1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2016 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2016 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2016 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
238 [@b{-o} @var{objfile}] [@b{-R}]
239 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
241 [@b{-v}] [@b{-version}] [@b{--version}]
242 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
243 [@b{-Z}] [@b{@@@var{FILE}}]
244 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
245 [@b{--elf-stt-common=[no|yes]}]
246 [@b{--target-help}] [@var{target-options}]
247 [@b{--}|@var{files} @dots{}]
249 @c Target dependent options are listed below. Keep the list sorted.
250 @c Add an empty line for separation.
253 @emph{Target AArch64 options:}
255 [@b{-mabi}=@var{ABI}]
259 @emph{Target Alpha options:}
261 [@b{-mdebug} | @b{-no-mdebug}]
262 [@b{-replace} | @b{-noreplace}]
263 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
264 [@b{-F}] [@b{-32addr}]
268 @emph{Target ARC options:}
269 [@b{-mcpu=@var{cpu}}]
270 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
277 @emph{Target ARM options:}
278 @c Don't document the deprecated options
279 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
280 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
281 [@b{-mfpu}=@var{floating-point-format}]
282 [@b{-mfloat-abi}=@var{abi}]
283 [@b{-meabi}=@var{ver}]
286 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
287 @b{-mapcs-reentrant}]
288 [@b{-mthumb-interwork}] [@b{-k}]
292 @emph{Target Blackfin options:}
293 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
300 @emph{Target CRIS options:}
301 [@b{--underscore} | @b{--no-underscore}]
303 [@b{--emulation=criself} | @b{--emulation=crisaout}]
304 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
305 @c Deprecated -- deliberately not documented.
310 @emph{Target D10V options:}
315 @emph{Target D30V options:}
316 [@b{-O}|@b{-n}|@b{-N}]
320 @emph{Target EPIPHANY options:}
321 [@b{-mepiphany}|@b{-mepiphany16}]
325 @emph{Target H8/300 options:}
329 @c HPPA has no machine-dependent assembler options (yet).
333 @emph{Target i386 options:}
334 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
335 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
339 @emph{Target i960 options:}
340 @c see md_parse_option in tc-i960.c
341 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
343 [@b{-b}] [@b{-no-relax}]
347 @emph{Target IA-64 options:}
348 [@b{-mconstant-gp}|@b{-mauto-pic}]
349 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
351 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
352 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
353 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
354 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
358 @emph{Target IP2K options:}
359 [@b{-mip2022}|@b{-mip2022ext}]
363 @emph{Target M32C options:}
364 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
368 @emph{Target M32R options:}
369 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
374 @emph{Target M680X0 options:}
375 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
379 @emph{Target M68HC11 options:}
380 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
381 [@b{-mshort}|@b{-mlong}]
382 [@b{-mshort-double}|@b{-mlong-double}]
383 [@b{--force-long-branches}] [@b{--short-branches}]
384 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
385 [@b{--print-opcodes}] [@b{--generate-example}]
389 @emph{Target MCORE options:}
390 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
391 [@b{-mcpu=[210|340]}]
395 @emph{Target Meta options:}
396 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
399 @emph{Target MICROBLAZE options:}
400 @c MicroBlaze has no machine-dependent assembler options.
404 @emph{Target MIPS options:}
405 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
406 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
407 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
408 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
409 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
410 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
411 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
412 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
413 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
414 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
415 [@b{-construct-floats}] [@b{-no-construct-floats}]
416 [@b{-mnan=@var{encoding}}]
417 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
418 [@b{-mips16}] [@b{-no-mips16}]
419 [@b{-mmicromips}] [@b{-mno-micromips}]
420 [@b{-msmartmips}] [@b{-mno-smartmips}]
421 [@b{-mips3d}] [@b{-no-mips3d}]
422 [@b{-mdmx}] [@b{-no-mdmx}]
423 [@b{-mdsp}] [@b{-mno-dsp}]
424 [@b{-mdspr2}] [@b{-mno-dspr2}]
425 [@b{-mmsa}] [@b{-mno-msa}]
426 [@b{-mxpa}] [@b{-mno-xpa}]
427 [@b{-mmt}] [@b{-mno-mt}]
428 [@b{-mmcu}] [@b{-mno-mcu}]
429 [@b{-minsn32}] [@b{-mno-insn32}]
430 [@b{-mfix7000}] [@b{-mno-fix7000}]
431 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
432 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
433 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
434 [@b{-mdebug}] [@b{-no-mdebug}]
435 [@b{-mpdr}] [@b{-mno-pdr}]
439 @emph{Target MMIX options:}
440 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
441 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
442 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
443 [@b{--linker-allocated-gregs}]
447 @emph{Target Nios II options:}
448 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
453 @emph{Target NDS32 options:}
454 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
455 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
456 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
457 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
458 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
459 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
460 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
465 @emph{Target PDP11 options:}
466 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
467 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
468 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
472 @emph{Target picoJava options:}
477 @emph{Target PowerPC options:}
479 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
480 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
481 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
482 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
483 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
484 @b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
485 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
486 [@b{-mregnames}|@b{-mno-regnames}]
487 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
488 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
489 [@b{-msolaris}|@b{-mno-solaris}]
490 [@b{-nops=@var{count}}]
494 @emph{Target RL78 options:}
496 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
500 @emph{Target RX options:}
501 [@b{-mlittle-endian}|@b{-mbig-endian}]
502 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
503 [@b{-muse-conventional-section-names}]
504 [@b{-msmall-data-limit}]
507 [@b{-mint-register=@var{number}}]
508 [@b{-mgcc-abi}|@b{-mrx-abi}]
512 @emph{Target s390 options:}
513 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
514 [@b{-mregnames}|@b{-mno-regnames}]
515 [@b{-mwarn-areg-zero}]
519 @emph{Target SCORE options:}
520 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
521 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
522 [@b{-march=score7}][@b{-march=score3}]
523 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
527 @emph{Target SPARC options:}
528 @c The order here is important. See c-sparc.texi.
529 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
530 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
531 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
536 @emph{Target TIC54X options:}
537 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
538 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
542 @emph{Target TIC6X options:}
543 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
544 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
545 [@b{-mpic}|@b{-mno-pic}]
549 @emph{Target TILE-Gx options:}
550 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
553 @c TILEPro has no machine-dependent assembler options
557 @emph{Target Visium options:}
558 [@b{-mtune=@var{arch}}]
562 @emph{Target Xtensa options:}
563 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
564 [@b{--[no-]absolute-literals}]
565 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
566 [@b{--[no-]transform}]
567 [@b{--rename-section} @var{oldname}=@var{newname}]
568 [@b{--[no-]trampolines}]
572 @emph{Target Z80 options:}
573 [@b{-z80}] [@b{-r800}]
574 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
575 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
576 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
577 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
578 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
579 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
583 @c Z8000 has no machine-dependent assembler options
592 @include at-file.texi
595 Turn on listings, in any of a variety of ways:
599 omit false conditionals
602 omit debugging directives
605 include general information, like @value{AS} version and options passed
608 include high-level source
614 include macro expansions
617 omit forms processing
623 set the name of the listing file
626 You may combine these options; for example, use @samp{-aln} for assembly
627 listing without forms processing. The @samp{=file} option, if used, must be
628 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
631 Begin in alternate macro mode.
633 @xref{Altmacro,,@code{.altmacro}}.
636 @item --compress-debug-sections
637 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
638 ELF ABI. The resulting object file may not be compatible with older
639 linkers and object file utilities. Note if compression would make a
640 given section @emph{larger} then it is not compressed.
643 @cindex @samp{--compress-debug-sections=} option
644 @item --compress-debug-sections=none
645 @itemx --compress-debug-sections=zlib
646 @itemx --compress-debug-sections=zlib-gnu
647 @itemx --compress-debug-sections=zlib-gabi
648 These options control how DWARF debug sections are compressed.
649 @option{--compress-debug-sections=none} is equivalent to
650 @option{--nocompress-debug-sections}.
651 @option{--compress-debug-sections=zlib} and
652 @option{--compress-debug-sections=zlib-gabi} are equivalent to
653 @option{--compress-debug-sections}.
654 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
655 sections using zlib. The debug sections are renamed to begin with
656 @samp{.zdebug}. Note if compression would make a given section
657 @emph{larger} then it is not compressed nor renamed.
661 @item --nocompress-debug-sections
662 Do not compress DWARF debug sections. This is usually the default for all
663 targets except the x86/x86_64, but a configure time option can be used to
667 Ignored. This option is accepted for script compatibility with calls to
670 @item --debug-prefix-map @var{old}=@var{new}
671 When assembling files in directory @file{@var{old}}, record debugging
672 information describing them as in @file{@var{new}} instead.
674 @item --defsym @var{sym}=@var{value}
675 Define the symbol @var{sym} to be @var{value} before assembling the input file.
676 @var{value} must be an integer constant. As in C, a leading @samp{0x}
677 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
678 value. The value of the symbol can be overridden inside a source file via the
679 use of a @code{.set} pseudo-op.
682 ``fast''---skip whitespace and comment preprocessing (assume source is
687 Generate debugging information for each assembler source line using whichever
688 debug format is preferred by the target. This currently means either STABS,
692 Generate stabs debugging information for each assembler line. This
693 may help debugging assembler code, if the debugger can handle it.
696 Generate stabs debugging information for each assembler line, with GNU
697 extensions that probably only gdb can handle, and that could make other
698 debuggers crash or refuse to read your program. This
699 may help debugging assembler code. Currently the only GNU extension is
700 the location of the current working directory at assembling time.
703 Generate DWARF2 debugging information for each assembler line. This
704 may help debugging assembler code, if the debugger can handle it. Note---this
705 option is only supported by some targets, not all of them.
707 @item --gdwarf-sections
708 Instead of creating a .debug_line section, create a series of
709 .debug_line.@var{foo} sections where @var{foo} is the name of the
710 corresponding code section. For example a code section called @var{.text.func}
711 will have its dwarf line number information placed into a section called
712 @var{.debug_line.text.func}. If the code section is just called @var{.text}
713 then debug line section will still be called just @var{.debug_line} without any
717 @item --size-check=error
718 @itemx --size-check=warning
719 Issue an error or warning for invalid ELF .size directive.
721 @item --elf-stt-common=no
722 @itemx --elf-stt-common=yes
723 These options control whether the ELF assembler should generate common
724 symbols with the @code{STT_COMMON} type. The default can be controlled
725 by a configure option @option{--enable-elf-stt-common}.
729 Print a summary of the command line options and exit.
732 Print a summary of all target specific options and exit.
735 Add directory @var{dir} to the search list for @code{.include} directives.
738 Don't warn about signed overflow.
741 @ifclear DIFF-TBL-KLUGE
742 This option is accepted but has no effect on the @value{TARGET} family.
744 @ifset DIFF-TBL-KLUGE
745 Issue warnings when difference tables altered for long displacements.
750 Keep (in the symbol table) local symbols. These symbols start with
751 system-specific local label prefixes, typically @samp{.L} for ELF systems
752 or @samp{L} for traditional a.out systems.
757 @item --listing-lhs-width=@var{number}
758 Set the maximum width, in words, of the output data column for an assembler
759 listing to @var{number}.
761 @item --listing-lhs-width2=@var{number}
762 Set the maximum width, in words, of the output data column for continuation
763 lines in an assembler listing to @var{number}.
765 @item --listing-rhs-width=@var{number}
766 Set the maximum width of an input source line, as displayed in a listing, to
769 @item --listing-cont-lines=@var{number}
770 Set the maximum number of lines printed in a listing for a single line of input
773 @item -o @var{objfile}
774 Name the object-file output from @command{@value{AS}} @var{objfile}.
777 Fold the data section into the text section.
779 @item --hash-size=@var{number}
780 Set the default size of GAS's hash tables to a prime number close to
781 @var{number}. Increasing this value can reduce the length of time it takes the
782 assembler to perform its tasks, at the expense of increasing the assembler's
783 memory requirements. Similarly reducing this value can reduce the memory
784 requirements at the expense of speed.
786 @item --reduce-memory-overheads
787 This option reduces GAS's memory requirements, at the expense of making the
788 assembly processes slower. Currently this switch is a synonym for
789 @samp{--hash-size=4051}, but in the future it may have other effects as well.
792 @item --sectname-subst
793 Honor substitution sequences in section names.
795 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
800 Print the maximum space (in bytes) and total time (in seconds) used by
803 @item --strip-local-absolute
804 Remove local absolute symbols from the outgoing symbol table.
808 Print the @command{as} version.
811 Print the @command{as} version and exit.
815 Suppress warning messages.
817 @item --fatal-warnings
818 Treat warnings as errors.
821 Don't suppress warning messages or treat them as errors.
830 Generate an object file even after errors.
832 @item -- | @var{files} @dots{}
833 Standard input, or source files to assemble.
841 @xref{AArch64 Options}, for the options available when @value{AS} is configured
842 for the 64-bit mode of the ARM Architecture (AArch64).
847 The following options are available when @value{AS} is configured for the
848 64-bit mode of the ARM Architecture (AArch64).
851 @include c-aarch64.texi
852 @c ended inside the included file
860 @xref{Alpha Options}, for the options available when @value{AS} is configured
861 for an Alpha processor.
866 The following options are available when @value{AS} is configured for an Alpha
870 @include c-alpha.texi
871 @c ended inside the included file
878 The following options are available when @value{AS} is configured for an ARC
882 @item -mcpu=@var{cpu}
883 This option selects the core processor variant.
885 Select either big-endian (-EB) or little-endian (-EL) output.
887 Enable Code Density extenssion instructions.
892 The following options are available when @value{AS} is configured for the ARM
896 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
897 Specify which ARM processor variant is the target.
898 @item -march=@var{architecture}[+@var{extension}@dots{}]
899 Specify which ARM architecture variant is used by the target.
900 @item -mfpu=@var{floating-point-format}
901 Select which Floating Point architecture is the target.
902 @item -mfloat-abi=@var{abi}
903 Select which floating point ABI is in use.
905 Enable Thumb only instruction decoding.
906 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
907 Select which procedure calling convention is in use.
909 Select either big-endian (-EB) or little-endian (-EL) output.
910 @item -mthumb-interwork
911 Specify that the code has been generated with interworking between Thumb and
914 Turns on CodeComposer Studio assembly syntax compatibility mode.
916 Specify that PIC code has been generated.
924 @xref{Blackfin Options}, for the options available when @value{AS} is
925 configured for the Blackfin processor family.
930 The following options are available when @value{AS} is configured for
931 the Blackfin processor family.
935 @c ended inside the included file
942 See the info pages for documentation of the CRIS-specific options.
946 The following options are available when @value{AS} is configured for
949 @cindex D10V optimization
950 @cindex optimization, D10V
952 Optimize output by parallelizing instructions.
957 The following options are available when @value{AS} is configured for a D30V
960 @cindex D30V optimization
961 @cindex optimization, D30V
963 Optimize output by parallelizing instructions.
967 Warn when nops are generated.
969 @cindex D30V nops after 32-bit multiply
971 Warn when a nop after a 32-bit multiply instruction is generated.
977 The following options are available when @value{AS} is configured for the
978 Adapteva EPIPHANY series.
981 @xref{Epiphany Options}, for the options available when @value{AS} is
982 configured for an Epiphany processor.
987 The following options are available when @value{AS} is configured for
988 an Epiphany processor.
991 @include c-epiphany.texi
992 @c ended inside the included file
1000 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1001 for an H8/300 processor.
1005 @c man begin OPTIONS
1006 The following options are available when @value{AS} is configured for an H8/300
1009 @c man begin INCLUDE
1010 @include c-h8300.texi
1011 @c ended inside the included file
1019 @xref{i386-Options}, for the options available when @value{AS} is
1020 configured for an i386 processor.
1024 @c man begin OPTIONS
1025 The following options are available when @value{AS} is configured for
1028 @c man begin INCLUDE
1029 @include c-i386.texi
1030 @c ended inside the included file
1035 @c man begin OPTIONS
1037 The following options are available when @value{AS} is configured for the
1038 Intel 80960 processor.
1041 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1042 Specify which variant of the 960 architecture is the target.
1045 Add code to collect statistics about branches taken.
1048 Do not alter compare-and-branch instructions for long displacements;
1055 The following options are available when @value{AS} is configured for the
1061 Specifies that the extended IP2022 instructions are allowed.
1064 Restores the default behaviour, which restricts the permitted instructions to
1065 just the basic IP2022 ones.
1071 The following options are available when @value{AS} is configured for the
1072 Renesas M32C and M16C processors.
1077 Assemble M32C instructions.
1080 Assemble M16C instructions (the default).
1083 Enable support for link-time relaxations.
1086 Support H'00 style hex constants in addition to 0x00 style.
1092 The following options are available when @value{AS} is configured for the
1093 Renesas M32R (formerly Mitsubishi M32R) series.
1098 Specify which processor in the M32R family is the target. The default
1099 is normally the M32R, but this option changes it to the M32RX.
1101 @item --warn-explicit-parallel-conflicts or --Wp
1102 Produce warning messages when questionable parallel constructs are
1105 @item --no-warn-explicit-parallel-conflicts or --Wnp
1106 Do not produce warning messages when questionable parallel constructs are
1113 The following options are available when @value{AS} is configured for the
1114 Motorola 68000 series.
1119 Shorten references to undefined symbols, to one word instead of two.
1121 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1122 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1123 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1124 Specify what processor in the 68000 family is the target. The default
1125 is normally the 68020, but this can be changed at configuration time.
1127 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1128 The target machine does (or does not) have a floating-point coprocessor.
1129 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1130 the basic 68000 is not compatible with the 68881, a combination of the
1131 two can be specified, since it's possible to do emulation of the
1132 coprocessor instructions with the main processor.
1134 @item -m68851 | -mno-68851
1135 The target machine does (or does not) have a memory-management
1136 unit coprocessor. The default is to assume an MMU for 68020 and up.
1144 @xref{Nios II Options}, for the options available when @value{AS} is configured
1145 for an Altera Nios II processor.
1149 @c man begin OPTIONS
1150 The following options are available when @value{AS} is configured for an
1151 Altera Nios II processor.
1153 @c man begin INCLUDE
1154 @include c-nios2.texi
1155 @c ended inside the included file
1161 For details about the PDP-11 machine dependent features options,
1162 see @ref{PDP-11-Options}.
1165 @item -mpic | -mno-pic
1166 Generate position-independent (or position-dependent) code. The
1167 default is @option{-mpic}.
1170 @itemx -mall-extensions
1171 Enable all instruction set extensions. This is the default.
1173 @item -mno-extensions
1174 Disable all instruction set extensions.
1176 @item -m@var{extension} | -mno-@var{extension}
1177 Enable (or disable) a particular instruction set extension.
1180 Enable the instruction set extensions supported by a particular CPU, and
1181 disable all other extensions.
1183 @item -m@var{machine}
1184 Enable the instruction set extensions supported by a particular machine
1185 model, and disable all other extensions.
1191 The following options are available when @value{AS} is configured for
1192 a picoJava processor.
1196 @cindex PJ endianness
1197 @cindex endianness, PJ
1198 @cindex big endian output, PJ
1200 Generate ``big endian'' format output.
1202 @cindex little endian output, PJ
1204 Generate ``little endian'' format output.
1210 The following options are available when @value{AS} is configured for the
1211 Motorola 68HC11 or 68HC12 series.
1215 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1216 Specify what processor is the target. The default is
1217 defined by the configuration option when building the assembler.
1219 @item --xgate-ramoffset
1220 Instruct the linker to offset RAM addresses from S12X address space into
1221 XGATE address space.
1224 Specify to use the 16-bit integer ABI.
1227 Specify to use the 32-bit integer ABI.
1229 @item -mshort-double
1230 Specify to use the 32-bit double ABI.
1233 Specify to use the 64-bit double ABI.
1235 @item --force-long-branches
1236 Relative branches are turned into absolute ones. This concerns
1237 conditional branches, unconditional branches and branches to a
1240 @item -S | --short-branches
1241 Do not turn relative branches into absolute ones
1242 when the offset is out of range.
1244 @item --strict-direct-mode
1245 Do not turn the direct addressing mode into extended addressing mode
1246 when the instruction does not support direct addressing mode.
1248 @item --print-insn-syntax
1249 Print the syntax of instruction in case of error.
1251 @item --print-opcodes
1252 Print the list of instructions with syntax and then exit.
1254 @item --generate-example
1255 Print an example of instruction for each possible instruction and then exit.
1256 This option is only useful for testing @command{@value{AS}}.
1262 The following options are available when @command{@value{AS}} is configured
1263 for the SPARC architecture:
1266 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1267 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1268 Explicitly select a variant of the SPARC architecture.
1270 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1271 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1273 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1274 UltraSPARC extensions.
1276 @item -xarch=v8plus | -xarch=v8plusa
1277 For compatibility with the Solaris v9 assembler. These options are
1278 equivalent to -Av8plus and -Av8plusa, respectively.
1281 Warn when the assembler switches to another architecture.
1286 The following options are available when @value{AS} is configured for the 'c54x
1291 Enable extended addressing mode. All addresses and relocations will assume
1292 extended addressing (usually 23 bits).
1293 @item -mcpu=@var{CPU_VERSION}
1294 Sets the CPU version being compiled for.
1295 @item -merrors-to-file @var{FILENAME}
1296 Redirect error output to a file, for broken systems which don't support such
1297 behaviour in the shell.
1302 The following options are available when @value{AS} is configured for
1307 This option sets the largest size of an object that can be referenced
1308 implicitly with the @code{gp} register. It is only accepted for targets that
1309 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1311 @cindex MIPS endianness
1312 @cindex endianness, MIPS
1313 @cindex big endian output, MIPS
1315 Generate ``big endian'' format output.
1317 @cindex little endian output, MIPS
1319 Generate ``little endian'' format output.
1337 Generate code for a particular MIPS Instruction Set Architecture level.
1338 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1339 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1340 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1341 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1342 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1343 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1344 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1345 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1346 MIPS64 Release 6 ISA processors, respectively.
1348 @item -march=@var{cpu}
1349 Generate code for a particular MIPS CPU.
1351 @item -mtune=@var{cpu}
1352 Schedule and tune for a particular MIPS CPU.
1356 Cause nops to be inserted if the read of the destination register
1357 of an mfhi or mflo instruction occurs in the following two instructions.
1360 @itemx -mno-fix-rm7000
1361 Cause nops to be inserted if a dmult or dmultu instruction is
1362 followed by a load instruction.
1366 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1367 section instead of the standard ELF .stabs sections.
1371 Control generation of @code{.pdr} sections.
1375 The register sizes are normally inferred from the ISA and ABI, but these
1376 flags force a certain group of registers to be treated as 32 bits wide at
1377 all times. @samp{-mgp32} controls the size of general-purpose registers
1378 and @samp{-mfp32} controls the size of floating-point registers.
1382 The register sizes are normally inferred from the ISA and ABI, but these
1383 flags force a certain group of registers to be treated as 64 bits wide at
1384 all times. @samp{-mgp64} controls the size of general-purpose registers
1385 and @samp{-mfp64} controls the size of floating-point registers.
1388 The register sizes are normally inferred from the ISA and ABI, but using
1389 this flag in combination with @samp{-mabi=32} enables an ABI variant
1390 which will operate correctly with floating-point registers which are
1394 @itemx -mno-odd-spreg
1395 Enable use of floating-point operations on odd-numbered single-precision
1396 registers when supported by the ISA. @samp{-mfpxx} implies
1397 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1401 Generate code for the MIPS 16 processor. This is equivalent to putting
1402 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1403 turns off this option.
1406 @itemx -mno-micromips
1407 Generate code for the microMIPS processor. This is equivalent to putting
1408 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1409 turns off this option. This is equivalent to putting @code{.set nomicromips}
1410 at the start of the assembly file.
1413 @itemx -mno-smartmips
1414 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1415 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1416 @samp{-mno-smartmips} turns off this option.
1420 Generate code for the MIPS-3D Application Specific Extension.
1421 This tells the assembler to accept MIPS-3D instructions.
1422 @samp{-no-mips3d} turns off this option.
1426 Generate code for the MDMX Application Specific Extension.
1427 This tells the assembler to accept MDMX instructions.
1428 @samp{-no-mdmx} turns off this option.
1432 Generate code for the DSP Release 1 Application Specific Extension.
1433 This tells the assembler to accept DSP Release 1 instructions.
1434 @samp{-mno-dsp} turns off this option.
1438 Generate code for the DSP Release 2 Application Specific Extension.
1439 This option implies -mdsp.
1440 This tells the assembler to accept DSP Release 2 instructions.
1441 @samp{-mno-dspr2} turns off this option.
1445 Generate code for the MIPS SIMD Architecture Extension.
1446 This tells the assembler to accept MSA instructions.
1447 @samp{-mno-msa} turns off this option.
1451 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1452 This tells the assembler to accept XPA instructions.
1453 @samp{-mno-xpa} turns off this option.
1457 Generate code for the MT Application Specific Extension.
1458 This tells the assembler to accept MT instructions.
1459 @samp{-mno-mt} turns off this option.
1463 Generate code for the MCU Application Specific Extension.
1464 This tells the assembler to accept MCU instructions.
1465 @samp{-mno-mcu} turns off this option.
1469 Only use 32-bit instruction encodings when generating code for the
1470 microMIPS processor. This option inhibits the use of any 16-bit
1471 instructions. This is equivalent to putting @code{.set insn32} at
1472 the start of the assembly file. @samp{-mno-insn32} turns off this
1473 option. This is equivalent to putting @code{.set noinsn32} at the
1474 start of the assembly file. By default @samp{-mno-insn32} is
1475 selected, allowing all instructions to be used.
1477 @item --construct-floats
1478 @itemx --no-construct-floats
1479 The @samp{--no-construct-floats} option disables the construction of
1480 double width floating point constants by loading the two halves of the
1481 value into the two single width floating point registers that make up
1482 the double width register. By default @samp{--construct-floats} is
1483 selected, allowing construction of these floating point constants.
1485 @item --relax-branch
1486 @itemx --no-relax-branch
1487 The @samp{--relax-branch} option enables the relaxation of out-of-range
1488 branches. By default @samp{--no-relax-branch} is selected, causing any
1489 out-of-range branches to produce an error.
1491 @item -mnan=@var{encoding}
1492 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1493 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1496 @item --emulation=@var{name}
1497 This option was formerly used to switch between ELF and ECOFF output
1498 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1499 removed in GAS 2.24, so the option now serves little purpose.
1500 It is retained for backwards compatibility.
1502 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1503 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1504 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1505 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1506 preferred options instead.
1509 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1516 Control how to deal with multiplication overflow and division by zero.
1517 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1518 (and only work for Instruction Set Architecture level 2 and higher);
1519 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1523 When this option is used, @command{@value{AS}} will issue a warning every
1524 time it generates a nop instruction from a macro.
1529 The following options are available when @value{AS} is configured for
1535 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1536 The command line option @samp{-nojsri2bsr} can be used to disable it.
1540 Enable or disable the silicon filter behaviour. By default this is disabled.
1541 The default can be overridden by the @samp{-sifilter} command line option.
1544 Alter jump instructions for long displacements.
1546 @item -mcpu=[210|340]
1547 Select the cpu type on the target hardware. This controls which instructions
1551 Assemble for a big endian target.
1554 Assemble for a little endian target.
1563 @xref{Meta Options}, for the options available when @value{AS} is configured
1564 for a Meta processor.
1568 @c man begin OPTIONS
1569 The following options are available when @value{AS} is configured for a
1572 @c man begin INCLUDE
1573 @include c-metag.texi
1574 @c ended inside the included file
1579 @c man begin OPTIONS
1581 See the info pages for documentation of the MMIX-specific options.
1587 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1588 for a NDS32 processor.
1590 @c ended inside the included file
1594 @c man begin OPTIONS
1595 The following options are available when @value{AS} is configured for a
1598 @c man begin INCLUDE
1599 @include c-nds32.texi
1600 @c ended inside the included file
1607 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1608 for a PowerPC processor.
1612 @c man begin OPTIONS
1613 The following options are available when @value{AS} is configured for a
1616 @c man begin INCLUDE
1618 @c ended inside the included file
1623 @c man begin OPTIONS
1625 See the info pages for documentation of the RX-specific options.
1629 The following options are available when @value{AS} is configured for the s390
1635 Select the word size, either 31/32 bits or 64 bits.
1638 Select the architecture mode, either the Enterprise System
1639 Architecture (esa) or the z/Architecture mode (zarch).
1640 @item -march=@var{processor}
1641 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1642 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1643 @samp{z196}, @samp{zEC12}, or @samp{z13}.
1645 @itemx -mno-regnames
1646 Allow or disallow symbolic names for registers.
1647 @item -mwarn-areg-zero
1648 Warn whenever the operand for a base or index register has been specified
1649 but evaluates to zero.
1657 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1658 for a TMS320C6000 processor.
1662 @c man begin OPTIONS
1663 The following options are available when @value{AS} is configured for a
1664 TMS320C6000 processor.
1666 @c man begin INCLUDE
1667 @include c-tic6x.texi
1668 @c ended inside the included file
1676 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1677 for a TILE-Gx processor.
1681 @c man begin OPTIONS
1682 The following options are available when @value{AS} is configured for a TILE-Gx
1685 @c man begin INCLUDE
1686 @include c-tilegx.texi
1687 @c ended inside the included file
1695 @xref{Visium Options}, for the options available when @value{AS} is configured
1696 for a Visium processor.
1700 @c man begin OPTIONS
1701 The following option is available when @value{AS} is configured for a Visium
1704 @c man begin INCLUDE
1705 @include c-visium.texi
1706 @c ended inside the included file
1714 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1715 for an Xtensa processor.
1719 @c man begin OPTIONS
1720 The following options are available when @value{AS} is configured for an
1723 @c man begin INCLUDE
1724 @include c-xtensa.texi
1725 @c ended inside the included file
1730 @c man begin OPTIONS
1733 The following options are available when @value{AS} is configured for
1734 a Z80 family processor.
1737 Assemble for Z80 processor.
1739 Assemble for R800 processor.
1740 @item -ignore-undocumented-instructions
1742 Assemble undocumented Z80 instructions that also work on R800 without warning.
1743 @item -ignore-unportable-instructions
1745 Assemble all undocumented Z80 instructions without warning.
1746 @item -warn-undocumented-instructions
1748 Issue a warning for undocumented Z80 instructions that also work on R800.
1749 @item -warn-unportable-instructions
1751 Issue a warning for undocumented Z80 instructions that do not work on R800.
1752 @item -forbid-undocumented-instructions
1754 Treat all undocumented instructions as errors.
1755 @item -forbid-unportable-instructions
1757 Treat undocumented Z80 instructions that do not work on R800 as errors.
1764 * Manual:: Structure of this Manual
1765 * GNU Assembler:: The GNU Assembler
1766 * Object Formats:: Object File Formats
1767 * Command Line:: Command Line
1768 * Input Files:: Input Files
1769 * Object:: Output (Object) File
1770 * Errors:: Error and Warning Messages
1774 @section Structure of this Manual
1776 @cindex manual, structure and purpose
1777 This manual is intended to describe what you need to know to use
1778 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1779 notation for symbols, constants, and expressions; the directives that
1780 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1783 We also cover special features in the @value{TARGET}
1784 configuration of @command{@value{AS}}, including assembler directives.
1787 This manual also describes some of the machine-dependent features of
1788 various flavors of the assembler.
1791 @cindex machine instructions (not covered)
1792 On the other hand, this manual is @emph{not} intended as an introduction
1793 to programming in assembly language---let alone programming in general!
1794 In a similar vein, we make no attempt to introduce the machine
1795 architecture; we do @emph{not} describe the instruction set, standard
1796 mnemonics, registers or addressing modes that are standard to a
1797 particular architecture.
1799 You may want to consult the manufacturer's
1800 machine architecture manual for this information.
1804 For information on the H8/300 machine instruction set, see @cite{H8/300
1805 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1806 Programming Manual} (Renesas).
1809 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1810 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1811 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1812 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1815 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1819 @c I think this is premature---doc@cygnus.com, 17jan1991
1821 Throughout this manual, we assume that you are running @dfn{GNU},
1822 the portable operating system from the @dfn{Free Software
1823 Foundation, Inc.}. This restricts our attention to certain kinds of
1824 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1825 once this assumption is granted examples and definitions need less
1828 @command{@value{AS}} is part of a team of programs that turn a high-level
1829 human-readable series of instructions into a low-level
1830 computer-readable series of instructions. Different versions of
1831 @command{@value{AS}} are used for different kinds of computer.
1834 @c There used to be a section "Terminology" here, which defined
1835 @c "contents", "byte", "word", and "long". Defining "word" to any
1836 @c particular size is confusing when the .word directive may generate 16
1837 @c bits on one machine and 32 bits on another; in general, for the user
1838 @c version of this manual, none of these terms seem essential to define.
1839 @c They were used very little even in the former draft of the manual;
1840 @c this draft makes an effort to avoid them (except in names of
1844 @section The GNU Assembler
1846 @c man begin DESCRIPTION
1848 @sc{gnu} @command{as} is really a family of assemblers.
1850 This manual describes @command{@value{AS}}, a member of that family which is
1851 configured for the @value{TARGET} architectures.
1853 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1854 should find a fairly similar environment when you use it on another
1855 architecture. Each version has much in common with the others,
1856 including object file formats, most assembler directives (often called
1857 @dfn{pseudo-ops}) and assembler syntax.@refill
1859 @cindex purpose of @sc{gnu} assembler
1860 @command{@value{AS}} is primarily intended to assemble the output of the
1861 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1862 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1863 assemble correctly everything that other assemblers for the same
1864 machine would assemble.
1866 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1869 @c This remark should appear in generic version of manual; assumption
1870 @c here is that generic version sets M680x0.
1871 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1872 assembler for the same architecture; for example, we know of several
1873 incompatible versions of 680x0 assembly language syntax.
1878 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1879 program in one pass of the source file. This has a subtle impact on the
1880 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1882 @node Object Formats
1883 @section Object File Formats
1885 @cindex object file format
1886 The @sc{gnu} assembler can be configured to produce several alternative
1887 object file formats. For the most part, this does not affect how you
1888 write assembly language programs; but directives for debugging symbols
1889 are typically different in different file formats. @xref{Symbol
1890 Attributes,,Symbol Attributes}.
1893 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1894 @value{OBJ-NAME} format object files.
1896 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1898 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1899 @code{b.out} or COFF format object files.
1902 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1903 SOM or ELF format object files.
1908 @section Command Line
1910 @cindex command line conventions
1912 After the program name @command{@value{AS}}, the command line may contain
1913 options and file names. Options may appear in any order, and may be
1914 before, after, or between file names. The order of file names is
1917 @cindex standard input, as input file
1919 @file{--} (two hyphens) by itself names the standard input file
1920 explicitly, as one of the files for @command{@value{AS}} to assemble.
1922 @cindex options, command line
1923 Except for @samp{--} any command line argument that begins with a
1924 hyphen (@samp{-}) is an option. Each option changes the behavior of
1925 @command{@value{AS}}. No option changes the way another option works. An
1926 option is a @samp{-} followed by one or more letters; the case of
1927 the letter is important. All options are optional.
1929 Some options expect exactly one file name to follow them. The file
1930 name may either immediately follow the option's letter (compatible
1931 with older assemblers) or it may be the next command argument (@sc{gnu}
1932 standard). These two command lines are equivalent:
1935 @value{AS} -o my-object-file.o mumble.s
1936 @value{AS} -omy-object-file.o mumble.s
1940 @section Input Files
1943 @cindex source program
1944 @cindex files, input
1945 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1946 describe the program input to one run of @command{@value{AS}}. The program may
1947 be in one or more files; how the source is partitioned into files
1948 doesn't change the meaning of the source.
1950 @c I added "con" prefix to "catenation" just to prove I can overcome my
1951 @c APL training... doc@cygnus.com
1952 The source program is a concatenation of the text in all the files, in the
1955 @c man begin DESCRIPTION
1956 Each time you run @command{@value{AS}} it assembles exactly one source
1957 program. The source program is made up of one or more files.
1958 (The standard input is also a file.)
1960 You give @command{@value{AS}} a command line that has zero or more input file
1961 names. The input files are read (from left file name to right). A
1962 command line argument (in any position) that has no special meaning
1963 is taken to be an input file name.
1965 If you give @command{@value{AS}} no file names it attempts to read one input file
1966 from the @command{@value{AS}} standard input, which is normally your terminal. You
1967 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1970 Use @samp{--} if you need to explicitly name the standard input file
1971 in your command line.
1973 If the source is empty, @command{@value{AS}} produces a small, empty object
1978 @subheading Filenames and Line-numbers
1980 @cindex input file linenumbers
1981 @cindex line numbers, in input files
1982 There are two ways of locating a line in the input file (or files) and
1983 either may be used in reporting error messages. One way refers to a line
1984 number in a physical file; the other refers to a line number in a
1985 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1987 @dfn{Physical files} are those files named in the command line given
1988 to @command{@value{AS}}.
1990 @dfn{Logical files} are simply names declared explicitly by assembler
1991 directives; they bear no relation to physical files. Logical file names help
1992 error messages reflect the original source file, when @command{@value{AS}} source
1993 is itself synthesized from other files. @command{@value{AS}} understands the
1994 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1995 @ref{File,,@code{.file}}.
1998 @section Output (Object) File
2004 Every time you run @command{@value{AS}} it produces an output file, which is
2005 your assembly language program translated into numbers. This file
2006 is the object file. Its default name is
2014 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2016 You can give it another name by using the @option{-o} option. Conventionally,
2017 object file names end with @file{.o}. The default name is used for historical
2018 reasons: older assemblers were capable of assembling self-contained programs
2019 directly into a runnable program. (For some formats, this isn't currently
2020 possible, but it can be done for the @code{a.out} format.)
2024 The object file is meant for input to the linker @code{@value{LD}}. It contains
2025 assembled program code, information to help @code{@value{LD}} integrate
2026 the assembled program into a runnable file, and (optionally) symbolic
2027 information for the debugger.
2029 @c link above to some info file(s) like the description of a.out.
2030 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2033 @section Error and Warning Messages
2035 @c man begin DESCRIPTION
2037 @cindex error messages
2038 @cindex warning messages
2039 @cindex messages from assembler
2040 @command{@value{AS}} may write warnings and error messages to the standard error
2041 file (usually your terminal). This should not happen when a compiler
2042 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2043 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2044 grave problem that stops the assembly.
2048 @cindex format of warning messages
2049 Warning messages have the format
2052 file_name:@b{NNN}:Warning Message Text
2056 @cindex file names and line numbers, in warnings/errors
2057 (where @b{NNN} is a line number). If both a logical file name
2058 (@pxref{File,,@code{.file}}) and a logical line number
2060 (@pxref{Line,,@code{.line}})
2062 have been given then they will be used, otherwise the file name and line number
2063 in the current assembler source file will be used. The message text is
2064 intended to be self explanatory (in the grand Unix tradition).
2066 Note the file name must be set via the logical version of the @code{.file}
2067 directive, not the DWARF2 version of the @code{.file} directive. For example:
2071 error_assembler_source
2077 produces this output:
2081 asm.s:2: Error: no such instruction: `error_assembler_source'
2082 foo.c:31: Error: no such instruction: `error_c_source'
2085 @cindex format of error messages
2086 Error messages have the format
2089 file_name:@b{NNN}:FATAL:Error Message Text
2092 The file name and line number are derived as for warning
2093 messages. The actual message text may be rather less explanatory
2094 because many of them aren't supposed to happen.
2097 @chapter Command-Line Options
2099 @cindex options, all versions of assembler
2100 This chapter describes command-line options available in @emph{all}
2101 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2102 for options specific
2104 to the @value{TARGET} target.
2107 to particular machine architectures.
2110 @c man begin DESCRIPTION
2112 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2113 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2114 The assembler arguments must be separated from each other (and the @samp{-Wa})
2115 by commas. For example:
2118 gcc -c -g -O -Wa,-alh,-L file.c
2122 This passes two options to the assembler: @samp{-alh} (emit a listing to
2123 standard output with high-level and assembly source) and @samp{-L} (retain
2124 local symbols in the symbol table).
2126 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2127 command-line options are automatically passed to the assembler by the compiler.
2128 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2129 precisely what options it passes to each compilation pass, including the
2135 * a:: -a[cdghlns] enable listings
2136 * alternate:: --alternate enable alternate macro syntax
2137 * D:: -D for compatibility
2138 * f:: -f to work faster
2139 * I:: -I for .include search path
2140 @ifclear DIFF-TBL-KLUGE
2141 * K:: -K for compatibility
2143 @ifset DIFF-TBL-KLUGE
2144 * K:: -K for difference tables
2147 * L:: -L to retain local symbols
2148 * listing:: --listing-XXX to configure listing output
2149 * M:: -M or --mri to assemble in MRI compatibility mode
2150 * MD:: --MD for dependency tracking
2151 * o:: -o to name the object file
2152 * R:: -R to join data and text sections
2153 * statistics:: --statistics to see statistics about assembly
2154 * traditional-format:: --traditional-format for compatible output
2155 * v:: -v to announce version
2156 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2157 * Z:: -Z to make object file even after errors
2161 @section Enable Listings: @option{-a[cdghlns]}
2171 @cindex listings, enabling
2172 @cindex assembly listings, enabling
2174 These options enable listing output from the assembler. By itself,
2175 @samp{-a} requests high-level, assembly, and symbols listing.
2176 You can use other letters to select specific options for the list:
2177 @samp{-ah} requests a high-level language listing,
2178 @samp{-al} requests an output-program assembly listing, and
2179 @samp{-as} requests a symbol table listing.
2180 High-level listings require that a compiler debugging option like
2181 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2184 Use the @samp{-ag} option to print a first section with general assembly
2185 information, like @value{AS} version, switches passed, or time stamp.
2187 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2188 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2189 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2190 omitted from the listing.
2192 Use the @samp{-ad} option to omit debugging directives from the
2195 Once you have specified one of these options, you can further control
2196 listing output and its appearance using the directives @code{.list},
2197 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2199 The @samp{-an} option turns off all forms processing.
2200 If you do not request listing output with one of the @samp{-a} options, the
2201 listing-control directives have no effect.
2203 The letters after @samp{-a} may be combined into one option,
2204 @emph{e.g.}, @samp{-aln}.
2206 Note if the assembler source is coming from the standard input (e.g.,
2208 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2209 is being used) then the listing will not contain any comments or preprocessor
2210 directives. This is because the listing code buffers input source lines from
2211 stdin only after they have been preprocessed by the assembler. This reduces
2212 memory usage and makes the code more efficient.
2215 @section @option{--alternate}
2218 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2221 @section @option{-D}
2224 This option has no effect whatsoever, but it is accepted to make it more
2225 likely that scripts written for other assemblers also work with
2226 @command{@value{AS}}.
2229 @section Work Faster: @option{-f}
2232 @cindex trusted compiler
2233 @cindex faster processing (@option{-f})
2234 @samp{-f} should only be used when assembling programs written by a
2235 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2236 and comment preprocessing on
2237 the input file(s) before assembling them. @xref{Preprocessing,
2241 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2242 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2247 @section @code{.include} Search Path: @option{-I} @var{path}
2249 @kindex -I @var{path}
2250 @cindex paths for @code{.include}
2251 @cindex search path for @code{.include}
2252 @cindex @code{include} directive search path
2253 Use this option to add a @var{path} to the list of directories
2254 @command{@value{AS}} searches for files specified in @code{.include}
2255 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2256 many times as necessary to include a variety of paths. The current
2257 working directory is always searched first; after that, @command{@value{AS}}
2258 searches any @samp{-I} directories in the same order as they were
2259 specified (left to right) on the command line.
2262 @section Difference Tables: @option{-K}
2265 @ifclear DIFF-TBL-KLUGE
2266 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2267 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2268 where it can be used to warn when the assembler alters the machine code
2269 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2270 family does not have the addressing limitations that sometimes lead to this
2271 alteration on other platforms.
2274 @ifset DIFF-TBL-KLUGE
2275 @cindex difference tables, warning
2276 @cindex warning for altered difference tables
2277 @command{@value{AS}} sometimes alters the code emitted for directives of the
2278 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2279 You can use the @samp{-K} option if you want a warning issued when this
2284 @section Include Local Symbols: @option{-L}
2287 @cindex local symbols, retaining in output
2288 Symbols beginning with system-specific local label prefixes, typically
2289 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2290 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2291 such symbols when debugging, because they are intended for the use of
2292 programs (like compilers) that compose assembler programs, not for your
2293 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2294 such symbols, so you do not normally debug with them.
2296 This option tells @command{@value{AS}} to retain those local symbols
2297 in the object file. Usually if you do this you also tell the linker
2298 @code{@value{LD}} to preserve those symbols.
2301 @section Configuring listing output: @option{--listing}
2303 The listing feature of the assembler can be enabled via the command line switch
2304 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2305 hex dump of the corresponding locations in the output object file, and displays
2306 them as a listing file. The format of this listing can be controlled by
2307 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2308 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2309 @code{.psize} (@pxref{Psize}), and
2310 @code{.eject} (@pxref{Eject}) and also by the following switches:
2313 @item --listing-lhs-width=@samp{number}
2314 @kindex --listing-lhs-width
2315 @cindex Width of first line disassembly output
2316 Sets the maximum width, in words, of the first line of the hex byte dump. This
2317 dump appears on the left hand side of the listing output.
2319 @item --listing-lhs-width2=@samp{number}
2320 @kindex --listing-lhs-width2
2321 @cindex Width of continuation lines of disassembly output
2322 Sets the maximum width, in words, of any further lines of the hex byte dump for
2323 a given input source line. If this value is not specified, it defaults to being
2324 the same as the value specified for @samp{--listing-lhs-width}. If neither
2325 switch is used the default is to one.
2327 @item --listing-rhs-width=@samp{number}
2328 @kindex --listing-rhs-width
2329 @cindex Width of source line output
2330 Sets the maximum width, in characters, of the source line that is displayed
2331 alongside the hex dump. The default value for this parameter is 100. The
2332 source line is displayed on the right hand side of the listing output.
2334 @item --listing-cont-lines=@samp{number}
2335 @kindex --listing-cont-lines
2336 @cindex Maximum number of continuation lines
2337 Sets the maximum number of continuation lines of hex dump that will be
2338 displayed for a given single line of source input. The default value is 4.
2342 @section Assemble in MRI Compatibility Mode: @option{-M}
2345 @cindex MRI compatibility mode
2346 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2347 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2348 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2349 configured target) assembler from Microtec Research. The exact nature of the
2350 MRI syntax will not be documented here; see the MRI manuals for more
2351 information. Note in particular that the handling of macros and macro
2352 arguments is somewhat different. The purpose of this option is to permit
2353 assembling existing MRI assembler code using @command{@value{AS}}.
2355 The MRI compatibility is not complete. Certain operations of the MRI assembler
2356 depend upon its object file format, and can not be supported using other object
2357 file formats. Supporting these would require enhancing each object file format
2358 individually. These are:
2361 @item global symbols in common section
2363 The m68k MRI assembler supports common sections which are merged by the linker.
2364 Other object file formats do not support this. @command{@value{AS}} handles
2365 common sections by treating them as a single common symbol. It permits local
2366 symbols to be defined within a common section, but it can not support global
2367 symbols, since it has no way to describe them.
2369 @item complex relocations
2371 The MRI assemblers support relocations against a negated section address, and
2372 relocations which combine the start addresses of two or more sections. These
2373 are not support by other object file formats.
2375 @item @code{END} pseudo-op specifying start address
2377 The MRI @code{END} pseudo-op permits the specification of a start address.
2378 This is not supported by other object file formats. The start address may
2379 instead be specified using the @option{-e} option to the linker, or in a linker
2382 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2384 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2385 name to the output file. This is not supported by other object file formats.
2387 @item @code{ORG} pseudo-op
2389 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2390 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2391 which changes the location within the current section. Absolute sections are
2392 not supported by other object file formats. The address of a section may be
2393 assigned within a linker script.
2396 There are some other features of the MRI assembler which are not supported by
2397 @command{@value{AS}}, typically either because they are difficult or because they
2398 seem of little consequence. Some of these may be supported in future releases.
2402 @item EBCDIC strings
2404 EBCDIC strings are not supported.
2406 @item packed binary coded decimal
2408 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2409 and @code{DCB.P} pseudo-ops are not supported.
2411 @item @code{FEQU} pseudo-op
2413 The m68k @code{FEQU} pseudo-op is not supported.
2415 @item @code{NOOBJ} pseudo-op
2417 The m68k @code{NOOBJ} pseudo-op is not supported.
2419 @item @code{OPT} branch control options
2421 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2422 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2423 relaxes all branches, whether forward or backward, to an appropriate size, so
2424 these options serve no purpose.
2426 @item @code{OPT} list control options
2428 The following m68k @code{OPT} list control options are ignored: @code{C},
2429 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2430 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2432 @item other @code{OPT} options
2434 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2435 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2437 @item @code{OPT} @code{D} option is default
2439 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2440 @code{OPT NOD} may be used to turn it off.
2442 @item @code{XREF} pseudo-op.
2444 The m68k @code{XREF} pseudo-op is ignored.
2446 @item @code{.debug} pseudo-op
2448 The i960 @code{.debug} pseudo-op is not supported.
2450 @item @code{.extended} pseudo-op
2452 The i960 @code{.extended} pseudo-op is not supported.
2454 @item @code{.list} pseudo-op.
2456 The various options of the i960 @code{.list} pseudo-op are not supported.
2458 @item @code{.optimize} pseudo-op
2460 The i960 @code{.optimize} pseudo-op is not supported.
2462 @item @code{.output} pseudo-op
2464 The i960 @code{.output} pseudo-op is not supported.
2466 @item @code{.setreal} pseudo-op
2468 The i960 @code{.setreal} pseudo-op is not supported.
2473 @section Dependency Tracking: @option{--MD}
2476 @cindex dependency tracking
2479 @command{@value{AS}} can generate a dependency file for the file it creates. This
2480 file consists of a single rule suitable for @code{make} describing the
2481 dependencies of the main source file.
2483 The rule is written to the file named in its argument.
2485 This feature is used in the automatic updating of makefiles.
2488 @section Name the Object File: @option{-o}
2491 @cindex naming object file
2492 @cindex object file name
2493 There is always one object file output when you run @command{@value{AS}}. By
2494 default it has the name
2497 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2511 You use this option (which takes exactly one filename) to give the
2512 object file a different name.
2514 Whatever the object file is called, @command{@value{AS}} overwrites any
2515 existing file of the same name.
2518 @section Join Data and Text Sections: @option{-R}
2521 @cindex data and text sections, joining
2522 @cindex text and data sections, joining
2523 @cindex joining text and data sections
2524 @cindex merging text and data sections
2525 @option{-R} tells @command{@value{AS}} to write the object file as if all
2526 data-section data lives in the text section. This is only done at
2527 the very last moment: your binary data are the same, but data
2528 section parts are relocated differently. The data section part of
2529 your object file is zero bytes long because all its bytes are
2530 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2532 When you specify @option{-R} it would be possible to generate shorter
2533 address displacements (because we do not have to cross between text and
2534 data section). We refrain from doing this simply for compatibility with
2535 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2538 When @command{@value{AS}} is configured for COFF or ELF output,
2539 this option is only useful if you use sections named @samp{.text} and
2544 @option{-R} is not supported for any of the HPPA targets. Using
2545 @option{-R} generates a warning from @command{@value{AS}}.
2549 @section Display Assembly Statistics: @option{--statistics}
2551 @kindex --statistics
2552 @cindex statistics, about assembly
2553 @cindex time, total for assembly
2554 @cindex space used, maximum for assembly
2555 Use @samp{--statistics} to display two statistics about the resources used by
2556 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2557 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2560 @node traditional-format
2561 @section Compatible Output: @option{--traditional-format}
2563 @kindex --traditional-format
2564 For some targets, the output of @command{@value{AS}} is different in some ways
2565 from the output of some existing assembler. This switch requests
2566 @command{@value{AS}} to use the traditional format instead.
2568 For example, it disables the exception frame optimizations which
2569 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2572 @section Announce Version: @option{-v}
2576 @cindex assembler version
2577 @cindex version of assembler
2578 You can find out what version of as is running by including the
2579 option @samp{-v} (which you can also spell as @samp{-version}) on the
2583 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2585 @command{@value{AS}} should never give a warning or error message when
2586 assembling compiler output. But programs written by people often
2587 cause @command{@value{AS}} to give a warning that a particular assumption was
2588 made. All such warnings are directed to the standard error file.
2592 @cindex suppressing warnings
2593 @cindex warnings, suppressing
2594 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2595 This only affects the warning messages: it does not change any particular of
2596 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2599 @kindex --fatal-warnings
2600 @cindex errors, caused by warnings
2601 @cindex warnings, causing error
2602 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2603 files that generate warnings to be in error.
2606 @cindex warnings, switching on
2607 You can switch these options off again by specifying @option{--warn}, which
2608 causes warnings to be output as usual.
2611 @section Generate Object File in Spite of Errors: @option{-Z}
2612 @cindex object file, after errors
2613 @cindex errors, continuing after
2614 After an error message, @command{@value{AS}} normally produces no output. If for
2615 some reason you are interested in object file output even after
2616 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2617 option. If there are any errors, @command{@value{AS}} continues anyways, and
2618 writes an object file after a final warning message of the form @samp{@var{n}
2619 errors, @var{m} warnings, generating bad object file.}
2624 @cindex machine-independent syntax
2625 @cindex syntax, machine-independent
2626 This chapter describes the machine-independent syntax allowed in a
2627 source file. @command{@value{AS}} syntax is similar to what many other
2628 assemblers use; it is inspired by the BSD 4.2
2633 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2637 * Preprocessing:: Preprocessing
2638 * Whitespace:: Whitespace
2639 * Comments:: Comments
2640 * Symbol Intro:: Symbols
2641 * Statements:: Statements
2642 * Constants:: Constants
2646 @section Preprocessing
2648 @cindex preprocessing
2649 The @command{@value{AS}} internal preprocessor:
2651 @cindex whitespace, removed by preprocessor
2653 adjusts and removes extra whitespace. It leaves one space or tab before
2654 the keywords on a line, and turns any other whitespace on the line into
2657 @cindex comments, removed by preprocessor
2659 removes all comments, replacing them with a single space, or an
2660 appropriate number of newlines.
2662 @cindex constants, converted by preprocessor
2664 converts character constants into the appropriate numeric values.
2667 It does not do macro processing, include file handling, or
2668 anything else you may get from your C compiler's preprocessor. You can
2669 do include file processing with the @code{.include} directive
2670 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2671 to get other ``CPP'' style preprocessing by giving the input file a
2672 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2673 Output, gcc.info, Using GNU CC}.
2675 Excess whitespace, comments, and character constants
2676 cannot be used in the portions of the input text that are not
2679 @cindex turning preprocessing on and off
2680 @cindex preprocessing, turning on and off
2683 If the first line of an input file is @code{#NO_APP} or if you use the
2684 @samp{-f} option, whitespace and comments are not removed from the input file.
2685 Within an input file, you can ask for whitespace and comment removal in
2686 specific portions of the by putting a line that says @code{#APP} before the
2687 text that may contain whitespace or comments, and putting a line that says
2688 @code{#NO_APP} after this text. This feature is mainly intend to support
2689 @code{asm} statements in compilers whose output is otherwise free of comments
2696 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2697 Whitespace is used to separate symbols, and to make programs neater for
2698 people to read. Unless within character constants
2699 (@pxref{Characters,,Character Constants}), any whitespace means the same
2700 as exactly one space.
2706 There are two ways of rendering comments to @command{@value{AS}}. In both
2707 cases the comment is equivalent to one space.
2709 Anything from @samp{/*} through the next @samp{*/} is a comment.
2710 This means you may not nest these comments.
2714 The only way to include a newline ('\n') in a comment
2715 is to use this sort of comment.
2718 /* This sort of comment does not nest. */
2721 @cindex line comment character
2722 Anything from a @dfn{line comment} character up to the next newline is
2723 considered a comment and is ignored. The line comment character is target
2724 specific, and some targets multiple comment characters. Some targets also have
2725 line comment characters that only work if they are the first character on a
2726 line. Some targets use a sequence of two characters to introduce a line
2727 comment. Some targets can also change their line comment characters depending
2728 upon command line options that have been used. For more details see the
2729 @emph{Syntax} section in the documentation for individual targets.
2731 If the line comment character is the hash sign (@samp{#}) then it still has the
2732 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2733 to specify logical line numbers:
2736 @cindex lines starting with @code{#}
2737 @cindex logical line numbers
2738 To be compatible with past assemblers, lines that begin with @samp{#} have a
2739 special interpretation. Following the @samp{#} should be an absolute
2740 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2741 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2742 new logical file name. The rest of the line, if any, should be whitespace.
2744 If the first non-whitespace characters on the line are not numeric,
2745 the line is ignored. (Just like a comment.)
2748 # This is an ordinary comment.
2749 # 42-6 "new_file_name" # New logical file name
2750 # This is logical line # 36.
2752 This feature is deprecated, and may disappear from future versions
2753 of @command{@value{AS}}.
2758 @cindex characters used in symbols
2759 @ifclear SPECIAL-SYMS
2760 A @dfn{symbol} is one or more characters chosen from the set of all
2761 letters (both upper and lower case), digits and the three characters
2767 A @dfn{symbol} is one or more characters chosen from the set of all
2768 letters (both upper and lower case), digits and the three characters
2769 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2775 On most machines, you can also use @code{$} in symbol names; exceptions
2776 are noted in @ref{Machine Dependencies}.
2778 No symbol may begin with a digit. Case is significant.
2779 There is no length limit; all characters are significant. Multibyte characters
2780 are supported. Symbols are delimited by characters not in that set, or by the
2781 beginning of a file (since the source program must end with a newline, the end
2782 of a file is not a possible symbol delimiter). @xref{Symbols}.
2784 Symbol names may also be enclosed in double quote @code{"} characters. In such
2785 cases any characters are allowed, except for the NUL character. If a double
2786 quote character is to be included in the symbol name it must be preceeded by a
2787 backslash @code{\} character.
2788 @cindex length of symbols
2793 @cindex statements, structure of
2794 @cindex line separator character
2795 @cindex statement separator character
2797 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2798 @dfn{line separator character}. The line separator character is target
2799 specific and described in the @emph{Syntax} section of each
2800 target's documentation. Not all targets support a line separator character.
2801 The newline or line separator character is considered to be part of the
2802 preceding statement. Newlines and separators within character constants are an
2803 exception: they do not end statements.
2805 @cindex newline, required at file end
2806 @cindex EOF, newline must precede
2807 It is an error to end any statement with end-of-file: the last
2808 character of any input file should be a newline.@refill
2810 An empty statement is allowed, and may include whitespace. It is ignored.
2812 @cindex instructions and directives
2813 @cindex directives and instructions
2814 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2815 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2817 A statement begins with zero or more labels, optionally followed by a
2818 key symbol which determines what kind of statement it is. The key
2819 symbol determines the syntax of the rest of the statement. If the
2820 symbol begins with a dot @samp{.} then the statement is an assembler
2821 directive: typically valid for any computer. If the symbol begins with
2822 a letter the statement is an assembly language @dfn{instruction}: it
2823 assembles into a machine language instruction.
2825 Different versions of @command{@value{AS}} for different computers
2826 recognize different instructions. In fact, the same symbol may
2827 represent a different instruction in a different computer's assembly
2831 @cindex @code{:} (label)
2832 @cindex label (@code{:})
2833 A label is a symbol immediately followed by a colon (@code{:}).
2834 Whitespace before a label or after a colon is permitted, but you may not
2835 have whitespace between a label's symbol and its colon. @xref{Labels}.
2838 For HPPA targets, labels need not be immediately followed by a colon, but
2839 the definition of a label must begin in column zero. This also implies that
2840 only one label may be defined on each line.
2844 label: .directive followed by something
2845 another_label: # This is an empty statement.
2846 instruction operand_1, operand_2, @dots{}
2853 A constant is a number, written so that its value is known by
2854 inspection, without knowing any context. Like this:
2857 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2858 .ascii "Ring the bell\7" # A string constant.
2859 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2860 .float 0f-314159265358979323846264338327\
2861 95028841971.693993751E-40 # - pi, a flonum.
2866 * Characters:: Character Constants
2867 * Numbers:: Number Constants
2871 @subsection Character Constants
2873 @cindex character constants
2874 @cindex constants, character
2875 There are two kinds of character constants. A @dfn{character} stands
2876 for one character in one byte and its value may be used in
2877 numeric expressions. String constants (properly called string
2878 @emph{literals}) are potentially many bytes and their values may not be
2879 used in arithmetic expressions.
2883 * Chars:: Characters
2887 @subsubsection Strings
2889 @cindex string constants
2890 @cindex constants, string
2891 A @dfn{string} is written between double-quotes. It may contain
2892 double-quotes or null characters. The way to get special characters
2893 into a string is to @dfn{escape} these characters: precede them with
2894 a backslash @samp{\} character. For example @samp{\\} represents
2895 one backslash: the first @code{\} is an escape which tells
2896 @command{@value{AS}} to interpret the second character literally as a backslash
2897 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2898 escape character). The complete list of escapes follows.
2900 @cindex escape codes, character
2901 @cindex character escape codes
2902 @c NOTE: Cindex entries must not start with a backlash character.
2903 @c NOTE: This confuses the pdf2texi script when it is creating the
2904 @c NOTE: index based upon the first character and so it generates:
2905 @c NOTE: \initial {\\}
2906 @c NOTE: which then results in the error message:
2907 @c NOTE: Argument of \\ has an extra }.
2908 @c NOTE: So in the index entries below a space character has been
2909 @c NOTE: prepended to avoid this problem.
2912 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2914 @cindex @code{ \b} (backspace character)
2915 @cindex backspace (@code{\b})
2917 Mnemonic for backspace; for ASCII this is octal code 010.
2920 @c Mnemonic for EOText; for ASCII this is octal code 004.
2922 @cindex @code{ \f} (formfeed character)
2923 @cindex formfeed (@code{\f})
2925 Mnemonic for FormFeed; for ASCII this is octal code 014.
2927 @cindex @code{ \n} (newline character)
2928 @cindex newline (@code{\n})
2930 Mnemonic for newline; for ASCII this is octal code 012.
2933 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2935 @cindex @code{ \r} (carriage return character)
2936 @cindex carriage return (@code{backslash-r})
2938 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2941 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2942 @c other assemblers.
2944 @cindex @code{ \t} (tab)
2945 @cindex tab (@code{\t})
2947 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2950 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2951 @c @item \x @var{digit} @var{digit} @var{digit}
2952 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2954 @cindex @code{ \@var{ddd}} (octal character code)
2955 @cindex octal character code (@code{\@var{ddd}})
2956 @item \ @var{digit} @var{digit} @var{digit}
2957 An octal character code. The numeric code is 3 octal digits.
2958 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2959 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2961 @cindex @code{ \@var{xd...}} (hex character code)
2962 @cindex hex character code (@code{\@var{xd...}})
2963 @item \@code{x} @var{hex-digits...}
2964 A hex character code. All trailing hex digits are combined. Either upper or
2965 lower case @code{x} works.
2967 @cindex @code{ \\} (@samp{\} character)
2968 @cindex backslash (@code{\\})
2970 Represents one @samp{\} character.
2973 @c Represents one @samp{'} (accent acute) character.
2974 @c This is needed in single character literals
2975 @c (@xref{Characters,,Character Constants}.) to represent
2978 @cindex @code{ \"} (doublequote character)
2979 @cindex doublequote (@code{\"})
2981 Represents one @samp{"} character. Needed in strings to represent
2982 this character, because an unescaped @samp{"} would end the string.
2984 @item \ @var{anything-else}
2985 Any other character when escaped by @kbd{\} gives a warning, but
2986 assembles as if the @samp{\} was not present. The idea is that if
2987 you used an escape sequence you clearly didn't want the literal
2988 interpretation of the following character. However @command{@value{AS}} has no
2989 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2990 code and warns you of the fact.
2993 Which characters are escapable, and what those escapes represent,
2994 varies widely among assemblers. The current set is what we think
2995 the BSD 4.2 assembler recognizes, and is a subset of what most C
2996 compilers recognize. If you are in doubt, do not use an escape
3000 @subsubsection Characters
3002 @cindex single character constant
3003 @cindex character, single
3004 @cindex constant, single character
3005 A single character may be written as a single quote immediately
3006 followed by that character. The same escapes apply to characters as
3007 to strings. So if you want to write the character backslash, you
3008 must write @kbd{'\\} where the first @code{\} escapes the second
3009 @code{\}. As you can see, the quote is an acute accent, not a
3010 grave accent. A newline
3012 @ifclear abnormal-separator
3013 (or semicolon @samp{;})
3015 @ifset abnormal-separator
3017 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3022 immediately following an acute accent is taken as a literal character
3023 and does not count as the end of a statement. The value of a character
3024 constant in a numeric expression is the machine's byte-wide code for
3025 that character. @command{@value{AS}} assumes your character code is ASCII:
3026 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3029 @subsection Number Constants
3031 @cindex constants, number
3032 @cindex number constants
3033 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3034 are stored in the target machine. @emph{Integers} are numbers that
3035 would fit into an @code{int} in the C language. @emph{Bignums} are
3036 integers, but they are stored in more than 32 bits. @emph{Flonums}
3037 are floating point numbers, described below.
3040 * Integers:: Integers
3045 * Bit Fields:: Bit Fields
3051 @subsubsection Integers
3053 @cindex constants, integer
3055 @cindex binary integers
3056 @cindex integers, binary
3057 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3058 the binary digits @samp{01}.
3060 @cindex octal integers
3061 @cindex integers, octal
3062 An octal integer is @samp{0} followed by zero or more of the octal
3063 digits (@samp{01234567}).
3065 @cindex decimal integers
3066 @cindex integers, decimal
3067 A decimal integer starts with a non-zero digit followed by zero or
3068 more digits (@samp{0123456789}).
3070 @cindex hexadecimal integers
3071 @cindex integers, hexadecimal
3072 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3073 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3075 Integers have the usual values. To denote a negative integer, use
3076 the prefix operator @samp{-} discussed under expressions
3077 (@pxref{Prefix Ops,,Prefix Operators}).
3080 @subsubsection Bignums
3083 @cindex constants, bignum
3084 A @dfn{bignum} has the same syntax and semantics as an integer
3085 except that the number (or its negative) takes more than 32 bits to
3086 represent in binary. The distinction is made because in some places
3087 integers are permitted while bignums are not.
3090 @subsubsection Flonums
3092 @cindex floating point numbers
3093 @cindex constants, floating point
3095 @cindex precision, floating point
3096 A @dfn{flonum} represents a floating point number. The translation is
3097 indirect: a decimal floating point number from the text is converted by
3098 @command{@value{AS}} to a generic binary floating point number of more than
3099 sufficient precision. This generic floating point number is converted
3100 to a particular computer's floating point format (or formats) by a
3101 portion of @command{@value{AS}} specialized to that computer.
3103 A flonum is written by writing (in order)
3108 (@samp{0} is optional on the HPPA.)
3112 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3114 @kbd{e} is recommended. Case is not important.
3116 @c FIXME: verify if flonum syntax really this vague for most cases
3117 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3118 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3121 On the H8/300, Renesas / SuperH SH,
3122 and AMD 29K architectures, the letter must be
3123 one of the letters @samp{DFPRSX} (in upper or lower case).
3125 On the ARC, the letter must be one of the letters @samp{DFRS}
3126 (in upper or lower case).
3128 On the Intel 960 architecture, the letter must be
3129 one of the letters @samp{DFT} (in upper or lower case).
3131 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3135 One of the letters @samp{DFRS} (in upper or lower case).
3138 One of the letters @samp{DFPRSX} (in upper or lower case).
3141 The letter @samp{E} (upper case only).
3144 One of the letters @samp{DFT} (in upper or lower case).
3149 An optional sign: either @samp{+} or @samp{-}.
3152 An optional @dfn{integer part}: zero or more decimal digits.
3155 An optional @dfn{fractional part}: @samp{.} followed by zero
3156 or more decimal digits.
3159 An optional exponent, consisting of:
3163 An @samp{E} or @samp{e}.
3164 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3165 @c principle this can perfectly well be different on different targets.
3167 Optional sign: either @samp{+} or @samp{-}.
3169 One or more decimal digits.
3174 At least one of the integer part or the fractional part must be
3175 present. The floating point number has the usual base-10 value.
3177 @command{@value{AS}} does all processing using integers. Flonums are computed
3178 independently of any floating point hardware in the computer running
3179 @command{@value{AS}}.
3183 @c Bit fields are written as a general facility but are also controlled
3184 @c by a conditional-compilation flag---which is as of now (21mar91)
3185 @c turned on only by the i960 config of GAS.
3187 @subsubsection Bit Fields
3190 @cindex constants, bit field
3191 You can also define numeric constants as @dfn{bit fields}.
3192 Specify two numbers separated by a colon---
3194 @var{mask}:@var{value}
3197 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3200 The resulting number is then packed
3202 @c this conditional paren in case bit fields turned on elsewhere than 960
3203 (in host-dependent byte order)
3205 into a field whose width depends on which assembler directive has the
3206 bit-field as its argument. Overflow (a result from the bitwise and
3207 requiring more binary digits to represent) is not an error; instead,
3208 more constants are generated, of the specified width, beginning with the
3209 least significant digits.@refill
3211 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3212 @code{.short}, and @code{.word} accept bit-field arguments.
3217 @chapter Sections and Relocation
3222 * Secs Background:: Background
3223 * Ld Sections:: Linker Sections
3224 * As Sections:: Assembler Internal Sections
3225 * Sub-Sections:: Sub-Sections
3229 @node Secs Background
3232 Roughly, a section is a range of addresses, with no gaps; all data
3233 ``in'' those addresses is treated the same for some particular purpose.
3234 For example there may be a ``read only'' section.
3236 @cindex linker, and assembler
3237 @cindex assembler, and linker
3238 The linker @code{@value{LD}} reads many object files (partial programs) and
3239 combines their contents to form a runnable program. When @command{@value{AS}}
3240 emits an object file, the partial program is assumed to start at address 0.
3241 @code{@value{LD}} assigns the final addresses for the partial program, so that
3242 different partial programs do not overlap. This is actually an
3243 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3246 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3247 addresses. These blocks slide to their run-time addresses as rigid
3248 units; their length does not change and neither does the order of bytes
3249 within them. Such a rigid unit is called a @emph{section}. Assigning
3250 run-time addresses to sections is called @dfn{relocation}. It includes
3251 the task of adjusting mentions of object-file addresses so they refer to
3252 the proper run-time addresses.
3254 For the H8/300, and for the Renesas / SuperH SH,
3255 @command{@value{AS}} pads sections if needed to
3256 ensure they end on a word (sixteen bit) boundary.
3259 @cindex standard assembler sections
3260 An object file written by @command{@value{AS}} has at least three sections, any
3261 of which may be empty. These are named @dfn{text}, @dfn{data} and
3266 When it generates COFF or ELF output,
3268 @command{@value{AS}} can also generate whatever other named sections you specify
3269 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3270 If you do not use any directives that place output in the @samp{.text}
3271 or @samp{.data} sections, these sections still exist, but are empty.
3276 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3278 @command{@value{AS}} can also generate whatever other named sections you
3279 specify using the @samp{.space} and @samp{.subspace} directives. See
3280 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3281 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3282 assembler directives.
3285 Additionally, @command{@value{AS}} uses different names for the standard
3286 text, data, and bss sections when generating SOM output. Program text
3287 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3288 BSS into @samp{$BSS$}.
3292 Within the object file, the text section starts at address @code{0}, the
3293 data section follows, and the bss section follows the data section.
3296 When generating either SOM or ELF output files on the HPPA, the text
3297 section starts at address @code{0}, the data section at address
3298 @code{0x4000000}, and the bss section follows the data section.
3301 To let @code{@value{LD}} know which data changes when the sections are
3302 relocated, and how to change that data, @command{@value{AS}} also writes to the
3303 object file details of the relocation needed. To perform relocation
3304 @code{@value{LD}} must know, each time an address in the object
3308 Where in the object file is the beginning of this reference to
3311 How long (in bytes) is this reference?
3313 Which section does the address refer to? What is the numeric value of
3315 (@var{address}) @minus{} (@var{start-address of section})?
3318 Is the reference to an address ``Program-Counter relative''?
3321 @cindex addresses, format of
3322 @cindex section-relative addressing
3323 In fact, every address @command{@value{AS}} ever uses is expressed as
3325 (@var{section}) + (@var{offset into section})
3328 Further, most expressions @command{@value{AS}} computes have this section-relative
3331 (For some object formats, such as SOM for the HPPA, some expressions are
3332 symbol-relative instead.)
3335 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3336 @var{N} into section @var{secname}.''
3338 Apart from text, data and bss sections you need to know about the
3339 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3340 addresses in the absolute section remain unchanged. For example, address
3341 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3342 @code{@value{LD}}. Although the linker never arranges two partial programs'
3343 data sections with overlapping addresses after linking, @emph{by definition}
3344 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3345 part of a program is always the same address when the program is running as
3346 address @code{@{absolute@ 239@}} in any other part of the program.
3348 The idea of sections is extended to the @dfn{undefined} section. Any
3349 address whose section is unknown at assembly time is by definition
3350 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3351 Since numbers are always defined, the only way to generate an undefined
3352 address is to mention an undefined symbol. A reference to a named
3353 common block would be such a symbol: its value is unknown at assembly
3354 time so it has section @emph{undefined}.
3356 By analogy the word @emph{section} is used to describe groups of sections in
3357 the linked program. @code{@value{LD}} puts all partial programs' text
3358 sections in contiguous addresses in the linked program. It is
3359 customary to refer to the @emph{text section} of a program, meaning all
3360 the addresses of all partial programs' text sections. Likewise for
3361 data and bss sections.
3363 Some sections are manipulated by @code{@value{LD}}; others are invented for
3364 use of @command{@value{AS}} and have no meaning except during assembly.
3367 @section Linker Sections
3368 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3373 @cindex named sections
3374 @cindex sections, named
3375 @item named sections
3378 @cindex text section
3379 @cindex data section
3383 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3384 separate but equal sections. Anything you can say of one section is
3387 When the program is running, however, it is
3388 customary for the text section to be unalterable. The
3389 text section is often shared among processes: it contains
3390 instructions, constants and the like. The data section of a running
3391 program is usually alterable: for example, C variables would be stored
3392 in the data section.
3397 This section contains zeroed bytes when your program begins running. It
3398 is used to hold uninitialized variables or common storage. The length of
3399 each partial program's bss section is important, but because it starts
3400 out containing zeroed bytes there is no need to store explicit zero
3401 bytes in the object file. The bss section was invented to eliminate
3402 those explicit zeros from object files.
3404 @cindex absolute section
3405 @item absolute section
3406 Address 0 of this section is always ``relocated'' to runtime address 0.
3407 This is useful if you want to refer to an address that @code{@value{LD}} must
3408 not change when relocating. In this sense we speak of absolute
3409 addresses being ``unrelocatable'': they do not change during relocation.
3411 @cindex undefined section
3412 @item undefined section
3413 This ``section'' is a catch-all for address references to objects not in
3414 the preceding sections.
3415 @c FIXME: ref to some other doc on obj-file formats could go here.
3418 @cindex relocation example
3419 An idealized example of three relocatable sections follows.
3421 The example uses the traditional section names @samp{.text} and @samp{.data}.
3423 Memory addresses are on the horizontal axis.
3427 @c END TEXI2ROFF-KILL
3430 partial program # 1: |ttttt|dddd|00|
3437 partial program # 2: |TTT|DDD|000|
3440 +--+---+-----+--+----+---+-----+~~
3441 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3442 +--+---+-----+--+----+---+-----+~~
3444 addresses: 0 @dots{}
3451 \line{\it Partial program \#1: \hfil}
3452 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3453 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3455 \line{\it Partial program \#2: \hfil}
3456 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3457 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3459 \line{\it linked program: \hfil}
3460 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3461 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3462 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3463 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3465 \line{\it addresses: \hfil}
3469 @c END TEXI2ROFF-KILL
3472 @section Assembler Internal Sections
3474 @cindex internal assembler sections
3475 @cindex sections in messages, internal
3476 These sections are meant only for the internal use of @command{@value{AS}}. They
3477 have no meaning at run-time. You do not really need to know about these
3478 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3479 warning messages, so it might be helpful to have an idea of their
3480 meanings to @command{@value{AS}}. These sections are used to permit the
3481 value of every expression in your assembly language program to be a
3482 section-relative address.
3485 @cindex assembler internal logic error
3486 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3487 An internal assembler logic error has been found. This means there is a
3488 bug in the assembler.
3490 @cindex expr (internal section)
3492 The assembler stores complex expression internally as combinations of
3493 symbols. When it needs to represent an expression as a symbol, it puts
3494 it in the expr section.
3496 @c FIXME item transfer[t] vector preload
3497 @c FIXME item transfer[t] vector postload
3498 @c FIXME item register
3502 @section Sub-Sections
3504 @cindex numbered subsections
3505 @cindex grouping data
3511 fall into two sections: text and data.
3513 You may have separate groups of
3515 data in named sections
3519 data in named sections
3525 that you want to end up near to each other in the object file, even though they
3526 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3527 use @dfn{subsections} for this purpose. Within each section, there can be
3528 numbered subsections with values from 0 to 8192. Objects assembled into the
3529 same subsection go into the object file together with other objects in the same
3530 subsection. For example, a compiler might want to store constants in the text
3531 section, but might not want to have them interspersed with the program being
3532 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3533 section of code being output, and a @samp{.text 1} before each group of
3534 constants being output.
3536 Subsections are optional. If you do not use subsections, everything
3537 goes in subsection number zero.
3540 Each subsection is zero-padded up to a multiple of four bytes.
3541 (Subsections may be padded a different amount on different flavors
3542 of @command{@value{AS}}.)
3546 On the H8/300 platform, each subsection is zero-padded to a word
3547 boundary (two bytes).
3548 The same is true on the Renesas SH.
3551 @c FIXME section padding (alignment)?
3552 @c Rich Pixley says padding here depends on target obj code format; that
3553 @c doesn't seem particularly useful to say without further elaboration,
3554 @c so for now I say nothing about it. If this is a generic BFD issue,
3555 @c these paragraphs might need to vanish from this manual, and be
3556 @c discussed in BFD chapter of binutils (or some such).
3560 Subsections appear in your object file in numeric order, lowest numbered
3561 to highest. (All this to be compatible with other people's assemblers.)
3562 The object file contains no representation of subsections; @code{@value{LD}} and
3563 other programs that manipulate object files see no trace of them.
3564 They just see all your text subsections as a text section, and all your
3565 data subsections as a data section.
3567 To specify which subsection you want subsequent statements assembled
3568 into, use a numeric argument to specify it, in a @samp{.text
3569 @var{expression}} or a @samp{.data @var{expression}} statement.
3572 When generating COFF output, you
3577 can also use an extra subsection
3578 argument with arbitrary named sections: @samp{.section @var{name},
3583 When generating ELF output, you
3588 can also use the @code{.subsection} directive (@pxref{SubSection})
3589 to specify a subsection: @samp{.subsection @var{expression}}.
3591 @var{Expression} should be an absolute expression
3592 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3593 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3594 begins in @code{text 0}. For instance:
3596 .text 0 # The default subsection is text 0 anyway.
3597 .ascii "This lives in the first text subsection. *"
3599 .ascii "But this lives in the second text subsection."
3601 .ascii "This lives in the data section,"
3602 .ascii "in the first data subsection."
3604 .ascii "This lives in the first text section,"
3605 .ascii "immediately following the asterisk (*)."
3608 Each section has a @dfn{location counter} incremented by one for every byte
3609 assembled into that section. Because subsections are merely a convenience
3610 restricted to @command{@value{AS}} there is no concept of a subsection location
3611 counter. There is no way to directly manipulate a location counter---but the
3612 @code{.align} directive changes it, and any label definition captures its
3613 current value. The location counter of the section where statements are being
3614 assembled is said to be the @dfn{active} location counter.
3617 @section bss Section
3620 @cindex common variable storage
3621 The bss section is used for local common variable storage.
3622 You may allocate address space in the bss section, but you may
3623 not dictate data to load into it before your program executes. When
3624 your program starts running, all the contents of the bss
3625 section are zeroed bytes.
3627 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3628 @ref{Lcomm,,@code{.lcomm}}.
3630 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3631 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3634 When assembling for a target which supports multiple sections, such as ELF or
3635 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3636 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3637 section. Typically the section will only contain symbol definitions and
3638 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3645 Symbols are a central concept: the programmer uses symbols to name
3646 things, the linker uses symbols to link, and the debugger uses symbols
3650 @cindex debuggers, and symbol order
3651 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3652 the same order they were declared. This may break some debuggers.
3657 * Setting Symbols:: Giving Symbols Other Values
3658 * Symbol Names:: Symbol Names
3659 * Dot:: The Special Dot Symbol
3660 * Symbol Attributes:: Symbol Attributes
3667 A @dfn{label} is written as a symbol immediately followed by a colon
3668 @samp{:}. The symbol then represents the current value of the
3669 active location counter, and is, for example, a suitable instruction
3670 operand. You are warned if you use the same symbol to represent two
3671 different locations: the first definition overrides any other
3675 On the HPPA, the usual form for a label need not be immediately followed by a
3676 colon, but instead must start in column zero. Only one label may be defined on
3677 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3678 provides a special directive @code{.label} for defining labels more flexibly.
3681 @node Setting Symbols
3682 @section Giving Symbols Other Values
3684 @cindex assigning values to symbols
3685 @cindex symbol values, assigning
3686 A symbol can be given an arbitrary value by writing a symbol, followed
3687 by an equals sign @samp{=}, followed by an expression
3688 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3689 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3690 equals sign @samp{=}@samp{=} here represents an equivalent of the
3691 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3694 Blackfin does not support symbol assignment with @samp{=}.
3698 @section Symbol Names
3700 @cindex symbol names
3701 @cindex names, symbol
3702 @ifclear SPECIAL-SYMS
3703 Symbol names begin with a letter or with one of @samp{._}. On most
3704 machines, you can also use @code{$} in symbol names; exceptions are
3705 noted in @ref{Machine Dependencies}. That character may be followed by any
3706 string of digits, letters, dollar signs (unless otherwise noted for a
3707 particular target machine), and underscores.
3711 Symbol names begin with a letter or with one of @samp{._}. On the
3712 Renesas SH you can also use @code{$} in symbol names. That
3713 character may be followed by any string of digits, letters, dollar signs (save
3714 on the H8/300), and underscores.
3718 Case of letters is significant: @code{foo} is a different symbol name
3721 Symbol names do not start with a digit. An exception to this rule is made for
3722 Local Labels. See below.
3724 Multibyte characters are supported. To generate a symbol name containing
3725 multibyte characters enclose it within double quotes and use escape codes. cf
3726 @xref{Strings}. Generating a multibyte symbol name from a label is not
3727 currently supported.
3729 Each symbol has exactly one name. Each name in an assembly language program
3730 refers to exactly one symbol. You may use that symbol name any number of times
3733 @subheading Local Symbol Names
3735 @cindex local symbol names
3736 @cindex symbol names, local
3737 A local symbol is any symbol beginning with certain local label prefixes.
3738 By default, the local label prefix is @samp{.L} for ELF systems or
3739 @samp{L} for traditional a.out systems, but each target may have its own
3740 set of local label prefixes.
3742 On the HPPA local symbols begin with @samp{L$}.
3745 Local symbols are defined and used within the assembler, but they are
3746 normally not saved in object files. Thus, they are not visible when debugging.
3747 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3748 to retain the local symbols in the object files.
3750 @subheading Local Labels
3752 @cindex local labels
3753 @cindex temporary symbol names
3754 @cindex symbol names, temporary
3755 Local labels are different from local symbols. Local labels help compilers and
3756 programmers use names temporarily. They create symbols which are guaranteed to
3757 be unique over the entire scope of the input source code and which can be
3758 referred to by a simple notation. To define a local label, write a label of
3759 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3760 To refer to the most recent previous definition of that label write
3761 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3762 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3763 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3765 There is no restriction on how you can use these labels, and you can reuse them
3766 too. So that it is possible to repeatedly define the same local label (using
3767 the same number @samp{@b{N}}), although you can only refer to the most recently
3768 defined local label of that number (for a backwards reference) or the next
3769 definition of a specific local label for a forward reference. It is also worth
3770 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3771 implemented in a slightly more efficient manner than the others.
3782 Which is the equivalent of:
3785 label_1: branch label_3
3786 label_2: branch label_1
3787 label_3: branch label_4
3788 label_4: branch label_3
3791 Local label names are only a notational device. They are immediately
3792 transformed into more conventional symbol names before the assembler uses them.
3793 The symbol names are stored in the symbol table, appear in error messages, and
3794 are optionally emitted to the object file. The names are constructed using
3798 @item @emph{local label prefix}
3799 All local symbols begin with the system-specific local label prefix.
3800 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3801 that start with the local label prefix. These labels are
3802 used for symbols you are never intended to see. If you use the
3803 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3804 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3805 you may use them in debugging.
3808 This is the number that was used in the local label definition. So if the
3809 label is written @samp{55:} then the number is @samp{55}.
3812 This unusual character is included so you do not accidentally invent a symbol
3813 of the same name. The character has ASCII value of @samp{\002} (control-B).
3815 @item @emph{ordinal number}
3816 This is a serial number to keep the labels distinct. The first definition of
3817 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3818 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3819 the number @samp{1} and its 15th definition gets @samp{15} as well.
3822 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3823 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3825 @subheading Dollar Local Labels
3826 @cindex dollar local symbols
3828 On some targets @code{@value{AS}} also supports an even more local form of
3829 local labels called dollar labels. These labels go out of scope (i.e., they
3830 become undefined) as soon as a non-local label is defined. Thus they remain
3831 valid for only a small region of the input source code. Normal local labels,
3832 by contrast, remain in scope for the entire file, or until they are redefined
3833 by another occurrence of the same local label.
3835 Dollar labels are defined in exactly the same way as ordinary local labels,
3836 except that they have a dollar sign suffix to their numeric value, e.g.,
3839 They can also be distinguished from ordinary local labels by their transformed
3840 names which use ASCII character @samp{\001} (control-A) as the magic character
3841 to distinguish them from ordinary labels. For example, the fifth definition of
3842 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3845 @section The Special Dot Symbol
3847 @cindex dot (symbol)
3848 @cindex @code{.} (symbol)
3849 @cindex current address
3850 @cindex location counter
3851 The special symbol @samp{.} refers to the current address that
3852 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3853 .long .} defines @code{melvin} to contain its own address.
3854 Assigning a value to @code{.} is treated the same as a @code{.org}
3856 @ifclear no-space-dir
3857 Thus, the expression @samp{.=.+4} is the same as saying
3861 @node Symbol Attributes
3862 @section Symbol Attributes
3864 @cindex symbol attributes
3865 @cindex attributes, symbol
3866 Every symbol has, as well as its name, the attributes ``Value'' and
3867 ``Type''. Depending on output format, symbols can also have auxiliary
3870 The detailed definitions are in @file{a.out.h}.
3873 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3874 all these attributes, and probably won't warn you. This makes the
3875 symbol an externally defined symbol, which is generally what you
3879 * Symbol Value:: Value
3880 * Symbol Type:: Type
3883 * a.out Symbols:: Symbol Attributes: @code{a.out}
3887 * a.out Symbols:: Symbol Attributes: @code{a.out}
3890 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3895 * COFF Symbols:: Symbol Attributes for COFF
3898 * SOM Symbols:: Symbol Attributes for SOM
3905 @cindex value of a symbol
3906 @cindex symbol value
3907 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3908 location in the text, data, bss or absolute sections the value is the
3909 number of addresses from the start of that section to the label.
3910 Naturally for text, data and bss sections the value of a symbol changes
3911 as @code{@value{LD}} changes section base addresses during linking. Absolute
3912 symbols' values do not change during linking: that is why they are
3915 The value of an undefined symbol is treated in a special way. If it is
3916 0 then the symbol is not defined in this assembler source file, and
3917 @code{@value{LD}} tries to determine its value from other files linked into the
3918 same program. You make this kind of symbol simply by mentioning a symbol
3919 name without defining it. A non-zero value represents a @code{.comm}
3920 common declaration. The value is how much common storage to reserve, in
3921 bytes (addresses). The symbol refers to the first address of the
3927 @cindex type of a symbol
3929 The type attribute of a symbol contains relocation (section)
3930 information, any flag settings indicating that a symbol is external, and
3931 (optionally), other information for linkers and debuggers. The exact
3932 format depends on the object-code output format in use.
3937 @c The following avoids a "widow" subsection title. @group would be
3938 @c better if it were available outside examples.
3941 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3943 @cindex @code{b.out} symbol attributes
3944 @cindex symbol attributes, @code{b.out}
3945 These symbol attributes appear only when @command{@value{AS}} is configured for
3946 one of the Berkeley-descended object output formats---@code{a.out} or
3952 @subsection Symbol Attributes: @code{a.out}
3954 @cindex @code{a.out} symbol attributes
3955 @cindex symbol attributes, @code{a.out}
3961 @subsection Symbol Attributes: @code{a.out}
3963 @cindex @code{a.out} symbol attributes
3964 @cindex symbol attributes, @code{a.out}
3968 * Symbol Desc:: Descriptor
3969 * Symbol Other:: Other
3973 @subsubsection Descriptor
3975 @cindex descriptor, of @code{a.out} symbol
3976 This is an arbitrary 16-bit value. You may establish a symbol's
3977 descriptor value by using a @code{.desc} statement
3978 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3979 @command{@value{AS}}.
3982 @subsubsection Other
3984 @cindex other attribute, of @code{a.out} symbol
3985 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3990 @subsection Symbol Attributes for COFF
3992 @cindex COFF symbol attributes
3993 @cindex symbol attributes, COFF
3995 The COFF format supports a multitude of auxiliary symbol attributes;
3996 like the primary symbol attributes, they are set between @code{.def} and
3997 @code{.endef} directives.
3999 @subsubsection Primary Attributes
4001 @cindex primary attributes, COFF symbols
4002 The symbol name is set with @code{.def}; the value and type,
4003 respectively, with @code{.val} and @code{.type}.
4005 @subsubsection Auxiliary Attributes
4007 @cindex auxiliary attributes, COFF symbols
4008 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4009 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4010 table information for COFF.
4015 @subsection Symbol Attributes for SOM
4017 @cindex SOM symbol attributes
4018 @cindex symbol attributes, SOM
4020 The SOM format for the HPPA supports a multitude of symbol attributes set with
4021 the @code{.EXPORT} and @code{.IMPORT} directives.
4023 The attributes are described in @cite{HP9000 Series 800 Assembly
4024 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4025 @code{EXPORT} assembler directive documentation.
4029 @chapter Expressions
4033 @cindex numeric values
4034 An @dfn{expression} specifies an address or numeric value.
4035 Whitespace may precede and/or follow an expression.
4037 The result of an expression must be an absolute number, or else an offset into
4038 a particular section. If an expression is not absolute, and there is not
4039 enough information when @command{@value{AS}} sees the expression to know its
4040 section, a second pass over the source program might be necessary to interpret
4041 the expression---but the second pass is currently not implemented.
4042 @command{@value{AS}} aborts with an error message in this situation.
4045 * Empty Exprs:: Empty Expressions
4046 * Integer Exprs:: Integer Expressions
4050 @section Empty Expressions
4052 @cindex empty expressions
4053 @cindex expressions, empty
4054 An empty expression has no value: it is just whitespace or null.
4055 Wherever an absolute expression is required, you may omit the
4056 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4057 is compatible with other assemblers.
4060 @section Integer Expressions
4062 @cindex integer expressions
4063 @cindex expressions, integer
4064 An @dfn{integer expression} is one or more @emph{arguments} delimited
4065 by @emph{operators}.
4068 * Arguments:: Arguments
4069 * Operators:: Operators
4070 * Prefix Ops:: Prefix Operators
4071 * Infix Ops:: Infix Operators
4075 @subsection Arguments
4077 @cindex expression arguments
4078 @cindex arguments in expressions
4079 @cindex operands in expressions
4080 @cindex arithmetic operands
4081 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4082 contexts arguments are sometimes called ``arithmetic operands''. In
4083 this manual, to avoid confusing them with the ``instruction operands'' of
4084 the machine language, we use the term ``argument'' to refer to parts of
4085 expressions only, reserving the word ``operand'' to refer only to machine
4086 instruction operands.
4088 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4089 @var{section} is one of text, data, bss, absolute,
4090 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4093 Numbers are usually integers.
4095 A number can be a flonum or bignum. In this case, you are warned
4096 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4097 these 32 bits are an integer. You may write integer-manipulating
4098 instructions that act on exotic constants, compatible with other
4101 @cindex subexpressions
4102 Subexpressions are a left parenthesis @samp{(} followed by an integer
4103 expression, followed by a right parenthesis @samp{)}; or a prefix
4104 operator followed by an argument.
4107 @subsection Operators
4109 @cindex operators, in expressions
4110 @cindex arithmetic functions
4111 @cindex functions, in expressions
4112 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4113 operators are followed by an argument. Infix operators appear
4114 between their arguments. Operators may be preceded and/or followed by
4118 @subsection Prefix Operator
4120 @cindex prefix operators
4121 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4122 one argument, which must be absolute.
4124 @c the tex/end tex stuff surrounding this small table is meant to make
4125 @c it align, on the printed page, with the similar table in the next
4126 @c section (which is inside an enumerate).
4128 \global\advance\leftskip by \itemindent
4133 @dfn{Negation}. Two's complement negation.
4135 @dfn{Complementation}. Bitwise not.
4139 \global\advance\leftskip by -\itemindent
4143 @subsection Infix Operators
4145 @cindex infix operators
4146 @cindex operators, permitted arguments
4147 @dfn{Infix operators} take two arguments, one on either side. Operators
4148 have precedence, but operations with equal precedence are performed left
4149 to right. Apart from @code{+} or @option{-}, both arguments must be
4150 absolute, and the result is absolute.
4153 @cindex operator precedence
4154 @cindex precedence of operators
4161 @dfn{Multiplication}.
4164 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4170 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4173 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4177 Intermediate precedence
4182 @dfn{Bitwise Inclusive Or}.
4188 @dfn{Bitwise Exclusive Or}.
4191 @dfn{Bitwise Or Not}.
4198 @cindex addition, permitted arguments
4199 @cindex plus, permitted arguments
4200 @cindex arguments for addition
4202 @dfn{Addition}. If either argument is absolute, the result has the section of
4203 the other argument. You may not add together arguments from different
4206 @cindex subtraction, permitted arguments
4207 @cindex minus, permitted arguments
4208 @cindex arguments for subtraction
4210 @dfn{Subtraction}. If the right argument is absolute, the
4211 result has the section of the left argument.
4212 If both arguments are in the same section, the result is absolute.
4213 You may not subtract arguments from different sections.
4214 @c FIXME is there still something useful to say about undefined - undefined ?
4216 @cindex comparison expressions
4217 @cindex expressions, comparison
4222 @dfn{Is Not Equal To}
4226 @dfn{Is Greater Than}
4228 @dfn{Is Greater Than Or Equal To}
4230 @dfn{Is Less Than Or Equal To}
4232 The comparison operators can be used as infix operators. A true results has a
4233 value of -1 whereas a false result has a value of 0. Note, these operators
4234 perform signed comparisons.
4237 @item Lowest Precedence
4246 These two logical operations can be used to combine the results of sub
4247 expressions. Note, unlike the comparison operators a true result returns a
4248 value of 1 but a false results does still return 0. Also note that the logical
4249 or operator has a slightly lower precedence than logical and.
4254 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4255 address; you can only have a defined section in one of the two arguments.
4258 @chapter Assembler Directives
4260 @cindex directives, machine independent
4261 @cindex pseudo-ops, machine independent
4262 @cindex machine independent directives
4263 All assembler directives have names that begin with a period (@samp{.}).
4264 The names are case insensitive for most targets, and usually written
4267 This chapter discusses directives that are available regardless of the
4268 target machine configuration for the @sc{gnu} assembler.
4270 Some machine configurations provide additional directives.
4271 @xref{Machine Dependencies}.
4274 @ifset machine-directives
4275 @xref{Machine Dependencies}, for additional directives.
4280 * Abort:: @code{.abort}
4282 * ABORT (COFF):: @code{.ABORT}
4285 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4286 * Altmacro:: @code{.altmacro}
4287 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4288 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4289 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4290 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4291 * Byte:: @code{.byte @var{expressions}}
4292 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4293 * Comm:: @code{.comm @var{symbol} , @var{length} }
4294 * Data:: @code{.data @var{subsection}}
4296 * Def:: @code{.def @var{name}}
4299 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4305 * Double:: @code{.double @var{flonums}}
4306 * Eject:: @code{.eject}
4307 * Else:: @code{.else}
4308 * Elseif:: @code{.elseif}
4311 * Endef:: @code{.endef}
4314 * Endfunc:: @code{.endfunc}
4315 * Endif:: @code{.endif}
4316 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4317 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4318 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4320 * Error:: @code{.error @var{string}}
4321 * Exitm:: @code{.exitm}
4322 * Extern:: @code{.extern}
4323 * Fail:: @code{.fail}
4324 * File:: @code{.file}
4325 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4326 * Float:: @code{.float @var{flonums}}
4327 * Func:: @code{.func}
4328 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4330 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4331 * Hidden:: @code{.hidden @var{names}}
4334 * hword:: @code{.hword @var{expressions}}
4335 * Ident:: @code{.ident}
4336 * If:: @code{.if @var{absolute expression}}
4337 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4338 * Include:: @code{.include "@var{file}"}
4339 * Int:: @code{.int @var{expressions}}
4341 * Internal:: @code{.internal @var{names}}
4344 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4345 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4346 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4347 * Lflags:: @code{.lflags}
4348 @ifclear no-line-dir
4349 * Line:: @code{.line @var{line-number}}
4352 * Linkonce:: @code{.linkonce [@var{type}]}
4353 * List:: @code{.list}
4354 * Ln:: @code{.ln @var{line-number}}
4355 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4356 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4358 * Local:: @code{.local @var{names}}
4361 * Long:: @code{.long @var{expressions}}
4363 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4366 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4367 * MRI:: @code{.mri @var{val}}
4368 * Noaltmacro:: @code{.noaltmacro}
4369 * Nolist:: @code{.nolist}
4370 * Octa:: @code{.octa @var{bignums}}
4371 * Offset:: @code{.offset @var{loc}}
4372 * Org:: @code{.org @var{new-lc}, @var{fill}}
4373 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4375 * PopSection:: @code{.popsection}
4376 * Previous:: @code{.previous}
4379 * Print:: @code{.print @var{string}}
4381 * Protected:: @code{.protected @var{names}}
4384 * Psize:: @code{.psize @var{lines}, @var{columns}}
4385 * Purgem:: @code{.purgem @var{name}}
4387 * PushSection:: @code{.pushsection @var{name}}
4390 * Quad:: @code{.quad @var{bignums}}
4391 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4392 * Rept:: @code{.rept @var{count}}
4393 * Sbttl:: @code{.sbttl "@var{subheading}"}
4395 * Scl:: @code{.scl @var{class}}
4398 * Section:: @code{.section @var{name}[, @var{flags}]}
4401 * Set:: @code{.set @var{symbol}, @var{expression}}
4402 * Short:: @code{.short @var{expressions}}
4403 * Single:: @code{.single @var{flonums}}
4405 * Size:: @code{.size [@var{name} , @var{expression}]}
4407 @ifclear no-space-dir
4408 * Skip:: @code{.skip @var{size} , @var{fill}}
4411 * Sleb128:: @code{.sleb128 @var{expressions}}
4412 @ifclear no-space-dir
4413 * Space:: @code{.space @var{size} , @var{fill}}
4416 * Stab:: @code{.stabd, .stabn, .stabs}
4419 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4420 * Struct:: @code{.struct @var{expression}}
4422 * SubSection:: @code{.subsection}
4423 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4427 * Tag:: @code{.tag @var{structname}}
4430 * Text:: @code{.text @var{subsection}}
4431 * Title:: @code{.title "@var{heading}"}
4433 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4436 * Uleb128:: @code{.uleb128 @var{expressions}}
4438 * Val:: @code{.val @var{addr}}
4442 * Version:: @code{.version "@var{string}"}
4443 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4444 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4447 * Warning:: @code{.warning @var{string}}
4448 * Weak:: @code{.weak @var{names}}
4449 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4450 * Word:: @code{.word @var{expressions}}
4451 @ifclear no-space-dir
4452 * Zero:: @code{.zero @var{size}}
4454 * Deprecated:: Deprecated Directives
4458 @section @code{.abort}
4460 @cindex @code{abort} directive
4461 @cindex stopping the assembly
4462 This directive stops the assembly immediately. It is for
4463 compatibility with other assemblers. The original idea was that the
4464 assembly language source would be piped into the assembler. If the sender
4465 of the source quit, it could use this directive tells @command{@value{AS}} to
4466 quit also. One day @code{.abort} will not be supported.
4470 @section @code{.ABORT} (COFF)
4472 @cindex @code{ABORT} directive
4473 When producing COFF output, @command{@value{AS}} accepts this directive as a
4474 synonym for @samp{.abort}.
4477 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4483 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4485 @cindex padding the location counter
4486 @cindex @code{align} directive
4487 Pad the location counter (in the current subsection) to a particular storage
4488 boundary. The first expression (which must be absolute) is the alignment
4489 required, as described below.
4491 The second expression (also absolute) gives the fill value to be stored in the
4492 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4493 padding bytes are normally zero. However, on some systems, if the section is
4494 marked as containing code and the fill value is omitted, the space is filled
4495 with no-op instructions.
4497 The third expression is also absolute, and is also optional. If it is present,
4498 it is the maximum number of bytes that should be skipped by this alignment
4499 directive. If doing the alignment would require skipping more bytes than the
4500 specified maximum, then the alignment is not done at all. You can omit the
4501 fill value (the second argument) entirely by simply using two commas after the
4502 required alignment; this can be useful if you want the alignment to be filled
4503 with no-op instructions when appropriate.
4505 The way the required alignment is specified varies from system to system.
4506 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4507 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4508 alignment request in bytes. For example @samp{.align 8} advances
4509 the location counter until it is a multiple of 8. If the location counter
4510 is already a multiple of 8, no change is needed. For the tic54x, the
4511 first expression is the alignment request in words.
4513 For other systems, including ppc, i386 using a.out format, arm and
4514 strongarm, it is the
4515 number of low-order zero bits the location counter must have after
4516 advancement. For example @samp{.align 3} advances the location
4517 counter until it a multiple of 8. If the location counter is already a
4518 multiple of 8, no change is needed.
4520 This inconsistency is due to the different behaviors of the various
4521 native assemblers for these systems which GAS must emulate.
4522 GAS also provides @code{.balign} and @code{.p2align} directives,
4523 described later, which have a consistent behavior across all
4524 architectures (but are specific to GAS).
4527 @section @code{.altmacro}
4528 Enable alternate macro mode, enabling:
4531 @item LOCAL @var{name} [ , @dots{} ]
4532 One additional directive, @code{LOCAL}, is available. It is used to
4533 generate a string replacement for each of the @var{name} arguments, and
4534 replace any instances of @var{name} in each macro expansion. The
4535 replacement string is unique in the assembly, and different for each
4536 separate macro expansion. @code{LOCAL} allows you to write macros that
4537 define symbols, without fear of conflict between separate macro expansions.
4539 @item String delimiters
4540 You can write strings delimited in these other ways besides
4541 @code{"@var{string}"}:
4544 @item '@var{string}'
4545 You can delimit strings with single-quote characters.
4547 @item <@var{string}>
4548 You can delimit strings with matching angle brackets.
4551 @item single-character string escape
4552 To include any single character literally in a string (even if the
4553 character would otherwise have some special meaning), you can prefix the
4554 character with @samp{!} (an exclamation mark). For example, you can
4555 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4557 @item Expression results as strings
4558 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4559 and use the result as a string.
4563 @section @code{.ascii "@var{string}"}@dots{}
4565 @cindex @code{ascii} directive
4566 @cindex string literals
4567 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4568 separated by commas. It assembles each string (with no automatic
4569 trailing zero byte) into consecutive addresses.
4572 @section @code{.asciz "@var{string}"}@dots{}
4574 @cindex @code{asciz} directive
4575 @cindex zero-terminated strings
4576 @cindex null-terminated strings
4577 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4578 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4581 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4583 @cindex padding the location counter given number of bytes
4584 @cindex @code{balign} directive
4585 Pad the location counter (in the current subsection) to a particular
4586 storage boundary. The first expression (which must be absolute) is the
4587 alignment request in bytes. For example @samp{.balign 8} advances
4588 the location counter until it is a multiple of 8. If the location counter
4589 is already a multiple of 8, no change is needed.
4591 The second expression (also absolute) gives the fill value to be stored in the
4592 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4593 padding bytes are normally zero. However, on some systems, if the section is
4594 marked as containing code and the fill value is omitted, the space is filled
4595 with no-op instructions.
4597 The third expression is also absolute, and is also optional. If it is present,
4598 it is the maximum number of bytes that should be skipped by this alignment
4599 directive. If doing the alignment would require skipping more bytes than the
4600 specified maximum, then the alignment is not done at all. You can omit the
4601 fill value (the second argument) entirely by simply using two commas after the
4602 required alignment; this can be useful if you want the alignment to be filled
4603 with no-op instructions when appropriate.
4605 @cindex @code{balignw} directive
4606 @cindex @code{balignl} directive
4607 The @code{.balignw} and @code{.balignl} directives are variants of the
4608 @code{.balign} directive. The @code{.balignw} directive treats the fill
4609 pattern as a two byte word value. The @code{.balignl} directives treats the
4610 fill pattern as a four byte longword value. For example, @code{.balignw
4611 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4612 filled in with the value 0x368d (the exact placement of the bytes depends upon
4613 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4616 @node Bundle directives
4617 @section Bundle directives
4618 @subsection @code{.bundle_align_mode @var{abs-expr}}
4619 @cindex @code{bundle_align_mode} directive
4621 @cindex instruction bundle
4622 @cindex aligned instruction bundle
4623 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4624 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4625 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4626 disabled (which is the default state). If the argument it not zero, it
4627 gives the size of an instruction bundle as a power of two (as for the
4628 @code{.p2align} directive, @pxref{P2align}).
4630 For some targets, it's an ABI requirement that no instruction may span a
4631 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4632 instructions that starts on an aligned boundary. For example, if
4633 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4634 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4635 effect, no single instruction may span a boundary between bundles. If an
4636 instruction would start too close to the end of a bundle for the length of
4637 that particular instruction to fit within the bundle, then the space at the
4638 end of that bundle is filled with no-op instructions so the instruction
4639 starts in the next bundle. As a corollary, it's an error if any single
4640 instruction's encoding is longer than the bundle size.
4642 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4643 @cindex @code{bundle_lock} directive
4644 @cindex @code{bundle_unlock} directive
4645 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4646 allow explicit control over instruction bundle padding. These directives
4647 are only valid when @code{.bundle_align_mode} has been used to enable
4648 aligned instruction bundle mode. It's an error if they appear when
4649 @code{.bundle_align_mode} has not been used at all, or when the last
4650 directive was @w{@code{.bundle_align_mode 0}}.
4652 @cindex bundle-locked
4653 For some targets, it's an ABI requirement that certain instructions may
4654 appear only as part of specified permissible sequences of multiple
4655 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4656 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4657 instruction sequence. For purposes of aligned instruction bundle mode, a
4658 sequence starting with @code{.bundle_lock} and ending with
4659 @code{.bundle_unlock} is treated as a single instruction. That is, the
4660 entire sequence must fit into a single bundle and may not span a bundle
4661 boundary. If necessary, no-op instructions will be inserted before the
4662 first instruction of the sequence so that the whole sequence starts on an
4663 aligned bundle boundary. It's an error if the sequence is longer than the
4666 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4667 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4668 nested. That is, a second @code{.bundle_lock} directive before the next
4669 @code{.bundle_unlock} directive has no effect except that it must be
4670 matched by another closing @code{.bundle_unlock} so that there is the
4671 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4674 @section @code{.byte @var{expressions}}
4676 @cindex @code{byte} directive
4677 @cindex integers, one byte
4678 @code{.byte} expects zero or more expressions, separated by commas.
4679 Each expression is assembled into the next byte.
4681 @node CFI directives
4682 @section CFI directives
4683 @subsection @code{.cfi_sections @var{section_list}}
4684 @cindex @code{cfi_sections} directive
4685 @code{.cfi_sections} may be used to specify whether CFI directives
4686 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4687 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4688 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4689 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4690 directive is not used is @code{.cfi_sections .eh_frame}.
4692 On targets that support compact unwinding tables these can be generated
4693 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4695 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4696 which is used by the @value{TIC6X} target.
4698 The @code{.cfi_sections} directive can be repeated, with the same or different
4699 arguments, provided that CFI generation has not yet started. Once CFI
4700 generation has started however the section list is fixed and any attempts to
4701 redefine it will result in an error.
4703 @subsection @code{.cfi_startproc [simple]}
4704 @cindex @code{cfi_startproc} directive
4705 @code{.cfi_startproc} is used at the beginning of each function that
4706 should have an entry in @code{.eh_frame}. It initializes some internal
4707 data structures. Don't forget to close the function by
4708 @code{.cfi_endproc}.
4710 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4711 it also emits some architecture dependent initial CFI instructions.
4713 @subsection @code{.cfi_endproc}
4714 @cindex @code{cfi_endproc} directive
4715 @code{.cfi_endproc} is used at the end of a function where it closes its
4716 unwind entry previously opened by
4717 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4719 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4720 @cindex @code{cfi_personality} directive
4721 @code{.cfi_personality} defines personality routine and its encoding.
4722 @var{encoding} must be a constant determining how the personality
4723 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4724 argument is not present, otherwise second argument should be
4725 a constant or a symbol name. When using indirect encodings,
4726 the symbol provided should be the location where personality
4727 can be loaded from, not the personality routine itself.
4728 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4729 no personality routine.
4731 @subsection @code{.cfi_personality_id @var{id}}
4732 @cindex @code{cfi_personality_id} directive
4733 @code{cfi_personality_id} defines a personality routine by its index as
4734 defined in a compact unwinding format.
4735 Only valid when generating compact EH frames (i.e.
4736 with @code{.cfi_sections eh_frame_entry}.
4738 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4739 @cindex @code{cfi_fde_data} directive
4740 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4741 used for the current function. These are emitted inline in the
4742 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4743 in the @code{.gnu.extab} section otherwise.
4744 Only valid when generating compact EH frames (i.e.
4745 with @code{.cfi_sections eh_frame_entry}.
4747 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4748 @code{.cfi_lsda} defines LSDA and its encoding.
4749 @var{encoding} must be a constant determining how the LSDA
4750 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4751 argument is not present, otherwise the second argument should be a constant
4752 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4753 meaning that no LSDA is present.
4755 @subsection @code{.cfi_inline_lsda} [@var{align}]
4756 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4757 switches to the corresponding @code{.gnu.extab} section.
4758 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4759 Only valid when generating compact EH frames (i.e.
4760 with @code{.cfi_sections eh_frame_entry}.
4762 The table header and unwinding opcodes will be generated at this point,
4763 so that they are immediately followed by the LSDA data. The symbol
4764 referenced by the @code{.cfi_lsda} directive should still be defined
4765 in case a fallback FDE based encoding is used. The LSDA data is terminated
4766 by a section directive.
4768 The optional @var{align} argument specifies the alignment required.
4769 The alignment is specified as a power of two, as with the
4770 @code{.p2align} directive.
4772 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4773 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4774 address from @var{register} and add @var{offset} to it}.
4776 @subsection @code{.cfi_def_cfa_register @var{register}}
4777 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4778 now on @var{register} will be used instead of the old one. Offset
4781 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4782 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4783 remains the same, but @var{offset} is new. Note that it is the
4784 absolute offset that will be added to a defined register to compute
4787 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4788 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4789 value that is added/substracted from the previous offset.
4791 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4792 Previous value of @var{register} is saved at offset @var{offset} from
4795 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4796 Previous value of @var{register} is saved at offset @var{offset} from
4797 the current CFA register. This is transformed to @code{.cfi_offset}
4798 using the known displacement of the CFA register from the CFA.
4799 This is often easier to use, because the number will match the
4800 code it's annotating.
4802 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4803 Previous value of @var{register1} is saved in register @var{register2}.
4805 @subsection @code{.cfi_restore @var{register}}
4806 @code{.cfi_restore} says that the rule for @var{register} is now the
4807 same as it was at the beginning of the function, after all initial
4808 instruction added by @code{.cfi_startproc} were executed.
4810 @subsection @code{.cfi_undefined @var{register}}
4811 From now on the previous value of @var{register} can't be restored anymore.
4813 @subsection @code{.cfi_same_value @var{register}}
4814 Current value of @var{register} is the same like in the previous frame,
4815 i.e. no restoration needed.
4817 @subsection @code{.cfi_remember_state},
4818 First save all current rules for all registers by @code{.cfi_remember_state},
4819 then totally screw them up by subsequent @code{.cfi_*} directives and when
4820 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4821 the previous saved state.
4823 @subsection @code{.cfi_return_column @var{register}}
4824 Change return column @var{register}, i.e. the return address is either
4825 directly in @var{register} or can be accessed by rules for @var{register}.
4827 @subsection @code{.cfi_signal_frame}
4828 Mark current function as signal trampoline.
4830 @subsection @code{.cfi_window_save}
4831 SPARC register window has been saved.
4833 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4834 Allows the user to add arbitrary bytes to the unwind info. One
4835 might use this to add OS-specific CFI opcodes, or generic CFI
4836 opcodes that GAS does not yet support.
4838 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4839 The current value of @var{register} is @var{label}. The value of @var{label}
4840 will be encoded in the output file according to @var{encoding}; see the
4841 description of @code{.cfi_personality} for details on this encoding.
4843 The usefulness of equating a register to a fixed label is probably
4844 limited to the return address register. Here, it can be useful to
4845 mark a code segment that has only one return address which is reached
4846 by a direct branch and no copy of the return address exists in memory
4847 or another register.
4850 @section @code{.comm @var{symbol} , @var{length} }
4852 @cindex @code{comm} directive
4853 @cindex symbol, common
4854 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4855 common symbol in one object file may be merged with a defined or common symbol
4856 of the same name in another object file. If @code{@value{LD}} does not see a
4857 definition for the symbol--just one or more common symbols--then it will
4858 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4859 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4860 the same name, and they do not all have the same size, it will allocate space
4861 using the largest size.
4864 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4865 an optional third argument. This is the desired alignment of the symbol,
4866 specified for ELF as a byte boundary (for example, an alignment of 16 means
4867 that the least significant 4 bits of the address should be zero), and for PE
4868 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4869 boundary). The alignment must be an absolute expression, and it must be a
4870 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4871 common symbol, it will use the alignment when placing the symbol. If no
4872 alignment is specified, @command{@value{AS}} will set the alignment to the
4873 largest power of two less than or equal to the size of the symbol, up to a
4874 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4875 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4876 @samp{--section-alignment} option; image file sections in PE are aligned to
4877 multiples of 4096, which is far too large an alignment for ordinary variables.
4878 It is rather the default alignment for (non-debug) sections within object
4879 (@samp{*.o}) files, which are less strictly aligned.}.
4883 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4884 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4888 @section @code{.data @var{subsection}}
4890 @cindex @code{data} directive
4891 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4892 end of the data subsection numbered @var{subsection} (which is an
4893 absolute expression). If @var{subsection} is omitted, it defaults
4898 @section @code{.def @var{name}}
4900 @cindex @code{def} directive
4901 @cindex COFF symbols, debugging
4902 @cindex debugging COFF symbols
4903 Begin defining debugging information for a symbol @var{name}; the
4904 definition extends until the @code{.endef} directive is encountered.
4907 This directive is only observed when @command{@value{AS}} is configured for COFF
4908 format output; when producing @code{b.out}, @samp{.def} is recognized,
4915 @section @code{.desc @var{symbol}, @var{abs-expression}}
4917 @cindex @code{desc} directive
4918 @cindex COFF symbol descriptor
4919 @cindex symbol descriptor, COFF
4920 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4921 to the low 16 bits of an absolute expression.
4924 The @samp{.desc} directive is not available when @command{@value{AS}} is
4925 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4926 object format. For the sake of compatibility, @command{@value{AS}} accepts
4927 it, but produces no output, when configured for COFF.
4933 @section @code{.dim}
4935 @cindex @code{dim} directive
4936 @cindex COFF auxiliary symbol information
4937 @cindex auxiliary symbol information, COFF
4938 This directive is generated by compilers to include auxiliary debugging
4939 information in the symbol table. It is only permitted inside
4940 @code{.def}/@code{.endef} pairs.
4943 @samp{.dim} is only meaningful when generating COFF format output; when
4944 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4950 @section @code{.double @var{flonums}}
4952 @cindex @code{double} directive
4953 @cindex floating point numbers (double)
4954 @code{.double} expects zero or more flonums, separated by commas. It
4955 assembles floating point numbers.
4957 The exact kind of floating point numbers emitted depends on how
4958 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4962 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4963 in @sc{ieee} format.
4968 @section @code{.eject}
4970 @cindex @code{eject} directive
4971 @cindex new page, in listings
4972 @cindex page, in listings
4973 @cindex listing control: new page
4974 Force a page break at this point, when generating assembly listings.
4977 @section @code{.else}
4979 @cindex @code{else} directive
4980 @code{.else} is part of the @command{@value{AS}} support for conditional
4981 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4982 of code to be assembled if the condition for the preceding @code{.if}
4986 @section @code{.elseif}
4988 @cindex @code{elseif} directive
4989 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4990 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4991 @code{.if} block that would otherwise fill the entire @code{.else} section.
4994 @section @code{.end}
4996 @cindex @code{end} directive
4997 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4998 process anything in the file past the @code{.end} directive.
5002 @section @code{.endef}
5004 @cindex @code{endef} directive
5005 This directive flags the end of a symbol definition begun with
5009 @samp{.endef} is only meaningful when generating COFF format output; if
5010 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5011 directive but ignores it.
5016 @section @code{.endfunc}
5017 @cindex @code{endfunc} directive
5018 @code{.endfunc} marks the end of a function specified with @code{.func}.
5021 @section @code{.endif}
5023 @cindex @code{endif} directive
5024 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5025 it marks the end of a block of code that is only assembled
5026 conditionally. @xref{If,,@code{.if}}.
5029 @section @code{.equ @var{symbol}, @var{expression}}
5031 @cindex @code{equ} directive
5032 @cindex assigning values to symbols
5033 @cindex symbols, assigning values to
5034 This directive sets the value of @var{symbol} to @var{expression}.
5035 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5038 The syntax for @code{equ} on the HPPA is
5039 @samp{@var{symbol} .equ @var{expression}}.
5043 The syntax for @code{equ} on the Z80 is
5044 @samp{@var{symbol} equ @var{expression}}.
5045 On the Z80 it is an eror if @var{symbol} is already defined,
5046 but the symbol is not protected from later redefinition.
5047 Compare @ref{Equiv}.
5051 @section @code{.equiv @var{symbol}, @var{expression}}
5052 @cindex @code{equiv} directive
5053 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5054 the assembler will signal an error if @var{symbol} is already defined. Note a
5055 symbol which has been referenced but not actually defined is considered to be
5058 Except for the contents of the error message, this is roughly equivalent to
5065 plus it protects the symbol from later redefinition.
5068 @section @code{.eqv @var{symbol}, @var{expression}}
5069 @cindex @code{eqv} directive
5070 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5071 evaluate the expression or any part of it immediately. Instead each time
5072 the resulting symbol is used in an expression, a snapshot of its current
5076 @section @code{.err}
5077 @cindex @code{err} directive
5078 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5079 message and, unless the @option{-Z} option was used, it will not generate an
5080 object file. This can be used to signal an error in conditionally compiled code.
5083 @section @code{.error "@var{string}"}
5084 @cindex error directive
5086 Similarly to @code{.err}, this directive emits an error, but you can specify a
5087 string that will be emitted as the error message. If you don't specify the
5088 message, it defaults to @code{".error directive invoked in source file"}.
5089 @xref{Errors, ,Error and Warning Messages}.
5092 .error "This code has not been assembled and tested."
5096 @section @code{.exitm}
5097 Exit early from the current macro definition. @xref{Macro}.
5100 @section @code{.extern}
5102 @cindex @code{extern} directive
5103 @code{.extern} is accepted in the source program---for compatibility
5104 with other assemblers---but it is ignored. @command{@value{AS}} treats
5105 all undefined symbols as external.
5108 @section @code{.fail @var{expression}}
5110 @cindex @code{fail} directive
5111 Generates an error or a warning. If the value of the @var{expression} is 500
5112 or more, @command{@value{AS}} will print a warning message. If the value is less
5113 than 500, @command{@value{AS}} will print an error message. The message will
5114 include the value of @var{expression}. This can occasionally be useful inside
5115 complex nested macros or conditional assembly.
5118 @section @code{.file}
5119 @cindex @code{file} directive
5121 @ifclear no-file-dir
5122 There are two different versions of the @code{.file} directive. Targets
5123 that support DWARF2 line number information use the DWARF2 version of
5124 @code{.file}. Other targets use the default version.
5126 @subheading Default Version
5128 @cindex logical file name
5129 @cindex file name, logical
5130 This version of the @code{.file} directive tells @command{@value{AS}} that we
5131 are about to start a new logical file. The syntax is:
5137 @var{string} is the new file name. In general, the filename is
5138 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5139 to specify an empty file name, you must give the quotes--@code{""}. This
5140 statement may go away in future: it is only recognized to be compatible with
5141 old @command{@value{AS}} programs.
5143 @subheading DWARF2 Version
5146 When emitting DWARF2 line number information, @code{.file} assigns filenames
5147 to the @code{.debug_line} file name table. The syntax is:
5150 .file @var{fileno} @var{filename}
5153 The @var{fileno} operand should be a unique positive integer to use as the
5154 index of the entry in the table. The @var{filename} operand is a C string
5157 The detail of filename indices is exposed to the user because the filename
5158 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5159 information, and thus the user must know the exact indices that table
5163 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5165 @cindex @code{fill} directive
5166 @cindex writing patterns in memory
5167 @cindex patterns, writing in memory
5168 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5169 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5170 may be zero or more. @var{Size} may be zero or more, but if it is
5171 more than 8, then it is deemed to have the value 8, compatible with
5172 other people's assemblers. The contents of each @var{repeat} bytes
5173 is taken from an 8-byte number. The highest order 4 bytes are
5174 zero. The lowest order 4 bytes are @var{value} rendered in the
5175 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5176 Each @var{size} bytes in a repetition is taken from the lowest order
5177 @var{size} bytes of this number. Again, this bizarre behavior is
5178 compatible with other people's assemblers.
5180 @var{size} and @var{value} are optional.
5181 If the second comma and @var{value} are absent, @var{value} is
5182 assumed zero. If the first comma and following tokens are absent,
5183 @var{size} is assumed to be 1.
5186 @section @code{.float @var{flonums}}
5188 @cindex floating point numbers (single)
5189 @cindex @code{float} directive
5190 This directive assembles zero or more flonums, separated by commas. It
5191 has the same effect as @code{.single}.
5193 The exact kind of floating point numbers emitted depends on how
5194 @command{@value{AS}} is configured.
5195 @xref{Machine Dependencies}.
5199 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5200 in @sc{ieee} format.
5205 @section @code{.func @var{name}[,@var{label}]}
5206 @cindex @code{func} directive
5207 @code{.func} emits debugging information to denote function @var{name}, and
5208 is ignored unless the file is assembled with debugging enabled.
5209 Only @samp{--gstabs[+]} is currently supported.
5210 @var{label} is the entry point of the function and if omitted @var{name}
5211 prepended with the @samp{leading char} is used.
5212 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5213 All functions are currently defined to have @code{void} return type.
5214 The function must be terminated with @code{.endfunc}.
5217 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5219 @cindex @code{global} directive
5220 @cindex symbol, making visible to linker
5221 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5222 @var{symbol} in your partial program, its value is made available to
5223 other partial programs that are linked with it. Otherwise,
5224 @var{symbol} takes its attributes from a symbol of the same name
5225 from another file linked into the same program.
5227 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5228 compatibility with other assemblers.
5231 On the HPPA, @code{.global} is not always enough to make it accessible to other
5232 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5233 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5238 @section @code{.gnu_attribute @var{tag},@var{value}}
5239 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5242 @section @code{.hidden @var{names}}
5244 @cindex @code{hidden} directive
5246 This is one of the ELF visibility directives. The other two are
5247 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5248 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5250 This directive overrides the named symbols default visibility (which is set by
5251 their binding: local, global or weak). The directive sets the visibility to
5252 @code{hidden} which means that the symbols are not visible to other components.
5253 Such symbols are always considered to be @code{protected} as well.
5257 @section @code{.hword @var{expressions}}
5259 @cindex @code{hword} directive
5260 @cindex integers, 16-bit
5261 @cindex numbers, 16-bit
5262 @cindex sixteen bit integers
5263 This expects zero or more @var{expressions}, and emits
5264 a 16 bit number for each.
5267 This directive is a synonym for @samp{.short}; depending on the target
5268 architecture, it may also be a synonym for @samp{.word}.
5272 This directive is a synonym for @samp{.short}.
5275 This directive is a synonym for both @samp{.short} and @samp{.word}.
5280 @section @code{.ident}
5282 @cindex @code{ident} directive
5284 This directive is used by some assemblers to place tags in object files. The
5285 behavior of this directive varies depending on the target. When using the
5286 a.out object file format, @command{@value{AS}} simply accepts the directive for
5287 source-file compatibility with existing assemblers, but does not emit anything
5288 for it. When using COFF, comments are emitted to the @code{.comment} or
5289 @code{.rdata} section, depending on the target. When using ELF, comments are
5290 emitted to the @code{.comment} section.
5293 @section @code{.if @var{absolute expression}}
5295 @cindex conditional assembly
5296 @cindex @code{if} directive
5297 @code{.if} marks the beginning of a section of code which is only
5298 considered part of the source program being assembled if the argument
5299 (which must be an @var{absolute expression}) is non-zero. The end of
5300 the conditional section of code must be marked by @code{.endif}
5301 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5302 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5303 If you have several conditions to check, @code{.elseif} may be used to avoid
5304 nesting blocks if/else within each subsequent @code{.else} block.
5306 The following variants of @code{.if} are also supported:
5308 @cindex @code{ifdef} directive
5309 @item .ifdef @var{symbol}
5310 Assembles the following section of code if the specified @var{symbol}
5311 has been defined. Note a symbol which has been referenced but not yet defined
5312 is considered to be undefined.
5314 @cindex @code{ifb} directive
5315 @item .ifb @var{text}
5316 Assembles the following section of code if the operand is blank (empty).
5318 @cindex @code{ifc} directive
5319 @item .ifc @var{string1},@var{string2}
5320 Assembles the following section of code if the two strings are the same. The
5321 strings may be optionally quoted with single quotes. If they are not quoted,
5322 the first string stops at the first comma, and the second string stops at the
5323 end of the line. Strings which contain whitespace should be quoted. The
5324 string comparison is case sensitive.
5326 @cindex @code{ifeq} directive
5327 @item .ifeq @var{absolute expression}
5328 Assembles the following section of code if the argument is zero.
5330 @cindex @code{ifeqs} directive
5331 @item .ifeqs @var{string1},@var{string2}
5332 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5334 @cindex @code{ifge} directive
5335 @item .ifge @var{absolute expression}
5336 Assembles the following section of code if the argument is greater than or
5339 @cindex @code{ifgt} directive
5340 @item .ifgt @var{absolute expression}
5341 Assembles the following section of code if the argument is greater than zero.
5343 @cindex @code{ifle} directive
5344 @item .ifle @var{absolute expression}
5345 Assembles the following section of code if the argument is less than or equal
5348 @cindex @code{iflt} directive
5349 @item .iflt @var{absolute expression}
5350 Assembles the following section of code if the argument is less than zero.
5352 @cindex @code{ifnb} directive
5353 @item .ifnb @var{text}
5354 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5355 following section of code if the operand is non-blank (non-empty).
5357 @cindex @code{ifnc} directive
5358 @item .ifnc @var{string1},@var{string2}.
5359 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5360 following section of code if the two strings are not the same.
5362 @cindex @code{ifndef} directive
5363 @cindex @code{ifnotdef} directive
5364 @item .ifndef @var{symbol}
5365 @itemx .ifnotdef @var{symbol}
5366 Assembles the following section of code if the specified @var{symbol}
5367 has not been defined. Both spelling variants are equivalent. Note a symbol
5368 which has been referenced but not yet defined is considered to be undefined.
5370 @cindex @code{ifne} directive
5371 @item .ifne @var{absolute expression}
5372 Assembles the following section of code if the argument is not equal to zero
5373 (in other words, this is equivalent to @code{.if}).
5375 @cindex @code{ifnes} directive
5376 @item .ifnes @var{string1},@var{string2}
5377 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5378 following section of code if the two strings are not the same.
5382 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5384 @cindex @code{incbin} directive
5385 @cindex binary files, including
5386 The @code{incbin} directive includes @var{file} verbatim at the current
5387 location. You can control the search paths used with the @samp{-I} command-line
5388 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5391 The @var{skip} argument skips a number of bytes from the start of the
5392 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5393 read. Note that the data is not aligned in any way, so it is the user's
5394 responsibility to make sure that proper alignment is provided both before and
5395 after the @code{incbin} directive.
5398 @section @code{.include "@var{file}"}
5400 @cindex @code{include} directive
5401 @cindex supporting files, including
5402 @cindex files, including
5403 This directive provides a way to include supporting files at specified
5404 points in your source program. The code from @var{file} is assembled as
5405 if it followed the point of the @code{.include}; when the end of the
5406 included file is reached, assembly of the original file continues. You
5407 can control the search paths used with the @samp{-I} command-line option
5408 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5412 @section @code{.int @var{expressions}}
5414 @cindex @code{int} directive
5415 @cindex integers, 32-bit
5416 Expect zero or more @var{expressions}, of any section, separated by commas.
5417 For each expression, emit a number that, at run time, is the value of that
5418 expression. The byte order and bit size of the number depends on what kind
5419 of target the assembly is for.
5423 On most forms of the H8/300, @code{.int} emits 16-bit
5424 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5431 @section @code{.internal @var{names}}
5433 @cindex @code{internal} directive
5435 This is one of the ELF visibility directives. The other two are
5436 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5437 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5439 This directive overrides the named symbols default visibility (which is set by
5440 their binding: local, global or weak). The directive sets the visibility to
5441 @code{internal} which means that the symbols are considered to be @code{hidden}
5442 (i.e., not visible to other components), and that some extra, processor specific
5443 processing must also be performed upon the symbols as well.
5447 @section @code{.irp @var{symbol},@var{values}}@dots{}
5449 @cindex @code{irp} directive
5450 Evaluate a sequence of statements assigning different values to @var{symbol}.
5451 The sequence of statements starts at the @code{.irp} directive, and is
5452 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5453 set to @var{value}, and the sequence of statements is assembled. If no
5454 @var{value} is listed, the sequence of statements is assembled once, with
5455 @var{symbol} set to the null string. To refer to @var{symbol} within the
5456 sequence of statements, use @var{\symbol}.
5458 For example, assembling
5466 is equivalent to assembling
5474 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5477 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5479 @cindex @code{irpc} directive
5480 Evaluate a sequence of statements assigning different values to @var{symbol}.
5481 The sequence of statements starts at the @code{.irpc} directive, and is
5482 terminated by an @code{.endr} directive. For each character in @var{value},
5483 @var{symbol} is set to the character, and the sequence of statements is
5484 assembled. If no @var{value} is listed, the sequence of statements is
5485 assembled once, with @var{symbol} set to the null string. To refer to
5486 @var{symbol} within the sequence of statements, use @var{\symbol}.
5488 For example, assembling
5496 is equivalent to assembling
5504 For some caveats with the spelling of @var{symbol}, see also the discussion
5508 @section @code{.lcomm @var{symbol} , @var{length}}
5510 @cindex @code{lcomm} directive
5511 @cindex local common symbols
5512 @cindex symbols, local common
5513 Reserve @var{length} (an absolute expression) bytes for a local common
5514 denoted by @var{symbol}. The section and value of @var{symbol} are
5515 those of the new local common. The addresses are allocated in the bss
5516 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5517 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5518 not visible to @code{@value{LD}}.
5521 Some targets permit a third argument to be used with @code{.lcomm}. This
5522 argument specifies the desired alignment of the symbol in the bss section.
5526 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5527 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5531 @section @code{.lflags}
5533 @cindex @code{lflags} directive (ignored)
5534 @command{@value{AS}} accepts this directive, for compatibility with other
5535 assemblers, but ignores it.
5537 @ifclear no-line-dir
5539 @section @code{.line @var{line-number}}
5541 @cindex @code{line} directive
5542 @cindex logical line number
5544 Change the logical line number. @var{line-number} must be an absolute
5545 expression. The next line has that logical line number. Therefore any other
5546 statements on the current line (after a statement separator character) are
5547 reported as on logical line number @var{line-number} @minus{} 1. One day
5548 @command{@value{AS}} will no longer support this directive: it is recognized only
5549 for compatibility with existing assembler programs.
5552 Even though this is a directive associated with the @code{a.out} or
5553 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5554 when producing COFF output, and treats @samp{.line} as though it
5555 were the COFF @samp{.ln} @emph{if} it is found outside a
5556 @code{.def}/@code{.endef} pair.
5558 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5559 used by compilers to generate auxiliary symbol information for
5564 @section @code{.linkonce [@var{type}]}
5566 @cindex @code{linkonce} directive
5567 @cindex common sections
5568 Mark the current section so that the linker only includes a single copy of it.
5569 This may be used to include the same section in several different object files,
5570 but ensure that the linker will only include it once in the final output file.
5571 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5572 Duplicate sections are detected based on the section name, so it should be
5575 This directive is only supported by a few object file formats; as of this
5576 writing, the only object file format which supports it is the Portable
5577 Executable format used on Windows NT.
5579 The @var{type} argument is optional. If specified, it must be one of the
5580 following strings. For example:
5584 Not all types may be supported on all object file formats.
5588 Silently discard duplicate sections. This is the default.
5591 Warn if there are duplicate sections, but still keep only one copy.
5594 Warn if any of the duplicates have different sizes.
5597 Warn if any of the duplicates do not have exactly the same contents.
5601 @section @code{.list}
5603 @cindex @code{list} directive
5604 @cindex listing control, turning on
5605 Control (in conjunction with the @code{.nolist} directive) whether or
5606 not assembly listings are generated. These two directives maintain an
5607 internal counter (which is zero initially). @code{.list} increments the
5608 counter, and @code{.nolist} decrements it. Assembly listings are
5609 generated whenever the counter is greater than zero.
5611 By default, listings are disabled. When you enable them (with the
5612 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5613 the initial value of the listing counter is one.
5616 @section @code{.ln @var{line-number}}
5618 @cindex @code{ln} directive
5619 @ifclear no-line-dir
5620 @samp{.ln} is a synonym for @samp{.line}.
5623 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5624 must be an absolute expression. The next line has that logical
5625 line number, so any other statements on the current line (after a
5626 statement separator character @code{;}) are reported as on logical
5627 line number @var{line-number} @minus{} 1.
5630 This directive is accepted, but ignored, when @command{@value{AS}} is
5631 configured for @code{b.out}; its effect is only associated with COFF
5637 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5638 @cindex @code{loc} directive
5639 When emitting DWARF2 line number information,
5640 the @code{.loc} directive will add a row to the @code{.debug_line} line
5641 number matrix corresponding to the immediately following assembly
5642 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5643 arguments will be applied to the @code{.debug_line} state machine before
5646 The @var{options} are a sequence of the following tokens in any order:
5650 This option will set the @code{basic_block} register in the
5651 @code{.debug_line} state machine to @code{true}.
5654 This option will set the @code{prologue_end} register in the
5655 @code{.debug_line} state machine to @code{true}.
5657 @item epilogue_begin
5658 This option will set the @code{epilogue_begin} register in the
5659 @code{.debug_line} state machine to @code{true}.
5661 @item is_stmt @var{value}
5662 This option will set the @code{is_stmt} register in the
5663 @code{.debug_line} state machine to @code{value}, which must be
5666 @item isa @var{value}
5667 This directive will set the @code{isa} register in the @code{.debug_line}
5668 state machine to @var{value}, which must be an unsigned integer.
5670 @item discriminator @var{value}
5671 This directive will set the @code{discriminator} register in the @code{.debug_line}
5672 state machine to @var{value}, which must be an unsigned integer.
5676 @node Loc_mark_labels
5677 @section @code{.loc_mark_labels @var{enable}}
5678 @cindex @code{loc_mark_labels} directive
5679 When emitting DWARF2 line number information,
5680 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5681 to the @code{.debug_line} line number matrix with the @code{basic_block}
5682 register in the state machine set whenever a code label is seen.
5683 The @var{enable} argument should be either 1 or 0, to enable or disable
5684 this function respectively.
5688 @section @code{.local @var{names}}
5690 @cindex @code{local} directive
5691 This directive, which is available for ELF targets, marks each symbol in
5692 the comma-separated list of @code{names} as a local symbol so that it
5693 will not be externally visible. If the symbols do not already exist,
5694 they will be created.
5696 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5697 accept an alignment argument, which is the case for most ELF targets,
5698 the @code{.local} directive can be used in combination with @code{.comm}
5699 (@pxref{Comm}) to define aligned local common data.
5703 @section @code{.long @var{expressions}}
5705 @cindex @code{long} directive
5706 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5709 @c no one seems to know what this is for or whether this description is
5710 @c what it really ought to do
5712 @section @code{.lsym @var{symbol}, @var{expression}}
5714 @cindex @code{lsym} directive
5715 @cindex symbol, not referenced in assembly
5716 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5717 the hash table, ensuring it cannot be referenced by name during the
5718 rest of the assembly. This sets the attributes of the symbol to be
5719 the same as the expression value:
5721 @var{other} = @var{descriptor} = 0
5722 @var{type} = @r{(section of @var{expression})}
5723 @var{value} = @var{expression}
5726 The new symbol is not flagged as external.
5730 @section @code{.macro}
5733 The commands @code{.macro} and @code{.endm} allow you to define macros that
5734 generate assembly output. For example, this definition specifies a macro
5735 @code{sum} that puts a sequence of numbers into memory:
5738 .macro sum from=0, to=5
5747 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5759 @item .macro @var{macname}
5760 @itemx .macro @var{macname} @var{macargs} @dots{}
5761 @cindex @code{macro} directive
5762 Begin the definition of a macro called @var{macname}. If your macro
5763 definition requires arguments, specify their names after the macro name,
5764 separated by commas or spaces. You can qualify the macro argument to
5765 indicate whether all invocations must specify a non-blank value (through
5766 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5767 (through @samp{:@code{vararg}}). You can supply a default value for any
5768 macro argument by following the name with @samp{=@var{deflt}}. You
5769 cannot define two macros with the same @var{macname} unless it has been
5770 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5771 definitions. For example, these are all valid @code{.macro} statements:
5775 Begin the definition of a macro called @code{comm}, which takes no
5778 @item .macro plus1 p, p1
5779 @itemx .macro plus1 p p1
5780 Either statement begins the definition of a macro called @code{plus1},
5781 which takes two arguments; within the macro definition, write
5782 @samp{\p} or @samp{\p1} to evaluate the arguments.
5784 @item .macro reserve_str p1=0 p2
5785 Begin the definition of a macro called @code{reserve_str}, with two
5786 arguments. The first argument has a default value, but not the second.
5787 After the definition is complete, you can call the macro either as
5788 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5789 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5790 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5791 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5793 @item .macro m p1:req, p2=0, p3:vararg
5794 Begin the definition of a macro called @code{m}, with at least three
5795 arguments. The first argument must always have a value specified, but
5796 not the second, which instead has a default value. The third formal
5797 will get assigned all remaining arguments specified at invocation time.
5799 When you call a macro, you can specify the argument values either by
5800 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5801 @samp{sum to=17, from=9}.
5805 Note that since each of the @var{macargs} can be an identifier exactly
5806 as any other one permitted by the target architecture, there may be
5807 occasional problems if the target hand-crafts special meanings to certain
5808 characters when they occur in a special position. For example, if the colon
5809 (@code{:}) is generally permitted to be part of a symbol name, but the
5810 architecture specific code special-cases it when occurring as the final
5811 character of a symbol (to denote a label), then the macro parameter
5812 replacement code will have no way of knowing that and consider the whole
5813 construct (including the colon) an identifier, and check only this
5814 identifier for being the subject to parameter substitution. So for example
5815 this macro definition:
5823 might not work as expected. Invoking @samp{label foo} might not create a label
5824 called @samp{foo} but instead just insert the text @samp{\l:} into the
5825 assembler source, probably generating an error about an unrecognised
5828 Similarly problems might occur with the period character (@samp{.})
5829 which is often allowed inside opcode names (and hence identifier names). So
5830 for example constructing a macro to build an opcode from a base name and a
5831 length specifier like this:
5834 .macro opcode base length
5839 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5840 instruction but instead generate some kind of error as the assembler tries to
5841 interpret the text @samp{\base.\length}.
5843 There are several possible ways around this problem:
5846 @item Insert white space
5847 If it is possible to use white space characters then this is the simplest
5856 @item Use @samp{\()}
5857 The string @samp{\()} can be used to separate the end of a macro argument from
5858 the following text. eg:
5861 .macro opcode base length
5866 @item Use the alternate macro syntax mode
5867 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5868 used as a separator. eg:
5878 Note: this problem of correctly identifying string parameters to pseudo ops
5879 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5880 and @code{.irpc} (@pxref{Irpc}) as well.
5883 @cindex @code{endm} directive
5884 Mark the end of a macro definition.
5887 @cindex @code{exitm} directive
5888 Exit early from the current macro definition.
5890 @cindex number of macros executed
5891 @cindex macros, count executed
5893 @command{@value{AS}} maintains a counter of how many macros it has
5894 executed in this pseudo-variable; you can copy that number to your
5895 output with @samp{\@@}, but @emph{only within a macro definition}.
5897 @item LOCAL @var{name} [ , @dots{} ]
5898 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5899 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5900 @xref{Altmacro,,@code{.altmacro}}.
5904 @section @code{.mri @var{val}}
5906 @cindex @code{mri} directive
5907 @cindex MRI mode, temporarily
5908 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5909 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5910 affects code assembled until the next @code{.mri} directive, or until the end
5911 of the file. @xref{M, MRI mode, MRI mode}.
5914 @section @code{.noaltmacro}
5915 Disable alternate macro mode. @xref{Altmacro}.
5918 @section @code{.nolist}
5920 @cindex @code{nolist} directive
5921 @cindex listing control, turning off
5922 Control (in conjunction with the @code{.list} directive) whether or
5923 not assembly listings are generated. These two directives maintain an
5924 internal counter (which is zero initially). @code{.list} increments the
5925 counter, and @code{.nolist} decrements it. Assembly listings are
5926 generated whenever the counter is greater than zero.
5929 @section @code{.octa @var{bignums}}
5931 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5932 @cindex @code{octa} directive
5933 @cindex integer, 16-byte
5934 @cindex sixteen byte integer
5935 This directive expects zero or more bignums, separated by commas. For each
5936 bignum, it emits a 16-byte integer.
5938 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5939 hence @emph{octa}-word for 16 bytes.
5942 @section @code{.offset @var{loc}}
5944 @cindex @code{offset} directive
5945 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5946 be an absolute expression. This directive may be useful for defining
5947 symbols with absolute values. Do not confuse it with the @code{.org}
5951 @section @code{.org @var{new-lc} , @var{fill}}
5953 @cindex @code{org} directive
5954 @cindex location counter, advancing
5955 @cindex advancing location counter
5956 @cindex current address, advancing
5957 Advance the location counter of the current section to
5958 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5959 expression with the same section as the current subsection. That is,
5960 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5961 wrong section, the @code{.org} directive is ignored. To be compatible
5962 with former assemblers, if the section of @var{new-lc} is absolute,
5963 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5964 is the same as the current subsection.
5966 @code{.org} may only increase the location counter, or leave it
5967 unchanged; you cannot use @code{.org} to move the location counter
5970 @c double negative used below "not undefined" because this is a specific
5971 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5972 @c section. doc@cygnus.com 18feb91
5973 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5974 may not be undefined. If you really detest this restriction we eagerly await
5975 a chance to share your improved assembler.
5977 Beware that the origin is relative to the start of the section, not
5978 to the start of the subsection. This is compatible with other
5979 people's assemblers.
5981 When the location counter (of the current subsection) is advanced, the
5982 intervening bytes are filled with @var{fill} which should be an
5983 absolute expression. If the comma and @var{fill} are omitted,
5984 @var{fill} defaults to zero.
5987 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5989 @cindex padding the location counter given a power of two
5990 @cindex @code{p2align} directive
5991 Pad the location counter (in the current subsection) to a particular
5992 storage boundary. The first expression (which must be absolute) is the
5993 number of low-order zero bits the location counter must have after
5994 advancement. For example @samp{.p2align 3} advances the location
5995 counter until it a multiple of 8. If the location counter is already a
5996 multiple of 8, no change is needed.
5998 The second expression (also absolute) gives the fill value to be stored in the
5999 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6000 padding bytes are normally zero. However, on some systems, if the section is
6001 marked as containing code and the fill value is omitted, the space is filled
6002 with no-op instructions.
6004 The third expression is also absolute, and is also optional. If it is present,
6005 it is the maximum number of bytes that should be skipped by this alignment
6006 directive. If doing the alignment would require skipping more bytes than the
6007 specified maximum, then the alignment is not done at all. You can omit the
6008 fill value (the second argument) entirely by simply using two commas after the
6009 required alignment; this can be useful if you want the alignment to be filled
6010 with no-op instructions when appropriate.
6012 @cindex @code{p2alignw} directive
6013 @cindex @code{p2alignl} directive
6014 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6015 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6016 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6017 fill pattern as a four byte longword value. For example, @code{.p2alignw
6018 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6019 filled in with the value 0x368d (the exact placement of the bytes depends upon
6020 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6025 @section @code{.popsection}
6027 @cindex @code{popsection} directive
6028 @cindex Section Stack
6029 This is one of the ELF section stack manipulation directives. The others are
6030 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6031 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6034 This directive replaces the current section (and subsection) with the top
6035 section (and subsection) on the section stack. This section is popped off the
6041 @section @code{.previous}
6043 @cindex @code{previous} directive
6044 @cindex Section Stack
6045 This is one of the ELF section stack manipulation directives. The others are
6046 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6047 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6048 (@pxref{PopSection}).
6050 This directive swaps the current section (and subsection) with most recently
6051 referenced section/subsection pair prior to this one. Multiple
6052 @code{.previous} directives in a row will flip between two sections (and their
6053 subsections). For example:
6065 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6071 # Now in section A subsection 1
6075 # Now in section B subsection 0
6078 # Now in section B subsection 1
6081 # Now in section B subsection 0
6085 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6086 section B and 0x9abc into subsection 1 of section B.
6088 In terms of the section stack, this directive swaps the current section with
6089 the top section on the section stack.
6093 @section @code{.print @var{string}}
6095 @cindex @code{print} directive
6096 @command{@value{AS}} will print @var{string} on the standard output during
6097 assembly. You must put @var{string} in double quotes.
6101 @section @code{.protected @var{names}}
6103 @cindex @code{protected} directive
6105 This is one of the ELF visibility directives. The other two are
6106 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6108 This directive overrides the named symbols default visibility (which is set by
6109 their binding: local, global or weak). The directive sets the visibility to
6110 @code{protected} which means that any references to the symbols from within the
6111 components that defines them must be resolved to the definition in that
6112 component, even if a definition in another component would normally preempt
6117 @section @code{.psize @var{lines} , @var{columns}}
6119 @cindex @code{psize} directive
6120 @cindex listing control: paper size
6121 @cindex paper size, for listings
6122 Use this directive to declare the number of lines---and, optionally, the
6123 number of columns---to use for each page, when generating listings.
6125 If you do not use @code{.psize}, listings use a default line-count
6126 of 60. You may omit the comma and @var{columns} specification; the
6127 default width is 200 columns.
6129 @command{@value{AS}} generates formfeeds whenever the specified number of
6130 lines is exceeded (or whenever you explicitly request one, using
6133 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6134 those explicitly specified with @code{.eject}.
6137 @section @code{.purgem @var{name}}
6139 @cindex @code{purgem} directive
6140 Undefine the macro @var{name}, so that later uses of the string will not be
6141 expanded. @xref{Macro}.
6145 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6147 @cindex @code{pushsection} directive
6148 @cindex Section Stack
6149 This is one of the ELF section stack manipulation directives. The others are
6150 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6151 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6154 This directive pushes the current section (and subsection) onto the
6155 top of the section stack, and then replaces the current section and
6156 subsection with @code{name} and @code{subsection}. The optional
6157 @code{flags}, @code{type} and @code{arguments} are treated the same
6158 as in the @code{.section} (@pxref{Section}) directive.
6162 @section @code{.quad @var{bignums}}
6164 @cindex @code{quad} directive
6165 @code{.quad} expects zero or more bignums, separated by commas. For
6166 each bignum, it emits
6168 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6169 warning message; and just takes the lowest order 8 bytes of the bignum.
6170 @cindex eight-byte integer
6171 @cindex integer, 8-byte
6173 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6174 hence @emph{quad}-word for 8 bytes.
6177 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6178 warning message; and just takes the lowest order 16 bytes of the bignum.
6179 @cindex sixteen-byte integer
6180 @cindex integer, 16-byte
6184 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6186 @cindex @code{reloc} directive
6187 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6188 @var{expression}. If @var{offset} is a number, the relocation is generated in
6189 the current section. If @var{offset} is an expression that resolves to a
6190 symbol plus offset, the relocation is generated in the given symbol's section.
6191 @var{expression}, if present, must resolve to a symbol plus addend or to an
6192 absolute value, but note that not all targets support an addend. e.g. ELF REL
6193 targets such as i386 store an addend in the section contents rather than in the
6194 relocation. This low level interface does not support addends stored in the
6198 @section @code{.rept @var{count}}
6200 @cindex @code{rept} directive
6201 Repeat the sequence of lines between the @code{.rept} directive and the next
6202 @code{.endr} directive @var{count} times.
6204 For example, assembling
6212 is equivalent to assembling
6221 @section @code{.sbttl "@var{subheading}"}
6223 @cindex @code{sbttl} directive
6224 @cindex subtitles for listings
6225 @cindex listing control: subtitle
6226 Use @var{subheading} as the title (third line, immediately after the
6227 title line) when generating assembly listings.
6229 This directive affects subsequent pages, as well as the current page if
6230 it appears within ten lines of the top of a page.
6234 @section @code{.scl @var{class}}
6236 @cindex @code{scl} directive
6237 @cindex symbol storage class (COFF)
6238 @cindex COFF symbol storage class
6239 Set the storage-class value for a symbol. This directive may only be
6240 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6241 whether a symbol is static or external, or it may record further
6242 symbolic debugging information.
6245 The @samp{.scl} directive is primarily associated with COFF output; when
6246 configured to generate @code{b.out} output format, @command{@value{AS}}
6247 accepts this directive but ignores it.
6253 @section @code{.section @var{name}}
6255 @cindex named section
6256 Use the @code{.section} directive to assemble the following code into a section
6259 This directive is only supported for targets that actually support arbitrarily
6260 named sections; on @code{a.out} targets, for example, it is not accepted, even
6261 with a standard @code{a.out} section name.
6265 @c only print the extra heading if both COFF and ELF are set
6266 @subheading COFF Version
6269 @cindex @code{section} directive (COFF version)
6270 For COFF targets, the @code{.section} directive is used in one of the following
6274 .section @var{name}[, "@var{flags}"]
6275 .section @var{name}[, @var{subsection}]
6278 If the optional argument is quoted, it is taken as flags to use for the
6279 section. Each flag is a single character. The following flags are recognized:
6283 bss section (uninitialized data)
6285 section is not loaded
6291 exclude section from linking
6297 shared section (meaningful for PE targets)
6299 ignored. (For compatibility with the ELF version)
6301 section is not readable (meaningful for PE targets)
6303 single-digit power-of-two section alignment (GNU extension)
6306 If no flags are specified, the default flags depend upon the section name. If
6307 the section name is not recognized, the default will be for the section to be
6308 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6309 from the section, rather than adding them, so if they are used on their own it
6310 will be as if no flags had been specified at all.
6312 If the optional argument to the @code{.section} directive is not quoted, it is
6313 taken as a subsection number (@pxref{Sub-Sections}).
6318 @c only print the extra heading if both COFF and ELF are set
6319 @subheading ELF Version
6322 @cindex Section Stack
6323 This is one of the ELF section stack manipulation directives. The others are
6324 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6325 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6326 @code{.previous} (@pxref{Previous}).
6328 @cindex @code{section} directive (ELF version)
6329 For ELF targets, the @code{.section} directive is used like this:
6332 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6335 @anchor{Section Name Substitutions}
6336 @kindex --sectname-subst
6337 @cindex section name substitution
6338 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6339 argument may contain a substitution sequence. Only @code{%S} is supported
6340 at the moment, and substitutes the current section name. For example:
6343 .macro exception_code
6344 .section %S.exception
6345 [exception code here]
6360 The two @code{exception_code} invocations above would create the
6361 @code{.text.exception} and @code{.init.exception} sections respectively.
6362 This is useful e.g. to discriminate between anciliary sections that are
6363 tied to setup code to be discarded after use from anciliary sections that
6364 need to stay resident without having to define multiple @code{exception_code}
6365 macros just for that purpose.
6367 The optional @var{flags} argument is a quoted string which may contain any
6368 combination of the following characters:
6372 section is allocatable
6374 section is excluded from executable and shared library.
6378 section is executable
6380 section is mergeable
6382 section contains zero terminated strings
6384 section is a member of a section group
6386 section is used for thread-local-storage
6388 section is a member of the previously-current section's group, if any
6389 @item @code{<number>}
6390 a numeric value indicating the bits to be set in the ELF section header's flags
6391 field. Note - if one or more of the alphabetic characters described above is
6392 also included in the flags field, their bit values will be ORed into the
6394 @item @code{<target specific>}
6395 some targets extend this list with their own flag characters
6398 Note - once a section's flags have been set they cannot be changed. There are
6399 a few exceptions to this rule however. Processor and application specific
6400 flags can be added to an already defined section. The @code{.interp},
6401 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6402 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6403 section may have the executable (@code{x}) flag added.
6405 The optional @var{type} argument may contain one of the following constants:
6409 section contains data
6411 section does not contain data (i.e., section only occupies space)
6413 section contains data which is used by things other than the program
6415 section contains an array of pointers to init functions
6417 section contains an array of pointers to finish functions
6418 @item @@preinit_array
6419 section contains an array of pointers to pre-init functions
6420 @item @@@code{<number>}
6421 a numeric value to be set as the ELF section header's type field.
6422 @item @@@code{<target specific>}
6423 some targets extend this list with their own types
6426 Many targets only support the first three section types. The type may be
6427 enclosed in double quotes if necessary.
6429 Note on targets where the @code{@@} character is the start of a comment (eg
6430 ARM) then another character is used instead. For example the ARM port uses the
6433 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6434 special and have fixed types. Any attempt to declare them with a different
6435 type will generate an error from the assembler.
6437 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6438 be specified as well as an extra argument---@var{entsize}---like this:
6441 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6444 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6445 constants, each @var{entsize} octets long. Sections with both @code{M} and
6446 @code{S} must contain zero terminated strings where each character is
6447 @var{entsize} bytes long. The linker may remove duplicates within sections with
6448 the same name, same entity size and same flags. @var{entsize} must be an
6449 absolute expression. For sections with both @code{M} and @code{S}, a string
6450 which is a suffix of a larger string is considered a duplicate. Thus
6451 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6452 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6454 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6455 be present along with an additional field like this:
6458 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6461 The @var{GroupName} field specifies the name of the section group to which this
6462 particular section belongs. The optional linkage field can contain:
6466 indicates that only one copy of this section should be retained
6471 Note: if both the @var{M} and @var{G} flags are present then the fields for
6472 the Merge flag should come first, like this:
6475 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6478 If @var{flags} contains the @code{?} symbol then it may not also contain the
6479 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6480 present. Instead, @code{?} says to consider the section that's current before
6481 this directive. If that section used @code{G}, then the new section will use
6482 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6483 If not, then the @code{?} symbol has no effect.
6485 If no flags are specified, the default flags depend upon the section name. If
6486 the section name is not recognized, the default will be for the section to have
6487 none of the above flags: it will not be allocated in memory, nor writable, nor
6488 executable. The section will contain data.
6490 For ELF targets, the assembler supports another type of @code{.section}
6491 directive for compatibility with the Solaris assembler:
6494 .section "@var{name}"[, @var{flags}...]
6497 Note that the section name is quoted. There may be a sequence of comma
6502 section is allocatable
6506 section is executable
6508 section is excluded from executable and shared library.
6510 section is used for thread local storage
6513 This directive replaces the current section and subsection. See the
6514 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6515 some examples of how this directive and the other section stack directives
6521 @section @code{.set @var{symbol}, @var{expression}}
6523 @cindex @code{set} directive
6524 @cindex symbol value, setting
6525 Set the value of @var{symbol} to @var{expression}. This
6526 changes @var{symbol}'s value and type to conform to
6527 @var{expression}. If @var{symbol} was flagged as external, it remains
6528 flagged (@pxref{Symbol Attributes}).
6530 You may @code{.set} a symbol many times in the same assembly provided that the
6531 values given to the symbol are constants. Values that are based on expressions
6532 involving other symbols are allowed, but some targets may restrict this to only
6533 being done once per assembly. This is because those targets do not set the
6534 addresses of symbols at assembly time, but rather delay the assignment until a
6535 final link is performed. This allows the linker a chance to change the code in
6536 the files, changing the location of, and the relative distance between, various
6539 If you @code{.set} a global symbol, the value stored in the object
6540 file is the last value stored into it.
6543 On Z80 @code{set} is a real instruction, use
6544 @samp{@var{symbol} defl @var{expression}} instead.
6548 @section @code{.short @var{expressions}}
6550 @cindex @code{short} directive
6552 @code{.short} is normally the same as @samp{.word}.
6553 @xref{Word,,@code{.word}}.
6555 In some configurations, however, @code{.short} and @code{.word} generate
6556 numbers of different lengths. @xref{Machine Dependencies}.
6560 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6563 This expects zero or more @var{expressions}, and emits
6564 a 16 bit number for each.
6569 @section @code{.single @var{flonums}}
6571 @cindex @code{single} directive
6572 @cindex floating point numbers (single)
6573 This directive assembles zero or more flonums, separated by commas. It
6574 has the same effect as @code{.float}.
6576 The exact kind of floating point numbers emitted depends on how
6577 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6581 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6582 numbers in @sc{ieee} format.
6588 @section @code{.size}
6590 This directive is used to set the size associated with a symbol.
6594 @c only print the extra heading if both COFF and ELF are set
6595 @subheading COFF Version
6598 @cindex @code{size} directive (COFF version)
6599 For COFF targets, the @code{.size} directive is only permitted inside
6600 @code{.def}/@code{.endef} pairs. It is used like this:
6603 .size @var{expression}
6607 @samp{.size} is only meaningful when generating COFF format output; when
6608 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6615 @c only print the extra heading if both COFF and ELF are set
6616 @subheading ELF Version
6619 @cindex @code{size} directive (ELF version)
6620 For ELF targets, the @code{.size} directive is used like this:
6623 .size @var{name} , @var{expression}
6626 This directive sets the size associated with a symbol @var{name}.
6627 The size in bytes is computed from @var{expression} which can make use of label
6628 arithmetic. This directive is typically used to set the size of function
6633 @ifclear no-space-dir
6635 @section @code{.skip @var{size} , @var{fill}}
6637 @cindex @code{skip} directive
6638 @cindex filling memory
6639 This directive emits @var{size} bytes, each of value @var{fill}. Both
6640 @var{size} and @var{fill} are absolute expressions. If the comma and
6641 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6646 @section @code{.sleb128 @var{expressions}}
6648 @cindex @code{sleb128} directive
6649 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6650 compact, variable length representation of numbers used by the DWARF
6651 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6653 @ifclear no-space-dir
6655 @section @code{.space @var{size} , @var{fill}}
6657 @cindex @code{space} directive
6658 @cindex filling memory
6659 This directive emits @var{size} bytes, each of value @var{fill}. Both
6660 @var{size} and @var{fill} are absolute expressions. If the comma
6661 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6666 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6667 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6668 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6669 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6677 @section @code{.stabd, .stabn, .stabs}
6679 @cindex symbolic debuggers, information for
6680 @cindex @code{stab@var{x}} directives
6681 There are three directives that begin @samp{.stab}.
6682 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6683 The symbols are not entered in the @command{@value{AS}} hash table: they
6684 cannot be referenced elsewhere in the source file.
6685 Up to five fields are required:
6689 This is the symbol's name. It may contain any character except
6690 @samp{\000}, so is more general than ordinary symbol names. Some
6691 debuggers used to code arbitrarily complex structures into symbol names
6695 An absolute expression. The symbol's type is set to the low 8 bits of
6696 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6697 and debuggers choke on silly bit patterns.
6700 An absolute expression. The symbol's ``other'' attribute is set to the
6701 low 8 bits of this expression.
6704 An absolute expression. The symbol's descriptor is set to the low 16
6705 bits of this expression.
6708 An absolute expression which becomes the symbol's value.
6711 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6712 or @code{.stabs} statement, the symbol has probably already been created;
6713 you get a half-formed symbol in your object file. This is
6714 compatible with earlier assemblers!
6717 @cindex @code{stabd} directive
6718 @item .stabd @var{type} , @var{other} , @var{desc}
6720 The ``name'' of the symbol generated is not even an empty string.
6721 It is a null pointer, for compatibility. Older assemblers used a
6722 null pointer so they didn't waste space in object files with empty
6725 The symbol's value is set to the location counter,
6726 relocatably. When your program is linked, the value of this symbol
6727 is the address of the location counter when the @code{.stabd} was
6730 @cindex @code{stabn} directive
6731 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6732 The name of the symbol is set to the empty string @code{""}.
6734 @cindex @code{stabs} directive
6735 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6736 All five fields are specified.
6742 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6743 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6745 @cindex string, copying to object file
6746 @cindex string8, copying to object file
6747 @cindex string16, copying to object file
6748 @cindex string32, copying to object file
6749 @cindex string64, copying to object file
6750 @cindex @code{string} directive
6751 @cindex @code{string8} directive
6752 @cindex @code{string16} directive
6753 @cindex @code{string32} directive
6754 @cindex @code{string64} directive
6756 Copy the characters in @var{str} to the object file. You may specify more than
6757 one string to copy, separated by commas. Unless otherwise specified for a
6758 particular machine, the assembler marks the end of each string with a 0 byte.
6759 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6761 The variants @code{string16}, @code{string32} and @code{string64} differ from
6762 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6763 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6764 are stored in target endianness byte order.
6770 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6771 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6776 @section @code{.struct @var{expression}}
6778 @cindex @code{struct} directive
6779 Switch to the absolute section, and set the section offset to @var{expression},
6780 which must be an absolute expression. You might use this as follows:
6789 This would define the symbol @code{field1} to have the value 0, the symbol
6790 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6791 value 8. Assembly would be left in the absolute section, and you would need to
6792 use a @code{.section} directive of some sort to change to some other section
6793 before further assembly.
6797 @section @code{.subsection @var{name}}
6799 @cindex @code{subsection} directive
6800 @cindex Section Stack
6801 This is one of the ELF section stack manipulation directives. The others are
6802 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6803 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6806 This directive replaces the current subsection with @code{name}. The current
6807 section is not changed. The replaced subsection is put onto the section stack
6808 in place of the then current top of stack subsection.
6813 @section @code{.symver}
6814 @cindex @code{symver} directive
6815 @cindex symbol versioning
6816 @cindex versions of symbols
6817 Use the @code{.symver} directive to bind symbols to specific version nodes
6818 within a source file. This is only supported on ELF platforms, and is
6819 typically used when assembling files to be linked into a shared library.
6820 There are cases where it may make sense to use this in objects to be bound
6821 into an application itself so as to override a versioned symbol from a
6824 For ELF targets, the @code{.symver} directive can be used like this:
6826 .symver @var{name}, @var{name2@@nodename}
6828 If the symbol @var{name} is defined within the file
6829 being assembled, the @code{.symver} directive effectively creates a symbol
6830 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6831 just don't try and create a regular alias is that the @var{@@} character isn't
6832 permitted in symbol names. The @var{name2} part of the name is the actual name
6833 of the symbol by which it will be externally referenced. The name @var{name}
6834 itself is merely a name of convenience that is used so that it is possible to
6835 have definitions for multiple versions of a function within a single source
6836 file, and so that the compiler can unambiguously know which version of a
6837 function is being mentioned. The @var{nodename} portion of the alias should be
6838 the name of a node specified in the version script supplied to the linker when
6839 building a shared library. If you are attempting to override a versioned
6840 symbol from a shared library, then @var{nodename} should correspond to the
6841 nodename of the symbol you are trying to override.
6843 If the symbol @var{name} is not defined within the file being assembled, all
6844 references to @var{name} will be changed to @var{name2@@nodename}. If no
6845 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6848 Another usage of the @code{.symver} directive is:
6850 .symver @var{name}, @var{name2@@@@nodename}
6852 In this case, the symbol @var{name} must exist and be defined within
6853 the file being assembled. It is similar to @var{name2@@nodename}. The
6854 difference is @var{name2@@@@nodename} will also be used to resolve
6855 references to @var{name2} by the linker.
6857 The third usage of the @code{.symver} directive is:
6859 .symver @var{name}, @var{name2@@@@@@nodename}
6861 When @var{name} is not defined within the
6862 file being assembled, it is treated as @var{name2@@nodename}. When
6863 @var{name} is defined within the file being assembled, the symbol
6864 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6869 @section @code{.tag @var{structname}}
6871 @cindex COFF structure debugging
6872 @cindex structure debugging, COFF
6873 @cindex @code{tag} directive
6874 This directive is generated by compilers to include auxiliary debugging
6875 information in the symbol table. It is only permitted inside
6876 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6877 definitions in the symbol table with instances of those structures.
6880 @samp{.tag} is only used when generating COFF format output; when
6881 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6887 @section @code{.text @var{subsection}}
6889 @cindex @code{text} directive
6890 Tells @command{@value{AS}} to assemble the following statements onto the end of
6891 the text subsection numbered @var{subsection}, which is an absolute
6892 expression. If @var{subsection} is omitted, subsection number zero
6896 @section @code{.title "@var{heading}"}
6898 @cindex @code{title} directive
6899 @cindex listing control: title line
6900 Use @var{heading} as the title (second line, immediately after the
6901 source file name and pagenumber) when generating assembly listings.
6903 This directive affects subsequent pages, as well as the current page if
6904 it appears within ten lines of the top of a page.
6908 @section @code{.type}
6910 This directive is used to set the type of a symbol.
6914 @c only print the extra heading if both COFF and ELF are set
6915 @subheading COFF Version
6918 @cindex COFF symbol type
6919 @cindex symbol type, COFF
6920 @cindex @code{type} directive (COFF version)
6921 For COFF targets, this directive is permitted only within
6922 @code{.def}/@code{.endef} pairs. It is used like this:
6928 This records the integer @var{int} as the type attribute of a symbol table
6932 @samp{.type} is associated only with COFF format output; when
6933 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6934 directive but ignores it.
6940 @c only print the extra heading if both COFF and ELF are set
6941 @subheading ELF Version
6944 @cindex ELF symbol type
6945 @cindex symbol type, ELF
6946 @cindex @code{type} directive (ELF version)
6947 For ELF targets, the @code{.type} directive is used like this:
6950 .type @var{name} , @var{type description}
6953 This sets the type of symbol @var{name} to be either a
6954 function symbol or an object symbol. There are five different syntaxes
6955 supported for the @var{type description} field, in order to provide
6956 compatibility with various other assemblers.
6958 Because some of the characters used in these syntaxes (such as @samp{@@} and
6959 @samp{#}) are comment characters for some architectures, some of the syntaxes
6960 below do not work on all architectures. The first variant will be accepted by
6961 the GNU assembler on all architectures so that variant should be used for
6962 maximum portability, if you do not need to assemble your code with other
6965 The syntaxes supported are:
6968 .type <name> STT_<TYPE_IN_UPPER_CASE>
6969 .type <name>,#<type>
6970 .type <name>,@@<type>
6971 .type <name>,%<type>
6972 .type <name>,"<type>"
6975 The types supported are:
6980 Mark the symbol as being a function name.
6983 @itemx gnu_indirect_function
6984 Mark the symbol as an indirect function when evaluated during reloc
6985 processing. (This is only supported on assemblers targeting GNU systems).
6989 Mark the symbol as being a data object.
6993 Mark the symbol as being a thead-local data object.
6997 Mark the symbol as being a common data object.
7001 Does not mark the symbol in any way. It is supported just for completeness.
7003 @item gnu_unique_object
7004 Marks the symbol as being a globally unique data object. The dynamic linker
7005 will make sure that in the entire process there is just one symbol with this
7006 name and type in use. (This is only supported on assemblers targeting GNU
7011 Note: Some targets support extra types in addition to those listed above.
7017 @section @code{.uleb128 @var{expressions}}
7019 @cindex @code{uleb128} directive
7020 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7021 compact, variable length representation of numbers used by the DWARF
7022 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7026 @section @code{.val @var{addr}}
7028 @cindex @code{val} directive
7029 @cindex COFF value attribute
7030 @cindex value attribute, COFF
7031 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7032 records the address @var{addr} as the value attribute of a symbol table
7036 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7037 configured for @code{b.out}, it accepts this directive but ignores it.
7043 @section @code{.version "@var{string}"}
7045 @cindex @code{version} directive
7046 This directive creates a @code{.note} section and places into it an ELF
7047 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7052 @section @code{.vtable_entry @var{table}, @var{offset}}
7054 @cindex @code{vtable_entry} directive
7055 This directive finds or creates a symbol @code{table} and creates a
7056 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7059 @section @code{.vtable_inherit @var{child}, @var{parent}}
7061 @cindex @code{vtable_inherit} directive
7062 This directive finds the symbol @code{child} and finds or creates the symbol
7063 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7064 parent whose addend is the value of the child symbol. As a special case the
7065 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7069 @section @code{.warning "@var{string}"}
7070 @cindex warning directive
7071 Similar to the directive @code{.error}
7072 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7075 @section @code{.weak @var{names}}
7077 @cindex @code{weak} directive
7078 This directive sets the weak attribute on the comma separated list of symbol
7079 @code{names}. If the symbols do not already exist, they will be created.
7081 On COFF targets other than PE, weak symbols are a GNU extension. This
7082 directive sets the weak attribute on the comma separated list of symbol
7083 @code{names}. If the symbols do not already exist, they will be created.
7085 On the PE target, weak symbols are supported natively as weak aliases.
7086 When a weak symbol is created that is not an alias, GAS creates an
7087 alternate symbol to hold the default value.
7090 @section @code{.weakref @var{alias}, @var{target}}
7092 @cindex @code{weakref} directive
7093 This directive creates an alias to the target symbol that enables the symbol to
7094 be referenced with weak-symbol semantics, but without actually making it weak.
7095 If direct references or definitions of the symbol are present, then the symbol
7096 will not be weak, but if all references to it are through weak references, the
7097 symbol will be marked as weak in the symbol table.
7099 The effect is equivalent to moving all references to the alias to a separate
7100 assembly source file, renaming the alias to the symbol in it, declaring the
7101 symbol as weak there, and running a reloadable link to merge the object files
7102 resulting from the assembly of the new source file and the old source file that
7103 had the references to the alias removed.
7105 The alias itself never makes to the symbol table, and is entirely handled
7106 within the assembler.
7109 @section @code{.word @var{expressions}}
7111 @cindex @code{word} directive
7112 This directive expects zero or more @var{expressions}, of any section,
7113 separated by commas.
7116 For each expression, @command{@value{AS}} emits a 32-bit number.
7119 For each expression, @command{@value{AS}} emits a 16-bit number.
7124 The size of the number emitted, and its byte order,
7125 depend on what target computer the assembly is for.
7128 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7129 @c happen---32-bit addressability, period; no long/short jumps.
7130 @ifset DIFF-TBL-KLUGE
7131 @cindex difference tables altered
7132 @cindex altered difference tables
7134 @emph{Warning: Special Treatment to support Compilers}
7138 Machines with a 32-bit address space, but that do less than 32-bit
7139 addressing, require the following special treatment. If the machine of
7140 interest to you does 32-bit addressing (or doesn't require it;
7141 @pxref{Machine Dependencies}), you can ignore this issue.
7144 In order to assemble compiler output into something that works,
7145 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7146 Directives of the form @samp{.word sym1-sym2} are often emitted by
7147 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7148 directive of the form @samp{.word sym1-sym2}, and the difference between
7149 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7150 creates a @dfn{secondary jump table}, immediately before the next label.
7151 This secondary jump table is preceded by a short-jump to the
7152 first byte after the secondary table. This short-jump prevents the flow
7153 of control from accidentally falling into the new table. Inside the
7154 table is a long-jump to @code{sym2}. The original @samp{.word}
7155 contains @code{sym1} minus the address of the long-jump to
7158 If there were several occurrences of @samp{.word sym1-sym2} before the
7159 secondary jump table, all of them are adjusted. If there was a
7160 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7161 long-jump to @code{sym4} is included in the secondary jump table,
7162 and the @code{.word} directives are adjusted to contain @code{sym3}
7163 minus the address of the long-jump to @code{sym4}; and so on, for as many
7164 entries in the original jump table as necessary.
7167 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7168 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7169 assembly language programmers.
7172 @c end DIFF-TBL-KLUGE
7174 @ifclear no-space-dir
7176 @section @code{.zero @var{size}}
7178 @cindex @code{zero} directive
7179 @cindex filling memory with zero bytes
7180 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7181 expression. This directive is actually an alias for the @samp{.skip} directive
7182 so in can take an optional second argument of the value to store in the bytes
7183 instead of zero. Using @samp{.zero} in this way would be confusing however.
7187 @section Deprecated Directives
7189 @cindex deprecated directives
7190 @cindex obsolescent directives
7191 One day these directives won't work.
7192 They are included for compatibility with older assemblers.
7199 @node Object Attributes
7200 @chapter Object Attributes
7201 @cindex object attributes
7203 @command{@value{AS}} assembles source files written for a specific architecture
7204 into object files for that architecture. But not all object files are alike.
7205 Many architectures support incompatible variations. For instance, floating
7206 point arguments might be passed in floating point registers if the object file
7207 requires hardware floating point support---or floating point arguments might be
7208 passed in integer registers if the object file supports processors with no
7209 hardware floating point unit. Or, if two objects are built for different
7210 generations of the same architecture, the combination may require the
7211 newer generation at run-time.
7213 This information is useful during and after linking. At link time,
7214 @command{@value{LD}} can warn about incompatible object files. After link
7215 time, tools like @command{gdb} can use it to process the linked file
7218 Compatibility information is recorded as a series of object attributes. Each
7219 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7220 string, and indicates who sets the meaning of the tag. The tag is an integer,
7221 and indicates what property the attribute describes. The value may be a string
7222 or an integer, and indicates how the property affects this object. Missing
7223 attributes are the same as attributes with a zero value or empty string value.
7225 Object attributes were developed as part of the ABI for the ARM Architecture.
7226 The file format is documented in @cite{ELF for the ARM Architecture}.
7229 * GNU Object Attributes:: @sc{gnu} Object Attributes
7230 * Defining New Object Attributes:: Defining New Object Attributes
7233 @node GNU Object Attributes
7234 @section @sc{gnu} Object Attributes
7236 The @code{.gnu_attribute} directive records an object attribute
7237 with vendor @samp{gnu}.
7239 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7240 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7241 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7242 2} is set for architecture-independent attributes and clear for
7243 architecture-dependent ones.
7245 @subsection Common @sc{gnu} attributes
7247 These attributes are valid on all architectures.
7250 @item Tag_compatibility (32)
7251 The compatibility attribute takes an integer flag value and a vendor name. If
7252 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7253 then the file is only compatible with the named toolchain. If it is greater
7254 than 1, the file can only be processed by other toolchains under some private
7255 arrangement indicated by the flag value and the vendor name.
7258 @subsection MIPS Attributes
7261 @item Tag_GNU_MIPS_ABI_FP (4)
7262 The floating-point ABI used by this object file. The value will be:
7266 0 for files not affected by the floating-point ABI.
7268 1 for files using the hardware floating-point ABI with a standard
7269 double-precision FPU.
7271 2 for files using the hardware floating-point ABI with a single-precision FPU.
7273 3 for files using the software floating-point ABI.
7275 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7276 floating-point registers, 32-bit general-purpose registers and increased the
7277 number of callee-saved floating-point registers.
7279 5 for files using the hardware floating-point ABI with a double-precision FPU
7280 with either 32-bit or 64-bit floating-point registers and 32-bit
7281 general-purpose registers.
7283 6 for files using the hardware floating-point ABI with 64-bit floating-point
7284 registers and 32-bit general-purpose registers.
7286 7 for files using the hardware floating-point ABI with 64-bit floating-point
7287 registers, 32-bit general-purpose registers and a rule that forbids the
7288 direct use of odd-numbered single-precision floating-point registers.
7292 @subsection PowerPC Attributes
7295 @item Tag_GNU_Power_ABI_FP (4)
7296 The floating-point ABI used by this object file. The value will be:
7300 0 for files not affected by the floating-point ABI.
7302 1 for files using double-precision hardware floating-point ABI.
7304 2 for files using the software floating-point ABI.
7306 3 for files using single-precision hardware floating-point ABI.
7309 @item Tag_GNU_Power_ABI_Vector (8)
7310 The vector ABI used by this object file. The value will be:
7314 0 for files not affected by the vector ABI.
7316 1 for files using general purpose registers to pass vectors.
7318 2 for files using AltiVec registers to pass vectors.
7320 3 for files using SPE registers to pass vectors.
7324 @subsection IBM z Systems Attributes
7327 @item Tag_GNU_S390_ABI_Vector (8)
7328 The vector ABI used by this object file. The value will be:
7332 0 for files not affected by the vector ABI.
7334 1 for files using software vector ABI.
7336 2 for files using hardware vector ABI.
7340 @node Defining New Object Attributes
7341 @section Defining New Object Attributes
7343 If you want to define a new @sc{gnu} object attribute, here are the places you
7344 will need to modify. New attributes should be discussed on the @samp{binutils}
7349 This manual, which is the official register of attributes.
7351 The header for your architecture @file{include/elf}, to define the tag.
7353 The @file{bfd} support file for your architecture, to merge the attribute
7354 and issue any appropriate link warnings.
7356 Test cases in @file{ld/testsuite} for merging and link warnings.
7358 @file{binutils/readelf.c} to display your attribute.
7360 GCC, if you want the compiler to mark the attribute automatically.
7366 @node Machine Dependencies
7367 @chapter Machine Dependent Features
7369 @cindex machine dependencies
7370 The machine instruction sets are (almost by definition) different on
7371 each machine where @command{@value{AS}} runs. Floating point representations
7372 vary as well, and @command{@value{AS}} often supports a few additional
7373 directives or command-line options for compatibility with other
7374 assemblers on a particular platform. Finally, some versions of
7375 @command{@value{AS}} support special pseudo-instructions for branch
7378 This chapter discusses most of these differences, though it does not
7379 include details on any machine's instruction set. For details on that
7380 subject, see the hardware manufacturer's manual.
7384 * AArch64-Dependent:: AArch64 Dependent Features
7387 * Alpha-Dependent:: Alpha Dependent Features
7390 * ARC-Dependent:: ARC Dependent Features
7393 * ARM-Dependent:: ARM Dependent Features
7396 * AVR-Dependent:: AVR Dependent Features
7399 * Blackfin-Dependent:: Blackfin Dependent Features
7402 * CR16-Dependent:: CR16 Dependent Features
7405 * CRIS-Dependent:: CRIS Dependent Features
7408 * D10V-Dependent:: D10V Dependent Features
7411 * D30V-Dependent:: D30V Dependent Features
7414 * Epiphany-Dependent:: EPIPHANY Dependent Features
7417 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7420 * HPPA-Dependent:: HPPA Dependent Features
7423 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7426 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7429 * i860-Dependent:: Intel 80860 Dependent Features
7432 * i960-Dependent:: Intel 80960 Dependent Features
7435 * IA-64-Dependent:: Intel IA-64 Dependent Features
7438 * IP2K-Dependent:: IP2K Dependent Features
7441 * LM32-Dependent:: LM32 Dependent Features
7444 * M32C-Dependent:: M32C Dependent Features
7447 * M32R-Dependent:: M32R Dependent Features
7450 * M68K-Dependent:: M680x0 Dependent Features
7453 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7456 * Meta-Dependent :: Meta Dependent Features
7459 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7462 * MIPS-Dependent:: MIPS Dependent Features
7465 * MMIX-Dependent:: MMIX Dependent Features
7468 * MSP430-Dependent:: MSP430 Dependent Features
7471 * NDS32-Dependent:: Andes NDS32 Dependent Features
7474 * NiosII-Dependent:: Altera Nios II Dependent Features
7477 * NS32K-Dependent:: NS32K Dependent Features
7480 * PDP-11-Dependent:: PDP-11 Dependent Features
7483 * PJ-Dependent:: picoJava Dependent Features
7486 * PPC-Dependent:: PowerPC Dependent Features
7489 * RL78-Dependent:: RL78 Dependent Features
7492 * RX-Dependent:: RX Dependent Features
7495 * S/390-Dependent:: IBM S/390 Dependent Features
7498 * SCORE-Dependent:: SCORE Dependent Features
7501 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7502 * SH64-Dependent:: SuperH SH64 Dependent Features
7505 * Sparc-Dependent:: SPARC Dependent Features
7508 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7511 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7514 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7517 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7520 * V850-Dependent:: V850 Dependent Features
7523 * Vax-Dependent:: VAX Dependent Features
7526 * Visium-Dependent:: Visium Dependent Features
7529 * XGATE-Dependent:: XGATE Features
7532 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7535 * Xtensa-Dependent:: Xtensa Dependent Features
7538 * Z80-Dependent:: Z80 Dependent Features
7541 * Z8000-Dependent:: Z8000 Dependent Features
7548 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7549 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7550 @c peculiarity: to preserve cross-references, there must be a node called
7551 @c "Machine Dependencies". Hence the conditional nodenames in each
7552 @c major node below. Node defaulting in makeinfo requires adjacency of
7553 @c node and sectioning commands; hence the repetition of @chapter BLAH
7554 @c in both conditional blocks.
7557 @include c-aarch64.texi
7561 @include c-alpha.texi
7577 @include c-bfin.texi
7581 @include c-cr16.texi
7585 @include c-cris.texi
7590 @node Machine Dependencies
7591 @chapter Machine Dependent Features
7593 The machine instruction sets are different on each Renesas chip family,
7594 and there are also some syntax differences among the families. This
7595 chapter describes the specific @command{@value{AS}} features for each
7599 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7600 * SH-Dependent:: Renesas SH Dependent Features
7607 @include c-d10v.texi
7611 @include c-d30v.texi
7615 @include c-epiphany.texi
7619 @include c-h8300.texi
7623 @include c-hppa.texi
7627 @include c-i370.texi
7631 @include c-i386.texi
7635 @include c-i860.texi
7639 @include c-i960.texi
7643 @include c-ia64.texi
7647 @include c-ip2k.texi
7651 @include c-lm32.texi
7655 @include c-m32c.texi
7659 @include c-m32r.texi
7663 @include c-m68k.texi
7667 @include c-m68hc11.texi
7671 @include c-metag.texi
7675 @include c-microblaze.texi
7679 @include c-mips.texi
7683 @include c-mmix.texi
7687 @include c-msp430.texi
7691 @include c-nds32.texi
7695 @include c-nios2.texi
7699 @include c-ns32k.texi
7703 @include c-pdp11.texi
7715 @include c-rl78.texi
7723 @include c-s390.texi
7727 @include c-score.texi
7732 @include c-sh64.texi
7736 @include c-sparc.texi
7740 @include c-tic54x.texi
7744 @include c-tic6x.texi
7748 @include c-tilegx.texi
7752 @include c-tilepro.texi
7756 @include c-v850.texi
7764 @include c-visium.texi
7768 @include c-xgate.texi
7772 @include c-xstormy16.texi
7776 @include c-xtensa.texi
7788 @c reverse effect of @down at top of generic Machine-Dep chapter
7792 @node Reporting Bugs
7793 @chapter Reporting Bugs
7794 @cindex bugs in assembler
7795 @cindex reporting bugs in assembler
7797 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7799 Reporting a bug may help you by bringing a solution to your problem, or it may
7800 not. But in any case the principal function of a bug report is to help the
7801 entire community by making the next version of @command{@value{AS}} work better.
7802 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7804 In order for a bug report to serve its purpose, you must include the
7805 information that enables us to fix the bug.
7808 * Bug Criteria:: Have you found a bug?
7809 * Bug Reporting:: How to report bugs
7813 @section Have You Found a Bug?
7814 @cindex bug criteria
7816 If you are not sure whether you have found a bug, here are some guidelines:
7819 @cindex fatal signal
7820 @cindex assembler crash
7821 @cindex crash of assembler
7823 If the assembler gets a fatal signal, for any input whatever, that is a
7824 @command{@value{AS}} bug. Reliable assemblers never crash.
7826 @cindex error on valid input
7828 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7830 @cindex invalid input
7832 If @command{@value{AS}} does not produce an error message for invalid input, that
7833 is a bug. However, you should note that your idea of ``invalid input'' might
7834 be our idea of ``an extension'' or ``support for traditional practice''.
7837 If you are an experienced user of assemblers, your suggestions for improvement
7838 of @command{@value{AS}} are welcome in any case.
7842 @section How to Report Bugs
7844 @cindex assembler bugs, reporting
7846 A number of companies and individuals offer support for @sc{gnu} products. If
7847 you obtained @command{@value{AS}} from a support organization, we recommend you
7848 contact that organization first.
7850 You can find contact information for many support companies and
7851 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7855 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7859 The fundamental principle of reporting bugs usefully is this:
7860 @strong{report all the facts}. If you are not sure whether to state a
7861 fact or leave it out, state it!
7863 Often people omit facts because they think they know what causes the problem
7864 and assume that some details do not matter. Thus, you might assume that the
7865 name of a symbol you use in an example does not matter. Well, probably it does
7866 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7867 happens to fetch from the location where that name is stored in memory;
7868 perhaps, if the name were different, the contents of that location would fool
7869 the assembler into doing the right thing despite the bug. Play it safe and
7870 give a specific, complete example. That is the easiest thing for you to do,
7871 and the most helpful.
7873 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7874 it is new to us. Therefore, always write your bug reports on the assumption
7875 that the bug has not been reported previously.
7877 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7878 bell?'' This cannot help us fix a bug, so it is basically useless. We
7879 respond by asking for enough details to enable us to investigate.
7880 You might as well expedite matters by sending them to begin with.
7882 To enable us to fix the bug, you should include all these things:
7886 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7887 it with the @samp{--version} argument.
7889 Without this, we will not know whether there is any point in looking for
7890 the bug in the current version of @command{@value{AS}}.
7893 Any patches you may have applied to the @command{@value{AS}} source.
7896 The type of machine you are using, and the operating system name and
7900 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7904 The command arguments you gave the assembler to assemble your example and
7905 observe the bug. To guarantee you will not omit something important, list them
7906 all. A copy of the Makefile (or the output from make) is sufficient.
7908 If we were to try to guess the arguments, we would probably guess wrong
7909 and then we might not encounter the bug.
7912 A complete input file that will reproduce the bug. If the bug is observed when
7913 the assembler is invoked via a compiler, send the assembler source, not the
7914 high level language source. Most compilers will produce the assembler source
7915 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7916 the options @samp{-v --save-temps}; this will save the assembler source in a
7917 file with an extension of @file{.s}, and also show you exactly how
7918 @command{@value{AS}} is being run.
7921 A description of what behavior you observe that you believe is
7922 incorrect. For example, ``It gets a fatal signal.''
7924 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7925 will certainly notice it. But if the bug is incorrect output, we might not
7926 notice unless it is glaringly wrong. You might as well not give us a chance to
7929 Even if the problem you experience is a fatal signal, you should still say so
7930 explicitly. Suppose something strange is going on, such as, your copy of
7931 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7932 library on your system. (This has happened!) Your copy might crash and ours
7933 would not. If you told us to expect a crash, then when ours fails to crash, we
7934 would know that the bug was not happening for us. If you had not told us to
7935 expect a crash, then we would not be able to draw any conclusion from our
7939 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7940 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7941 option. Always send diffs from the old file to the new file. If you even
7942 discuss something in the @command{@value{AS}} source, refer to it by context, not
7945 The line numbers in our development sources will not match those in your
7946 sources. Your line numbers would convey no useful information to us.
7949 Here are some things that are not necessary:
7953 A description of the envelope of the bug.
7955 Often people who encounter a bug spend a lot of time investigating
7956 which changes to the input file will make the bug go away and which
7957 changes will not affect it.
7959 This is often time consuming and not very useful, because the way we
7960 will find the bug is by running a single example under the debugger
7961 with breakpoints, not by pure deduction from a series of examples.
7962 We recommend that you save your time for something else.
7964 Of course, if you can find a simpler example to report @emph{instead}
7965 of the original one, that is a convenience for us. Errors in the
7966 output will be easier to spot, running under the debugger will take
7967 less time, and so on.
7969 However, simplification is not vital; if you do not want to do this,
7970 report the bug anyway and send us the entire test case you used.
7973 A patch for the bug.
7975 A patch for the bug does help us if it is a good one. But do not omit
7976 the necessary information, such as the test case, on the assumption that
7977 a patch is all we need. We might see problems with your patch and decide
7978 to fix the problem another way, or we might not understand it at all.
7980 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7981 construct an example that will make the program follow a certain path through
7982 the code. If you do not send us the example, we will not be able to construct
7983 one, so we will not be able to verify that the bug is fixed.
7985 And if we cannot understand what bug you are trying to fix, or why your
7986 patch should be an improvement, we will not install it. A test case will
7987 help us to understand.
7990 A guess about what the bug is or what it depends on.
7992 Such guesses are usually wrong. Even we cannot guess right about such
7993 things without first using the debugger to find the facts.
7996 @node Acknowledgements
7997 @chapter Acknowledgements
7999 If you have contributed to GAS and your name isn't listed here,
8000 it is not meant as a slight. We just don't know about it. Send mail to the
8001 maintainer, and we'll correct the situation. Currently
8003 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8005 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8008 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8009 information and the 68k series machines, most of the preprocessing pass, and
8010 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8012 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8013 many bug fixes, including merging support for several processors, breaking GAS
8014 up to handle multiple object file format back ends (including heavy rewrite,
8015 testing, an integration of the coff and b.out back ends), adding configuration
8016 including heavy testing and verification of cross assemblers and file splits
8017 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8018 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8019 port (including considerable amounts of reverse engineering), a SPARC opcode
8020 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8021 assertions and made them work, much other reorganization, cleanup, and lint.
8023 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8024 in format-specific I/O modules.
8026 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8027 has done much work with it since.
8029 The Intel 80386 machine description was written by Eliot Dresselhaus.
8031 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8033 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8034 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8036 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8037 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8038 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8039 support a.out format.
8041 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8042 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8043 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8044 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8047 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8048 simplified the configuration of which versions accept which directives. He
8049 updated the 68k machine description so that Motorola's opcodes always produced
8050 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8051 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8052 cross-compilation support, and one bug in relaxation that took a week and
8053 required the proverbial one-bit fix.
8055 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8056 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8057 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8058 PowerPC assembler, and made a few other minor patches.
8060 Steve Chamberlain made GAS able to generate listings.
8062 Hewlett-Packard contributed support for the HP9000/300.
8064 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8065 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8066 formats). This work was supported by both the Center for Software Science at
8067 the University of Utah and Cygnus Support.
8069 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8070 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8071 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8072 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8073 and some initial 64-bit support).
8075 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8077 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8078 support for openVMS/Alpha.
8080 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8083 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8084 Inc.@: added support for Xtensa processors.
8086 Several engineers at Cygnus Support have also provided many small bug fixes and
8087 configuration enhancements.
8089 Jon Beniston added support for the Lattice Mico32 architecture.
8091 Many others have contributed large or small bugfixes and enhancements. If
8092 you have contributed significant work and are not mentioned on this list, and
8093 want to be, let us know. Some of the history has been lost; we are not
8094 intentionally leaving anyone out.
8096 @node GNU Free Documentation License
8097 @appendix GNU Free Documentation License
8101 @unnumbered AS Index