1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2021 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2021 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2021 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-<N>}] [@b{--gdwarf-sections}]
234 [@b{--gdwarf-cie-version}=@var{VERSION}]
235 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
236 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
237 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
238 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
239 [@b{--no-pad-sections}]
240 [@b{-o} @var{objfile}] [@b{-R}]
242 [@b{-v}] [@b{-version}] [@b{--version}]
243 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
244 [@b{-Z}] [@b{@@@var{FILE}}]
245 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
246 [@b{--elf-stt-common=[no|yes]}]
247 [@b{--generate-missing-build-notes=[no|yes]}]
248 [@b{--target-help}] [@var{target-options}]
249 [@b{--}|@var{files} @dots{}]
252 @c Target dependent options are listed below. Keep the list sorted.
253 @c Add an empty line for separation.
257 @emph{Target AArch64 options:}
259 [@b{-mabi}=@var{ABI}]
263 @emph{Target Alpha options:}
265 [@b{-mdebug} | @b{-no-mdebug}]
266 [@b{-replace} | @b{-noreplace}]
267 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
268 [@b{-F}] [@b{-32addr}]
272 @emph{Target ARC options:}
273 [@b{-mcpu=@var{cpu}}]
274 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
281 @emph{Target ARM options:}
282 @c Don't document the deprecated options
283 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
284 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
285 [@b{-mfpu}=@var{floating-point-format}]
286 [@b{-mfloat-abi}=@var{abi}]
287 [@b{-meabi}=@var{ver}]
290 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
291 @b{-mapcs-reentrant}]
292 [@b{-mthumb-interwork}] [@b{-k}]
296 @emph{Target Blackfin options:}
297 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
304 @emph{Target BPF options:}
309 @emph{Target CRIS options:}
310 [@b{--underscore} | @b{--no-underscore}]
312 [@b{--emulation=criself} | @b{--emulation=crisaout}]
313 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
314 @c Deprecated -- deliberately not documented.
319 @emph{Target C-SKY options:}
320 [@b{-march=@var{arch}}] [@b{-mcpu=@var{cpu}}]
321 [@b{-EL}] [@b{-mlittle-endian}] [@b{-EB}] [@b{-mbig-endian}]
322 [@b{-fpic}] [@b{-pic}]
323 [@b{-mljump}] [@b{-mno-ljump}]
324 [@b{-force2bsr}] [@b{-mforce2bsr}] [@b{-no-force2bsr}] [@b{-mno-force2bsr}]
325 [@b{-jsri2bsr}] [@b{-mjsri2bsr}] [@b{-no-jsri2bsr }] [@b{-mno-jsri2bsr}]
326 [@b{-mnolrw }] [@b{-mno-lrw}]
327 [@b{-melrw}] [@b{-mno-elrw}]
328 [@b{-mlaf }] [@b{-mliterals-after-func}]
329 [@b{-mno-laf}] [@b{-mno-literals-after-func}]
330 [@b{-mlabr}] [@b{-mliterals-after-br}]
331 [@b{-mno-labr}] [@b{-mnoliterals-after-br}]
332 [@b{-mistack}] [@b{-mno-istack}]
333 [@b{-mhard-float}] [@b{-mmp}] [@b{-mcp}] [@b{-mcache}]
334 [@b{-msecurity}] [@b{-mtrust}]
335 [@b{-mdsp}] [@b{-medsp}] [@b{-mvdsp}]
339 @emph{Target D10V options:}
344 @emph{Target D30V options:}
345 [@b{-O}|@b{-n}|@b{-N}]
349 @emph{Target EPIPHANY options:}
350 [@b{-mepiphany}|@b{-mepiphany16}]
354 @emph{Target H8/300 options:}
358 @c HPPA has no machine-dependent assembler options (yet).
362 @emph{Target i386 options:}
363 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
364 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
368 @emph{Target IA-64 options:}
369 [@b{-mconstant-gp}|@b{-mauto-pic}]
370 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
372 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
373 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
374 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
375 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
379 @emph{Target IP2K options:}
380 [@b{-mip2022}|@b{-mip2022ext}]
384 @emph{Target LOONGARCH options:}
385 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
389 @emph{Target M32C options:}
390 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
394 @emph{Target M32R options:}
395 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
400 @emph{Target M680X0 options:}
401 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
405 @emph{Target M68HC11 options:}
406 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
407 [@b{-mshort}|@b{-mlong}]
408 [@b{-mshort-double}|@b{-mlong-double}]
409 [@b{--force-long-branches}] [@b{--short-branches}]
410 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
411 [@b{--print-opcodes}] [@b{--generate-example}]
415 @emph{Target MCORE options:}
416 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
417 [@b{-mcpu=[210|340]}]
421 @emph{Target Meta options:}
422 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
425 @emph{Target MICROBLAZE options:}
426 @c MicroBlaze has no machine-dependent assembler options.
430 @emph{Target MIPS options:}
431 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
432 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
433 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
434 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
435 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
436 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
437 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
438 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
439 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
440 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
441 [@b{-construct-floats}] [@b{-no-construct-floats}]
442 [@b{-mignore-branch-isa}] [@b{-mno-ignore-branch-isa}]
443 [@b{-mnan=@var{encoding}}]
444 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
445 [@b{-mips16}] [@b{-no-mips16}]
446 [@b{-mmips16e2}] [@b{-mno-mips16e2}]
447 [@b{-mmicromips}] [@b{-mno-micromips}]
448 [@b{-msmartmips}] [@b{-mno-smartmips}]
449 [@b{-mips3d}] [@b{-no-mips3d}]
450 [@b{-mdmx}] [@b{-no-mdmx}]
451 [@b{-mdsp}] [@b{-mno-dsp}]
452 [@b{-mdspr2}] [@b{-mno-dspr2}]
453 [@b{-mdspr3}] [@b{-mno-dspr3}]
454 [@b{-mmsa}] [@b{-mno-msa}]
455 [@b{-mxpa}] [@b{-mno-xpa}]
456 [@b{-mmt}] [@b{-mno-mt}]
457 [@b{-mmcu}] [@b{-mno-mcu}]
458 [@b{-mcrc}] [@b{-mno-crc}]
459 [@b{-mginv}] [@b{-mno-ginv}]
460 [@b{-mloongson-mmi}] [@b{-mno-loongson-mmi}]
461 [@b{-mloongson-cam}] [@b{-mno-loongson-cam}]
462 [@b{-mloongson-ext}] [@b{-mno-loongson-ext}]
463 [@b{-mloongson-ext2}] [@b{-mno-loongson-ext2}]
464 [@b{-minsn32}] [@b{-mno-insn32}]
465 [@b{-mfix7000}] [@b{-mno-fix7000}]
466 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
467 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
468 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
469 [@b{-mfix-r5900}] [@b{-mno-fix-r5900}]
470 [@b{-mdebug}] [@b{-no-mdebug}]
471 [@b{-mpdr}] [@b{-mno-pdr}]
475 @emph{Target MMIX options:}
476 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
477 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
478 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
479 [@b{--linker-allocated-gregs}]
483 @emph{Target Nios II options:}
484 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
489 @emph{Target NDS32 options:}
490 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
491 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
492 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
493 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
494 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
495 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
496 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
500 @c OpenRISC has no machine-dependent assembler options.
504 @emph{Target PDP11 options:}
505 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
506 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
507 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
511 @emph{Target picoJava options:}
516 @emph{Target PowerPC options:}
518 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
519 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mgekko}|
520 @b{-mbroadway}|@b{-mppc64}|@b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|
521 @b{-me6500}|@b{-mppc64bridge}|@b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|
522 @b{-mpower6}|@b{-mpwr6}|@b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
523 @b{-mcell}|@b{-mspe}|@b{-mspe2}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
524 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
525 [@b{-mregnames}|@b{-mno-regnames}]
526 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
527 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
528 [@b{-msolaris}|@b{-mno-solaris}]
529 [@b{-nops=@var{count}}]
533 @emph{Target PRU options:}
536 [@b{-mno-warn-regname-label}]
540 @emph{Target RISC-V options:}
541 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
542 [@b{-march}=@var{ISA}]
543 [@b{-mabi}=@var{ABI}]
544 [@b{-mlittle-endian}|@b{-mbig-endian}]
548 @emph{Target RL78 options:}
550 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
554 @emph{Target RX options:}
555 [@b{-mlittle-endian}|@b{-mbig-endian}]
556 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
557 [@b{-muse-conventional-section-names}]
558 [@b{-msmall-data-limit}]
561 [@b{-mint-register=@var{number}}]
562 [@b{-mgcc-abi}|@b{-mrx-abi}]
566 @emph{Target s390 options:}
567 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
568 [@b{-mregnames}|@b{-mno-regnames}]
569 [@b{-mwarn-areg-zero}]
573 @emph{Target SCORE options:}
574 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
575 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
576 [@b{-march=score7}][@b{-march=score3}]
577 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
581 @emph{Target SPARC options:}
582 @c The order here is important. See c-sparc.texi.
583 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
584 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
585 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
586 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
587 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
588 @b{-Asparcvisr}|@b{-Asparc5}]
589 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
590 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
591 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
592 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
593 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
594 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
597 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
601 @emph{Target TIC54X options:}
602 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
603 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
607 @emph{Target TIC6X options:}
608 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
609 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
610 [@b{-mpic}|@b{-mno-pic}]
614 @emph{Target TILE-Gx options:}
615 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
618 @c TILEPro has no machine-dependent assembler options
622 @emph{Target Visium options:}
623 [@b{-mtune=@var{arch}}]
627 @emph{Target Xtensa options:}
628 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
629 [@b{--[no-]absolute-literals}]
630 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
631 [@b{--[no-]transform}]
632 [@b{--rename-section} @var{oldname}=@var{newname}]
633 [@b{--[no-]trampolines}]
634 [@b{--abi-windowed}|@b{--abi-call0}]
638 @emph{Target Z80 options:}
639 [@b{-march=@var{CPU}@var{[-EXT]}@var{[+EXT]}}]
640 [@b{-local-prefix=}@var{PREFIX}]
643 [@b{-fp-s=}@var{FORMAT}]
644 [@b{-fp-d=}@var{FORMAT}]
648 @c Z8000 has no machine-dependent assembler options
657 @include at-file.texi
660 Turn on listings, in any of a variety of ways:
664 omit false conditionals
667 omit debugging directives
670 include general information, like @value{AS} version and options passed
673 include high-level source
679 include macro expansions
682 omit forms processing
688 set the name of the listing file
691 You may combine these options; for example, use @samp{-aln} for assembly
692 listing without forms processing. The @samp{=file} option, if used, must be
693 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
696 Begin in alternate macro mode.
698 @xref{Altmacro,,@code{.altmacro}}.
701 @item --compress-debug-sections
702 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
703 ELF ABI. The resulting object file may not be compatible with older
704 linkers and object file utilities. Note if compression would make a
705 given section @emph{larger} then it is not compressed.
708 @cindex @samp{--compress-debug-sections=} option
709 @item --compress-debug-sections=none
710 @itemx --compress-debug-sections=zlib
711 @itemx --compress-debug-sections=zlib-gnu
712 @itemx --compress-debug-sections=zlib-gabi
713 These options control how DWARF debug sections are compressed.
714 @option{--compress-debug-sections=none} is equivalent to
715 @option{--nocompress-debug-sections}.
716 @option{--compress-debug-sections=zlib} and
717 @option{--compress-debug-sections=zlib-gabi} are equivalent to
718 @option{--compress-debug-sections}.
719 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
720 sections using zlib. The debug sections are renamed to begin with
721 @samp{.zdebug}. Note if compression would make a given section
722 @emph{larger} then it is not compressed nor renamed.
726 @item --nocompress-debug-sections
727 Do not compress DWARF debug sections. This is usually the default for all
728 targets except the x86/x86_64, but a configure time option can be used to
732 Ignored. This option is accepted for script compatibility with calls to
735 @item --debug-prefix-map @var{old}=@var{new}
736 When assembling files in directory @file{@var{old}}, record debugging
737 information describing them as in @file{@var{new}} instead.
739 @item --defsym @var{sym}=@var{value}
740 Define the symbol @var{sym} to be @var{value} before assembling the input file.
741 @var{value} must be an integer constant. As in C, a leading @samp{0x}
742 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
743 value. The value of the symbol can be overridden inside a source file via the
744 use of a @code{.set} pseudo-op.
747 ``fast''---skip whitespace and comment preprocessing (assume source is
752 Generate debugging information for each assembler source line using whichever
753 debug format is preferred by the target. This currently means either STABS,
754 ECOFF or DWARF2. When the debug format is DWARF then a @code{.debug_info} and
755 @code{.debug_line} section is only emitted when the assembly file doesn't
759 Generate stabs debugging information for each assembler line. This
760 may help debugging assembler code, if the debugger can handle it.
763 Generate stabs debugging information for each assembler line, with GNU
764 extensions that probably only gdb can handle, and that could make other
765 debuggers crash or refuse to read your program. This
766 may help debugging assembler code. Currently the only GNU extension is
767 the location of the current working directory at assembling time.
770 Generate DWARF2 debugging information for each assembler line. This
771 may help debugging assembler code, if the debugger can handle it. Note---this
772 option is only supported by some targets, not all of them.
775 This option is the same as the @option{--gdwarf-2} option, except that it
776 allows for the possibility of the generation of extra debug information as per
777 version 3 of the DWARF specification. Note - enabling this option does not
778 guarantee the generation of any extra information, the choice to do so is on a
782 This option is the same as the @option{--gdwarf-2} option, except that it
783 allows for the possibility of the generation of extra debug information as per
784 version 4 of the DWARF specification. Note - enabling this option does not
785 guarantee the generation of any extra information, the choice to do so is on a
789 This option is the same as the @option{--gdwarf-2} option, except that it
790 allows for the possibility of the generation of extra debug information as per
791 version 5 of the DWARF specification. Note - enabling this option does not
792 guarantee the generation of any extra information, the choice to do so is on a
795 @item --gdwarf-sections
796 Instead of creating a .debug_line section, create a series of
797 .debug_line.@var{foo} sections where @var{foo} is the name of the
798 corresponding code section. For example a code section called @var{.text.func}
799 will have its dwarf line number information placed into a section called
800 @var{.debug_line.text.func}. If the code section is just called @var{.text}
801 then debug line section will still be called just @var{.debug_line} without any
804 @item --gdwarf-cie-version=@var{version}
805 Control which version of DWARF Common Information Entries (CIEs) are produced.
806 When this flag is not specificed the default is version 1, though some targets
807 can modify this default. Other possible values for @var{version} are 3 or 4.
810 @item --size-check=error
811 @itemx --size-check=warning
812 Issue an error or warning for invalid ELF .size directive.
814 @item --elf-stt-common=no
815 @itemx --elf-stt-common=yes
816 These options control whether the ELF assembler should generate common
817 symbols with the @code{STT_COMMON} type. The default can be controlled
818 by a configure option @option{--enable-elf-stt-common}.
820 @item --generate-missing-build-notes=yes
821 @itemx --generate-missing-build-notes=no
822 These options control whether the ELF assembler should generate GNU Build
823 attribute notes if none are present in the input sources.
824 The default can be controlled by the @option{--enable-generate-build-notes}
830 Print a summary of the command-line options and exit.
833 Print a summary of all target specific options and exit.
836 Add directory @var{dir} to the search list for @code{.include} directives.
839 Don't warn about signed overflow.
842 @ifclear DIFF-TBL-KLUGE
843 This option is accepted but has no effect on the @value{TARGET} family.
845 @ifset DIFF-TBL-KLUGE
846 Issue warnings when difference tables altered for long displacements.
851 Keep (in the symbol table) local symbols. These symbols start with
852 system-specific local label prefixes, typically @samp{.L} for ELF systems
853 or @samp{L} for traditional a.out systems.
858 @item --listing-lhs-width=@var{number}
859 Set the maximum width, in words, of the output data column for an assembler
860 listing to @var{number}.
862 @item --listing-lhs-width2=@var{number}
863 Set the maximum width, in words, of the output data column for continuation
864 lines in an assembler listing to @var{number}.
866 @item --listing-rhs-width=@var{number}
867 Set the maximum width of an input source line, as displayed in a listing, to
870 @item --listing-cont-lines=@var{number}
871 Set the maximum number of lines printed in a listing for a single line of input
874 @item --no-pad-sections
875 Stop the assembler for padding the ends of output sections to the alignment
876 of that section. The default is to pad the sections, but this can waste space
877 which might be needed on targets which have tight memory constraints.
879 @item -o @var{objfile}
880 Name the object-file output from @command{@value{AS}} @var{objfile}.
883 Fold the data section into the text section.
886 @item --sectname-subst
887 Honor substitution sequences in section names.
889 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
894 Print the maximum space (in bytes) and total time (in seconds) used by
897 @item --strip-local-absolute
898 Remove local absolute symbols from the outgoing symbol table.
902 Print the @command{as} version.
905 Print the @command{as} version and exit.
909 Suppress warning messages.
911 @item --fatal-warnings
912 Treat warnings as errors.
915 Don't suppress warning messages or treat them as errors.
924 Generate an object file even after errors.
926 @item -- | @var{files} @dots{}
927 Standard input, or source files to assemble.
935 @xref{AArch64 Options}, for the options available when @value{AS} is configured
936 for the 64-bit mode of the ARM Architecture (AArch64).
941 The following options are available when @value{AS} is configured for the
942 64-bit mode of the ARM Architecture (AArch64).
945 @include c-aarch64.texi
946 @c ended inside the included file
954 @xref{Alpha Options}, for the options available when @value{AS} is configured
955 for an Alpha processor.
960 The following options are available when @value{AS} is configured for an Alpha
964 @include c-alpha.texi
965 @c ended inside the included file
972 The following options are available when @value{AS} is configured for an ARC
976 @item -mcpu=@var{cpu}
977 This option selects the core processor variant.
979 Select either big-endian (-EB) or little-endian (-EL) output.
981 Enable Code Density extension instructions.
986 The following options are available when @value{AS} is configured for the ARM
990 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
991 Specify which ARM processor variant is the target.
992 @item -march=@var{architecture}[+@var{extension}@dots{}]
993 Specify which ARM architecture variant is used by the target.
994 @item -mfpu=@var{floating-point-format}
995 Select which Floating Point architecture is the target.
996 @item -mfloat-abi=@var{abi}
997 Select which floating point ABI is in use.
999 Enable Thumb only instruction decoding.
1000 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
1001 Select which procedure calling convention is in use.
1003 Select either big-endian (-EB) or little-endian (-EL) output.
1004 @item -mthumb-interwork
1005 Specify that the code has been generated with interworking between Thumb and
1008 Turns on CodeComposer Studio assembly syntax compatibility mode.
1010 Specify that PIC code has been generated.
1018 @xref{Blackfin Options}, for the options available when @value{AS} is
1019 configured for the Blackfin processor family.
1023 @c man begin OPTIONS
1024 The following options are available when @value{AS} is configured for
1025 the Blackfin processor family.
1027 @c man begin INCLUDE
1028 @include c-bfin.texi
1029 @c ended inside the included file
1037 @xref{BPF Options}, for the options available when @value{AS} is
1038 configured for the Linux kernel BPF processor family.
1042 @c man begin OPTIONS
1043 The following options are available when @value{AS} is configured for
1044 the Linux kernel BPF processor family.
1046 @c man begin INCLUDE
1048 @c ended inside the included file
1053 @c man begin OPTIONS
1055 See the info pages for documentation of the CRIS-specific options.
1061 @xref{C-SKY Options}, for the options available when @value{AS} is
1062 configured for the C-SKY processor family.
1066 @c man begin OPTIONS
1067 The following options are available when @value{AS} is configured for
1068 the C-SKY processor family.
1070 @c man begin INCLUDE
1071 @include c-csky.texi
1072 @c ended inside the included file
1078 The following options are available when @value{AS} is configured for
1081 @cindex D10V optimization
1082 @cindex optimization, D10V
1084 Optimize output by parallelizing instructions.
1089 The following options are available when @value{AS} is configured for a D30V
1092 @cindex D30V optimization
1093 @cindex optimization, D30V
1095 Optimize output by parallelizing instructions.
1099 Warn when nops are generated.
1101 @cindex D30V nops after 32-bit multiply
1103 Warn when a nop after a 32-bit multiply instruction is generated.
1109 The following options are available when @value{AS} is configured for the
1110 Adapteva EPIPHANY series.
1113 @xref{Epiphany Options}, for the options available when @value{AS} is
1114 configured for an Epiphany processor.
1118 @c man begin OPTIONS
1119 The following options are available when @value{AS} is configured for
1120 an Epiphany processor.
1122 @c man begin INCLUDE
1123 @include c-epiphany.texi
1124 @c ended inside the included file
1132 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1133 for an H8/300 processor.
1137 @c man begin OPTIONS
1138 The following options are available when @value{AS} is configured for an H8/300
1141 @c man begin INCLUDE
1142 @include c-h8300.texi
1143 @c ended inside the included file
1151 @xref{i386-Options}, for the options available when @value{AS} is
1152 configured for an i386 processor.
1156 @c man begin OPTIONS
1157 The following options are available when @value{AS} is configured for
1160 @c man begin INCLUDE
1161 @include c-i386.texi
1162 @c ended inside the included file
1167 @c man begin OPTIONS
1169 The following options are available when @value{AS} is configured for the
1175 Specifies that the extended IP2022 instructions are allowed.
1178 Restores the default behaviour, which restricts the permitted instructions to
1179 just the basic IP2022 ones.
1185 The following options are available when @value{AS} is configured for the
1186 Renesas M32C and M16C processors.
1191 Assemble M32C instructions.
1194 Assemble M16C instructions (the default).
1197 Enable support for link-time relaxations.
1200 Support H'00 style hex constants in addition to 0x00 style.
1206 The following options are available when @value{AS} is configured for the
1207 Renesas M32R (formerly Mitsubishi M32R) series.
1212 Specify which processor in the M32R family is the target. The default
1213 is normally the M32R, but this option changes it to the M32RX.
1215 @item --warn-explicit-parallel-conflicts or --Wp
1216 Produce warning messages when questionable parallel constructs are
1219 @item --no-warn-explicit-parallel-conflicts or --Wnp
1220 Do not produce warning messages when questionable parallel constructs are
1227 The following options are available when @value{AS} is configured for the
1228 Motorola 68000 series.
1233 Shorten references to undefined symbols, to one word instead of two.
1235 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1236 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1237 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1238 Specify what processor in the 68000 family is the target. The default
1239 is normally the 68020, but this can be changed at configuration time.
1241 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1242 The target machine does (or does not) have a floating-point coprocessor.
1243 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1244 the basic 68000 is not compatible with the 68881, a combination of the
1245 two can be specified, since it's possible to do emulation of the
1246 coprocessor instructions with the main processor.
1248 @item -m68851 | -mno-68851
1249 The target machine does (or does not) have a memory-management
1250 unit coprocessor. The default is to assume an MMU for 68020 and up.
1258 @xref{Nios II Options}, for the options available when @value{AS} is configured
1259 for an Altera Nios II processor.
1263 @c man begin OPTIONS
1264 The following options are available when @value{AS} is configured for an
1265 Altera Nios II processor.
1267 @c man begin INCLUDE
1268 @include c-nios2.texi
1269 @c ended inside the included file
1275 For details about the PDP-11 machine dependent features options,
1276 see @ref{PDP-11-Options}.
1279 @item -mpic | -mno-pic
1280 Generate position-independent (or position-dependent) code. The
1281 default is @option{-mpic}.
1284 @itemx -mall-extensions
1285 Enable all instruction set extensions. This is the default.
1287 @item -mno-extensions
1288 Disable all instruction set extensions.
1290 @item -m@var{extension} | -mno-@var{extension}
1291 Enable (or disable) a particular instruction set extension.
1294 Enable the instruction set extensions supported by a particular CPU, and
1295 disable all other extensions.
1297 @item -m@var{machine}
1298 Enable the instruction set extensions supported by a particular machine
1299 model, and disable all other extensions.
1305 The following options are available when @value{AS} is configured for
1306 a picoJava processor.
1310 @cindex PJ endianness
1311 @cindex endianness, PJ
1312 @cindex big endian output, PJ
1314 Generate ``big endian'' format output.
1316 @cindex little endian output, PJ
1318 Generate ``little endian'' format output.
1326 @xref{PRU Options}, for the options available when @value{AS} is configured
1327 for a PRU processor.
1331 @c man begin OPTIONS
1332 The following options are available when @value{AS} is configured for a
1335 @c man begin INCLUDE
1337 @c ended inside the included file
1342 The following options are available when @value{AS} is configured for the
1343 Motorola 68HC11 or 68HC12 series.
1347 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1348 Specify what processor is the target. The default is
1349 defined by the configuration option when building the assembler.
1351 @item --xgate-ramoffset
1352 Instruct the linker to offset RAM addresses from S12X address space into
1353 XGATE address space.
1356 Specify to use the 16-bit integer ABI.
1359 Specify to use the 32-bit integer ABI.
1361 @item -mshort-double
1362 Specify to use the 32-bit double ABI.
1365 Specify to use the 64-bit double ABI.
1367 @item --force-long-branches
1368 Relative branches are turned into absolute ones. This concerns
1369 conditional branches, unconditional branches and branches to a
1372 @item -S | --short-branches
1373 Do not turn relative branches into absolute ones
1374 when the offset is out of range.
1376 @item --strict-direct-mode
1377 Do not turn the direct addressing mode into extended addressing mode
1378 when the instruction does not support direct addressing mode.
1380 @item --print-insn-syntax
1381 Print the syntax of instruction in case of error.
1383 @item --print-opcodes
1384 Print the list of instructions with syntax and then exit.
1386 @item --generate-example
1387 Print an example of instruction for each possible instruction and then exit.
1388 This option is only useful for testing @command{@value{AS}}.
1394 The following options are available when @command{@value{AS}} is configured
1395 for the SPARC architecture:
1398 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1399 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1400 Explicitly select a variant of the SPARC architecture.
1402 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1403 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1405 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1406 UltraSPARC extensions.
1408 @item -xarch=v8plus | -xarch=v8plusa
1409 For compatibility with the Solaris v9 assembler. These options are
1410 equivalent to -Av8plus and -Av8plusa, respectively.
1413 Warn when the assembler switches to another architecture.
1418 The following options are available when @value{AS} is configured for the 'c54x
1423 Enable extended addressing mode. All addresses and relocations will assume
1424 extended addressing (usually 23 bits).
1425 @item -mcpu=@var{CPU_VERSION}
1426 Sets the CPU version being compiled for.
1427 @item -merrors-to-file @var{FILENAME}
1428 Redirect error output to a file, for broken systems which don't support such
1429 behaviour in the shell.
1434 @c man begin OPTIONS
1435 The following options are available when @value{AS} is configured for
1440 This option sets the largest size of an object that can be referenced
1441 implicitly with the @code{gp} register. It is only accepted for targets that
1442 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1444 @cindex MIPS endianness
1445 @cindex endianness, MIPS
1446 @cindex big endian output, MIPS
1448 Generate ``big endian'' format output.
1450 @cindex little endian output, MIPS
1452 Generate ``little endian'' format output.
1470 Generate code for a particular MIPS Instruction Set Architecture level.
1471 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1472 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1473 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1474 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1475 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1476 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1477 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1478 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1479 MIPS64 Release 6 ISA processors, respectively.
1481 @item -march=@var{cpu}
1482 Generate code for a particular MIPS CPU.
1484 @item -mtune=@var{cpu}
1485 Schedule and tune for a particular MIPS CPU.
1489 Cause nops to be inserted if the read of the destination register
1490 of an mfhi or mflo instruction occurs in the following two instructions.
1493 @itemx -mno-fix-rm7000
1494 Cause nops to be inserted if a dmult or dmultu instruction is
1495 followed by a load instruction.
1498 @itemx -mno-fix-r5900
1499 Do not attempt to schedule the preceding instruction into the delay slot
1500 of a branch instruction placed at the end of a short loop of six
1501 instructions or fewer and always schedule a @code{nop} instruction there
1502 instead. The short loop bug under certain conditions causes loops to
1503 execute only once or twice, due to a hardware bug in the R5900 chip.
1507 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1508 section instead of the standard ELF .stabs sections.
1512 Control generation of @code{.pdr} sections.
1516 The register sizes are normally inferred from the ISA and ABI, but these
1517 flags force a certain group of registers to be treated as 32 bits wide at
1518 all times. @samp{-mgp32} controls the size of general-purpose registers
1519 and @samp{-mfp32} controls the size of floating-point registers.
1523 The register sizes are normally inferred from the ISA and ABI, but these
1524 flags force a certain group of registers to be treated as 64 bits wide at
1525 all times. @samp{-mgp64} controls the size of general-purpose registers
1526 and @samp{-mfp64} controls the size of floating-point registers.
1529 The register sizes are normally inferred from the ISA and ABI, but using
1530 this flag in combination with @samp{-mabi=32} enables an ABI variant
1531 which will operate correctly with floating-point registers which are
1535 @itemx -mno-odd-spreg
1536 Enable use of floating-point operations on odd-numbered single-precision
1537 registers when supported by the ISA. @samp{-mfpxx} implies
1538 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1542 Generate code for the MIPS 16 processor. This is equivalent to putting
1543 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1544 turns off this option.
1547 @itemx -mno-mips16e2
1548 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1549 to putting @code{.module mips16e2} at the start of the assembly file.
1550 @samp{-mno-mips16e2} turns off this option.
1553 @itemx -mno-micromips
1554 Generate code for the microMIPS processor. This is equivalent to putting
1555 @code{.module micromips} at the start of the assembly file.
1556 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1557 @code{.module nomicromips} at the start of the assembly file.
1560 @itemx -mno-smartmips
1561 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1562 equivalent to putting @code{.module smartmips} at the start of the assembly
1563 file. @samp{-mno-smartmips} turns off this option.
1567 Generate code for the MIPS-3D Application Specific Extension.
1568 This tells the assembler to accept MIPS-3D instructions.
1569 @samp{-no-mips3d} turns off this option.
1573 Generate code for the MDMX Application Specific Extension.
1574 This tells the assembler to accept MDMX instructions.
1575 @samp{-no-mdmx} turns off this option.
1579 Generate code for the DSP Release 1 Application Specific Extension.
1580 This tells the assembler to accept DSP Release 1 instructions.
1581 @samp{-mno-dsp} turns off this option.
1585 Generate code for the DSP Release 2 Application Specific Extension.
1586 This option implies @samp{-mdsp}.
1587 This tells the assembler to accept DSP Release 2 instructions.
1588 @samp{-mno-dspr2} turns off this option.
1592 Generate code for the DSP Release 3 Application Specific Extension.
1593 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1594 This tells the assembler to accept DSP Release 3 instructions.
1595 @samp{-mno-dspr3} turns off this option.
1599 Generate code for the MIPS SIMD Architecture Extension.
1600 This tells the assembler to accept MSA instructions.
1601 @samp{-mno-msa} turns off this option.
1605 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1606 This tells the assembler to accept XPA instructions.
1607 @samp{-mno-xpa} turns off this option.
1611 Generate code for the MT Application Specific Extension.
1612 This tells the assembler to accept MT instructions.
1613 @samp{-mno-mt} turns off this option.
1617 Generate code for the MCU Application Specific Extension.
1618 This tells the assembler to accept MCU instructions.
1619 @samp{-mno-mcu} turns off this option.
1623 Generate code for the MIPS cyclic redundancy check (CRC) Application
1624 Specific Extension. This tells the assembler to accept CRC instructions.
1625 @samp{-mno-crc} turns off this option.
1629 Generate code for the Global INValidate (GINV) Application Specific
1630 Extension. This tells the assembler to accept GINV instructions.
1631 @samp{-mno-ginv} turns off this option.
1633 @item -mloongson-mmi
1634 @itemx -mno-loongson-mmi
1635 Generate code for the Loongson MultiMedia extensions Instructions (MMI)
1636 Application Specific Extension. This tells the assembler to accept MMI
1638 @samp{-mno-loongson-mmi} turns off this option.
1640 @item -mloongson-cam
1641 @itemx -mno-loongson-cam
1642 Generate code for the Loongson Content Address Memory (CAM) instructions.
1643 This tells the assembler to accept Loongson CAM instructions.
1644 @samp{-mno-loongson-cam} turns off this option.
1646 @item -mloongson-ext
1647 @itemx -mno-loongson-ext
1648 Generate code for the Loongson EXTensions (EXT) instructions.
1649 This tells the assembler to accept Loongson EXT instructions.
1650 @samp{-mno-loongson-ext} turns off this option.
1652 @item -mloongson-ext2
1653 @itemx -mno-loongson-ext2
1654 Generate code for the Loongson EXTensions R2 (EXT2) instructions.
1655 This option implies @samp{-mloongson-ext}.
1656 This tells the assembler to accept Loongson EXT2 instructions.
1657 @samp{-mno-loongson-ext2} turns off this option.
1661 Only use 32-bit instruction encodings when generating code for the
1662 microMIPS processor. This option inhibits the use of any 16-bit
1663 instructions. This is equivalent to putting @code{.set insn32} at
1664 the start of the assembly file. @samp{-mno-insn32} turns off this
1665 option. This is equivalent to putting @code{.set noinsn32} at the
1666 start of the assembly file. By default @samp{-mno-insn32} is
1667 selected, allowing all instructions to be used.
1669 @item --construct-floats
1670 @itemx --no-construct-floats
1671 The @samp{--no-construct-floats} option disables the construction of
1672 double width floating point constants by loading the two halves of the
1673 value into the two single width floating point registers that make up
1674 the double width register. By default @samp{--construct-floats} is
1675 selected, allowing construction of these floating point constants.
1677 @item --relax-branch
1678 @itemx --no-relax-branch
1679 The @samp{--relax-branch} option enables the relaxation of out-of-range
1680 branches. By default @samp{--no-relax-branch} is selected, causing any
1681 out-of-range branches to produce an error.
1683 @item -mignore-branch-isa
1684 @itemx -mno-ignore-branch-isa
1685 Ignore branch checks for invalid transitions between ISA modes. The
1686 semantics of branches does not provide for an ISA mode switch, so in
1687 most cases the ISA mode a branch has been encoded for has to be the
1688 same as the ISA mode of the branch's target label. Therefore GAS has
1689 checks implemented that verify in branch assembly that the two ISA
1690 modes match. @samp{-mignore-branch-isa} disables these checks. By
1691 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1692 branch requiring a transition between ISA modes to produce an error.
1694 @item -mnan=@var{encoding}
1695 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1696 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1699 @item --emulation=@var{name}
1700 This option was formerly used to switch between ELF and ECOFF output
1701 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1702 removed in GAS 2.24, so the option now serves little purpose.
1703 It is retained for backwards compatibility.
1705 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1706 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1707 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1708 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1709 preferred options instead.
1712 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1719 Control how to deal with multiplication overflow and division by zero.
1720 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1721 (and only work for Instruction Set Architecture level 2 and higher);
1722 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1726 When this option is used, @command{@value{AS}} will issue a warning every
1727 time it generates a nop instruction from a macro.
1733 The following options are available when @value{AS} is configured for
1739 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1740 The command-line option @samp{-nojsri2bsr} can be used to disable it.
1744 Enable or disable the silicon filter behaviour. By default this is disabled.
1745 The default can be overridden by the @samp{-sifilter} command-line option.
1748 Alter jump instructions for long displacements.
1750 @item -mcpu=[210|340]
1751 Select the cpu type on the target hardware. This controls which instructions
1755 Assemble for a big endian target.
1758 Assemble for a little endian target.
1767 @xref{LoongArch-Options}, for the options available when @value{AS} is configured
1768 for a LoongArch processor.
1772 @c man begin OPTIONS
1773 The following options are available when @value{AS} is configured for a
1774 LoongArch processor.
1776 @c man begin INCLUDE
1777 @include c-loongarch.texi
1778 @c ended inside the included file
1786 @xref{Meta Options}, for the options available when @value{AS} is configured
1787 for a Meta processor.
1791 @c man begin OPTIONS
1792 The following options are available when @value{AS} is configured for a
1795 @c man begin INCLUDE
1796 @include c-metag.texi
1797 @c ended inside the included file
1802 @c man begin OPTIONS
1804 See the info pages for documentation of the MMIX-specific options.
1810 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1811 for a NDS32 processor.
1813 @c ended inside the included file
1817 @c man begin OPTIONS
1818 The following options are available when @value{AS} is configured for a
1821 @c man begin INCLUDE
1822 @include c-nds32.texi
1823 @c ended inside the included file
1830 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1831 for a PowerPC processor.
1835 @c man begin OPTIONS
1836 The following options are available when @value{AS} is configured for a
1839 @c man begin INCLUDE
1841 @c ended inside the included file
1849 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1850 for a RISC-V processor.
1854 @c man begin OPTIONS
1855 The following options are available when @value{AS} is configured for a
1858 @c man begin INCLUDE
1859 @include c-riscv.texi
1860 @c ended inside the included file
1865 @c man begin OPTIONS
1867 See the info pages for documentation of the RX-specific options.
1871 The following options are available when @value{AS} is configured for the s390
1877 Select the word size, either 31/32 bits or 64 bits.
1880 Select the architecture mode, either the Enterprise System
1881 Architecture (esa) or the z/Architecture mode (zarch).
1882 @item -march=@var{processor}
1883 Specify which s390 processor variant is the target, @samp{g5} (or
1884 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1885 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1886 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1887 @samp{z13} (or @samp{arch11}), @samp{z14} (or @samp{arch12}), or @samp{z15}
1890 @itemx -mno-regnames
1891 Allow or disallow symbolic names for registers.
1892 @item -mwarn-areg-zero
1893 Warn whenever the operand for a base or index register has been specified
1894 but evaluates to zero.
1902 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1903 for a TMS320C6000 processor.
1907 @c man begin OPTIONS
1908 The following options are available when @value{AS} is configured for a
1909 TMS320C6000 processor.
1911 @c man begin INCLUDE
1912 @include c-tic6x.texi
1913 @c ended inside the included file
1921 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1922 for a TILE-Gx processor.
1926 @c man begin OPTIONS
1927 The following options are available when @value{AS} is configured for a TILE-Gx
1930 @c man begin INCLUDE
1931 @include c-tilegx.texi
1932 @c ended inside the included file
1940 @xref{Visium Options}, for the options available when @value{AS} is configured
1941 for a Visium processor.
1945 @c man begin OPTIONS
1946 The following option is available when @value{AS} is configured for a Visium
1949 @c man begin INCLUDE
1950 @include c-visium.texi
1951 @c ended inside the included file
1959 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1960 for an Xtensa processor.
1964 @c man begin OPTIONS
1965 The following options are available when @value{AS} is configured for an
1968 @c man begin INCLUDE
1969 @include c-xtensa.texi
1970 @c ended inside the included file
1978 @xref{Z80 Options}, for the options available when @value{AS} is configured
1979 for an Z80 processor.
1983 @c man begin OPTIONS
1984 The following options are available when @value{AS} is configured for an
1987 @c man begin INCLUDE
1989 @c ended inside the included file
1995 * Manual:: Structure of this Manual
1996 * GNU Assembler:: The GNU Assembler
1997 * Object Formats:: Object File Formats
1998 * Command Line:: Command Line
1999 * Input Files:: Input Files
2000 * Object:: Output (Object) File
2001 * Errors:: Error and Warning Messages
2005 @section Structure of this Manual
2007 @cindex manual, structure and purpose
2008 This manual is intended to describe what you need to know to use
2009 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
2010 notation for symbols, constants, and expressions; the directives that
2011 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
2014 We also cover special features in the @value{TARGET}
2015 configuration of @command{@value{AS}}, including assembler directives.
2018 This manual also describes some of the machine-dependent features of
2019 various flavors of the assembler.
2022 @cindex machine instructions (not covered)
2023 On the other hand, this manual is @emph{not} intended as an introduction
2024 to programming in assembly language---let alone programming in general!
2025 In a similar vein, we make no attempt to introduce the machine
2026 architecture; we do @emph{not} describe the instruction set, standard
2027 mnemonics, registers or addressing modes that are standard to a
2028 particular architecture.
2030 You may want to consult the manufacturer's
2031 machine architecture manual for this information.
2035 For information on the H8/300 machine instruction set, see @cite{H8/300
2036 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
2037 Programming Manual} (Renesas).
2040 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
2041 see @cite{SH-Microcomputer User's Manual} (Renesas) or
2042 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
2043 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
2046 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
2050 @c I think this is premature---doc@cygnus.com, 17jan1991
2052 Throughout this manual, we assume that you are running @dfn{GNU},
2053 the portable operating system from the @dfn{Free Software
2054 Foundation, Inc.}. This restricts our attention to certain kinds of
2055 computer (in particular, the kinds of computers that @sc{gnu} can run on);
2056 once this assumption is granted examples and definitions need less
2059 @command{@value{AS}} is part of a team of programs that turn a high-level
2060 human-readable series of instructions into a low-level
2061 computer-readable series of instructions. Different versions of
2062 @command{@value{AS}} are used for different kinds of computer.
2065 @c There used to be a section "Terminology" here, which defined
2066 @c "contents", "byte", "word", and "long". Defining "word" to any
2067 @c particular size is confusing when the .word directive may generate 16
2068 @c bits on one machine and 32 bits on another; in general, for the user
2069 @c version of this manual, none of these terms seem essential to define.
2070 @c They were used very little even in the former draft of the manual;
2071 @c this draft makes an effort to avoid them (except in names of
2075 @section The GNU Assembler
2077 @c man begin DESCRIPTION
2079 @sc{gnu} @command{as} is really a family of assemblers.
2081 This manual describes @command{@value{AS}}, a member of that family which is
2082 configured for the @value{TARGET} architectures.
2084 If you use (or have used) the @sc{gnu} assembler on one architecture, you
2085 should find a fairly similar environment when you use it on another
2086 architecture. Each version has much in common with the others,
2087 including object file formats, most assembler directives (often called
2088 @dfn{pseudo-ops}) and assembler syntax.@refill
2090 @cindex purpose of @sc{gnu} assembler
2091 @command{@value{AS}} is primarily intended to assemble the output of the
2092 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
2093 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
2094 assemble correctly everything that other assemblers for the same
2095 machine would assemble.
2097 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
2100 @c This remark should appear in generic version of manual; assumption
2101 @c here is that generic version sets M680x0.
2102 This doesn't mean @command{@value{AS}} always uses the same syntax as another
2103 assembler for the same architecture; for example, we know of several
2104 incompatible versions of 680x0 assembly language syntax.
2109 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
2110 program in one pass of the source file. This has a subtle impact on the
2111 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
2113 @node Object Formats
2114 @section Object File Formats
2116 @cindex object file format
2117 The @sc{gnu} assembler can be configured to produce several alternative
2118 object file formats. For the most part, this does not affect how you
2119 write assembly language programs; but directives for debugging symbols
2120 are typically different in different file formats. @xref{Symbol
2121 Attributes,,Symbol Attributes}.
2124 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
2125 @value{OBJ-NAME} format object files.
2127 @c The following should exhaust all configs that set MULTI-OBJ, ideally
2129 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2130 SOM or ELF format object files.
2135 @section Command Line
2137 @cindex command line conventions
2139 After the program name @command{@value{AS}}, the command line may contain
2140 options and file names. Options may appear in any order, and may be
2141 before, after, or between file names. The order of file names is
2144 @cindex standard input, as input file
2146 @file{--} (two hyphens) by itself names the standard input file
2147 explicitly, as one of the files for @command{@value{AS}} to assemble.
2149 @cindex options, command line
2150 Except for @samp{--} any command-line argument that begins with a
2151 hyphen (@samp{-}) is an option. Each option changes the behavior of
2152 @command{@value{AS}}. No option changes the way another option works. An
2153 option is a @samp{-} followed by one or more letters; the case of
2154 the letter is important. All options are optional.
2156 Some options expect exactly one file name to follow them. The file
2157 name may either immediately follow the option's letter (compatible
2158 with older assemblers) or it may be the next command argument (@sc{gnu}
2159 standard). These two command lines are equivalent:
2162 @value{AS} -o my-object-file.o mumble.s
2163 @value{AS} -omy-object-file.o mumble.s
2167 @section Input Files
2170 @cindex source program
2171 @cindex files, input
2172 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2173 describe the program input to one run of @command{@value{AS}}. The program may
2174 be in one or more files; how the source is partitioned into files
2175 doesn't change the meaning of the source.
2177 @c I added "con" prefix to "catenation" just to prove I can overcome my
2178 @c APL training... doc@cygnus.com
2179 The source program is a concatenation of the text in all the files, in the
2182 @c man begin DESCRIPTION
2183 Each time you run @command{@value{AS}} it assembles exactly one source
2184 program. The source program is made up of one or more files.
2185 (The standard input is also a file.)
2187 You give @command{@value{AS}} a command line that has zero or more input file
2188 names. The input files are read (from left file name to right). A
2189 command-line argument (in any position) that has no special meaning
2190 is taken to be an input file name.
2192 If you give @command{@value{AS}} no file names it attempts to read one input file
2193 from the @command{@value{AS}} standard input, which is normally your terminal. You
2194 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2197 Use @samp{--} if you need to explicitly name the standard input file
2198 in your command line.
2200 If the source is empty, @command{@value{AS}} produces a small, empty object
2205 @subheading Filenames and Line-numbers
2207 @cindex input file linenumbers
2208 @cindex line numbers, in input files
2209 There are two ways of locating a line in the input file (or files) and
2210 either may be used in reporting error messages. One way refers to a line
2211 number in a physical file; the other refers to a line number in a
2212 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2214 @dfn{Physical files} are those files named in the command line given
2215 to @command{@value{AS}}.
2217 @dfn{Logical files} are simply names declared explicitly by assembler
2218 directives; they bear no relation to physical files. Logical file names help
2219 error messages reflect the original source file, when @command{@value{AS}} source
2220 is itself synthesized from other files. @command{@value{AS}} understands the
2221 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2222 @ref{File,,@code{.file}}.
2225 @section Output (Object) File
2231 Every time you run @command{@value{AS}} it produces an output file, which is
2232 your assembly language program translated into numbers. This file
2233 is the object file. Its default name is @code{a.out}.
2234 You can give it another name by using the @option{-o} option. Conventionally,
2235 object file names end with @file{.o}. The default name is used for historical
2236 reasons: older assemblers were capable of assembling self-contained programs
2237 directly into a runnable program. (For some formats, this isn't currently
2238 possible, but it can be done for the @code{a.out} format.)
2242 The object file is meant for input to the linker @code{@value{LD}}. It contains
2243 assembled program code, information to help @code{@value{LD}} integrate
2244 the assembled program into a runnable file, and (optionally) symbolic
2245 information for the debugger.
2247 @c link above to some info file(s) like the description of a.out.
2248 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2251 @section Error and Warning Messages
2253 @c man begin DESCRIPTION
2255 @cindex error messages
2256 @cindex warning messages
2257 @cindex messages from assembler
2258 @command{@value{AS}} may write warnings and error messages to the standard error
2259 file (usually your terminal). This should not happen when a compiler
2260 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2261 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2262 grave problem that stops the assembly.
2266 @cindex format of warning messages
2267 Warning messages have the format
2270 file_name:@b{NNN}:Warning Message Text
2274 @cindex file names and line numbers, in warnings/errors
2275 (where @b{NNN} is a line number). If both a logical file name
2276 (@pxref{File,,@code{.file}}) and a logical line number
2278 (@pxref{Line,,@code{.line}})
2280 have been given then they will be used, otherwise the file name and line number
2281 in the current assembler source file will be used. The message text is
2282 intended to be self explanatory (in the grand Unix tradition).
2284 Note the file name must be set via the logical version of the @code{.file}
2285 directive, not the DWARF2 version of the @code{.file} directive. For example:
2289 error_assembler_source
2295 produces this output:
2299 asm.s:2: Error: no such instruction: `error_assembler_source'
2300 foo.c:31: Error: no such instruction: `error_c_source'
2303 @cindex format of error messages
2304 Error messages have the format
2307 file_name:@b{NNN}:FATAL:Error Message Text
2310 The file name and line number are derived as for warning
2311 messages. The actual message text may be rather less explanatory
2312 because many of them aren't supposed to happen.
2315 @chapter Command-Line Options
2317 @cindex options, all versions of assembler
2318 This chapter describes command-line options available in @emph{all}
2319 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2320 for options specific
2322 to the @value{TARGET} target.
2325 to particular machine architectures.
2328 @c man begin DESCRIPTION
2330 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2331 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2332 The assembler arguments must be separated from each other (and the @samp{-Wa})
2333 by commas. For example:
2336 gcc -c -g -O -Wa,-alh,-L file.c
2340 This passes two options to the assembler: @samp{-alh} (emit a listing to
2341 standard output with high-level and assembly source) and @samp{-L} (retain
2342 local symbols in the symbol table).
2344 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2345 command-line options are automatically passed to the assembler by the compiler.
2346 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2347 precisely what options it passes to each compilation pass, including the
2353 * a:: -a[cdghlns] enable listings
2354 * alternate:: --alternate enable alternate macro syntax
2355 * D:: -D for compatibility
2356 * f:: -f to work faster
2357 * I:: -I for .include search path
2358 @ifclear DIFF-TBL-KLUGE
2359 * K:: -K for compatibility
2361 @ifset DIFF-TBL-KLUGE
2362 * K:: -K for difference tables
2365 * L:: -L to retain local symbols
2366 * listing:: --listing-XXX to configure listing output
2367 * M:: -M or --mri to assemble in MRI compatibility mode
2368 * MD:: --MD for dependency tracking
2369 * no-pad-sections:: --no-pad-sections to stop section padding
2370 * o:: -o to name the object file
2371 * R:: -R to join data and text sections
2372 * statistics:: --statistics to see statistics about assembly
2373 * traditional-format:: --traditional-format for compatible output
2374 * v:: -v to announce version
2375 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2376 * Z:: -Z to make object file even after errors
2380 @section Enable Listings: @option{-a[cdghlns]}
2390 @cindex listings, enabling
2391 @cindex assembly listings, enabling
2393 These options enable listing output from the assembler. By itself,
2394 @samp{-a} requests high-level, assembly, and symbols listing.
2395 You can use other letters to select specific options for the list:
2396 @samp{-ah} requests a high-level language listing,
2397 @samp{-al} requests an output-program assembly listing, and
2398 @samp{-as} requests a symbol table listing.
2399 High-level listings require that a compiler debugging option like
2400 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2403 Use the @samp{-ag} option to print a first section with general assembly
2404 information, like @value{AS} version, switches passed, or time stamp.
2406 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2407 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2408 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2409 omitted from the listing.
2411 Use the @samp{-ad} option to omit debugging directives from the
2414 Once you have specified one of these options, you can further control
2415 listing output and its appearance using the directives @code{.list},
2416 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2418 The @samp{-an} option turns off all forms processing.
2419 If you do not request listing output with one of the @samp{-a} options, the
2420 listing-control directives have no effect.
2422 The letters after @samp{-a} may be combined into one option,
2423 @emph{e.g.}, @samp{-aln}.
2425 Note if the assembler source is coming from the standard input (e.g.,
2427 is being created by @code{@value{GCC}} and the @samp{-pipe} command-line switch
2428 is being used) then the listing will not contain any comments or preprocessor
2429 directives. This is because the listing code buffers input source lines from
2430 stdin only after they have been preprocessed by the assembler. This reduces
2431 memory usage and makes the code more efficient.
2434 @section @option{--alternate}
2437 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2440 @section @option{-D}
2443 This option has no effect whatsoever, but it is accepted to make it more
2444 likely that scripts written for other assemblers also work with
2445 @command{@value{AS}}.
2448 @section Work Faster: @option{-f}
2451 @cindex trusted compiler
2452 @cindex faster processing (@option{-f})
2453 @samp{-f} should only be used when assembling programs written by a
2454 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2455 and comment preprocessing on
2456 the input file(s) before assembling them. @xref{Preprocessing,
2460 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2461 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2466 @section @code{.include} Search Path: @option{-I} @var{path}
2468 @kindex -I @var{path}
2469 @cindex paths for @code{.include}
2470 @cindex search path for @code{.include}
2471 @cindex @code{include} directive search path
2472 Use this option to add a @var{path} to the list of directories
2473 @command{@value{AS}} searches for files specified in @code{.include}
2474 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2475 many times as necessary to include a variety of paths. The current
2476 working directory is always searched first; after that, @command{@value{AS}}
2477 searches any @samp{-I} directories in the same order as they were
2478 specified (left to right) on the command line.
2481 @section Difference Tables: @option{-K}
2484 @ifclear DIFF-TBL-KLUGE
2485 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2486 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2487 where it can be used to warn when the assembler alters the machine code
2488 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2489 family does not have the addressing limitations that sometimes lead to this
2490 alteration on other platforms.
2493 @ifset DIFF-TBL-KLUGE
2494 @cindex difference tables, warning
2495 @cindex warning for altered difference tables
2496 @command{@value{AS}} sometimes alters the code emitted for directives of the
2497 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2498 You can use the @samp{-K} option if you want a warning issued when this
2503 @section Include Local Symbols: @option{-L}
2506 @cindex local symbols, retaining in output
2507 Symbols beginning with system-specific local label prefixes, typically
2508 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2509 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2510 such symbols when debugging, because they are intended for the use of
2511 programs (like compilers) that compose assembler programs, not for your
2512 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2513 such symbols, so you do not normally debug with them.
2515 This option tells @command{@value{AS}} to retain those local symbols
2516 in the object file. Usually if you do this you also tell the linker
2517 @code{@value{LD}} to preserve those symbols.
2520 @section Configuring listing output: @option{--listing}
2522 The listing feature of the assembler can be enabled via the command-line switch
2523 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2524 hex dump of the corresponding locations in the output object file, and displays
2525 them as a listing file. The format of this listing can be controlled by
2526 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2527 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2528 @code{.psize} (@pxref{Psize}), and
2529 @code{.eject} (@pxref{Eject}) and also by the following switches:
2532 @item --listing-lhs-width=@samp{number}
2533 @kindex --listing-lhs-width
2534 @cindex Width of first line disassembly output
2535 Sets the maximum width, in words, of the first line of the hex byte dump. This
2536 dump appears on the left hand side of the listing output.
2538 @item --listing-lhs-width2=@samp{number}
2539 @kindex --listing-lhs-width2
2540 @cindex Width of continuation lines of disassembly output
2541 Sets the maximum width, in words, of any further lines of the hex byte dump for
2542 a given input source line. If this value is not specified, it defaults to being
2543 the same as the value specified for @samp{--listing-lhs-width}. If neither
2544 switch is used the default is to one.
2546 @item --listing-rhs-width=@samp{number}
2547 @kindex --listing-rhs-width
2548 @cindex Width of source line output
2549 Sets the maximum width, in characters, of the source line that is displayed
2550 alongside the hex dump. The default value for this parameter is 100. The
2551 source line is displayed on the right hand side of the listing output.
2553 @item --listing-cont-lines=@samp{number}
2554 @kindex --listing-cont-lines
2555 @cindex Maximum number of continuation lines
2556 Sets the maximum number of continuation lines of hex dump that will be
2557 displayed for a given single line of source input. The default value is 4.
2561 @section Assemble in MRI Compatibility Mode: @option{-M}
2564 @cindex MRI compatibility mode
2565 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2566 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2567 compatible with the @code{ASM68K} assembler from Microtec Research.
2568 The exact nature of the
2569 MRI syntax will not be documented here; see the MRI manuals for more
2570 information. Note in particular that the handling of macros and macro
2571 arguments is somewhat different. The purpose of this option is to permit
2572 assembling existing MRI assembler code using @command{@value{AS}}.
2574 The MRI compatibility is not complete. Certain operations of the MRI assembler
2575 depend upon its object file format, and can not be supported using other object
2576 file formats. Supporting these would require enhancing each object file format
2577 individually. These are:
2580 @item global symbols in common section
2582 The m68k MRI assembler supports common sections which are merged by the linker.
2583 Other object file formats do not support this. @command{@value{AS}} handles
2584 common sections by treating them as a single common symbol. It permits local
2585 symbols to be defined within a common section, but it can not support global
2586 symbols, since it has no way to describe them.
2588 @item complex relocations
2590 The MRI assemblers support relocations against a negated section address, and
2591 relocations which combine the start addresses of two or more sections. These
2592 are not support by other object file formats.
2594 @item @code{END} pseudo-op specifying start address
2596 The MRI @code{END} pseudo-op permits the specification of a start address.
2597 This is not supported by other object file formats. The start address may
2598 instead be specified using the @option{-e} option to the linker, or in a linker
2601 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2603 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2604 name to the output file. This is not supported by other object file formats.
2606 @item @code{ORG} pseudo-op
2608 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2609 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2610 which changes the location within the current section. Absolute sections are
2611 not supported by other object file formats. The address of a section may be
2612 assigned within a linker script.
2615 There are some other features of the MRI assembler which are not supported by
2616 @command{@value{AS}}, typically either because they are difficult or because they
2617 seem of little consequence. Some of these may be supported in future releases.
2621 @item EBCDIC strings
2623 EBCDIC strings are not supported.
2625 @item packed binary coded decimal
2627 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2628 and @code{DCB.P} pseudo-ops are not supported.
2630 @item @code{FEQU} pseudo-op
2632 The m68k @code{FEQU} pseudo-op is not supported.
2634 @item @code{NOOBJ} pseudo-op
2636 The m68k @code{NOOBJ} pseudo-op is not supported.
2638 @item @code{OPT} branch control options
2640 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2641 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2642 relaxes all branches, whether forward or backward, to an appropriate size, so
2643 these options serve no purpose.
2645 @item @code{OPT} list control options
2647 The following m68k @code{OPT} list control options are ignored: @code{C},
2648 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2649 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2651 @item other @code{OPT} options
2653 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2654 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2656 @item @code{OPT} @code{D} option is default
2658 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2659 @code{OPT NOD} may be used to turn it off.
2661 @item @code{XREF} pseudo-op.
2663 The m68k @code{XREF} pseudo-op is ignored.
2668 @section Dependency Tracking: @option{--MD}
2671 @cindex dependency tracking
2674 @command{@value{AS}} can generate a dependency file for the file it creates. This
2675 file consists of a single rule suitable for @code{make} describing the
2676 dependencies of the main source file.
2678 The rule is written to the file named in its argument.
2680 This feature is used in the automatic updating of makefiles.
2682 @node no-pad-sections
2683 @section Output Section Padding
2684 @kindex --no-pad-sections
2685 @cindex output section padding
2686 Normally the assembler will pad the end of each output section up to its
2687 alignment boundary. But this can waste space, which can be significant on
2688 memory constrained targets. So the @option{--no-pad-sections} option will
2689 disable this behaviour.
2692 @section Name the Object File: @option{-o}
2695 @cindex naming object file
2696 @cindex object file name
2697 There is always one object file output when you run @command{@value{AS}}. By
2698 default it has the name @file{a.out}.
2699 You use this option (which takes exactly one filename) to give the
2700 object file a different name.
2702 Whatever the object file is called, @command{@value{AS}} overwrites any
2703 existing file of the same name.
2706 @section Join Data and Text Sections: @option{-R}
2709 @cindex data and text sections, joining
2710 @cindex text and data sections, joining
2711 @cindex joining text and data sections
2712 @cindex merging text and data sections
2713 @option{-R} tells @command{@value{AS}} to write the object file as if all
2714 data-section data lives in the text section. This is only done at
2715 the very last moment: your binary data are the same, but data
2716 section parts are relocated differently. The data section part of
2717 your object file is zero bytes long because all its bytes are
2718 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2720 When you specify @option{-R} it would be possible to generate shorter
2721 address displacements (because we do not have to cross between text and
2722 data section). We refrain from doing this simply for compatibility with
2723 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2726 When @command{@value{AS}} is configured for COFF or ELF output,
2727 this option is only useful if you use sections named @samp{.text} and
2732 @option{-R} is not supported for any of the HPPA targets. Using
2733 @option{-R} generates a warning from @command{@value{AS}}.
2737 @section Display Assembly Statistics: @option{--statistics}
2739 @kindex --statistics
2740 @cindex statistics, about assembly
2741 @cindex time, total for assembly
2742 @cindex space used, maximum for assembly
2743 Use @samp{--statistics} to display two statistics about the resources used by
2744 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2745 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2748 @node traditional-format
2749 @section Compatible Output: @option{--traditional-format}
2751 @kindex --traditional-format
2752 For some targets, the output of @command{@value{AS}} is different in some ways
2753 from the output of some existing assembler. This switch requests
2754 @command{@value{AS}} to use the traditional format instead.
2756 For example, it disables the exception frame optimizations which
2757 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2760 @section Announce Version: @option{-v}
2764 @cindex assembler version
2765 @cindex version of assembler
2766 You can find out what version of as is running by including the
2767 option @samp{-v} (which you can also spell as @samp{-version}) on the
2771 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2773 @command{@value{AS}} should never give a warning or error message when
2774 assembling compiler output. But programs written by people often
2775 cause @command{@value{AS}} to give a warning that a particular assumption was
2776 made. All such warnings are directed to the standard error file.
2780 @cindex suppressing warnings
2781 @cindex warnings, suppressing
2782 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2783 This only affects the warning messages: it does not change any particular of
2784 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2787 @kindex --fatal-warnings
2788 @cindex errors, caused by warnings
2789 @cindex warnings, causing error
2790 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2791 files that generate warnings to be in error.
2794 @cindex warnings, switching on
2795 You can switch these options off again by specifying @option{--warn}, which
2796 causes warnings to be output as usual.
2799 @section Generate Object File in Spite of Errors: @option{-Z}
2800 @cindex object file, after errors
2801 @cindex errors, continuing after
2802 After an error message, @command{@value{AS}} normally produces no output. If for
2803 some reason you are interested in object file output even after
2804 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2805 option. If there are any errors, @command{@value{AS}} continues anyways, and
2806 writes an object file after a final warning message of the form @samp{@var{n}
2807 errors, @var{m} warnings, generating bad object file.}
2812 @cindex machine-independent syntax
2813 @cindex syntax, machine-independent
2814 This chapter describes the machine-independent syntax allowed in a
2815 source file. @command{@value{AS}} syntax is similar to what many other
2816 assemblers use; it is inspired by the BSD 4.2
2821 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2825 * Preprocessing:: Preprocessing
2826 * Whitespace:: Whitespace
2827 * Comments:: Comments
2828 * Symbol Intro:: Symbols
2829 * Statements:: Statements
2830 * Constants:: Constants
2834 @section Preprocessing
2836 @cindex preprocessing
2837 The @command{@value{AS}} internal preprocessor:
2839 @cindex whitespace, removed by preprocessor
2841 adjusts and removes extra whitespace. It leaves one space or tab before
2842 the keywords on a line, and turns any other whitespace on the line into
2845 @cindex comments, removed by preprocessor
2847 removes all comments, replacing them with a single space, or an
2848 appropriate number of newlines.
2850 @cindex constants, converted by preprocessor
2852 converts character constants into the appropriate numeric values.
2855 It does not do macro processing, include file handling, or
2856 anything else you may get from your C compiler's preprocessor. You can
2857 do include file processing with the @code{.include} directive
2858 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2859 to get other ``CPP'' style preprocessing by giving the input file a
2860 @samp{.S} suffix. @url{https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html#Overall-Options,
2861 See the 'Options Controlling the Kind of Output' section of the GCC manual for
2864 Excess whitespace, comments, and character constants
2865 cannot be used in the portions of the input text that are not
2868 @cindex turning preprocessing on and off
2869 @cindex preprocessing, turning on and off
2872 If the first line of an input file is @code{#NO_APP} or if you use the
2873 @samp{-f} option, whitespace and comments are not removed from the input file.
2874 Within an input file, you can ask for whitespace and comment removal in
2875 specific portions of the by putting a line that says @code{#APP} before the
2876 text that may contain whitespace or comments, and putting a line that says
2877 @code{#NO_APP} after this text. This feature is mainly intend to support
2878 @code{asm} statements in compilers whose output is otherwise free of comments
2885 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2886 Whitespace is used to separate symbols, and to make programs neater for
2887 people to read. Unless within character constants
2888 (@pxref{Characters,,Character Constants}), any whitespace means the same
2889 as exactly one space.
2895 There are two ways of rendering comments to @command{@value{AS}}. In both
2896 cases the comment is equivalent to one space.
2898 Anything from @samp{/*} through the next @samp{*/} is a comment.
2899 This means you may not nest these comments.
2903 The only way to include a newline ('\n') in a comment
2904 is to use this sort of comment.
2907 /* This sort of comment does not nest. */
2910 @cindex line comment character
2911 Anything from a @dfn{line comment} character up to the next newline is
2912 considered a comment and is ignored. The line comment character is target
2913 specific, and some targets multiple comment characters. Some targets also have
2914 line comment characters that only work if they are the first character on a
2915 line. Some targets use a sequence of two characters to introduce a line
2916 comment. Some targets can also change their line comment characters depending
2917 upon command-line options that have been used. For more details see the
2918 @emph{Syntax} section in the documentation for individual targets.
2920 If the line comment character is the hash sign (@samp{#}) then it still has the
2921 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2922 to specify logical line numbers:
2925 @cindex lines starting with @code{#}
2926 @cindex logical line numbers
2927 To be compatible with past assemblers, lines that begin with @samp{#} have a
2928 special interpretation. Following the @samp{#} should be an absolute
2929 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2930 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2931 new logical file name. The rest of the line, if any, should be whitespace.
2933 If the first non-whitespace characters on the line are not numeric,
2934 the line is ignored. (Just like a comment.)
2937 # This is an ordinary comment.
2938 # 42-6 "new_file_name" # New logical file name
2939 # This is logical line # 36.
2941 This feature is deprecated, and may disappear from future versions
2942 of @command{@value{AS}}.
2947 @cindex characters used in symbols
2948 @ifclear SPECIAL-SYMS
2949 A @dfn{symbol} is one or more characters chosen from the set of all
2950 letters (both upper and lower case), digits and the three characters
2956 A @dfn{symbol} is one or more characters chosen from the set of all
2957 letters (both upper and lower case), digits and the three characters
2958 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2964 On most machines, you can also use @code{$} in symbol names; exceptions
2965 are noted in @ref{Machine Dependencies}.
2967 No symbol may begin with a digit. Case is significant.
2968 There is no length limit; all characters are significant. Multibyte characters
2969 are supported. Symbols are delimited by characters not in that set, or by the
2970 beginning of a file (since the source program must end with a newline, the end
2971 of a file is not a possible symbol delimiter). @xref{Symbols}.
2973 Symbol names may also be enclosed in double quote @code{"} characters. In such
2974 cases any characters are allowed, except for the NUL character. If a double
2975 quote character is to be included in the symbol name it must be preceded by a
2976 backslash @code{\} character.
2977 @cindex length of symbols
2982 @cindex statements, structure of
2983 @cindex line separator character
2984 @cindex statement separator character
2986 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2987 @dfn{line separator character}. The line separator character is target
2988 specific and described in the @emph{Syntax} section of each
2989 target's documentation. Not all targets support a line separator character.
2990 The newline or line separator character is considered to be part of the
2991 preceding statement. Newlines and separators within character constants are an
2992 exception: they do not end statements.
2994 @cindex newline, required at file end
2995 @cindex EOF, newline must precede
2996 It is an error to end any statement with end-of-file: the last
2997 character of any input file should be a newline.@refill
2999 An empty statement is allowed, and may include whitespace. It is ignored.
3001 @cindex instructions and directives
3002 @cindex directives and instructions
3003 @c "key symbol" is not used elsewhere in the document; seems pedantic to
3004 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
3006 A statement begins with zero or more labels, optionally followed by a
3007 key symbol which determines what kind of statement it is. The key
3008 symbol determines the syntax of the rest of the statement. If the
3009 symbol begins with a dot @samp{.} then the statement is an assembler
3010 directive: typically valid for any computer. If the symbol begins with
3011 a letter the statement is an assembly language @dfn{instruction}: it
3012 assembles into a machine language instruction.
3014 Different versions of @command{@value{AS}} for different computers
3015 recognize different instructions. In fact, the same symbol may
3016 represent a different instruction in a different computer's assembly
3020 @cindex @code{:} (label)
3021 @cindex label (@code{:})
3022 A label is a symbol immediately followed by a colon (@code{:}).
3023 Whitespace before a label or after a colon is permitted, but you may not
3024 have whitespace between a label's symbol and its colon. @xref{Labels}.
3027 For HPPA targets, labels need not be immediately followed by a colon, but
3028 the definition of a label must begin in column zero. This also implies that
3029 only one label may be defined on each line.
3033 label: .directive followed by something
3034 another_label: # This is an empty statement.
3035 instruction operand_1, operand_2, @dots{}
3042 A constant is a number, written so that its value is known by
3043 inspection, without knowing any context. Like this:
3046 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
3047 .ascii "Ring the bell\7" # A string constant.
3048 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
3049 .float 0f-314159265358979323846264338327\
3050 95028841971.693993751E-40 # - pi, a flonum.
3055 * Characters:: Character Constants
3056 * Numbers:: Number Constants
3060 @subsection Character Constants
3062 @cindex character constants
3063 @cindex constants, character
3064 There are two kinds of character constants. A @dfn{character} stands
3065 for one character in one byte and its value may be used in
3066 numeric expressions. String constants (properly called string
3067 @emph{literals}) are potentially many bytes and their values may not be
3068 used in arithmetic expressions.
3072 * Chars:: Characters
3076 @subsubsection Strings
3078 @cindex string constants
3079 @cindex constants, string
3080 A @dfn{string} is written between double-quotes. It may contain
3081 double-quotes or null characters. The way to get special characters
3082 into a string is to @dfn{escape} these characters: precede them with
3083 a backslash @samp{\} character. For example @samp{\\} represents
3084 one backslash: the first @code{\} is an escape which tells
3085 @command{@value{AS}} to interpret the second character literally as a backslash
3086 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3087 escape character). The complete list of escapes follows.
3089 @cindex escape codes, character
3090 @cindex character escape codes
3091 @c NOTE: Cindex entries must not start with a backlash character.
3092 @c NOTE: This confuses the pdf2texi script when it is creating the
3093 @c NOTE: index based upon the first character and so it generates:
3094 @c NOTE: \initial {\\}
3095 @c NOTE: which then results in the error message:
3096 @c NOTE: Argument of \\ has an extra }.
3097 @c NOTE: So in the index entries below a space character has been
3098 @c NOTE: prepended to avoid this problem.
3101 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3103 @cindex @code{ \b} (backspace character)
3104 @cindex backspace (@code{\b})
3106 Mnemonic for backspace; for ASCII this is octal code 010.
3109 @c Mnemonic for EOText; for ASCII this is octal code 004.
3111 @cindex @code{ \f} (formfeed character)
3112 @cindex formfeed (@code{\f})
3114 Mnemonic for FormFeed; for ASCII this is octal code 014.
3116 @cindex @code{ \n} (newline character)
3117 @cindex newline (@code{\n})
3119 Mnemonic for newline; for ASCII this is octal code 012.
3122 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3124 @cindex @code{ \r} (carriage return character)
3125 @cindex carriage return (@code{backslash-r})
3127 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3130 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3131 @c other assemblers.
3133 @cindex @code{ \t} (tab)
3134 @cindex tab (@code{\t})
3136 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3139 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3140 @c @item \x @var{digit} @var{digit} @var{digit}
3141 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3143 @cindex @code{ \@var{ddd}} (octal character code)
3144 @cindex octal character code (@code{\@var{ddd}})
3145 @item \ @var{digit} @var{digit} @var{digit}
3146 An octal character code. The numeric code is 3 octal digits.
3147 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3148 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3150 @cindex @code{ \@var{xd...}} (hex character code)
3151 @cindex hex character code (@code{\@var{xd...}})
3152 @item \@code{x} @var{hex-digits...}
3153 A hex character code. All trailing hex digits are combined. Either upper or
3154 lower case @code{x} works.
3156 @cindex @code{ \\} (@samp{\} character)
3157 @cindex backslash (@code{\\})
3159 Represents one @samp{\} character.
3162 @c Represents one @samp{'} (accent acute) character.
3163 @c This is needed in single character literals
3164 @c (@xref{Characters,,Character Constants}.) to represent
3167 @cindex @code{ \"} (doublequote character)
3168 @cindex doublequote (@code{\"})
3170 Represents one @samp{"} character. Needed in strings to represent
3171 this character, because an unescaped @samp{"} would end the string.
3173 @item \ @var{anything-else}
3174 Any other character when escaped by @kbd{\} gives a warning, but
3175 assembles as if the @samp{\} was not present. The idea is that if
3176 you used an escape sequence you clearly didn't want the literal
3177 interpretation of the following character. However @command{@value{AS}} has no
3178 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3179 code and warns you of the fact.
3182 Which characters are escapable, and what those escapes represent,
3183 varies widely among assemblers. The current set is what we think
3184 the BSD 4.2 assembler recognizes, and is a subset of what most C
3185 compilers recognize. If you are in doubt, do not use an escape
3189 @subsubsection Characters
3191 @cindex single character constant
3192 @cindex character, single
3193 @cindex constant, single character
3194 A single character may be written as a single quote immediately followed by
3195 that character. Some backslash escapes apply to characters, @code{\b},
3196 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3197 as for strings, plus @code{\'} for a single quote. So if you want to write the
3198 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3199 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3202 @ifclear abnormal-separator
3203 (or semicolon @samp{;})
3205 @ifset abnormal-separator
3207 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3212 immediately following an acute accent is taken as a literal character
3213 and does not count as the end of a statement. The value of a character
3214 constant in a numeric expression is the machine's byte-wide code for
3215 that character. @command{@value{AS}} assumes your character code is ASCII:
3216 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3219 @subsection Number Constants
3221 @cindex constants, number
3222 @cindex number constants
3223 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3224 are stored in the target machine. @emph{Integers} are numbers that
3225 would fit into an @code{int} in the C language. @emph{Bignums} are
3226 integers, but they are stored in more than 32 bits. @emph{Flonums}
3227 are floating point numbers, described below.
3230 * Integers:: Integers
3238 @subsubsection Integers
3240 @cindex constants, integer
3242 @cindex binary integers
3243 @cindex integers, binary
3244 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3245 the binary digits @samp{01}.
3247 @cindex octal integers
3248 @cindex integers, octal
3249 An octal integer is @samp{0} followed by zero or more of the octal
3250 digits (@samp{01234567}).
3252 @cindex decimal integers
3253 @cindex integers, decimal
3254 A decimal integer starts with a non-zero digit followed by zero or
3255 more digits (@samp{0123456789}).
3257 @cindex hexadecimal integers
3258 @cindex integers, hexadecimal
3259 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3260 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3262 Integers have the usual values. To denote a negative integer, use
3263 the prefix operator @samp{-} discussed under expressions
3264 (@pxref{Prefix Ops,,Prefix Operators}).
3267 @subsubsection Bignums
3270 @cindex constants, bignum
3271 A @dfn{bignum} has the same syntax and semantics as an integer
3272 except that the number (or its negative) takes more than 32 bits to
3273 represent in binary. The distinction is made because in some places
3274 integers are permitted while bignums are not.
3277 @subsubsection Flonums
3279 @cindex floating point numbers
3280 @cindex constants, floating point
3282 @cindex precision, floating point
3283 A @dfn{flonum} represents a floating point number. The translation is
3284 indirect: a decimal floating point number from the text is converted by
3285 @command{@value{AS}} to a generic binary floating point number of more than
3286 sufficient precision. This generic floating point number is converted
3287 to a particular computer's floating point format (or formats) by a
3288 portion of @command{@value{AS}} specialized to that computer.
3290 A flonum is written by writing (in order)
3295 (@samp{0} is optional on the HPPA.)
3299 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3301 @kbd{e} is recommended. Case is not important.
3303 @c FIXME: verify if flonum syntax really this vague for most cases
3304 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3305 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3308 On the H8/300 and Renesas / SuperH SH architectures, the letter must be
3309 one of the letters @samp{DFPRSX} (in upper or lower case).
3311 On the ARC, the letter must be one of the letters @samp{DFRS}
3312 (in upper or lower case).
3314 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3318 One of the letters @samp{DFRS} (in upper or lower case).
3321 One of the letters @samp{DFPRSX} (in upper or lower case).
3324 The letter @samp{E} (upper case only).
3329 An optional sign: either @samp{+} or @samp{-}.
3332 An optional @dfn{integer part}: zero or more decimal digits.
3335 An optional @dfn{fractional part}: @samp{.} followed by zero
3336 or more decimal digits.
3339 An optional exponent, consisting of:
3343 An @samp{E} or @samp{e}.
3344 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3345 @c principle this can perfectly well be different on different targets.
3347 Optional sign: either @samp{+} or @samp{-}.
3349 One or more decimal digits.
3354 At least one of the integer part or the fractional part must be
3355 present. The floating point number has the usual base-10 value.
3357 @command{@value{AS}} does all processing using integers. Flonums are computed
3358 independently of any floating point hardware in the computer running
3359 @command{@value{AS}}.
3362 @chapter Sections and Relocation
3367 * Secs Background:: Background
3368 * Ld Sections:: Linker Sections
3369 * As Sections:: Assembler Internal Sections
3370 * Sub-Sections:: Sub-Sections
3374 @node Secs Background
3377 Roughly, a section is a range of addresses, with no gaps; all data
3378 ``in'' those addresses is treated the same for some particular purpose.
3379 For example there may be a ``read only'' section.
3381 @cindex linker, and assembler
3382 @cindex assembler, and linker
3383 The linker @code{@value{LD}} reads many object files (partial programs) and
3384 combines their contents to form a runnable program. When @command{@value{AS}}
3385 emits an object file, the partial program is assumed to start at address 0.
3386 @code{@value{LD}} assigns the final addresses for the partial program, so that
3387 different partial programs do not overlap. This is actually an
3388 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3391 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3392 addresses. These blocks slide to their run-time addresses as rigid
3393 units; their length does not change and neither does the order of bytes
3394 within them. Such a rigid unit is called a @emph{section}. Assigning
3395 run-time addresses to sections is called @dfn{relocation}. It includes
3396 the task of adjusting mentions of object-file addresses so they refer to
3397 the proper run-time addresses.
3399 For the H8/300, and for the Renesas / SuperH SH,
3400 @command{@value{AS}} pads sections if needed to
3401 ensure they end on a word (sixteen bit) boundary.
3404 @cindex standard assembler sections
3405 An object file written by @command{@value{AS}} has at least three sections, any
3406 of which may be empty. These are named @dfn{text}, @dfn{data} and
3411 When it generates COFF or ELF output,
3413 @command{@value{AS}} can also generate whatever other named sections you specify
3414 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3415 If you do not use any directives that place output in the @samp{.text}
3416 or @samp{.data} sections, these sections still exist, but are empty.
3421 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3423 @command{@value{AS}} can also generate whatever other named sections you
3424 specify using the @samp{.space} and @samp{.subspace} directives. See
3425 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3426 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3427 assembler directives.
3430 Additionally, @command{@value{AS}} uses different names for the standard
3431 text, data, and bss sections when generating SOM output. Program text
3432 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3433 BSS into @samp{$BSS$}.
3437 Within the object file, the text section starts at address @code{0}, the
3438 data section follows, and the bss section follows the data section.
3441 When generating either SOM or ELF output files on the HPPA, the text
3442 section starts at address @code{0}, the data section at address
3443 @code{0x4000000}, and the bss section follows the data section.
3446 To let @code{@value{LD}} know which data changes when the sections are
3447 relocated, and how to change that data, @command{@value{AS}} also writes to the
3448 object file details of the relocation needed. To perform relocation
3449 @code{@value{LD}} must know, each time an address in the object
3453 Where in the object file is the beginning of this reference to
3456 How long (in bytes) is this reference?
3458 Which section does the address refer to? What is the numeric value of
3460 (@var{address}) @minus{} (@var{start-address of section})?
3463 Is the reference to an address ``Program-Counter relative''?
3466 @cindex addresses, format of
3467 @cindex section-relative addressing
3468 In fact, every address @command{@value{AS}} ever uses is expressed as
3470 (@var{section}) + (@var{offset into section})
3473 Further, most expressions @command{@value{AS}} computes have this section-relative
3476 (For some object formats, such as SOM for the HPPA, some expressions are
3477 symbol-relative instead.)
3480 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3481 @var{N} into section @var{secname}.''
3483 Apart from text, data and bss sections you need to know about the
3484 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3485 addresses in the absolute section remain unchanged. For example, address
3486 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3487 @code{@value{LD}}. Although the linker never arranges two partial programs'
3488 data sections with overlapping addresses after linking, @emph{by definition}
3489 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3490 part of a program is always the same address when the program is running as
3491 address @code{@{absolute@ 239@}} in any other part of the program.
3493 The idea of sections is extended to the @dfn{undefined} section. Any
3494 address whose section is unknown at assembly time is by definition
3495 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3496 Since numbers are always defined, the only way to generate an undefined
3497 address is to mention an undefined symbol. A reference to a named
3498 common block would be such a symbol: its value is unknown at assembly
3499 time so it has section @emph{undefined}.
3501 By analogy the word @emph{section} is used to describe groups of sections in
3502 the linked program. @code{@value{LD}} puts all partial programs' text
3503 sections in contiguous addresses in the linked program. It is
3504 customary to refer to the @emph{text section} of a program, meaning all
3505 the addresses of all partial programs' text sections. Likewise for
3506 data and bss sections.
3508 Some sections are manipulated by @code{@value{LD}}; others are invented for
3509 use of @command{@value{AS}} and have no meaning except during assembly.
3512 @section Linker Sections
3513 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3518 @cindex named sections
3519 @cindex sections, named
3520 @item named sections
3523 @cindex text section
3524 @cindex data section
3528 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3529 separate but equal sections. Anything you can say of one section is
3532 When the program is running, however, it is
3533 customary for the text section to be unalterable. The
3534 text section is often shared among processes: it contains
3535 instructions, constants and the like. The data section of a running
3536 program is usually alterable: for example, C variables would be stored
3537 in the data section.
3542 This section contains zeroed bytes when your program begins running. It
3543 is used to hold uninitialized variables or common storage. The length of
3544 each partial program's bss section is important, but because it starts
3545 out containing zeroed bytes there is no need to store explicit zero
3546 bytes in the object file. The bss section was invented to eliminate
3547 those explicit zeros from object files.
3549 @cindex absolute section
3550 @item absolute section
3551 Address 0 of this section is always ``relocated'' to runtime address 0.
3552 This is useful if you want to refer to an address that @code{@value{LD}} must
3553 not change when relocating. In this sense we speak of absolute
3554 addresses being ``unrelocatable'': they do not change during relocation.
3556 @cindex undefined section
3557 @item undefined section
3558 This ``section'' is a catch-all for address references to objects not in
3559 the preceding sections.
3560 @c FIXME: ref to some other doc on obj-file formats could go here.
3563 @cindex relocation example
3564 An idealized example of three relocatable sections follows.
3566 The example uses the traditional section names @samp{.text} and @samp{.data}.
3568 Memory addresses are on the horizontal axis.
3572 @c END TEXI2ROFF-KILL
3575 partial program # 1: |ttttt|dddd|00|
3582 partial program # 2: |TTT|DDD|000|
3585 +--+---+-----+--+----+---+-----+~~
3586 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3587 +--+---+-----+--+----+---+-----+~~
3589 addresses: 0 @dots{}
3596 \line{\it Partial program \#1: \hfil}
3597 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3598 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3600 \line{\it Partial program \#2: \hfil}
3601 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3602 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3604 \line{\it linked program: \hfil}
3605 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3606 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3607 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3608 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3610 \line{\it addresses: \hfil}
3614 @c END TEXI2ROFF-KILL
3617 @section Assembler Internal Sections
3619 @cindex internal assembler sections
3620 @cindex sections in messages, internal
3621 These sections are meant only for the internal use of @command{@value{AS}}. They
3622 have no meaning at run-time. You do not really need to know about these
3623 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3624 warning messages, so it might be helpful to have an idea of their
3625 meanings to @command{@value{AS}}. These sections are used to permit the
3626 value of every expression in your assembly language program to be a
3627 section-relative address.
3630 @cindex assembler internal logic error
3631 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3632 An internal assembler logic error has been found. This means there is a
3633 bug in the assembler.
3635 @cindex expr (internal section)
3637 The assembler stores complex expression internally as combinations of
3638 symbols. When it needs to represent an expression as a symbol, it puts
3639 it in the expr section.
3641 @c FIXME item transfer[t] vector preload
3642 @c FIXME item transfer[t] vector postload
3643 @c FIXME item register
3647 @section Sub-Sections
3649 @cindex numbered subsections
3650 @cindex grouping data
3656 fall into two sections: text and data.
3658 You may have separate groups of
3660 data in named sections
3664 data in named sections
3670 that you want to end up near to each other in the object file, even though they
3671 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3672 use @dfn{subsections} for this purpose. Within each section, there can be
3673 numbered subsections with values from 0 to 8192. Objects assembled into the
3674 same subsection go into the object file together with other objects in the same
3675 subsection. For example, a compiler might want to store constants in the text
3676 section, but might not want to have them interspersed with the program being
3677 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3678 section of code being output, and a @samp{.text 1} before each group of
3679 constants being output.
3681 Subsections are optional. If you do not use subsections, everything
3682 goes in subsection number zero.
3685 Each subsection is zero-padded up to a multiple of four bytes.
3686 (Subsections may be padded a different amount on different flavors
3687 of @command{@value{AS}}.)
3691 On the H8/300 platform, each subsection is zero-padded to a word
3692 boundary (two bytes).
3693 The same is true on the Renesas SH.
3697 Subsections appear in your object file in numeric order, lowest numbered
3698 to highest. (All this to be compatible with other people's assemblers.)
3699 The object file contains no representation of subsections; @code{@value{LD}} and
3700 other programs that manipulate object files see no trace of them.
3701 They just see all your text subsections as a text section, and all your
3702 data subsections as a data section.
3704 To specify which subsection you want subsequent statements assembled
3705 into, use a numeric argument to specify it, in a @samp{.text
3706 @var{expression}} or a @samp{.data @var{expression}} statement.
3709 When generating COFF output, you
3714 can also use an extra subsection
3715 argument with arbitrary named sections: @samp{.section @var{name},
3720 When generating ELF output, you
3725 can also use the @code{.subsection} directive (@pxref{SubSection})
3726 to specify a subsection: @samp{.subsection @var{expression}}.
3728 @var{Expression} should be an absolute expression
3729 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3730 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3731 begins in @code{text 0}. For instance:
3733 .text 0 # The default subsection is text 0 anyway.
3734 .ascii "This lives in the first text subsection. *"
3736 .ascii "But this lives in the second text subsection."
3738 .ascii "This lives in the data section,"
3739 .ascii "in the first data subsection."
3741 .ascii "This lives in the first text section,"
3742 .ascii "immediately following the asterisk (*)."
3745 Each section has a @dfn{location counter} incremented by one for every byte
3746 assembled into that section. Because subsections are merely a convenience
3747 restricted to @command{@value{AS}} there is no concept of a subsection location
3748 counter. There is no way to directly manipulate a location counter---but the
3749 @code{.align} directive changes it, and any label definition captures its
3750 current value. The location counter of the section where statements are being
3751 assembled is said to be the @dfn{active} location counter.
3754 @section bss Section
3757 @cindex common variable storage
3758 The bss section is used for local common variable storage.
3759 You may allocate address space in the bss section, but you may
3760 not dictate data to load into it before your program executes. When
3761 your program starts running, all the contents of the bss
3762 section are zeroed bytes.
3764 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3765 @ref{Lcomm,,@code{.lcomm}}.
3767 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3768 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3771 When assembling for a target which supports multiple sections, such as ELF or
3772 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3773 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3774 section. Typically the section will only contain symbol definitions and
3775 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3782 Symbols are a central concept: the programmer uses symbols to name
3783 things, the linker uses symbols to link, and the debugger uses symbols
3787 @cindex debuggers, and symbol order
3788 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3789 the same order they were declared. This may break some debuggers.
3794 * Setting Symbols:: Giving Symbols Other Values
3795 * Symbol Names:: Symbol Names
3796 * Dot:: The Special Dot Symbol
3797 * Symbol Attributes:: Symbol Attributes
3804 A @dfn{label} is written as a symbol immediately followed by a colon
3805 @samp{:}. The symbol then represents the current value of the
3806 active location counter, and is, for example, a suitable instruction
3807 operand. You are warned if you use the same symbol to represent two
3808 different locations: the first definition overrides any other
3812 On the HPPA, the usual form for a label need not be immediately followed by a
3813 colon, but instead must start in column zero. Only one label may be defined on
3814 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3815 provides a special directive @code{.label} for defining labels more flexibly.
3818 @node Setting Symbols
3819 @section Giving Symbols Other Values
3821 @cindex assigning values to symbols
3822 @cindex symbol values, assigning
3823 A symbol can be given an arbitrary value by writing a symbol, followed
3824 by an equals sign @samp{=}, followed by an expression
3825 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3826 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3827 equals sign @samp{=}@samp{=} here represents an equivalent of the
3828 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3831 Blackfin does not support symbol assignment with @samp{=}.
3835 @section Symbol Names
3837 @cindex symbol names
3838 @cindex names, symbol
3839 @ifclear SPECIAL-SYMS
3840 Symbol names begin with a letter or with one of @samp{._}. On most
3841 machines, you can also use @code{$} in symbol names; exceptions are
3842 noted in @ref{Machine Dependencies}. That character may be followed by any
3843 string of digits, letters, dollar signs (unless otherwise noted for a
3844 particular target machine), and underscores.
3848 Symbol names begin with a letter or with one of @samp{._}. On the
3849 Renesas SH you can also use @code{$} in symbol names. That
3850 character may be followed by any string of digits, letters, dollar signs (save
3851 on the H8/300), and underscores.
3855 Case of letters is significant: @code{foo} is a different symbol name
3858 Symbol names do not start with a digit. An exception to this rule is made for
3859 Local Labels. See below.
3861 Multibyte characters are supported. To generate a symbol name containing
3862 multibyte characters enclose it within double quotes and use escape codes. cf
3863 @xref{Strings}. Generating a multibyte symbol name from a label is not
3864 currently supported.
3866 Each symbol has exactly one name. Each name in an assembly language program
3867 refers to exactly one symbol. You may use that symbol name any number of times
3870 @subheading Local Symbol Names
3872 @cindex local symbol names
3873 @cindex symbol names, local
3874 A local symbol is any symbol beginning with certain local label prefixes.
3875 By default, the local label prefix is @samp{.L} for ELF systems or
3876 @samp{L} for traditional a.out systems, but each target may have its own
3877 set of local label prefixes.
3879 On the HPPA local symbols begin with @samp{L$}.
3882 Local symbols are defined and used within the assembler, but they are
3883 normally not saved in object files. Thus, they are not visible when debugging.
3884 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3885 to retain the local symbols in the object files.
3887 @subheading Local Labels
3889 @cindex local labels
3890 @cindex temporary symbol names
3891 @cindex symbol names, temporary
3892 Local labels are different from local symbols. Local labels help compilers and
3893 programmers use names temporarily. They create symbols which are guaranteed to
3894 be unique over the entire scope of the input source code and which can be
3895 referred to by a simple notation. To define a local label, write a label of
3896 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3897 To refer to the most recent previous definition of that label write
3898 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3899 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3900 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3902 There is no restriction on how you can use these labels, and you can reuse them
3903 too. So that it is possible to repeatedly define the same local label (using
3904 the same number @samp{@b{N}}), although you can only refer to the most recently
3905 defined local label of that number (for a backwards reference) or the next
3906 definition of a specific local label for a forward reference. It is also worth
3907 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3908 implemented in a slightly more efficient manner than the others.
3919 Which is the equivalent of:
3922 label_1: branch label_3
3923 label_2: branch label_1
3924 label_3: branch label_4
3925 label_4: branch label_3
3928 Local label names are only a notational device. They are immediately
3929 transformed into more conventional symbol names before the assembler uses them.
3930 The symbol names are stored in the symbol table, appear in error messages, and
3931 are optionally emitted to the object file. The names are constructed using
3935 @item @emph{local label prefix}
3936 All local symbols begin with the system-specific local label prefix.
3937 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3938 that start with the local label prefix. These labels are
3939 used for symbols you are never intended to see. If you use the
3940 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3941 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3942 you may use them in debugging.
3945 This is the number that was used in the local label definition. So if the
3946 label is written @samp{55:} then the number is @samp{55}.
3949 This unusual character is included so you do not accidentally invent a symbol
3950 of the same name. The character has ASCII value of @samp{\002} (control-B).
3952 @item @emph{ordinal number}
3953 This is a serial number to keep the labels distinct. The first definition of
3954 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3955 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3956 the number @samp{1} and its 15th definition gets @samp{15} as well.
3959 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3960 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3962 @subheading Dollar Local Labels
3963 @cindex dollar local symbols
3965 On some targets @code{@value{AS}} also supports an even more local form of
3966 local labels called dollar labels. These labels go out of scope (i.e., they
3967 become undefined) as soon as a non-local label is defined. Thus they remain
3968 valid for only a small region of the input source code. Normal local labels,
3969 by contrast, remain in scope for the entire file, or until they are redefined
3970 by another occurrence of the same local label.
3972 Dollar labels are defined in exactly the same way as ordinary local labels,
3973 except that they have a dollar sign suffix to their numeric value, e.g.,
3976 They can also be distinguished from ordinary local labels by their transformed
3977 names which use ASCII character @samp{\001} (control-A) as the magic character
3978 to distinguish them from ordinary labels. For example, the fifth definition of
3979 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3982 @section The Special Dot Symbol
3984 @cindex dot (symbol)
3985 @cindex @code{.} (symbol)
3986 @cindex current address
3987 @cindex location counter
3988 The special symbol @samp{.} refers to the current address that
3989 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3990 .long .} defines @code{melvin} to contain its own address.
3991 Assigning a value to @code{.} is treated the same as a @code{.org}
3993 @ifclear no-space-dir
3994 Thus, the expression @samp{.=.+4} is the same as saying
3998 @node Symbol Attributes
3999 @section Symbol Attributes
4001 @cindex symbol attributes
4002 @cindex attributes, symbol
4003 Every symbol has, as well as its name, the attributes ``Value'' and
4004 ``Type''. Depending on output format, symbols can also have auxiliary
4007 The detailed definitions are in @file{a.out.h}.
4010 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
4011 all these attributes, and probably won't warn you. This makes the
4012 symbol an externally defined symbol, which is generally what you
4016 * Symbol Value:: Value
4017 * Symbol Type:: Type
4019 * a.out Symbols:: Symbol Attributes: @code{a.out}
4022 * COFF Symbols:: Symbol Attributes for COFF
4025 * SOM Symbols:: Symbol Attributes for SOM
4032 @cindex value of a symbol
4033 @cindex symbol value
4034 The value of a symbol is (usually) 32 bits. For a symbol which labels a
4035 location in the text, data, bss or absolute sections the value is the
4036 number of addresses from the start of that section to the label.
4037 Naturally for text, data and bss sections the value of a symbol changes
4038 as @code{@value{LD}} changes section base addresses during linking. Absolute
4039 symbols' values do not change during linking: that is why they are
4042 The value of an undefined symbol is treated in a special way. If it is
4043 0 then the symbol is not defined in this assembler source file, and
4044 @code{@value{LD}} tries to determine its value from other files linked into the
4045 same program. You make this kind of symbol simply by mentioning a symbol
4046 name without defining it. A non-zero value represents a @code{.comm}
4047 common declaration. The value is how much common storage to reserve, in
4048 bytes (addresses). The symbol refers to the first address of the
4054 @cindex type of a symbol
4056 The type attribute of a symbol contains relocation (section)
4057 information, any flag settings indicating that a symbol is external, and
4058 (optionally), other information for linkers and debuggers. The exact
4059 format depends on the object-code output format in use.
4063 @subsection Symbol Attributes: @code{a.out}
4065 @cindex @code{a.out} symbol attributes
4066 @cindex symbol attributes, @code{a.out}
4069 * Symbol Desc:: Descriptor
4070 * Symbol Other:: Other
4074 @subsubsection Descriptor
4076 @cindex descriptor, of @code{a.out} symbol
4077 This is an arbitrary 16-bit value. You may establish a symbol's
4078 descriptor value by using a @code{.desc} statement
4079 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4080 @command{@value{AS}}.
4083 @subsubsection Other
4085 @cindex other attribute, of @code{a.out} symbol
4086 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4091 @subsection Symbol Attributes for COFF
4093 @cindex COFF symbol attributes
4094 @cindex symbol attributes, COFF
4096 The COFF format supports a multitude of auxiliary symbol attributes;
4097 like the primary symbol attributes, they are set between @code{.def} and
4098 @code{.endef} directives.
4100 @subsubsection Primary Attributes
4102 @cindex primary attributes, COFF symbols
4103 The symbol name is set with @code{.def}; the value and type,
4104 respectively, with @code{.val} and @code{.type}.
4106 @subsubsection Auxiliary Attributes
4108 @cindex auxiliary attributes, COFF symbols
4109 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4110 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4111 table information for COFF.
4116 @subsection Symbol Attributes for SOM
4118 @cindex SOM symbol attributes
4119 @cindex symbol attributes, SOM
4121 The SOM format for the HPPA supports a multitude of symbol attributes set with
4122 the @code{.EXPORT} and @code{.IMPORT} directives.
4124 The attributes are described in @cite{HP9000 Series 800 Assembly
4125 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4126 @code{EXPORT} assembler directive documentation.
4130 @chapter Expressions
4134 @cindex numeric values
4135 An @dfn{expression} specifies an address or numeric value.
4136 Whitespace may precede and/or follow an expression.
4138 The result of an expression must be an absolute number, or else an offset into
4139 a particular section. If an expression is not absolute, and there is not
4140 enough information when @command{@value{AS}} sees the expression to know its
4141 section, a second pass over the source program might be necessary to interpret
4142 the expression---but the second pass is currently not implemented.
4143 @command{@value{AS}} aborts with an error message in this situation.
4146 * Empty Exprs:: Empty Expressions
4147 * Integer Exprs:: Integer Expressions
4151 @section Empty Expressions
4153 @cindex empty expressions
4154 @cindex expressions, empty
4155 An empty expression has no value: it is just whitespace or null.
4156 Wherever an absolute expression is required, you may omit the
4157 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4158 is compatible with other assemblers.
4161 @section Integer Expressions
4163 @cindex integer expressions
4164 @cindex expressions, integer
4165 An @dfn{integer expression} is one or more @emph{arguments} delimited
4166 by @emph{operators}.
4169 * Arguments:: Arguments
4170 * Operators:: Operators
4171 * Prefix Ops:: Prefix Operators
4172 * Infix Ops:: Infix Operators
4176 @subsection Arguments
4178 @cindex expression arguments
4179 @cindex arguments in expressions
4180 @cindex operands in expressions
4181 @cindex arithmetic operands
4182 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4183 contexts arguments are sometimes called ``arithmetic operands''. In
4184 this manual, to avoid confusing them with the ``instruction operands'' of
4185 the machine language, we use the term ``argument'' to refer to parts of
4186 expressions only, reserving the word ``operand'' to refer only to machine
4187 instruction operands.
4189 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4190 @var{section} is one of text, data, bss, absolute,
4191 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4194 Numbers are usually integers.
4196 A number can be a flonum or bignum. In this case, you are warned
4197 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4198 these 32 bits are an integer. You may write integer-manipulating
4199 instructions that act on exotic constants, compatible with other
4202 @cindex subexpressions
4203 Subexpressions are a left parenthesis @samp{(} followed by an integer
4204 expression, followed by a right parenthesis @samp{)}; or a prefix
4205 operator followed by an argument.
4208 @subsection Operators
4210 @cindex operators, in expressions
4211 @cindex arithmetic functions
4212 @cindex functions, in expressions
4213 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4214 operators are followed by an argument. Infix operators appear
4215 between their arguments. Operators may be preceded and/or followed by
4219 @subsection Prefix Operator
4221 @cindex prefix operators
4222 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4223 one argument, which must be absolute.
4225 @c the tex/end tex stuff surrounding this small table is meant to make
4226 @c it align, on the printed page, with the similar table in the next
4227 @c section (which is inside an enumerate).
4229 \global\advance\leftskip by \itemindent
4234 @dfn{Negation}. Two's complement negation.
4236 @dfn{Complementation}. Bitwise not.
4240 \global\advance\leftskip by -\itemindent
4244 @subsection Infix Operators
4246 @cindex infix operators
4247 @cindex operators, permitted arguments
4248 @dfn{Infix operators} take two arguments, one on either side. Operators
4249 have precedence, but operations with equal precedence are performed left
4250 to right. Apart from @code{+} or @option{-}, both arguments must be
4251 absolute, and the result is absolute.
4254 @cindex operator precedence
4255 @cindex precedence of operators
4262 @dfn{Multiplication}.
4265 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4271 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4274 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4278 Intermediate precedence
4283 @dfn{Bitwise Inclusive Or}.
4289 @dfn{Bitwise Exclusive Or}.
4292 @dfn{Bitwise Or Not}.
4299 @cindex addition, permitted arguments
4300 @cindex plus, permitted arguments
4301 @cindex arguments for addition
4303 @dfn{Addition}. If either argument is absolute, the result has the section of
4304 the other argument. You may not add together arguments from different
4307 @cindex subtraction, permitted arguments
4308 @cindex minus, permitted arguments
4309 @cindex arguments for subtraction
4311 @dfn{Subtraction}. If the right argument is absolute, the
4312 result has the section of the left argument.
4313 If both arguments are in the same section, the result is absolute.
4314 You may not subtract arguments from different sections.
4315 @c FIXME is there still something useful to say about undefined - undefined ?
4317 @cindex comparison expressions
4318 @cindex expressions, comparison
4323 @dfn{Is Not Equal To}
4327 @dfn{Is Greater Than}
4329 @dfn{Is Greater Than Or Equal To}
4331 @dfn{Is Less Than Or Equal To}
4333 The comparison operators can be used as infix operators. A true results has a
4334 value of -1 whereas a false result has a value of 0. Note, these operators
4335 perform signed comparisons.
4338 @item Lowest Precedence
4347 These two logical operations can be used to combine the results of sub
4348 expressions. Note, unlike the comparison operators a true result returns a
4349 value of 1 but a false results does still return 0. Also note that the logical
4350 or operator has a slightly lower precedence than logical and.
4355 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4356 address; you can only have a defined section in one of the two arguments.
4359 @chapter Assembler Directives
4361 @cindex directives, machine independent
4362 @cindex pseudo-ops, machine independent
4363 @cindex machine independent directives
4364 All assembler directives have names that begin with a period (@samp{.}).
4365 The names are case insensitive for most targets, and usually written
4368 This chapter discusses directives that are available regardless of the
4369 target machine configuration for the @sc{gnu} assembler.
4371 Some machine configurations provide additional directives.
4372 @xref{Machine Dependencies}.
4375 @ifset machine-directives
4376 @xref{Machine Dependencies}, for additional directives.
4381 * Abort:: @code{.abort}
4383 * ABORT (COFF):: @code{.ABORT}
4386 * Align:: @code{.align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4387 * Altmacro:: @code{.altmacro}
4388 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4389 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4390 * Attach_to_group:: @code{.attach_to_group @var{name}}
4391 * Balign:: @code{.balign [@var{abs-expr}[, @var{abs-expr}]]}
4392 * Bss:: @code{.bss @var{subsection}}
4393 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4394 * Byte:: @code{.byte @var{expressions}}
4395 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4396 * Comm:: @code{.comm @var{symbol} , @var{length} }
4397 * Data:: @code{.data @var{subsection}}
4398 * Dc:: @code{.dc[@var{size}] @var{expressions}}
4399 * Dcb:: @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4400 * Ds:: @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4402 * Def:: @code{.def @var{name}}
4405 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4411 * Double:: @code{.double @var{flonums}}
4412 * Eject:: @code{.eject}
4413 * Else:: @code{.else}
4414 * Elseif:: @code{.elseif}
4417 * Endef:: @code{.endef}
4420 * Endfunc:: @code{.endfunc}
4421 * Endif:: @code{.endif}
4422 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4423 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4424 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4426 * Error:: @code{.error @var{string}}
4427 * Exitm:: @code{.exitm}
4428 * Extern:: @code{.extern}
4429 * Fail:: @code{.fail}
4430 * File:: @code{.file}
4431 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4432 * Float:: @code{.float @var{flonums}}
4433 * Func:: @code{.func}
4434 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4436 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4437 * Hidden:: @code{.hidden @var{names}}
4440 * hword:: @code{.hword @var{expressions}}
4441 * Ident:: @code{.ident}
4442 * If:: @code{.if @var{absolute expression}}
4443 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4444 * Include:: @code{.include "@var{file}"}
4445 * Int:: @code{.int @var{expressions}}
4447 * Internal:: @code{.internal @var{names}}
4450 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4451 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4452 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4453 * Lflags:: @code{.lflags}
4454 @ifclear no-line-dir
4455 * Line:: @code{.line @var{line-number}}
4458 * Linkonce:: @code{.linkonce [@var{type}]}
4459 * List:: @code{.list}
4460 * Ln:: @code{.ln @var{line-number}}
4461 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4462 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4464 * Local:: @code{.local @var{names}}
4467 * Long:: @code{.long @var{expressions}}
4469 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4472 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4473 * MRI:: @code{.mri @var{val}}
4474 * Noaltmacro:: @code{.noaltmacro}
4475 * Nolist:: @code{.nolist}
4477 * Nops:: @code{.nops @var{size}[, @var{control}]}
4478 * Octa:: @code{.octa @var{bignums}}
4479 * Offset:: @code{.offset @var{loc}}
4480 * Org:: @code{.org @var{new-lc}, @var{fill}}
4481 * P2align:: @code{.p2align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4483 * PopSection:: @code{.popsection}
4484 * Previous:: @code{.previous}
4487 * Print:: @code{.print @var{string}}
4489 * Protected:: @code{.protected @var{names}}
4492 * Psize:: @code{.psize @var{lines}, @var{columns}}
4493 * Purgem:: @code{.purgem @var{name}}
4495 * PushSection:: @code{.pushsection @var{name}}
4498 * Quad:: @code{.quad @var{bignums}}
4499 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4500 * Rept:: @code{.rept @var{count}}
4501 * Sbttl:: @code{.sbttl "@var{subheading}"}
4503 * Scl:: @code{.scl @var{class}}
4506 * Section:: @code{.section @var{name}[, @var{flags}]}
4509 * Set:: @code{.set @var{symbol}, @var{expression}}
4510 * Short:: @code{.short @var{expressions}}
4511 * Single:: @code{.single @var{flonums}}
4513 * Size:: @code{.size [@var{name} , @var{expression}]}
4515 @ifclear no-space-dir
4516 * Skip:: @code{.skip @var{size} [,@var{fill}]}
4519 * Sleb128:: @code{.sleb128 @var{expressions}}
4520 @ifclear no-space-dir
4521 * Space:: @code{.space @var{size} [,@var{fill}]}
4524 * Stab:: @code{.stabd, .stabn, .stabs}
4527 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4528 * Struct:: @code{.struct @var{expression}}
4530 * SubSection:: @code{.subsection}
4531 * Symver:: @code{.symver @var{name},@var{name2@@nodename}[,@var{visibility}]}
4535 * Tag:: @code{.tag @var{structname}}
4538 * Text:: @code{.text @var{subsection}}
4539 * Title:: @code{.title "@var{heading}"}
4541 * Tls_common:: @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
4544 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4547 * Uleb128:: @code{.uleb128 @var{expressions}}
4549 * Val:: @code{.val @var{addr}}
4553 * Version:: @code{.version "@var{string}"}
4554 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4555 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4558 * Warning:: @code{.warning @var{string}}
4559 * Weak:: @code{.weak @var{names}}
4560 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4561 * Word:: @code{.word @var{expressions}}
4562 @ifclear no-space-dir
4563 * Zero:: @code{.zero @var{size}}
4565 * 2byte:: @code{.2byte @var{expressions}}
4566 * 4byte:: @code{.4byte @var{expressions}}
4567 * 8byte:: @code{.8byte @var{bignums}}
4568 * Deprecated:: Deprecated Directives
4572 @section @code{.abort}
4574 @cindex @code{abort} directive
4575 @cindex stopping the assembly
4576 This directive stops the assembly immediately. It is for
4577 compatibility with other assemblers. The original idea was that the
4578 assembly language source would be piped into the assembler. If the sender
4579 of the source quit, it could use this directive tells @command{@value{AS}} to
4580 quit also. One day @code{.abort} will not be supported.
4584 @section @code{.ABORT} (COFF)
4586 @cindex @code{ABORT} directive
4587 When producing COFF output, @command{@value{AS}} accepts this directive as a
4588 synonym for @samp{.abort}.
4593 @section @code{.align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4595 @cindex padding the location counter
4596 @cindex @code{align} directive
4597 Pad the location counter (in the current subsection) to a particular storage
4598 boundary. The first expression (which must be absolute) is the alignment
4599 required, as described below. If this expression is omitted then a default
4600 value of 0 is used, effectively disabling alignment requirements.
4602 The second expression (also absolute) gives the fill value to be stored in the
4603 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4604 padding bytes are normally zero. However, on most systems, if the section is
4605 marked as containing code and the fill value is omitted, the space is filled
4606 with no-op instructions.
4608 The third expression is also absolute, and is also optional. If it is present,
4609 it is the maximum number of bytes that should be skipped by this alignment
4610 directive. If doing the alignment would require skipping more bytes than the
4611 specified maximum, then the alignment is not done at all. You can omit the
4612 fill value (the second argument) entirely by simply using two commas after the
4613 required alignment; this can be useful if you want the alignment to be filled
4614 with no-op instructions when appropriate.
4616 The way the required alignment is specified varies from system to system.
4617 For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
4618 s390, sparc, tic4x and xtensa, the first expression is the
4619 alignment request in bytes. For example @samp{.align 8} advances
4620 the location counter until it is a multiple of 8. If the location counter
4621 is already a multiple of 8, no change is needed. For the tic54x, the
4622 first expression is the alignment request in words.
4624 For other systems, including ppc, i386 using a.out format, arm and
4625 strongarm, it is the
4626 number of low-order zero bits the location counter must have after
4627 advancement. For example @samp{.align 3} advances the location
4628 counter until it is a multiple of 8. If the location counter is already a
4629 multiple of 8, no change is needed.
4631 This inconsistency is due to the different behaviors of the various
4632 native assemblers for these systems which GAS must emulate.
4633 GAS also provides @code{.balign} and @code{.p2align} directives,
4634 described later, which have a consistent behavior across all
4635 architectures (but are specific to GAS).
4638 @section @code{.altmacro}
4639 Enable alternate macro mode, enabling:
4642 @item LOCAL @var{name} [ , @dots{} ]
4643 One additional directive, @code{LOCAL}, is available. It is used to
4644 generate a string replacement for each of the @var{name} arguments, and
4645 replace any instances of @var{name} in each macro expansion. The
4646 replacement string is unique in the assembly, and different for each
4647 separate macro expansion. @code{LOCAL} allows you to write macros that
4648 define symbols, without fear of conflict between separate macro expansions.
4650 @item String delimiters
4651 You can write strings delimited in these other ways besides
4652 @code{"@var{string}"}:
4655 @item '@var{string}'
4656 You can delimit strings with single-quote characters.
4658 @item <@var{string}>
4659 You can delimit strings with matching angle brackets.
4662 @item single-character string escape
4663 To include any single character literally in a string (even if the
4664 character would otherwise have some special meaning), you can prefix the
4665 character with @samp{!} (an exclamation mark). For example, you can
4666 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4668 @item Expression results as strings
4669 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4670 and use the result as a string.
4674 @section @code{.ascii "@var{string}"}@dots{}
4676 @cindex @code{ascii} directive
4677 @cindex string literals
4678 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4679 separated by commas. It assembles each string (with no automatic
4680 trailing zero byte) into consecutive addresses.
4683 @section @code{.asciz "@var{string}"}@dots{}
4685 @cindex @code{asciz} directive
4686 @cindex zero-terminated strings
4687 @cindex null-terminated strings
4688 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4689 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''. Note that
4690 multiple string arguments not separated by commas will be concatenated
4691 together and only one final zero byte will be stored.
4693 @node Attach_to_group
4694 @section @code{.attach_to_group @var{name}}
4695 Attaches the current section to the named group. This is like declaring
4696 the section with the @code{G} attribute, but can be done after the section
4697 has been created. Note if the group section does not exist at the point that
4698 this directive is used then it will be created.
4701 @section @code{.balign[wl] [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4703 @cindex padding the location counter given number of bytes
4704 @cindex @code{balign} directive
4705 Pad the location counter (in the current subsection) to a particular
4706 storage boundary. The first expression (which must be absolute) is the
4707 alignment request in bytes. For example @samp{.balign 8} advances
4708 the location counter until it is a multiple of 8. If the location counter
4709 is already a multiple of 8, no change is needed. If the expression is omitted
4710 then a default value of 0 is used, effectively disabling alignment requirements.
4712 The second expression (also absolute) gives the fill value to be stored in the
4713 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4714 padding bytes are normally zero. However, on most systems, if the section is
4715 marked as containing code and the fill value is omitted, the space is filled
4716 with no-op instructions.
4718 The third expression is also absolute, and is also optional. If it is present,
4719 it is the maximum number of bytes that should be skipped by this alignment
4720 directive. If doing the alignment would require skipping more bytes than the
4721 specified maximum, then the alignment is not done at all. You can omit the
4722 fill value (the second argument) entirely by simply using two commas after the
4723 required alignment; this can be useful if you want the alignment to be filled
4724 with no-op instructions when appropriate.
4726 @cindex @code{balignw} directive
4727 @cindex @code{balignl} directive
4728 The @code{.balignw} and @code{.balignl} directives are variants of the
4729 @code{.balign} directive. The @code{.balignw} directive treats the fill
4730 pattern as a two byte word value. The @code{.balignl} directives treats the
4731 fill pattern as a four byte longword value. For example, @code{.balignw
4732 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4733 filled in with the value 0x368d (the exact placement of the bytes depends upon
4734 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4738 @section @code{.bss @var{subsection}}
4739 @cindex @code{bss} directive
4741 @code{.bss} tells @command{@value{AS}} to assemble the following statements
4742 onto the end of the bss section.
4744 For ELF based targets an optional @var{subsection} expression (which must
4745 evaluate to a positive integer) can be provided. In this case the statements
4746 are appended to the end of the indicated bss subsection.
4749 @node Bundle directives
4750 @section Bundle directives
4751 @subsection @code{.bundle_align_mode @var{abs-expr}}
4752 @cindex @code{bundle_align_mode} directive
4754 @cindex instruction bundle
4755 @cindex aligned instruction bundle
4756 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4757 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4758 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4759 disabled (which is the default state). If the argument it not zero, it
4760 gives the size of an instruction bundle as a power of two (as for the
4761 @code{.p2align} directive, @pxref{P2align}).
4763 For some targets, it's an ABI requirement that no instruction may span a
4764 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4765 instructions that starts on an aligned boundary. For example, if
4766 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4767 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4768 effect, no single instruction may span a boundary between bundles. If an
4769 instruction would start too close to the end of a bundle for the length of
4770 that particular instruction to fit within the bundle, then the space at the
4771 end of that bundle is filled with no-op instructions so the instruction
4772 starts in the next bundle. As a corollary, it's an error if any single
4773 instruction's encoding is longer than the bundle size.
4775 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4776 @cindex @code{bundle_lock} directive
4777 @cindex @code{bundle_unlock} directive
4778 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4779 allow explicit control over instruction bundle padding. These directives
4780 are only valid when @code{.bundle_align_mode} has been used to enable
4781 aligned instruction bundle mode. It's an error if they appear when
4782 @code{.bundle_align_mode} has not been used at all, or when the last
4783 directive was @w{@code{.bundle_align_mode 0}}.
4785 @cindex bundle-locked
4786 For some targets, it's an ABI requirement that certain instructions may
4787 appear only as part of specified permissible sequences of multiple
4788 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4789 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4790 instruction sequence. For purposes of aligned instruction bundle mode, a
4791 sequence starting with @code{.bundle_lock} and ending with
4792 @code{.bundle_unlock} is treated as a single instruction. That is, the
4793 entire sequence must fit into a single bundle and may not span a bundle
4794 boundary. If necessary, no-op instructions will be inserted before the
4795 first instruction of the sequence so that the whole sequence starts on an
4796 aligned bundle boundary. It's an error if the sequence is longer than the
4799 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4800 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4801 nested. That is, a second @code{.bundle_lock} directive before the next
4802 @code{.bundle_unlock} directive has no effect except that it must be
4803 matched by another closing @code{.bundle_unlock} so that there is the
4804 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4807 @section @code{.byte @var{expressions}}
4809 @cindex @code{byte} directive
4810 @cindex integers, one byte
4811 @code{.byte} expects zero or more expressions, separated by commas.
4812 Each expression is assembled into the next byte.
4814 @node CFI directives
4815 @section CFI directives
4816 @subsection @code{.cfi_sections @var{section_list}}
4817 @cindex @code{cfi_sections} directive
4818 @code{.cfi_sections} may be used to specify whether CFI directives
4819 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4820 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4821 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4822 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4823 directive is not used is @code{.cfi_sections .eh_frame}.
4825 On targets that support compact unwinding tables these can be generated
4826 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4828 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4829 which is used by the @value{TIC6X} target.
4831 The @code{.cfi_sections} directive can be repeated, with the same or different
4832 arguments, provided that CFI generation has not yet started. Once CFI
4833 generation has started however the section list is fixed and any attempts to
4834 redefine it will result in an error.
4836 @subsection @code{.cfi_startproc [simple]}
4837 @cindex @code{cfi_startproc} directive
4838 @code{.cfi_startproc} is used at the beginning of each function that
4839 should have an entry in @code{.eh_frame}. It initializes some internal
4840 data structures. Don't forget to close the function by
4841 @code{.cfi_endproc}.
4843 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4844 it also emits some architecture dependent initial CFI instructions.
4846 @subsection @code{.cfi_endproc}
4847 @cindex @code{cfi_endproc} directive
4848 @code{.cfi_endproc} is used at the end of a function where it closes its
4849 unwind entry previously opened by
4850 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4852 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4853 @cindex @code{cfi_personality} directive
4854 @code{.cfi_personality} defines personality routine and its encoding.
4855 @var{encoding} must be a constant determining how the personality
4856 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4857 argument is not present, otherwise second argument should be
4858 a constant or a symbol name. When using indirect encodings,
4859 the symbol provided should be the location where personality
4860 can be loaded from, not the personality routine itself.
4861 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4862 no personality routine.
4864 @subsection @code{.cfi_personality_id @var{id}}
4865 @cindex @code{cfi_personality_id} directive
4866 @code{cfi_personality_id} defines a personality routine by its index as
4867 defined in a compact unwinding format.
4868 Only valid when generating compact EH frames (i.e.
4869 with @code{.cfi_sections eh_frame_entry}.
4871 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4872 @cindex @code{cfi_fde_data} directive
4873 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4874 used for the current function. These are emitted inline in the
4875 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4876 in the @code{.gnu.extab} section otherwise.
4877 Only valid when generating compact EH frames (i.e.
4878 with @code{.cfi_sections eh_frame_entry}.
4880 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4881 @code{.cfi_lsda} defines LSDA and its encoding.
4882 @var{encoding} must be a constant determining how the LSDA
4883 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4884 argument is not present, otherwise the second argument should be a constant
4885 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4886 meaning that no LSDA is present.
4888 @subsection @code{.cfi_inline_lsda} [@var{align}]
4889 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4890 switches to the corresponding @code{.gnu.extab} section.
4891 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4892 Only valid when generating compact EH frames (i.e.
4893 with @code{.cfi_sections eh_frame_entry}.
4895 The table header and unwinding opcodes will be generated at this point,
4896 so that they are immediately followed by the LSDA data. The symbol
4897 referenced by the @code{.cfi_lsda} directive should still be defined
4898 in case a fallback FDE based encoding is used. The LSDA data is terminated
4899 by a section directive.
4901 The optional @var{align} argument specifies the alignment required.
4902 The alignment is specified as a power of two, as with the
4903 @code{.p2align} directive.
4905 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4906 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4907 address from @var{register} and add @var{offset} to it}.
4909 @subsection @code{.cfi_def_cfa_register @var{register}}
4910 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4911 now on @var{register} will be used instead of the old one. Offset
4914 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4915 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4916 remains the same, but @var{offset} is new. Note that it is the
4917 absolute offset that will be added to a defined register to compute
4920 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4921 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4922 value that is added/subtracted from the previous offset.
4924 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4925 Previous value of @var{register} is saved at offset @var{offset} from
4928 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4929 Previous value of @var{register} is CFA + @var{offset}.
4931 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4932 Previous value of @var{register} is saved at offset @var{offset} from
4933 the current CFA register. This is transformed to @code{.cfi_offset}
4934 using the known displacement of the CFA register from the CFA.
4935 This is often easier to use, because the number will match the
4936 code it's annotating.
4938 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4939 Previous value of @var{register1} is saved in register @var{register2}.
4941 @subsection @code{.cfi_restore @var{register}}
4942 @code{.cfi_restore} says that the rule for @var{register} is now the
4943 same as it was at the beginning of the function, after all initial
4944 instruction added by @code{.cfi_startproc} were executed.
4946 @subsection @code{.cfi_undefined @var{register}}
4947 From now on the previous value of @var{register} can't be restored anymore.
4949 @subsection @code{.cfi_same_value @var{register}}
4950 Current value of @var{register} is the same like in the previous frame,
4951 i.e. no restoration needed.
4953 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4954 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4955 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4956 places them in the current row. This is useful for situations where you have
4957 multiple @code{.cfi_*} directives that need to be undone due to the control
4958 flow of the program. For example, we could have something like this (assuming
4959 the CFA is the value of @code{rbp}):
4969 .cfi_def_cfa %rsp, 8
4972 /* Do something else */
4975 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4976 to the instructions before @code{label}. This means we'd have to add multiple
4977 @code{.cfi} directives after @code{label} to recreate the original save
4978 locations of the registers, as well as setting the CFA back to the value of
4979 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4991 .cfi_def_cfa %rsp, 8
4995 /* Do something else */
4998 That way, the rules for the instructions after @code{label} will be the same
4999 as before the first @code{.cfi_restore} without having to use multiple
5000 @code{.cfi} directives.
5002 @subsection @code{.cfi_return_column @var{register}}
5003 Change return column @var{register}, i.e. the return address is either
5004 directly in @var{register} or can be accessed by rules for @var{register}.
5006 @subsection @code{.cfi_signal_frame}
5007 Mark current function as signal trampoline.
5009 @subsection @code{.cfi_window_save}
5010 SPARC register window has been saved.
5012 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
5013 Allows the user to add arbitrary bytes to the unwind info. One
5014 might use this to add OS-specific CFI opcodes, or generic CFI
5015 opcodes that GAS does not yet support.
5017 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
5018 The current value of @var{register} is @var{label}. The value of @var{label}
5019 will be encoded in the output file according to @var{encoding}; see the
5020 description of @code{.cfi_personality} for details on this encoding.
5022 The usefulness of equating a register to a fixed label is probably
5023 limited to the return address register. Here, it can be useful to
5024 mark a code segment that has only one return address which is reached
5025 by a direct branch and no copy of the return address exists in memory
5026 or another register.
5029 @section @code{.comm @var{symbol} , @var{length} }
5031 @cindex @code{comm} directive
5032 @cindex symbol, common
5033 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
5034 common symbol in one object file may be merged with a defined or common symbol
5035 of the same name in another object file. If @code{@value{LD}} does not see a
5036 definition for the symbol--just one or more common symbols--then it will
5037 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
5038 absolute expression. If @code{@value{LD}} sees multiple common symbols with
5039 the same name, and they do not all have the same size, it will allocate space
5040 using the largest size.
5043 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
5044 an optional third argument. This is the desired alignment of the symbol,
5045 specified for ELF as a byte boundary (for example, an alignment of 16 means
5046 that the least significant 4 bits of the address should be zero), and for PE
5047 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
5048 boundary). The alignment must be an absolute expression, and it must be a
5049 power of two. If @code{@value{LD}} allocates uninitialized memory for the
5050 common symbol, it will use the alignment when placing the symbol. If no
5051 alignment is specified, @command{@value{AS}} will set the alignment to the
5052 largest power of two less than or equal to the size of the symbol, up to a
5053 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
5054 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5055 @samp{--section-alignment} option; image file sections in PE are aligned to
5056 multiples of 4096, which is far too large an alignment for ordinary variables.
5057 It is rather the default alignment for (non-debug) sections within object
5058 (@samp{*.o}) files, which are less strictly aligned.}.
5062 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5063 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5067 @section @code{.data @var{subsection}}
5068 @cindex @code{data} directive
5070 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5071 end of the data subsection numbered @var{subsection} (which is an
5072 absolute expression). If @var{subsection} is omitted, it defaults
5076 @section @code{.dc[@var{size}] @var{expressions}}
5077 @cindex @code{dc} directive
5079 The @code{.dc} directive expects zero or more @var{expressions} separated by
5080 commas. These expressions are evaluated and their values inserted into the
5081 current section. The size of the emitted value depends upon the suffix to the
5082 @code{.dc} directive:
5086 Emits N-bit values, where N is the size of an address on the target system.
5090 Emits double precision floating-point values.
5092 Emits 32-bit values.
5094 Emits single precision floating-point values.
5096 Emits 16-bit values.
5097 Note - this is true even on targets where the @code{.word} directive would emit
5100 Emits long double precision floating-point values.
5103 If no suffix is used then @samp{.w} is assumed.
5105 The byte ordering is target dependent, as is the size and format of floating
5109 @section @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
5110 @cindex @code{dcb} directive
5111 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5112 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5113 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5114 @var{size} suffix, if present, must be one of:
5118 Emits single byte values.
5120 Emits double-precision floating point values.
5122 Emits 4-byte values.
5124 Emits single-precision floating point values.
5126 Emits 2-byte values.
5128 Emits long double-precision floating point values.
5131 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5133 The byte ordering is target dependent, as is the size and format of floating
5137 @section @code{.ds[@var{size}] @var{number} [,@var{fill}]}
5138 @cindex @code{ds} directive
5139 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5140 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5141 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5142 @var{size} suffix, if present, must be one of:
5146 Emits single byte values.
5148 Emits 8-byte values.
5150 Emits 4-byte values.
5152 Emits values with size matching packed-decimal floating-point ones.
5154 Emits 4-byte values.
5156 Emits 2-byte values.
5158 Emits values with size matching long double precision floating-point ones.
5161 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}
5162 suffixes do not indicate that floating-point values are to be inserted.
5164 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5166 The byte ordering is target dependent.
5171 @section @code{.def @var{name}}
5173 @cindex @code{def} directive
5174 @cindex COFF symbols, debugging
5175 @cindex debugging COFF symbols
5176 Begin defining debugging information for a symbol @var{name}; the
5177 definition extends until the @code{.endef} directive is encountered.
5182 @section @code{.desc @var{symbol}, @var{abs-expression}}
5184 @cindex @code{desc} directive
5185 @cindex COFF symbol descriptor
5186 @cindex symbol descriptor, COFF
5187 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5188 to the low 16 bits of an absolute expression.
5191 The @samp{.desc} directive is not available when @command{@value{AS}} is
5192 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5193 object format. For the sake of compatibility, @command{@value{AS}} accepts
5194 it, but produces no output, when configured for COFF.
5200 @section @code{.dim}
5202 @cindex @code{dim} directive
5203 @cindex COFF auxiliary symbol information
5204 @cindex auxiliary symbol information, COFF
5205 This directive is generated by compilers to include auxiliary debugging
5206 information in the symbol table. It is only permitted inside
5207 @code{.def}/@code{.endef} pairs.
5211 @section @code{.double @var{flonums}}
5213 @cindex @code{double} directive
5214 @cindex floating point numbers (double)
5215 @code{.double} expects zero or more flonums, separated by commas. It
5216 assembles floating point numbers.
5218 The exact kind of floating point numbers emitted depends on how
5219 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5223 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5224 in @sc{ieee} format.
5229 @section @code{.eject}
5231 @cindex @code{eject} directive
5232 @cindex new page, in listings
5233 @cindex page, in listings
5234 @cindex listing control: new page
5235 Force a page break at this point, when generating assembly listings.
5238 @section @code{.else}
5240 @cindex @code{else} directive
5241 @code{.else} is part of the @command{@value{AS}} support for conditional
5242 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5243 of code to be assembled if the condition for the preceding @code{.if}
5247 @section @code{.elseif}
5249 @cindex @code{elseif} directive
5250 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5251 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5252 @code{.if} block that would otherwise fill the entire @code{.else} section.
5255 @section @code{.end}
5257 @cindex @code{end} directive
5258 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5259 process anything in the file past the @code{.end} directive.
5263 @section @code{.endef}
5265 @cindex @code{endef} directive
5266 This directive flags the end of a symbol definition begun with
5271 @section @code{.endfunc}
5272 @cindex @code{endfunc} directive
5273 @code{.endfunc} marks the end of a function specified with @code{.func}.
5276 @section @code{.endif}
5278 @cindex @code{endif} directive
5279 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5280 it marks the end of a block of code that is only assembled
5281 conditionally. @xref{If,,@code{.if}}.
5284 @section @code{.equ @var{symbol}, @var{expression}}
5286 @cindex @code{equ} directive
5287 @cindex assigning values to symbols
5288 @cindex symbols, assigning values to
5289 This directive sets the value of @var{symbol} to @var{expression}.
5290 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5293 The syntax for @code{equ} on the HPPA is
5294 @samp{@var{symbol} .equ @var{expression}}.
5298 The syntax for @code{equ} on the Z80 is
5299 @samp{@var{symbol} equ @var{expression}}.
5300 On the Z80 it is an error if @var{symbol} is already defined,
5301 but the symbol is not protected from later redefinition.
5302 Compare @ref{Equiv}.
5306 @section @code{.equiv @var{symbol}, @var{expression}}
5307 @cindex @code{equiv} directive
5308 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5309 the assembler will signal an error if @var{symbol} is already defined. Note a
5310 symbol which has been referenced but not actually defined is considered to be
5313 Except for the contents of the error message, this is roughly equivalent to
5320 plus it protects the symbol from later redefinition.
5323 @section @code{.eqv @var{symbol}, @var{expression}}
5324 @cindex @code{eqv} directive
5325 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5326 evaluate the expression or any part of it immediately. Instead each time
5327 the resulting symbol is used in an expression, a snapshot of its current
5331 @section @code{.err}
5332 @cindex @code{err} directive
5333 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5334 message and, unless the @option{-Z} option was used, it will not generate an
5335 object file. This can be used to signal an error in conditionally compiled code.
5338 @section @code{.error "@var{string}"}
5339 @cindex error directive
5341 Similarly to @code{.err}, this directive emits an error, but you can specify a
5342 string that will be emitted as the error message. If you don't specify the
5343 message, it defaults to @code{".error directive invoked in source file"}.
5344 @xref{Errors, ,Error and Warning Messages}.
5347 .error "This code has not been assembled and tested."
5351 @section @code{.exitm}
5352 Exit early from the current macro definition. @xref{Macro}.
5355 @section @code{.extern}
5357 @cindex @code{extern} directive
5358 @code{.extern} is accepted in the source program---for compatibility
5359 with other assemblers---but it is ignored. @command{@value{AS}} treats
5360 all undefined symbols as external.
5363 @section @code{.fail @var{expression}}
5365 @cindex @code{fail} directive
5366 Generates an error or a warning. If the value of the @var{expression} is 500
5367 or more, @command{@value{AS}} will print a warning message. If the value is less
5368 than 500, @command{@value{AS}} will print an error message. The message will
5369 include the value of @var{expression}. This can occasionally be useful inside
5370 complex nested macros or conditional assembly.
5373 @section @code{.file}
5374 @cindex @code{file} directive
5376 @ifclear no-file-dir
5377 There are two different versions of the @code{.file} directive. Targets
5378 that support DWARF2 line number information use the DWARF2 version of
5379 @code{.file}. Other targets use the default version.
5381 @subheading Default Version
5383 @cindex logical file name
5384 @cindex file name, logical
5385 This version of the @code{.file} directive tells @command{@value{AS}} that we
5386 are about to start a new logical file. The syntax is:
5392 @var{string} is the new file name. In general, the filename is
5393 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5394 to specify an empty file name, you must give the quotes--@code{""}. This
5395 statement may go away in future: it is only recognized to be compatible with
5396 old @command{@value{AS}} programs.
5398 @subheading DWARF2 Version
5401 When emitting DWARF2 line number information, @code{.file} assigns filenames
5402 to the @code{.debug_line} file name table. The syntax is:
5405 .file @var{fileno} @var{filename}
5408 The @var{fileno} operand should be a unique positive integer to use as the
5409 index of the entry in the table. The @var{filename} operand is a C string
5410 literal enclosed in double quotes. The @var{filename} can include directory
5411 elements. If it does, then the directory will be added to the directory table
5412 and the basename will be added to the file table.
5414 The detail of filename indices is exposed to the user because the filename
5415 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5416 information, and thus the user must know the exact indices that table
5419 If DWARF-5 support has been enabled via the @option{-gdwarf-5} option then
5420 an extended version of the @code{file} is also allowed:
5423 .file @var{fileno} [@var{dirname}] @var{filename} [md5 @var{value}]
5426 With this version a separate directory name is allowed, although if this is
5427 used then @var{filename} should not contain any directory components. In
5428 addtion an md5 hash value of the contents of @var{filename} can be provided.
5429 This will be stored in the the file table as well, and can be used by tools
5430 reading the debug information to verify that the contents of the source file
5431 match the contents of the compiled file.
5434 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5436 @cindex @code{fill} directive
5437 @cindex writing patterns in memory
5438 @cindex patterns, writing in memory
5439 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5440 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5441 may be zero or more. @var{Size} may be zero or more, but if it is
5442 more than 8, then it is deemed to have the value 8, compatible with
5443 other people's assemblers. The contents of each @var{repeat} bytes
5444 is taken from an 8-byte number. The highest order 4 bytes are
5445 zero. The lowest order 4 bytes are @var{value} rendered in the
5446 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5447 Each @var{size} bytes in a repetition is taken from the lowest order
5448 @var{size} bytes of this number. Again, this bizarre behavior is
5449 compatible with other people's assemblers.
5451 @var{size} and @var{value} are optional.
5452 If the second comma and @var{value} are absent, @var{value} is
5453 assumed zero. If the first comma and following tokens are absent,
5454 @var{size} is assumed to be 1.
5457 @section @code{.float @var{flonums}}
5459 @cindex floating point numbers (single)
5460 @cindex @code{float} directive
5461 This directive assembles zero or more flonums, separated by commas. It
5462 has the same effect as @code{.single}.
5464 The exact kind of floating point numbers emitted depends on how
5465 @command{@value{AS}} is configured.
5466 @xref{Machine Dependencies}.
5470 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5471 in @sc{ieee} format.
5476 @section @code{.func @var{name}[,@var{label}]}
5477 @cindex @code{func} directive
5478 @code{.func} emits debugging information to denote function @var{name}, and
5479 is ignored unless the file is assembled with debugging enabled.
5480 Only @samp{--gstabs[+]} is currently supported.
5481 @var{label} is the entry point of the function and if omitted @var{name}
5482 prepended with the @samp{leading char} is used.
5483 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5484 All functions are currently defined to have @code{void} return type.
5485 The function must be terminated with @code{.endfunc}.
5488 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5490 @cindex @code{global} directive
5491 @cindex symbol, making visible to linker
5492 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5493 @var{symbol} in your partial program, its value is made available to
5494 other partial programs that are linked with it. Otherwise,
5495 @var{symbol} takes its attributes from a symbol of the same name
5496 from another file linked into the same program.
5498 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5499 compatibility with other assemblers.
5502 On the HPPA, @code{.global} is not always enough to make it accessible to other
5503 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5504 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5509 @section @code{.gnu_attribute @var{tag},@var{value}}
5510 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5513 @section @code{.hidden @var{names}}
5515 @cindex @code{hidden} directive
5517 This is one of the ELF visibility directives. The other two are
5518 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5519 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5521 This directive overrides the named symbols default visibility (which is set by
5522 their binding: local, global or weak). The directive sets the visibility to
5523 @code{hidden} which means that the symbols are not visible to other components.
5524 Such symbols are always considered to be @code{protected} as well.
5528 @section @code{.hword @var{expressions}}
5530 @cindex @code{hword} directive
5531 @cindex integers, 16-bit
5532 @cindex numbers, 16-bit
5533 @cindex sixteen bit integers
5534 This expects zero or more @var{expressions}, and emits
5535 a 16 bit number for each.
5538 This directive is a synonym for @samp{.short}; depending on the target
5539 architecture, it may also be a synonym for @samp{.word}.
5543 This directive is a synonym for @samp{.short}.
5546 This directive is a synonym for both @samp{.short} and @samp{.word}.
5551 @section @code{.ident}
5553 @cindex @code{ident} directive
5555 This directive is used by some assemblers to place tags in object files. The
5556 behavior of this directive varies depending on the target. When using the
5557 a.out object file format, @command{@value{AS}} simply accepts the directive for
5558 source-file compatibility with existing assemblers, but does not emit anything
5559 for it. When using COFF, comments are emitted to the @code{.comment} or
5560 @code{.rdata} section, depending on the target. When using ELF, comments are
5561 emitted to the @code{.comment} section.
5564 @section @code{.if @var{absolute expression}}
5566 @cindex conditional assembly
5567 @cindex @code{if} directive
5568 @code{.if} marks the beginning of a section of code which is only
5569 considered part of the source program being assembled if the argument
5570 (which must be an @var{absolute expression}) is non-zero. The end of
5571 the conditional section of code must be marked by @code{.endif}
5572 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5573 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5574 If you have several conditions to check, @code{.elseif} may be used to avoid
5575 nesting blocks if/else within each subsequent @code{.else} block.
5577 The following variants of @code{.if} are also supported:
5579 @cindex @code{ifdef} directive
5580 @item .ifdef @var{symbol}
5581 Assembles the following section of code if the specified @var{symbol}
5582 has been defined. Note a symbol which has been referenced but not yet defined
5583 is considered to be undefined.
5585 @cindex @code{ifb} directive
5586 @item .ifb @var{text}
5587 Assembles the following section of code if the operand is blank (empty).
5589 @cindex @code{ifc} directive
5590 @item .ifc @var{string1},@var{string2}
5591 Assembles the following section of code if the two strings are the same. The
5592 strings may be optionally quoted with single quotes. If they are not quoted,
5593 the first string stops at the first comma, and the second string stops at the
5594 end of the line. Strings which contain whitespace should be quoted. The
5595 string comparison is case sensitive.
5597 @cindex @code{ifeq} directive
5598 @item .ifeq @var{absolute expression}
5599 Assembles the following section of code if the argument is zero.
5601 @cindex @code{ifeqs} directive
5602 @item .ifeqs @var{string1},@var{string2}
5603 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5605 @cindex @code{ifge} directive
5606 @item .ifge @var{absolute expression}
5607 Assembles the following section of code if the argument is greater than or
5610 @cindex @code{ifgt} directive
5611 @item .ifgt @var{absolute expression}
5612 Assembles the following section of code if the argument is greater than zero.
5614 @cindex @code{ifle} directive
5615 @item .ifle @var{absolute expression}
5616 Assembles the following section of code if the argument is less than or equal
5619 @cindex @code{iflt} directive
5620 @item .iflt @var{absolute expression}
5621 Assembles the following section of code if the argument is less than zero.
5623 @cindex @code{ifnb} directive
5624 @item .ifnb @var{text}
5625 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5626 following section of code if the operand is non-blank (non-empty).
5628 @cindex @code{ifnc} directive
5629 @item .ifnc @var{string1},@var{string2}.
5630 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5631 following section of code if the two strings are not the same.
5633 @cindex @code{ifndef} directive
5634 @cindex @code{ifnotdef} directive
5635 @item .ifndef @var{symbol}
5636 @itemx .ifnotdef @var{symbol}
5637 Assembles the following section of code if the specified @var{symbol}
5638 has not been defined. Both spelling variants are equivalent. Note a symbol
5639 which has been referenced but not yet defined is considered to be undefined.
5641 @cindex @code{ifne} directive
5642 @item .ifne @var{absolute expression}
5643 Assembles the following section of code if the argument is not equal to zero
5644 (in other words, this is equivalent to @code{.if}).
5646 @cindex @code{ifnes} directive
5647 @item .ifnes @var{string1},@var{string2}
5648 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5649 following section of code if the two strings are not the same.
5653 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5655 @cindex @code{incbin} directive
5656 @cindex binary files, including
5657 The @code{incbin} directive includes @var{file} verbatim at the current
5658 location. You can control the search paths used with the @samp{-I} command-line
5659 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5662 The @var{skip} argument skips a number of bytes from the start of the
5663 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5664 read. Note that the data is not aligned in any way, so it is the user's
5665 responsibility to make sure that proper alignment is provided both before and
5666 after the @code{incbin} directive.
5669 @section @code{.include "@var{file}"}
5671 @cindex @code{include} directive
5672 @cindex supporting files, including
5673 @cindex files, including
5674 This directive provides a way to include supporting files at specified
5675 points in your source program. The code from @var{file} is assembled as
5676 if it followed the point of the @code{.include}; when the end of the
5677 included file is reached, assembly of the original file continues. You
5678 can control the search paths used with the @samp{-I} command-line option
5679 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5683 @section @code{.int @var{expressions}}
5685 @cindex @code{int} directive
5686 @cindex integers, 32-bit
5687 Expect zero or more @var{expressions}, of any section, separated by commas.
5688 For each expression, emit a number that, at run time, is the value of that
5689 expression. The byte order and bit size of the number depends on what kind
5690 of target the assembly is for.
5694 On most forms of the H8/300, @code{.int} emits 16-bit
5695 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5702 @section @code{.internal @var{names}}
5704 @cindex @code{internal} directive
5706 This is one of the ELF visibility directives. The other two are
5707 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5708 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5710 This directive overrides the named symbols default visibility (which is set by
5711 their binding: local, global or weak). The directive sets the visibility to
5712 @code{internal} which means that the symbols are considered to be @code{hidden}
5713 (i.e., not visible to other components), and that some extra, processor specific
5714 processing must also be performed upon the symbols as well.
5718 @section @code{.irp @var{symbol},@var{values}}@dots{}
5720 @cindex @code{irp} directive
5721 Evaluate a sequence of statements assigning different values to @var{symbol}.
5722 The sequence of statements starts at the @code{.irp} directive, and is
5723 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5724 set to @var{value}, and the sequence of statements is assembled. If no
5725 @var{value} is listed, the sequence of statements is assembled once, with
5726 @var{symbol} set to the null string. To refer to @var{symbol} within the
5727 sequence of statements, use @var{\symbol}.
5729 For example, assembling
5737 is equivalent to assembling
5745 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5748 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5750 @cindex @code{irpc} directive
5751 Evaluate a sequence of statements assigning different values to @var{symbol}.
5752 The sequence of statements starts at the @code{.irpc} directive, and is
5753 terminated by an @code{.endr} directive. For each character in @var{value},
5754 @var{symbol} is set to the character, and the sequence of statements is
5755 assembled. If no @var{value} is listed, the sequence of statements is
5756 assembled once, with @var{symbol} set to the null string. To refer to
5757 @var{symbol} within the sequence of statements, use @var{\symbol}.
5759 For example, assembling
5767 is equivalent to assembling
5775 For some caveats with the spelling of @var{symbol}, see also the discussion
5779 @section @code{.lcomm @var{symbol} , @var{length}}
5781 @cindex @code{lcomm} directive
5782 @cindex local common symbols
5783 @cindex symbols, local common
5784 Reserve @var{length} (an absolute expression) bytes for a local common
5785 denoted by @var{symbol}. The section and value of @var{symbol} are
5786 those of the new local common. The addresses are allocated in the bss
5787 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5788 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5789 not visible to @code{@value{LD}}.
5792 Some targets permit a third argument to be used with @code{.lcomm}. This
5793 argument specifies the desired alignment of the symbol in the bss section.
5797 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5798 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5802 @section @code{.lflags}
5804 @cindex @code{lflags} directive (ignored)
5805 @command{@value{AS}} accepts this directive, for compatibility with other
5806 assemblers, but ignores it.
5808 @ifclear no-line-dir
5810 @section @code{.line @var{line-number}}
5812 @cindex @code{line} directive
5813 @cindex logical line number
5815 Change the logical line number. @var{line-number} must be an absolute
5816 expression. The next line has that logical line number. Therefore any other
5817 statements on the current line (after a statement separator character) are
5818 reported as on logical line number @var{line-number} @minus{} 1. One day
5819 @command{@value{AS}} will no longer support this directive: it is recognized only
5820 for compatibility with existing assembler programs.
5823 Even though this is a directive associated with the @code{a.out} or
5824 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5825 when producing COFF output, and treats @samp{.line} as though it
5826 were the COFF @samp{.ln} @emph{if} it is found outside a
5827 @code{.def}/@code{.endef} pair.
5829 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5830 used by compilers to generate auxiliary symbol information for
5835 @section @code{.linkonce [@var{type}]}
5837 @cindex @code{linkonce} directive
5838 @cindex common sections
5839 Mark the current section so that the linker only includes a single copy of it.
5840 This may be used to include the same section in several different object files,
5841 but ensure that the linker will only include it once in the final output file.
5842 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5843 Duplicate sections are detected based on the section name, so it should be
5846 This directive is only supported by a few object file formats; as of this
5847 writing, the only object file format which supports it is the Portable
5848 Executable format used on Windows NT.
5850 The @var{type} argument is optional. If specified, it must be one of the
5851 following strings. For example:
5855 Not all types may be supported on all object file formats.
5859 Silently discard duplicate sections. This is the default.
5862 Warn if there are duplicate sections, but still keep only one copy.
5865 Warn if any of the duplicates have different sizes.
5868 Warn if any of the duplicates do not have exactly the same contents.
5872 @section @code{.list}
5874 @cindex @code{list} directive
5875 @cindex listing control, turning on
5876 Control (in conjunction with the @code{.nolist} directive) whether or
5877 not assembly listings are generated. These two directives maintain an
5878 internal counter (which is zero initially). @code{.list} increments the
5879 counter, and @code{.nolist} decrements it. Assembly listings are
5880 generated whenever the counter is greater than zero.
5882 By default, listings are disabled. When you enable them (with the
5883 @samp{-a} command-line option; @pxref{Invoking,,Command-Line Options}),
5884 the initial value of the listing counter is one.
5887 @section @code{.ln @var{line-number}}
5889 @cindex @code{ln} directive
5890 @ifclear no-line-dir
5891 @samp{.ln} is a synonym for @samp{.line}.
5894 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5895 must be an absolute expression. The next line has that logical
5896 line number, so any other statements on the current line (after a
5897 statement separator character @code{;}) are reported as on logical
5898 line number @var{line-number} @minus{} 1.
5902 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5903 @cindex @code{loc} directive
5904 When emitting DWARF2 line number information,
5905 the @code{.loc} directive will add a row to the @code{.debug_line} line
5906 number matrix corresponding to the immediately following assembly
5907 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5908 arguments will be applied to the @code{.debug_line} state machine before
5909 the row is added. It is an error for the input assembly file to generate
5910 a non-empty @code{.debug_line} and also use @code{loc} directives.
5912 The @var{options} are a sequence of the following tokens in any order:
5916 This option will set the @code{basic_block} register in the
5917 @code{.debug_line} state machine to @code{true}.
5920 This option will set the @code{prologue_end} register in the
5921 @code{.debug_line} state machine to @code{true}.
5923 @item epilogue_begin
5924 This option will set the @code{epilogue_begin} register in the
5925 @code{.debug_line} state machine to @code{true}.
5927 @item is_stmt @var{value}
5928 This option will set the @code{is_stmt} register in the
5929 @code{.debug_line} state machine to @code{value}, which must be
5932 @item isa @var{value}
5933 This directive will set the @code{isa} register in the @code{.debug_line}
5934 state machine to @var{value}, which must be an unsigned integer.
5936 @item discriminator @var{value}
5937 This directive will set the @code{discriminator} register in the @code{.debug_line}
5938 state machine to @var{value}, which must be an unsigned integer.
5940 @item view @var{value}
5941 This option causes a row to be added to @code{.debug_line} in reference to the
5942 current address (which might not be the same as that of the following assembly
5943 instruction), and to associate @var{value} with the @code{view} register in the
5944 @code{.debug_line} state machine. If @var{value} is a label, both the
5945 @code{view} register and the label are set to the number of prior @code{.loc}
5946 directives at the same program location. If @var{value} is the literal
5947 @code{0}, the @code{view} register is set to zero, and the assembler asserts
5948 that there aren't any prior @code{.loc} directives at the same program
5949 location. If @var{value} is the literal @code{-0}, the assembler arrange for
5950 the @code{view} register to be reset in this row, even if there are prior
5951 @code{.loc} directives at the same program location.
5955 @node Loc_mark_labels
5956 @section @code{.loc_mark_labels @var{enable}}
5957 @cindex @code{loc_mark_labels} directive
5958 When emitting DWARF2 line number information,
5959 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5960 to the @code{.debug_line} line number matrix with the @code{basic_block}
5961 register in the state machine set whenever a code label is seen.
5962 The @var{enable} argument should be either 1 or 0, to enable or disable
5963 this function respectively.
5967 @section @code{.local @var{names}}
5969 @cindex @code{local} directive
5970 This directive, which is available for ELF targets, marks each symbol in
5971 the comma-separated list of @code{names} as a local symbol so that it
5972 will not be externally visible. If the symbols do not already exist,
5973 they will be created.
5975 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5976 accept an alignment argument, which is the case for most ELF targets,
5977 the @code{.local} directive can be used in combination with @code{.comm}
5978 (@pxref{Comm}) to define aligned local common data.
5982 @section @code{.long @var{expressions}}
5984 @cindex @code{long} directive
5985 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5988 @c no one seems to know what this is for or whether this description is
5989 @c what it really ought to do
5991 @section @code{.lsym @var{symbol}, @var{expression}}
5993 @cindex @code{lsym} directive
5994 @cindex symbol, not referenced in assembly
5995 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5996 the hash table, ensuring it cannot be referenced by name during the
5997 rest of the assembly. This sets the attributes of the symbol to be
5998 the same as the expression value:
6000 @var{other} = @var{descriptor} = 0
6001 @var{type} = @r{(section of @var{expression})}
6002 @var{value} = @var{expression}
6005 The new symbol is not flagged as external.
6009 @section @code{.macro}
6012 The commands @code{.macro} and @code{.endm} allow you to define macros that
6013 generate assembly output. For example, this definition specifies a macro
6014 @code{sum} that puts a sequence of numbers into memory:
6017 .macro sum from=0, to=5
6026 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
6038 @item .macro @var{macname}
6039 @itemx .macro @var{macname} @var{macargs} @dots{}
6040 @cindex @code{macro} directive
6041 Begin the definition of a macro called @var{macname}. If your macro
6042 definition requires arguments, specify their names after the macro name,
6043 separated by commas or spaces. You can qualify the macro argument to
6044 indicate whether all invocations must specify a non-blank value (through
6045 @samp{:@code{req}}), or whether it takes all of the remaining arguments
6046 (through @samp{:@code{vararg}}). You can supply a default value for any
6047 macro argument by following the name with @samp{=@var{deflt}}. You
6048 cannot define two macros with the same @var{macname} unless it has been
6049 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
6050 definitions. For example, these are all valid @code{.macro} statements:
6054 Begin the definition of a macro called @code{comm}, which takes no
6057 @item .macro plus1 p, p1
6058 @itemx .macro plus1 p p1
6059 Either statement begins the definition of a macro called @code{plus1},
6060 which takes two arguments; within the macro definition, write
6061 @samp{\p} or @samp{\p1} to evaluate the arguments.
6063 @item .macro reserve_str p1=0 p2
6064 Begin the definition of a macro called @code{reserve_str}, with two
6065 arguments. The first argument has a default value, but not the second.
6066 After the definition is complete, you can call the macro either as
6067 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
6068 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
6069 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
6070 @samp{0}, and @samp{\p2} evaluating to @var{b}).
6072 @item .macro m p1:req, p2=0, p3:vararg
6073 Begin the definition of a macro called @code{m}, with at least three
6074 arguments. The first argument must always have a value specified, but
6075 not the second, which instead has a default value. The third formal
6076 will get assigned all remaining arguments specified at invocation time.
6078 When you call a macro, you can specify the argument values either by
6079 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
6080 @samp{sum to=17, from=9}.
6084 Note that since each of the @var{macargs} can be an identifier exactly
6085 as any other one permitted by the target architecture, there may be
6086 occasional problems if the target hand-crafts special meanings to certain
6087 characters when they occur in a special position. For example, if the colon
6088 (@code{:}) is generally permitted to be part of a symbol name, but the
6089 architecture specific code special-cases it when occurring as the final
6090 character of a symbol (to denote a label), then the macro parameter
6091 replacement code will have no way of knowing that and consider the whole
6092 construct (including the colon) an identifier, and check only this
6093 identifier for being the subject to parameter substitution. So for example
6094 this macro definition:
6102 might not work as expected. Invoking @samp{label foo} might not create a label
6103 called @samp{foo} but instead just insert the text @samp{\l:} into the
6104 assembler source, probably generating an error about an unrecognised
6107 Similarly problems might occur with the period character (@samp{.})
6108 which is often allowed inside opcode names (and hence identifier names). So
6109 for example constructing a macro to build an opcode from a base name and a
6110 length specifier like this:
6113 .macro opcode base length
6118 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
6119 instruction but instead generate some kind of error as the assembler tries to
6120 interpret the text @samp{\base.\length}.
6122 There are several possible ways around this problem:
6125 @item Insert white space
6126 If it is possible to use white space characters then this is the simplest
6135 @item Use @samp{\()}
6136 The string @samp{\()} can be used to separate the end of a macro argument from
6137 the following text. eg:
6140 .macro opcode base length
6145 @item Use the alternate macro syntax mode
6146 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6147 used as a separator. eg:
6157 Note: this problem of correctly identifying string parameters to pseudo ops
6158 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6159 and @code{.irpc} (@pxref{Irpc}) as well.
6162 @cindex @code{endm} directive
6163 Mark the end of a macro definition.
6166 @cindex @code{exitm} directive
6167 Exit early from the current macro definition.
6169 @cindex number of macros executed
6170 @cindex macros, count executed
6172 @command{@value{AS}} maintains a counter of how many macros it has
6173 executed in this pseudo-variable; you can copy that number to your
6174 output with @samp{\@@}, but @emph{only within a macro definition}.
6176 @item LOCAL @var{name} [ , @dots{} ]
6177 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6178 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6179 @xref{Altmacro,,@code{.altmacro}}.
6183 @section @code{.mri @var{val}}
6185 @cindex @code{mri} directive
6186 @cindex MRI mode, temporarily
6187 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6188 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6189 affects code assembled until the next @code{.mri} directive, or until the end
6190 of the file. @xref{M, MRI mode, MRI mode}.
6193 @section @code{.noaltmacro}
6194 Disable alternate macro mode. @xref{Altmacro}.
6197 @section @code{.nolist}
6199 @cindex @code{nolist} directive
6200 @cindex listing control, turning off
6201 Control (in conjunction with the @code{.list} directive) whether or
6202 not assembly listings are generated. These two directives maintain an
6203 internal counter (which is zero initially). @code{.list} increments the
6204 counter, and @code{.nolist} decrements it. Assembly listings are
6205 generated whenever the counter is greater than zero.
6208 @section @code{.nop [@var{size}]}
6210 @cindex @code{nop} directive
6211 @cindex filling memory with no-op instructions
6212 This directive emits no-op instructions. It is provided on all architectures,
6213 allowing the creation of architecture neutral tests involving actual code. The
6214 size of the generated instruction is target specific, but if the optional
6215 @var{size} argument is given and resolves to an absolute positive value at that
6216 point in assembly (no forward expressions allowed) then the fewest no-op
6217 instructions are emitted that equal or exceed a total @var{size} in bytes.
6218 @code{.nop} does affect the generation of DWARF debug line information.
6219 Some targets do not support using @code{.nop} with @var{size}.
6222 @section @code{.nops @var{size}[, @var{control}]}
6224 @cindex @code{nops} directive
6225 @cindex filling memory with no-op instructions
6226 This directive emits no-op instructions. It is specific to the Intel 80386 and
6227 AMD x86-64 targets. It takes a @var{size} argument and generates @var{size}
6228 bytes of no-op instructions. @var{size} must be absolute and positive. These
6229 bytes do not affect the generation of DWARF debug line information.
6231 The optional @var{control} argument specifies a size limit for a single no-op
6232 instruction. If not provided then a value of 0 is assumed. The valid values
6233 of @var{control} are between 0 and 4 in 16-bit mode, between 0 and 7 when
6234 tuning for older processors in 32-bit mode, between 0 and 11 in 64-bit mode or
6235 when tuning for newer processors in 32-bit mode. When 0 is used, the no-op
6236 instruction size limit is set to the maximum supported size.
6239 @section @code{.octa @var{bignums}}
6241 @c FIXME: double size emitted for "octa" on some? Or warn?
6242 @cindex @code{octa} directive
6243 @cindex integer, 16-byte
6244 @cindex sixteen byte integer
6245 This directive expects zero or more bignums, separated by commas. For each
6246 bignum, it emits a 16-byte integer.
6248 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6249 hence @emph{octa}-word for 16 bytes.
6252 @section @code{.offset @var{loc}}
6254 @cindex @code{offset} directive
6255 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6256 be an absolute expression. This directive may be useful for defining
6257 symbols with absolute values. Do not confuse it with the @code{.org}
6261 @section @code{.org @var{new-lc} , @var{fill}}
6263 @cindex @code{org} directive
6264 @cindex location counter, advancing
6265 @cindex advancing location counter
6266 @cindex current address, advancing
6267 Advance the location counter of the current section to
6268 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6269 expression with the same section as the current subsection. That is,
6270 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6271 wrong section, the @code{.org} directive is ignored. To be compatible
6272 with former assemblers, if the section of @var{new-lc} is absolute,
6273 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6274 is the same as the current subsection.
6276 @code{.org} may only increase the location counter, or leave it
6277 unchanged; you cannot use @code{.org} to move the location counter
6280 @c double negative used below "not undefined" because this is a specific
6281 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6282 @c section. doc@cygnus.com 18feb91
6283 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6284 may not be undefined. If you really detest this restriction we eagerly await
6285 a chance to share your improved assembler.
6287 Beware that the origin is relative to the start of the section, not
6288 to the start of the subsection. This is compatible with other
6289 people's assemblers.
6291 When the location counter (of the current subsection) is advanced, the
6292 intervening bytes are filled with @var{fill} which should be an
6293 absolute expression. If the comma and @var{fill} are omitted,
6294 @var{fill} defaults to zero.
6297 @section @code{.p2align[wl] [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
6299 @cindex padding the location counter given a power of two
6300 @cindex @code{p2align} directive
6301 Pad the location counter (in the current subsection) to a particular
6302 storage boundary. The first expression (which must be absolute) is the
6303 number of low-order zero bits the location counter must have after
6304 advancement. For example @samp{.p2align 3} advances the location
6305 counter until it is a multiple of 8. If the location counter is already a
6306 multiple of 8, no change is needed. If the expression is omitted then a
6307 default value of 0 is used, effectively disabling alignment requirements.
6309 The second expression (also absolute) gives the fill value to be stored in the
6310 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6311 padding bytes are normally zero. However, on most systems, if the section is
6312 marked as containing code and the fill value is omitted, the space is filled
6313 with no-op instructions.
6315 The third expression is also absolute, and is also optional. If it is present,
6316 it is the maximum number of bytes that should be skipped by this alignment
6317 directive. If doing the alignment would require skipping more bytes than the
6318 specified maximum, then the alignment is not done at all. You can omit the
6319 fill value (the second argument) entirely by simply using two commas after the
6320 required alignment; this can be useful if you want the alignment to be filled
6321 with no-op instructions when appropriate.
6323 @cindex @code{p2alignw} directive
6324 @cindex @code{p2alignl} directive
6325 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6326 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6327 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6328 fill pattern as a four byte longword value. For example, @code{.p2alignw
6329 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6330 filled in with the value 0x368d (the exact placement of the bytes depends upon
6331 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6336 @section @code{.popsection}
6338 @cindex @code{popsection} directive
6339 @cindex Section Stack
6340 This is one of the ELF section stack manipulation directives. The others are
6341 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6342 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6345 This directive replaces the current section (and subsection) with the top
6346 section (and subsection) on the section stack. This section is popped off the
6352 @section @code{.previous}
6354 @cindex @code{previous} directive
6355 @cindex Section Stack
6356 This is one of the ELF section stack manipulation directives. The others are
6357 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6358 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6359 (@pxref{PopSection}).
6361 This directive swaps the current section (and subsection) with most recently
6362 referenced section/subsection pair prior to this one. Multiple
6363 @code{.previous} directives in a row will flip between two sections (and their
6364 subsections). For example:
6376 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6382 # Now in section A subsection 1
6386 # Now in section B subsection 0
6389 # Now in section B subsection 1
6392 # Now in section B subsection 0
6396 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6397 section B and 0x9abc into subsection 1 of section B.
6399 In terms of the section stack, this directive swaps the current section with
6400 the top section on the section stack.
6404 @section @code{.print @var{string}}
6406 @cindex @code{print} directive
6407 @command{@value{AS}} will print @var{string} on the standard output during
6408 assembly. You must put @var{string} in double quotes.
6412 @section @code{.protected @var{names}}
6414 @cindex @code{protected} directive
6416 This is one of the ELF visibility directives. The other two are
6417 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6419 This directive overrides the named symbols default visibility (which is set by
6420 their binding: local, global or weak). The directive sets the visibility to
6421 @code{protected} which means that any references to the symbols from within the
6422 components that defines them must be resolved to the definition in that
6423 component, even if a definition in another component would normally preempt
6428 @section @code{.psize @var{lines} , @var{columns}}
6430 @cindex @code{psize} directive
6431 @cindex listing control: paper size
6432 @cindex paper size, for listings
6433 Use this directive to declare the number of lines---and, optionally, the
6434 number of columns---to use for each page, when generating listings.
6436 If you do not use @code{.psize}, listings use a default line-count
6437 of 60. You may omit the comma and @var{columns} specification; the
6438 default width is 200 columns.
6440 @command{@value{AS}} generates formfeeds whenever the specified number of
6441 lines is exceeded (or whenever you explicitly request one, using
6444 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6445 those explicitly specified with @code{.eject}.
6448 @section @code{.purgem @var{name}}
6450 @cindex @code{purgem} directive
6451 Undefine the macro @var{name}, so that later uses of the string will not be
6452 expanded. @xref{Macro}.
6456 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6458 @cindex @code{pushsection} directive
6459 @cindex Section Stack
6460 This is one of the ELF section stack manipulation directives. The others are
6461 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6462 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6465 This directive pushes the current section (and subsection) onto the
6466 top of the section stack, and then replaces the current section and
6467 subsection with @code{name} and @code{subsection}. The optional
6468 @code{flags}, @code{type} and @code{arguments} are treated the same
6469 as in the @code{.section} (@pxref{Section}) directive.
6473 @section @code{.quad @var{bignums}}
6475 @cindex @code{quad} directive
6476 @code{.quad} expects zero or more bignums, separated by commas. For
6477 each bignum, it emits
6479 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6480 warning message; and just takes the lowest order 8 bytes of the bignum.
6481 @cindex eight-byte integer
6482 @cindex integer, 8-byte
6484 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6485 hence @emph{quad}-word for 8 bytes.
6488 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6489 warning message; and just takes the lowest order 16 bytes of the bignum.
6490 @cindex sixteen-byte integer
6491 @cindex integer, 16-byte
6495 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6497 @cindex @code{reloc} directive
6498 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6499 @var{expression}. If @var{offset} is a number, the relocation is generated in
6500 the current section. If @var{offset} is an expression that resolves to a
6501 symbol plus offset, the relocation is generated in the given symbol's section.
6502 @var{expression}, if present, must resolve to a symbol plus addend or to an
6503 absolute value, but note that not all targets support an addend. e.g. ELF REL
6504 targets such as i386 store an addend in the section contents rather than in the
6505 relocation. This low level interface does not support addends stored in the
6509 @section @code{.rept @var{count}}
6511 @cindex @code{rept} directive
6512 Repeat the sequence of lines between the @code{.rept} directive and the next
6513 @code{.endr} directive @var{count} times.
6515 For example, assembling
6523 is equivalent to assembling
6531 A count of zero is allowed, but nothing is generated. Negative counts are not
6532 allowed and if encountered will be treated as if they were zero.
6535 @section @code{.sbttl "@var{subheading}"}
6537 @cindex @code{sbttl} directive
6538 @cindex subtitles for listings
6539 @cindex listing control: subtitle
6540 Use @var{subheading} as the title (third line, immediately after the
6541 title line) when generating assembly listings.
6543 This directive affects subsequent pages, as well as the current page if
6544 it appears within ten lines of the top of a page.
6548 @section @code{.scl @var{class}}
6550 @cindex @code{scl} directive
6551 @cindex symbol storage class (COFF)
6552 @cindex COFF symbol storage class
6553 Set the storage-class value for a symbol. This directive may only be
6554 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6555 whether a symbol is static or external, or it may record further
6556 symbolic debugging information.
6561 @section @code{.section @var{name}}
6563 @cindex named section
6564 Use the @code{.section} directive to assemble the following code into a section
6567 This directive is only supported for targets that actually support arbitrarily
6568 named sections; on @code{a.out} targets, for example, it is not accepted, even
6569 with a standard @code{a.out} section name.
6573 @c only print the extra heading if both COFF and ELF are set
6574 @subheading COFF Version
6577 @cindex @code{section} directive (COFF version)
6578 For COFF targets, the @code{.section} directive is used in one of the following
6582 .section @var{name}[, "@var{flags}"]
6583 .section @var{name}[, @var{subsection}]
6586 If the optional argument is quoted, it is taken as flags to use for the
6587 section. Each flag is a single character. The following flags are recognized:
6591 bss section (uninitialized data)
6593 section is not loaded
6599 exclude section from linking
6605 shared section (meaningful for PE targets)
6607 ignored. (For compatibility with the ELF version)
6609 section is not readable (meaningful for PE targets)
6611 single-digit power-of-two section alignment (GNU extension)
6614 If no flags are specified, the default flags depend upon the section name. If
6615 the section name is not recognized, the default will be for the section to be
6616 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6617 from the section, rather than adding them, so if they are used on their own it
6618 will be as if no flags had been specified at all.
6620 If the optional argument to the @code{.section} directive is not quoted, it is
6621 taken as a subsection number (@pxref{Sub-Sections}).
6626 @c only print the extra heading if both COFF and ELF are set
6627 @subheading ELF Version
6630 @cindex Section Stack
6631 This is one of the ELF section stack manipulation directives. The others are
6632 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6633 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6634 @code{.previous} (@pxref{Previous}).
6636 @cindex @code{section} directive (ELF version)
6637 For ELF targets, the @code{.section} directive is used like this:
6640 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6643 @anchor{Section Name Substitutions}
6644 @kindex --sectname-subst
6645 @cindex section name substitution
6646 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6647 argument may contain a substitution sequence. Only @code{%S} is supported
6648 at the moment, and substitutes the current section name. For example:
6651 .macro exception_code
6652 .section %S.exception
6653 [exception code here]
6668 The two @code{exception_code} invocations above would create the
6669 @code{.text.exception} and @code{.init.exception} sections respectively.
6670 This is useful e.g. to discriminate between ancillary sections that are
6671 tied to setup code to be discarded after use from ancillary sections that
6672 need to stay resident without having to define multiple @code{exception_code}
6673 macros just for that purpose.
6675 The optional @var{flags} argument is a quoted string which may contain any
6676 combination of the following characters:
6680 section is allocatable
6682 section is a GNU_MBIND section
6684 section is excluded from executable and shared library.
6686 section references a symbol defined in another section (the linked-to
6687 section) in the same file.
6691 section is executable
6693 section is mergeable
6695 section contains zero terminated strings
6697 section is a member of a section group
6699 section is used for thread-local-storage
6701 section is a member of the previously-current section's group, if any
6703 retained section (apply SHF_GNU_RETAIN to prevent linker garbage
6704 collection, GNU ELF extension)
6705 @item @code{<number>}
6706 a numeric value indicating the bits to be set in the ELF section header's flags
6707 field. Note - if one or more of the alphabetic characters described above is
6708 also included in the flags field, their bit values will be ORed into the
6710 @item @code{<target specific>}
6711 some targets extend this list with their own flag characters
6714 Note - once a section's flags have been set they cannot be changed. There are
6715 a few exceptions to this rule however. Processor and application specific
6716 flags can be added to an already defined section. The @code{.interp},
6717 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6718 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6719 section may have the executable (@code{x}) flag added. Also note that the
6720 @code{.attach_to_group} directive can be used to add a section to a group even
6721 if the section was not originally declared to be part of that group.
6723 The optional @var{type} argument may contain one of the following constants:
6727 section contains data
6729 section does not contain data (i.e., section only occupies space)
6731 section contains data which is used by things other than the program
6733 section contains an array of pointers to init functions
6735 section contains an array of pointers to finish functions
6736 @item @@preinit_array
6737 section contains an array of pointers to pre-init functions
6738 @item @@@code{<number>}
6739 a numeric value to be set as the ELF section header's type field.
6740 @item @@@code{<target specific>}
6741 some targets extend this list with their own types
6744 Many targets only support the first three section types. The type may be
6745 enclosed in double quotes if necessary.
6747 Note on targets where the @code{@@} character is the start of a comment (eg
6748 ARM) then another character is used instead. For example the ARM port uses the
6751 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6752 special and have fixed types. Any attempt to declare them with a different
6753 type will generate an error from the assembler.
6755 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6756 be specified as well as an extra argument---@var{entsize}---like this:
6759 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6762 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6763 constants, each @var{entsize} octets long. Sections with both @code{M} and
6764 @code{S} must contain zero terminated strings where each character is
6765 @var{entsize} bytes long. The linker may remove duplicates within sections with
6766 the same name, same entity size and same flags. @var{entsize} must be an
6767 absolute expression. For sections with both @code{M} and @code{S}, a string
6768 which is a suffix of a larger string is considered a duplicate. Thus
6769 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6770 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6772 If @var{flags} contains the @code{o} flag, then the @var{type} argument
6773 must be present along with an additional field like this:
6776 .section @var{name},"@var{flags}"o,@@@var{type},@var{SymbolName}|@var{SectionIndex}
6779 The @var{SymbolName} field specifies the symbol name which the section
6780 references. Alternatively a numeric @var{SectionIndex} can be provided. This
6781 is not generally a good idea as section indicies are rarely known at assembly
6782 time, but the facility is provided for testing purposes. An index of zero is
6783 allowed. It indicates that the linked-to section has already been discarded.
6785 Note: If both the @var{M} and @var{o} flags are present, then the fields
6786 for the Merge flag should come first, like this:
6789 .section @var{name},"@var{flags}"Mo,@@@var{type},@var{entsize},@var{SymbolName}
6792 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6793 be present along with an additional field like this:
6796 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6799 The @var{GroupName} field specifies the name of the section group to which this
6800 particular section belongs. The optional linkage field can contain:
6804 indicates that only one copy of this section should be retained
6809 Note: if both the @var{M} and @var{G} flags are present then the fields for
6810 the Merge flag should come first, like this:
6813 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6816 If both @code{o} flag and @code{G} flag are present, then the
6817 @var{SymbolName} field for @code{o} comes first, like this:
6820 .section @var{name},"@var{flags}"oG,@@@var{type},@var{SymbolName},@var{GroupName}[,@var{linkage}]
6823 If @var{flags} contains the @code{?} symbol then it may not also contain the
6824 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6825 present. Instead, @code{?} says to consider the section that's current before
6826 this directive. If that section used @code{G}, then the new section will use
6827 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6828 If not, then the @code{?} symbol has no effect.
6830 The optional @var{unique,@code{<number>}} argument must come last. It
6831 assigns @var{@code{<number>}} as a unique section ID to distinguish
6832 different sections with the same section name like these:
6835 .section @var{name},"@var{flags}",@@@var{type},@var{unique,@code{<number>}}
6836 .section @var{name},"@var{flags}"G,@@@var{type},@var{GroupName},[@var{linkage}],@var{unique,@code{<number>}}
6837 .section @var{name},"@var{flags}"MG,@@@var{type},@var{entsize},@var{GroupName}[,@var{linkage}],@var{unique,@code{<number>}}
6840 The valid values of @var{@code{<number>}} are between 0 and 4294967295.
6842 If no flags are specified, the default flags depend upon the section name. If
6843 the section name is not recognized, the default will be for the section to have
6844 none of the above flags: it will not be allocated in memory, nor writable, nor
6845 executable. The section will contain data.
6847 For ELF targets, the assembler supports another type of @code{.section}
6848 directive for compatibility with the Solaris assembler:
6851 .section "@var{name}"[, @var{flags}...]
6854 Note that the section name is quoted. There may be a sequence of comma
6859 section is allocatable
6863 section is executable
6865 section is excluded from executable and shared library.
6867 section is used for thread local storage
6870 This directive replaces the current section and subsection. See the
6871 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6872 some examples of how this directive and the other section stack directives
6878 @section @code{.set @var{symbol}, @var{expression}}
6880 @cindex @code{set} directive
6881 @cindex symbol value, setting
6882 Set the value of @var{symbol} to @var{expression}. This
6883 changes @var{symbol}'s value and type to conform to
6884 @var{expression}. If @var{symbol} was flagged as external, it remains
6885 flagged (@pxref{Symbol Attributes}).
6887 You may @code{.set} a symbol many times in the same assembly provided that the
6888 values given to the symbol are constants. Values that are based on expressions
6889 involving other symbols are allowed, but some targets may restrict this to only
6890 being done once per assembly. This is because those targets do not set the
6891 addresses of symbols at assembly time, but rather delay the assignment until a
6892 final link is performed. This allows the linker a chance to change the code in
6893 the files, changing the location of, and the relative distance between, various
6896 If you @code{.set} a global symbol, the value stored in the object
6897 file is the last value stored into it.
6900 On Z80 @code{set} is a real instruction, use @code{.set} or
6901 @samp{@var{symbol} defl @var{expression}} instead.
6905 @section @code{.short @var{expressions}}
6907 @cindex @code{short} directive
6909 @code{.short} is normally the same as @samp{.word}.
6910 @xref{Word,,@code{.word}}.
6912 In some configurations, however, @code{.short} and @code{.word} generate
6913 numbers of different lengths. @xref{Machine Dependencies}.
6917 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6920 This expects zero or more @var{expressions}, and emits
6921 a 16 bit number for each.
6926 @section @code{.single @var{flonums}}
6928 @cindex @code{single} directive
6929 @cindex floating point numbers (single)
6930 This directive assembles zero or more flonums, separated by commas. It
6931 has the same effect as @code{.float}.
6933 The exact kind of floating point numbers emitted depends on how
6934 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6938 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6939 numbers in @sc{ieee} format.
6945 @section @code{.size}
6947 This directive is used to set the size associated with a symbol.
6951 @c only print the extra heading if both COFF and ELF are set
6952 @subheading COFF Version
6955 @cindex @code{size} directive (COFF version)
6956 For COFF targets, the @code{.size} directive is only permitted inside
6957 @code{.def}/@code{.endef} pairs. It is used like this:
6960 .size @var{expression}
6967 @c only print the extra heading if both COFF and ELF are set
6968 @subheading ELF Version
6971 @cindex @code{size} directive (ELF version)
6972 For ELF targets, the @code{.size} directive is used like this:
6975 .size @var{name} , @var{expression}
6978 This directive sets the size associated with a symbol @var{name}.
6979 The size in bytes is computed from @var{expression} which can make use of label
6980 arithmetic. This directive is typically used to set the size of function
6985 @ifclear no-space-dir
6987 @section @code{.skip @var{size} [,@var{fill}]}
6989 @cindex @code{skip} directive
6990 @cindex filling memory
6991 This directive emits @var{size} bytes, each of value @var{fill}. Both
6992 @var{size} and @var{fill} are absolute expressions. If the comma and
6993 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6998 @section @code{.sleb128 @var{expressions}}
7000 @cindex @code{sleb128} directive
7001 @var{sleb128} stands for ``signed little endian base 128.'' This is a
7002 compact, variable length representation of numbers used by the DWARF
7003 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
7005 @ifclear no-space-dir
7007 @section @code{.space @var{size} [,@var{fill}]}
7009 @cindex @code{space} directive
7010 @cindex filling memory
7011 This directive emits @var{size} bytes, each of value @var{fill}. Both
7012 @var{size} and @var{fill} are absolute expressions. If the comma
7013 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
7018 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
7019 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
7020 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
7021 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
7029 @section @code{.stabd, .stabn, .stabs}
7031 @cindex symbolic debuggers, information for
7032 @cindex @code{stab@var{x}} directives
7033 There are three directives that begin @samp{.stab}.
7034 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
7035 The symbols are not entered in the @command{@value{AS}} hash table: they
7036 cannot be referenced elsewhere in the source file.
7037 Up to five fields are required:
7041 This is the symbol's name. It may contain any character except
7042 @samp{\000}, so is more general than ordinary symbol names. Some
7043 debuggers used to code arbitrarily complex structures into symbol names
7047 An absolute expression. The symbol's type is set to the low 8 bits of
7048 this expression. Any bit pattern is permitted, but @code{@value{LD}}
7049 and debuggers choke on silly bit patterns.
7052 An absolute expression. The symbol's ``other'' attribute is set to the
7053 low 8 bits of this expression.
7056 An absolute expression. The symbol's descriptor is set to the low 16
7057 bits of this expression.
7060 An absolute expression which becomes the symbol's value.
7063 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
7064 or @code{.stabs} statement, the symbol has probably already been created;
7065 you get a half-formed symbol in your object file. This is
7066 compatible with earlier assemblers!
7069 @cindex @code{stabd} directive
7070 @item .stabd @var{type} , @var{other} , @var{desc}
7072 The ``name'' of the symbol generated is not even an empty string.
7073 It is a null pointer, for compatibility. Older assemblers used a
7074 null pointer so they didn't waste space in object files with empty
7077 The symbol's value is set to the location counter,
7078 relocatably. When your program is linked, the value of this symbol
7079 is the address of the location counter when the @code{.stabd} was
7082 @cindex @code{stabn} directive
7083 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
7084 The name of the symbol is set to the empty string @code{""}.
7086 @cindex @code{stabs} directive
7087 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
7088 All five fields are specified.
7094 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
7095 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
7097 @cindex string, copying to object file
7098 @cindex string8, copying to object file
7099 @cindex string16, copying to object file
7100 @cindex string32, copying to object file
7101 @cindex string64, copying to object file
7102 @cindex @code{string} directive
7103 @cindex @code{string8} directive
7104 @cindex @code{string16} directive
7105 @cindex @code{string32} directive
7106 @cindex @code{string64} directive
7108 Copy the characters in @var{str} to the object file. You may specify more than
7109 one string to copy, separated by commas. Unless otherwise specified for a
7110 particular machine, the assembler marks the end of each string with a 0 byte.
7111 You can use any of the escape sequences described in @ref{Strings,,Strings}.
7113 The variants @code{string16}, @code{string32} and @code{string64} differ from
7114 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
7115 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
7116 are stored in target endianness byte order.
7122 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
7123 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
7128 @section @code{.struct @var{expression}}
7130 @cindex @code{struct} directive
7131 Switch to the absolute section, and set the section offset to @var{expression},
7132 which must be an absolute expression. You might use this as follows:
7141 This would define the symbol @code{field1} to have the value 0, the symbol
7142 @code{field2} to have the value 4, and the symbol @code{field3} to have the
7143 value 8. Assembly would be left in the absolute section, and you would need to
7144 use a @code{.section} directive of some sort to change to some other section
7145 before further assembly.
7149 @section @code{.subsection @var{name}}
7151 @cindex @code{subsection} directive
7152 @cindex Section Stack
7153 This is one of the ELF section stack manipulation directives. The others are
7154 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
7155 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
7158 This directive replaces the current subsection with @code{name}. The current
7159 section is not changed. The replaced subsection is put onto the section stack
7160 in place of the then current top of stack subsection.
7165 @section @code{.symver}
7166 @cindex @code{symver} directive
7167 @cindex symbol versioning
7168 @cindex versions of symbols
7169 Use the @code{.symver} directive to bind symbols to specific version nodes
7170 within a source file. This is only supported on ELF platforms, and is
7171 typically used when assembling files to be linked into a shared library.
7172 There are cases where it may make sense to use this in objects to be bound
7173 into an application itself so as to override a versioned symbol from a
7176 For ELF targets, the @code{.symver} directive can be used like this:
7178 .symver @var{name}, @var{name2@@nodename}[ ,@var{visibility}]
7180 If the original symbol @var{name} is defined within the file
7181 being assembled, the @code{.symver} directive effectively creates a symbol
7182 alias with the name @var{name2@@nodename}, and in fact the main reason that we
7183 just don't try and create a regular alias is that the @var{@@} character isn't
7184 permitted in symbol names. The @var{name2} part of the name is the actual name
7185 of the symbol by which it will be externally referenced. The name @var{name}
7186 itself is merely a name of convenience that is used so that it is possible to
7187 have definitions for multiple versions of a function within a single source
7188 file, and so that the compiler can unambiguously know which version of a
7189 function is being mentioned. The @var{nodename} portion of the alias should be
7190 the name of a node specified in the version script supplied to the linker when
7191 building a shared library. If you are attempting to override a versioned
7192 symbol from a shared library, then @var{nodename} should correspond to the
7193 nodename of the symbol you are trying to override. The optional argument
7194 @var{visibility} updates the visibility of the original symbol. The valid
7195 visibilities are @code{local}, @code{hidden}, and @code{remove}. The
7196 @code{local} visibility makes the original symbol a local symbol
7197 (@pxref{Local}). The @code{hidden} visibility sets the visibility of the
7198 original symbol to @code{hidden} (@pxref{Hidden}). The @code{remove}
7199 visibility removes the original symbol from the symbol table. If visibility
7200 isn't specified, the original symbol is unchanged.
7202 If the symbol @var{name} is not defined within the file being assembled, all
7203 references to @var{name} will be changed to @var{name2@@nodename}. If no
7204 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
7207 Another usage of the @code{.symver} directive is:
7209 .symver @var{name}, @var{name2@@@@nodename}
7211 In this case, the symbol @var{name} must exist and be defined within
7212 the file being assembled. It is similar to @var{name2@@nodename}. The
7213 difference is @var{name2@@@@nodename} will also be used to resolve
7214 references to @var{name2} by the linker.
7216 The third usage of the @code{.symver} directive is:
7218 .symver @var{name}, @var{name2@@@@@@nodename}
7220 When @var{name} is not defined within the
7221 file being assembled, it is treated as @var{name2@@nodename}. When
7222 @var{name} is defined within the file being assembled, the symbol
7223 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7228 @section @code{.tag @var{structname}}
7230 @cindex COFF structure debugging
7231 @cindex structure debugging, COFF
7232 @cindex @code{tag} directive
7233 This directive is generated by compilers to include auxiliary debugging
7234 information in the symbol table. It is only permitted inside
7235 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7236 definitions in the symbol table with instances of those structures.
7240 @section @code{.text @var{subsection}}
7242 @cindex @code{text} directive
7243 Tells @command{@value{AS}} to assemble the following statements onto the end of
7244 the text subsection numbered @var{subsection}, which is an absolute
7245 expression. If @var{subsection} is omitted, subsection number zero
7249 @section @code{.title "@var{heading}"}
7251 @cindex @code{title} directive
7252 @cindex listing control: title line
7253 Use @var{heading} as the title (second line, immediately after the
7254 source file name and pagenumber) when generating assembly listings.
7256 This directive affects subsequent pages, as well as the current page if
7257 it appears within ten lines of the top of a page.
7261 @section @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
7263 @cindex @code{tls_common} directive
7264 This directive behaves in the same way as the @code{.comm} directive
7265 (@pxref{Comm}) except that @var{symbol} has type of STT_TLS instead of
7271 @section @code{.type}
7273 This directive is used to set the type of a symbol.
7277 @c only print the extra heading if both COFF and ELF are set
7278 @subheading COFF Version
7281 @cindex COFF symbol type
7282 @cindex symbol type, COFF
7283 @cindex @code{type} directive (COFF version)
7284 For COFF targets, this directive is permitted only within
7285 @code{.def}/@code{.endef} pairs. It is used like this:
7291 This records the integer @var{int} as the type attribute of a symbol table
7298 @c only print the extra heading if both COFF and ELF are set
7299 @subheading ELF Version
7302 @cindex ELF symbol type
7303 @cindex symbol type, ELF
7304 @cindex @code{type} directive (ELF version)
7305 For ELF targets, the @code{.type} directive is used like this:
7308 .type @var{name} , @var{type description}
7311 This sets the type of symbol @var{name} to be either a
7312 function symbol or an object symbol. There are five different syntaxes
7313 supported for the @var{type description} field, in order to provide
7314 compatibility with various other assemblers.
7316 Because some of the characters used in these syntaxes (such as @samp{@@} and
7317 @samp{#}) are comment characters for some architectures, some of the syntaxes
7318 below do not work on all architectures. The first variant will be accepted by
7319 the GNU assembler on all architectures so that variant should be used for
7320 maximum portability, if you do not need to assemble your code with other
7323 The syntaxes supported are:
7326 .type <name> STT_<TYPE_IN_UPPER_CASE>
7327 .type <name>,#<type>
7328 .type <name>,@@<type>
7329 .type <name>,%<type>
7330 .type <name>,"<type>"
7333 The types supported are:
7338 Mark the symbol as being a function name.
7341 @itemx gnu_indirect_function
7342 Mark the symbol as an indirect function when evaluated during reloc
7343 processing. (This is only supported on assemblers targeting GNU systems).
7347 Mark the symbol as being a data object.
7351 Mark the symbol as being a thread-local data object.
7355 Mark the symbol as being a common data object.
7359 Does not mark the symbol in any way. It is supported just for completeness.
7361 @item gnu_unique_object
7362 Marks the symbol as being a globally unique data object. The dynamic linker
7363 will make sure that in the entire process there is just one symbol with this
7364 name and type in use. (This is only supported on assemblers targeting GNU
7369 Changing between incompatible types other than from/to STT_NOTYPE will
7370 result in a diagnostic. An intermediate change to STT_NOTYPE will silence
7373 Note: Some targets support extra types in addition to those listed above.
7379 @section @code{.uleb128 @var{expressions}}
7381 @cindex @code{uleb128} directive
7382 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7383 compact, variable length representation of numbers used by the DWARF
7384 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7388 @section @code{.val @var{addr}}
7390 @cindex @code{val} directive
7391 @cindex COFF value attribute
7392 @cindex value attribute, COFF
7393 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7394 records the address @var{addr} as the value attribute of a symbol table
7400 @section @code{.version "@var{string}"}
7402 @cindex @code{version} directive
7403 This directive creates a @code{.note} section and places into it an ELF
7404 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7409 @section @code{.vtable_entry @var{table}, @var{offset}}
7411 @cindex @code{vtable_entry} directive
7412 This directive finds or creates a symbol @code{table} and creates a
7413 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7416 @section @code{.vtable_inherit @var{child}, @var{parent}}
7418 @cindex @code{vtable_inherit} directive
7419 This directive finds the symbol @code{child} and finds or creates the symbol
7420 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7421 parent whose addend is the value of the child symbol. As a special case the
7422 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7426 @section @code{.warning "@var{string}"}
7427 @cindex warning directive
7428 Similar to the directive @code{.error}
7429 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7432 @section @code{.weak @var{names}}
7434 @cindex @code{weak} directive
7435 This directive sets the weak attribute on the comma separated list of symbol
7436 @code{names}. If the symbols do not already exist, they will be created.
7438 On COFF targets other than PE, weak symbols are a GNU extension. This
7439 directive sets the weak attribute on the comma separated list of symbol
7440 @code{names}. If the symbols do not already exist, they will be created.
7442 On the PE target, weak symbols are supported natively as weak aliases.
7443 When a weak symbol is created that is not an alias, GAS creates an
7444 alternate symbol to hold the default value.
7447 @section @code{.weakref @var{alias}, @var{target}}
7449 @cindex @code{weakref} directive
7450 This directive creates an alias to the target symbol that enables the symbol to
7451 be referenced with weak-symbol semantics, but without actually making it weak.
7452 If direct references or definitions of the symbol are present, then the symbol
7453 will not be weak, but if all references to it are through weak references, the
7454 symbol will be marked as weak in the symbol table.
7456 The effect is equivalent to moving all references to the alias to a separate
7457 assembly source file, renaming the alias to the symbol in it, declaring the
7458 symbol as weak there, and running a reloadable link to merge the object files
7459 resulting from the assembly of the new source file and the old source file that
7460 had the references to the alias removed.
7462 The alias itself never makes to the symbol table, and is entirely handled
7463 within the assembler.
7466 @section @code{.word @var{expressions}}
7468 @cindex @code{word} directive
7469 This directive expects zero or more @var{expressions}, of any section,
7470 separated by commas.
7473 For each expression, @command{@value{AS}} emits a 32-bit number.
7476 For each expression, @command{@value{AS}} emits a 16-bit number.
7481 The size of the number emitted, and its byte order,
7482 depend on what target computer the assembly is for.
7485 @c on sparc the "special treatment to support compilers" doesn't
7486 @c happen---32-bit addressability, period; no long/short jumps.
7487 @ifset DIFF-TBL-KLUGE
7488 @cindex difference tables altered
7489 @cindex altered difference tables
7491 @emph{Warning: Special Treatment to support Compilers}
7495 Machines with a 32-bit address space, but that do less than 32-bit
7496 addressing, require the following special treatment. If the machine of
7497 interest to you does 32-bit addressing (or doesn't require it;
7498 @pxref{Machine Dependencies}), you can ignore this issue.
7501 In order to assemble compiler output into something that works,
7502 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7503 Directives of the form @samp{.word sym1-sym2} are often emitted by
7504 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7505 directive of the form @samp{.word sym1-sym2}, and the difference between
7506 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7507 creates a @dfn{secondary jump table}, immediately before the next label.
7508 This secondary jump table is preceded by a short-jump to the
7509 first byte after the secondary table. This short-jump prevents the flow
7510 of control from accidentally falling into the new table. Inside the
7511 table is a long-jump to @code{sym2}. The original @samp{.word}
7512 contains @code{sym1} minus the address of the long-jump to
7515 If there were several occurrences of @samp{.word sym1-sym2} before the
7516 secondary jump table, all of them are adjusted. If there was a
7517 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7518 long-jump to @code{sym4} is included in the secondary jump table,
7519 and the @code{.word} directives are adjusted to contain @code{sym3}
7520 minus the address of the long-jump to @code{sym4}; and so on, for as many
7521 entries in the original jump table as necessary.
7524 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7525 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7526 assembly language programmers.
7529 @c end DIFF-TBL-KLUGE
7531 @ifclear no-space-dir
7533 @section @code{.zero @var{size}}
7535 @cindex @code{zero} directive
7536 @cindex filling memory with zero bytes
7537 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7538 expression. This directive is actually an alias for the @samp{.skip} directive
7539 so it can take an optional second argument of the value to store in the bytes
7540 instead of zero. Using @samp{.zero} in this way would be confusing however.
7544 @section @code{.2byte @var{expression} [, @var{expression}]*}
7545 @cindex @code{2byte} directive
7546 @cindex two-byte integer
7547 @cindex integer, 2-byte
7549 This directive expects zero or more expressions, separated by commas. If there
7550 are no expressions then the directive does nothing. Otherwise each expression
7551 is evaluated in turn and placed in the next two bytes of the current output
7552 section, using the endian model of the target. If an expression will not fit
7553 in two bytes, a warning message is displayed and the least significant two
7554 bytes of the expression's value are used. If an expression cannot be evaluated
7555 at assembly time then relocations will be generated in order to compute the
7558 This directive does not apply any alignment before or after inserting the
7559 values. As a result of this, if relocations are generated, they may be
7560 different from those used for inserting values with a guaranteed alignment.
7563 @section @code{.4byte @var{expression} [, @var{expression}]*}
7564 @cindex @code{4byte} directive
7565 @cindex four-byte integer
7566 @cindex integer, 4-byte
7568 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7569 long values into the output.
7572 @section @code{.8byte @var{expression} [, @var{expression}]*}
7573 @cindex @code{8byte} directive
7574 @cindex eight-byte integer
7575 @cindex integer, 8-byte
7577 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7578 byte long bignum values into the output.
7581 @section Deprecated Directives
7583 @cindex deprecated directives
7584 @cindex obsolescent directives
7585 One day these directives won't work.
7586 They are included for compatibility with older assemblers.
7593 @node Object Attributes
7594 @chapter Object Attributes
7595 @cindex object attributes
7597 @command{@value{AS}} assembles source files written for a specific architecture
7598 into object files for that architecture. But not all object files are alike.
7599 Many architectures support incompatible variations. For instance, floating
7600 point arguments might be passed in floating point registers if the object file
7601 requires hardware floating point support---or floating point arguments might be
7602 passed in integer registers if the object file supports processors with no
7603 hardware floating point unit. Or, if two objects are built for different
7604 generations of the same architecture, the combination may require the
7605 newer generation at run-time.
7607 This information is useful during and after linking. At link time,
7608 @command{@value{LD}} can warn about incompatible object files. After link
7609 time, tools like @command{gdb} can use it to process the linked file
7612 Compatibility information is recorded as a series of object attributes. Each
7613 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7614 string, and indicates who sets the meaning of the tag. The tag is an integer,
7615 and indicates what property the attribute describes. The value may be a string
7616 or an integer, and indicates how the property affects this object. Missing
7617 attributes are the same as attributes with a zero value or empty string value.
7619 Object attributes were developed as part of the ABI for the ARM Architecture.
7620 The file format is documented in @cite{ELF for the ARM Architecture}.
7623 * GNU Object Attributes:: @sc{gnu} Object Attributes
7624 * Defining New Object Attributes:: Defining New Object Attributes
7627 @node GNU Object Attributes
7628 @section @sc{gnu} Object Attributes
7630 The @code{.gnu_attribute} directive records an object attribute
7631 with vendor @samp{gnu}.
7633 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7634 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7635 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7636 2} is set for architecture-independent attributes and clear for
7637 architecture-dependent ones.
7639 @subsection Common @sc{gnu} attributes
7641 These attributes are valid on all architectures.
7644 @item Tag_compatibility (32)
7645 The compatibility attribute takes an integer flag value and a vendor name. If
7646 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7647 then the file is only compatible with the named toolchain. If it is greater
7648 than 1, the file can only be processed by other toolchains under some private
7649 arrangement indicated by the flag value and the vendor name.
7652 @subsection M680x0 Attributes
7655 @item Tag_GNU_M68K_ABI_FP (4)
7656 The floating-point ABI used by this object file. The value will be:
7660 0 for files not affected by the floating-point ABI.
7662 1 for files using double-precision hardware floating-point ABI.
7664 2 for files using the software floating-point ABI.
7668 @subsection MIPS Attributes
7671 @item Tag_GNU_MIPS_ABI_FP (4)
7672 The floating-point ABI used by this object file. The value will be:
7676 0 for files not affected by the floating-point ABI.
7678 1 for files using the hardware floating-point ABI with a standard
7679 double-precision FPU.
7681 2 for files using the hardware floating-point ABI with a single-precision FPU.
7683 3 for files using the software floating-point ABI.
7685 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7686 floating-point registers, 32-bit general-purpose registers and increased the
7687 number of callee-saved floating-point registers.
7689 5 for files using the hardware floating-point ABI with a double-precision FPU
7690 with either 32-bit or 64-bit floating-point registers and 32-bit
7691 general-purpose registers.
7693 6 for files using the hardware floating-point ABI with 64-bit floating-point
7694 registers and 32-bit general-purpose registers.
7696 7 for files using the hardware floating-point ABI with 64-bit floating-point
7697 registers, 32-bit general-purpose registers and a rule that forbids the
7698 direct use of odd-numbered single-precision floating-point registers.
7702 @subsection PowerPC Attributes
7705 @item Tag_GNU_Power_ABI_FP (4)
7706 The floating-point ABI used by this object file. The value will be:
7710 0 for files not affected by the floating-point ABI.
7712 1 for files using double-precision hardware floating-point ABI.
7714 2 for files using the software floating-point ABI.
7716 3 for files using single-precision hardware floating-point ABI.
7719 @item Tag_GNU_Power_ABI_Vector (8)
7720 The vector ABI used by this object file. The value will be:
7724 0 for files not affected by the vector ABI.
7726 1 for files using general purpose registers to pass vectors.
7728 2 for files using AltiVec registers to pass vectors.
7730 3 for files using SPE registers to pass vectors.
7734 @subsection IBM z Systems Attributes
7737 @item Tag_GNU_S390_ABI_Vector (8)
7738 The vector ABI used by this object file. The value will be:
7742 0 for files not affected by the vector ABI.
7744 1 for files using software vector ABI.
7746 2 for files using hardware vector ABI.
7750 @subsection MSP430 Attributes
7753 @item Tag_GNU_MSP430_Data_Region (4)
7754 The data region used by this object file. The value will be:
7758 0 for files not using the large memory model.
7760 1 for files which have been compiled with the condition that all
7761 data is in the lower memory region, i.e. below address 0x10000.
7763 2 for files which allow data to be placed in the full 20-bit memory range.
7767 @node Defining New Object Attributes
7768 @section Defining New Object Attributes
7770 If you want to define a new @sc{gnu} object attribute, here are the places you
7771 will need to modify. New attributes should be discussed on the @samp{binutils}
7776 This manual, which is the official register of attributes.
7778 The header for your architecture @file{include/elf}, to define the tag.
7780 The @file{bfd} support file for your architecture, to merge the attribute
7781 and issue any appropriate link warnings.
7783 Test cases in @file{ld/testsuite} for merging and link warnings.
7785 @file{binutils/readelf.c} to display your attribute.
7787 GCC, if you want the compiler to mark the attribute automatically.
7793 @node Machine Dependencies
7794 @chapter Machine Dependent Features
7796 @cindex machine dependencies
7797 The machine instruction sets are (almost by definition) different on
7798 each machine where @command{@value{AS}} runs. Floating point representations
7799 vary as well, and @command{@value{AS}} often supports a few additional
7800 directives or command-line options for compatibility with other
7801 assemblers on a particular platform. Finally, some versions of
7802 @command{@value{AS}} support special pseudo-instructions for branch
7805 This chapter discusses most of these differences, though it does not
7806 include details on any machine's instruction set. For details on that
7807 subject, see the hardware manufacturer's manual.
7811 * AArch64-Dependent:: AArch64 Dependent Features
7814 * Alpha-Dependent:: Alpha Dependent Features
7817 * ARC-Dependent:: ARC Dependent Features
7820 * ARM-Dependent:: ARM Dependent Features
7823 * AVR-Dependent:: AVR Dependent Features
7826 * Blackfin-Dependent:: Blackfin Dependent Features
7829 * BPF-Dependent:: BPF Dependent Features
7832 * CR16-Dependent:: CR16 Dependent Features
7835 * CRIS-Dependent:: CRIS Dependent Features
7838 * C-SKY-Dependent:: C-SKY Dependent Features
7841 * D10V-Dependent:: D10V Dependent Features
7844 * D30V-Dependent:: D30V Dependent Features
7847 * Epiphany-Dependent:: EPIPHANY Dependent Features
7850 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7853 * HPPA-Dependent:: HPPA Dependent Features
7856 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7859 * IA-64-Dependent:: Intel IA-64 Dependent Features
7862 * IP2K-Dependent:: IP2K Dependent Features
7865 * LoongArch-Dependent:: LoongArch Dependent Features
7868 * LM32-Dependent:: LM32 Dependent Features
7871 * M32C-Dependent:: M32C Dependent Features
7874 * M32R-Dependent:: M32R Dependent Features
7877 * M68K-Dependent:: M680x0 Dependent Features
7880 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7883 * S12Z-Dependent:: S12Z Dependent Features
7886 * Meta-Dependent :: Meta Dependent Features
7889 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7892 * MIPS-Dependent:: MIPS Dependent Features
7895 * MMIX-Dependent:: MMIX Dependent Features
7898 * MSP430-Dependent:: MSP430 Dependent Features
7901 * NDS32-Dependent:: Andes NDS32 Dependent Features
7904 * NiosII-Dependent:: Altera Nios II Dependent Features
7907 * NS32K-Dependent:: NS32K Dependent Features
7910 * OpenRISC-Dependent:: OpenRISC 1000 Features
7913 * PDP-11-Dependent:: PDP-11 Dependent Features
7916 * PJ-Dependent:: picoJava Dependent Features
7919 * PPC-Dependent:: PowerPC Dependent Features
7922 * PRU-Dependent:: PRU Dependent Features
7925 * RISC-V-Dependent:: RISC-V Dependent Features
7928 * RL78-Dependent:: RL78 Dependent Features
7931 * RX-Dependent:: RX Dependent Features
7934 * S/390-Dependent:: IBM S/390 Dependent Features
7937 * SCORE-Dependent:: SCORE Dependent Features
7940 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7943 * Sparc-Dependent:: SPARC Dependent Features
7946 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7949 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7952 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7955 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7958 * V850-Dependent:: V850 Dependent Features
7961 * Vax-Dependent:: VAX Dependent Features
7964 * Visium-Dependent:: Visium Dependent Features
7967 * WebAssembly-Dependent:: WebAssembly Dependent Features
7970 * XGATE-Dependent:: XGATE Dependent Features
7973 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7976 * Xtensa-Dependent:: Xtensa Dependent Features
7979 * Z80-Dependent:: Z80 Dependent Features
7982 * Z8000-Dependent:: Z8000 Dependent Features
7989 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7990 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7991 @c peculiarity: to preserve cross-references, there must be a node called
7992 @c "Machine Dependencies". Hence the conditional nodenames in each
7993 @c major node below. Node defaulting in makeinfo requires adjacency of
7994 @c node and sectioning commands; hence the repetition of @chapter BLAH
7995 @c in both conditional blocks.
7998 @include c-aarch64.texi
8002 @include c-alpha.texi
8018 @include c-bfin.texi
8026 @include c-cr16.texi
8030 @include c-cris.texi
8034 @include c-csky.texi
8039 @node Machine Dependencies
8040 @chapter Machine Dependent Features
8042 The machine instruction sets are different on each Renesas chip family,
8043 and there are also some syntax differences among the families. This
8044 chapter describes the specific @command{@value{AS}} features for each
8048 * H8/300-Dependent:: Renesas H8/300 Dependent Features
8049 * SH-Dependent:: Renesas SH Dependent Features
8056 @include c-d10v.texi
8060 @include c-d30v.texi
8064 @include c-epiphany.texi
8068 @include c-h8300.texi
8072 @include c-hppa.texi
8076 @include c-i386.texi
8080 @include c-ia64.texi
8084 @include c-ip2k.texi
8088 @include c-lm32.texi
8092 @include c-loongarch.texi
8096 @include c-m32c.texi
8100 @include c-m32r.texi
8104 @include c-m68k.texi
8108 @include c-m68hc11.texi
8112 @include c-s12z.texi
8116 @include c-metag.texi
8120 @include c-microblaze.texi
8124 @include c-mips.texi
8128 @include c-mmix.texi
8132 @include c-msp430.texi
8136 @include c-nds32.texi
8140 @include c-nios2.texi
8144 @include c-ns32k.texi
8148 @include c-or1k.texi
8152 @include c-pdp11.texi
8168 @include c-riscv.texi
8172 @include c-rl78.texi
8180 @include c-s390.texi
8184 @include c-score.texi
8192 @include c-sparc.texi
8196 @include c-tic54x.texi
8200 @include c-tic6x.texi
8204 @include c-tilegx.texi
8208 @include c-tilepro.texi
8212 @include c-v850.texi
8220 @include c-visium.texi
8224 @include c-wasm32.texi
8228 @include c-xgate.texi
8232 @include c-xstormy16.texi
8236 @include c-xtensa.texi
8248 @c reverse effect of @down at top of generic Machine-Dep chapter
8252 @node Reporting Bugs
8253 @chapter Reporting Bugs
8254 @cindex bugs in assembler
8255 @cindex reporting bugs in assembler
8257 Your bug reports play an essential role in making @command{@value{AS}} reliable.
8259 Reporting a bug may help you by bringing a solution to your problem, or it may
8260 not. But in any case the principal function of a bug report is to help the
8261 entire community by making the next version of @command{@value{AS}} work better.
8262 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
8264 In order for a bug report to serve its purpose, you must include the
8265 information that enables us to fix the bug.
8268 * Bug Criteria:: Have you found a bug?
8269 * Bug Reporting:: How to report bugs
8273 @section Have You Found a Bug?
8274 @cindex bug criteria
8276 If you are not sure whether you have found a bug, here are some guidelines:
8279 @cindex fatal signal
8280 @cindex assembler crash
8281 @cindex crash of assembler
8283 If the assembler gets a fatal signal, for any input whatever, that is a
8284 @command{@value{AS}} bug. Reliable assemblers never crash.
8286 @cindex error on valid input
8288 If @command{@value{AS}} produces an error message for valid input, that is a bug.
8290 @cindex invalid input
8292 If @command{@value{AS}} does not produce an error message for invalid input, that
8293 is a bug. However, you should note that your idea of ``invalid input'' might
8294 be our idea of ``an extension'' or ``support for traditional practice''.
8297 If you are an experienced user of assemblers, your suggestions for improvement
8298 of @command{@value{AS}} are welcome in any case.
8302 @section How to Report Bugs
8304 @cindex assembler bugs, reporting
8306 A number of companies and individuals offer support for @sc{gnu} products. If
8307 you obtained @command{@value{AS}} from a support organization, we recommend you
8308 contact that organization first.
8310 You can find contact information for many support companies and
8311 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8315 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8319 The fundamental principle of reporting bugs usefully is this:
8320 @strong{report all the facts}. If you are not sure whether to state a
8321 fact or leave it out, state it!
8323 Often people omit facts because they think they know what causes the problem
8324 and assume that some details do not matter. Thus, you might assume that the
8325 name of a symbol you use in an example does not matter. Well, probably it does
8326 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8327 happens to fetch from the location where that name is stored in memory;
8328 perhaps, if the name were different, the contents of that location would fool
8329 the assembler into doing the right thing despite the bug. Play it safe and
8330 give a specific, complete example. That is the easiest thing for you to do,
8331 and the most helpful.
8333 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8334 it is new to us. Therefore, always write your bug reports on the assumption
8335 that the bug has not been reported previously.
8337 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8338 bell?'' This cannot help us fix a bug, so it is basically useless. We
8339 respond by asking for enough details to enable us to investigate.
8340 You might as well expedite matters by sending them to begin with.
8342 To enable us to fix the bug, you should include all these things:
8346 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8347 it with the @samp{--version} argument.
8349 Without this, we will not know whether there is any point in looking for
8350 the bug in the current version of @command{@value{AS}}.
8353 Any patches you may have applied to the @command{@value{AS}} source.
8356 The type of machine you are using, and the operating system name and
8360 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8364 The command arguments you gave the assembler to assemble your example and
8365 observe the bug. To guarantee you will not omit something important, list them
8366 all. A copy of the Makefile (or the output from make) is sufficient.
8368 If we were to try to guess the arguments, we would probably guess wrong
8369 and then we might not encounter the bug.
8372 A complete input file that will reproduce the bug. If the bug is observed when
8373 the assembler is invoked via a compiler, send the assembler source, not the
8374 high level language source. Most compilers will produce the assembler source
8375 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8376 the options @samp{-v --save-temps}; this will save the assembler source in a
8377 file with an extension of @file{.s}, and also show you exactly how
8378 @command{@value{AS}} is being run.
8381 A description of what behavior you observe that you believe is
8382 incorrect. For example, ``It gets a fatal signal.''
8384 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8385 will certainly notice it. But if the bug is incorrect output, we might not
8386 notice unless it is glaringly wrong. You might as well not give us a chance to
8389 Even if the problem you experience is a fatal signal, you should still say so
8390 explicitly. Suppose something strange is going on, such as, your copy of
8391 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8392 library on your system. (This has happened!) Your copy might crash and ours
8393 would not. If you told us to expect a crash, then when ours fails to crash, we
8394 would know that the bug was not happening for us. If you had not told us to
8395 expect a crash, then we would not be able to draw any conclusion from our
8399 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8400 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8401 option. Always send diffs from the old file to the new file. If you even
8402 discuss something in the @command{@value{AS}} source, refer to it by context, not
8405 The line numbers in our development sources will not match those in your
8406 sources. Your line numbers would convey no useful information to us.
8409 Here are some things that are not necessary:
8413 A description of the envelope of the bug.
8415 Often people who encounter a bug spend a lot of time investigating
8416 which changes to the input file will make the bug go away and which
8417 changes will not affect it.
8419 This is often time consuming and not very useful, because the way we
8420 will find the bug is by running a single example under the debugger
8421 with breakpoints, not by pure deduction from a series of examples.
8422 We recommend that you save your time for something else.
8424 Of course, if you can find a simpler example to report @emph{instead}
8425 of the original one, that is a convenience for us. Errors in the
8426 output will be easier to spot, running under the debugger will take
8427 less time, and so on.
8429 However, simplification is not vital; if you do not want to do this,
8430 report the bug anyway and send us the entire test case you used.
8433 A patch for the bug.
8435 A patch for the bug does help us if it is a good one. But do not omit
8436 the necessary information, such as the test case, on the assumption that
8437 a patch is all we need. We might see problems with your patch and decide
8438 to fix the problem another way, or we might not understand it at all.
8440 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8441 construct an example that will make the program follow a certain path through
8442 the code. If you do not send us the example, we will not be able to construct
8443 one, so we will not be able to verify that the bug is fixed.
8445 And if we cannot understand what bug you are trying to fix, or why your
8446 patch should be an improvement, we will not install it. A test case will
8447 help us to understand.
8450 A guess about what the bug is or what it depends on.
8452 Such guesses are usually wrong. Even we cannot guess right about such
8453 things without first using the debugger to find the facts.
8456 @node Acknowledgements
8457 @chapter Acknowledgements
8459 If you have contributed to GAS and your name isn't listed here,
8460 it is not meant as a slight. We just don't know about it. Send mail to the
8461 maintainer, and we'll correct the situation. Currently
8463 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8465 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8468 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8469 information and the 68k series machines, most of the preprocessing pass, and
8470 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8472 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8473 many bug fixes, including merging support for several processors, breaking GAS
8474 up to handle multiple object file format back ends (including heavy rewrite,
8475 testing, an integration of the coff and b.out back ends), adding configuration
8476 including heavy testing and verification of cross assemblers and file splits
8477 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8478 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8479 port (including considerable amounts of reverse engineering), a SPARC opcode
8480 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8481 assertions and made them work, much other reorganization, cleanup, and lint.
8483 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8484 in format-specific I/O modules.
8486 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8487 has done much work with it since.
8489 The Intel 80386 machine description was written by Eliot Dresselhaus.
8491 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8493 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8494 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8496 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8497 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8498 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8499 support a.out format.
8501 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8502 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8503 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8504 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8507 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8508 simplified the configuration of which versions accept which directives. He
8509 updated the 68k machine description so that Motorola's opcodes always produced
8510 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8511 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8512 cross-compilation support, and one bug in relaxation that took a week and
8513 required the proverbial one-bit fix.
8515 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8516 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8517 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8518 PowerPC assembler, and made a few other minor patches.
8520 Steve Chamberlain made GAS able to generate listings.
8522 Hewlett-Packard contributed support for the HP9000/300.
8524 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8525 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8526 formats). This work was supported by both the Center for Software Science at
8527 the University of Utah and Cygnus Support.
8529 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8530 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8531 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8532 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8533 and some initial 64-bit support).
8535 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8537 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8538 support for openVMS/Alpha.
8540 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8543 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8544 Inc.@: added support for Xtensa processors.
8546 Several engineers at Cygnus Support have also provided many small bug fixes and
8547 configuration enhancements.
8549 Jon Beniston added support for the Lattice Mico32 architecture.
8551 Many others have contributed large or small bugfixes and enhancements. If
8552 you have contributed significant work and are not mentioned on this list, and
8553 want to be, let us know. Some of the history has been lost; we are not
8554 intentionally leaving anyone out.
8556 @node GNU Free Documentation License
8557 @appendix GNU Free Documentation License
8561 @unnumbered AS Index