example, assembling
5587 is equivalent to assembling
5595 For some caveats with the spelling of @var{symbol}, see also the discussion
5599 @section @code{.lcomm @var{symbol} , @var{length}}
5601 @cindex @code{lcomm} directive
5602 @cindex local common symbols
5603 @cindex symbols, local common
5604 Reserve @var{length} (an absolute expression) bytes for a local common
5605 denoted by @var{symbol}. The section and value of @var{symbol} are
5606 those of the new local common. The addresses are allocated in the bss
5607 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5608 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5609 not visible to @code{@value{LD}}.
5612 Some targets permit a third argument to be used with @code{.lcomm}. This
5613 argument specifies the desired alignment of the symbol in the bss section.
5617 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5618 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5622 @section @code{.lflags}
5624 @cindex @code{lflags} directive (ignored)
5625 @command{@value{AS}} accepts this directive, for compatibility with other
5626 assemblers, but ignores it.
5628 @ifclear no-line-dir
5630 @section @code{.line @var{line-number}}
5632 @cindex @code{line} directive
5633 @cindex logical line number
5635 Change the logical line number. @var{line-number} must be an absolute
5636 expression. The next line has that logical line number. Therefore any other
5637 statements on the current line (after a statement separator character) are
5638 reported as on logical line number @var{line-number} @minus{} 1. One day
5639 @command{@value{AS}} will no longer support this directive: it is recognized only
5640 for compatibility with existing assembler programs.
5643 Even though this is a directive associated with the @code{a.out} or
5644 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5645 when producing COFF output, and treats @samp{.line} as though it
5646 were the COFF @samp{.ln} @emph{if} it is found outside a
5647 @code{.def}/@code{.endef} pair.
5649 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5650 used by compilers to generate auxiliary symbol information for
5655 @section @code{.linkonce [@var{type}]}
5657 @cindex @code{linkonce} directive
5658 @cindex common sections
5659 Mark the current section so that the linker only includes a single copy of it.
5660 This may be used to include the same section in several different object files,
5661 but ensure that the linker will only include it once in the final output file.
5662 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5663 Duplicate sections are detected based on the section name, so it should be
5666 This directive is only supported by a few object file formats; as of this
5667 writing, the only object file format which supports it is the Portable
5668 Executable format used on Windows NT.
5670 The @var{type} argument is optional. If specified, it must be one of the
5671 following strings. For example:
5675 Not all types may be supported on all object file formats.
5679 Silently discard duplicate sections. This is the default.
5682 Warn if there are duplicate sections, but still keep only one copy.
5685 Warn if any of the duplicates have different sizes.
5688 Warn if any of the duplicates do not have exactly the same contents.
5692 @section @code{.list}
5694 @cindex @code{list} directive
5695 @cindex listing control, turning on
5696 Control (in conjunction with the @code{.nolist} directive) whether or
5697 not assembly listings are generated. These two directives maintain an
5698 internal counter (which is zero initially). @code{.list} increments the
5699 counter, and @code{.nolist} decrements it. Assembly listings are
5700 generated whenever the counter is greater than zero.
5702 By default, listings are disabled. When you enable them (with the
5703 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5704 the initial value of the listing counter is one.
5707 @section @code{.ln @var{line-number}}
5709 @cindex @code{ln} directive
5710 @ifclear no-line-dir
5711 @samp{.ln} is a synonym for @samp{.line}.
5714 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5715 must be an absolute expression. The next line has that logical
5716 line number, so any other statements on the current line (after a
5717 statement separator character @code{;}) are reported as on logical
5718 line number @var{line-number} @minus{} 1.
5722 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5723 @cindex @code{loc} directive
5724 When emitting DWARF2 line number information,
5725 the @code{.loc} directive will add a row to the @code{.debug_line} line
5726 number matrix corresponding to the immediately following assembly
5727 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5728 arguments will be applied to the @code{.debug_line} state machine before
5731 The @var{options} are a sequence of the following tokens in any order:
5735 This option will set the @code{basic_block} register in the
5736 @code{.debug_line} state machine to @code{true}.
5739 This option will set the @code{prologue_end} register in the
5740 @code{.debug_line} state machine to @code{true}.
5742 @item epilogue_begin
5743 This option will set the @code{epilogue_begin} register in the
5744 @code{.debug_line} state machine to @code{true}.
5746 @item is_stmt @var{value}
5747 This option will set the @code{is_stmt} register in the
5748 @code{.debug_line} state machine to @code{value}, which must be
5751 @item isa @var{value}
5752 This directive will set the @code{isa} register in the @code{.debug_line}
5753 state machine to @var{value}, which must be an unsigned integer.
5755 @item discriminator @var{value}
5756 This directive will set the @code{discriminator} register in the @code{.debug_line}
5757 state machine to @var{value}, which must be an unsigned integer.
5759 @item view @var{value}
5760 This option causes a row to be added to @code{.debug_line} in reference to the
5761 current address (which might not be the same as that of the following assembly
5762 instruction), and to associate @var{value} with the @code{view} register in the
5763 @code{.debug_line} state machine. If @var{value} is a label, both the
5764 @code{view} register and the label are set to the number of prior @code{.loc}
5765 directives at the same program location. If @var{value} is the literal
5766 @code{0}, the @code{view} register is set to zero, and the assembler asserts
5767 that there aren't any prior @code{.loc} directives at the same program
5768 location. If @var{value} is the literal @code{-0}, the assembler arrange for
5769 the @code{view} register to be reset in this row, even if there are prior
5770 @code{.loc} directives at the same program location.
5774 @node Loc_mark_labels
5775 @section @code{.loc_mark_labels @var{enable}}
5776 @cindex @code{loc_mark_labels} directive
5777 When emitting DWARF2 line number information,
5778 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5779 to the @code{.debug_line} line number matrix with the @code{basic_block}
5780 register in the state machine set whenever a code label is seen.
5781 The @var{enable} argument should be either 1 or 0, to enable or disable
5782 this function respectively.
5786 @section @code{.local @var{names}}
5788 @cindex @code{local} directive
5789 This directive, which is available for ELF targets, marks each symbol in
5790 the comma-separated list of @code{names} as a local symbol so that it
5791 will not be externally visible. If the symbols do not already exist,
5792 they will be created.
5794 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5795 accept an alignment argument, which is the case for most ELF targets,
5796 the @code{.local} directive can be used in combination with @code{.comm}
5797 (@pxref{Comm}) to define aligned local common data.
5801 @section @code{.long @var{expressions}}
5803 @cindex @code{long} directive
5804 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5807 @c no one seems to know what this is for or whether this description is
5808 @c what it really ought to do
5810 @section @code{.lsym @var{symbol}, @var{expression}}
5812 @cindex @code{lsym} directive
5813 @cindex symbol, not referenced in assembly
5814 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5815 the hash table, ensuring it cannot be referenced by name during the
5816 rest of the assembly. This sets the attributes of the symbol to be
5817 the same as the expression value:
5819 @var{other} = @var{descriptor} = 0
5820 @var{type} = @r{(section of @var{expression})}
5821 @var{value} = @var{expression}
5824 The new symbol is not flagged as external.
5828 @section @code{.macro}
5831 The commands @code{.macro} and @code{.endm} allow you to define macros that
5832 generate assembly output. For example, this definition specifies a macro
5833 @code{sum} that puts a sequence of numbers into memory:
5836 .macro sum from=0, to=5
5845 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5857 @item .macro @var{macname}
5858 @itemx .macro @var{macname} @var{macargs} @dots{}
5859 @cindex @code{macro} directive
5860 Begin the definition of a macro called @var{macname}. If your macro
5861 definition requires arguments, specify their names after the macro name,
5862 separated by commas or spaces. You can qualify the macro argument to
5863 indicate whether all invocations must specify a non-blank value (through
5864 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5865 (through @samp{:@code{vararg}}). You can supply a default value for any
5866 macro argument by following the name with @samp{=@var{deflt}}. You
5867 cannot define two macros with the same @var{macname} unless it has been
5868 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5869 definitions. For example, these are all valid @code{.macro} statements:
5873 Begin the definition of a macro called @code{comm}, which takes no
5876 @item .macro plus1 p, p1
5877 @itemx .macro plus1 p p1
5878 Either statement begins the definition of a macro called @code{plus1},
5879 which takes two arguments; within the macro definition, write
5880 @samp{\p} or @samp{\p1} to evaluate the arguments.
5882 @item .macro reserve_str p1=0 p2
5883 Begin the definition of a macro called @code{reserve_str}, with two
5884 arguments. The first argument has a default value, but not the second.
5885 After the definition is complete, you can call the macro either as
5886 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5887 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5888 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5889 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5891 @item .macro m p1:req, p2=0, p3:vararg
5892 Begin the definition of a macro called @code{m}, with at least three
5893 arguments. The first argument must always have a value specified, but
5894 not the second, which instead has a default value. The third formal
5895 will get assigned all remaining arguments specified at invocation time.
5897 When you call a macro, you can specify the argument values either by
5898 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5899 @samp{sum to=17, from=9}.
5903 Note that since each of the @var{macargs} can be an identifier exactly
5904 as any other one permitted by the target architecture, there may be
5905 occasional problems if the target hand-crafts special meanings to certain
5906 characters when they occur in a special position. For example, if the colon
5907 (@code{:}) is generally permitted to be part of a symbol name, but the
5908 architecture specific code special-cases it when occurring as the final
5909 character of a symbol (to denote a label), then the macro parameter
5910 replacement code will have no way of knowing that and consider the whole
5911 construct (including the colon) an identifier, and check only this
5912 identifier for being the subject to parameter substitution. So for example
5913 this macro definition:
5921 might not work as expected. Invoking @samp{label foo} might not create a label
5922 called @samp{foo} but instead just insert the text @samp{\l:} into the
5923 assembler source, probably generating an error about an unrecognised
5926 Similarly problems might occur with the period character (@samp{.})
5927 which is often allowed inside opcode names (and hence identifier names). So
5928 for example constructing a macro to build an opcode from a base name and a
5929 length specifier like this:
5932 .macro opcode base length
5937 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5938 instruction but instead generate some kind of error as the assembler tries to
5939 interpret the text @samp{\base.\length}.
5941 There are several possible ways around this problem:
5944 @item Insert white space
5945 If it is possible to use white space characters then this is the simplest
5954 @item Use @samp{\()}
5955 The string @samp{\()} can be used to separate the end of a macro argument from
5956 the following text. eg:
5959 .macro opcode base length
5964 @item Use the alternate macro syntax mode
5965 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5966 used as a separator. eg:
5976 Note: this problem of correctly identifying string parameters to pseudo ops
5977 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5978 and @code{.irpc} (@pxref{Irpc}) as well.
5981 @cindex @code{endm} directive
5982 Mark the end of a macro definition.
5985 @cindex @code{exitm} directive
5986 Exit early from the current macro definition.
5988 @cindex number of macros executed
5989 @cindex macros, count executed
5991 @command{@value{AS}} maintains a counter of how many macros it has
5992 executed in this pseudo-variable; you can copy that number to your
5993 output with @samp{\@@}, but @emph{only within a macro definition}.
5995 @item LOCAL @var{name} [ , @dots{} ]
5996 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5997 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5998 @xref{Altmacro,,@code{.altmacro}}.
6002 @section @code{.mri @var{val}}
6004 @cindex @code{mri} directive
6005 @cindex MRI mode, temporarily
6006 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6007 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6008 affects code assembled until the next @code{.mri} directive, or until the end
6009 of the file. @xref{M, MRI mode, MRI mode}.
6012 @section @code{.noaltmacro}
6013 Disable alternate macro mode. @xref{Altmacro}.
6016 @section @code{.nolist}
6018 @cindex @code{nolist} directive
6019 @cindex listing control, turning off
6020 Control (in conjunction with the @code{.list} directive) whether or
6021 not assembly listings are generated. These two directives maintain an
6022 internal counter (which is zero initially). @code{.list} increments the
6023 counter, and @code{.nolist} decrements it. Assembly listings are
6024 generated whenever the counter is greater than zero.
6027 @section @code{.nops @var{size}[, @var{control}]}
6029 @cindex @code{nops} directive
6030 @cindex filling memory with no-op instructions
6031 This directive emits @var{size} bytes filled with no-op instructions.
6032 @var{size} is absolute expression, which must be a positve value.
6033 @var{control} controls how no-op instructions should be generated. If
6034 the comma and @var{control} are omitted, @var{control} is assumed to be
6037 Note: For Intel 80386 and AMD x86-64 targets, @var{control} specifies
6038 the size limit of a no-op instruction. The valid values of @var{control}
6039 are between 0 and 4 in 16-bit mode, between 0 and 7 when tuning for
6040 older processors in 32-bit mode, between 0 and 11 in 64-bit mode or when
6041 tuning for newer processors in 32-bit mode. When 0 is used, the no-op
6042 instruction size limit is set to the maximum supported size.
6045 @section @code{.octa @var{bignums}}
6047 @c FIXME: double size emitted for "octa" on some? Or warn?
6048 @cindex @code{octa} directive
6049 @cindex integer, 16-byte
6050 @cindex sixteen byte integer
6051 This directive expects zero or more bignums, separated by commas. For each
6052 bignum, it emits a 16-byte integer.
6054 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6055 hence @emph{octa}-word for 16 bytes.
6058 @section @code{.offset @var{loc}}
6060 @cindex @code{offset} directive
6061 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6062 be an absolute expression. This directive may be useful for defining
6063 symbols with absolute values. Do not confuse it with the @code{.org}
6067 @section @code{.org @var{new-lc} , @var{fill}}
6069 @cindex @code{org} directive
6070 @cindex location counter, advancing
6071 @cindex advancing location counter
6072 @cindex current address, advancing
6073 Advance the location counter of the current section to
6074 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6075 expression with the same section as the current subsection. That is,
6076 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6077 wrong section, the @code{.org} directive is ignored. To be compatible
6078 with former assemblers, if the section of @var{new-lc} is absolute,
6079 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6080 is the same as the current subsection.
6082 @code{.org} may only increase the location counter, or leave it
6083 unchanged; you cannot use @code{.org} to move the location counter
6086 @c double negative used below "not undefined" because this is a specific
6087 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6088 @c section. doc@cygnus.com 18feb91
6089 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6090 may not be undefined. If you really detest this restriction we eagerly await
6091 a chance to share your improved assembler.
6093 Beware that the origin is relative to the start of the section, not
6094 to the start of the subsection. This is compatible with other
6095 people's assemblers.
6097 When the location counter (of the current subsection) is advanced, the
6098 intervening bytes are filled with @var{fill} which should be an
6099 absolute expression. If the comma and @var{fill} are omitted,
6100 @var{fill} defaults to zero.
6103 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6105 @cindex padding the location counter given a power of two
6106 @cindex @code{p2align} directive
6107 Pad the location counter (in the current subsection) to a particular
6108 storage boundary. The first expression (which must be absolute) is the
6109 number of low-order zero bits the location counter must have after
6110 advancement. For example @samp{.p2align 3} advances the location
6111 counter until it a multiple of 8. If the location counter is already a
6112 multiple of 8, no change is needed.
6114 The second expression (also absolute) gives the fill value to be stored in the
6115 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6116 padding bytes are normally zero. However, on most systems, if the section is
6117 marked as containing code and the fill value is omitted, the space is filled
6118 with no-op instructions.
6120 The third expression is also absolute, and is also optional. If it is present,
6121 it is the maximum number of bytes that should be skipped by this alignment
6122 directive. If doing the alignment would require skipping more bytes than the
6123 specified maximum, then the alignment is not done at all. You can omit the
6124 fill value (the second argument) entirely by simply using two commas after the
6125 required alignment; this can be useful if you want the alignment to be filled
6126 with no-op instructions when appropriate.
6128 @cindex @code{p2alignw} directive
6129 @cindex @code{p2alignl} directive
6130 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6131 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6132 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6133 fill pattern as a four byte longword value. For example, @code{.p2alignw
6134 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6135 filled in with the value 0x368d (the exact placement of the bytes depends upon
6136 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6141 @section @code{.popsection}
6143 @cindex @code{popsection} directive
6144 @cindex Section Stack
6145 This is one of the ELF section stack manipulation directives. The others are
6146 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6147 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6150 This directive replaces the current section (and subsection) with the top
6151 section (and subsection) on the section stack. This section is popped off the
6157 @section @code{.previous}
6159 @cindex @code{previous} directive
6160 @cindex Section Stack
6161 This is one of the ELF section stack manipulation directives. The others are
6162 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6163 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6164 (@pxref{PopSection}).
6166 This directive swaps the current section (and subsection) with most recently
6167 referenced section/subsection pair prior to this one. Multiple
6168 @code{.previous} directives in a row will flip between two sections (and their
6169 subsections). For example:
6181 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6187 # Now in section A subsection 1
6191 # Now in section B subsection 0
6194 # Now in section B subsection 1
6197 # Now in section B subsection 0
6201 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6202 section B and 0x9abc into subsection 1 of section B.
6204 In terms of the section stack, this directive swaps the current section with
6205 the top section on the section stack.
6209 @section @code{.print @var{string}}
6211 @cindex @code{print} directive
6212 @command{@value{AS}} will print @var{string} on the standard output during
6213 assembly. You must put @var{string} in double quotes.
6217 @section @code{.protected @var{names}}
6219 @cindex @code{protected} directive
6221 This is one of the ELF visibility directives. The other two are
6222 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6224 This directive overrides the named symbols default visibility (which is set by
6225 their binding: local, global or weak). The directive sets the visibility to
6226 @code{protected} which means that any references to the symbols from within the
6227 components that defines them must be resolved to the definition in that
6228 component, even if a definition in another component would normally preempt
6233 @section @code{.psize @var{lines} , @var{columns}}
6235 @cindex @code{psize} directive
6236 @cindex listing control: paper size
6237 @cindex paper size, for listings
6238 Use this directive to declare the number of lines---and, optionally, the
6239 number of columns---to use for each page, when generating listings.
6241 If you do not use @code{.psize}, listings use a default line-count
6242 of 60. You may omit the comma and @var{columns} specification; the
6243 default width is 200 columns.
6245 @command{@value{AS}} generates formfeeds whenever the specified number of
6246 lines is exceeded (or whenever you explicitly request one, using
6249 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6250 those explicitly specified with @code{.eject}.
6253 @section @code{.purgem @var{name}}
6255 @cindex @code{purgem} directive
6256 Undefine the macro @var{name}, so that later uses of the string will not be
6257 expanded. @xref{Macro}.
6261 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6263 @cindex @code{pushsection} directive
6264 @cindex Section Stack
6265 This is one of the ELF section stack manipulation directives. The others are
6266 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6267 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6270 This directive pushes the current section (and subsection) onto the
6271 top of the section stack, and then replaces the current section and
6272 subsection with @code{name} and @code{subsection}. The optional
6273 @code{flags}, @code{type} and @code{arguments} are treated the same
6274 as in the @code{.section} (@pxref{Section}) directive.
6278 @section @code{.quad @var{bignums}}
6280 @cindex @code{quad} directive
6281 @code{.quad} expects zero or more bignums, separated by commas. For
6282 each bignum, it emits
6284 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6285 warning message; and just takes the lowest order 8 bytes of the bignum.
6286 @cindex eight-byte integer
6287 @cindex integer, 8-byte
6289 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6290 hence @emph{quad}-word for 8 bytes.
6293 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6294 warning message; and just takes the lowest order 16 bytes of the bignum.
6295 @cindex sixteen-byte integer
6296 @cindex integer, 16-byte
6300 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6302 @cindex @code{reloc} directive
6303 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6304 @var{expression}. If @var{offset} is a number, the relocation is generated in
6305 the current section. If @var{offset} is an expression that resolves to a
6306 symbol plus offset, the relocation is generated in the given symbol's section.
6307 @var{expression}, if present, must resolve to a symbol plus addend or to an
6308 absolute value, but note that not all targets support an addend. e.g. ELF REL
6309 targets such as i386 store an addend in the section contents rather than in the
6310 relocation. This low level interface does not support addends stored in the
6314 @section @code{.rept @var{count}}
6316 @cindex @code{rept} directive
6317 Repeat the sequence of lines between the @code{.rept} directive and the next
6318 @code{.endr} directive @var{count} times.
6320 For example, assembling
6328 is equivalent to assembling
6336 A count of zero is allowed, but nothing is generated. Negative counts are not
6337 allowed and if encountered will be treated as if they were zero.
6340 @section @code{.sbttl "@var{subheading}"}
6342 @cindex @code{sbttl} directive
6343 @cindex subtitles for listings
6344 @cindex listing control: subtitle
6345 Use @var{subheading} as the title (third line, immediately after the
6346 title line) when generating assembly listings.
6348 This directive affects subsequent pages, as well as the current page if
6349 it appears within ten lines of the top of a page.
6353 @section @code{.scl @var{class}}
6355 @cindex @code{scl} directive
6356 @cindex symbol storage class (COFF)
6357 @cindex COFF symbol storage class
6358 Set the storage-class value for a symbol. This directive may only be
6359 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6360 whether a symbol is static or external, or it may record further
6361 symbolic debugging information.
6366 @section @code{.section @var{name}}
6368 @cindex named section
6369 Use the @code{.section} directive to assemble the following code into a section
6372 This directive is only supported for targets that actually support arbitrarily
6373 named sections; on @code{a.out} targets, for example, it is not accepted, even
6374 with a standard @code{a.out} section name.
6378 @c only print the extra heading if both COFF and ELF are set
6379 @subheading COFF Version
6382 @cindex @code{section} directive (COFF version)
6383 For COFF targets, the @code{.section} directive is used in one of the following
6387 .section @var{name}[, "@var{flags}"]
6388 .section @var{name}[, @var{subsection}]
6391 If the optional argument is quoted, it is taken as flags to use for the
6392 section. Each flag is a single character. The following flags are recognized:
6396 bss section (uninitialized data)
6398 section is not loaded
6404 exclude section from linking
6410 shared section (meaningful for PE targets)
6412 ignored. (For compatibility with the ELF version)
6414 section is not readable (meaningful for PE targets)
6416 single-digit power-of-two section alignment (GNU extension)
6419 If no flags are specified, the default flags depend upon the section name. If
6420 the section name is not recognized, the default will be for the section to be
6421 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6422 from the section, rather than adding them, so if they are used on their own it
6423 will be as if no flags had been specified at all.
6425 If the optional argument to the @code{.section} directive is not quoted, it is
6426 taken as a subsection number (@pxref{Sub-Sections}).
6431 @c only print the extra heading if both COFF and ELF are set
6432 @subheading ELF Version
6435 @cindex Section Stack
6436 This is one of the ELF section stack manipulation directives. The others are
6437 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6438 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6439 @code{.previous} (@pxref{Previous}).
6441 @cindex @code{section} directive (ELF version)
6442 For ELF targets, the @code{.section} directive is used like this:
6445 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6448 @anchor{Section Name Substitutions}
6449 @kindex --sectname-subst
6450 @cindex section name substitution
6451 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6452 argument may contain a substitution sequence. Only @code{%S} is supported
6453 at the moment, and substitutes the current section name. For example:
6456 .macro exception_code
6457 .section %S.exception
6458 [exception code here]
6473 The two @code{exception_code} invocations above would create the
6474 @code{.text.exception} and @code{.init.exception} sections respectively.
6475 This is useful e.g. to discriminate between ancillary sections that are
6476 tied to setup code to be discarded after use from ancillary sections that
6477 need to stay resident without having to define multiple @code{exception_code}
6478 macros just for that purpose.
6480 The optional @var{flags} argument is a quoted string which may contain any
6481 combination of the following characters:
6485 section is allocatable
6487 section is a GNU_MBIND section
6489 section is excluded from executable and shared library.
6493 section is executable
6495 section is mergeable
6497 section contains zero terminated strings
6499 section is a member of a section group
6501 section is used for thread-local-storage
6503 section is a member of the previously-current section's group, if any
6504 @item @code{<number>}
6505 a numeric value indicating the bits to be set in the ELF section header's flags
6506 field. Note - if one or more of the alphabetic characters described above is
6507 also included in the flags field, their bit values will be ORed into the
6509 @item @code{<target specific>}
6510 some targets extend this list with their own flag characters
6513 Note - once a section's flags have been set they cannot be changed. There are
6514 a few exceptions to this rule however. Processor and application specific
6515 flags can be added to an already defined section. The @code{.interp},
6516 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6517 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6518 section may have the executable (@code{x}) flag added.
6520 The optional @var{type} argument may contain one of the following constants:
6524 section contains data
6526 section does not contain data (i.e., section only occupies space)
6528 section contains data which is used by things other than the program
6530 section contains an array of pointers to init functions
6532 section contains an array of pointers to finish functions
6533 @item @@preinit_array
6534 section contains an array of pointers to pre-init functions
6535 @item @@@code{<number>}
6536 a numeric value to be set as the ELF section header's type field.
6537 @item @@@code{<target specific>}
6538 some targets extend this list with their own types
6541 Many targets only support the first three section types. The type may be
6542 enclosed in double quotes if necessary.
6544 Note on targets where the @code{@@} character is the start of a comment (eg
6545 ARM) then another character is used instead. For example the ARM port uses the
6548 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6549 special and have fixed types. Any attempt to declare them with a different
6550 type will generate an error from the assembler.
6552 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6553 be specified as well as an extra argument---@var{entsize}---like this:
6556 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6559 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6560 constants, each @var{entsize} octets long. Sections with both @code{M} and
6561 @code{S} must contain zero terminated strings where each character is
6562 @var{entsize} bytes long. The linker may remove duplicates within sections with
6563 the same name, same entity size and same flags. @var{entsize} must be an
6564 absolute expression. For sections with both @code{M} and @code{S}, a string
6565 which is a suffix of a larger string is considered a duplicate. Thus
6566 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6567 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6569 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6570 be present along with an additional field like this:
6573 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6576 The @var{GroupName} field specifies the name of the section group to which this
6577 particular section belongs. The optional linkage field can contain:
6581 indicates that only one copy of this section should be retained
6586 Note: if both the @var{M} and @var{G} flags are present then the fields for
6587 the Merge flag should come first, like this:
6590 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6593 If @var{flags} contains the @code{?} symbol then it may not also contain the
6594 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6595 present. Instead, @code{?} says to consider the section that's current before
6596 this directive. If that section used @code{G}, then the new section will use
6597 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6598 If not, then the @code{?} symbol has no effect.
6600 If no flags are specified, the default flags depend upon the section name. If
6601 the section name is not recognized, the default will be for the section to have
6602 none of the above flags: it will not be allocated in memory, nor writable, nor
6603 executable. The section will contain data.
6605 For ELF targets, the assembler supports another type of @code{.section}
6606 directive for compatibility with the Solaris assembler:
6609 .section "@var{name}"[, @var{flags}...]
6612 Note that the section name is quoted. There may be a sequence of comma
6617 section is allocatable
6621 section is executable
6623 section is excluded from executable and shared library.
6625 section is used for thread local storage
6628 This directive replaces the current section and subsection. See the
6629 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6630 some examples of how this directive and the other section stack directives
6636 @section @code{.set @var{symbol}, @var{expression}}
6638 @cindex @code{set} directive
6639 @cindex symbol value, setting
6640 Set the value of @var{symbol} to @var{expression}. This
6641 changes @var{symbol}'s value and type to conform to
6642 @var{expression}. If @var{symbol} was flagged as external, it remains
6643 flagged (@pxref{Symbol Attributes}).
6645 You may @code{.set} a symbol many times in the same assembly provided that the
6646 values given to the symbol are constants. Values that are based on expressions
6647 involving other symbols are allowed, but some targets may restrict this to only
6648 being done once per assembly. This is because those targets do not set the
6649 addresses of symbols at assembly time, but rather delay the assignment until a
6650 final link is performed. This allows the linker a chance to change the code in
6651 the files, changing the location of, and the relative distance between, various
6654 If you @code{.set} a global symbol, the value stored in the object
6655 file is the last value stored into it.
6658 On Z80 @code{set} is a real instruction, use
6659 @samp{@var{symbol} defl @var{expression}} instead.
6663 @section @code{.short @var{expressions}}
6665 @cindex @code{short} directive
6667 @code{.short} is normally the same as @samp{.word}.
6668 @xref{Word,,@code{.word}}.
6670 In some configurations, however, @code{.short} and @code{.word} generate
6671 numbers of different lengths. @xref{Machine Dependencies}.
6675 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6678 This expects zero or more @var{expressions}, and emits
6679 a 16 bit number for each.
6684 @section @code{.single @var{flonums}}
6686 @cindex @code{single} directive
6687 @cindex floating point numbers (single)
6688 This directive assembles zero or more flonums, separated by commas. It
6689 has the same effect as @code{.float}.
6691 The exact kind of floating point numbers emitted depends on how
6692 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6696 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6697 numbers in @sc{ieee} format.
6703 @section @code{.size}
6705 This directive is used to set the size associated with a symbol.
6709 @c only print the extra heading if both COFF and ELF are set
6710 @subheading COFF Version
6713 @cindex @code{size} directive (COFF version)
6714 For COFF targets, the @code{.size} directive is only permitted inside
6715 @code{.def}/@code{.endef} pairs. It is used like this:
6718 .size @var{expression}
6725 @c only print the extra heading if both COFF and ELF are set
6726 @subheading ELF Version
6729 @cindex @code{size} directive (ELF version)
6730 For ELF targets, the @code{.size} directive is used like this:
6733 .size @var{name} , @var{expression}
6736 This directive sets the size associated with a symbol @var{name}.
6737 The size in bytes is computed from @var{expression} which can make use of label
6738 arithmetic. This directive is typically used to set the size of function
6743 @ifclear no-space-dir
6745 @section @code{.skip @var{size} [,@var{fill}]}
6747 @cindex @code{skip} directive
6748 @cindex filling memory
6749 This directive emits @var{size} bytes, each of value @var{fill}. Both
6750 @var{size} and @var{fill} are absolute expressions. If the comma and
6751 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6756 @section @code{.sleb128 @var{expressions}}
6758 @cindex @code{sleb128} directive
6759 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6760 compact, variable length representation of numbers used by the DWARF
6761 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6763 @ifclear no-space-dir
6765 @section @code{.space @var{size} [,@var{fill}]}
6767 @cindex @code{space} directive
6768 @cindex filling memory
6769 This directive emits @var{size} bytes, each of value @var{fill}. Both
6770 @var{size} and @var{fill} are absolute expressions. If the comma
6771 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6776 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6777 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6778 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6779 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6787 @section @code{.stabd, .stabn, .stabs}
6789 @cindex symbolic debuggers, information for
6790 @cindex @code{stab@var{x}} directives
6791 There are three directives that begin @samp{.stab}.
6792 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6793 The symbols are not entered in the @command{@value{AS}} hash table: they
6794 cannot be referenced elsewhere in the source file.
6795 Up to five fields are required:
6799 This is the symbol's name. It may contain any character except
6800 @samp{\000}, so is more general than ordinary symbol names. Some
6801 debuggers used to code arbitrarily complex structures into symbol names
6805 An absolute expression. The symbol's type is set to the low 8 bits of
6806 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6807 and debuggers choke on silly bit patterns.
6810 An absolute expression. The symbol's ``other'' attribute is set to the
6811 low 8 bits of this expression.
6814 An absolute expression. The symbol's descriptor is set to the low 16
6815 bits of this expression.
6818 An absolute expression which becomes the symbol's value.
6821 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6822 or @code{.stabs} statement, the symbol has probably already been created;
6823 you get a half-formed symbol in your object file. This is
6824 compatible with earlier assemblers!
6827 @cindex @code{stabd} directive
6828 @item .stabd @var{type} , @var{other} , @var{desc}
6830 The ``name'' of the symbol generated is not even an empty string.
6831 It is a null pointer, for compatibility. Older assemblers used a
6832 null pointer so they didn't waste space in object files with empty
6835 The symbol's value is set to the location counter,
6836 relocatably. When your program is linked, the value of this symbol
6837 is the address of the location counter when the @code{.stabd} was
6840 @cindex @code{stabn} directive
6841 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6842 The name of the symbol is set to the empty string @code{""}.
6844 @cindex @code{stabs} directive
6845 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6846 All five fields are specified.
6852 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6853 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6855 @cindex string, copying to object file
6856 @cindex string8, copying to object file
6857 @cindex string16, copying to object file
6858 @cindex string32, copying to object file
6859 @cindex string64, copying to object file
6860 @cindex @code{string} directive
6861 @cindex @code{string8} directive
6862 @cindex @code{string16} directive
6863 @cindex @code{string32} directive
6864 @cindex @code{string64} directive
6866 Copy the characters in @var{str} to the object file. You may specify more than
6867 one string to copy, separated by commas. Unless otherwise specified for a
6868 particular machine, the assembler marks the end of each string with a 0 byte.
6869 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6871 The variants @code{string16}, @code{string32} and @code{string64} differ from
6872 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6873 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6874 are stored in target endianness byte order.
6880 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6881 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6886 @section @code{.struct @var{expression}}
6888 @cindex @code{struct} directive
6889 Switch to the absolute section, and set the section offset to @var{expression},
6890 which must be an absolute expression. You might use this as follows:
6899 This would define the symbol @code{field1} to have the value 0, the symbol
6900 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6901 value 8. Assembly would be left in the absolute section, and you would need to
6902 use a @code{.section} directive of some sort to change to some other section
6903 before further assembly.
6907 @section @code{.subsection @var{name}}
6909 @cindex @code{subsection} directive
6910 @cindex Section Stack
6911 This is one of the ELF section stack manipulation directives. The others are
6912 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6913 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6916 This directive replaces the current subsection with @code{name}. The current
6917 section is not changed. The replaced subsection is put onto the section stack
6918 in place of the then current top of stack subsection.
6923 @section @code{.symver}
6924 @cindex @code{symver} directive
6925 @cindex symbol versioning
6926 @cindex versions of symbols
6927 Use the @code{.symver} directive to bind symbols to specific version nodes
6928 within a source file. This is only supported on ELF platforms, and is
6929 typically used when assembling files to be linked into a shared library.
6930 There are cases where it may make sense to use this in objects to be bound
6931 into an application itself so as to override a versioned symbol from a
6934 For ELF targets, the @code{.symver} directive can be used like this:
6936 .symver @var{name}, @var{name2@@nodename}
6938 If the symbol @var{name} is defined within the file
6939 being assembled, the @code{.symver} directive effectively creates a symbol
6940 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6941 just don't try and create a regular alias is that the @var{@@} character isn't
6942 permitted in symbol names. The @var{name2} part of the name is the actual name
6943 of the symbol by which it will be externally referenced. The name @var{name}
6944 itself is merely a name of convenience that is used so that it is possible to
6945 have definitions for multiple versions of a function within a single source
6946 file, and so that the compiler can unambiguously know which version of a
6947 function is being mentioned. The @var{nodename} portion of the alias should be
6948 the name of a node specified in the version script supplied to the linker when
6949 building a shared library. If you are attempting to override a versioned
6950 symbol from a shared library, then @var{nodename} should correspond to the
6951 nodename of the symbol you are trying to override.
6953 If the symbol @var{name} is not defined within the file being assembled, all
6954 references to @var{name} will be changed to @var{name2@@nodename}. If no
6955 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6958 Another usage of the @code{.symver} directive is:
6960 .symver @var{name}, @var{name2@@@@nodename}
6962 In this case, the symbol @var{name} must exist and be defined within
6963 the file being assembled. It is similar to @var{name2@@nodename}. The
6964 difference is @var{name2@@@@nodename} will also be used to resolve
6965 references to @var{name2} by the linker.
6967 The third usage of the @code{.symver} directive is:
6969 .symver @var{name}, @var{name2@@@@@@nodename}
6971 When @var{name} is not defined within the
6972 file being assembled, it is treated as @var{name2@@nodename}. When
6973 @var{name} is defined within the file being assembled, the symbol
6974 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6979 @section @code{.tag @var{structname}}
6981 @cindex COFF structure debugging
6982 @cindex structure debugging, COFF
6983 @cindex @code{tag} directive
6984 This directive is generated by compilers to include auxiliary debugging
6985 information in the symbol table. It is only permitted inside
6986 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6987 definitions in the symbol table with instances of those structures.
6991 @section @code{.text @var{subsection}}
6993 @cindex @code{text} directive
6994 Tells @command{@value{AS}} to assemble the following statements onto the end of
6995 the text subsection numbered @var{subsection}, which is an absolute
6996 expression. If @var{subsection} is omitted, subsection number zero
7000 @section @code{.title "@var{heading}"}
7002 @cindex @code{title} directive
7003 @cindex listing control: title line
7004 Use @var{heading} as the title (second line, immediately after the
7005 source file name and pagenumber) when generating assembly listings.
7007 This directive affects subsequent pages, as well as the current page if
7008 it appears within ten lines of the top of a page.
7012 @section @code{.type}
7014 This directive is used to set the type of a symbol.
7018 @c only print the extra heading if both COFF and ELF are set
7019 @subheading COFF Version
7022 @cindex COFF symbol type
7023 @cindex symbol type, COFF
7024 @cindex @code{type} directive (COFF version)
7025 For COFF targets, this directive is permitted only within
7026 @code{.def}/@code{.endef} pairs. It is used like this:
7032 This records the integer @var{int} as the type attribute of a symbol table
7039 @c only print the extra heading if both COFF and ELF are set
7040 @subheading ELF Version
7043 @cindex ELF symbol type
7044 @cindex symbol type, ELF
7045 @cindex @code{type} directive (ELF version)
7046 For ELF targets, the @code{.type} directive is used like this:
7049 .type @var{name} , @var{type description}
7052 This sets the type of symbol @var{name} to be either a
7053 function symbol or an object symbol. There are five different syntaxes
7054 supported for the @var{type description} field, in order to provide
7055 compatibility with various other assemblers.
7057 Because some of the characters used in these syntaxes (such as @samp{@@} and
7058 @samp{#}) are comment characters for some architectures, some of the syntaxes
7059 below do not work on all architectures. The first variant will be accepted by
7060 the GNU assembler on all architectures so that variant should be used for
7061 maximum portability, if you do not need to assemble your code with other
7064 The syntaxes supported are:
7067 .type <name> STT_<TYPE_IN_UPPER_CASE>
7068 .type <name>,#<type>
7069 .type <name>,@@<type>
7070 .type <name>,%<type>
7071 .type <name>,"<type>"
7074 The types supported are:
7079 Mark the symbol as being a function name.
7082 @itemx gnu_indirect_function
7083 Mark the symbol as an indirect function when evaluated during reloc
7084 processing. (This is only supported on assemblers targeting GNU systems).
7088 Mark the symbol as being a data object.
7092 Mark the symbol as being a thread-local data object.
7096 Mark the symbol as being a common data object.
7100 Does not mark the symbol in any way. It is supported just for completeness.
7102 @item gnu_unique_object
7103 Marks the symbol as being a globally unique data object. The dynamic linker
7104 will make sure that in the entire process there is just one symbol with this
7105 name and type in use. (This is only supported on assemblers targeting GNU
7110 Note: Some targets support extra types in addition to those listed above.
7116 @section @code{.uleb128 @var{expressions}}
7118 @cindex @code{uleb128} directive
7119 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7120 compact, variable length representation of numbers used by the DWARF
7121 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7125 @section @code{.val @var{addr}}
7127 @cindex @code{val} directive
7128 @cindex COFF value attribute
7129 @cindex value attribute, COFF
7130 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7131 records the address @var{addr} as the value attribute of a symbol table
7137 @section @code{.version "@var{string}"}
7139 @cindex @code{version} directive
7140 This directive creates a @code{.note} section and places into it an ELF
7141 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7146 @section @code{.vtable_entry @var{table}, @var{offset}}
7148 @cindex @code{vtable_entry} directive
7149 This directive finds or creates a symbol @code{table} and creates a
7150 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7153 @section @code{.vtable_inherit @var{child}, @var{parent}}
7155 @cindex @code{vtable_inherit} directive
7156 This directive finds the symbol @code{child} and finds or creates the symbol
7157 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7158 parent whose addend is the value of the child symbol. As a special case the
7159 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7163 @section @code{.warning "@var{string}"}
7164 @cindex warning directive
7165 Similar to the directive @code{.error}
7166 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7169 @section @code{.weak @var{names}}
7171 @cindex @code{weak} directive
7172 This directive sets the weak attribute on the comma separated list of symbol
7173 @code{names}. If the symbols do not already exist, they will be created.
7175 On COFF targets other than PE, weak symbols are a GNU extension. This
7176 directive sets the weak attribute on the comma separated list of symbol
7177 @code{names}. If the symbols do not already exist, they will be created.
7179 On the PE target, weak symbols are supported natively as weak aliases.
7180 When a weak symbol is created that is not an alias, GAS creates an
7181 alternate symbol to hold the default value.
7184 @section @code{.weakref @var{alias}, @var{target}}
7186 @cindex @code{weakref} directive
7187 This directive creates an alias to the target symbol that enables the symbol to
7188 be referenced with weak-symbol semantics, but without actually making it weak.
7189 If direct references or definitions of the symbol are present, then the symbol
7190 will not be weak, but if all references to it are through weak references, the
7191 symbol will be marked as weak in the symbol table.
7193 The effect is equivalent to moving all references to the alias to a separate
7194 assembly source file, renaming the alias to the symbol in it, declaring the
7195 symbol as weak there, and running a reloadable link to merge the object files
7196 resulting from the assembly of the new source file and the old source file that
7197 had the references to the alias removed.
7199 The alias itself never makes to the symbol table, and is entirely handled
7200 within the assembler.
7203 @section @code{.word @var{expressions}}
7205 @cindex @code{word} directive
7206 This directive expects zero or more @var{expressions}, of any section,
7207 separated by commas.
7210 For each expression, @command{@value{AS}} emits a 32-bit number.
7213 For each expression, @command{@value{AS}} emits a 16-bit number.
7218 The size of the number emitted, and its byte order,
7219 depend on what target computer the assembly is for.
7222 @c on sparc the "special treatment to support compilers" doesn't
7223 @c happen---32-bit addressability, period; no long/short jumps.
7224 @ifset DIFF-TBL-KLUGE
7225 @cindex difference tables altered
7226 @cindex altered difference tables
7228 @emph{Warning: Special Treatment to support Compilers}
7232 Machines with a 32-bit address space, but that do less than 32-bit
7233 addressing, require the following special treatment. If the machine of
7234 interest to you does 32-bit addressing (or doesn't require it;
7235 @pxref{Machine Dependencies}), you can ignore this issue.
7238 In order to assemble compiler output into something that works,
7239 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7240 Directives of the form @samp{.word sym1-sym2} are often emitted by
7241 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7242 directive of the form @samp{.word sym1-sym2}, and the difference between
7243 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7244 creates a @dfn{secondary jump table}, immediately before the next label.
7245 This secondary jump table is preceded by a short-jump to the
7246 first byte after the secondary table. This short-jump prevents the flow
7247 of control from accidentally falling into the new table. Inside the
7248 table is a long-jump to @code{sym2}. The original @samp{.word}
7249 contains @code{sym1} minus the address of the long-jump to
7252 If there were several occurrences of @samp{.word sym1-sym2} before the
7253 secondary jump table, all of them are adjusted. If there was a
7254 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7255 long-jump to @code{sym4} is included in the secondary jump table,
7256 and the @code{.word} directives are adjusted to contain @code{sym3}
7257 minus the address of the long-jump to @code{sym4}; and so on, for as many
7258 entries in the original jump table as necessary.
7261 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7262 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7263 assembly language programmers.
7266 @c end DIFF-TBL-KLUGE
7268 @ifclear no-space-dir
7270 @section @code{.zero @var{size}}
7272 @cindex @code{zero} directive
7273 @cindex filling memory with zero bytes
7274 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7275 expression. This directive is actually an alias for the @samp{.skip} directive
7276 so in can take an optional second argument of the value to store in the bytes
7277 instead of zero. Using @samp{.zero} in this way would be confusing however.
7282 @section @code{.2byte @var{expression} [, @var{expression}]*}
7283 @cindex @code{2byte} directive
7284 @cindex two-byte integer
7285 @cindex integer, 2-byte
7287 This directive expects zero or more expressions, separated by commas. If there
7288 are no expressions then the directive does nothing. Otherwise each expression
7289 is evaluated in turn and placed in the next two bytes of the current output
7290 section, using the endian model of the target. If an expression will not fit
7291 in two bytes, a warning message is displayed and the least significant two
7292 bytes of the expression's value are used. If an expression cannot be evaluated
7293 at assembly time then relocations will be generated in order to compute the
7296 This directive does not apply any alignment before or after inserting the
7297 values. As a result of this, if relocations are generated, they may be
7298 different from those used for inserting values with a guaranteed alignment.
7300 This directive is only available for ELF targets,
7303 @section @code{.4byte @var{expression} [, @var{expression}]*}
7304 @cindex @code{4byte} directive
7305 @cindex four-byte integer
7306 @cindex integer, 4-byte
7308 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7309 long values into the output.
7312 @section @code{.8byte @var{expression} [, @var{expression}]*}
7313 @cindex @code{8byte} directive
7314 @cindex eight-byte integer
7315 @cindex integer, 8-byte
7317 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7318 byte long bignum values into the output.
7323 @section Deprecated Directives
7325 @cindex deprecated directives
7326 @cindex obsolescent directives
7327 One day these directives won't work.
7328 They are included for compatibility with older assemblers.
7335 @node Object Attributes
7336 @chapter Object Attributes
7337 @cindex object attributes
7339 @command{@value{AS}} assembles source files written for a specific architecture
7340 into object files for that architecture. But not all object files are alike.
7341 Many architectures support incompatible variations. For instance, floating
7342 point arguments might be passed in floating point registers if the object file
7343 requires hardware floating point support---or floating point arguments might be
7344 passed in integer registers if the object file supports processors with no
7345 hardware floating point unit. Or, if two objects are built for different
7346 generations of the same architecture, the combination may require the
7347 newer generation at run-time.
7349 This information is useful during and after linking. At link time,
7350 @command{@value{LD}} can warn about incompatible object files. After link
7351 time, tools like @command{gdb} can use it to process the linked file
7354 Compatibility information is recorded as a series of object attributes. Each
7355 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7356 string, and indicates who sets the meaning of the tag. The tag is an integer,
7357 and indicates what property the attribute describes. The value may be a string
7358 or an integer, and indicates how the property affects this object. Missing
7359 attributes are the same as attributes with a zero value or empty string value.
7361 Object attributes were developed as part of the ABI for the ARM Architecture.
7362 The file format is documented in @cite{ELF for the ARM Architecture}.
7365 * GNU Object Attributes:: @sc{gnu} Object Attributes
7366 * Defining New Object Attributes:: Defining New Object Attributes
7369 @node GNU Object Attributes
7370 @section @sc{gnu} Object Attributes
7372 The @code{.gnu_attribute} directive records an object attribute
7373 with vendor @samp{gnu}.
7375 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7376 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7377 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7378 2} is set for architecture-independent attributes and clear for
7379 architecture-dependent ones.
7381 @subsection Common @sc{gnu} attributes
7383 These attributes are valid on all architectures.
7386 @item Tag_compatibility (32)
7387 The compatibility attribute takes an integer flag value and a vendor name. If
7388 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7389 then the file is only compatible with the named toolchain. If it is greater
7390 than 1, the file can only be processed by other toolchains under some private
7391 arrangement indicated by the flag value and the vendor name.
7394 @subsection MIPS Attributes
7397 @item Tag_GNU_MIPS_ABI_FP (4)
7398 The floating-point ABI used by this object file. The value will be:
7402 0 for files not affected by the floating-point ABI.
7404 1 for files using the hardware floating-point ABI with a standard
7405 double-precision FPU.
7407 2 for files using the hardware floating-point ABI with a single-precision FPU.
7409 3 for files using the software floating-point ABI.
7411 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7412 floating-point registers, 32-bit general-purpose registers and increased the
7413 number of callee-saved floating-point registers.
7415 5 for files using the hardware floating-point ABI with a double-precision FPU
7416 with either 32-bit or 64-bit floating-point registers and 32-bit
7417 general-purpose registers.
7419 6 for files using the hardware floating-point ABI with 64-bit floating-point
7420 registers and 32-bit general-purpose registers.
7422 7 for files using the hardware floating-point ABI with 64-bit floating-point
7423 registers, 32-bit general-purpose registers and a rule that forbids the
7424 direct use of odd-numbered single-precision floating-point registers.
7428 @subsection PowerPC Attributes
7431 @item Tag_GNU_Power_ABI_FP (4)
7432 The floating-point ABI used by this object file. The value will be:
7436 0 for files not affected by the floating-point ABI.
7438 1 for files using double-precision hardware floating-point ABI.
7440 2 for files using the software floating-point ABI.
7442 3 for files using single-precision hardware floating-point ABI.
7445 @item Tag_GNU_Power_ABI_Vector (8)
7446 The vector ABI used by this object file. The value will be:
7450 0 for files not affected by the vector ABI.
7452 1 for files using general purpose registers to pass vectors.
7454 2 for files using AltiVec registers to pass vectors.
7456 3 for files using SPE registers to pass vectors.
7460 @subsection IBM z Systems Attributes
7463 @item Tag_GNU_S390_ABI_Vector (8)
7464 The vector ABI used by this object file. The value will be:
7468 0 for files not affected by the vector ABI.
7470 1 for files using software vector ABI.
7472 2 for files using hardware vector ABI.
7476 @node Defining New Object Attributes
7477 @section Defining New Object Attributes
7479 If you want to define a new @sc{gnu} object attribute, here are the places you
7480 will need to modify. New attributes should be discussed on the @samp{binutils}
7485 This manual, which is the official register of attributes.
7487 The header for your architecture @file{include/elf}, to define the tag.
7489 The @file{bfd} support file for your architecture, to merge the attribute
7490 and issue any appropriate link warnings.
7492 Test cases in @file{ld/testsuite} for merging and link warnings.
7494 @file{binutils/readelf.c} to display your attribute.
7496 GCC, if you want the compiler to mark the attribute automatically.
7502 @node Machine Dependencies
7503 @chapter Machine Dependent Features
7505 @cindex machine dependencies
7506 The machine instruction sets are (almost by definition) different on
7507 each machine where @command{@value{AS}} runs. Floating point representations
7508 vary as well, and @command{@value{AS}} often supports a few additional
7509 directives or command-line options for compatibility with other
7510 assemblers on a particular platform. Finally, some versions of
7511 @command{@value{AS}} support special pseudo-instructions for branch
7514 This chapter discusses most of these differences, though it does not
7515 include details on any machine's instruction set. For details on that
7516 subject, see the hardware manufacturer's manual.
7520 * AArch64-Dependent:: AArch64 Dependent Features
7523 * Alpha-Dependent:: Alpha Dependent Features
7526 * ARC-Dependent:: ARC Dependent Features
7529 * ARM-Dependent:: ARM Dependent Features
7532 * AVR-Dependent:: AVR Dependent Features
7535 * Blackfin-Dependent:: Blackfin Dependent Features
7538 * CR16-Dependent:: CR16 Dependent Features
7541 * CRIS-Dependent:: CRIS Dependent Features
7544 * D10V-Dependent:: D10V Dependent Features
7547 * D30V-Dependent:: D30V Dependent Features
7550 * Epiphany-Dependent:: EPIPHANY Dependent Features
7553 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7556 * HPPA-Dependent:: HPPA Dependent Features
7559 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7562 * IA-64-Dependent:: Intel IA-64 Dependent Features
7565 * IP2K-Dependent:: IP2K Dependent Features
7568 * LM32-Dependent:: LM32 Dependent Features
7571 * M32C-Dependent:: M32C Dependent Features
7574 * M32R-Dependent:: M32R Dependent Features
7577 * M68K-Dependent:: M680x0 Dependent Features
7580 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7583 * S12Z-Dependent:: S12Z Dependent Features
7586 * Meta-Dependent :: Meta Dependent Features
7589 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7592 * MIPS-Dependent:: MIPS Dependent Features
7595 * MMIX-Dependent:: MMIX Dependent Features
7598 * MSP430-Dependent:: MSP430 Dependent Features
7601 * NDS32-Dependent:: Andes NDS32 Dependent Features
7604 * NiosII-Dependent:: Altera Nios II Dependent Features
7607 * NS32K-Dependent:: NS32K Dependent Features
7610 * PDP-11-Dependent:: PDP-11 Dependent Features
7613 * PJ-Dependent:: picoJava Dependent Features
7616 * PPC-Dependent:: PowerPC Dependent Features
7619 * PRU-Dependent:: PRU Dependent Features
7622 * RISC-V-Dependent:: RISC-V Dependent Features
7625 * RL78-Dependent:: RL78 Dependent Features
7628 * RX-Dependent:: RX Dependent Features
7631 * S/390-Dependent:: IBM S/390 Dependent Features
7634 * SCORE-Dependent:: SCORE Dependent Features
7637 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7640 * Sparc-Dependent:: SPARC Dependent Features
7643 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7646 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7649 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7652 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7655 * V850-Dependent:: V850 Dependent Features
7658 * Vax-Dependent:: VAX Dependent Features
7661 * Visium-Dependent:: Visium Dependent Features
7664 * WebAssembly-Dependent:: WebAssembly Dependent Features
7667 * XGATE-Dependent:: XGATE Dependent Features
7670 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7673 * Xtensa-Dependent:: Xtensa Dependent Features
7676 * Z80-Dependent:: Z80 Dependent Features
7679 * Z8000-Dependent:: Z8000 Dependent Features
7686 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7687 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7688 @c peculiarity: to preserve cross-references, there must be a node called
7689 @c "Machine Dependencies". Hence the conditional nodenames in each
7690 @c major node below. Node defaulting in makeinfo requires adjacency of
7691 @c node and sectioning commands; hence the repetition of @chapter BLAH
7692 @c in both conditional blocks.
7695 @include c-aarch64.texi
7699 @include c-alpha.texi
7715 @include c-bfin.texi
7719 @include c-cr16.texi
7723 @include c-cris.texi
7728 @node Machine Dependencies
7729 @chapter Machine Dependent Features
7731 The machine instruction sets are different on each Renesas chip family,
7732 and there are also some syntax differences among the families. This
7733 chapter describes the specific @command{@value{AS}} features for each
7737 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7738 * SH-Dependent:: Renesas SH Dependent Features
7745 @include c-d10v.texi
7749 @include c-d30v.texi
7753 @include c-epiphany.texi
7757 @include c-h8300.texi
7761 @include c-hppa.texi
7765 @include c-i386.texi
7769 @include c-ia64.texi
7773 @include c-ip2k.texi
7777 @include c-lm32.texi
7781 @include c-m32c.texi
7785 @include c-m32r.texi
7789 @include c-m68k.texi
7793 @include c-m68hc11.texi
7797 @include c-s12z.texi
7801 @include c-metag.texi
7805 @include c-microblaze.texi
7809 @include c-mips.texi
7813 @include c-mmix.texi
7817 @include c-msp430.texi
7821 @include c-nds32.texi
7825 @include c-nios2.texi
7829 @include c-ns32k.texi
7833 @include c-pdp11.texi
7849 @include c-riscv.texi
7853 @include c-rl78.texi
7861 @include c-s390.texi
7865 @include c-score.texi
7873 @include c-sparc.texi
7877 @include c-tic54x.texi
7881 @include c-tic6x.texi
7885 @include c-tilegx.texi
7889 @include c-tilepro.texi
7893 @include c-v850.texi
7901 @include c-visium.texi
7905 @include c-wasm32.texi
7909 @include c-xgate.texi
7913 @include c-xstormy16.texi
7917 @include c-xtensa.texi
7929 @c reverse effect of @down at top of generic Machine-Dep chapter
7933 @node Reporting Bugs
7934 @chapter Reporting Bugs
7935 @cindex bugs in assembler
7936 @cindex reporting bugs in assembler
7938 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7940 Reporting a bug may help you by bringing a solution to your problem, or it may
7941 not. But in any case the principal function of a bug report is to help the
7942 entire community by making the next version of @command{@value{AS}} work better.
7943 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7945 In order for a bug report to serve its purpose, you must include the
7946 information that enables us to fix the bug.
7949 * Bug Criteria:: Have you found a bug?
7950 * Bug Reporting:: How to report bugs
7954 @section Have You Found a Bug?
7955 @cindex bug criteria
7957 If you are not sure whether you have found a bug, here are some guidelines:
7960 @cindex fatal signal
7961 @cindex assembler crash
7962 @cindex crash of assembler
7964 If the assembler gets a fatal signal, for any input whatever, that is a
7965 @command{@value{AS}} bug. Reliable assemblers never crash.
7967 @cindex error on valid input
7969 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7971 @cindex invalid input
7973 If @command{@value{AS}} does not produce an error message for invalid input, that
7974 is a bug. However, you should note that your idea of ``invalid input'' might
7975 be our idea of ``an extension'' or ``support for traditional practice''.
7978 If you are an experienced user of assemblers, your suggestions for improvement
7979 of @command{@value{AS}} are welcome in any case.
7983 @section How to Report Bugs
7985 @cindex assembler bugs, reporting
7987 A number of companies and individuals offer support for @sc{gnu} products. If
7988 you obtained @command{@value{AS}} from a support organization, we recommend you
7989 contact that organization first.
7991 You can find contact information for many support companies and
7992 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7996 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8000 The fundamental principle of reporting bugs usefully is this:
8001 @strong{report all the facts}. If you are not sure whether to state a
8002 fact or leave it out, state it!
8004 Often people omit facts because they think they know what causes the problem
8005 and assume that some details do not matter. Thus, you might assume that the
8006 name of a symbol you use in an example does not matter. Well, probably it does
8007 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8008 happens to fetch from the location where that name is stored in memory;
8009 perhaps, if the name were different, the contents of that location would fool
8010 the assembler into doing the right thing despite the bug. Play it safe and
8011 give a specific, complete example. That is the easiest thing for you to do,
8012 and the most helpful.
8014 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8015 it is new to us. Therefore, always write your bug reports on the assumption
8016 that the bug has not been reported previously.
8018 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8019 bell?'' This cannot help us fix a bug, so it is basically useless. We
8020 respond by asking for enough details to enable us to investigate.
8021 You might as well expedite matters by sending them to begin with.
8023 To enable us to fix the bug, you should include all these things:
8027 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8028 it with the @samp{--version} argument.
8030 Without this, we will not know whether there is any point in looking for
8031 the bug in the current version of @command{@value{AS}}.
8034 Any patches you may have applied to the @command{@value{AS}} source.
8037 The type of machine you are using, and the operating system name and
8041 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8045 The command arguments you gave the assembler to assemble your example and
8046 observe the bug. To guarantee you will not omit something important, list them
8047 all. A copy of the Makefile (or the output from make) is sufficient.
8049 If we were to try to guess the arguments, we would probably guess wrong
8050 and then we might not encounter the bug.
8053 A complete input file that will reproduce the bug. If the bug is observed when
8054 the assembler is invoked via a compiler, send the assembler source, not the
8055 high level language source. Most compilers will produce the assembler source
8056 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8057 the options @samp{-v --save-temps}; this will save the assembler source in a
8058 file with an extension of @file{.s}, and also show you exactly how
8059 @command{@value{AS}} is being run.
8062 A description of what behavior you observe that you believe is
8063 incorrect. For example, ``It gets a fatal signal.''
8065 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8066 will certainly notice it. But if the bug is incorrect output, we might not
8067 notice unless it is glaringly wrong. You might as well not give us a chance to
8070 Even if the problem you experience is a fatal signal, you should still say so
8071 explicitly. Suppose something strange is going on, such as, your copy of
8072 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8073 library on your system. (This has happened!) Your copy might crash and ours
8074 would not. If you told us to expect a crash, then when ours fails to crash, we
8075 would know that the bug was not happening for us. If you had not told us to
8076 expect a crash, then we would not be able to draw any conclusion from our
8080 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8081 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8082 option. Always send diffs from the old file to the new file. If you even
8083 discuss something in the @command{@value{AS}} source, refer to it by context, not
8086 The line numbers in our development sources will not match those in your
8087 sources. Your line numbers would convey no useful information to us.
8090 Here are some things that are not necessary:
8094 A description of the envelope of the bug.
8096 Often people who encounter a bug spend a lot of time investigating
8097 which changes to the input file will make the bug go away and which
8098 changes will not affect it.
8100 This is often time consuming and not very useful, because the way we
8101 will find the bug is by running a single example under the debugger
8102 with breakpoints, not by pure deduction from a series of examples.
8103 We recommend that you save your time for something else.
8105 Of course, if you can find a simpler example to report @emph{instead}
8106 of the original one, that is a convenience for us. Errors in the
8107 output will be easier to spot, running under the debugger will take
8108 less time, and so on.
8110 However, simplification is not vital; if you do not want to do this,
8111 report the bug anyway and send us the entire test case you used.
8114 A patch for the bug.
8116 A patch for the bug does help us if it is a good one. But do not omit
8117 the necessary information, such as the test case, on the assumption that
8118 a patch is all we need. We might see problems with your patch and decide
8119 to fix the problem another way, or we might not understand it at all.
8121 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8122 construct an example that will make the program follow a certain path through
8123 the code. If you do not send us the example, we will not be able to construct
8124 one, so we will not be able to verify that the bug is fixed.
8126 And if we cannot understand what bug you are trying to fix, or why your
8127 patch should be an improvement, we will not install it. A test case will
8128 help us to understand.
8131 A guess about what the bug is or what it depends on.
8133 Such guesses are usually wrong. Even we cannot guess right about such
8134 things without first using the debugger to find the facts.
8137 @node Acknowledgements
8138 @chapter Acknowledgements
8140 If you have contributed to GAS and your name isn't listed here,
8141 it is not meant as a slight. We just don't know about it. Send mail to the
8142 maintainer, and we'll correct the situation. Currently
8144 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8146 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8149 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8150 information and the 68k series machines, most of the preprocessing pass, and
8151 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8153 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8154 many bug fixes, including merging support for several processors, breaking GAS
8155 up to handle multiple object file format back ends (including heavy rewrite,
8156 testing, an integration of the coff and b.out back ends), adding configuration
8157 including heavy testing and verification of cross assemblers and file splits
8158 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8159 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8160 port (including considerable amounts of reverse engineering), a SPARC opcode
8161 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8162 assertions and made them work, much other reorganization, cleanup, and lint.
8164 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8165 in format-specific I/O modules.
8167 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8168 has done much work with it since.
8170 The Intel 80386 machine description was written by Eliot Dresselhaus.
8172 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8174 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8175 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8177 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8178 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8179 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8180 support a.out format.
8182 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8183 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8184 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8185 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8188 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8189 simplified the configuration of which versions accept which directives. He
8190 updated the 68k machine description so that Motorola's opcodes always produced
8191 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8192 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8193 cross-compilation support, and one bug in relaxation that took a week and
8194 required the proverbial one-bit fix.
8196 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8197 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8198 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8199 PowerPC assembler, and made a few other minor patches.
8201 Steve Chamberlain made GAS able to generate listings.
8203 Hewlett-Packard contributed support for the HP9000/300.
8205 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8206 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8207 formats). This work was supported by both the Center for Software Science at
8208 the University of Utah and Cygnus Support.
8210 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8211 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8212 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8213 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8214 and some initial 64-bit support).
8216 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8218 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8219 support for openVMS/Alpha.
8221 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8224 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8225 Inc.@: added support for Xtensa processors.
8227 Several engineers at Cygnus Support have also provided many small bug fixes and
8228 configuration enhancements.
8230 Jon Beniston added support for the Lattice Mico32 architecture.
8232 Many others have contributed large or small bugfixes and enhancements. If
8233 you have contributed significant work and are not mentioned on this list, and
8234 want to be, let us know. Some of the history has been lost; we are not
8235 intentionally leaving anyone out.
8237 @node GNU Free Documentation License
8238 @appendix GNU Free Documentation License
8242 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob